ArticlePDF Available

The History and Operation of Gasworks (Manufactured Gas Plants)

April 2013

Project: Characterisation of former gasworks

Authors:

A profile of the gas manufacturing process, it's design, development, application and the types of waste and by-products which may be associated with the processes used.. The author is grateful to fellow members of Institution of Gas Engineers and Managers (IGEM) Panel for the History of the Industry and the staff of the National Gas Archive for their kind assistance.

A picture of a diorama of George Dixon demonstrating burning coal gas.

…

William Murdoch.

…

Murdoch's original circular gasholder at the Soho work.

…

Sketch Portrait of Frederick Winsor.

…

+64

A Schematic simple bench of 3 directly fired retorts which would be found in a small gasworks

…

Figures - uploaded by Russell Thomas

Content may be subject to copyright.

Content uploaded by Russell Thomas

Content may be subject to copyright.

The History and Operation of Gasworks (Manufactured Gas Plants). 1 Written by Dr Russell Thomas (28/1/2013)

The History and Operation of

Gasworks (Manufactured Gas

Plants).

A profile of the gas manufacturing process, it’s

design, development, application and the types of

waste and by-products which may be associated

with the processes used.

Prepared by Dr Russell Thomas, Technical

Director Parsons Brinckerhoff Ltd, Redland,

Bristol, UK, 0117-933-9262,

thomasru@pbworld.com or

gasworkshistory@gmail.com. The author is

grateful to fellow members of Institution of Gas

Engineers and Managers (IGEM) Panel for the

History of the Industry and the staff of the

National Gas Archive for their kind assistance.

Introduction

This article describes the historical development

of the manufactured gas industry in Britain, giving

a description of the processes used to

manufacture of gas from coal and a brief

description of other processes. All images

courtesy of the National Gas Archive, unless

stated.

Gas was manufactured in the Britain between

1792, when William Murdock first used coal gas

to light his house and office in Redruth and 1981

when the last gasworks closed in Britain. Britain

now uses natural gas, it started to convert from

manufactured gas in 1967, an operation taking 10

years to complete. This profile aims to give a brief

description of a complex and ever evolving

industry, to those who have a professional or

personal interest in the subject.

A brief summary of the historical development

of gas

Ancient times and the early awareness of gas

People were aware of the existence of flammable

gas, in ancient times, when “Eternal Flames”

formed the centrepiece of religious shrines. The

external flames were seepages of combustible

gases from sources of gas in the ground below.

The Chinese were known to have captured

natural gas seepages and transported it through

bamboo pipes to be burnt to heat salt pans,

evaporating water to produce salt. They had also

worked out how to capture the gas in animal

skins so it could be stored and transported.

It is however, not until much later that the great

potential of gas was realised, and a practical

process to manufacture it developed. Many

people from across Europe experimented with the

distillation of coal, splitting it into its constituent

parts of inflammable gas, ammonia rich water, tar

and coke.

Jean Tardin documented in “Histoire naturelle de

la fontaine qui brusle pres de Grenoble (1618)”,

that he had heated crushed coal in a closed

vessel producing coal gas after identifying that

the source of the fire well in Grenoble, was gas

escaping from burning coal beds.

Thomas Shirley made an early observation

(1659) of ‘carburetted hydrogen’ emanating from

a natural spring, when he put a candle to the

surface of the water, it ignited. Shirley believed

the source of the gas was coal below the ground.

Dr. John Clayton, the Dean of Kildare, continued

Shirley’s work and years later (1684) excavated

the base of the spring to find coal 18 inches

below. The gas escaping from the coal measures

was inflammable and Clayton assumed that the

coal was the source of the gas. Clayton’s work

continued with the distillation of coal in an open

retort he noted ‘At first there came over only

Flegm, afterwards a black Oyle and then a spirit

arose which I could no ways condense….’,

Clayton collected the gas in bladders, which if

pricked with a pin and squeezed, the gas could

be ignited. Much of this work was unknown until

Clayton published the work circa 1739.

Figure 1. A picture of a diorama of George

Dixon demonstrating burning coal gas.

In 1760 George Dixon (Figure1), undertook

experiments heating coal in a kettle and igniting

the gas which escaped from it’s spout.

Carlisle Spedding the manager at Lord

Lonsdale’s Saltom mine in Whitehaven (1765), lit

The History and Operation of Gasworks (Manufactured Gas Plants). 2 Written by Dr Russell Thomas (28/1/2013)

his office with mines gas otherwise known as “fire

damp” which was vented from the mine. He had

offered to supply the town with gas for street

lighting, an offer they refused. This had followed

earlier work (1733) by Sir James Lowther in

burning fire damp at the surface of a mine from

which it was being vented.

Archibald Cochrane otherwise known as Lord

Dundonald, had spotted a market for coal tar with

the Royal Navy, by tarring the wooden hulls of the

Navy fleet he believed it would prevent them from

rotting and fouling. Tar distillation ovens were

built at the family home, Culross Abbey in Fife.

The gas produced from the distillation of the coal

was reputed to have been lighted producing a

bright flame visible from many miles away.

Abroad others were active, in experimenting with

coal gas. Jean Pierre Minklelers a professor at

Louvain lighted his lecture room in 1785. In 1786

Professor Pickel lit his chemistry laboratory in

Wurzburg, Bavaria. In France Philippe Lebon

obtained gas from heating sawdust in a retort and

also lighted a room by gas in 1791.

Most credit for the discovery of a commercial

process for coal gas manufacture goes to William

Murdoch, a genius Scottish engineer born in 1754

at Bello Mill, near the town of Lugar in Ayrshire,

Scotland. After walking to the Boulton and Watt

factory at Smethwick, Birmingham from Lugar in

1877, Murdoch found employment. Mathew

Boulton was particularly taken aback by an oval

shaped wooden hat that Murdoch was wearing.

He had made himself on a lathe of his own

design.

Murdoch performed well and within a few years

(1779) he was given the difficult task of selling

and installing steam powered water pumping

equipment to the Cornish mine owners. This was

at the time the most prosperous industry in Britain

and Boulton and Watt’s most valuable market.

Murdoch was so well liked in Cornwall that he

married the daughter of a local mine owner called

Ann Paynter.

A strong and beautiful light

Murdoch was based in Redruth and it was whilst

being based here that he experimented with the

production of gas from coal in a small iron retort

in his back yard, the gas was piped into the

house allowing him to light his house and office in

1792. Murdoch was an engineering genius, much

overlooked when compared to some of his peers,

he also built the first working model steam

carriage at the same house in Redruth in 1784.

Figure 2. William Murdoch.

Between 1795 and 1796 Murdoch experimented

further at the Neath Abbey Iron Works with the

design of retorts. He lit the counting houses of the

works describing the light produced by the gas as

a “Strong and Beautiful light”. At the same time

Murdoch lit a factory in Old Cumnock, Ayrshire.

He did this by filling small bladders with gas from

a retort outside the factory and then attached

them to light fittings within the factory and burning

the gas.

Recalled to Birmingham in 1798, Murdoch

continued to experiment with gas lighting, without

much support from his employers, until Gregory

Watt had visited Paris and discovered the rival

work being undertaken by Philippe Lebon.

Figure 3. Murdoch’s original circular

gasholder at the Soho work.

With more encouragement Murdoch went on to

light the Soho Works of Boulton and Watt in

1802. To celebrate the Peace of Amiens, the

exterior of the Soho works were illuminated, the

first public lighting exhibition. Murdoch had

experimented with a vertical retort design with the

coal held in baskets, but this proved impractical

and he developed horizontal retorts by 1802.

Murdoch operated the retorts in a way that he lit

the furnace shortly before the gas was required,

an inefficient form of operation. It relied on a

colleague of Murdoch, John Southern to point out

that if the gas could be stored then fewer retorts

would be required and they could be operated

continuously. Murdoch examined the process of

coal gas manufacture in great detail, costing his

employers an estimated £5000. In 1805 the

Boulton and Watt factory was the only supplier of

gas making plant in the world; Murdoch also

The History and Operation of Gasworks (Manufactured Gas Plants). 3 Written by Dr Russell Thomas (28/1/2013)

developed the world’s first circular gasholder in

1805.

Following on from the success at the Soho works,

Murdoch looked for opportunities to install gas

plants at other sites. In 1804 George Lee of

“Philips and Lee” in Salford was the first

industrialist to employ Murdoch to build a gas

plant and install gas lighting in a mill, initially

George Lee’s house was lighted by gas. Once it’s

safety had been proved, Murdoch lighted their

Salford Twist Mill, one of the biggest factories in

Britain at this time. The mill was fully lit by gas in

1805 and in 1806 Chapel Street, Salford was the

world’s first street to be lighted by gas.

Murdoch was not alone in his interest in gas

lighting, a former colleague Samuel Clegg had

set up as a rival and was busy installing a gas

plant at Henry Lodge’s Mill at Sowerby Bridge in

Yorkshire. Clegg is believed to have beaten

Murdoch by two weeks on the installation of gas

at Sowerby Bridge.

Despite this success the ambitions of Boulton and

Watt, Murdoch’s employers, in the field of gas

lighting, were limited. It was a small part of a

large business empire focussed on manufacturing

steam engines. It was this lack of interest which

caused Clegg to depart and for other employees

to set up as gas engineering contractors to rival

there former employer. Other engineers in the

Birmingham area had also seen the potential for

gas lighting and engineers such as Josiah

Pembleton started designing there own plant for

smaller works. Boulton and Watt focussed on the

large manufactories, who could afford their plant

and they went on to light some of the larger

establishments in Britain such as the Strutt’s

Calico Mill in Derby, Gott’s Woollen mill in Leeds

and two flax mills in Shrewsbury.

By 1815 the Boulton and Watt Company, and

Murdoch had started to withdraw from the

manufacture of gasworks plant. Other specialist

gas engineers had taken the lead. Gas was

adopted in many large mills and factories across

Britain most notably the mills across the north of

England.

Mills had predominantly been lighted by Tallow

candles or oil lamps, using up to 1500 candles

per night in the winter. Both candles and oil

lamps could easily be knocked over, and were

responsible for many mills burning down with the

loss of a many lives. George Lee was offered a

greatly reduced insurance cost (one third of the

previous cost) for having their Salford twist mill

converted to gas lighting, a great incentive.

The development of the public gas supply

In 1808 Murdock presented a paper to the Royal

Society entitled ”An account of the application of

coal gas to economical purposes.” for which he

received the Rumford Gold Medal.

The philosophy of William Murdoch was to build

small gasworks to provide gas to a single

establishment. Other proponents however, had

greater plans, a key figure being the Moravian

Frederick Albrect Winzer. To succeed in Britain,

he change his name to Fredrick Albert Winsor, he

was an impresario who had seen Lebon’s early

experiments in Paris.

Winsor proposed the concept of centralised

gasworks providing gas to multiple

establishments through gas mains under the

street. It should be noted that Lebon had been

murdered in 1804, after which the development of

gas in Paris almost ceased until renewed interest

in the 1820’s. If Lebon had not been murdered

then gas may have been adopted in France much

earlier on. Lebon’s work on the Thermolamp

cannot be underestimated. It was very influential

in continental Europe and led to much of the

development outside of Britain in Europe.

Figure 4. Sketch Portrait of Frederick Winsor.

Winsor thought London a suitable place to

develop a gas industry. He gained a reputation,

undertaking nightly lectures and demonstrations

of gas lighting at the Lyceum Theatre in London,

he went on to demonstrate gas lighting on Pall

Mall in 1807. In the same year the Golden Lane

Brewery was lit with gas and also the street

outside the Brewery.

Winsor had a very commercial outlook, much

more so than Murdoch and had unsuccessfully

challenged Murdoch for a patent for lighting by

coal gas. Winsor was intent on setting up a

company to produce gas from a centralised

gasworks, he first proposed the National Light

The History and Operation of Gasworks (Manufactured Gas Plants). 4 Written by Dr Russell Thomas (28/1/2013)

and Heat Company in 1807 with the grand aim of

supplying the whole country with gas. Making

applications to parliament for a charter he found

strong opposition from Murdoch and his friends.

He was persistent and eventually on 30th of April

1812 the Gas Light and Coke Company (GL&C

Co) received its Royal Charter. Their first

gasworks built on Cannon Row, Westminster

failed. They then moved to Great Peter Street,

Westminster, where they succeeded.

Winsor’s success with the GL&C Co was short

lived, he was ousted by the ruling court and in

1813 he was given an annuity of £600, this was

however suspended in 1815 and Winsor had to

flee the country to avoid his creditors. He

returned to France where he floated a short lived

gas company, he died in 1830 a disappointed

man, but his influence on the gas industry cannot

be underestimated.

The first gas engineer

Samuel Clegg was another key figure; Clegg was

an apprentice at Boulton and Watt and became

an assistant to William Murdoch in 1801. Clegg

realised the limitations of working at Boulton and

Watt, where gas was just one of many

departments, so he split from the company in

1805. At the same time Murdoch was installing

gas at the Phillips and Lee mill in Salford, Clegg

was installing a gas plant at the mill of Henry

Lodge in Sowerby Bridge. Clegg is believed to

have beaten Murdoch by two weeks on the

installation of gas at Sowerby Bridge.

Clegg experimented with the purification of gas

using lime, he installed such a plant at the

gasworks he installed at Stonyhurst College

(Preston, England) in 1811. Clegg also invented

the first gas meter the first self acting governor

and adapted the Argand burner for burning gas.

Clegg later went to London to establish a small

gasworks for a famous publisher called Rudolph

Ackerman in 1812, This proved an excellent

advert for Clegg’s skills as an engineer. On the

25th December 1812, Clegg began work for the

Chartered Gas Light and Coke Company (GL&C

Co) which proved vital for the survival of the

GL&C Co as its existing technical experts Winsor,

Accum and Hargreaves were not engineers, so

Clegg maintained the GL&C Co gasworks, almost

single handed for the first few years.

Clegg even took to lighting the gas lights on

Westminster Bridge as the lamplighters originally

refused to light them for fear of explosion. Clegg

left the GL&C Co in 1817, he installed gas at the

Royal Mint and then went on to establish gas in

various towns and cities including Birmingham,

Bristol and Chester.

Clegg had developed the large circular

gasholders at the GL&C Co. and he spent much

time persuading others that they were safe and

not liable to suddenly explode. This included

instructing a gas worker to put a pick axe into the

side of a holder and then lighting the resulting gas

leaking from the vessel.

These fears over gasholder safety required many

of the very early gasholders to be housed within a

building. Later on the need for these buildings

was dispensed with in Britain.

The great expansion into provinces

Following on the heels of the Gas Light and Coke

Company, many other gas companies were

established in London, in 1850 these numbered

13, the most notable rival being The South

Metropolitan Gas Company which had been

Figure

A Schematic simple bench of 3 directly fired retorts which would be

found in a small gasworks

Hydraulic Main

Ascension pipe

Retorts

Furnace

The History and Operation of Gasworks (Manufactured Gas Plants). 5 Written by Dr Russell Thomas (28/1/2013)

formed in 1834. Outside of London, Preston

became the first provincial town to have a public

gas supply, securing an act of Parliament in 1815

to “light, watch, pave, repair, cleanse and

improve’ the towns streets”. The Preston Gas

Light Company was formed and Samuel Clegg

provided his assistant John Grafton to act as

engineer. On the 20th of February 1816 Preston

became the first town outside London to be lit by

gas. Exeter and Liverpool soon followed with Acts

of Parliament in 1816, In Scotland the "The

Glasgow Gas Light Company" received an Act of

Parliament giving it statutory powers in 1817, with

gas lighting commencing in 1818. In Wales a

public Gas supply was first provided to Swansea

in 1821.

Gas spread rapidly throughout the country, often

through the passing of “lighting and watching”

Acts.

Figure 6. Servicing a gas street lamp.

Expansion abroad

In order to export Britain’s new found experience

in gas manufacture abroad, the Imperial

Continental Gas Association (ICGA) was formed

in 1824 by Major-General Sir William Congreve.

By this time the manufacture of gas had already

started to be introduced in some European

Towns and Cities following its success in Britain.

In 1825 Congreve toured Europe to establish

business ventures; success was mixed as some

places already had established local rivals. Their

first venture was a small gasworks in Ghent

which they had purchased from a local company,

this was an oil gasworks which they later

converted to use coal.

Figure 7. Mechanical charging machine

loading horizontal retorts.

The ICGA went on to operate in the Netherlands,

Belgium, Germany, Austria, Hungary and France.

Due to the nature of their short to medium term

contracts and political changes and war in Europe

the business changed considerably. The

company continued to operate until 1987,

although its business had much changed.

The ICGA was not unique and other British

companies were established to target Europe,

such as the European Gas Company and the

Continental Gas and Water Company. The British

Empire was also targeted by companies such as

the Colonial Gas Company. With British support

and independently, gasworks were built across

the globe on all continents except Antarctica.

Figure 8. An early painting of depicting

conditions with Brick Lane gasworks.

Private and Municipal undertakings.

Gas undertakings were all privately owned until

the Manchester Police commissioners took an

interest in gas lighting. Their first involvement

came in 1806 when a gas light was installed at

the King Street police station. They were

responsible for lighting (and watching) the streets

with oil lamps. The police commissioners in

Manchester passed a resolution in 1817 to build a

gasworks to light the police stations, principal

streets and sell any surplus to private customers.

This was the first example of a municipally owned

gas undertaking.

The History and Operation of Gasworks (Manufactured Gas Plants). 6 Written by Dr Russell Thomas (28/1/2013)

The gas undertaking transferred to the

Manchester Corporation in 1843 making it the

first municipal gas undertaking. Many gas

undertakings came under municipal ownership, in

particular in the Midlands and North of England.

The Continued development and growth of gas.

The telescopic gasholder was developed by Tate

in 1824 with the first example being built at

Leeds. This gave gasworks the added benefit of

increasing gas storage without increasing the

footprint required by the gasholders. Telescopic

gasholder consisted of vessels (lifts) situated one

inside the other, when the inner lift was fully

extended the next outer lift would also start to

rise.

In 1826 James Sharp who was then the assistant

manager of the Northampton Gas Company

experimented with the possibility of cooking with

gas, he installed an experimental gas cooker in

his home, the relative success of this cooker won

him the patronage of Earl Spencer in 1834 and

he went on to produce cookers commercially.

However cooking with gas did not become

popular until much later on.

The first gas heated bath was developed in 1850

although such new developments were not

without there inherent safety risks.

The gas industry had remained largely

unregulated in its early years, no restrictions were

placed on prices charged or profits made by the

gas undertakings, they generally just had to

provide the parish gas lighting at a cheaper rate.

In 1847 the Gasworks Clauses Act was

introduced to regulate the construction of

gasworks and supplying towns with gas. It

regulated all aspects of the gas industry including

laying of pipes, profits, annual accounts, penalties

waste produced and by-products. It was just one

of a number of important acts to be passed which

would regulate the gas industry over the coming

century.

Parliment relied upon the competion in the gas

market to keep prices low. In London to almost all

areas having two potential gas companies

supplying them. This system was regarded as

uneconomic and very inconvenient as it led to

excessive digging up of the roads, so in 1853

London South of the Thames adopted

“Districting“ where specified companies would

supply specified districts. This concept was later

adopted in the Metropolis Gas Act of 1860 for the

whole of London.

Figure 9. An early apparatus for the

production of aniline dyes, from the “British

Coal Tar Industry” by William Gardner.

In 1856 William Perkin was an assistant of

August Wilhelm von Hofmann at The Royal

College of Chemistry. One summer whilst Von

Hoffman was abroad, Perkin made the discovery

of the dye Mauveine. Perkin had been working on

a way to sythesise quinine in the fight against

malaria but discovered Mauvine. Perkin patented

the dye and as a result founded the aniline dye

industry. Coal tar from the gas industry was the

substance from which Mauvine was extracted.

The coal tar based dye industry became

important and a considerable industry in its own

right. It became very important, flourishing in

Germany in particular.

A bright future?

In 1855 Robert Bunsen, a German chemist

invented the atmospheric gas burner known to

many as the “Bunsen burner”. This made much

more effective use of the gas burnt and it allowed

a much greater range of developments to be

made especially in commercial and domestic

heating applications. This development ultimately

was a saviour to the gas industry as heating

applications became ever more important as the

industry evolved.

Figure 10. A schematic of a Bunsen burner.

Carl Auer von Welsbach, was an Austrian

chemist who made a major contribution to the

gas industry, he invented the gas mantle in 1887.

He discovered that the oxides of certain rare

metals had the ability to emit light when in a state

of incandescence. The mantle was produced by

by soaking a textile in a mixture of 99% thorium

dioxide and 1% cerium(IV) oxide. When the

Air

Gas

The History and Operation of Gasworks (Manufactured Gas Plants). 7 Written by Dr Russell Thomas (28/1/2013)

mantle was heated by the Bunsen burner it

produced a brilliant light.

It should be noted that in 1826 Drummond used

incandescence in the commercial application of

lime-light through the oxy-hydrogen heating of

calcium oxide. Platinum mantles had also been

used to light the town of Narbonne, France in

1848 and also by Hogg who used an aerated

flame burner with a platinum mantle. None of

these developments had anywhere near the

Impact of Carl Auer’s invention once it had been

perfected, which took a few years.

Figure 11. High pressure gas street lighting.

Carl Auer’s Invention was timely as the gas

industry faced a new rival the electric light bulb.

Humphrey Davy demonstrated the first electric

arc lamp in 1806 but it was not practical and at

this time it went no further, The more robust light

bulb for everyday use was developed by Joseph

Swan (UK) in 1878 and Thomas Edison (USA) in

1879, both later collaborated to form the Edison

Swan Electric Company Limited otherwise known

as Ediswan. Electricity did not become a practical

reality until metal filament lamps had been

perfected in 1911 and the Electricity (Supply) Act

had been passed in 1926, which led to the

establishment of the National Grid. The gas

mantle had allowed the gas industry to compete

with its new rival electricity for much longer than

would have otherwise occurred; gas lighting was

still preferred in some towns in the 1950’s.

New markets ahead

Another significant development occurred in 1856

when Frederick Siemens developed a combined

gas producer and regenerative furnace. This

could operate at a high temperature by using

regenerative preheating of fuel and air. This

system was gradually improved and introduced to

the UK through his brother William Siemens.

Producer gas plants provided a great benefit by

allowing the production of heat at high and

uniform temperatures. They became used for

heating all forms of gas retort later. This allowed

the gas making process to proceed at higher and

more efficient temperatures than previously.

Dowson developed a complete suction gas

producer plant in 1878 which could be used both

industrially and domestically. The effectiveness of

gas engines was demonstrated by Dowson in

1881 when he combined a producer gas plants

with a gas engine. Gas producers were used in

industry for producing a low quality gas to power

gas engines and heat furnaces.

The only producer based process which made

gas for distribution was the Mond Gas process,

which also produced large amounts of ammonium

sulphate. Mond gas was rich in hydrogen and

carbon dioxide and little use for lighting, although

it could be used for industrial purposes. This is

covered by a separate Producer gas profile.

In 1863 the British Association of Gas Managers

was formed, this was the forerunner to the current

Institute of Gas Engineers and Managers.

Thomas Fletcher who was originally a dentist,

had an interest in engineering, he original

developed dental equipment, but by the early

1880’s he was manufacturing gas appliances.

Fletcher took Bunsen’s invention and developed

many different applications for it including

furnaces, fires, cookers and water heaters as well

as laboratory equipment under the name of

Fletcher Russell and Co. Gas Engineers. Many

other engineers developed appliances such as

John Wright featured in the advert below.

Figure 12. Advert circa 1898 for gas fires by

John Wright and Co. From The Gas Engineers

Textbook and Gas Companies Register 1898.

A name synonymous with the gas industry was

Sugg, The Sugg name has been associated with

The History and Operation of Gasworks (Manufactured Gas Plants). 8 Written by Dr Russell Thomas (28/1/2013)

the Gas industry through its entirety, from the

original gas pipes laid in London to the present

day. Sugg specialised in gas lighting, making

many notable developments in this field.

The development of new products and the gas

mantle gave the gas industry greater flexibility to

target new markets and produce a different type

of gas, no longer dependent upon a high

illuminating power.

In November 1869 the first work on the

construction of the Beckton Gasworks of the Gas

Light and Coke Company started. Beckton

(Figure 13) went on to be the largest gasworks

ever built in Britain and the world.

Figure 13. A painting of the original Beckton

gasworks which use to hang in the station

engineers office.

Prepayment gas meters were invented in 1870 by

T.S. Lacey. This was a major development as it

made gas available to those who could not have

previously purchased gas and could not have

afforded its installation costs. This opened up gas

as a viable alternative fuel to a whole new group

of people and led to a great expansion in the gas

industry in Britain. British gas companies also

started to hire out cookers and other appliances

to customers.

New technology drives the industry forward.

One major issue with making gas from coal was

the time taken to get the gas plant operational

and producing gas. This led to a heavy reliance

on storage in gas holders. If sufficient storage

was not possible then the continuous heating of

coal gas plant was required, so rapid increases in

gas production could be more readily

accommodated. This was both inefficient and

uneconomic for the gas manufacturer.

An alternative method to meet peak demand for

gas was water gas, this had also been discovered

early on but it was not until circa 1873 when a

commercially viable system was developed by

Lowe. Lowe devised an intermittent system which

produced gas on a cyclical basis, first heating the

system and then injecting steam to produce a gas

comprised of hydrogen and carbon dioxide. This

gas lacked illuminating power, but could be

enriched by the injection of oil, a process called

Carburetted Water Gas (CWG). The first major

installation of a CWG plant in Britain was at

Beckton gasworks nr London. This subject is

covered in a separate Water gas profile.

Figure 13. Women stokers during the war.

During the period of 1885 to 1905 a large amount

of development work was undertaken by gas

engineers, developing inclined and vertical retort

systems. After early work by the likes of Rowan,

Coze, Rice, Schilling, Bueb, Settle and Padfield,

two companies established themselves as the

market leaders in vertical retorts. These

companies were Woodhall Duckham and Glover

West, they constructed many of the vertical retort

plants in the UK.

Vertical retort plants operated with the coal being

fed vertically through the retort rather than

horizontally, this could allow continuous

operation. These are described in detail later.

The inter war years.

World War 1 had a major effect on all aspects of

British life, and the gas industry was equally

affected. The war had diverted funds away from

the gas industry whilst, driving up the prices of

raw materials, enforcing price controls and

requiring it to produce chemicals for the war effort

for fuels, textiles and munitions manufacture.

The war also took skilled staff and diverted

engineering materials away from the gas industry,

leading the industry in stagnation and decline.

During this time many small gas companies

struggled, some went bankrupt and others had to

amalgamate to survive, this lead to many of the

smaller works closing and being supplied from a

large more economic gasworks.

The Gas Regulation Act was introduced in 1920,

it changed the basis of charging for gas. It also

introduced a national basis for the testing and

reporting of gas quality. Gas quality had from the

middle of the 19th century been based on its

illuminating power, the act changed the basis to

the calorific value of the gas. With the invention of

the gas mantle and the move away from lighting

The History and Operation of Gasworks (Manufactured Gas Plants). 9 Written by Dr Russell Thomas (28/1/2013)

markets the illuminating power of gas was now

largely irrelevant.

Figure 14. Mr Therm, the gas industry mascot

exploring the treasures of coal tar.

A development in the 1930's was the increasing

number formation of holding companies such as

the Devon Gas Association and the Severn

Valley Gas Corporation. These Holding

companies bought up control of predominantly

small gas undertakings. They allowed the

undertakings to trade as the original company,

but provided central control and assistance in

financial, managerial and technical capacity.

Many of these small undertakings would have

collapsed without the holdings company’s

intervention.

In 1932 Eric Fraser created “Mr Therm” as an

advertising symbol for the Gas Light & Coke

Company, he was later adopted by the British

Commercial Gas association on behalf of the

wider British Gas Industry.

As the end of the 1930’s loomed so again did the

prospect of another world war. The Second World

War took a greater toll on the gas infrastructure

than had occurred during the First World War.

The industry had seen gas demand increase as it

was essential to the war effort, with its by-

products ranging from explosives to motor fuel

also essential. The gas industry was instrumental

in producing hydrogen gas for the barrage

balloons, they formed an important part of the

British air defences.

The aerial bombing of gasworks and gas mains

was hugely damaging and again skilled staff was

lost from the industry to the war effort and funds

for new plant were hard to obtain. The damage

incurred by the Gas Industry would require major

investment to reconstruct it.

Figure 15. Installing new gas mains, pre

nationalisation.

In 1944 the minister of fuel and power appointed

Geoffrey Heyworth to be the chairman a review

the gas industry, to look at how the industry could

develop and cheapen gas supplies to all types of

consumers. The Heyworth review highlighted

many issues such as the need for improvement of

the gas transmission network achieved through

some form of amalgamation to larger companies.

The incoming Labour Government decided that

the best course of action for the gas industry was

nationalisation on the basis of the Heyworth

Report. Nationalisation occurred through The Gas

Act of 1948. The 1,064 local gas undertakings

were vested in twelve Area Gas Boards. Each of

the gas boards were an autonomous body with its

own chairman and board structure..

Figure 16. A map showing the area boards in

England and Wales in 1949, the 12th board

covered all of Scotland.

To ensure communication between the area gas

boards and the Ministry of Fuel and Power, the

The History and Operation of Gasworks (Manufactured Gas Plants). 10 Written by Dr Russell Thomas (28/1/2013)

Gas Council was established. Each area board

divided its region into geographical groups or

divisions

The search for alternative sources of gas.

With ever increasing coal cost the gas industry

started to look for alternative gas feedstock’s or

gas supplies.

One such alternative supply was mines gas which

was rich in methane, the Point of Ayr Colliery in

North Wales, proved to be a valuable source of

this gas. The 95% pure methane gas could not be

used directly, but was reformed first, this process

basically split with the help of steam the methane

into a “town gas” of hydrogen, carbon monoxide

and carbon dioxide. It produced a lean gas which

was then enriched with methane to the required

British thermal unit standard. Although a useful

source mines gas could only supply a small

portion of that required by Britain.

Figure 17. The Isle of Grain SEGAS plant.

The Gas Council had joined forces with the

German Lurgi company to develop new

approaches to gasifying lower grade coal, this is

discussed later in this document.

Early on-shore exploration for gas in Britain had

found small gas fields in Heathfield (Sussex),

Whitby (Yorkshire) and Cousland (Scotland) but

nothing significant on a national scale.

As an alternative to coal the gas industry started

to use oil more as a feedstock for gas

manufacture, which led to the construction of oil

gas plants such as SEGAS plants (Figure 17).

Later on as by-products of the petroleum industry

became available at economic prices. new

reforming plants were built across Britain which

used butane, naphtha and Primary Flash

Distillate (PFD) as feedstock’s.

The demise of gas manufacture

The economic advantages of reformed “town gas”

were the start of the end for the production of gas

from coal in Britain. In the USA there had already

been a switch to natural gas after the discovery of

large supplies of natural gas and the construction

of a pipeline infrastructure to transport the gas

cross country.

Figure 18. The Methane Pioneer, one of the

first LNG importation ships docked at the LNG

importation facility at Canvey Island.

Without a plentiful local supply of natural gas

available, the British gas industry was already

looking elsewhere for new sources of gas. The

North Thames Gas Board in the 1950’s had been

looking at the potential of importing Liquefied

Natural Gas (LNG) to a special facility built at

Canvey Island; this was achieved in 1959 when

the first import of LNG from the Gulf of Mexico

occurred. This was the first successful LNG

transportation by an Ocean going ship.

From 1964 regular trips started between Algeria

and Canvey Island importing up to 700,000

tonnes of LNG per year. The Canvey Island

project would have developed further if it had not

been for the discovery of gas within the North and

Irish Seas. The first discovery of gas in Britain off-

shore was made near Grimsby.

Figure 19. Building the national gas

transmission system.

As the need for better gas transmission and

distribution across the country became apparent.

The History and Operation of Gasworks (Manufactured Gas Plants). 11 Written by Dr Russell Thomas (28/1/2013)

In 1966 Feeder 1 was built from London to Leeds,

this signalled the creation of the National

Transmission System (NTS). The NTS has since

expanded significantly and is an essential part of

delivering and storing gas in Britain.

Also in 1966 the Chairman of the Gas Council, Sir

Henry Jones formally announced that Britain was

switching to natural gas. In 1967 North Sea gas

was being brought ashore at the Easington

terminal. The Bacton terminal, Norfolk opened in

1968, Theddlethorpe Lincolnshire opened in 1972

and St. Fergus, Aberdeenshire opened in 1977.

Figure 20. The Conversion Programme.

Flaring off towns gas from the gas mains.

In order for Britain to switch from manufactured

towns gas to natural gas all the fittings used for

burning towns gas had to be replaced by sets

suitable for burning natural gas. This required the

largest engineering feat undertaken in Britain

since the end of world war two, called the

“Conversion Programme”. It required the physical

conversion of every gas appliance in the country.

Half way through the conversion programme the

Gas Act of 1972 abolished the Gas Council and

the British Gas Corporation was formed,

centralising the gas industry into a single

business, although the regional structure was

retained.

The conversion programme took ten years to

complete, with it’s completion it signalled an end

to the manufacture of gas in England and Wales,

with the switching off of gas production at

Romford Gasworks in on the 26th of August 1976.

The last gasworks making gas from coal were to

be found in the remote areas of Scotland. The

last gasworks to close in Britain was the small

hand charged horizontal retort gasworks in

Millport on the Isle of Cumbrae, it closed in 1981.

Whilst the gas industry has continued to thrive

and meet new challenges, the story of gas

manufacture in Britain ends here.

The environmental legacy which remains

As the gasworks sites became redundant, only

the distribution, office and depot land was

required. The production areas were often sold

for redevelopment, unless they were retained as

for redevelopment by the gas company.

Due to the nature of the gas making process and

the by-products formed (both described further in

the next section). The land had the potential to be

contaminated. There would be inevitable

spillages and leaks from the gas making process

plant, pipework and tanks during the usually long

operating history of the sites. The by-products or

wastes can generally be found in the ground on

former gasworks sites which have not been

remediated. Such contamination was not usually

intentional and where value could be obtained

from by-products it would.

The gas industry would generate additional

revenues from the sale of the by-products formed

where markets existed or could be developed.

These markets developed with the growth of the

manufactured gas industry and also disappeared

as the industry declined. For example the coal tar

could be sold as a wood preservative or as a

feedstock for the chemical industry; the spent

oxide would be used for the manufacture of

sulphuric acid; coke for domestic heating and the

ammonical liquor for the manufacture of fertilizer.

Some of these processes were carried out on the

larger gasworks, but some small gasworks in

remote areas could struggle to sell the by-

products formed, so these could be dumped on-

site or nearby.

Figure 21. Tarry soils excavated from a former

gasworks site. Source Parsons Brinckerhoff.

Most former gasworks sites are now under

multiple ownership, with some, but not all areas

remediated. Many small gasworks were also

redeveloped many years ago, when safety and

environmental standards were less stringent.

There were over 4000 gasworks in Great Britain

alone, leaving a considerable legacy.

The History and Operation of Gasworks (Manufactured Gas Plants). 12 Written by Dr Russell Thomas (28/1/2013)

How a gasworks operated

General introduction

This section explains in simple terms how a

gasworks operated, listing the plant used and

they way in which they operated. It also details

the by-products they produced and how they

were processed.

Different scales of gasworks.

Gasworks were built at a wide range of different

scales to supply everything from large houses up

to cities. With the increasing scales the type of

plant used and its efficiency changed. Below is a

brief description of the various differences in plant

at gasworks at different scales.

Country house gasworks

Country house gasworks were often the smallest

scale gasworks plant that could be purchased.

These gasworks were often supplied as a kit

form, which could be easily erected at the

purchasers home. This simple kit generally

consisted of a retort house, coal store,

condensers, washer, purifier and Gasholder.

Famous gas engineers such as Bower, Holmes,

Edmundson and Porter supplied gasworks kits

worldwide, at scales ranging from country houses

up to towns. They would be shipped as kits and

erected by local engineers. Such an example of a

gasworks built by the gas engineers H. Skoines

and Co. is shown in Figure 22.

The gasworks could be housed in there own

separate building Figure 23 or within the

outbuildings of a farm or stables. The gasholder

is often the only indication of the gasworks, being

marked on the map as a “gasometer”. Country

house gasworks were popular from the early 19th

century up until the start of the 20th century when

they started to be phased out by alternative

lighting methods such as acetylene, petrol air gas

or electricity.

Figure 22. A simple design of a country house

gasworks by H. Skoines and Co.

Many hundreds of former country house

gasworks were built in Great Britain and Ireland.

Many country house gasworks also supplied

outbuildings such as stables and saw mills. Many

estate villages were often provided with a supply

from the gasworks as well, although generally at

a cost, subsidising the estate owners own use.

The gasworks were usually built about 1 mile

away from the country house to keep the air and

water pollution away from the house.

The gasworks were sometimes built in an ornate

design so that they blended in with other estate

buildings, often taking the design of a small

country brewery with the distinctive louvered roof.

Ancillary purification plant would be hidden out of

site not visible from the roads or bridleways.

Figure 23. The remains of a country house

gasworks retort house in Gloucestershire.

Similar sized gasworks were also built at schools,

hospitals, asylums, mills and some industrial

buildings and factories. Those built at mills being

the original early examples of such small

gasworks. Some mill gasworks could be closer in

scale to the village and small town gasworks

because the mills they had to supply were large

and required a considerable amount of lighting.

Small town and village gasworks

Every town in Britain which had a population of

over 10,000 in the mid 19th century was lit by gas.

In addition to this many villages (including estate

The History and Operation of Gasworks (Manufactured Gas Plants). 13 Written by Dr Russell Thomas (28/1/2013)

villages as mentioned above) had their own

gasworks. This would provide some limited street

lighting, supply municipal buildings such as

churches and supply those lucky residents

wealthy enough to afford a supply. Such

gasworks were often private businesses

established by wealthy local businessmen.

Figure 24. A typical village gasworks in

Somerton, Somerset. The main building is the

retort house with gasholder behind.

Large town and city gasworks

Most large towns and cities developed large

gasworks outside of the town or city which had

the room to grow and would not create too much

pollution for neighbouring residents. The most

famous such example being Beckton, built by the

Gas Light and Coke Company in East Ham, a

long way from London. The works developed to

be the largest gasworks ever constructed

anywhere in the world. The largest gasworks

were also the most efficient, they could process

large amount of coal and supply gas at a cheaper

cost than the smaller works. These large

gasworks could often enable their owners to

purchase smaller nearby gas undertakings and

close their less efficient gasworks. The gas

supply would then be provided by a new gas

main linking their large gasworks to the gas

network of the small gas company. The holders of

the small gas company often being retained

Figure 25. A typical large gasworks.

Coal used for gas making

Coal is a highly variable substance and has an

incredibly complex chemistry which is still not fully

understood, this is in part because of the difficulty

in analysing coal. It is primarily composed of a

complex mixture of aromatic compounds, as coal

proceeds through the coalification process, the

carbon content increases and the oxygen content

drops. The coal becomes more ordered forming

large collections of aromatic ring structures,

eventually forming anthracite and graphite.

Not all coals were suitable for gas making. The

types of coals of preference varied through the

history of the gas industry based on the primary

purpose of the gas (lighting or heating), the type

of carbonising plant they were using and the coal

types available.

The types of coal used are slightly confused by

the different methods that were used for

classifying coal. Using (Marie) Stopes

classification by Maceral, the suitable types of

coal for gasification included:

 Bright (Soft) Coal: Vitrain, Clarain, and

Fusain;

 Dull (Hard) Coal: Durain;

 Cannel Coals; and

 Bogheads and Torbanites.

Alternatively the Seyler Classification (based on

elementary composition and suited to British

Carboniferous coals) would identify suitable coal

as being from the Meta bituminous to Meta

lignitous, the Meta lignitous being the preferential

coals used in vertical retorts circa 1950.

In Britain coal used for gas making would be high

volatile coals with medium to strong caking

properties, although slightly caking coals could be

used in vertical retorts. These coals covered

British National Coal Board coal types 401, 501,

601 and 701. The ASTM method used in the USA

suggested that “Bituminous-Common Banded

Coal” was the most suitable for gas making.

Figure 26. An advert for Scottish cannel coal.

Cannel was the coal of preference when gas was

used for lighting prior to the gas mantle as it pr

oduced a gas with a greater percentage of

illuminants which made it more suitable for

lighting. Cannel coal was limited in supply and

expensive so it was often mixed with other coals.

The History and Operation of Gasworks (Manufactured Gas Plants). 14 Written by Dr Russell Thomas (28/1/2013)

This was the coal of preference for many country

house and estate gasworks (especially in

Scotland) as it left little ash and made the

management of a small gasworks very simple.

It is likely that the industry would have moved

away from Cannel coal before the Gas

Regulation Act was introduced in 1920, when the

switch was made from illuminating power to the

calorific value of the gas. This was recognition of

the changing markets which the gas industry was

serving, moving from lighting to heating.

Figure 27. A coastal collier taking its cargo of

gas coal down the Thames to the gasworks,

on its journey from the northeast.

Convenience to market in combination with coal

type had a considerable influence on the type of

carbonisation process used in UK gasworks.

There was a preference for the Durham and

Northumberland gas coals to be used in

horizontal retorts. This coal was transported

along the eastern and southern coasts of

England, and influenced gas production there.

Further inland Midland and Yorkshire coal were

more easily available by rail transport and there

was a preference to carbonise these in vertical

retorts (when they later became available). The

coals in Scotland were preferentially carbonised

in vertical retort plants (when available). The

South Wales coal field contained the entire

spectrum of coals, some of which would have

been suitable for gas production. Other smaller

coal fields would have provided locally important

coals for gas production (e.g. North Somerset).

Coal was transported from the coal mines to the

gasworks by ship (Collier), canal barge or train. If

train sidings or navigable water routes were not

adjacent to the gasworks then it would have to be

further transported to the gas works by cart or

wagon. Transport by cart or wagon was both

expensive and inefficient.

Figure 28. Unloading coal from a coastal

collier by steam cranes at the wharf at

Beckton.

As the available quantities of suitable gas coals

diminished, the gas industry eventually looked

towards the gasification of low grade coal through

complete gasification and the Lurgi process,

before the later switch to oil and then natural gas.

At the gasworks the large lumps of coal were

broken up into smaller pieces at a coal crushing

plant. At larger gasworks the coal would be taken

to hoppers for loading into the retorts.

The retort house

The retort house was where the gas was

manufactured. It housed the retorts which were

grouped together into benches. Within the retorts,

coal was heated in an oxygen-free environment

where instead of combusting, the volatile

components were driven off, leaving a relatively

pure form of carbon called coke as residue.

Figure 29. Inside a large horizontal retort

house.

Retort technology changed over the years,

getting gradually more advanced. Although

William Murdoch experimented with a variety of

different designs, the design which was favoured

in the early years on the industry was a horizontal

retort.

The History and Operation of Gasworks (Manufactured Gas Plants). 15 Written by Dr Russell Thomas (28/1/2013)

Horizontal retorts

A horizontal retort was primarily a D-shaped

vessel, around 6.7m (22ft) long, 0.55m (22

inches) wide and 0.45m (18 inches) high.

Originally retorts were made of cast iron and were

circular, but these were not very durable, so they

were further improved through the use of fireclay

and later silica. The retorts would suffer from

wear and tear so they had to be replaced on a

regular basis and the settings were designed to

be taken apart and rebuilt.

These retorts were initially designed so that they

were closed at one end with an air tight iron door

and ascension pipe at the other, this design was

referred to as “stop ended”. A development by

George Lowe in 1831 saw a change in design so

that they had doors on both sides, this allowed

coal to be pushed into the retort at one end and

once the carbonisation process was completed

the remaining coke was pushed out through the

back of the retort. This was referred to as a

“through retort” design.

Beneath the retort bench was a furnace or

producer, which was used to heat the retorts. The

coal was heated for a period of between 8 to 12

hours. During this time the structure of the coal

was changed significantly, the large aromatic

compounds within the coal were broken down by

the action of heat, releasing gas and vapour

phase compounds from the coal which escaped

up the ascension pipe, leaving the spongy coke

(largely pure carbon) behind.

The horizontal retorts could be heated by various

methods, the earliest method being the direct

fired setting (Figure 5), the more advanced semi-

gaseous setting and gaseous fired settings

(Figure 30) appeared as a result of Siemens work

in 1857, but was not effectively introduced to the

gas industry until 1881, when it was introduced at

Glasgow and led to a great improvement the in

efficiency of gas manufacture.

Figure 30. Cross section of a gaseous fired

horizontal retort, showing the gas producer.

Early retorts were heated directly by a shallow

fuel bed (1ft (0.3m) deep) of coke lit beneath in

the furnace (Figure 5). The direct radiant heat

from the furnace and the hot waste gases heated

the retort. This approach was only heated the

retorts to temperatures circa 600°C, as a result

the amount of gas produced was relatively low

and the decomposition of the organic compounds

in the tar fog produced was limited. This method

of heating was used on early gasworks and later

on in small gasworks as it was simple and robust.

The semi-gaseous setting had a deeper fuel bed

and provided some control over air supply,

allowing some carbon monoxide gas to escape

and burn adjacent to the retorts. It allowed

greater carbonisation temperatures to be

achieved with lower fuel consumption.

Figure 31. Loading a retort with a mechanical

charger.

A later development was the gaseous fired

setting which used a gas producer to heat the

retorts. After success at Glasgow in 1881 this

system was then adopted on all the following

modern retort designs. The fuel bed in a producer

would be circa 1.5m to 1.8m (5 to 6 ft) deep and

the primary air supply was very carefully

controlled to enable the correct composition of

the producer gas.

The gas producers channelled gas to a

combustion chamber directly around the retorts,

where it was mixed with a secondary supply of air

and burned. The gaseous fired setting was the

most fuel efficient and exerted the most accurate

temperature control, with even heating along the

retort and the highest carbonisation temperatures

Secondary Air

Primary Air

Combustion

Chamber

Retorts

Producer

Gas

Producer

The History and Operation of Gasworks (Manufactured Gas Plants). 16 Written by Dr Russell Thomas (28/1/2013)

if required. Another important factor was whether

the waste gas from the producer was used to

heat incoming air, thus enabling great efficiency

and higher carbonisation temperatures to be

achieved. This was called a “recuperative” or

“regenerative” gaseous fired setting.

Figure 32. Emptying hot coke from a stop

ended horizontal retort manually.

The development of the through ended retort by

Lowe (1831) made it much easier to mechanise

the process by which a retort could be loaded and

emptied. The mechanical pusher had a

mechanical arm which could push all the way

through the retort, pushing the spent hot coke

through the rear door of the retort (Figure 33),

sometimes being collected on a conveyor or a

carriage. Another mechanical arm would then be

inserted which would load the retort with a new

charge of coal. This would then be levelled by the

use of a levelling arm giving a consistent charge

across the retort.

At the front of the retort (above and behind the

door) was the accession pipe. Some through

retorts had a second accession pipe on the rear

door. The role of the ascension pipe was to allow

the gas and vapours to escape from the retort

and rise up into the water filled hydraulic main

which acted as both a water seal and primary

condenser removing a large portion of the tar and

liquor from the gas. From the hydraulic main, gas

would leave the retort house via the foul main.

Figure 33. Unloading a through ended retort

mechanically.

The retort house was controlled by the team of

stokers under the guidance of the engineer. The

stokers and engineers had very little equipment to

measure the performance of the system just a u-

tube filled with water to measure gas pressure.

Most of the judgements were made on knowledge

and experience by checking the colour of the

flames. The retort house was subject to very

harsh working conditions and very high

temperatures, for this reason the roof of the retort

house was louvered to allow heat to escape.

Horizontal retorts were used on all sizes of

gasworks initially. Later gasworks used ever

larger horizontal retort houses with mechanical

charging and emptying of the retorts employed,

such as that shown in Figure 33. In the early 20th

century new types of retort became commercially

available such as inclined and vertical retorts and

chamber ovens, some of which could enable

continuous operation.

Figure 34. Advert for an inclined retort.

The inclined retort

In the late 19th century inclined retorts were

developed based on work undertaken by Coze at

Rheims in France (Figure 34). Inclined retorts

were designed to make loading and unloading of

the retorts easier, unfortunately this was often not

the case. The retort was placed at 32° to the

horizontal, this was the theoretical angle of

repose for coal. In theory the system benefitted

The History and Operation of Gasworks (Manufactured Gas Plants). 17 Written by Dr Russell Thomas (28/1/2013)

from less wear and tear and could be used

without the same charging machinery used on a

horizontal retort. It would take skill to get an even

charge within the retort and it was harder to get

an even temperature. The coal was prone to

creep down the retort when heated, so only

certain types of coal were suitable for use in this

method. The coke could be hard to remove even

with the aid of mechanical pushers. It also had

higher fuel consumption for heating than

horizontal retorts and they were more difficult to

operate and maintain.

The inclined retorts were never very popular in

Britain, although they were used in some

gasworks, such as those in the original public

gasworks in Coventry. With the development of

the vertical retort they were soon superseded,

although the design was still popular in some

small gasworks.

The inclined retorts were about 3.60m (12 ft) in

length and tapered from 0.60m (24 inches) by

0.38m (15 inches) at the bottom to 0.55m (22

inches) by 0.38m (15 inches) at the top. The

carbonisation process within the inclined retort

would take about 8 hours.

The vertical retort

A later development was the vertical retort, as the

name suggests the retort was rotated by 90° so

that it was in the vertical plane.

Vertical retorts came in different designs, the

original systems called the Intermittent Vertical

System was patented in England by Bueb in

1904, after previous trial at the Dessau Gas

Works in Germany. It had great advantages over

the horizontal system by reducing labour, as

much of the movement of the coal could be

achieved by gravity once the plant was loaded.

The plant also took up much less ground space,

although the retort houses were much taller than

there horizontal counterparts.

It was further developed by the introduction of the

continuous vertical retort, which could as the

name suggests operate continuously. The first

continuous vertical retorts were built at

Bournemouth gasworks by the gas engineering

company Woodhall Duckham, commercial

operation started with this plant in 1906. The rival

Glover West Company built a Continuous vertical

retort plant at St. Helens in 1907. An example of

the Glover West vertical retort is shown in Figure

35, it shows the customary vertical retort stack

with coal being fed vertically down the retort from

the hopper. Following on from these two plants

Waste Heat Boiler

Waste Gas Circulating

Flues

Waste Gas Flue

Combustion Chamber

Secondary Air

‘Hot Gas’ Mechanical

Producer

Dust Arresters

Producer Gas

Coal Band

Coal Bunkers

Coal Valves

Gas Off takes

Foul Gas Main

Producer Gas

Coke Extraction

and Discharge

Coke Bands

Figure

35.

Cross s

ection

of Glover

West vertical retort

The History and Operation of Gasworks (Manufactured Gas Plants). 18 Written by Dr Russell Thomas (28/1/2013)

built by Woodhall Duckham and Glover West,

further vertical retort plants were built at many of

the medium sized and larger gasworks across the

UK, other manufactures also entered this market.

The process operated as follows. Coal of a

suitable size was carried by conveyer to the top

of the retort house where it was fed into a hopper.

The hopper would feed coal down into a coal box

on top of the retort, which held enough coal for an

hour, coal would feed down into the top of the

retort (charging). The hopper and the coal box

were separated by a ‘coal valve’, which stopped

the gas escaping, the valve would be opened

once an hour to refill the coal box.

The coal passed down through the producer gas

heated retort vessel by gravity. As the coal

passed down the retort it was gradually

carbonised until it was removed at the base of the

retort as coke aided by extractor gear, (effectively

an Archimedes screw). The extractor gear

ultimately controlled the rate at which the coal

would pass through the vertical retort and

therefore the extent to which the coal was

carbonised.

From the base of the retort, the hot coke was

discharged into a metal cart or hopper, removed

and cooled by quenching it with water. Some

vertical retort plants could cool the coke in the

retort as well. Vertical retorts were all heated by

the use of a gas producer, described earlier.

The yield of gas in the vertical retorts could be

increased by a process called "steaming", where

steam was introduced at the base of the vertical

retort. The effect of the steaming process was

two fold, it helped cool the coke by quenching it

within the retort and it also induced the water gas

reaction converting more of the coke to gas as

carbon monoxide, carbon dioxide and hydrogen,

it increased the amount of gas made but reduced

its calorific value. Steaming was used

preferentially in the winter to increase the amount

of gas made at times of highest demand, and was

most popular between the world war one (about

the time it was discovered) and world war two. In

some gasworks steaming was used all year and

continued until production ceased.

Vertical retorts were used at many medium and

large gasworks, although some large works such

as Beckton choose to keep horizontal retorts

because of the more saleable tars they produced.

Many small gasworks continued to operate

horizontal retorts until closure often because they

could not justify the expense or did not have the

demand for gas to build a vertical retort plant.

Intermittent vertical chamber ovens

There was also another type of plant similar to an

intermittent vertical retort, called an Intermittent

Vertical Chamber Oven (IVCO). These were less

popular than the CVR in the UK, but included the

White Lund gasworks, built in Morecambe, the

last traditional coal gasworks to be built in

England.

The IVCO operated in a batch process. The

ovens within the IVCO were rectangular in shape

and constructed to hold a mass of 1 to 7 tonnes

of coal. They were also heated by external gas

producers. The process differed as coke breeze

(fine coke) was added to the base of the vertical

chamber oven prior to the coal being loaded. The

reason for this was to keep the oven door cool

and to ensure the coal was fully carbonised.

Towards the end of the carbonisation process the

chamber would be steamed, this would allow the

IVCO system to produced water gas. The water

gas produced had a lower calorific value than the

coal gas and would effectively dilute the calorific

value of the coal gas.

Complete gasification

Complete gasification was a concept whereby the

carbonisation and the water gas process

(described later) could be operated

simultaneously; it was also referred to as a

double gas plant. Coal usually graded to the size

of closely graded nuts or cobbles was used. The

complete gasification plant aimed to try to

combine the prior gasification of the coal in a

retort followed by the cyclical water gas process.

The coal was carbonised in a vertical retort and

the resulting coke or char would move by gravity

down into the water gas plant below.

These plants produced a gas which was different

to a normal town gas, if the whole base load was

supplied by this plant, the gas was denser and

had a higher carbon monoxide content.

The water gas phase could be operated with or

without oil enrichment. The best known example

in Britain was the Tulley Gas Plant, of which

many were built in Britain.

Coke ovens

Coke ovens were of limited importance on

gasworks in Britain, as very few were built on

gasworks, notable exceptions being at the very

large gasworks at Beckton and East Greenwich.

Coke ovens did have a big impact on the British

gas industry as they did in other parts of the

world. Coke oven gas was taken by many gas

undertakings which had coke ovens in their

district. The supply of coke oven gas in some

areas was such that the gasworks stopped

manufacturing gas except of Carburetted Water

Gas (CWG) at peak times of demand.

Coke ovens were not originally designed to

produce either gas or by-products such as tar. It

was not until the value of these by-products were

The History and Operation of Gasworks (Manufactured Gas Plants). 19 Written by Dr Russell Thomas (28/1/2013)

realised that by-product coke ovens were

constructed. The type of coke oven where there

was no attempt to recover the by-products were

generally referred to as “beehive coke ovens”.

These were as the name suggests the shape of a

beehive and built from brick, any by-products

formed were burnt or released into the air

escaping from the top of the ovens.

Figure 36. Beckton coke ovens.

The by-product coke oven was a different design

to a retort, although the principles of operation

were similar especially to the horizontal retort.

The by-product coke ovens were larger than

gasworks retorts and designed to produce

metallurgical coke for iron and steel manufacture

rather than specifically for gas or by-product

manufacture.

Coke ovens are the only remaining operational

coal carbonising plant in Britain. The coke oven

was effectively a long rectangular box

constructed of refractory (heat resistant) material,

roughly 12m (40ft) long and 4.5m (15ft) high, but

only 0.3m (12 inches) to 0.5m (20 inches) wide

with large iron doors at both end. The coke ovens

were lined up into a battery of often over 100

ovens and were heated by a system of flues built

into the walls of the ovens. The combustion of

gas takes place with the preheated air in a series

of vertical flues adjacent to one side of the oven,

the hot gases are channelled through crossover

flues across the top of the oven and down the

opposing side wall. The flow of gases through the

flues was regularly switched to ensure even

heating throughout the oven and reduce the

deterioration of the refractory materials. The coke

ovens are kept hot continuously; if they cooled

the refractory material would be damaged,

incurring a costly replacement.

Figure 37. A set of two atmospheric

condensers at the former Gunnislake

gasworks in Cornwall.

Coke ovens can be heated by one of two forms of

gas, current practice uses coke oven gas to heat

the ovens, however, historically it was common

practice to heat the ovens with gas manufactured

in a separate gas producer. Coke oven gas is

used now as the value of coke oven gas is limited

and it cannot be supplied in the gas mains as it

once was. In addition the value of the coke that

would be used in producers has risen so that it is

uneconomical to operate gas producers now.

Coke ovens used coal in a different form to

gasworks, coal was used in the form of solid

lumps (e.g. nuts or cobbles) in a gasworks, in a

coke oven the coal was crushed into a fine

powder. The coal used often being a blend of

various different types of coal. The coal was

stored in a large bunker in the middle of the coke

battery prior to being dispensed into the charging

car in measured quantities. The charging car

moved along the top of the battery charging

ovens as required. Prior to charging the oven with

coal, both iron doors on either end of the oven

were closed. Firstly the stoppers in the top of the

oven would be removed then the crushed coal

would be poured into the top of the hot ovens,

once sufficiently full the coke was levelled off

using a levelling arm, so a void space was left at

the top of the oven. The coal was then

carbonised for about 16 hours.

Once complete the oven doors at the side of the

oven were removed and a pushing arm was

pushed through the oven forcing the red hot coke

into a hot coke car. Once full the hot coke car is

taken to the quenching machine where water

would be sprayed on to the coke to cool it down.

Coke oven gas and by-products recovery was

similar to that of a gasworks, the main plant

involved are described later in this document.

Whilst most coke ovens in Britain operated at

high temperatures, there were a few examples of

low temperature coke oven the most notable

The History and Operation of Gasworks (Manufactured Gas Plants). 20 Written by Dr Russell Thomas (28/1/2013)

being the former Coalite works at Bolsover in

Derbyshire. The composition of these by-products

was different due to the lower carbonisation

temperatures used.

Lurgi gas plant

The Lurgi process was developed in 1927 in

Germany to look at the complete gasification of

the brown coal deposits in the East Elbe. The

Lurgi process used the mixture of oxygen, steam

and high pressure to achieve the effective

complete gasification. The first plant was built in

Hirschfelde in 1936 and further plants were built

in Germany and Czechoslovakia where a plentiful

supply of low grade brown coal was available.

Plants have also been built in Australia, South

Africa, the USA and more recently China.

Unlike conventional gasification, which would

have produced carbon monoxide and hydrogen

from the steam and oxygen, the Lurgi process

because it operated continuously at high pressure

formed methane instead. The Lurgi gas generator

had similarities to a conventional producer gas or

water gas generator, but was surrounded by a

water jacket. It had a fixed fuel bed fitted with a

stirring mechanism on a rotating grate. As a

pressure vessel, the addition of coal and removal

of ash was through locks, the ash was removed

in a solid state.

An early Lurgi gas plant was developed and built

at the Gas Councils Midland Research Station in

Birmingham. An advanced version of the Lurgi

process called a slagging gasifier was built for the

Scottish Gas Board at Westfield, Fife, jointly

developed with Lurgi. It used a locally sourced

low grade coal. The gas produced was produced

at high pressure (300psi) and supplied a low

toxicity gas to a high pressure grid system in the

Fife and central area of Scotland. A second plant

was later built in Coleshill, Warwickshire. The

process may have gone on to provide a greater

part of Britain’s gas supply, but decisions had

been made to switch to natural gas, especially

when the North Sea gas fields were discovered.

The condensers

Once the gas left the retorts via the ascension

pipe, hydraulic main and foul main it entered the

condensers. The hydraulic and foul mains both

acted as primary condensers helping to remove

much of the tar and some of the ammonia from

the gas.

Figure 38. A horizontal atmospheric

condenser.

The role of the condenser was to both cool the

gas and also to remove coal tar from the gas,

draining the tar to a below ground tar tank or well.

Many different designs were employed. On small

gasworks cooling the gas would generally be

achieved by the use of an atmospheric condenser

(Figure 37 & 38).

This relied on the temperature differential

between the ambient air temperature and that of

the hot gas to cool the gas, this process was

more successful when the outside air

temperature was cold in the winter.

The annular condenser was a slightly more

advance design, it was formed from two

concentric cylinders, both internal and external

faces of the condenser being open to the

atmosphere. The gas passed through the annular

space between the two cylinders and the tar

would condense over the surface of the

condenser in a thin layer, draining to the well.

Figure 39. A vertical tube condenser.

Another more advanced design was the water

tube condenser. This worked by passing the gas

through a vessel containing many water filled

tubes. The cold water in the tubes flowed in a

counter current direction to the gas, cooling the

The History and Operation of Gasworks (Manufactured Gas Plants). 21 Written by Dr Russell Thomas (28/1/2013)

gas and condensing out tar. The tubes could be

mounted in either a vertical or horizontal

direction.

The very early gasworks built by the Neath Abbey

Iron Company had a very simple design these

consisted of a long water filled trough through

which water passed and within the trough were

placed the gas pipes. A more advanced version

of this design was used at the Old Kent Road

Gasworks of the South Metropolitan gas

company.

Figure 40. A more advanced multipass vertical

tube condenser mounted on a tar and liquor

separator at the former Romford gasworks

Another form of condenser was the Pelouse and

Audoin condenser, which as the name suggests

originated from France. The purpose of this

condenser was to break up the suspended tarry

particles in the gas and remove them from the

gas. This apparatus consisted of an outer

cylindrical cast iron chamber through which the

gas would enter and leave and an outlet for the

tar to drain away. It contained a cylinder of

perforated sheet iron which formed the

condenser. The sides of the condensing

chambers were two thin sheets of iron, these had

a concentric space between the inner sheet with

fine perforations and the outer sheet with larger

slots. As the gas went through the fine

perforations it was forced into jets and would

strike against the solid surface, depositing the tar.

Exhauster

The exhauster was often referred to as the heart

of the gasworks, it kept the gas flowing, drawing

the gas out from the retorts at the rate it was

produced and pulling it through the condensers.

The exhauster would then push the gas through

the washer and scrubber and the remaining

purification plant into the gasholder. If primary

and secondary condensers were used then the

exhauster would normally be positioned between

the two. Without an exhauster the back pressure

of all the processing plant and gasholder would

push against the retorts causing significant back

pressure. Exhausters were classed as either

rotary or reciprocating.

Electrostatic detarrer

On some large gasworks a later process was

used after 1930. This was the electrostatic

detarrer. Gas passed through the this cylindrical

plant (Figure 41) as it would a condenser, instead

of using cooling to remove the tar an electrical

current was used instead.

As the gas particles passed through the

electrostatic detarrer, they were exposed to a

very high negative voltage; the tar particles would

gain a negative electrical charge. As the gas

continued through the detarrer it was exposed to

high positive voltage, the negative charge

obtained by the tar particles would then attract

them to the positive electrode where the tar would

be removed. A spray of oil helped wash the tar

from the positive electrode, it would collect at the

base of the detarrer and the flow away to the tar

tank.

Figure 41. Electrostatic detarrer.

The first electrostatic detarrer was installed at the

gasworks in Hinckley, Leicestershire in 1926,

believed to be an American design. The First

British designed electrostatic detarrer was built by

The History and Operation of Gasworks (Manufactured Gas Plants). 22 Written by Dr Russell Thomas (28/1/2013)

Simon-Carves Ltd and Ferranti Ltd and used

static electrical rectifiers. It was installed on a

coke oven battery at Billingham on Teesside in

1929, the first installation of these on a gasworks

was at Southall Gasworks in West London in

1931. Parallels for the introduction of this

technology in Europe and the North America also

happened, although America adopted it prior to

Britain. This type of technology is still used to

today to remove particulate matter from the

smoke in power station chimneys and other

processes that generate dust.

Figure 42. A Livesey washer.

the tar washers

Gas washing systems were employed for two

purposes, firstly to remove remaining tar trapped

in the gas and secondly to remove soluble

components such as ammonia.

Following the condenser small amounts of tar

were still present within the gas which required

removing. Prior to the introduction of electrostatic

detarrers and for a majority of gasworks which

were too small to justify their purchase, another

piece of plant was required to remove the trace

amounts of tar, the tar washer.

Figure 43. A schematic of inside a Livesey

washer. Source author.

The commonly used version of the tar washer

was the Livesey Washer, developed by the

famous gas engineer George Livesey of the

South Metropolitan Gas Company. The gas was

bubbled through small perforated holes in gauze

under water. The tar collected on the surface of

the gauze whilst the gas passed through and out

of the tar washer. The tar was collected and

drained to the tar well.

Ammonia washing and scrubbing

Following the condensers and tar washer almost

all of the tar would have been removed and about

50% of the soluble impurities of ammonium and

phenolic compounds. To remove the remaining

50%, the gas required further washing and

scrubbing.

For most of the 19th century non mechanical

means were used to perform this function, but

from the 1880’s onwards mechanical plant started

to be introduced.

The purpose of all these items of plant was to

achieve the most intimate contact between the

gas and washing medium, to enable the greatest

quantity of the soluble impurities to be removed.

Figure 44. A rotary mechanical washer.

This dissolved the ammonium and phenol,

forming ammoniacal liquor, which drained to the

tar and liquor tank by gravity, where it would float

on top of the tar.

The washing of the gas would take the form of

bubbling through seals or perforations or to pass

through weirs of liquor. The scrubbing of the gas

was the exposure of the gas to wetted surfaces.

The liquor used in washers was much stronger

than that used in the scrubber.

The washer/scrubber could come in a wide range

of designs, but there were three main types of

plant employed to further wash the gas, these

were the tower scrubber, the mechanical washer

and the washer scrubber.

Scrubbers were normally used after the washers,

although sometimes at small gasworks scrubbers

could be used on there own. The most common

Outlet Water

Level

Inlet Water

Level

Foam Foam Foam

The History and Operation of Gasworks (Manufactured Gas Plants). 23 Written by Dr Russell Thomas (28/1/2013)

form of the scrubber was the tall cast iron circular

towers (right) filled with coke, bricks, wooden

boards or ceramic rings.

As the gas flowed slowly up the tower scrubber it

met a spray of cooled water passing down the

scrubber which would cover the filter media (e.g.

coke) providing the largest possible surface area

which would absorb the ammonia and phenol and

then fall into the base of the scrubber where it

would drain to the tar well. These tower scrubbers

were relatively simple and problem free.

Figure 45. Two tower scrubbers.

The mechanical washer-scrubber benefitted from

having a very large freshly wetted surface and

also the mechanical means to break up the gas

into the fine bubbles. The mechanical washer

scrubber could also carry out some of the tar

removal function which the Livesey washer would

undertake.

If two washing units are used then it was typical

that the latter unit would be fed by clean water in

order to maximise the amount of ammonia which

could be removed from the gas.

In small gasworks it was common to have only

one or two tower scrubbers, with no mechanical

washing equipment. The most popular

combination was the mechanical washer-

scrubber which was then followed by either one

or two tower scrubbers.

Later scrubbers employed rotating horizontal

(Figure 46) or vertical cylinders, like the tower

scrubber (Figure 45), the gas and water ran

counter current. The Kirkham, Hulett and

Chandler’s Rotary Washer-Scrubber was the best

known examples of the washer scrubber, a cross

section of this horizontal washer scrubber are

shown in Figure 46.

The rotary washer scrubber was filled with the

corrugated iron filter material shown in Figure 47.

Figure 47. The corrugated filter material used

inside the standard washer-scrubber. Source

Modern Gasworks Practice, 1916.

Figure 46. A s

chematic of a

Kirkham, Hulett and Chandler’s s

tandard rotary washer

scrubber

Liquor

Overflow

Water

inlet

Gas inlet Gas outlet

Water

The History and Operation of Gasworks (Manufactured Gas Plants). 24 Written by Dr Russell Thomas (28/1/2013)

Purifying the gas

Once the coal tar and ammoniacal liquor was

removed from the gas two other poisonous

substances were removed, these were hydrogen

sulphide and hydrogen cyanide. Hydrogen

sulphide was present in the gas at much higher

concentration than cyanide and if it was not

removed it could lead to both noxious fumes and

acid corrosion through sulphuric acid formation

when burnt.

Gas purification to remove sulphuretted

hydrogen, as hydrogen sulphide was known, was

first tried when Samuel Clegg placed lime within

the water in the base of a gas holder, however, it

was not a success, later at a gas works he

installed in Coventry, Clegg developed a paddle

system to agitate the lime.

By 1812 Clegg had developed a separate tank

which contained a agitated wet lime based

purification system (Figure 48). This system was

incorporated in the small gasworks built by Clegg

for the Soho publisher Mr Ackerman.

Figure 48. The wet lime purifier developed by

Samuel Clegg. Source, bibliography ref 1.

The Wet lime purifier was further developed by

Clegg, Malam and others. The better known dry

lime purifier did not appear till later on. The main

driver for the replacement of the wet lime system

was not performance, but issues with the disposal

of the waste product known as “Blue Billy”, the

blue pungent wet lime waste created from the

process, caused problems for the gas companies

to both transport and to dispose of.

Figure 49. An example of box purifiers at the

Fakenham Gas Museum, Norfolk.

The first work on a dry lime purifier was

undertaken by Reuben Phillips of Exeter. Mr

Philips purifier was in many ways similar to the

system employed later on in most gasworks, as it

worked on the basis of forcing the gas through

layers of hydrate of lime, but it was flawed as it

was water sealed and the purifier had no solid

base. This was later rectified by adding a solid

base and a removable lid (Figures 49 and 50).

The lime used was actually hydrated rather than

dry as moisture was required to make the

process work. The hydrated lime would react with

the hydrogen sulphide forming calcium sulphide

and with hydrogen cyanide to form calcium

thiocyanate and to some extent calcium

ferrocyanide.

Figure 50. Removing the lid from a purifier.

Lime was later superseded by the use of bog iron

ore, although they were sometimes mixed and

used together. Bog iron ore (hydrated iron oxide)

was developed for use in gas purification in

1849/50, it was the invention of Richard Laming

and Frank Hills. It was adopted for use worldwide

in the 1860’s but not in Britain.

Figure 51. A large purifier house.

The British Sulphur Act was enacted in 1860 to

require the removal of the relatively high levels of

sulphur from gas. The net effect of this act was to

make it impossible to replace lime purification

with iron oxide purification, as it was not quite as

The History and Operation of Gasworks (Manufactured Gas Plants). 25 Written by Dr Russell Thomas (28/1/2013)

effective. Bog iron ore was more economical and

less troublesome than lime. This was not rectified

until 1905 when a new sulphur act was brought in

and then iron oxide could completely replace

lime.

When the hydrogen cyanide present in coal gas

was passed over bog iron ore it would

predominantly form ferric ferrocyanide also

known as "Prussian blue". The hydrogen sulphide

would react with the bog iron ore leading to the

formation of ferric sulphide, ferrous sulphide and

sulphur.

Figure 52. Foul lime excavated on a former

gasworks. Source Parsons Brinckerhoff.

The purifiers were usually square or rectangular,

and constructed of iron, although later on much

larger Tower purifiers (Figure 54) were used on

some large gasworks and coking works. The

slaked lime or hydrated iron oxide would be laid

on wooden (often oak) grids inside the boxes in

layers 12 inch (30cm) to 18 inch (45cm) deep,

sometimes with lime mixed in with the iron oxide.

The moisture content in the boxes was important

and this was regulated by the addition of steam,

the gas was also heated prior to entry into the

purifiers so the reaction could operate at the

optimum conditions.

Both the lime and iron oxide could be

regenerated a number of times (2-3) times by

exposure to air within the yard (a process called

revivification), before it became either “Foul” or

“spent”, respectively containing high

concentrations of cyanide (>6%) and sulphur (50-

60%). Opening the purifier boxes could be

hazardous, as the purifying medium would rapidly

oxidise on exposure to air and could

spontaneously combust, producing toxic gas.

Later processes were developed which would

revivify the oxide within the purifiers removing

some arduous manual handling.

Figure 53. Spent oxide.

Foul lime (Figure 52), was a rock solid material of

a greenish white colour and high pH (pH11). It

was sold to farmers or allotment holders as a

fertiliser. Spent oxide (Figure 53) was a

blueish/greenish material of low pH (pH4) used

as a by-product for the production of sulphuric

acid, but also occasionally use as a weedkiller.

Liquid purification

Gas could also be purified by passing it through

alkaline solutions of sodium carbonate, these

methods were not adopted in Britain as they were

deemed inferior to purification by iron oxide and

caused more nuisance from smells.

Another process developed was the Thylox

process, this washed the hydrogen sulphide from

the gas using ammoniumthioarsenate. The

solution was highly effective at removing

hydrogen sulphide and could be regenerated by

exposure to oxygen with the sulphur precipitating

out as foam which could be collected. The Thylox

process would also remove cyanides in the gas

as thiocyanates. As may be expected there were

health and environmental issues with using

arsenic based solution so the process only

achieved limited success.

Figure 54. A schematic of a tower purifier at

the former Southall Gasworks.

The most successful of these liquid processes

was the Stretford process, it was developed by

the North Western Gas Board and the Clayton

Aniline Company in England to remove hydrogen

sulphide from town gas. The original process

utilized an aqueous solution of carbonate/

bicarbonate and anthraquinone disulphonic acid

(ADA). The process initially suffered because the

solution used only had a very low capacity for

dissolved sulphides, this resulted in having large

liquid circulation rates, the sulphur formation

reaction was also very slow requiring large

The History and Operation of Gasworks (Manufactured Gas Plants). 26 Written by Dr Russell Thomas (28/1/2013)

amount of solution to be stored. There was also a

significant amount of thiosulphate formation as a

by-product. These problems were largely over

came by the use of alkali vanadates in the

solution, this replaced dissolved oxygen as the

direct oxidant in the conversion of hydrosulphide

ions to elemental sulphur. Although the vanadium

additive used in the Stretford Process increased

the reaction rate converting the hydrosulphide

ions to sulphur, it was still a slow reaction limiting

its use and it produced a significant amount of by-

product thiosulphate.

Water Gas

One of the major issues with coal gas was the

time taken to get the plant operational and

producing gas, this made it unsuitable for rapidly

dealing with periods of high demand. In order to

handle this peak demand gas plant would have to

be operated inefficiently or more gas storage

would be required.

Another process called water gas was developed,

most notably in the US which could produce gas

much more quickly and cope with periods of peak

demand. The process worked by steaming coke

to produce a gas consisting hydrogen and carbon

dioxide. The operation was split into two phases,

the Blow and the Run phases. The purpose of

the blow was to store as much heat in the

generator fuel bed as possible. Hot gases from

the generator heated the carburettor and

superheater. During the run steam was injected

into the generator which reacted with the carbon,

forming carbon monoxide and hydrogen. The run

phase would gradually cool the fuel bed

increasing the proportion of inert substances

(carbon dioxide) in the gas. A regular switching

between the bow and run was required making it

an intermittent process. Water gas was a

relatively poor quality gas, it could however be

enriched by injecting oil into the carburetter. This

was called Carburetted Water Gas (CWG) and it

was used at many medium to large scale

gasworks in Britain and across the world,

becoming a vital gas manufacturing process. In

parts of the USA this became the primary form of

gas manufacture. This subject is discussed in

much greater detail in the separate Water gas

profile.

Figure 55. The inside of the water gas plant

building at the former East Greenwich

Producer Gas

Producer gas plant was used on former gasworks

primarily to heat retorts and occasionally to

supplement gas supplies at times of peak

demand. A brief summary of gas producers is

given below.

Producer gas plants started to become popular in

the early 1880 and were in extensive use by

1910. The producer gas plants evolved from the

first plant built by Bischof through to their demise

in the mid 20th century, many varied types

evolved. Following Bischof’s early development of

the gas producer the next major development

was that of Fredrick Siemens who developed a

combined gas producer and regenerative furnace

in 1857. This system was gradually improved and

introduced to the UK through William Siemens.

Producer gas plants provided a great benefit to

those industries requiring high and uniform

temperatures. This greatly aided those industrial

processes which were unable or found it very

difficult to use directly fired solid fuel furnaces and

could not obtain a suitably priced gas supply. It

saved fuel as the gas could be burnt at the exact

point required achieving higher temperatures

rather than relying directly on radiant heat.

Gasworks were one of the major users of gas

producers, as they were used to heat the retorts,

using the by-product coke in the generator. They

were also used to heat coke ovens in the same

way. This subject is discussed in more detail in a

separate Producer gas profile.

Oil gas

The production of oil gas dates back to the start

of the gas industry. in its earliest years the gas

industry faced competition from gas made from

oil, primarily whale oil, although other oils

(vegetable) and resins (rosin) were used. These

gasworks were built in places such as Bristol, and

Edinburgh. They were short-lived and soon faced

closure after a few years due to oil shortages and

being uneconomic, some converted to coal gas

production. Oil gas was more successful on the

European continent.

Oil gas was also the gas of choice on the

railways, used for lighting carriages. This method

of lighting was developed by Julius Pintch a

German engineer. The gas which was a form of

vaporised naphtha oil was produced at Pintch gas

plants, located at stations or works and stored in

mobile gasholders which would provide gas to the

carriages for burning in special lamps.

The History and Operation of Gasworks (Manufactured Gas Plants). 27 Written by Dr Russell Thomas (28/1/2013)

As the available coal resources for gas making

became more expensive and of lower quality the

gas Industry looked at alternative feedstock.

Liquid feedstocks such as crude petroleum oils

and its derived distillate fractions were present in

abundant amounts from oil refineries, providing a

cheaper viable alternative. Early types of oil gas

plant which had seen popularity on the west coast

of the USA (Jones process) were never popular

in Britain.

Oils could range from being highly paraffinic to

highly aromatic. The greatest difference in gas

making efficiencies of liquid feedstock’s was the

relative size of the constituent molecules forming

the feedstock. The light distillate fractions had

the highest efficiency and the heavy fuel oil the

lowest efficiency.

An advantage of oil gas over coal gas was the

lack of ammonium and cyanide, which both

reduced capital costs and the amount of land

required to undertake the process. If oils were

used which were rich in unsaturated, naphthenic

or aromatic compounds then there would be a

much lower gas yield, especially methane and

ethylene and an increase in tar and/or carbon

produced. To reduce tar formation it was possible

to introduce oxygen or hydrogen in the form of

steam to enable combustion, hydrocarbon

hydrolysis or water gas reactions to occur. This

could also be achieved by increased pressure.

The combustible components of a typical oil gas

may be composed of 48.6% hydrogen, 26.3%

methane, 12.7% carbon monoxide, and 3.8%

illuminants.

Non catalytic cyclic method of gas production

The first major use of petroleum based oils for the

manufacture of town gas were undertaken on the

pacific coast of the USA and were referred to as

the “Pacific Coast Oil Gas Processes”, the main

one being the “Jones” process.

Sever cracking conditions were used to produce

a 500 Btu/cuft gas. It gave a gas composed of

about 40% water gas, but the efficiency was poor

with only 50% of the oil converted to gas, the rest

being predominantly carbon black and small

amounts of viscous tar rich in naphthalene and

carbon content. This process was later extended

to a wider range of oil feedstocks and also

adapted to increase carbon black production if

desired, producing a gas with a lower calorific

value 350 Btu/cuft and little or no tar. Carbon

black could be sold at a price which made such a

lower calorific value viable.

Jones process

The Jones process was little used in Britain, with

the only known plant built at the Gloucester

Hempstead gasworks. The economics of the

process was based on the price received from the

sale of the carbon black, which was the primary

product; the gas produced was of 360 Btu/cuft.

The system consisted of two main generator units

in which the oil was gasified. The generators

would be heated by injecting oil into them for 5

minutes and blowing air into them to reach 870 –

925ºC. Steam would then be added into the 1st

generator for one minute, then oil injected with

steam into the 1st and 2nd Generators for roughly

seven minuets. Steam alone would then be

injected into the generators for two minutes.

Air was blown into the generator to burn off the

carbon, cleaning the unit and reheating it at the

same time. This system allows about seven

gallons of oil to produce 1,000 cubic feet of gas.

A similar method called the straight shot, carried

out a similar process but within a single generator

unit which was divided into sections with heating

undertaken at the base of the unit. This method

required 8.6 gallons of oil per 1,000 cuft of gas.

In both manufacturing processes the oil gas

would exit the generators through the carbon

recovery unit and gas washing unit. The

manufacture of oil gas produced a significant

amount of naphthalene requiring the gas to be

passed through a naphthalene scrubber. The

remaining purification process was similar to that

of Carburetted Water Gas except for the removal

of lampblack. The water from the scrubbers and

the wash box was passed to the lampblack

separator. The lampblack was removed from the

separator and dewatered, or it was filtered dried

and briquetted. It could then be used as either

boiler or Carburetted Water Gas fuel.

Hall type process

The Hall process produced a high calorific value

gas (1000 Btu/cuft) which was equivalent to

natural gas. It was originally undertaken using

adapted water gas plants, later plants were

specifically designed for this purpose.

Distillates, crude oil or residual oil could be

gasified, although its efficiency would decline with

heavier oils and could fail due to the deposition of

carbon and pitch within the generators. The

efficiency of the Hall process was 82% of the

thermal value of the feedstock on light distillate to

50% on heavy fuel oil. The tar produced would

range from less than 5% for light distillate to 20-

30% for heavy fuel oil. Other types of non

catalytic oil gas plant were also developed.

Cyclic catalytic processes

Catalytic gas manufacturing processes were also

more common on former gasworks sites in

Britain. These plants would operate at a low

The History and Operation of Gasworks (Manufactured Gas Plants). 28 Written by Dr Russell Thomas (28/1/2013)

pressure and their design was influenced by the

type of feedstock being processed into gas.

The process used a catalyst to convert the oil to

gas and this was dependent on the feedstock

being used. Lime catalysts were used for the

range gas oil to medium fuel oil, nickel catalysts

were best suited for light distillate.

Figure 56. Reforming plant at Ambergate

Derbyshire.

If oil with a high content of naphthenes and

aromatic compounds were used then provision

would have to be made to remove the

naphthalene and tars by means of a naphthalene

washer and electrostatic detarrer.

SEGAS Process

The SEGAS (standing for South East Gas) plant

produced a gas similar to town gas with a Btu/cuft

of 500. It had a regenerative design of the plant

and the catalyst. The catalyst was in the form of

cylindrical pellets of magnesia and free lime as

the active agent which would last three years).

The gasification efficiency of 70% was achieved

to make a 500 Btu/cuft gas as compared to the

catalyst free Jones process which only achieved

50%. If higher throughput, gasification efficiencies

and a cleaner gas were required then a nickel

catalyst could be used instead of lime.

The gas exiting the SEGAS plant would pass

through a wash box, a direct contact cooler

known as a Lymn washer, electrostatic detarrer

and then into a relief holder. The SEGAS process

was robust gasifying a range of oil feedstocks

and could be brought into action quickly. It was

one of the most economical processes for

gasifying residual oils and a number of such

plants were built across the UK, with a notable

plant built at the Isle of Grain.

Onia-Gegi oil gas process

The Onia-Gegi process was developed by the

French “Office National Industriel de l’Azote” in

co-operation with the “Gaz a l’Eau et Gaz

Industriels”, hence the name Onia-Gegi. It was

originally developed for the production of

synthesis gas but later used for producing town

gas. The Onia-Gegi plant was designed to

produce a gas similar to town gas with a Btu/cuft

of 500, using a nickel catalyst. The system

operated at atmospheric pressure and at 900°C

to promote reaction by the Nickel catalyst with

steam, carbon and hydrocarbons. This produce a

higher gas content and a lower tar/carbon yield

than the Jones system. The Onia-Gegi system

produced similar amounts of tar to the SEGAS

process under the same conditions.

Micro Simplex process

The M.S. which was also known as the Micro-

simplex process was developed jointly by Gaz de

France and Messrs. Stein and Roubaix for the

reforming of hydrocarbon gases and liquefied

petroleum gases. The process used a nickel

catalyst. Later M.S. plants were developed to

operate on light distillates including naphtha and

primary flash distillate.

The process would produce small amounts of tar

which could be removed by electrostatic

precipitators or deposited in dry purifiers.

UGI/CCCR process

The United Gas Improvement Company of

America (UGI) Cyclic Catalytic Reforming

Process (CCCR) process was developed by

United Engineers and Constructors and United

Gas Improvement Company of America. It was

one of the earliest cyclic reforming processes

developed using a nickel catalyst. It was used to

produce a lean gas with a calorific value of 300-

350 Btu/cuft, it was later developed to use light

distillate and kerosene as a feedstock and would

be enriched by natural gas or liquid petroleum

gas. The gas yields and by-products produced

were similar to those plants mentioned above. A

wide range of other oil gas processes were

developed.

Continuous catalytic reforming of petroleum

gases and light distillate.

A range of continuous catalytic reforming

processes were developed, these processes

continuously reformed hydrocarbon feedstocks

with a low sulphur content at pressures ranging

from atmospheric to 40 atmospheres and at

temperature between 700-950°C. The gases

made normally consisted of hydrogen, carbon

monoxide, carbon dioxide, some methane and

undecomposed steam. These processes did not

produced tar, some (Power Gas/I.C.I continuous

reformer with enrichment by the gas recycle

hydrogenator) did produce small amounts of

benzol which were recovered and could be burnt

to heat the reformer. The main potential

contaminant from these processes would be the

light distillates feedstock, if leakage occurred,

although they would readily volatilise.

The History and Operation of Gasworks (Manufactured Gas Plants). 29 Written by Dr Russell Thomas (28/1/2013)

Storing the gas

The purified and metered gas was stored in a

gasholder for distribution later. The gasholder has

been an integral part of the gasworks since

Murdoch’s early Soho Gasworks.

The gasholder would act as a buffer and

generally hold a gas supply of between 24 to 36

hours maximum production, this would give the

gasworks more flexibility about when they

produced gas, meaning they did not need to

operate 24 hours a day.

Figure 57. A Column Guided Gasholder with

two sets of horizontal trusses and diagonal

bracing.

Before the development of booster pumps to

pressurise the gas mains, the gas in the mains

was pressurised purely by the weight thrown by

the gasholder tank.

The gasholder consisted of a cylindrical vessel

closed at the top but open at the base which sat

in a tank, filled with water. As gas entered the

gasholder it would make the vessel rise up in the

tank. The water filled tank acted as a seal to

prevent the gas from escaping. The pressure

thrown by the weight of the tank would then

pressurise the gas mains via the control provided

by the Governor.

Figure 58. A schematic diagram of a guide

framed gasholder with a below ground tank.

Source author.

The first gasholders were of single lift

construction. The movement of the tank up and

down was aided by wheels which ran along

guided tracks of the supporting columns.

With the advent of the development of the

telescopic gasholder by Tate in 1824, additional

storage capacity could be added without a

greater footprint. The telescopic gasholder

(Figures 57-59) consisted of vessels situated one

inside the other, when the inner vessel (otherwise

known as a lift) was fully extended, it would

couple to the outer lift through engagement of the

cups and dips. Telescopic gasholders could have

up to 6 lifts, one inside the other.

Many gasholders had tanks filled with water

which were built underground. These tanks were

built of brick, stone or concrete, generally made

water tight by the inclusion of a layer of puddle

clay, on the outside face of the tank walls and

beneath the base of the tank. Building the tank

underground helped reinforce the tank wall as it

would be supported by compacted ground around

it.

Figure 59. Spiral guided gasholder.

Later developments of the gasholders led to the

construction of above ground gasholders, which

used above ground iron, steel or reinforced

concrete tanks, rather than an underground tank;

The next major invention was the development of

the spiral guided gasholder (Figure 59). The

spirally guided gasholder was the invention of Mr.

William Gadd of Manchester. The first spiral

guided gasholder built in the UK was built at

Northwich, Cheshire in 1890. These gasholders

did away with the external columns or guide

frames and instead used spiral rails on the inside

or outside of the lift. As the gasholder was filled

and emptied of gas it moved up and down in a

screw like fashion. It was cheaper to construct

without the columns or guide frames, but more

delicate to operate especially in the winter.

Waterless or dry gasholders were introduced to

the UK from Germany (MAN and Klonne) and the

USA (Wiggins, Figure 60). These allowed for a

Dumpling

Crown

Lift

Gasholder tank

Rim of brick tank

Pier

Dry

Well

Ground level

Standard

Trellis cross

girder

The History and Operation of Gasworks (Manufactured Gas Plants). 30 Written by Dr Russell Thomas (28/1/2013)

simplified system, where the only major moving

part was the piston. The outer cylindrical shell

remained static and of the same diameter and the

roof of the structure was permanently fixed. The

piston was able to rise and fall inside the shell by

means of guide rollers. The Wiggins holder also

used a piston, but the gas was also stored within

a large neoprene/nylon “bag” within the holder. A

major benefit of this design was that they did not

require a water tank. Many of these vessels are

still used by the steel industry worldwide for the

storage of coke oven and blast furnace gases.

Figure 60. Waterless Gasholder of the

Wiggins Design.

Another later form of gas storage were high

pressure static vessels, which had no tanks or

moving parts, receiving and storing gas at much

higher pressure than those vessels listed above,

these bullet shaped or spherical tanks are shown

in Figure 61. In addition to this, in more recent

years use has been made of gas storage within

high pressure gas mains, as liquefied natural gas

and within depleted gas fields or salt caverns.

The subject of gasholders is discussed in more

detail within a separate profile, Gasholders and

their tanks.

Figure 61. High Pressure Bullet Tanks.

Station Meter and Governor

The Station Meter was generally housed within its

own building or along with the Station Governor.

The purpose of the meter as its name suggests

was to register the amount of gas produced at the

gasworks. These meters were quite ornate as

can be seen from Figure 62.

The meter was a cast iron drum of about 4ft in

diameter and 5ft long and half filled with water.

Inside was a drum of tin which was divided into

compartments from which the flow of gas

displaced water making the drum rotate. The

rotation of the drum was counted allowing the

meter to be via clock face type dials on the front

of the meter allowing a reading to be taken.

The gas would be metered at the site receiving

the gas as well. This meter was essential to the

early gas industry as it allowed the gas

companies to provide some measure of how

much gas consumers were using and how much

they should be billed. Prior to the gas meter

consumers would be allowed to have a certain

number of gas lamps lit for a certain period of

time, this was not easy to enforce.

Figure 62. Station Meters (right) in the meter

house.

The role of the Station Governor was to ensure

that gas was delivered from the gasworks at a

uniform pressure at all periods, free from

fluctuations. The governor was located between

the gasholder and the district gas main. It would

control the pressure exerted by the gasholders

onto the gas mains to a level that was sufficient

for supply but no more. The governor would

automatically keep the gas pressure uniform

despite fluctuations in production and

consumption. The station governor would consist

of a small tinned iron bell floating freely in a cast

iron tank containing water. As gas mains

developed and became more complex, regulation

of the gas pressure in the system became more

complex, so district governors were introduced,

especially important for districts at different

altitudes.

The History and Operation of Gasworks (Manufactured Gas Plants). 31 Written by Dr Russell Thomas (28/1/2013)

Figure 63. The whole gas making process from excavation of the coal to distribution to the customer. Source Russell Thomas.

The History and Operation of Gasworks (Manufactured Gas Plants). 32 Written by Dr Russell Thomas (28/1/2013)

Hanging down from below the inside of the crown

was a parabolic plug. The gas entered in through

the gas main and was directed up through the

centre of the governor through a conical seated

flange which exactly fitted the parabolic plug. By

adjusting the gas holder, it could alter the degree

to which gas could pass through the flange.

Weights would be placed on the gasholder to

alter the gas pressure to the mains. Fully un-

weighted the gasholder would rise such that the

parabolic plug would fill the conical flange cutting

off the gas supply, fully weighted, the reverse

would happen.

Figure 64. Interior of a tar tank at the former

gasworks, Sydenham.

Tar Tanks and Wells

The tar and ammoniacal liquor recovered from

the hydraulic and foul mains, condensers,

electrostatic detarrer, washers and scrubbers was

usually drained by gravity (pumps could also be

used) to underground tar and liquor tanks. These

tanks could be of a wide range of designs from

simple cylindrical structures cut into clay to large

cast iron, steel, brick or concrete structures.

Many of early gasholders on former gasworks

were converted to tar tanks when they became

too small for efficient use as gasholders. Such

conversi<

The History and Operation of Gasworks (Manufactured Gas Plants)

Abstract and Figures