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The History and Operation of Gasworks (Manufactured Gas Plants)


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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.
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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
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, or 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.
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
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
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
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
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
A Schematic simple bench of 3 directly fired retorts which would be
found in a small gasworks
Hydraulic Main
Ascension pipe
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”
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
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
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
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
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
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
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
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
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
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
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
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
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
Secondary Air
Secondary Air
Primary Air
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
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
Waste Gas Flue
Combustion Chamber
Secondary Air
‘Hot Gas’ Mechanical
Dust Arresters
Producer Gas
Coal Band
Coal Bunkers
Coal Valves
Gas Off takes
Foul Gas Main
Producer Gas
Coke Extraction
and Discharge
Coke Bands
Cross s
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
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
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
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
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
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
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.
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
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
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
Inlet Water
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
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
Gas inlet Gas outlet
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
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
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
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
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%
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
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
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
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
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
Gasholder tank
Rim of brick tank
Ground level
Trellis cross
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
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
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