Particulate matter from refinery flares and Health Effects of Soot

Abstract

Flaring is a high-temperature oxidation process used to burn combustible components, mostly hydrocarbons, of waste gases from industrial operations. Smoking results from combustion, depending upon waste gas components and the quantity and distribution of combustion air. Waste gases containing heavy hydrocarbons such as paraffins above methane, olefins, and aromatics, cause smoke.
New scientific evidence has led to recognition of the significant role of black particles (black carbon or soot) as one of the short-lived climate forcers. Measures focused on black carbon and methane are expected to achieve a significant short-term reduction in global warming. If they were to be implemented immediately, together with measures to reduce CO2 emissions, the chances of keeping the earth’s temperature increase to less than 2°C relative to pre-industrial levels would be greatly improved. The same measures would also directly benefit global health and food security. An external momentum force, such as steam injection is used for efficient steam/waste gas mixing and turbulence, which promotes smokeless flaring of heavy hydrocarbon waste gas. In Oil and Gas industry, all the tail gas containing H2, CO, CO2 and C2 to C5, vary its composition and smoke cannot be seen some times but unburnt hydrocarbon escapes.

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International Journal of Information Technology and Business Management
29th October 2012. Vol.6 No.1
© 2012 JITBM & ARF. All rights reserved
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78
ENVIRONMENT MANAGEMENT: PARTICULATE MATTER FROM
REFINERY FLARES AND HEALTH EFFECTS OF SOOT
REKHAPALLI SRINIVASA RAO, Dr. KVSG MURALI KRISHNA
Email: rekhapalli_sri@yahoo.co.in
Abstract
Flaring is a high-temperature oxidation process used to burn combustible components, mostly hydrocarbons, of waste gases
from industrial operations. Smoking results from combustion, depending upon waste gas components and the quantity and
distribution of combustion air. Waste gases containing heavy hydrocarbons such as paraffins above methane, olefins, and aromatics,
cause smoke.
New scientific evidence has led to recognition of the significant role of black particles (black carbon or soot) as one of the
short-lived climate forcers. Measures focused on black carbon and methane are expected to achieve a significant short-term reduction
in global warming. If they were to be implemented immediately, together with measures to reduce CO2 emissions, the chances of
keeping the earth’s temperature increase to less than 2°C relative to pre-industrial levels would be greatly improved. The same
measures would also directly benefit global health and food security. An external momentum force, such as steam injection is used
for efficient steam/waste gas mixing and turbulence, which promotes smokeless flaring of heavy hydrocarbon waste gas. In Oil and
Gas industry, all the tail gas containing H2, CO, CO2 and C2 to C5, vary its composition and smoke cannot be seen some times but
unburnt hydrocarbon escapes.
Key Words: Black Carbon, Flares, Green House Gases, Poly Aromatic Hydrocarbons, Soot, Waste gases.
Introduction:
Flaring is a technique used extensively in the oil and
gas industry to burn unwanted flammable gases. Oxidation
of the gas can preclude emissions of methane (a potent
greenhouse gas); however flaring creates other pollutant
emissions such as particulate matter (PM) in the form of soot
or black carbon (BC) [1]. As of the end of 2011, 150 × 109
cubic meters (5.3 × 1012 cubic feet) of associated gas are
flared annually. That is equivalent to about 25 per cent of the
annual natural gas consumption in the United States or about
30 per cent of the annual gas consumption in the European
Union.[2,5]
As of 2010, 10 countries accounted for 70% of the
flaring, and twenty for 85%. The top ten leading contributors
to world gas flaring in 2010, were (in declining order):
Russia (26%), Nigeria (11%), Iran (8%), Iraq (7%), Algeria
(4%), Angola (3%), Kazakhstan (3%), Libya (3%), Saudi
Arabia (3%) and Venezuela (2%).[3]
That amount of flaring and burning of associated gas from
oil drilling sites is a significant source of carbon dioxide
(CO2) emissions. Some 400 × 106 tons of carbon dioxide are
emitted annually in this way and it amounts to about 1.2 per
cent of the worldwide emissions of carbon dioxide [4].
Unlike carbon dioxide and other greenhouse gasses, which
can survive in the atmosphere for decades and centuries,

International Journal of Information Technology and Business Management
29th October 2012. Vol.6 No.1
© 2012 JITBM & ARF. All rights reserved
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black carbon has a relatively short life span of
approximately one to two weeks. Black carbon is part of a
group of pollution sources known as Short-Lived Climate
Forcers (SLCFs), including methane gas and ozone, which
are produced on earth.
During their lifetime, black carbon particles are coated with
airborne chemicals, which laboratory tests have shown can
act like lenses capable of increasing the ability of the
particles to absorb sunlight and heat the atmosphere.
What is Soot?
A black powdery substance that consists mainly of carbon
and is formed through the incomplete combustion of wood,
coal, diesel oil or other materials.
Why Soot is Black?
Because it absorbs energy from sunlight rather than
reflecting it, Soot is believed to be a cause of global
warming, especially when it settles on snow and ice,
reducing their reflectivity.
Soot formation pathway:
Smoke burns up in high temp region [smokes if soot exits
this region before being consumed].Smoke forms when C-C
bonds in hydrocarbon crack and aromatic structures grow in
to multi ring molecules [>3 ring=primary soot particle].
Other Polyaromatic hydrocarbons [PAH] form a long
reaction route to soot. The optimal combustion of fuel at
high temperature, such as the current low-sulfur fossil diesel
fuel in modern diesel engines, results in the emission of
large numbers of very small soot particles (aerodynamic
diameter 1–5 nm) that rapidly grow in size (10–100 nm) in
(fig-1) the tail pipe by coagulation to form aggregated chains
(fig-2), and further by condensation of the simultaneously
released semi-volatile organic substances on their surfaces in
the atmosphere.

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Figure-1
Figure-2
Figure-3
Particulates:
Small, solid particles and liquid droplets are collectively
termed “particulates”. These are present in the atmosphere in
fairly large numbers and some times pose a serious air
pollution problem. The most important physical property is
size. Particulates range in size from a diameter of 0.0002μ
(about the size of small molecule) to a diameter of 500μ with
life times varying from a few seconds to several months.
This life time depends upon the size and density of the
particles and turbulence of air. The number of particles in
the atmosphere varies from several hundreds per cm3 in
clean air to more than 100,000 per cm3 in highly polluted
area. The particulates possess large surface areas in general
and hence present good sites for sorption of various
inorganic and organic matter.
Inorganic Particulate Matter:
Metal oxides comprise a major class of inorganic particles in
the atmosphere. They are produced whenever fuels
containing metals are burnt. They are produced whenever
fuels containing metals are burnt.
Organic Particulate Matter:
It occurs in a wide variety of compounds in the atmosphere.
A typical average formula of a benzene- extractable fraction
of organic particulate matter is C32.4 H48 O3.8 S0.083 (halogen)
0.065 (alkoy) 0.12 .The bulk of this organic matter is in the
respirable 1μ range.
Polycyclic aromatic hydrocarbons (PAH) are important
components of organic particulate matter because of their
carcinogenic nature. Some typical PAH compounds are:
benzo ( -) pyrene, Chrysene, benzofluoranthene. PAH
compounds occur in urban atmospheres at levels of about 20
μg/m3. They are mostly found in the solid phase. It is known
that most PAH compounds are sorbed onto soot particles.
Soot itself is a highly condensed product of PAH
compounds. A soot particle consists of several thousand
interconnected crystallites which are made up of graphitic
platelets. The latter (platelets) consist of roughly 100
condensed aromatic rings. Soot consists of 1-3% H and 5-
10% O trace metals such as Be, Cd, Cr, Mn, Ni, and V and
also toxic organic such as benzo ( -) pyrene adsorbed on its
surface. This is shown in (fig-4)

International Journal of Information Technology and Business Management
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Figure-4
Emission factors:
For a very rough order of magnitude estimate, considering
gas flared volumes of 139 billion m3/year as estimated from
satellite data [6] and estimating a single valued soot emission
factor of 0.51 kg soot/103 m3, flaring might produce 70.9
Gg of soot annually. This amounts to 1.6% of global BC
emissions from energy related combustion, based on
estimates of 4400 Gg for the year 2000 [7]
Soot in concentration values [8]:
Non smoking flares, 0μg/L;
Lightly smoking flares, 40μg/L;
Average smoking flares, 177 μg/L; and
Heavily smoking flares, 274μg/L.
Soot Load Measurement
Measurement of soot can be accomplished using a number
of different methods. Below is a general review [9] of each:
• Thermogravimetric Analysis (TGA) - This widely
accepted technique provides the most accurate estimate of
the concentration of soot as a percent by weight. The test
involves progressively heating the sample in a nitrogen-rich
atmosphere over time to vaporize volatile fractions until the
weight of the sample levels off, typically occurring at around
600º C. Then, the nitrogen environment is replaced by air
and the temperature is further raised allowing the oil to
oxidize until the weight again stabilizes. Soot concentration
is then calculated by subtracting the weight of the volatile
ash components from the weight of the original sample.
Infrared Analysis - Infrared Analysis has become very
popular for measuring soot concentration. Results seem to
correlate very well with TGA and the technique is relatively
low cost, especially with the proliferation of labs now
offering Fourier Transform Infrared (FTIR) analysis. There
are also several reasonably priced on-site instruments
available for soot measurement. Essentially, soot absorbs
infrared energy. Unlike many parameters measured with
FTIR, soot creates a broadband change in absorption
(baseline shift). So, FTIR instruments generally search for
soot in 2000 wave number region. That region is relatively
clear of interference from other oil constituents or
contaminants making soot measurement relatively easy. The
primary interferences related to this method include the
disproportionately increasing absorption of infrared energy
as soot particles increase in size, and other particles, like
dirt, also absorb broad-band infrared energy and are
indistinguishable in measurement from soot.
• Insolubles Test - This test involves the separation of
insolubles from the oil after it has been mixed with various
solvents like pentane and toluene. The pentane or toluene
insolubles are removed by high-speed centrifugation or by
filtration onto a membrane disc. When centrifuged, the
insolubles are measured as either mass or volume. When
filtered, the weight of the new filter is subtracted from that
of the prepared filter to determine weight. The technique is
relatively inexpensive and very well established. The main
drawback is that all insolubles are measured together, not
just the soot. Also, the solvent selected affects the outcome.
If pentane is used, organic oxides are included in the
measurement of total insolubles. Toluene leaves the organic
oxides dissolved.
Adsorbed
Organics
(e.g., benzo-alpha-pyrene)
Adsorbed toxic metals
(Be, Cd, Cr, etc)
0.1- 20 microns
Soot
Particle

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• Light Extinction Measurement (LEM) - The LEM
method, researched by Analysts, Inc., method involves
casting light at the visible and near infrared frequencies
through an object area containing a volume of oil. The light
obscured by the oil, as measured by the voltage drop across
the object area, is purported to vary with soot concentration.
This technique offers simplicity, low cost and a quantitative
result. The major drawback lies in the fact that anything that
blocks or scatters light is subject to inclusion in the soot
estimate (e.g., particles, water, air bubbles, insoluble
oxidation by-products, etc.).
• The Blotter Method - This sample method requires only a
drop or two of oil on standard chromatography paper. The
insolubles separate from the oil and provide a quick visual
identification of soot. Further, the paper can be diluted in
different solvents to provide an indication of the different
insolubles present in the sample. The blotter method offers
elegant simplicity, but fails to quantify soot concentration.
However, a trained eye can estimate concentration given
enough experience; but still, any quantification of soot load
must be viewed as suspect.
Health Effects of Soot:
Soot particles in the air are a contributing factor in
respiratory diseases. The fine particles (<3μ) are the worst
causes of lung damage due to their ability to penetrate into
the deep air passage. Larger particles (>3 μ) are trapped in
the nose and the throat from which they are easily
eliminated, but finer particles can stay intact for years in the
inner most regions of the lungs, which have no effective
mechanism for particle removal. The lodged particles in the
lungs can cause severe breathing trouble by physical
blockage and irritation of the lung capillaries.
Emissions of fine particulate matter (PM and ultrafines)
in diesel exhaust have been of growing community, industry
and government concern. Their combination of extremely
small size and chemical composition increases the likelihood
that particles will carry irritants and toxic compounds into
the deepest and most sensitive areas of the lungs. This can
lead to severe bronchial problems and increased
susceptibility to respiratory infection, such as pneumonia,
bronchitis, and asthma. Carbon soot particles from diesel
engines adsorb onto their surfaces other metals and toxic
substances produced by diesel engines such as cancer-
causing aldehydes (like formaldehyde) and polycyclic
aromatic hydrocarbons (PAH). Occupational health studies
link cancers, particularly lung cancer to diesel exhaust
exposures. Traffic studies suggest increased rates of
respiratory and cardiovascular disease and risk of premature
death near busy urban streets or highways and thus must be
addressed by industry and government.
Conclusions
Soot particles can penetrate deep into the lungs and have
been linked to a wide range of serious health effects,
including premature death, heart attacks, and strokes, as well
as acute bronchitis and aggravated asthma among children.
EPA’s proposal would strengthen the annual health standard
for harmful fine particle pollution (PM2.5) to a level within
a range of 13 μg/m3 to12 μg/m3 [10]. The current annual
standard is 15μg/m3. The proposed changes, which are
consistent with the advice from the agency’s independent
science advisors, are based on an extensive body of
scientific evidence that includes thousands of studies –
including many large studies which show negative health
impacts at lower levels than previously understood. By
proposing a range, the agency will collect input from the
public as well as a number of stakeholders, including
industry and public health groups, to help determine the
most appropriate final standard to protect public health.
References:
1. “Black Carbon Particulate Matter Emission Factors for
Buoyancy Driven Associated Gas Flares”-James D.N.
McEwen and Matthew R. Johnson
2. Instrument Review - "The Soot Meter for Condition-
Based Maintenance", Practicing Oil Analysis Magazine,
September/October, 1998.
3. Mansfield, C. (1999) - Email exchange between Dr.
Clifton T. Mansfield, of Equilon Corp., and the author.
4. Global Gas Flaring Reduction Partnership (GGFR),
World Bank, October 2011 Brochure.
5. Estimated Flared Volumes from Satellite Data, 2006-
2010. From the web site of the World Bank.
6. Elvidge, C. D.; Ziskin, D.; Baugh, K. E.; Tuttle, B. T.;
Ghosh, T.; Pack, D. W.; Erwin, E. H.; Zhizhin, M. A Fifteen
Year Record of Global Natural Gas Flaring Derived from
Satellite Data. Energies 2009, 2, 595-622; doi:
10.3390/en20300595.

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7. Bond, T. C.; Bhardwaj, E.; Dong, R.; Jogani, R.; Jung, S.;
Roden, C.; Streets, D. G.; Trautmann, N. M. Historical
emissions of black and organic carbon aerosol from energy-
related combustion, 1850–2000. Global Biogeochemical
Cycles 2007, 21, 1-16.
8. Flare Efficiency Study, EPA-600/2-83-052, U. S.
Environmental Protection Agency, Cincinnati, OH, July
1983.
9. Lubrizol On-line Reference Library (1998) "New
Emissions Standards for Heavy-Duty Diesel Engines".
10. EPA Proposes Clean Air Standards for Harmful Soot
Pollution/99 percent of U.S. counties projected to meet
proposed standards without any additional actions .Release
Date: 06/15/2012
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