Fly Ash Safety
The noncombustible residue from the
burning of pulverized coal. Fly ash is
pozzolanic and is frequently used to
replace a portion of the cement and reduce
its density.
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• Fly ash is one of largest emissions of the
industrial waste residues. Nowadays, the yearly
industrial slags have reached 30 million tons, and
with the development of power industry, the
emissions of fly ash from coal-fired power
factories will increase year by year. A large
number of unprocessed fly ash will generate dust
and pollute the atmosphere; if discharged into
the water system, the fly ash can cause the rivers
blockage and the toxic chemicals contained in it
will be harmful to the human body and life-forms.
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• Fly ash is a byproduct from burning pulverized coal in
electric power generating plants. During combustion,
mineral impurities in the coal (clay, feldspar, quartz, and
shale) fuse in suspension and float out of the combustion
chamber with the exhaust gases. As the fused material
rises, it cools and solidifies into spherical glassy particles
called fly ash. Fly ash is collected from the exhaust gases by
electrostatic precipitators or bag filters. The fine powder
does resemble portland cement but it is chemically
different. Fly ash chemically reacts with the byproduct
calcium hydroxide released by the chemical reaction
between cement and water to form additional
cementitious products that improve many desirable
properties of concrete. All fly ashes exhibit cementitious
properties to varying degrees depending on the chemical
and physical properties of both the fly ash and cement.
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• Two types of fly ash are commonly used in concrete:
Class C and Class F. Class C are often high-calcium fly
ashes with carbon content less than 2%; whereas, Class
F are generally low-calcium fly ashes with carbon
contents less than 5% but sometimes as high as 10%. In
general, Class C ashes are produced from burning sub-
bituminous or lignite coals and Class F ashes
bituminous or anthracite coals. Performance properties
between Class C and F ashes vary depending on the
chemical and physical properties of the ash and how
the ash interacts with cement in the concrete. Many
Class C ashes when exposed to water will react and
become hard just like cement, but not Class F ashes.
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Problems of Fly ash
When fly ash gets into the natural draining system,
it results in siltation and clogs the system.
It also reduces the pH balance and portability of water.
Fly ash interferes with the process of photosynthesis of aquatic
plants and thus disturbs the food chain.
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What are Ash Piles and where does it
come from?
Fly ash is the fine powder Fine ash particles Course ash particles
formed from the mineral
matter in coal .1< d < .6 microns 1< d < 100 microns
Bottom ash is a coarse,
granular and collected
from the bottom of
furnaces
Bottom Slag-Similar to
bottom ash
Flue Product-produced by
chemical “scrubber”
emission control systems
that remove sulfur and
oxides from power plant
Ash Pile – The
incombustible products
from a coal-burning
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Toxins and Health Hazards
• Fly Ash also contains
Crystalline Silica, which
can cause lung damage in
sufficient amounts, so
Occupational Safety and
Health Administration
(OSHA) allows only 0.10
mg/m3 in air
11.4% of coal burned is waste - 120million tons of waste coal!
(another site says around 150million)
Chemical Composition of waste - chemicals which are considered
toxic: Arsenic, Cadmium, Beryllium, and Mercury
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May contain
• While it is true that fly
ash contains trace
amounts of certain
elements, which can
be toxic in larger
concentrations, it is
unlikely that fly ash as
used in the oilfield
would exhibit leaching
characteristics.
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Scope
Database
Risk Identification
Select aspects/Events
Consequence Likelihood
Analysis Analysis
Actions to Actions to
Reduce Reduce
Consequences Frequencies
Estimate
Risk Levels
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Toxicity vs. Hazard
• Toxicity is the inherent potential for a substance to cause
harm. It is only one factor in determining whether a hazard
exists.
• Hazard is the practical likelihood that the chemical will cause
harm and that depends on exposure, susceptibility, and
sensitivity.
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Inhalation Health Hazards:
Acute: Respiratory tract irritation causing coughing, wheezing,
and difficulty breathing
Chronic: The primary routes of exposure are inhalation and
contact with eyes and skin. Fly ash is composed of inert dust
(possibly irritating to mucous membranes), crystalline silica (a
pneumoconiosis producing dust and animal carcinogen),and
low concentrations of calcium oxide (possibly irritating to
mucous membranes and wet skin). Fly ash contains trace
amount of inorganic arsenic (identified as a carcinogen).
Skin and Eye Health Hazards:
Acute: Eye contact can cause severe, mechanical irritation.
Skin contact may cause irritation.
Chronic: Skin contact may cause irritation.
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Wear the Gear
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Exposure Controls and Personal
Protective Equipment
General: Do not use compressed air to remove fly ash.
Ventilation: Use local exhaust ventilation to remove airborne fly ash from work areas when
feasible.
Eye Protection: Employees should use dust-proof safety goggles in areas of high levels of
airborne fly ash. Eye wash facilities should be available in case of eye exposure.
Skin Protection: Employees should wear protective clothing to prevent repeated or prolonged
skin contact with fly ash.
Respiratory Protection: Respiratory protection is selected based on a hazard assessment of the
work location, including the specific airborne agents, the concentration of the agents, and the
permissible exposure levels (PEL). Selection must be done by a knowledgeable person following
the requirements in OSHA’s Respiratory Protection Standard, 29CFR1910.134(d) in order to
obtain adequate protection from the respirators. Employees must be qualified to use a respirator,
and all respirators must be certified by NIOSH. Protect against other airborne particulates
associated with fly ash that are not regulated by substance, such as aluminum and iron oxides.
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Handle and Storage
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Drilling Fluids Help
• Water based drilling muds typically contain clays, barite,
lime, caustic soda and other chemicals, such as polymers.
Land disposal of these wastes raises the possibility of
groundwater pollution which can be abated if the waste is
stabilized either by chemical reaction or by solidification
through some form of cementation. Many ASTM high-
calcium (Class C) fly ashes are cementitious and thus may
be useful in stabilization of drilling mud. The basic idea is to
stabilize the clay-containing muds using the model of soil
and roadbed stabilization with high-calcium fly ash. Fly ash
that is not utilized is considered to be a solid waste, so this
application would actually constitute co-disposal of two
wastes.
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On our site
• Many of the horizontal sections of the wells
are drilled using water-based muds (WBMs).
When WBMs are used for drilling, the drill
cuttings are placed in the reserve pit. At the
end of the drilling job, the cuttings are
stabilized with fly ash and then are buried in
place after all liquids have been removed. The
used WBMs are disposed of using land
application.
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Mixed with
• Solidify and stabilize the drilling mud remaining on the
Cement, fly ash, lime
cuttings or shale.
or calcium oxide can be used to
solidify the remaining drilling
mud waste. This is done to bind the waste mud
with the cuttings and make the resultant waste suitable
for waste handling. It also makes the waste mud less
toxic and more appropriate for land burial
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Other Uses
• In the technique, iron salts were chosen as gel
breaker, fly ash and lime were chosen as
curing agents and loess was chosen as
supplementary material. The results showed
that it was effective to use the technique for
treating the waste drilling fluid.
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Read the MSDS before Use!
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