Transcript Techniques for controlling dust emissions - IQ

CEMENT INDUSTRY
GRUPO 5
PILAR DELICADO HERRERAS
REBECA DIEZ MORALES
CRISTINA MARTÍN SERRANO
GENERAL INFORMATION ABOUT
CEMENT INDUSTRY
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Cement is a basic material for building and civil
engineering construction.
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Cement is a finely ground, non-metallic, inorganic
powder when mixed with water forms a paste that
sets and hardens.
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World cement production has grown steadily since
the early 1950s, withincreased production in
developing countries, particularly in Asia.
CEMENT PRODUCTION IN THE UE
AND THE WORLD
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Producers in the European Union have increased
cement output per man/year from 1700 tonnes in
1970 to 3500 in 1991.
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As a result of the introduction of larger scale
production units.
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The number of people employed in the cement
industry in the European Union is now less than
60000.
EMISSIONS
The emissions from cement plants which cause
greatest concern are:
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Nitrogen oxides (NOx)
Sulphur dioxide (SO2)
Dust
Carbon oxides (CO, CO2)
Volatile organic compounds
Polychlorinated dibenzodioxins (PCDDs) and
dibenzofurans (PCDFs)
Metals and their compounds
APPLIED PROCESSES AND
TECHNIQUES
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It begins with the decomposition of calcium
carbonate (CaCO3) at about 900°C to leave
calcium oxide (CaO, lime) and liberate
gaseous carbon dioxide (CO2).
CALCINATION
MAIN PROCESS ROUTES FOR THE
MANUFACTURE OF CEMENT
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There are four main process routes:
1) Dry process: raw materials are ground
and dried to raw meal in the form of a
flowable powder.
2) Semi-wet process: the slurry is first
dewatered in filter presses.
MAIN PROCESS ROUTES FOR THE
MANUFACTURE OF CEMENT
3) Semi-dry process: dry raw meal is
pelletised with water and fed into a grate
preheater before the kiln or to a long kiln
equipped with crosses.
4) Wet process, the raw materials (often with
high moisture content) are ground in water to
form a pumpable slurry.
SUB-PROCESSES
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Winning of raw materials
Raw materials storage and preparation
Fuels storage and preparation
Clinker burning
Cement grinding and storage
Packing and dispatch
TECHNIQUES TO CONSIDER THE
DETERMINATION OF BAT
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Consumption of raw materials
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Use of energy
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To optimise the input of energy.
Process selection
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Reduce the total consumption of raw materials.
The selected process will affect the releases of all pollutants,
and will also have a significant effect on the energy use.
General techniques
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Optimisation of the clinker burning process is usually done
to reduce the heat consumption, to improve the clinker
quality and to increase the lifetime of the equipment
Reduction of emissions, such as NOx, SO2 and dust, are
secondary effects of this optimisation.
TECHNIQUES TO CONSIDER THE
DETERMINATION OF BAT
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Careful selection and control of substances entering the kiln
can reduce emissions.
Specific techniques
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Control
Control
Control
Control
NOx emissions
SO2 emissions
dust emissions
other emissions to air
DUST EMISSIONS
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Main point sources:
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Kiln systems
Clinker coolers
Cement mills
Techniques for controlling it:
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Electrostatic precipitators
Fabric filters
Fugitive dust abatement
ELECTROSTATIC PRECIPITATORS
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Generate an electrostatic field.
The particles become negatively charged and migrate
towards positively charged collection plates.
The collection plates are vibrated periodically,
dislodging the material so that it falls.
CONDITIONS
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High temperatures (up to approximately 400ºC).
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High humidity.
ELECTROSTATIC PRECIPITATORS
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Efficiency is affected by:
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Flue gas flow rate
Strength of the electric field
Particulate loading rate
SO2 concentration
Moisture content
Shape and area of the electrodes
ELECTROSTATIC PRECIPITATORS
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Electronics precipitators can reduce levels down to
5-15 mg/m3 as monthly average.
Besides dust, the EP also removes substances that
adsorb to the dust particles, such as dioxins and
metals if present.
EPs are not installed if emissions at startups and
shut downs are very high.
FABRIC FILTERS
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Fabric membrane which is permeable to gas but
which will retain the dust.
As the dust cake thickens, the gas pressure drop
across the filter increases
Periodic cleaning
The use of modern fabric filters can reduce dust
emissions to below 5 mg/m3.
Also removes substances that adsorb to the dust
particles, such as dioxins and metals.
FUGITIVE DUST ABATEMENT
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Fugitive emission sources mainly arise from storage
and handling of substances and from vehicle traffic
at the manufacturing site.
Some techniques for fugitive dust abatement are:
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Open pile wind protection
Water spray and chemical dust suppressors
Paving, road wetting and housekeeping
Mobile and stationary vacuum cleaning
Ventilation and collection in fabric filters
Closed storage with automatic handling system
COMPARISON
BEST AVAILABLE TECHNIQUES FOR
THE CEMENT INDUSTRY
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The BAT for the production of cement clinker is
considered to be a dry process kiln with multi-stage
preheating and precalcination.
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Process control optimisation.
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The use of modern, gravimetric solid fuel feed
systems.
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Preheating and precalcination to the extent possible,
considering the existing kiln system configuration.
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The use of modern clinker coolers.
BEST AVAILABLE TECHNIQUES FOR
THE CEMENT INDUSTRY
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Heat recovery from waste gas.
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Power management systems.
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Grinding equipment and other electricity based
equipment with high energy efficiency.
Careful selection and control of substances entering
the kiln can reduce emissions.
BAT FOR REDUCING DUST
EMISSIONS
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The combination of the above described general
primary measures and:
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Minimisation/prevention of dust emissions from
fugitive sources.
Efficient removal of particulate matter from point
sources by application of:
- Electrostatic precipitators with fast measuring and
control equipment to minimise thenumber of CO trips.
- Fabric filters with multiple compartments and ‘burst bag
detectors’.
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The BAT emission level associated with these
techniques is 20-30 mg dust/m3 on a daily average
basis.
EMERGING TECHNIQUES IN THE
CEMENT INDUSTRY
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Fluidised bed cement manufacturing
technology
Staged combustion combined with SNCR
FLUIDISED BED CEMENT
MANUFACTURING TECHNOLOGY
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Consists of a suspension preheater (SP), a spouted
bed granulating kiln (SBK), a fluidised bed sintering
kiln (FBK), a fluidised bed quenching cooler (FBK) and
a packed bed cooler.
SP: conventional 4-stage cyclone preheater.
Granulating kiln: granulating the raw meal into
granules of about 1,5-2,5 mm diameter at a 1300ºC.
FLUIDISED BED CEMENT
MANUFACTURING TECHNOLOGY
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The sintering of the granules is completed at a
1400ºC.
The fluidised bed quenching cooler quickly cools
the cement clinker from 1400 to 1000ºC.
The cement clinker is cooled down to about 100ºC
in the packed bed cooler.
Configuration of the 20
tonnes clinker/day
fluidised bed cement
kiln system:
FLUIDISED BED CEMENT
MANUFACTURING TECHNOLOGY
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The final target of the technical development
of the fluidised bed cement kiln system are:
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Reduction of heat use by 10-12%.
Reduction of CO2 emission by 10-12%.
A NOx emission level of 380 mg/m3 or less
(converted to 10% O2).
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To maintain the current SOx emission level.
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Reduction of construction cost by 30%.
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Reduction of installation area by 30%.
STAGED COMBUSTION COMBINED
WITH SNCR
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In theory, a combination of staged
combustion and SNCR could be comparable
to SCR in performance, that is NOx emission
levels of 100-200 mg/m3.
This combination is considered very promising
by suppliers but is not yet proven.
CEMENT INDUSTRY
GRUPO 5
PILAR DELICADO HERRERAS
REBECA DIEZ MORALES
CRISTINA MARTÍN SERRANO