Download - POLLUTION CONTROL IN REFINERIES
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POLLUTION CONTROL IN
REFINERIES & PETROCHEMICALUNITS
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INTRODUCTIONPOLLUTION ROUTES
Crude oil production & Transportation-
Oil spillages
Pollution while processing
Thermal pollution of water bodies.
PROCESS LIQUIDWASTES
Distillation NH3, H2S,phenols
Desalting NaCl,phenols,H2S
VaccumDistillation
Phenol & Oil
Naphthahydrotreating
Sourcondensate
CatalyticHydrotreatin
g
H2S,Phenols,
Cyanides
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CHARACTERISTICS OF LIQUIDEFFLUENTS
Waste Concentration
Free oil 2000-3000mg/l
H2S & Sulphides 10-220 mg/l
Phenols 12-30 mg/l
Suspended Solids 200-400 mg/l
5 Day BOD at 20dgC 100-300 mg/l
Alkalinity 10-250 mg/l
In a n average refinery
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In a petrochemical industry
waste Concentration
pH 5.5-9.0
Suspended solids 100 mg/l
Dissolved O2 5 mg/l
BOD 100 mg/l
COD 250 mg/lPhenolic compounds 1 mg/l
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TREATMENT METHODS INPLANT MEASURES
STEAM STRIPPING
OXIDATION
REMOVAL OF PHENOLS
BIOLOGICAL TREATMENT DISPOSAL OF SLUDGES
LIQUID EFFLUENT TREATMENT
AIR POLLUTION CONTROL
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INPLANT MEASURESProper maintenance of pumps to prevent
water leakages
Isolation of oil-water emulsion stream andseparation by air flotation->COD 60-80%
Rectangular separator-Gravity settling
use Tilted plate separator
Oil droplets impinge , coalesce, & collecton top.
Acids & Coalesce aiding membrane structures
Good house kee in
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Tilted plate separator
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Corrugated plate interceptor
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Corrugated plate rack
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Steam strippingDuring catalytic reduction & distillation->sour
water containing NH3 , H2S & mercapton are formed
To remove this sour water strippers are used.
Physico- chemical & biological treatment isused
Air stripping at higher pH NH3.OxidationNH3 water & N2Sulphides thiosulphatesAir as an oxidizing agent
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Removal of phenolsA multistage modified activated sludge
process
Adsorption of phenol on activated charcoalBiological oxidation if specially cultured
microrganisms & optimum conditions exist
Solvent extraction->to recover phenols fromcaustic cresylates.
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BIOLOGICAL TREATMENTTrickling filters
Multistage activated sludge
Oxidation ponds
Aerated lagoons
Anaerobic digestion
Ferrobiological process
UNOX process
Maximum efficiencies for biological treatment-
>(80-95)%
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Oxidation pond
SOUR TASTE
WATERSTRIPP
ER
STORMWATER
PROCESS
WATERSEWE
RBASI
NAPISEPARATO
R
RETENTIONPOND OXIDATION
PONDLAGOO
N
ACID/ALKALINEUTRALIZEDWATER
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Oxidation ponds
Used for the treatment of integral effluents
Removal of oil, sulphides, phenols, BOD,
suspended solids.Includes API separator, chemical treatment, &
clariflocculator.
Coke-bed separator->removal of fine carbonparticles.
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Sludge disposalOil Sludge Chemical
SludgeBiological
Sludge
Formation Oil water
separations,precipitation
Chemical &
Oilprocessing
Biological
Oxidation
Processing Thickeningby gravity,centrifugation, filtration
Chemicalrecovery,cementmanufacture,land fills,
drained.
Anaerobicdigestion forbiogasproduction
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Treatment of effluentsfrom petrochemicals Process similar to refinery
For chemical recovery
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Air pollution
Air pollutants-H2S, NH3, SO2, NOx,mercaptons.
1)CONTROL OF SULPHUR DIOXIDE Recovered to meet shortage & pollution
control.
Acceptable range-50-500 ppm
Processes most commonly used & feasible
Cat-OX=>SO->catalyst->SO3->Sulphuric acid
Cal-OX=>SO2->Scrubbed with alkalinesolution ->lime re eneration
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B) REMOVAL OF H2S
Regenerative
H2S conc is high
CO2 is present
Scrubbed at low T with an alkaline solution inpacked plate units
Nonregenerative
H2S conc is low
Sulphur recovery isnot economical.
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Processes for removal of
H2SEthyl Amine Proces
Monoethyl amine-Highest capacity,
combines with CO2Diethyl amine- meets most requirements
triethyl amine -
-is used for absorption of H2S, CO2.Absorption efficiency->high at lower temp.
Phosphate process
Dilute potassium phosphate soln as scrubber
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K3PO4+H2S K2HPO4+KHS
Chemicals- nonvolatile & stable
ADSORPTION
By activated carbon, alumina, zeolite, bauxite
or iron oxideSpent adsorbant regenerated by roasting in
air.
OTHER PROCESSES
Thylox
Arsenite arsenate
Iron cyanide
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REMOVAL OF AMMONIA
Absorption by dilute sulphuric acid
Oxidation to NO2->absorption in water-
>HNO3REMOVAL OF PARTICULATES, NOX& HYDROCARBONS
A). PARTICULATESCyclone seperators
Scrubbers
Filters
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B).Nox
Less air, 2 stage combustion, recirculate partof flue gas
C).HYDROCARBONS
Cooling & adsorption
Disposed of by catalytic or non catalytic
combustion
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THANK YOU