ENVIRONMENT PROTECTION (ACTS / REGULATIONS)

IN OIL REFINERIES

INDUSTRY – ACADEMIA WORKSHOP

ON

SAFETY, HEALTH & ENVIRONMENT

S.C. TANDON - Former ED, IOCL (Ref. Divn.) & Associate President, MRPL-ONGC

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C O N T E N T S

Brief Introduction to Refinery Processes Waste Liquid Streams / Treatment / Standards Control of Atmospheric Emissions / Standards Control of Fugitive Emissions Solid Waste – Oily Sludge Processing in Coker Conclusions

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Petroleum Refining Industry employs a wide variety of processes depending upon the type of crudes processed and chosen slate of products complying with required quality specifications, particularly for MS, ATF, HSD apart from petrochemical feedstocks. General categories of refinery processes are: 1. Separation Process: Atm. Distillation Vacuum Distillation

2. Conversion Process: FCC, Cat. Refining, Hydrocracking unit, Coking / VIS Breaking, etc.

3. Treating Process: Hydrodesulphurisation of diesel, SRU Hydrogen production, Isomerisation (ISOM), Sulphur Recovery Unit, etc.

Typical flow diagrams of some of these processes are shown in flow diagrams – followed.

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WASTE STREAM GENERATED FROM REFINERY

Desalter effluent from crude unit.

Sour water from Process units, CDU / FCCU / Coker, etc.

Spent caustic from Fuel Gas / LPG / Gasoline treatment for removal of H2S, Removal of organic acidity / Phenols from crude, Oily effluent from Process units, Storage tanks, Loading facilities, etc.

Storm water stream from Process unit / Offsite facilities.

Treatment of some of above streams is recommended before routing to Effluent Treatment Plant.

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DESALTER BRINE TREATMENT UNIT Treatment of Desalter Brine, which may contain 1,000 to 10,000 PPM oil / emulsion is contracted with 3 to 5%, Naphtha and Surfactant chemical:

Water-oil-solvent shown is mixed in an in-line low shear, mixer before routing to separator vessel, where electrostatic field is established to maintain sharp hydrocarbon/ water interface for effective separation.

Oil stream from top of vessel routed to Distillation unit.

Treated water with typically 100 PM oil is routed to ETP.

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TREATMENT OF SPENT CAUSTIC

Typical composition of Spent Caustic generated from refinery:

Ph … 12-13

Oil … 4,000 – 6,000 PPM

Sulphides … 4000

Phenol … 500

COD Mg/Lt. .. 17,500

BOD Mg/Lt. … 6,000

Wet air oxidation is prominently employed for spent caustic treatment.

Steam is injected to the warm spent caustic to maintain reaction temperature of about 115 oC at about 1.2 bar pressure in the reactor.

Oxidation of sulphide to sulphate via thiosulphide takes place in the reaction zones of reactor which are separated by sieve trays.

2Na2S+2O2+H2O Na2S2O3+2 NaOH

Na2S2O3+2NaOH+2O2 2Na2SO4+H2O

Hydrocarbon in the offgas is in traces. Reactor liquid from bottom is routed to Effluent Treatment Plant.

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TREATMENT OF SOUR WATER STREAM

Oil refineries process units operation generate sour water containing H2S and other impurities like NH3 , phenols, CO2, cyanides and entrained hydrocarbon from CDU/VDU, Hydrotreating units, FCCU, Hydrocracker, etc.

Two stage sour water strippers are generally employed for removal of H2S with control of pH level at 5.0 followed by ammonia removal stripper at pH of 10.0.

Offgases containing H2S are routed to SRU for recovery of Sulphur.

Stripped water can be used in Desalter operation or partly routed to ETP.

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STORM WATER STREAMS

Process units & offsite facilities having large area are water washed periodically for housekeeping.

Some oil spills or drips find way to storm water channel.

Storm water is routed to API settler, after recovery of oil, storm water is discharged along with treated effluent.

Best practice is to use centralized vacuum cleaning of floor rather water washing to conserve water resource thereby avoiding generation sludge in basin.

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CONTROL OF OILY SEWERAGE (OWS)

In-plant collection of oily drain, Gravity settler / Coalescer for separation of oil, allowing cleaner effluent to ETP. Oil to be processed in CDU.

Collection of oily sewerage / drains from storage tanks (crude / product streams), Loading, facilities etc., in underground vessel, separated oil to be pumped to CDU slop tank.

Separated oil from flare, fuel gas knock out drums to be routed to CDU / VDU.

With an approach for pretreatment of polluting streams as elaborated above the final waste stream is routed to ETP (Effluent Treatment Plant) which includes following processes:

Influent TPI/API Separator Flash Mixer DAF Unit H2O2

Bioreactor Clarifier Trikling Filter Equalisation Tank

Clarifier Dual Media Filter Guard Pond (for TSS Removal) Final Disposal Quality treated effluent shall be better than stipulated standards as follows.

Part of treated effluent can be used as make-up water for cooling tower.

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LIQUID EFFLUENT TREATMENT PROCESS Primary Treatment : Removal of settleable organic &

inorganic pollutants. - Tilted Plate Interceptor (TPI) : Removal of free oil and grease &

TSS. - Flash Mixing Tank (H2O2) : Removal of sulphides and phenols - Dissolved Air Floatation Separator : Removal of emulsified oil (DAFS) Biological Treatment : Removal of BOD & COD (Secondary Treatment) - Trickling Filters : Growth of Microorganisms (Attached Growth Process) - Aeration Tank with Surface Aerators: BOD & COD reduction Final Treatment - Clarifier : Turbidity removal - Dual Media Filters : Further removal of TSS - Granular Activated Carbon Filters : Odor & colour improvement

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OIL REFINERY EFFLUENT STANDARDS AS PER ENVIRONMENT

(POLLUTION RULES 1986) SIGNIFICANT PARAMETERS

S. No. Parameter Limiting Values for Concentration

(Mg/lit except pH)

Permissible Quantity

(Kg./1000 Mt of Crude Processed)

1 pH 6.0-8.5 -

2 Oil & Grease 5.0 2.0

3 BOD 3 days at 27oC 15.0 6.0

4 COD 125 50

5 Phenols 0.35 0.14

6 Sulphides 0.50 0.20

7 CN 0.20 0.08

8 Ammonia (NH3) 15.0 6.0

9 Suspended Solids 20.0 8.0

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POLLUTANT DISCHARGE CONCENTRATION AT PETROLEUM REFINERIES AS PER EPA-USA, 1996

Pollutant Con. Values (Mg./Lit)

pH 5.0-8.0

Oil & Grease 5.0

Ammonia (NH3) 4.0

COD 8.6

Phenols 0.1

Sulphides 0.1

TSS 10

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CONCLUSION

(FOR UPGRADED QUALITY OF TREATED EFFLUENT)

1. Treated effluent, if better than standards can be used as make-up water for cooling tower.

2. Treated effluent along with storm water after removal of oil traces is also used for Greenbelt irrigation.

3. Treated effluent after dual bed / ultrafilteration can be further treated in Reverse Osmosis process to boiler feed quality water. Such facility is installed at Panipat (IOC); HPCL, Mumbai; GS Refinery at Bathinda. Cooling tower slow down having higher salts can be blended in feed to RO system.

4. Rejects from RO can be blended with storm water for irrigation of Greenbelt.

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ENVIRONMENTAL STANDARDS FOR PETROLEUM OIL REFINERIES

STANDARDS FOR EMISSION FROM FURNACES, BOILERS & POWER PLANTS – ENVIRONMENT (PROTECTION) RULES, 2008.

S. No.

Parameter Limiting Concentration in mg/Nm3, unless stated

US-EPA (AP-42)

Emissions Factor

Existing Refineries

New Refineries, Furnaces,

Boilers

1. Sulphur Dioxide (SO2)

Gas firing 50 50 LBs 142x’S’ /1000 gallon in Fuel Oil Liquid Firing 1700 850

2. Oxides of Nitrogen (NO2)

Gas Firing 350 250 20 LBs /1000 gallon in Fuel Oil Liquid Firing 450 350

3. Particulate Matter (PM)

Gas Firing 10 5 20 LBs/1000 gallon in Fuel Oil Liquid Firing 100 50

4. Carbon Monoxide (CO)

Gas Firing 150 100 5 LBS /1000 gallon in Fuel Oil Liquid Firing 200 150

5. Nickel + Vanadium (Ni+V)

Liquid Firing 5 5

6. Hydrogen Sulphide (H2S) in Fuel Gas

- 150 150

7. Sulphur Content in Liquid Fuel, Weight %)

- 1.0 0.5

Continuous monitoring system for SO2, NOx for furnaces with heater duty of 10 MKCal/hr or more. 98% of compliance required.

Ni & Va to be determined every six months.

With sufficient availability of desulphurised fuel gas in refinery having FCC, Coker units, etc. 50 PPM limit can be easily achieved.

FCC slurry oil along with part of hydrocrator bottom mix serves fuel with less than 0.5% S in case low ‘S’ crude is not available for processing.

Low NOx Buners can bring down oxide of nitrogen limit.

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STANDARDS FOR EMISSION FROM FCC REGENERATORS

S. No.

Parameter

Limiting Concentration in mg/Nm3, unless stated

US-EPA (AP-42)

Emissions Factor

LBs / 1000 bbl Fresh Feed

Existing Refineries New Refineries or

FCC Hydro-

processing of FCC Feed

Other than Hydro-

processing of FCC Feed

1. Sulphur Dioxide (SO2)

500 1700 500

(for hydro-processed

feed)

850

(for other feed)

493

2. Oxides of Nitrogen (NO2)

400 450 350 71

3. Particulate Matter (PM)

100 100 50 242

4. Carbon Monoxide (CO)

400 400 300 13,700

5. Nickel + Vanadium (Ni+V)

2 5 2 -

6. Opacity, % 30 30 30 -

FCC Regenerators to be provided with continuous monitoring for SO2 & NOx for min. 98% compliance.

Data on ‘S’, ‘Ni’ (ppm) and ‘V’ (ppm) in feed to FCC needs to be reported.

FCC feed desulphurisation is best option to comply with emissions limits. Technology option of conversion of 580 oC end pt. feed leads to economic option for Euro Grade IV fuels.

CO in flue gas get converted in case of CO boiler provision for steam / power generation.

EPA – Specified limits are based on non-hydroprocessed feed. Di-SOx additive is used for controlling SOx.

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COMPARISON OF EMISSION STANDARDS IN EUROPIAN

REFINERIES WITH INDIAN STANDARDS FOR FCC

Parameter Existing Units, 2000 2009

Netherlands France UK Germany Belgium India

SO2 1000* 1500* 1700* 750* 1300* 1700

NOx 350 500 450 300 450 450

Particulates 50 100 50 50 150 100

Notes: All values in mg/Nm3 * Non-hydrotreated feed for FCC. Automatic monitoring systems

will be installed.

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STANDARDS FOR EMISSIONS FROM SULPHUR RECOVERY UNITS

S.

No.

Plant Capacity

(Tonnes/Day)

Parameter

Existing

Refineries

New

Refineries or SRU

1. Above 20 Sulphur Recovery, % 98.7 99.5

H2S, mg/Nm3 15 10

2. 5 – 20 Sulphur Recovery, % 96 98

3. 1 – 5 Sulphur Recovery, % 94 96

4. All Capacity Oxides of Nitrogen

(NOx)

350 250

5. All Capacity Carbon Monoxide (CO) 150 100

6. All Capacity H2S, mg/Nm3

15 10

Notes: 1. Sulphur recovery units having capacity above 20 TPD shall have

continuous systems for monitoring of SO2. Manual monitoring for all the emission parameters shall be carried out once in a month.

2. Data on sulphur dioxide, NOx and CO emissions (mg/Nm3) shall be reported.

3. Sulphur recovery efficiency shall be calculated on monthly basis, using quantity of sulphur in the feed to SRU and quantity of sulphur recovered.

4. Tail gas treatment is required for achieving sulphur recovery to 99.5 or more.

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CONTROL OF FUGITIVE EMISSIONS

Legislative Requirement

Environment (Protection) Act 1986 / Amended Rules March 2008 includes

directives for control of Fugitive Emissions apart from stricter compliance

norms for Atmospheric emissions (SO2, NOx, CO, SPM).

Ex. Floating Roof / Int. Floating Roof Tanks (,>500 M3) with V.P. 10 to 76

KPA to have double seals. [Max Seal Gap = 4 cms (Primary Seal), 1.3 cms

(Secondary Seal)] for recovery of 96%.

Establish LDAR system for process pumps / compressor / valves / flanges

to limit Fugitive Emissions with effect from 01.01.2009.

- Pumps / Compressors = 5000 PPM (For benzene Service <2000 PPM)

- Valves / Flanges = 3000 PPM (For Benzene Service < 1000)

Other Directives includes:

a) Close loop sampling,

b) Low Emissions Packing for Valves &

c) High Integrity Sealing material for flanges.

Pressure Relief Valves – Discharge to VRU or Flare.

Oily waste water separator / equalisation tanks to be covered (Floating /

Fixed). Offgases to VRU.

Waste water from BTX units – Benzene <10 PPM.

Frequency for Monitoring specified. Records to be documented for

Immediate / Quarterly / Yearly data.

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EMISSION ESTIMATION METHODS

Fugitive Emission Methods specified by EPA – USA for estimation of

Fugitive Emissions.

Average Screening factor based on monitoring by sampling air from

Potential Leak interface for individual piece of equipment.

Unit specific co-relation Mass emission rate based on enclosing sampling

bag on piece of equipment. Data collected on several pieces to develop

unit specific factor.

EPA – specified method for calculation of emission from storage tanks.

Remote sensing methods using fixed beam (open path) – optical method

based on absorption of Electro-magnetic waves (IR or UV) for gases. Can

be used for estimating emission from loading / unloading, Influent sump /

API Separator etc.

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MEASUREMENT OF FUGITIVE EMISSION – API METHOD 21

Portable Instrument – approved by API based on Flame Ionisation, Infra

Red Absorption or Photo Ionisation type is recommended.

Intrinsically safe, electrical driven pump for collection of sample, Tip of

probe to be placed close to surface of component interface with maximum

gap of tip (1 cm).

Probe is moved along the interface periphery while observing Inst.

Readout, where leakage is maximum indicated & same is recorded.

Application of Technique is used for:

- Valves

- Flanges

- Process Drains / Vents etc.

This method is recommended by EP Act / Rules notification of March 2008

for establishing LDAR system.

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PROCESS FUGITIVE EMISSION FACTORS WHERE

LDAR SYSTEMS IN PLACE

Source Emission Factor (kg/hr-

source)

Valves Gas 0.0056

Light 0.0071

Heavy 0.0023

Pump Seals* Light 0.0494

Heavy 0.0214

Compressor Seals Gas 0.2280

Pressure Relief Seals Gas 0.104

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STRATEGIES FOR MINIMISATION OF FUGITIVE EMISSION FROM VALVES

Survey of Typical Refinery – as per Concawe report shows 50% emission from Process Units & 50% from Offsite Facilities.

With LDAR Programme in European / American Refineries, Fugitive Emissions from valves / flanges is pegged between 100 to 500 PPM.

Replace block valves, if emissions persists between 1000 to 10,000 ppm. (Replaced valve can be used for non-critical services).

Upgrade packing of valves to limit emission below 500 PPM.

Packings could be 3 rings of PTFE impregnated meta-armid non woven material. End rings of carbon material (PTEE / Graphite impregnation for Temp. below 250°C.

Badly Leaking valves lead to Minimum loss of 1 T/yr of Gasoline, when refurbished saving could be Rs. 60,000/year for one valves.

Sealing of valves at temperature above 250°C packing developed for older valves – leads to 4 Ring Combination – High density expanded graphite. End rings form braided expanded graphite with carbon filament yarn corners giving protection against gap extrusion.

Replacement of 2” to 3” dia valve with higher leak would be justified as compared to refurbishment cost.

Use of Bellow Seals – stem of heavy walled bellows made from metals or polymeric material for high temperature – use for toxic fluids or High hazardous applications.

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CONTROL OF EMISSIONS FROM PIPEWORK JOINTS / FLANGES

Leakage from Flanges depends upon time dependant factors.

Relaxation of bolts.

Process / ambient temperature fluctuations.

Degradation of Gasket & other typical defects like a) Non-Parallel Flange faces, b) Incorrect bolt specs / tightening procedure & c) Unsuitable Gaskets.

Selection of High Integrity Gaskets (Non Asbestos) Teflon / flexible graphite / ceramic fibres in form of spiral wound / jacketed. After Replacement Gaskets – need periodic tightening.

Minimise use of Flanges particularly on Pipe rack or Non process use.

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REDUCTION OF EMISSIONS FROM PUMPS

Double Mechanical seals for volatile hydrocarbons service pumps to aim VOCs emission below 500 PPM.

Dual Seals – best choice for maximum containment of process fluid with nil leakage by maintaining required pressure of barrier fluid.

For Zero leak, seal less pumps are used.

o Canned pump where motor and pump unit are totally enclosed in a shell.

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CONTROL OF EMISSIONS FROM COMPRESSORS Centrifugal Compressors

Use of lubricated mechanical seals emission controlling vent system to collect Process Gas – Oil leak inward through seal rings under differential pressure.Leaking lube with entrained gas is collected in trap before return to oil reservoir. Gas from trap is routed to emission control vent (VRU) or to suction of compressor.

Use of Dry Seals for lower emissions. One seal of Silicon Carbide and another of carbon held under pressure differential. Clean (Filtered Gas) in between seals – Leakage to Emission Controlling Vent.

Reciprocating Compressors

Major Source of Emissions from the existing reciprocating compressors from Piston Rod Packing, Cylinder Valve Covers and Unloading Actuator Packing.

Emission reduction by improved ‘O’ ring seal design along Piston rod packing & use of buffer gas in actuator stem seal.

Purge gas / VOC Emissions collected to vapour recovery system (Favorable for H2 – Compressors).

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CONTROL OF EMISSIONS FROM PRESSURE SAFETY VALVES

Spring loaded safety valves with abrupt pressure fluctuations / Popping leads to improper re-seating of discs.

To minimise fugitive emissions, install rupture disc u/s of PSV designed to burst at specific pressure.

Alternatively, pipe the exhaust port of relief valve to – VRU System if flare recovery system is not provided in a refinery.

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CONTROL OF FUGITIVE EMISSIONS BY PROCESS DESIGN

Large complex refineries can integrate off gasses / vent connections / PSV releases / split pressure control streams from overhead Process Vessels, H2 rich gases from compressor purge gases, LPG rich gas routed to Fuel Gas System from stabiliser / light end fractionators etc.

The above gas streams are compressed and processed through sweetening treatment and Drying followed by cold box – bank of Plate & Heat Exchangers & receiving vessels kept under dry N2 atmosphere. Vapours in cold box are sub-cooled by combination of propane refrigerant & expanding vapours in stages.

o Part of cooled vapour stream condenses for routing to De-ethaniser /

Debutaniser for recovery of LPG.

o H2 rich vapours from cold box routed to PSA for recovery of H2 (99.9%).

Typical such Process Scheme involving Naphtha Hydro Pretreater, Depentaniser / Debutaniser / De-isopentaniser / De-hexaniser / CRU are under implementation in an upcoming Refinery in Tamil Nadu, which is a unique combination of emission control and process optimisation.

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EFFLUENT GENERATION / COLLECTION / TREATMENT

Maximum VOCs generation in Raw effluent (OWS) inlet chamber (SUMP) and API separator.

Oil Content in Desalter effluent (brine) range 150-1000 PPM.

Crude Oil / Product Tank water drain.

Spillage from product loading facilities.

VOCs from Oily Sludge Lagoons.

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REDUCTION / CONTROL STRATEGIES

Provision of close blow down system within Process Units (Underground Vessel).

Ensure installation of water seals (Traps) on OWS. Underground Piping Network from Process Units Block & Storage Tanks for recovery of Oil through Mobile units.

Water Drainage from Crude / Light Product Tanks (MS / Naphtha) to Common Vessel to recover Oil.

No hot water / steam condensate to be routed to OWS leading to ETP.

Best approach to minimise oil content from 150 to 500 PPM to <20 PPM in desalter effluent is by installing Brine Treatment facility.

Significant Oil Content reduction is achievable with above steps. Installation of Vapour recovery from sump / API may not be practical. Alternate approach is to provide water sheet spray system over the sump (Blanketing by use of treated effluent).

Install treatment facilities within BTX Plant to reduce Benzene content to less than <10 PPM for Benzene and 20 PPM for Toluene and xylene.

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CONTROL OF VOCs FROM OILY SLUDGE

Main thrust needed to minimise sludge generation in ETP by control of Oil & Solids in influent. One Kg of Solids generate 10 Kgs of Oily Sludge.

Use of Centralised Vacuum cleaning in Process Units instead of water washing especially in FCC / Coker.

Avoid storage of Oily Sludge by use of Centrifuge or pumping Oily Sludge from ETP for injection to hot coke chambers for oil recovery. Typical scheme is shown.

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EMISSIONS FROM CRUDE OIL & PRODUCT STORAGE TANKS

VOCs emitted form operation of Crude Oil and Light Products (MS / Naphtha) Tanks are significant.

Fixed Roof Tanks – Emissions are mainly from breathing losses – depends upon temperature / pressure / level.

Refineries have generally Floating Roof Tanks / Int. Floating Roof Tanks.

Emissions Limited to Evaporative losses from

Imperfect Rim Seal (Non-Uniform Gap)

Fittings in the Floating Deck, Dip Hatches

Exposed Liquid on the tank wall during Withdrawal Operation.

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NATIONAL AMBIENT AIR QUALITY STANDARDS

Sl. No.

Pollutant

Time

Weighted Average

Concentration in Ambient Air

Industrial, Residual, Rural &

Other Area

Ecologically Sensitive

Area (Notified by

Central Government)

1. Sulphur Dioxide (SO2), µg / m3

Annual 50 20

24 Hours 80 80

2. Nitrogen Dioxide (NOx), µg / m3

Annual 40 30

24 Hours 80 80

3. Particulate Matter (size less than 10 µg ) or PM10 , µg / m3

Annual 60 60

24 Hours 100 100

4. Particulate Matter (size less than 2.5 µg ) or PM2.5, µg / m3

Annual 40 40

24 Hours 60 60

5. Ozone (O3), µg / m3

8 Hours 100 100

1 Hour 180 180

6. Load (Pb) µg / m3

Annual 0.50 0.50

24 Hours 1.0 1.0

7. Carbon Monoxide (CO) µg / m3

8 Hours 02 02

1 Hour 04 04

8. Ammonia (NH3) µg / m3

Annual 100 100

24 Hours 400 400

9. Benzene µg / m3

Annual (104 Measurement

05 05

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CONCLUSION

Indian Refineries have well structured. Environmental Protection Policy & dedicated set-up headed by very senior functionaries.

Atmospheric emission standards compliance fairly good with reference to SO2, NOx, CO, etc., pertaining to 2008 EP Act Rules.

Refineries are complying with stipulated total SO2 emissions from furnace stacks.

Refineries have been upgrading process technologies for production of Euro-III / Euro-IV specification fuels – MS/HSD etc., by hydrosulphurisation of FCC feed, hydrotreating of gasoline, kerosene and diesel components.

Spare capacity / standby sulphur recovery units are provided.

Apart from internal HSE Audit, periodic External Audits co-ordinated by OISD are undertaken.

Ambient Air Monitoring Stations are installed for compliance with National Ambient Air Quality Standards.

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THANKS

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