Petroleum refining

Industrial wastewater pollution: prevention and control

IOCL refinery, Panipat

Desalter

Desalter Effluent

Spent caustic

Sour water

Schematic flowchart: Process & Process waste-streams

Crude oil storage tank

Tank bottom draws

150⁰C

200⁰C

400⁰C

(Marine Fuel Oil)

Unit operations/ processes Water use Waste Water

Crude Storage Tanksto store the raw material – crude oil

No addition of water Water and sediments that are picked up when the oil is extracted from the wells

Desaltingto extract corrosive, catalyst-prohibitive and equipment-fouling salts and compounds

Hot water to extract salts and chemical compounds

High temperature, high salt, suspended solids, phenols, H2S

Distillationto separate crude oil into groups of hydrocarbon compounds of different boiling-point ranges

Steam is used as stripping medium

Oily sour water (condensed steam containing H2S, NH3)

Catalytic crackingto break down (decompose) the heavy hydrocarbons (HC) into smaller desired HC products

Diluent to reduce hydrocarbon partial pressure

H2S, NH3, High pH, phenols suspended solids, BOD, COD.

Solvent Extractionfor extraction of acid components in intermediate streams

Caustic solution Spent caustics – residual H2S, phenols, organic acids, HCN, CO2

Major contaminantsParameter Untreated combined

effluent(mg/L)

MINAS (mg/L)

pH 6 – 10 6.0-8.5

Temperature 30 – 45 ⁰C --

Suspended solids 100 – 500 20.0

BOD 300 – 500(5 days, 20⁰C)

15.0(3 days, 27⁰C)

Oil and grease 500 – 3000 5.0

Sulphide 50 – 120 0.5

Phenols 20 – 40 0.35

Ammonia as N 50 – 70 15.0

Treatment optionsPrimary Biological Tertiary

Sour water stripper

H2S, NH3 removal from sour water streams

Oil / Water/ Solids separators

1. API separators(Gravity separation)

2. DAF or IAF separators

Organics, BOD removal

Suspended growth processASPSBR

Attached growth processBio tower

Residual contaminants

TSS, TDSMembrane filtration

MF/UFMF/UF + ROMF/UF + NF

Ion exchange softening (also for dissolved inorganics)

Dissolved COD, PAHActivated carbon

COD, metal & their compounds, non-biodegradablesChemical oxidation

Primary oil / water separation

Secondary oil / water separation

Equalization Biological Treatment

ClarificationTertiary

Treatment

Wastewater Reuse Upgrade

(R.O)

Brine Concentration Crystallizer

Salt crystals to Disposals

R.O Reject Brine

Water WaterPermeate

Refinery Effluent

Recycle Water to Refinery

Refinery WW

Oil to slop

Oil to slop

Sludge Sludge

Zero Liquid Discharge (ZLD)

1.

Waste minimization

Improved housekeeping

Establish leak detection and repair program, Refurbish or eliminate underground piping, Remove unnecessary storage tanks from service, Replace old boilers, Segregate process waste streams

Equipment redesign Modernization of Fired Heaters, Sonic Soot Blowers instead of conventional soot blowers

Process control/ modification

Control of surfactants in wastewater, Minimize solids leaving the desalter, Modernization of Instrumentation and Advanced Control Strategies, Offsite Automation facilities

Substitution of less hazardous material

Switch from Naphtha to Regasified Liquid Natural Gas (RLNG) as feed to Reformer in Hydrogen Unit and firing of all the furnaces – no pretreatment of naphtha to remove sulphur

Recovery, Reuse, Recycle

Recycle and regenerate spent caustics, Minimize cooling tower blow down, Part of the treated effluents to be recycled for greenbelt development, fire water make up, chemical preparation and other peripheral applications in the Refinery Complex. The remaining treated effluents to be reclaimed for refinery process reuse through ZLD scheme

Pollution prevention opportunities

2.

Design of recycling technology to conserve, recover

Raw material Reduce the generation of tank bottoms, Detailed Hydrocarbon loss study and remedial measures, Electronic themoprobes for accurate tank temperature to minimize hydrocarbon loss

Energy Adoption of co-generation principle for generation of steam / power, etc. which includes installation of FCCU Co – Boiler, Maximization of crude preheat by optimization of Heat Exchanger Train using Pinch Technology, Effective use of Waste Heat, On-line oxygen analyzers, Mass flow meters on furnaces / boilers to improve furnace efficiency

Water Minimize cooling tower blow down, Reclamation of city sewage water for refinery use by employing conventional physico-chemical based tertiary treatment process followed by membrane separation of contaminants through reverse osmosis. An additional train of Reverse osmosis membranes to recover R.O. rejects

By products Identify benzene sources and install upstream water treatment, Hydrogen gas recovery from process units – green fuel

3.

Waste utilization

Sludge Mechanical Oil recovery from oily sludge, Processing of Oily sludge to recover oil, Bio-remediation for oily sludge treatment to produce organic fertilizers

References

1. OSHA technical manual - section IV: chapter 2 – Petroleum refining processwww.osha.gov/dts/osta/otm/otm_iv/otm_iv_2.html 1/

2. IPIECA Operations Best Practice Series: Petroleum refining water/wastewater use and management, 2010

3. Treatment of Oilfield and Refinery Wastes, Joseph M. Wong and Yung-Tse Hung, Taylor & Francis Group, LLC, 2006

4. EPA Office of Compliance Sector Notebook Project: Profile of the Petroleum Refining Industry, September 1995

5. The Oil and Gas Sector Overview in India 2009, KPMG India Private Ltd.

6. Official website: Chennai Petroleum Corporation Ltd.http://www.cpcl.co.in

7. Official website: Hindustan Petroleum Corporation Ltd. http://www.hindustanpetroleum.com