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Industry Description and Practices

The petroleum industry is organized into fourbroad sectors: exploration and production ofcrude oil and natural gas; transport; refining; andmarketing and distribution. This document ad-

dresses only petroleum refining.Crude oil is fractionated into liquefied petro-leum gas, naphtha (used to produce gasoline byblending with octane boosters), kerosene/avia-tion turbine fuel, diesel oil, and residual fuel oil.Catalytic cracking and reforming, thermal crack-ing, and other secondary processes are used toachieve the desired product specifications. Cer-tain refineries also produce feedstocks for themanufacture of lubricating oils and bitumens.Some refineries also manufacture coke.

Waste Characteristics

Boilers, process heaters, and other process equip-ment are responsible for the emission of particu-lates, carbon monoxide, nitrogen oxides (NOx),sulfur oxides (SOx), and carbon dioxide. Catalystchangeovers and cokers release particulates.Volatile organic compounds (VOCs) such asbenzene, toluene, and xylene are released fromstorage, product loading and handling facili-ties, and oil-water separation systems and asfugitive emissions from flanges, valves, seals,and drains. For each ton of crude processed,emissions from refineries may be approximatelyas follows:

Particulate matter: 0.8 kilograms (kg), rangingfrom less than 0.1 to 3 kg.

Sulfur oxides: 1.3 kg, ranging 0.206 kg; 0.1 kgwith the Claus sulfur recovery process.

Nitrogen oxides: 0.3 kg, ranging 0.060.5 kg.

Benzene, toluene, and xylene (BTX): 2.5 grams(g), ranging 0.75 to 6 g; 1 g with the Claus sul-fur recovery process. Of this, about 0.14 g ben-zene, 0.55 g toluene, and 1.8 g xylene may bereleased per ton of crude processed.

VOC emissions depend on the production

techniques, emissions control techniques,equipment maintenance, and climate condi-tions and may be 1 kg per ton of crude pro-cessed (ranging from 0.5 to 6 kg/t of crude).

Petroleum refineries use relatively large vol-umes of water, especially for cooling systems.Surface water runoff and sanitary wastewatersare also generated. The quantity of wastewatersgenerated and their characteristics depend on theprocess configuration. As a general guide, ap-proximately 3.55 cubic meters (m3) of wastewa-ter per ton of crude are generated when cooling

water is recycled. Refineries generate pollutedwastewaters, containing biochemical oxygen de-mand (BOD) and chemical oxygen demand(COD) levels of approximately 150250 milli-grams per liter (mg/l) and 300600 mg/l, respec-tively; phenol levels of 20200 mg/l; oil levels of100300 mg/l in desalter water and up to 5,000mg/l in tank bottoms; benzene levels of 1100mg/l; benzo(a)pyrene levels of less than 1 to 100mg/l; heavy metals levels of 0.1100 mg/l forchrome and 0.210 mg/l for lead; and other pol-lutants. Refineries also generate solid wastes and

sludges (ranging from 3 to 5 kg per ton of crudeprocessed), 80% of which may be considered haz-ardous because of the presence of toxic organicsand heavy metals.

Accidental discharges of large quantities of pollut-ants can occur as a result of abnormal operation in arefinery and potentially pose a major local environ-mental hazard.

Pollution Prevention and Abatement HandbWORLD BANK GRO

Effective July 1

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Pollution Prevention and Control

Petroleum refineries are complex plants, and thecombination and sequence of processes is usu-ally very specific to the characteristics of the raw

materials (crude oil) and the products. Specificpollution prevention or source reduction mea-sures can often be determined only by the tech-nical staff. However, there are a number of broadareas where improvements are often possible,and site-specific waste reduction measures inthese areas should be designed into the plant andtargeted by management of operating plants.Areas where efforts should be concentrated arediscussed here.

Reduction of Air Emissions

Minimize losses from storage tanks and prod-uct transfer areas by methods such as vaporrecovery systems and double seals.

Minimize SOx emissions either through des-ulfurization of fuels, to the extent feasible, orby directing the use of high-sulfur fuels to unitsequipped with SOxemissions controls.

Recover sulfur from tail gases in high-effi-ciency sulfur recovery units.

Recover non-silica-based (i.e., metallic) cata-lysts and reduce particulate emissions.

Use low-NOx

burners to reduce nitrogen ox-ide emissions.

Avoid and limit fugitive emissions by properprocess design and maintenance.

Keep fuel usage to a minimum.

Elimination or Reduction of Pollutants

Consider reformate and other octane boostersinstead of tetraethyl lead and other organiclead compounds for octane boosting.

Use non-chrome-based inhibitors in coolingwater, where inhibitors are needed.

Use long-life catalysts and regenerate to ex-tend the catalysts life cycle.

Recycling and Reuse

Recycle cooling water and, where cost-effec-tive, treated wastewater.

Maximize recovery of oil from oily wastewa-ters and sludges. Minimize losses of oil to theeffluent system.

Recover and reuse phenols, caustics, and sol-vents from their spent solutions.

Return oily sludges to coking units or crudedistillation units.

Operating Procedures

Segregate oily wastewaters from stormwatersystems.

Reduce oil losses during tank drainage carriedout to remove water before product dispatch.

Optimize frequency of tank and equipmentcleaning to avoid accumulating residue at thebottom of the tanks.

Prevent solids and oily wastes from enteringthe drainage system. Institute dry sweeping instead of washdown

to reduce wastewater volumes. Establish and maintain an emergency pre-

paredness and response plan and carry out fre-quent training.

Practice corrosion monitoring, prevention, andcontrol in underground piping and tank bot-toms.

Establish leak detection and repair programs.

Target Pollution Loads

Implementation of pollution prevention mea-sures can yield both economic and environmen-tal benefits. However, a balance on energy usageand environmental impacts may have to bestruck. The production-related targets describedbelow can be achieved by measures such as thosedetailed in the previous section. The values re-late to the production processes before the addi-tion of pollution control measures.

New refineries should be designed to maxi-mize energy conservation and reduce hydrocar-bon losses. A good practice target for simplerefineries (i.e., refineries with distillation, cata-lytic reforming, hydrotreating, and offsite facili-ties) is that the total quantity of oil consumed asfuel and lost in production operations should notexceed 3.5% of the throughput. For refineries withsecondary conversion units (i.e., hydrocrackers

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379Petroleum Refining

or lubricating oil units), the target should be 56% (and, in some cases, up to 10%) of the through-put. Fugitive VOC emissions from the processunits can be reduced to 0.05% of the throughput,with total VOC emissions of less than 1 kg per

ton of crude (or 0.1% of throughput). Methods ofestimating these figures include emissions moni-toring, mass balance, and inventories of emis-sions sources. Design assumptions should berecorded to allow for subsequent computationand reduction of losses.

Vapor recovery systems to control losses ofVOCs from storage tanks and loading areasshould achieve 90100% recovery.

Plant operators should aim at using fuel withless than 0.5% sulfur (or an emissions level cor-responding to 0.5% sulfur in fuel). High-sulfurfuels should be directed to units equipped withSOxcontrols. Fuel blending is another option. Asulfur recovery system that achieves at least 97%(but preferably over 99%) sulfur recovery shouldbe used when the hydrogen sulfide concentra-tion in tail gases exceeds 230 mg/Nm3. The totalrelease of sulfur dioxide should be below 0.5 kgper ton for a hydroskimming refinery and below1 kg per ton for a conversion refinery.

A wastewater generation rate of 0.4 m3/t ofcrude processed is achievable with good designand operation, and new refineries should achievethis target as a minimum.

The generation rate of solid wastes and slud-ges should be less than 0.5% of the crude pro-cessed, with a target of 0.3%.

Treatment Technologies

Air Emissions

Control of air emissions normally includes thecapture and recycling or combustion of emissionsfrom vents, product transfer points, storagetanks, and other handling equipment. Boilers,heaters, other combustion devices, cokers, andcatalytic units may require particulate mattercontrols. Use of a carbon monoxide boiler is nor-mally a standard practice in the fluidized cata-lytic cracking units. Catalytic cracking unitsshould be provided with particular removal de-vices. Steam injection in flaring stacks can reduceparticulate matter emissions.

Liquid Effluents

Refinery wastewaters often require a combina-tion of treatment methods to remove oil and con-taminants before discharge. Separation of

different streams, such as stormwater, coolingwater, process water, sanitary, sewage, etc., is es-sential for minimizing treatment requirements.A typical system may include sour water strip-per, gravity separation of oil and water, dissolvedair flotation, biological treatment, and clarifica-tion. A final polishing step using filtration, acti-vated carbon, or chemical treatment may also berequired. Achievable pollutant loads per ton ofcrude processed include BOD, 6 g; COD, 50 g;suspended solids, 10 g; and oil and grease, 2 g.

Solid and Hazardous Wastes

Sludge treatment is usually performed using landapplication (bioremediation) or solvent extrac-tion followed by combustion of the residue or byuse for asphalt, where feasible. In some cases, theresidue may require stabilization prior to dis-posal to reduce the leachability of toxic metals.

Oil is recovered from slops using separationtechniques such as gravity separators and cen-trifuges.

Emissions Guidelines

Emissions levels for the design and operation ofeach project must be established through the en-vironmental assessment (EA) process on the ba-sis of country legislation and thePollution Preventionand Abatement Handbook,as applied to local con-ditions. The emissions levels selected must bejustified in the EA and acceptable to the WorldBank Group.

The guidelines given below present emissionslevels normally acceptable to the World BankGroup in making decisions regarding provisionof World Bank Group assistance. Any deviationsfrom these levels must be described in the WorldBank Group project documentation. The emis-sions levels given here can be consistentlyachieved by well-designed, well-operated, andwell-maintained pollution control systems.

The guidelines are expressed as concentrationsto facilitate monitoring. Dilution of air emissions

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or effluents to achieve these guidelines is unac-ceptable.

All of the maximum levels should be achievedfor at least 95% of the time that the plant or unitis operating, to be calculated as a proportion of

annual operating hours.

Air Emissions

The emissions levels presented in Table 1 shouldbe achieved.

Liquid Effluents

The emissions levels presented in Table 2 shouldbe achieved.

Effluent requirements are for direct discharge

to surface waters. Discharge to an offsite waste-water treatment plant should meet applicablepretreatment requirements.

Solid Wastes and Sludges

Wherever possible, generation of sludges shouldbe minimized to 0.3 kg per ton of crude pro-cessed, with a maximum of 0.5 kg per ton of crudeprocessed. Sludges must be treated and stabilizedto reduce concentrations of toxics (such as ben-zene and lead) in leachate to acceptable levels,

for example, below 0.05 milligram per kg.

Ambient Noise

Noise abatement measures should achieve eitherthe levels given below or a maximum increase inbackground levels of 3 decibels (measured on the

A scale) [dB(A)]. Measurements are to be takenat noise receptors located outside the projectproperty boundary.

Maximum allowable logequivalent (hourly

measurements), in dB(A)

Day Night

Receptor (07:0022:00) (22:0007:00)

Residential,

institutional,

educational 55 45

Industrial,

commercial 70 70

Monitoring and Reporting

Frequent sampling may be required during start-up and upset conditions. Once a record of con-sistent performance has been established,sampling for the parameters listed in this docu-ment should be as described below.

Air emissions from stacks should be monitoredonce every shift, if not continuously, for opacity(maximum level, 10%). Air emissions of hydro-

Table 1. Emissions from the Petroleum Industry

(milligrams per normal cubic meter)

Parameter Maximum value

PM 50

Nitrogen oxidesa 460

Sulfur oxides 150 for sulfur recovery

units; 500 for other units

Nickel and vanadium

(combined) 2

Hydrogen sulfide 152

a. Excludes NOxemissions from catalytic units.

Table 2. Effluents from the Petroleum Industry

(milligrams per liter)

Parameter Maximum value

pH 69

BOD 30COD 150

TSS 30

Oil and grease 10

Chromium

Hexavalent 0.1

Total 0.5

Lead 0.1

Phenol 0.5

Benzene 0.05

Benzo(a)pyrene 0.05

Sulfide 1

Nitrogen (total)a 10

Temperature increase 3Cb

a. The maximum effluent concentration of nitrogen (total) maybe up to 40 mg/l in processes that include hydrogenation.b. The effluent should result in a temperature increase of nomore than 3C at the edge of the zone where initial mixing anddilution take place. Where the zone is not defined, use 100meters from the point of discharge, provided there are no sen-sitive ecosystems within this range.

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381Petroleum Refining

gen sulfide from a sulfur recovery unit shouldbe monitored on a continuous basis. Annual emis-sions monitoring of combustion sources shouldbe carried out for sulfur oxides (sulfur content ofthe fuel monitored on a supply-tank basis) and

for nitrogen oxides.Liquid effluents should be monitored daily forall the parameters listed above, except that met-als should be monitored at least monthly.

Monitoring data should be analyzed and re-viewed at regular intervals and compared withthe operating standards so that any necessarycorrective actions can be taken. Records of moni-toring results should be kept in an acceptableformat. The results should be reported to theresponsible authorities and relevant parties, asrequired.

Key Issues

The key production and control practices that willlead to compliance with emissions guidelines canbe summarized as follows: Use vapor recovery systems to reduce VOC

emissions. Install sulfur recovery systems, where feasible. Use low-NOxburners. Maintain fuel and losses to 3.5% for simple

refineries and below 6% (with 10% as themaximum) for refineries with secondary pro-cessing.

Recover and recycle oily wastes.

Regenerate and reuse spent catalysts and sol-vents.

Recycle cooling water and minimize waste-waters.

Segregate storm water from process waste-

water. Use nonchrome-based inhibitors (use only tothe extent needed in cooling water).

Minimize the generation of sludges. Install spill prevention and control measures.

Sources

Bounicore, Anthony J., and Wayne T. Davis, eds. 1992.Air Pollution Engineering Manual. New York: VanNostrand Reinhold.

Commission of the European Communities. DG XI A3.1991. Technical Note on the Best Available Tech-nologies to Reduce Emissions of Pollutants into theAir from the Refining Industry. Brussels.

______. DG XI A3. 1993. Technoeconomic Study onthe Reduction Measures, based on Best AvailableTechnology, of Water Discharges and Waste Gen-eration from Refineries. Brussels.

USEPA (U.S. Environmental Protection Agency). 1982.Development Document for Effluent LimitationsGuidelines and Standards for the Petroleum Refin-ing Point Source Category. Washington, D.C.

World Bank. 1996. Pollution Prevention and Abate-ment: Petroleum Refining. Draft Technical Back-ground Document. Environment Department,Washington, D.C.