Pollution Prevention and Abatement Handbook WORLD BANK GROUP Effective July 1998 Petroleum Refining Industry Description and Practices • Benzene, toluene, and xylene (BTX): 2.5 grams (g), ranging 0.75 to 6 g; 1 g with the Claus sul- The petroleum industry is organized into four fur recovery process. Of this, about 0.14 g ben- broad sectors: exploration and production of zene, 0.55 g toluene, and 1.8 g xylene may be crude oil and natural gas; transport; refining; and released per ton of crude processed. marketing and distribution. This document ad- • VOC emissions depend on the production dresses only petroleum refining. techniques, emissions control techniques, Crude oil is fractionated into liquefied petro- equipment maintenance, and climate condi- leum gas, naphtha (used to produce gasoline by tions and may be 1 kg per ton of crude pro- blending with octane boosters), kerosene/avia- cessed (ranging from 0.5 to 6 kg/t of crude). tion turbine fuel, diesel oil, and residual fuel oil. Petroleum refineries use relatively large vol- Catalytic cracking and reforming, thermal crack- umes of water, especially for cooling systems. ing, and other secondary processes are used to Surface water runoff and sanitary wastewaters achieve the desired product specifications. Cer- are also generated. The quantity of wastewaters tain refineries also produce feedstocks for the generated and their characteristics depend on the manufacture of lubricating oils and bitumens. process configuration. As a general guide, ap- Some refineries also manufacture coke. proximately 3.5–5 cubic meters (m3) of wastewa- ter per ton of crude are generated when cooling Waste Characteristics water is recycled. Refineries generate polluted wastewaters, containing biochemical oxygen de- Boilers, process heaters, and other process equip- mand (BOD) and chemical oxygen demand ment are responsible for the emission of particu- (COD) levels of approximately 150–250 milli- lates, carbon monoxide, nitrogen oxides (NO ), x grams per liter (mg/l) and 300–600 mg/l, respec- sulfur oxides (SO ), and carbon dioxide. Catalyst x tively; phenol levels of 20–200 mg/l; oil levels of changeovers and cokers release particulates. 100–300 mg/l in desalter water and up to 5,000 Volatile organic compounds (VOCs) such as mg/l in tank bottoms; benzene levels of 1–100 benzene, toluene, and xylene are released from mg/l; benzo(a)pyrene levels of less than 1 to 100 storage, product loading and handling facili- mg/l; heavy metals levels of 0.1–100 mg/l for ties, and oil-water separation systems and as chrome and 0.2–10 mg/l for lead; and other pol- fugitive emissions from flanges, valves, seals, lutants. Refineries also generate solid wastes and and drains. For each ton of crude processed, sludges (ranging from 3 to 5 kg per ton of crude emissions from refineries may be approximately processed), 80% of which may be considered haz- as follows: ardous because of the presence of toxic organics • Particulate matter: 0.8 kilograms (kg), ranging and heavy metals. from less than 0.1 to 3 kg. Accidental discharges of large quantities of pollut- • Sulfur oxides: 1.3 kg, ranging 0.2–06 kg; 0.1 kg ants can occur as a result of abnormal operation in a with the Claus sulfur recovery process. refinery and potentially pose a major local environ- • Nitrogen oxides: 0.3 kg, ranging 0.06–0.5 kg. mental hazard. 377 378 PROJECT GUIDELINES: INDUSTRY SECTOR GUIDELINES Pollution Prevention and Control • Maximize recovery of oil from oily wastewa- ters and sludges. Minimize losses of oil to the Petroleum refineries are complex plants, and the effluent system. combination and sequence of processes is usu- • Recover and reuse phenols, caustics, and sol- ally very specific to the characteristics of the raw vents from their spent solutions. materials (crude oil) and the products. Specific • Return oily sludges to coking units or crude pollution prevention or source reduction mea- distillation units. sures can often be determined only by the tech- nical staff. However, there are a number of broad Operating Procedures areas where improvements are often possible, and site-specific waste reduction measures in • Segregate oily wastewaters from stormwater these areas should be designed into the plant and systems. targeted by management of operating plants. • Reduce oil losses during tank drainage carried Areas where efforts should be concentrated are out to remove water before product dispatch. discussed here. • Optimize frequency of tank and equipment cleaning to avoid accumulating residue at the Reduction of Air Emissions bottom of the tanks. • Prevent solids and oily wastes from entering • Minimize losses from storage tanks and prod- the drainage system. uct transfer areas by methods such as vapor • Institute dry sweeping instead of washdown recovery systems and double seals. to reduce wastewater volumes. • Minimize SOx emissions either through des- • Establish and maintain an emergency pre- ulfurization of fuels, to the extent feasible, or paredness and response plan and carry out fre- by directing the use of high-sulfur fuels to units quent training. equipped with SOx emissions controls. • Practice corrosion monitoring, prevention, and • Recover sulfur from tail gases in high-effi- control in underground piping and tank bot- ciency sulfur recovery units. toms. • Recover non-silica-based (i.e., metallic) cata- • Establish leak detection and repair programs. lysts and reduce particulate emissions. • Use low-NOx burners to reduce nitrogen ox- Target Pollution Loads ide emissions. • Avoid and limit fugitive emissions by proper Implementation of pollution prevention mea- process design and maintenance. sures can yield both economic and environmen- • Keep fuel usage to a minimum. tal benefits. However, a balance on energy usage and environmental impacts may have to be Elimination or Reduction of Pollutants struck. The production-related targets described below can be achieved by measures such as those • Consider reformate and other octane boosters detailed in the previous section. The values re- instead of tetraethyl lead and other organic late to the production processes before the addi- lead compounds for octane boosting. tion of pollution control measures. • Use non-chrome-based inhibitors in cooling New refineries should be designed to maxi- water, where inhibitors are needed. mize energy conservation and reduce hydrocar- • Use long-life catalysts and regenerate to ex- bon losses. A good practice target for simple tend the catalysts’ life cycle. refineries (i.e., refineries with distillation, cata- lytic reforming, hydrotreating, and offsite facili- Recycling and Reuse ties) is that the total quantity of oil consumed as fuel and lost in production operations should not • Recycle cooling water and, where cost-effec- exceed 3.5% of the throughput. For refineries with tive, treated wastewater. secondary conversion units (i.e., hydrocrackers Petroleum Refining 379 or lubricating oil units), the target should be 5– Liquid Effluents 6% (and, in some cases, up to 10%) of the through- put. Fugitive VOC emissions from the process Refinery wastewaters often require a combina- units can be reduced to 0.05% of the throughput, tion of treatment methods to remove oil and con- with total VOC emissions of less than 1 kg per taminants before discharge. Separation of ton of crude (or 0.1% of throughput). Methods of different streams, such as stormwater, cooling estimating these figures include emissions moni- water, process water, sanitary, sewage, etc., is es- toring, mass balance, and inventories of emis- sential for minimizing treatment requirements. sions sources. Design assumptions should be A typical system may include sour water strip- recorded to allow for subsequent computation per, gravity separation of oil and water, dissolved and reduction of losses. air flotation, biological treatment, and clarifica- Vapor recovery systems to control losses of tion. A final polishing step using filtration, acti- VOCs from storage tanks and loading areas vated carbon, or chemical treatment may also be should achieve 90–100% recovery. required. Achievable pollutant loads per ton of Plant operators should aim at using fuel with crude processed include BOD, 6 g; COD, 50 g; less than 0.5% sulfur (or an emissions level cor- suspended solids, 10 g; and oil and grease, 2 g. responding to 0.5% sulfur in fuel). High-sulfur fuels should be directed to units equipped with Solid and Hazardous Wastes SOx controls. Fuel blending is another option. A sulfur recovery system that achieves at least 97% Sludge treatment is usually performed using land (but preferably over 99%) sulfur recovery should application (bioremediation) or solvent extrac- be used when the hydrogen sulfide concentra- tion followed by combustion of the residue or by tion in tail gases exceeds 230 mg/Nm3. The total use for asphalt, where feasible. In some cases, the release of sulfur dioxide should be below 0.5 kg residue may require stabilization prior to dis- per ton for a hydroskimming refinery and below posal to reduce the leachability of toxic metals. 1 kg per ton for a conversion refinery. Oil is recovered from slops using separation A wastewater generation rate of 0.4 m3/t of techniques such as gravity separators and cen- crude processed is achievable with good design trifuges. and operation, and new refineries should achieve this target as a minimum. Emissions Guidelines The generation rate of solid wastes and slud- ges should be less than 0.5% of the crude pro- Emissions levels for the design and operation of cessed, with a target of 0.3%. each project must be established through the en- vironmental assessment (EA) process on the ba- Treatment Technologies sis of country legislation and the Pollution Prevention and Abatement Handbook, as applied to local con- Air Emissions ditions. The emissions levels selected must be justified in the EA and acceptable to the World Control of air emissions normally includes the Bank Group. capture and recycling or combustion of emissions The guidelines given below present emissions from vents, product transfer points, storage levels normally acceptable to the World Bank tanks, and other handling equipment.