Emissions from Oil Refining Activities

Crude oil refining is one of the major industrial activities that emits C02 and many toxic air pollutants and has a high energy consumption. Because of the presence of trace elements, this C02 is not readily absorbed by the ecosystem, creating an imbalance into the atmosphere. Szklo and Schaeffer (2002) reported that crude oil refining processes are highly energy-intensive, requiring between 7% and 15% of the crude oil from the refinery processes. The study showed that the energy use in the Brazilian refining industry will further increase by 30% between 2002 and 2009 to reduce the sulfur content of diesel and gasoline as well as to reduce C02 emissions. For example, lube oil production needs about 1500 MJ/barrel and alkylation with sulfuric acid and hydrofluoric acid requires 360 MJ/ barrel and 430 MJ/barrel respectively. The energy consumption would further increase to meet the more stringent environmental quality specifications for oil products worldwide. The full recovery of such chemicals or catalysts is not possible, leading to environmental hazards.

Concawe (1999) reported that COz emissions during the refining process of petroleum products were natural gas (56 kg C02/GJ), LPG (64 kg C02/GJ), distillate fuel oil (74 kg C02/GJ), residual fuel (79 kg C02/GJ), and coke (117 kg C02/GJ). Cetin et al. (2003) carried out a study located around a petrochemical complex and an oil refinery and reported that the volatile organic compounds (VOCs) concentrations measured were 4-20 folds higher than those measured at a suburban site in Izmir, Turkey. Ethylene dichloride, a leaded gasoline additive used in petroleum refining was the most abundant volatile organic compound, followed by ethyl alcohol and acetone. In addition to the VOCs, other pollutants such as sulfur dioxide, reduced sulfur compounds, carbon monoxide, nitrogen oxides and particulate matter are also emitted from petroleum refineries (Buonicare and Davis 1992). Rao et al. (2005) reported that several hazardous air pollutants (HAPs) including hydrocarbons such as Maleic anhydride (pyridines, sulfonates, sulfones, ammonia, carbon disulfide, methylethylamine, arsenic, coppers, beryllium, etc.), benzoic acid (benzene, xylene, toluene, formic acid, diethylamine, cobalt, zinc, formaldehyde, cadmium, antimony, etc.), and ketones and aldehydes (phenols, cresols, chromates, cyanides, nickel, molybdenum, aromatic amines, barium, radionuclides, chromium, etc.) are emitted during refining.

Some studies have shown that oil refineries fail to report millions of pounds of harmful emissions that have substantial negative impacts on health and air quality. A report prepared by the Special Investigation Division, Committee on Government Reform for the

U.S. House of Representatives concluded that oil refineries vastly underreport fugitive emissions to federal and state regulators that exceed 80 million pounds of VOCs and 15 million pounds of toxic pollutants (USHR 1999). The total VOCs emission was reported to be 492 million pounds in the U.S. This report confirms that the leaks in the valves are 5 times higher than the leaks reported to the state and federal regulators. Among other toxic air pollutants, it was also reported that oil refineries were the largest emitter of benzene (over 2.9 million pounds) in the U.S. during that report period. Other emissions reported were 4.2 million pounds of xylenes, 4.1 million pounds of methyl ethyl ketone, and 7 million pounds of toluene.

Some of these pollutants are by-products of the catalysts or additives used during the refining process. Other pollutants, such as VOCs, are formed during high temperature and pressure use in the refining process. However, by improving the refining process, it is possible that the emissions can be reduced. For example, mild hydrotreating is conventionally used to remove sulfur and olefins, while severe hydrotreating removes nitrogen compounds, and reduces sulfur content and aromatic rings (Gucchait et al. 2005). Hence, a search for processes that release fewer emissions and use more environment-friendly catalysts is very important in reducing the emissions from refineries and energy utilization.

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