BTEX
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BTEX is an acronym that stands for benzene, toluene, ethylbenzene, and xylene. These chemicals are volatile organic compounds (VOCs), which are naturally occurring and human-made compounds that appear as gases or vapors at room temperature. BTEX is found in petroleum products such as gasoline, home heating, and diesel fuel.[1][2][3][4]
Background
BTEX is a natural component of petroleum, gasoline, and diesel fuel. BTEX is also used to manufacture fuel additives, synthetic materials, and consumer products. Below are descriptions of benzene, ethylbenzene, toluene, and xylene.[5]
- Benzene is a hydrocarbon and petrochemical made up of six carbon atoms and one hydrogen atom. It is colorless with a sweet odor and is a flammable substance. Benzene is found in gasoline- and petroleum-based products such as plastics, paints, detergents, cosmetics, and synthetic rubber. Sources of benzene include tobacco smoke, automobile exhaust, and industrial emissions. Benzene is a carcinogen and labelled by the U.S. Department of Health and Human Services as a cancer-causing agent.[3][6][7]
- Toluene is a colorless, flammable, water-insoluble liquid and a derivative of benzene. Toluene naturally occurs in crude oil and petroleum products and is found in paints, oils, gums, and resins. It is used as a solvent and in the manufacturing of synthetic drugs, plastics, trinitrotoluene (TNT), paint thinners, rubber, glues, and disinfectants. Toluene may also be used to break up red blood cells in order to extract hemoglobin (a red protein responsible for transporting oxygen in the blood) in biochemical experiments. As of 2012, the Environmental Protection Agency concluded that there is inadequate information to classify toluene as a carcinogen (cancer-causing agent).[3][6][8]
- Ethylbenzene is a colorless, flammable liquid. It is used in the production of styrene, a common type of plastic. Ethylbenzene is also used as an additive found in paints and pesticides, a solvent in ink, and a rubber adhesive. The U.S. Occupational Safety and Health Administration (OSHA) limits exposure to ethylbenzene to an average of 100 parts per million (ppm) for an 8-hour period in a 40-hour work week.[3][6]
- Xylene is a colorless hydrocarbon that is found naturally in petroleum and coal. It also exists at lower levels in gasoline and aircraft fuel. Xylene is used as a solvent in the production printing, leather, and rubber, and paint.[3][6]
Abatement
Industries and other entities that handle BTEX can implement several systems to limit BTEX emissions:[6]
- Thermal oxidation involves raising exhaust steam temperatures to a point where chemical bonds between molecules are disrupted. The volatile organic chemicals (VOCs) found in the exhaust steam are changed into different combinations of carbon dioxide, water, and thermal energy when exposed to high temperatures in a combustion chamber.[9]
- Regenerative thermal oxidation (RTO) involves the use of high temperature, turbulence, and oxygen to convert VOCs to carbon dioxide and water vapor. VOCs are pushed or pulled into an RTO unit through a fan system. The VOCs are directed into chambers where they are preheated and moved to a combustion chamber. After the VOCs are oxidized and removed, the hot air containing carbon dioxide and water vapor moves to a recovery cannister, which absorbs the heat generated during oxidation. The cooler air is then emitted into atmosphere through an exhaust stack.[10][11]
- BTEX eliminators are heat exchanger condensing systems that capture and recycle BTEX. BTEX is transferred into a column and then to a heat exchanger, where liquid is condensed and sent elsewhere in the system. As liquid levels rise, a valve is opened to send the liquids to storage tanks. The remaining VOCs are sent to a burner.[12]
Regulation
The Clean Air Act requires the Environmental Protection Agency (EPA) and state governments to regulate hazardous air pollutants, including volatile organic compounds (VOCs) like BTEX, from large industrial facilities. States must adopt state implementation plan outlining how they will achieve emissions reductions for regulated pollutants like VOCs. Each plan requires owners or operators of sources of VOCs to submit a statement outlining the amount of VOCs emitted by a facility or source. States may waive this requirement for sources that emit less than 25 tons of VOCs per year.[13]
VOC standards are developed by the EPA to limit emissions from various sources. The EPA sets technology-based requirements for these sources; facilities must install the maximum achievable emission control technology for sources that emit higher levels of VOCs. These technology-based standards also take into account the emissions that are already being controlled at low-emitting sources. The Clean Air Act requires the EPA to review its standards within 8 years of setting them. After this period, the EPA must assess whether the technology standards adequately addressed the potential adverse health and environmental effects of VOC emissions. The agency may implement further regulations if it determines that the previous standards were inadequate.[14]
See also
Footnotes
- ↑ United States Geological Survey, “BTEX,” accessed January 23, 2014
- ↑ Society of Petroleum Engineers, “Hydraulic Fracturing 101: What Every Representative, Environmentalist, Regulator, Reporter, Investor, University Researcher, Neighbor and Engineer Should Know About Estimating Frac Risk and Improving Frac Performance in Unconventional Gas and Oil Wells,” accessed January 30, 2014
- ↑ 3.0 3.1 3.2 3.3 3.4 Ohio Bureau of Environmental Health, "BTEX," January 12, 2014
- ↑ Maryland Department of the Environment, "BTEX," February 12, 2007
- ↑ Phoslab Environmental Services, "BTEX: Risk and control measures," accessed March 8, 2017
- ↑ 6.0 6.1 6.2 6.3 6.4 Gulf Coast Environmental Systems, "What is BTEX?" accessed March 8, 2017
- ↑ World Health Organization, "Exposure to benzene: A major public health concern," accessed March 8, 2017
- ↑ U.S. Environmental Protection Agency, "Toluene," accessed March 8, 2017
- ↑ Exterran, "Thermal Oxidizer," accessed March 8, 2017
- ↑ Gulf Coast Environmental Systems, "Regenerative Thermal Oxidizers (RTO)," accessed March 8, 2017
- ↑ Anguil, "Regenerative Thermal Oxidizer (RTO)," accessed March 8, 2017
- ↑ Exterran, "BTEX Eliminator," accessed March 8, 2017
- ↑ U.S. Senate Committee on Environment and Public Works, "The Clean Air Act Amendments of 1990," accessed March 3, 2017
- ↑ Environmental Protection Agency, "Reducing Emissions of Hazardous Air Pollutants," accessed March 3, 2017
