Updates on choices of appropriate technology for control of voc emissions

Abstract

As the federal, state, and local agencies have promulgated regulations that require greater control for emissions of volatile organic compounds and hazardous air pollutants, new technologies and new strategies for controlling air pollutant emissions have developed. This article updates an earlier article published in Metal Finishing (page 238, vol. 92, no. 5A, 1994) to include some recent developments in air pollutant emission control for solvents used in metal finishing. Volatile organic compounds (VOCs) and Hazardous Air Pollutants (HAPs) have specific regulatory definitions; but for the purpose of this article, organic compounds that are subject to regulatory control as either VOCs or HAPs will be called VOCs, since they are subject to the same types of emission control. VOCs are used in the metal-finishing and other U.S. industries in production, manufacture, and surface coating. With stricter air pollution regulations being promulgated, it is necessary for industry to minimize its use of solvents and/or control solvent emissions. In some cases it may be possible to substitute other compounds; in other cases control technologies will be required to minimize emissions of the regulated compounds. A number of control technology choices are available to control the emissions of VOCs. Two possible approaches to control VOC emissions are recovery and destruction (see Table I). Recovery methods include adsorption and condensation. Destruction methods include incineration and biodegradation. It is also possible to use hybrid combinations such as concentration with condensation or concentration with oxidation. The choice of control technology will depend on economic, safety, and/or regulatory factors. Recovery technologies provide the benefit of both cost and energy savings. Recovery saves the energy for production of new material and the cost of purchasing additional material for the same or a similar application. Destruction technologies provide the benefit of not requiring subsequent disposal of the VOC. High-value VOCs favor recovery methods. Mixtures of VOCs or low-value solvents favor destruction methods.