Gaseous emissions, control

Air pollution control methods, 26 667-729 gaseous emissions control, 26 678-694 hierarchical approach in, 26 675-678 measurement of air pollution, 26 672-675... 

N02 diffusion from the catalyst in/on the filter wall back to the soot layer (so-called back diffusion ). 1-3 and 5 have been covered extensively (Bissett, 1984 Haralampous et al., 2004 Huynh et al., 2003 Konstandopoulos and Johnson, 1989 York et al., 2005, 2007), and are also covered in part elsewhere in this volume (Konstandopoulos et al., this volume). The application of a coated filter as a gaseous emissions control device has received far less attention and will be discussed now. 

The removal of gaseous pollutants from dryer exhaust may be accomplished by several possible processes. Among these are absorption, adsorption, condensation, and incineration [11-16]. The choice of a given process is usually determined by physical and chemical characteristics of the dried product and by economic and environmental considerations. Table 53.3 summarizes some of the basic characteristics of the gaseous emission control equipment. 

There are four chemical-engineering unit operations commonly used for the control of gaseous emissions ... 

Petroleum products are obtained from crude oil. In the process of getting the crude oil from the ground to the refinery, many possibilities for emission of hydrocarbon and reduced sulfur gaseous emissions occur. In many cases, these operations take place in relatively remote regions and affect only those employed by the industry, so that little or no control is attempted. 

A widely used system for the control of organic gaseous emissions is oxidation of the combustible components to water and carbon dioxide. 

Most petrochemical processes are essentially enclosed and normally vent only a small amount of fugitive emissions. However, the petrochemical processes that use air-oxidation-type reactions normally vent large, continuous amounts of gaseous emissions to the atmosphere (10). Six major petrochemical processes employ reactions using air oxidation. Table 30-5 lists the atmospheric emissions from these processes along with applicable control measures. 

The code provides for the testing of gas turbines supplied with gaseous or liquid fuels (or solid fuels converted to liquid or gas prior to entrance to the gas turbine). Test of gas turbines with water or steam injection for emission control and/or power augmentation are included. The tests can be applied to gas turbines in combined-cycle power plants or with other heat recovery systems. 

Wet scrubbers rely on a liquid spray to remove dust particles from a gas stream. They are primarily used to remove gaseous emissions, with particulate control a secondary function. The major types are venturi scrubbers, jet (fume) scrubbers, and spray towers or chambers. Venturi scrubbers consume large quantities of scrubbing liquid (such as water) and electric power and incur high pressure drops. Jet or fume scrubbers rely on the kinetic energy of the liquid stream. The typical removal efficiency of a jet or fume scrubber (for particles 10 g. or less) is lower than that of a venturi scrubber. Spray towers can handle larger gas flows with minimal pressure drop and are therefore often used as precoolers. Because wet scrubbers may contribute to corrosion, removal of water from the effluent gas of the scrubbers may be necessary. 

Absorption is widely used as a raw material and/or product recovery technique in separation and purification of gaseous streams containing high concentrations of VOC, especially water-soluble compounds such as methanol, ethanol, isopropanol, butanol, acetone, and formaldehyde. Hydrophobic VOC can be absorbed using an amphiphilic block copolymer dissolved in water. However, as an emission control... 

A variety of containment strategies employ floating solid objects to control the rate of gaseous emissions from surface impoundments. These include synthetic membrane covers, rafts, and hollow plastic spheres. Synthetic membrane covers are feasible where the out-gassing of volatiles due to biological activity is not expected. Selection of the liner material must be... 

Emission abatement methods covered are suitable for the emission control of volatile organic compounds (VOCs). The VOCs include organic compounds existing in the gaseous phase in air at 293.15 K. However, or ganic compounds, which are not regarded as VOCs, can be treated by the methods covered in this section. 

Emissions monitoring is essential in controlling industrial environments and processes to ensure good air quality standards are maintained. It is also required in order that the various regulations and guidelines related to air quality are met. In addition to gaseous emissions, such as sulfur dioxide, carbon monoxide, nitrogen oxides, hydrocarbons, and many others, the emissions of particulate material and heavy metals must also be controlled. 

Controlling methane release from wetland, rice paddies and gaseous emissions from animals is more problematic. The release from rice paddies and wet lands is slow, intermittent and takes place over a wide geographic area, and thus very difficult to control. Gaseous emissions from agricultural animals contribute to atmospheric accumulation of methane due to fermentative digestion that produces methane in... 

Waste treatment prior to disposal may introduce phase changes which result in quite different pollution control considerations. For example, the gases generated by incineration of a solid waste can be scrubbed with liquid in order to meet an acceptable discharge criterion hence, in addition to ash for disposal, a liquid effluent stream is produced and requires treatment. Other waste treatment processes may result in the liberation of flammable or toxic gaseous emissions as exemplified in Table 16.5. 

Are design details and specifications for end-of-pipe emission control systems fully documented in an inventory Provide details of all end-of-pipe control systems (for aqueous emissions, gaseous emissions, and waste). Identify the risk category. 

Direct acidihcation of cyanide waste streams was once a relatively common treatment. Cyanide is acidified in a sealed reactor that is vented to the atmosphere through an air emission control system. Cyanide is converted to gaseous hydrogen cyanide, treated, vented, and dispersed. 

A process is described [224] in which an exothermic reaction takes place in a semi-batch reactor at elevated temperatures and under pressure. The solid and liquid raw materials are both toxic and flammable. Spontaneous ignition is possible when the reaction mass is exposed to air. Therefore, the system must be totally enclosed and confined in order to contain safely any emissions arising from the loss of reactor control, and to prevent secondary combustion reactions upon discharge of the materials to the atmosphere. Further, procedures and equipment are necessary for the safe collection and disposal of solid, liquid, and gaseous emission products. 

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