Particulate matter control

Figure 30-lE includes a hot ESP for fly ash collection prior to a catalytic NO , unit. Having a hot ESP dictates the use of a conventional wet scrubber and perhaps the need for a second particulate matter control device at the end of the system. Fly ash and scrubber sludge would be separate byproducts, but sludge could be contaminated with NH4 from the catalytic NO process. 

The electric arc furnace process accounted for about 25% of the 1982 U.S. steelmaking capacity (14). Most of the raw material used for the process is steel scrap. Pollutants generated by the electric furnace process are primarily particulate matter and CO. The furnaces are hooded, and the gas stream containing the particulate matter is collected, cooled, and passed to a bag-house for cleaning. Venturi scrubbers and ESPs are used as control devices at some mills. Charging and tapping emissions are also collected by hoods and ducted to the particulate matter control device. 

EC/R, 1996. EC/R, Inc., "Evaluation of Fine Particulate Matter Control Technology Final Draft," prepared for U.S. EPA, Integrated Policy and Strategies Group, Durham, NC, September, 1996. 

To control the emission of organics, these units must comply with similar DRE requirements to the other hazardous waste combustion units. Owners or operators of MACT combustion units must select POHCs and demonstrate a DRE of 99.99% for each POHC in the hazardous wastestream. Sources that bum hazardous waste have a required DRE of 99.9999% for each POHC designated. Additionally, for dioxins and furans, U.S. EPA promulgated more stringent standards under MACT. For example, MACT incinerators and cement kilns that bum waste with dioxins and furans must not exceed an emission limitation of either 0.2 ng of toxicity equivalence per dry standard cubic meter (TEQ/m3) or 0.4 ng TEQ/m3 at the inlet to the dry particulate matter control device. This unit of measure is based on a method for assessing risks associated with exposures to dioxins and furans. 

E. Bakke, "The AppHcation of Wet Electrostatic Precipitators for Control of Eiue Particulate Matter," Preprint, Symposium on Control of Tine Particulate Emissions from Industrial Sources, Joint U.S.-USSR Working Group, Stationay Source Air Pollution ControlTechnology, San Francisco, Calif, Jan. 15—18, 1974. 

E. A. Wolfe, Gas Flow Rate and Particulate Matter Determination of Gaseous Effluents, Bay Area Air Pollution Control District 1480, San Erancisco, Calif., 1961. 

Optimized modern dry scrubbing systems for incinerator gas cleaning are much more effective (and expensive) than their counterparts used so far for utility boiler flue gas cleaning. Brinckman and Maresca [ASME Med. Waste Symp. (1992)] describe the use of dry hydrated lime or sodium bicarbonate injection followed by membrane filtration as preferred treatment technology for control of acid gas and particulate matter emissions from modular medical waste incinerators, which have especially high dioxin emissions. 

Pollutant Formation and Control in Flames Key combustion-generated air pollutants include nitrogen oxides (NOJ, sulfur oxides (principally SO9), particulate matter, carbon monoxide, and unburned hydrocarbons. 

Fig. 4-3. Seasonal variation of suspended particulate matter concentration. Composite of 20 nonurban sites. United States. Source Pirtas, R., and Levin, H. ]. Air PoUut. Control Assoc. 21(6), 329-333, 1971.

In the production of clay, talc, cement, chalk, etc., an emission of particulate matter will usually accompany each process. These processes may involve grinding, drying, and sieving, which can be enclosed and controlled to prevent the emission of particles. In many cases, the recovered particles can be returned to the process for a net economic gain. 

The most widely used pulping process is the kraft process, as shown in Fig. 6-11, which results in recovery and regeneration of the chemicals. This occurs in the recovery furnace, which operates with both oxidizing and reducing zones. Emissions from such recovery furnaces include particulate matter, very odorous reduced sulfur compounds, and oxides of sulfur. If extensive and expensive control is not exercised over the kraft pulp process, the odors and aerosol emissions will affect a wide area. Odor complaints have been reported over 100 km away from these plants. A properly controlled and operated kraft plant will handle huge amounts of material and produce millions of kilograms of finished products per day, with little or no complaint regarding odor or particulate emissions. 

EPA is required to issue guidance on reasonably available control measures (RACM) and best available control measures (BACM) for other sources of particulate matter emissions. 

In the past, for many air pollution control situations, a change to a less polluting fuel offered the ideal solution to the problem. If a power plant was emitting large quantities of SO2 and fly ash, conversion to natural gas was cheaper than instaUing the necessary control equipment to reduce the pollutant emissions to the permitted values. If the drier at an asphalt plant was emitting 350 mg of particulate matter per standard cubic meter of effluent when fired with heavy oil of 4% ash, it was probable that a switch to either oil of a lower ash content or natural gas would allow the operation to meet an emission standard of 250 mg per standard cubic meter. 

List the similarities and differences of pollubon control systems for solid particulate matter and liquid droplets. 

ESPs), and some of the previously discussed novel devices. Series combinations of control devices may be necessary to achieve the required level of particulate matter emission. A commonly used system is a multiple cyclone followed by a fine-particle control system, such as a baghouse, scrubber, or ESP. 

Opacity reduction is the control of fine particulate matter less than 1 ixm). It can be accomplished through the application of the systems and devices discussed for control of particulate matter and by use of combustion control systems to reduce smoke and aerosol emission. In addition, operational practices such as continuous soot blowing and computerized fuel and air systems should be considered. 

Figure 30-lA presents the integrated environmental control potential for maximum control of particulate matter and SO2. Cooling tower water blowdown and treatment by-products may be used to satisfy scrubber makeup requirements. Fly ash and scrubber sludge will be produced separately. If the catalytic NO, process is required, the integration issues will be increased significantly. 

Figure 30-lC is distinctly different from the first two in the type of SO2 control processes used and the sequence of the particulate matter and SOj controls. It is a promising approach for up to 90% SO2 control of western United States coal, and there is a single waste product. Other features include the collection of particulate matter at temperatures below 90°C and the possibility for spray dryer cooling tower water integration. This. system may or may not include a catalytic NO unit. 

Air pollution control systems using wet scrubbers will remove some water-soluble gases, but the removal of particulate matter is the primary concern for a control system. The air pollution control system, therefore, is usually a single device such as a wet scrubber, small-diameter multiple cyclones, fabric filters, or ESPs. The multicyclones are the least expensive system and the ESPs the most expensive. 

Alfalfa dehydration is carried out in a direct-fired rotary dryer. The dried product is transported pneumatically to an air cooler and then to a collecting cyclone. The collected particles are ground or pelletized and then packaged for shipment. The major atmospheric emission from the process is particulate matter, which is controlled by baghouses. Odors may also be a problem, but they disperse rapidly and are no longer a problem at distances of over 1 km. 

Control of particulate matter emissions from the kilns, dryers, grinders, etc. is by means of standard devices and systems (1) multiple cyclones (80% efficiency), (2) ESPs (95% -I- efficiency), (3) multiple cyclones followed by ESPs (97.5% efficiency), and (4) baghouses (99.8% efficiency). 

Effective with the 1982 model year, particulate matter from diesel vehicles was regulated by the U.S. Environmental Protection Agency for the first time, at a level of 0.37 gm km . Diesel vehicles were allowed to meet an NO level of 0.93 gm km under an Environmental Protection Agency waiver. These standards were met by a combination of control systems, primarily exhaust gas recirculation and improvements in the combustion process. For the 1985 model year, the standards decreased to 0.12 gm of particulate matter per kilometer and 0.62 gm of NO per kilometer. This required the use of much more extensive control systems (1). The Clean Air Act Amendments of 1990 (2) have kept the emission standards at the 1985 model level with one exception diesel-fueled heavy trucks shall be required to meet an NO standard of 4.0 gm per brake horsepower hour. 

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