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IEE - Environmental Info. Page 4 of 8 such as baffles and perforated walls, which cause the exhaust gases to twist, turn, change directions and squeeze their way through the passages in the system. This forces the exhaust gases to mix thoroughly with the oxygen introduced into the system, while exposing them to the temperatures maintained in the afterchamber. As with temperature, too much turbulence can cause other problems. Some of these problems are overheating of the cremation chamber and the puffing of smoke out of the charging door at the entrance to the cremation chamber. Controlling Controlling usually refers to the ability of a device to measure process variable (temperature, opacity, CO3 02) compare it to a desired setpoint specified by the operator, and take action to maintain the setpoint. The device can automatically perform the action, such as adjusting a valve position, as necessary to alter the equipments operation. These devices often display the selected set point as well as the actual level of the process variable. More sophisticated control equipment may also have the ability to record on paper the action being taken to maintain the process variable, and send this information to a computer and printer. Wet Scrubbers A wet scrubber is an add-on pollution control device attached to the cremator exhaust stack. It is similar to a large shower with an entrance and an exit. Exhaust gases from the cremator are dUCted into the wet scrubber, where they are subjected to water sprayed from different directions by several nozzles. Water droplets capture the particles or solids in the exhaust stream. When the droplets fall to the bottom of the scrubber, they are drained out. Often the scrubber drain water is taken to a settling or recirculation tank, where the heaviest particulate matter settles out as sediment. The sediment i� disposed of in accordance with local regulations. Sometimes the water is reused (because of expense) after being PH-treated to reduce corrosiveness. In other instances, the scrubber water is not reused and is simply drained to the sewer. Wet scrubbers are not commonly found on cremation equipment because their pollution-reducing benefits do not offset their prohibitive cost ($30,000 to $60,000). Bag Houses A bag house is another type of add-on pollution control device. It is usually a large metal box, with an entrance and an exit, through which the exhaust gases are directed. Inside the box are filter bags of different sizes. Often these bags have shaker arms attached; when the bags become dirty, the shaker arms can be rattled and the heavy particulate matter that collects on the bags will fall out into a collection hopper at the bottom of the box. Although bag houses appear to be effective in reducing particulate output, the exhaust must be substantially cooled (to before 500°F) prior to its entrance into the bag house. Otherwise, the filter bags become so hot they ignite, which renders then ineffective and adds to pollutant output. Bag houses have been required in the United States on only a few occasions; their success has been minimal, at best. Ambient Dust Collectors Ambient dust collectors are devices used to minimize operator exposure to dust. Like small bag houses, they have an entrance and exit to the collector and internal filters. Both stationary and portable models are convenient for use in a typical workplace. Since they are not part of the cremation equipment, they are not exposed to high temperature and can be effective in protecting the operator. Air Pollution Permits http://wwwaeeco.com/environ2.htm 06/21/2001