Pollution Engineering - March 2009 - (Page 33)

Thermal Oxidizers “ Above is an example of the Flexeramic ceramic heat exchange material supplied by Koch Knight. Owners of thermal oxidizers have a number of options available when installing a new system or replacing the media bed of an existing system. types of random packing, the saddle shape minimized pressure drop (for lower electricity consumption by the induction fan) and maximized surface area (for higher heat transfer efficiency). Over the years, RTO media suppliers have refined the design of ceramic saddles. Modern saddles provide a high open area and aerodynamic design that limits nesting and reduces pressure drop by 20 percent from older media. Several manufacturers coat or impregnate today's saddle with a metal catalyst for use in RCOs. Saddle packing is also available in a glaze resistant alumina to resist exposure to alkaline chemical attack, which may result from cleaning chemical fumes or the metallic salts used in electroplating applications. Monolith structured block. Another alternative media design for very clean, low particulate streams is the imported Cordierite ceramic honeycomb monolith. Monolith block is a form of structured packing that is placed in a formal arrangement, rather than randomly dumped. Cells extend through the ” Upstream particulate removal Although oxidizer systems are primarily used for the abatement of VOCs, all emission streams contain some quantity of particulate matter, and these particles can lead to bed fouling, performance degradation, or even to dangerous and destructive fires. Some methods of upstream particulate removal methods include cascade (water wash), baffle and media filtration. Others, such as wet or dry electrostatic precipitators (ESP) or cyclone dust collectors, can reduce, but not eliminate particulate matter entering the RTO. This is because of so-called “dead zones,” which, as they grow, reduce the surface area exposed to the air stream and result in less media mass available to retain heat energy. Moreover, buildup of particulate presents a serious fire hazard. The only remediation solution for these symptoms is wash or bake out the material from the media bed, processes that involve costly downtime. Over time, the frequency of these cleaning procedures typically increases until the only viable solution is a complete media change-out. Types of media Over the past few decades, several different types of heat transfer media have been used for RTOs. Three main categories are random packing, monolithic structured block and corrugated structure packing. Random packing. Originally, in the 1970s, a variety of random packing materials were employed in RTOs, including gravel, ceramic balls and shapes of all kinds. The packing material was randomly dumped into the RTO to form a media bed. Random arrangement was preferred in order to prevent nesting that would constrict flow and cause dead areas that collected particulate. In the 1980s, RTO manufacturers and owners discovered that the ceramic saddles developed for chemical mass transfer operations provided an optimal shape for RTO random packing. Relative to other Impact of particulate buildup Particulate that penetrates deeper into the media bed will tend to burn off. However, chemically reactive particles can cause problems, even when they penetrate deep into the media. A portion of the particulate that enters the RTO will collect on the cold face of the media bed. Depending on the design of the media, the particulate buildup can rapidly lead to plugging the media bed. Plugging causes several significant problems. Blocking airflow results in a rise in pressure drop, forcing the induced draft fan to work harder and consume more electricity. The capacity of the RTO is reduced, as the media bed becomes less effective at transferring heat. Thermo Fisher Scientiﬁc The new Thermo Scientiﬁc Multi-gas Analyzer, Mod el 60i, is the on ly factory designed NDIR multi-gas analy zer with built in safegua rds against moi sture damage. For m ore informatio n call (866) 520-0430 or visit us on th e web. www.thermo.co m/aqi MARCH2009 www.pollutionengineering.com 33 http://www.pollutionengineering.com

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Pollution Engineering - March 2009 Contents The Editor’s Desk EnviroNews PE Events Legal Lookout Green Connections Get Ready to Count Carbon Getting Rid of Foreign Oil Green Goes Underground Thermal Oxidizers Ocean-Front Remediation Pumps, Pipes and Valve Products Air Monitoring Equipment PE Products Classified Marketplace Advertisers Index State Rules

Pollution Engineering - March 2009

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