New Generation Technology – Hot Gas Filters for Simultaneous Removal of Particulate Matter, So and No in the Steel Industry

by Manfred Salinger, Steffen Heidenreich, Manfred Nacken

Publisher - Pall GmbH, Pall Filtersystems GmbHM

Category - General Novel

Ceramic hot gas filter systems have been successfully used in many applications worldwide to assist with environmental management challenges. More stringent emission limits for particulate matter, SOx and NOx, are in conflict with increasing pressure to reduce the flue gas cleaning costs. A new, cost-effective blowback filter system that removes the particulate matter and NOx simultaneously is presented. The core of this new technology resides in the catalytic filter that combines both cleaning steps, filtration and catalysis, in a single unit. Existing technology includes two-step flue gas cleaning processes consisting of a particle filter with a subsequent low-dust selective catalytic reduction (SCR) catalyst unit, or a high dust SCR catalyst unit with a subsequent particle filter. Both technologies have disadvantages from a process engineering point of view. In the first variant, the flue gas has to be reheated up to the catalyst operating temperature of 300°C. In the second variant, the catalyst quickly deactivates by the deposition of particles. By combining the filtration and catalysis steps, a single catalytic filtration unit becomes the most economically viable solution with respect to the capital cost, operating costs and operating stability and flexibility. The catalytic filter is a hot gas filter equipped with catalytic filter elements and designed for a catalyst operating temperature of 300°C. The catalytic filter elements are catalytically activated ceramic hot gas filter elements consisting of SiC, which provide a highly efficient particle separation by means of a fine filtering outer membrane. If the catalytic filter is combined with the injection of sorbents into the flue gas stream upstream of the filter, SOx can be removed in addition to particle and NOx removal. NO conversion as a function of the reaction temperature at different NO inlet concentrations and filtration velocities is presented. Optimal catalytic performance of the catalytic filter is achieved when the temperature is adjusted between 280 and 320°C.

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