Use of a hybrid filter in a basic oxygen steel plant.

Objective. The basic oxygen steel plant of Krupp Hoesch Stahl AG in Dortmund-Horde has a primary and a secondary off-gas collection and dedusting system. The secondary dedusting system has been modernised to improve the level of pollution control. It is the first time that ''hybrid filter'' technology has been used in this respect in a steel plant of this magnitude. Documented in the following are the results that have been achieved. Summary. The hybrid filter differs from wet-type electrostatic precipitators in that only the dust collecting electrodes are continually wet with a film of running water. If an adequate distribution of water and an almost identical pressure ratio on both sides of the flexible collecting electrodes are ensured, then the new filter system fulfills the requirements in hand better than conventional equipment of this type. It has been possible, for example, to reduce the residual dust content in the cleaned gas by an average of 70%. Furthermore, within the scope of the structural and technical measures, the noise level has been decreased and the diffuse fuse dust emissions lessened by an increased volumetric now rate during extraction. It has also been possible to reduce the number of safety-related filter shutdowns from once or twice per day to approximately once per month.