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The control of emissions of sulphur compounds during the treatment of blast furnace slag

Procedures are being developed for avoiding gaseous sulphur emissions during slag granulation. Emission data were compiled and analysed with regard to formation of gaseous sulphur compounds during slag granulation, mass transport in the plant and mass transport during steam condensation. This was followed by designing a laboratory scale transparent hot model of a slag granulation plant. Optimal conditions for steam suction and condensation were determined. Operational measurements verified these data resulting in a reduced suction of air leak. Further, the influence of granulation and condensation water flow on gaseous sulphur constituents removal was determined. The remaining exhaust air from the condensing tower had to be treated by absorption. A newly designed test scrubber for removal of hydrogen sulphide was built and put into operation. The absorption of gaseous sulphur constituents was examined for different operating conditions. Drop in pressure was determined in the test scrubber and a drop separator was chosen. An examination of the effects of washing water circulation on absorption were carried out, based on theoretical examinations and a new designed concept for washing water circulation was then realized. Absorption of gaseous sulphur constituents was examined during washing water circulation by industrial tests. Additionally, the sulphide concentration in the washing water circulation was determined, confirming the concept for washing water circulation. It was found that a sub-volume must be removed from the washing water circuit as washing waste for deelutriation. Treatment of washing waste water is necessary before its delivery. Optimal operation parameters were found and water, energy and sulphur balances were drawn up. Operating parameters have to be found for each operational slag granulation plant but they have to be examined periodically. An optimum operation of the plant will be reached for scrubber and washing waste water treatment involving measuring and regulation techniques.

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