Operating Results of Exhaust Gas Desulfurization Plant at Nippon Kokan's Fertilizer Division (Koyasu Works)

Abstract

Exhaust gas from the Lurgi type contact sulfuric acid plant is treated by a desulfurizing plant based on the lime-qygsum process in the Koyasu Works, Fertilizer Division, Nippon, Kokan. The exhaust gas, discharged in an amount of approximately 60, 000 Nm3/hr contains sulfur oxides consisting of 2, 000-3, 000 ppm of SO2 and about 400 ppm of SO3, which decreases to less than 300 ppm after treatment. This exhaust gas desulfurizer, installed in July 1964, has an object to convert SO2 absorbed by lime milk into calcium sulfite and to obtain high quality gypsum through air oxidation. Initial difficulties in operation caused by the trouble in treating slurry were solved by the modifications and improvements made in the plant and the operating practices, and in January 1966, the plant was successfully brought into continuous operation under stable conditions. Further improvements in facilities and automation have been made in an attempt to save labor.With a view to developing the exhaust gas desulfurization process applicable to ordinary emissions, a pilot plant of 2, 000Nm3/hr based on the use of boiler exhaust gas was constructed in the Koyasu works with reference to the exhaust gas desulfurizing technique and the experience acquired in operating this sulfuric acid plant. Experiments were started in October 1971, and the results permitted establishment of a exhaust gas desulfurizing technique applicable to ordinary exhaust gas.