AIR POLLUTION CONTROL SYSTEM UPGRADE AT TUBATSE FERROCHROME

Three electric arc furnaces (EAFs) were constructed by Union Carbide at Tubatse Ferrochrome (TFC) in 1975. This plant was expanded to four furnaces at the East Plant in 1985 and the gas cleaning system was enlarged without taking flow dynamics into consideration. In order to improve competitiveness, TFC has increased furnace capacity, partially substituted coal for coke, and changed the charge mix. These changes increase the heat and dust load into the air pollution con-trol (APC) system. TFC embarked on a project to improve the APC capacity by: • Quantifying the required off-gas capacity • Optimising the aerodynamic flow through the system by means of Computational Fluid Dynamics (CFD) • Converting the old Brandt Koyo top entry baghouses to bottom entry • Upgrading the cleaning system • Installing Gore-tex ® ePTFE membrane filter bags The estimation of required off-gas capacity is traditionally done by rule-of-thumb methods such as specific extraction. A more elegant evaluation method was developed for simulating the effects of changes in charge mix on the furnace reaction gas volume and the APC system. Reaction gases are calculated by modelling the reactions taking place in the furnace and off-gas volumes are compared to both fan and baghouse capacity. This enables identification of bottle-necks in the off-gas system. CFD techniques were utilized to evaluate ge-ometric imbalances and propose solutions to ensure optimal use of off-gas capacity. The system modifications were completed over several months and the modified equipment went into service in May 2006. 1