Coal washing at Tata Steel - some R&D efforts

摘要

Coal beneficiation plays an important role in the overall economics of iron and steel making at Tata Steel. High raw coal ash in its captive collieries at West Bokaro and Jharia has necessitated the setting up of coal washing facilities at these locations. At present, about 2.4 Mtpa of clean coal at 17 percent ash is produced from these washeries. To improve the performance of these washeries, research and development activities were undertaken. Optimisation of DM cyclone geometry and plant feed rate have resulted in an increase in clean coal yield. Further improvement in the DM cyclone performance has been achieved by using a dispersant for controlling the viscosity' of the dense media. Efforts have also been made to use the magnetic fraction of blast furnace flue dust (a waste material), as an alternative to magnetite, used as dense media in the coal wash cries. As an alternative to be DM cyclone, a Vorsyl separator has been successfully tested. Studies have also been conducted to imp rove the performance of the fine coal beneficiation circuit. Performance of the flotation cells has been imp roved and the cost of the frother has been reduced by replacing pine oil with a synthetic frother Two-stage reagent addition, instead of single stage, has been explored for further improvement. Efforts have also been made to recover carbon values from the flotation tailings. The amenability of column flotation for treating the tailings has been established on a pilot scale. To reduce the moisture of the clean coal, use of surfactants as dewatering aid has proved successful. Studies have also been carried out to develop a strategy for modernization of the Jamadoba washery by incorporating spirals for treating the intermediate size fraction (-2+0.25 mm).