Abstract for presentation at Chemeca 2007

Coal desulfurization prior to usage is a necessary preprocessing in order to achieve clean fuel and avoid environmental impacts such as acid rain. Desulfurization of Tabas Mezino coal was conducted with two consecutive steps of froth flotation at ambient temperature followed by leaching at various conditions. In this research, reducing the ash content of Mezino coal by 35.71wt% and its total sulfur content by 36.93% using froth flotation process was successful. HCl and HNO3 were used, separately, to leach the floated coal, and the effectiveness of each acid on Mezino coal desulfurization was investigated. Nitric acid was found to be much more effective than HCl and the effects of reaction time, acid concentration and temperatures as well as stirring speed were studied as major parameters in the nitric leaching process. Taguchi orthogonal experiment with the above mentioned parameter elements; one at three levels was used to optimize the experiment parameters by the analysis of variances. Applying of the Taguchi technique significantly reduced the time and cost required for the experimental investigation. The findings indicated that acid concentration, with a high contribution, had the most dominant effect on desulfurization performance, followed by temperature, stirring speed and time. The total sulfur and ash removal after flotation and leaching at optimum conditions reached to 75.36 and 53.21% respectively that is an unprecedented and welcome result compared to the previous works.