Physical and physicochemical cleaning of lignite and the effect of cleaning on biodesulfurization

In this work, physical, physicochemical and biological processes were combined to decrease the sulfur and ash content of finely ground coal. Two separation methods – flotation and a multigravity separator (MGS) – were studied to determine the optimum conditions of separation. The results showed that it is possible to obtain clean lignite that contains 34.36% ash and has a 77.39% combustible recovery by using MGS and 39.22% ash with a 37.38% combustible recovery by using flotation techniques. When the MGS and flotation products were treated by biological methods, the total sulfur contents of lignite were reduced by 54.39% and 47.08%, respectively, whereas the ash contents of MGS and flotation product were decreased by 67.61% and 60.95%, respectively.