Research Of Shanxi High Sulfur Coal Desulfurization With Microwave Irradiation

The using of high sulfur coal not only pollutes the environment, the remaining sulfur can also cause hot shortness in steel during coke making process. Development of an effective method to remove sulfur in coal has a great significance for China’s energy strategy.This investigation analyzed high sulfur coal samples collected from Shanxi, determined its sulfur occurrence state, and measured various forms of sulfur and their contents in the coal samples. The investigation used HAC and H2O2as oxidants and NaOH as extractant to desulfurizate coal samples by microwave irradiation. The effectiveness of desulfurization was evaluated by following factors:desulfurization mechanism by XRD and XPS; frequencies of microwave reaction for desulfurization; basic nature of model compounds by quantum mechanical calculations. The results of this investigation can provide support for industrial microwave desulfurization. The results of this investigation include:1.The sulfur-containing states found from the selected coal samples are:inorganic sulfur, thiols thioethers sulfur, thiophenes sulfur, sulfoxide and sulfone sulfur; raw coal particle size less than0.5mm and50ml HAC/H2O2mixture (1:1v/v);260W.2.Inorganic sulfur and thiols thioethers can be removed completely in the mixture of glacial acetic acid and hydrogen peroxide system under microwave irradiation. It is believed that part of thiophenes have been oxy-genated into thiophene sulfoxide and thiophene sulfone. Xinyang coal samples, particle size less than0.5mm, reached max desulfurization rate in HAC/H2O2mixture (1:1v/v) under260W and2450MHZ after15min microwave irradiation.3.When compared with the mixture of glacial acetic acid and hydrogen peroxide system, the result became less effective when NaOH solution is used as extractant. Significant amount of inorganic sulfur still left in coal samples and can partially remove thiophene and sulfones sulfur (sulfoxide), after analyzing and processing. Xinyang coal samples, particle size less than0.5mm, reached max desulfurization rate in300g/L NaOH solution under260W and2450MHZ after6min microwave irradiation.4.The desulfurization was not effective during directly microwave irradiation, but when the frequencies of840MHZ and915MHZ were used, desulfurization was more effective than that of2450MHZ.Under840MHZ microwave irradiation, organic sulfur in the coal sample changed, the content of mercaptan sulfide decreased and the content of thiophene increased.5.Simulation of chemistry quantum suggests that the C-S bond length appears to be longer in the model compound; the C-S bond length appears to be shorter than the branched chain of the C-S bond in the ring structure; the C-S bond order appears to be equal to the C-C bond order in the thiophene ring structure. Hence, the C-S bond in the thiophene ring structure cannot be broken easily; the S atoms of the model compound stretch larger in HOMO, S atoms lose electrons easily and become highly reactive.