The Organic Sulfur Transformation Of High Sulfur Coal During Microwave Irradiation

Coal is one of the most important energy in China.A large number of exploitation and utilization of high-quality coal in the recent years.The proportion of high-quality coal resource sharply declined.The middle and high sulfur coals account for the 33% of the total coal resource reserve in China.The organic sulfur in high sulfur coal accounts for the 30%~50% of the total sulfur content.Using the low quality high sulfur coal can relieve the energy security of our country.However,the organic sulfur in high sulfur coal is a complicated structure and differences in thermal stability.It is difficult to remove the sulfur from coal and severely limited its development and utilization.Microwave irradiation comes with bulk-heating,selectivity and penetrability,there are some potential advantages to develop microwave irradiation desulfurization technology for clean and effective utilization of high sulfur coal.In order to effectively control the emission of pollutants in the process of microwave irradiation high organic sulfur coal.The change and transformation mechanisms of high organic sulfur during microwave irradiation have been focused in this paper.The study mainly includes the several parts as following:(1)Two high organic sulfur coals(NTC and LGC)were selected as the original samples.In order to avoid effected by the inorganic sulfur,nitric acid was chosen to remove the inorganic sulfur.The changes of sulfur containing minerals and sulfur containing functional groups were analyzed.The FeS2 functional groups disappeared,the rest of sulfur containing functional groups and C,O,H containing functional groups had almost no changing.The structures of coal matrix would not be broken by nitric acid treatment.The rank of sulfur containing functional groups contents is S=O >-S-H >-S-S-> FeS2 in both two coals.The proportion of C-O functional groups in LGC is bigger than that in NTC.The O containing functional groups in both NTC and LGC are mainly-C-O,C=O?COOH.(2)The organic sulfur transformation behaviors during microwave irradiation was researched.Under microwave irradiation condition,a part of organic sulfur in coals transformed into gaseous sulfur,pyritic sulfur,the sulfate sulfur.The optimum conditions for NTC and LGC were obtained as 10-minutes irradiation time,1000 W irradiation power.The desulfurization rate of NTC was 6.31%,the desulfurization rate of LGC was 8.33%.The local temperature of S=O and-S-H functional groups raised by dielectric loss.Their content declined due to react with active oxygen and hydrogen to generate SO2 and H2 S.The content of-S-S-functional group kept invariant.The rank of three kinds of sulfur containing functional groups retention proportion is-S-S->-S-H >S=O.(3)The microwave irradiation was used to desulfurize the coals leached with different concentration ratio of NaOH and H2O2.The results showed that a part of organic sulfur in coals transformed into liquid sulfur,pyritic sulfur,sulfate sulfur and gaseous sulfur in the process of solvent assisted microwave irradiation.The optimum conditions for NTC was obtained as NaOH: H2O2 =1: 2,the desulfurization rate is 14.56%.The optimum conditions for LGC was obtained as NaOH: H2O2 =1: 4,the desulfurization rate is 23.03%.NaOH and H2O2 produced a synergistic effect,the desulfurization efficiency of NaOH and H2O2 synergistic effect is better than any one of them.Nonpolar-S-S-functional group can be dissolved by H2O2.The retention rate of-S-S-functional group is the lowest,when the NaOH: H2O2 = 1: 1,the retention proportion of NTC was 57.23%,the proportion of LGC was 19.68%.The rank of three kinds of sulfur containing functional groups retention proportion is S=O >-S-H >-S-Sin both two coals.