Dielectric response characteristics of coal’s sulfur-containing model compounds and theirs effects on the microwave desulfurization

In order to reveal the mechanism of microwave action in the process of coal microwave desulfurization,the dielectric property of coal’s sulfur-containing and sulfur-free model compounds,the change of dielectric properties for pure coals mixed with different proportions of sulfur-containing compounds were measured by the transmission reflec- tion method. Then the effect of dielectric properties of sulfur-containing compounds on their desulfurization rates by mi- crowaving was expounded. The results showed that the real part of dielectric constant ε′,imaginary part ε″ and loss tangent tan δ of sulfur-containing compounds are higher than those of sulfur-free compounds with similar struc- tures. Among of them,the ε″ and tan δ of the diphenyl disulfide,dibenzothiophene sulfone and diphenyl sulfone have their own characteristic peaks. Therefore,the selective heating of sulfur contents in coal could be realized by adjusting the microwave frequency. When the pure coal was loaded with sulfur-containing compounds,the ε′ of them usually changed drastically. However,subtle changes in the ε″ and tan δ were observed. The ε″ and tan δ of mixture appeared the obvious characteristic peaks of corresponding sulfur-containing model compounds. So the selective desulfurization of high organic sulfur coal could be realized by adjusting the microwave frequency. The desulfurization results sugges- ted that under the condition of microwave combined with oxidizing agent,the desulfurization rate of the sulfur ether are significantly higher than that of thiophene,and the ε″ and tan δ of former are also higher than those of latter. Disulfide is more easily removed by oxidation.