Dielectric properties of organic sulfur components and application in coal microwave desulfurization

Abstract

ABSTRACT Changes in the dielectric properties of benzene mercaptan, benzene sulfide, and dibenzothiophene at 915 MHz frequency within 20 °C–100°C was studied for the first time. Coal-like substances were prepared by loading the compounds onto low-sulfur coal, and desulfurization test was performed under the microwave condition of 915 MHz and microwave – HCOOH–H2O2 system. The desulfurization reaction path and mechanism were summarized, and the relationship between the dielectric properties of organic sulfur and desulfurization efficiency was established. Results showed that the microwave-absorption ability of dibenzothiophene was weaker than that of benzene mercaptan and phenyl sulfide, and its dielectric properties changed irregularly with temperature. Dibenzothiophene cannot be removed by microwave radiation. Benzene mercaptan and phenyl sulfide had the highest efficiency of absorbing microwave energy and converting it into heat energy at 60°C. Moreover, they have the highest microwave desulfurization rate of up to 14%. In the microwave – HCOOH–H2O2 oxidation system, the highest desulfurization rates of phenyl sulfide occurred at 100°C because water-soluble products (such as sulfonate and sulfate) increased in the oxidation products. However, phenyl sulfide still had the highest desulfurization efficiency at 60°C. The desulfurization rates at 60°C and 100°C were 38% and 51%, respectively.