Fractal desulfurization kinetics of high-sulfur coal

The pore structure characteristics of high-sulfur coal from Wansheng in Chongqing have been studied by a nitrogen adsorption method (BET). The effects of grinding and pre-treating with nitric acid on the inorganic sulfur content of coal have been investigated. Organic sulfur in coal pretreated with nitric acid was desulfurized by using propylene-glycol–KOH (PG–KOH). Fractal kinetic properties of these two desulfurization procedures were investigated by using fractal geometric theory. The results show that both the specific surface area and pore volume increased with the decrease in particle diameter. The microspore surface of coal had fractal characteristics; the fractal dimension was 2.48. The sulfur content decreased with the decrease in particle diameter by grinding. After pretreatment with nitric acid, the desulfurization ratio (DFR) of inorganic sulfur increased to over 99% and the DFR of total sulfur to over 70%. The desulfurization procedure of inorganic sulfur had fractal kinetic characteristics; its reactive fractal dimension was 2.94. The organic sulfur desulfurization procedure by PG–KOH was also tallied with fractal kinetic properties; the reactive fractal dimension was 2.57. The effect of temperature on the desulfurization ratio of organic sulfur can be described with an Arrhenius empirical equation. The rate constant, pre-exponential factor and the activation energy of the reaction increased with the decrease in particle diameter.