Evaluation and mechanism of ultrasound-assisted electrochemical desulfurization using citric acid as the electrolyte solution

Abstract

ABSTRACT Achieving the clean utilization of coal is the priority of the coal industries. This paper proposed an efficient electrochemical technology for coal desulfurization before combustion. It was explored that citric acid can chemically provide enough acidic conditions for desulfurization reactions, and the ultrasonic-enhanced treatment physically helps to remove sulfur from coal due to its cavitation effect and mechanical effect. So the experiments of ultrasound-assisted electrochemical desulfurization using citric acid as the electrolyte solution were conducted. They combined physical and chemical methods to effectively remove sulfur from coal. The optimal operating parameters of the desulfurization effect were achieved by qualitative and quantitative analysis of coal samples(coal slurry concentration of 66 g/L, electrolysis time of 8 h, electrolyte concentration of 1.5 mol/L, electrolysis voltage of 4 V, electrolysis temperature of 30°C, ultrasonic strengthening time of 1 h and ultrasonic intensity of 320 W.). The total sulfur removal efficiency reached 45.09%. The electrolytic desulfurization experiments removed samples’ sulfur contents, ash contents, and water. The crystal structures of gypsum, white iron ore, zinc sulfide, and the molybdenite mineral composition were also destroyed for purification. Gaussian simulations showed that C-S bonds and S-S bonds contained in non-thiophene organic sulfur are easier to remove, and S-S bonds are more likely to break than C-S bonds. This study realized the promotion of desulfurization with the ultrasonic wave and citric acid solution. It provides a new idea of synergistic desulfurization and is beneficial to reduce atmospheric sulfur pollution.