Rapid desulfurization of CWS via ultrasonic enhanced metal boron hydridesreduction under ambient conditions

Abstract

The present work investigated a rapid desulfurization method for industrial coal water slurry (CWS) using ultrasound-assisted metal boron hydrides (NaBH₄, KBH₄) reduction. Under ambient pressure and temperature conditions of ultrasonic time (10 min), ultrasonic frequency (20 KHz), deoxidizer concentration (10 mM), CWS concentration (60 g L⁻¹) and coal particle size (≤ 120 mesh), the desulfurization efficiency of CWS can reach about 42% (NaBH₄) and 45% (KBH₄), respectively. On addition of Ni²⁺ catalyst (1 mM), the desulfurization efficiency, up to a maximum value of 57%, was significantly improved. Meanwhile, the nitrogen reduction (N) of CWS was reduced by 11.5%. The decrease of S and N greatly cut down SO_x and NO_x emissions from CWS combustion. After the processing, the ash content and volatile matter were decreased contributing to the slight improvement of combustion characteristics.