High voltage pulse-enabled coal desulfurization and deashing – Part 1: Selective breakdown of mineral matter

Abstract

Coal desulfurization and deashing are the common challenges that the coal industry worldwide is facing. A new technique is presented in this paper using high voltage pulse (HVP) selective breakdown of mineral matter that exhibits higher electric conductivity/permittivity than coal, followed by size-based separation to reject the pyritic sulfur-bearing and ash-bearing mineral matter. Part1 of this study demonstrates HVP selective breakdown of mineral matter, and Part 2 reports the optimization of the HVP treatment to minimize coal loss during the coal desulfurization and deashing process. Two coal samples, one bituminous and one anthracite, were collected from two coal mines in China and used to assess the viability of this new HVP technique for the coal industry. In the paired-particle tests with one low-density (<1.47 RD) particle and one high-density (greater than1.77 RD) particle in each batch subjected to one HVP discharge, over 75% of probabilities were observed that the high-density particles broken and the low-density particles remained intact, resulting in distinct product size distributions of the two density groups. In the multi-particle tests to treat the as-received Coal B sample without prior density-fractionation, the particles remaining on the parent size fraction (19–26.5 mm feed) after HVP treatment contained 0.49% sulfur, 13.4% ash, and 87.6% carbon, changing from 1.92% sulfur, 30.1% ash, and 78.5% carbon contents in the feed. The HVP treatment with <1 kWh/t specific energy (spark) resulted in 89.8% sulfur, 82.2% ash, and 55.6% carbon reporting to the −19 mm stream.