Role of gas coal in sulfur regulation from the release behavior and mass transfer condition of volatiles

Abstract

There were new restrictions on sulfur regulation of high organic-sulfur coal (HOSC: A) brought by the differences in the pyrolysis characteristics of different gas coals (GC: B and C) and the mass transfer conditions of their volatiles. Firstly, the role of volatiles from GC in the sulfur regulation along vertical and horizontal directions was revealed by designing two stacking modes in a cylindrical crucible and using the parallel and cylindrical baffles to block the volatiles’ migration. Secondly, the different performances of volatiles from two different GC on the sulfur regulation were associated with their volatiles’ release behaviors. And finally, the effect of mass transfer conditions of volatiles on the sulfur regulation was discussed and reflected in the sulfur spatial distribution in chars. Contrast experiments with or without parallel and cylindrical baffles indicated that the monodirectional migration of volatiles from GC helped reduce the sulfur contents along both vertical and horizontal directions. The maximum distances of effective sulfur removal by volatiles from GC along vertical and horizontal directions varied respectively within 5 ∼ 15 and 8 ∼ 15 mm as changing GC. The performance of different GC in sulfur removal depended on the good match of its intensive volatiles release to the high permeability of HOSC and the continuous supply of hydrogen-rich volatiles. The effective distance of bi-directional vertical migration of volatiles was shortened to 3 ∼ 6 mm. It was promising to use the effective distance of sulfur removal by volatiles migrating vertically to evaluate the potential of GC as a sulfur regulator. The bi-directional migration of volatiles from GC helped extend the effective distance in the horizontal direction (>15 mm), which was related to the temperature gradient. The proper temperature gradient helped the volatiles of GC spontaneously or forcedly complement the hydrogen-rich volatiles in the HOSC layer. The temperature gradient is promising to maximize the potential of GC as a sulfur regulator and break the limits on sulfur removal by GC’s volatiles.