Influence of low pressure on mercury removal from coals via mild pyrolysis

Abstract

Anthropogenic Hg emission control has drawn worldwide attention along with enactments of strict legislation. In response to the need for mercury emission control from flue gases in coal combustion, studies have focused on mild pyrolysis as a promising technology for mercury removal before combustion. However, reaction pressure has not yet been studied, which might affect mercury removal in mild pyrolysis. In this paper, three types of powdery bituminous coal, Coals A-C, from the western plateau area of China, were studied. The core aim was to explore the effect of low reaction pressure on the efficiency of Hg removal. Data of the three coals under different pyrolysis pressures showed that reducing the pressure would improve the mercury removal rate and removal efficiency and that the effect was distinguished by coal type. The role of pyrolysis pressure in Hg removal was limited. When the residence time was long enough, the eventual Hg removal was dependent on the thermal decomposition temperature. These findings might be of some guidance for designing pyrolysis reactors. Furthermore, this article aims to provide some explanation about the mechanism and offer guidance for optimizing the technological parameters of Hg removal by mild pyrolysis.