The Effects of Ca(OH)<sub>2</sub> on the Steam Gasification Process of Acid-Washed and Raw Lignite

Abstract

The effect of Ca (OH)2 prepared by the wet-mixing method on acid-washed and raw lignite steam gasification process at 800°C were analyzed in a spout-fluid bed reactor. The addition of Ca (OH)2 on acid-washed lignite obviously increased the coal conversion, gas yield and reduced the tar yield, and the Ca (OH)2 addition on raw lignite significantly reduced the tar yield but just slightly increased the coal conversion and gas yield. As a catalyst, Ca (OH)2 can promote the tar steam reforming in the gasification process. Based on GC-MS data, it can be deduced that Ca (OH)2 has different catalytic activity on the steam reforming of tar with different molecular structures. Aliphatic hydrocarbons, Class 2 and Class 5 tars were clearly catalytic reformed, while the concentration of Class 4 tars increased. The CO concentration decreased and the CO2 and H2 concentration increased with the addition of Ca (OH)2 on both acid-washed and raw lignites, which was mainly caused by the catalytic effect of Ca (OH)2 on WGS reaction. The effect of Ca (OH)2 addition on acid-washed lignite was more significant than on raw lignite, and no adsorption of CO2 was detected in the process by using active carbon as a model compound.