Structural Characteristics of Lignite Char from Different Pyrolysis Reactors and the Influence on Their Gasification Reactivity

Abstract

The gasification reactivity of coal char is affected by numerous experimental variables, and char structure is one of the dominant factors. In this work, Raman spectroscopy, powder X-ray diffraction (XRD), and N2 adsorption were used to investigate the physical and chemical structure of char prepared under different pyrolysis conditions. Three kinds of pyrolysis reactors, fluidizedbed reactor (FL), entrained-flow-bed reactor (EF), and fixed-bed reactor (PT), were designed and used to prepare the char samples. Lignite was pyrolyzed in a fixed-bed reactor with a heating rate of 10 ºC min-1, and the final temperature was 1000 ºC. The gasification reactivity of char was characterized in a quartz fixed-bed reactor under CO2, H2O, and their mixtures at 750 ºC. FB reactor produces chars with a smaller interlayer spacing of aromatic layers (d002), and FL reactor produces chars with a larger mean crystallite size along the c-axis (Lc) and aromaticity (ƒa) but inhibits the growth of mean crystallite size along the a-axis (La). The content of small aromatic rings, which is higher in the FL reactor, positively affects the initial intrinsic reactivity.

Recent Progress on Hydrogen-Rich Syngas Production from Coal Gasification

“…The Ca-induced coal char exhibits better gasification performance owing to the Ca species facilitating the decomposition of ether and carbonyl groups; the char with Si and Al has the lowest number of active sites, resulting in poor gasification reactivity. The influence of structural characteristics of lignite coal on gasification reactivity was investigated by Zhang et al [138], finding that the content of small aromatic rings positively initializes the intrinsic reactivity. Kim et al [139] carried out investigations experimentally to study the effects of particle size and coal type on the CO 2 gasification of char prepared from 12 kinds of bituminous coal.…”