Influence of Reactant Atmospheres and Temperature on Mechanism of Gasification of Coal Char Derived from Lignite

Abstract

The structural characteristics and reactivity of char derived from lignite were studied to explore the mechanism of char gasification and existence of a maximum reaction rate under an atmosphere of CO2 and H2O in a pressured thermogravimetric analyzer system. Gasification was carried out at temperatures of 1123, 1173, and 1223 K. When the temperature was below 1173 K, the mechanism of char gasification in the mixture of H2O and CO2 proceeded through the separate active sites assumption, whereas if the temperature was higher than 1173 K, it favored common active sites. The reaction rate increased and then decreased during the remaining time, which was in agreement with the total surface area. The existence of a maximum reaction rate depended highly on the surface area: a larger surface area resulted in a higher reaction rate. The total surface in H2O was the largest and the addition of CO2 inhibited the formation of pores. The reaction of char with CO2 mainly took place on the microporous surface first, and then took place on a mesoporous surface, and the reaction of char with H2O took place on both the micro‐ and mesoporous surfaces simultaneously.

Techno‐economic analysis of novel power generation system based on coal partial gasification technology

“…When the carbon conversion reaches ~82.5%, the efficiency is the maximum. According to mechanism of coal conversion process, coal gasification is a two‐step process, including pyrolysis and char gasification . In the pyrolysis process, volatile components of coal are released and the reaction rate is fast.…”

Characteristics of Coal Partial Gasification on a Circulating Fluidized Bed Reactor

“…It is also proved the point that the reaction rate increases and then decreases in the coal gasification, which is stated in the literature. 7,13 A conclusion can be drawn that, when the oxygen/coal ratio is 0.54, the performance of the coal partial gasification is relatively appropriate. In the case of the gas composition, the volume fractions of CO and H 2 decrease by ∼5 and ∼10%, respectively, while the volume fraction of CO 2 increases by ∼14% as the oxygen/coal ratio increases, which could account for combustible gas combustion.…”

“…As the existed literature reports, the reaction rate first increases and then decreases as the reaction proceeds. 7 The coal would become more ordered as the activated part is consumed generally by testing the variation of the functional group of coal by Zhang et al 8 The single conversion of coal is not more suitable for the modern economic and environmental development. On the basis of the property of the coal gasification, the coal partial gasification technology is proposed.…”

Impacts of char structure evolution and inherent alkali and alkaline earth metallic species catalysis on reactivity during the coal char gasification with CO2 /H2 O

“…Valdés et al studied the impact of the atmosphere on the properties of coal pyrolysis products and found that compared with the N 2 atmosphere, the char obtained in the CO 2 atmosphere has a larger specific surface area because of intraparticle side reactions. Ye et al reported that the highest total surface area of the char was obtained under H 2 O atmosphere and the presence of CO 2 during the gasification of coal char is unfavorable for the formation of pores. Huang et al discovered that the CO 2 gasification process primarily produces micropores with the pore sizes mostly ranging from 0.4 to 0.9 nm, while during H 2 O gasification, the micropores are produced at the beginning, and then, the mesopores are developed.…”