Kinetic and thermodynamic investigations of CO2 gasification of coal chars prepared via conventional and microwave pyrolysis

Peng Jiang,Ziyao Lu,Xiang Luo,Yang Meng,Tao Wu,Gang Yang,Kaiqi Shi,Lan Xu

doi:10.1007/s40789-020-00358-5

Abstract

This study examined an isothermal CO2 gasification of four chars prepared via two different methods, i.e., conventional and microwave-assisted pyrolysis, by the approach of thermogravimetric analysis. Physical, chemical, and structural behaviours of chars were examined using ultimate analysis, X-ray diffraction, and scanning electronic microscopy. Kinetic parameters were calculated by applying the shrinking unreacted core (SCM) and random pore (RPM) models. Moreover, char-CO2 gasification was further simulated by using Aspen Plus to investigate thermodynamic performances in terms of syngas composition and cold gas efficiency (CGE). The microwave-induced char has the largest C/H mass ratio and most ordered carbon structure, but the smallest gasification reactivity. Kinetic analysis indicates that the RPM is better for describing both gasification conversion and reaction rates of the studied chars, and the activation energies and pre-exponential factors varied in the range of 78.45–194.72 kJ/mol and 3.15–102,231.99 s−1, respectively. In addition, a compensation effect was noted during gasification. Finally, the microwave-derived char exhibits better thermodynamic performances than the conventional chars, with the highest CGE and CO molar concentration of 1.30% and 86.18%, respectively. Increasing the pyrolysis temperature, gasification temperature, and CO2-to-carbon molar ratio improved the CGE.

Highlights

Coal is a important energy resource and is currently responsible for approximately 70% of total energy consumption in China (Lan et al 2018; Zhu et al 2020)
This study examined an isothermal CO2 gasification of four chars prepared via two different methods, i.e., conventional and microwave-assisted pyrolysis, by the approach of thermogravimetric analysis
Char-CO2 gasification was further simulated by using Aspen Plus to investigate thermodynamic performances in terms of syngas composition and cold gas efficiency (CGE)

Summary

Introduction

Coal is a important energy resource and is currently responsible for approximately 70% of total energy consumption in China (Lan et al 2018; Zhu et al 2020). Microwave heating can produce rapid, volumetric, selective, noncontact heating of coal by directly converting electromagnetic energy into thermal energy (Parvez et al 2019). This is quite different from conventional heating mechanisms in which heat is transferred from the coal surface to the coal interior via conduction (Wu et al 2015). It was demonstrated that microwave pyrolysis showed more gaseous and less tar, high quality liquid fuels and more energy-efficient than conventional pyrolysis (Abdelsayed et al 2018; Reddy and Vinu 2016)

Methods

Results

Conclusion