Steam gasification of yak manure: Kinetic modeling by a sequential and coupling method. (1st December 2022)

• Record Type: Journal Article
• Authors: Fu, Zhufu; Xue, Yuan; Li, Jian; Yan, Beibei; Han, Zixi; Chen, Guanyi
• Is Part Of: Fuel. Volume 329(2022)
• Publication Date: 2022-12-01
• Subjects: Yak manure -- Steam gasification -- Kinetic analysis -- Waste management -- Renewable energy; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.125464
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Steam gasification of yak manure produces hydrogen-rich gas (greater than 50 %). The process consists of pyrolysis, char-condensation and steam-solid reaction. The activation energies of the three stages are 175, 215 and 307 kJ/mol. The presence of steam slightly inhibited the pyrolysis reaction. Temperature and steam improved the gas–solid reactions through WGS reaction. Abstract: Considering yak manure's low moisture and biomass-rich properties, steam gasification to produce hydrogen-rich gas provides a feasible approach for waste management and energy usage, which is important in Tibet regions. Prior to large-scale application, kinetic study of the multi-stage thermochemical process is necessary for mechanistic understanding and process design. By employing a sequential and coupling method, a comprehensive kinetic model was built to elucidate reaction mechanisms of each stage, and key kinetic parameters were obtained with the help of Flynn-Wall-Ozawa (FWO)/Kissinger-Akahira-Sunose (KAS), Coats-Redfern (CR)/Kissinger and distributed activation energy model (DAEM) methods. The effects of steam concentration and heating rate on mass loss behavior and gaseous product evolution were examined. During the thermal decomposition, the presence of steam slightly inhibited the pyrolysis reaction, and significantly improved the gas–solid reactions when steam concentration was over 20 %. For pyrolysis stage, the activation energy associated was around 175 kJ/mol. For gas–solid reaction stage, parallel reactions including both char condensation (215 kJ/mol) and steam-char reaction (307 kJ/mol) were confirmed by DAEM modelling. Based on Thermal Gravimetric Analysis (TGA) study, investigation of yak manure steam gasification to produce hydrogen-rich gases was further conducted in a semi-batch reactor by changing temperature and steam flow rate. It was found that the increase of temperature greatly promoted tar cracking and gas–solid reactions. Temperature and steam flow rate exerted positive impacts to increased hydrogen concentration of dry gas through enhanced water–gas shift reactions.