Session: 12-02: Hydrogen Energy, Alternative Fuels, Bioenergy, and Biofuels

Paper Number: 130362

130362 - Performance Study of Biomass Pyrolysis, Char Gasification and Oxy-Fuel Combustion Integrated System 

Abstract: 

To study the technical feasibility of integrating biomass pyrolysis, char gasification and oxy-fuel combustion, Aspen Plus was applied to evaluate the performance of different systems. Three technical routes were proposed that oxy-fuel combustion is coupled with biomass pyrolysis and char gasification in “Route 1” and “Route 2”, which aims to recover high-temperature flue gas by char gasification, while oxy-fuel combustion is only coupled with biomass pyrolysis in “Route 3”. Besides, all syngas from char gasification is used as alternative fuel to NG in oxy-fuel furnace in “Route 1”, while syngas is even mixed with pyrolysis gas in “Route 2”. The energy saving and fossil CO₂ emissions were compared for different technical routes, and the economic evaluation was performed. Two feedstock types (reed straw or municipal solid waste, MSW) were chosen here. The results indicate that more NG consumption is saved in “Route 2”, while the flue gas flow rate will also increase. Due to the poor quality of MSW, the waste char gasification temperature is 10% lower than that of biochar, and the combustible gas content (CO+H₂) in syngas from waste char gasification is also lower than that from biochar gasification by 18% under the same feedstock input (1t/h) and same flue gas recycle ratio (10% or 20%). Biomass is more advantageous in reducing fossil CO₂ emissions than MSW whatever technical route is chosen. Especially in “Route 2-Bio”, the fossil CO₂ emissions decrease by 95% to the “Normal” case. When taking MSW as feedstock, there are some differences in the results. As estimated, MSW in China typically contains 15% fossil carbon and 85% biogenic carbon. Compared with “Route 1”, there is less fossil carbon from NG, while more fossil carbon from feedstock input in “Route 2”. Hence, the fossil CO₂ emissions in “Route 2-MSW” are comparable to those in “Route 1-MSW”, which decrease by 52% to the “Normal” case. Without taking CO₂ tax into account, if MSW is used as feedstock, the OPEX costs of different technical routes are saved compared to the “Normal” case due to the government's subsidy policy for waste disposal. If biomass is used as feedstock, the price of biomass counts. In the case of a 46 tons/d oxy-fuel glass furnace, “Route 2” is the most promising one in OPEX savings, as long as the price of biomass raw materials is lower than 870 RMB/ton, it can bring OPEX savings. If CO₂ tax is considered, biomass as feedstock is more competitive than MSW in OPEX savings.

Presenting Author: Ruochen Liu ShanghaiTech

Presenting Author Biography: Ruochen Liu received a Ph.D. degree in Thermal Engineering from Tongji University, Shanghai, China in 2018. After graduation, she has 5 years of research experience in process engineering & combustion group at Air Liquide R&D (China) Co., Ltd. Now she is working at the Institute of Carbon Neutrality, ShanghaiTech University. Her research interests include the technology of combustion, heat recovery and bioenergy conversion.

Authors:

Ruochen Liu ShanghaiTech
Mingxi Zhou ShanghaiTech