This study evaluates the biomass-to-synthetic natural gas (SNG) using calcium looping gasification (CLG) with CaO sorbent (CLG-SNG) via thermochemical methods. The CLG-SNG process consists of three steps in sequence: steam gasification in situ CO2 capture using CaO sorbents, gas cleaning, and methanation. The concept of interconnected fluidized beds was adopted for repeated carbonation/calcination cycles of CaO sorbents in the gasification unit. A process simulation was conducted based on the chemical equilibrium method using Aspen Plus. Then, the effects of some key variables on the thermodynamic performances, such as the gas composition, yield of SNG (Y SNG), cold gas efficiency (ηcold), the overall energy efficiency (η), exergy efficiency (ψ) of the process, and the unit power consumption (WSNG) were investigated. The variables include CaO-to-biomass ratio (Ca/B) in the range of 0.7-1, steam-to-biomass ratio (S/B) in the range of 0.1-1.5, and gasification temperature (tG) in the range of 600-700 C. At Ca/B = 0.83, i.e., a stoichiometric number of SN = 1, the CH4 content in SNG and WSNG each reach the maximum while the YSNG reaches the minimum. With S/B increasing from 0.1 to 1.5, CH4 content in SNG gradually decreases while WSNG shows an increasing tendency. YSNG, ηcold, η, and ψ reach the maximum at S/B = 0.6 (i.e., when the gasifier reach the heat equilibrium). Generally, lower tG values are favorable for the thermodynamic performances (mainly YSNG and ηcold) of the CLG-SNG process. The optimal performances demonstrate that the CLG-SNG process has a strong competitiveness, compared to the traditional SNG production process.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology