Chemical-Looping Gasification of Biomass for Hydrogen-Enriched Gas Production with In-Process Carbon Dioxide Capture

摘要

The research presents an innovative idea of developing a continuous H_2 production process employing fluidized-bed technology from agricultural biomass with in situ CO_2 capture and sorbent regeneration. Novelty of the process lies in the generation of relatively pure H_2 from biomass with CO_2 as a byproduct using steam as the gasifying agent. Another unique feature of the process is internal regeneration of the sorbent, fouled in the gasifier. Thus, the technology will serve the twin purpose of regenerating the sorbent and generation of N_2-free H_2 and CO_2. This work reports theoretical energy analysis and experimental investigation of the process. The system efficiency of the chemical-looping gasification process at an ideal scenario is found to be 87.49% with biomass as fuel. A sensitivity analysis for system efficiency is also conducted by varying carbon-capture and regeneration efficiencies. The experiments conducted in a batch-type fluidized-bed steam gasifier using CaO as the sorbent shows a 71 % concentration of H_2 and nearly 0% concentration of CO_2 in the product gas when sawdust was used as the feedstock. In a separate test using a circulating fluidized-bed reactor as the regenerator, a 40% regeneration of CaO is also achieved at a calcination temperature of 800 ℃.