Experimental investigation of the influence of calcium oxide on product quality, tar cracking efficiency, heating value, and syngas ratio in two-stage fixed bed gasification

Abstract

ABSTRACT Biomass gasification is a thermochemical process used to generate hydrogen and methane for energy applications. This experimental study compares the products formed from sugarcane bagasse, bamboo, and rice-straw and evaluates the calorific value of the gas and the efficiency of homogeneous cracking in a novel, two-stage, downdraft, fixed-bed reactor. The formation of tar and the presence of carbon oxides (COx) in the gaseous product are some of the major problems with biomass gasification. In order to solve these issues, calcium oxide (CaO) is introduced with the feed in a 1:1 mass ratio as a CO2 sorbent, and its effect on the amount of tar is studied across the chosen biomasses. Experiments are conducted with the pyrolysis stage at 773 K and the air-gasification stage at 1073 K. The tar cracking efficiency of 97% is obtained with CaO for all biomasses. Rice-straw showed the highest syngas ratio of 1.83 and the volume of hydrogen increased by 13% after the addition of CaO, while bamboo had a 16% rise in hydrogen and showed the highest LHV of 12.21 MJ/m3, followed by bagasse with an LHV of 11.50 MJ/m3. The gasification efficiency for bamboo is the highest overall for both the processes.