Experimental results of gasification of walnut shell and pistachio shell in a bubbling fluidized bed gasifier under air and steam atmospheres

Abstract

The present study investigates gasification of biomass in a laboratory scale set-up to obtain product gas. The gasifier is a bubbling fluidized bed (BFB) type. The bed material in the reactor is silica sand. Walnut shell and pistachio shell are gasified in the reactor under air and steam atmospheres. A gas analyzer is used to measure the CO, CO2, CH4, H2 and O2 concentrations of the product gas. The effects of equivalence ratio (ER) and steam to fuel ratio on the components of the product gas are studied for air and steam gasification cases, respectively. The lower heating value (LHV) of the product gas is calculated by using the measurement of concentrations. In the case of air gasification, the components and LHV of the product gas linearly change with varying ER. The LHV of pistachio shell is higher than that of walnut shell by 8–12% for the ER range of 0.2–0.4. The LHV increases from 3.2 to 5.4MJ/Nm3 with the decrease in ER from 0.4 to 0.2 for pistachio shell. In the case of steam gasification, the LHV is nearly constant with changing steam to fuel ratio. A product gas with a calorific value of 9.9MJ/Nm3 is generated. A recent review on biomass gasification in both pilot and laboratory scale bubbling fluidized bed gasifiers is presented. The operating conditions of the gasifiers and the components of the product gas are provided for air and steam gasification cases.