Air-Steam Gasification of Dairy Biomass Using Small Scale Fixed Bed Gasifier

Abstract

The composition of gases obtained from gasification of biomass fuels depends principally upon parameters like fuel and oxidizing medium supplied, equivalence ratio (Φ), steam-fuel ratio (S:F), pressure, reaction temperature, and residence time in the gasifier. Gasification with steam only is an endothermic process which produces rich mixtures of CO and H2 while gasification with air-steam may not require heat input in order to produce H2 rich mixtures of CO and CO2. Furthermore, gases produced by gasification with-air-steam can be supplied to a shift reactor to produce mixtures of H2, CO2, and N2. When pure O2 is used instead of air, the H2 separated from CO2 can be used for in situ sustainable green power generation. The gasification process can handle low quality fuel and larger sized particles. While coal has higher fixed carbon (FC) providing more heat for gasification, the Dairy biomass (DB) selected in current study has lower FC and hence contributes less heat. While most of the past studies deal with gasification of coal, current study concentrates on DB as fuel. Experimental results are presented for gasification of i) dairy biomass (DB) and ii) DB ash blends (DBAB) using a 10 KW fixed bed counter-flow gasifier and air-steam as oxidizing source. The results show that the reactor operates almost adiabatically. The effects of the Φ and S:F ratio on peak temperatures, gas composition, gross heating value of the products (HHV), and energy conversion efficiency (ECE) are investigated. A mass spectrometer has been used to analyze the composition of gases in real time continuously. Increasing Φ or S:F increases the production of H2 and CO2 but decreases the production of CO; thus, the reaction of CO+H2O→CO2+H2 seems to control the composition of gases. The operating parameters include 1.59<Φ<6.36 and 0.36<S:F<0.8. Energy Conversion efficiencies (ECE) range from 0.26 to 0.80.