An experimental study of hydrogen production by gasification of biomass in the presence of a CO2 sorbent

Madhukar R. Mahishi
D.Y. Goswami
Mechanical & Aerospace Engineering, University of Florida, PO Box 116300, Gainesville, FL 32611, USA
Clean Energy Research Center, University of South Florida, 4202 E. Fowler Avenue, Tampa, FL 33620, USA
Received 10 June 2006; received in revised form 18 December 2006; accepted 19 March 2007
Available online 10 May 2007.

Abstract
The paper presents a novel technique that enhances the hydrogen yield of conventional biomass steam gasification. This is done by integrating
the gasification and absorption reactions. The method involves steam gasification of a carbonaceous fuel (biomass) in presence of a CO2
sorbent. Experiments were conducted by gasifying pine bark in presence of calcium oxide. The gasification was carried out at atmospheric
pressure in the temperature range 500.700 ◦C. The hydrogen yield, total gas yield and carbon conversion efficiency increased by 48.6%, 62.2%
and 83.5%, respectively, in the presence of sorbent at a gasification temperature of 600 ◦C. This was attributed to the reforming of tars and
hydrocarbons in the raw product gas in presence of calcium oxide. The CO and CH4 concentrations in the product gas were lower while using
the sorbent. The calcium oxide played the dual role of sorbent and catalyst.
2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
Keywords: Biomass; Calcium oxide; CO2; Gasification; Hydrogen; Sorbent.

CH1.43O0.62 + 0.38H2O → CO + 1.1H2
HR = 112.7kJ/mol. (1)
(biomass chemical formula obtained from the elemental anal-
ysis: Table 1).
This is followed by the water–gas shift reaction:
CO + H2O → CO2 + H2, HR =−41.2kJ/mol. (2)
A sorbent, such as calcium oxide absorbs the product CO2
and releases heat as per the following reaction:
CaO + CO2 → CaCO3, HR =−178.3kJ/mol. (3)
The concept of using sorbents combines the biomass reform-
ing, water–gas shift and CO2 absorption reactions into a single
step:
CH1.43O0.62 + 1.38H2O + CaO → CaCO3 + 2.2H2,
HR =−106.8kJ/mol. (4)
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