Le Duc Dung, Kayoko Morishita and Takayuki Takarada

Additional information is available at the end of the chapter http://dx. doi. org/10.5772/55356

1. Introduction

Tar is a viscous black liquid derived from pyrolysis of organic matter as well as a complex mixture of hydrocarbons. The presence of tar in product gas may cause blockage and corrosion of equipment and be responsible for fouling or reducing overall efficiency of processes. By far, tar removal is the most problematic during biomass gasification. Hence, the successful implementation of gasification technology for gas engine, gas turbine or fuel cell based power projects depends much on the effective and efficient removal or conversion of tar from the product gas. Beside that the catalytic steam reforming tar is one of the most promising methods to suppress the problems. Biomass product gas is usually low high heating value; therefore enhancement of product gas quality is other important target. We propose a research topic that use of nickel loaded brown coal char as a new catalyst for decomposing tar from biomass gasification in fluidized bed gasifier. The method is promising to achieve some advantages of low cost by use of low rank coal as catalyst support material, high catalyst activity and enhancement of product gas quality. Yallourn brown coal has been selected for preparing catalyst support. The coal is low rank with high moisture content, low heat value and high oxygen content. It is hard to use for generating energy. However, it has many outstanding features such as less ash and sulfur content, and including abundant of oxygen-containing functional groups such as carboxyl and phenol groups which are available for ion-exchange with metals. In this research work, a nickel loaded brown coal char (Ni/BCC) was prepared by ion-exchange method, dried at 380 K in nitrogen for 24 h, and then pyrolysed at 923 K in nitrogen for 90 min. The works have been carried out is that using nickel loaded brown coal to decompose tar in pyrolysis and steam gasification process. It was carried out in a two-stage fixed-bed reactor and a lab scale fluidized bed gasifier under mild conditions (temperature, steam, space velocity, operation time). Inside of gasifier is constructed by two beds, the primary one is a fluidized bed with sand, and the second one is a catalyst bed. The new catalyst has shown high catalytic

© 2013 Dung et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons. org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

activity and stable activity and given the high quality of product gas in presence of steam, approximately 90% of biomass tar was decomposed and useful gas components (CH4, CO, and H2) yields were higher than those of Ni/AhO3 catalyst. Ni/BCC catalyst was characterized and exhibited good dispersion of nickel particles, ultra-fine Ni less than 15 nm and having a large surface area about 350 m2/g. Moreover, at the end of catalyst life span, the catalyst can be disposed of simply by gasifying/burning the coal char, during which the energy value of the char support can be recovered. Also, the agglomerated nickel residues could be used as functional materials of powder metallurgy and battery development. The general results suggest that the Ni/BCC catalyst offers a potential to be used as a tar steam reforming catalyst in biomass gasification.