アグロテクノロジー

概要

Kenaf as a Bioresource for Production of Hydrogen-rich Gas

Yasuo Kojima, Yoshiaki Kato, Seung-Lak Yoon and Myong-Ku Lee

The two-step gasification of biomass via carbonization-step followed by steam gasification, which produces hydrogen-rich water gas without any by products, was achieved using a small laboratory system. Carbonization of kenaf from 600 to 1000°C produced suitable chars for further steam gasification, which generated clean hydrogenrich gases without any byproducts. On the other hand, carbonization of kenaf at 400°C yielded an insufficient char that still contained raw chemical components, and generated hydrocarbons and tar-like materials during gasification. Importantly, the wood gas generated during carbonization had a sufficient Higher Heating Value (HHV) to serve as the heating source for the gasification. A lower gasification temperature induced the water-gas shift reaction, which led to a change the hydrogen content in the water gas composition. Raising the gasification temperature increased the specific HHV and decreased the gas yield. In addition, at these gasification temperatures, the H2 concentration in the water gases was greater than 58%, and the H2/CO ratio ranged from 1.8 to 3.0. On the other hand, increasing the steam supply rate decreased the specific HHV and CO yield and increased the H2 and CO2 yields. Therefore, the water-gas shift reaction played an important role under these conditions. On the basis of all of the above results, it was concluded that the water-gas reaction, C + H2O → CO + H2, leads to effective gasification of the kenaf char.