Air-Steam gasification of lignite in a fixed bed gasifier: Influence of steam to lignite ratio on performance of downdraft gasifier

Abstract

This work aims to identify the optimum Steam to Lignite ratio, w/w (SLR) to achieve higher H2 yield and lower tar yield in the producer gas. Experiments were carried out in a 10kWe atmospheric pressure downdraft gasifier. Low-rank high ash lignite (22–25 mm) was used as a feedstock to investigate the effect of six different SLRs (0, 0.06, 0.14, 0.18, 0.24, 0.30 and 0.48). The producer gas Lower Heating Value (LHV) and Cold Gas Efficiency (CGE) were found in the range of 4.96 MJ Nm−3–5.62 MJ Nm−3 and 70.6%–81%, respectively for different SLR. The optimal SLR was identified to be 0.24, having lower specific fuel consumption (1.437 kg kWh−1), lower tar content (112.28 mg Nm−3), lower Particulate Matter (PM) (27.34 mg Nm−3), higher LHV (5.62 MJ Nm−3) and higher CGE (81%). H2 yield and H2/CO ratio improved by 34.7% and 52%, respectively whereas tar yield reduced by 78.31% at 0.24 SLR compared to air gasification. The mass balance, exergy analysis, heat loss analysis were also carried out for this study. The study concludes that the 0.24 SLR offered better results among the selected ratios to achieve higher H2 yield and lower tar yield in the producer gas.