Effect of steam to biomass ratio and calcite bed material on the performance of a 100kwth dual fluidised bed gasifier

In this study, a series of experiments has been conducted in a 100kWth dual fluidised bed gasifier to investigate the influence of steam to biomass (S/B) ratio and calcite loading in the bed material on gas composition, H2/CO and H2/CO2 ratios, NH3, H2S and tar content of the producer gas. In the experiments, wood pellets of radiata pine sawdust were used as the feedstock. The gasification temperature was set at 710-750 degreesC while the combustion temperature was maintained at 825 degreesC. The S/B ratio of the gasification process was varied from 0.67 to 1.0 kg/kgdry at each calcite loading of 0%, 50% and 100%. The results of this study showed that the performance of the DFB steam gasifier increased with the calcite loading. The H2/CO ratio increased from 0.7 to 3.4 by increasing the calcite loading from 0% to 100%. In addition, the 100% calcite loading also has a catalytic effect on reducing the concentrations of CH4 and light hydrocarbons (LH) by 14% and 46%, respectively, compared with 0% calcite loading. Furthermore, the total tar concentration decreased significantly from 4.7 to 0.7 g/Nm3 with the increase in calcite loading from 0 to 100%. With 100% calcite loading, the H2/CO was further increased from 3.4 to 4.3 with the increase in the S/B ratio. However, the influence of S/B ratio was insignificant on CH4, LH, NH3, H2S and Tar.Woei Lean Saw, Janjira Hongrapipat, Shusheng Pan