High Temperature Air Gasification of Wood-based Biomass by a Pebble Bed Slagging Gasifier

Abstract

High temperature air gasification of wood sawdust was done using 200 kg/day scale pebble bed slagging gasifier, where ceramic balls were packed below the entrained bed section. Tar free syngas was successfully produced, where achieved calorific value of the syngas was 3 697 MJ/Nm3 (883 kcal/Nm3), the cold gas efficiency was 53% and the carbon conversion rate was 86%. Compared with the experiment using crushed coal as a fuel, the carbon conversion rate was low due to poorer capturing efficiency of char in the pebble bed caused by low ash content of sawdust. To raise carbon conversion rate, two measures were tested. One measure is to increase the air exoess ratio. Another is to increase the length of the entrained bed section to enhance the reaction time of fuel in the entrained bed section. Both measures were effective for increasing the carbon conversion rate, where increase of the length of entrained bed section is effective for both increasing the carbon conversion rate and the cold gas efficiency.