Biomass steam gasification for hydrogen-rich gas production in a decoupled dual loop gasification system

Abstract

In order to improve tar destruction and hydrogen-rich gas production in steam gasification of biomass, a novel decoupled dual loop gasification system (DDLG) has been proposed. In the system, fuel pyrolysis/gasification, tar cracking/reforming and char combustion are decoupled into three reactors correspondingly, i.e. fuel reactor, reformer and combustor. Both the fuel reactor and the reformer are separately interconnected with the combustor, forming two bed material circulation loops, one for fuel pyrolysis/gasification and the other for tar cracking/reforming. In this way, the above-mentioned reactions could be optimized separately under appropriate conditions. With pine sawdust as feedstock and calcined olivine as both solid heat carrier and in-situ tar cracking/reforming catalyst, the steam gasification performance of the system has been investigated. It has been indicated that the configuration of the system provides an effective way to strengthen the tar cracking/reforming reaction for efficient tar removal. Specifically, a product gas with hydrogen concentration of 40.8vol%, tar content as low as 14.1g/Nm3 and dry gas yield of 1.0Nm3/kgdaf was obtained at the fuel reactor temperature 800°C, reformer temperature 850°C, steam to carbon mass ratio 1.2 and circulation ratio 10.