External Circulating Moving Bed Catalytic Gasification Of Biomass For Hydrogen

The research is a part of the project Supported by National Natural Science Foundation, named as "External concurrent circulating moving bed catalytic gasification system of biomass for hydrogen production" (serial number of the subject:50776013).For optimizing the energy utilizations and reducing environmental problems, more and more people pay much attention to hydrogen energy. Gasification of the renewable biomass for hydrogen production is a promising technology. However, there are still many obstacles required to resolve until the commercial breakthrough could be obtained, such as high tar content in dry gas and low hydrogen yield. The addition of steam and catalyst favor hydrogen production and tar reduction.In this thesis, a novel process of catalytic gasification of biomass with solid heat carrier is proposed, which is called External Circulating Countercurrent Moving-Bed gasification system. The gasification system is composed of three reactors, a gas-solid countercurrent moving-bed gasifier, a pyrolyzer and a riser-type combustor, and the gases are completed separated between the combustor and the other reactors. A circulation loop of bed material is achieved through the three reactors. The circulating bed material acts as not only solid heat carrier from the combustor to the gasifier, which supplies the required energy of gasification reactions of biomass, but also catalyst in tar reduction. Rapid pyrolysis of biomass in the pyrolzer, catalytic reforming of tar in the gasifier sequently occurs. A dry gas with low tar content and high hydrogen content should be obtained in the process. In the combustor, reheating of solid heat carrier and regenerated catalyst are made by burning off the residual char and coke on catalyst. At the same time, the highest yield of hydrogen can be obtained from biomass. During the process, fast prolysis of biomass, reforming of tar, heating of solid carrier and catalyst regeneration occur simultaneously and continuously.This paper mainly includs four parts as follows:1) Material balance and heat balance of the process system of the external circulating countercurrent moving-bed gasification were calculated.2)A lab-scale facility was designed and established to demonstrate this process concept, which includes a pyrolyzer, a gasifier, a combustor, a feed system of biomass , a circulating loop of heat carrier solid and a purification system of product gas and so on. 3) By a series of cold state experiments, we investigated the performances of the gasifier, the pyrolyzer and the combustor and carried out the steady circulation of solid heat carrier for the hot state experiments.4) A series of preliminary hot state experiments were seriously conducted with pine sawdust as the material. The experiments verified the hydrogen production is feasible.