This project is directed at the development of a fluidised bed gasification process for the production of a hydrogen rich gas from biomass. It is proposed to design and build a pilot scale unit that could integrate with a commercially available fuel cell power plant that is at present being modified for operation with hydrogen feed. In order to achieve the necessary high hydrogen yield, steam has been chosen as the gasification agent and suitable catalytic agents will be included in the bed inventory. The fluidisation system will consist of both a gasification and a combustion zone. The heat necessary for the gasification process will be generated by the combustion process and transferred by circulating the bed material through the two zones. A laboratory scale test rig (100 kWth) incorporating the above circulatory, heat transfer principle, using sand as bed material, has been operated successfully yielding encouraging results in straightforward gasification applications. The objective of the proposed project is the maximisation of the hydrogen content of the product gas in a scaled up, pilot-plant unit capable of fully demonstrating the feasibility of an economically viable industrial plant.
To demonstrate one potentially powerful application of the product gas, it is proposed to use it for electrical energy production in a fuel cell. Phosphoric Acid Fuel Cells (PAFC) have been chosen as these represent an industrial reality, with well defined operating characteristics, readily available for field operation. An additional attraction of this application is that sufficient steam is generated as a by-product of the fuel cell operation to provide all the requirements for the steam fluidised gasifier.
Achieving the above objective involves the construction and operation of a pilot-scale test unit consisting of a 500 kWth biomass steam gasifier, a PAFC module and the necessary gas cleaning and CO steam reforming facilities.
In order to minimise the tar content and maximise the hydrogen yield (the PAFC fuel) in the product gas, the fluidised bed inventory will be chosen so as to be catalytically active for both the cracking and reforming of high molecular weight gasification products, and for methane conversion into hydrogen. Natural mineral substances (dolomite, olivine, alumina), as well as commercial and tailored Ni catalysts with perovskite structures, will be utilised. A further advantage of the dual fluidised bed configuration of the gasifier is that it enables carbon deactivation of the catalyst particles to be dealt with (by regeneration in the combustion zone) without provision in the plant layout of secondary, high temperature, catalytic reactors. The design will also seek to minimise particle-particle and particle-wall frictional effects in the solids circulation system so as to reduce catalyst losses related to the production of fines by attrition.
Funding SchemeCSC - Cost-sharing contracts
WC1E 7JE London