IS THERMO-CHEMICAL CONVERSION PROCESS OF BIOMASS – A ROUTE FOR FUEL CELL APPLICATION?

摘要

The paper attempts to justify the use of the renewable hydrogen rich syn-gas generation for fuel cell application. Air gasification process generates producer gas with about 20 % hydrogen and an average gasification efficiency of about 80 %, captures 35 – 40 grams of hydrogen from biomass. Producer gas as a fuel in internal combustion engines and gas turbines has been extensively researched and also commercialized (1). In the recent times, with established gasification process, oxy-steam gasification process developed at the Indian Institute of Science provides an opportunity to generate hydrogen rich syn-gas amounting to about 100 g of hydrogen per kg of biomass (2). The enhanced hydrogen yield is essentially due to the presence of steam enhancing the char-steam reaction process. The process parameters for oxy-steam gasification addresse the need to meet various combination of CO and H_2 in syngas for applications in FT and DME. Coupled with steam- reforming, the process provides a route for enriching the hydrogen fraction in syngas. With about 50% hydrogen and 25 % carbon monoxide in the gas and having a calorific value of 9 MJ/kg, the fuel is good for SOFC applications with very limited cell ouput derating. The paper also presents the other process coupled with the gasification system to address hydrogen generation for meeting PEM quality. Mass and energy balance for the oxy-steam process towards generating hydrogen rich syn-gas and subsequently the process involved in the generation of 99.99 % pure hydrogen is evaluated. An insight into technoeconomic feasibility of such an operation is also brought about comparing with other renewable process towards generating hydrogen.