Co-production of Hydrogen and Electricity from Lignocellulosic Biomass: Process Design and Thermo-economic Optimization
The thermochemical production of hydrogen from lignocellulosic biomass is systematically analyzed by developing environomic models combining thermodynamics with economic analysis, process integration techniques and optimization strategies for the conceptual process design. H2 is produced by biomass gasification and subsequent gas treatment by reforming, water gas shift and cold gas cleaning, followed by H2 purification by CO2 removal. It is shown how the overall efficiency is improved by including process integration computing the optimal utility integration to allow waste heat valorization and combined production of heat and power. In the conversion process, electricity can be generated in steam and gas turbine cycles using the combustion of the off-gases and a Rankine cycle recovering available process heat. Additional electricity can be produced by burning part of the H2 -rich intermediate or of the purified H2 product. The trade-off between H2 and electricity co-production and H2 or electricity only generation is assessed with regard to energy, economic and environmental considerations. Based on multi-objective optimization the most promising options for the poly-generation of H2, power and heat are identified with regard to different process configurations and operating conditions. The best compromise between efficiency, H2 and/or electricity production, cost and CO2 capture is identified for competitive processes. In a future sustainable energy system biomass based H2 and electricity reveal to be a competitive alternative.