CHP Gasification Systems Fed by Torrefied Biomass: Assessment of the Energy Performance

The aim of this work is to assess the effect of torrefaction pre-treatment on the energy efficiency of cogeneration biomass gasification systems, using a multistage modelling approach. The gasification unit has been simulated by means of an enhanced gas–solid thermodynamic model assessing the theoretical yield and composition of the reaction products (syngas, char). Syngas utilization units for power generation have been coupled to the gasification stage considering the gas clean-up and heat recovery sections. The whole system has been then simulated proposing three different power generation units; internal combustion engine, gas turbine and combined cycle gas turbine. A parametric analysis has been performed varying feedstock, torrefaction and gasification temperatures, gasifying agent and evaluating the electrical and thermal efficiencies according to the different plant configurations. In particular, the effect of the torrefaction temperature on the system performance has been assessed. This theoretical analysis allowed the definition of some scale parameters useful for the feasibility assessment of energy conversion systems fed by torrefied biomass.