Thermodynamic and economic analysis of biomass partial gasification process

A biomass partial gasification model based on the principle of cascade utilization of chemical energy is proposed. The compositions of biomass which are easily to be gasified will be gasified (referred to active compositions), while the left are not participating the gasification (referred to inactive compositions), which will be fed into boiler as fuel. The carbon conversion ratio is adopted to reflect the extent of partial gasification process from the kinetic analysis. The thermodynamic and economic analysis of proposed process is carried out as well as the influences of several key operating parameters. The results indicate that the exergy efficiency decreases with increase in carbon conversion ratio, the product of exergy destruction and time (PEDT) increases exponentially after the carbon conversion ratio exceeding 0.7. Moreover, the capacity of main equipment (gasifier) decreases and the investment cost of process decreases subsequently. In the case study, the cold gas efficiency and net heat efficiency at the carbon conversion ratio of 0.7 are 46.08% and 44.25%, respectively. The exergy efficiency can reach to 67.97% considering both bio-gas and char as the outputs. In addition, the initial capital cost saving ratio is 12.93% compared with the complete biomass gasification process.