Process development for a novel polygeneration purpose based on tars produced by a biomass gasification unit; feasibility study from the thermodynamic, economic, and environmental viewpoints

Abstract

The tar produced by biomass gasification can be challenging to handle in processing units. To address this issue, a new polygeneration structure based on tar combustion has been designed in this study. This structure has been developed using Aspen HYSYS software and consists of subsystems, including the tar combustion section integrated with a gas turbine cycle, a low-grade temperature section, a Goswami utility section, and a hydrogen production section. The products of this structure are 7920.65 kg/s of hot water, 33.52 kg/s of cold water, 0.56 kg/s of hydrogen, 4.444 kg/s of oxygen, and 222100 kW of power. The system is examined from various perspectives: energy, exergy, environment, and economics. The overall energy and exergy efficiencies are 89.72% and 54.53%, respectively. The exergy analysis exhibits a total irreversibility of 859,492 kW, in which the low-grade temperature section has the highest exergy destruction with a share of 72%. Accordingly, the environmental analysis demonstrates that the new process has zero indirect carbon dioxide emissions, and its footprint is equivalent to 0.22 kgCO2/kWh. Also, the products have been produced according to economic estimates with a cost of energy of 0.0068 $/kWh and a total unit cost of products of 0.0274 $/GJ.