Exergy, exergoeconomic and carbon emission analysis of a novel biomass pyrolysis system with self-heating and torrefaction

In this study, a self-heating corn straw pyrolysis system with throughput of ten-thousand-ton scale per year was modeled and simulated based on Aspen Plus. The energy required for the pyrolysis reaction in this system is mainly provided by burning biomass and combustible gases, with ceramic spheres as heat carriers for transfer. The results of the energy analysis show that feedstocks with different moisture contents have a very significant effect on the energy consumption of the pyrolysis and torrefaction units. In the economic analysis, the economic viability of the project was demonstrated in terms of internal rate of return (13 %) and payback period (6.6 years). Sensitivity analysis indicates that variations in the selling price of bio-oil exert the most significant influence on net present value and internal rate of return. In the exergoeconomic analysis, the torrefaction and pyrolysis units had energy economics variables of 0.392 and 0.490, which need to be optimized in terms of nonenergy costs and reduction of exergy losses. In the Life Cycle Assessment, the entire system is operating with negative carbon emissions. Therefore, the results of this study will help to optimize the system from the point of view of reducing energy consumption and improving economic efficiency.