Techno-economic Analysis Of Biomass Co-firing In Coal-fired Boiler

Retrofitting existing coal-fired boiler to co-firing with biomass is a generally accepted method of decreasing dependency on fossil fuels and reducing carbon dioxide emissions.Thus,assessing the technical feasibility and economic performance of co-firing biomass in utility boilers is of great importance.This paper carried a detailed evaluation of a 600MW China supercritical coal-fired power retrofitted to co-firing biomass generation system,from three aspects,technology,economic and environment.First,this paper established a process simulation of coal-fired boiler retrofitting to co-firing biomass by considering three co-firing options,namely,biomass direct co-firing,biomass gasification co-firing,biomass pyrolysis co-firing.A 600 MW coal-fired plant was taken as an example to investigate the effect of biomass quantity and quality on the performance of the boiler.The effects of biomass co-firing on power plant performance were analyzed in terms of energy efficiency,exergy efficiency.Results show that the energy and exergy efficiencies of coal-fired boiler were 91.04%and 50.58%respectively,and boiler efficiency decreased when co-firing biomass compared to the baseline coal-fired power plant because of the introduction of water in biomass.Biomass pyrolysis co-firing will provide the greatest energy and exergy efficiency loss of boiler among the three co-firing options,while direct co-fiirng bring the least efficiency lost.As for biomass quality,sawdust cause minimum effect on co-firing system.Then,LCA evaluation of co-firing biomass in coal-fired boiler is carried out according to the technical framework and principles of Life Cycle Assessment?LCA?.CO₂ emission in the whole life cycle of co-firing biomass in coal-fired boiler is obtained.The results show that the CO₂ emission of generating 1kWh electricity in the whole life cycle is 1.075kg for the traditional coal-fired boiler.When co-firing sawdust and corn straw,CO₂ emissions of the three co-firing options can be reduced to varying degrees,but CO₂ emission will increase when co-firing rice husk.Finally,in order to evaluate the economic feasibility of the technology of co-firing biomass in coal-fired boiler in China,the electricity cost of three co-firing options under different parameter operation conditions is calculated.The results showed that the electricity generation cost of traditional coal-fired boiler is 0.302?/kWh.When co-firing sawdust and corn straw,the electricity generation cost of three co-firing options increased.When co-firing rice husk,the electricity generation cost decreased when pyrolysis co-firing and gasification co-firng were adopted,due to the income from the sale of by-product bio-char.Considering the advantages of reduced CO₂ emission in co-firing system,if the carbon tax on CO₂emission of power plant is levied,co-firing biomass in coal-fired boiler is expected to achieve the same economic performance of traditional power plant.