Impact of different kinds of biomass mixtures on combustion performance, interaction and synergistic effects in cofiring of coal and biomass in steam power plants

Abstract

Abstract The cofiring of biomass and coal may be one of the most effective methods to improve energy utilization efficiency and reduce greenhouse gas emissions. This study aims to investigate combustion performance, interaction and synergistic effects in the cofiring of coal and three types of biomass. Blended fuel consisting of coal and three types of biomass such as sawdust, rice husk and solid recovery fuel was selected as the research object. Ultimate and proximate analysis and differential thermogravimetric analysis with heating rates of between 10°C and 40°C/minute are used to analyse combustion characteristics. Simulation of combustion in a 600-MWe steam power plant with a Carolina-type boiler is also carried out with the help of computational fluid dynamic (CFD) analysis to see the effect of the interaction and synergy of the mixed fuel on the performance of the steam generator. The effect on the combustion process in the combustion chamber of a steam power plant is also simulated. Based on the analysis of several test results of parameters such as ignition temperature, burnout temperature, calorific value of the fuel mixtures as well as CFD simulation, the results of the study show a strong indication of a positive synergy in mixing some of these biomasses as compared with a fuel mixture consisting only of coal and one type of biomass. Practically no power derating of the boiler occurs until the biomass content in the fuel mixture is ~30% on a mass basis. The reduction in greenhouse gas emissions also appears significant from the results of the CFD simulation of this study, which is characterized by a decrease in the fraction of CO2 in flue gas from 21.5% for coal alone as fuel to 15.9% in the case of cofiring excluding the CO2 attributed to the biomass.