Experimental And Kinetics Study On Combustion Characteristics Of Biomass And Coal

Coal plays a leading role in China's energy structure,but a large amount of pollutants are generated during coal combustion.Biomass is a kind of clean and renewable energy source,ranking the fourth in the world's total energy consumption.There are many amount of biomass in China.The development and utilization of biomass resources is of great significance to the ecological construction and energy distribution in China.Coal and biomass or biomass and biomass blending combustion technique can achieve efficient and clean use of energy,which can not only can reduce the release of pollutants and optimize the combustion performance of fuel,but also enrich the energy utilization of agricultural and forestry biomass waste and achieve efficient and clean utilization of energy.Four kinds of biomass?tobacco stem,corncob,rice husk and poplar sawdust?and two kinds of coal?blue-coal and datong anthracite?were selected as the research objects in this paper.Thermogravimetric analysis was used to study the effects of individual fuel combustion performance and kinetic parameters on coal and biomass before and after pretreatment.At the same time,the influences of different types of biomass,pretreatment way,blending heating rate and blending ratio on the combustion characteristics,kinetic parameters and synergy of mixed fuels were identified.The experimental results show that the burning process of biomass,coal and their mixture can be divided into three stages:the water loss stage,the volatile component combustion stag and the fixed carbon combustion stage.Biomass ha s better combustion characteristics than coal.Pretreatment can make TG and DTG curves of rice husk combustion shift to higher temperature section,and the maximum weight loss rate and temperature increases.Washing can increase the comprehensive combustion index2.5×10^-7?5.9×10^-7 of rice husk,while pickling decreases it 11×10^-7?11.9×10^-7.After different pretreatment?washing and pickling?,the activation energy of rice husk in volatile component combustion phase is higher than that of the original sample.Compared with the activation energy of the original rice husk fixed carbon combustion stage,it is reduced16.94 kJ/mol after pickling and increases after washing.The maximum combustion rate decreased,the burnout temperature and the maximum combustion temperature increased,and the comprehensive combustion characteristic index decreased of washing and pickling blue-coal.,but the pickling decreased slightly.After washing with liquid-solid ratio of 30and 45,the activation energy of blue-coal increases by about 4.56kJ/mol.After 40°C and70°C hot water washing,the activation energy decreases by about 5.06k J/mol.After washing with different mass fractions of hydrochloric acid,the activation energy decreases by a large margin.For the mixed fuel of herbal biomass and woody biomass,increasing the blending ratio of herbal biomass reduces the ignition temperature and burnout temperature of the fuel,the activation energy in the volatile component combustion stag increases and in the fixed carbon combustion stage decreases.With the increases of the heating rate of the fuel,the comprehensive combustion characteristic index and residual rate of the mixed fuel improves.The 70%rice husk and the 30%poplar sawdust blended fuel produces a synergistic effect at a heating rate of 40?/min.Compared with burning coal alone,the results shows that the ignition and burnout temperature of the coal and biomass blending decreases,indicating the combustion characteristics of the coal are enhanced.With the increasing biomass blending ratio,the co-combustion performance is improved further,the activation energy of the blended fuel reduces.The peak value of volatilization analysis of the fuel composed of different proportion of blue-coal and rice husk increases after washing.The 30%rice husk and the70%blue-coal blended fuel produces a synergistic effect at a heating rate of 20?/min.The combustion kinetic of biomass,coal and mixtures are studied by using the first-order reaction kinetics pattern and the correlation coefficients of the fitting curves are greater than 0.955.The activation energies of volatile component combustion stage are higher than those of the fixed carbon combustion stage.The experimental results can provide reference and theoretical basis for the application of coal and biomass co-firing in the thermal power generation industry.