Simulation Of Co-combustion Of Coal And Biomass Gas In 600MW Unit Boiler

With the rapid development of China's economy,the demand for electric power is increasing.At present,coal-fired power generation is the main source of electric power in China,not only consumes a large number of non-renewable coal resources,but also emissions of pollutants on the environment has caused a serious impact.Biomass is abound resources and widely distributed in our country.Using biomass gasification gas with coal to generate electricity has many advantages:low construction cost,cost of material controllable,effective energy-saving and emission-reduction,good versatility,little impact on the original system,suitable for large scale power station,and a large amount of non-condensed tar contained in the high temperature gasification gas can be directly used to reduce energy loss.Because of the complexity of mixed combustion system of biomass gasification,it is difficult to realize the experimental research.Therefore,it is an effective method to simulate the mixed combustion of biomass gasification by computer.In this paper,two kinds of numerical simulation software,Aspen Plus and Fluent,are used to simulate the mixed combustion system of biomass gasification.Firstly,Aspen Plus was used to model the circulating fluidized bed gasifier and HG1952/25.4-YM1 type boiler integrated system.I use the model to study the equivalent proportion,carbon conversion rate,effect of preheating air temperature and recycle ratio on gasification characteristics of biomass.And I compared the simulated value and the actual value of each parameter of working condition of the boiler BMCR,and found that the error is small,which proves that the model is accurate and reliable.Subsequently,the effects of low,medium,and high?7.168MJ/kg,5.347MJ/kg,3.708MJ/kg?three kinds of calorific value of biomass gas on the combustion and heat transfer process of the boiler under the condition of different mixed fuel ratio were studied,and the conclusions are as follows:With the increase of mixed fuel ratio,the volume flow rate of flue gas is increased,the temperature of flue gas is reduced,the exhaust temperature of flue gas is reduced,the heat loss is increased,and the efficiency of boiler is reduced;In the gas components,the content of H₂O is increased,the content of O₂ is decreased,and the content of NO_X and SO_X are also decreased;The lower the calorific value of biomass gas,the larger the volume flow rate of flue gas,the lower the flue gas temperature,the higher the exhaust temperature,the greater the heat loss,the lower the boiler thermal efficiency.Finally,I use Fluent to model the 600MW opposed boiler,and choose the realizable k-?turbulence model,Euler-Lagrange gas-solid two-phase flow model,stochastic trajectory model,discrete term model,two step racing pulverized coal evaporation model,diffusion/dynamic coke combustion model,P1 radiation heat transfer model,and post processing NO_X generation model.Replacing fuel with the analog value of the biomass gas of calorific value using Aspen Plus,the effects of mixture ratio of 0%,10%and 20%on the combustion characteristics and pollutant emission of the boiler were studied,and the conclusions are as follows:The CO combustion of biomass gas and coal has little effect on the particle trajectory and velocity field;With the increase of mixed fuel ratio,it is helpful to promote the combustion of the boiler,but the increase of the amount of flue gas makes the boiler combustion temperature decrease;the combustion temperature decreases by 50?when the mixed fuel ratio increases by about 10%;With the increase of the mixed fuel ratio,the content of O₂ in the boiler decreased,the combustion intensified,CO reacted rapidly and the production of CO₂ increased,while the concentrations of SO₂ and NO_X decreased.That is to say,the biomass gasification co-combustion can not only save the coal resources,but also make use of the excess waste biomass and reduce the boiler combustion pollutants emission.The research and conclusions of this paper have some practical significance for promoting the development of biomass gasification co-combustion technology.