Numerical Simulation And Optimization Analysis Of Biomass Mixed Burning In A 1000 MW Coal-fired Boiler

Renewable energy gradually replaces non-renewable energy is the trend of energy development.Biomass energy is a kind of abundant renewable clean energy.Effective use of biomass energy is one of the best ways to alleviate the energy crisis and improve the proportion of renewable energy consumption.As a typical carbon neutral fuel,the development of biomass energy is of great significance to achieve the strategic goal of’carbon peak and carbon neutral’.To improve the domestic new energy consumption an d storage capacity,and promote clean,low-carbon,safe and efficient use of energy,biomass and coal-fired coupling power generation technology is one of the best models to promo te the process of energy structure optimization in China.In this paper,a 1000 MW swirling front and rear wall opposed coal-fired boiler in a power plant is taken as the research object,and various combustion conditions are simulated in Fluent software.Firstly,the rationality of the model was verified by numerical simulation of pure coal combustion,and then the co-combustion characteristics and optimization analysis of biomass and pulverized coal were studied.The waste paper was selected as the co-combustion object,and the co-combustion ratio was 20%.Biomass was injected in to five burners at different locations to study the co-combustion characteristics.The results show that compared with pure coal combustion,the maximum temperature in the furnace is reduced,the outlet temperature of the furnace is increased,the O ₂concentration at the outlet of the furnace is reduced,the NO emission is reduced and the fuel combustion is promoted.Compared with each mixed combustion condition,the NO emission reduction is the most obvious when the biomass is injected from the uppermost burner,and the NO emission is lower when the biomass is injected from the burner with the same layer interval than that from the connected burner.The co-combustion was optimized by exploring the biomass blending ratio,blending type,excess air coefficient and burnout rate.The results show that when the biomass blending ratios are 10%,15%and 20%,the higher the blending ratio is,the lower the maximum temperature in the furnace is,the higher the flue gas temperature at the furnace outlet is,the low er the O₂volume fraction at the outlet is,the higher the CO₂ volume fraction is,and the lower the NO emission in the furnace is.When waste paper,corn straw and wheat straw are mixed respectively,the difference of velocity field,temperature field and flue gas composition field in the furnace is small.The higher the volatile matter and the lower the nitrogen content,the lower the NO emission,that is,the NO emission of waste paper is the lowest.When the excess air coefficient is 1.10,1.14 and1.18,the greater the excess air coefficient,the higher the maximum temperature in the furnace,the lower the flue gas temperature at the furnace outlet,the greater the O₂ volume fraction at the furnace outlet and the smaller the CO ₂ volume fraction,the higher the NO emission.When the exhaust air rate is 21.05%,25.44%and 29.82%respectively,the greater the exhaust air rate,the higher the highest temperature in the furnace,the higher the flue gas temperature of the furnace outlet,the content of the flue gas components at the furnace outlet is basically the same,and the lower the no discharged by the furnace.For all the research conditions in this paper,when the blending ratio is 20%,the blending material is waste paper,the excess air coefficient is 1.14,and the over-fire air rate is 29.82%,the NO emission is the lowest when the burner is injected from the third layer.