| In recent years,the excessive use of fossil energy by human beings has caused great impact on the environment.Biomass energy has gradually become the research focus of scientific researchers because of its characteristics of large reserves and small pollution,to alleviate energy pressure.There are a large number of biochemical analysis boilers in our country transformed from coal-fired chain grate boiler,but the emission of pollutants from biomass boiler system is large.In this paper,the boiler of a sewage heating and heat source plant in Shuozhou is studied,and the fuel is made from straw in Shuozhou.The structure of the boiler is improved by numerical simulation to reduce the emission of pollutants.In this paper,a numerical simulation method for biomass boiler combustion simulation is proposed based on combustion theory analysis.The boiler bed part and the gas phase part in the furnace are separated into two parts,and the chain furnace bed part is simulated and analyzed by FLIC software,the irregular curves derived from FLIC are sampled at intervals of 0.05m along the x direction,and the discrete sampling points are fitted to a function expression based on Gaussian function,trigonometric function or rational function by the curve fitting algorithm,then by writing the UDF built-in in the FLUENT,the above functions expression is inputted into the gas-phase combustion model inside the furnace as an inlet boundary condition,then,the results of gas-phase combustion in FLUENT are input back to FLIC.After several iterations,the stable numerical simulation results of biomass boiler are obtained.A set of industrial control system for data acquisition is established,fit the actual boiler out with sensors and other data acquisition equipment,data received by the PLC processing,establish the monitoring interface of upper computer,so as to facilitate the analysis of real-time data and historical data archiving,to verify the correctness of numerical simulation.Based on the results of numerical simulation,the influences of air distribution in main compartment,early air distribution in separate compartment,late air distribution in separate compartment,common furnace arch,higher furnace arch and herringbone furnace arch on boiler system are compared,finally,the scheme of changing the air distribution in the main compartment into postponing the air distribution in the main compartment and matching with the herringbone arch is selected,and satisfactory numerical results are obtained by contrasting with real data.Finally,in the numerical simulation of the modified boiler,it is found that the combustion process of the open boiler is similar to liquid siphon,and the gaseous material is difficult to be mixed together,resulting in the large amount of material emissions such as NO_xand CO.Therefore,it is suggested that a part of furnace arch be added in the middle of the furnace to transform the furnace into a curved shaped structure,extend the length of flue,and the secondary air is added in proper positions by adopting the classified air distribution strategy,in order to reduce the emission of pollutants,a spontaneous SNCR environment is formed in the furnace by changing the flow pattern of gaseous material and enhancing the mixing degree of the material.The feasibility of the method is verified by numerical simulation. |
