The Key Technology Research Of Reconstructing Boiler From Coal-burning To Gas-burning

Industrial boiler which is widely used in industrial production,is an important energy conversion equipment.China is the world’s largest industrial boiler producer and user,and the emissions of existing large number of small-capacity coal-fired boilers are the main sources of air pollution.With the gradual implementation of the national energy saving and emission reduction policies,the abolishment or gas transformation of small-capacity coal-fired boiler is an inevitable trend.Compared to the reconstruction of gas-burning boilers,reconstructing boiler from coal-burning to gas-burning is an economical and efficient measure.Most of the existing gas reform scheme need to change the structural significant,and cost more money.The hearth blackness is decreased,which will affect the furnace heat transfer effect of the hearth.Therefore,this paper proposes to change the hearth but not change the pot,as well as attaching the intermediate radiator in the hearth to make the scheme more economical.First of all,choosing the typical SZL15-1.25-AII type chain grate coal-burning boiler as the object to transform the design of gas reform scheme,and adding the intermediate radiator to the hearth.The ternary radiation system of furnace gas,water-cooled wall and intermediate radiator was constructed by radiation network method,and the effect of intermediate radiator was proved by analyzing the heat transfer of water wall.The results show that the re-radiating effect of the intermediate radiator decreases the space thermal resistance between furnace gas and water wall,improves the blackness of furnace system,and strengthens the heat transfer between water wall.From the theoretical calculation,it can be seen that the blackness of the furnace gas and the area of the intermediate radiator are the important factors affecting the heat transfer in the furnace.The lower the blackness of the furnace gas is,the more the effect of the intermediate radiator is;the larger the area of the intermediate radiator is,the greater the amount of heat transfer from the furnace gas to the water wall.In order to investigate the effects of intermediate radiators on the actual hearth,this paper establishes a mathematical model of SZL15-1.25-AII type grate boiler after changing to gas.The ICEM software is used to solve the boiler furnace and do the discrete treatment.The FLUENT software is used to solve the three-dimensional mathematical model considering the combustion,flow and heat transfer of the furnace.According to the simulation results,the higher the height of the intermediate radiator is,the bigger the area is,and the better the heat transfer effect is.For the object of this study,the maximum growth rate of water temperature is 12.06%.For the boiler,the thermal parameters of the furnace is also an important factor which affecting heat transfer,the fuel when the air excess coefficient is 1.05 has been completely burned.In addition,when air preheating temperature is in the range of 400K-550K,the preheating temperature increased 50K,water temperature will changes around 1K.