Design And Experimental Study On The Heating Surface Of The Biomass Briquette Chain-steam Boiler

With the energy situation becoming increasingly severe,the efficient use of biomass has received extensive attention because biomass energy is a kind of clean,low-carbon renewable energy.This paper was completed under the support of Henan Province Science and Technology innovation outstanding talent plan(144200510015)and Zhengzhou City Science and Technology innovation team(131PCXTD588)“Design and research of biomass briquette chain boiler”.The main work contents of this paper are as follows:(1)According to the study on design method of heating surface of biomass boiler,this paper has designed a heating surface structure for 1t/h biomass briquette chain-steam boiler.The boiler has single longitudinal layout drum and water-fire tube shell.The radiant heating surface include vertical water wall tube and eight curved pipe which are arranged alternately on both sides of the furnace.Eight type wall is laid on the upper part of the curved pipe connecting the vault.Convection heating surface include the flue convection tube and the screw smoke tube in the drum.This structure can ensure high heat transfer efficiency when flue gas flow rate is reasonable.Rear heating surface is economizer which has been arranged in the tail flue of the boiler.The economizer can preheat the water and absorb the convective heat transfer of flue gas.Boiler heating surface thermodynamic calculation results show the radiation outlet flue temperature of the heating surface gas is 858℃,heat transfer is 6718.9k J/kg.For the flue convection tube is 626℃,1910.1k J/kg.For the screw smoke tube is 225℃,3474.1k J/kg.For the economizer is 126℃,825.3 k J/kg.(2)The thermal calculation of heating surface has been completed.The results of the thermal performance tests are as follows: the difference between the flue gas temperature and the design value of each heating surface is less than 2.5%.The thermal efficiency of each heating surface reach 92.6%.Heat transfer efficiency of the screw smoke tube reach 70.9%.As the smoke flow,heating surface energy efficiency increased gradually to the economizer at up to 60.8%.The radiation heat flux is the highest in the width of the water wall tube group is 1.5 ~ 1.8m,and the height is 0.2m~ 0.3m.When the excess air coefficient is 1.4 ~ 1.6,the heat transfer of the heating surface is better,and the air supply quantity is the best.(3)In the three different fuel burning,boiler positive balanced efficiency are above 81.9%,balance efficiency in reverse are above 82.8%.The content of CO,NOx,SO2,smoke dust are lower than 395*10-6,147*10-6,52*10-6,28.9mg/m3 meeting the requirements of the relevant standards.Through the positive and negative balance of energy efficiency of boiler,study the actual situation of energy conversion and the degree of perfection of thermal energy utilization.Draw the energy flow diagram and analyse the utilization and losses of energy(4)Different levels of deposition are found in the heating surface after 45 days of boiler operation.The surface of the deposition is irregular,with a small amount of corrosion pits under the surface.Based on the study of the mechanism of deposition and corrosion,several reasonable methods of blowing ash,flue gas recirculation,pipe wall spraying and fuel pretreatment was put forward in order to reduce the deposition and corrosion of the heating surface.