Study On Recovery And Utilization Of Flue Gas Heat In Dense Curing Barn

The main fuel for tobacco baking in China is coal,and the cost of tobacco production increases with the rising price of coal.More seriously,as the important equipment for tobacco baking,intensive baking room's combustion efficiency is low,The heat loss of chimney exhaust gas has never been higher,a large number of flue gas waste heat resources directly discharged into the atmospheric environment,which not only wasted a lot of energy,but also severely polluted the environment.Therefore,designing reasonable flue gas waste heat recovery system and selecting the appropriate heat exchanger to recover this potential energy source can not only respond to the policy of energy saving and emission reduction proposed by the state but also reduce the flue curing costs.Firstly,the flue gas composition and smoke exhaust temperature in different baking stages are tested and analyzed,on this basis,the waste heat recovery system of flue gas in dense barn was designed,the basic structure parameters of the heat pipe and heat pipe heat exchanger are obtained by theoretical analysis and design.The operation performance of flue gas waste heat recovery system under six steady temperature conditions was tested and analyzed by means of tobacco baking test.Finally,the comparative experiment of tobacco leaf baking was carried out.The energy saving effect and the effect of flue cured tobacco curing were analyzed,and the comprehensive benefits of flue gas heat recovery intensive flue curing barn were evaluated.The main results are as follows:(1)The test results of the composition and temperature of flue gas during the curing of tobacco leaves are shown:the flue gas composition of dense barn is complicated,the content of SO2 was seriously exceeded,even exceeding the nation's SO2 emissions standards by 23 times,the concentrations of soot,CO,NO and NOx are relatively high;the flue gas temperature is between 70?220 centigrade during the whole baking stage,the temperature fluctuates greatly and the waste heat of the flue gas is abundant.(2)According to the analysis of heat pipe and heat pipe heat exchanger theory,and the characteristics of flue gas emission and the structure of dense roast house,the main structural parameters of heat pipe and heat pipe heat exchanger used in dense baking flue gas heat recovery are determined.heat pipe is a steel-water gravity heat pipe,diameter 16mm,length 500mm;the structure of the heat exchanger is 550mm 220mm 550mm(length,width and height),with 63 heat pipes,a total of 14 rows,2 rows of 9 heat pipes and forks arranged in rows,the distance between the tubes is 30mm,and the length ratio of the evaporation section and the condensing section is 1:1.(3)The performance test of the flue gas waste heat recovery system shows that:in the six stage of tobacco baking temperature stability,baking room temperature at 33 DEG C,flue gas heat recovery efficiency of the average minimum is 33.1%,the baking room temperature at 48 degrees,the average recovery of flue gas heat efficiency up to 70.4%,the most abundant in the waste heat of flue gas three constant temperature stage,the average recovery efficiency reached the waste heat of flue gas more than 67%;the average heat exchange efficiency of heat pipe heat exchanger in 58.2%?76.1%is six at the steady temperature stage.(4)In the tobacco baking experiment,compared with the common barn,flue gas heat recovery type bulk curing barn 1kg dry tobacco average coal consumption was 1.015 kg,0.362 kg than the control barn saving,coal saving rate of 26.29%,lower the cost of baking 0.33 yuan/kg,this rate reached 19.88%times the average savings per pit the baking cost 235.3 yuan,flue-cured tobacco appearance quality,chemical composition and control barn compared with no obvious differences,the proportion of superior tobacco leaves increased by 0.45%fold compared with the common barn rose 0.1kg/yuan.(5)The flue gas waste heat recovery type intensive barn has a lower transformation rate,only 2780,but the comprehensive efficiency is remarkable.In terms of economic benefits,the return on investment of the project is 1.4 years,the net present value of the economy is 1783 yuan,and the economic benefit is 31.6%;In terms of environmental benefits,flue gas emissions per year in Yiliang County:1.03×107m3,9.87t,104t,C02:1.90×104t,SO2:173.76t,NOx:270.76t;in social terms,it can reduce the baking cost 9 million 227 thousand and 800 yuan per year in Yiliang County,Yiliang County farmers increase income 218 thousand yuan.