| With the rapid development of Chinese economy,people's requirement for the ecological environment is getting higher and higher.As one of the most important industries,tobacco industry is also trying to explore the measures of energy conservation and emission reduction in all stages of production and modulation.In this paper,the research object is the thermal performance of natural gas-powered tobacco baking system.After investigation of direction of energy conservation and emissions reduction about bulk baking barn,in order to improve the baking thermal efficiency,heat and moisture load of baking barn was analyzed and calculated firstly.Then the natural gas hot stove as the most important device of baking system was designed and calculated,combined with the natural gas combustion characteristics and tobacco baking load request.Finally,the tobacco baking experiments using the natural gas-powered baking system were conducted,and the result was discussed from system performance,energy conservation benefits,economic benefits,environmental benefits and tobacco quality.The main conclusions are as follows:(1)During different baking stage,the baking heat load of barn is different with different dehydration rate,the maximum heat load appears in the stage of color fixing period.The maximum dehydration heat load and heating cold air load are 37.17k W,18.04 k W especially,the maximum baking heat load is about 55.21k W.(2)The maximum power of heating device was selected as 60k W after the analysis of heat and moisture load,and the quantity of supplying air was selected as 23000m~3/h based on barn design standard.Through the analysis of different heating mode,the optimal mode was obtained:the ratio of bypass air in the recirculated air is about40%?60%,this mode is appropriate for heat device.(3)The natural gas-powered tobacco leaf baking system was designed on the whole.Combined with the fuel combustion characteristics and basic technical parameters,the natural gas hot stove was designed and calculated,the results are as follows:hot stove overall size is 1.3m×1.2m×2.8m,the combustion cylinder size is diameter of 0.6m,length of 1.2m,effective radiation area of 5.09m~2.The whole size of two-stage heat exchangers are both 1m×0.85m×0.4m,the heat transfer area of two-stage heat exchangers are both 9.31m~2;the power of hot stove is 59.9k W,the power of the fuel combustion is 44.6k W,the power of two-stage heat exchangers are 12k W?3.3k W,especially.(4)In order to verify the feasibility of the natural gas-powered tobacco leaf baking system,tobacco baking experiments were conducted on March and July 2019 in Yuxi,Yunnan.According to the results,the natural gas-powered baking system has advantages of stable operation,high temperature control precision and fast load response speed;Compared with traditional coal barn,the baking thermal efficiency increases by 23%,energy saving effect is remarkable;labor cost and intensity decreases obviously with a high degree of automation,the cost of producing 1kg dry tobacco leaf saves?0.32,the total baking cost in all china will save?640 million,economic benefit is remarkable;environmental benefit is also remarkable with a lower output of pollutant emission;the ratio of superior tobacco improves compared with other researches,tobacco overall quality improves in some degree.Therefore,the natural gas-powered tobacco leaf baking system can cut down operation cost and achieve energy conservation and emission reduction.The technology of tobacco leaf baking with natural gas can be further promoted and applicated. |
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