| Tobacco is an important economic crop in China,which plays an irreplaceable role in promoting the development of China’s economic and the prosperity of mountain farmers.As a highly energy-consuming part of tobacco production,the traditional bulk curing barn with open-type dehumidification curing method directly exhausts the hot and humid airflow to the outdoors,which has problems such as large waste heat loss,high pollutant emissions,high curing energy consumption and serious loss of aroma-causing substances in tobacco leaves.Heat pump drying technology,as an environment-friendly technology,has the advantages of low energy consumption,high self-control performance,good drying quality and hot air circulation.Therefore,improving the curing method and applying heat pump drying technology to tobacco leaves curing is of great significance to China’s tobacco industry to achieve energy saving and emission reduction,reduce labor and cost,and improve quality and efficiency.This thesis in view of the shortcomings of the open-type dehumidification of traditional bulk curing barns,combined with the advantages of air source heat pump drying technology,an air source heat pump tobacco curing system in the fully closed hot air circulation bulk curing barn was constructed,and the main components of the system were designed and calculated,with the Honghuadajinyuan as the experimental material,experimental research was carried out on the operation characteristics,system performance and comprehensive curing benefits of the system.The main work and results of the thesis include the following aspects:（1）The air source heat pump tobacco curing system in the fully closed hot air circulation bulk curing barn was proposed.The system could realize 6 operation modes.The theoretical analysis and calculation of flue-cured tobacco load of the bulk curing barn showed that the peak load was 36.20 k W.Furthermore,based on the results of load calculation,the main components of the thesis system were designed,calculated and selected,which laid the foundations for the construction and testing of experimental platform.（2）An experimental platform was set up to carry out the experimental research on the tobacco curing system with air source heat pump in the fully closed hot air circulation bulk curing barn.Firstly,the operating characteristics of the system were tested and analyzed,the results showed that the maximum hourly heat supply of the system was 35.30 k W when 4022 kg fresh tobacco leaves were cured,the maximum average dehumidification capacity was 31.62 kg/h,the average power consumption was 6.57 k W·h per hour,the maximum exhaust temperature of the compressor was within the range that the compressor and lubricating oil could withstand,the temperature and humidity control accuracy of the system were±0.80℃and±0.59℃,the system could meet the requirements of flue-cured tobacco.Secondly,the system performance was calculated and analyzed,it was found that the average coefficient of performance（COP）of each curing stage was between 1.84 to 3.67,the average specific moisture extraction rate（SMER）was 2.49 kg/（k W·h）,and the evaporator moisture absorption coefficient was from 1.20 to 3.64,the system performance was excellent.Thirdly,the relationship between COP and the unit load rate and return air temperature was obtained by fitting"Three times ten coefficient"model,and the experimental values verified that the model fitted well and could meet the application requirements.Finally,the operation modes of the system were analyzed,different operation modes were switched at different curing stages to make the tobacco curing process more in line with the requirements of the curing technology.（3）The thesis carried out the comprehensive benefits analysis of flue-cured tobacco in the fully closed hot air circulation air source heat pump bulk curing barn,and the biomass pellet bulk curing barn was set as the control barn.The results showed that compared with the control bulk curing barn,25.00%curing energy consumption was saved for 1 kg of dried tobacco leaves in the experimental bulk curing barn,and a large amount of CO2,SO2 and dust particles were reduced during the curing process,the advantages of energy saving and emission reduction of the experimental bulk curing barn were obvious.Meanwhile,the cost of getting 1kg of dried tobacco leaves in the experimental bulk curing barn was 59.60%lower than the control bulk curing barn,and the appearance quality of the dried tobacco leaves was better,the chemical composition contents was more harmonious,the total score for the smoking quality was higher,the proportion of superior and medium tobacco increased by 3.41%,the average price of dried tobacco increased 1.16 yuan/kg,and the static payback period of experimental bulk curing barn was about 4 years,the economic benefits of the experimental bulk curing barn were significant. |
PDF Full Text Request