高湿稻谷节能干燥工艺系统设计与试验

为了降低高湿稻谷干燥耗能、提高干燥系统作业效率,基于高湿稻谷干燥特性和干燥传递理论,绘制出了高湿稻谷贮存干燥仓内通风去湿降温过程状态参数变化图,设计出了高湿稻谷贮存干燥仓,能够利用常温自然空气实现高湿稻谷干燥和有效回收干燥系统的烟气余热。应用结果显示,在风量谷物比为149 m3/(h·t)时,每间隔1 h,通风2 h,累计贮藏干燥18 h,可使初始含水率31.3%的稻谷平均含水率降低11.36%,回收烟气废热55.3%。针对南方高温高湿的气候特点,设计出了5HNH-15型稻谷逆流热风干燥机和节能干燥工艺系统。试验结果表明,系统的单位耗热量为2 939 kJ/kg,与国标≤7 400 kJ/kg相比,最高节能可达60%。该文指出了实现高湿稻谷优质、高效节能干燥,合理的工艺系统设计应以客观能势的利用为主,人为提供主观热能消耗为辅。研究结果为粮食干燥设计指明了高效节能途径,为大型粮食集中干燥工艺系统设计提供了参考。

Design and test on energy-saving drying system for paddy with high moisture content

Abstract: Moisture content of paddy in South china is mostly above 22%-28%. The energy consumption of drying process is higher in high temperature and high humidity environment than in other environment. Its main reasons are new theory and technology application, and lack of the reasonable design of drying process system. According to the researches at present, evaporation from grains with high moisture content was little affected by grain features, and moisture binding energy of grains with low moisture content was significantly decreased with increasing temperature. The law of binding energy of high moisture content paddy changed with moisture content was obtained. Energy structure of drying system was revealed based on the drying exergy transferring theory of grain. In order to develop industrial application, reduce the energy consumption in the drying process of high moisture content paddy and improve drying efficiency, based on the drying characteristics and exergy transferring theory of high moisture content paddy, a drying process system of high moisture content paddy was designed which could make full use of the normal temperature natural air, be effective recovery of waste heat of flue gas, and achieve energy-efficient drying of high moisture content paddy. Its process curve of ventilate cooling and dehumidifying was drew out and the principle of design was explained. The energy-saving effect was verified by tests. It was pointed out that the segmented dry process model was one of the important ways to solve the problem of high energy consumption. The results of practical applications in a high moisture paddy drying storage warehouse showed that the average moisture content of 31% (dry basis) of high moisture paddy was decreased to 11.36% and the waste flue gas heat was recycled more than 50%, when the ratio of air flux to grain mass was 149 m3/(h·t), ventilation for 2 hours while intervals of 1 hour, and the accumulative storage dry 18 hours. According to the southern climate characteristics of high temperature and high humidity, type 5HNH-15 paddy countercurrent dryer and energy-saving drying process system were designed. Test showed that the subjective heat in drying system wasting converting into a unit heat consumption of high moisture paddy was 2 939 kJ/kg. Compared with national standard, which was less than 7 400 kJ/kg, the highest energy saving could reach 60%. The results pointed out that, in order to realize high quality, high efficiency, energy-saving in high moisture paddy drying, the reasonable process system design was given priority to objective potential use and subjective thermal energy consumption was complementary. The reliability of the technology solutions were confirmed by theory and experiment. The results of the study pointed out a high efficiency and energy-saving way of design for grain drying, and it provided reference for the large grain drying process system design.