Studies On The Characteristics Of Thin-Layer-Alfalfa Drying And The Design Of Rotary Dryer

As the establishment of our country grain-economy crop- foodstuff three ways plant construction, planting the pasture and raising the grazing animals become new driving point in economy development in China. Alfalfa being rich in protein, various vitamins and minerals, its products have wide oversea and domestic market. However, as a leguminous pasture, It is difficulty to store the fresh alfalfa being more colloid materials and less carbohydrates than the gramineous pasture. The alfalfa must be dried in time, otherwise it would become mildewy even putrid, lowering its feeding value and market value.The correlations were analyzed between the critical velocities of the alfalfa segments and its parameters including moister content, diameters and lengths at the drying laboratory Northeast Agriculture University. The regularity that drying parameters involve in hot air temperature, air velocity, initial moister content and drying duration impacting on drying characters of the alfalfa in terms of final moister content, drying rate in every minute and energy consuming in unit duration was obtained by the thin layer dry experiment table. The combination of the optimum drying parameters in the alfalfa thin layer was obtained, which provides the basis for designing alfalfa dryer. An alfalfa dryer was designed and manufactured.The following research results were obtained:1.The critical velocity of the alfalfa segment is related with the moister content, diameters and lengths. As the decline of the moister content, the critical velocity also decline, along with the increase of the alfalfa segment for diameter and length but increase.2.On the thin layer dry experiment table, through the single factors experiment analyses, some results were obtained that the final alfalfa moister content lower with the increasing of hot air temperature and hot air velocity. With the decreasing of the initial moister content of the alfalfa, the dry duration is shorten, and establishes the dry characteristic curve of thin layer of alfalfa.3. A mathematics model was build .which describes the relation of the range of precipitation and medium temperature under different dry duration. In theory, if the velocity of the hot air is 0.4m/s, the dry duration is 5 minutes, and drying temperature is 131 if the dry duration is 1 minutes, the drying temperature is 375.4. The drying parameters involve in hot air temperature, air velocity, initial moister content and drying duration impacting on drying characters of the alfalfa in terms of final moister content, drying rate in every minute and energy consuming in unit duration was Studied byquadratic orthogonal rotation combination design text of four factors and five levels. The mathematics model of each evaluation index sign and dry factors were established through weighted value evaluation and the frequency number analyses to multi-targets to get the precise solution, four equal important evaluation target in theoretical and get the optimizing drying craft parameter: hot air temperature 177±1℃,hot air velocity 0.44±0.01m/s ,the original water of material 63.5±1.5%, dry duration l.1±0.1min. if the final water of material and the unit energy are regarded as important targets optimum craft parameter: hot air temperature 178±1℃,hot air speed 0.35±0.02m/s ,the original water of material 53.5±1.5%, dry duration 1.2±0.05min.5. Designing and manufacturing diminutive rotary pasture dry machine, its technique parameters is: Throughput 360kg/h, the heat output 1.24+106kJ/h, the fiux of medium 9.9 +103m3/h.Candidate: Zhao Yanzhong Major: Agricultural Mechanization Engineering Supervisor: Associate prof.Chen li...