Experimental Research On Intermittent Microwave Drying Theory And Technology Optimization Of Chinese Prickly Ash

Chinese prickly ash, which is chiefly produced in China, and now has formed a characteristic agricultural product industry. At present its cultivation area surpasses 120 thousand hm~2. Annual production resches to 120 million kilogram and annual income reaches to 1.5 billion. But it's drying is a difficult problem in industrialization. Therefore, studies of its drying technology and equipment cannot be substituted.Used home-made microwave drying and testing device, came with the intermittent technology, some foundational researches have been done to it. Therefore, its microwave drying characteristics and energy consumption have been discussed systematically.The mathematical description of drying process was emphatically discussed and folium drying mathematical model was established. Used the orthogonal experiment design and Data Processing System to analyze the tentative data in technology optimization stage, the drying technology was optimized and microwave-hot air combination drying was put forward as drying direction. The influence of drying conditions on the quality of dried Chinese prickly ash was discussed and some proposals has been put forward, future research direction, also pointed.The experimental researches indicated:(1) The drying process can be divided into three stages: acceleration, constant speed and deceleration. Comparing to the time of hot air drying, the time of microwave drying greatly reduces, but the quality is bad. In the experimental scope, the main problem which affects quality is dryly excessively.(2) Regarding the folium microwave drying, monomial proliferation model can describe the water ratio of Chinese prickly ash change with drying time and weight-power ratio rationally. The equation fitting is:MR = (0.779548+ 0.280610P - 0.023487P~2 )exp((0.146936- 0.108584P + 0.003349P~2))(3) Technology optimization experiment reflected that microwave-on time and microwave-off time has certain interaction. During in intermittent microwave drying process, different intermittent ratios and loadage reflected different drying velocity, quality and energy consumption. In experimental scope, the quality, energy consumption and drying time of Chinese prickly ash were influenced by microwave-off time and loadage, remarkably influenced by microwave-on time.(4)All factors considered, the condition (microwave-on time 7s, microwave-off time 40s and loadage 70 g) is the optimization technology of Chinese prickly ash intermittent microwave drying . But the results of pure microwave drying is not ideal, it should be combined with hot-air. According to empirical data and experiment, the drying technology design is: loadage, 70g, firstly hot air drying which constant temperature is 37℃ lasted 1.5h, then, intermittent microwave drying (microwave-on time 7s, microwave-off time 40s), until to security moisture content (around 11%). The experiment showed that, the product quality greatly enhanced.Microwave drying is a new technology.The thesis has deeply researched the microwave drying characteristics and technology optimization. Studies results showed that the research of technology and equipment of microwave-hot air combination drying, the uniformity of microwave's heating were key points of future research's work.