China is the world's largest grain producer, with an annual output of 500 million tons of grain. The annual loss of mildew caused by seasonal rain and dry equipment in the publication is as high as 5%. After more than 30 years of development, China's grain drying equipment and technology have reached a certain level and played an important role in agricultural modernization. However, compared with the demand for drying equipment in China, there is still a big gap. Taking rice drying as an example, the number of rice dryers in Japan has reached 1.1 million units, and the level of rice drying mechanization has reached more than 90%. However, China's mechanical drying of rice is less than 1%, and rice drying equipment is less than 10,000. station. The reasons for the above gaps are multifaceted, and the lack of research work on food drying technology standards is also an important reason. At present, China still adopts the national standards of the 1980s (such as the grain dryer test method, grain drying technology conditions), and some of the conditions and indicators have not adapted to the needs of the current dryer development, such as the lack of dryer production in the existing standards. The calculation method of capacity and unit heat consumption, the indicators related to drying quality are not perfect and reasonable, some indicators do not stipulate a unified test method, and some indicators are relatively backward, thus restricting the development, promotion and application of new equipment and new technology for grain drying. . International food drying technology standards have been revised many times, such as 501 Qiao 20 l: 1997; agricultural grain dryer drying performance measurement, such as 15011520-2:2 printed l. In these new drying technology standards, there are conversion methods for the main drying performance parameters, and the models and formulas used are as many as dozens [because it is a complicated and difficult problem to solve, there is no standard in China's grain drying technology standards. Provisions in this regard.
Grain drying is a very complicated processing process, with many influencing factors and varied drying conditions. The influencing factors are medium parameters (such as hot air temperature, hot air volume and hot air humidity), and grain parameters (such as grain type, grain moisture, grain temperature). And food flow), environmental conditions (such as atmospheric temperature and atmospheric humidity), drying processes (such as downstream drying, countercurrent drying, cross-flow drying, mixed-flow drying) and structural parameters of the dryer. A grain dryer may work at very low ambient temperatures (minus 20 ° C), or it may work in environmental conditions up to 30 ° C. The operating conditions are completely different, even far apart. Therefore, the measured performance must be measured. The indicators are converted and converted to a uniform recognized dry condition. The research and development of this standard needs to be directed to different environmental conditions, food conditions, female [I atmospheric temperature, atmospheric relative humidity, initial moisture, final moisture, precipitation amplitude, grain type, quality, heating method, hot air temperature, hot air relative humidity A series of parameters such as hot air volume and drying method are subject to a large number of tests and verifications. It is more difficult to form a formal national standard. The most likely way to achieve results is to complete the research report, give a conversion factor that is not completely accurate, publish it as a guiding technical document, and then compare and evaluate it. Therefore, the conversion of dryer production capacity and unit heat consumption is a very important standard. Unit heat consumption and drying capacity are key indicators of grain drying equipment. For different types or the same type of grain drying equipment, when there are differences in the conditions of acceptance conditions, they must be converted to standard working conditions through the relevant conversion factors, in order to determine the unit heat consumption and drying capacity. Comparison. At present, there is no uniform specification for the conversion coefficient of heat consumption and drying capacity of drying units in China. This topic will study the conversion coefficient, study and formulate a unified national standard for conversion factors. The conversion of heat consumption and drying capacity of grain drying units has always been an important problem that plagues the performance evaluation and identification of grain dryers. Over the years, this problem has not been solved due to the large amount of research work and the lack of research funding. The Heilongjiang Academy of Agricultural Reclamation has proposed a solution, but it has not become a national standard because it cannot be applied to a variety of drying processes and models, and the selection of standard conditions and models is not reasonable enough. On the basis of in-depth analysis and research on the existing research results of drying technology at home and abroad, the author determined the standard drying conditions by means of experiments and theoretical analysis, and gave the conversion factors for various dryer types and different grain drying. Calculation method and conditions of use.
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