Variable Temperature Drying And Research On-line Control For Paddy

During the harvest time, the paddy with moisture content higher than 21%should be dried in time. However, in our country, the paddy was mainly dried bynatural resources such as sun and wind and less than 8% of the paddy was dried bymachinery. Million tons of paddy was ruined because of high moisture content. Thehigh cost of paddy dying was one of the main reasons which makes the machinerycan only be bought by a few people and hard to promote. So, under the conditionsof ensuring the quality of paddy drying, how to improve production efficiency ofdrier and reduce the drying cost was an important research topic. The driers used inour country were mainly based on thermostat dry, which had low energy efficiencyand high drying cost. Aimed to improve this condition, the technical programmainly based on variable-temperature drying.The process of paddy variable-temperature drying had been studied anddeveloped mainly based on the characteristics of paddy drying and the mechanismof inducing crack as well as the theory of heat and mass transfer. Using acombination methods of theoretical analysis and field test, optimizing the processparameters and operating parameters of paddy variable-temperature drying, we cannot only know the relationship between parameters were obtained which containthe moisture content of paddy, the temperature and humidity of dryingmedium, grain temperature as well as the efficiency of precipitation but also therelationship between the ratio of paddy drying time and tempering time and thequality of dried paddy was obtained, which provide the basis for the on-line controlresearch of paddy variable-temperature drying.Based on principle of the fuzzy control, the control method of double inputand single output was designed in the control system of variable-temperature dryingfor high moisture content paddy. The elements taken as input linguistics variablesinclude the real-time ratio of paddy moisture content, grain temperature, the settingmoisture content of paddy as well as the deviation value deviation grain temperature, while the hot air temperature and the flow values relatively were takenas output linguistic variables. The control between host and slave computers andSTEP 7-Micro/Win software programmable logic controller belonged to SIMENSwere adopted in this system. According to the timing moisture content andtemperature of paddy, PLC control procedures were established to actualize onlinecontrol for the drier of paddy moisture content and temperature. The softwareADP6.0 of HITECHT Company was used to write the human-computer interactionprogram, the computer remote monitor was actualized.Batch spot experiments of drier showed using the paddy variable temperaturedrying, compared to the thermostat drying, about 20% energy can be saved and theproduct quality was better, the rice kernel cracking was less than 3%. Fuzzy controlmethod can on-line control the paddy variable temperature drying. Output grainmoisture content was remained about 14.5%, paddy temperature was controlledbelow 37.5, and the drying time was shortened. The effect was good, and thequality of paddy after drying was better, at the same time, the drying costs wasdecreased.In the item, the study of the process of paddy variable-temperature drying andthe design of the advanced project of fuzzy control provide a certain degree oftheoretical and practical value. For the design of new type drier and transformationin existing driers'technical, what's more,it has broad prospects for development.