Study On Temperature-Accumulation Quality Properties Of Grain With Measurement And Control Method In Drying Process

Drying is an important part of post-harvest processing and storage,and the drying process has a great influence on the quality of the grain.To develop grain drying industry and speed up the mechanization of food production will minimize the loss of food in warehousing,improve the quality and quality of grain processing,maximize the economic benefits of grain production and increase the enthusiasm of grain producers in their production and operation.Improving food drying process,optimizing process parameters,improving the intelligent level of drying process,and developing automatic control system with high precision and strong anti-interference ability are important means to realize intelligent control technology of drying process.In order to improve the large delay in the drying process,inaccurate on-line moisture measurement,difficult to guarantee the quality of the drying and other issues,the research group for the first time the equivalent accumulated temperature theory for grain drying process control.In this research,the theory of equivalent accumulated temperature is applied to grain drying process control for the first time.In this paper,the concept and calculation method of drying equivalent accumulated temperature were proposed.A mathematical model of drying equivalent accumulated temperature and drying process parameters of corn was established by thin-layer drying test with multiple parameters controlled by temperature and humidity.Based on the heat and mass transfer model of grain drying,the variation law of drying equivalent accumulated temperature and quality in drying process was numerically simulated and validated by building a drying test platform.A accumulated temperature quality measurement and control system suitable for 500T/D drying equipment was established and preliminary application was made to process 10000 t wet grain.Compared with the traditional drying method,the relative germination rate of the grain dried by this system has been improved,which has been affirmed by the users.The main research contents are as follows:(1)The concept of equivalent accumulated temperature of grain drying is put forward for the first time.The equilibrium temperature of grain drying was determined by using the model of grain microenvironment hygrothermal equilibrium model(C AE model).The calculation model and method for the equivalent accumulative temperature of grain drying were established.(2)The influence of four factors,hot air temperature,grain humidity,grain initial moisture content and hot air velocity,on grain drying was studied.A drying equivalent accumulated temperature model and table of corn were established according to multiparameter controlled thin-layer test.(3)Based on the grain drying quality model and the model of moisture content and drying equivalent accumulated temperature during drying process,the relation between grain relative germination rate and drying equivalent accumulated temperature in drying process was simulated by computer.(4)Based on the establishment of continuous drying measurement and control system,a new method using drying equivalent accumulated temperature model to control was studied,which realized the purpose of controlling the moisture and quality of grain after drying by using the drying equivalent accumulated temperature.(5)A continuous drying measurement and control system for grain drying equivalent temperature was developed.The drying equivalent accumulated temperature control model adopts a combination of drying process control,reverse process control,drying parameter optimization and feedback control.It has shown in the grain production test in the grain storage of Heilongjiang Province Hulan Kai De company,which shows that the system can control the water content of grain leaving within 0.8% of the target moisture.The quality of the dried food is improved compared with the traditional drying method,which provides a theoretical basis for the practical application of the food drying and is conducive to the upgrading of food drying equipment technology in China.