Research On Grain Drying Process Simulation And New Measurement And Control Methods

Drying is an important link of the storage and processing after grain harvest, and thedrying process has a great influence on grain quality. It is an important means to configurereasonable drying process, parameters and control methods for the sake of improving thequality of the grain after drying.It is an important way to ensure grain harvest and stabilize the total amount of grain. forthe sake of developing grain drying industry, accelerating the full mechanization of grainproduction and minimizing loss of grain storage. And it affects the level of grain, processingand eating quality. Thus, it affects not only the farmer, the economic benefits of graincirculation enterprises and people’s quality of life but also the enthusiasm of production andoperation of the food farmer and dealer. And thus grain drying process should be improved,the process parameters should be optimized, intelligent level of drying process should beimproved, and the antijamming of precise control system should be developed not only toimprove grain drying quality and reduce grain loss but also to improve the drying efficiency,reduce costs, and further expand the industrial applications of food.In this paper, grain drying process was seen as the research object. On the basis of thesimulation analysis and experimental research, for deep-bed drying process, grain circulationdrying process, continuous cross-flow drying process, the influence on grain-drying processwas analyzed, and control models were established. The fixed deep bed drying andcirculation drying process were simulated. State parameters of grain moisture and hot airtemperature in the drying process were simulated and analyzed. Grain moisture and dryingquality were regarded as control target, drying process was studied deeply by theoreticalanalysis, model prediction, simulation analysis, test research, dry operation productionpractices and other methods.The main innovation points are as follows:A new constant-rate but variable temperature measurement and control method of massand electricity two-parameter was presented in circulation drying. A new variable ratemeasurement and control method of combining high and low material level and mass andelectricity two-parameter was presented in continuous drying. The measurement and controlsystems based on two new methods were established and drying operation test wasconducted.The main content of the full text is as follows: (1)The grain moisture measurement theory based on the two-parameter method of massand electricity (ME for short) in grain drying process was studied. The mass and electricitytwo-parameter calculation model of on-line grain moisture measuring by was established.The on-line grain moisture measurement method based on the two-parameter method ofmass and electricity was developed and then applied to the drying process and production.(2)The most common type of drying is the deep bed drying, also known as fixed beddrying in practical production. The deep bed drying control is simplified as thin layer dryingcontrol, and thin layer drying equations was used to solve the problem of deep bed drying.The mathematical relationship between the state of grain and measured parameters wasexplored in the grain drying process.The deep bed drying model numerical simulationplatform was established, and the simulation analysis of fixed bed drying process was carriedout.The actual drying process was simulated.The distribution regularity of drying parameterswas studied. The influence of various parameters on the drying process was analyzed. Thus,we can understand the status of the dry internal parameters change better. According to that,we can improve the design of the grain drier and the operation of grain drying system andcontrol method.(3)According to the characteristics of the circulation drying, a new constant-rate butvariable temperature measurement and control method of mass and electricity two-parameterwas presented in circulation drying. The mass parameters and electricity parameters werefused to achieve constant-rate but variable temperature control. The system of newmeasurement and control method was developed and the drying control system tests werecarried out. According to thin layer drying models, combined with heat medium temperatureand humidity, grain moisture, wind speed and other parameters in dry operation, thecirculation drying control model of constant-rate but variable temperature was created, andthe numerical was simulated.(4)A new variable rate measurement and control method of combining high and lowmaterial level and mass and electricity two-parameter was presented in continuous drying toachieve alternate online moisture measuring of the mass parameters and electricityparameters and to control grain discharging speed. The system of new measurement andcontrol method was developed and the drying control system tests were carried out.Continuous cross-flow grain drying control model was established. Control model is madeup by four different kinds of models which are drying process control, anti-process control,drying parameters optimizing and feedback control. After drying machine control system test, it shows the two-parameter method of mass andelectricity is feasible for on-line measuring dry grain moisture. The precision and stability ofthe grain moisture on-line detection was improved, and its precision is higher than that ofelectrical measuring method. The method fusion of mass method and electrical measuringmethod is more close to the actual operation of the dryer. Two new measurement and controlmethods are maneuverability, and which contribute to the development of automatic controlsystem for grain drying. And thus will be beneficial to improve our country grain dryingequipment. The numerical simulation experiments of grain circulation drying process werecarried out, and the variation of parameters during the drying process was studied.And thusprovided a theoretical basis for practical application. The part of the dry process controlstrategy was tested. The drying process realized the real-time automatic control, and it washigh precision and strong predictive control accuracy.And thus improved the dryingefficiency and quality.