Moisture Detection And Automatic Control Of Grain Drying Process

Food is a major topic of people's livelihood, food security storage is particularlyimportant. Use of grain drying equipment to reduce grain moisture is an important part ofsafe storage of food. While in the process of grain drying, on-line monitoring and control ofwater is a main restricting issue. As the impact of complex factors, direct measuring isdifficult, while some indirect affecting factors are easy to measure. Generally grain moistureis indirectly measured by measuring some affecting factors such as grain temperature, airtemperature and overall grain weight change, etc. For more precise control, you need tomeasure these variables, and then by controlling one or a few factors to indirectly control thewater content of the discharge, in order to achieve automatic control of the grain dryingprocess.On the basis of comprehensive analysis and study of moisture monitoring and controlduring food drying process, the paper made numerical simulation analysis of the corndeep-bed drying process, study the change characteristic of corn temperature and therelationship between the temperature and moisture change of corn. explored the feasibility ofmoisture prediction by change rate of corn temperature; studied grain moisture detectionmethod based on the change of the partial pressure and the total weight of granary; at leastdeveloped intelligent control system based on fieldbus and touch screen technology. Thisresearch work is based on the sub-project CNC Grain Drying technology and VacuumCombination Drying Process from12th Five-Year National Science and Technology SupportProgram: Research, Development and Demonstration of Grain Energy-saving and QualityDrying Technology and Equipment. From both theoretical and experimental aspects, thegrain drying process moisture detection and automatic control were studied. The maincontents are as follows:1. Researched the relationship and changes between temperature and humidity duringdeep-bed drying process by Numerical Simulation; established the simulation equations ofcorn temperature and moisture content. And carried out a series of experimental verification;explore the feasibility of using changing rate of corn temperature to control water;2. From both the theoretical and experimental aspects,studied the changing relationshipbetween the static-dynamic pressure and moisture content in the rectangular silos, in order to investigate the detection of moisture content using the saturated pressure;3. Studied the structure and data acquisition system of the pressure-type moisture sensor,using the BP neural network nonlinear correction for temperature to detect water online;4. Established the simulation system of circulating dryer based on the detection for thetotal grain weight, analyzing the impact of total mass change on the water, and laid thefoundation for the control of the actual drying process;5. Developed a intelligent control system for corn drying process based on fieldbus andtouch-screen technology, succeed in using the actual dryer to, the total grain weight, graintemperature and saturation pressure within the machine are three ways to achieve thedetection and control of food moisture.