Research On Heat And Mass Transfer Model And Control System Optimization For Wood Raw Coal During The Drying Process

As the world’s growing energy crisis and worsening environmental pollution, wind, solar,biomass and other renewable energy how effective to alternative fossil energy has graduallybecome the focus of research scientists around the world. Biomass energy as an importantlong-term survival of the human race, is second only to coal, oil and natural gas while living inthe world’s fourth of total energy consumption energy, it’s an important role in the whole energysystem.Wood coal as an important component of biomass resources into products is theprofessional equipment for loose through biomass feedstock drying and pulverizing treatment, ata certain temperature, humidity and pressure conditions to produce a regular shape and highdensity biomass solid fuel.Wood coal research for improving the density and strength of biomassmaterials, transportation and storage of raw materials to reduce costs, improve performance andefficiency of combustion have a very significant effect, with a high research value.This topic is relying on the National Development and Reform Commission,"an annualoutput of200,000tons of wood coal production line"，around the wood coal production processraw drying section in a study of the major energy-consuming work. Through the domesticproduction of wood coal production line drying section of field research and found that the rawmaterial drying system control mode backward, Control accuracy is low, the system response isslow, poor robustness, high heat loss, uneven final moisture content of raw materials and so on,seriously affecting the processing of raw materials results in the subsequent section. Aiming atthese problems, on the one hand the use of the means of production research field data collectionand laboratory simulation combining the raw material drying process drying rate, movementpatterns, heat and mass transfer mechanism is analyzed to establish a suitable drying wood rawcoal the heat and mass transfer models to achieve wood raw coal drying process optimization; Onthe other hand, mechanical transmission structure of production line LH3015-T-typethree-channel flue gas drying equipment and auxiliary equipment for the research subject, addingfuzzy controller based on the traditional PID control mode on the design of parallel fuzzy-PIDcontroller for control mode drying system improvements. Research results to improve the energyefficiency of the drying system and control quality, reduces energy losses in the system, and hasimportant practical and economic effects.The main topics of research results and innovations:1、Theoretical study of wood raw coal drying processReference materials drying process parameters（Flue gas temperature, gas flow rates, raw material feed rate and speed the drying cylinder）under the quantitative changes in theenvironment. Test results LH3015-T-type three-channel at the outlet of the flue gas dryingequipment final moisture content of raw data were performed univariate analysis, two-factororthogonal analysis and multivariate analysis of experimental interactive proposed a finalmoisture content of raw regression model to determine optimal parameters of the wood raw coaldrying. The moisture content of the raw materials inside the saturation point as an interface andraw materials were established internal migration models and raw liquid internal heat transportmodel. With the basic theory of porous media transport, from the solid phase, liquid and gas mass,momentum and energy conservation as a starting point for the raw heat and mass transfer modelsimplification and numerical solution; By combining the raw material drying apparatus fordrying process simulation, material derived motion model to calculate the residence time ofdrying materials.2、Optimization of wood raw coal drying control systemWood raw coal drying control system is the presence of large lag, nonlinear, time-varyingcomplex control systems to the traditional PID control mode to control the system, but qualitycontrol is difficult to obtain satisfactory results. In the current situation the lack of precise controlmodel, developed in parallel by Fuzzy-PID controller is used to optimize the design of wood coalraw control system. And the focus on how accurate and stable raw material drying equipment atthe outlet of the moisture content, expand secondary structures drying control systems work toimprove the stability and robustness of the other indicators drying control system.The results offield test indicate that the system’s stability has been increased by2.7times by the final moisturecontent of raw material at the drying equipment outlet compared with original system,thequalification rate of drying increased from71.2percent to more than94.1percent.3、Moisture content of raw materials to build prediction models and develop predictivedeviceAccording to the production line in the moisture content of the drying process of the rawmaterial requirements through a large number of field data collection and analysis, first proposedthe predictive model to an exponential decay as a function of the moisture content of the rawmaterial, made an excellent prediction. For the production line data output update rate problem ofpoor, developed based on the ARM920T core16/32bit microprocessor S3C2410feedstockmoisture prediction means to enhance the accuracy and update speed of drying field datadetection.The test results show the device based on exponential decay model to the predictionerror of moisture content of raw material less than1.5percent,the prediction error of weight isnot more than2percent and made the detection time from20minutes sharply fall to10~15seconds. 4、Build drying system configuration network and develop monitoring interface of woodraw coalPower supply, CPU, signal modules and other equipment to be installed on the rack bySIEMENS STEP7programming software hardware configuration window HW Config, and setand modify the parameters of the module. Generate a field device layer identical to its networkconfiguration, and achieve the centralized management of the drying field devices in STEP7.Meanwhile, achieve monitor interface design by using SIEMENS WinCC configuration software.In the form of reports and curves, monitor and display the operating status of field devices dryingproduction line level, flue gas temperature, gas flow rate, the amount of raw material feeding,alarm and other information.