| Hot air drying equipment is widely used in dehydrated vegetable processing, but domestic hot air equipment capacity is small, energy consumption is high and low efficiency.Foreign countries are widespread use of perforated steel belt multi-level dryer, which has a series advantages than mesh belt dryer such as high output, drying efficiency, energy saving and so on. while the drying stage will be taken according to the optimal process parameters to obtain optimum product quality. Compared with domestic and international multi-level dryer,to meet the research needs of drying fruits and vegetables a new type of energy-saving fruits and vegetables drying bench was designed. The bench uses perforated steel plate, heat preservation, double recycling of airflow circulation and exhaust dehumidification. The structural and technical parameters of this bench such as plate porosity, commutation interval, airflow temperature, airflow relative humidity, airflow velocity can be adjusted flexibly in a certain range according to different properties of materials and technology requirements. The bench has high-volume loading, material height up to 70cm.In addition, based on the PLC programmable logic controller designed the bench control system, which can switch between manual and automatic operation, switch between left and right circulation, and processing parameters inputting in single circulation. According to the temperature control has object s complexity, electric heating lag, nonlinear and time-varying characteristics, this article analyzes the PID controller and fuzzy controller and their classification,designed a two-mode fuzzy-PID controller combine the PID controller and adaptive fuzzy-PID controller. Through design the fuzzy controller structure, the input-output subordination functions selection, and the tables of the fuzzy control rules establishment, completed the controller design, ensure temperature parameters stable. Through the touch screen software designed the monitor and control interface, the system has monitoring process date, processing parameters inputting, real—time data acquisition and displaying and historical data downloads functions.Meanwhile, this article also did a set of experiments for the bench applicability test, selected pepper as dry object, in the constant airflow speed 1.2m/s,cuting the pepper length of 1.5 cm, the airflow Commutation in 0.5 hour。Using hot-air drying bench research the energy-saving technology, study the different combination of pre-drying temperature, Post temperature and material thickness the impact degree of energy consumption per kg evaporated-water, evaporated-water by hour and pepper chroma .The pre-temperature in the range 50～70℃, post temperature in the range 50～60℃, material thickness in the range 10-14cm,the conclusions as follows:Used pre-drying temperature combination 70℃20min+60℃40min,post-drying temperature 55℃, material thickness 10cm will get the least energy consumption per kg evaporatedwater. Used pre-drying temperature combination 70℃20min+60℃40min,post-drying temperature 60℃, material thickness 12cm will get the most evaporation of water per hour. Used pre-drying temperature 50℃1 hour, post-drying temperature 50℃, material thickness 12cm will get the best pepper chroma.The experiment also verified the bench variable-temperature drying can save energy, the bench is applicable to simulation perforated steel belt multi-level dryer production process to energy-saving technology research.. |
PDF Full Text Request