Research And Design Of Control System Of Large Refining Process For Lactic Acid

Large lactic acid refining process is a complex physical purification process, numerouscontrol equipment is coupled with many factors. Through process analysis three key technicaldifficulties are discovered. Wiped film level measurement and control, wiped film feed flowcontrol, built-in thermostat water temperature control.The wiped film level measurement and control was studied. The level sensor condition isharsh, through analysis and comparison, ultimately differential pressure sensor is determinedto measure the level. Three control algorithms are designed for wiped film level control.Through simulation analysis, the integral separation PID control is found with high precisionand strong anti-jamming capability advantagesThe wiped film feed flow control was studied. Traditional PID algorithm used in thewiped film feed flow control will generate high-frequency vibration, cannot meet therequirements. PID controller with differential in advance is used to avoid the high-frequencyvibration caused by the frequently changed set value.The built-in thermostat water temperature control was studied. The ordinary PID is poorstability and the control accuracy easily changed. The expert PID can be used to improvesystem stability, through the cooling water temperature to compensate for the PID parameter.Finally, large lactic acid refining process control system is designed based on S7400PLC, including hardware design and software design. The three key technical difficulties’control algorithms is verified by the experiment. The result shows that the wiped film levelmeasurement and control, wiped film flow control, built-in thermostat water temperaturecontrol met the process requirements and achieved good effect.