Design And Development Of Control System Software For Precipitation Process In Alumina Producton

The precipitation process is an important step in the production of alumina by the Bayer process,and its main function is to separate aluminum hydroxide from the sodium aluminate solution obtained by sedimentation.The goal of the precipitation process is to ensure that the content of the precipitation rate index in the target range is as close to the upper limit as possible while ensuring that the particle size of the aluminum hydroxide is qualified.The precipitation process has complicated processes,long processes,many equipment,and complicated material conversion processes.It is difficult to realize the automatic operation of the entire process.Key circuits such as the intermediate cooling process of the precipitation process affect the precipitation rate.The process has large inertia,nonlinearity,and strong interference.Comprehensive complexity,manual control by operators based on experience,resulting in reduced production efficiency and product quality.Therefore,the automatic control of the precipitation process is the key to ensure the precipitation goal.In view of the above problems,this article has developed a software for the control system of alumina production and precipitation process based on a domestic alumina project.The main work of this article is as follows:(1)The precipitation intermediate cooling process model has the characteristics of strong nonlinearity and time-varying model parameters.Based on the principle of non-steady-state energy balance,a mechanism model of the intermediate cooling process is established.The usual cascade control is diffcult to control the precipitation temperature of the precipitation tank within the specified range of the process.An unmodeled dynamic compensation cascade PI control method based on the unmodeled dynamic compensation of the temperature difference between the inlet and outlet of the heat exchanger slurry is proposed.The inner loop of the cooling water flow adopts PI control,and the outer loop of the temperature difference between the slurry inlet and outlet adopts PI control based on unmodeled dynamic compensation.(2)According to the process requirements of the precipitation process,the DCS control system is combined with the precipitation process,and the precipitation process control system software is designed.The software consists of loop control software,logic control software,and process monitoring software.The loop control software realizes stable control of the cyclone feed pressure and concentration,the cyclone underflow concentration,and the heat exchanger slurry temperature difference.The logic control realizes the start-stop control of the single tank equipment such as the precipitation tank stirring motor,the grading feed pump,electric butterfly valve,the bottom flow pump,and the plate heat exchanger feed pump,and the safety interlock control of the upstream and downstream equipment.The process monitoring software monitors the precipitation process data and equipment status,automatically alerts when abnormalities are found,and so on.(3)Based on the DCS control system platform,using the configuration software tool Studio 5000 and modular programming ideas,the precipitation process logic control software module and loop control software module were developed.The logic control software module uses standard pins to achieve external interlocking conditions.With flexible definition,the loop control software module implements the cascade loop control algorithm for slurry temperature difference between the inlet and outlet of the slurry and other conventional loop control algorithms.Using the monitoring configuration software FactoryTalk View SE,a precipitation process monitoring software module based on the C/S architecture was developed to achieve real-time monitoring of the precipitation process.(4)Combined with the hardware-in-the-loop simulation system,the simulation software for the intermediate cooling process model was developed,and the cascade control software for the temperature difference between the slurry inlet and outlet was developed to conduct simulation experiments.The software’s logic control module and process monitoring module carry out software function test,system test and industrial field test.