Study On Simulation And Control Method Of Concentration Process Of Thickener In Coal Preparation

In the "Made in China 2025" environment,improving innovation capacity and reducing energy consumption ratio have become a new direction for the development of coal mining enterprises.At present,under the premise that coal mining enterprises basically realize mechanized production,multi-angle and multi-level analysis should be used to consider the shortcomings in the production process,which is conducive to the realization of automation and intelligentization of the whole process.The coal slurry water treatment system of the coal preparation plant is an important process link that affects the production efficiency and system stability of the coal preparation plant.The thickener is one of the core links in the process of slime water treatment,which directly affects the effect of flocculation and sedimentation of coal slurry water and closed cycle of washing water in coal preparation plant.In this paper,the relevant core variables of the thickener of Hexi Coal Preparation Plant cannot be monitored online in real time.The internal conditions of the thickener cannot be transparent.The original flocculant and coagulant dosing system are only realized by separate control.The concentrating machine discharge is still completed manually.In other cases,the research on simulation and control of thickener concentration process was put forward.For the field staff,since the internal condition of the thickener is non-transparent,the sedimentation of the slime water is a complicated and multiinterference process,which makes it impossible to adjust the thickener in time for the specific situation.Therefore,this paper uses FLUENT software to simulate the thickener.According to the velocity field,there are four areas inside the thickener: A inlet recirculation zone,B central recirculation zone,C outlet recirculation zone and D upper overflow zone.Different areas have different effects on the sedimentation of coal particles.The concentration field can be used to analyze the distribution of coal slurry water concentration.At the same time,the PBM model can be used to observe the distribution of different particle sizes inside the thickener,so that the simulation of the thickener is transparent to the internal conditions of the thickener,which is more convenient for people to learn about the operation of the thickener.According to the actual situation of the site,the concentration of the internal flow field of the thickener was simulated for 30 minutes under the condition of adding chemicals,different flow rates,different concentrations and different particle sizes.It was found that the PBM model can simulate the dosing of the thickener and improve the accuracy of the model.Increasing the feed flow rate increases the internal velocity of the thickener and increases the average particle size of the granules inside the thickener.Increasing the concentration of the feed increases the concentration growth rate at the bottom of the thickener and also increases the average particle size of the particles inside the thickener.The composition of the particle size of the feed has little effect on the sedimentation of the slime,but with the increase of the proportion of fine particles,the average particle size of the slime particles increases continuously.According to the actual data on the site,the analysis of the internal conditions of the thickener is of great significance for the formulation of the automatic control system of the thickener and the advance prediction of the abnormal situation to ensure the stability of the system.According to the actual situation of the working process of the thickener,it is found that the sedimentation thickness of the thickener and the concentration of the bottom of the thickener,which are important indicators of the thickener control system,can only be obtained by manual means,and have great hysteresis to the control thickener.Therefore,the GSA-LSSVM with the concentration of the thickener,the feed flow rate,the overflow concentration,the flocculant dosing amount and the coagulant dosing amount as input variables,and the slime thickness and the bottom related position concentration as the output variables are proposed.The model predicts the thickness of the thickener slime and the concentration of the thickener at different locations.The advanced acquisition of key parameters in the thickener provides a solid theoretical basis for the automatic control of the thickener.The main core of the automatic control system for the concentration process of the thickener is the automatic addition of the drug system and the start and stop of the automatic discharge of the thickener.For the addition of pharmaceutical agents,this paper uses the thickener system evaluation model established by expert rules to complete the rapid adjustment of the pharmaceutical system.The process is realized by Matlab/Simulink as the running platform of the model and the overall control of PLC control is realized by OPC technology.The evaluation model uses the overflow concentration,slime thickness and bottom concentration as expert rule variables,and uses the set knowledge base for the variables outside the range to adjust the amount of flocculant and coagulant added to make the system re-stable within a reasonable range.The addition of the dosing amount is realized by the PLC controller and the new dosing amount is recalculated under the GSA-LSSVM model,and then the evaluation model is used to check whether it is reasonable.After several rapid adjustments,the final dosage and overflow concentration of the drug are finally made.The variables are within the allowable range in the shortest time,ensuring that the error between the predicted and actual values of slime thickness and bottom concentration within 30 minutes is within the specified range and the overall stability of the control system is improved.For the automatic discharge of the thickener,it is necessary to consider whether the sedimentation of the thickener is up to standard,and also consider the level of the liquid level in the slime bucket in the next step,and complete the inlet valve of the slime bucket through the PLC controller,and concentrate.The bottom flow pump of the machine and the underflow valve of the thickener are controlled to realize the automation of the automatic discharging of the thickener.And each time the valve is closed,the initial setting of the flocculant and coagulant is completed using the concentration and flow rate of the thickener at the moment,ready for the prediction of the next cycle model.The system uses the PLC controller to realize the acquisition of the sensor signal and the control of the actuator through the switch to realize the information interaction.The data is transmitted to the Matlab platform through OPC for model calculation and the host computer software to display the data.At the same time,the modified data is transmitted back to the PLC controller through the Ethernet to complete the adjustment of the actuator.Online monitoring and optimization of the thickener concentration process is realized.The system also adopts FLUENT parallel simulation,which can judge the settlement situation of the thickener ahead of time,and adjust with the actual situation on the site to complete the mutual adjustment and mutual correction of the fluid simulation and actual working conditions,so as to achieve more accurate monitoring and control of the thickener.Through the practical application in Hexi Coal Preparation Plant,it was found that the variation range of slime thickness was reduced by 0.33 m,the average concentration of 30 min was reduced from 34.11 g·L-1 to 12.14 g·L-1,and the moisture content of filter cake was reduced by 3.1.%,indicating that after the system is put into use,the system stability is enhanced and the production efficiency is higher,which further improves the economic benefits of the coal preparation plant and provides new ideas for the coal preparation plant.