| The evaporation process is the key link in the production of alumina by the bayer process.Its main purpose is to eliminate excess water in the production process and increase the circulating spent liquor concentration of the solution by heating and evaporating.Under the condition of ensuring the stable operation of the system,it is of great significance to control the concentration of the evaporated discharge within the range required by the process,to prepare a qualified circulating spent liquor for the subsequent lye preparation process and to ensure the normal production.The actual evaporation process usually uses multi-stage multi-effect evaporation,which has a long process,multiple time scales,strong nonlinearity,and an unclear reaction mechanism.It is difficult to establish accurate mathematical models,the operation index of caustic soda concentration is difficult to be measured online.It is difficult to adopt existing operation optimization techniques,at present,the two-layer structure of manual flow setting control and flow tracking control is used to control the caustic soda concentration,which often causes problems such as large fluctuations in the concentration of the evaporated discharge and low qualification rates of the caustic liquid.In view of the above problems,this paper relies on the actual engineering project of an alumina plant to carry out research on the intelligent setting method and setting software of alumina evaporation process.The main works of this paper are as follows:(1)Based on the experience of excellent operators and the data of evaporation process,the intelligent setting method of evaporation process based on rule reasoning is proposed to realize the intelligent setting of the original flash feed flow control loop and the four-effect feed flow control loop.The intelligent setting method consists of feedback compensation and feedforward compensation based on rule reasoning.The feed flow rate feedback compensation value is given based on the error and error change rate of caustic soda concentration,feed flow rate feedforward compensation value is given based on the change trend of temperature and concentration,so as to control the concentration of the evaporated discharge within the range required by the process.(2)The intelligent setting software for the alumina evaporation process is designed and developed using the proposed intelligent setting algorithm for the evaporation process.The basic hardware platform of the software consists of distributed control system(DCS),monitoring computer,cloud virtual machine,process historical database(PHD)and other related devices.The basic function module realizes the functions of data collection,data processing,data storage and index monitoring.The intelligent setting module realizes the function of intelligent setting of caustic soda concentration of the evaporation process.The software part is composed of basic function module,intelligent setting module,human-machine interaction and other related modules.This software realizes data communication based on OPC(OLE for Process Control)protocol.Matlab is utilized to realize software function development,foxdraw is used to complete the development of human-computer interaction interface including evaporation process screen and the whole software.(3)The application research on the intelligent setting software of alumina evaporation process is carried out in the evaporation process of an alumina plant.The application verification results show that the intelligent setting software of the evaporation process runs stably,the human-machine interface interacts well.Compared with humans,the pass rate of the caustic soda concentration under the setting control is increased by 25%,which can meet the actual evaporation process operation requirements and has a great practical application value. |
