Research On Complex Control Of LNG Receiving Station Based On DCS

The functions of the LNG terminal mainly include the import,storage and transportation of liquid natural gas,and the DCS control system is usually used to realize the automatic process control.The core process of the LNG terminal is to recover and process the boil-off gas(BOG)generated in the storage tank.During the unloading period,the amount of BOG generated in the storage tank increases exponentially,which makes the pressure of the storage tank increase rapidly.The lag and overshoot in the control system’s control of the pressure process can threaten production safety.With the continuous growth of the number and volume of LNG receiving stations,enterprises need more intelligent and efficient advanced control algorithms to improve economic benefits.However,as far as the current industrial application is concerned,the application threshold of advanced control in the industrial field is high,and the investment high cost issues.This subject conducts in-depth research on the process flow of the LNG receiving station,analyzes the advantages and disadvantages of BOG direct compression process and BOG recondensation process,and selects Honeywell PKS system as the control system to complete the overall project design.The configuration PKS control system is divided into hardware and software.The hardware part of PKS system includes system cabinet,terminal cabinet,power cabinet,network cabinet,DCS server,operation station,clock server,safety instrumented system server,fire alarm system server and switch hardware configuration.The software part includes the arrangement of process control points,the establishment of LNG engineering projects,the establishment of channels in batches,the establishment of control loops in batches,the configuration of PKS system,and the drawing of HMI process flow diagrams.The HMI process flow chart includes the LNG storage tank pressure flow chart,the BOG compressor unit flow chart,and the recondensation system flow chart.By viewing the HMI flow chart on the Station,the operator can monitor the system status in real time and quickly perform related operations on the system.Based on the limitations of the classical PID algorithm,this topic researches and compares the current commonly used advanced control algorithms.According to the relevant characteristics of the controlled object of the LNG receiving station,two advanced algorithms,fuzzy control PID and RBF neural network PID,are selected to participate in the process control of the LNG receiving station.Use the Simulink simulation function of Matlab software to tune and optimize the algorithm parameters.Through simulation experiments,the control curves of fuzzy control PID,neural network PID and classical PID under the same controlled object are obtained.The experimental analysis shows that the fuzzy PID and the RBF neural network PID have a good effect of suppressing overshoot,and the RBF neural network responds faster than the classical PID and the fuzzy PID.Therefore,the RBF neural network PID and fuzzy PID can be applied to suitable controlled objects in the LNG receiving station according to the algorithm control characteristics.Based on the openness of OPC technology,OPC communication technology is selected to communicate with the PKS server and the three-party server running the advanced control algorithm,so as to realize the combination of the advanced control algorithm and the PKS system.So as to achieve a more excellent control effect and improve the economic benefits of the LNG terminal.