Design And Experimental Research Of Automatic Mixing System For Multi-element Gas

As a large agricultural country,Chinese fruit and vegetable production ranks among the top in the world,but the high loss rate of fruits and vegetables has severely restricted the development of my country's fruit and vegetable industry.The reason is closely related to the commonly used cold storage methods of fruits and vegetables in China.The commonly used cold storage method of fruits and vegetables in China is low-temperature storage,but at present,modified atmosphere packaging or modified atmosphere storage of fruits and vegetables after harvest has become an important trend in the development of agricultural products storage and fresh-keeping processing industry technology.As the core equipment of air conditioning equipment,the multi-element gas mixing system has always been a technical bottleneck for the development of domestic industries.Aiming at the existing problem of domestic carbon dioxide(CO2),oxygen(O2),nitrogen(N2)ternary gas mixing equipment,the low gas concentration mixing accuracy and poor stability,as well as the high cost of imported equipment and small gas flow,this paper proposed automatic ternary gas mixing system based on ideal gas law and Dalton's law of partial pressure.The system used S7-200 Smart PLC as the control unit of the entire system.The PLC was developed in STEP-7-Micro/WIN SMART.The host used ST40 module,with EM AQ04 as the analog output module,and EM AE08 module was used to complete the extension of analog input.The expansion of quantity output,combined with gas concentration,pressure sensor,temperature sensor,etc.,completed the collection of temperature and other parameters and the control of the execution components.Using PC combined with software MCGS to configure the man-machine interface,completed the control of the gas mixing process,the setting and display of gas parameters,data processing,alarm output and other functions.Through the communication interface,the communication between the PLC and the PC was realized,and the monitoring and continuous adjustment of the gas mixing process were realized.The system had been successfully applied to modified atmosphere packaging equipment and put into use.The use results showed that the control system is stable and easy to operate,which greatly reduces the cost of air conditioning equipment and can perform well in the gas mixing control process,the control accuracy has been significantly improved,and it can meet the design requirements.