| In recent years, the development of biogas projects is remarkable in China. However, thecontrol level is not enough. Manual control is still widely employed; as a result, the fermentationprocess is unstable, which caused lower gas production. The solution is to create computermonitoring and control system based on advanced control and industrial automation devices. Atpresent PLC as generic industrial automation device, with its powerful features, is widely used inindustrial automatic control in various fields. The industrial configuration software provided asoftware platform for process control with real-time data processing and management. Theautomatic control system with the application of PLC and configuration software in biogas projectwould greatly improve the anaerobic fermentation process automatic control level and the effect ofanaerobic fermentation of biogas projects.In this study, the object is biogas fermentation system. By referring to the existing anaerobicfermentation control technologies and correlation studies, a detailed analysis of the two-phaseanaerobic fermentation process was made. Then the control parameters and tasks were determinedfor the control system designed in present assay. Therefore, based on PLC and configurationsoftware combining with anaerobic fermentation device and process conditions, an automaticcontrol system was designed aiming to providing better service for biogas projects.The control system of anaerobic fermentation process was a two surveillance system. Thehost computer used Yan Xiang IPC and optional power control configuration software as systemdevelopment platform for developing an interactive interface of anaerobic fermentation processcontrol system. As to the lower computer, the Siemens S7-300series PLC, the power modulePS307(10A), CPU313C-2DP, SM321/SM322-DI/DO and SM331/SM332-AI/AO wereconfigured. The anaerobic fermentation process controlling ladder was designed based on theSTEP7V5.4programming software to achieve logic control of field devices and the constanttemperature fuzzy control of the fermentation tank.The functions of anaerobic fermentation process automatic control system based on PLC andforce control configuration software were as follows.(1) Acquisition and processing of fermentation state parameters. The collection, processingand controlling of the parameters of the fermenter material level, temperature, pH value, redoxpotential of the fermentation state were obtained by the control system. (2) Logic automatic control. The control system obtained precise control of the operation andthe order for all anaerobic fermentation devices by the logic control and sequence control.(3) Real-time monitoring and management of the fermentation process. The real-timedynamic display of the fermentation parameters was obtained through the host computerinteractive interface. the functions of displaying the status and monitoring real-time for thefermentation process, switching the mode between manual and automatic control, setting andmodifying the control parameter, processing, storing and querying the data, alarming functionswhen overrun were also realized(4) Report query, print, and failure alarm. The historical data can be investigated whilegenerating report and printing at any time. When the fermentation parameter exceeds preset upperand lower limit, the system will automatically alarm by prompting the operator troubleshooting.The installation and commissioning of the anaerobic fermentation process control systemhave completed, and have been officially put into practice. The operation results showed that: thesystem is running stable and reliable as well as easy to operate. The control requirement of theprocess is preferably met. The two-phase anaerobic fermentation environment is certainlyappropriate and then strains activity at different stages have been markedly improved. The controleffects of the system satisfied the requirements of process control, and fast, efficient and stable gasproduction was achieved. |
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