| As a new type of ecological liquid fertilizer,humic acid liquid fertilizer contains rich humic acid and inorganic nutrients,which plays an important role in promoting crop growth,improving crop quality,controlling non-point source pollution and improving soil physical and chemical properties.At present,due to the low degree of automation and low control accuracy of reactor temperature in the production process of humic acid liquid fertilizer in China,the humic acid liquid fertilizer produced is easy to precipitate and crystallize,so that the product nutrients cannot meet the needs of crops.Based on a humic acid liquid fertilizer plant,the production control system of humic acid liquid fertilizer was studied and designed in this thesis.Firstly,based on the analysis of the production process of humic acid liquid fertilizer and the main factors affecting product quality,according to the characteristics of long distance,scattered control points and multiple related equipment in the actual production of humic acid liquid fertilizer,the production control scheme of humic acid liquid fertilizer based on distributed control（DCS）was proposed and the overall structure of the system was designed.At the same time,the research on the production process of humic acid liquid fertilizer reveals that there are problems such as low precision and time lag of reactor temperature control in the process of production control,analyzes the control stages of reactor temperature and establishes the mathematical model of reactor thermostat stage,determines the control algorithm based on dynamic matrix（DMC）series-level PID in the automatic control of reactor temperature,and verifies the performance of the algorithm in the control of reactor temperature through simulation and actual production.The superiority of this algorithm in terms of control accuracy was verified by simulation and actual production results.Secondly,the lower computer design of the humic acid liquid fertilizer production control system was carried out.Through comprehensive analysis of the performance,structure,application and cost of the humic acid liquid fertilizer production control system,the monitoring layer,control layer and field equipment were selected and their I/O points were assigned,and the electrical circuit design of the control system and PLC terminal wiring were completed;Then,we used Siemens PCS7 configuration software to configure the system hardware and designed the software of humic acid liquid fertilizer production control system according to the system control requirements;OPC technology was used to make PLC and MATLAB interact with each other,and the application of temperature control optimization algorithm of reactor in the production control system of humic acid liquid fertilizer was realized.Finally,the upper computer configuration design of the humic acid liquid fertilizer production control system was carried out,including the design of each section control interface,overall process flow interface,formulation interface,abnormal alarms and other interfaces,so that engineers and operators can monitor the process of humic acid liquid fertilizer production and control the whole humic acid liquid fertilizer production process in real time.It also carried out on-site debugging of the electrical wiring,network communication and equipment operation of the humic acid liquid fertilizer production control system,so that the system can operate stably and safely and realize the intelligent control of the humic acid liquid fertilizer production control system. |
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