| In this thesis, a 20T/h steam boiler of refinery is taken as the object of study and a steam boiler automatic control system, which is based on IPC+PLC and combines the structure and technological process of steam boiler is designed.The lower machine of the designed system utilizes SIEMENS S7-300 series PLC. Besides, some modules are configured for the system, such as 319-3PN/DP CPU module, DI/DO modules of SM321 / SM322 series, AI/AO modules of SM331 / SM332 series and 10A power module of PS307 series. The LADDER program of the control system is completed by using the STEP 7 V5.4 software. In order to maintain the stability of the drum level, the method of three impulse cascade control is employed and as a result, the influence of"false water level"on the drum level has greatly reduced. In the part of hearth negative pressure control, the system uses the feed-forward - feedback control, which takes the amount of blown air as the feed-forward signals and the drawn air as the control signal. The stability of the hearth negative pressure is controlled by controlling the speed of the induced fan.The upper machine of the designed system utilizes DELL industrial PC and chooses KINGVIEW 6.53 as the exploration platform. 8 humane-computer interfaces, such as showing the general appearance of the boiler, the interface of parameter setting, and the interface of real-time data query are designed. These interfaces realize such functions as the display of system interface, real-time monitoring, parameters setting and adjusting, data management, safety management and so on.The communication network of the system was realized by using STEP 7 software and the communication between PLC and KINGVIEW software was realized by using industrial Ethernet. The design, installation and debugging of the system have been completed and the system has been put into operation. The result of the operation shows a good control effect of the system and the expected requirement has been achieved fairly well. |
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