| Tube furnace is a direct furnace heating equipment, mainly for heating liquid or gas chemical raw materials, and is a essential device for the petrochemical industry. It is an energy consumption equipment, as it emits a lot of heat and smoke on the environment ,which is caused pollution, and its heating efficiency is not high either. In recent years, many petrochemical companies start to focus on energy conservation, which makes line monitoring and optimal control of the industry become a hot researching subject.As the tube furnace production process is complex and the use of common DCS control effect is not very good, it is difficult for the tube furnaces to improve their heating efficiency. This research is based on spot conditions, using PLC centralized data collection, which can transmit the data through the wireless transmission module to the central control room for data processing, achieved the monitoring and adjustment of decision-making furnace in the tubular heater's control room. The research is mainly constituted by following several parts:1. Acquisition system is composed of temperature and flue gas acquisition .Temperature acquisition system composed by a thermocouple and temperature transmitter. The flue gas analyzer is used to analyze the three gases (CO, O2, SO2) of the flue gas. Master controller uses S7-200 (CPU224) for temperature and flue gas acquisition, in which the temperature signal use RS-485 to connect with the PLC through the Port0 , using MODBUS protocol for reading data. Flue gas collects the three kinds of gas through the 4-20 mA signal three collection, and then transformed to achieve the gas through the range of flue gas acquisition.Wireless transmission system is composed of two ZIGBEE transmission modules, PLC, and with the KingView software components. Since the PPI protocol of PLC is not open, this research uses its free port protocol to achieve communication between the host machine of the control room and site controller.2. As models of the furnace tube are difficult to establish by the mechanism analysis, the numerical modeling is used to approach its model in this research. Based on the structure of the CARMA model, field data were normalized by the data processing, identified its parameter by prediction error method. Data were collected from the spot, including blower pressure, fuel flow, flue gas baffle opening of the pressure value as the three input values of a model , and before and after preheater temperature, oxygen content after the preheater as the three output values of a model to achieve its modeling. After the final model validation, drawn numerical analysis method used in this research has good accuracy.3. This research presents a redundant decision-making system, including the precise control of model-based decision-making system and rule-based decision system libraries, to achieve the online optimization.Model-based stability in the system under control is controlled by the generalized predictive control (GPC) of the identified model; rule-based decision system is usually composed of workers'experience and expertise, and it uses in the instability system.4. According to the control objectives of system, this research solved the MATLAB and configuration software'communication problems by using OPC technology. The KingView completed the basic configuration of the data acquisition front, and simple operations, history statements, and presented a good view of the configuration screen. The MATLAB completed the model control algorithm in the background. The combination of both gives the better proposals of tone furnace to greatly increase the furnace's heating efficiency. |
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