| Prebaked anode aluminum reduction cell is the main production plant equipment, so whether the matches condition of various technologies is in the best case, which play a very important role in improving the electrolysis current efficiency, product quality and maintaining the aluminum tank in good condition. Accurate and timely gain the changes of technical parameters, has been the electrolytic process optimization goals. The shell temperature of the aluminum reduction cell is an important parameter in the run operation, Through online testing shell temperature, we can monitor the running condition in real-time and effectively avoid the occurrence of leakage ducts, extend the life of aluminum reduction cell, and provide reference data for the electrolytic process analysis. The traditional way is through the instruments, meters and other measurement for manual inspection, so that not only introduced the man-made measurement or analytical error, but also largely increased the labor intensity, and it is negative for improving labor productivity, especially in detecting the cooling hole of the aluminum reduction cell, cathode steel bar and the bottom plate temperature, this phenomenon is more obvious when more measurement points, and shorter measurement time interval. The production of electrolytic aluminum is in the complex environments of strong magnetic field, dust, high temperature, the common electrical sensor is difficult to reliable use in long-term. For the technical problems, we developed a fiber grating temperature sensor. FBG sensors have the characteristics of intrinsic resistance to electromagnetic interference, corrosion resistance, small size, light weight and easy to combine with the measured object. Temperature, strain, vibration, ultrasonic and other sensors which made by optical fiber grating have been widely used. Temperature measurement range of common fiber is generally -40℃-150℃, while the aluminum tank shell can reach the maximum temperature of 350℃. Thesis make a particular fiber through rare earth co-doped fiber and use the ultraviolet laser to periodically irradiate the phase mask method, Which solve the key technical issues ---the fiber grating refractive index modulation is easy to erase in the high temperature.According to the monitoring requirements, we use the optical time-division multiplexing and wavelength division multiplexing technology to build a multi-point temperature monitoring network, development of online multi-point temperature monitoring system, achieve a real-time online monitoring of aluminum tank shell temperature. Firstly, paper analyzes the signification of the aluminum tank shell temperature detection to aluminum technics and the health condition calculation of aluminum reduction cell. Research the status quo of the aluminum reduction cell shell temperature detection. Then, using two-dimensional reduction cell temperature distribution model, based on the temperature distribution condition of the aluminum reduction cell, meshing the reduction cell, using finite difference method for numerical calculation, and we focus on the electrolysis temperature, trough-shaped and the influence of different morbidity conditions on the reduction cell shell temperature field. We establish the temperature sensor mathematical model for fiber grating, analyzing the method which can improve the fiber grating temperature performance, Using the chemical vapor deposition to make the tin-Er-germanium and tin-special germanium co-doped fiber, using the ultraviolet irradiation method of periodic phase mask to write fiber grating, and anneal fiber grating of written delay within 500℃. Experimentally study the characteristics of fiber grating, the change characteristics of the high temperature annealing reflectivity, temperature response sensitivity, stability and other performance indicators. The high temperature fiber grating which designed by the co-doped photosensitive method, after high temperature annealing,still have high reflectivity, and in high temperature area, fiber Bragg grating wavelength changes with eh temperature has a good responsiveness, which meet the requirement of aluminum reduction shell temperature detection to sensor.Then, analysis of the structure of reduction shell and production technology, and studied the heat transfer principles, the factors which affect the heat balance, Then confirm that the temperature monitoring object of shell is cathode steel bar, steel side, the bottom of the plate. According to factors, such as the installation requirement of cathode steel bar, steel side, the bottom of the plate, temperature detection range, we designed high temperature fiber Bragg grating sensor. Fiber Bragg grating are made through ultraviolet radiating different period mask in the Sb-Ge co-doped silica fiber, and we respectively test the changes trends of grating wavelength with temperature, response time and stability, which gained good results.Through the analysis of the aluminum reduction cell Heat loss model, we know that cathode steel bar heat loss is 8%, steel side is 40%, the bottom plate is 7%, the change of temperature can reflect the reduction shell state of thermal equilibrium, we can analyze the technics state and health condition of reduction shell, rely on the data detected. Using the method of ultraviolet radiating different period mask in the Sb-Ge co-doped silica fiber to make the high temperature fiber Bragg grating, according to the cathode steel bar, steel side plate and the bottom of the installation location requirements, designed fiber Bragg grating sensor which is suitable for aluminum reduction cell shell temperature detection.Wavelength demodulation of fiber grating sensor technology is a key technology for accurate system detection, The system compares the advantages and disadvantages of various demodulation methods, analyze the phase grating demodulation principle, described the phase grating which achieve multi-points FBG demodulation system design. By analyzing the aluminum reduction cell shell temperature detection requirements, we make a systematic monitoring group design for detection pointer which based on the cathode steel bars, side plates, and bottom plates. Finally, the use of somatic phase grating demodulation device to design a multi-point temperature monitoring system, and a detailed analysis of software are illustrated.Finally, according to the multi-points sensor monitoring system, installed the self-developed sensors in the specified points, and point out the problem when we install the sensors. Combined with aluminum production process technics, we analyze the system detection data, and focused on the production process of the anode effect, the temperature change characteristics of the moment. The cathode steel bar grating temperature sensor as the study object, with reference to Infrared Thermometer test data, studied the accuracy of the sensor, and finally, the sources of sensor detection data error are analyzed.The development of the system successfully replaces the original tank shell regular temperature monitoring methods which using the hand-held infrared temperature gun manual inspection, provide a detailed scientific data for the study of the aluminum electrolytic process. Through analysis of the data, we can predict the cell's health condition, prevent accidents, protect the normal production of aluminum. In addition, this reduce labor intensity, improve the working environment, and it is significant for improving the he automation of management degree. |
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