Research On Impedance Water-content Meter Used In Sinter Mixture

In the sintering production process of the iron and steel industry, sinter mixture moisture affects permeability of material layers, balling effect and helps combusting, thereby affecting the yield and quality of sinter mine. Moisture is the basic link of sinter mixture automatic control, moisture measurement precision directly affects its control accuracy. The topic is based on the mixes of second sintering zone of Tianjin Iron and Steel Group Co., researching the sinter mixture moisture measurement in real time by impedance water-content meter.Firstly, the moisture meter system hardware circuit is designed, and software features are improved. The hardware circuit mainly includes power circuit, AD5933 measuring circuit,4-20mA circuit, keyboard circuit, display circuit, Micro SD card circuit, communication circuit, etc. Lower machine software is written by C language, the mixture impedance value, the temperature value and moisture are stored in the Micro SD card in real time. PC software is written by Lab VIEW, which can display impedance value, temperature value and moisture value of the mixture.Secondly, the thesis selects special sensor to achieve the real-time measurement of sinter mixture moisture. Its operation and maintenance period is prolonged to six months or more.Thirdly, the optimal excitation frequency is determined for sinter mixture. In order to determine optimal excitation frequency, the thesis uses different frequencies to measure 218Ω～2kQ resistances, and analyzes the maximum absolute error, the maximum relative error and the maximum mean square of different frequency measurement points. Meanwhile, the thesis uses different frequencies to measure moisture of different water-content sinter mixture, and analyzes measurement stability.Finally, under the laboratory conditions, the excitation frequency selection experiments, the moisture meter static calibration experiments, the comparative experiments with conductivity moisture meter, the stability experiments and reproducibility experiments are completed.The measurement relative error is 0.5% when measuring resistances. For the moisture content of 6% to 9% of the sinter mixture, the measurement absolute error is ±0.3%(moisture percentage). The optimal excitation frequency is selected as 60 kHz.