Electrode Insertion Depth Detection Method In Submerged Arc Furnace Based On Ultrasonic Guided Wave

Electrode insertion depth(EID)is a key parameter in the production control of submerged arc furnace smelting.The EID detection is an important basis for the control of the electrode insertion depth,temperature field,power balance and charge reaction speed.It is important to reduce the power consumption of mineral furnace,reduce carbon emissions and improve product quality.However,due to the extremely high temperature in the furnace,it is very difficult to detect the EID.Therefore,aiming at the problem that the EID cannot be accurately measured,this thesis intends to use ultrasonic guided wave detection technology to study the acoustic detection method of the EID.A new method of electrode insertion depth detection based on the ultrasonic guided wave is creatively proposed in this paper,combined with the smelting process and characteristics of submerged arc furnaces.In order to select the optimal guided wave mode,excitation frequency,and waveguide structure size,a finite element method based on the Floquet boundary condition is established to calculate the dispersion curve of the cylindrical waveguide,and the propagation characteristics of graphite guided waves rod with different diameters are analyzed.Therefore,the optimal guided wave mode,excitation frequency,and waveguide structure size are selected for the proposed ultrasonic guided wave detection method.The reliability of the theoretical calculation is verified by experiments.Numerical simulation and experimental results show that the longitudinal guided wave mode is the ideal mode to realize the electrode tip position measurement.When the diameter of the graphite waveguide is 50 mm and the excitation frequency of the transducer is 45 k Hz,the best detection effect is obtained.Then,in order to successfully excite and receive longitudinal guided wave modes,the sandwich piezoelectric ultrasonic transducer is selected as the design prototype.The electromechanical equivalent circuit model of the piezoelectric oscillator and the mechanical vibration model of the front and rear panels are established by using the Mason method and the wave transmission line theory respectively.Based on these,a theoretical calculation model of the structure size of the sandwich piezoelectric ceramic transducer is established by using the half-wave oscillator theory.The initial size of the transducer is obtained.Then,based on the initial value of the transducer structure,the numerical analysis model of the transducer was established by using the finite element analysis software.Some important parameters of the transducer,such as radiated sound pressure field,transmitting voltage response pattern,directivity index and beam pattern,are simulated and analyzed.The numerical simulation results show that the central frequency of the transducer is 45 k Hz and the frequency band range is 35-58 k Hz.At the center frequency of 45 k Hz,the beam angle of the transducer is 58°.In order to improve the ultrasonic intensity and obtain a higher SNR received signal,the directivity optimization method of the transducer is studied.An acoustic focusing scheme using an inverted conical luffing rod is proposed.The optimal parameters of the luffing rod focusing system are studied,by combining theoretical analysis with numerical model.The simulation results show that the transducer has the best directivity when the diameter of the small end and the large end of the inverted conical rod are 30 mm and 45 mm,respectively.When the diameter of the big end of the luffing rod focusing system is equal to that of the straight rod,the change of the small end diameter hardly affects the directivity of the transducer.The increase of the large end diameter can effectively improve the directivity of the transducer and reduce the beam angle,but the amplitude of the side lobe will also increase.In addition,the effective bandwidth of the transducer component will increase after adding the luffing rod focusing system,but the smoothness will decrease.At the same time,the near field radiation sound pressure value of the transducer will be reduced,but the far field radiation sound pressure value will be effectively increased.Finally,the accuracy of the ultrasonic guided wave detection system is verified by experiments.The temperature compensation mechanism of the system is established by analyzing the influence of high temperature on the velocity of the longitudinal waves in the graphite waveguide.The experimental results show that the error of ultrasonic guided wave detection system is less than 15 mm after temperature compensation.