Splattering Suppression And Smelting Characteristic Recognition Of Fused Magnesium Furnace Based On The Arc Acoustic Signal

Fused magnesium oxide is a kind of refractory material with good properties,it can be produced on a large scale with three phase AC fused magnesium furnaces smelting magnesite.Magnesia smelting industry contains high energy consumption and high emission,and its related energy resource conservation and pollution reduction are the key issues of magnesium industrial development.Additionally,it has an important guiding function on magnesia smelting process optimization and an important significance on low-carbon production for metallurgical industry to reduce the energy consumption per ton.Traditional magnesium furnace smelting control systems only apply three-phase currents and voltages as input parameters and control basis and cannot effectively follow the combustion state of the arc neither the molten state of the magnesium oxide molten pool.Previous researches show that arc acoustic signal is an important accompanying information signal in arc combustion and it could be acquired by means of non-contact measurements.Meanwhile,the arc acoustic signal can preferably reflect the combustion state of the arc and the molten level of the molten pool.The arc acoustic signal contains a great deal of information related to the smelting state of the arc furnace.Especially before the furnace splattering,the characteristics of the signal will change significantly.Hence,based on the characteristics of acoustic signals during the fused magnesium furnace operation,the time frequency analysis and speech recognition methods are adopted in this paper to systematically study the furnace splattering suppression and molten characteristics identification.Herein,the research objective is to optimize the existing control system of fused magnesium furnace,to reduce the energy consumption per ton of smelting magnesium oxide,as well as to increase the output of high purity crystals.This study provides an important theoretical guidance and an experimental reference for the improvement of the smelting process of magnesium furnace.It is of great practical significance for the magnesium oxide industry to achieve energy saving,emission reduction,and production costs reduction.The primary research contents and results are as follows:(1)According to the principle of fused magnesium furnace making sound,the modeling problem of the acoustical signal from the fused magnesium furnace could be ascribed to the problem of sound wave transmission with arc as the sound source,and an arc acoustic mathematical model based on power is proposed.The characteristic frequency of acousticsignal in AC arc furnaces was calculated by this model,the result showed that thecombustion state of the arc could be monitored by the frequency distribution of the acoustic signal.The model was also used to calculate the spatial distribution of 100 Hz arc acousticsignal intensity inside the furnace.Considering the superiority of the arc sound channel model in speech signal recognition,a method of identification the molten state of magnesium oxide pool by using the arc sound channel model of arc furnace was put forward.(2)The hardware system and software system of arc acoustic signal acquisition were constructed with virtual instrument technology,and the characteristics of data type and program structure in graphic programming technology were further analyzed.Then the acquisition process of acoustic signal from the fused magnesium furnace was designed,and the location of arc sound signal measurement point was determined.Furthermore,aming at the identification of different running states of the fused magnesium furnace,the acoustic signals at different smelting states during the operation were collected,and the characteristics of the average sound intensity and the characteristics of time-frequency images are compared.Additionally,the criterions of different smelting states,such as the starting up stage,the steady stage,the splattering state and the feeding stage were summarized according to the fluctuation trend of the effective values of the three-phase currents.The results showed that the 100 Hz acoustic signal could accurately reflect the combustion state of the arc and the 200 Hz acoustic signal could be used as an effective criterion to judge whether the fused magnesium furnace was in the splattering state.(3)Aming at the splattering phenomenon during smelting magnesium oxide,the acoustic signals and image signals before and after the furnace splattering were collected.According to the changing characteristics of 200 Hz acoustic signals during the furnace splattering,the changing law of arc acoustic signals in the early stage of furnace splattering was found,and a furnace splattering suppression system was developed.The furnace splattering suppression system was embedded into the original control system of the fused magnesium furnace.An experimental production of a 5000 kVA fused magnesium furnace in a magnesium oxide smelting workshop in China was conducted,the furnace splattering was restrained effectively and the energy consumption per ton of the magnesium oxide smelting was reduced.The average energy consumption per ton was 445.5 kW h/t lower than that before the deployment of the spray suppression system.(4)Based on the characteristics of the molten state change of the fused magnesium furnace in each feeding cycle,the arc sound channel model and the waveform reconstruction method based on linear predictive coding were used to extracted the 10 dimensional molten state feature vector.Furthermore,the principal component analysis was used to reduce the dimensionality of the molten state feature vector to 2 dimensions.The four different molten states of molten pool were mapped to the molten state map,and the real-time identification of molten state is realized.The molten state identification program was designed.By using this program,the accuracy of the molten state identification could be improved by adjusting the position and radius of each state circle in the molten state map.According to the result of identification,both of the ore delivery process and current injection process were optimized.The average smelting energy consumption per ton was reduced by 82.0 kW·h/t,while the average content of the crystals with a purity above 98%was raised by 2%.