Method for Determining at Least One State Variable of an Electric Arc Furnace, and Electric Arc Furnace

Abstract

In a method for determining a state variable of an electric arc furnace, especially for determining the level of the foamed slag ( 15 ) in a furnace, the energy supplied to the furnace is determined with the aid of at least one electric sensor while solid-borne noise is measured in the form of oscillations on the furnace. The state variable is determined by a transfer function which is determined by evaluating the measured oscillations and evaluating measured data of the electric sensor. The state of the foamed slag level can thus be reliably recognized and be monitored over time. The foamed slag level is decisive for the effectiveness with which energy is fed into the furnace. Furthermore, losses caused by radiation are reduced by covering the arc with the foamed slag. The improved measuring method allows the foamed slag level to be automatically controlled or regulated in a reliable manner.

1 . A method for determining at least one state variable of an electric arc furnace with at least one electrode, comprising the steps of:
 determining the energy supplied to the electric arc furnace with the aid of at least one electric sensor,   measuring structure-borne noise oscillations on the electric arc furnace, and   determining the at least one state variable with the aid of a transfer function which is determined by evaluation of the measured structure-borne noise oscillations and by evaluation of measured data of the at least one electric sensor.   
   
   
       2 . The method according to  claim 1 , wherein the level of the foamed slag is determined as the state variable. 
   
   
       3 . The method according to  claim 1 , wherein structure-borne noise oscillations on the electric arc furnace are measured with the aid of at least one acceleration sensor. 
   
   
       4 . The method according to  claim 1 , wherein structure-borne noise oscillations which emanate from at least one arc of the at least one electrode of the electric arc furnace are measured. 
   
   
       5 . The method according to  claim 1 , wherein the transfer function is determined from an excitation signal and from an output signal, the excitation signal being determined by evaluating measured data of the at least one electric sensor, and the output signal being determined by evaluating the structure-borne noise oscillations measured on the electric arc furnace. 
   
   
       6 . The method according to  claim 5 , wherein a current signal is measured with the aid of the at least one electric sensor and is used to form the excitation signal. 
   
   
       7 . The method a according to  claim 6 , wherein the excitation signal is formed by squaring the current signal. 
   
   
       8 . The method according to  claim 1 , wherein a voltage signal is measured with the aid of the at least one electric sensor and is used to form the excitation signal. 
   
   
       9 . The method according to  claim 8 , wherein the excitation signal is formed by multiplication of the current signal by the voltage signal. 
   
   
       10 . The method according to  claim 1 , wherein the transfer function is determined by way of a cross-power spectrum. 
   
   
       11 . The method according to  claim 1 , wherein the transfer function is evaluated at at least one discrete frequency. 
   
   
       12 . The method according to  claim 11 , wherein the at least one discrete frequency is a multiple of the frequency of the power feed into the arc. 
   
   
       13 . The method according to  claim 11 , wherein the level of the foamed slag is determined in dependence on the change in the transfer function at the one or more discrete frequencies. 
   
   
       14 . A method for controlling an electric arc furnace, comprising the steps of:
 determining the energy supplied to the electric arc furnace with the aid of at least one electric sensor,   measuring structure-borne noise oscillations on the electric arc furnace,   determining the at least one state variable with the aid of a transfer function which is determined by evaluation of the measured structure-borne noise oscillations and by evaluation of measured data of the lat least one electric sensor, and   determining actuating and/or regulating signals for the electric arc furnace with the aid of the at least one specific state variable.   
   
   
       15 . The method according to  claim 14 , wherein actuating and/or regulating signals are emitted to a feeding device of the electric arc furnace. 
   
   
       16 . The method according to  claim 14 , wherein actuating and/or regulating signals that influence the blowing-in of oxygen are emitted. 
   
   
       17 . The method according to  claim 14 , wherein actuating and/or regulating signals that influence the blowing-in of carbon are emitted. 
   
   
       18 . The method according to  claim 14 , wherein actuating and/or regulating signals that influence the blowing-in of lime are emitted. 
   
   
       19 . The method according to  claim 14 , wherein actuating and/or regulating signals for influencing the position of the at least one electrode are emitted. 
   
   
       20 . The method according to  claim 14 , wherein a neural network is used for determining the actuating and/or regulating signals. 
   
   
       21 . An electric arc furnace comprising:
 a furnace casing,   at least one electrode,   a current lead for each electrode,   at least one electric sensor on a current lead and at least one structure-borne noise sensor for sensing structure-borne noise oscillations is provided on the wall of the furnace casing.   
   
   
       22 . The electric arc furnace according to  claim 21 , wherein an electric sensor is provided for each electrode. 
   
   
       23 . The electric arc furnace according to  claim 21 , wherein the at least one structure-borne noise sensor is formed as an acceleration sensor. 
   
   
       24 . The electric arc furnace according to  claim 21  comprising a structure-borne noise sensor for each electrode. 
   
   
       25 . The electric arc furnace according to  claim 24 , wherein the one or more structure-borne noise sensors are arranged on a wall of the furnace casing that is opposite the respective electrode. 
   
   
       26 . The electric arc furnace according to  claim 21 , wherein the at least one electric sensor and the at least one structure-borne noise sensor are coupled with a signal processing device. 
   
   
       27 . The electric arc furnace according to  claim 21 , comprising at least one optical waveguide for coupling the at least one structure-borne noise sensor with the signal processing device. 
   
   
       28 . The electric arc furnace according to  claim 27 , wherein the at least one structure-borne noise sensor is connected to the optical waveguide by way of at least one signal line and by way of an optical device arranged ahead of the optical waveguide. 
   
   
       29 . The electric arc furnace according to  claim 28 , wherein the at least one signal line is formed such that it is routed in a protected manner. 
   
   
       30 . The electric arc furnace according to  claim 26 , wherein the signal processing device is coupled with a regulating device for the electric arc furnace.