Method for operating an electric arc furnace and melting plant having an electric arc furnace operated according to said method

Patent metadata

Field	Value
Publication number	US-9949322-B2
Application number	US-201214233886-A
Country	US
Kind code	B2
Filing date	Jul 12, 2012
Priority date	Jul 19, 2011
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

In a method for operating an electric arc furnace operated with an alternating voltage, a structure-borne sound signal occurring on a wall of the electric arc furnace is detected, from which structure-borne sound signal a parameter characterizing the flicker properties of the electric arc furnace is calculated. At least one process variable of the electric arc furnace is controlled on the basis of the calculated parameter. An electric arc furnace operated according to the method is used in and for a melting plant.

First claim

The invention claimed is:

1. A method for operating an alternating voltage electric arc furnace, comprising:
detecting, by a structure-borne sound sensor arranged on a wall of the electric arc furnace, a structure-borne sound signal arising at the wall;
calculating a parameter which predicts a flicker value of the electric arc furnace, the parameter being calculated based on the structure-borne sound signal, wherein the flicker value corresponds to a variation in light intensity from a light source over time caused by fluctuations of voltage in the electric arc furnace; and
controlling a process variable for the electric arc furnace by reference to the parameter to avoid flicker.

2. The method as claimed in claim 1 , wherein the parameter is a numeric measure related to a Kst value, the Kst value specifying characteristics, including at least one of weight and density, of scrap metal disposed in the electric arc furnace.

3. The method as claimed in claim 2 , wherein calculating the parameter comprises:
subjecting the structure-borne sound signal to a Fourier transformation;
determining amplitudes of the Fourier transform at a plurality of frequencies; and
calculating the parameter from the amplitudes.

4. The method as claimed in claim 3 , wherein
a measure for a low-frequency scrap movement is calculated from amplitudes of the Fourier transform at frequencies f which lie below a fundamental frequency f 0 ,
a measure for a high frequency vibration is calculated from amplitudes of the Fourier transform at frequencies f which lie above the fundamental frequency f 0 and do not include harmonic frequencies mf 0 ,
a measure which characterizes stability of the electric arc is calculated from amplitudes of the Fourier transform at frequencies f which lie at and between the harmonic frequencies mf 0 , and
the parameter is calculated from the measures.

5. The method as claimed in claim 4 , wherein the parameter is determined using:

SV
=

B
*
E

⁢

⁢
where

(
1
)

B
=

∑

n
=

n
⁢

⁢
0

n
⁢

⁢
1

⁢

F

-
α

⁡

(

f
n

)

(
2
)

where B is the measure for a low-frequency scrap movement, where E is the measure for a high frequency vibration, where F is the Fourier transform, where f n1 <f 0 and f n+1 −f n =Δf«f 0
and where

E
=

∑

n
=

n
⁢

⁢
2

n
⁢

⁢
3

⁢

F
β

⁡

(

f
n

)

(
3
)

where f n ≠m*f 0 and f n2 >f 0 , 2≤β≤10 and m is a natural number,
and

SSG
=

(

∑

k
=
2

k
max

⁢

F
⁡

(

k
⁢

⁢

f
0

)

)

*

(

∑
n

Assignees

• Doebbeler Arno
• Fink Dieter
• Rieger Detlef
• Primetals Technologies Germany Gmbh

Inventors

• Döbbeler Arno
• Fink Dieter
• Rieger Detlef

Classifications

• F27B3/28

  Arrangement of controlling, monitoring, alarm or the like devices · CPC title

• F27B3/085

  Arc furnaces · CPC title

• H05B7/148 Primary

  Automatic control of power (electrode feeding arrangements H05B7/109; automatic feeding of electrodes for spot or seam welding or cutting B23K9/12; disposition of electrodes in or on furnaces F27D11/10; control of position in general G05D3/00; regulating electric characteristics of arcs in general G05F1/02; regulating electric power in general G05F1/66) · CPC title

• F27B3/20

  Arrangements of heating devices · CPC title

• F27D2099/0021

  Arc heating · CPC title