Method and apparatus for controlling the pressure in the exhaust gas duct of a converter

Abstract

The invention relates to a method and an apparatus for controlling the pressure in the exhaust gas duct of a converter in a steel mill using a pressure control loop. To optimize the defined pressure setpoint for the pressure control loop so as to prevent excessive amounts of outside air from being drawn in via the converter mouth, the pressure setpoint is determined according to the invention by adapting a raw value based on the extent to which smoke or flames is/are formed at the mouth (120) of the converter (100).

Claims

1-12. (canceled)

13. A method for controlling pressure in an exhaust gas duct (110) of a converter (100) in a steel mill to a defined pressure setpoint by the appropriate adjustment of control variables, characterized by the following steps for determining the pressure setpoint: defining a raw value for the pressure setpoint dependent on a measured degree of openness of an adjustment ring (122) at a converter mouth (120), and determining the pressure setpoint by adaptation of the raw value in form of an increase of the raw value when an extent of smoke or flame formation at the mouth (120) of the converter is reduced, and vice versa.

14. The method according to claim 13, characterized in that the extent of smoke and flame formation is determined by analyzing image material that shows the current smoke and flame formation at the mouth (120) of the converter during a converter operation.

15. The method according to claim 14, characterized in that, in the image material analysis, essentially only portions in the infrared spectral range are analyzed, while interference signals in the visible spectral range are suppressed.

16. The method according to claim 13, characterized in that the raw value is further adapted so that the raw value is decreased when the quantity of oxygen that is supplied is increased, and vice versa.

17. The method according to claim 13, characterized in that the control variables are used either solely for actuating a damper (112) or for simultaneously actuating the damper (112) and a suction fan (114) in the exhaust gas duct of the converter.

18. An apparatus in a steel mill that has a converter (100) for melting metallic material (300), said apparatus comprising: a pressure control loop (200) for controlling the pressure in the exhaust gas duct (110) of the converter (100) to a defined pressure setpoint by the appropriate adjustment of control variables for control elements (112, 114) in the exhaust gas duct, wherein a pressure setpoint calculation unit (210) is assigned to the pressure control loop (200); characterized in that: a mouth (120) of the converter is equipped with a variably positionable adjustment ring (122) for opening and closing the converter mouth (120) in the transition to an exhaust gas duct (110); a position measuring device (150) is provided for detecting an opening position of the adjustment ring at the converter mouth; a conversion device (160) is provided for converting different detected opening positions to a raw value for the pressure setpoint; an image device (130) is provided for generating image material that shows the converter mouth (120) and the area surrounding it during operation of the converter; an image analysis device (132) is provided for analyzing the image material to determine the extent of smoke and flame formation at the converter mouth (120); and the pressure setpoint calculation unit (210) is designed to calculate the pressure setpoint by adapting a defined raw value (R) for the pressure setpoint based on the extent of smoke and flame formation at the mouth (120) of the converter (100).

19. The apparatus according to claim 18, characterized in that the image capturing device (130) is a CMOS camera system, preferably with an IR filter.

20. The apparatus according to claim 18, characterized in that an oxygen detection device (140) is provided for detecting the quantity of active oxygen that is supplied to the converter (100); and the pressure setpoint calculation unit (210) is further designed to calculate the pressure setpoint by adapting the raw value so that the raw value is decreased when the quantity of oxygen that is supplied is increased, and vice versa.

Description

[0018] The invention is accompanied by a FIGURE showing the apparatus according to the invention.

[0019] The FIGURE shows a converter 100 for melting down metal material 300, typically scrap metal or iron ore. At its upper end, converter 100 has a converter mouth 120 as a transition to an exhaust gas duct 110. In exhaust gas duct 110, dampers 112 and/or a suction fan 114 are provided as control elements for controlling the pressure in the exhaust gas duct 110. Converter mouth 120 is shielded with respect to the ambient air by a variably positionable adjustment ring 122. The degree of openness of the adjustment ring can be variably adjusted, for example with the aid of hydraulic cylinders 124. Also shown is an oxygen lance 126 for supplying active oxygen into the interior of the converter. The technical elements described thus far are all part of the prior art and are objects in a steel mill.

[0020] The apparatus according to the invention comprises a pressure control loop 200 for controlling the pressure in exhaust gas duct 110 of converter 100. The pressure is controlled to a defined pressure setpoint P.sub.setpoint. As part of the control process, the defined pressure setpoint is compared with the actual pressure P.sub.actual, measured by means of a pressure gauge 128 at converter mouth 120. From the control deviation between the pressure setpoint and the actual pressure value (P.sub.setpoint minus P.sub.actual), a controller determines suitable control variables, i.e. control signals for the damper 112 or for the damper and the suction fan 114 in exhaust gas duct 110. The actual pressure in the converter mouth is then adjusted to match the defined pressure setpoint P.sub.setpoint by adjusting the position of dampers 112 and/or the power of suction fan 114.

[0021] The present invention provides that the pressure setpoint P.sub.setpoint, used as an input variable for pressure control loop 200, is obtained by adapting a defined raw value R for the pressure setpoint. To determine the raw value, a position measuring device 150 is provided for detecting the opening position of adjustment ring 122 at converter mouth 120. The opening position of adjustment ring 122 thus detected is converted to raw value R for the pressure setpoint in a conversion device 160 with the aid of a table.

[0022] However, since the conversion table cease to enable an optimal determination of raw values as the total number of operating hours of the converter increases, the invention provides for said raw value to be adapted to the current process situation. For this purpose, an image capturing device 130 is provided, typically a CMOS camera, preferably with an infrared filter, for generating image material that shows the converter mouth and optionally the area surrounding the converter mouth during operation of the converter. More particularly, image capturing device 130 serves to detect smoke and flame formation at converter mouth 120. An image analysis device 132 analyzes the image material thus obtained with respect to the extent of smoke or flame formation. The current extent of smoke or flame formation determined in this manner is supplied to a pressure setpoint calculation unit 210, also called a raw value adaptation unit, which calculates the pressure setpoint to be supplied to pressure control loop 200 by adapting the raw value. In other words, pressure setpoint calculation unit 210 performs an adaptation of the raw value, which has likewise been supplied to it, based on the extent to which smoke or flames is/are formed at the converter mouth, and thus determines the pressure setpoint P.sub.setpoint to be supplied to pressure control loop 200 as an input variable.

[0023] The adaptation of raw value R can be further optimized by factoring into the adaptation not only the extent of smoke or flame formation but also the quantity of active oxygen that is supplied to converter 100. For this purpose, an oxygen detection device 140 is provided for detecting the amount of active oxygen that is supplied to the converter. The total quantity of supplied oxygen is made up of the quantity of oxygen supplied via oxygen lance 126 plus the quantity of oxygen supplied with the iron ore, which is bound in the iron ore and is released during combustion.

LIST OF REFERENCE SIGNS

[0024] 100 converter [0025] 110 exhaust gas duct [0026] 112 damper [0027] 114 suction fan [0028] 120 converter mouth [0029] 122 adjustment ring [0030] 124 hydraulic cylinder [0031] 126 oxygen lance [0032] 128 pressure gauge [0033] 130 image capturing device [0034] 132 image analysis device [0035] 140 oxygen detection device [0036] 150 position measuring device [0037] 160 conversion device [0038] 200 pressure control loop [0039] 210 pressure setpoint calculation unit [0040] 300 metal material [0041] R raw value for pressure setpoint