Descaling device and method for chemically descaling a metal strip

Abstract

A descaling device (2) for chemically descaling a metal strip (4): A spraying device (12, 12a-12d) for spraying a pickling agent (14) onto a top or bottom side (16, 18) of the metal strip (4). The spraying device (12, 12a-12d) has a first outer spraying unit (50) for spraying the pickling agent (14) onto a first edge region (52) of the top/bottom side (16, 18) of the metal strip (4) and a second outer spraying unit (54) for spraying the pickling agent (14) onto a second edge region (56) of the top/bottom side (16, 18) of the metal strip (4), which second edge region lies opposite the first edge region (52). At least one of the two outer spraying units (50, 54) has one or more solid stream nozzles (20), in particular a plurality of rows of solid stream nozzles (20), and/or one or more slotted nozzles (22).

1 . A descaling device for chemical descaling of a metal strip, wherein the metal strip passes through the descaling device; the metal strip having a first edge region and a second edge region extending inwardly from respective lateral edges of the metal strip passing through the descaling device; the metal strip having a middle region situated between the first and the second edge regions of the metal strip; the metal strip having a top side and a bottom side;
 the descaling device, comprising:   at least one first spraying device and at least one second spraying device for respectively spraying a pickling agent onto a top side/bottom side of the metal strip;   each of the first spraying device and the second spraying device comprises a respective first outer spraying unit for spraying the pickling agent onto the first edge region of the top side/bottom side of the metal strip and a second outer spraying unit for spraying the pickling agent onto the second edge region of the top side/bottom side of the metal strip, wherein the second edge region of the metal strip is situated opposite the first edge region of the metal strip and extending inwardly from the respective lateral edges of the metal strip; and   the first spraying device further comprises a middle spraying unit for spraying the pickling agent onto a middle region of the top side/bottom side of the metal strip, the middle region is between the first and the second edge regions;   at least one of the spraying units of the first/second spraying device comprises multiple rows of solid stream nozzles;   each of the spraying units of the first/second spraying device comprises its own respective pickling agent distribution chamber;   at least one of the two outer spraying units of the second spraying device comprises at least one slotted nozzle; and   each of the two outer spraying units ( 50 ,  54 ) of the first and second spraying device devices comprises its own respective pickling agent distribution chamber.   
     
     
         2 . The descaling device as claimed in  claim 1 , further comprising the at least one second spraying device comprises a middle spraying unit situated between the end regions for spraying the pickling agent onto a middle region of the top side/bottom side of the metal strip;
 wherein the middle spraying unit of the second spraying device comprises at least one of the slotted nozzles and comprises its own pickling agent distribution chamber.   
     
     
         3 . The descaling device as claimed in  claim 1 , wherein each of the spraying devices comprises a spray bar. 
     
     
         4 . The descaling device as claimed in  claim 1 , further comprising a control device configured for adjusting a pickling agent dispersing rate of each respective spraying unit of each of the spraying devices. 
     
     
         5 . The descaling device as claimed in  claim 4 , further comprising the control device being operable for adjusting the pickling agent dispersing rate of the middle spraying unit independently of the pickling agent dispersing rate of the first outer spraying unit and independently of the pickling agent dispersing rate of the second outer spraying unit. 
     
     
         6 . The descaling device as claimed in  claim 4  further comprising the control device comprises multiple pickling agent delivery pumps configured for adjusting the pickling agent dispersing rates of the spraying units, wherein the pickling agent delivery pumps have an exit side connected to the respective ones of spraying device. 
     
     
         7 . The descaling device as claimed in  claim 4 , further comprising the control device comprises multiple valves configured for adjusting the pickling agent dispersing rates of the spraying units, wherein each spraying device is connected at an entry side of the spraying device to the valves. 
     
     
         8 . The descaling device as claimed in  claim 4 , further comprising the control device comprises a sensor unit having at least one sensor for detecting a surface parameter of the metal strip, and the control device is configured to adjust the pickling agent dispersing rate of the respective spraying unit in dependence on an output signal of the sensor unit. 
     
     
         9 . A method for chemical descaling of a metal strip, comprising:
 spraying a pickling agent onto a top side/bottom side of the metal strip by at least one first spraying device onto the top side of the strip and by at least one second spraying device onto the bottom side of the strip;   wherein the spraying of the pickling agent is by a first outer spraying unit of the first spraying device, and by a first outer spraying unit of the second spraying device onto a first edge region of the top side/bottom side of the metal strip; and   the spraying of the pickling agent is also by a second outer spraying unit of the first spraying device and by a second outer spraying unit of the second spraying device onto a second edge region of the top side/bottom side of the metal strip wherein the second edge region is situated opposite the first edge region and, both of the first and the second edge region extending inwardly from respective lateral edges of the metal strip; and   the spraying of the pickling agent is also by a middle spraying unit of the first spraying device onto a middle region of the top side/bottom side of the metal strip, wherein the middle region is situated between the first and second edge regions of the metal strip;   the spraying of the pickling agent onto the top side/bottom side of the metal strip is by at least one of the spraying units of the first spraying device through multiple rows of solid stream nozzles; and   by the spraying by at least one of the two outer spraying units of the further spraying device through one or more slotted nozzles.   
     
     
         10 . The method as claimed in  claim 9 , further comprising:
 spraying the pickling agent onto a middle region of the top side/bottom side of the metal strip, the middle region is situated between the first and second edge regions, of the metal strip, the spraying being through at least one slotted nozzle of a middle spraying unit of the at least one second spraying device.   
     
     
         11 . The method as claimed in  claim 10 , further comprising:
 setting a pickling agent dispersing rate of the first outer spraying unit and a pickling agent dispersing rate of the second outer spraying unit of the at least one first spraying device and/or of the at least one second spraying device, wherein the dispersing rate is set by a control device each time at a value which is different from a pickling agent dispersing rate of the respective middle spraying unit of the first spraying device and of the second spraying device.   
     
     
         12 . The method as claimed in  claim 11 , further comprising:
 setting the pickling agent dispersing rate of the respective spraying unit of the at least one first spraying device and/or of the at least one second spraying device with the aid of the control device for acting upon the metal strip in a width direction of the strip by the first spraying device and/or by the second spraying device with a given pickling agent spray profile, wherein the pickling agent spray profile increases or decreases to a respective lateral outside of the metal strip in the first and/or in the second edge region.   
     
     
         13 . The method as claimed in  claim 12 , wherein the pickling agent spray profile has no plateau. 
     
     
         14 . The method as claimed in  claim 12 , wherein the pickling agent spray profile has a plateau between the two edge regions. 
     
     
         15 . The descaling device of  claim 8 , wherein the surface parameter of the metal strip is dependent on the thickness of the scale layer of the metal strip.