JP2011046988A - Continuous annealing furnace of metal strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably prevent intrusion of combustion gas from a direct heating zone to an indirect heating zone by using inert gas which is wastefully discharged. <P>SOLUTION: A refiner 3 has driers 35A, 35B for drying refined atmospheric gas, and a gas feed pipe 44 for feeding inert gas to regenerate the driers 35A, 35B. A gas injection nozzle 2 for forming a gas curtain between a direct heating zone 12 and an indirect heating zone 13 of a continuous annealing furnace, and a gas feed pipe 41 for feeding inert gas after regenerating the driers 35A, 35B to the gas injection nozzle 2 are provided. The pair of driers 35A, 35B are provided in parallel, the service condition and the regenerating condition of one drier and the other drier are alternately changed, and the inert gas fed to the drier in the regenerated condition is fed to the gas injection nozzle 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a continuous annealing furnace for a metal strip, and more particularly to an improvement of a continuous annealing furnace provided with a plating tank downstream thereof so that the metal strip can be plated.

  As this type of continuous annealing furnace, a so-called galbarium furnace is known in which a metal strip is annealed under a reducing atmosphere gas, and then plated by passing through a zinc-aluminum alloy plating bath in a plating tank. Yes. And in such a continuous annealing furnace, in order to prevent wasteful consumption of reducing atmosphere gas and to prevent deposition of volatilized plating bath components in the furnace, it was brought together with plating bath components and metal strips. A polluted atmosphere gas contaminated with moisture, oxygen or the like is refined by a refiner provided outside the furnace and refluxed again into the furnace (Patent Document 1).

JP-A-10-176225

  By the way, in the conventional continuous annealing furnace, a direct heating zone for directly heating a metal strip in a non-oxidizing atmosphere in which a direct fire burner is burned at an air ratio of less than 1.0 is used, and a radiant tube is used downstream thereof. An indirect heating zone for indirectly heating the metal strip in a reducing gas atmosphere is provided. In this case, the furnace pressure in the indirect heating zone must be sufficiently higher than that in the direct heating zone so that the combustion gas in the direct heating zone does not enter the indirect heating zone. In the above annealing furnace, which is refined with a refiner provided outside and recirculated back into the furnace, it is difficult to maintain the furnace pressure in the indirect heating zone sufficiently high, since the amount of reducing atmosphere gas can be reduced. There was a problem. On the other hand, the refiner is provided with a dryer, but an inert gas such as N2 gas is used during regeneration of the dryer, and at present, the inert gas after regeneration of the dryer is released without being used as it is.

  Therefore, the present invention solves such problems, and a continuous metal strip that reliably prevents the invasion of combustion gas from the direct heating zone into the indirect heating zone by using the inert gas exhausted wastefully. An object is to provide an annealing furnace.

  In order to achieve the above object, in the present invention, at least a direct heating zone (12) and an indirect heating zone (13) are provided in this order from the upstream side in the furnace through which the metal strip (S) passes, and indirect heating zone. In a continuous annealing furnace for a metal strip provided with a refiner (3) for sucking a polluted atmosphere gas from (13), purifying it and returning it to the furnace downstream of the indirect heating zone (13) again, the refiner (3 ) Is provided with a dryer (35A, 35B) for drying the purified atmospheric gas, and a first gas supply path (44) for supplying an inert gas for regenerating the dryer (35A, 35B). In addition, a gas injection nozzle (2) for forming a gas curtain is provided between the direct heating zone (12) and the indirect heating zone (13), and the dryers (35A, 35B) are regenerated. A second gas supply path (41) for supplying a later inert gas to the gas injection nozzle (2) is provided, and a pair of dryers (35A, 35B) are provided in parallel, and the usage state of one dryer and the other dryer is provided. And the regeneration state are alternately switched, and the inert gas supplied to the dryer in the regeneration state is supplied to the gas injection nozzle (2).

  In the present invention, since the gas curtain is formed, the combustion gas in the direct heating zone does not enter the indirect heating zone even when the furnace pressure in the indirect heating zone is not sufficiently higher than the direct heating zone. In addition, since the inert gas after the regeneration of the dryer, which has been conventionally wasted in the formation of the gas curtain, is used, a new gas supply for forming the gas curtain is unnecessary, and an increase in cost can be avoided.

  The reference numerals in the parentheses indicate the correspondence with specific means described in the embodiments described later.

  As described above, according to the continuous annealing furnace for a metal strip of the present invention, the gas curtain is formed using the inert gas discharged from the dryer, so that the direct heating zone is changed to the indirect heating zone. It is possible to reliably prevent the invasion of the combustion gas without increasing the cost.

It is a schematic sectional drawing of the metal strip continuous annealing furnace in one Embodiment of this invention. It is a systematic diagram which shows the internal structure of the refiner in one Embodiment of this invention.

  FIG. 1 shows an example of a metal strip continuous annealing furnace. In FIG. 1, the continuous annealing furnace 1 includes a pre-tropical zone 11, a direct heating zone 12, an indirect heating zone 13, a cooling zone 14, a holding zone 15, and a cooling zone 16, and a down chute 17 extends from the cooling zone 16. Then, the snout 18 provided at the tip thereof is immersed in, for example, a zinc-aluminum alloy plating bath L in the plating tank 19. The metal strip S reaches the cooling zone 16 from the pre-tropical zone 11 while being supported by a roller at an appropriate position, and is annealed during this time. Thereafter, the metal strip S is passed through the plating bath L through the down chute 17 and the snout 18, and during this time, plating is performed.

  Here, in the direct heating zone 12, the metal strip S is directly heated in a non-oxidizing atmosphere in which an open flame burner is burned at an air ratio of less than 1.0. In the indirect heating zone 13, a radiant tube is used to reduce the gas under the reducing atmosphere gas. The metal strip S is indirectly heated. The furnaces of the indirect heating zone 13, the cooling zones 14 and 16, and the holding zone 15 are filled with a reducing atmosphere gas composed of N2 and H2.

  In order to form a gas curtain between the heating zones 12 and 13 at the boundary wall portion between the direct heating zone 12 and the indirect heating zone 13, it is necessary toward the upstream side at the upper and lower positions of the metal strip S. A plurality of gas injection nozzles 2 are installed, and these gas injection nozzles 2 are connected to a refiner 3, which will be described later in detail, by a gas supply pipe 41 as a second gas supply path. The refiner 3 is also connected to the indirect heating zone 13 by a gas supply pipe 42, and is connected to the cooling zones 14, 16, the holding zone 15 and the down chute 17 through a valve by a gas supply pipe 43. The refiner 3 is connected to a gas supply pipe 44 as a first gas supply path for supplying N2 gas as an inert gas.

  The internal structure of the refiner 3 is shown in FIG. The refiner 3 is provided with a pair of filters 31A and 31B, a cooler 32, a suction fan 33, a deoxygenator 34, and a pair of dryers 35A and 35B from the upstream side. Filters 31A and 31B are provided with filter media, for example, filter paper, filter cloth, filter net, etc. in a sealed container, such as a plating bath evaporation metal in the polluted atmosphere gas flowing from the indirect heating zone 13 through the gas supply pipe 42. Remove dust. The deoxygenator 34 fills an airtight container with an oxidation reaction catalyst, and reacts oxygen in the atmosphere with hydrogen to remove moisture from the oxygen. The dryers 35A and 35B are filled with an adsorbent made of alumina or zeolite in a sealed container. The moisture in the contaminated atmosphere gas and the moisture generated by the deoxygenator 34 are adsorbed and removed to finally form a purified atmosphere gas. . Since the adsorbent does not adsorb moisture when the amount of moisture on the surface increases, regeneration is performed periodically. The regeneration is performed by removing moisture from the adsorbent by circulating N2 gas while raising the temperature with a heater provided in the dryers 35A and 35B.

  The filters 31A and 31B are connected in parallel to each other via three-way valves 51 and 52, a gas supply pipe 42 is connected to the three-way valve 51, and a pipe to the cooler 32 is connected to the three-way valve 52. Yes. When the port between the three-way valves 51 and 52 is switched to the communication position shown by the solid line in FIG. 2, the filter 31A is in a use state, and the filter 31B is in a standby state for replacing or cleaning the filter media. It has become. When the ports of the three-way valves 51 and 52 are switched to the communication state indicated by the broken line in FIG. 2, the use state and the standby state of the filters 31A and 31B are reversed.

  The dryers 35A and 35B are connected in parallel to each other via four-way valves 53 and 54. The four-way valve 53 is connected to a pipe to the deoxygenator 34 and a gas supply pipe 44. Gas supply pipes 41 and 43 are connected. When the ports of the four-way valves 53 and 54 are switched to the communication position indicated by the solid line in FIG. 2, the dryer 35A is in use, and the purified atmospheric gas from which moisture has been removed by the dryer 34A is gas. The supply pipe 43 supplies the cooling zones 14 and 16, the holding zone 15, and the down chute 17. At this time, the dryer 35B is in a regenerated state, and the N2 gas supplied by the gas supply pipe 44 carries away moisture on the surface of the adsorbent in the dryer 35B, so that the adsorbent is regenerated. When the ports of the four-way valves 53 and 54 are switched to the communication state indicated by the broken line in FIG. 2, the use state and the regeneration state of the dryers 35A and 35B are reversed.

  The N2 gas containing moisture by regenerating the dryers 35A and 35B is supplied from the refiner 3 to the gas injection nozzle 2 through the gas supply pipe 41, and is injected directly from the tip toward the heating zone 12, and indirectly with the direct heating zone 12. A gas curtain is formed at the boundary of the heating zone 13. Since the direct heating zone 12 is heated by an open flame burner, there is no problem even if N2 gas containing a lot of moisture flows into the furnace. By forming such a gas curtain, the combustion gas in the direct heating zone 12 may enter the indirect heating zone 13 even when the furnace pressure in the indirect heating zone 13 is not sufficiently higher than the direct heating zone 12. It is surely prevented. In addition, since the N2 gas after the regeneration of the dryer, which has been released in the past, is used for the formation of the gas curtain in this case, a new gas supply for forming the gas curtain is unnecessary, and an increase in cost is avoided. be able to.

  DESCRIPTION OF SYMBOLS 1 ... Continuous annealing furnace, 12 ... Direct heating zone, 13 ... Indirect heating zone, 2 ... Gas injection nozzle, 3 ... Refiner, 35A, 35B ... Dryer, 41 ... Gas supply pipe (2nd gas supply path), 44 ... Gas Supply pipe (first gas supply path), S ... metal strip.

Claims (1)

At least a direct heating zone and an indirect heating zone are provided in this order from the upstream side in the furnace through which the metal strip passes, and the contaminated atmospheric gas is sucked from the indirect heating zone and purified, and again downstream of the indirect heating zone. In a continuous annealing furnace for a metal strip provided with a refiner for refluxing into the furnace, the refiner is provided with a dryer for drying the purified atmospheric gas, and supplied with an inert gas for regenerating the dryer. A gas supply path is provided, and a gas injection nozzle for forming a gas curtain is provided between the direct heating zone and the indirect heating zone, and an inert gas after regenerating the dryer is supplied to the gas injection nozzle. A second gas supply path is provided, and a pair of the dryers are provided in parallel, and the use state and the regeneration state of one dryer and the other dryer are determined. Mutually switched, continuous annealing furnace of a metal strip which inert gas supplied to the dryer became playback state is adapted to be supplied to the gas injection nozzle.

Images