JPH0581275U - Steel strip pickling device with waste acid recovery tank - Google Patents

Abstract

(57) [Summary] [Purpose] The pickling solution that flows out from the ringer roll provided between the final pickling tank and the rinsing tank is recovered as rinse wastewater without being treated. [Structure] An acid concentration meter 2 is provided between a final pickling tank 1 and a rinse tank 9 of a horizontal pickling apparatus including a plurality of pickling tanks 1 and a rinse tank 9.
4 is provided, and control valves 25 and 26 are provided in a conduit 23 that connects the waste acid recovery tank 22 and each upstream pickling tank 1 or each upstream acid solution storage tank 2 to control the acid solution concentration. A control unit 27 is provided to control the opening and closing of the control valves 25 and 26 of the upstream pickling tanks 1 or the upstream acid solution storage tanks 2 according to the total acid concentration of 24. [Effect] The pickling solution flowing out from the final pickling tank can be recovered and reused, and the unit consumption of the pickling solution and the cost of the neutralization treatment can be reduced.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a horizontal pickling apparatus including a plurality of pickling tanks and a rinse tank for continuously pickling and removing an oxide scale film formed on the surface of a steel strip in a hot rolling process or the like.

[0002]

[Prior Art]

 There are various types of pickling equipment that removes the oxide scale film on the surface by passing the steel strip through a pickling solution such as hydrochloric acid or sulfuric acid, but recently, from the viewpoint of saving heat energy, the depth of the pickling tank is deep. Shallow bath immersion type such as low bath type, charo type, etc., turbulence type, jet type, etc. that has a shallow bath depth and agitates the pickling solution in the bath to shorten the pickling time. The jet agitation type pickling device is widely used.

A turbulence type will be described as an example of the steel strip pickling apparatus. As shown in FIG. 4 and FIG. 5, the turbulence type pickling device is normally provided with 3 to 5 pickling tanks 31 (three tanks in FIG. 4) connected in series. Is pressurized by the pump 33 and is sprayed from the main header 34 and the side header 35 onto the steel strip 36 passing through each of the pickling tanks 31, and the oxide scale film on the surface of the steel strip 36 is removed. The pickling solution sprayed into each pickling tank 31 returns to each pickling solution storage tank 32 through each return pipe 37, and is again sprayed into each pickling tank 31.

A pre-rinse tank 38 and a plurality of rinse tanks 39 are connected to the rear part of the final pickling tank 31, and a pump 40 pressurizes the pickling solution remaining on the surface of the steel strip 36. The rinse water is sprayed from the spray header 41. The rinse wastewater that has been sprayed in the pre-rinse tank 38 and contains the pickling solution is discharged to the outside of the tank through the pipe 42. Between the respective pickling tanks 31, 31, the final pickling tank 31 and the pre-rinse tank 38, and the pre-rinse tank 38 and the rinse tank 39, pickling solution and rinse water are moved between the respective tanks. To prevent this, a pair of upper and lower ringer rolls 43, 44 and 45 are provided. Further, a new pickling solution is supplied to the pickling solution storage tank 32 of the final pickling tank 31 via a replenishment pipe 46, and the final pickling tank 31 is sequentially replenished to the pickling tank 31 upstream by a cascade pump 47. An amount of pickling solution corresponding to the amount is supplied, and during this time, the pickling solution which has reacted with the acid scale on the surface of the steel strip 36 and becomes waste acid is recovered from the most upstream pickling tank 31 by a pump 48, not shown. It is sent to the apparatus and returned to the acid solution storage tank 32 of the final pickling tank 31 through the regenerated supply pipe 46.

[0005]

[Problems to be solved by the device]

 In the above-mentioned conventional pickling apparatus, the ringer roll 44 provided between the final pickling tank 31 and the pre-rinsing tank 38 prevents the pickling solution from flowing out (moving) to the pre-rinsing tank 38. The outflow amount is not constant because it largely depends on the surface condition of the ringer roll 44 and the steel strip passing speed. That is, the outflow amount of the pickling solution increases as the wear of the ringer roll 44 progresses and as the steel strip passing speed increases, and the acid concentration of the rinse waste water discharged from the pre-rinse tank 38 becomes high. Become. The rinse wastewater discharged under such conditions contains a large amount of pickling solution and is still in a state in which it can be sufficiently used. Therefore, if this rinse wastewater is neutralized and discarded, the cost of the pickling solution and the cost of neutralization will increase, resulting in a large loss. Further, the rinse water sprayed from the spray header 41 flows into the final pickling tank 31, the acid solution concentration in the final pickling tank 31 cannot be secured, and a large amount of acid solution is added to secure the concentration. The basic unit of acid liquid deteriorates.

An object of the present invention is to provide a pickling apparatus capable of recovering a pickling solution flowing out from a ringer roll provided between a final pickling tank and a rinse tank without treating it as rinse wastewater.

[0007]

[Means for Solving the Problems]

 The present inventors have conducted extensive studies to achieve the above object. As a result, an exhausted acid recovery tank is provided between the final pickling tank and the pre-rinse tank, and the exhausted acid recovery tank and the upstream pickling tank or the upstream pickling solution storage tank for storing the low-concentration pickling solution are provided by conduits. It was concluded that the connection makes it possible to recover the pickling solution flowing out from the ringer roll provided between the final pickling tank and the pre-rinsing tank without treating it as a rinse wastewater, and arrived at the present invention.

That is, the present invention provides a horizontal pickling apparatus including a plurality of pickling tanks and a rinsing tank, which is provided with an exhausted acid recovery tank between the final pickling tank and the rinse tank, This is a steel strip pickling device equipped with a waste acid recovery tank that is connected to a tank or an upstream acid solution storage tank by a conduit.

Further, an exhaust acid recovery tank having an acid concentration meter is provided between the final pickling tank and the rinse tank of the horizontal pickling apparatus including a plurality of pickling tanks and a rinse tank, and the exhaust acid recovery tank and the upstream side are provided. A control valve is installed in the conduit that connects each pickling tank or each upstream acid solution storage tank, and opens or closes the control valve of each upstream pickling tank or each upstream acid solution storage tank according to the acid concentration of the acid solution concentration meter. It is a steel strip pickling apparatus equipped with a waste acid recovery tank provided with a control unit for controlling.

Further, an exhaust acid recovery tank is provided between the final pickling tank and the rinse tank of the horizontal pickling apparatus including a plurality of pickling tanks and a rinse tank, and the exhaust acid recovery tank and the upstream pickling tank or the upstream pickling tank are provided. In a steel strip pickling device that connects a liquid storage tank with a conduit, a ringer roll is provided between the partition wall that divides the final pickling tank and the pre-rinse tank and the water spray nozzle of the pre-rinse tank, and a line is provided upstream of the ringer roll. It is a steel strip pickling device equipped with an exhaust acid recovery tank provided with a spray nozzle that sprays water in conjunction with a state where the speed is below a predetermined value.

[0011]

[Action]

 In this invention, an exhaust acid recovery tank is provided between the final pickling tank and the rinsing tank, and the exhaust acid recovery tank and the upstream pickling tank or the upstream acid solution storage tank are connected by a conduit. The pickling solution that could not be blocked by the Ringer roll between the tank and the pre-rinse tank was partially diluted with the rinse water, but most of it was dropped into the waste acid recovery tank and separated from the rinse waste water. , And is collected in the upstream low-concentration pickling tank or acid solution storage tank for reuse.

Further, an exhaust acid recovery tank having an acid solution concentration meter is provided between the final pickling tank and the rinse tank, and the exhaust acid recovery tank is connected to each upstream pickling tank or each upstream acid solution storage tank. A control valve is installed in the conduit to control the opening and closing of the control valve of each upstream pickling tank or each upstream acid solution storage tank according to the acid concentration of the acid concentration meter. Since the concentration of the recovered pickling solution is measured and sent to the upstream pickling tank or the upstream pickling solution storage tank under the optimum concentration condition, the reuse efficiency of the pickling solution can be further increased.

Furthermore, since the ringer roll is provided between the partition wall that divides the final pickling tank and the pre-rinse tank and the water spray nozzle of the pre-rinse tank, the rinse water is suppressed from mixing into the waste acid recovery tank, and the pickling solution is It is possible to prevent the concentration from decreasing and to enhance the reuse value. Further, a spray nozzle for injecting water is provided on the upstream side of the ringer roll in conjunction with a state where the line speed is a predetermined value or less (for example, line stop or a certain speed or less, specifically 20 to 30 m / min or less). Therefore, when the line speed falls below a predetermined value, the spray nozzle water is sprayed in tandem with this, and it is possible to prevent pickling discoloration due to the drying of the steel strip surface between the ringer rolls.

[0014]

【Example】

 This invention will be described in detail below with reference to FIGS. Fig. 1 is a cross-sectional view showing an example of a turbulence-type jet agitation type horizontal pickling apparatus according to the present invention, Fig. 3 is a detailed cross-sectional view of a waste pickling tank, and Fig. 3 is a ringer of the final pickling tank. FIG. 3 is a detailed cross-sectional view of the waste acid recovery tank part when a ringer roll and a spray nozzle that sprays water in conjunction with line stop are provided between the roll and the rinse water spray nozzle of the pre-rinse tank.

In FIG. 1 and FIG. 2, three pickling tanks 1 are connected in series, and the pickling solution in each pickling solution storage tank 2 is pressurized by a pump 3 in each pickling tank 1. It is sprayed from the header 4 and the side header 5 onto the steel strip 6 passing through each pickling tank 1, and the oxide scale film on the surface of the steel strip 6 is removed. The pickling solution sprayed into each pickling tank 1 returns to each pickling solution storage tank 2 through the return pipe 7 and is again sprayed into each pickling tank 1. Further, in the rear part of the final pickling tank 1, a pre-rinse tank 8 and a partition wall 21 are connected, and an exhaust acid recovery tank 22, a pre-rinse tank 8 and a plurality of rinse tanks 9 (only one tank in the drawing) are connected to each other. Rinse water pressurized by the pump 10 is sprayed from the spray header 11 in order to wash away the pickling solution remaining on the surface of the strip 6. The rinse wastewater that has been sprayed in the pre-rinse tank 8 and contains the pickling solution is discharged to the outside of the tank through the pipe 12.

Between the pickling tanks 1 and 1, between the final pickling tank 1 and the waste acid recovery tank 22, and between the pre-rinsing tank 8 and the rinse tank 9, pickling solution and rinse water are passed between the tanks. In order to prevent the movement, a pair of upper and lower ringer rolls 13, 14 and 15 are provided. Further, the final pickling tank 1 is supplied with a new pickling solution adjusted to a predetermined concentration (for example, HCl: 12 to 15%) via the replenishment pipe 16, and the pickling solution from the final pickling tank 1 is sequentially supplied to the upstream pickling solution. The amount of pickling solution commensurate with the supply amount is transferred to the washing tank 1 by the cascade pump 17, and during this period, the pickling solution which has reacted with the oxide scale on the surface of the steel strip 6 and becomes waste acid is the most upstream pickling tank 1. Is sent from a pump 18 to an acid recovery device (not shown), and is returned to the final pickling tank 1 via the regenerated supply pipe 16.

Further, the discharged acid recovery tank 22 is connected to each upstream acid solution storage tank 2 by a conduit 23. Further, the conduit 23 is provided with an acid solution concentration meter 24, and opening / closing valves 25, 26 for delivering the solution to a specific acid solution storage tank 2 or a pickling tank 1 are provided in the conduit 23 according to the measured acid solution concentration. It is provided after the inside of the acid concentration meter 24. The acid solution concentration measured by the acid solution concentration meter 24 is output to the control unit 27 of the opening / closing valves 25 and 26. According to the acid solution concentration input from the acid solution concentration meter 24, the control unit 27 sends to the uppermost stream side acid solution storage tank 2 if the acid solution concentration is 5 to 7% or less, and if the acid solution concentration is 7% or more. For example, the on-off valves 25 and 26 are controlled to be opened and closed so as to guide the recovered waste acid to the next highest acid solution storage tank 2.

Further, as shown in FIG. 3, a ringer roll 28 is further provided between the spray header 11 and the partition wall 21 of the pre-rinse tank 8, and the line is stopped between the ringer roll 28 and the ringer roll 14. A spray nozzle 29 for spraying water is provided in conjunction with the spray nozzle 29. When the line is stopped, water is sprayed from the spray nozzle 29 onto the surface of the steel strip 6.

With the above-described structure, the relatively high-concentration pickling solution that cannot be captured by the Ringer roll 14 of the final pickling tank 1 and is discharged is stored in the waste acid recovery tank 22 and passes through the conduit 23. And is introduced into the upstream acid solution storage tank 2 having a relatively low concentration. Although the acid concentration of the pickling solution recovered in the waste acid recovery tank 22 changes depending on the operating conditions, it is measured by an acid solution concentration meter 24 provided in the middle of the conduit 23 and output to the opening / closing control unit 27. The on-off valves 25 and 26 are controlled to open and close according to the concentration, and if the acid solution concentration is 5 to 7% or less, it goes to the most upstream acid solution storage tank 2. If the acid solution concentration is 7% or more, the next most upstream acid solution is used. The recovered waste acid is introduced into the liquid storage tank 2. As a result, the relatively high-concentration pickling solution discharged from the final pickling tank 1, which was conventionally neutralized as rinse wastewater, can be recovered and reused. It is possible to reduce the cost of the neutralization treatment.

Further, since the ringer roll 28 is further provided between the spray header 11 and the partition wall 21 of the pre-rinse tank 8, it is possible to prevent the rinse water from the spray header 11 from mixing into the waste acid recovery tank 22. To be done. Further, since the spray nozzle 29 for spraying water is provided between the ringer roll 28 and the ringer roll 14 in conjunction with the line stop, if the line is stopped, the water is sprayed from the spray nozzle 29 onto the surface of the steel strip 6. Therefore, it is possible to prevent discoloration due to pickling due to drying of the surface of the steel strip 6 between the Ringer roll 28 and the Ringer roll 14 when the line is stopped.

In the above-mentioned embodiment, the turbulence type pickling apparatus having the three pickling tanks 1 and the pre-rinsing tank 8 is taken as an example. The present invention can also be applied to the case where the final pickling tank is directly connected to the rinse tank without equipping the tank, or to the case of another type of horizontal pickling device. Further, when there is no difference in height in the conduit 23 and the recovered acid cannot be introduced from the recovered acid recovery tank 22 into the acid solution storage tank 2, a dedicated pump can be provided in the conduit 23 for pressure feeding.

[0022]

[Effect of the device]

 As described above, according to the present invention, the pickling solution flowing out from the final pickling tank can be collected and reused, and compared with the conventional method in which the flowing pickling solution was wastefully neutralized. However, even if the amount of pickling solution flowing out is increased to a large extent, most of the pickling solution can be effectively recovered, which makes it easy to maintain and manage the ringer roll. Moreover, it is possible to reduce the basic unit of the pickling solution and the cost of the neutralization treatment.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a turbulence type jet agitation type horizontal pickling apparatus according to the present invention.

FIG. 2 is a detailed cross-sectional view of an exhaust acid recovery tank portion.

[Fig. 3] Detailed cross section of the waste acid recovery tank when a ringer roll in the final pickling tank and a rinse water spray nozzle in the pre-rinse tank are provided with a ringer roll and a spray nozzle that sprays water in conjunction with the line stop. It is a figure.

FIG. 4 is a cross-sectional view showing an example of a conventional turbulence jet agitation type horizontal pickling apparatus.

FIG. 5 is an enlarged cross-sectional view of a final pickling tank and a pre-rinse tank portion of a conventional turbulence jet agitation type horizontal pickling apparatus.

[Explanation of symbols]

1,31 Pickling tank 2,32 Acid solution storage tank 3,10,18,33,40,48 Pump 4,34 Main header 5,35 Side header 6,36 Steel strip 7,37 Return pipe 8,38 Pre-rinse tank 9,39 Rinse tank 11,41 Spray header 12,42 Piping 13,14,15,28,43,44,45 Ringer roll 16,46 Replenishment piping 17,47 Cascade pump 21 Partition wall 22 Waste acid recovery tank 23 Conduit 24 Acid solution concentration meter 25,26 Open / close valve 27 Control unit 29 Spray nozzle

Claims (3)

[Scope of utility model registration request] 1. A horizontal pickling apparatus comprising a plurality of pickling tanks and a rinsing tank, wherein an exhausted acid recovery tank is provided between the final pickling tank and the rinse tank, and the exhausted acid recovery tank and the upstream pickling tank or upstream. A steel strip pickling apparatus having an exhaust acid recovery tank, characterized in that it is connected to an acid liquid storage tank by a conduit. 2. A horizontal pickling apparatus comprising a plurality of pickling tanks and a rinsing tank, an exhaust acid recovery tank having an acid concentration meter is provided between the final pickling tank and the rinse tank, and the exhaust acid recovery tank and the upstream side are provided. A control valve is installed in the conduit connecting each pickling tank or each upstream acid solution storage tank, and the control valve of each upstream pickling tank or each upstream acid solution storage tank is opened and closed according to the acid concentration of the acid concentration meter. A steel strip pickling apparatus having an exhaust acid recovery tank, which is provided with a control unit for controlling. 3. An exhaust acid recovery tank is provided between a final pickling tank and a rinse tank of a horizontal pickling apparatus including a plurality of pickling tanks and a rinse tank, and the exhaust acid recovery tank and the upstream pickling tank or the upstream acid is provided. In a steel strip pickling apparatus in which a liquid storage tank is connected by a conduit, a ringer roll is provided between the partition wall that partitions the final pickling tank and the pre-rinse tank and the pre-rinse tank water spray nozzle, and a line is provided on the upstream side of the ringer roll. A steel strip pickling apparatus having an exhaust acid recovery tank, characterized in that a spray nozzle for injecting water is provided in association with a state in which the speed is below a predetermined value.