EP1477583A1 - Installation and process for pickling steel materials - Google Patents

Abstract

Pickling is carried out by spraying pickling fluid (B) in a booth (1), in batch operation, with no nitric acid in the tank (2). Tank and booth are vented together, gases liberated in the booth being returned to the tank. Following pickling, rinse water (C) from a tank (3) is sprayed over the objects in the booth, with gas exchange between booth and tank. Residual gases from rinsing are partly recycled to the rinse water tank, without releasing effluent gases to the surroundings. An independent claim is included for the corresponding plant.

Description

The invention relates to a method for pickling articles made of steel, in particular stainless steel, with a pickling agent containing no nitric acid, that from a pickling tank to those kept in a pickling booth Spraying objects, and a plant for pickling objects of steel, in particular stainless steel, with a pickling tank, one Pickling booth with a nozzle arrangement, a pickling feed from the Pickling tank for nozzle arrangement in the pickling booth and a flushing water tank, the to the nozzle assembly of the pickling booth via a Spülwasserzuführleitung connected.

Such methods and installations for the surface treatment of metals are known in various embodiments in the prior art. at The processing of metals, especially of precious metals, is on whose surface often forms a metal oxide layer or scale layer, which both the appearance and the possible further processing of Materials impaired. For stainless steel, this unwanted sticks Layer very firmly on the surface, leaving aggressive acids for pickling Find use. A common Beizsäuremischung is nitric acid and Hydrofluoric acid used in aqueous solution.

In the prior art, the manual spray pickling is known in which the Beizmittel is applied with a spray lance by hand. The stain is adjusted viscous and adheres well to the metal surface. After a Exposure time of ½ to 2 hours then the stain with water washed. In this procedure directly nitrous gases from the nitric acid and fluorine gas from the hydrofluoric acid, because of their harmful effects must be extracted. To the To limit polluting effects, the exhaust air must be with a Exhaust air scrubbers are cleaned, with about 50% of the nitrous gases and 98 % of the fluorine gas are washed out. The squeegee must be sprayed and wash off the stain wear suitable protective clothing with respiratory protection, since corresponding limit values are exceeded at the workplace.

In addition Tauchbeizverfahren are known in which the to be pickled Object through a pickling agent received in a pickling tank to be led. When using the usual Beizsäuremischung arise also nitrous gases and fluorine gases. An edge suction on the pickling tank is therefore also required. To the uncontrolled escape of gases from the dip tank, is known from DE 26 08 550 C2, to cover the plunge pools by plane-like covers. nevertheless Toxic exhaust air is produced, if necessary also via an exhaust air scrubber is clean.

Furthermore, the so-called. Autoclave pickling is known in which the pickled goods in a empty airtight lockable basin is placed and flooded with stain. The while displaced from the basin air must also be via exhaust air scrubbers getting cleaned. After the pickling time, the stain is back in The pickling tank pumped, disadvantage is that a large volume Pickling liquid must be moved.

Furthermore, Spritzbeizverfahren are known in which the pickling solution via nozzles is sprayed finely dosed onto the workpiece to be treated. This Method is, as DE 198 42 971 A1 describes, for pickling planar, used in particular band-shaped items to be treated. The mordant Can be recycled so that collected in the spray area Beizmittel in turn is sprayed through the nozzles. nevertheless must be sucked off the resulting gases and, when using nitric acid containing pickling, be cleaned via an exhaust air scrubber.

To the increasingly stringent health and safety and environmental regulations Therefore, pickling plants are often airtight completed pickling cabins used. EP 0 949 355 A1 proposes a housed, working at permanent vacuum pickling before, with an air supply and a suction works. Furthermore, from the DE 36 35 525 C3 a completed plant for pickling workpieces known in which a held under negative pressure, hermetically sealed Cabin contain the treatment stations of the pickling plant.

Furthermore, pickling solutions have been proposed which are particularly applicable to the Use of the usual nitric acid waive the Improve environmental characteristics. For example, the DE 197 21 135 A1 a containing a hydrochloric acid as the only acid Pickling solution, which is applied in a spray treatment. Alternatively it will in DE 38 37 053 A1 a from an aqueous hydrofluoric acid proposed existing pickling bath, the continuous ozone as an oxidizing agent is supplied. From EP 0 958 405 B1 is a pickling solution with for example, sulfuric acid and hydrofluoric acid and hydrogen peroxide and a stabilizer known, with a good cleaning result without Use of environmentally critical nitric acid is achieved. About that In addition, EP 0 808 919 B1 discloses a pickling process with a pickling agent Hydrochloric and sulfuric acid and activation with a hydrogen peroxide solution known.

To reduce water consumption and environmental features improve, for example, from DE 42 20 401 A1 a system for the Treatment of workpieces with a process bath and subsequent Rinsing baths with a water circulation guide known in the refreshment the rinsing baths and regulation of the process solution concentration Water is recovered from the process solution itself.

In DE 41 17 760 C1 is an endless product, such as pipes, wires, belts in a treatment bath continuously in the dipping process with a Treated dressing. In this case, a suction is provided by Training a slight negative pressure the unwanted release of prevents toxic fumes. The exhaust air duct must be in compliance with Environmental protection requirements to be equipped with elaborate filter systems.

DE 44 11 163 A1 describes a method for the treatment of parts or components by spraying and / or flooding with a Solvent that works in batch mode. As a solvent in particular Dichloromethane uses, due to its physicochemical Features special precautions in the processing needs. In the Treatment chamber is created a vacuum, in which the dichloromethane is sprayed. After several spraying operations, the treatment chamber, the products contained therein as well as those formed in the chamber Air-gas mixture can be cleaned consuming. This requires the air-gas mixture evacuated several times from the chamber and cleaned. The cleaned air is then released to the environment. To refuel the Reservoir for the dichloromethane, a gas displacement line is provided.

The object of the present invention is a process and an installation for Spritzbeizen in such a way that improved environmental compatibility and resource conservation compared to the prior art.

This object is achieved by a method according to claim 1 and a Plant according to claim 6.

Characterized in that when spraying the pickling a gas balance between Beizkabine and pickling tank is carried out, bringing in the pickling booth Part of the resulting gases are returned to the pickling tank, is a pressure equalization between the emptying pickling tank and the through reached the spraying of the pickling applied pickling booth, without while releasing exhaust air to the environment. It's the same in itself closed system without exhaust air discharge also for pickling subsequent rinsing applied when after pickling from a Rinsing water tank Rinse water on the objects stored in the pickling booth sprayed on and a gas balance between pickling and Spülwassertank is carried out, thus resulting in the rinse Residual gases are partially returned to the rinse water tank.

In concrete terms, this is achieved by the fact that the pickling cabin, the Beizen tank and the flushing water tank are sealed to the outside and between the pickling tank and the pickling cabin, a first gas displacement line and a second one between the flushing water tank and the pickling booth Gas pendulum line are provided.

Preference is given both for the mordant and for the rinse water used the same nozzle arrangement in the pickling booth. Becomes advantageous also a large part of the supply line alternating for pickling agent or Rinse water used. This is already at the beginning of the flushing Most of the supply line and the nozzle assembly with the rinse water rinsed and thus cleaned of the aggressive stain. An undesirable Remain of mordant in the nozzle assembly and in a Most of the supply lines is thus safely avoided.

The common use of the supply lines by accordingly reached arranged shut-off valves. Furthermore, also in the gas displacement lines Shut-off valves should be provided to prevent excessive mixing the different exhaust gas concentrations forming in the two process steps to avoid from the mordant. During the Beizvorgangs forming significantly concentrated exhaust gases, mostly fluorine gas, can thus be mixed with the less concentrated Exhaust gases of the same substance during the flushing process and in the flushing water tank be prevented.

The rinse water may already contain fractions of the mordant, so it must not be particularly pure and serves to rinse off the on the object Adhesive residue residues.

If the rinsing process is carried out in several stages from several rinse water tanks, wherein with each rinse the purity of the rinse water increases, is realized a multi-stage Spülkaskade, which is a particularly effective Cleaning the pickling goods possible. The first flushing process takes place here with a more heavily loaded with mordant rinse water, the second Rinse with a little polluted water and so on until Finally, the last rinse with pure rinse water takes place.

Due to the fact that the pickling agent collecting on the cabin floor during and / or after the pickling process and that on the cabin floor collecting rinse water during and / or after the rinse (s) fed back into the pickling tank or the / rinse water tanks Thus, both the mordant and the rinse are thus used several times, what both the pickling and the rinse water consumption greatly reduced.

The fact that at the bottom of the pickling cabin a collecting means for collecting the sprayed liquids is formed, from the return lines to Beizenmittelank or lead to flushing water tank, both the dripping Pickling as well as the rinse water collected in the pickling booth and returned to the tanks. Here are also the gas displacement lines active and allow a gas balance between pickling cabin and the respective refilled tank.

If fresh water is misted in the pickling booth after flushing, where the lightly acidic water collecting on the cabin floor becomes Rinse water tank with the utmost purity of the rinse water is promoted, binds This spray that originated in the gas space of the cabin from the pickling agent Gases and these sink as aerosols. For this spray fresh water is preferably used, the separate particularly fine Fog nozzles above the nozzle assembly is discharged in the pickling booth. The resulting moisture binds namely the remaining gas particles the washable pickling agent. This moisture settles and collects at the cabin floor. From there it will be slightly contaminated Fresh water in the detergent tank or the detergent tank with purest Rinse water pumped.

Before opening the pickling booth, the sinking of the aerosols will be as far as possible fully waited for, then the surface-treated objects to be removed from the pickling booth. Preferably, the additionally pickled and rinsed workpieces manually from a pickler High pressure water be sprayed. On a suction can here be waived since the limits to be respected for the exhaust gases of Beizmittels, mostly fluorine gas, significantly below.

Preference is given to the rinsing process or after Frischwasservernebelung a passivation, preferably with stabilized citric acid, and followed by a water rinse. Furthermore, it should be before pickling a degreasing of intended for pickling objects carried out become.

Below is an embodiment of a system according to the invention for pickling with reference to the accompanying drawings described in detail.

Fig. 1

eine Anlage zur Oberflächenbehandlung in einem schematisierten Leitungsplan.

It shows:

Fig. 1

a system for surface treatment in a schematic pipeline plan.

The pickling cabin 1 is hermetically sealed to the environment. In the Beizkabine 1 are the objects to be dressed, for example, in one Pickling basket A submitted. Above the pickling basket A is a nozzle assembly 11 for spraying the workpieces to be picked in the pickling basket A with a pickling agent B. The pickling B is in a pickling tank 2, which also after formed outside sealed, stockpiled. From the pickling tank 2 leads a pickling agent supply line 21 to the nozzle assembly 11 in the pickling 1. The mordant B is thereby by means of feed pump 22 to the nozzle assembly. 1 promoted.

In Beizkabine 1 is at the bottom below the pickling basket A a collection agent 12 arranged for dripping mordant B. The collecting means 12 leads in a suitable gradient the impinging liquids to an am Collection means 12 provided collection point 13, of which a return line 14 leads to the seed tank 2. For the return of the pickling agent B is the same feed pump 22 of the pickling supply line 21 intended. Accordingly, shut-off valves 211, 212, 141, 142 in the associated lines 21 and 14 are provided. Furthermore, between the Beizmitteltank 2 and the pickling booth 1 a first gas displacement line 23 with a shut-off valve 231 is provided.

Next, a flushing water tank 3 is shown in Fig. 1, in the rinse water C. is stored. At the flushing water tank 3 performs a Spülwasserzuführleitung 31 also to the nozzle assembly 11 of the pickling cabin 1. To promote of the rinse water C via the supply line 31 to the nozzle assembly 11 in the Beizkabine 1, a feed pump 32 is provided in the supply line 31. From the pickling A dripping rinse water is collected via collection 12th led to the collection point 13 and there via a return line 15 in the Rinsing water tank 3 fed back. The return conveyance via return line 15 is also performed via the feed pump 32. For that are corresponding shut-off valves 311, 312, 151, 152 in the associated Lines 31 and 15 are provided. Further, between the flushing water tank 3 and the pickling cabin 1, a second gas displacement line 33 is provided, the an associated shut-off valve 331 has.

Further, above the nozzle assembly 11 in the pickling booth 1 is a mist nozzle arrangement 16 arranged with a supply line 17. The feed line leads fresh water D to pickling 1. For controlling the fresh water supply a shut-off valve 171 is provided in the supply line 17.

Subsequently, the pickling method according to the invention with reference to the in Fig. 1 illustrated embodiment explained.

First, the pickling booth 1 with the objects to be dressed, for example loaded in a pickling basket A, equipped. For larger items These can also be set directly into the pickling booth 1 become. Possibly. the stains are degreased before the pickling process. At the beginning of the process are all shut-off valves 141, 142, 151, 152, 171, 211, 212, 231, 311, 312, 331 closed and the feed pumps 22, 23 are not activated.

Now the pickling booth 1 is closed and the pickling process started. To the shut-off valves 211, 212 of the supply line 21 are opened. Further the shut-off valve 231 of the gas displacement line 23 is opened and the Feed pump 22 controlled. Now, pickling agent B is removed from the mordant tank 2 via the supply line 21 to the nozzle assembly 11 in the Beizkabine 1 promoted. The pickling agent B is in the so-called Spritzbeizverfahren sprayed over the nozzle assembly 11 finely and on the underlying, sprayed on to be addressed items A.

During the promotion of the pickling agent B from the mordant tank 2 via Feed line 21 by means of feed pump 22, the liquid level decreases in the Beizmitteltanks 2, thus consequently via the gas displacement line 23 a gas equalizing flow is triggered by the pickling booth 1 in the pickling tank 2. It is enriched with mordant B air in the mordant tank. 2 reach. After sufficient pickling on the pickling A is the feed pump 22 is stopped and the shut-off valves 211, 212 and the Beizmittelzuführleitung 21 closed.

Now the valves 141, 142 of the return conveyor 14 are opened. In the meantime, collection means 12 collect at collection point 13 the pickling A dripping Beizmittel B, via the return line 14th is fed back into the mordant tank 2 by means of feed pump 22. Corresponding the delivery pump 22 is activated. To be an uncontrolled To avoid backflow of detergent B via the line 14 is there preferably a check valve 143 arranged. In this return of the Beizmittels increases the liquid level in the mordant tank 2, so that via the first gas displacement line 23, a gas equalizing flow from Beizmitteltank 2 to Beizkabine 1 arises. After now essentially was fed back from the pickling A dripping mordant B, the delivery pump 22 and the valves 231, 141, 142 are closed.

Now the rinsing process is activated. For this purpose, the shut-off valves 311 and 312 of the supply delivery line 31 and the shut-off valve 331 of the second Gas displacement line 33 is opened and the feed pump 32 is started. Now Rinse water C from the rinsing water tank 3 via the Spülwasserzuführleitung 31 of the nozzle assembly 11 in the pickling booth 1 fed. In this case, a part of the supply line of the pickling agent supply is also preferred Commonly used to aggressive mordant B already in the Feed line 21, 31 via the nozzle assembly 11 discharge.

Now, the objects in the pickling basket A with rinse water C the Spray nozzle assembly 11. During the flushing the sinks Liquid level in the flushing water tank 3, so that over the second Gas displacement line 33 air mixed with pickling agent in low concentration passes from the pickling booth 1 in the detergent tank 3.

Upon reaching the desired washing result, the feed pump 32nd stopped and the shut-off valves 311 and 312 of Spülwasserzuführleitung 31 closed. At the same time on the collecting means 12 in Collection point 13 at the bottom of the pickling booth 1, the rinse water C, with Residues of the pickling agent B is offset, collected.

Now, by opening the shut-off valves 151 and 152 and starting the feed pump 32 via the return line 15, the rinse water C in the Rinsing water tank 3 fed back. At the collection point 13 is in the return line 15 also a check valve 153 provided to a uncontrolled backflow of the rinse water C in the pickling booth 1 to prevention.

During the return conveyance of the rinsing water C in the rinsing water tank 3 increases There, the liquid level, which is to pressure balance air over the second Gas displacement line 33 is pushed back to pickling booth 1. When in the essentially the drained rinse water on the return line 15th is discharged, the feed pump 32 is stopped and the valves 151st and 152 of the return line 15 as the shut-off valve 331 of the second Gas displacement line 33 closed.

Now, by opening the shut-off valve 171 of Frischwasserzuführleitung 17 fresh water D of the mist nozzle assembly 16 in the pickling 1 fed. About the mist nozzle assembly 16, the fresh water is special finely sprayed. This will be the remaining in this water mist remaining mordant gases, mostly fluorine gas, bound and slightly acidic Water on the collecting means 12 on the cabin floor sink. Only when the water mist has essentially set, that will be at the collection point 13 accumulated slightly acidic fresh water D by opening the shut-off valves 151, 152 and 331 and starting the feed pump 32 in the flushing water tank 3 promoted. The second gas displacement line 33 serves the Pressure compensation.

Now the pickling cabin 1 can be opened and the stained objects be removed. Possibly. an operator can pickled and stained cumswash rinsed workpieces with high pressure water. Because of the good Cleaning effect and the air wash can in this work on a Extraction completely dispensed with. It is particularly important that as mordant a mordant without nitric acid is used as the nitrous acid which forms when using a mordant with nitric acid Do not wash gases with water from the air.

LIST OF REFERENCE NUMBERS

1

pickling booth

11

nozzle assembly

12

mopping-up

13

assembly point

14

Return line

141

shut-off valve

142

shut-off valve

143

check valve

15

Return line

151

shut-off valve

152

shut-off valve

153

check valve

16

Fog nozzle arrangement

17

Frischwasserzuführleitung

171

shut-off valve

2

pickling-agent

21

Beizmittelzuführleitung

211

shut-off valve

212

shut-off valve

22

feed pump

23

first gas transmission line

231

shut-off valve

3

flush water tank

31

Spülwasserzuführleitung

311

shut-off valve

312

shut-off valve

32

feed pump

33

second gas displacement line

331

shut-off valve

A

Pickling basket or pickling object

B

mordant

C

dishwater

D

fresh water

Claims (12)

Process for pickling steel objects, in particular Stainless steel, in batch mode with a no nitric acid containing pickling agent from a mordant tank on the in sprayed onto a pickling booth wherein during the spraying of the pickling a gas balance between Beizkabine and maid tank is carried out, which in the Beizkabine gases partially to the pickling tank be recycled, and after pickling from a Rinsing water tank Rinse water stored in the pickling booth Objects sprayed on and a gas balance between pickling booth and rinse water tank is carried out, bringing the rinse Partly resulting residual gases partially returned to the rinse water tank without releasing exhaust air to the environment. A method according to claim 1, characterized in that the rinsing process is carried out in several stages from several rinse water tanks, wherein with each rinse the purity of the rinse water increases. A method according to claim 1 or 2, characterized in that the pickling agent collecting on the car floor during and / or after the pickling process and the rinsing water collecting on the car floor during and / or after the / rinsing operations in the pickling tank or the / Rinsing water tanks are fed back. A method according to claim 1, 2 or 3, characterized in that after flushing fresh water is misted in the pickling cabin, wherein the lightly acidic water collecting on the cabin floor is conveyed to the rinse water tank with the greatest purity of the rinse water. Method according to one of the preceding claims, characterized in that passivation, preferably with stabilized citric acid, and subsequent water rinsing are carried out after the rinsing process or after the fresh water misting. Plant for pickling objects made of steel, in particular stainless steel, in batch operation with a pickling tank (2), a pickling booth (1) with a nozzle arrangement (11), a pickling agent supply line (21) from the pickling tank (2) to the nozzle arrangement (11) in the pickling booth (1) and a rinsing water tank (3) which is connected to the nozzle assembly (11) of the pickling booth (1) via a Spülwasserzuführleitung (31), in particular for carrying out the method according to one of claims 1 to 5, characterized in that the pickling cabin (1), the mordant tank (2) and the flushing water tank (3) are sealed to the outside and between the mordant tank (2) and the pickling cabin (1) a first gas displacement line (23) and between the flushing water tank (3) and the pickling cabin (1 ) a second gas displacement line (33) are provided, wherein the self-contained system has no exhaust air discharge. Installation according to claim 6, characterized in that the nozzle arrangement (11) is successively formed by the pickling means (B) and the rinsing water (C) acted upon. Installation according to claim 7, characterized in that provided in the seed dressing and Spülwasserzuführleitungen (21, 31) and / or in the gas displacement lines (23, 33) can be shut off valves (211, 212, 311, 312, 231, 331). Installation according to claim 7 or 8, characterized in that a collection means (12) is formed for collecting the sprayed liquids (B, C) at the bottom of the pickling booth (1) from the recirculation lines (14, 15) for pickling-agent tank (2) or lead to the rinse water tank (3). Installation according to claim 9, characterized in that in the return lines (14, 15) lockable valves (141, 142, 151, 152) are provided. Installation according to claim 7, 8, 9 or 10, characterized in that in the supply lines (21, 31) and / or in the return lines (14, 15) pumps (22, 32) are provided. Installation according to one of claims 6 to 11, characterized in that above the nozzle arrangement (11) in the pickling booth (1) a mist nozzle arrangement (16) is provided which can be acted upon with fresh water (D).

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