JP2013095623A - Method and apparatus for treating waste hydrochloric acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of using an evaporator comprising a titanium-palladium alloy with high reliability for a long period by preventing wall thinning of the evaporator.SOLUTION: When waste hydrochloric acid containing an iron component is supplied into an evaporator 1 made of a titanium-palladium alloy and heated to recover hydrochloric acid vapor, the Feconcentration in the evaporator into which the waste hydrochloric acid is supplied is kept to be ≥5 g/L.

Description

  The present invention relates to a waste hydrochloric acid treatment method and a treatment apparatus for supplying waste hydrochloric acid containing an iron component into an evaporator made of titanium palladium alloy and recovering hydrochloric acid vapor by heating, and specifically, For example, the present invention relates to a processing method and a processing apparatus for waste hydrochloric acid containing high-concentration iron contained in a cleaning process of steel wires, steel plates, steel products, etc. in steel wire manufacturing plants, steel plate manufacturing plants, plating plants and the like. More specifically, the present invention aims to reuse and reduce waste residue by evaporating and recovering effective hydrochloric acid remaining in waste hydrochloric acid, which has been mostly treated as industrial waste. The present invention relates to a method for recycling waste hydrochloric acid.

  For example, in the conventional vapor compression evaporator shown in the drawing of Japanese Patent Laid-Open No. 59-026184, a large number of heat transfer tubes are provided in the upper part of a sealed evaporator having a stock solution reservoir in the lower part. It is configured to evaporate the raw solution sent by the raw solution pump on the outer surface of each heat transfer tube by spraying it with a sprayer. The steam generated by this evaporation is compressed by a blower compressor, the temperature is raised, and the heated steam is supplied to each heat transfer tube through a duct so that it is dispersed on the outer surface of each heat transfer tube. The stock solution is heated and evaporated.

  The evaporator of such a waste hydrochloric acid treatment apparatus is manufactured from a fluororesin or a carbon material in consideration of durability against the strong acidity and corrosivity of the waste hydrochloric acid to be concentrated and durability against the treatment temperature and pressure conditions. In most cases. However, carbon materials and the like have problems such as an increase in equipment size and cost due to strength, and it is necessary to produce an evaporator using a metal material. As the metal material, titanium palladium alloy was cited as a candidate material. Such an alloy has been considered to be extremely resistant to corrosion and sufficiently strong, so that it is not easily deteriorated even when waste hydrochloric acid is treated.

JP 59-026184 A

However, even if an evaporator made of an alloy having a high durability is used, if concentrated hydrochloric acid is continuously concentrated and washed away, it gradually deteriorates and the wall of the evaporator is melted and thinned. The progress of deterioration of the evaporator made of titanium palladium alloy is usually very low in an environment where an oxidizing agent (NO ₃ ⁻ , Fe ^3+, etc.) is present. When there is no or very low oxidizing agent, abnormal thinning may be observed, and countermeasures for such a situation are required.

  Therefore, in view of the above situation, an object of the present invention is to provide a technique capable of preventing the thickness reduction of the evaporator and using the evaporator made of titanium palladium alloy with high reliability over a long period of time.

[Configuration 1]
The characteristic configuration of the waste hydrochloric acid treatment method of the present invention for achieving the above object is that waste hydrochloric acid containing an iron component is supplied into an evaporator made of titanium palladium alloy and heated to recover hydrochloric acid vapor. This is a method for treating waste hydrochloric acid, wherein the concentration of Fe ³⁺ contained in the waste hydrochloric acid in the evaporator is maintained at 5 g / L or more.

[Function 1]
According to the present inventors, when corrosion thinning of an evaporator made of titanium palladium alloy is observed, it is clear that a sufficient passive film is not formed on the inner wall surface of the evaporator. Became. As a result of diligent research based on this new knowledge, when the Fe ³⁺ concentration present in the evaporator is sufficiently high, the passive film is formed and exhibits high durability, but is somewhat low It was experimentally clarified that the above-mentioned passive film was insufficient and sufficient durability was not exhibited. The present invention has been made by accumulating such experimental facts. When the concentration of Fe ³⁺ contained in the waste hydrochloric acid supplied to the evaporator is less than 5 g / L, the thickness of the evaporator is reduced. However, by maintaining the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator at 5 g / L or more, Fe ³⁺ is deposited on the inner wall of the titanium palladium alloy evaporator. It has been clarified that it acts as an oxidant to form, forming a stable passive film in the evaporator and contributing to increasing the durability of the evaporator.

[Configuration 2]
In the above configuration, an oxygen-containing gas is blown into the waste hydrochloric acid supplied to the evaporator, and Fe ²⁺ in the waste hydrochloric acid is oxidized to Fe ³⁺ , so that Fe contained in the waste hydrochloric acid in the evaporator ^{The 3+} concentration can be maintained above 5 g / L.

[Operation effect 2]
That is, when maintaining the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator at 5 g / L or more, the waste hydrochloric acid targeted by the present invention contains an iron component, so that the iron component is Fe. ^It should be oxidized to ³⁺ . At this time, in order to oxidize Fe ²⁺ to Fe ³⁺ , air oxidation can be adopted as the most commonly used technique. In order to perform air oxidation, a simple apparatus configuration in which oxygen-containing gas is simply blown into the waste hydrochloric acid supplied to the evaporator can be used. Therefore, the inner wall of the titanium palladium alloy evaporator can be easily and efficiently removed. A dynamic membrane can be formed.

[Configuration 3]
In the above configuration, Fe ³⁺ can be added to the waste hydrochloric acid supplied to the evaporator to maintain the concentration of Fe ³⁺ contained in the waste hydrochloric acid in the evaporator at 5 g / L or more.

[Operation effect 3]
According to the above-described configuration, it is empirically possible to efficiently increase the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator to 5 g / L or more, but even with waste hydrochloric acid containing an iron component, It does not necessarily contain a sufficient amount of iron component stably, and it does not necessarily mean that Fe ²⁺ in the waste hydrochloric acid can be oxidized to Fe ³⁺ with good responsiveness. Therefore, if Fe ³⁺ is added directly to the waste hydrochloric acid, the concentration of Fe ³⁺ contained in the waste hydrochloric acid in the evaporator can be maintained at 5 g / L or more. It can act as an oxidizing agent to form a passive film.

[Configuration 4]
The characteristic configuration of the waste hydrochloric acid treatment apparatus of the present invention is a waste hydrochloric acid treatment apparatus that supplies waste hydrochloric acid containing an iron component into an evaporator made of titanium palladium alloy and recovers hydrochloric acid vapor by heating. lies in that the Fe ³⁺ concentration of the waste hydrochloric acid in the evaporator within the can with a Fe ³⁺ concentration adjusting unit that maintained above 5 g / L.

[Operation effect 4]
According to the Fe ³⁺ concentration adjusting unit, since the concentration of Fe ³⁺ contained in the waste hydrochloric acid in the evaporator is maintained at 5 g / L or more, the method for treating the waste hydrochloric acid can be performed. As a result, Fe ³⁺ works as an oxidizing agent that forms a passive film on the inner wall of the titanium palladium alloy evaporator, and the passive film in the evaporator can be stably obtained, increasing the durability of the evaporator. Contribute to.

[Configuration 5]
In addition, a waste hydrochloric acid storage tank that stores waste hydrochloric acid supplied to the evaporator may be provided, and a bubbling unit that blows oxygen-containing gas into the waste hydrochloric acid storage tank may be provided as the Fe ³⁺ concentration adjusting unit.

[Operation effect 5]
If a bubbling unit for blowing an oxygen-containing gas into the waste hydrochloric acid storage tank is provided as the Fe ³⁺ concentration adjusting unit, the Fe ³⁺ concentration contained in the waste hydrochloric acid may be reduced before supplying the waste hydrochloric acid to the evaporator. It can be adjusted. In this case, in the waste hydrochloric acid storage tank, it is easy to ensure a sufficient time for gas-liquid contact by bubbling the oxygen-containing gas, and Fe ²⁺ can be efficiently oxidized to Fe ³⁺ .

[Configuration 6]
The bubbling unit is provided with a waste hydrochloric acid circulation path for extracting the waste hydrochloric acid stored in the waste hydrochloric acid storage tank and re-supplying the waste hydrochloric acid storage tank, and the re-supplied waste hydrochloric acid supplies air as an oxygen-containing gas. The structure provided with the ejector part supplied to the said waste hydrochloric acid storage tank, sucking in may be sufficient.

[Operation effect 6]
That is, if bubbling is performed with the ejector section, the waste hydrochloric acid stored in the waste hydrochloric acid storage tank is extracted and re-supplied with a simple piping provided with a waste hydrochloric acid circulation path that is re-supplied to the waste hydrochloric acid storage tank. Since hydrochloric acid sucks oxygen-containing gas, fine bubbles can be generated and supplied to the waste hydrochloric acid storage tank, and bubbling can be continued with a small amount of power, making it easy to perform efficient oxidation treatment.

[Configuration 7]
Further, an FeCl ₃ addition unit as the Fe ³⁺ concentration adjusting unit may be provided in a pipe for supplying waste hydrochloric acid to the evaporator.

[Operation effect 7]
If an FeCl ₃ addition part for directly adding Fe ³⁺ to waste hydrochloric acid is provided, the Fe ³⁺ concentration in the waste hydrochloric acid is increased, and the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator is increased. It can be maintained at 5 g / L or more, and can act as an oxidizing agent for forming a passive film in the evaporator.

[Configuration 8]
Further, the evaporator is provided with a corrosion potential monitor for measuring the corrosion potential, and the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator is 5 g / L based on the measured corrosion potential in the corrosion potential monitor. It can also be added FeCl ₃ addition amount control device for determining the FeCl ₃ added amount for maintaining the above.

[Operation effect 8]
In particular, Fe ³⁺ concentration waste hydrochloric acid to be treated contains is required Fe ³⁺ concentration adjustment in the Fe ³⁺ concentration adjusting unit in the case that not stable. At this time, if a sufficient amount of Fe ³⁺ is added, there is no problem in forming the passive film in the evaporator, and the Fe ³⁺ concentration may be too high as a result of the Fe ³⁺ concentration adjustment. However, it is economically disadvantageous to add too much Fe ³⁺ more than necessary, so the minimum amount necessary to make the concentration of Fe ³⁺ contained in the waste hydrochloric acid in the evaporator can be 5 g / L or more. It is preferable to adjust the Fe ³⁺ concentration using the Fe ³⁺ addition amount as a target value. As the Fe ³⁺ concentration increases, the corrosion potential of the evaporator wall tends to increase. Therefore, instead of directly monitoring the Fe ³⁺ concentration, the corrosion potential of the evaporator should be measured and monitored. Can do. Therefore, a corrosion potential monitoring unit for measuring the corrosion potential of the evaporator is provided, and the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator is 5 g / L based on the measured corrosion potential value in the corrosion potential monitoring unit. The amount of FeCl ₃ added for maintaining the above can be determined. The FeCl ₃ addition amount control device for determining the FeCl ₃ added amount, maintaining the Fe ³⁺ concentration of the waste hydrochloric acid in the evaporator in the can than 5 g / L, while maintaining the FeCl ₃ added amount of the minimum necessary Thus, excessive FeCl ₃ addition can be suppressed, and Fe ²⁺ can be oxidized to Fe ^{3 +} by economically efficient FeCl ₃ addition.

[Configuration 9]
In addition, a corrosion potential monitoring unit is provided in the waste hydrochloric acid storage tank or a pipeline extending from the waste hydrochloric acid storage tank to the evaporator, and the waste in the evaporator can be determined based on the measured corrosion potential in the corrosion potential monitoring unit. it may comprise FeCl ₃ addition amount control device for determining the FeCl ₃ amount to maintain the Fe ³⁺ concentration of the hydrochloric acid more than 5 g / L.

When the corrosion potential monitor is provided in the evaporator, the corrosion potential that directly reflects the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator can be obtained. Providing in the evaporator may be accompanied by a change in the design of the evaporator and may not be preferable. In such a case, when the corrosion potential monitoring unit is provided in the waste hydrochloric acid storage tank or a pipeline extending from the waste hydrochloric acid storage tank to the evaporator, Fe ³⁺ contained in the waste hydrochloric acid supplied to the evaporator The concentration can be monitored. Since the Fe ³⁺ concentration obtained here has a correlation with the Fe ³⁺ concentration in the evaporator, the waste hydrochloric acid in the evaporator can be determined based on the measured corrosion potential in the corrosion potential monitor. The amount of FeCl ₃ added for maintaining the concentration of Fe ³⁺ contained at 5 g / L or more can be determined. That is, similarly to the case of providing a corrosion potential monitoring unit to the evaporator, by FeCl ₃ addition amount control device for determining the FeCl ₃ addition amount of Fe ³⁺ concentration of the waste hydrochloric acid in the evaporator in the reactor 5 g / L It can be maintained above.

[Configuration 10]
The corrosion potential monitoring unit preferably includes a noble metal electrode.

[Operation effect 10]
In the corrosion potential monitoring unit, the corrosion potential of the evaporator wall can be directly obtained. That is, in this case, referring directly to the surface potential of the titanium palladium alloy, the relationship between the Fe ³⁺ concentration and the corrosion potential does not show an ideal proportional relationship depending on the state of formation of the passive film. It obtains a relational expression between the Fe ³⁺ concentration and corrosion potential, in accordance with this relation, thus obtaining the Fe ³⁺ concentration. However, if the corrosion potential monitoring unit is equipped with a noble metal electrode, the potential measured at the noble metal electrode is close to proportional, regardless of the state of generation of the passive state inside the evaporator. The Fe ³⁺ concentration can be obtained with high accuracy from the applied potential.
Similarly, in the case where the corrosion potential monitoring unit is provided in the waste hydrochloric acid storage tank or the pipe from the waste hydrochloric acid storage tank to the evaporator, the corrosion potential monitoring unit is proportionally provided that it is a noble metal electrode. From the close relationship, the Fe ³⁺ concentration can be obtained with higher accuracy.

  Therefore, it becomes possible to maintain the condition where the inner surface of the evaporator is always covered with a passive film, and the corrosion thinning of the evaporator can be efficiently suppressed, and it can be used reliably over a long period of time. It has become possible to provide a waste hydrochloric acid treatment apparatus and a waste hydrochloric acid treatment method that can be performed.

It is a flow sheet which shows an example of concentration processing of waste hydrochloric acid by the present invention. Diagram showing the relationship between Fe ³⁺ concentration and reduced ^thickness of evaporator Graph showing Fe ³⁺ concentration adjustment by bubbling Graph showing the relationship between corrosion potential and Fe ³⁺ concentration Graph showing the relationship between corrosion potential and Fe ³⁺ concentration when using noble metal electrodes

  Below, the processing apparatus of the waste hydrochloric acid of this invention is demonstrated. Preferred examples are described below, but these examples are described in order to more specifically illustrate the present invention, and various modifications can be made without departing from the spirit of the present invention. The present invention is not limited to the following description.

[Waste hydrochloric acid treatment equipment]
As shown in FIG. 1, the waste hydrochloric acid treatment apparatus of the present invention includes a titanium palladium alloy-made evaporator (calandria-type evaporator) 1 having a plurality of heat transfer tubes 11, and the evaporator 1 has waste hydrochloric acid. A waste hydrochloric acid storage tank 2 is provided, and waste hydrochloric acid to be concentrated is boosted from the waste hydrochloric acid storage tank 2 through the line 21 to a predetermined pressure in the pump 22 and then introduced into the evaporator 1 from the line 23. The Although not shown, if necessary, a strainer can be provided on the upstream side of the pump 22 and a flow meter can be provided on the downstream side. Waste hydrochloric acid is introduced into the evaporator 1 at a position of 15 to 50% of the liquid depth from the liquid level in the evaporator to the upper part of the heat transfer tube (position downward from the liquid level).

  The waste hydrochloric acid is heated, for example, as shown in the following example, with the recovered steam (boiler, cogeneration) generated in steel wire manufacturing / processing factories, steel plate manufacturing / processing factories, plating factories, etc. Steam recovered from the steam generator 3 such as equipment). Further, the exhaust heat of the exhaust gas itself such as a gas engine can be used instead of the recovered steam.

  At this time, when the steam to be used is at a low temperature and low pressure (110 ° C. or less / about 0.15 MPa or less), the compressor 32 performs compression and temperature increase in advance. That is, the steam from the steam generator 3 is supplied to the compressor 32 via the line 31, compressed and heated here, and then supplied to the outside of the heat transfer tube 11 of the evaporator 1 via the lines 33 and 34. The liquid in the heat tube 11 is heated and evaporated. When high-temperature and high-pressure steam is obtained, this steam is supplied to the evaporator 1 through lines 33 and 34 as it is via a line 35 that bypasses the compressor 32. By such an operation, the steam itself outside the heat transfer tube 11 is condensed and liquefied. The condensate is discharged from the line 14 through the steam trap 13 from the line 12 connected to the lower part of the heat transfer tube 11 in the evaporator 1. The condensate is reused as necessary for supplying water to the steam generator 3 or as diluting water for preventing solidification of the concentrated liquid extracted from the line 41 as necessary. Furthermore, this condensed water can be used as a preheating source of the stock solution in a preheater (not shown) provided in the line 23 on the outlet side of the pump 22 prior to reuse.

  As the low-temperature / low-pressure compressor 32, a screw-type compressor having a pair of male and female rotors in an aluminum alloy casing can be used.

The vapor of hydrochloric acid and water generated in the evaporator 1 is cooled by a cooler 53 having a cooling water line 52 through a line 51, condensed, and then stored in the distillate tank 5 through a line 54. The hydrochloric acid aqueous solution thus regenerated can be used again for the surface treatment of steel products.

  In the upper space of the evaporator 1, a demister 15 such as a filler, a filter, and a dripping wall is disposed to prevent entrainment of the raw liquid splash or the liquid splash in the can.

  Non-condensable gas such as air in the evaporator 1 that affects the efficiency and power consumption of the compressor 32 is discharged out of the evaporator 1 by opening and closing the electromagnetic valve 43 provided in the steam line 42 outside the heat transfer tube 11. Is done. The opening and closing of the electromagnetic valve 43 may be performed in conjunction with the pressure inside the evaporator 1 or may be automatically performed by setting a timer. If necessary, the exhaust gas can be subjected to an adsorption treatment with activated carbon or the like, and the exhaust gas may be bubbled into the liquid in the concentrate tank 4.

  The concentrated liquid accumulated in the evaporator 1 is concentrated through a line 41 and a control valve (not shown) from the bottom of the evaporator 1 according to a signal from a liquid level gauge (not shown) in the evaporator 1. It is discharged into the tank 4. Alternatively, the concentrated liquid can be extracted from an overflow pipe (not shown) communicating with the bottom of the evaporator 1 at a position corresponding to the liquid level in the evaporator 1 without using a control valve.

  When it is necessary to prevent solidification of the discharged concentrated liquid, water or condensed water from the line 14 may be supplied into the line 41 or the concentrated liquid tank 4 to dilute the concentrated liquid.

  If necessary, the liquid in the evaporator 1 is extracted from the liquid extraction line 41 by a circulation pump (not shown) and circulated to the line 23 to which waste hydrochloric acid is supplied, thereby reducing the liquid flow rate in the heat transfer tube. Increase the heat transfer coefficient. When the operating pressure in the evaporator 1 is a decompression system, a vacuum pump (not shown) that interlocks with the opening and closing of the electromagnetic valve 43 is provided on the downstream side of the electromagnetic valve 43. When operating in a reduced pressure system, a condensate pump (not shown) is provided on the line 14, and a concentrate pump (not shown) is provided on the line 41.

[Fe ³⁺ concentration adjuster]
A waste hydrochloric acid circulation path 24 is provided for extracting the waste hydrochloric acid stored in the waste hydrochloric acid storage tank 2 and supplying it again to the waste hydrochloric acid storage tank. The re-supplied waste hydrochloric acid sucks air as an oxygen-containing gas. A bubbling unit 25 including an ejector supplied to the waste hydrochloric acid storage tank 2 is provided. By this bubbling unit 25, the waste hydrochloric acid re-supplied from the waste hydrochloric acid circulation path generates fine bubbles while sucking the oxygen-containing gas and supplies the fine bubbles to the waste hydrochloric acid storage tank, and Fe ²⁺ in the waste hydrochloric acid storage tank. ^Is oxidized to Fe ^3+, and the concentration of Fe ³⁺ contained in the waste hydrochloric acid in the evaporator can be maintained at 5 g / L or more, which functions as the Fe ³⁺ concentration adjusting unit C.

The line 23 is provided with a sub tank 26 and a corrosion potential monitoring unit 27 provided with an electrode for measuring the corrosion potential of the titanium palladium alloy surface in the sub tank. Thus, the corrosion potential of the evaporator can be measured, and the Fe ³⁺ concentration contained in the waste hydrochloric acid can be known based on the measured corrosion potential value. Further, another FeCl ₃ addition unit 28 as an Fe ³⁺ concentration adjusting unit C is provided on the downstream side of the sub tank 26, and is included in the waste hydrochloric acid in the evaporator based on the measured corrosion potential. An FeCl ₃ addition amount control device 29 is provided for determining the addition amount of FeCl ₃ for maintaining the Fe ³⁺ concentration at 5 g / L or more.

[Relationship between Fe ³⁺ concentration and reduced ^thickness of evaporator]
FIG. 2 shows the relationship between the Fe ³⁺ concentration in the waste hydrochloric acid and the wall thinning rate of the wall of the evaporator 1 made of titanium palladium alloy. In FIG. 2, a test piece made of titanium palladium alloy was immersed in test waste hydrochloric acid having an HCl concentration of 114 to 119 g / L, and the weight loss of the test piece when left at 110 ° C. for 2 to 4 weeks was determined. The thickness reduction rate per year of the test piece was determined from the weight reduction.

From FIG. 2, thinning rate has Fe ³⁺ concentration and highly relevant, the one that Fe ³⁺ concentration of the waste hydrochloric acid in the evaporator is rapidly increased if the lower 5g / L, 5g / L or more If it exists, it can be read that the thinning rate is stable at 0.1 mm / y or less. This is ^presumably because the passive film formed on the surface of the titanium palladium alloy is not sufficiently maintained when the Fe ³⁺ concentration is less than 5 g / L.

Therefore, according to the waste hydrochloric acid treatment apparatus, the waste can be made durable by performing the waste hydrochloric acid treatment method in which the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator is maintained at 5 g / L or more. It turns out that it can be used highly.

[Fe ³⁺ concentration adjustment by bubbling part]
When the bubbling part 25 as the Fe ³⁺ concentration adjusting part C examined the oxidation performance when air was blown into the waste hydrochloric acid, it was as shown in FIG. In FIG. 3, HCl concentration 114 g / L, Fe ²⁺ concentration 85 g / L, the test waste hydrochloric acid Fe ³⁺ concentration 1 g / L to 6 m ³ accommodated in the waste hydrochloric acid storage tank 2 of the tank capacity 20 m ³ as waste hydrochloric acid, The test is conducted in a configuration in which air is bubbled into waste hydrochloric acid at a rate of 235 L / min while circulating at a circulation pump pressure of 0.16 MPa and 6 m ³ / h.

From FIG. 3, there is a proportional relationship between the bubble supply time for waste hydrochloric acid and the amount of increase in Fe ³⁺ concentration. According to this apparatus, waste hydrochloric acid is supplied in a configuration in which the waste hydrochloric acid is bubbled for about 25 minutes. It was found that an increase in the Fe ³⁺ concentration of about 5 g / L can be seen if performed.

[Relationship between corrosion potential and Fe ³⁺ concentration]
FIG. 4 shows the corrosion potentials of titanium palladium alloys placed in waste hydrochloric acid having various Fe ³⁺ concentrations. The potential is obtained as a potential with the Ag / AgCl electrode as a reference electrode. Corrosion potential than 4 monotonically increases with increasing Fe ³⁺ concentrations, can be determined Fe ³⁺ concentration based on corrosion potential measurements. Based on this Fe ³⁺ concentration, the FeCl ₃ addition amount for maintaining the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator at 5 g / L or more is determined by the FeCl ₃ addition amount control device 29. can do. Based on FeCl ₃ added amount obtained by adding the concentrated solution of FeCl ₃ in the line 23 from the FeCl ₃ added 28, to maintain the inner surface of the evaporator, coated with always passive film Availability As a result, it is possible to efficiently suppress the corrosion thinning of the evaporator.

In each of the above embodiments, the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator is maintained to be 5 g / L or more. However, the Fe ³⁺ concentration is 5 g / L or more. May be 10 g / L or more, and by setting it to 10 g / L, the lower thinning rate can be maintained more stably than in FIG. 2, and the change in potential with respect to the Fe ³⁺ concentration is more linear than in FIG. Therefore, there is an advantage that it is more accurate when ^obtaining the Fe ³⁺ concentration.

When the electrode for measuring the Fe ³⁺ concentration is a noble metal electrode, the potential in the waste hydrochloric acid having the same Fe ³⁺ concentration is measured as shown in FIG. 5, and the corrosion potential is increased by increasing the Fe ³⁺ concentration. It can be seen that the Fe ³⁺ concentration can be obtained more accurately based on the measured value of the corrosion potential.

  Further, the corrosion potential monitoring unit 27 may be provided directly on the evaporator, and in this case, an electrode is provided to corrode the waste hydrochloric acid at the lower part of the evaporator that is in a relatively mild environment in the evaporator. It is preferable to monitor the potential from the viewpoint of the corrosion resistance of the electrode.

  Therefore, the waste hydrochloric acid treatment apparatus of the present invention can maintain the state where the inner surface of the evaporator is always covered with the passive film, and can efficiently suppress the corrosion thinning of the evaporator. And can be used reliably over a long period of time.

1: Evaporator 11: Heat transfer tube 12: Line 13: Steam trap 14: Line 15: Demister 2: Waste hydrochloric acid storage tank 21: Line 22: Pump 23: Line 24: Waste hydrochloric acid circulation path 25: Bubbling part 26: Sub tank 27 : Corrosion potential monitoring unit 28: FeCl ₃ addition unit 29: FeCl ₃ addition amount control device 3: Steam generator 31: Line 32: Compressor 33: Line 34: Line 35: Line 4: Concentrated liquid tank 41: Line 42: Steam line 43: Solenoid valve 5: Distillate tank 51: Line 52: Cooling water line 53: Cooler 54: Line C: Concentration adjustment unit

Claims (10)

A method for treating waste hydrochloric acid in which waste hydrochloric acid containing an iron component is supplied into an evaporator made of titanium palladium alloy and heated to collect hydrochloric acid vapor, and is contained in the waste hydrochloric acid in the evaporator. ^A method of treating waste hydrochloric acid that maintains a ³⁺ concentration of 5 g / L or more. Oxygen-containing gas is blown into the waste hydrochloric acid supplied to the evaporator, and Fe ²⁺ in the waste hydrochloric acid is oxidized to Fe ³⁺ to ^{reduce the} concentration of Fe ³⁺ contained in the waste hydrochloric acid in the evaporator. The processing method of the waste hydrochloric acid of Claim 1 maintained at 5 g / L or more. The waste hydrochloric acid according to claim 1 or 2, wherein Fe ³⁺ is added to the waste hydrochloric acid supplied to the evaporator and the concentration of Fe ³⁺ contained in the waste hydrochloric acid in the evaporator is maintained at 5 g / L or more. Processing method. A waste hydrochloric acid treatment device for supplying waste hydrochloric acid containing an iron component into an evaporator made of titanium palladium alloy and recovering hydrochloric acid vapor by heating, wherein Fe contained in the waste hydrochloric acid in the evaporator A waste hydrochloric acid treatment apparatus equipped with an Fe ³⁺ concentration adjusting unit for maintaining the ³⁺ concentration at 5 g / L or more. The waste according to claim 4, further comprising a waste hydrochloric acid storage tank for storing waste hydrochloric acid to be supplied to the evaporator, wherein a bubbling portion for blowing an oxygen-containing gas into the waste hydrochloric acid storage tank is provided as the Fe ³⁺ concentration adjusting portion. Hydrochloric acid treatment equipment.   The bubbling unit is provided with a waste hydrochloric acid circulation path for extracting the waste hydrochloric acid stored in the waste hydrochloric acid storage tank and re-supplying the waste hydrochloric acid storage tank, and the re-supplied waste hydrochloric acid supplies air as an oxygen-containing gas. The waste hydrochloric acid treatment apparatus according to claim 5, further comprising an ejector section that is supplied to the waste hydrochloric acid storage tank while sucking. The waste hydrochloric acid treatment apparatus according to any one of claims 4 to 6, wherein an FeCl ₃ addition unit serving as the Fe ³⁺ concentration adjusting unit is provided in a pipe for supplying the waste hydrochloric acid to the evaporator. The evaporator is provided with a corrosion potential monitor for measuring the corrosion potential, and the Fe ³⁺ concentration contained in the waste hydrochloric acid in the evaporator is 5 g / L or more based on the measured corrosion potential in the corrosion potential monitor. processor of the waste hydrochloric acid according to claim 7 having a FeCl ₃ addition amount control device for determining the FeCl ₃ amount to maintain. A corrosion potential monitoring unit is provided in the waste hydrochloric acid storage tank or a pipe from the waste hydrochloric acid storage tank to the evaporator, and the waste hydrochloric acid in the evaporator can be changed based on the measured corrosion potential in the corrosion potential monitoring unit. processor of the waste hydrochloric acid according to Fe ³⁺ concentration in claim 7 having a FeCl ₃ addition amount control device for determining the FeCl ₃ added amount for maintaining the above 5 g / L included.   The waste hydrochloric acid treatment apparatus according to claim 8 or 9, wherein the corrosion potential monitoring unit includes a noble metal electrode.

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