JP2018034095A - Method for regenerating cation exchange resin, method for treating liquid to be treated, and treatment facility containing cation exchange resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus capable of accurately regenerating a cation exchange resin.SOLUTION: When a cation exchange resin is regenerated which is used for removing metal ions by the cation exchange resin and captures the metal, a strongly acidic cation exchange resin is used as the cation exchange resin, and the strongly acidic cation exchange resin and at least one aqueous solution of a regenerant of an organic acid and organic acid alkali metal salt having an acid dissociation index (pKa) is 1.0 or less are brought into contact with each other, and the metal is eluted.SELECTED DRAWING: None

Description

  The present invention relates to a method for regenerating a cation exchange resin, a method for treating a liquid to be treated, and a treatment facility including the cation exchange resin.

  Equipment that uses the reactivity of subcritical water without using a catalyst or equipment that uses a catalyst as a technology to convert / reform or decompose the wastewater treatment under high temperature and high pressure, that is, subcritical conditions It has been known. For example, hydrothermal gasification equipment uses a catalyst to convert organic matter in wastewater into valuable gas such as methane and recover it under high temperature and high pressure conditions (subcritical conditions) at a temperature of about 200 to 350 ° C. and a pressure of about 5 to 15 MPaG. .

  Here, the subcritical condition in water is a region where the liquid phase coexists under a high temperature and high pressure of over 100 ° C. to 374 ° C. in a broad sense and about 250 ° C. to 374 ° C. in a narrow sense. The treated wastewater to be treated is, for example, an organic matter, an oxidizable inorganic substance such as a cyanide excluding nitrate radical, a nitrogen compound such as ammonia, and a sulfur compound excluding sulfate radical.

In these treatment facilities, materials having excellent corrosion resistance are used.
In general, a material having excellent corrosion resistance has a non-conductive film formed on the surface, and the coating is locally broken by an external factor, and becomes a starting point of pitting corrosion or stress corrosion cracking.
Stress corrosion cracking occurs when the three factors of environment, material, and stress are simultaneously and moderately involved. Low-alloy steel, austenitic stainless steel, martensitic stainless steel, Al-Mg alloy, Al-Cu-Mg alloy, Al-Mg-Zn alloy, Al as metals that cause stress corrosion cracking in the presence of chloride ions -Zn-Mg-Mn alloy, Al-Zn-Mg-Cu-Mn alloy, titanium, titanium alloy. In particular, it is said that stress corrosion cracking of stainless steel is likely to occur in an environment containing chloride ions.
Stress corrosion cracking is generated even in a very short time, and it is necessary to wipe out in advance the serious concern of being a container under high temperature and high pressure under subcritical conditions.

  For this reason, in a system composed of materials having these metals in the wetted part, the chlorine concentration (including organic chlorine) is required to be sufficiently low in order to prevent stress corrosion cracking.

  Moreover, in order to prevent precipitation of metals during the reaction, it is required that the metal concentration other than the alkali metal is sufficiently low. Metals may hydrolyze and precipitate when the pH of the solution changes or the ligand of the metal complex is removed due to decomposition or conversion of organic matter, which may cause blockage of equipment.

  One method for removing metals is an ion exchange method using a cation exchange resin. As a general cation exchange resin, there is softening treatment of hard water, and Na-type strongly acidic cation exchange resin is used to replace metals such as Ca and Mg with Na. A moderate NaCl aqueous solution is used.

  As a pretreatment of the liquid supplied to equipment operating under high temperature and high pressure, that is, in a subcritical state, it is conceivable to remove metal ions using a cation exchange resin. In addition, there exists a thing of patent documents 1-3 as an example of the equipment which operate | moves on these subcritical conditions.

JP 2009-178657 A JP 2004-352756 A Japanese Patent No. 5330751

  However, when NaCl water or hydrochloric acid aqueous solution is used for the regeneration of the cation exchange resin, there is a high possibility that corrosion cracking will occur in the metal in the wetted part unless the Cl ion concentration is sufficiently lowered. Stress corrosion cracking corrodes the equipment material in a very short time (in some cases, several hours) unlike the case of general corrosion such as carbon steel, and generates pores.

In an attempt to search for a cleaning method, after regeneration using NaCl water, pure water was flowed in the same flow as the regenerant, but the chloride ion concentration was about several ppm even when flowing more than 30 times the amount of resin. I understood that it was only possible.
Since the NaCl concentration used for regeneration is several percent or more, a cleaning effect of 4 to 5 digits or more is necessary to make it several ppm or less. Care must also be taken when high-concentration NaCl is mixed due to carelessness in the washing operation.

It is also conceivable to use ions or salts other than chlorides, such as carbonates, sulfates, nitrates, phosphates.
In this case, for example, when calcium ions are contained in the treatment target liquid, precipitation of calcium carbonate, calcium sulfate, and calcium phosphate may occur during regeneration. In the case of carbonate radicals, bubbles may be generated, which may cause incomplete elution or hinder resin exchange ability. In the case of nitrate radicals, the N content in the wastewater is increased, which is unfavorable for the environment, and high concentrations of nitric acid oxidize and modify the resin.

  Therefore, a main problem to be solved by the present invention is to provide a method and apparatus capable of accurately regenerating the cation exchange resin.

The present invention for solving this problem is used for removing metal ions with a cation exchange resin, and when regenerating the cation exchange resin capturing the metal,
A strong acidic cation exchange resin is used as the cation exchange resin, and the strong acid cation exchange resin is contacted with at least one regenerant of an organic acid and an organic acid alkali metal salt to elute the metal. This is a method for regenerating a cation exchange resin.

  The adsorption / desorption property of metals by the ion exchange resin depends on the equilibrium relationship between the metal ion bonded to the ion exchange group of the ion exchange resin and the metal ion dissolved on the water phase side. Since an organic acid forms a complex with many metals, the equilibrium shifts to the aqueous phase side at the time of elution, and metal removal on the surface of the cation exchange resin can be performed better than when NaCl water is used.

  A cation exchange resin having a sulfo group can be used.

  Examples of the regenerant include sodium acetate and sodium propionate as organic acid alkali metal salts, and acid dissociation index (pka) of 2.0 or less, preferably 1.0 or less, particularly preferably 0.6 or less as an acid. The acid can be selected from one or a combination thereof. In particular, sodium acetate as an organic acid alkali metal salt is an inexpensive drug and has a high desorption effect. In practice, the use of sodium propionate is also desirable.

On the other hand, according to the present invention, the liquid contact portion of a liquid containing a processed material under a subcritical condition, that is, a high temperature and high pressure condition, is used in an apparatus composed of a material containing a metal material in which stress corrosion cracking due to chloride ions may occur. The liquid supplied to the treatment is suitable for regenerating the cation exchange resin containing the metal, which is used to remove the metal ions by passing through the cation exchange resin.
In particular, since the regenerant is an organic acid alkali metal salt and / or organic acid, even if a very small amount remains and migrates, it is originally a facility for treating organic substances and oxidizable inorganic substances in wastewater. And the organic acid alkali metal salts are treated and cause no problems or are small.

The processing method of the processing liquid of the present invention includes:
A metal ion removing step of removing a metal ion by passing a liquid to be treated containing an organic substance and / or an oxidizable inorganic substance through a strongly acidic cation exchange resin;
A treatment step of treating the liquid to be treated under subcritical conditions in an apparatus composed of a metal in which a wetted part may cause stress corrosion cracking due to chloride ions;
A regeneration step of passing at least one aqueous solution of an organic acid alkali metal salt and an organic acid through the cation exchange resin.

From the device aspect of the present invention,
A treatment facility for treating a liquid containing an organic substance or an oxidizable inorganic substance under a subcritical condition in an apparatus composed of a metal in which a wetted part may cause stress corrosion cracking due to chloride ions;
A plurality of ion-exchange treatment tanks arranged in parallel or having a series of ion-exchange treatment layers having a strongly acidic cation exchange resin through which a liquid to be treated is passed before being supplied to the treatment facility,
A liquid flow changing means for alternately changing the liquid flow type between the first ion exchange treatment tank through which the liquid to be treated is passed and the second ion exchange treatment tank through which the regenerant is passed. Having means for changing the flow type over time in a series of ion exchange treatment tanks;
A treatment facility including a strongly acidic cation exchange resin is proposed, wherein the regenerant is an aqueous solution of at least one organic acid alkali metal salt and organic acid.

As described above, according to the present invention, the cation exchange resin can be properly regenerated.
On the other hand, in the case of regeneration of a cation exchange resin that removes metal ions from a liquid supplied to the treatment of a liquid containing an organic substance or an oxidizable inorganic substance under subcritical conditions, the organic acid component of the regenerant (eluent) is Even if a part of the material remains, there is almost no effect because the target equipment is equipment that treats organic substances and oxidizable inorganic substances.

It is a schematic diagram of the example of processing equipment of the present invention. It is a schematic diagram of an experimental device. It is a graph which shows a breakthrough curve.

  First, after theoretically explaining the cation exchange resin and the regeneration method, a mode for carrying out the present invention will be described later.

The cation exchange resin is a polymer acid in which a sulfo group, a carboxyl group, an acidic hydroxyl group and the like are bonded to the resin matrix (R), and has a strongly acidic cation exchange resin having a sulfo group and a carboxyl group or an acidic hydroxyl group. Broadly divided into weakly acidic cation exchange resins.
The strongly acidic cation exchange resin R-SO ₃ H, when a weakly acidic cation exchange resin represents the R-COOH, each in a state in which H ⁺ is dissociated in aqueous solution ^{_{R-SO 3 -, R-}} COO - expressed as be able to. At this time, since the resin itself is negatively charged, a cation is held as an counter ion in the negatively charged portion in order to maintain electrical neutrality. Since this counter ion is on the liquid phase side, it is mobile and can easily exchange places with other cations.

  Cation exchange adsorption characteristics differ between strongly acidic cation exchange resins and weakly acidic cation exchange resins, and this mechanism will be exemplified and described.

(Strongly acidic cation exchange resin)
In strongly acidic cation exchange resins, the sulfo group of the ion exchange resin is a group that shows strong acidity but little coordination, so the selectivity of the cation to be exchanged depends on the charge of the cation or water. It is said that it depends on the mass action law based on the sum ion radius and ion concentration.
That is, in general, a cation having a high valence is exchanged and adsorbed more strongly than a cation having a low valence, and the atomic number is within an alkali metal that produces a monovalent ion, and within an alkaline earth metal that produces a divalent ion. The larger the value, the stronger the exchange adsorptivity.
When viewed in the alkali metal, the exchange adsorption power is strong in the following order.

This corresponds to a rank in which the hydrated ion radius decreases as the atomic number increases.
That is, as the atomic number increases, the ionic radius increases. On the other hand, since the charge amount is the same, the number of hydrated waters decreases, and as a result, the larger the atomic number, the smaller the hydrated ion radius tends to be.

  The present inventors have studied the regeneration of the cation exchange resin using Na salt, but if it can be exchanged with Na salt, an alkali metal after Na can be used.

このとき、選択係数Ｋ_Li ^Caは式（２）の逆方向での表現であるので以下の式であらわされる。

On the other hand, although it is Li salt, this can be considered from a mass action law.
Consider eluting a strongly acidic ion exchange resin on which Ca is adsorbed with a CH ₃ COOLi solution.
Here, the eluted Ca ²⁺ ion actually forms a part of the one-coordination complex Ca (OOCCH ₃ ) ⁺ with the acetate ion, but the hydrolyzable metal is represented by Ca and the formation of the complex Since it works in a direction that promotes the elution of Ca, it is ignored here.
This reaction is generally described as follows.

At this time, since the selection coefficient K _Li ^Ca is expressed in the reverse direction of the equation (2), it is expressed by the following equation.

の選択係数は

すなわち、

となる。 "Perry's Chemical Engineers' Handbook, seventh edition, 16-14 " in is given a K _Li ^Ca = 5.16 to cross-linking degree of 8% of a strongly acidic cation exchange resin, also in the article K _Li ^{Since Na} = 1.98 is given, the reaction to replace the Na ⁺ form with Ca ²⁺

Is the selection factor

That is,

It becomes.

とするには（［Ｌｉ⁺］／［Ｎａ⁺］）²＝１．９７７、すなわち［Ｌｉ⁺］／［ Ｎａ⁺］＝１．４１が得られ、平衡を考えた場合、再生剤として使用する酢酸リチウムの濃度を酢酸ナトリウムの場合に対しモル濃度で１．４１倍にすればよいことがわかる。 The regenerative amount of the ion exchange resin is the same as that of sodium acetate, that is,

([Li ⁺ ] / [Na ⁺ ]) ² = 1.977, ie, [Li ⁺ ] / [Na ⁺ ] = 1.41 is obtained, and is used as a regenerant when equilibrium is considered. It can be seen that the lithium acetate concentration may be 1.41 times the molar concentration of sodium acetate.

  It can be seen that the alkali metal ion is a metal that dissociates completely in an aqueous solution, and the regeneration effect performed with sodium acetate can be performed with all alkali metal salts of acetic acid.

ならびに、強酸に対しては強酸性陽イオン交換樹脂（スルホ基）の見かけの酸解離指数（ｐｋａ'）が２程度であることから、例えば２．０以下、好ましくは１．０以下、特に好ましくは０．６以下の酸を使用することで、スルホ基のＨ⁺の解離が少なくなりＨ型として再生される。 Strong acid cation exchange resins can also be regenerated with acids.
In the H-type regeneration of the ion exchange resin, generally, an inorganic acid such as hydrochloric acid is used.
This means that H ⁺ ions are in the following order relative to the exchange order in the alkali metal.

In addition, the strong acid cation exchange resin (sulfo group) has an apparent acid dissociation index (pka ′) of about 2 with respect to a strong acid, for example, 2.0 or less, preferably 1.0 or less, particularly preferably By using an acid of 0.6 or less, the dissociation of H ⁺ of the sulfo group is reduced and it is regenerated as the H type.

The present inventors have, R (-SO ₃ ^-) a Ca ²⁺ held in ₂ Ca ^2+, it was also examined whether not play with organic acids.
As organic acids, sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, and benzenesulfonic acid are very strong acids, and nitric acid such as acid dissociation index (pka) of -1.92, -1.68, and -2.8, respectively. It is said that the acid can be regenerated with these acids, and it is almost obvious that it can be regenerated with these acids, so select from carboxylic acids, acetic acid, acid dissociation index, the most common organic acid. Citric acid with a small (high acidity) and easy to form a complex with dissociated Ca ²⁺ was selected. Oxalic acid was also considered, but oxalic acid formed a precipitate with Ca ²⁺ and was excluded because Ca ²⁺ is a metal that is likely to be mixed in a hydrolyzable metal-containing solution such as wastewater.

The acid dissociation index (pka) of a typical carboxylic acid at an ionic strength of 0.1 and the stability index of a Ca ²⁺ complex are shown below.
However, for the acid that dissociates in multiple stages, the dissociation index (pka ₁ ) of the first stage was shown, and the stability index showed the value of the first-stage dissociated carboxylic acid complex.
pka ₁ log K _ML
Formic acid (HCOOH) 3.65 −
Acetic acid (CH ₃ COOH) 4.65 0.5
Oxalic acid ((COOH) ₂ ) 1.1 Precipitated citric acid (C (OH) (CH ₂ COOH) ₂ COOH) 3.0 10.9
Benzoic acid (C ₆ H ₅ COOH) 4.7 −

Concentrations of acetic acid and citric acid were strongly acidic positively saturated with Ca in an aqueous solution adjusted to 10 wt% and 32.8 wt%, respectively, so as to have a concentration of 10 wt% and the same molar concentration as that obtained by regeneration with a normal NaCl solution. Although liquid was passed through the ion exchange resin, it was hardly regenerated (to H type).
It was thought that the organic acid had a stronger acidity.

When the cation exchange resin is regenerated to H type, it is performed by increasing the H ⁺ ion concentration. Regeneration of strongly acidic cation exchange resin to H-type is often performed with 3 to 8% HCl aqueous solution, and this concentration corresponds to approximately 1 to 2 mol / L. Since HCl is totally dissociated, H ⁺ concentration is also high. It becomes the same value. That is, when it sees by pH, it will be about 0--0.3. The solubility of the organic acid used varies depending on the substance, but when the usual organic acid concentration is 5 mol / L at the maximum, the acid dissociation index (pka) at which the pH becomes 0 is calculated as 0.60. It can be considered that the acid dissociation index of these organic acids was large as the reason why acetic acid and citric acid were not effective in Example 2 described later.

  That is, when the organic acid is used to effectively regenerate the H-form, the acid dissociation index (pka) of the organic acid is 2.0 or less, preferably 1.0 or less, particularly preferably 0.6 or less.

(Weakly acidic cation exchange resin)
Weakly acidic cation exchange resins include R-COOH type and R-PO (OH) ₂ type. When represented by R-COOH, examples of inorganic ion exchange reactions include the following.

The operation of removing the hydrolyzable metal, which is the object of the present invention, is to remove the metal by a reaction corresponding to the formula (10) using an H-type resin and regenerate it into a H-type with a weak or strong acid, or Na-type. The resin is used to regenerate Na-type by the reverse reaction of the reaction corresponding to the formula (12).
The apparent acid dissociation index pka ′ of the weakly acidic cation exchange resin is said to be approximately 5 to 6, and even a weak acid having a pH of 4 or less can be regenerated into the H-type.
In the removal by the formula (9), since the target metal is a hydrolyzable metal, most of the metal is precipitated as a hydroxide precipitate in the reverse reaction regeneration, and the reverse reactions of the formulas (10) and (12) are targeted.
However, in the adsorption operation according to the formula (10), an acid is generated, and a neutralization operation is necessary after removing the metal. Further, in the formula (12), the forward reaction occurs easily, but the reverse reaction is difficult or slight even if it is difficult or difficult to remove the metal adsorbed by the complex formation of the ligand possessed by the ion exchange resin. It is said that.
Therefore, when the hydrolyzable metal is removed using Na type so as not to fluctuate the pH of the target liquid, for regeneration, it is once made H type with a weak acid or strong acid, and then the formula (9) or (10 ) In the reaction corresponding to

  With a strongly acidic cation exchange resin, the metathesis reaction corresponding to formula (12) is reversible and can be carried out based on the mass action law. For this reason, when a hydrolyzable metal is simply removed by ion exchange and is regenerated, it can be easily carried out without changing the pH of the target solution by using a strongly acidic cation exchange resin as the Na type. .

  When the present inventors regenerated the strong acid cation exchange resin capturing the metal, which was used for removing metal ions by the strong acid cation exchange resin, the organic acid alkali metal salt and the acid dissociation index (pka) Has been found to be effective to use at least one organic acid regenerating agent having an organic acid value of 2.0 or less, preferably 1.0 or less, particularly preferably 0.6 or less.

As the regenerating agent of the present invention, an organic acid alkali metal salt such as an organic acid, sodium acetate or sodium propionate having an acid dissociation index (pka) of 2.0 or less, preferably 0.6 or less can be used as an acid. These organic acids and organic acid alkali metal salts can be used alone or in combination.
As shown in the experimental examples described later, organic acid alkali metal salts are desirable, and sodium acetate and sodium propionate are particularly preferable.

  Oxalic acid is an acid having a low acid dissociation index and a relatively strong acidity, but it forms a precipitate with Ca and is not preferable in an aqueous solution treatment system in which Ca is likely to be mixed.

  Strongly acidic cation exchange resins include Diaion (registered trademark) manufactured by Mitsubishi Chemical Corporation, gel-type SK series, gel-type UKB series, porous-type SK series, and high-porous type. Of the HKP25 / RCP series, Amberlite (registered trademark) 200CT (trade name) sold by Organo, Dowex Marathon (registered trademark) C, Dowex Monosphere (registered trademark) C, Purolite, sold by Muromachi Chemical Co., Ltd. A series or C series can be used.

Next, description will be made with reference to the apparatus configuration example shown in FIG.
As a technology for converting / reforming or decomposing organic substances and oxidizable inorganic substances in wastewater under high temperature and high pressure, that is, under subcritical conditions, facilities and catalysts that utilize the reactivity of subcritical water without using catalysts are used. An apparatus to be implemented is known.

  Here, the subcritical condition in water is a region where the liquid phase coexists under high temperature and high pressure of over 100 to 374 ° C. in a broad sense and about 250 to 374 ° C. in a narrow sense. An apparatus that converts or hydrolyzes organic substances using the high reactivity of subcritical water, an apparatus that generally oxidizes organic substances and oxidizable inorganic substances in the presence of oxygen or air at a temperature of 150 to 350 ° C., called the Zimmermann process, and a catalyst Hydrothermal gasifier that converts organic substances into valuable gases such as methane at a temperature of 200 to 350 ° C. using a catalyst, and oxidizes organic substances and oxidizable inorganic substances in the presence of oxygen or air at a temperature of 150 to 300 ° C. using a catalyst. The device is known.

Examples of the oxidizable inorganic substance include cyanide except for nitrate radicals, nitrogen compounds such as ammonia, and sulfur compounds other than sulfate radicals.
Specifically, ammonia, hydrazine, hydroxylamine, hydrazoic acid, hydrocyanic acid, cyanic acid, thiocyanic acid, hyponitrous acid, nitrous acid, hydrosulfuric acid, thiosulfuric acid, dithionic acid, sulfurous acid, disulfurous acid, dithione It refers to acids, polythioic acids and alkali metal salts of these acids.

2 is a waste liquid treatment device, and the wetted part is made of a material containing metal that may cause stress corrosion cracking due to chloride ions (for example, stainless steel), and it is organic and oxidizable under subcritical conditions. In the example, a liquid containing an inorganic substance is processed, and the hydrothermal gasifier is shown. However, other apparatuses may be used, for example.
Metals that may cause stress corrosion cracking due to chloride ions at the wetted parts include low alloy steel, austenitic stainless steel, martensitic stainless steel, Al-Mg alloy, Al-Cu-Mg alloy, Al- One or more of Mg—Zn alloy, Al—Zn—Mg—Mn alloy, Al—Zn—Mg—Cu—Mn alloy, titanium, and titanium alloy can be employed. It can also be used in combination with materials other than those described above, and it is also possible to combine a plurality of metals in which the liquid contact portion may cause stress corrosion cracking due to chloride ions in other materials. The alloy steel is a steel to which one or more alloy elements Ni, Cr, Mo and the like are added in order to change the properties of the steel and obtain characteristics suitable for the purpose of use, and the total amount of these alloy elements is 10.5. % Or less is called low alloy steel.

  Cation exchange resin tanks 1A and 1B containing a strongly acidic cation exchange resin in order to remove the metal ions by passing the liquid supplied to the waste liquid treatment apparatus 2 through the cation exchange resin. Is provided.

Although not limited to the operation mode of the cation exchange resin tanks 1A and 1B, in order to avoid time loss, metal ion exchange is performed in one tank, and (substitution) washing and elution (regeneration) of liquid in the other tank. -It is desirable to operate to perform pure water cleaning.
For example, in one cation exchange resin tank 1A, ion exchange is performed over 10 days to 2 weeks, and in the other tank, liquid replacement-elution (regeneration) -pure water washing is performed in about one day. When the ion exchange is completed, the tank is replaced.

  The device configuration example shows an example in which two cation exchange resin tanks are alternately switched and continuously processed, but the time required for resin regeneration is shorter than the time required for the metal ion exchange operation. An operation for stopping the metal ion exchange process at the time of regeneration as one series may be used.

  The processing stock solution 10 is supplied to the processing apparatus 2 through the processing water flow path 13 after flowing into the cation exchange resin tank 1A. The processing apparatus 2 is operated at a high temperature and a high pressure of, for example, 200 ° C. to 350 ° C. and 5 MPa to 15 MPa, and in the case of hydrothermal gasification processing, the recovered fuel gas 14 and the treated water 15 are discharged.

If the operation in the processing apparatus 2 proceeds and, for example, the ion exchange operation in the cation exchange resin tank 1A is at an appropriate time before the start of the metal ion breakthrough, the ion exchange in the cation exchange resin tank 1A is performed. Stop and change to ion exchange in the cation exchange resin tank 1B.
The (substituted) pure water cleaning liquid 30 is caused to flow through the flow path 31a to the stopped cation exchange resin tank 1A, and the cleaning liquid is discharged from the drain flow path 33 through the flow path 32a.

Thereafter, the eluent (regeneration liquid) 20 is circulated through the cation exchange resin tank 1A, and the discharged eluent is discharged as eluent wastewater through the flow path 22a.
When the elution process is completed, the pure water cleaning liquid 30 is flowed through the flow path 31a, and the cleaning liquid is discharged from the drain flow path 33 through the flow path 32a.

  Such an operation is also performed for the cation exchange resin tank 1B with a time difference. Here, the description will not be made in order to avoid inconvenience, but the number 10 generation refers to the processing system of the processing stock solution 10, and the number 20 generation refers to the processing system using the eluent (regeneration solution) 20. The operation procedure will be clear by stating that the thirties represent a treatment system for the cleaning liquid 30.

  As mentioned above, in equipment that has a high corrosion resistance metal typified by stainless steel in the wetted part, the chlorine concentration (including organic chlorine) must be low enough to prevent stress corrosion cracking from corrosion resistance under subcritical conditions. Required.

  The operation in the processing device 2 is disclosed in, for example, the aforementioned Patent Documents 1 to 3.

Examples will now be described.
(Comparative Example 1)
The experimental apparatus is shown in FIG. 2, and the liquid to be treated is sent from the liquid tank 40 to be treated by the pump 41 to the ion exchange column 42 filled with the strongly acidic cation exchange resin, and the waste liquid is collected in the collection liquid tank 43. To do.
As a strongly acidic cation exchange resin, Purolite Co., Ltd. C-150 / 1621 was used.

  In such an experimental apparatus, the operation of passing a liquid to be treated with a Ca concentration adjusted to about 250 mg / kg, replacing with pure water, passing a 10 wt% NaCl solution, and finally washing with pure water was absorbed 12 times. The breakthrough curve was examined by repeating desorption and analyzing the Ca concentration of the treatment liquid when the treatment liquid was passed through.

The results of the twelfth time are shown in FIG.
The breakthrough curve before the 12th time moved slightly, but it was a sign that the adsorption / desorption was not yet stable, but at the 12th time the amount of regenerant and washing water was doubled so far. The breakthrough curve retreated to the high adsorption side, and the Ca balance of the treatment liquid obtained by the subsequent regeneration operation was 98.3%, a value close to 100%.
It was confirmed that the Ca accumulation of the cation exchange resin can be sufficiently suppressed if the amount of the regenerant and the amount of the washing water are sufficient.

Example 1
The same experiment was carried out continuously using the cation exchange resin as described above as it was, using a 14 wt sodium acetate aqueous solution as the other alkali metal salt as an eluent (regenerant). The concentration of the sodium acetate aqueous solution was set to the same concentration as that of the 10 wt% NaCl aqueous solution.
The results are shown in FIG. The effectiveness of sodium acetate can be seen.

(Example 2)
In order to examine the effects of other organic acids and organic acid alkali metal salts, the same experimental apparatus was used, and the liquid to be treated was adjusted to a Ca concentration of about 500 mg / kg. The following operation was performed on the resin that had been saturated with Ca in advance.
(1) Pure water replacement (160 ml was collected by passing 120 minutes at 1.3 ml / min), (2) Regenerant flowing (128 ml was collected by passing 96 minutes at 1.3 ml / min) , (3) pure water washing (960 ml was collected at a flow rate of 2.6 ml / min for 360 minutes), (4) liquid to be treated (Ca was adsorbed at 6 ml / min), in that order. Each operation was performed.

  In (4) passing the liquid to be treated, 125 g of each was sampled at intervals of 20 minutes from the start of the liquid flow, and after performing these three times, 1425 g was passed for the fourth time. This third flow-through sample was used for Ca analysis. In order to examine the effects of organic acids and organic acid alkali metal salts, the regenerant in (3) was compared as 10 wt% acetic acid, 32.8% citric acid, and 16.7 wt% sodium propionate. In addition, these aqueous solution was made into the density | concentration (1.7 mol / kg) in which a molar concentration is the same as 10 wt% NaCl aqueous solution and 14 wt% sodium acetate aqueous solution.

The Ca concentration of the sample after the third treatment liquid flow in (4) was measured. At that time, the sample was evaporated to dryness and ignited at 450 ° C., 10 ml of (1 + 2) HCl was added, dissolved under heating and filtered, and after constant volume, ICP emission spectroscopic analysis was performed.
The results are shown in Table 1.

  According to Table 1, although the effectiveness of sodium propionate became clear, it turned out that the organic acid of an acetic acid and a citric acid has little effect.

  Based on the above experimental result group and other findings, the acid dissociation index (pka) is 2.0 or less, preferably 0.6 or less as an acid, and the salt is an organic acid alkali metal such as sodium acetate or sodium propionate. Salt can be used. It was found that these organic acids and organic acid alkali metals can be used alone or in combination.

  In the present embodiment, the application to the equipment used in the region where the liquid phase coexists under the subcritical condition is disclosed, but the liquid and the wetted part where chloride ions exist under the condition other than the subcritical condition The present invention can also be widely applied to facilities composed of materials including metal materials that may cause stress corrosion cracking due to chloride ions. For example, the present invention can be applied to facilities in which soft water is used under conditions of 80 ° C. to boiling point at normal pressure. Application examples include a water supply pipe to the boiler, a cooling can provided at the lower part of the waste liquid combustion furnace, and its drain pipe.

DESCRIPTION OF SYMBOLS 1A, 1B ... Ion exchange resin tank, 2 ... Hydrothermal gasification processing apparatus, 10 ... Liquid flow path to be processed, 11a, 12a, 11b, 12b ... Flow path, 13 ... Processing Water channel, 14 ... recovered fuel gas channel, 15 ... hydrothermal gasification treated water channel, 20 ... eluent supply channel, 21a, 2a, 21b, 22b ... eluent tank channel , 23... Eluent drainage channel, 30... Cleaning fluid channel, 31a, 32a, 31b, 32b... Cleaning fluid channel, 33.

Claims (9)

When regenerating the cation exchange resin that has captured the metal, the metal ion is removed by the cation exchange resin.
As the cation exchange resin, a strong acid cation exchange resin is used, and the strong acid cation exchange resin is brought into contact with an aqueous solution of a regenerant containing at least one of an organic acid alkali metal salt and an organic acid, thereby bringing the metal into contact. A method for regenerating a cation exchange resin, characterized by elution.   The method for regenerating a cation exchange resin according to claim 1, wherein the cation exchange resin is a cation exchange resin having a sulfo group.   2. The regenerant comprises at least one selected from the group consisting of sodium acetate and sodium propionate as the alkali metal salt of an organic acid, and an organic acid having an acid dissociation index of 2.0 or less as an acid, or a combination thereof. The regeneration method of cation exchange resin as described.   Treating organic substances and / or oxidizable inorganic substances in the liquid under high pressure using a container composed of a material containing a metal material in which the wetted part may cause stress corrosion cracking in the presence of chloride ions The liquid supplied to the waste liquid treatment step is passed through the cation exchange resin to remove metal ions, and the cation exchange resin containing the metal is regenerated. The regeneration method of cation exchange resin as described.   5. The method for regenerating a strongly acidic cation exchange resin according to claim 4, wherein the waste liquid treatment step is a treatment step performed in a region where the aqueous phase is present under high pressure at a temperature exceeding 100 ° C. to 374 ° C. The waste liquid treatment step uses an apparatus for waste liquid treatment in a container composed of a metal material in which the liquid contact portion may cause stress corrosion cracking in the presence of chloride ions, and
The method for regenerating a cation exchange resin according to any one of claims 1 to 3, wherein the treatment is carried out in a region where the aqueous phase exists under high pressure at a temperature exceeding 100 ° C to 374 ° C.   The method for regenerating a cation exchange resin according to claim 4, wherein the metal material is a material containing at least one of low alloy steel, austenitic stainless steel, and martensitic stainless steel. A metal ion removing step of removing a metal ion by passing a liquid to be treated containing an organic substance and / or an oxidizable inorganic substance through a strongly acidic cation exchange resin;
A treatment step of treating the liquid to be treated under subcritical conditions in an apparatus composed of a metal in which a wetted part may cause stress corrosion cracking due to chloride ions;
A regeneration step of passing an aqueous solution of at least one organic acid alkali metal salt and organic acid through the cation exchange resin;
A method for treating a liquid to be treated, comprising: A treatment facility for treating a liquid containing an organic substance and / or an oxidizable inorganic substance under subcritical conditions in an apparatus in which a wetted part is made of a metal that may cause stress corrosion cracking due to chloride ions; A plurality of ion-exchange treatment tanks arranged in parallel having a strongly acidic cation exchange resin that allows the liquid to be treated to flow before being supplied to the treatment facility,
A flow changing means or a series for alternately changing the flow type between the first ion exchange treatment tank through which the liquid to be treated is passed and the second ion exchange treatment tank through which the regenerant is passed. In the ion exchange treatment tank, there is a means for changing the flow type over time,
The processing equipment containing a cation exchange resin, wherein the regenerant is an aqueous solution of at least one organic acid alkali metal salt and organic acid.

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