REGENERATION METHOD AND REGENERATION DEVICE OF OH TYPE Mg-Al-BASED LAYERED DOUBLE HYDROXIDE

Abstract

To provide a regeneration method and a regeneration device of an OH type Mg-Al-based layered double hydroxide which suppress a burden on a waste liquid treatment facility and can efficiently and economically regenerate the layered double hydroxide, in regeneration treatment of an Mg-Al-based layered double hydroxide broken by contact with acidic gas.SOLUTION: A regeneration method of an OH type Mg-Al-based layered double hydroxide for replacing interlaminate anions of an OH type Mg-Al-based layered double hydroxide broken by contact with acidic gas with hydroxide ions, and regenerating an OH type Mg-Al-based layered double hydroxide, brings a regenerated liquid agent containing hydroxide ions into contact with the broken OH type Mg-Al-based layered double hydroxide, recovers the regenerated liquid agent after contact, and brings the recovered regenerated liquid agent into contact with the broken OH type Mg-Al-based layered double hydroxide and thereby circularly uses the regenerated liquid agent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for regenerating OH-type Mg-Al-based layered double hydroxide that has broken through due to contact with an acidic gas. [Background technology]

[0002] The combustion exhaust gas generated from the incinerator at an incineration facility contains hydrogen chloride, sulfur oxides (SO x ) and nitrogen oxides (NO x ) and other acidic gases. In accordance with harmful gas regulations, such acidic gases are removed from combustion exhaust gases before they are released into the atmosphere, and it has been proposed to use layered double hydroxides for this removal process.

[0003] For example, Patent Document 1 discloses a method for treating acidic exhaust gas using an OH-type Mg-Al layered double hydroxide. Patent Document 1 also describes that OH-type Mg-Al layered double hydroxide that breaks through during the treatment of acidic exhaust gas is regenerated by ion exchange of interlayer anions into hydroxide ions using a regenerant such as sodium hydroxide, and the regenerated product is used for the treatment of acidic exhaust gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7130197 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 describes that the breakthrough OH-type Mg-Al layered double hydroxide is mixed with an aqueous sodium hydroxide solution, stirred, and regenerated by ion exchange. However, this type of regeneration process has problems such as a large amount of waste liquid being generated, which places a large burden on the waste liquid treatment equipment, and the use of large amounts of water and regenerants, which increases the cost of the regeneration process.

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide a method and apparatus for regenerating OH-type Mg-Al-based layered double hydroxide, which can reduce the load on waste liquid treatment equipment and enable efficient and economical regeneration in the regeneration treatment of Mg-Al-based layered double hydroxide that has broken through due to contact with acidic gas. [Means for solving the problem]

[0007] The present invention is based on the discovery of a method for efficiently regenerating breakthrough Mg-Al-based layered double hydroxide using a smaller amount of regenerating solution than in the past.

[0008] The present invention provides the following means. [1] A method for regenerating an OH-type Mg-Al-based layered double hydroxide by exchanging interlayer anions of an OH-type Mg-Al-based layered double hydroxide that has broken through due to contact with an acidic gas for hydroxide ions, the method comprising contacting a regenerating solution containing hydroxide ions with the breakthrough OH-type Mg-Al-based layered double hydroxide, recovering the regenerating solution after contact and contacting it with the breakthrough OH-type Mg-Al-based layered double hydroxide, thereby circulating the regenerating solution. [2] The method for regenerating an OH-type Mg-Al-based layered double hydroxide according to [1], wherein the regenerating solution is circulated through the breakthrough OH-type Mg-Al-based layered double hydroxide. [3] The method for regenerating an OH-type Mg-Al-based layered double hydroxide according to [1] or [2], wherein the regenerating liquid is a metal hydroxide solution. [4] A method for regenerating an OH-type Mg-Al-based layered double hydroxide according to any one of [1] to [3], in which a cleaning solution is brought into contact with the OH-type Mg-Al-based layered double hydroxide after contacting with the regenerating solution, the cleaning solution after contact is recovered, and the cleaning solution is brought into contact with the OH-type Mg-Al-based layered double hydroxide after said circulating contact, thereby circulating the cleaning solution. [5] The method for regenerating an OH-type Mg-Al-based layered double hydroxide according to [4], wherein the cleaning liquid is circulated through the OH-type Mg-Al-based layered double hydroxide after the circulating contact. [6] The method for regenerating an OH-type Mg-Al-based layered double hydroxide according to [4] or [5], wherein the cleaning liquid is water.

[0009] [7] An apparatus for regenerating OH-type Mg-Al-based layered double hydroxide by exchanging interlayer anions of OH-type Mg-Al-based layered double hydroxide that has broken through due to contact with an acidic gas for hydroxide ions, the apparatus comprising: a reactor for accommodating the breakthrough OH-type Mg-Al-based layered double hydroxide; a first storage tank for accommodating a regenerating solution containing hydroxide ions; and a first flow path connecting the reactor and the first storage tank, the reactor having a liquid inlet and a liquid outlet, and the first flow path being connected so that the regenerating solution can be circulated between the reactor and the first storage tank. [8] The regeneration apparatus for OH-type Mg-Al-based layered double hydroxide according to [7], which has a liquid inlet at the top of the reactor and a liquid outlet at the bottom of the reactor, and in which the regeneration liquid agent is injected from the top of the reactor and discharged from the bottom. [9] The apparatus for regenerating an OH-type Mg-Al-based layered double hydroxide according to [7] or [8], further comprising a second storage tank for storing a cleaning liquid, and a second flow path connecting the reactor and the second storage tank, the second flow path being connected so that the cleaning liquid can be circulated between the reactor and the second storage tank.

[10] The apparatus for regenerating an OH-type Mg-Al-based layered double hydroxide according to [9], wherein the reactor has a liquid inlet at an upper portion and a liquid outlet at a lower portion, and the washing liquid is injected from the upper portion of the reactor and discharged from the lower portion. Effect of the Invention

[0010] According to the method for regenerating OH-type Mg-Al-based layered double hydroxide of the present invention, the load on the waste liquid treatment equipment is suppressed during regeneration treatment of OH-type Mg-Al-based layered double hydroxide that has broken through due to contact with an acidic gas, and the OH-type Mg-Al-based layered double hydroxide can be regenerated efficiently and economically. Furthermore, by using the regeneration device for OH-type Mg-Al-based layered double hydroxide of the present invention, the above regeneration method can be effectively carried out. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram showing a schematic diagram of an apparatus for regenerating an OH-type Mg—Al-based layered double hydroxide according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In this specification, a numerical range expressed using "~" means that the numerical values ​​before and after "~" are the lower limit and upper limit.

[0013] [Method for regenerating OH-type Mg-Al-based layered double hydroxide] A method for regenerating an OH-type Mg-Al-based layered double hydroxide according to an embodiment of the present invention (hereinafter also referred to as this embodiment) is a method for regenerating an OH-type Mg-Al-based layered double hydroxide by exchanging interlayer anions of the OH-type Mg-Al-based layered double hydroxide that has broken through due to contact with an acidic gas for hydroxide ions, in which a regenerating liquid containing hydroxide ions is brought into contact with the breakthrough OH-type Mg-Al-based layered double hydroxide, the regenerating liquid after contact is recovered, and then brought into contact with the breakthrough OH-type Mg-Al-based layered double hydroxide, thereby circulating and reusing the regenerating liquid.

[0014] The OH-type Mg-Al-based layered double hydroxide is composed of a hydroxide base layer ([Mg 2+ 1-x Al 3+ x (OH) 2 ]) and an intermediate layer consisting of interlayer hydroxide ions and interlayer water ([(OH - ) x ·yH 2 These nanoparticles have a structure in which the hydroxide base layer has a positive charge equivalent to x, and hydroxide ions exist between the layers as anions with a negative charge to compensate for this, making it a non-stoichiometric compound. Although OH-type Mg-Al layered double hydroxide is a naturally occurring clay mineral called meixnerite, synthetic powder is usually used. The synthesis method is not particularly limited, and known methods can be used (for example, see Journal of Materials Science, 200, Vol. 42, p. 9210-9215).

[0015] From the viewpoint of ease of handling, the OH-type Mg-Al-based layered double hydroxide is preferably granulated by a known method such as extrusion granulation, and may be molded using a binder or the like as necessary. The shape is preferably, for example, spherical or cylindrical, taking into consideration the reactivity with acidic gases and the pressure difference during gas passage in the reactor. The particle size of the granulated product is preferably 0.5 to 30 mm, more preferably 1 to 20 mm, and even more preferably 3 to 10 mm. In this specification, the term "particle size" refers to the mode diameter of a particle.

[0016] When an OH-type Mg-Al layered double hydroxide is brought into contact with an acidic gas, it can capture the acidic gas, such as hydrogen chloride, sulfur oxides, and nitrogen oxides, between the layers while maintaining the hydroxide base layer. For this reason, it is used, for example, to treat the combustion exhaust gas generated from the incinerator in an incineration facility, and the acidic gas can be removed by bringing the combustion exhaust gas into contact with the OH-type Mg-Al layered double hydroxide.

[0017] In this way, the OH-type Mg-Al-based layered double hydroxide exhibits the ability to remove acidic gases by exchanging the hydroxide ions of the interlayer anions with anions derived from the acidic gases. However, as the ion exchange progresses and the hydroxide ions of the interlayer anions decrease, the acidic gas removal ability decreases and the gas passes through. The OH-type Mg-Al-based layered double hydroxide that has broken through can be regenerated by exchanging the interlayer anions derived from the acidic gas with hydroxide ions.

[0018] In the regeneration method of this embodiment, a regenerated liquid containing hydroxide ions is brought into contact with the breakthrough OH-type Mg-Al-based layered double hydroxide, the regenerated liquid after contact is recovered, and the recovered regenerated liquid is brought into contact with the breakthrough OH-type Mg-Al-based layered double hydroxide, thereby circulating and reusing the regenerated liquid. By recycling the regenerated solution in this way, the amount of regenerated solution used and the amount of waste liquid can be reduced compared to when treatment with the regenerated solution is performed in a one-time manner, the load on the waste liquid treatment equipment is reduced, and the cost of regenerating the breakthrough OH-type Mg-Al-based layered double hydroxide is also reduced. The regenerated OH-type Mg-Al-based layered double hydroxide can be reused in acid gas removal treatment.

[0019] In the regeneration method, from the viewpoint of improving the efficiency of the treatment by shortening the time and simplifying the operation, it is preferable to circulate the regenerated solution through the breakthrough OH-type Mg-Al-based layered double hydroxide. For example, it is preferable to continuously supply a predetermined amount of the regenerated solution to the breakthrough OH-type Mg-Al-based layered double hydroxide using a circulation pump or the like, and repeatedly use the regenerated solution recovered after contact with the breakthrough OH-type Mg-Al-based layered double hydroxide for circulation.

[0020] The regeneration liquid is not particularly limited as long as it is a liquid that can regenerate the breakthrough OH-type Mg-Al-based layered double hydroxide. From the viewpoint of ease of reaction of ion exchange of interlayer anions to hydroxide ions, a metal hydroxide solution is preferred. As the metal hydroxide, for example, sodium hydroxide, potassium hydroxide, etc. are relatively inexpensive and are preferable from the viewpoint of reducing costs. The regenerating liquid is preferably a solution so that it can be easily and uniformly permeated into the breakthrough OH-type Mg-Al-based layered double hydroxide, and from the viewpoints of ease of handling, cost, etc., an aqueous solution is preferred.

[0021] The regenerating solution is preferably an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution, and particularly preferably an aqueous sodium hydroxide solution. In this case, from the viewpoint of sufficient ion exchange reactivity and prevention of dissolution of Al constituting the hydroxide base layer of the OH-type Mg-Al-based layered double hydroxide, the aqueous solution has a concentration of preferably 2 to 10 w / v%, more preferably 3 to 8 w / v%, and even more preferably 3 to 5 w / v%.

[0022] From the viewpoints of sufficient ion exchange reactivity, prevention of the increase in the scale of the apparatus, and reduction of the load on the wastewater treatment equipment, the amount of the regenerating solution used is preferably 0.2 to 5 times the volume (bed volume) of the breakthrough OH-type Mg-Al-based layered double hydroxide, more preferably 0.3 to 3 times, and even more preferably 0.5 to 2 times. The amount used here is the amount per batch of the regenerated solution that is recycled. The regenerated solution that is recycled may be replaced with a new batch of regenerated solution during the treatment, taking into account the treatment efficiency and cost.

[0023] The flow rate when circulating the regenerated liquid is preferably 1 to 10 times the volume (bed volume) of the breakthrough OH-type Mg-Al-based layered double hydroxide per hour, more preferably 2 to 8 times, and even more preferably 2 to 6 times, from the viewpoints of good reaction efficiency of ion exchange, reducing the load on equipment such as a circulation pump, and preventing damage to the OH-type Mg-Al-based layered double hydroxide.

[0024] The total time for circulating the regenerated liquid depends on the volume (bed volume) of the breakthrough OH-type Mg-Al-based layered double hydroxide, but from the viewpoints of treatment efficiency and prevention of dissolution of Al constituting the hydroxide base layer of the OH-type Mg-Al-based layered double hydroxide, it is preferably 1 to 72 hours, more preferably 1 to 60 hours, and even more preferably 1 to 48 hours. From the viewpoints of achieving good reaction efficiency in ion exchange and preventing loss of the OH-type Mg—Al-based layered double hydroxide, the temperature of the regenerated solution circulated is preferably 10 to 80° C., more preferably 15 to 70° C., and even more preferably 20 to 60° C. The regenerated solution may be circulated at normal temperature (room temperature) without being heated.

[0025] The OH-type Mg-Al-based layered double hydroxide after contact with the regenerated liquid as described above is in a regenerated state in which the interlayer anions derived from the acidic gas have been exchanged for hydroxide ions, and therefore the regenerated OH-type Mg-Al-based layered double hydroxide can be used as is. However, it is preferable to carry out a washing treatment to remove salts produced by the reaction between the interlayer anions derived from the acidic gas and the regenerated liquid.

[0026] The cleaning treatment can be carried out by running a cleaning liquid over the substrate or by immersing the substrate in the cleaning liquid, but is preferably carried out in the following embodiment of the present invention. The cleaning treatment of this embodiment involves contacting a cleaning liquid with the OH-type Mg-Al-based layered double hydroxide after contacting with the regenerated solution in the manner described above, recovering the cleaning liquid after contact, and contacting the recovered cleaning liquid with the OH-type Mg-Al-based layered double hydroxide after the aforementioned circulating contact, thereby circulating the cleaning liquid. By recycling the cleaning liquid in this manner, the amount of cleaning liquid used and the amount of waste liquid can be reduced compared to when treatment with a cleaning liquid is carried out in a one-time manner, the load on the waste liquid treatment equipment can be reduced, and the cost of regenerating the breakthrough OH-type Mg—Al-based layered double hydroxide can also be reduced.

[0027] In the washing treatment, from the viewpoint of improving the efficiency of the treatment by shortening the time and simplifying the operation, it is preferable to circulate the washing liquid to the OH-type Mg-Al-based layered double hydroxide after the treatment with the regenerated solution. For example, it is preferable to continuously supply a predetermined amount of washing liquid to the OH-type Mg-Al-based layered double hydroxide after the treatment with the regenerated solution using a circulation pump or the like, recover the washing liquid that has come into contact with the OH-type Mg-Al-based layered double hydroxide after the treatment with the regenerated solution, and repeatedly use this recovered liquid for circulation.

[0028] The cleaning liquid is not particularly limited as long as it can sufficiently remove impurities such as salts generated by the reaction between the interlayer anions derived from acidic gas and the regenerating liquid from the OH-type Mg-Al-based layered double hydroxide after treatment with the regenerating liquid. From the viewpoints of cleaning ability and cost, water is preferred, and for example, industrial water, river water, pure water, etc. can be used. From the viewpoint of suppressing the inclusion of impurities such as salts, pure water is more preferred.

[0029] The amount of the washing liquid used is preferably 0.2 to 5 times, more preferably 0.3 to 3 times, and even more preferably 0.5 to 2 times the volume (bed volume) of the breakthrough OH-type Mg-Al-based layered double hydroxide, from the viewpoints of sufficiently removing impurities such as salts, preventing the apparatus from becoming large-scale, and reducing the load on the waste liquid treatment equipment. The amount of cleaning solution used here is the amount per batch of cleaning solution that is recycled. The cleaning solution that is recycled may be replaced with a new batch of cleaning solution during the process, taking into account the cleaning efficiency and cost.

[0030] From the viewpoints of achieving good cleaning efficiency, reducing the load on equipment such as a circulation pump, and preventing wear of the OH-type Mg-Al-based layered double hydroxide, the flow rate when circulating the cleaning solution is preferably 1 to 10 times the volume (bed volume) of the breakthrough OH-type Mg-Al-based layered double hydroxide per hour, more preferably 2 to 8 times, and even more preferably 2 to 6 times.

[0031] The total time for circulating the washing liquid depends on the volume (bed volume) of the breakthrough OH-type Mg-Al-based layered double hydroxide, but from the viewpoint of good washing efficiency, etc., it is preferably 1 to 72 hours, more preferably 1 to 60 hours, and even more preferably 1 to 48 hours. From the viewpoints of good cleaning efficiency and prevention of wear of the OH type Mg—Al-based layered double hydroxide, the temperature of the cleaning liquid circulated is preferably 10 to 80° C., more preferably 15 to 70° C., and even more preferably 20 to 60° C. The cleaning liquid may be circulated at normal temperature (room temperature) without heating.

[0032] [Regeneration device for OH-type Mg-Al-based layered double hydroxide] The regeneration device for OH-type Mg-Al-based layered double hydroxide according to an embodiment of the present invention is a device that regenerates OH-type Mg-Al-based layered double hydroxide by exchanging interlayer anions of the OH-type Mg-Al-based layered double hydroxide that have broken through due to contact with an acidic gas with hydroxide ions. The following description will be given with reference to the conceptual diagram of the playback device of this embodiment shown in FIG.

[0033] The regeneration device shown in Fig. 1 includes a reactor 1 for accommodating the breakthrough OH-type Mg-Al-based layered double hydroxide, a first storage tank 2 for accommodating a regenerated liquid agent containing hydroxide ions, and a first flow path 3 for connecting the reactor 1 and the first storage tank 2, the reactor 1 having a liquid inlet 1a and a liquid outlet 1b, and the first flow path 3 is connected so that the regenerated liquid agent can circulate between the reactor 1 and the first storage tank 2. The circulation of the regenerated liquid agent is preferably performed by a first circulation pump 4 capable of controlling the flow rate. By using such an apparatus, the above-mentioned method for regenerating an OH-type Mg—Al-based layered double hydroxide of this embodiment can be suitably carried out.

[0034] In addition, as shown in FIG. 1, it is preferable that the regeneration device has a liquid inlet 1a at the top of the reactor 1 and a liquid outlet 1b at the bottom of the reactor 1, and the regeneration liquid agent is injected from the top of the reactor 1 and discharged from the bottom (in the direction of the arrow in the figure). The liquid flow direction for circulating the regenerated liquid may be the opposite direction to that of the arrow shown in Fig. 1, that is, the regenerated liquid may be injected from the bottom of the reactor 1 and discharged from the top. However, in this case, since the reactor 1 is always filled with the regenerated liquid while the regenerated liquid is circulated, a larger amount of the regenerated liquid is used. From the viewpoint of preventing the device from becoming large-scale, it is preferable to inject the regenerating liquid agent from the top of the reactor 1 and discharge it from the bottom.

[0035] One embodiment of the method for regenerating an OH-type Mg—Al-based layered double hydroxide using the regeneration apparatus will be described below. First, a predetermined amount of regenerated liquid agent prepared at a predetermined concentration is charged into the first storage tank 2, circulated by the first circulation pump 4, and injected into the reactor 1 from the liquid inlet 1a at the top of the reactor 1. The regenerated liquid agent injected into the reactor 1 flows downward while contacting and permeating the breakthrough OH-type Mg-Al-based layered double hydroxide, and is discharged from the liquid outlet 1b at the bottom of the reactor 1. The regenerated liquid agent discharged from the reactor 1 is stored in the first storage tank 2, and then circulated by the first circulation pump 4, and injected into the reactor 1 from the liquid inlet 1a at the top of the reactor 1. After the regenerated liquid has been circulated for a predetermined time, the operation of the first circulation pump 4 is stopped and the regenerated liquid in the reactor 1 is recovered in the first storage tank 2.

[0036] The circulation of the regenerated liquid can be completed, for example, by analyzing the concentration of anions (e.g., chloride ions) derived from the acidic gas, the hydroxide ion concentration, the metal ion concentration in the regenerated liquid, the electrical conductivity, the density, etc., of the regenerated liquid near the liquid outlet 1b at the bottom of the reactor 1 or in the first storage tank 2, and using the analytical values ​​as indicators.

[0037] 1 includes a second storage tank 5 for storing a cleaning liquid, and a second flow path 6 connecting the reactor 1 and the second storage tank 5, and the second flow path 6 is connected so that the cleaning liquid can circulate between the reactor 1 and the second storage tank 5. The circulation of the cleaning liquid is preferably performed by a second circulation pump 7 capable of controlling the flow rate. It is preferable that the regeneration device is provided with a configuration for carrying out such a cleaning process.

[0038] In addition, as in the regeneration device shown in FIG. 1, it is preferable that the reactor 1 has a liquid inlet 1c at the top and a liquid outlet 1d at the bottom, and the washing liquid is injected from the top of the reactor 1 and discharged from the bottom (in the direction of the arrows in the figure). The direction of flow of the cleaning liquid circulating may be opposite to that of the arrow shown in Fig. 1, i.e., the cleaning liquid may be injected from the bottom of the reactor 1 and discharged from the top. In this case, however, the reactor 1 is always filled with the cleaning liquid while the cleaning liquid is circulating, so that a larger amount of the cleaning liquid is used. From the viewpoint of preventing the device from becoming large-scale, it is preferable to inject the cleaning liquid from the top of the reactor 1 and discharge it from the bottom.

[0039] In the regeneration device, the OH type Mg-Al-based layered double hydroxide after treatment with the regeneration solution can be washed as follows. First, a predetermined amount of cleaning solution is charged into the second storage tank 5, circulated by the second circulation pump 7, and injected into the reactor 1 from the liquid inlet 1c at the top of the reactor 1. The cleaning solution injected into the reactor 1 flows downward while contacting and permeating the OH-type Mg-Al-based layered double hydroxide after treatment with the regenerated solution, and is discharged from the liquid outlet 1d at the bottom of the reactor 1. The cleaning solution discharged from the reactor 1 is stored in the second storage tank 5, and then circulated by the second circulation pump 7, and injected into the reactor 1 from the liquid inlet 1c at the top of the reactor 1. After the cleaning liquid has been circulated for a predetermined time, the operation of the second circulation pump 7 is stopped and the cleaning liquid in the reactor 1 is recovered in the second storage tank 5 .

[0040] The circulation of the cleaning liquid can be completed, for example, by analyzing the concentration of anions (e.g., chloride ions) derived from acidic gas, the hydroxide ion concentration, the metal ion concentration in the regenerated liquid, the electrical conductivity, the density, etc., of the cleaning liquid near the liquid outlet 1d at the bottom of the reactor 1 or in the second storage tank 5, and using the analytical values ​​as indicators. EXAMPLES

[0041] The present invention will be described in detail below with reference to examples. The present invention is not limited to the following examples, and various modifications are possible without departing from the gist of the present invention.

[0042] [Test 1] 30 g (volume: 55 mL) of granulated product with a particle size of 3 mm of OH-type Mg-Al layered double hydroxide (Cl-type Mg-Al layered double hydroxide) breakthrough by hydrogen chloride gas was packed into an acrylic column with an inner diameter of 40 mm. Using an aqueous sodium hydroxide solution with a concentration of 4 w / v% as the regeneration liquid agent and pure water as the washing liquid, regeneration from Cl-type Mg-Al layered double hydroxide to OH-type Mg-Al layered double hydroxide was carried out by each operation shown in the following examples and comparative examples. The evaluation of regeneration was carried out by determining the Cl desorption rate from the granulated product of Cl-type Mg-Al layered double hydroxide as follows.

[0043] <Cl desorption rate> During or after the operations of each example and comparative example, the granulated product was appropriately recovered from the column, dried in a constant temperature dryer at 105 °C for 12 hours, ground in a mortar, and about 0.5 g was weighed as a sample. 100 mL of HNO 3 with a concentration of 2 mol / L was added to the sample, filtered, 2 mL of the filtrate was collected, diluted 50 times with pure water, and chloride ions (Cl - ) were quantified by ion chromatography, and the Cl content (C 1 ) per unit weight was measured. Samples were also prepared in the same manner for the granulated products before the operations of each example and comparative example, and the Cl content (C 0 ) per unit weight before the operation was measured. The Cl desorption rate was calculated by the formula (C 0 - C 1 ) / C 0 × 100 [%].

[0044] (Example 1) 40 mL of the regeneration liquid agent placed in a beaker was injected from the top of the column at 3 mL / min by a tube pump. The discharge liquid from the bottom of the column was returned to the beaker and circulated through the column for 1 hour so as to be injected from the top of the column. The operation of the tube pump was stopped, and the circulated liquid was recovered in the beaker. Next, 30 mL of the cleaning solution placed in a beaker was injected from the top of the column at 3 mL / min using a tube pump. The solution discharged from the bottom of the column was returned to the beaker and injected from the top of the column, and circulation was carried out for 1 hour. The tube pump was stopped, and the circulated solution was collected in the beaker. Circulation of 30 mL (1 batch) of cleaning solution was carried out twice. The Cl desorption rate was 70%.

[0045] Example 2 In Example 1, after circulation of the regenerated liquid, the washing liquid was injected from the top of the column at 3 mL / min using a tube pump, and discharged from the bottom of the column without circulating, and collected in a beaker. The amount of washing solution used when the Cl desorption rate reached 70% was 660 mL.

[0046] Comparative Example 1 In Example 1, the tap at the bottom of the column was closed and 40 mL of regenerating solution was injected from the top of the column while the liquid was not being discharged. The column was left to stand for 1 hour to allow the granulated material to be soaked in the solution, after which the tap was opened and the discharged liquid was collected in a beaker. Next, the stopcock at the bottom of the column was closed, and 30 mL of washing solution was poured into the top of the column without discharging the liquid. The column was left to stand for 1 hour to soak the granules, and then the stopcock was opened and the discharged liquid was collected in a beaker. The soaking with 30 mL of washing solution (1 batch) was repeated twice. The Cl desorption rate was 61%.

[0047] Since the Cl release rate was reached when the cleaning solution was circulated for cleaning (Example 1) and when it was washed in a pass-through manner (Example 2), it can be said that the Cl release rate does not decrease even if the cleaning solution after contacting with the granulated material is circulated for contact with the granulated material. It was also confirmed that the amount of cleaning solution used in Example 1 until the Cl release rate reached 70% was 1 / 10 or less of that in Example 2. In addition, it was confirmed that, even when the same amount of washing solution was used, the Cl desorption rate was higher when the washing solution was circulated (Example 1) than when the granulated material was left to stand and then immersed in the washing solution (Comparative Example 1).

[0048] [Test 2] 70 g (volume 130 mL) of 3 mm particle size granules of OH-type Mg-Al-based layered double hydroxide (Cl-type Mg-Al-based layered double hydroxide) that had been broken through by hydrogen chloride gas was packed into an acrylic column with an inner diameter of 40 mm. Using a 4 w / v% sodium hydroxide aqueous solution as the regenerating solution and pure water as the washing solution, the Cl-type Mg-Al-based layered double hydroxide was regenerated to OH-type Mg-Al-based layered double hydroxide by the operations shown in the following examples. The regeneration was evaluated based on the Cl release rate, as in Test 1.

[0049] Example 3 160 mL of the regenerated liquid in a beaker was pumped into the top of the column at 12 mL / min using a tube pump. The liquid discharged from the bottom of the column was returned to the beaker and pumped into the top of the column for 48 hours. The tube pump was stopped, and the liquid that had been circulated was collected in the beaker. Next, 130 mL of the cleaning solution placed in a beaker was injected from the top of the column at 12 mL / min using a tube pump. The solution discharged from the bottom of the column was returned to the beaker and injected from the top of the column, and circulation was continued for 24 hours. The tube pump was stopped, and the circulated solution was collected in the beaker. Circulation washing with 130 mL (1 batch) of cleaning solution was performed twice. The Cl desorption rate was 94%.

[0050] Example 4 160 mL of the regenerated liquid in a beaker was pumped into the bottom of the column at 6 mL / min using a tube pump. The liquid that overflowed from the top of the column was collected in a beaker and circulated for 2.5 hours. The tube pump was stopped, and the circulated liquid was collected in the beaker. Next, 130 mL of the cleaning solution in a beaker was injected from the bottom of the column at 6 mL / min using a tube pump. The liquid that overflowed from the top of the column was received in the beaker and circulated for 2.5 hours. The tube pump was stopped, and the circulated liquid was collected in the beaker. Circulation washing with 130 mL (1 batch) of cleaning solution was performed twice. The Cl desorption rate was 91%.

[0051] It was found that by increasing the processing volume compared to Example 1 and increasing the flow rate and time for circulating the regenerating solution and the cleaning solution, respectively, the Cl desorption rate improved both in the case where the regenerating solution and the cleaning solution were injected from the top of the column (Example 3) and in the case where the solution was injected from the bottom of the column (Example 4). [Explanation of symbols]

[0052] 1. Reactor 2. First tank 3. First Channel 4. First Circulation Pump 5. Second tank 6 Second flow path 7 Second Circulation Pump

Claims

1. 1. A method for regenerating an OH-type Mg-Al-based layered double hydroxide by exchanging interlayer anions of the OH-type Mg-Al-based layered double hydroxide that has broken through due to contact with an acidic gas with hydroxide ions, comprising: a regenerated liquid agent containing hydroxide ions is brought into contact with the breakthrough OH-type Mg—Al-based layered double hydroxide, the regenerated liquid agent after the contact is recovered, and the recovered liquid agent is brought into contact with the breakthrough OH-type Mg—Al-based layered double hydroxide, thereby circulating and reusing the regenerated liquid agent. A method for regenerating OH-type Mg-Al-based layered double hydroxide.

2. 2. The method for regenerating an OH-type Mg-Al-based layered double hydroxide according to claim 1, wherein the regenerating solution is circulated through the breakthrough OH-type Mg-Al-based layered double hydroxide.

3. 3. The method for regenerating an OH-type Mg-Al-based layered double hydroxide according to claim 1, wherein the regenerating solution is a metal hydroxide solution.

4. 2. A method for regenerating an OH-type Mg-Al-based layered double hydroxide according to claim 1, comprising the steps of: contacting a cleaning liquid with the OH-type Mg-Al-based layered double hydroxide after the contact using the regenerating liquid agent in a circulating manner; recovering the cleaning liquid after the contact; and contacting the recovered cleaning liquid with the OH-type Mg-Al-based layered double hydroxide after the circulating contact, thereby circulating the cleaning liquid.

5. 5. The method for regenerating an OH-type Mg-Al-based layered double hydroxide according to claim 4, wherein the cleaning liquid is circulated through the OH-type Mg-Al-based layered double hydroxide after the circulating contact.

6. 6. The method for regenerating an OH-type Mg-Al-based layered double hydroxide according to claim 4 or 5, wherein the cleaning liquid is water.

7. An apparatus for regenerating an OH-type Mg-Al-based layered double hydroxide by exchanging interlayer anions of the OH-type Mg-Al-based layered double hydroxide that has broken through due to contact with an acidic gas with hydroxide ions, comprising: The apparatus includes a reactor for accommodating the breakthrough OH-type Mg—Al-based layered double hydroxide, a first storage tank for accommodating a regenerating solution containing hydroxide ions, and a first flow path connecting the reactor and the first storage tank; The reactor has a liquid inlet and a liquid outlet, The first flow path is connected so that the regenerating liquid can be circulated between the reactor and the first storage tank. A regeneration device for OH-type Mg-Al-based layered double hydroxide.

8. 8. The regeneration device for OH-type Mg-Al-based layered double hydroxide according to claim 7, wherein the reactor has a liquid inlet at an upper portion thereof and a liquid outlet at a lower portion thereof, and the regeneration liquid agent is injected from the upper portion of the reactor and discharged from the lower portion thereof.

9. The apparatus further includes a second storage tank for storing a cleaning liquid, and a second flow path connecting the reactor and the second storage tank, 9. The apparatus for regenerating an OH-type Mg—Al-based layered double hydroxide according to claim 7 or 8, wherein the second flow path is connected so that the cleaning liquid can be circulated between the reactor and the second storage tank.

10. 10. The regeneration apparatus for OH-type Mg-Al-based layered double hydroxide according to claim 9, wherein the reactor has a liquid inlet at an upper portion and a liquid outlet at a lower portion, and the washing liquid is injected from the upper portion of the reactor and discharged from the lower portion.

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