JP2012201521A - Method for recovering calcium chloride - Google Patents

Abstract

[Object] To recover calcium chloride while minimizing adverse effects on operation due to scale adhesion in a final disposal site or cement manufacturing process.
A solution containing calcium chloride is separated into a solution having a high calcium chloride concentration and a solution having a low calcium chloride concentration using an amphoteric ion exchange resin, and the calcium chloride is recovered from the solution having a high calcium chloride concentration. . Calcium chloride can be recovered by evaporating water from a solution having a high calcium chloride concentration. Calcium chloride can be recovered as a liquid having a calcium chloride concentration of 35% or more and a solid having a calcium chloride concentration of 40% or more. The solution containing calcium chloride may be a liquid that induces calcium scale, and can also be a leachate from a final disposal site, or a filtrate obtained by washing incineration ash or / and chlorine bypass dust with water.
[Selection] Figure 1

Description

  The present invention relates to a method for recovering calcium chloride, and more particularly to a method for recovering calcium chloride from salt water or the like that occurs in a final disposal site, a cement manufacturing process, etc., and induces scale trouble.

  Calcium chloride is highly hygroscopic, strong in deliquescence, easily dissolved in water, and hard to freeze even at low temperatures, so it can be used for snow melting agents, dehumidifying agents, paper / textile sizing, wastewater treatment, reagents, etc. used. In order to produce this calcium chloride, it is common to concentrate an aqueous solution of calcium chloride produced during the production of anhydrous sodium carbonate using salt and limestone as main raw materials and ammonia as a secondary raw material. It can also be reacted to produce calcium chloride.

  On the other hand, final disposal sites such as garbage disposal sites are facilities for disposing of wastes that are difficult to recycle. However, in view of the danger of exhaustion, wastes that have been treated at the final disposal site so far Effective use is promoted. For example, incineration ash generated when municipal waste is incinerated has recently been recycled as a cement raw material instead of disposal at a final disposal site (see, for example, Patent Document 1).

  In addition, chlorine bypass equipment that removes chlorine that causes problems such as preheater clogging is used in cement manufacturing facilities. Chlorine brought into cement kilns as waste treatment increases in recent years. The amount of volatile components such as chlorine is increasing, and the amount of chlorine bypass dust generated is also increasing. Therefore, all the chlorine bypass dust cannot be used in the cement pulverization process, and the chlorine bypass dust is also washed with water (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 11-100343 JP 2001-129513 A

  Although salt water such as leachate from the above final disposal site and chlorine bypass dust washing filtrate contains calcium chloride, there is no conventional method for separating calcium chloride, so calcium chloride. Could not be used effectively.

On the other hand, at the final disposal site, calcium ions (Ca ²⁺ ) contained in the leachate and calcium sulfate (CaSO ₄ ) are generated from SO ₄ ^2- and adhere to the equipment as a scale in the filtration device and the wastewater treatment process at the later stage. However, there is a problem that stable operation is hindered. In addition, the incineration ash and chlorine bypass dust washing filtrate in the cement manufacturing process have the same problems as the leachate in the final disposal site.

  Therefore, the present invention has been made in view of the above problems in the conventional technology, and minimizes adverse effects on operation due to adhesion of scale in the final disposal site and cement manufacturing process, etc. The purpose is to recover calcium chloride from salt water such as leaching water and chlorine bypass dust washing filtrate.

  In order to achieve the above object, the present invention provides a method for recovering calcium chloride, which comprises converting a solution containing calcium chloride into a solution having a high calcium chloride concentration and a solution having a low calcium chloride concentration using an amphoteric ion exchange resin. Separating and recovering calcium chloride from the solution having a high calcium chloride concentration.

  And according to this invention, calcium chloride can be collect | recovered from the solution containing calcium chloride using amphoteric ion exchange resin.

  In the calcium chloride recovery method, water can be recovered by evaporating water from a solution having a high calcium chloride concentration, and a liquid or solid having a high calcium chloride concentration can be obtained.

  The calcium chloride can be recovered as a liquid having a calcium chloride concentration of 35% or more, and the recovered liquid can be effectively used as a snow melting agent or the like. Further, the calcium chloride can be recovered as a liquid having a calcium chloride concentration of 25% or more or a solid having a calcium chloride concentration of 40% or more.

  Further, in the calcium chloride recovery method, the solution containing the calcium chloride can be made into a liquid that induces calcium scale, and the chloride is reduced while minimizing the adverse effect on the operation of the apparatus and the like due to the adhesion of the calcium scale. Calcium can be recovered.

  By using the solution containing calcium chloride as the filtrate obtained by washing the leachate from the final disposal site, incineration ash or / and chlorine bypass dust with water, due to the adhesion of scale in the final disposal site, cement manufacturing process, etc. Calcium chloride can be recovered while minimizing adverse effects on operation.

  As described above, according to the present invention, it is possible to recover calcium chloride while minimizing adverse effects on operation due to scale adhesion in final disposal sites, cement manufacturing processes, and the like.

It is a flowchart which shows an example of the leachate treatment system of the final disposal site to which the recovery method of calcium chloride concerning this invention is applied. It is the schematic for demonstrating operation | movement of the ion exchange resin used for the processing system shown in FIG. It is a graph which shows the operation example of the ion exchange resin shown in FIG. It is a flowchart which shows 1st Example of the processing system shown in FIG. It is a flowchart which shows 2nd Example of the processing system shown in FIG. It is a flowchart which shows 3rd Example of the processing system shown in FIG.

  Next, modes for carrying out the present invention will be described with reference to the drawings. In the following description, a case where calcium chloride is recovered from the leachate at the final disposal site will be described as an example.

FIG. 1 shows a leachate treatment system (hereinafter abbreviated as “treatment system”) at a final disposal site to which the method for recovering calcium chloride according to the present invention is applied. The adjustment tank 3 for storing the leachate W, the leachate W from the adjustment tank 3 is a solution having a high calcium ion concentration and a high calcium chloride concentration (hereinafter referred to as “calcium chloride-containing water”) L3, and a low calcium ion concentration. An amphoteric ion exchange resin 4 that is separated into a SO ₄ ²⁻ high ^- concentration solution (hereinafter referred to as “SO ₄ -containing water”) L 4, a reclaimed water tank 5 that stores reclaimed water L 5 that is supplied to the amphoteric ion exchange resin 4, and amphoteric ions and replacing calcium chloride respectively storing the calcium chloride-containing water L3 and SO ₄ containing water L4 discharged from the resin 4 containing water tank 6, SO ₄ containing water tank 7, to remove heavy metals And location 8, and a COD processor 9.

  The adjustment tank 3 collects leachate W such as rainwater that has permeated through the waste layer of the final disposal site 2 and is prepared to equalize the change of water quality and quantity of the leachate W. A sand settling tank for sedimentation and separation of earth and sand is provided.

  The amphoteric ion exchange resin 4 is provided for recovering calcium chloride contained in the leachate W discharged from the adjustment tank 3. The amphoteric ion exchange resin has a function of allowing ion exchange with both cation and anion by making the base material cross-linked polystyrene or the like and having a quaternary ammonium group and a carboxylic acid group in the same functional group chain. Resin. For example, amphoteric ion exchange resin, Diaion (registered trademark), AMP03 manufactured by Mitsubishi Chemical Corporation can be used. The amphoteric ion exchange resin 4 can separate the electrolyte and the non-electrolyte in the aqueous solution, and can also separate the electrolytes from each other.

The heavy metal removing device 8 is provided for removing heavy metals such as lead contained in the SO ₄ -containing water L4, and a commonly used device such as a chemical reaction tank or a filter press can be used.

The COD treatment device 9 is provided to reduce the COD of the SO ₄ -containing water L4 from which heavy metals have been removed by the heavy metal removal device 8, and a general septic tank or the like can be used.

  Next, the operation of the processing system 1 having the above configuration will be described with reference to FIG.

After the leachate W from the final disposal site 2 is collected in the adjustment tank 3 and the change in water quality and quantity is suppressed, it is supplied to the amphoteric ion exchange resin 4, and the leachate W is supplied with calcium chloride-containing water L3 and SO ₄ -containing water L4. To separate. As shown in FIG. 2, this amphoteric ion exchange resin 4 performs batch processing continuously, and is previously filled with water (FIG. 2A), and then the amphoteric ion exchange resin from the adjustment tank 3. Leached water W is introduced into 4 and then reclaimed water L5 for regenerating the amphoteric ion exchange resin 4 is introduced (FIG. 2 (b)). Then, as shown in FIG. 2 (c), it is first discharged SO ₄ containing water L4 is then calcium chloride-containing water L3 is discharged in this order over time.

Here, the switching timing of the SO ₄ -containing water L4 and calcium chloride-containing water L3 is determined according to the concentration of Ca ²⁺ , SO ₄ ²⁻ , chloride and Pb ^{2+ in} the treatment liquid discharged from the amphoteric ion exchange resin 4. Control can be based on one or more measurement results selected from the group consisting of measurement results, electrical conductivity and pH. The SO ₄ -containing water L4 and the calcium chloride-containing water L3 discharged from the amphoteric ion exchange resin 4 are temporarily stored in the SO ₄ -containing water tank 7 and the calcium chloride-containing water tank 6, respectively.

Next, calcium chloride is recovered from the calcium chloride-containing water L3 stored in the calcium chloride-containing water tank 6. Calcium chloride may be recovered by evaporating water from the calcium chloride-containing water L3, and recovered as a liquid having a calcium chloride concentration of 25% or more, preferably 35% or more, or having a calcium chloride concentration of 40% or more. You may collect | recover as a granular solid. On the other hand, the SO ₄ -containing water L ₄ stored in the SO ₄ -containing water tank 7 removes heavy metals using the heavy metal removing device 8, further reduces COD by the COD processing device 9, and then discharges it.

Next, a first embodiment of the calcium chloride recovery method used in the processing system 1 will be described. As the amphoteric ion exchange resin 4, the amphoteric ion exchange resin, Diaion AMP03 manufactured by Mitsubishi Chemical Corporation, is used, and the leachate W of the final disposal site 2 having the chemical components shown in Table 1 is used as the raw water. No. 4 was passed, and fresh water twice the amount of leachate W was passed as reclaimed water L5. Table 2, FIG. 3 and FIG. 4 show the relationship between the flow rate and the concentration of each component contained in the treatment liquid that has passed through the amphoteric ion exchange resin 4 and the water balance in the treatment system 1 at that time. In FIG. 4, the numbers in the ellipses indicate the weight ratio of each water. Incidentally, Table 1, Table 2 and Figure 3, the measured electric conductivity Cl ^- shows in terms of concentration.

In the graph shown in FIG. 3, the water flow rate / raw water amount 0.14 to 1.43 is SO ₄ -containing water L4, and the water flow rate / raw water amount 1.43 and later is calcium chloride-containing water L3. In addition, since SO ₄ -containing water L4 can separate Na ⁺ , Pb ²⁺ , COD and NH ₄ ⁺ in addition to SO ₄ ^2- , these are only slightly contained in calcium chloride-containing water L3. The calcium chloride concentration of the calcium chloride-containing water L3 can be increased.

As clearly shown in Table 2 and FIG. 3, calcium chloride-containing water L3 and SO ₄ -containing water L4 are utilized by utilizing the phenomenon that calcium chloride (Ca ²⁺ and Cl ⁻ ) passes slowly in the amphoteric ion exchange resin. Switching timing can be controlled based on the calcium ion concentration of the solution discharged from the amphoteric ion exchange resin 4, and it is possible to avoid contamination of harmful substances such as lead into the calcium chloride-containing water L3. At this time, the solution discharged from the amphoteric ion exchange resin 4 is 1/20 or more of the calcium ion concentration of 3000 mg / l of the leachate W introduced into the amphoteric ion exchange resin 4, that is, 150 mg / l or more, preferably 1 / The calcium chloride concentration can be accurately adjusted by setting it to 100 mg or more, 30 mg / l or more, more preferably 1/300 or more to 10 mg / l or more.

  Alternatively, when the solution discharged from the amphoteric ion exchange resin 4 becomes 1/10 or less of the chlorine ion concentration of 7,000 mg / l of the leachate W introduced into the amphoteric ion exchange resin 4, that is, preferably 700 mg / l or less. Is 1/2 or less, that is, 3500 mg / l or less, more preferably 2/3 or less, that is, 4700 mg / l or less, so that the calcium chloride concentration can be adjusted with high accuracy. Since the chlorine ion concentration and the electric conductivity are in a proportional relationship, the electric conductivity can be controlled instead of the chlorine ion concentration.

Further, as shown in FIG. 4, when the leaching water W having a weight of 0.67 and the reclaimed water L5 having a weight of 1.33 are supplied to the amphoteric ion exchange resin 4 as shown in FIG. And an SO ₄ -containing water L4 having a weight of 1 are generated.

FIG. 5 shows the water balance in the second embodiment of the method for recovering calcium chloride used in the treatment system 1, and this embodiment uses the recycled water L5 in order to make the waste water treatment facility of the treatment system 1 small. The case where the amount is suppressed is shown. In FIG. 5, the numbers in the ellipses indicate the weight ratio of each water. In this embodiment, the same amount of reclaimed water L5 as that of the leachate W at the final disposal site 2 is passed through to generate a weight 1 calcium chloride-containing water L3 and a weight 1 SO ₄ -containing water L4.

  FIG. 6 shows a third embodiment of the method of recovering calcium chloride used in the treatment system 1. In this embodiment, in addition to the configuration shown in FIG. A hazardous substance treatment apparatus 10 such as a heavy metal treatment apparatus for treating a harmful substance slightly contained in the calcium chloride-containing water L3 discharged from the calcium-containing water tank 6 is provided to remove harmful substances containing heavy metals such as lead. ing.

  In the above embodiment, the case where the calcium chloride recovery method according to the present invention is applied to the leachate treatment system at the final disposal site is exemplified. In addition to this leachate treatment system, incineration ash and cement production Calcium chloride can also be recovered from salt water such as filtrate obtained by washing the chlorine bypass dust obtained in the process with water.

  For example, the filtrate obtained by washing the chlorine bypass dust with water is passed through the amphoteric ion exchange resin and separated into a solution with a high calcium chloride concentration and a solution with a low calcium chloride concentration. Calcium can also be recovered.

Table 3 shows, as test examples, raw water before passing the amphoteric ion exchange resin (filtrate obtained by washing the chlorine bypass dust with water), calcium chloride concentration after passing the raw water through the amphoteric ion exchange resin. Chemical analysis values of a low solution (KCl water) and a high calcium chloride concentration solution (CaCl ₂ water) are shown. Since each liquid is sampled and subjected to chemical analysis, the total amount of KCl water and CaCl ₂ water of each chemical component is not necessarily a chemical component of raw water. Table 4 shows chemical analysis values after drying the raw water, KCl water and CaCl ₂ water.

As shown in Table 4, because Ca concentration of CaCl ₂ water is 19.8% and this is converted to _{CaCl 2, CaCl 2 (%)} = 19.8 × Cl 2 Ca / Ca
= 19.8 × (40 + 35.5 × 2) / 40
= 54.9
Thus, calcium chloride-containing water having a CaCl ₂ concentration of about 55% is obtained.

1 Final disposal site leachate treatment system 2 Final disposal site 3 Conditioning tank 4 Amphoteric ion exchange resin 5 Reclaimed water tank 6 Calcium chloride containing water tank 7 SO ₄ containing water tank 8 Heavy metal removal device 9 COD treatment device 10 Toxic substance treatment device

Claims (8)

  A solution containing calcium chloride is separated into a solution having a high calcium chloride concentration and a solution having a low calcium chloride concentration using an amphoteric ion exchange resin, and the calcium chloride is recovered from the solution having a high calcium chloride concentration. To recover calcium chloride.   The method for recovering calcium chloride according to claim 1, wherein water is evaporated from the solution having a high calcium chloride concentration to recover calcium chloride.   The method for recovering calcium chloride according to claim 1 or 2, wherein the calcium chloride is recovered as a liquid having a calcium chloride concentration of 35% or more.   The method for recovering calcium chloride according to claim 1 or 2, wherein the calcium chloride is recovered as a liquid having a calcium chloride concentration of 25% or more.   The method for recovering calcium chloride according to claim 1 or 2, wherein the calcium chloride is recovered as a solid having a calcium chloride concentration of 40% or more.   The method for recovering calcium chloride according to claim 1, wherein the solution containing calcium chloride is a liquid that induces calcium scale.   The method for recovering calcium chloride according to any one of claims 1 to 6, wherein the solution containing calcium chloride is leachate from a final disposal site.   The method for recovering calcium chloride according to any one of claims 1 to 6, wherein the solution containing calcium chloride is a filtrate obtained by washing incineration ash and / or chlorine bypass dust with water.

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