JP2017039062A - Boron removal method and boron removal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boron removal method from boron-containing water excellent in boron removability, capable of reducing the using amount of a medicine, and also, capable of reducing sludge generation.SOLUTION: Provided is a boron removal method comprising: a concentration step where boron-containing water 1 is concentrated into concentrated water 2 with a boron concentration of 2,000 mg/L or higher and non-concentrated water 6 having a boron concentration of 10 mg/L or lower; a reaction step where the concentrated water is added with a calcium compound without adding an aluminum compound to form a reaction liquid 3 in which insoluble precipitates are dispersed; a sludge dehydration step where the reaction liquid is separated into a dehydrated filtrate 5 and dehydrated sludge 4; a mixing step where a part or the whole quantity of the dehydrated filtrate 5 is mixed with the non-concentrated water to obtain a mixed liquid 7; and a step where the remaining part 5' of the dehydrated filtrate not introduced into the mixing step in the hydrated filtrate is introduced into the concentration step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boron removal method and a boron removal apparatus from boron-containing water.

  Conventional methods for removing boron from boron-containing water include coagulation and precipitation using an aluminum compound and calcium compound, and adsorption using a boron adsorbent such as an ion exchange resin that selectively adsorbs boron. It has been. However, in the conventional coagulation sedimentation method, it is necessary to use a large amount of chemicals, and there is a problem that the amount of sludge generated increases as the chemical usage increases. In the adsorption method, there is a problem that a large amount of adsorbent is required because the adsorption capacity of commercially available adsorbent is small. Further, since boron is periodically desorbed from the adsorbent and regenerated, it is necessary to separately treat a regenerated waste liquid in which the discharged boron is concentrated to a high concentration.

  In order to solve these problems, a method is known in which boron-containing water is concentrated to increase the boron concentration, and then an aluminum compound is added to the concentrated water to roughly treat boron to about several hundred mg / L ( Patent Documents 1 and 2). Also known is a method of treating a treatment liquid with an adsorbent after adding a polyvalent metal ion (aluminum compound, magnesium compound, etc.) to concentrated water and aggregating and precipitating (Patent Document 3). By reducing the amount of chemicals used and sludge generation by roughing the concentrated water, it is still necessary to use a large amount of chemicals even with these methods. Will occur.

  On the other hand, a method using a calcium compound that is less expensive than an aluminum compound or a magnesium compound among metal compounds is known. For example, Patent Document 4 discloses a method of treating a radioactive waste liquid containing boron at a high concentration by adding a calcium compound and aging the mixture so that the pH of the liquid is 12 or more. Although this method can reduce the cost of medicine, there is a problem that the apparatus needs to be reacted for a long time for aging and the apparatus becomes large. Further, the boron concentration of the treated water is about 5,000 mg / L or more, and there is a problem that a high concentration of boron remains.

  Further, a method is known in which a first step of adding a calcium compound to boron-containing water and aggregating treatment and a second step of adding a calcium compound and an aluminum compound to supernatant water and aggregating the same are performed (Patent Document). 5). However, the boron-containing water studied in Patent Document 5 is a process wastewater for inkjet recording materials, and contains silica and polyvinyl alcohol. Silica and polyvinyl alcohol are known as substances that contribute to boron removal (Patent Documents 6 and 7), and boron removal in the first step is an effect of these substances. Therefore, it cannot be applied to boron-containing water that does not contain silica or polyvinyl alcohol.

JP 2011-218338 A JP 2001-198581 A Japanese Patent Laid-Open No. 10-314798 JP 59-12400 A JP 2003-236562 A JP 2001-079564 A JP 2002-186976 A

  As described above, in the prior art, it is not sufficient to reduce the amount of chemical used and the amount of sludge generated, and it is necessary to search for an effective method.

  An object of the present invention is to provide an efficient method for removing boron from boron-containing water and an apparatus for removing boron that are excellent in boron removability, can reduce the amount of chemicals used, and can reduce the amount of sludge generated.

A method for removing boron from boron-containing water according to an embodiment of the present invention is a method for separating boron-containing water into concentrated water having a boron concentration of 2,000 mg / L or more and non-concentrated water having a boron concentration of 10 mg / L or less. A reaction step of adding a calcium compound without adding an aluminum compound to the concentrated water to form a reaction solution in which insoluble precipitates are dispersed; and sludge for separating the reaction solution into dehydrated filtrate and dehydrated sludge A dehydration step, a mixing step in which a part or all of the dehydrated filtrate is mixed with the non-concentrated water to obtain a mixed solution, and a remaining portion of the dehydrated filtrate that has not been introduced into the mixing step in the dehydrated filtrate. And introducing into the concentration step.

  Moreover, the boron removing apparatus according to an aspect of the present invention includes a concentrating apparatus that separates boron-containing water into concentrated water having a boron concentration of 2,000 mg / L or more and non-concentrated water having a boron concentration of 10 mg / L or less, A reaction vessel for forming a reaction solution in which a calcium compound is added to the concentrated water to disperse insoluble precipitates; a sludge dehydrator for separating the reaction solution into dehydrated filtrate and dehydrated sludge; and one of the dehydrated filtrates. A mixing tank for mixing a part or the whole amount with the non-concentrated water to obtain a mixed liquid, and a mechanism for introducing the remaining portion of the dehydrated filtrate that has not been introduced into the mixing tank among the dehydrated filtrate into the concentrator. Prepare.

  According to the present invention, a high boron removal rate can be obtained with a small amount of added calcium compound, and as a result, the amount of generated sludge can be reduced. Further, by mixing the dehydrated filtrate after solid-liquid separation and non-concentrated water, waste water that satisfies a predetermined drainage standard can be easily obtained.

It is a flowchart explaining the outline of the boron removal method which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of the process description which showed 1st embodiment of the boron removal method from the boron containing water of this invention, and the boron removal apparatus from the boron containing water used for the implementation. It is a figure which shows schematic structure of the process description which showed 2nd embodiment of the boron removal method from the boron containing water of this invention, and the boron removal apparatus from the boron containing water used for the implementation. It is the figure showing the relationship between the chemical | medical agent addition amount and boron removal rate in Examples 1-6 and Comparative Examples 1-9. It is the figure showing the relationship between the reaction liquid SS density | concentration and the boron removal rate in Examples 1-6 and Comparative Examples 1-9. It is the figure showing the relationship between the concentrated water boron density | concentration and the boron removal rate in Comparative Examples 13 and 21 and Examples 7-12. It is a figure showing the relationship between reaction pH and the boron removal rate in Example 3 and Examples 13-17. It is the figure showing the relationship between the water temperature at the time of reaction in Examples 18-22, and a boron removal rate.

  As a result of intensive studies on a method for removing boron from boron-containing water using a plurality of metal compounds such as a calcium compound, an aluminum compound, a magnesium compound, and an iron compound, the present inventors have obtained the following new findings. That is, when the boron concentration is less than 2,000 mg / L, the boron removal reaction by the calcium compound hardly occurs and the boron removal rate is remarkably low as compared with other metal compounds such as an aluminum compound, but the boron concentration is 2 When concentrated to 2,000 mg / L or more, the boron removal rate by calcium compounds increases dramatically, and a high boron removal rate can be obtained with less chemical addition than other metal compounds, and the amount of generated sludge can be reduced. Furthermore, it has been found that these phenomena are specific phenomena that occur only in calcium compounds among many metal compounds. This is because insoluble calcium borate is generated by adding a calcium compound after concentrating the boron concentration to 2,000 mg / L or more. The present inventors further examined a method for efficiently producing calcium borate, and that there exist conditions (boron concentration, reaction pH, calcium addition amount, water temperature) that can produce calcium borate efficiently, and that The present inventors have found that the conditions are different from high water temperature (40 ° C. or higher) and high pH (12 or higher), which are conventionally suitable for the production of calcium borate.

  In addition, under the conditions that the calcium borate found by the present inventors is efficiently generated, the use of an aluminum compound that is conventionally used for removing boron, a specific phenomenon in which the generation efficiency of calcium borate is deteriorated. Was found to be expressed. Although the cause has not been clarified, it is assumed that the produced aluminum hydroxide hinders the formation of calcium borate.

  The present invention has been made based on the above findings. Hereinafter, implementation of the method for removing boron from boron-containing water according to the present invention will be described with reference to the drawings.

  FIG. 1 is a flowchart for explaining the outline of the boron removing method according to the present invention. As shown in FIG. 1, the boron removal method according to the present invention separates boron-containing water 1 into concentrated water 2 having a boron concentration of 2,000 mg / L or more and non-concentrated water 6 having a boron concentration of 10 mg / L or less. A concentration step A, a reaction step B in which a calcium compound is added to the concentrated water 2 without adding an aluminum compound to form a reaction solution 3 in which insoluble precipitates are dispersed, and the reaction solution 3 is dehydrated with a dehydrated filtrate 5. Sludge dewatering step C to be separated into sludge 4, mixing step D in which a part or all of the dehydrated filtrate 5 is mixed with non-concentrated water 6 to obtain a mixed solution 7, and introduction into the mixing step D of the dehydrated filtrate A step of introducing the remaining 5 ′ of the dehydrated filtrate that has not been introduced into the concentration step A again.

  In the following, embodiments of the boron removal method according to the present invention will be described based on differences in removal devices. This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

(1) First Embodiment FIG. 2 is a process explanation showing a first embodiment of a method for removing boron from boron-containing water according to the present invention, and an apparatus for removing boron from boron-containing water used in the embodiment. It is a figure which shows schematic structure. The boron removing apparatus 100 from boron-containing water in this embodiment is generally configured by a pH adjusting tank 10, an evaporation concentrating apparatus 20, a reaction tank 30, a sludge dehydrator 40, and a mixing tank 50.

  The pH-adjusting tank 10 is where the boron-containing water 1 (raw water) is introduced, and a pH adjuster 8 is introduced as necessary to adjust the pH of the boron-containing water 1. Further, among the dehydrated filtrate recovered from the sludge dehydrator described later, the remaining portion 5 'that is not introduced into the mixing tank 50 is also mixed with the raw water.

  The evaporative concentrator 20 is where the pH-adjusted boron-containing water 1 is introduced from the pH adjusting tank 10 to evaporate the water and concentrate it so that the boron concentration becomes 2,000 mg / L or more (concentration step A). ). As an apparatus (also referred to as a concentrating apparatus) used in the concentration step A, an adsorption concentrating apparatus or a membrane separation apparatus using a boron adsorbent as in a second embodiment to be described later can be applied in addition to an evaporation concentrating apparatus. The evaporative concentration apparatus 20 evaporates the water to obtain the concentrated water 2, the discharge port for discharging the concentrated water from the evaporation tank, and the non-concentrated water 6 containing almost no boron by condensing the evaporated water. It has a condenser and a discharge port for discharging the obtained non-concentrated water 6.

  The reaction tank 30 is a tank in which the concentrated water 2 is introduced from the evaporative concentration apparatus 20 and the calcium compound 9 is introduced to generate insoluble precipitates. At this time, in order to adjust to a pH at which insoluble precipitates are easily generated, a pH adjuster 8 is also added. Thereby, the reaction liquid 3 in which insoluble precipitates are dispersed in the reaction tank 30 is formed (reaction step B). In addition, a temperature control tank for adjusting the temperature of the concentrated water 2 from the evaporation concentrator 20 may be provided in the front stage of the reaction tank 30, and the concentration for adjusting the boron concentration in the concentrated water 2 to a constant concentration. An adjustment tank may be provided.

  The sludge dewatering machine 40 is where the reaction liquid 3 containing insoluble precipitates is introduced from the reaction tank 30, and this reaction liquid 3 is dehydrated and separated into dehydrated sludge 4 and dehydrated filtrate 5 (sludge dewatering step C). .

  As the sludge dehydrator 40, a pressure dehydrator such as a filter press or a belt press is suitable, but a centrifugal separator, a vacuum filter, or the like can also be applied.

  The mixing tank 50 is where the dehydrated filtrate 5 from the sludge dewatering machine 40 and the non-concentrated water 6 from the evaporative concentration apparatus 20 are mixed to obtain a mixed liquid 7 (mixing step D). In the mixing tank 50, the pH adjusting agent 8 is introduced as necessary to adjust the pH of the liquid in the mixing tank 50 to near neutrality, and the mixed liquid 7 is used as treated water suitable for drainage.

  Next, a method for removing boron from boron-containing water using the boron removing apparatus 100 according to the present embodiment will be described.

First, in the pH adjustment tank 10, wastewater from the enamel factory, wastewater from the flue gas desulfurization unit of the coal-fired power plant, smoke drainage from the incineration plant, wastewater from the nickel plating factory, wastewater from the glass manufacturing factory, Boron-containing water 1 such as seawater or salt lake brine is introduced, and a pH adjuster 8 is added to adjust pH.
As the pH adjuster 8, a base such as sodium hydroxide (NaOH), an acid such as hydrochloric acid (HCl), sulfuric acid (H ₂ SO ₄ ), or the like can be used.

  In the pH adjustment tank 10, it is preferable to adjust the pH of the boron-containing water to 7 to 10. By adjusting the pH of the boron-containing water to 7 to 10, corrosion of the subsequent evaporation and concentration apparatus 20 can be prevented.

  Next, the boron-containing water 1 whose pH has been adjusted is introduced from the pH adjusting tank 10 to the evaporation concentrating device 20, and is evaporated and concentrated so that the boron concentration becomes 2,000 mg / L or more.

  Next, concentrated water 2 containing 2,000 mg / L or more of boron is introduced from the evaporative concentration apparatus 20 to the reaction tank 30, a calcium compound 9 is added to the concentrated water 2, and a pH adjuster 8 is added as necessary. Then, a reaction solution 3 in which insoluble precipitates are dispersed is formed. In the reaction tank 30, boron contained in the concentrated water 2 is adsorbed on the surface of the generated insoluble precipitate, or boron contained in the concentrated water 2 is taken into the inside of the insoluble precipitate.

As the calcium compound 9, slaked lime (calcium hydroxide: Ca (OH) ₂ ), calcium chloride (CaCl ₂ ), calcium carbonate (CaCO ₃ ), quick lime (calcium oxide: CaO) and the like can be used.

The addition amount of the calcium compound 9 is preferably about Ca / B = 0.5 to 5.0 by mass ratio with respect to boron present in the concentrated water 2. When the concentrated water 2 contains a component that reacts with a calcium compound (such as carbonate ion: CO ₃ ²⁻ , sulfate ion: SO ₄ ²⁻ ), it is preferable to increase the amount of calcium compound 9 added.

  In the reaction tank 30, it is preferable to adjust the pH of the liquid in the reaction tank 30 to 7 to 12, and more preferably to 8 to 10.

  Next, the reaction liquid 3 is introduced from the reaction tank 30 to the sludge dewatering machine 40, the reaction liquid 3 is dehydrated, and separated into the dehydrated sludge 4 and the dehydrated filtrate 5.

  Next, the dehydrated filtrate 5 is introduced into the mixing tank 50 from the sludge dehydrator 40, and the non-concentrated water 6 is introduced into the mixing tank 50 from the evaporation concentrator 20, and the dehydrated filtrate 5 and the non-concentrated water 6 are introduced as necessary. A pH adjuster 8 is added to the mixed solution, and the pH of the mixed solution is adjusted to near neutrality to obtain a mixed solution 7.

The amount of water of the dehydrated filtrate 5 introduced into the mixing tank 50 is adjusted in accordance with the required boron concentration of the mixed solution 7 that can be drained as treated water. The amount of water in the dehydrated filtrate 5 is preferably within the range of the following formula.
A * (B-10) / (2,000-B) to A * B / (500-B)
(However, A is the amount of non-concentrated water, and B is the boron concentration of the liquid mixture 7 (arbitrarily set according to the desired water quality))
The remaining portion 5 ′ of the dehydrated filtrate 5 that has not been introduced into the mixing tank 50 is introduced into the pH adjustment tank 10.

(2) Second Embodiment FIG. 3 is a process explanation showing a second embodiment of the method for removing boron from boron-containing water according to the present invention, and an apparatus for removing boron from boron-containing water used in the embodiment. It is a figure which shows schematic structure. 3, the same components as those of the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The apparatus 200 for removing boron from boron-containing water in this embodiment is generally composed of a pH adjustment tank 10, an adsorption tower 60, a reaction tank 30, a sludge dehydrator 40, and a mixing tank 50.

  In the present embodiment, an adsorption tower 60 using a boron adsorbent is used as the concentrating device in the concentration step A. Boron-containing water 1 whose pH has been adjusted is introduced into the adsorption tower 60 from the pH adjusting tank 10, and boron contained in the boron-containing water 1 is adsorbed to the adsorbent filled therein (adsorption process). E).

  As an adsorbent to be packed in the adsorption tower 60, an anion exchange resin, a granule carrying a rare earth element hydrated oxide, an ion exchange resin into which an N-methylglucamine group is introduced, or an N-methylglucamine group are used. One kind or two or more kinds of known adsorbents selected from the group of introduced fibrous adsorbents can be used.

  In addition, when the boron-containing water 1 contains fine particles (insoluble matter) that cause clogging in the adsorption tower 60, a filtration device that removes the fine particles may be installed in the front stage of the adsorption tower 60.

  If the adsorption tower 60 continues to pass the boron-containing water 1, the adsorption amount of boron in the adsorbent is saturated. Therefore, the elution agent 61 is periodically passed through the adsorption tower 60 to remove boron from the adsorbent. Elution is performed to remove concentrated water 2 containing high-concentration boron (regeneration step F). In addition, the process combining the adsorption process E and the regeneration process F described above corresponds to the concentration process A. The boron-containing water 1 that has passed through the adsorption tower 60 becomes non-concentrated water 6 having a boron concentration of 10 mg / L or less. That is, the flow of the eluting drug 61 may be performed by monitoring the boron concentration in the outlet water from the adsorption tower and before or when the boron concentration exceeds 10 mg / L.

  The eluting agent 61 may be appropriately selected according to the adsorbent filled in the adsorption tower 60, and examples thereof include acids such as hydrochloric acid and sulfuric acid, and alkalis such as sodium hydroxide.

In this embodiment, only the boron can be selectively concentrated among the components contained in the boron-containing water. Therefore, it is also applied to boron-containing water that is difficult to evaporate and concentrate, such as boron-containing water having a high salt concentration and boron-containing water containing a component that easily generates scale such as gypsum (calcium sulfate: CaSO ₄ ). be able to.

  In the reaction tank 30, the concentrated water 2 is introduced from the adsorption tower 60, the calcium compound 9 and the pH adjuster 8 are introduced as necessary, and the pH of the liquid in the reaction tank 30 is adjusted to disperse insoluble precipitates. The reaction solution 3 is to be formed (reaction step B).

  The sludge dewatering machine 40 is where the reaction liquid 3 containing insoluble precipitates is introduced from the reaction tank 30, and this reaction liquid 3 is dehydrated and separated into dehydrated sludge 4 and dehydrated filtrate 5 (sludge dewatering step C). .

  In the mixing tank 50, the dehydrated filtrate 5 is introduced from the sludge dehydrator 40, the non-concentrated water 6 from which the boron is adsorbed and removed is introduced from the adsorption tower 60, and the pH adjuster 8 is introduced as necessary. The pH of the liquid in the mixing tank 50 is adjusted to near neutral to obtain a mixed liquid 7 (mixing step D).

  Next, a method for removing boron from boron-containing water using the boron removing apparatus 200 of the present embodiment will be described.

  First, the boron-containing water 1 is introduced into the pH adjusting tank 10, and the pH adjusting agent 8 is added to the boron-containing water 1 to adjust the pH. In the pH adjusting tank 10, the pH of the boron-containing water 1 is adjusted to a pH suitable for boron adsorption in the adsorption tower 60 at the subsequent stage.

  Next, boron-containing water 1 with adjusted pH is introduced from the pH adjusting tank 10 to the adsorption tower 60, and boron contained in the boron-containing water 1 is adsorbed to the adsorbent filled in the adsorption tower 60. The non-concentrated water 6 from which is removed is obtained.

  Before the adsorption amount of boron in the adsorbent in the adsorption tower 60 is saturated and the ability of the adsorbent to adsorb boron decreases, the elution agent 61 is periodically passed through the adsorption tower 60 to adsorb. The adsorbent is regenerated by eluting boron from the material and taking out the concentrated water 2. The concentrated water 2 taken out here contains boron at a high concentration of about 2,000 mg / L or more.

  The interval at which the eluting agent 61 is passed into the adsorption tower 60 is determined based on the saturated adsorption amount of boron (the total amount of boron that can be adsorbed) of the adsorbent filled in the adsorption tower 60 and the pH adjustment tank 10 to the adsorption tower 60. It adjusts suitably according to the quantity of the boron contained in the introduce | transduced boron containing waste water 1. FIG.

  Then, the concentrated water 2 containing about 2,000 mg / L or more of boron is introduced from the adsorption tower 60 to the reaction tank 30, and the calcium compound 9 is added to the concentrated water 2, and the pH adjusting agent 8 is added as necessary. To form a reaction solution 3 in which insoluble precipitates are dispersed.

  Thereafter, similarly to the first embodiment, the mixed liquid 7 is drained as treated water through the sludge dewatering process C in the sludge dewatering machine 40 and the mixing process D in the mixing tank 50. The remaining portion 5 ′ of the dehydrated filtrate 5 is introduced into the pH adjustment tank 10 and is again subjected to a series of steps together with new boron-containing water 1.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

(Examples 1-6)
In the experiment, boron-containing water in which boric acid was dissolved in pure water and the boron concentration was adjusted to 500 mg / L was evaporated 10 times, and concentrated water with a boron concentration of 5,000 mg / L was used. After standing to cool until the water temperature of the concentrated water reaches room temperature (20-30 ° C.), a predetermined amount of calcium compound was added, the pH was adjusted to 9.0 using sodium hydroxide or hydrochloric acid, and the mixture was reacted for 60 minutes. . A part of this reaction solution was collected and the suspended solid (SS) concentration was measured. A part of the reaction solution was sampled and filtered through a 5 A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. Moreover, about Example 3, the said reaction liquid was dehydrated with the filter press type dehydrator, and the moisture content of the obtained dewatered sludge was measured. Further, the boron content and boron removal rate in the dewatered sludge were calculated from the concentrated water boron concentration, the filtrate boron concentration, the reaction solution SS concentration, and the water content of the dehydrated sludge.

Dehydration by a filter press type dehydrator was performed at a filtration pressure of 0.4 MPa, a filtration time of 15 minutes, a pressing pressure of 0.7 MPa, and a pressing time of 30 minutes.
Table 1 shows the type and amount of calcium compound added, reaction solution SS concentration, filtrate boron concentration, dehydrated sludge moisture content, boron content in dehydrated sludge, and boron removal rate.

(Comparative Examples 1-9)
In the concentrated water having a boron concentration of 5,000 mg / L used in Examples 1 to 6, any of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), magnesium chloride (MgCl ₂ ), or ferric chloride (FeCl ₃ ) After adding a predetermined amount of one kind of metal compound, the pH was adjusted with sodium hydroxide and reacted for 60 minutes. A part of this reaction solution was sampled and the SS concentration was measured. A part of the reaction solution was sampled and filtered through a 5 A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. For Comparative Examples 2, 5, and 8, the reaction solution was dehydrated with a filter press dehydrator, and the moisture content of the obtained dewatered sludge was measured. Further, the boron content and boron removal rate of the dewatered sludge were calculated from the concentrated water boron concentration, the filtrate boron concentration, the reaction solution SS concentration, and the water content of the dehydrated sludge.
Dehydration by a filter press type dehydrator was performed at a filtration pressure of 0.4 MPa, a filtration time of 60 minutes, a pressing pressure of 0.7 MPa, and a pressing time of 30 minutes.
Table 2 shows the types and addition amounts of the metal compounds, the reaction solution SS concentration, the filtrate boron concentration, the dehydrated sludge moisture content, and the boron removal rate.

(Comparative Examples 10-12)
After adding aluminum sulfate and slaked lime to the concentrated water having a boron concentration of 5,000 mg / L used in Examples 1 to 6, the pH is adjusted to 9.0 using sodium hydroxide or hydrochloric acid and reacted for 60 minutes. It was. A part of this reaction solution was collected and the suspended solid (SS) concentration was measured. A part of the reaction solution was sampled and filtered through a 5 A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. Further, the moisture content of the dewatered sludge obtained by dehydrating the reaction solution with a filter press dehydrator was measured. Further, the boron content and boron removal rate of the dewatered sludge were calculated from the concentrated water boron concentration, the filtrate boron concentration, the reaction solution SS concentration, and the water content of the dehydrated sludge.
Dehydration by a filter press type dehydrator was performed at a filtration pressure of 0.4 MPa, a filtration time of 60 minutes, a pressing pressure of 0.7 MPa, and a pressing time of 30 minutes.
Table 3 shows the type and amount of calcium compound added, reaction solution SS concentration, filtrate boron concentration, dehydrated sludge moisture content, boron content in dehydrated sludge, and boron removal rate.

FIG. 4 shows the relationship between the added amount of each agent shown in Tables 1 and 2 and the boron removal rate.
The relationship between the reaction solution SS concentration in Tables 1 and 2 and the boron removal rate is shown in FIG.
From FIG. 4, it was confirmed that the calcium compound (Example) had a high boron removal rate despite the smaller amount of drug added than the other drugs (Comparative Example).
From FIG. 5, it was confirmed that the SS concentration when the boron removal rate is equivalent is lower in the calcium compound (Example) than in the other drugs (Comparative Example).

Moreover, the dehydrated sludge moisture content of Example 3 was lower than the dehydrated sludge moisture content of Comparative Example 2, Comparative Example 5, and Comparative Example 8, and it was confirmed that the sludge produced | generated in an Example has good dehydration property.
From the above, it was confirmed that the amount of sludge generation can be reduced in the example as compared with the comparative example.

  From Example 3 and Comparative Example 10 in Table 3, it can be seen that the boron removal rate hardly changes even when aluminum sulfate is added. On the other hand, in Comparative Example 10, the SS concentration increased due to the formation of aluminum hydroxide. In addition, since aluminum hydroxide has poor dewaterability, the water content is also increasing. From the above, it can be seen that the addition of aluminum sulfate hardly contributes to boron removal, but increases the amount of sludge generated. Further, from Comparative Examples 11 and 12, since the boron removal rate tends to decrease when the amount of aluminum sulfate added is increased, the boron removal principle of the example is a treatment using a conventional aluminum compound and calcium compound in combination. It turns out that it is different from the method.

(Comparative Examples 13 to 20)
After adding a predetermined amount of any one metal compound of slaked lime, aluminum sulfate, magnesium chloride or ferric chloride to boron-containing water having a boron concentration of 500 mg / L used in Examples 1 to 6, sodium hydroxide Alternatively, the pH was adjusted with hydrochloric acid and reacted for 60 minutes. The reaction solution was filtered through a 5 A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. Further, the boron removal rate was calculated from the boron-containing water boron concentration and the filtrate boron concentration.
Table 4 shows the types and addition amounts of the metal compounds, the filtrate boron concentration, and the boron removal rate.

  From the results in Table 4, it is more efficient to use aluminum sulfate, magnesium chloride, or ferric chloride for boron-containing water having a boron concentration of 500 mg / L, and further, the boron removal rate is increased by increasing the addition amount. Has improved. On the other hand, in the case of slaked lime, it was found that the removal effect was small compared with other chemicals, and the improvement of the boron removal rate was small even when the addition amount was increased.

(Example 7)
In the experiment, simulated concentrated water in which boric acid was dissolved in pure water and the boron concentration was adjusted to 2,000 mg / L was used. After adding slaked lime to the simulated concentrated water so that the mass ratio was Ca / B = 2, the pH was adjusted to 9.0 using sodium hydroxide or hydrochloric acid and reacted for 60 minutes. The reaction solution was filtered through a 5 A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. Further, the boron removal rate was calculated from the concentrated water boron concentration and the filtrate boron concentration.
Concentrated water boron concentration, slaked lime addition amount, filtrate boron concentration and boron removal rate are shown in Table 5.

(Example 8)
The same operation as in Example 7 was performed except that the boron concentration of the simulated concentrated water used in the experiment was 3,000 mg / L.
Concentrated water boron concentration, slaked lime addition amount, filtrate boron concentration and boron removal rate are shown in Table 5.

Example 9
The same operation as in Example 7 was performed except that the boron concentration of the simulated concentrated water used in the experiment was 5,000 mg / L.
Concentrated water boron concentration, slaked lime addition amount, filtrate boron concentration and boron removal rate are shown in Table 5.

(Example 10)
The same operation as in Example 7 was performed except that the boron concentration of the simulated concentrated water used in the experiment was 8,000 mg / L.
Concentrated water boron concentration, slaked lime addition amount, filtrate boron concentration and boron removal rate are shown in Table 5.

(Example 11)
The same operation as in Example 7 was performed except that the boron concentration of the simulated concentrated water used in the experiment was 10,000 mg / L.
Concentrated water boron concentration, slaked lime addition amount, filtrate boron concentration and boron removal rate are shown in Table 5.

(Example 12)
The same operation as in Example 7 was performed except that the boron concentration of the simulated concentrated water used in the experiment was 20,000 mg / L.
Concentrated water boron concentration, slaked lime addition amount, filtrate boron concentration and boron removal rate are shown in Table 5.

(Comparative Example 21)
The same operation as in Example 7 was performed except that the boron concentration of the simulated concentrated water used in the experiment was 1,000 mg / L.
Concentrated water boron concentration, slaked lime addition amount, filtrate boron concentration and boron removal rate are shown in Table 5.

FIG. 6 shows the relationship between the concentrated water boron concentration in Table 5 and the boron removal rate.
FIG. 6 shows that the boron removal rate dramatically increases when the boron concentration of the concentrated water is 2,000 mg / L or more.

(Examples 13 to 17)
After adding 8,000 mg / L of slaked lime as calcium to the concentrated water having a boron concentration of 5,000 mg / L used in Examples 1 to 6, it was adjusted to a predetermined pH using sodium hydroxide or hydrochloric acid, and then for 60 minutes. Reacted. This reaction solution was filtered through a 5A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. Further, the boron removal rate was calculated from the concentrated water boron concentration and the filtrate boron concentration.
The relationship between the reaction pH and the boron removal rate is shown in Table 6 and FIG.
From FIG. 7, it was confirmed that the boron removing method according to the present invention is particularly efficient in the range of pH 8-10.

(Examples 18 to 22)
After adjusting the concentrated water having a boron concentration of 5,000 mg / L used in Examples 1 to 6 to a predetermined water temperature, adding 8,000 mg / L of slaked lime as calcium while maintaining the water temperature, sodium hydroxide or hydrochloric acid was added. The pH was adjusted to 9.0 and reacted for 60 minutes. This reaction solution was filtered through a 5A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. Further, the boron removal rate was calculated from the concentrated water boron concentration and the filtrate boron concentration.
The relationship between the water temperature during the reaction and the boron removal rate is shown in Table 7 and FIG.
From FIG. 8, it was found that the boron removal method according to the present invention is more effective as the water temperature during the reaction is lower, and a high boron removal rate of 80% or more can be obtained under the condition of 40 ° C. or lower.

(Example 23)
The flue gas desulfurization effluent of a coal-fired power plant containing 800 mg / L of boron was evaporated and concentrated 10 times to obtain 8,000 mg / L of concentrated water. After allowing the concentrated water to cool to room temperature (20-30 ° C.), 15,000 mg / L of slaked lime as calcium was added, and then the pH was adjusted to 9.0 using hydrochloric acid and reacted for 60 minutes. . The reaction solution was filtered through a 5 A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. Further, the boron removal rate was calculated from the concentrated water boron concentration and the filtrate boron concentration.
The results are shown in Table 8.

(Example 24)
Salt lake brine containing 200 mg / L of boron is filtered through 5 types A filter specified in JIS P 3801, and hydrochloric acid is added to adjust the pH to 7.0. Was passed through an adsorption tower filled with an adsorbent at 120 mL / h.
As the adsorbent, a chelate fiber “GRY-HW” (trade name) manufactured by Kirest Co., Ltd., having a density of 0.35 g / mL and a space of 40 mL in volume was used.
The water flow rate to the adsorption tower was set to 25 times (25 Bed Volume), and when the boron concentration at the outlet of the adsorption tower exceeded 10 mg / L, the water flow of the salt lake was stopped, and 1N HCl was used as the eluting agent. Then, boron adsorbed on the adsorbent was eluted, and concentrated water containing boron at a high concentration was taken out from the adsorption tower.
The boron concentration of the obtained concentrated water was 3,400 mg / L.
After adding 7,000 mg / L of slaked lime as calcium to this concentrated water, the pH was adjusted to 9.0 using sodium hydroxide and reacted for 60 minutes. The reaction solution was filtered through a 5 A filter specified in JIS P 3801, and the boron concentration of the obtained clear filtrate was measured. Further, the boron removal rate was calculated from the concentrated water boron concentration and the filtrate boron concentration.
The results are shown in Table 8.

  From Table 8, it was confirmed that the boron removal method according to the present invention is effective for flue gas desulfurization effluent and salt lake brine in a coal-fired power plant.

  Boron removal method from boron-containing water according to the present invention includes wastewater from enamel manufacturing plants, wastewater from flue gas desulfurization equipment at coal-fired power plants, smoke washing wastewater from waste incineration plants, wastewater from nickel plating plants, Applicable for removing boron from water containing boron, such as wastewater from glass manufacturing plants, seawater, salt water

DESCRIPTION OF SYMBOLS 1 Boron-containing water 2 Concentrated water 3 Reaction liquid 4 Dehydrated sludge 5 Dehydrated filtrate 6 Non-concentrated water 7 Mixture 8 pH adjuster 9 Calcium compound 100 The boron removal apparatus 200 from the boron-containing water in 1st embodiment 2nd Boron removal device 10 from boron-containing water in the embodiment 10 pH adjustment tank 20 Evaporation concentration apparatus 30 Reaction tank 40 Sludge dehydrator 50 Mixing tank 60 Adsorption tower 61 Eluent

Claims (14)

  A concentration step of separating the boron-containing water into concentrated water having a boron concentration of 2,000 mg / L or more and non-concentrated water having a boron concentration of 10 mg / L or less; and a calcium compound without adding an aluminum compound to the concentrated water A reaction step of forming a reaction solution in which insoluble precipitates are dispersed by addition, a sludge dehydration step of separating the reaction solution into a dehydrated filtrate and a dehydrated sludge, and a part or all of the dehydrated filtrate is non-concentrated. A boron removal method comprising: a mixing step of mixing with water to obtain a mixed solution; and a step of introducing the remaining portion of the dehydrated filtrate that has not been introduced into the mixing step into the concentration step.   The boron removal method according to claim 1, wherein the concentrated water is obtained by evaporating and concentrating boron-containing water.   In the concentrated water, boron-containing water is anion exchange resin, a granule carrying a rare earth element hydrous oxide, an ion-exchange resin having an N-methylglucamine group introduced therein, or an N-methylglucamine group is introduced. Contact with one or more adsorbents selected from the group of fibrous adsorbents, adsorb and remove boron from the boron-containing water, and elute boron with acid or alkali from the adsorbent adsorbed boron The boron removal method according to claim 1, wherein   The boron concentration method according to any one of claims 1 to 3, wherein an aluminum concentration of the concentrated water is 1,000 mg / L or less.   The boron removal method as described in any one of Claims 1-4 including the process of adjusting pH to 8-10 after adding a calcium compound at the said reaction process.   The boron temperature removal method according to any one of claims 1 to 5, wherein a water temperature of the reaction solution in the reaction step is 40 ° C or lower.   The amount of the calcium compound added in the reaction step is in a range of Ca / B = 0.5 to 5.0 by mass ratio with respect to boron present in the concentrated water. The method for removing boron according to one item. The boron removal method according to any one of claims 1 to 7, wherein an amount of water of the dehydrated filtrate introduced into the mixing step is within a range represented by the following formula.
A * (B-10) / (2,000-B) to A * B / (500-B)
(However, A is the amount of non-concentrated water, B is the boron concentration of the mixed solution (arbitrary setting depending on the desired water quality)   The boron removal method according to any one of claims 1 to 8, wherein the boron content of the dewatered sludge is 4% or more.   A concentration device that separates the boron-containing water into concentrated water having a boron concentration of 2,000 mg / L or more and non-concentrated water having a boron concentration of 10 mg / L or less, and a calcium compound is added to the concentrated water to form insoluble precipitates. A reaction tank for forming a dispersed reaction liquid, a sludge dewatering machine that separates the reaction liquid into dehydrated filtrate and dewatered sludge, and a mixed liquid obtained by mixing a part or all of the dehydrated filtrate with the non-concentrated water And a mechanism for introducing a remaining portion of the dehydrated filtrate that has not been introduced into the mixing vessel into the concentrator.   The boron removing apparatus according to claim 10, wherein the concentrating device is an evaporation concentrating device.   The concentrator is an anion exchange resin, a granule carrying a rare earth element-containing hydrous oxide, an ion exchange resin having an N-methylglucamine group introduced therein, or a fibrous adsorbent having an N-methylglucamine group introduced thereinto. The boron according to claim 10, which is an adsorption tower packed with one or more adsorbents selected from the group of the above, wherein the concentrated liquid is obtained by eluting boron adsorbed on the adsorbent with an eluting agent. Removal device.   A mechanism for introducing a remaining portion of the dehydrated filtrate that has not been introduced into the mixing tank into the concentrating apparatus is provided in the pH adjusting tank. The boron removing apparatus according to any one of claims 10 to 12, wherein the remainder of the dehydrated filtrate is introduced.   The boron removal apparatus according to any one of claims 10 to 13, wherein at least one of the reaction tank and the mixing tank has a mechanism for introducing a pH adjusting agent.

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