TW201825409A - Treatment device and treatment method of silica-containing water - Google Patents

Abstract

This invention provides a silica-containing water treatment device and a silica-containing water treatment method capable of effectively treating silica-containing water. A silica-containing water treatment device 1 according to this invention comprises a magnesium dissolution vessel 10 wherein magnesium salt and acid are mixed, and are caused to react at PH of ≤ 7 for preparing magnesium-containing liquid, and a magnesium reaction vessel 12 wherein mixture liquid formed by mixing silica-containing water and magnesium-containing liquid is caused to react at PH of 10~12.

Description

Device and method for treating silicon oxide-containing water

The present invention relates to a silicon oxide-containing water treatment device and method for treating silicon oxide in silicon oxide-containing water.

When silicon oxide-containing water containing silicon oxide is to be recovered and reused, scale generation in piping, reverse-osmosis membrane (RO) devices at the rear stage, etc. becomes a problem, so it may be difficult to improve the oxidation-containing water. The recovery rate of silicon water is difficult to run stably. Therefore, it is necessary to reduce the amount of silicon oxide in water containing silicon oxide.

Some people have studied the method of using magnesium salt as a method to reduce the amount of silica in water containing silica.

For example, Patent Document 1 describes that by adding a magnesium salt to silicon oxide-containing water, the silicon oxide is adsorbed on the generated Mg (OH) ₂ , and then an iron salt is added to aggregate the silicon oxide, and solid-liquid separation is performed to reduce oxidation. In the method of the amount of silicon, the water containing silicon oxide is heated to more than 50 ° C to achieve a high silicon oxide removal rate. However, since the method of Patent Document 1 requires a heat source for heating, the processing cost becomes a problem.

Non-Patent Document 1 describes a method in which silicon oxide-containing water is added to magnesium slurry containing MgO and the like, and sulfuric acid is obtained, and the solid content is separated to reduce the amount of silicon oxide. The addition of sulfuric acid further improves the removal rate of silicon oxide. However, in the method of Non-Patent Document 1, there is about 20 mg / L of silicon oxide residue in the treated water. If the risk of silica scale is considered, when the reverse osmosis membrane device is installed in the later stage, the recovery rate of the reverse osmosis membrane device is improved difficult. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-168742 [Non-Patent Document]

[Non-Patent Document 1] Isabel Latour, Ruben Miranda, Angeles Blanco, "Silica removal with sparingly soluble magnesium compounds. Part I", Separation and Purification Technology, 138 (2014), pp.210-218

[Problems to be Solved by the Invention] The object of the present invention is to provide a silicon oxide-containing water treatment device and a method capable of efficiently treating silicon oxide-containing water.

The invention is a silicon oxide-containing water treatment device, comprising: a magnesium dissolving member, which is prepared by mixing a magnesium salt with an acid and reacting it at a pH of 7 or less; and a magnesium reaction member, which is mixed with The mixed solution of the silicon oxide-containing water and the magnesium-containing liquid is reacted in a range of pH 10 to 12.

Preferably, the silicon oxide-containing water treatment device is provided with a magnesium dissolution tank as the magnesium dissolution member, and the magnesium salt is mixed with the acid and reacted at a pH of 7 or less to prepare the magnesium-containing liquid. As a magnesium reaction tank of the magnesium reaction member, the silica-containing water is mixed with the magnesium-containing liquid and the obtained mixed liquid is reacted in a range of pH 10 to 12.

It is preferable that the treatment device for water containing silicon oxide is provided with a magnesium dissolving tank as the magnesium dissolving member, and the magnesium salt and the acid are mixed in the water containing silicon oxide and reacted at a pH of 7 or lower to prepare The mixed liquid in which the magnesium-containing liquid and the silicon oxide-containing water are mixed is provided with a magnesium reaction tank as the magnesium reaction member so that the mixed liquid is reacted in a range of pH 10 to 12.

The treatment device for silica-containing water is preferably provided with a removing member, which separates and removes insoluble matter obtained by the reaction using the magnesium reaction member at the rear stage of the magnesium reaction member.

The silicon oxide-containing water treatment device preferably includes the following members as the removing member: an agglomerating member, which aggregates the insoluble matter using a coagulant; and a solid-liquid separation member, which aggregates the latter after the agglomerating member. The condensate is separated into solid and liquid.

In the treatment device for silica-containing water, the coagulant is preferably at least one of an iron-based inorganic coagulant and a cationic polymer coagulant.

In addition, the present invention is a method for treating silica-containing water, including the following steps: a magnesium dissolving step, mixing a magnesium salt with an acid and reacting it at a pH below 7 to prepare a magnesium-containing liquid; and a magnesium reaction step, The reaction is performed by mixing a mixed liquid in which silicon oxide-containing water and the magnesium-containing liquid are mixed in a range of pH 10 to 12.

It is suitable to prepare the magnesium-containing liquid in the magnesium dissolving step of the method for treating silica-containing water, to mix the magnesium salt with the acid and to react it at a pH below 7 to prepare the magnesium-containing liquid. The silicon oxide water is mixed with the magnesium-containing liquid and the obtained mixed liquid is reacted in a range of pH 10 to 12.

Preferably, in the magnesium dissolving step of the method for treating silicon oxide-containing water, the magnesium salt and the acid are mixed in the silicon oxide-containing water and allowed to react below pH 7 to prepare a mixture containing the magnesium-containing liquid and In the magnesium reaction step, the mixed solution of the silica-containing water is reacted in a range of pH 10 to 12.

The method for treating the silicon oxide-containing water preferably includes a removing step of separating and removing insoluble matter obtained by the reaction of the magnesium reaction step in a later stage of the magnesium reaction step.

The method for treating silicon oxide-containing water preferably includes the following steps as the removing step: a coagulation step for coagulating the insoluble matter using a coagulant; and a solid-liquid separation step for coagulating the coagulation step after the coagulation step. The condensate is separated by solid-liquid.

In the method for treating silica-containing water, the coagulant is preferably at least one of an iron-based inorganic coagulant and a cationic polymer coagulant. [Effect of the invention]

According to the present invention, water containing silicon oxide can be efficiently treated.

Hereinafter, embodiments of the present invention will be described. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

The method for treating silica-containing water and the apparatus for treating silica-containing water according to the embodiments of the present invention are: preparing a magnesium-containing liquid by mixing a magnesium salt with an acid and reacting it at a pH of 7 or less (magnesium dissolution step) , The mixed liquid mixed with the silicon oxide-containing water and the obtained magnesium-containing liquid is reacted in a range of pH 10 to 12 (magnesium reaction step). After the magnesium reaction step, the insoluble matter obtained by the reaction in the magnesium reaction step is separated and removed as necessary (removal step).

An example of a processing apparatus equipped with a magnesium dissolution tank for preparing a liquid containing magnesium and a magnesium reaction tank for reacting a mixed liquid containing silica-containing water and the obtained magnesium-containing liquid is shown below. However, it is not limited to the following constitution. As an example of a processing device to which the method for treating silicon oxide-containing water according to this embodiment is applied, the following is an example of a device in which a magnesium dissolution tank is separated from a process for obtaining treated water from silicon oxide-containing water through a magnesium reaction tank. (FIG. 1) and the example of an apparatus 2 (FIG. 2) which obtains a treated water from the silicon oxide containing water via the magnesium dissolution tank and the magnesium reaction tank arrange | positioned in series, and the structure is demonstrated.

[Equipment Example 1] The silicon oxide-containing water treatment device 1 shown in FIG. 1 includes a magnesium dissolution tank 10 for preparing a magnesium-containing liquid by mixing a magnesium salt with an acid and reacting it at a pH of 7 or less; The magnesium reaction tank 12 is used for mixing the water containing silicon oxide with the liquid containing magnesium and reacting the obtained mixed liquid in a range of pH 10 to 12. The processing device 1 for silicon oxide-containing water is an example of an apparatus in which a magnesium dissolution tank 10 is separated from a process for obtaining treated water from silicon oxide-containing water through a magnesium reaction tank 12.

A silicon oxide-containing water pipe 18 is connected to the silicon oxide-containing water inlet of the magnesium reaction tank 12 and a processed water pipe 20 is connected to the treated water outlet. The outlet of the magnesium dissolution tank 10 and the magnesium-containing liquid inlet of the magnesium reaction tank 12 are connected by a magnesium-containing liquid pipe 26. Each of the magnesium dissolution tank 10 and the magnesium reaction tank 12 is provided with stirring devices 14 and 16 provided with stirring blades as stirring members. An acid addition pipe 22 and a magnesium salt addition pipe 24 are connected to the magnesium dissolution tank 10. A pH adjuster addition pipe 28 is connected to the magnesium reaction tank 12.

The method for processing silicon oxide-containing water and the operation of the silicon oxide-containing water treatment device 1 according to this embodiment will be described.

In the magnesium dissolving tank 10, an acid is added through the acid addition pipe 22, and an aqueous slurry such as a magnesium salt is added through the magnesium salt addition pipe 24. The magnesium salt and the acid are stirred and mixed by the stirring device 14, and the pH is adjusted to 7 or less. Reaction to prepare a magnesium-containing liquid (magnesium dissolution step). A solid magnesium salt may be directly added to the magnesium dissolution tank 10 and mixed with an acid.

On the other hand, the silicon oxide-containing water containing silicon oxide is supplied to the magnesium reaction tank 12 through the silicon oxide-containing water pipe 18. In the magnesium reaction tank 12, the magnesium-containing liquid containing the magnesium salt and the acid obtained through the magnesium dissolution step is added to the silicon oxide-containing water through the magnesium-containing liquid pipe 26, and is stirred and mixed by the stirring device 16. Further, in the magnesium reaction tank 12, a pH adjuster is added to the magnesium-containing liquid through the pH adjuster adding pipe 28, and the reaction is performed within a pH range of 10 to 12, thereby insolubilizing the silicon oxide (magnesium reaction step). The reaction liquid was treated as treated water and was discharged through the treated water pipe 20. Alternatively, after the magnesium reaction step, if necessary, the reaction solution may be separated and removed by a removal member (not shown) to remove insoluble matter obtained by the reaction in the magnesium reaction step (removal step).

In the silicon oxide-containing water treatment device 1, the magnesium dissolving tank 10, the stirring device 14, and the like function as a magnesium dissolving member that prepares a liquid containing magnesium by mixing a magnesium salt with an acid and reacting it at pH 7 or less. The reaction tank 12, the stirring device 16, and the like function as a magnesium reaction member that causes a mixed solution in which silica-containing water and a magnesium-containing liquid are mixed to react within a range of pH 10 to 12.

The inventors of the present case have found that a liquid containing magnesium is prepared by reacting an acid with a magnesium salt at a pH of 7 or less, and a mixed liquid containing the obtained magnesium-containing liquid and silica-containing water is reacted at a pH of 10 to 12. , Can effectively treat water containing silicon oxide. It was further found that by separating and removing the insoluble silicon oxide (removing step) at the rear stage of the magnesium reaction tank 12, the silicon oxide removal rate can be greatly improved.

As a result, the treated water from which silicon oxide has been removed to a high degree is obtained. Therefore, when the treated water is to be recovered and reused by using a reverse osmosis membrane device at the subsequent stage of the silicon oxide-containing water treatment device 1, the silicon oxide accumulation can be suppressed. The formation of scale and increase the recovery rate.

[Equipment Example 2] The silicon oxide-containing water treatment device 3 shown in FIG. 2 includes a magnesium dissolution tank 30 for preparing a magnesium salt and an acid in a silicon oxide-containing water and reacting them at a pH of 7 or less. A mixed liquid of a magnesium-containing liquid and a silicon oxide-containing water is mixed; and a magnesium reaction tank 32 for reacting the mixed liquid within a range of pH 10 to 12. The processing device 3 for silica-containing water is an example of an apparatus that obtains treated water from silica-containing water through a magnesium dissolution tank 30 and a magnesium reaction tank 32 arranged in series.

A silica-containing water pipe 38 is connected to the silica-containing water inlet of the magnesium dissolution tank 30. The outlet of the magnesium dissolution tank 30 and the inlet of the magnesium reaction tank 32 are connected by a liquid pipe 40 containing magnesium. A treated water pipe 42 is connected to the outlet of the magnesium reaction tank 32. Each of the magnesium dissolution tank 30 and the magnesium reaction tank 32 is provided with stirring devices 34 and 36 provided with stirring blades as stirring members. An acid addition pipe 44 and a magnesium salt addition pipe 46 are connected to the magnesium dissolution tank 30. A pH adjusting agent adding pipe 48 is connected to the magnesium reaction tank 32.

The method for treating the silicon oxide-containing water and the operation of the silicon oxide-containing water treatment device 3 according to this embodiment will be described.

The silicon oxide-containing water containing silicon oxide is supplied to the magnesium dissolution tank 30 through the silicon oxide-containing water pipe 38. For the silica-containing water in the magnesium dissolution tank 30, an acid is added through the acid addition pipe 44 and, for example, an aqueous slurry of magnesium salt is added through the magnesium salt addition pipe 46. The magnesium salt, the acid, and the silicon oxide-containing water are stirred and mixed by the stirring device 34, and reacted at a pH of 7 or lower to prepare a mixed solution in which the magnesium-containing liquid and the silicon oxide-containing water are mixed (the magnesium dissolution step). A solid magnesium salt may be directly added to the magnesium dissolution tank 30 and mixed with an acid.

The mixed liquid obtained by the magnesium dissolving step and containing the magnesium salt-containing acid and the magnesium-containing liquid and the silicon oxide-containing water is supplied to the magnesium reaction tank 32 through the magnesium-containing liquid pipe 40 and stirred by the stirring device 36 . Further, in the magnesium reaction tank 32, a pH adjuster is added to the mixed solution through the pH adjuster adding pipe 48, and the reaction is performed in a pH range of 10 to 12 to insolubilize the silicon oxide (magnesium reaction step). The reaction liquid was treated as treated water and was discharged through the treated water pipe 42. Alternatively, after the magnesium reaction step, if necessary, the reaction solution may be separated and removed by a removal member (not shown) to remove insoluble matter obtained by the reaction in the magnesium reaction step (removal step).

In the silicon oxide-containing water treatment device 3, the magnesium dissolving tank 30, the stirring device 34, and the like function as a magnesium dissolving member that prepares a liquid containing magnesium by mixing a magnesium salt with an acid and reacting it at a pH of 7 or less. The reaction tank 32, the stirring device 36, and the like function as a magnesium reaction member that causes a mixed liquid in which silica-containing water and a magnesium-containing liquid are mixed to react within a range of pH 10 to 12.

When the silicon oxide-containing water treatment device 1 shown in FIG. 1 is used, since the magnesium salt and the acid are directly mixed in the magnesium dissolution tank 10, the dissolution time of the magnesium salt can be shortened, and the volume of the magnesium dissolution tank can be reduced. In addition, the magnesium dissolving step can be performed as a batch process. In addition, even when the silica concentration in the silica-containing water to be treated is changed, the influence on the treatment can be reduced.

The silicon oxide-containing water treatment device 3 shown in FIG. 2 is a device effective when the silicon oxide-containing water is acidic. In addition, since the silicon oxide and the dissolved magnesium flow into the magnesium reaction tank 32 in a coexisting state in the silicon oxide-containing water, the reactivity of the silicon oxide and magnesium is high, and a higher silicon oxide removal rate can be obtained than the treatment device 1 .

The concentration of silicon oxide in the silicon oxide-containing water to be treated is, for example, in a range of 10 mg / L to 500 mg / L.

The silicon oxide-containing water to be treated is not particularly limited as long as it is water containing silicon oxide, and examples thereof include silicon oxide-containing water generated from a semiconductor manufacturing plant, and silicon oxide-containing water generated from a power plant.

The magnesium salt is not particularly limited as long as it is a magnesium salt such as magnesium oxide (MgO), magnesium hydroxide (Mg (OH) ₂ ), or magnesium chloride (MgCl ₂ ･ 6H ₂ O), or a hydrate thereof, but it is considered from the viewpoint of the cost of a drug, etc. Of these, magnesium hydroxide (Mg (OH) ₂ ) is preferred. Magnesium salts can also use magnesium-containing minerals such as dolomite represented by the chemical formula of CaMg (CO ₃ ) ₂ . In consideration of workability and the like, the magnesium salt is preferably used as a slurry of a solvent such as water.

The acid is not particularly limited, and an inorganic acid such as hydrochloric acid or sulfuric acid may be used. Organic acids such as oxalic acid and citric acid can also be added as the acid. However, due to the difference in raw water, some may reduce the removal rate of silicon oxide due to the chelation reaction with magnesium, so attention must be paid.

The amount of magnesium salt added is preferably in the range of 0.1 to 10 times the magnesium concentration, and more preferably in the range of 0.5 to 5 times the weight concentration of silicon oxide in the silicon oxide-containing water. If the added amount of the magnesium salt is less than 0.1 times the weight concentration of the silicon oxide in the water containing the silicon oxide, the insolubilization reaction of the silicon oxide may become insufficient. If it exceeds 10 times, the sludge may be generated. When the amount becomes excessive.

The pH of the magnesium dissolving step may be 7 or less, but it is preferably in the range of 4 to 7, and more preferably in the range of 4 to 6. If the pH of the magnesium dissolving step exceeds 7, the dissolution of the magnesium salt becomes insufficient, and if it does not reach 4, the silicon oxide removal rate hardly rises and the acid injection cost may be wasted. However, if the pH is lowered, the reaction time of the magnesium dissolution step can be shortened even more.

The temperature of the magnesium dissolving step is not particularly limited as long as magnesium can dissolve, and is, for example, in a range of 1 ° C to 50 ° C, and preferably in a range of 10 ° C to 50 ° C. If the temperature of the magnesium dissolution step is less than 1 ° C, the dissolution of the magnesium salt may become insufficient, and if it is 50 ° C or higher, the treatment cost may increase.

The reaction time of the magnesium dissolving step is not particularly limited as long as the magnesium can be dissolved, and is, for example, in the range of 1 minute to 60 minutes, and preferably in the range of 5 minutes to 30 minutes. If the reaction time of the magnesium dissolution step is less than 1 minute, the dissolution of the magnesium salt may become insufficient, and if it exceeds 60 minutes, the reaction tank may become excessively large. As described above, the reaction time can be shortened by lowering the pH of the magnesium dissolution step.

As the pH adjuster, an alkali such as sodium hydroxide or calcium hydroxide may be used, and an inorganic acid such as hydrochloric acid or sulfuric acid may be used as necessary.

The pH of the magnesium reaction step may be in the range of pH 10 to 12, but is preferably in the range of 10.5 to 11.5, and more preferably in the range of 11 to 11.5. If the pH of the magnesium reaction step does not reach 10 or exceeds 12, the silicon oxide removal rate becomes low.

The temperature of the magnesium reaction step is not particularly limited as long as it is a temperature at which the insolubilization reaction of silicon oxide proceeds. For example, the temperature ranges from 1 ° C to 50 ° C, and preferably ranges from 10 ° C to 50 ° C. If the temperature of the magnesium reaction step is less than 1 ° C, the insolubilization reaction of silicon oxide may become insufficient, and if it is 50 ° C or higher, the treatment cost may increase.

The reaction time of the magnesium reaction step is not particularly limited as long as the insolubilization reaction of silicon oxide can be performed, and is, for example, in the range of 1 minute to 60 minutes, and preferably in the range of 5 minutes to 30 minutes. If the reaction time of the magnesium reaction step is less than 1 minute, the insolubilization reaction of silicon oxide may become insufficient, and if it exceeds 60 minutes, the reaction tank may become excessively large.

For the separation and removal of silicon oxide, for example, agglomeration precipitation method, pressure floatation method, sand filtration method, and membrane filtration method (such as membrane filtration using precision filtration membrane (MF membrane), ultrafiltration membrane (UF membrane), etc.) The method for reducing the silicon oxide is sufficient, and considering the viewpoint of the amount of sludge generated, a coacervation method is preferred.

It is also possible to separate and remove the insoluble silicon oxide in the subsequent stages of the treatment devices 1 and 3 containing silicon oxide water, and then perform reverse osmosis membrane (RO membrane) treatment, decarbonation treatment, ion exchange treatment, and distillation treatment. Wait. The treated water obtained by separating and removing the insoluble silicon oxide in the subsequent stages of the silicon oxide-containing water treatment devices 1 and 3, since the silicon oxide has been removed at a high silicon oxide removal rate, the Waiting for treatment will still reduce the risk of scaling.

[Equipment Example 3] FIG. 3 shows a schematic configuration of an example of a silicon oxide-containing water treatment device when the insoluble silicon oxide is separated and removed by a coacervation method at a later stage of the magnesium reaction tank.

The silicon oxide-containing water treatment device 5 shown in FIG. 3 is an example of a configuration when the agglomeration and sedimentation treatment is performed at the rear stage of the magnesium reaction tank 32 of the silicon oxide-containing water treatment device 3 configured in FIG. 2. The silicon oxide-containing water treatment device 5 in FIG. 3 includes a magnesium dissolving tank 30 for mixing a magnesium salt and an acid in silicon oxide-containing water and reacting them at a pH of 7 or less to prepare a magnesium-containing liquid and A mixed solution of silicon oxide-containing water; a magnesium reaction tank 32 for reacting the mixed solution in a pH range of 10 to 12; and an aggregation tank 50, a floc formation tank 52, and a precipitation tank 54 as removal members.

A silicon piping-containing water pipe 38 is connected to the silicon oxidizing water inlet of the magnesium dissolution tank 30. The outlet of the magnesium dissolution tank 30 and the inlet of the magnesium reaction tank 32 are connected by a magnesium-containing liquid pipe 40. An outlet of the magnesium reaction tank 32 and an inlet of the aggregation tank 50 are connected by a reaction liquid pipe 60. The outlet of the coagulation tank 50 and the inlet of the floc formation tank 52 are connected by a coagulation liquid pipe 62. The outlet of the floc formation tank 52 and the inlet of the sedimentation tank 54 are connected by a floc formation liquid pipe 64. A treated water pipe 66 is connected to the treated water outlet of the sedimentation tank 54. A sludge pipe 68 is connected to the sludge outlet of the sedimentation tank 54. Each of the magnesium dissolution tank 30, the magnesium reaction tank 32, the aggregation tank 50, and the floc formation tank 52 is provided with stirring devices 34, 36, 56, and 58 having stirring blades as stirring members. An acid addition pipe 44 and a magnesium salt addition pipe 46 are connected to the magnesium dissolution tank 30. A pH adjusting agent adding pipe 48 is connected to the magnesium reaction tank 32. An inorganic flocculant addition pipe 70 is connected to the flocculation tank 50. A polymer flocculant addition pipe 72 is connected to the floc formation tank 52.

The silicon oxide-containing water containing silicon oxide is supplied to the magnesium dissolution tank 30 through the silicon oxide-containing water pipe 38. For the silica-containing water in the magnesium dissolution tank 30, an acid is added through the acid addition pipe 44 and, for example, an aqueous slurry of magnesium salt is added through the magnesium salt addition pipe 46. The magnesium salt, the acid, and the silicon oxide-containing water are stirred and mixed by the stirring device 34, and reacted at a pH of 7 or lower to prepare a mixed solution in which the magnesium-containing liquid and the silicon oxide-containing water are mixed (the magnesium dissolution step). A solid magnesium salt may be directly added to the magnesium dissolution tank 10 and mixed with an acid.

The mixed solution obtained by mixing the magnesium-containing liquid containing the magnesium salt and the acid and the silicon oxide-containing water obtained through the magnesium dissolution step is supplied to the magnesium reaction tank 32 through the magnesium-containing liquid pipe 40, and is supplied by the stirring device 36. Stir. Further, in the magnesium reaction tank 32, a pH adjuster is added to the mixed solution through the pH adjuster adding pipe 48, and the reaction is performed in a pH range of 10 to 12 to insolubilize the silicon oxide (magnesium reaction step). The reaction solution is supplied to the aggregation tank 50 through the reaction solution pipe 60.

In the coagulation tank 50, an inorganic coagulant is added to the reaction liquid through the inorganic coagulant addition pipe 70, and an insoluble matter is coagulated (coagulation step). The coagulation liquid is supplied to the floc formation tank 52 through the coagulation liquid pipe 62.

In the floc formation tank 52, a polymer flocculant is added to the flocculant through the polymer flocculant addition pipe 72 to form a floc (a floc formation step). The floc formation liquid is supplied to the sedimentation tank 54 through the floc formation liquid pipe 64.

In the precipitation tank 54, the aggregate obtained by the formation of the floes is subjected to solid-liquid separation (solid-liquid separation step). The treated water is discharged through the treated water pipe 66. On the other hand, the sludge is discharged through the sludge pipe 68.

A reverse osmosis membrane (RO membrane) treatment, a decarbonation treatment, an ion exchange treatment, a distillation treatment, or the like may be further performed at the rear stage of the water treatment device 5 containing silicon oxide. Since the treated water obtained by the silicon oxide-containing water treatment device 5 has removed the silicon oxide with a high silicon oxide removal rate, even if such treatment is performed in a later stage, the risk of scale generation will be reduced.

Examples of the inorganic coagulant used in the coagulation step include iron-based inorganic coagulants such as ferric chloride, and aluminum-based inorganic coagulants such as polyaluminum chloride (PAC). Considering the viewpoint of the cost of the drug and the coagulation pH range, the iron-based inorganic coagulant Better.

The addition amount of the inorganic coagulant is preferably in a range of 0.1 to 10 times the amount by weight ratio relative to the amount of the added magnesium salt, and more preferably in a range of 1 to 5 times. If the added amount of the inorganic coagulant is less than 0.1 times by weight based on the amount of the added magnesium salt, the aggregation may become insufficient. If it exceeds 10 times, the amount of sludge generated may become excessive. Situation.

The pH of the aggregation step is, for example, in a range of 3 to 11. If the pH of the agglomeration step is less than 3 or more than 11, agglomeration failure may occur. In addition, if the pH of the agglomeration step does not reach 9, silica may be dissolved from the floc in some cases. Therefore, it is preferable to perform the agglomeration step in a range of pH 9 to 11.

The temperature in the aggregation step is, for example, in a range of 1 ° C to 80 ° C. If the temperature in the agglomeration step does not reach 1 ° C or exceeds 80 ° C, agglomeration failure may occur.

Examples of the polymer flocculant used in the floc formation step include cationic polymer flocculants such as polyacrylamide, polyacrylates, anionic polymer flocculants, and nonionic polymer flocculants. Considering cohesiveness From the viewpoints, a cationic polymer flocculant is preferred.

Commercially available polymer flocculants include cationic polymer flocculants such as Orfloc OX-304 (manufactured by ORGANO).

The addition amount of the polymer coagulant is preferably in the range of 0.1 to 10 mg / L relative to the amount of water in the raw water, and more preferably in the range of 1 to 5 mg / L. If the amount of polymer coagulant added to the raw water is less than 0.1 mg / L, there may be cases where floc formation is not promoted. If it exceeds 10 mg / L, there may be cases where the dissolved polymer coagulant remains in the treated water. .

The pH of the floc formation step is, for example, in the range of 3 to 11. If the pH of the floc formation step does not reach 3 or exceeds 11, agglomeration failure may occur. In addition, if the pH of the flocculation step is less than 9, there may be a case where the silicon oxide is dissolved from the floc, so it is preferable to perform the floc formation step in the range of pH 9-11.

The temperature of the floc formation step is, for example, in a range of 1 ° C to 80 ° C. If the temperature of the floc formation step does not reach 1 ° C or exceeds 80 ° C, poor aggregation may occur.

The above-mentioned agglomeration treatment includes an agglomeration step and a floc formation step, and uses an inorganic agglomerating agent and a polymer agglomerating agent. However, as long as at least one of an inorganic agglomerating agent and a polymer agglomerating agent is used, an iron-based inorganic agent is preferably used. At least one of a coagulant and a cationic polymer coagulant. When agglomerating silica which has not been dissolved by reaction with a magnesium salt, the use of at least one of an iron-based inorganic flocculant and a cationic polymer flocculant can improve cohesiveness and solid-liquid separation.

Examples of solid-liquid separation include sedimentation separation, and pressurized floatation treatment, membrane filtration treatment, and the like. In consideration of separation and the like, sedimentation separation is preferred. [Example]

Examples and comparative examples are given below to describe the present invention more specifically and in detail, but the present invention is not limited to the following examples.

<Example 1 and Comparative Example 1> Using the processing device 5 shown in FIG. 3, for the water containing silicon oxide, the pH of the magnesium dissolution tank was adjusted to 4, 5, 6, 7 (the above is Example 1), 8, and 8, The order of 9, 10 (the above is Comparative Example 1) was changed, and a continuous water flow experiment was performed to confirm the removal effect of silicon oxide. The experimental conditions are shown in Table 1.

【Table 1】

The experimental results are shown in FIG. 4. In addition, a spectrophotometer (U-3900, manufactured by Hitachi High-Tech Science Co., Ltd.) was used to measure the silicon oxide concentration by a molybdenum yellow absorbance method.

As shown in FIG. 4, it has been confirmed that the concentration of silica in the agglomerated sedimentation treatment water can be greatly reduced by setting the pH of the magnesium dissolution tank to 7 or less.

<Comparative Example 2> Under the conditions described in Non-Patent Document 1 (magnesium salt: Mg (OH) ₂ + sulfuric acid, dissolving pH: 9.5, reaction pH: 11), the amount of added magnesium salt (250 mg / L, 500 mg / L, 750 mg / L, 1000 mg / L, 1500 mg / L), and the experimental results when this method is applied are shown in FIG. 5. The results of Example 1 (addition amount of magnesium salt: 230 mg / L, 460 mg / L, and 920 mg / L) were also set to a pH of 7 in a magnesium dissolving tank, as shown in FIG. 5.

As shown in FIG. 5, if the same amount of magnesium salt is added for comparison, the method of Example 1 has a higher silicon oxide removal rate than the method of Comparative Example 2 described in Non-Patent Document 1.

From the above results, since the treated water in which the silicon oxide has been removed to a high degree is obtained, even if a reverse osmosis membrane treatment is performed in the later stage and the treated water is recovered and reused, the risk of silica scale and the like can still be reduced.

As described above, the method according to the embodiment can efficiently treat silicon oxide-containing water.

1‧‧‧ Water treatment device containing silicon oxide

3‧‧‧ Water treatment device containing silicon oxide

5‧‧‧ Water treatment device containing silicon oxide

10‧‧‧Magnesium dissolution tank

12‧‧‧Magnesium reaction tank

14‧‧‧mixing device

16‧‧‧mixing device

18‧‧‧ Water pipe containing silica

20‧‧‧ Treatment water piping

22‧‧‧Acid addition piping

24‧‧‧Magnesium salt piping

26‧‧‧ Magnesium-containing liquid piping

28‧‧‧pH adjusting agent adding pipe

30‧‧‧Magnesium dissolution tank

32‧‧‧Magnesium reaction tank

34‧‧‧mixing device

36‧‧‧mixing device

38‧‧‧ Water pipe containing silica

40‧‧‧ Magnesium-containing liquid piping

42‧‧‧ Treatment water piping

44‧‧‧Acid addition piping

46‧‧‧Magnesium salt piping

48‧‧‧ pH adjusting agent adding pipe

50‧‧‧ Condensation tank

52‧‧‧ floc formation trough

54‧‧‧Sedimentation tank

56‧‧‧mixing device

58‧‧‧mixing device

60‧‧‧Reaction liquid piping

62‧‧‧ Condensate piping

64‧‧‧flocculation liquid piping

66‧‧‧ Treatment water piping

68‧‧‧Sludge pipe

70‧‧‧ inorganic coagulant addition piping

72‧‧‧ Polymer coagulant addition piping

FIG. 1 is a schematic configuration diagram showing an example of a silicon oxide-containing water treatment device according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing another example of a silicon oxide-containing water treatment device according to an embodiment of the present invention. 3 is a schematic configuration diagram showing another example of a silicon oxide-containing water treatment device according to an embodiment of the present invention. FIG. 4 is a graph showing the concentration of silicon oxide (mg / L) and the removal rate of silicon oxide (%) with respect to the pH of the magnesium dissolution tank in the examples of the agglomerated precipitation treatment water. FIG. 5 is a graph showing a silicon oxide removal rate (%) and an added amount (mg / L) of a magnesium salt in Examples and Comparative Examples.

Claims (12)

A silicon oxide-containing water treatment device includes: a magnesium dissolving member that mixes a magnesium salt with an acid and reacts it at a pH of 7 or less to prepare a magnesium-containing liquid; and a magnesium reaction member that mixes a silicon oxide-containing liquid The mixed solution of water and the magnesium-containing liquid is reacted in the range of pH 10 to 12. For example, the treatment device for silicon oxide-containing water according to item 1 of the patent application includes a magnesium dissolving tank as the magnesium dissolving member, and the magnesium salt is mixed with the acid and reacted at a pH of 7 or less to prepare the device. The magnesium-containing liquid is provided with a magnesium reaction tank as the magnesium reaction member to mix the silica-containing water with the magnesium-containing liquid and cause the obtained mixed liquid to react within a range of pH 10 to 12. For example, a silicon oxide-containing water treatment device according to item 1 of the scope of the patent application, which includes a magnesium dissolution tank as the magnesium dissolving member, and mixes the magnesium salt with the acid in the silicon oxide-containing water. The reaction is performed at pH 7 or lower to prepare the mixed solution in which the magnesium-containing liquid and the silicon oxide-containing water are mixed, and a magnesium reaction tank is provided as the magnesium reaction member so that the mixed solution reacts in a range of pH 10 to 12. . For example, the silicon oxide-containing water treatment device according to any one of the claims 1 to 3 includes: a removing member, which is provided after the magnesium reaction member by insoluble matter obtained by using the reaction of the magnesium reaction member. Separate and remove. For example, the silicon oxide-containing water treatment device according to item 4 of the patent application scope includes the following components as the removing member: an agglomerating member that aggregates the insoluble matter using a coagulant; and a solid-liquid separating member that is attached to the agglomerating member. The condensate formed in the subsequent stage is subjected to solid-liquid separation. For example, the treatment device for water containing silicon oxide according to item 5 of the patent application, wherein the coagulant is at least one of an iron-based inorganic coagulant and a cationic polymer coagulant. A method for treating silicon oxide-containing water includes the following steps: a magnesium dissolving step is a method of preparing a magnesium-containing liquid by mixing a magnesium salt with an acid and reacting the acid at a pH of less than 7; and a magnesium reaction step of mixing a liquid containing The mixed solution of the silicon oxide water and the magnesium-containing liquid is reacted in the range of pH 10 to 12. For example, in the method for treating silicon oxide-containing water according to item 7 of the patent application scope, in the magnesium dissolving step, the magnesium salt is mixed with the acid and reacted at a pH below 7 to prepare the magnesium-containing liquid, In the magnesium reaction step, the silicon oxide-containing water is mixed with the magnesium-containing liquid and the obtained mixed liquid is reacted in a range of pH 10 to 12. For example, in the method for treating silicon oxide-containing water according to item 7 of the application, in the magnesium dissolving step, the magnesium salt and the acid are mixed in the silicon oxide-containing water and reacted at a pH below 7 to prepare The mixed liquid in which the magnesium-containing liquid and the silicon oxide-containing water are mixed, and in the magnesium reaction step, the mixed liquid is reacted in a range of pH 10 to 12. For example, the method for treating silicon oxide-containing water according to any one of claims 7 to 9 includes: a removing step, in which the insoluble matter obtained by the reaction of the magnesium reaction step is separated in a stage after the magnesium reaction step; Remove. For example, the method for treating silicon oxide-containing water in the scope of patent application No. 10 includes the following steps as the removal step: a coagulation step, which uses the coagulant to agglomerate the insoluble matter; and a solid-liquid separation step, which is in the coagulation step The agglomerated aggregate is subjected to solid-liquid separation in a later stage. For example, the method for treating silica-containing water according to item 11 of the application, wherein the coagulant is at least one of an iron-based inorganic coagulant and a cationic polymer coagulant.