JP7042692B2 - Treatment liquid treatment method and exhaust gas treatment method - Google Patents

Description

The present invention relates to a method for treating a treatment liquid and a method for treating exhaust gas.

In a glass melting furnace, molten glass is produced by heating a powdery or granular glass raw material with a burner or the like that burns gas fuel. The molten glass becomes various glass articles such as a glass plate and a glass tube through a predetermined molding process.

At this time, the exhaust gas generated from the glass melting furnace contains a part of the components contained in the glass raw material in the state of gas or minute solid. Therefore, the exhaust gas contains many components that can be recycled as a raw material for glass. Therefore, if the recycled raw material can be recovered from the exhaust gas, it can contribute to the saving of the glass raw material. At the same time, it is possible to consider the environment.

As one of such methods, for example, Patent Document 1 discloses that a recycled raw material containing boron is recovered from the exhaust gas of a glass melting furnace for melting a glass raw material containing boron. Specifically, the exhaust gas is wet-collected, neutralized, solid-liquid separated, etc. to obtain a treatment liquid (extraction liquid) containing boron, calcium, and other impurities, and then the treatment liquid is distributed to an anion exchange resin. It is disclosed that impurities are removed from the treatment liquid to obtain a boron solution containing a recycled raw material.

Japanese Unexamined Patent Publication No. 2013-180284

The above-mentioned treatment liquid contains, for example, boron derived from a glass raw material, and calcium is added to neutralize the treatment liquid.

Further, the above-mentioned treatment liquid contains, for example, a halide such as chlorine (including a halide ion or a halide salt) as an impurity. The halide is derived from a clarifying agent or the like. Impurities are removed by circulating the treatment liquid through an anion exchange resin.

The treatment liquid further contains nitrite. Nitrite is derived from the nitrogen component of glass raw materials and / or gas fuels. If nitrite is contained in the treatment liquid, the anion exchange resin is likely to be deteriorated, and the resin life may be significantly shortened. This is thought to be due to the oxidizing action of nitrite.

An object of the present invention is to extend the life of an anion exchange resin for removing impurities from a treatment liquid.

The present invention, which was devised to solve the above problems, is a removal step of removing impurities from the treatment liquid to obtain a boron solution by circulating a treatment liquid containing boron, calcium and nitrite through an anion exchange resin. The method for treating a treatment solution comprising the above, further comprising a reduction step of adding a reducing agent containing sulfurous acid to the treatment solution before distributing the treatment solution to an anion exchange resin. According to such a configuration, the nitrite contained in the treatment liquid is reduced by the reducing agent. As a result, nitrite can be reduced from the treatment liquid before the treatment liquid is circulated through the anion exchange resin. Therefore, the life of the anion exchange resin can be extended. Here, the term "boron" also includes boron compounds such as boron oxide and boric acid and their ions. The term "calcium" also includes calcium compounds such as slaked lime and their ions. The term "nitrite" includes nitrite compounds such as nitrite ions and nitrites. The terms "impurity" and "sulfurous acid" also include the ions of each term. The term "removing impurities from the treatment liquid" includes not only the case of completely removing impurities but also the case of reducing the amount of impurities. The term "boron solution" means a solution containing boron as a main component.

In the above configuration, the sulfurous acid is preferably sulfamic acid. Sulfurous acid may be sodium sulfite, sodium thiosulfate, or the like, but may react with calcium dissolved in the treatment solution to precipitate calcium. On the other hand, sulfamic acid does not easily react with calcium dissolved in the treatment liquid, and can prevent the precipitation of calcium. Therefore, when sulfamic acid is used, removal equipment such as a filter for removing precipitated calcium becomes unnecessary, and the equipment cost can be reduced.

In the above configuration, the reducing agent is preferably added in the pipe through which the treatment liquid flows. In this way, the reducing agent is automatically agitated by the flow of the processing liquid flowing through the pipe. Therefore, since a stirring facility such as a stirring blade is not required, the facility cost can be reduced.

In the above configuration, the anion exchange resin is preferably a weakly basic anion exchange resin. By doing so, it is possible to prevent boron from being adsorbed on the anion exchange resin, so that the efficiency of boron recovery can be improved.

In the above configuration, in the removal step, it is preferable to distribute the treatment liquid to the cation exchange resin before the anion exchange resin. If the treatment liquid contains too much calcium, the ion exchange performance of the anion exchange resin may deteriorate. Therefore, by circulating the treatment liquid through the cation exchange resin before the anion exchange resin, the calcium in the treatment liquid is adsorbed on the cation exchange resin, and the calcium in the treatment liquid is removed (including reduction). Is preferable.

The present invention, which was devised to solve the above problems, is a method for treating exhaust gas from a glass melting furnace that melts a glass raw material containing boron, and is obtained by subjecting the exhaust gas to wet collection or dry collection. By a collection step of obtaining a collection containing boron and nitrite from, a neutralization step of adding a neutralizing agent containing calcium to the collection, and a solution separation of the collection after the neutralization step. It is characterized by comprising a solid-liquid separation step for obtaining a treatment liquid and a treatment step for treating the treatment liquid to obtain a boron solution by a method appropriately provided with the above configuration. With such a configuration, a boron solution capable of recovering a high concentration of boron from the exhaust gas can be efficiently obtained, and for the reasons already described, the life of the anion exchange resin can be extended.

According to the present invention as described above, it is possible to extend the life of the anion exchange resin that removes impurities from the treatment liquid.

It is a flow chart of the exhaust gas treatment method which concerns on embodiment.

Hereinafter, embodiments of the exhaust gas treatment method will be described with reference to the accompanying drawings. In addition, among the following embodiments of the exhaust gas treatment method, the embodiment of the treatment liquid treatment method will also be described. Of course, the treatment liquid treatment method is not limited to the case where it is incorporated into the exhaust gas treatment method, and can be carried out independently as a method for treating the treatment liquid.

As shown in FIG. 1, the method for treating exhaust gas according to the present embodiment includes a melting step, a collecting step, a neutralizing step, a solid-liquid separation step (extraction step), a recovery step, a removing step, and a reducing step. Of these, the treatment method for the treatment liquid according to the present embodiment is a portion corresponding to the removal step and the reduction step.

(Melting process)
In the melting step, the glass raw material a containing boron prepared to have a desired glass composition is heated by a burner in the glass melting furnace 1 to produce molten glass to be borosilicate glass. From the molten glass, glass articles such as a glass plate, a glass roll obtained by winding a glass ribbon into a roll, and a glass tube are manufactured.

As the gas fuel for the burner, for example, it is preferable to use LPG or LNG having a low sulfur content. Further, it is preferable to use a glass raw material a having a low sulfur content. Further, from the viewpoint of reducing nitrite in the treatment liquid described later, it is preferable to use oxygen combustion. Alternatively, instead of or in combination with the burner, the glass raw material a may be energized and heated by an electrode immersed in molten glass.

The exhaust gas b generated from the glass melting furnace 1 contains minute solids and vaporized substances derived from the glass raw material a and the gas fuel of the burner. Therefore, the exhaust gas b contains impurities such as nitrite and halide derived from the glass raw material a and / or the glass fuel in addition to boron (including a boron compound) which is a recycled raw material.

(Collecting process)
In the collection step, the exhaust gas b generated from the glass melting furnace 1 is introduced into the collection device 2, and the collection liquid c containing boron, nitrite and impurities is obtained from the exhaust gas b.

In the collection device 2, the exhaust gas b is cooled to, for example, 60 to 70 ° C., and boron contained in the exhaust gas b in a vaporized state is deposited.

In the present embodiment, the collection device 2 is a wet collection device including a spray tower 3 and a wet electrostatic precipitator 4. The wet electrostatic precipitator 4 may be omitted because it plays an auxiliary role of the spray tower 3. The type of the collecting device 2 is not particularly limited as long as it can wet-collect boron from the exhaust gas b.

Boron (micro solids and vaporized substances) contained in the exhaust gas b is cooled and precipitated by coming into contact with the washing water sprayed in the spray tower 3, and is collected as the collected liquid c. Boron remaining in the exhaust gas d that has passed through the spray tower 3 is also collected as the collected liquid c by coming into contact with the washing water of the wet electrostatic precipitator 4. These collected liquids c become the collected material. As boron is collected by the collection device 2, nitrite and impurities contained in the exhaust gas b are also collected as the collection liquid c. Here, since the cleaning water containing boron is used as the cleaning water of the spray tower 3 and the wet electrostatic precipitator 4, the boron concentration of the collected liquid c becomes saturated or close to it. Therefore, a part of boron contained in the collected liquid c becomes undissolved.

The exhaust gas e that has passed through the wet electrostatic precipitator 4 and has been cleaned is discharged from the chimney 5 into the atmosphere (outside the system).

(Neutralization process)
In the neutralization step, the collected liquid c collected by the spray tower 3 and the wet electrostatic precipitator 4 is introduced into the neutralization tank 6.

In the neutralization tank 6, an alkaline neutralizing agent f containing calcium such as slaked lime is added to the collecting liquid c to neutralize the collecting liquid c showing acidity. Specifically, the collected liquid c is neutralized so that the hydrogen ion concentration (pH) is preferably 7.5 to 12.0, more preferably 8.0 to 10.0. As a result, it is possible to prevent corrosion of pipes and the like due to acid in the subsequent process, and to reduce the solubility of boron in the collected liquid c to improve its recovery efficiency.

(Solid-liquid separation process)
In the solid-liquid separation step, the collected liquid g neutralized in the neutralization tank 6 is introduced into the solid-liquid separation device 7.

In the solid-liquid separation device 7, the collected liquid g is solid-liquid separated and separated into a filtrate h and a cake i. Therefore, the filtrate h is the treatment liquid in the treatment liquid treatment method according to the present embodiment.

Calcium, nitrite, and impurities contained in the collected liquid g are often dissolved in the collected liquid g, and most of them are recovered as the filtrate h. On the other hand, as described above, a part of boron in the collected liquid g is undissolved and contained. In addition, a part of calcium in the collected liquid g is also contained in an undissolved state. Therefore, of the boron and calcium contained in the collected liquid g, a part is recovered as the filtrate h and the rest is recovered as the cake i. Therefore, the filtrate h contains boron, calcium, nitrite, and impurities (halides). In addition, each of these substances may be contained in the state of a compound such as an ion or a salt.

Examples of the solid-liquid separation device 7 include a filter press, centrifugation, vacuum filtration, and the like, but the type thereof is not particularly limited.

(Recovery process)
In the recovery step, the cake i is introduced into the dryer 8 as a recovery means, and the recycled raw material j is recovered from the cake i.

In the dryer 8, the water contained in the cake i is dried and removed to obtain a dried powdery recycled raw material j. The obtained recycled raw material j is supplied to the glass melting furnace 1 together with the glass raw material a.

Here, since the cake i to be dried contains boron, it is possible to recover boron having few impurities by removing water by drying. Further, since calcium can be used as a raw material for glass as, for example, calcium oxide, there is no problem even if it is recovered together with boron. Of course, the cake i (or the recycled material j) may be subjected to calcium removal treatment so that calcium is not recovered.

Examples of the dryer 8 include a vacuum dryer, a rotary dryer, a band dryer, a spray dryer, and the like, but the type thereof is not particularly limited.

(Removal process)
In the removing step, the filtrate h, which is a treatment solution, is introduced into the ion exchange resin column 9, and impurities are removed from the filtrate h to obtain a boron solution k.

The ion exchange resin tower 9 includes a cation exchange resin 10 arranged on the upstream side (solid-liquid separation device 7 side) and an anion exchange resin 11 arranged on the downstream side. For example, the cation exchange resin 10 is a strongly acidic cation exchange resin, and the anion exchange resin 11 is a weakly basic anion exchange resin. When a weakly basic anion exchange resin is used, the adsorption of boron in the filtrate h can be suppressed.

In the cation exchange resin 10, calcium contained in the filtrate h is removed (including reduction), and in the anion exchange resin 11, impurities (for example, halides) contained in the filtrate h are removed (including reduction). Will be done. Thereby, calcium and impurities can be removed from the filtrate h to obtain a boron solution k. The obtained boron solution k is supplied as washing water to the above-mentioned collection device 2 (spray tower 3 and / or wet electrostatic precipitator 4). By doing so, the boron concentration of the washing water becomes saturated or close to it, so that it becomes difficult for boron to dissolve in the collected liquid c. As a result, boron tends to remain as an undissolved substance, and it becomes easy to recover it as cake i by solid-liquid separation.

The solid-liquid separation device 7 and the cation exchange resin 10 and the cation exchange resin 10 and the anion exchange resin 11 are connected by pipes, respectively.

The boron solution k may contain calcium. Further, the cation exchange resin 10 may be omitted. However, if the amount of calcium is too large, the ion exchange performance of the anion exchange resin 11 may deteriorate. Therefore, it is preferable to dispose the cation exchange resin 10 on the upstream side of the anion exchange resin 11.

(Reduction process)
Here, the filtrate h contains nitrite. Nitrite causes deterioration of the anion exchange resin 11 and shortens the resin life. Therefore, the method for treating exhaust gas according to the present embodiment includes a reduction step of adding a reducing agent m containing sulfurous acid to the filtrate h before the removal step. Sulfurous acid may be contained in the ionic state.

The reducing agent m reduces nitrite contained in the filtrate h. As a result, nitrite can be removed (including reduction) from the filtrate h before the filtrate h is circulated through the anion exchange resin 11. Therefore, the life of the anion exchange resin 11 can be extended. Specifically, for example, the life of the anion exchange resin 11 is extended from 1 year to 3 years.

Examples of the sulfurous acid contained in the reducing agent m include sodium sulfite, sodium thiosulfate, sulfamic acid (also referred to as amidosulfate), and the like, and sulfamic acid is used in this embodiment. Sulfamic acid does not easily react with calcium dissolved in the filtrate h, and can prevent calcium precipitation. Therefore, when sulfamic acid is used, removal equipment such as a filter for removing precipitated calcium becomes unnecessary, and the equipment cost can be reduced.

The reaction between nitrite (MNO ₂ ) and sulfamic acid (H ₃ NSO ₃ ) is represented by the following reaction formula. The nitrogen gas generated by the reaction is released into the atmosphere (outside the system) from the ion exchange resin tower 9. Further, hydrogen sulfate ion (MHSO ₄ ) is removed (including reduction) by the anion exchange resin 11.
MNO ₂ + H ₃ NSO ₃ → MHSO ₄ + N ₂ + H ₂ O
However, M is a monovalent cation.

The amount of sulfamic acid added is appropriately adjusted according to the concentration of nitrite. When the concentration of nitrite is about 1000 ppm, the amount of sulfamic acid added can be 100 ppm to 1000 ppm. In order to increase the reaction rate by excessively adding sulfamic acid, the amount of sulfamic acid added may be more than 1000 ppm, preferably 5000 ppm or more. Since the improvement in reaction rate due to excessive addition is saturated, the amount of sulfamic acid added is preferably 15,000 ppm or less.

In the present embodiment, the reducing agent m is added in the pipe from the solid-liquid separation device 7 to the cation exchange resin 10. As a result, the reducing agent m is automatically agitated by the flow of the filtrate h flowing in the pipe. As a result, since it is not necessary to separately install the stirring equipment, the equipment cost can be reduced.

Here, the reaction between nitrite and sulfamic acid tends to occur in an acidic environment. After removing calcium with the cation exchange resin 10, a halide (for example, chlorine) remains, so that the pH of the filtrate h drops and becomes acidic. Therefore, it is considered that the reaction between the nitrite and sulfamic acid mainly occurs on the downstream side of the cation exchange resin 10, that is, between the cation exchange resin 10 and the anion exchange resin 11. However, it is considered that the reaction between nitrite and sulfamic acid proceeds slowly even on the upstream side of the cation exchange resin 10.

The position and method of adding the reducing agent m are not particularly limited as long as they are on the upstream side of the anion exchange resin 11. For example, the reducing agent m may be added in the pipe from the cation exchange resin 10 to the anion exchange resin 11. Further, a tank for temporarily storing the filtrate h and the reducing agent m may be provided on the upstream side of the anion exchange resin 11, and a stirring facility such as a stirring blade may be provided in the tank.

The present invention is not limited to the above-described embodiment, and is not limited to the above-mentioned effects. The present invention can be modified in various ways without departing from the gist of the present invention.

In the above embodiment, the case where the boron solution obtained in the removal step is supplied to the collecting means has been described, but the boron solution may be mixed with the cake obtained by solid-liquid separation (for example, Patent Document). 1 of FIG. 1 and FIG. 2). In this case, in order to obtain a recycled raw material, the water content of the mixture of the boron solution and the cake may be dried and removed as it is with a spray dryer or the like, or the water content of the cake obtained by solid-liquid separation of the mixture may be dried under reduced pressure. It may be removed by drying with a machine or the like.

In the above embodiment, the case where the collected liquid is separated by the solid-liquid separation device only once has been described, but the solid-liquid separation may be performed a plurality of times. In this case, for example, the filtrate obtained in each solid-liquid separation is supplied to the ion exchange resin column, and the boron solution obtained in each ion exchange resin column is mixed with the cake obtained in each solid-liquid separation. (For example, the configuration of FIG. 2 of Patent Document 1).

In the above embodiment, the case where boron is wet-collected from the exhaust gas has been described as the collection means, but boron may be dry-collected from the exhaust gas. Examples of the dry collection means include those equipped with a cooling tower and a bag filter. In the case of dry collection, since the collected material becomes collected powder, it is preferable to mix it with a liquid component (for example, pure water or a boron solution obtained in the removal step) before solid-liquid separation (for example). For example, the configuration of FIG. 3 of Patent Document 1).

1 Glass melting furnace 2 Collection device 3 Spray tower 4 Wet electrostatic collector 5 Chimney 6 Neutralization tank 7 Solid-liquid separator 8 Dryer 9 Ion exchange resin tower 10 Ion exchange resin 11 Anion exchange resin a Glass raw material b Exhaust gas c Collection liquid (collection)
e Exhaust gas f Neutralizer g Collected liquid (collected material)
h Filtration i Cake j Recycled raw material k Boron solution m Reducing agent

Claims (6)

A treatment liquid treatment method comprising a removal step of removing impurities from the treatment liquid to obtain a boron solution by circulating a treatment liquid containing boron, calcium and nitrite through an anion exchange resin.
A method for treating a treatment liquid, which further comprises a reduction step of adding a reducing agent containing sulfurous acid to the treatment liquid before distributing the treatment liquid to the anion exchange resin. The method for treating a treatment liquid according to claim 1, wherein the sulfurous acid is sulfamic acid. The method for treating a treatment liquid according to claim 1 or 2, wherein the reducing agent is added in a pipe through which the treatment liquid flows. The method for treating a treatment liquid according to any one of claims 1 to 3, wherein the anion exchange resin is a weakly basic anion exchange resin. The method for treating a treatment liquid according to any one of claims 1 to 4, wherein in the removal step, the treatment liquid is circulated through the cation exchange resin before the anion exchange resin. A method for treating exhaust gas from a glass melting furnace that melts glass raw materials containing boron.
A collection step of obtaining a collection containing boron and nitrite from the exhaust gas by subjecting the exhaust gas to wet collection or dry collection.
A neutralization step of adding a neutralizing agent containing calcium to the collected material,
A solid-liquid separation step of obtaining a treatment liquid by solid-liquid separation of the collected material that has undergone the neutralization step,
A method for treating exhaust gas, which comprises a treatment step of treating the treatment liquid to obtain a boron solution by the method according to any one of claims 1 to 5.

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