JP2002045690A - Treatment material, treatment element, treatment equipment and treatment process for exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas treatment process which comprises adsorbing and removing ammonia in an exhaust gas with an adsorbing material, thereafter desorbing the adsorbed ammonia from the adsorbing material and repeatedly performing such adsorption/desorption of ammonia to remove ammonia from the ammonia-containing exhaust gas, and enables inhibition of reduction in performance with respect to adsorption of gases other than ammonia of the adsorbing material and remarkable enhancement of ammonia treatment performance of the adsorbing material. SOLUTION: This exhaust gas treatment process involves a stage for bringing an ammonia-containing exhaust gas into contact with a honeycomb-shaped adsorbing material obtained by impregnating an acidic substance to a honeycomb-shaped base material of the adsorbing material, to adsorb ammonia on the adsorbing material, and thereafter desorbing the adsorbed ammonia from the adsorbing material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing material, a processing element, a processing apparatus and a processing method which are preferably used when processing harmful substances and the like in exhaust gas by an adsorption / desorption method. For example, the present invention relates to a processing material, a processing element, a processing apparatus, and a processing method that are particularly preferably used when continuously processing an exhaust gas containing a basic substance such as ammonia by an adsorption / desorption method.

[0002]

2. Description of the Related Art As a method of treating exhaust gas containing harmful substances (for example, malodorous substances), Japanese Patent Application Laid-Open No. 54-91 discloses a method.
No. 66 discloses a method of adsorbing and desorbing exhaust gas using activated carbon as an adsorbent. Thus, conventionally,
2. Description of the Related Art When harmful substances are adsorbed and desorbed, a method of using activated carbon as a treatment material and adsorbing and desorbing exhaust gas has been used.

[0003] However, although activated carbon has excellent adsorption performance for various types of malodorous substances, it has such a low boiling point as ammonia, for example, that it has an extremely low adsorption performance for basic substances having a small molecular weight. When treating an exhaust gas containing a basic substance, sufficient treatment performance could not be obtained.

On the other hand, as a method for improving the adsorption performance of ammonia in exhaust gas, for example, Japanese Patent Laid-Open Publication No.
No. 589 discloses the use of a treatment agent obtained by impregnating an activated carbon adsorbent with an acid such as an inorganic acid such as sulfuric acid or phosphoric acid or an organic acid such as citric acid.

As a method for continuously absorbing and desorbing a basic gas such as ammonia in exhaust gas, Japanese Unexamined Patent Publication (Kokai) No. 52-136895 discloses a method for treating fine particles containing an ammonium salt of an inorganic hydrogen acid or an inorganic acid. Discloses a method of treating activated carbon in a fluidized bed type continuous gas adsorption apparatus.

[0006] However, as described above, when a strong acid such as phosphoric acid is added to the treatment material, the performance of adsorbing a basic substance such as ammonia is dramatically improved. Strongly ionically bonded, and in some cases, becomes an irreversible reaction, and the adsorbent that has adsorbed the basic substance cannot be sufficiently desorbed even when heated with high-temperature air at a temperature higher than the adsorption temperature to 200 ° C. It was thought that the treatment could not be performed by repeatedly performing adsorption and desorption of the toxic substance.

In addition, since a strong acid is used, the crystal structure and pore structure of the adsorbent change, the adsorbability of organic substances other than basic substances, for example, decreases, or the treatment material is combined with other constituent materials. Granular, sheet and honeycomb shapes (Fig. 1)
When processing into an adsorption element, the processing agent may fall off, the strength of the processed material may be reduced, the wear resistance may be reduced, and continuous use may not be possible. Had a problem.

Thus, the basic substance in the exhaust gas is
After adsorption and removal by the adsorbent, desorption is performed, and by repeatedly performing adsorption and desorption, in the treatment of exhaust gas containing a basic substance, a processing material, a processing element and a processing apparatus capable of obtaining sufficient processing performance can be obtained. It is not currently done. In particular, at present, a honeycomb-type treatment element and a honeycomb-type continuous gas adsorption device, which are currently the mainstream of concentrators, have not been obtained because of the compactness of the fluidized bed type continuous gas adsorption device.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a method of desorbing and removing a basic substance such as ammonia in exhaust gas by adsorbing and removing the same with an adsorbent. In an exhaust gas treatment for treating a basic substance-containing exhaust gas by repeatedly performing adsorption and desorption, it has excellent processing performance for a basic substance and also excellent adsorption for an organic compound other than the basic substance, for example. It is an object of the present invention to provide a processing material, a processing element, a processing apparatus, and a processing method that can exhibit performance.

In order to solve the above-mentioned problems, the present inventor has made intensive studies on the structure of the adsorbent substrate applied as a treatment material, the type of adsorbent to be adsorbed on the adsorbent substrate, the amount of the adsorbent, and the desorption method. did.

As a result, an acidic substance is selected as an impregnating agent to be adhered to the adsorbing substrate, and the acidic substance is impregnated on the adsorbing substrate, so that the excellent adsorbing property for the basic substance can be maintained while maintaining the original adsorption performance of the adsorbing substrate. Demonstrates performance and is above the adsorption temperature ~ 20
It has been found that desorption with hot air at 0 ° C. is possible and continuous use by adsorption and desorption with a honeycomb structure is possible.

Furthermore, it has been found that by using a strong acid having a higher acidity than that of a weak acid having a low acidity as an impregnating agent, for example, phosphoric acid as an impregnating agent, excellent adsorption performance for a basic substance can be exhibited.

Further, it has been found that when a weak acid is used, the adsorbed basic substance can be sufficiently desorbed with heated air at a temperature higher than the adsorption temperature to 200 ° C., and can be used continuously by adsorption and desorption. Further, even when a strong acid is used, a part of the adsorbed basic substance and the strong acid, for example, when phosphoric acid is used, about 40% of the adsorbed basic substance is strongly bonded, so that the adsorption temperature is higher than the adsorption temperature. Desorption by heated air at ~ 200 ° C is not possible, but about 60% is desorbable, and it has been found that continuous use by adsorption and desorption is possible even when a strong acid is used.

[0014] Regarding the type of the above-mentioned adsorbent substrate, the use of a porous adsorbent substrate, particularly activated carbon, makes it possible to maximize the adsorbing performance of the adsorbent for basic substances and to use hydrocarbons. Etc., which exhibit excellent adsorption performance to organic compounds such as
It has been found that desorption with heated air at 0 ° C. is also possible. Furthermore, it has been found that when a strong acid is used, the basic gas exhibits excellent adsorption performance, but the performance decrease for organic compounds such as hydrocarbons is larger than when a weak acid is used.

[0015] Further, when a strong acid is used, the reduction in strength when processing the material into a granular shape, a sheet shape or a honeycomb shape by combining the processing material with other constituent materials should be examined, and a honeycomb type continuous gas adsorption apparatus should be applied. Thus, it was found that abrasion resistance was not required because the material was not a fluidized bed, so that continuous processing was possible even if a certain degree of strength reduction occurred. further,
When phosphoric acid or the like, which is a strong acid, is used as a weak acid, the strength of the constituent material is reduced more strongly. I found an advantage.

Further, regarding the amount of impregnated acidic substance, it has been found that when the amount impregnated exceeds a certain amount, no improvement in adsorption performance for basic substances is observed, and the adsorption performance for organic compounds other than basic substances is reduced. Was.

The present inventors have conducted further studies based on the above findings, and as a result, have completed the present invention.

[0018]

That is, the present invention provides an exhaust gas treating material obtained by attaching an acidic substance to a porous adsorption substrate.

In a preferred embodiment of the exhaust gas treating material of the present invention, the acidic substance is an inorganic acid or an inorganic acid salt.
In a further preferred embodiment, the acidic substance is phosphoric acid,
It is a phosphate compound.

In a preferred embodiment of the exhaust gas treating material of the present invention, the porous adsorption substrate is activated carbon.

The present invention also provides an exhaust gas treatment element formed by forming an adsorbent obtained by impregnating an acidic substance onto a porous adsorption substrate into a honeycomb structure.

Further, the present invention provides a step of bringing an exhaust gas containing a basic substance into contact with an adsorbent obtained by attaching an acidic substance to a porous adsorbent substrate, and a step of adsorbing the basic substance on the adsorbent. And an exhaust gas treatment apparatus and method including a step of desorbing a basic substance adsorbed on the adsorbent.

Further, the present invention provides a process for bringing an exhaust gas containing a basic substance into contact with an adsorbent obtained by impregnating an acidic substance to a porous adsorbent substrate with a treatment element formed into a honeycomb structure, An object of the present invention is to provide an exhaust gas treatment apparatus and a treatment method including a step of adsorbing a basic substance on a material and a step of desorbing the basic substance adsorbed on the adsorbent.

A preferred embodiment of the present invention for desorbing the basic substance is a desorption method using heated air.

In a preferred embodiment of the method for treating exhaust gas according to the present invention, the basic gas is ammonia.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, it is necessary that an impregnating agent to be impregnated on a porous adsorption substrate is an acidic substance. Because it is an acidic substance, it exhibits extremely high adsorption performance to a basic substance such as ammonia. Further, by using a strong acid having a higher acidity than a weak acid having a lower acidity, the adsorption performance of a basic substance is improved.

Here, the acidic substance refers to a salt formed by reacting various acids and metal ions with various acids so that the pH of the aqueous solution becomes 7 or less, such as phosphoric acid, hydrochloric acid, and sulfuric acid. And phosphate compounds, carbonate compounds,
Examples thereof include a silicate compound and a sulfate compound, and any acidic substance that exhibits acidity when used as an aqueous solution as described above may be used.

Among the above-mentioned acidic substances, inorganic acids, especially phosphoric acid and phosphate compounds, are stable to heat treatment, have high heat resistance, have high safety by heating during desorption operation, and have an adsorbing group. It is preferable because it has a high adhesiveness to the material and can be easily attached to the adsorption substrate.

In the present invention, the adsorbent substrate to which the adsorbent is attached must be a porous adsorbent substrate. This is because, if it is porous, excellent adsorbing performance of a basic substance can be exhibited by holding an adsorbent for a basic substance such as ammonia on the porous surface.

The porous adsorbent substrate may be appropriately selected depending on the adsorption performance for the organic compound to be treated, and is not particularly limited. Usually, activated carbon, zeolite, or the like is preferably used.

Among them, activated carbon is more preferable because it has a high expression rate of adsorption performance for basic substances due to the impregnated acidic substance, and has a low desorption efficiency because of its low water adsorption performance due to its hydrophobicity. Specifically, coconut shell charcoal,
There is activated carbon such as cellulose, but it is not particularly limited.

In the present invention, the amount of the acidic substance to be attached to the porous adsorption substrate is preferably 1 to 50% by weight,
-40% by weight is more preferable, and 15-30% by weight is particularly preferable. When the amount is less than 1% by weight, the adsorption performance for base gas is weak and insufficient. When the amount exceeds 50% by weight, the pore surface of the porous adsorbent substrate is almost covered with the impregnating agent. This is because the adsorptive base material does not sufficiently exhibit the adsorptive performance to the organic compound originally possessed. In addition, when a strong acid is used, an increase in the amount of application causes a large decrease in the strength of the granular, sheet-like, or honeycomb-like processing element, and when it exceeds 50% by weight, continuous use becomes difficult.

For example, when phosphoric acid is impregnated on activated carbon, if it is about 15 to 30% by weight, good adsorption / desorption performance can be exhibited for both basic substances and organic compounds.

In the present invention, the method of attaching the acidic substance to the porous adsorbent substrate is not particularly limited as long as the acidic substance can be uniformly fixed on the porous surface of the adsorbent substrate. For example, an acidic substance such as phosphoric acid can be easily attached by drying after impregnating the adsorbent in an aqueous phosphoric acid solution because the acidic substance itself acts as a binder. Conversely, since phosphoric acid or the like acts as a binder, when it is impregnated with fine-grained charcoal, the fine-grained charcoal is combined with each other to form a lump, which significantly reduces fluidity.

As the exhaust gas treatment element of the present invention, an adsorption element filled with a granulation of the above-described treatment material, an adsorption element formed by molding the adsorbent into a honeycomb structure, and the like are preferably used. On the other hand, an adsorption element formed into a honeycomb-like structure is preferable because it is convenient for industrial use. FIG. 1 shows a schematic diagram of a treatment material and a honeycomb structure.

The exhaust gas treatment apparatus and method of the present invention include a step of bringing an exhaust gas containing a basic substance, preferably ammonia, into contact with an adsorbent obtained by impregnating an acidic substance with a porous adsorption substrate; It is necessary to include a step of adsorbing a basic substance on the adsorbent and a step of desorbing the basic substance adsorbed on the adsorbent. This is because the adsorbent is used for a long time to process the ammonia-containing exhaust gas.

The ammonia-containing exhaust gas to be treated by the method for treating ammonia-containing exhaust gas of the present invention may be a mixed gas containing a malodorous substance such as ammonia and another organic solvent, rather than a simple ammonia gas. The present invention can be applied.

Specifically, an adsorbent to which an acidic substance is attached divides an adsorption element formed into a honeycomb-like structure into an adsorption zone and a desorption zone, and vents exhaust gas into the adsorption zone to remove ammonia contained in the exhaust gas. Exhaust gas treatment apparatus and method for removing ammonia by continuously repeating the operation of adsorbing and removing ammonia and the operation of desorbing the adsorbed ammonia by continuously passing a small amount of heated air through the desorption zone (FIG. 2) However, any exhaust gas apparatus and processing method including a step of contacting an exhaust gas containing ammonia with an adsorbent to which an acidic substance is attached and desorbing the ammonia after adsorbing the ammonia on the adsorbent may be used, and in particular, It is not limited to these. Also, the desorbed ammonia is, for example,
It is oxidized and decomposed by a combustion device to produce clean air.

The method for measuring various characteristics of the method for treating ammonia-containing exhaust gas in the present invention is as follows.

Measurement of adsorption performance (adsorption rate q and Q) of ammonia and toluene (according to JIS-K-1474) Place the adsorption element in a U-shaped tube for adsorption test, temperature 25 ° C. ± 0.5
50 ° C in the solvent vapor adsorption performance tester (Fig. 3)
A mixture of 0 ppm ammonia mixed air and 3000 ppm toluene mixed air is allowed to flow for adsorption for 60 minutes, and the weight increase of the adsorption element is measured. The adsorption rates q and Q are determined by the following equations. q and Q (g / l) = P / S × 100 where P is the increase in the amount of the adsorption element (g) S is the volume of the adsorption element (l) The toluene blank of the activated carbon material adsorption element shown in Examples and Comparative Examples The adsorption rate is determined by an activated carbon material adsorption element Q = 25.0 (vol%) Measurement of treatment performance (removal rate) The treatment performance (η) is measured using an exhaust gas treatment device (FIG. 2). The removal rate is calculated by the following equation. η (%) = (IO) / I × 100 where I is the processing gas inlet concentration (ppm) O is the processing gas outlet concentration (ppm) The measurement of the I processing gas inlet concentration and the O processing gas outlet concentration is At every hour from the start of the operation of the apparatus, the adsorption and desorption operations are sufficiently repeated until the processing gas outlet concentration shows a constant concentration and does not change, that is, until the processing gas outlet concentration is stabilized. The ammonia processing performance shown in Table 1 is calculated from the measured values of the processing gas inlet concentration and the processing gas outlet concentration measured when the processing gas outlet concentration is stabilized. Measurement of fluidity and abrasion resistance Fluidity: The fluidity is evaluated using a fluidity evaluation device (FIG. 4). It was measured whether fine-grained activated carbon flows at a diameter of 5.6 mmφ. The fluidity was determined by comparing the fine granular activated carbon with the fine granular activated carbon impregnated with the impregnating material. Abrasion resistance: The fine-grained activated carbon to which the impregnating material was impregnated was put into an Erlenmeyer flask and stirred at a constant strength for a constant time. The subsequent crushing of the fine granular activated carbon was visually determined.

[0041]

EXAMPLES The method for treating ammonia-containing exhaust gas of the present invention will be described based on the following examples and comparative examples. (Example 1) 60% by weight of powdered activated carbon as an adsorbent
And an adsorbing element having a honeycomb-like structure having a wavelength of 3.1 mm and a wave height of 2.1 mm composed of 40% by weight of Kevlar, glass, PVA, and polyvinyl acetate emulsion as other constituent materials, and a phosphoric acid aqueous solution of 30% by weight. Impregnated at 100 ° C
For 1 hour to obtain a honeycomb-shaped adsorption element using activated carbon impregnated with 30% by weight of phosphoric acid. Good results were obtained without the adsorbent falling off. Next, the ammonia adsorption performance of this honeycomb-shaped adsorption element and the adsorption performance of toluene, which is a malodorous component other than ammonia, were measured. By using phosphoric acid, the ammonia adsorption performance was dramatically improved, and good results were obtained with little decrease in toluene adsorption performance (Table 1). Next, this honeycomb-shaped adsorbing element is adapted to an exhaust gas treatment apparatus (FIG. 2), the element is divided into an adsorption zone and a desorption zone, and an ammonia gas is adsorbed and removed by passing 100 ppm ammonia exhaust gas through the adsorption zone. On the other hand, 130 ° C. heated air was blown into the desorption zone at a rate of 1/20 of the air flow to the adsorption zone, and the operation of desorbing ammonia was continuously performed to measure the ammonia treatment performance. did. By using the activated carbon adsorbent impregnated with phosphoric acid, good results were obtained in which the ammonia treatment performance was dramatically improved.

(Example 2) 60% by weight of powdered activated carbon as an adsorbent and Kevlar, glass,
An adsorption element having a honeycomb structure having a wavelength of 3.1 mm and a wave height of 2.1 mm composed of PVA and polyvinyl acetate emulsion of 40% by weight is impregnated with a 30% by weight aqueous solution of sodium phosphate monobasic at 100 ° C. After drying for a time, a honeycomb-shaped adsorption element using activated carbon impregnated with monosodium phosphate at 30% by weight was obtained. The ammonia adsorption performance of this honeycomb-shaped adsorption element and the adsorption performance of toluene, which is a malodorous component other than ammonia, were measured. By using monobasic sodium phosphate, the adsorption performance of ammonia was dramatically improved, and good results were obtained with little decrease in toluene adsorption performance (Table 1). Next, this honeycomb-shaped adsorption element is adapted to an exhaust gas treatment apparatus (FIG. 2), and the element is divided into an adsorption zone and a desorption zone.
m and exhausting ammonia to adsorb and remove ammonia, and on the other hand, passing 130 ° C. heated air at 1/20 of the air flow to the desorption zone with respect to the air flow to the adsorption zone to remove ammonia. The desorption operation was continuously performed, and the treatment performance of ammonia was measured. By using the activated carbon adsorbent impregnated with phosphoric acid, good results were obtained in which the ammonia treatment performance was dramatically improved.

Comparative Example 1 60% by weight of powdered activated carbon was used as an adsorbent, and Kevlar, glass,
An adsorbing element having a honeycomb structure having a wavelength of 3.1 mm and a wave height of 2.1 mm, comprising PVA and polyvinyl acetate emulsion at 40% by weight, was prepared. The ammonia adsorption performance of the honeycomb-shaped adsorption element was measured. The ammonia adsorption performance was significantly lower than that of the example. Next, this honeycomb-shaped adsorption element is adapted to an exhaust gas treatment device (FIG. 2),
The device is divided into an adsorption zone and a desorption zone, and an operation of passing 100 ppm of ammonia exhaust gas through the adsorption zone to adsorb and remove ammonia is performed. 13 of 20 airflow
The operation of desorbing ammonia by continuously passing heated air at 0 ° C. was performed, and the treatment performance of ammonia was measured. As a result, the ammonia treatment performance was significantly lower than that of the example.
(Table 1)

(Comparative Example 2) A wavelength of 3.1 mm, a wave height of 2.1 composed of Kevlar, glass, PVA, and polyvinyl acetate emulsion as other constituent materials without using an adsorbent.
The adsorption element having a honeycomb-shaped structure having a thickness of 2 mm was impregnated with a 30% by weight aqueous phosphoric acid solution and dried at 100 ° C. for 1 hour to obtain a honeycomb-shaped adsorption element using granular activated carbon impregnated with 30% by weight of sodium hexametaphosphate. . The ammonia adsorption performance of this honeycomb element was measured. Since the phosphoric acid was contained, ammonia was adsorbed, but the results were significantly lower than those of Examples (Table 1). From this,
It is considered that the porosity, which is a characteristic of the adsorbent, affects the adsorption of ammonia by the adsorbent.

Comparative Example 3 Fine-grained activated carbon was impregnated with a 30% by weight aqueous solution of phosphoric acid and dried at 100 ° C. for 1 hour to obtain fine-grained activated carbon impregnated with 30% by weight of phosphoric acid. Its fluidity and wear resistance were measured. Activated carbon was powdered and fluidity was poor. Also, when a strong acid such as phosphoric acid is used, continuous treatment with a fluidized bed type is considered to be less advantageous than continuous treatment with a honeycomb system due to a decrease in fluidity and abrasion resistance.

[0046]

[Table 1]

[0047]

As described above, in the method for treating ammonia-containing exhaust gas according to the present invention, the ammonia-containing exhaust gas is brought into contact with an adsorbent to which an inorganic acid is attached, and the ammonia is adsorbed on the adsorbent. In particular, the use of phosphoric acid as the inorganic acid and the use of activated carbon as the adsorbent reduce the adsorption performance of the adsorbent other than ammonia, and the adsorption and desorption of ammonia The effect of the treatment is that the treatment performance of ammonia can be made extremely high.

[Brief description of the drawings]

FIG. 1 shows a honeycomb shape which is a shape of a heat resistant adsorption element of the present invention.

FIG. 2 shows an exhaust gas treatment method that uses a honeycomb-shaped adsorption element, divides the element into an adsorption zone and a desorption zone, and repeats adsorption and desorption operations to continuously remove an organic solvent.

FIG. 3 shows an apparatus for evaluating the adsorption performance of an adsorbent.

FIG. 4 shows an apparatus for evaluating the fluidity of an adsorbent.

[Explanation of symbols]

A1, A2 Serpentine tube for temperature control B1, B2, B3 Gas washing bottle with common grounding filter plate (250 ml) C Mixing bottle (sphere inner diameter 60 mm two-ball continuous type) D U-tube for adsorption test E Three-way cock F1 Solvent vapor generated air flow rate Meter F2 Dilution air flow meter N Constant temperature bath or constant temperature water bath H Excess gas outlet I Dry air inlet J Exhaust port K1, K2 Gas flow control cock L Solvent 2a Flute portion 2b Liner portion d Diameter

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Claims (8)

[Claims] An exhaust gas treatment element characterized in that an exhaust gas treatment material obtained by adhering an acidic substance to a porous adsorption substrate is formed into a honeycomb-like structure. 2. The exhaust gas treatment material and treatment element according to claim 1, wherein the acidic substance is an inorganic acid or an inorganic acid salt. 3. The exhaust gas treatment material and treatment element according to claim 1, wherein the acidic substance is a phosphate compound. 4. The exhaust gas treatment material and treatment element according to claim 1, wherein the acidic substance is phosphoric acid. 5. The exhaust gas treatment material and treatment element according to claim 1, wherein the porous adsorption substrate is activated carbon. 6. A step of contacting the treatment element according to claim 6 with an exhaust gas containing a basic substance, a step of adsorbing the basic substance on the adsorbent, and a step of adsorbing the basic substance adsorbed on the adsorbent. An exhaust gas treatment apparatus and method comprising a step of desorption. 7. The exhaust gas processing apparatus and method according to claim 6, wherein the step of desorbing the basic substance is a desorption method using heated air. 8. A method for treating exhaust gas according to claim 1, wherein the basic substance contained in the exhaust gas is ammonia.