JP2002066255A - Treatment material, treatment element, treatment apparatus, and treatment method of waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste gas treatment method with an extremely high ammonia treatment capability by suppressing the absorption capability of an adsorbent for gases other than ammonia, in a waste gas treatment method for removing an ammonia-containing waste gas by repeating adsorption and desorption steps of removing ammonia in the waste gas by adsorption with the adsorbent and desorbing ammonia after the adsorption. SOLUTION: The ammonia-containing waste gas treatment method comprises the steps of bringing an ammonia-containing waste gas into contact with an adsorbent bearing an acidic substance to adsorb ammonia in the adsorbent and then desorbing ammonia from the adsorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment material, a treatment element and a treatment method preferably used for treating harmful substances and the like in exhaust gas by an adsorption / desorption method. TECHNICAL FIELD 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 the above by an adsorption / desorption method. Furthermore, the present invention relates to a treatment material having heat resistance and optimally used for exhaust gas treatment in terms of heat safety.

[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 a low boiling point, such as ammonia, and remarkably low adsorption performance for basic substances having a low molecular weight. In the case of treating exhaust gas containing a volatile 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 treating 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.

Further, as a method of continuously absorbing and desorbing a basic gas such as ammonia in exhaust gas and treating the same, for example, Japanese Patent Application Laid-Open No. Sho 52-136895 discloses a method in which an ammonium salt of inorganic hydrogen acid or a fine particle to which inorganic acid is added is disclosed. Discloses a method of treating activated carbon in a fluidized bed type continuous gas adsorption apparatus.

However, as described above, when a strong acid is added to the treatment material, the performance of adsorbing a basic substance such as ammonia is dramatically improved, but the basic substance is strongly ion-bonded to the strong acid. , In some cases an irreversible reaction,
The adsorbent that has adsorbed the basic substance is placed at a temperature higher than the adsorption temperature to 200
It has been considered that even if heated with high-temperature air at a temperature of, for example, desorption cannot be sufficiently performed, and treatment cannot be carried out by repeatedly adsorbing and desorbing a basic substance.

In addition, since a strong acid is used, the crystal structure and the pore structure of the adsorbent change, the adsorbing performance of, for example, an organic substance other than the basic substance is reduced, or the treatment material is combined with other constituent materials. When processing into a granular, sheet-like, or honeycomb-shaped adsorption element (Fig. 1), other constituent materials are also damaged, so that the processing material falls off, the processing strength decreases, and the wear resistance decreases. However, there has been a problem that continuous use is not possible.

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, 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 impregnated on the adsorbing base material, and by adhering to the adsorbing base material, an excellent adsorbent for a basic substance can be obtained while maintaining the original adsorbing performance of the adsorbing base material. Demonstrates performance and is above the adsorption temperature ~ 20
It has been found that desorption with heated air at 0 ° C. is possible and continuous use by adsorption and desorption 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.

In addition, 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. Furthermore, even when using strong acids,
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 desorption by heated air at a temperature higher than the adsorption temperature to 200 ° C is required. Although it was not possible, it was found that about 60% could be desorbed, and even when a strong acid was used, continuous use by adsorption and desorption was possible.

With respect to the type of the above-mentioned adsorbent base material, the use of powdered activated carbon makes it possible to maximize the adsorbing performance of the adsorbent for basic substances and to reduce organic compounds such as hydrocarbons. It has also been found that it exhibits excellent adsorption performance and that desorption with heated air at a temperature higher than the adsorption temperature to 200 ° C. is possible. Furthermore, it has been found that when a strong acid is used, excellent adsorption performance is exhibited for a basic gas, but the decrease in adsorption performance for organic compounds such as hydrocarbons is greater than when a weak acid is used.

Further, when a strong acid is used, the reduction in strength when processing the material into a granular, sheet, or honeycomb shape by combining the processing material with another constituent material is examined, and a honeycomb type continuous gas adsorption device is applied. Thus, since it is not a fluidized bed, there is no need for abrasion resistance, and it has been found that continuous processing is possible even if a certain degree of strength reduction occurs. further,
It has been found that when phosphoric acid or the like, which is a strong acid, is used in comparison with a weak acid, the strength of the constituent material is more strongly reduced, but the strength can be suppressed by the amount of the acidic substance and the ratio and the amount of the constituent material.

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 impregnating an acidic substance with powdered activated carbon.

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 substances are phosphoric acid and phosphate compounds.

The present invention also provides an exhaust gas treatment element formed by forming an adsorbent obtained by impregnating an acidic substance into powdered activated carbon into a honeycomb structure.

Further, the present invention relates to a step of bringing an exhaust gas containing a basic substance into contact with an adsorbent obtained by impregnating an acidic substance with powdered activated carbon, a step of adsorbing the basic substance to the adsorbent, and a step of adsorbing the basic substance. An object of the present invention is to provide an exhaust gas treatment apparatus and a treatment method including a step of desorbing a basic substance adsorbed on an adsorbent.

Further, the present invention provides a step of bringing an exhaust gas containing a basic substance into contact with an adsorbent obtained by impregnating an acidic substance into powdered activated carbon 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 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.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, it is necessary that an impregnating agent to be impregnated on powdered activated carbon 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 in heat treatment, have high heat resistance, and are safe by heating during desorption, as used as flame retardants. It is preferable because it has a high property and has high adhesiveness to the adsorption substrate, so that it can be easily attached to the adsorption substrate.

In the present invention, the adsorbent substrate to which the adsorbent is attached must be powdered activated carbon. This is because powdery activated carbon can exhibit excellent basic substance adsorption performance by retaining an adsorbent for a basic substance such as ammonia on the porous surface of the powdered activated carbon.

The powdered activated carbon may be appropriately selected depending on the adsorption performance for the organic compound to be treated, and is not particularly limited.

The powdered activated carbon preferably has a particle size of 100 μm or less. If it is 100 μm or more, it is difficult to form a honeycomb shape due to a large amount of falling off.

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

In the present invention, the amount of the acidic substance to be impregnated on the powdered activated carbon is preferably 1 to 50% by weight, and more preferably 3 to 50% by weight.
It is more preferably 40% by weight, particularly preferably 15 to 30% by weight. 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 surface of the pores of the powdered activated carbon is almost covered with the impregnating agent. The reason for this is that the adsorption performance for organic compounds originally possessed is not sufficiently exhibited.

When phosphoric acid is impregnated on powdered 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.

Further, since the phosphoric acid compound has a flame retardant effect of making the material difficult to burn, it is also stable in the heat treatment, and the safety by heating during the desorption operation can be enhanced.

In the present invention, the method of attaching the acidic substance to the powdered activated carbon is not particularly limited as long as the acidic substance can be uniformly fixed on the porous surface of the powdered activated carbon. Acidic substances such as phosphoric acid can be easily attached by impregnating the adsorbent in an aqueous phosphoric acid solution and then drying, since the acidic substance itself acts as a binder.

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.

The exhaust gas treatment apparatus and method according to the present invention include a step of contacting an exhaust gas containing a basic substance, preferably ammonia, with an adsorbent obtained by impregnating an acidic substance with powdered activated carbon. It is necessary to include a step of adsorbing a basic substance on a material 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 ammonia and other malodorous substances such as other organic solvents 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 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 method may be used as long as it is an exhaust gas treatment 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. It is not limited. The desorbed ammonia 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 was determined by the activated carbon material adsorption element Q = 25.0 (vol%) Measurement of treatment performance (removal rate) The treatment performance (η) was measured using an exhaust gas treatment device (FIG. 2). The removal rate is calculated by the following equation. η (%) = (I−O) / 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 wear 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. 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 placed in 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. Measurement of flame retardancy The adsorption element was placed in a sample tube and placed in a thermostat, and the temperature of the thermostat was adjusted to 5 while supplying 4.0 m / s of air to the adsorption element.
The temperature is raised at ° C / min. At that time, the temperature of the adsorption element and the generated CO concentration are measured to determine the flame retardancy.

[0042]

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
To obtain a honeycomb-shaped adsorption element using powdered activated carbon impregnated with 30% by weight of phosphoric acid. 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 adsorption element is adapted to an exhaust gas treatment device (FIG. 2), and the element is divided into an adsorption zone and a desorption zone.
The operation of adsorbing and removing ammonia by passing the exhaust gas through, and on the other hand, passing 130 ° C. of heated air at 1/20 of the air flow to the desorption zone with respect to the air flow to the adsorption zone to desorb ammonia This operation was continuously performed, and the treatment performance of ammonia was measured. By using the powdered activated carbon adsorbent to which phosphoric acid was impregnated, ammonia could be desorbed, and good results were obtained in which the ammonia treatment performance was dramatically improved (Table 1). In addition, the flame retardancy was measured. No sudden rise in temperature of the honeycomb-shaped adsorption element was observed, and the adsorption element after the measurement maintained its strength.

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 this honeycomb-shaped adsorption element was measured. The ammonia adsorption performance was significantly lower than that of the example. 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 100 ppm ammonia gas is passed through the adsorption zone to adsorb and remove ammonia. Operation and, on the other hand, in the desorption zone,
Heating air at 130 ° C. was blown at 1/20 of the air flow to the adsorption zone, and the operation for desorbing ammonia was continuously performed to measure the ammonia treatment performance. Although desorption of ammonia was possible, the result that the ammonia treatment performance was significantly lower than that of the example was obtained (Table 1). Also,
The flame retardancy was measured. A sudden rise in the temperature of the honeycomb-shaped adsorption element was observed, and the adsorption element after measurement was incinerated white and the strength was not maintained, and the element was burning.

(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 adsorbing element having a honeycomb structure having a thickness of 3 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 adsorbing element to which 30% by weight of phosphoric acid was impregnated. 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 adsorption of the ammonia by the adsorbent is affected by the porosity which is a characteristic of the adsorbent.

Comparative Example 3 Powdered activated carbon was impregnated with a 30% by weight aqueous phosphoric acid solution and dried at 100 ° C. for 1 hour to obtain a powdered activated carbon impregnated with 30% by weight of phosphoric acid. The fluidity and abrasion 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. (Table 1)

[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. Including the step of desorption after, especially using phosphoric acid as the inorganic acid, by using powdered activated carbon as the adsorbent, without lowering the adsorption performance of the adsorbent other than ammonia, In addition, processing can be performed without damaging other constituent materials when processing into a sheet shape or a honeycomb shape, and by using the adsorbent, ammonia can be adsorbed and desorbed, thereby greatly improving the processing performance of ammonia. It has the effect of making things possible.

[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 ground 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 F2 Flow meter for dilution air 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

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D002 AA13 AB01 BA03 BA12 CA05 DA26 EA08 4G066 AA05C AA50B AA71D AC12D AC26D AE01B BA07 BA36 CA08 CA29 DA02 FA12 FA25 FA28 GA01 GA06 GA16

Claims (9)

[Claims] 1. A flame-retardant exhaust gas treatment material comprising an acidic substance impregnated in powdered activated carbon. 2. The exhaust gas treating material according to claim 1, wherein the acidic substance is an inorganic acid or an inorganic acid salt. 3. The exhaust gas treating material according to claim 1, wherein the acidic substance is a phosphate compound. 4. The exhaust gas treating material according to claim 1, wherein the acidic substance is phosphoric acid. 5. The exhaust gas treatment element according to claim 1, wherein the adsorbent obtained by impregnating the acidic substance with the powdered activated carbon is formed into a honeycomb structure. 6. A step of bringing an exhaust gas containing a basic substance into contact with an adsorbent obtained by attaching an acidic substance to powdered activated carbon, a step of causing the adsorbent to adsorb a basic substance, and an step of adsorbing the adsorbent. The exhaust gas processing apparatus and method according to any one of claims 1 to 5, further comprising a step of desorbing the basic substance. 7. A step of bringing an exhaust gas containing a basic substance into contact with an adsorbent obtained by impregnating an acidic substance to powdered activated carbon with a treatment element formed in a honeycomb structure, wherein the basic substance is added to the adsorbent. The exhaust gas treatment apparatus and method according to any one of claims 1 to 6, comprising a step of adsorbing and a step of desorbing a basic substance adsorbed on the adsorbent. 8. 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. 9. The exhaust gas treatment method according to claim 7, wherein the basic gas is ammonia.