WO1997010051A1

WO1997010051A1 - Adsorbent and method for treatment of exhaust gas

Info

Publication number: WO1997010051A1
Application number: PCT/JP1996/002593
Authority: WO
Inventors: Hideo Kato; Masao Yashiro; Toshiyuki Higuchi; Masayuki Tuchida
Original assignee: The Sangyo Shinko Co., Ltd.
Priority date: 1995-09-13
Filing date: 1996-09-11
Publication date: 1997-03-20

Abstract

An adsorbent for use in the dry exhaust gas treatment method for removing organochlorine compounds or the like by adsorption, which comprises balloon particles and porous aluminosilicate crystals layered on the surface of each particle; and a method for treating exhaust gas containing organochlorine compounds or the like therewith.

Description

Description Adsorbent for exhaust gas treatment and exhaust gas treatment method

〔Technical field〕

The present invention relates to an adsorbent for exhaust gas treatment for efficiently separating and removing organochlorine compounds contained in exhaust gas, and a method for treating exhaust gas.

(Background technology)

Exhaust gas generated from garbage incinerators and the like contains harmful substances such as nitrogen oxides, sulfur oxides, hydrogen chloride, and heavy metals, and technologies for removing them have been developed and put into practical use from the viewpoint of environmental protection. ing.

In addition, the dry method, the wet method, or a combination of these methods is being put to practical use for the removal of trace amounts of organic chlorine compounds such as highly toxic dioxins, which have recently become a problem, but the system is simplified. At present, the dry method, which has a compact equipment size, is dominant.

In the dry method, for example, as disclosed in Japanese Patent Application Laid-Open No. 4-87664, the conventional bag filter dust collection method with slaked lime powder is improved and powdered activated carbon or activated carbon is added to the bag filter surface. There is a method of forming a clay powder layer and passing exhaust gas through this powder layer to remove organic chlorine-based compounds together with dust collection.

Japanese Unexamined Patent Publication No. Hei 4-887624 discloses a test in which dioxin was removed from flue gas using a combination of slaked lime and activated carbon, which is currently considered to be the most effective adsorbent for bag filters. The results are described. According to the results, the efficiency of dioxin removal from exhaust gas has been improved to around 97%. However, even with such a high removal efficiency, it is difficult to achieve a global dioxin emission allowance (emission control concentration of 0.1 ng—TEQ / m ³ _N ).

Further, according to the study of the present inventor, in order to continuously feed slaked lime and activated carbon to the exhaust gas treatment process by the above-mentioned bag filter method, it is necessary to provide two charging devices in parallel. The installation of two sets of input devices is economically excessive. In addition, it is necessary to discharge these adsorbing and removing materials continuously. Ri, the amount of waste generated in order to increase 2. 2 g / m ³ over the exhaust gas content, it takes an excessive burden on waste disposal.

That is, for example, the amount of exhaust gas is, in about 1 0 0, 0 0 0 m ³ scale incinerator per hour, per day of the slaked lime and active carbon as described above, the increase in waste 1 0 0 0 0 0 m ³ / hour X 2 4 hours X 2.2 g = 5280 kg, and if it is operated for 30 days a month, a huge amount of waste of about 〖58 tons increases in a month. Will be added.

Accordingly, an object of the present invention is to provide an adsorbent for exhaust gas treatment that efficiently adsorbs an organic chlorine-based compound with respect to an adsorbent used in a dry method for adsorbing and removing an organic chlorine-based compound.

Further, another object of the present invention is to provide a dry method for adsorptive removal of organic chlorine-based compounds, etc., by efficiently removing organic chlorine-based compounds from exhaust gas, thereby reducing the amount of waste generated in the exhaust gas treatment. An object of the present invention is to provide a method for treating exhaust gas which can suppress an increase in the amount of exhaust gas.

[Disclosure of the Invention]

In order to achieve the above object, according to the present invention, as a result of intensive studies on the production of organic chlorine-based compounds such as dioxins in the exhaust gas treatment step, the temperature range in which the organic chlorine-based compound is produced in the exhaust gas treatment step, By focusing on the presence of organic chlorine compounds in the exhaust gas treatment process, we have found an adsorbent for exhaust gas treatment and an exhaust gas treatment method that can efficiently adsorb organic chlorine compounds in the exhaust gas treatment process. Was completed.

The invention according to claim 1 is an adsorbent for an organochlorine compound, wherein a porous aluminoate crystal is laminated on the surface of a hollow spherical particle.

The invention described in claim 2 is directed to a coal ash containing at least 10 wt% of alumina and having an amorphous alumina ratio of at least 50 wt% in the alumina, having a concentration of at least 1.5 N. 2. The adsorbent for an organochlorine compound according to claim 1, wherein the adsorbent is formed by a hydrothermal reaction by adding an aqueous solution.

The invention according to claim 3 is characterized in that the adsorbent according to claim 1 or 2 is formed into a granular form using an inorganic binder, and the adsorbent according to claim 3 is characterized in that it absorbs an organochlorine compound. It is a material.

The invention according to claim 4 is a method for removing an organochlorine compound in an exhaust gas, and the method according to claim 1, 2, or 3, further comprising: A method for adsorbing an organic chlorine compound in an exhaust gas by contacting the exhaust gas with the exhaust gas.

The invention according to claim 5 is the method for treating exhaust gas according to claim 4, wherein in the adsorption step, exhaust gas that has passed through a dust collection step is brought into contact with the adsorbent. Processing method.

Hereinafter, the present invention will be described in detail.

(Organic chlorine compounds in exhaust gas treatment process)

As shown in FIG. 1 and FIG. 2, organochlorine compounds represented by dioxins are particularly produced by reaction in an exhaust gas treatment line, and the production temperature range is about 300 to 500 ^e C. This temperature range is located between the melting point and boiling point of the compound, but in the exhaust gas treatment process after the production of the substance, the process temperature gradually decreases (see Fig. 2), The existence form is a mixture of solid state, liquid state (mist state) and gaseous state. In particular, organic chlorine-based compounds such as dioxins are easily soluble in oils, are mixed in oily substances in exhaust gas, and those in a liquid phase have a high affinity for a water-absorbing and oil-absorbing adsorbent.

Also, as shown in FIG. 3, dioxins are generated from precursors on fly ash such as aromatic hydrocarbons and gas phase precursors such as chlorine gas in exhaust gas. After that, it is desorbed from the fly ash to produce gaseous dioxin, dechlorinated on the fly ash to produce low chlorinated dioxins, or decomposed on the fly ash . Also, once gasified dioxins may be in liquid phase or solid phase, and dioxins on fly ash may be desorbed in the liquid or solid state as they are.

Therefore, in order to adsorb dioxins efficiently, an adsorbent having adsorption performance in any of these existing forms is required.

The present inventor has obtained these findings and, based on these findings, has been found to use a microbore (2 nm or less) excellent in gas adsorption and a liquid phase It is concluded that a spherical adsorbent that has both mesopores (pore diameter of 2 to 50 nm) and macropores (pore diameter of 50 nm or more), which are excellent in adsorbing substances, is effective, and adsorbs this compound efficiently. It has been found that contacting this adsorbent with the exhaust gas is effective in removing and suppressing the increase in the amount of waste associated with the exhaust gas treatment.

The exhaust gas referred to in the present invention contains an organic chlorine-based compound, and a representative example thereof is exhaust gas generated when garbage or industrial waste is treated in a combustion furnace, a reaction furnace, or a melting furnace. it can.

Examples of the organochlorine compound of the present invention include polychlorodibenzo-P-dioxin (PCDD) which is a dioxin and polychlorodibenzofuran (PCDF) which is a dibenzofuran.

(Adsorbent for organic chlorine compounds)

The adsorbent useful in the present invention is obtained by laminating a porous aluminoate crystal on the surface of a hollow spherical particle.

The aluminoate crystals on the surface of the adsorbent have micropores in the crystal structure with a diameter of about 0.4 to 0.5 nm, and as shown in FIG. A three-dimensional laminated structure with a layer thickness of about zm is formed. Then, as a result of lamination of these crystals 200, there is a mesopore having a diameter of 2 to 50 nm between the crystals 200, so that the crystal has a distribution of two types of bore sizes. An example of the pore size distribution of the adsorbent is shown in FIG.

Further, the skeleton portion of the adsorbent is composed of hollow spherical particles 220, and the particle size of the particles 220 is 2 to several tens of m, and cracks and pinholes are included in the particles 220. Since there is usually 240 (see Fig. 5), this surface layer has a macropore (pore hole 50 nm or more) smaller than the particle diameter, and the hollow inside of the particle 220 An oily or aqueous liquid material can be stored in the cavity.

(Adsorption function of organic chlorine compounds)

The gaseous dioxins and other organic chlorine compounds can be adsorbed in the micropores' mesopores of the adsorbent.

In addition, the mesopores and the macropores adsorb the organic chlorine-based compound in the liquid phase, and further trap and remove the solid-phase organic chlorine-based compound in the powder adsorbent layer. You can leave.

Further, as shown in FIG. 5, since the surface of the three-dimensional laminated structure of the aluminosilicate crystal body 200 is uneven, an oily or aqueous substance is removed on the uneven surface. It can also be adsorbed. In addition, since the shape of the adsorbent is spherical, it has low airflow resistance and is excellent as a gas adsorption treatment material.

The adsorbent has a form of hollow spherical particles. The adsorbent in the form of hollow spherical particles can be easily attached to and detached from the filter cloth.

The basicity of the adsorbent is preferably pH 8 or more. This is because it is also useful for the action of adsorbing and removing hydrogen chloride and the like that promote the production of dioxins and the like. Here, the basicity is measured with an electrode pH meter after mixing and stirring at a ratio of water 5 to adsorbent 2 to form a slurry.

(Adsorbent manufacturing method)

As an adsorbent having such a structure, there is a modified coal ash obtained by treating coal ash with hot water.

This upgraded coal ash, eluted by amorphous structure component having an _{(S i 0 2, A 1} 2 0 3) months ^ coal ash contained in coal ash is treated Al Chikararinetsu water, The structure as the above-mentioned adsorbent is formed by being precipitated and crystallized as aluminoate on the surface of the coal ash. That is, the hollow spherical particles, which are the skeleton part of the adsorbent, are hollow spherical particles of coal ash, and the crystals of the porous aluminoate on the surface are aluminoates precipitated and crystallized by hydrothermal treatment. is there.

Resulting modified coal ash are generally chemical _{composition, M e O · A 1 2} 0 3 · m S i 0 2 ■ n H 2 ◦ (M e is such _{_{N a 2, K 2, C}} a This is a porous compound containing zeolite, which is an alkali metal or an alkaline earth metal and varies depending on the alkali component used. The crystal structure of zeolite contained is mainly P-type (filpsite), but it is also possible to manufacture those with H-type (hydroxyl sodalite) structure by changing the concentration of alkaline aqueous solution. Can be done. In addition, modified coal ash generally has a high cation exchange capacity (CEC)

Adsorbents made from coal ash are inexpensive and non-combustible, so It is more economical and safer than activated carbon as a material, and the adsorbent is more hydrophilic than water-repellent activated carbon. It is also superior.

In particular, when coal ash is subjected to hydrothermal treatment with an alkaline solution, a NaOH solution having a concentration of 1.5 N or more is preferable. Since NaOH is inexpensive and easily available, there is an advantage that the cost of the exhaust gas treatment process can be reduced.

The composition of a typical modified coal ash is shown below. table 1

True specific gravity: about 2.5 Cation exchange capacity: about 200meq / 100g

Bulk specific gravity: about 0.7 Specific surface area: about 70m ² / g

Average particle size: 10 Aim

The cation exchange capacity and the specific surface area were measured using the Shorenberger method and the BET method, respectively. The coal ash reforming conditions in Table 1 are the same as those in the examples described later. When coal ash is used as a raw material, it is necessary that the crystal morphology distribution (amorphous alumina / total alumina) of alumina contained in the raw material is 50 wt% or more in order to secure a spherical shape. . If the crystal form distribution is less than 5 Owt, the proportion of crushed particles increases.

In addition, in order for modified coal ash as an adsorbent to maintain a high adsorption function, the cation exchange capacity (CEC), which is representative of the crystallization rate of aluminoate, must be sufficiently high. In order to obtain coal ash having a high cation exchange capacity, as shown in Table 2, the proportion of total alumina in the raw material coal ash must be 10 wt% or more. Table 2

As the modified coal ash having two pore sizes suitable for the present invention, specifically, JP-A-59-86667, JP-A-61-109745 and JP-A-61-1 There is a modified coal ash obtained by the method disclosed in Japanese Patent Publication No. 7841/16. This modified coal ash is a porous crystal obtained by adding an alkaline solution such as caustic soda to coal ash and heat-treating it at 70 to 100 ° C. Has a function.

As a method for modifying coal ash, preferably, for example, (1) an alkaline aqueous solution and a coal ash are added to a coal ash by adding an aqueous solution of alkali metal and performing hot water treatment to modify the porous ash. Coal ash reforming method characterized by agitating and treating with hot water with a reaction solid-liquid ratio of 0.5 to 3.0 liters / kg (Japanese Patent Application No. 5-107090) (2) After adjusting the solid-liquid ratio of the slurry after the hot water treatment to 2.5 liters Zkg or more, the surplus aqueous solution and the porous crystal are continuously separated. Coal ash modified by the method for modifying coal ash (Japanese Patent Application No. 5-107090).

(Granular adsorbent)

Further, as the adsorbent used in the present invention, those obtained by granulating these adsorbents with an appropriate inorganic binder are also suitable. Such granulated adsorbents include, for example, a modified coal ash and a cell having a blending amount of 15% by weight or more based on the dry weight of the entire raw material. Using the ment binder as the main raw material, the raw material is mixed with the initial rotational speed given, and the applied mechanical force allows water to flow out from the modified coal ash of the raw material to form a paste, which is then rotated at a lower speed than the initial rotational speed. Ion exchange granulation of modified coal ash, characterized in that kneading and drying are performed at a speed and granulation and drying are performed at a rotation speed suitable for the target particle size when the appropriate granulated moisture is reached. The granulated products obtained by the methods described in Japanese Patent Application Nos. 5-1111569 and 5-1150770 can be mentioned. In this granulated product, sodium-type zeolite is replaced by calcium-type zeolite, or a part of sodium is replaced by calcium, and both sodium-type zeolite and calcium-type zeolite are mixed. It is a thing that goes. In addition, a modified coal ash obtained by further pulverizing the granulated material may be used.

(Effect of adsorbent in exhaust gas treatment process)

Organic chlorine compounds such as gasified dioxins are adsorbed in the microbore / mesopore of the adsorbent. Therefore, in the exhaust gas treatment step after the generation of dioxins and the like, by disposing this adsorbent, the dioxins in a gasified state after the generation are adsorbed and the dioxins and the like are removed from the exhaust gas.

The organic chlorine-based compound in a liquid phase is adsorbed to the mesopores and macropores, and the organic chlorine-based compound in a solid phase is captured and removed in the powder adsorbent layer. Therefore, in the exhaust gas treatment process after the generation of dioxins, by disposing this adsorbent, dioxins in a liquid phase or a solid phase are adsorbed or supplemented and removed, and dioxins are removed from exhaust gas.

Furthermore, in the exhaust gas treatment step, the abundance of the aromatic compound having a benzene ring, which is a precursor of dioxins, in the liquid phase is high. Here, an oily substance such as an aromatic compound is adsorbed to the mesopore or macropore, and a chlorine-based substance, which is another precursor of dioxin, is adsorbed by a microbore. Therefore, by disposing this adsorbent in the exhaust gas treatment step before or during the generation of dioxins, the precursors described above are adsorbed and removed, and the generation of dioxins is suppressed.

In addition, even if this adsorbent is provided in the process after dioxins are produced, it is possible to adsorb and remove unreacted aromatic compounds and chlorine compounds to further purify exhaust gas. Wear.

Furthermore, the present inventors have found that in order to more effectively remove organic chlorine-based compounds using this adsorbent and to suppress an increase in the amount of waste, the contact between the dust in the exhaust gas and the adsorbent must be reduced. It was important to avoid as much as possible.

That is, it is effective to carry out the exhaust gas dust collection step prior to the adsorption of the organochlorine compound by the adsorbent. By removing the dust in the exhaust gas in advance, the airflow resistance of the treatment device is stably maintained at a low level, and the adsorption performance of the organic chlorine compound to the limit of the amount of the organic chlorine compound adsorbed by the adsorbent is exhibited. As a result, there is no need to supply an excessive amount of adsorbent, and the increase in waste is suppressed. Specifically, the increase in waste will be reduced by a factor of about 40 compared to the past.

Furthermore, since the adsorbent can be used over the original usage period of the adsorbent, frequent replacement of the adsorbent can be avoided. Specifically, the processing equipment can be stably and continuously operated for two weeks or more.

In this way, in the exhaust gas treatment process after the dust collection process, by disposing this adsorbent, dioxins in a gas state, a liquid phase state or a solid phase state are absorbed after generation, and dioxins and the like are removed from the exhaust gas. Can be removed.

The method of collecting dust from the exhaust gas is not particularly limited. Any means can be used as long as it can capture and collect dust in the exhaust gas. For example, an electric dust collector or a bag filter can be used. .

When the dust concentration of the exhaust gas does not exceed 0.5 g / m ³ N, it is effective to capture dust in the exhaust gas at the same time as the step of adsorbing the organic salt compound. When the dust concentration of the exhaust gas does not exceed 0.5 g Zm ³ N, that is, when the dust concentration is sufficiently low, the increase in the ventilation resistance of the adsorbent layer due to dust is suppressed, and the dust is not removed for a long time. The adsorbent makes it possible to simultaneously capture and remove dust and adsorb and remove organochlorine compounds. In other words, the ventilation resistance is stabilized at a low level, stable operation is possible for a long period of time, the adsorption performance of organic chlorine compounds can be exhibited to the limit of the adsorbent, and no excessive adsorbent is required, and the amount of waste is reduced. The increase is suppressed. In addition, according to this simultaneous removal, a conventional exhaust gas treatment device capable of performing a dust collection process can perform both the dust collection process and the organic chlorine compound adsorption process. What In addition, efficient removal of organic chlorine compounds and suppression of increase in waste volume are achieved. In addition, the equipment is compact and the processing time is reduced.

When the external dimensions of the dust contained in the exhaust gas were 50 m or more or the specific gravity was 2 g Z cm ³ or more, the adsorbent that adsorbed the organochlorine compound was simultaneously captured. It is effective to have a step of discharging together with the dust, and to separate the dust from the adsorbent, and to further use this adsorbent to carry out the step of adsorbing the organochlorine compound.

When the size of the dust is within the above range, it is possible to separate the adsorbent and the dust, take out only the adsorbent, and reuse the adsorbent. For the separation of adsorbent and dust, the adsorbent that adsorbs organochlorine compounds and captures dust is discharged from the exhaust gas treatment process, and then the mixture is subjected to classification and sieving operations. Only the adsorbent is recovered using the body separation method, and reused in the exhaust gas treatment process again for the adsorption of organochlorine compounds.

According to this method, before the adsorbent layer is clogged by dust, the adsorbent and the trapped dust are separated from the adsorbent, and the adsorbent is reused to reach the limit of the original adsorbed amount of the adsorbent. Adsorption performance can be demonstrated.

In particular, when the adsorbent is in the form of granules, it is possible to form a moving bed that makes orthogonal contact with the exhaust gas. In this case, the organic chlorine-based compound is adsorbed by the granular adsorbent, and the dust can be captured in the bed.

Also, in the moving bed, the granular adsorbent is moving downward, is discharged together with the dust captured from the lower part of the moving bed, and after separating the dust by the classification and sieving operation, transports the adsorbent again above the moving bed. Thus, the granular adsorbent can be easily reused.

Furthermore, in the exhaust gas treatment step, the presence ratio of aromatic compounds having a benzene ring, which are precursors of dioxins, are high in the liquid phase. Here, mesopores and macropores can adsorb oily substances such as aromatic compounds, and chlorinated substances as precursors can be adsorbed by microbore. Therefore, by disposing this adsorbent in the exhaust gas treatment step, the precursor can be adsorbed and removed, and the regeneration of dioxins can be suppressed. In addition, unreacted aromatic compounds and Adsorb and remove chlorine-based compounds to further purify exhaust gas Can be

The temperature of the exhaust gas in the dust collection step is preferably from 120 ° C to 450 ° C. The reason for setting the temperature at 450 ° C or lower is that organic chlorine-based compounds such as dioxins often exist in the liquid phase, so that it is effective to adsorb in the liquid phase, and the heat resistance temperature of the adsorbent. Is 500 ° C. On the other hand, if the temperature is lower than 120 ° C, the acid gas (SO _x , NO, etc.) contained in the exhaust gas generates a dew point, and the probability of damaging the exhaust gas treatment equipment increases.

The adsorbent used in the removal process of the organic chlorine-based compound is desorbed from the filter medium, and then put into an incinerator, melting furnace, or reaction furnace, etc., and adsorbed at a high temperature under high temperature. Can be decomposed.

Hereinafter, the present invention will be described in more detail based on embodiments.

Coal ash and alkali solution are charged into reaction vessel (2) so as to have a predetermined solid-liquid ratio, mixed, stirred and boiled at a predetermined temperature to convert coal ash into porous crystalline material I do.

Here, the raw material coal ash used in the present invention is not particularly limited, and fly ash, clean ash, coal combustion ash, or the like can be used. Such coal ash is, for example, coal ash generated when pulverized coal or the like is burned by thermal power generation or the like, and is collected from the flue of a flue. Therefore, the particle size of coal ash at the time of collection is rather small and can be used as it is.

In order to enhance the reactivity, usually, particles of 50 m or less are 98% or more, preferably particles of 20 m or less are 50% or more, and more preferably particles of 10 m or less are 40% or more. It is preferable to use it after adjusting.

When the content of the coal ash having a particle size of 30 zm or less is 30% or less, the contact area with the alkaline solution is reduced, and the reaction efficiency is reduced. .

Next, the concentration of the adjusted alkali solution is not particularly limited, but is usually in the range of 1 to 4 N, preferably 1.5 to 3 N, and more preferably 1.8 to 2.3 N. is there. When the concentration of the alkaline solution is less than 1 N, the cation exchange capacity (CEC) of the obtained porous crystal is not sufficient, and when the concentration exceeds 4 N, Although the CEC of the obtained porous crystal material is sufficient, the crystal structure of the porous crystal material having a flip-site structure (effective minimum diameter of 4 to 5 angstroms) is greatly reduced, and the height of the hole is reduced. It is not preferable because the xiso-dalite structure (effective minimum diameter: 2 to 3 angstroms) rapidly increases, and it becomes difficult to adsorb a gas having a large molecular size. The alkali solution used in the present invention is not particularly limited. For example, an aqueous solution such as sodium hydroxide or potassium hydroxide can be used.

The solid-liquid ratio between the coal ash and the alkaline solution used in the present invention is usually 0

The range is from 5 to 3.0 liters Z kg, preferably from 1.5 to 2.5 liters kg, more preferably from 2.0 to 2.2 liters Zkg. The temperature at the time of the hydrothermal reaction is usually 90 to 100, preferably 95 to 100'C, more preferably 98 to 100 ° C. If the temperature is less than 9 (TC, the reaction rate is greatly reduced and the reaction takes a long time.If it exceeds 100, large pressure equipment is required and heating is required. It is not preferable because the effect is not enough to justify the cost.

The slurry after the reaction is solid-liquid separated by a dewatering device. The filter cake of the slurry obtained from the liquid B is further stirred and washed with washing water.

Porous crystalline material containing slurry after washing, dried, the solids and containing not obtained porous crystalline material, this state was dried by air drying or the like, the chemical composition, MeO * A l ₂ 〇 ₃ · mS i 0 ₂ · nH ₂₀ (Me is an alkali metal such as Na ₂ , K ₂ , or Ca or an alkaline earth metal, and depends on the type of alkaline solution used.) O The modified coal ash contained is considered as the adsorbent of the present invention.

Further, by performing ion exchange using different cation aqueous solutions, it is possible to obtain an adsorbent having various types of aluminosilicate crystal structures, for example, changing a sodium type into a calcium type. The cation to be ion-exchanged may be a cation-exchangeable cation regardless of sodium calcium. Also, this adsorbent can be granulated into granules with an inorganic binder. The adsorbent thus obtained is used so as to be brought into contact with the exhaust gas in the exhaust gas treatment step of the gas-permeable fixed bed system or the moving bed system.

The adsorbent of the present invention can be used as an adsorbent used in a conventionally known fixed bed type adsorption step. For example, a powdery adsorbent can be attached to the surface of a filter cloth to form an adsorbent layer, placed in an exhaust gas treatment process, and brought into contact with exhaust gas to remove organochlorine compounds. . Further, an adsorbent layer may be formed by laminating or filling a granular adsorbent.

Similarly, the adsorbent of the present invention can be used as an adsorbent used in a conventionally known moving bed type adsorption step. For example, during the exhaust gas treatment process, the adsorbent may be moved so as to be orthogonal to the direction of exhaust gas flow, and the moving adsorbent may be brought into contact with the exhaust gas to remove organic chlorine-based compounds. it can. In this case, the adsorbent is preferably in the form of granules.

Furthermore, since the adsorbent can also adsorb the precursor of the organochlorine compound, it can be effectively used by contacting the exhaust gas with a fixed bed or a moving bed before or during the formation of the organochlorine compound. Therefore, the production of the organochlorine compound can be suppressed, and the subsequent adsorption and removal of the organochlorine compound can be efficiently performed.

For example, as shown in Fig. 6, after passing exhaust gas from incinerator 100 through bag filter 102 for dust collection, this adsorbent is adhered and retained for adsorption of organochlorine compounds. A bag filter 104 can be provided. According to this exhaust gas treatment method, dust in the exhaust gas is removed by the dust collecting bag filter 1102, so that the adsorbent does not become clogged with dust. In addition, the adsorption of the organochlorine compound is similarly performed by the moving bed method using the granular adsorbent.

Furthermore, when the dust concentration of the exhaust gas does not exceed 0.5 g Zm ³ N, as shown in Fig. 7, the bag filter 1 12 for collecting the exhaust gas from the incinerator 110 The adsorbent can be provided so as to adhere and hold it, thereby capturing dust and simultaneously removing the organic chlorine-based compound. According to this exhaust gas treatment method, it is possible to prevent an increase in the airflow resistance of the adsorbent layer due to the adhesion of dust, and to adsorb the organic chlorine-based compound at the same time as capturing the dust for a long period of time.

Furthermore, the external dimensions of the dust contained in the exhaust gas are 50〃m or more, or If the specific gravity is 2 g Z cm ³ or more, this adsorbent is introduced into the exhaust gas treatment process from the incinerator 120 as shown in Fig. 8, and the exhaust gas is The adsorbent that captures the dust and adsorbs the organochlorine compound is discharged and collected, and the adsorbent and the dust are separated and separated by the separation / separation device 124, and the adsorbent is discharged again. It can be recycled to return to the processing step. According to this exhaust gas treatment method, since the dust and the adsorbent can be separated, the adsorbent can be reused while avoiding an increase in the ventilation resistance due to the dust. Simultaneous removal of chlorine-based compounds is possible.

When the adsorbent is in the form of granules, as shown in Fig. 9, a moving bed 1332 that is perpendicular to the direction of exhaust gas flow from the incinerator 130 is formed, And adsorb the organochlorine compound to the granular adsorbent, and capture dust in this layer. The moving bed can be continuously used, and the granular adsorbent and the dust can be separated by the separating device 134 to be circulated and used again so as to return to the exhaust gas treatment step. According to this method, regardless of the dust concentration, the ventilation resistance is low and stable, and the dust and organic chlorine compounds can be removed simultaneously, and the granular adsorbent can be reused. It is possible.

As described above, according to the adsorbent of the present invention, an organic chlorine-based compound in a gas state or a liquid phase can be adsorbed in an exhaust gas treatment step, so that the organic chlorine-based compound is efficiently removed from the exhaust gas. be able to.

Further, according to the exhaust gas treatment method of the present invention, by contacting the exhaust gas with an adsorbent obtained by laminating a porous aluminoate crystal on the surface of the hollow spherical particles, the exhaust gas can be efficiently used by the adsorbent. It is possible to adsorb and remove the organic chlorine compounds in the waste gas and to suppress the amount of waste increased by the exhaust gas treatment.

[Brief description of drawings]

Fig. 1 is a diagram showing the outline of a garbage incinerator and the area where organochlorine compounds are generated in the exhaust gas treatment process.

FIG. 2 is a diagram showing a temperature range for generating an organochlorine compound in an exhaust gas treatment step.

Figure 3 shows the mechanism of the production of dioxins in the exhaust gas treatment process. FIG.

FIG. 4 is a diagram showing the distribution of the bore size of the adsorbent.

FIG. 5 is a partial cross-sectional view of the adsorbent showing the structure of the adsorbent.

FIG. 6 is a diagram schematically showing an embodiment of the present invention.

FIG. 7 is a diagram schematically showing an embodiment of the present invention.

FIG. 8 is a diagram schematically showing an embodiment of the present invention.

FIG. 9 is a diagram schematically showing an embodiment of the present invention.

FIG. 10 is a diagram showing an outline of the device configuration of the embodiment.

[Best mode for carrying out the invention]

Hereinafter, examples of the present invention will be described.

Used in this embodiment, coal ash, total A 1 ₂ 0 ₃ minutes is 2 3 wt%, Of these, the proportion of amorphous A 12 0 ₃ is 7 OWT, particle size, the average 1 It was 0 zm. 100 kg of this coal ash and 2100 L of a 2 N aqueous sodium hydroxide solution adjusted to 100 were charged into a reaction tank, the reaction temperature was adjusted to 100 ° C, and the stirrer of the reaction tank was used. stirring, subjected to boiling, the coal ash, the chemical composition _{_{mainly, Na 2 0, a l 2}} 0 3 - 3. 5 S i 0 2 - 4. P type represented by 5 H ₂ 0 (Fi Rippusai g) The reaction was performed for 5 hours to obtain a modified coal ash, which is a porous crystalline material having the following crystal structure.

The slurry containing the porous crystals after the hot water treatment was drained, and the obtained filter cake was washed with a water washing tank and then dehydrated. The solid matter was added with calcium chloride equivalent to 15% by weight in a weight ratio. Add, add 5 times more water to form a slurry, stir, perform reaction for 2 hours, then remove, wash, and dehydrate to form a porous crystal having a Ca-type zeolite crystal structure. Substance-containing solid was obtained. Further, this solid was dried at 1 3 0 ^e C, to give a powdered adsorbent C a type Zeorai preparative porous crystalline镜層to the surface to be hollow spherical particles were.

The obtained powder particles had a three-dimensional laminated structure in which calcium zeolite (calcium aluminosilicate) crystals were precipitated on the surface of hollow spherical particles having a diameter of about 10 m. Cracks and pinholes are generated on the surface of the hollow spherical particles, and a 2 nm-diameter mesh formed by the in-layer structure of zeolite crystal particles. It had a microbore of 0.5 nm based on the crystal structure of soboa and zeolite.

This powder was actually incinerated by a device shown in FIG. 10 and an adsorption test of PCDD and PCDF was performed using a part of the exhaust gas from the incinerator. The test equipment consists of an incinerator 10, a cooler 12, a dust filter 14, a suction device 16, and a bag filter (test machine) 18 for removing organic chlorine-based compounds. The high-temperature exhaust gas discharged from the incinerator 10 is cooled by the cooler 12, sent to the bag filter 14 to remove dust, and the exhaust gas that has passed through the bag filter 14 is filtered by the bag filter 18. In this example, PCD (polychlorodibenzo-ρ-dioxin) and PCDF (polychlorodibenzofuran) are to be adsorbed by the adsorbent of this embodiment.

A cylindrical body was provided in the bag filter 18, and the adsorbent was held by spraying the adsorbent onto the filter cloth wound around the cylindrical body. The filter cloth was made of heat-resistant nylon.

The adsorption test was performed under the following conditions

〔Test condition〕

Test machine adsorption layer area 1 0.8 m ²

Amount of adsorbent 20 kg

Processing air volume 1 0m "/ Ίτι i η

The temperature characteristics of the gas were as follows.

[Gas temperature characteristics]

Bag filter entrance 250. C

Bag filter exit 1 2 0. C

Testing machine entrance 100. C

Testing machine outlet Constant at almost 60'C

The analysis of dioxins and dibenzofurans was performed according to the Manual for Measurement and Analysis of Dioxins in Waste Disposal, issued by the Waste Management Foundation. _C showing the results of test are shown in Table 3

Table 3

ND: below detection limit (less than 0.033ng / m ³ _N )

_{TEQ: 2.2.1, 8-T 4} CDD toxic equivalent concentration, conversion factor, due to your Ru dioxins measurement analysis Manual "to the above-mentioned Γ waste processing. The following is clear from this result.

That is, in the exhaust gas after the bag filter 14 in this test apparatus, PCDD and PCDF are detected at the inlet of the removing bag filter 18, but at the outlet of the removing bag filter 18, The detection limit was below the detection limit for all types of substances. From this result, almost 100% of PCDD and PCDF were removed from the exhaust gas after the bag filter 18 in this test apparatus.

In other words, as shown in Fig. 10, most of the PCDs, etc. and their low chlorinated products, which are formed on fly ash and remain attached to the fly ash, and decomposed products, fly to the bag filter. PCDs that are attached to the ash and are dispersed and gasified in the exhaust gas, PCDs in the liquid phase after gasification, and PCDs that are still attached to some fly ash are bugs. After passing through the filter, it was adsorbed and removed by the adsorbent adhering to the filter cloth in the testing machine 內.

In this bag filter 18, the temperature of the exhaust gas was 100. C and is in contact is, in this temperature range, although dioxins are below the melting point, for example, 2, 3, 7, the vapor pressure of 8- TCDD is 1 0 ⁴ kingdom, during the process, It is known that it exists not only in liquid and solid phases but also in gaseous state. That is, according to the adsorbent, dioxins and the like in any existing form can be adsorbed, so that dioxins and the like can be removed from the exhaust gas that has passed through the bag filter 14 with high efficiency.

Further, in the present embodiment, dioxins and the like from the exhaust gas are removed from the exhaust gas that has passed through the dust collection step, so that the adsorbent layer formed on the bag filter 18 is prematurely blocked by dust. However, the adsorption activity of the adsorbent was maintained for a long time, and the adsorption of dioxins and the like was performed efficiently. As a result,酎用period of adsorbent becomes more than a 5 day, generated gas amount is 1 0 0, 0 0 O m 3 / even when using the incinerator hr, waste due to the removal of organic chlorine compounds The increase was reduced to about 4 tons per month.

In this embodiment, the tester is provided after the dust collection step using a bag filter. However, since this adsorbent has a macropore and a mesopore capable of adsorbing oily substances and the like efficiently, the collection is performed. Removal of dust and dioxins can be performed simultaneously. In the present embodiment, powder is used as the adsorbent, but the adsorbent of the present invention may be granulated with an inorganic binder. In the granulated product, it is used not only as a fixed bed but also as a moving bed in a direction perpendicular to the direction of exhaust gas flow, and adsorbs and captures dioxins and other substances together with an adsorbent using a bag filter. It can be used effectively.

Claims

The scope of the claims

1. An adsorbent for organochlorine compounds, characterized in that porous aluminosilicate crystals are laminated on the surface of hollow spherical particles.

2. To a coal ash containing 1 O wt% or more of alumina and having an amorphous alumina ratio of 5 O wt% or more in the alumina, add an alkaline solution having a concentration of 1.5 N or more to the hydrothermal reaction. An adsorbent for an organochlorine compound according to claim 1, wherein the adsorbent is formed by

3. An adsorbent for an organochlorine compound, wherein the adsorbent according to claim 1 or 2 is formed into a granular shape using an inorganic binder.

4. A method for removing an organochlorine compound in an exhaust gas, wherein the exhaust gas is brought into contact with the adsorbent for an organochlorine compound according to any one of claims 1, 2, and 3 to thereby remove the organochlorine compound from the exhaust gas. A method for treating exhaust gas, which comprises a step of adsorbing an organic chlorine compound.

5. The method for treating exhaust gas according to claim 4, wherein in the adsorption step, exhaust gas that has passed through a dust collection step is brought into contact with the adsorbent.