JPH0975667A - Treatment of exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently adsorb an organochlorine compd. in an exhaust gas treatment process by executing an exhaust gas dust collecting process and bringing exhaust gas passed through the dust collecting process into contact with an adsorbent obtained by laminating porous aluminosilicate crystals on the surfaces of hollow spherical particles. SOLUTION: An effective adsorbent is obtained by laminating porous aluminosilicate crystals on the surfaces of hollow spherical particles. This adsorbent can be used in an air permeable fixed or moving bed type exhaust gas treatment process. For example, after the exhaust gas from a combustion furnace 100 is passed through a dust collecting bag filter 102, a bag filter 104 having this adsorbent bonded and held thereto can be provided for the purpose of adsorbing an organochlorine compd. Since dust in exhaust gas is removed by the dust collecting bag filter 102 in this exhaust gas treatment method, the clogging of the adsorbent by dust is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas treatment method for efficiently separating and removing an organic chlorine compound contained in exhaust gas.

[0002]

2. Description of the Related Art Conventionally, exhaust gas generated from refuse incinerators contains harmful substances such as nitric oxide, sulfur oxide, hydrogen chloride and heavy metals, and a technology for removing them has been developed from the viewpoint of environmental protection. Have been put to practical use. On the other hand, for the removal of trace amounts of organochlorine compounds such as highly toxic dioxins, which have become a problem in recent years, dry methods, wet methods or combination methods are being put to practical use, but the system is simple and the equipment scale is large. At present, the compact dry method is the mainstream.

The dry method includes, for example, Japanese Patent Laid-Open No. 4-8762.
As disclosed in Japanese Patent Publication No. 4, the conventional bag filter dust collection method using slaked lime powder is improved to form a powder layer of powdered activated carbon or activated clay on the surface of the bag filter, and exhaust gas passes through this powder layer. By doing so, there is a method of removing the organic chlorine-based compound as well as collecting the dust.

[0004]

However, according to the results obtained by the bag filter system in which slaked lime and activated carbon are used in combination, the removal efficiency has been improved to around 97%, but the global acceptance standard ( It is difficult to achieve the emission control concentration of 0.1 ng-TEQ / m ³ _N ) and the guideline for domestic incinerators (0.5 ng-TEQ / m ³ _N ). Further, according to the research by the present inventor, in order to continuously feed slaked lime and activated carbon to the exhaust gas treatment process by the bag filter method, it is necessary to install two series of feeding devices, which is economically excessive. At the same time
Since it is necessary to continuously discharge the adsorbed and removed material that has been input,
The amount of waste generated also increased by 2.2 g / m ³ -exhaust gas content, and an excessive burden was placed on the treatment of this waste. That is, for example, the exhaust gas amount is about 100,00 per hour.
In a 0 m ³ scale incinerator, the increase in waste per day is 100,000 m ³ / hour x 24 hours x
2.2g = 5280kg, and if it operates for 30 days a month, a huge amount of waste of about 158 tons will increase in a month.

Therefore, the present invention relates to a dry method for adsorbing and removing organic chlorine compounds and the like, and is capable of removing the organic chlorine compounds from the exhaust gas and suppressing an increase in the amount of waste generated by the exhaust gas treatment. An object is to provide a method for treating exhaust gas.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, as a result of diligent study on the production of organic chlorine compounds such as dioxins in the exhaust gas treatment process, the organic chlorine compounds are produced in the exhaust gas treatment process. By paying attention to the temperature range and the existence form of the organochlorine compound in the exhaust gas treatment step, a method for treating exhaust gas capable of efficiently adsorbing the organochlorine compound in the exhaust gas treatment step was found, and the following inventions were completed.

The invention according to claim 1 is a method for removing an organochlorine compound in exhaust gas, which comprises performing a step of collecting exhaust gas, and further, forming a porous aluminosilicate on the surface of hollow spherical particles. And a step of adsorbing the organic chlorine compound in the exhaust gas by bringing the exhaust gas that has undergone the dust collection step into contact with an adsorbent formed by stacking the crystalline bodies. The invention according to claim 2 is a method for removing an organochlorine compound in exhaust gas, wherein dust is contained in an adsorbent obtained by laminating porous aluminosilicate crystals on the surface of hollow spherical particles. Concentration is 0.5
This is a method for treating exhaust gas, which comprises adsorbing an organic chlorine compound in the exhaust gas and capturing dust in the exhaust gas by contacting the exhaust gas that does not exceed g / m ³ N. The invention according to claim 3 is a method for removing an organic chlorine-based compound in exhaust gas, wherein an adsorbent obtained by laminating porous aluminosilicate crystals on the surface of hollow spherical particles A step of adsorbing an organic chlorine-based compound in the exhaust gas and capturing the dust in the exhaust gas by contacting the exhaust gas having an outer dimension of 50 μm or more or a specific gravity of 2 g / cm ³ or more,
Performing a step of discharging the adsorbent that adsorbed the organochlorine compound together with the captured dust, a step of separating the adsorbent and the dust, and an adsorption step of the organochlorine compound using the separated adsorbent The exhaust gas treatment method is characterized by The invention according to claim 4 is a method for removing an organic chlorine compound in exhaust gas,
In a moving layer that is made to be in orthogonal contact with exhaust gas using a granular adsorbent obtained by granulating hollow spherical particles formed by laminating a crystalline body of a porous aluminosilicate on the surface,
A step of adsorbing an organic chlorine compound by contacting exhaust gas with the granular adsorbent and capturing dust, a step of separating the granular adsorbent and the dust that have passed through the moving layer, and the separated granular adsorbent This is a method for treating exhaust gas in which an adsorption step of an organic chlorine compound is carried out using a material.

Hereinafter, the present invention will be described in detail. As shown in FIGS. 1 and 2, an organic chlorine-based compound represented by dioxins is produced by reaction particularly in an exhaust gas treatment line, and its production temperature range is about 300 to 500 ° C. This temperature range is located between the melting point and the 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), and the existence form after the production Is a mixture of a solid phase state, a liquid phase state (mist state) and a gas phase state. In particular, organic chlorine compounds such as dioxins are easily dissolved in oil and are mixed in an oily substance in exhaust gas, and those in a liquid phase have a high affinity with a water-absorbing adsorbent. Also, FIG.
As shown in (1), dioxins are produced from a fly ash precursor such as an aromatic hydrocarbon and a gas phase precursor such as chlorine gas in exhaust gas. Furthermore, after that, it is desorbed from the fly ash to produce gaseous dioxin, or dechlorinated on the fly ash to produce low-chlorinated dioxins,
It may be decomposed on fly ash. Further, once gasified dioxins may be in a liquid phase or solid phase, and dioxins on fly ash may be desorbed as they are in a liquid phase or solid phase. Therefore, in order to efficiently adsorb dioxins, an adsorbent having adsorbability in any of these existing forms is required.

The present inventor has obtained these findings and, on the basis of these, efficiently adsorbs and removes the compound,
In order to suppress the increase in the amount of waste due to exhaust gas treatment, micropores (pore diameter 2 nm or less) excellent in gas adsorption, mesopores (pore diameter 2-50 nm) excellent in adsorption of substances in the liquid phase state.
It was found that it is effective to bring the exhaust gas into contact with the exhaust gas, which is also spherical and has a spherical shape.

That is, the adsorbent effective in the present invention is one in which a porous aluminosilicate crystal is laminated on the surface of hollow spherical particles. Examples of such adsorbents include those obtained by subjecting coal ash to alkaline hot water treatment to elute SiO ₂ and Al ₂ O ₃ from the coal ash and crystallizing it as an aluminosilicate on the surface of the coal ash. Specifically, it is produced by hydrothermal reaction by adding an alkaline solution having a concentration of 1.5 N or more to coal ash containing 10 wt% or more of alumina and the ratio of amorphous alumina in the alumina is 50 wt% or more. Included items. The crystal structure of aluminosilicate has a diameter of 0.4 to 0.5 nm in the crystal structure.
In addition to having micropores of the order of magnitude, as shown in FIG. 5, the crystal body 200 forms a three-dimensional laminated structure having a layer thickness of about 1 μm. Then, these crystal bodies 200
As a result of stacking the
Since it has m mesopores, it has two types of pore size distributions. An example of the pore size distribution of such an adsorbent is shown in FIG.

Further, the skeleton of the adsorbent is composed of hollow spherical particles 220 of coal ash as a raw material, and the particle size of the particles 220 is 2 to several tens of μm, and the particles 220 are cracked. Since there are usually pinholes 240 (see FIG. 5), the surface layer portion has macropores (pore diameter of 50 nm or more) smaller than the particle diameter, and the oil inside the hollow portion of the particle 220 is Aqueous liquid substances can be stored.

The micropores and mesopores of this adsorbent can adsorb gasified organic chlorine compounds such as dioxins. Further, with mesopores, and further with macropores, it is possible to adsorb an organic chlorine-based compound in a liquid phase state, and further capture and remove an organic chlorine-based compound in a solid phase state in the powder adsorbent layer. Further, as shown in FIG. 5, since the surface of the three-dimensional laminated structure of the aluminosilicate crystal 200 is uneven, it is possible to adsorb oily or aqueous substances on the uneven surface.

Such an adsorbent having 2 pore sizes is specifically obtained by the method disclosed in JP-A-59-86687, JP-A-61-90745 and JP-A-61-178416. There is modified coal ash. The modified coal ash is a porous crystalline substance obtained by adding an alkaline solution such as caustic soda to the coal ash and heat-treating it at 70 to 100 ° C., and has a cation exchange function and an adsorption function.

As a method for reforming coal ash to obtain modified coal ash, preferably, for example, (1) when an alkaline aqueous solution is added to coal ash and hot water treatment is performed to reform it into a porous crystalline substance. , The solid-liquid ratio of alkaline aqueous solution and coal ash is 0.5 to
A method of reforming coal ash characterized by stirring and hot water treatment in a range of 3.0 liter / kg (Japanese Patent Application No. 5-107).
No. 090), (2) after adjusting the reaction solid-liquid ratio of the slurry after hot water treatment to 2.5 liter / kg or more, the excess alkaline aqueous solution and the porous crystalline substance are continuously separated. Method for reforming coal ash (Japanese Patent Application No. 5-107090)
No.) etc. Further, as the adsorbent used in the present invention, a granular adsorbent obtained by granulating these adsorbents with a suitable inorganic binder is also suitable. In addition, you may use the modified coal ash obtained by further pulverizing this granulated material.

The adsorbent in the present invention is obtained by subjecting coal ash to an alkaline hot water treatment in this manner. This is because the one having an amorphous structure contained in the coal ash is subjected to an alkaline hot water treatment. The chemical composition is generally MeO.Al ₂ O.
₃ · mSiO ₂ · nH ₂ O (Me is Na ₂ , K ₂ , C
It is an alkali metal or alkaline earth metal such as a, and varies depending on the alkali component used for hot water treatment. ) Is a modified coal ash having a zeolite represented by), and its crystal structure is mainly P-type (phillipsite), but has H-type (hydroxysodalite) structure by changing the concentration of the alkaline aqueous solution. Can also be manufactured. The basicity of the adsorbent is pH 8
It is preferable that it is above. This is because it is also useful for the action of adsorbing and removing hydrogen chloride and the like, which promotes the production of dioxins and the like. Here, the basicity is obtained by mixing the adsorbent 2 with water at a ratio of 5 to form a slurry,
Measured with a meter. The composition of a typical adsorbent is shown below.

[0016]

[Table 1] True specific gravity: Approx. 2.5 Cation exchange capacity: Approx. 200 meq / 100 g Bulk specific gravity: Approx. 0.7 Specific surface area: Approx. 70 m ² / g Average particle size: 10 μm Cation exchange capacity and specific surface area are Schorenberger method and BET method, respectively. Was measured using. Since the adsorbent made from coal ash is cheap and non-combustible, it is more economical and safe than the activated carbon as the adsorbent, and compared to activated carbon that is water repellent. hand,
The adsorbent is hydrophilic, has excellent adsorbability for liquid substances, and is functionally superior.

In the present invention, the adsorbent has the 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. Moreover, since the shape of the adsorbent is spherical, the adsorbent has little ventilation resistance and is excellent as a gas adsorption treatment material.

Further, the present inventors have found that in order to more effectively remove the organic chlorine compound by using this adsorbent and suppress the increase of the amount of waste, the dust in the exhaust gas and the adsorbent are used. It was found that it is important to avoid as much contact as possible. That is, it is effective to carry out the exhaust gas dust collecting step prior to the adsorption of the organic chlorine compound by the present adsorbent. By removing the dust in the exhaust gas in advance, the ventilation resistance of the treatment device is stably maintained at a low level, and the adsorption performance of the organic chlorine compound is exhibited up to the limit of the adsorption amount of the organic chlorine compound of the present adsorbent. As a result, it is not necessary to supply an excessive amount of adsorbent, and an increase in waste amount is suppressed. Specifically, the amount of waste increased by about 40
It is reduced by a factor of 1. Further, 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 device can be stably and continuously operated for 2 weeks or more.

As described above, by disposing this adsorbent in the exhaust gas treatment process after the dust collection process, the dioxins in the gas state, the liquid phase state or the solid phase state after being produced are adsorbed and the dioxins are converted from the exhaust gas. Etc. can be removed. Further, the dust collection of the exhaust gas is not particularly limited to any means as long as it can capture and collect the dust in the exhaust gas, and for example, an electric dust collector or a bag filter can be used.

The concentration of dust in the exhaust gas is 0.5 g / m ³ N
If it does not exceed, it is effective to capture dust in the exhaust gas at the same time as the adsorption step of the organic chlorine compound. When the dust concentration of the exhaust gas does not exceed 0.5 g / m ³ N, that is, when the dust concentration is sufficiently low, the increase of the ventilation resistance of the adsorbent layer due to the dust is suppressed, and the adsorbent of the present invention is used for a long time. Thus, it is possible to simultaneously capture and remove the dust and remove the organic chlorine compound by adsorption. That is, the ventilation resistance is stabilized at a low level, stable operation is possible for a long period of time, the adsorption performance of organochlorine compounds can be exhibited up to the limit of the adsorbent, no excess adsorbent is required, and the amount of waste is reduced. The increase is suppressed. Further, according to this simultaneous removal, in the conventional exhaust gas treatment apparatus capable of carrying out the dust collecting step, it is possible to serve both as the dust collecting step and the organic chlorine compound adsorbing step, without providing new equipment, Efficient removal of organic chlorine compounds and suppression of increase in waste amount are achieved.
In addition, the device is made compact and the processing time is shortened.

The external dimensions of dust contained in the exhaust gas are 50 μm or more, or the specific gravity thereof is 2 g / cm.
^In the case of ³ or more, there is a step of discharging the adsorbent adsorbed the organochlorine compound, together with the dust captured, by separating the dust from the adsorbent, by using this adsorbent, It is effective to carry out the adsorption step of the organic chlorine 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 treatment of the adsorbent and the dust, after adsorbing the organic chlorine-based compound and further adsorbing the trapped dust, the adsorbent is discharged from the exhaust gas treatment step, then, from this mixture, classification, sieving operation, etc. Only the adsorbent is recovered by using the separation method and reused again for the adsorption of the organic chlorine compound in the exhaust gas treatment step. According to this method, before the clogging of the adsorbent layer due to dust occurs, the adsorbent and the trapped dust are separated from the adsorbent, and the adsorbent is reused to adsorb the adsorbent to the limit of the original adsorption amount. It can demonstrate its performance.

When the adsorbent is in the form of granules, it is possible to form a moving layer which makes orthogonal contact with the exhaust gas.
In this case, the granular adsorbent adsorbs the organochlorine compound, and at the same time, dust can be captured in the layer. In the moving bed, the granular adsorbent is moving downward and is discharged together with the dust captured from the lower part of the moving bed, and after separating the dust by classification and sieving operation, the adsorbent is conveyed again above the moving bed. Thus, the granular adsorbent can be easily reused.

Further, in the exhaust gas treatment step, the benzene ring-containing aromatic compound, which is a precursor of dioxins, has a high abundance ratio in the liquid phase. Here, mesopores and macropores can adsorb an oily substance such as an aromatic compound, and further, a chlorine-based substance as a precursor can be adsorbed by micropores. Therefore, by disposing this adsorbent in the exhaust gas treatment step, the above-mentioned precursor can be adsorbed and removed, and the regeneration of dioxins can be suppressed. In addition, unreacted aromatic compounds and chlorine The exhaust gas can be further purified by adsorbing and removing the system compound.

In order to bring the adsorbent into contact with the exhaust gas in the present invention, the adsorbent is adhered to the surface of the filter (filter cloth) of the bag filter device to form an adsorbent layer, and the exhaust gas is adsorbed on the surface of the adsorbent layer. It can be performed by contacting or passing. It is also possible to form a moving layer of the granular adsorbent which is orthogonal to the ventilation direction of the exhaust gas, and bring the granular adsorbent of the moving layer into contact with the exhaust gas.

The temperature of the exhaust gas in the dust collecting process is
It is preferably 120 ° C. or higher and 450 ° C. or lower. The temperature of 450 ° C or lower is often because organic chlorine compounds such as dioxins are present in a liquid state, and it is effective to adsorb in a liquid state, and the heat-resistant temperature of the adsorbent is 500 ° C. Because it is. Further, when the temperature is lower than 120 ° C., the acid gas (SO _x , NO _x, etc.) contained in the exhaust gas has a dew point, and the probability of damaging the exhaust gas treatment equipment increases.

The adsorbent used in the step of removing the organochlorine compound is desorbed from the filter medium and then placed in an incinerator, a melting furnace, a reaction furnace or the like and adsorbed at a high temperature. Can be decomposed.

Here, the organochlorine compound means polychlorodibenzo-p-dioxin (P
Examples thereof include CDD) and polychlorodibenzofuran (PCDF) which is a dibenzofuran.

The exhaust gas referred to in the present invention contains an organic chlorine compound, and a typical example thereof is an exhaust gas when waste or industrial waste is processed in a combustion furnace, a reaction furnace or a melting furnace. You can

[0029]

According to the present invention, the exhaust gas is brought into contact with the adsorbent in which the porous aluminosilicate crystal is laminated on the surface of the hollow spherical particles, so that the organic material in the exhaust gas can be efficiently absorbed by the adsorbent. It is possible to adsorb and remove chlorine compounds and suppress the amount of waste that increases due to exhaust gas treatment.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail based on the embodiments. The adsorbent used in the present invention is a modified coal ash obtained by hot water treatment of coal ash and an alkaline solution.

The raw material coal ash used in the present invention is not particularly limited, and fly ash, clinker ash, coal fuel ash or the like can be used. Such coal ash is, for example, coal ash generated when pulverized coal or the like is burned in thermal power generation or the like, and is collected from the airflow of a flue or the like. Therefore, the particle size of the coal ash at the time of collection is quite small, and it can be used as it is. In order to enhance the reactivity, particles having a particle size of 50 μm or less are usually 98% or more, preferably particles having a particle size of 20 μm or less are 50% or more, more preferably particles having a particle size of 10 μm or less are 4% or more.
It is preferable to adjust the content to 0% or more before use.
When the amount of particles of the coal ash having a particle size of 30 μm or less is 30% or less, the contact area with the alkaline solution is decreased and the reaction efficiency is decreased, so that the crystallization rate is decreased, which is not preferable.

Next, the concentration of the alkali solution whose concentration has been adjusted is not particularly limited, but is usually 1 to 4 N, preferably 1.5 to 3 N, and more preferably 1.8 to 2.
It is in the range of 3N. If the concentration of the alkaline solution is less than 1N, the cation exchange capacity (CEC) of the obtained porous crystal is insufficient, and if it exceeds 4N, the CEC of the obtained porous crystal is obtained. Is sufficient, but the crystalline structure of the porous crystalline material is significantly reduced when it has a phillipsite structure (effective minimum diameter of 4 to 5 angstroms),
The number of those having a hydroxy sodalite structure (effective minimum diameter of 2 to 3 angstroms) is rapidly increased, which makes it difficult to adsorb a gas having a large molecular size, which is not preferable. The type of alkaline solution is not particularly limited, and for example, an aqueous solution of sodium hydroxide, potassium hydroxide or the like can be used.

The coal ash and the alkaline solution are stirred and reacted in a reaction tank at a reaction temperature in the range of 90 to 100 ° C. to obtain modified coal ash as a porous crystal substance. The slurry after the reaction is subjected to solid-liquid separation by the liquid removing device. The drained slurry filter cake is further washed by stirring with washing water. The porous crystalline material-containing slurry after washing is dehydrated,
The solid substance containing the obtained porous crystal product is dried by air drying as it is, and the chemical composition is MeO.Al ₂ O ₃
・ MSiO ₂・ nH ₂ O (Me is Na ₂ , K ₂ , Ca
Alkali metal or alkaline earth metal such as, depending on the type of alkaline solution used. ) A modified coal ash containing zeolite shown by the above) is used as the adsorbent of the present invention. Further, by performing ion exchange using different cation solutions, it is possible to obtain an adsorbent having a crystal structure of various types of aluminosilicate, for example, changing sodium type to calcium type. The cation to be ion-exchanged may be a cation-exchangeable cation regardless of sodium or calcium. The adsorbent can also be granulated with an inorganic binder.

The adsorbent or the granular adsorbent thus obtained can be used in the exhaust gas treatment process of the aeration type fixed bed system or the moving bed system. For example,
As shown in FIG. 6, after the exhaust gas from the incinerator 100 has passed through the bag filter 102 for collecting dust, a bag filter 104 to which the adsorbent is attached and held is provided for adsorbing the organic chlorine compound. it can. According to this exhaust gas treatment method, the dust in the exhaust gas is collected by the bag filter 1 for dust collection.
Since it is excluded by 02, the adsorbent is not clogged with dust. In addition, the adsorption of the organic chlorine compound is similarly performed by a moving bed method using a granular adsorbent.

Further, the dust concentration of the exhaust gas is 0.5 g / m
If it does not exceed ³ N, as shown in Fig. 7, incinerator 1
The present adsorbent can be attached and held on the bag filter 112 for collecting the dust of the exhaust gas from 10, and the adsorbent can be provided to capture the dust and at the same time remove the organochlorine compound. According to this exhaust gas treatment method, it is possible to prevent an increase in the ventilation resistance of the adsorbent layer due to the adhesion of dust, and the adsorption of the organochlorine compound is carried out simultaneously with the capture of the dust for a long period of time.

Further, the external dimensions of the dust contained in the exhaust gas are 50 μm or more, or the specific gravity thereof is 2 g / c.
In the case of m ³ or more, as shown in FIG. 8, the present adsorbent is introduced into the exhaust gas treatment process from the incinerator 120 and brought into contact with the exhaust gas on the surface of the bag filter 122, and at the same time, the dust is captured and the organic chlorine system is used. The adsorbent that has adsorbed the compound can be discharged and collected, the adsorbent and the dust can be separated and removed by the classifying / classifying device 124, and the adsorbent can be recycled for returning to the exhaust gas treatment 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 ventilation resistance due to the dust, and the dust and the organochlorine compound can be used regardless of the dust-containing concentration. Can be simultaneously removed.

When the adsorbent is in the form of granules, as shown in FIG. 9, a moving layer 132 which is orthogonal to the ventilation direction of the exhaust gas from the incinerator 130 is formed to bring the moving layer and the exhaust gas into contact with each other. Then, the organic chlorine-based compound is adsorbed on the granular adsorbent and dust is trapped in this layer. This moving bed can be continuously used by separating the granular adsorbent from the dust by the classifying / sorting device 134 and returning the granular adsorbent to the exhaust gas treatment step again. According to this method, the dust and the organochlorine compound can be simultaneously removed while the ventilation resistance is stabilized at a low level regardless of the dust concentration, and the granular adsorbent can be reused. .

[0038]

Embodiments of the present invention will be described below. The coal ash used in this example has a total Al ₂ O ₃ content of 23 wt.
%, Of which the ratio of amorphous Al ₂ O ₃ is 70
wt% and the average particle size was 10 μm. 100 kg of this coal ash and 210 L of 2N sodium hydroxide aqueous solution adjusted to 100 ° C. are charged into a reaction tank, and the reaction temperature is set to 1
The temperature is set to 00 ° C., the mixture is stirred and boiled by the stirrer in the reaction tank,
From coal ash, the chemical composition is mainly Na ₂ O ・ Al ₂ O ₃・
3.5SiO went ₂ · 4.5H ₂ O with P type shown (Philip site) porous crystalline material serving 5 hours the reaction for reforming to the reforming coal ash having a crystal structure of the.

The slurry containing the porous crystal substance after the hot water treatment was drained, and the obtained filter cake was washed in a water washing tank and then dehydrated to obtain a solid substance containing the porous crystal substance. Calcium chloride corresponding to a weight ratio of 15 wt% was added to this solid matter, and further 5 times the amount of water was added to form a slurry,
After stirring and reacting for 2 hours, the liquid was removed, washed with water, and dehydrated to obtain a Ca-type porous crystal-containing solid. further,
This solid was dried at 130 ° C. to obtain a powder of an adsorbent of hollow spherical particles having Ca-type zeolite porous crystals laminated on the surface.

The obtained powder particles had a three-dimensional laminated structure in which crystals of calcium type zeolite (calcium aluminosilicate) were deposited on the surface of hollow spherical particles having a diameter of about 10 μm. And, on the surface of the hollow spherical particles,
In addition to the occurrence of cracks and pinholes, it had mesopores with a diameter of 2 nm formed by a laminated structure of zeolite crystal particles and micropores with a diameter of 0.5 nm based on the crystal structure of zeolite. The powder was actually incinerated by a device having a schematic configuration 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 device includes an incinerator 10, a cooler 12, a dust collecting bag filter 14, and a suction device 16.
And a bag filter 18 for removing organic chlorine compounds, which is an exhaust gas treatment device, cools high-temperature exhaust gas discharged from the incinerator 10 with a cooler 12, and sends it to a bag filter 14 as a dust collector to remove dust. The exhaust gas that has been captured and removed and that has passed through the bag filter 14 is further subjected to PCDD and P with the adsorbent of this embodiment in the bag filter 18.
It is intended to adsorb CDF. A tubular body was disposed inside the bag filter 18, and the adsorbent was held by spraying the adsorbent on the filter cloth wrapped around the tubular body. The material of the filter cloth was heat-resistant nylon.

The adsorption test was conducted under the following conditions [Test conditions] Removal bag filter adsorption layer area: 10.8 m ² Adsorbent amount: 20 kg Treated air flow rate: 10 m ³ / min The gas temperature characteristics are as follows. It was as it was. [Gas temperature characteristics] Dust collection bag filter inlet: 250 ° C Dust collection bag filter outlet: 120 ° C Organic chlorine-based compound removal bag filter inlet: 100 ° C Organic chlorine-based compound removal bag filter outlet: Approximately 60
Constant at ℃ Analysis of dioxins and dibenzofurans
It was conducted in accordance with "Manual for measuring and analyzing dioxins in waste treatment" issued by the Waste Research Foundation.

Table 2 shows the results of the test.

[Table 2] ND: Less than detection limit (0.033 ng / m ³ _N or less) TEQ: 2,2,7,8-T ₄ CDD Toxic equivalent concentration, conversion factor is described in the above-mentioned “Manual for measurement and analysis of dioxins in waste treatment” by.

From this result, the following is clear. That is, the bag filter 1 in this test device
In the exhaust gas after 4, bag filter 18 for removal
Although PCDD and PCDF were detected at the entrance of the above, at the exit of the removal bag filter 18, the detection was below the detection limit for all kinds of substances. From this result, in the exhaust gas after the bag filter 18 in this test apparatus, almost 100% of PCDD and PCDF were removed. That is, as shown in FIG. 10, most of PCDD and the like, as well as its low-chlorinated products, which are produced on fly ash and are still attached, are attached to the bag filter together with the fly ash and are contained in the exhaust gas. PCDD which is dispersed and gasified, or PCDD in liquid state after gasification
Further, some of the PCDD and the like still attached to the fly ash passed through the bag filter and were adsorbed and removed by the adsorbent attached to the filter cloth in the tester.

Further, in this bug filter 18,
The temperature of the exhaust gas is 100 ° C., and in this temperature range, dioxins are below the melting point.
The vapor pressure of 2,3,7,8-TCDD is 10 ^-4 mmHg, and it is known that it exists not only in the liquid or solid phase but also in the gas during the process. That is, since this adsorbent can adsorb any existing form of dioxins and the like, it is possible to remove dioxins and the like from the exhaust gas that has passed through the bag filter 14 with high efficiency.

Further, in the present embodiment, since the removal of dioxins and the like from the exhaust gas is performed on the exhaust gas that has undergone the dust collecting step, early blockage due to dust in the adsorbent layer formed on the bag filter 18 is observed. However, the adsorption activity of the adsorbent was maintained for a long period of time, and the dioxins and the like were efficiently adsorbed. As a result, the service life of the adsorbent becomes more than 15 days, generated gas amount is 100,000 m ³
Even when it was used in an incinerator of / hr, the amount of increase in waste due to the removal of organochlorine compounds was reduced to about 4 tons / month.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a refuse incinerator and a production region of an organic chlorine compound in an exhaust gas treatment process thereof.

FIG. 2 is a diagram showing a production temperature range of an organochlorine compound in an exhaust gas treatment process.

FIG. 3 is a diagram showing a mechanism of generation of dioxins in an exhaust gas treatment process.

FIG. 4 is a diagram showing a pore size distribution of an adsorbent.

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

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

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

FIG. 8 is a diagram showing an outline of 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 a device configuration of an example.

Front page continuation (72) Inventor Masao Yatsushiro 1-5-7 Kameido, Koto-ku, Tokyo Industrial Promotion Co., Ltd. (72) Toshiyuki Higuchi 1-9-3 Minamienkajima, Taisho-ku, Osaka, Osaka Osaka Steel Co., Ltd. (72) Inventor Masayuki Tsuchida 1-3-9 Minami Enkajima, Taisho-ku, Osaka City, Osaka Prefecture Osaka Steel Co., Ltd.

Claims (4)

[Claims] 1. A method for removing an organochlorine compound in exhaust gas, which comprises performing a dust collecting step of exhaust gas, and further laminating a porous aluminosilicate crystal on the surface of hollow spherical particles. A method for treating exhaust gas, comprising the step of adsorbing an organic chlorine-based compound in the exhaust gas by contacting the adsorbent with the exhaust gas that has undergone the dust collection step. 2. A method for removing an organochlorine compound in exhaust gas, wherein an adsorbent comprising a porous spherical aluminosilicate crystal layer laminated on the surface of hollow spherical particles has a dust-containing concentration of 0. By adsorbing the exhaust gas not exceeding 5 g / m ³ N, the organic chlorine compound in the exhaust gas is adsorbed, and
A method for treating exhaust gas, which comprises capturing dust in the exhaust gas. 3. A method for removing an organochlorine compound in exhaust gas, comprising an adsorbent comprising a hollow spherical particle surface on which a porous aluminosilicate crystal is laminated, and the external shape of dust in the exhaust gas. A step of adsorbing an organic chlorine-based compound in the exhaust gas and capturing dust in the exhaust gas by contacting the exhaust gas with a size of 50 μm or more or a specific gravity of 2 g / cm ³ or more, and adsorbing the organic chlorine-based compound And a step of discharging the adsorbent, together with the dust that is captured, and a step of separating the adsorbent and the dust.
A method for treating exhaust gas, which comprises performing an adsorption step of an organochlorine compound using the separated adsorbent. 4. A method for removing an organic chlorine compound in exhaust gas, which comprises using a granular adsorbent obtained by granulating hollow spherical particles having a porous aluminosilicate crystal layer laminated on the surface thereof. In a moving bed that is made to be in orthogonal contact with the exhaust gas, a step of adsorbing an organic chlorine compound and capturing dust by bringing the exhaust gas into contact with the granular adsorbent, and a granular shape passing through the moving bed A method for treating exhaust gas, which comprises a step of separating an adsorbent and a dust and an adsorbing step of an organochlorine compound using the separated granular adsorbent.