JP3036522B2 - Dioxin adsorption removal equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dioxin adsorption and removal apparatus, and more particularly to an adsorption and removal apparatus for easily removing dioxins and the like from exhaust gas of an incinerator by effectively utilizing artificial zeolite.

[0002]

2. Description of the Related Art Dioxin is a common name for polychlorinated dibenzoparadioxin (PCDD _S ), and there are eight homologs and 75 isomers depending on the number and position of chlorine substitution. Of these, 2,3,7,8-4 dibenzoparadioxin chloride (2,3,7,8-T ₄ CDD) has the strongest toxicity. Polychlorinated dibenzofuran (PCDF _S ) is a compound having a similar structure and properties, and there are eight homologs and 135 isomers depending on the number and position of chlorine substitution. Generally, dioxins and furans are collectively referred to as dioxins, but it is widely known that dioxins have strong acute toxicity. The toxicity of this dioxin varies greatly between homologues and isomers, so the most toxic 2,3,7,8-T ₄ CD
The toxicity is evaluated as the total amount by converting to the toxicity of D. The relative value with the toxicity of 2,3,7,8-T ₄ CDD as 1 is the Toxicity Equivalent Conversion Factor (TEF).
The sum of the values obtained by multiplying the respective TEFs is called a toxicity equivalent concentration (TEQ) and is used as an index of toxicity.

[0003]

It is known that such dioxins are also generated from incinerators for general and industrial wastes, and various companies have various methods for removing dioxins generated from incinerators. Proposed. However, to realize these methods in a small incinerator, there is a problem in terms of cost, so that it is unlikely to be put into practical use. In the end, there is a social demand to reduce the emission of dioxins. There is no fact. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dioxin adsorption and removal apparatus which is small and inexpensive, and is particularly suitable for application to a small incinerator. .

[0004]

In order to achieve the above-mentioned object, a dioxin adsorption and removal apparatus according to the present invention comprises a pre-cooling method for exhaust gas from an incinerator by air cooling or water cooling .
A cooling unit for viewing, and a suction portion for passing the exhaust gas from the cooling unit into granules of artificial <br/> zeolite incorporated in the cartridge, the suction portion is about 0.99 ° C. to 180 ° C.
Has been maintained . As the zeolite, it is preferable to use an artificial zeolite obtained by mixing fly ash with an aqueous alkali solution and heating the mixture to about 90 ° C. Here, the alkali is preferably sodium hydroxide NaOH.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The feature of the present invention resides in that zeolite is used as an adsorbent for dioxins. _{Zeolite, X m Y n O 2n ·} SH 2 O (X = Na, Ca, K
(Y = Si + Al, S is undefined), but in the present invention, it is preferable to use an artificial zeolite instead of a natural zeolite or a synthetic zeolite. The artificial zeolite refers to a zeolite synthesized using coal ash or the like as a raw material, and is distinguished from a synthetic zeolite that requires a somewhat pure raw material (silicic acid, aluminum hydroxide, or the like). This artificial zeolite contains organic products such as intermediate products and activated carbon that have not been converted into zeolite, and the content and crystallinity of pure zeolite are located between synthetic zeolite and natural zeolite. . However, artificial zeolites not only have the advantage of being less expensive than synthetic zeolites (equal to or less than natural zeolites), but also have the adsorbing performance and surface acidity due to impurities (intermediate products and unburned carbon) contained. It has useful properties such as: Further, the cation exchange capacity is equal to or about three times that of natural zeolite.

As the artificial zeolite, a commercially available one may be used, but the use of one manufactured from fly ash is advantageous in terms of cost. As fly ash, incinerated ash such as coal and pulp is preferable in that it does not include miscellaneous ash. However, incinerated ash of general waste or industrial waste can also be used. When producing an artificial zeolite, first, fly ash and a NaOH aqueous solution (normality 2.5
N to 3.5N) at about 90 ° C for 12 to 28 hours. Thereafter, calcium chloride CaCl ₂ is reacted for about 2 hours to replace Na with Ca. Then, if the powder is dried after washing with water, Ca-type artificial zeolite is produced. It should be noted that the product produced by this treatment should be called an alkali-treated product of coal ash containing zeolite.

[0007] In order to adsorb hydrogen chloride gas in the exhaust gas, it is preferable to add a Ca compound to the above-mentioned Ca-type artificial zeolite. After mixing both, the mixture is formed into a granular or cylindrical shape with a binder made of an organic or inorganic substance. Just do it. Ca compounds include, for example, calcium hydroxide C
a (OH) ₂ and calcium oxide CaO, the amount of which depends on the amount of hydrogen chloride HCl gas in the exhaust gas.
% To about 20% by weight. For example, when the amount of HCl gas is small, the content of the Ca compound is about 5%, and when the amount of HCl gas is large, 1%.
It is about 5%.

[0008] The particle size of the adsorbent is not particularly limited, but is usually about 2 mmφ to 5 mmφ. In addition, when the amount of exhaust gas is small and pressure loss becomes a problem, 5 mmφ ~
It may be set to 10 mmφ. The operating temperature of the adsorbent is 100 to 2 in consideration of the adsorption performance of the Ca-type artificial zeolite, the resynthesis of dioxin, and the corrosion temperature of the device.
The temperature is preferably set to 50 ° C, preferably 120 to 200 ° C, and more preferably about 150 to 180 ° C. The temperature of the exhaust gas from the incinerator is usually 800 to 1000 ° C.
It is necessary to pre-cool to about 50 ° C.

When the adsorption performance of the adsorbent deteriorates due to use, it is necessary to replace the adsorbent. However, since the small incinerator incinerates garbage in a batch process, the adsorbent is replaced when not operating. In consideration of the work at this time, it is preferable to store the adsorbent in an appropriate cartridge. Dioxins and the like are adsorbed on the recovered adsorbent, and if this is discarded as it is, the problem of environmental pollution arises again. Therefore, the recovered adsorbent is heated at 90 ° C.
NaOH or KOH aqueous solution (2.5N ~
3.5N) and 10-20% by weight of alcohol,
The dioxins are decomposed by reacting for about an hour, but the adsorbent of the present invention has an advantage that artificial zeolite is resynthesized by this treatment. In order to realize the decomposition of dioxins and the resynthesis of artificial zeolite, it is sufficient to use 8 to 15 parts by weight or more of alkali alcohol per 1 part by weight of the adsorbent. It is preferable to use methanol or ethanol as the alcohol. Note that N
It has been explained using the NaOH, KOH, etc. NH ₄ OH, or NaOH and NH ₄ OH or KOH and NH ₄ O
A mixed solution such as H may be used. The artificial zeolite thus re-synthesized can be reused as a material for the adsorbent.

By the way, dioxins generated from incinerators and the like include gaseous or gaseous dioxins and particulates contained in dust and the like. Therefore, it is preferable to provide a filter section for capturing the passing fine particles in the flow path of the exhaust gas. Here, the filter section should preferably be provided on the downstream side of the adsorbing section, and is preferably one capable of capturing fine particles having a particle diameter of about 0.1 μm or more. With such a configuration, dioxins in a gaseous state are removed by the adsorption section made of zeolite, and dioxins contained in dust and the like are removed by the filter section. In addition, as a material for forming the filter portion, Teflon fiber, glass fiber, cellulosic fiber, ceramic, or the like can be used.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. FIG. 1 illustrates a configuration in which exhaust gas generated from a small combustion furnace 1 is supplied to an adsorption and removal device 2 to adsorb and remove dioxins and the like in the exhaust gas. This adsorption and removal apparatus 2 treats exhaust gas from a small incinerator 1 having an incineration capacity of less than 5 t / day, and dioxins and the like discharged from the incinerator 1 are adsorbed by a built-in artificial zeolite cartridge. It has become so. FIGS. 2 and 3 show a schematic configuration of the adsorption removing device 2, and are respectively a plan view (FIG. 2A), a right side view (FIG. 2B), and a front view (FIG. 3). Is shown.

The adsorbing and removing apparatus 2 is constituted by connecting a cooling tower 3 for spraying atomized water to the exhaust gas to be introduced and an adsorption tower 4 for removing dioxins from the exhaust gas. Exhaust gas is circulated by the blower 6 and the backup blower 8. Exhaust gas from the small incinerator 1 is introduced from the inlet 3a of the cooling tower 3 and moves vertically downward. At this time, the exhaust gas is cooled by cooling water injected from the spray nozzle 5. The cooled exhaust gas is supplied to a blower 6
The exhaust gas pushed out toward the adsorption tower 4 by the (induction type draft fan IDF) and introduced into the adsorption tower 4 passes through the artificial zeolite cartridge 7 and is discharged from the outlet 4a of the adsorption tower 4. Dioxins in exhaust gas (PC
DD _S and PCDF _S ) are adsorbed on the artificial zeolite layer while passing through the artificial zeolite cartridge 7.
A temperature sensor (not shown) is arranged at the center of the zeolite layer, and is controlled so that the temperature of the passing exhaust gas is maintained in a predetermined range. Specifically, the spray amount from the spray nozzle 5 is controlled according to the output value of the temperature sensor.

Next, a description will be given of practical data using the adsorption and removal apparatus 2 shown in the figure. In the small incinerator 1, vinyl chloride resin PVC (10% by weight) was added to cardboard (90% by weight) and burned, and the concentration of the generated exhaust gas was measured several times.
1% and carbon dioxide 1 to 8%. Also, HCl gas concentration 250~1300ppm, SO _X concentration 1:10
It was 00 ppm. Such exhaust gas is directly discharged from the small incinerator 1 (A), the inlet 3a of the cooling tower 3
(B), outlet (C) of blower 6, outlet 4a of adsorption tower 4
The dioxin concentration was measured for the four exhaust gases in (D). At this time, the measurement was performed three times each by changing the flow rate of the exhaust gas and the internal temperature of the adsorption tower 4. The adsorbent used was 85% artificial zeolite, calcium oxide CaO
Mix 15%, harden with binder and 2mmφ ~ 5mmφ
It is made into a granular form. Note that, as the artificial zeolite, a Ca-type artificial zeolite produced from coal ash by the method described above was used.

[0014]

[Table 1]

Table 1 shows that when the internal temperature of the adsorption tower 4 is controlled at 150 to 180 ° C. and when the internal temperature of the adsorption tower 4 is controlled at 250 ° C. to 300 ° C. under the condition of SV = 1000 / h, 3
The result of the measurement is shown. When the temperature of the adsorption tower 4 is 150 to
When controlled at 180 ° C., the removal rate of dioxin was 99.03% on average, but when controlled at 250 ° C. to 300 ° C., it was evident that it decreased to 88.5% on average. . The SV (space velocity) is 1000, and an exhaust gas having a volume 1000 times the volume of the artificial zeolite cartridge is circulated per hour.

[0016]

[Table 2]

Table 2 shows the results of three measurements in the case where the same experiment was performed under the condition of SV = 5000 / h. When the internal temperature of the adsorption tower 4 is controlled at 150 to 180 ° C., the dioxin removal rate is 99.1% on average.
However, when the temperature was controlled at 250 ° C. to 300 ° C., it was found that the average was reduced to 89.5%. In addition,
In the experiments in Tables 1 and 2, the oxygen concentration in the exhaust gas was 12%. From the above results, the flow rate of the exhaust gas was 1000 to
There is no problem at about 5000 / h.
It is thought that it will be about 5000 / h. The temperature of the artificial zeolite layer is 100 to 250 ° C without any problem, preferably 120 to 200 ° C, more preferably about 150 to 180 ° C. In addition,
At 250 ° C. or higher, it is expected that the amount of adsorption will decrease due to the decrease in physical adsorption.

[0018]

[Table 3]

[0019] Table 3 shows the result of measuring the removal rate of the HCl gas and SO _X, HCl gas contained in the original flue gas is 80-90% adsorbed on calcium oxide CaO
It was confirmed that the degree was removed. It was also confirmed that the SO _X component was removed by 90% or more by washing with water and adsorbing zeolite. Since the adsorption performance for HCl and SO _X deteriorates faster than the adsorption performance for dioxins, the replacement time of the artificial zeolite cartridge can be determined based on the amount of SO _X discharged.

[0020]

[Table 4]

Table 4 shows measurement data confirming that the used artificial zeolite can decompose dioxin by the method of the present invention. This measurement data shows the result of throwing used artificial zeolite into a NaOH alcohol solution and reacting for several hours while stirring at 90 ° C. Reaction time 1 hour, 2
The TEQ removal rate is calculated every time the time changes from 3 hours to 3 hours.
The Q removal rate is calculated. According to this result, it was confirmed that the artificial zeolite can be resynthesized by reacting with a NaOH alcohol solution having a normality of 2.5N to 3.5N for about 3 hours. In addition, it was recognized that the zeolite whose surface had collapsed also recrystallized.

FIG. 4 shows a processing cycle of production and maintenance of the adsorbent used in the present invention. First, fly ash is collected from the incinerator, and is then formed into artificial zeolite by the method described above. Specifically, it is mixed with an aqueous NaOH solution (2.5 to 3.5 N),
After reacting for 12 to 28 hours under heating (90 ° C.), react with CaCl ₂ for 2 hours, then wash with water and dry. Then, when an appropriate amount of Ca (OH) ₂ is added and solidified with a binder, an adsorbent (a zeolite cartridge) used in the present invention is produced. In addition, since slaked lime is used in the incinerator, when fly ash contains a large amount of slaked lime (for example, 20% or more), the fly ash collected from the incinerator is first converted to HCl. React to C
The component a is removed. After removing CaCl ₂ by washing with water, fly ash is mixed with an aqueous NaOH solution (2.5 to 3.5 N) and reacted under heating (90 ° C.) for 12 to 28 hours to produce an artificial zeolite.

By the way, from actual incinerators, not only gaseous substances but also dioxins contained in dust and the like are generated to a considerable extent. Is
It became clear that dust and the like could not be captured sufficiently and these were discharged together with dioxins. That is, gaseous dioxins can be removed almost 100% by the artificial zeolite cartridge 7. However, depending on the type of incinerated material in the incinerator and the state of filling of the artificial zeolite, dioxins contained in dust and the like are directly discharged. Was sometimes done. Therefore, in another embodiment of the present invention, as shown in FIG. 5, a filter section 9 is provided on the downstream side of the artificial zeolite cartridge 7 and a blower 6 (induction type draft fan I
DF). Further, the auxiliary blower 8 is operated as necessary, for example, to prevent backflow of the exhaust gas. When the preliminary blower 8 is operated, the temperature of the exhaust gas can be further lowered by the supplied outside air. As the filter unit 9, a filter made of Teflon fiber, glass fiber, cellulosic fiber, or a ceramic filter can be used. However, if a filter capable of capturing fine particles having a particle diameter of about 0.1 μm or more can be obtained, excellent effects can be obtained. Obtained. The filter material capable of capturing fine particles of about 0.1 μm or more is attached to the end of the adsorption tower 4 in a state of being housed in a container, and can be replaced as needed.

[0024]

As described above, in the present invention, dioxins are adsorbed and removed using zeolite.
It is possible to realize a dioxin adsorption and removal apparatus which is small and inexpensive and is suitable for application to a small incinerator. That is, according to the present invention, the Ministry of Health and Welfare guidelines (5ngTEQ
/ Nm ³ ) can be realized.

[Brief description of the drawings]

FIG. 1 illustrates an example of use of an adsorption and removal apparatus according to the present invention.

FIG. 2 is a plan view (a) and a right side view (b) of an example of the adsorption removal device.

FIG. 3 is a front view of the adsorption and removal apparatus shown in FIG. 2;

FIG. 4 illustrates a zeolite cartridge manufacturing and maintenance processing cycle.

FIG. 5 illustrates another embodiment of the adsorption removal device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Small incinerator 2 Adsorption removal apparatus 3 Cooling part (cooling tower) 4 Adsorption part (adsorption tower)

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Nakamura 7-7 Horie-cho, Matsuyama-shi, Ehime Miura Industrial Co., Ltd. (72) Inventor Tadaaki Wakimoto 4-15-19 Tarumi, Matsuyama-shi, Ehime (56) Document JP-A-10-249138 (JP, A) JP-A-9-75667 (JP, A) European Patent Application Publication 666098 (EP, A2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53/70 B01D 53/34 B01D 53/81

Claims (4)

(57) [Claims] 1. Exhaust gas from an incinerator is air-cooled or water-cooled
A cooling unit which only pre-cooled by, incorporated in the cartridge
And an adsorbing section for passing the exhaust gas from the cooling section to the granular artificial zeolite, wherein the adsorbing section has a temperature of 150 ° C.
An adsorption and removal device for dioxins, which is maintained at about 180 ° C. 2. The cooling unit according to claim 1, wherein water is sprayed.
Item 2. The adsorption removal device according to Item 1. 3. The adsorption removal apparatus according to claim 1, wherein the zeolite is an artificial zeolite obtained by mixing fly ash with an alkaline aqueous solution and heating the mixture to about 90 ° C. 4. The zeolite has a particle size of at least 2
The diameter is not less than mmφ.
3. The adsorption removal device according to item 1.