JP3037688B1 - Dioxin adsorption removal method using porous fired body - Google Patents

Abstract

A method for adsorbing and removing dioxins contained in exhaust gas discharged from a refuse incinerator is provided. SOLUTION: The water content of a) a combustible organic substance, b) a clay mineral as a binder, and c) zeolite, calcium carbonate, or a powdery inorganic waste containing any of them is previously determined. Is mixed at a ratio of 2 to 20 parts by weight of component b) and 0.3 to 8 parts by weight of component c) with respect to 100 parts by weight of component a) adjusted to be 70%. , Components b and c are uniformly coated, heated to 600 to 700 ° C. using a rotary kiln to cause self-combustion, then fired by self-combustion, and a ceramic layer is formed on the surface of carbon generated by carbonization. Is formed, and the obtained fired product is finely pulverized (Step A), and the obtained porous fired body is blown into exhaust gas transferred from a garbage incinerator to a dust collector, and the fired material is mixed with dust in the exhaust gas. The body is separated and removed from the exhaust gas (step B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adsorbing and removing dioxin contained in exhaust gas discharged from a refuse incinerator using a porous fired body.

[0002]

2. Description of the Related Art Recently, dioxin (polychlorinated dibenzo-p-dioxin, PC
Environmental pollution due to DD) has become a major social problem, and regulations on dioxin concentration in exhaust gas discharged from refuse incinerators are being strengthened. Therefore, in the case of a new furnace, it is equipped with the latest equipment for removing gas and soot containing dioxin, but in the case of an existing furnace, in order to suppress the generation of dioxin,
It is necessary to take measures such as continuously operating the furnace at a high temperature (for example, 850 ° C. or higher), and at present, there is almost no proposal for a method capable of effectively removing dioxin under existing processing conditions.

Conventionally, in the manufacture of activated carbon, some combustibles such as wood (thinned wood) and sawdust have been used. However, agricultural products such as thinned wood chips, sawdust and fir husks have been used. Most of residues such as residues and coffee have been disposed of or disposed of by incineration, and it is desired to reuse such organic waste from the viewpoint of environmental problems. At present, waste chips generated in large quantities at construction sites, punched paper chips, waste paper pulp, bamboo chips, and the like generated from semiconductor-related factories are also disposed of or incinerated. Therefore, recently, as one of recycling of flammable organic substances such as fir husks, Japanese Patent Application Laid-Open No. H10-19486 has been proposed.
No. 5 discloses that charcoal with improved adsorption to harmful organic gases is used for combustible organic substances such as wood and fir husks.
A porous fired body manufactured by adding bentonite containing SiO ₂ and Al ₂ O ₃ as main components and performing firing is disclosed. However, a fired product modified (functionality improved) by further adding components other than clay minerals such as bentonite has not been proposed. The functionality is not disclosed.

[0004] Further, similarly to the above-mentioned organic waste, inorganic wastes such as dust generated from a crushed stone plant and shells generated from a food processing plant can be procured at low cost, but their effective use is possible. The law has hardly been found, and most of them have been disposed of. Currently, there is a demand for the reuse of these inorganic wastes from the viewpoint of environmental problems.

[0005]

SUMMARY OF THE INVENTION The present invention relates to organic wastes such as thinned wood chips and fir hulls, and zeolites or calcium carbonate-containing inorganic materials such as quarry sludge and shell crushed materials that have been hardly used until now. Provide a method that can recycle system waste and effectively adsorb and remove dioxins contained in exhaust gas discharged from garbage incinerators by using fired bodies obtained from these wastes The task is to The present inventor has conducted various studies to solve the above problems, and as a result, when carbonizing and burning a combustible organic substance in a rotary open furnace, a clay mineral (kaolinite,
Zeolite, along with halloysite, bentonite, etc.)
Calcium carbonate, and a powdered additive selected from the group consisting of zeolite or calcium carbonate-containing inorganic waste is blended, fired, and then finely pulverized to obtain a porous fired body, which is then incinerated. When blown into the exhaust gas on the way from the furnace to the dust collector, dioxin contained in the exhaust gas is efficiently adsorbed by the porous fired body, and this porous fired body is removed from the exhaust gas by the dust collector together with the dust in the exhaust gas. It has been found that dioxin can be effectively removed from exhaust gas by separation and removal, and the present invention has been completed.

[0006]

The dioxin adsorption and removal method of the present invention is a method of adsorbing and removing dioxin contained in exhaust gas discharged from a garbage incinerator by a porous fired body. : A) a combustible organic substance, b) a clay mineral as a binder, and c) a powdered additive selected from the group consisting of zeolite, calcium carbonate, and inorganic waste containing zeolite or calcium carbonate. The mixture was mixed at a ratio of 2 to 20 parts by weight of the clay mineral and 0.3 to 8 parts by weight of the powdery additive with respect to 100 parts by weight of the flammable organic substance previously adjusted to have a water content of 70%. Then, after uniformly covering the surface of the flammable organic material with the clay mineral and the powdery additive, 600 to 700 ° C. using a rotary kiln.
To produce self-combustion, followed by self-combustion and firing to obtain a fired product in which the surface of carbon generated by carbonization of the flammable organic substance is coated with a ceramic layer, and then the fired product is ground. And a step of producing a porous fired body having a particle diameter of 90% or more and 200 μm or less, and step B: transferring the porous fired body obtained in the above step A from a refuse incinerator to a dust collector. Blowing the exhaust gas to be transferred, adsorbing dioxin contained in the exhaust gas to the porous fired body, and separating and removing the porous fired body from the exhaust gas together with the dust in the exhaust gas by the dust collector. It is characterized by.

Further, in the present invention, in the above method for adsorbing and removing dioxin, the blowing amount of the porous fired body in the step B may be from 50 to 1 Nm ^{3 of the} exhaust gas.
It is also characterized by being 1000 mg. Further, the present invention is characterized in that in the above-described method for removing and adsorbing dioxin, the porous fired body has an average pore diameter of 20 to 60 °. In addition, the present invention provides the method for removing and adsorbing dioxin, wherein the combustible organic substance contains thinned wood chips, construction waste chips, coffee residue,
Fir hulls, punched paper pieces, waste paper pulp and bamboo chips, wherein the clay mineral is one selected from the group consisting of kaolinite, halloysite and bentonite. is there.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, each component as a raw material for producing a porous fired body used as an adsorbent in the dioxin adsorption and removal method of the present invention will be described. The flammable organic substance used as the component a in the production of the porous fired body capable of effectively adsorbing and removing dioxin (Step A) contains a carbon component, has a solid flammability, and when fired. Any material that changes to carbide may be used, but those that are granular before firing are preferred, and particularly preferred are thinned wood chips, construction waste chips, coffee residue, fir husks, punched paper chips, waste paper pulp, and bamboo chips. The advantages and disadvantages of using these flammable organic substances are as follows. (1) Thinned wood chips Although procurement costs are relatively high, unused wood resources can be used effectively. (2) Construction waste chips Stable procurement is possible, and procurement costs are almost negligible. (3) Coffee residue The particle size is small and uniform, and the procurement cost is low. (4) Fir husk Although stable procurement is difficult, it is inexpensive and contains a large amount of SiO ₂ components. (5) Punched paper pieces Uniform particle size, low procurement cost, and contain inorganic components. (6) Waste paper pulp The procurement cost is low, it is fibrous, and it can be pelletized. (7) Bamboo chip It has electrical conductivity, and it is easy to collect with an electrostatic precipitator.

The clay mineral used as the component b is
Acting as a binder,
Various substances containing iO ₂ and Al ₂ O ₃ as main components can be used, and examples thereof include bentonite, halloysite, and kaolinite. Among them, in terms of an excellent effect of suppressing the oxidation of the combustible organic substance, Bentonite is preferred, and the main mineral of the bentonite is montmorillonite.

[0010] Further, the powdery additive used as the component c is added to improve the dioxin adsorption performance of the porous fired body obtained by firing,
Zeolite, calcium carbonate, and selected from the group consisting of zeolite or calcium carbonate-containing inorganic waste;
The properties and functions of the fired bodies obtained by the respective physical properties and the additions are as follows.

(I) Zeolite A zeolite is a natural porous mineral mainly composed of hydrated alumina silicate, and its particle size is suitably 25 to 300 μm, and particularly preferably 50 to 150 μm. Further, those having a specific surface area of 5000 cm ² / g or more are used.
It is preferably at least 00 cm ² / g. The fired body obtained by adding zeolite is particularly excellent in porosity, and has a large dioxin adsorption performance due to its porous structure. In the present invention, a high-temperature vitrified zeolite can be used.

(Ii) Calcium carbonate A powder having a purity of 90% or more, preferably 99% or more. The calcined product obtained by adding calcium carbonate generally shows strong alkalinity of pH 11 or more, and has a slightly lower dioxin adsorption property than the calcined product obtained using zeolite, but carbon produced by carbonization of flammable organic substances. ceramic layer coated on the surface comprises calcium oxide or calcium carbonate, they show the advantage of the reaction or removed by adsorbing them as HCl and SO _x present in the exhaust gas.

(Iii) Inorganic waste containing zeolite or calcium carbonate (quarry sludge, shell crushed material, etc.) Examples of the quarry sludge (crushed dust generated in a quarry plant) include hard sandstone, rhyolite, and quartz porphyry. Is suitable to contain a porous mineral such as zeolite or vermiculite as a main component, and has a specific gravity of 2.0 to 3.0.
0, preferably 2.5 to 2.7, and the particle size is 25 to 3
00 μm is suitable, and 50 to 150 μm is particularly preferred. The specific surface area is at 1100 cm ² / g or more, preferably at least 5000 cm ² / g, excellent adsorption performance by the above-mentioned porous mineral is shown. In addition, the fired body obtained by adding the quarry sludge is extremely cheap (about 3 to 50 yen) compared with bentonite (market price about 30 to 50 yen / kg).
5 yen / kg), which can reduce the cost by 70% or more compared to the case where only bentonite is used. In addition, the crushed shell material contains a large amount of calcium component and can be used in place of the calcium carbonate described above. Like quarry sludge, it can be procured at low cost (about 10 to 20 yen / kg), and only bentonite is used. 4 compared to when
Cost reduction of 0% or more can be achieved. The specific gravity and the particle size of the preferable shell crushed product are the same as those of the above-mentioned quarry sludge.

The compounding ratio of the component b (clay mineral) and the component c (powder additive) with respect to the component a (flammable organic substance) is determined in advance so that the water content is 70%. 2 to 10 clay minerals per 100 parts by weight of organic matter
Parts by weight, preferably 3 to 5 parts by weight, powdery additives 1 to 8
Parts by weight, preferably 5 to 7 parts by weight.

Next, step A in the method of the present invention, that is, a process for producing a fired body having a ceramics layer formed on a carbon surface formed by carbonization of a flammable organic substance using the above-described components a to c, The steps will be described. First, 100 parts by weight of combustible organic matter such as thinned wood chips and construction waste chips (having the water content of the chips adjusted to about 70% by weight, preferably about 60 to 80% by weight) are mixed with the clay mineral. 2 to 20 parts by weight and a powdery additive are added at a ratio of 0.3 to 8 parts by weight, and then kneaded by a kneader,
The surface of the combustible organic material is uniformly coated with the clay mineral and the powdery additive. In the present invention, the surface of the flammable organic material,
Coating of clay minerals and powdered additives is carried out in the presence of water, when adjusting the water content, when the original combustible organic matter has low moisture, such as thinning wood chips and fir shells Although the addition of water is necessary, the addition of water is not necessary in the case of raw materials containing much water, for example, coffee residue.

Then, the pulverized material whose surface is coated in this manner is transferred to a rotary kiln (rotary carbonization furnace) through a charging hopper and is uniformly heated by the rotary kiln. Upon reaching the surface, the surface of the raw material pulverized material (inner material) is sealed. For example, in the case of fir husks, when the temperature reaches 600 ° C., raw gas is generated from the inner material. When the temperature is further increased to 650 ° C., the raw gas ignites and the material itself starts self-combustion. In the present invention, the heating temperature is slightly different depending on the kind of the flammable organic substance, but the temperature required to cause self-combustion is 600 to 7
00 ° C. It is up to this point that the energy supply for combustion is required.
When the temperature rises to about the same level and the residue is burned together, the product is transferred from the furnace to the cooling device when the gas has burned out, and cooled by the cooling device to obtain a porous fired body.

According to the present invention, all the space occupied by ultra-fine bubbles and residues generated in the material at the stage of self-combustion becomes hollow, forming pores on the surface of the carbide, A ceramic component is coated on the surface of carbon generated by carbonization of the volatile organic material to form a ceramic layer, and a fired body having a porous structure is produced. The content ratio of carbon in the fired body is generally 30 to
It is 60% by weight, preferably 30 to 50% by weight, and the content ratio of ceramics in the fired body is 70 to 40% by weight, preferably 70 to 50% by weight. This is because when the content of carbon is extremely less than 30% by weight and the content of ceramics extremely exceeds 70% by weight, the specific surface area (pore volume) of the fired body becomes small, and the porous structure collapses. On the other hand, when the content ratio of carbon is extremely higher than 60% by weight and the content ratio of ceramics is extremely lower than 40% by weight, a porous structure is obtained. The dioxin adsorption ability provided by the ceramic layer is undesirably reduced.

The fired body thus obtained has a structure in which the fired carbon particles are firmly bonded to each other, and has an advantage that it is very easy to handle. Easy. Moreover, the fired body is composed of carbon and ceramic components harmless to the human body, and is excellent in safety. In the step A of the present invention, the fired product obtained under the above firing conditions is pulverized and sized by a mill pulverizer, a granulator or the like, and 90% or more of the porous calcined material has a particle size of 200 μm or less. The powder is finely pulverized so as to form a porous body, but in order to enhance the adsorbability of dioxin, the particle size of the porous fired body is preferably 90% or more and 100 μm or less. In the case of activated carbon having no ceramic layer having such a particle size, since the ignition point is low (for example, 350 ° C. or lower), dust explosion may occur when activated carbon is blown into exhaust gas. The porous fired body used in the above has a high ignition point (350 ° C. or more) because of having a certain amount of a clay mineral and a ceramic layer formed from additives, and thus has a higher firing point than ordinary activated carbon. Extremely safe.

Next, step B in the method of the present invention will be described. Dioxins, which are problematic during garbage incineration, have a large molecular weight and are difficult to adsorb with conventional activated carbon having a small pore diameter.
The porous fired body (carbide) obtained by is suitable for adsorption of those having a relatively large pore diameter and a large molecular weight,
In particular, for adsorption of dioxins, those having an average pore diameter (by BET adsorption method) of 20 to 60 ° are preferable, and those having an average pore diameter of 30 to 60 °.
An angle of 50 ° is particularly preferred. In the present invention, dioxins can be efficiently adsorbed simply by blowing a porous fired body having such an average pore diameter into exhaust gas transferred from a garbage incinerator to a dust collector, and in the case of filtration dust collection. Then, the porous fired body is blown into the exhaust gas immediately before being sent to the bag filter, and in the case of electric dust collection, the porous fired body is blown into the exhaust gas immediately before being sent to the electric dust collector. The blowing amount of the porous fired body in the step B is 1 N of exhaust gas.
It is preferably 50 to 1000 mg / m ³ , 50 to 500 mg / Nm ^{3 for} a bag filter system, and 100 to 1000 mg / N for an electric dust collector.
m ³ is preferred. In addition, the firing point temperature (D
(According to TA measurement) is 380 ° C. or higher, and it can be easily pulverized into fine powder. The fired body after adsorbing dioxins can be easily separated and removed by an electric dust collector or a bag filter. There is also an advantage that the adsorbent can be easily recovered.

FIG. 1 shows an example of equipment of a continuous combustion incineration plant for carrying out the adsorption removal method of the present invention.
The collected trash is put into the trash pit 2 from the input gate 1 and sent to the input hopper 4 by the trash crane 3. Then, the refuse supplied into the incinerator 6 is burned on the combustion stoker 5 to be incinerated ash and sent out of the furnace, and the boiler 7 collects waste heat. The exhaust gas that has passed through the boiler 7 is then sent to a dust collector 9 for removing dust (an electric dust collector is used in the incineration facility shown in FIG. 1, but the present invention is not limited to this). However, in the method of the present invention, the above-described porous fired body supplied from the porous fired body supply silo 8 is powder-injected at a position immediately before the dust collector 9, and at this time, dioxin in exhaust gas is discharged. Are adsorbed in a porous ceramic layer coated on the surface of the fired body, and the fired body is separated from the exhaust gas by the dust collector 9 together with the dust in the exhaust gas. In the method of the present invention, the porous fired body blown into the exhaust gas,
Since it has a pore diameter of a size suitable for the adsorption of dioxins, a dioxin removal rate of 80% or more can be achieved in the case of the above-mentioned blowing amount, and dioxin in the exhaust gas has pores of the ceramic layer, It is considered that the carbon was adsorbed on both pores of carbon generated by carbonization. In the present invention, in order to increase the dioxin removal rate, a bag filter method is particularly preferable. In this case, a high dioxin removal rate of 95% or more can be obtained. The exhaust gas after dioxins are adsorbed and removed by the method of the present invention is:
Ash discharged from the chimney 10 and generated by combustion is sent to an ash pit 12 via an ash conveyor 11 and discharged by an ash crane 13 (FIG. 1). Hereinafter, the present invention will be described in detail with reference to Examples of the present invention, but the present invention is not limited to those described in the Examples.

[0021]

EXAMPLES Example 1 Production Example of a Porous Fired Body (When No Activation is Performed) A waste chip 10 whose water content is adjusted to about 70% by weight.
0 parts by weight, 3 parts by weight of bentonite and 7 parts by weight of zeolite were added, and the mixture was kneaded for about 15 minutes with a kneader to uniformly coat the surface of the waste chip with bentonite and zeolite, and then using a rotary kiln. To 650 ° C,
After that, firing by self-combustion, after the combustion is completed,
The fired product is transferred to a cooling device to be cooled, and the final product is taken out, whereby the fired product in which a ceramic layer is formed on the surface of carbon generated by carbonization of the flammable organic substance (particle size: about 0.5
５5 mm). Thereafter, the fired product is crushed and sized by a mill crusher and a sizing machine, and 90% or more
A porous fired body having a particle size of not more than μm was obtained.

Example 2 Production Example of Porous Fired Body (When Activated) The fired product obtained in Example 1 was fired at about 1100 ° C. while supplying steam into a firing furnace in a reducing atmosphere. Then, the resultant was pulverized in the same manner as in Example 1 to produce a porous fired body.

The physical properties of the two kinds of porous fired bodies (Examples 1 and 2) thus produced are shown in Table 1 below.

[0024]

[Table 1]

As shown in Table 1 above, in the manufacturing process of the porous fired body, the fired body (Example 2) which was activated after carbonization was different from the fired body which was only carbonized (Example 1). The results were high in any of the items such as the absorption capacity and the adsorption capacity.

Example 3: Experiment for adsorbing dioxin in exhaust gas discharged from a garbage incineration facility (in the case of filtration and dust collection) In an incineration facility as shown in FIG. The porous fired body of Example 1 or 2 was injected into the exhaust gas immediately before the filter (blowing amount: 50 mg / Nm ³ ), and the dioxin concentration at the inlet of the dust collector and the outlet of the dust collector were measured. The dioxin concentration of each was measured. The results are shown in Table 2 below.

[0027]

[Table 2]

Example 4: Experiment for adsorbing dioxin in exhaust gas discharged from a garbage incineration facility (in the case of electric dust collection) In an incineration facility as shown in FIG. 1 in which an electric dust collector is installed as a dust collector, electricity is collected. The porous fired body of Example 1 or 2 was injected into the exhaust gas immediately before the dust collector (blowing amount: 100 mg / Nm ³ ), and the dioxin concentration at the inlet of the dust collector and the outlet of the dust collector were measured. Was measured, and the dioxin removal rate was calculated. The results are shown in Table 3 below.

[0029]

[Table 3]

As a result of conducting the experiments of Examples 3 and 4 in two different garbage incineration facilities, as shown in Tables 2 and 3, the dioxin adsorption / removal was not activated. The fired body (Example 1) showed a higher dioxin removal rate in all experiments.

[0031]

According to the dioxin adsorption and removal method of the present invention, dioxin in exhaust gas generated at the time of garbage incineration, which has recently become a major problem, can be relatively easily removed.
And it can be effectively adsorbed and removed. When producing a porous fired body used by the method of the present invention,
Thinned wood chips, construction waste chips, coffee residue, fir husks, etc. can be used as flammable organic substances, and quarry sludge and crushed shells can be used as inorganic wastes. It also has the advantage of contributing to protection.

[Brief description of the drawings]

FIG. 1 is an example of a continuous combustion incineration facility for carrying out the adsorption removal method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input gate 2 Garbage pit 3 Garbage crane 4 Charging hopper 5 Burning stoker 6 Incinerator 7 Boiler 8 Porous fired body supply silo 9 Dust collector 10 Chimney 11 Ashing conveyor 12 Ash pit 13 Ash crane

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 53/70 B01D 53/34 B01J 20/18

Claims (4)

(57) [Claims] 1. A method for adsorbing and removing dioxin contained in exhaust gas discharged from a refuse incinerator, comprising: step A: a) a combustible organic substance; b) a clay mineral as a binder; c) The combustible organic material 100 which has been previously adjusted with zeolite, calcium carbonate, and a powdery additive selected from the group consisting of zeolite or calcium carbonate-containing inorganic waste to have a water content of 70%. 2 to 20 parts by weight of the clay mineral and 0.3 to 8 parts by weight of the powdery additive are mixed with respect to parts by weight, and the clay mineral and the powdery additive are added to the surface of the combustible organic material. After uniform coating, use a rotary kiln at 600 to 700 ° C.
To produce self-combustion, followed by self-combustion and firing to obtain a fired product in which the surface of carbon generated by carbonization of the flammable organic substance is coated with a ceramic layer, and then the fired product is ground. And a step of producing a porous fired body having a particle diameter of 90% or more and 200 μm or less, and step B: transferring the porous fired body obtained in the above step A from a refuse incinerator to a dust collector. Blowing the exhaust gas to be transferred, adsorbing dioxin contained in the exhaust gas to the porous fired body, and separating and removing the porous fired body from the exhaust gas together with the dust in the exhaust gas by the dust collector. A method for adsorbing and removing dioxin using a porous fired body, characterized in that: 2. The blowing amount of the porous fired body in the step B is 50 to 10 with respect to 1 Nm ^{3 of the} exhaust gas.
2. The method for removing and adsorbing dioxin according to claim 1, wherein the amount is 00 mg. 3. The porous fired body has an average pore diameter of 20 to 3.
3. The method for removing and adsorbing dioxin according to claim 1, wherein the angle is 60 [deg.]. 4. The flammable organic substance is selected from the group consisting of thinned wood chips, construction waste chips, coffee residue, fir hulls, punched paper chips, waste paper pulp and bamboo chips, and the clay mineral is kaori The method for removing and adsorbing dioxin according to any one of claims 1 to 3, wherein the method is selected from the group consisting of knight, halloysite, and bentonite.