JP2000102710A - Waste gas purifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the residue of harmful components and to evade the re-synthesis of the harmful components in a waste gas system by mixing cooling air with a waste gas passing through a discharge pipeline and introducing the waste gas to be decreased in a temp. in a purifying device to purify it. SOLUTION: In a stage before a waste gas (a) generated in a heat treating furnace is sucked by a blower to be passed through a discharge pipeline 34 to be introduced into a purifying device, cooling air is led at the flow speed of the waste gas (a), flows in the waste gas (a) and is mixed with each other to decreases the temp. of the waste gas (a) to equal to or below the endurance temp. of the purifying device. At the same time, a waste gas purifying agent 44 is also led at the flow speed of the waste gas (a), is introduced into the purifying device while being brought in contact with remaining harmful components in the waste gas (a) to catalytically react with the harmful components in the waste gas (a) at a high temp. and to remove them. As a result, the possibility of the re-synthesis of dioxin is reduced even if the temp. of waste gas (a) is decreased, the purification of the waste gas (a) is efficiently performed, the cooling is easily carried out by introducing air into the high temp. waste gas (a) and at the same time, a special means for the supply of the purifying agent is unneccessitated.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying exhaust gas generated when a waste or the like is subjected to a heat treatment, and more particularly to a method for purifying exhaust gas introduced into an exhaust gas purifying apparatus with cooling air. The present invention relates to an exhaust gas purifying method for lowering the temperature of exhaust gas by flowing a waste gas and an exhaust gas purifying agent, and for purifying the exhaust gas with a purifier more effectively. [0002] General waste such as municipal waste, industrial waste, shredder dust, vinyl chloride and other wastes contain large amounts of halogen substances (chlorine, bromine, iodine, fluorine, astatine), especially chlorine components. If it is subjected to heat treatment such as incineration, a large amount of chlorine-based gas (hydrogen chloride, chlorine) is generated, and the treated powder used in the generated exhaust gas and used in a bag filter for exhaust gas treatment It is known that highly toxic dioxins are generated and remain in fly ash in exhaust gas and residue (processed ash) after incineration. [0003] In order to treat exhaust gas from refuse incineration plants and the like,
A bag filter is used as an exhaust gas purifying device in an exhaust system between an incinerator and a chimney. An example of this bag filter device is disclosed in Japanese Patent Application Laid-Open No. 8-108026. In this publication, a plurality of filter cloths are provided in a container, slaked lime as a reactive agent and exhaust gas are introduced from a lower bag filter house hopper section, slaked lime is attached to the filter cloth, and the filter cloth is passed through. By removing chlorine-based gas and dioxins in exhaust gas,
Particularly, there is described an example of a bag filter device in which a layer of slaked lime is uniformly formed on a plurality of filter cloths to thereby achieve high exhaust gas treatment performance with a small amount of slaked lime. In addition, instead of the incineration means, there is also known a method in which an object to be treated is thermally decomposed (dry-distilled), and the residue after decomposition is reduced in volume by carbonization or incineration. In this treatment method, pyrolysis is performed using a single rotary processing furnace (rotary kiln), the discharged residue is incinerated with a stoker, the pyrolysis gas is burned in a reburning chamber, and the generated high-temperature gas is boiled. After that, there is a method in which slaked lime slurry is sprayed by a reaction or the like in the same manner as described above to react with the exhaust gas (for example, JP-A-5-33916). [0005] The above-mentioned Japanese Patent Application Laid-Open No. Hei 8-10
In the conventional bag filter device described in No. 8026 or the like, while purifying the exhaust gas by spraying the treating agent into the bag filter device and passing the treatment agent through the device, in this device example, Slaked lime is used as a purifying agent, and the purifying agent after contact reaction with exhaust gas contains chlorine components or generated dioxins, so it cannot be reused even if there is an unreacted purifying agent. . Therefore, these purifying agents must be subjected to predetermined detoxification treatment before being subjected to landfill disposal and the like. Further, the object to be treated is heated (dry distillation, combustion).
If the heat treatment can be performed under uniform heating conditions,
Although uniform treatment of exhaust gas can be expected, in the case of non-uniform heat treatment, decomposition of harmful substances may not be performed uniformly, and harmful components may partially remain. [0007] Alternatively, in the exhaust system between the combustion furnace and the chimney, when the temperature of the exhaust gas decreases (about 300 ° C), harmful substances (eg, dioxins) may be resynthesized. As a countermeasure, it is conceivable to burn the exhaust gas again at a high temperature (about 800 ° C. or higher) to decompose harmful substances (components) in the exhaust gas. However, if such high-temperature exhaust gas is directly introduced into the bag filter device, the bag filter device is generally configured to introduce exhaust gas having a temperature of 200 ° C. or lower, so that the bag filter device is damaged. Therefore, cooling is performed by replacing the exhaust gas with warm water or the like (heat recovery) before introducing the exhaust gas into the bag filter device. However, if the temperature of the exhaust gas before purification by the bag filter device is lowered again, the harmful substances may be re-synthesized again. Is discharged in a state of being adsorbed by the purifying agent. Therefore, as described above, there are problems such as the necessity of performing a predetermined detoxification process on the purified agent after the treatment. [0010] The present invention has been made in view of such problems, and supplies a purifying agent to high-temperature exhaust gas before it is introduced into a purifying device such as a bag filter, and at the same time, supplies the exhaust gas with:
An object of the present invention is to solve the above problem by lowering the temperature of exhaust gas by mixing cooling air. [0011] Heat treatment of an object to be processed generates exhaust gas due to thermal decomposition or the like. This exhaust gas contains harmful components, which need to be removed.
The flue gas generally contains combustible components such as tar, depending on the nature of the material to be treated. Cleaned by the device and discharged into the atmosphere. According to the present invention, since the exhaust gas and the exhaust gas after burning by the exhaust gas combustion means are at a high temperature, and the harmful components (substances) remaining in the exhaust gas are in a decomposed state and an activated state, Focusing on supplying an exhaust gas purifying agent that reacts with harmful components, the reaction with harmful components can be performed effectively.Furthermore, in a discharge line introduced into the purification device, a blower with a considerably high flow rate is used. Focusing on the fact that the exhaust gas is passing, the cooling air and exhaust gas purifying agent are supplied into the exhaust line using the flow velocity of the suction of the blower, and simultaneously cooling of the exhaust gas and effective purification of the exhaust gas are performed simultaneously. It is something to do. Means for solving the above-mentioned problems in the present invention is to heat-treat an object to be processed in a heat treatment furnace, and to exhaust gas generated by decomposition during the heat treatment to a purification device through an exhaust pipe. In the exhaust gas purifying method, wherein the exhaust gas is introduced into the exhaust gas and then discharged into the atmosphere after being purified, the exhaust gas is mixed with exhaust gas passing through the exhaust line and cooling air. Air cooling means for lowering the temperature of the exhaust gas is provided, and the exhaust gas cooled by the air cooling means is introduced into a purification device to be purified. In the case where exhaust gas combustion means for burning combustible components in exhaust gas is provided in the exhaust pipe, air cooling means is provided in the exhaust pipe of the exhaust gas combustion means on the purification device side, and the exhaust gas combustion means is provided with the exhaust gas combustion means. The temperature of the exhaust gas that has become high is reduced to 200 ° C. or less, which is the endurance temperature of the purification device. As the air cooling means, means for adjusting the inflow of air or the inflow of exhaust gas is provided, and the temperature of the exhaust gas is controlled by adjusting the amount of air mixed in the exhaust gas or the exhaust gas. Adjust to a predetermined temperature. This air cooling means may be formed by an air introduction pipe which is connected at one end to a discharge pipe so as to communicate with the inside of the discharge pipe, and provided with an inflow control means at the other end and opened to the atmosphere. ,
Alternatively, the end of the discharge pipe is connected to the air inlet pipe to adjust the mixing ratio of the exhaust gas or the cooling air. Next, the supply of the exhaust gas purifying agent is performed by providing a purifying agent supply means in the above-mentioned exhaust pipe or air introducing pipe. This purifying agent supply means can be easily supplied by introducing the exhaust gas purifying agent by guiding the flow rate of the exhaust gas or the cooling air. The exhaust gas purifying agent may be any reactive substance that reacts with harmful components in the exhaust gas to perform adsorption and replacement with a detoxifying substance. The form of the reactant is a powder (for example, Japanese Patent Application No. 9-38725, filed by the applicant of the present application).
Preferred are alkaline substance bodies described in JP-A-9-160910 and JP-A-9-38736, or porous powder (for example, Japanese Patent Application No. 10-183530 filed by the present applicant). The above-mentioned purifying device is preferably formed by a bag filter device generally used at present. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of the configuration of an embodiment of the present invention, in which two heat treatment furnaces are provided. In the figure, reference numeral 10 denotes a first heat treatment furnace, and reference numeral 20 denotes a second heat treatment furnace.
3 shows a heating furnace. The first heat treatment furnace 10 includes a rotatable cylindrical body 11, a heating jacket 12 for forming a gas duct on the outer periphery of the cylindrical body 11 and heating the cylindrical body 11 by introducing a hot gas, and a cylindrical body 11. A supply port 13 provided at one end of the cylindrical body 11 for supplying an object to be processed into the cylindrical body 11;
And a discharge port 14 provided at the other end of the cylindrical body 11, and the cylindrical body 11 is rotationally driven by rotational driving means (not shown). The rotation driving means of the cylindrical body 11 comprises a normal driving motor and a driving gear, a driven gear provided on the cylindrical body, and the like. The heating jacket 12 is fixed, and a mechanical seal is applied to a rotating contact portion with the cylindrical body 11. Reference numeral 15 denotes a supply port 13 of the first heat treatment furnace 10.
A mixture of the material to be treated and the dechlorinating agent is introduced into the cylindrical body 11 through a supply duct provided on the side. The structure of the second heat treatment furnace 20 is substantially the same as the structure of the first heat treatment furnace 10, and comprises a rotatable cylindrical body 21 and a hot gas introduced around the outer periphery of the cylindrical body 21. A heating jacket 22 for heating the cylindrical body 21 is provided on one end of the cylindrical body 21, in this example, on the side of the discharge port 14 of the first heating unit 10, and supplies an object to be processed into the cylindrical body 21. It comprises a supply port 23 and a discharge port 24 provided at the other end of the cylindrical body 21. Reference numeral 16 denotes an outlet 14 of the first heat treatment furnace 10.
Side and the supply port 23 side of the second heat treatment furnace 20,
The mixture is transferred from the first heat treatment furnace 10 to the second heat treatment furnace 2
2 shows an introduction duct to be introduced into a zero. Reference numeral 25 denotes a cylindrical body 21 of the second heat treatment furnace 20.
Is a discharge side duct that surrounds the discharge port 24 side and discharges an object to be processed (residue) heated in the second heat treatment furnace 20 to a melting tank or the like (not shown). The cylindrical body 11 of the first heat treatment furnace 10 and the cylindrical body 21 of the second heat treatment furnace 20 are disposed vertically, and although not shown, the cylindrical bodies 11 and 21 are not shown. The heating jackets 12 and 21 provided on the outer periphery are supported and fixed by fixing members, and a plurality of blades for transferring the mixture of the object to be processed and the dechlorinating agent while stirring are provided inside the cylindrical bodies 11 and 21. The mixture is supplied to the supply port 1 by the rotation of the cylinders 11 and 21 themselves as shown by the dashed line in FIG.
It is configured to transfer from the 3 side to the discharge port 24 side. Further, the duct 1 which comes into rotational contact with the cylindrical body 11
A mechanical seal is applied to the contact portions of the ducts 5 and 16 and the contact portions of the ducts 16 and 25 that are in rotational contact with the cylindrical body 21. Reference numeral 30 denotes a hopper. The crushed object and a dechlorinating agent made of an alkaline substance are mixed and thrown into the hopper 30, and the hopper 30 can be supplied from the supply port 13 of the cylindrical body 11 into the cylindrical body 11. . The hopper 30 may have both the function of crushing the object to be treated and the function of mixing the dechlorinating agent, and may mix the dechlorinating agent while crushing the solid, The material and the dechlorinating agent may be mixed and charged into the hopper 30. Reference numeral 31 denotes a hot gas generator, for example, LN
When burning G, LNG supplied from an LNG tank (not shown) is burned to generate hot gas. This hot gas is supplied into the heating jacket 22 provided on the outer periphery of the cylindrical body 21 of the second heat treatment furnace 20 to heat the cylindrical body 21, and then the heat gas of the first heat treatment furnace 10 is It is fed into the heating jacket 12 of the cylindrical body 11. At this time, outside air is taken into the communication pipe 26, and the temperature of the hot gas is adjusted. The hot gas after heating the cylindrical body 11 is supplied to the discharge pipe 3
2 and is sent to the exhaust gas combustion means 33. The exhaust gas combustion means 33 is supplied from the hot gas generator 31 to the gas in the introduction duct 16 communicating the discharge side of the first heat treatment furnace 10 and the supply side of the second heat treatment furnace 20. Then, the gas after heating each heat treatment furnace is burned, and the cooling air / exhaust gas purifying agent supply unit 40 described below is burned.
Is sent to the purification device 35 via. In the heat treatment of the object to be treated such as waste, the object to be treated is crushed in advance by a crusher, and an alkali substance as a dechlorinating agent is added to and mixed with the object to be treated. This dechlorinating agent is used in any of a lump, a plate, a porous form, a powder, a suspension, or a combination thereof. In parallel with this, LN is generated by the hot gas generator 31.
G is burned to generate hot gas, which is supplied to the heating jacket 22 and the heating jacket 12 so as to be supplied to the first heat treatment furnace 10.
And the inside of the furnace of the second heat treatment furnace 20 is heated,
The mixture of the object and the dechlorinating agent is supplied from the hopper 30 to the supply port 1
3 and supplied into the cylindrical body 11 of the first heat treatment furnace 10. The cylindrical body 11 is rotationally driven by a rotation driving means (not shown). In the heat treatment in the first heat treatment furnace 10, after sufficiently mixing a mixture of the object to be treated and the dechlorinating agent, the mixture is heated at 100 ° C. to 150 ° C. to remove contained water. A heat treatment is performed by a drying step of drying.
By removing water (H ₂ O) from the object, the next decomposition reaction step can be effectively performed. The object to be processed dried in the first heat treatment furnace 10 is supplied to the second heat treatment furnace 20 through the introduction duct 16. In the second heat treatment furnace 20, a decomposition reaction (dechlorination) treatment is performed in a decomposition reaction step of decomposing and depositing a chlorinated gas from the object to be processed and reacting it with a dechlorinating agent. The temperature and time at which the chlorine-based gas decomposes and precipitates are investigated in advance to understand the properties of the object to be treated, and the temperature (200 ° C. to 350 ° C.) and time (30 minutes) that can sufficiently cover the results of this investigation. ). Note that the temperature at which the chlorine-based gas is decomposed and precipitated from the object to be treated is preferably from 250 ° C to 350 ° C. The heating temperature and time in the second heat treatment furnace 20 depend on the state of the heat treatment furnace (conditions depending on the furnace such as heating means, etc.) and the amount of the object to be treated. Because it is related, it is necessary to conduct sufficient surveys and the like in advance, and it is necessary to collect and accumulate data. The heating in the second heat treatment furnace 20 is as follows.
If the treatment is performed by "steaming and pyrolysis" instead of "combustion and incineration", the harmful chlorine-based gas deposited and the dechlorinating agent of the alkaline substance can be effectively contacted and reacted, and the harmful HCl gas can be reacted. Can be replaced with a harmless chloride. In the second heat treatment furnace 20, HC
Although a chlorine-based gas containing the l component is generated, the HCl component in the chlorine-based gas reacts with the added alkali substance, for example, when sodium bicarbonate is used, and is harmless by reacting with the sodium bicarbonate. Produces chloride, sodium chloride (NaCl). Thereby, the detoxification of the HCl component and the detoxification of the residue in the decomposition gas can be performed at the same time. In the above example, the first heat treatment furnace 10 is used for the drying step, and the second heat treatment furnace 20 is used for the decomposition reaction step. The second heat treatment furnace 20 may be a volume reduction step by carbonization or incineration. In this case, the first heat treatment furnace 10 heat-treats at a temperature of 200 ° C. to 350 ° C. at which decomposition reaction occurs. Then, the second heat treatment furnace 20 is heated to a temperature of 350 ° C. to 700 ° C. at which the object is carbonized or 800 ° C. or more at which the object is incinerated. Numeral 34 denotes a discharge line, which is a heat treatment furnace 10 described above.
Exhaust gas generated by thermal decomposition or the like when the object to be treated is subjected to heat treatment in step 20 is introduced into the purification device 35.
Depending on the properties of the material to be treated, the exhaust gas may contain a large amount of combustible components such as tar components. In this case, an exhaust gas combustion means 33 is provided in the discharge pipe 34 to burn and remove the combustible components. . The exhaust gas combustion means 33 has a combustion device 36 for burning LNG as fuel. Purification device 35
For example, a bag filter device generally used at present can be used. Reference numeral 37 denotes a blower provided in the purification device 35, which introduces exhaust gas into the purification device 35,
The exhaust gas purified by the above is discharged through a chimney 38. Reference numeral 40 denotes a cooling air / exhaust gas purifying agent supply unit (hereinafter, abbreviated as an air / agent supply unit) which is a feature of the present invention. The empty / agent supply section 40 is configured as shown in FIG. FIG. 2 is a sectional view of the air / agent supply section 40, and FIG. 2 (A) shows the flow rate of the exhaust gas a and the cooling air b.
(B) shows exhaust gas a in cooling air b.
Is shown. In these figures, reference numeral 41 denotes an air introduction pipe constituting an air cooling means. In FIG. 4A, one end communicates with the discharge pipe 34, the other end is opened to the atmosphere, and flows into the middle. It has an inflow amount adjusting means 42 composed of a valve or the like for adjusting the air amount. In FIG. 5B, one end of the air introduction pipe 41 is connected to the purifier 38, the other end is open, and the end of the discharge pipe 34 is opened into the air introduction pipe 41. . Reference numeral 43 denotes a purifying agent supply means,
, The bottom of which is opened in the processing air introduction pipe 41 and the outlet thereof has adjusting means 45 such as a valve.
When the cooling air flows through the inside 1, it is guided by this flow and supplies the exhaust gas purifying agent into the discharge pipe 34 or the air introduction pipe 41, reacts with the harmful components in the exhaust gas and introduces it into the purifying device 35. The location of the purifying agent supply means 43 may be provided in the air introduction pipe 41 or the discharge pipe 34 as shown in FIG. 2, but is indicated by a dashed line 4 in FIGS.
As shown by 3 ′, it may be provided on the heat treatment furnace side of the air introduction pipe 41 or on the discharge pipe 34. The introduction of the cooling air into the discharge line
3, an opening 46 is provided in the discharge line 34, and the opening area of the opening is adjusted to adjust the air inflow amount without providing the air introduction tube 41 as shown in FIG. 42 'may be provided. Next, a description will be given of an exhaust gas treatment method according to the above configuration. Now, the exhaust gas generated in the heat treatment furnace 10 or 20 is sucked by the blower 37, passes through the discharge line 34, and passes through the purifier 35. Will be introduced. At this time, in FIG. 2A, before the cooling air is introduced into the purification device 35, the cooling air is guided by the flow velocity of the exhaust gas a, flows into the exhaust gas and mixes, and the temperature of the exhaust gas is reduced. At the same time, the exhaust gas purifying agent 44 is guided by the flow rate of the exhaust gas, flows in, and is introduced into the purification device while contacting harmful components remaining in the exhaust gas. The exhaust gas is purified by contact reaction with harmful components existing in the air. In the example shown in FIG. 5B, the cooling air b is mainly sucked by the blower of the purifying device 35, and the exhaust gas a
The mixture is cooled by being mixed with cooling air in a form guided by this. Even when the exhaust pipe 34 has exhaust gas combustion means, the temperature of the exhaust gas is reduced to 200 ° C. or less by increasing the amount of cooling air introduced even when the exhaust gas is heated at about 800 ° C. and becomes high temperature. And introduce it into the purification device. At this time, the exhaust gas purifying agent used is the above-mentioned alkaline substance (for example,
Not only alkali metal, alkali metal compound, alkaline earth and alkaline earth metal compound) but also a treating agent conventionally used for a bag filter may be used, or various known purifying agents such as activated carbon may be applied. As described above, when the exhaust gas purifying agent is supplied into the exhaust gas, the exhaust gas purifying agent and a harmful component (eg, hydrogen chloride) in the exhaust gas come into contact with each other at a high temperature to remove the harmful component from the exhaust gas. Thus, even if the exhaust gas temperature decreases, the possibility of resynthesizing dioxins is extremely reduced. Post-treatment of the exhaust gas purifying agent reacted with hydrogen chloride can be easily and safely performed with a general solvent (water, acidic solution, etc.). As described above, according to the present invention, the air cooling of exhaust gas and the exhaust gas purifying agent are performed before the exhaust gas is introduced into the purifier by utilizing the flow rate of the suction force of the blower when the exhaust gas is introduced into the purifier. The following effects can be obtained since the supply of (1) By supplying the purifying agent to the high-temperature exhaust gas before being introduced into the purification device, the exhaust gas can be effectively contacted with the harmful substance components and purified, thereby purifying the exhaust gas effectively. (2) Air is introduced to cool the high-temperature exhaust gas, and a purifying agent can be supplied so as to be guided by the introduction of the cooling air or the exhaust gas. No special means is required. (3) Since high-temperature exhaust gas is cooled by air, a simple cooling means is sufficient.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of a processing apparatus for describing an embodiment of the present invention. FIG. 2 is an explanatory view of an embodiment of the air cooling means of the present invention. FIG. 3 is an explanatory view of another embodiment of the air cooling means of the present invention. [Description of Signs] 10 first heat treatment furnaces 11 and 21 cylindrical bodies 12 and 22 heating jackets 13 and 23 supply ports 14 and 24 discharge ports 15 and 25 supply duct 16 introduction duct 26 Communication pipe 30 Hopper 31 Hot gas generator 32 Exhaust pipe 33 Exhaust gas combustion means 34 Exhaust line 35 Purifier 36 Combustion device 37 Blower 38 Chimney 40 Empty / agent supply section 41 Air introduction Pipe 42 inflow amount adjusting means 43 purifying agent supplying means 44 exhaust gas purifying agent 45 adjusting means 46 opening

Claims (1)

Claims 1. An object to be processed is subjected to heat treatment in a heat treatment furnace, and exhaust gas generated by decomposition during the heat treatment is introduced into a purification device through an exhaust pipe, and is purified by the purification device. In the exhaust gas purifying method, the exhaust gas is exhausted after the exhaust gas is provided.In the exhaust pipe, an exhaust gas passing through the exhaust pipe and air cooling means for lowering the temperature of the exhaust gas by mixing cooling air are provided. An exhaust gas purifying method, wherein the exhaust gas cooled by the air cooling means is introduced into a purifier to purify the exhaust gas. 2. An exhaust gas combustion means for burning a combustible component in exhaust gas is provided in a discharge pipe, and an air cooling means is provided in a discharge pipe of the exhaust gas combustion means on a purification device side. 2. The method for purifying exhaust gas according to 1. 3. The air cooling means is formed by an air introduction pipe having an inflow amount adjusting means, and cooling air flows from the air introduction pipe by being guided by the flow rate of the exhaust gas. 3. The exhaust gas purification method according to 1 or 2. 4. The air cooling means is formed by an air introduction pipe,
3. The method for purifying exhaust gas according to claim 1, wherein the exhaust gas is guided by the flow velocity of the cooling air so that the exhaust gas flows from the exhaust pipe. 5. The exhaust gas purifying method according to claim 1, further comprising a purifying agent supply means for feeding an exhaust gas purifying agent to the discharge pipe or the air introduction pipe. 6. The exhaust gas purifying method according to claim 5, wherein the exhaust gas purifying agent is a reactant which reacts with a harmful component in the exhaust gas to perform adsorption and substitution with a detoxifying substance. 7. The exhaust gas purifying method according to claim 6, wherein the reactant has an alkali characteristic. 8. The exhaust gas purifying method according to claim 6, wherein the reactant is a powder or a porous powder. 9. The exhaust gas purifying method according to claim 1, wherein the purifying device is a bag filter device.