JP3819587B2 - Exhaust gas treatment apparatus and exhaust gas treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas treatment device and an exhaust gas treatment method, and more particularly to an exhaust gas treatment device and an exhaust gas treatment method suitable for removing malodorous components and harmful components in exhaust gas.
[0002]
[Prior art]
In exhaust gas discharged from reaction processes such as chemical industry, exhaust gas discharged from manufacturing processes (firing, drying, washing) of resins, plywood, semiconductors, etc., or exhaust gas discharged from baking and drying processes of painting processes Contains trace amounts of malodorous and harmful ingredients. Typical examples of malodorous or harmful components in exhaust gases in the chemical industry include cracked gas from raw materials, organic acids such as carbon monoxide, hydrocarbons and acetic acid, or aldehydes as unyield, The exhaust gas discharged from the production process of resin and the coating process contains alcohol-based aromatic hydrocarbons such as toluene and acetone used as a solvent.
[0003]
The exhaust gas containing these components emits a bad odor when exhausted as it is, and is harmful to the human body. Therefore, it must be deodorized and made harmless before exhaust from the viewpoint of pollution prevention.
Conventional techniques for treating exhaust gas containing these malodors and harmful components are roughly classified into three methods: an adsorption method, an absorption method, and a combustion oxidation method. Among these, the adsorption method is a method that utilizes the adsorption power of silica gel, alumina gel, zeolite, clay mineral, activated carbon, and the like. The absorption method uses the chemical reactivity (acid-base reaction, etc.) of the substance to be treated. For basic compounds such as ammonia and amines, washing with acid is used. For acidic mercaptans, Alkaline cleaning is effectively used. Furthermore, aqueous solutions of hypochlorous acid, chlorine, potassium permanganate and the like are strong oxidizing agents, and there is a method of absorbing and oxidizing and decomposing harmful components using these aqueous solutions.
[0004]
The combustion oxidation method is roughly classified into a direct combustion method and a catalytic combustion method. The direct combustion method is generally a method in which exhaust gas is heated using auxiliary fuel, and malodor and harmful components in the exhaust gas are burned at a temperature of 800 ° C. or higher to form carbon dioxide and water. On the other hand, the catalytic combustion method burns malodorous and harmful components in exhaust gas at a relatively low temperature of 500 ° C. or lower due to the oxidizing action of the catalyst.
[0005]
These treatment methods are selected in consideration of exhaust gas conditions and economy, but the adsorption method is suitable when the amount of components removed in the exhaust gas is very small (ppm or less). This is because the lifetime decreases in proportion to the amount of the removed component, and the adsorbent must be regenerated or replaced in a short time. Further, since the adsorbed removal component is desorbed and discharged during regeneration of the adsorbent, a downstream removal process is required. On the other hand, the absorption method is not suitable for the treatment of exhaust gas containing different types of removal components because of the selectivity of the absorption solution used, and also requires post-treatment of the absorption solution and waste water.
[0006]
As a result, as a method for removing malodors and harmful components, a treatment method using a combustion oxidation method has been widely adopted. Recently, the catalytic combustion method is a cause of saving auxiliary fuel and secondary pollution compared to the direct combustion method. Since it has advantages such as no generation of NOx, it has attracted attention and has been adopted.
FIG. 3 is a flowchart showing an example of an exhaust gas treatment apparatus using a catalytic combustion method in the prior art. In FIG. 3, the exhaust gas 1 sucked by the exhaust gas fan 2 (if the exhaust gas 1 is introduced in a pressurized state, the exhaust gas fan 2 may be unnecessary) enters the heat exchanger 3 and the heat exchanger 3 is heated by heat exchange with the combustion treatment exhaust gas 10 to be preheated exhaust gas 4 and led to the catalytic reactor 6. The upstream of the catalytic reactor 6 includes LPG, natural gas, and city gas as auxiliary fuel 12 for heating the preheated exhaust gas 4 at the time of starting the apparatus and for backup heating when the heat exchanger 3 does not heat to the required temperature. Alternatively, an exhaust gas heating device 5 having an auxiliary combustion burner 11 using high-quality oil such as light oil and kerosene is provided, and the exhaust gas 1 can be stably heated by the heat exchanger 3 and the exhaust gas heating device 5 at a temperature at which catalytic combustion can be continued stably. For example, it is preheated to 150 to 400 ° C.
[0007]
A combustion catalyst layer 7 is provided inside the catalyst reactor 6, and the preheated exhaust gas 4 is introduced from above the catalyst reactor 6 and supplied to the combustion catalyst layer 7. When the preheated exhaust gas 4 passes through the combustion catalyst layer 7, malodorous components and harmful components are burned at a low temperature due to the oxidizing action of the catalyst, and are discharged from the lower part of the catalyst reactor 6 as non-polluting combustion treatment exhaust gas 10. In most cases, combustion of the exhaust gas in the combustion catalyst layer 7 is an exothermic reaction, so that the temperature of the combustion treatment exhaust gas 10 at the outlet of the combustion catalyst layer 7 is higher than the temperature of the preheated exhaust gas 4 at the inlet of the combustion catalyst layer 7. Accordingly, the combustion treatment exhaust gas 10 exiting the catalytic reactor 6 is introduced into the heat exchanger 3 to give waste heat to the exhaust gas 1 and, in some cases, the waste heat is recovered by the waste heat recovery device 15 downstream thereof, and then the chimney. 16 is discharged as exhaust 17.
[0008]
As the combustion catalyst of the combustion catalyst layer 7, a precious metal such as platinum or palladium and / or a base metal such as manganese, copper or cobalt is used, and the shape of the catalyst is generally in the form of pellets or honeycombs. The combustion catalyst layer 7 is formed by filling these pellet-shaped catalysts or laminating honeycomb-shaped catalysts.
The combustion catalyst layer 7 is supported inside the catalyst reactor 6 by a porous plate-like or lattice-like catalyst receiver 8. Generally, in order to make the gas flow the same as the load direction of the combustion catalyst layer 7, A method is adopted in which the preheated exhaust gas 4 is supplied as a downward flow from the upper part of the reactor 6 to the combustion catalyst layer 7 and the combustion catalyst layer 7 is supported on the outlet side of the combustion treated exhaust gas 10.
[0009]
Reference numeral 20 denotes a catalyst differential pressure gauge for managing the abnormality of the combustion catalyst layer 7.
[0010]
[Problems to be solved by the invention]
In the above prior art, dirt components such as dust and tar are contained in the exhaust gas, the dirt components in the exhaust gas adhere to the combustion catalyst layer 7, and the flow resistance (catalyst layer differential pressure) of the combustion catalyst layer 7 increases. Even in this case, the operation is continued, so that the load applied to the catalyst receiver 8 on the outlet side of the combustion catalyst layer 7 is increased and the catalyst receiver 8 is broken or the internal pressure on the catalyst layer inlet side is increased to cause a catalytic reaction. There was a risk that the critical pressure of the reactor 6 would be exceeded and the container of the catalytic reactor 6 would be destroyed. That is, if the weight of the combustion catalyst layer is W1, the combustion catalyst layer inlet pressure is P1, the combustion catalyst layer outlet pressure is P2, and the pressure receiving area of the combustion catalyst layer is A, the flow generated by the exhaust gas passing through the combustion catalyst layer The resistance ΔPc is P2-P1. When the combustion catalyst layer is clogged or clogged with dirt, this flow resistance ΔPc increases. In this case, since the direction of the load due to the weight of the combustion catalyst layer is the same as the flow direction of the exhaust gas, the load applied to the catalyst receiver is (W1 + ΔPc · A), and the catalyst receiver is applied as ΔPc increases. The load increases. When the load applied to the catalyst receiver 8 exceeds the limit load on the strength of the catalyst receiver 8, there is a risk that the catalyst receiver 8 is broken. Further, since the pressure P2 at the outlet of the combustion catalyst layer is constant, the pressure P1 at the inlet side of the combustion catalyst layer increases as the flow resistance ΔPc increases. If the combustion catalyst layer inlet pressure P1 exceeds the container limit pressure of the catalyst reactor, there is a risk that the container will be destroyed. In order to avoid such a danger, when the pressure difference of the combustion catalyst layer 7 is detected and an abnormality such as clogging occurs in the combustion catalyst layer 7, a method of detecting in advance and stopping the apparatus is taken. However, there are many cases where the clogging of the combustion catalyst layer 7 occurs instantaneously, and detection of the differential pressure in the combustion catalyst layer 7 causes a time lag and often cannot be dealt with.
[0011]
Further, in the above prior art, since the combustion catalyst layer 7 is supported on the outlet side where the temperature of the exhaust gas becomes high, it is necessary to use a high-grade material having high heat resistance for the material of the catalyst receiver 8, which is economically burdensome. There was a problem that became larger.
An object of the present invention is to solve the above-described problems in the prior art, and the safety of the catalytic reaction vessel is not destroyed even if a pressure increase occurs due to the clogging of the combustion catalyst layer due to dirt components in the exhaust gas. In addition, another object is to provide an exhaust gas treatment apparatus and a treatment method that can use an inexpensive material for the catalyst receiver.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the invention claimed in the present application is as follows.
(1) In an exhaust gas treatment apparatus that introduces exhaust gas containing harmful components into a combustion catalyst layer and heats and removes the harmful components by catalytic combustion, the catalytic reactor including the combustion catalyst layer and means for supporting the catalyst layer When the means for introducing the catalytic combustion initiation temperature or higher of the exhaust gas from below the catalyst layer of the reactor, means for discharging the exhaust gas after passing through the combustion catalyst layer from the top of the reactor, the combustion catalyst layer An exhaust gas treatment apparatus provided with weight means for adjusting the load of the catalyst layer on an upper part .
[0013]
(2) An exhaust gas heating device that is provided upstream of the catalytic reactor and heats the exhaust gas to a temperature equal to or higher than the catalytic combustion start temperature, and a heat exchanger that recovers the combustion heat in the exhaust gas discharged from the catalytic reactor. The exhaust gas treatment apparatus as described in ( 1) above .
(3) The exhaust gas treatment apparatus according to ( 1) or (2), characterized in that means for supporting the catalyst layer in the catalyst reactor is provided below the catalyst layer.
[0014]
( 4) An exhaust gas treatment method for introducing exhaust gas containing harmful components into a combustion catalyst layer and heating and removing the harmful components by catalytic combustion, wherein the exhaust gas is heated to a catalytic combustion start temperature by an exhaust gas heating device, Heated exhaust gas is introduced from below the catalyst layer into a catalyst reactor having a combustion catalyst layer supported by a catalyst receiver from below and provided with weight means for adjusting the load at the top, and passes through the catalyst layer. converting mechanism is discharged from the combustion catalyst layer upward After heating remove harmful components in the exhaust gas, the product [Delta] P · a of the passage cross-sectional area a of the exhaust gas pressure difference [Delta] P and the catalyst layer before and after passing through the combustion catalyst layer of the combustion catalyst when becomes greater than the weight W2 of the weight W 1 and the weight unit, the blow-by of exhaust gas is generated in the catalyst layer, and wherein the suppressing an excessive increase of the exhaust gas pressure of the catalyst layer inlet waste gas Processing method.
[0015]
( 5) The exhaust gas treatment method according to (4) , wherein exhaust gas discharged from above the combustion catalyst layer is introduced into a heat exchanger to recover combustion heat in the exhaust gas.
In the present invention, since the direction of the load due to the weight of the combustion catalyst layer and the flow direction of the exhaust gas are opposed to each other, the load applied to the catalyst receiver becomes W1−ΔPc · A, ΔPc increases, and W1 <ΔPc · A. At this point, the combustion catalyst layer is pushed up by the exhaust gas, and the packed bed of the pellets or the honeycomb stack is collapsed. This collapse becomes a blow-off portion of the exhaust gas, and further increase in ΔPc is suppressed. Therefore, the combustion catalyst layer serves as a safety device so that an excessive load is not applied to the catalyst receiver, and an increase in the combustion catalyst layer inlet pressure P1 is suppressed.
[0016]
Furthermore, since the weight of the combustion catalyst layer becomes W1 + W2 by placing a weight of weight W2 on top of the combustion catalyst layer, the value of ΔPc by which the combustion catalyst layer is pushed up can be freely adjusted. In addition, since the load direction due to the weight of the combustion catalyst layer and the flow direction of the exhaust gas are opposed to each other, the combustion catalyst layer can be supported on the exhaust gas inlet side having a low temperature, and it is not necessary to use a high-grade heat-resistant material.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a flowchart of an exhaust gas treatment apparatus that is an example of an embodiment of the present invention. In FIG. 1, the exhaust gas 1 sucked by the exhaust gas fan 2 (when the exhaust gas 1 is introduced in a necessary pressurized state, the exhaust gas fan 2 may be unnecessary) enters the heat exchanger 3. In the heat exchanger 3, the exhaust gas 1 is heated by heat exchange with its combustion treatment exhaust gas 10, and becomes preheated exhaust gas 4, which is led to the catalytic reactor 6. The upstream of the catalytic reactor 6 includes LPG, natural gas, and city gas as auxiliary fuel 12 for heating the preheated exhaust gas 4 at the time of starting the apparatus and for backup heating when the heat exchanger 3 does not heat to the required temperature. Alternatively, an exhaust gas heating device 5 having an auxiliary combustion burner 11 that uses high-quality oil such as light oil and kerosene is provided, and the exhaust gas heating device 5 and the heat exchanger 3 can always stably and continuously continue catalytic combustion (general). Specifically, the exhaust gas 1 is preheated up to 150 to 400 ° C. A combustion catalyst layer 7 is provided inside the catalyst reactor 6, and the preheated exhaust gas 4 is introduced into the lower part of the catalyst reactor 6 and supplied to the combustion catalyst layer 7. When the preheated exhaust gas 4 passes through the combustion catalyst layer 7, malodorous components and harmful components are burned at a low temperature due to the oxidizing action of the catalyst, and discharged from the upper part of the catalyst reactor 6 as non-polluting combustion treatment exhaust gas 10. A weight (catalyst presser) 9 is placed on the upper part of the combustion catalyst layer 7, that is, on the combustion treatment exhaust gas outlet side, and a load is added to the weight of the combustion catalyst layer 7. The combustion treatment exhaust gas 10 exiting the catalytic reactor 6 is introduced into the heat exchanger 3 where waste heat is given to the exhaust gas 1 and, in some cases, after the waste heat is recovered by the waste heat recovery device 15 in the downstream flow, It is discharged from the chimney 16 as exhaust 17.
[0018]
In this embodiment, the combustion catalyst layer 7 is provided with a porous plate-like or lattice-like catalyst receiver 8 inside the catalyst reactor 6, and a noble metal system such as platinum and palladium and / or manganese is provided on the catalyst receiver 8. A base metal catalyst such as copper or cobalt, which is formed by filling or laminating a pellet-shaped (granular) catalyst or a honeycomb-shaped catalyst. As the weight 9 placed on the upper side of the combustion catalyst layer 7, a lattice-like structure that does not increase the flow resistance of the exhaust gas as shown in the schematic diagram of FIG. 2 is preferably used.
[0019]
According to this embodiment, since the combustion catalyst layer 7 is supported by the catalyst receiver 8 on the inlet side of the preheated exhaust gas 4, the load of the combustion catalyst layer 7 acts downward on the catalyst receiver 8, but the preheated exhaust gas 4 Since it is supplied as an upward flow from the lower part of the catalytic reactor 6, the pushing force of the combustion catalyst layer 7 due to the flow of exhaust gas acts upward on the combustion catalyst layer 7. Therefore, the acting force on the catalyst receiver 8 is reduced, and the damage can be prevented.
[0020]
【The invention's effect】
According to the present invention, the catalytic reactor having a combustion catalyst layer which is supported from below by a catalyst support means, by introducing heated gas from below the catalyst layer, flowing through the combustion catalyst layer as an upward stream When the exhaust gas contains dirt components such as dust and tar, the dirt components in the exhaust gas adhere to the combustion catalyst layer, and the flow resistance of the combustion catalyst layer (catalyst layer differential pressure) increases , Since the filled catalyst layer collapses and an exhaust gas blow-off part is formed, there is no risk of the catalyst receiver and catalyst reaction vessel supporting the combustion catalyst layer being destroyed, and safe installation is possible even when instantaneous catalyst clogging occurs. Can be operated. Further, since the combustion catalyst layer is supported on the combustion catalyst layer inlet side where the temperature of the exhaust gas is low, an inexpensive material can be used for the catalyst receiver.
[Brief description of the drawings]
FIG. 1 is a flowchart of an exhaust gas treatment apparatus as an example of an embodiment of the present invention.
FIG. 2 is a schematic diagram showing the structure of a weight placed on a combustion catalyst layer used in one embodiment of the present invention.
FIG. 3 is a flowchart showing an example of an exhaust gas treatment apparatus in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Exhaust gas, 2: Exhaust gas fan, 3 ... Heat exchanger, 4 ... Pre-heating exhaust gas, 5 ... Exhaust gas heating device, 6 ... Catalyst reactor, 7 ... Combustion catalyst layer, 8 ... Catalyst receiver, 9 ... Weight (catalyst holding) DESCRIPTION OF SYMBOLS 10 ... Combustion process waste gas, 11 ... Auxiliary burner, 12 ... Auxiliary fuel, 13 ... Combustion air, 14 ... Combustion air fan, 15 ... Waste heat recovery device, 16 ... Chimney, 17 ... Exhaust, 18 ... Control valve, 19 ... Temperature controller, 20 ... Catalyst differential pressure gauge.

Claims (5)

In an exhaust gas treatment apparatus that introduces exhaust gas containing harmful components into a combustion catalyst layer and heats and removes the harmful components by catalytic combustion, a catalyst reactor including the combustion catalyst layer and means for supporting the catalyst layer, Means for introducing exhaust gas at a temperature equal to or higher than the catalyst combustion start temperature from below the catalyst layer of the reactor, means for discharging exhaust gas after passing through the combustion catalyst layer from the upper part of the reactor, and the upper part of the combustion catalyst layer. An exhaust gas treatment apparatus provided with weight means for adjusting the load of the catalyst layer . An exhaust gas heating device provided in the upstream of the catalyst reactor for heating the exhaust gas to a temperature equal to or higher than the catalyst combustion start temperature, and a heat exchanger for recovering the combustion heat in the exhaust gas discharged from the catalyst reactor. The exhaust gas treatment apparatus according to claim 1, wherein The exhaust gas treatment apparatus according to claim 1 or 2, wherein means for supporting the catalyst layer in the catalyst reactor is provided below the catalyst layer. An exhaust gas treatment method for introducing exhaust gas containing harmful components into a combustion catalyst layer and heating and removing the harmful components by catalytic combustion, wherein the exhaust gas is heated to a catalytic combustion start temperature by an exhaust gas heating device, and the heated The exhaust gas is introduced from below the catalyst layer into the catalyst reactor supported by the catalyst receiver from below and provided with a combustion catalyst layer provided with a weight means for adjusting the load at the top, and passes through the catalyst layer to pass through the catalyst layer. as well as discharged from the combustion catalyst layer upward After heating remove harmful components, the weight W 1 of the product [Delta] P · a of the passage cross-sectional area a of the exhaust gas pressure difference [Delta] P and the catalyst layer before and after passing through the combustion catalyst layer wherein the combustion catalyst wherein when the greater than the weight W2 of the weight unit, the catalyst layer to generate a blow of exhaust gas, exhaust gas treatment, characterized in that suppresses an excessive increase of the exhaust gas pressure of the catalyst layer inlet and Law. The exhaust gas treatment method according to claim 4 , wherein exhaust gas discharged from above the combustion catalyst layer is introduced into a heat exchanger to recover the combustion heat in the exhaust gas.

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