JP2005003247A - Structure of thermal storage body of thermal storage type exhaust gas treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a thermal storage body of a thermal storage type exhaust gas treatment device capable of effectively inhibiting the attachment of silica. <P>SOLUTION: This thermal storage type exhaust gas treatment device comprises the thermal storage body 4 which is faced to a combustion chamber for heating and decomposing an exhaust gas for alternately circulating an exhaust gas introduced into the combustion chamber and an exhaust gas discharged from the combustion chamber, and heated by the discharged exhaust gas for heating the introduced exhaust gas. Heat-proof coating layers C for reducing the surface energy, are formed on faces of the thermal storage body 4 to be exposed to the exhaust gas, concretely its upper face 4a faced to the combustion chamber and a face of a gas passage 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat storage body structure of a heat storage type exhaust gas treatment device that can effectively suppress silica adhesion.
[0002]
[Prior art]
Exhaust gas from paint drying furnaces and metal heat treatment furnaces includes organic solvents, plasticizers, oils, surfactants, etc., as well as high-boiling, polymeric spear components generated by thermal decomposition of these, ammonia, sulfide It contains harmful components such as hydrogen or dioxins. Therefore, conventionally, exhaust gas containing harmful components is generally supplied to a regenerative exhaust gas treatment device, also called a deodorizing device, and the harmful components are thermally decomposed and made harmless, and then diffused from the exhaust tower to the atmosphere. ing.
[0003]
The heat storage type exhaust gas treatment apparatus has at least two or more heat storage bodies having one end communicating with the combustion chamber, and an on-off valve communicating with the other end of these heat storage bodies, and stores the introduced exhaust gas from the introduction duct through the on-off valve. Circulate to any one of the body, preheat it with the heat storage body, introduce it into the combustion chamber, where the harmful components are thermally decomposed and rendered harmless, and the harmless exhaust gas is circulated to other heat storage bodies After the temperature is lowered by exchanging, it is discharged to an exhaust duct through an on-off valve and diffused from the exhaust tower to the atmosphere. When a predetermined time has elapsed, the open / close state of the on-off valve is switched and preheated by circulating the introduced exhaust gas to the heat storage body heated by the exhaust exhaust gas in the previous process, while being stored by the introduced exhaust gas in the previous process. Repeat the process of circulating hot exhaust gas to the body to heat it and then dissipate it into the atmosphere.
[0004]
The heat accumulator is formed by laminating a plurality of stages of heat accumulating materials having a ceramic honeycomb structure so that exhaust gas can be circulated therein, and by laminating ceramic spherical heat accumulating materials at a predetermined height, and Is composed of a plurality of ceramic pipes cut into a predetermined length.
[0005]
By the way, in some cases, silicon compounds such as organic silicon and silane coupling agents are contained in the exhaust gas, and these silicon compounds in the exhaust gas are oxidized in a high-temperature furnace atmosphere to form particulate silicon oxide ( SiO ₂ : hereinafter referred to as silica). This particulate silica extends from the surface facing the combustion chamber to a considerable depth in the direction in which the exhaust gas flows, and grows by adhering to the heat accumulator, eventually clogging and clogging the heat accumulator. Let In particular, the surface of the heat storage body facing the combustion chamber has the highest temperature, and silica is fused and deposited on this surface and its periphery. If the heat accumulator is clogged by the adhesion and fusion of silica, the pressure loss increases and the heat accumulator is scattered, thereby hindering the continuous operation of the heat accumulator.
[0006]
Conventionally, in order to prevent clogging of the surface of the heat storage body and the inside where the exhaust gas circulates, the heat storage body is regularly cleaned, but the fused silica is extremely hard and is removed. It was extremely difficult, and the apparatus could not be operated during the cleaning period, thus lowering the operation efficiency. In view of such a point, as disclosed in Patent Document 1, the applicant of the present application controls the amount of heat (energy) received while exhaust gas passes through the heat storage body in order to control the adhesion growth of silica on the heat storage body. Focusing on what is necessary, an “exhaust gas treatment method using a regenerative exhaust gas treatment apparatus” was proposed in which the atmosphere temperature in the combustion chamber was maintained at 750 ° C. or more and 810 ° C. or less.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-61822
[Problems to be solved by the invention]
Although the disclosed technique of Patent Document 1 exhibits a sufficient effect of preventing the blockage of the heat storage body, the inventor of the present application has obtained knowledge about the adhesion mechanism of silica, and further the state of the surface of the heat storage body exposed to the exhaust gas. In addition, an effective adhesion prevention technique has been completed.
[0009]
An object of this invention is to provide the thermal storage body structure of the thermal storage type exhaust gas processing apparatus which can suppress the adhesion of a silica effectively.
[0010]
[Means for Solving the Problems]
The heat storage structure of the heat storage type exhaust gas processing apparatus according to the present invention is provided facing a combustion chamber for thermally decomposing exhaust gas, and the exhaust gas introduced into the combustion chamber and the exhaust gas discharged from the combustion chamber alternately In a regenerative exhaust gas treatment apparatus equipped with a heat accumulator that is heated by exhaust gas that is distributed and discharged and heats the introduced exhaust gas, the surface energy of the heat accumulator exposed to the exhaust gas is reduced. A heat-resistant coating layer is formed.
[0011]
The coating layer has heat resistance that can withstand the heat of the exhaust gas, and can reduce the surface energy of the surface of the heat accumulator, thereby effectively preventing silica from adhering to the surface of the heat accumulator. Then, the blockage of the heat storage body can be suppressed.
[0012]
Further, the coating layer is formed on the surface of the heat storage body having a surface temperature of at least 750 ° C. or more. The coating layer may be formed on the surface of the heat storage body of at least 750 ° C. where the silica adhesion becomes significant. By specifying the formation range of the coating layer and reducing the coating amount, the silica adhesion preventing function can be achieved. It becomes possible to obtain the provided heat storage body easily and inexpensively.
[0013]
As a coating material for forming the coating layer, a material containing boron nitride, molybdenum or mica is preferable.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
EMBODIMENT OF THE INVENTION Below, suitable one Embodiment of the thermal storage body structure of the thermal storage type exhaust gas processing apparatus concerning this invention is described in detail with reference to an accompanying drawing. A regenerative exhaust gas treatment apparatus 1 according to this embodiment in which a heat storage body structure according to the present invention is employed is provided with a combustion chamber 2 that includes a burner 3 as a heating means and thermally decomposes exhaust gas, and faces the combustion chamber 2. And at least two (three in the figure) heat storage bodies 4 (4A, 4B, 4C) provided in communication with each heat storage body 4 and introducing exhaust gas containing silicon compounds and harmful components from the introduction duct P1 The first on-off valve V1 (V1a, V1b, V1c) that is circulated through any one of the heat storage bodies 4 and the exhaust gas that is communicated with each heat storage body 4 and has been subjected to thermal decomposition treatment of harmful components in the combustion chamber 2 A second on-off valve V2 (V2a, V2b, V2c) that circulates the body 4 and exhausts to the exhaust duct P2, and a third on-off valve V3 (V3a, V3b, V3c) that supplies purge gas to the remaining heat storage body 4 Prepare. Note that it is not always necessary to provide each of the heat storage bodies 4 with a plurality of on-off valves V1, V2, V3, and the supply / exhaust to each heat storage body 4 may be switched with a single rotary valve.
[0015]
An exhaust fan F is provided in the exhaust duct P2, and a branch duct P4 is provided on the downstream side of the exhaust fan F. The branch duct P4 is connected to the third on-off valve V3, and the exhaust gas is used as a purge gas.
[0016]
Next, an exhaust gas treatment method by the regenerative exhaust gas treatment apparatus 1 having the above-described configuration will be described. First, in the case where the harmful component (solvent) concentration in the introduced exhaust gas containing the silicon compound is lower than its self-flammability limit concentration, the combustion chamber 2 has the burner 3 based on the measured temperature of the temperature measuring means TB provided therein. Is controlled to maintain the atmospheric temperature at 750 to 810 ° C.
[0017]
When the first on-off valve V1a, the second on-off valve V2c, the third on-off valve V3b, and the on-off valve V6 provided in the branch duct P4 are opened and the other is closed, the exhaust fan F is driven, and the exhaust gas introduced (for example, paint) Exhaust gas containing organic silicon and organic solvent from the drying furnace) flows from the introduction duct P1 through the first on-off valve V1a to the combustion chamber 2 through the first heat storage body 4A. Thermally decomposed. After that, the exhaust gas flows through the third heat storage body 4C, is cooled by exchanging heat with the heat storage body 4C, cooled to about 230 ° C., and then discharged from the exhaust tower 5 through the exhaust duct P2 from the second on-off valve V2c. To be dissipated.
[0018]
Further, a part of the exhaust gas flows through the second heat storage body 4B through the branch duct P4 and the third on-off valve V3b by the exhaust fan F, and the exhaust gas remaining in the heat storage body 4B is purged into the combustion chamber 2 To do. And each on-off valve V1, V2, V3 switches for every predetermined time.
[0019]
That is, when a predetermined time (for example, 1 minute) elapses, the first on-off valve V1a, the second on-off valve V2c, and the third on-off valve V3b are closed, and the first on-off valve V1c, the second on-off valve V2b, and the third on-off valve V3a. Is opened, the introduced exhaust gas is distributed to the third heat storage body 4C heated by the exhaust gas in the previous process, preheated and then thermally decomposed in the combustion chamber 2, and the exhaust gas is purged in the previous process. 2 It is dissipated from the heat storage body 4B to the atmosphere from the exhaust tower 5 through the exhaust duct P2. On the other hand, purge gas is supplied to the first heat storage body 4A, and the exhaust gas remaining in the heat storage body 4A is purged into the combustion chamber 2 as described above. Thereafter, the on-off valves V1, V2, and V3 are switched so that the exhaust gas is circulated through the first heat storage body 4A, the introduced exhaust gas is circulated through the second heat storage body 4B, and the purge gas is supplied to the third heat storage body 4C. Repeat the process.
[0020]
By the way, in the same way as in the past, the heat storage body 4 itself has a structure in which a plurality of heat storage materials having a ceramic honeycomb structure shown in FIG. Between the on-off valves V1, V2, and V3 side and the combustion chamber 2 side, such as those in which spherical heat storage materials are laminated at a predetermined height, or a plurality of ceramic pipes cut to a predetermined length A plurality of gas passages 10 communicating with each other are provided.
[0021]
And the present inventors obtained the following knowledge as a result of earnest research about the obstruction | occlusion mechanism of the thermal storage body 4 by a silica. First, the silica adhesion layer exists from the surface of the heat storage body 4 having the highest temperature facing the combustion chamber 2, in the illustrated example, from the upper surface 4 a to a considerable depth in the gas passage 10. As a result, it was confirmed that the silica layer adhered to the upper surface 4a of the heat accumulator 4 and further fused to grow into a layer, and this layered silica passed through the gas passage 10. As the result, the silica gradually accumulates on the surface of the heat storage body 4 exposed to the exhaust gas, specifically, the upper surface 4a of the heat storage body 4 and the passage surface of the gas passage 10, It is considered that the heat storage body 4 is blocked by the above.
[0022]
Further, the silica itself, which is formed by oxidizing a silicon compound such as organic silicon in the combustion chamber 2 at a high temperature, is a small particle having a minimum particle size of less than 1 μm as a result of observing the sample collected in the combustion chamber 2. It was an aggregate. In such a small particle, the specific surface area is extremely large, so the surface tension (surface energy) also becomes considerably large, and fusion occurs at a temperature much lower than that of a large particle at the contact portion of the particle. become. For this reason, fine silica powder adheres to the upper surface 4a of the heat storage body 4 or the passage surface of the gas passage 10 by agglomeration or collision, and because it is a fine particle, it is fused and fixed even when the combustion chamber temperature is around 810 ° C. It is estimated that. The partial appearance of the shell pattern described above indicates that the particles are fused. Judging from the temperature distribution of the heat accumulator 4, fusion occurs at a temperature of 750 ° C. or higher, and it is considered that this fusion is inevitable in a high temperature state required for the thermal decomposition treatment.
[0023]
Second, and this point is important, as shown in FIG. 4, the surface of the heat accumulator 4 has a fine diameter of about several tens of micrometers in order to prevent it from being damaged by thermal shock. There are an infinite number of macropores 12 that are pores, and it is estimated that the presence of the macropores 12 enhances the adsorptivity of gaseous substances on the surface of the heat storage body 4, that is, silica. This is also understood from the fact that silica was clogged in the macropores 12 on the upper surface 4a of the heat accumulator that faced the combustion chamber 2 and was exposed to exhaust gas.
[0024]
Therefore, the sticking occurs on the surface of the heat storage body 4 is caused by the high temperature as one of the causes, and the surface of the heat storage body 4 attracts the cause gas (exhaust gas) that is going to become silica. It is presumed that the surface is easy to show gas adsorbability. For this reason, if the silica fine particles adhere to the surface of the heat storage body 4 and the temperature is above a certain level, it is considered that clogging with silica occurs with a considerable probability.
[0025]
Based on the above findings, the inventors of the present application can solve the blockage if the surface of the heat storage body 4 to which the silica adheres can be made difficult to adhere so that the frosted glass repels water. The conclusion was reached. For example, the surface energy can be reduced by applying a fluorine compound or a silane coupling agent to a glass having a high gloss property. And when water with higher surface energy adheres, the behavior of these glazing glasses and water is such that the surface energy is kept to a minimum, i.e. in this example the surface area of water with higher surface energy. In order to minimize the water, the water tends to approach the sphere, and it is very slick.
[0026]
Based on the above examination, in this embodiment, as shown in FIG. 2, the introduced exhaust gas introduced into the combustion chamber 2 and the exhaust exhaust gas discharged from the combustion chamber 2 are alternately circulated, In order to heat the introduced exhaust gas, the surface energy is applied to the surface of the heat storage body 4 having the macropores 12 exposed to the exhaust gas, specifically, the upper surface 4a and the passage surface of the gas passage 10 in order to heat the introduced exhaust gas. A heat-resistant coating layer C to be reduced is formed.
[0027]
The surface energy of the heat storage body 4 is reduced to form a so-called hydrophobic coating layer C, so that the macropores 12 on the surface of the heat storage body 4 are covered to form a surface that is difficult to adsorb. be able to. Even if it cannot be covered, the surface energy at the entrance of the macropore 12 can be lowered by the coating layer C, and the intrusion of silica into the macropore 12 can be prevented. The surface of the coating layer C is preferably a flat surface.
[0028]
As the coating material for forming the coating layer C, it is preferable to employ a material containing boron nitride or molybdenum which is used as a mold release material and is in the form of fine particles and has stable heat resistance in a high temperature state. Moreover, you may use the coating material containing a mica. Actually, when water is adhered to the coating layer C formed by the coating material containing boron nitride formed on the surface of the heat storage body 4, the surface energy of the coating layer C is lower than that of water, so that the water droplets are kept in a spherical shape. Was observed. On the other hand, it was observed that when a water droplet approaches the surface of the normal heat storage body 4, it absorbs water instantly.
[0029]
In this way, the coating layer C has heat resistance that can withstand the atmospheric temperature in the combustion chamber 2 and the heat of the exhaust gas flowing, and reduces the surface energy of the surface of the heat storage body 4. 4, for example, the upper surface 4 a and the passage surface of the gas passage 10 can be appropriately prevented, and the heat storage body 4 can be prevented from being blocked. As a result, it becomes possible to make the heat storage body 4 maintenance-free, reduce pressure loss and prevent the heat storage body 4 from being scattered, and allow the heat storage type exhaust gas treatment apparatus 1 to operate continuously over a long period of time. It becomes.
[0030]
Further, the coating layer C may be formed on the surface of the heat storage body 4 in the region R where the surface temperature reaches at least 750 ° C., in which the silica adheres significantly, thereby identifying the formation range R of the coating layer C. By reducing the coating amount, the heat storage body 4 having a silica adhesion preventing function can be obtained easily and inexpensively.
[0031]
On the other hand, in order to reduce fusion, it is preferable to combine with the technique which suppresses the atmospheric temperature in the combustion chamber 2 to 810 degrees C or less which the applicant of this application disclosed by the said patent document 1. FIG. In this patent document 1, the atmospheric temperature of the combustion chamber 2 is set as low as about 750 to 810 ° C., and the amount of heat stored in the heat storage body 4 is reduced, so that the heat energy supplied to the exhaust gas is reduced, and the silicon compound is silica. The reaction time required to become longer is made longer, thereby suppressing the silica adhesion growth in the heat storage body 4.
[0032]
Specifically, as shown in FIG. 1, a dilution gas supply pipe P3 having a first control valve V4 is provided in the introduction duct P1, and the first control valve V4 is opened and closed by a signal from the temperature measuring means TB. When the atmospheric temperature in the combustion chamber 2 rises to 810 ° C., the first control valve V4 is opened to supply dilution gas (for example, air) into the introduced exhaust gas, and the atmospheric temperature in the combustion chamber 2 becomes 750 to 810 ° C. Control to be.
[0033]
Further, the exhaust gas treatment amount (flow rate) is adjusted by controlling the exhaust fan F to maintain the inside of the introduction duct P1 at a predetermined pressure. As described above, the dilution gas is supplied to the introduction duct P1. Therefore, when the first control valve V4 is opened, the pressure in the introduction duct P1 increases because it approaches atmospheric pressure, and the amount of exhaust gas containing silicon compounds and harmful substances decreases. Therefore, the pressure in the introduction duct P1 is detected in order to prevent a reduction in the amount of exhaust gas treated due to the opening of the first control valve V4, and when the detected pressure fluctuates, the exhaust in order to maintain the pressure in the introduction duct P1 at a predetermined value. The number of rotations of the motor M of the fan F is increased.
[0034]
Further, when the atmospheric temperature of the combustion chamber 2 rises even if the dilution gas is supplied into the introduced exhaust gas, when the atmospheric temperature of the combustion chamber 2 reaches 820 ° C., the second control valve V5 is received by a signal from the temperature measuring means TB. Is opened, and a part of the high-temperature atmosphere in the combustion chamber 2 is directly discharged to the exhaust duct P2 via the branch exhaust duct P5 to suppress an increase in the atmosphere temperature in the combustion chamber 2. The combination with such temperature control in the combustion chamber 2 can effectively prevent the heat storage body 4 from being blocked.
[0035]
Next, a method for forming the heat storage body 4 of the heat storage type exhaust gas treatment apparatus 1 will be described. Basically, the coating layer C may be formed by spraying a heat-resistant coating material that reduces the surface energy on the surface of the heat storage body 4 exposed to the exhaust gas. In spraying, a general pressurized spray may be used. The coating operation can be performed with the heat storage body 4 attached to the heat storage type exhaust gas treatment device 1.
[0036]
First, before spraying a coating material, the foreign material adhering to the heat storage body 4 is removed so that the aperture of the gas passage 10 may not be narrowed. The coating material is diluted with water. By diluting the coating material with water, the viscosity of the sprayed coating material can be lowered to ensure smooth spraying and uniform spraying on the surface of the heat storage body 4 by spraying. The coating material is sprayed onto the heat storage body 4 in a normal temperature state. Due to the high water absorption of the heat storage body 4 itself, moisture is immediately absorbed by the heat storage body 4, and only the coating material is in close contact with the heat storage body 4. The spraying of the coating material is performed over the portion of the gas passage 10 that reaches 750 ° C. or more from the upper surface 4 a facing the combustion chamber 2. By the procedure as described above, the coating layer C can be easily formed on the heat storage body.
[0037]
【The invention's effect】
In short, in the heat storage body structure of the heat storage type exhaust gas treatment apparatus according to the present invention, silica adhesion to the heat storage body can be effectively suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a heat storage type exhaust gas treatment apparatus in which a heat storage body structure of a heat storage type exhaust gas treatment apparatus according to the present invention is adopted.
FIG. 2 is a partial perspective view showing a preferred embodiment of a heat storage structure of a heat storage type exhaust gas treatment apparatus according to the present invention.
FIG. 3 is a perspective view of a heat storage body upper surface portion showing a general structure of a heat storage body of a heat storage type exhaust gas treatment apparatus.
4 is a partial side cross-sectional view of a heat storage body showing macropores existing on the surface of the heat storage body of FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thermal storage type exhaust gas processing apparatus 2 Combustion chamber 4 Thermal storage body 4a Upper surface 10 of thermal storage body Gas passage C Coating layer

Claims (3)

The exhaust gas is provided facing the combustion chamber where the exhaust gas is thermally decomposed, and the exhaust gas introduced into the combustion chamber and the exhaust gas discharged from the combustion chamber are alternately circulated, heated by the exhaust gas discharged, and introduced. In a heat storage type exhaust gas treatment apparatus equipped with a heat storage body for heating the exhaust gas to be heated, a heat storage type coating is provided on the surface of the heat storage body exposed to the exhaust gas, and a heat-resistant coating layer for reducing the surface energy is formed. Heat storage structure of exhaust gas treatment equipment. The heat storage structure of a heat storage type exhaust gas treatment apparatus according to claim 1, wherein the coating layer is formed on a surface of the heat storage body having a surface temperature of at least 750 ° C or higher. The heat storage structure of a heat storage type exhaust gas treatment apparatus according to claim 1 or 2, wherein the coating layer is formed of a coating material containing boron nitride, molybdenum, or mica.

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