JP3662650B2 - Catalyst structure and gas combustion decomposition apparatus using the same - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a catalyst structure and a gas combustion decomposition apparatus using the catalyst structure, and in particular, an inexpensive catalyst structure that has good start-up characteristics and can easily cope with load fluctuations, and uses the same. The present invention relates to a harmful gas combustion decomposition apparatus.
[0002]
[Prior art]
In recent years, it has been proposed to increase the thermal efficiency of the reaction by using a plate-shaped catalyst body having a heat exchange function (for example, JP-A Nos. 62-237947 and 63-16835). In addition, a method for more directly controlling the catalytic reaction by passing an electric current through the catalyst body has been proposed (Japanese Patent Laid-Open No. 2-227135).
[0003]
However, since the conventional plate-shaped catalyst body was mainly intended to effectively use the heat of reaction, it cannot be satisfied from the viewpoint of rapid control of the reaction. Next, for example, since this was assembled into a honeycomb structure and placed in the reaction chamber, there was a disadvantage that it had to be expensive.
[0004]
In addition, the method of heating the catalyst body by passing an electric current has advantages such as maintaining the catalyst itself at a uniform temperature, good start-up characteristics, and being able to easily cope with load fluctuations. Since it is necessary to electrically insulate the medium from other supporting members and the like, if this is used for the catalyst structure, it must be more expensive.
Further, this method has a disadvantage that it cannot be used for a reaction using a flammable gas because there is a possibility of explosion due to an electric spark.
[0005]
On the other hand, these catalysts have been conventionally used to purify volatile organic compounds such as toluene, xylene, trichlorethylene, and harmful gases such as vinyl chloride monomer, methyl chloride, and acrylonitrile, which have recently caused air pollution. It is used to burn. In this case, a honeycomb type catalyst body with less pressure loss is used to improve the processing efficiency. However, since the space velocity (SV) of the gas flow rate is about 40,000 at the maximum, the processing speed is not sufficient. Since the material is ceramic, there is a drawback that it is vulnerable to thermal shock.
[0006]
Even if an electric heating means is added for the purpose of quickly controlling the catalytic reaction or reactivating the deteriorated catalyst, the temperature rise characteristics are poor due to the low thermal conductivity of the ceramic, and the rapid reaction. There was a drawback that it was not possible to sufficiently respond to the demand for control and catalyst reactivation.
A similar defect exists also in the case of a denitration catalyst body of exhaust gas whose base material is ceramic, and there is a defect that it is difficult to regenerate the catalytic activity.
[0007]
Furthermore, when a ceramic substrate is used, the apparatus cannot be processed in a large size, and there is a disadvantage that workability is poor.
Examples of using an anodic oxidation catalyst suitable for an increase in size are disclosed in, for example, Japanese Utility Model Laid-Open No. 3-123532 and Japanese Patent Laid-Open No. 4-200745. In this case, the SV is as small as about 3,000. , Could not be a practical device.
[0008]
In order to solve such drawbacks, a method using a honeycomb heater made of stainless steel has also been proposed (for example, JP-A-2-223622). However, in this method, the stainless steel is directly energized. In addition, it is necessary to flow a large current at a low voltage, which is difficult to use and has a disadvantage that the safety of the electrode portion is not sufficient in a high temperature range of about 350 ° C.
[0009]
[Problems to be solved by the invention]
Therefore, the present inventors have conducted extensive studies to obtain a heat exchange type catalyst structure with low pressure loss, high performance, easy reaction control, and low cost. After anodizing the inside of the aluminum heat exchanger in which corrugated fins are alternately stacked, the catalyst is further supported, and when the electric heating means is arranged on the outer wall, it is inexpensive, It has high thermal efficiency, facilitates reaction control, is safe to use in the case of flammable gas, and is very easy to use because it is highly safe even at high temperatures. As a result, the present inventors have found that the catalyst structure is suitable.
[0010]
Accordingly, a first object of the present invention is to provide an inexpensive catalyst structure having excellent thermal efficiency and reaction controllability, which has good start-up characteristics and can easily cope with load fluctuations. is there.
A second object of the present invention is to provide a catalyst structure that can achieve a space velocity larger than that of a conventional product and can be made compact.
A third object of the present invention is to provide an inexpensive catalyst structure that is safe and easy to use even at high temperatures.
A fourth object of the present invention is to provide an inexpensive and high-performance combustion decomposition apparatus suitable for purification of exhaust gas containing volatile organic compounds and harmful gases.
[0011]
[Means for Solving the Problems]
The above-mentioned objects of the present invention include an internal structure in which separate sheets and corrugated fins are alternately stacked, and at least the corrugated fins are made of a metal having a surface that can be anodized, and have a gas inlet and outlet. A catalyst structure obtained by anodizing the interior of the exchanger and then carrying out hydrothermal treatment or simultaneously carrying the catalyst on the hydrothermal treatment, having an electric heating means with an insulation coating on the outer wall And a combustion cracking apparatus using the catalyst structure .
[0012]
In the present invention, superimposed corrugated fins and separate sheet made of a metal having the anodized surface capable (separate sheet is rather good not be identical substrate and the corrugated fins, which may be a material that can not be anodized) and alternately Then, the inside of the heat exchanger disposed inside the casing is subjected to sequential anodization, hydrothermal treatment, and catalyst support treatment (including firing), and then an electric heating means is provided on the outer wall . As the heat exchanger before the anodization, a commercial product having corrugated fins made of a metal having an anodizable surface may be used.
[0013]
A catalyst structure using a commercially available product has a small manufacturing process and can reduce the number of man-hours for management, so that it is particularly inexpensive and is a preferred embodiment in the present invention.
The commercially available heat exchanger has an internal structure in which separate sheets and corrugated fins are alternately stacked and brazed, and specific examples thereof include, for example, a plate fin type heat exchanger manufactured by Sumitomo Seimitsu Kogyo Co., Ltd. (Product name: Sumarex).
[0014]
When used in the present invention, among these heat exchangers, in particular, at least the substrate surface of the corrugated fin needs to be anodizable. Examples of such a substrate include aluminum alone, a metal provided with an aluminum layer on the surface by a cladding method or a thermal spraying method, or an alloy such as duralumin containing 60% by weight or more of aluminum.
Further, the corrugated fin may have any shape such as a plate fin type, a herringbone type, or a serrate type, but usually the gas flow rate in the catalyst body is in a laminar flow state of 0.5 to 1.5 m / sec. In particular, a herringbone type or a serate type that generates turbulent flow so that the gas can easily come into contact with the catalyst is preferable from the viewpoint of increasing the reaction efficiency.
[0015]
Anodizing the inside of such a complex structure is impossible even by simply applying a known anodizing method. Therefore, the electrolytic solution is allowed to flow through the structure serving as the anode, and the flow of the electrolytic solution is not obstructed in the vicinity of the inlet and the outlet of the structure with respect to the inlet and the outlet. Thus, it is necessary to dispose a cathode, and to pass a current between the two cathodes and the structure serving as the anode.
[0016]
The flow rate of the electrolytic solution in the present invention cannot be limited because it varies depending on the length of the structure, the current density, the acid concentration, and the like, and it is only necessary to select conditions suitable for the formation of the target anodic oxide film. . For example, when an anodized film having a uniform film thickness is formed, the flow rate may be adjusted so that the difference between the temperature near the inlet and the temperature near the outlet is within 2 ° C. In addition, when the film thickness distribution is formed from the inlet toward the outlet, the flow rate may be adjusted so that a temperature difference is generated between the vicinity of the inlet and the vicinity of the outlet.
[0017]
The electrolyte used in the present invention can be appropriately selected from known electrolytes used for anodization, such as sulfuric acid, chromic acid, oxalic acid, phosphoric acid, etc., but is easy to handle and control of anodization. From this viewpoint, oxalic acid is most preferable.
The acid concentration can be appropriately selected within the range of 1 wt% to 10 wt%, the liquid temperature is 5 ° C. to 45 ° C., and the current density is within the range of 10 A / m ^{2 to} 1,000 A / m ^2. It is preferable that the liquid temperature is 15 ° C. to 25 ° C., and the current is 50 A / m ^{2 to} 100 A / m ² .
By anodizing for 30 minutes to 50 hours under the conditions described above, an anodized film of 30 μm to 500 μm can be freely formed on the inner surface of the structure.
[0018]
The catalyst structure of the present invention is anodized in the form of the heat exchanger as it is by the above method to form an anodized film on at least the surface of the corrugated fin, and then hydrothermal treatment (hydration treatment) To increase the BET surface area of the surface of the oxide film, or simultaneously with the hydrothermal treatment, a catalyst supporting treatment is performed, followed by a firing treatment.
The hot water treatment is preferably performed by immersing the anodized heat exchanger in the treatment solution for 15 minutes to 3 hours.
[0019]
If the hydrothermal treatment is carried out with heated water or steam, it is necessary to carry out the catalyst supporting treatment in the next step, but if the hydrothermal treatment is carried out in an aqueous solution in which the water-soluble salt of the catalyst is dissolved, simultaneously with the hydrothermal treatment A catalyst carrying treatment can be performed. The hydrothermal treatment is preferably performed at 5 ° C to 80 ° C. Moreover, as a subsequent baking process, it is preferable to use the method of air baking at 300 to 500 degreeC.
[0020]
In addition, the base material of the outer wall of the catalyst structure of the present invention may be a base material on which the catalyst is supported. However, as long as the thermal conductivity is good, for example, stainless steel is used. Other substrates can be used as necessary.
The electric heating means used in the present invention applies heat to the inside of the structure through the outer wall of the structure of the present invention, and is a known electric heating means such as a planar heater or a linear heater coated with insulation. It can be used by appropriately selecting from among them. The heat output of the electric heating means to be used can be appropriately determined according to the temperature of the catalytic reaction, the size of the catalyst structure to be used, and the like.
[0021]
The heat given from the heating means to the structure is directly supplied to the reaction gas in contact with the outer wall of the structure, and is also supplied to the corrugated fins by heat conduction, thereby quickly controlling the catalyst surface temperature. . Therefore, the start-up characteristic and load fluctuation characteristic of the catalyst structure of the present invention are remarkably improved.
[0022]
The catalyst structure of the present invention is preferably portable so that the total weight is 25 kg or less. In addition, in the case where a large catalyst structure is required, both ends of the catalyst structure are formed so as to be connectable to other catalyst structures from the viewpoint of enabling connection of the individual catalyst structures to each other. It is preferable to do.
The length in the flow direction of the catalyst structure of the present invention is preferably 50 to 200 mm from the viewpoint of improving the handleability. If a larger size is required, a plurality of catalyst structures may be connected as described above.
[0023]
Next, the catalyst structure of the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a schematic perspective view showing an example of the catalyst structure of the present invention.
Reference numeral 1 in the figure denotes a catalyst structure of the present invention, and reference numeral 2 denotes a corrugated fin carrying a catalyst, in which the inside of the structure is finely divided in order to increase the contact area between the gas and the catalyst. It has become. Reference numeral 3 denotes a separate sheet for partitioning the gas flow path into multiple layers. If this substrate is also an anodizable substrate, the catalyst is naturally supported on this surface. Reference numeral 4 denotes an electric heater arranged on the wall of the structure, and 5 denotes an outlet.
Moreover, although FIG. 1 is a one-way flow type, it is a matter of course that a cross flow type and a heat exchange function may be provided.
[0024]
When the outer wall of the catalyst structure of the present invention is heated by the heater 4, a part of the heat of the heater 4 is given to the reaction gas through the outer wall, but most of the heat is transferred to the metal plate carrying the catalyst, Heat.
As a result, the surface temperature of the catalyst can be raised rapidly, so that not only the start-up characteristics can be improved, but also the surface temperature of the catalyst can be changed quickly by adjusting the current flowing through the heater for electric heating. Therefore, it is possible to easily cope with load fluctuations.
By providing a temperature sensor on the catalyst surface, the heater current can be automatically controlled so that the catalyst surface temperature becomes constant.
[0025]
Next, the case where two catalyst structures of the present invention are connected and used will be described with reference to FIG.
Reference numeral 6 in the figure is a piece bent in an elbow shape for receiving a piece 7 provided at the lower end of the rear part of another structure in order to connect the catalyst structures to each other. This is a piece for connecting and fixing the structure. For connection, after the other catalyst piece 7 is inserted into the L-shaped piece 6, the ends of the structures are aligned and fixed with each other piece 8. As the fixing means, known means such as screwing can be used.
[0026]
For connection between structures, a male edge 10 is provided on the outer periphery of one end of the structure, and a female edge 11 is fitted on the outer periphery of the other end to which the male edge of the structure to be connected fits. May be provided (see FIG. 3). In this case, the fitting portion is preferably provided with a packing 12 in order to improve the seal (see FIG. 3). Two or more structures can be used not only in series but also bundled in parallel.
In this way, the catalyst structure can be assembled into an arbitrary size depending on the type or amount of catalytic reaction to be applied.
[0027]
Next, the combustion decomposition apparatus of the present invention using the catalyst structure of the present invention will be described.
Normally, volatile organic compounds (VOC) and odorous substances contained in exhaust gas etc. are completely burned under the catalyst using oxygen in the air, and are converted into harmless and odorless CO ₂ and H ₂ O as shown in the following formula. Become.
C _X H _Y O _Z + mO ₂ → XCO ₂ + (Y / 2) H ₂ O
The combustion flow in this case is shown, for example, in FIG. 4, and the combustion decomposition apparatus of the present invention includes at least a gas heating device and a catalyst portion to be combusted. A pretreatment device such as a filter or a heat exchange function can be provided.
[0028]
Hereinafter, the combustion decomposition apparatus of this invention is explained in full detail based on drawing.
FIG. 5 is a conceptual diagram of a basic box-type combustion decomposition apparatus of the present invention using the catalyst structure of the present invention as a reaction chamber.
In the figure, reference numeral 20 is a gas inlet, 21 is a gas heating means, 22 is a reaction chamber comprising the catalyst structure of the present invention, and two structures 22-a and 22-b are used in this figure. However, it is natural that only one or three or more may be used. When a plurality of structures are used, it is preferable to wire each structure so that the temperature can be controlled independently.
Reference numeral 23 is a fan for exhausting gas, 24 is a flow meter, 25 is an exhaust port, and 26 is a central partition plate for preventing gas flow between the two reaction chambers other than the gas flow path 30. It is.
[0029]
A pre-processing means such as a filter may be provided in the preceding stage of the gas heating means 21 as appropriate. The gas heating means can be appropriately selected from known heating means such as a heater, but a heat storage body may be installed from the viewpoint of thermal efficiency. In this case, it is preferable to further arrange a heater in the gas flow path 30 connecting the two reaction chambers.
Of course, it is naturally possible to use a simple cylindrical shape instead of the box shape as shown in the figure. In the case of such a shape, for example, it can be incorporated into the exhaust pipe of an automobile.
[0030]
FIG. 6 is another embodiment of the combustion cracking apparatus of the present invention having two sets of dampers 27-a and 27-b for reversing the gas flow path as required. Reversing the gas flow path in this way is meaningful, for example, when the catalyst in the first structure is different from the catalyst in the second structure.
In this case, since each reaction chamber is completely equivalent, the gas heating means 21 and a heat storage body that may be provided if necessary must be provided for each reaction chamber.
The combustion decomposition apparatus of the present invention thus obtained can be used as an exhaust gas treatment apparatus for automobiles and the like, and as a waste gas treatment apparatus from an incinerator or factory. Further, the catalyst structure can be used with heat exchange ability.
[0031]
The catalyst structure of the present invention, the corrugated fin comprising a material capable of positive pole oxidation, and, it becomes a stack of the separate sheet alternately in heat exchange with an inlet and an outlet of the gas structure inside the Obtained after anodizing at least the corrugated fins and, if necessary, hydrothermal treatment, or by carrying the catalyst support simultaneously with the hydrothermal treatment using an aqueous solution containing a catalyst salt, and then calcining. It can be obtained by disposing an insulating heating means on the outer wall of the structure.
[0032]
Further, the gas combustion decomposition apparatus of the present invention comprises a gas inlet (20), a heating means (21) for heating the introduced gas, a reaction chamber (22) for burning and decomposing the heated gas, and a reaction. Gas combustion comprising a fan (23) for letting gas flow out from the chamber (22) to the exhaust port (25), and a flow meter (24) provided between the fan (23) and the exhaust port (25). It can be obtained by arranging the catalyst structure of the present invention as the reaction chamber in the decomposition apparatus.
[0033]
【The invention's effect】
The catalyst structure of the present invention is a heat exchange type structure in which an electric heating means is arranged on the outer wall of the catalyst structure, so that not only thermal efficiency is good, but also startup characteristics can be improved and load fluctuations can be achieved. It can also be easily applied to flammable gases. In addition, the catalyst structure of the present invention is easy to use because of its high safety even at high temperatures.
[0034]
Furthermore, the catalyst structure of the present invention is inexpensive because it can be manufactured by modifying a heat exchanger that has already been manufactured. In addition, since it can be easily connected and lightweight, it can be carried. Therefore, it is easy to set the size appropriately according to the catalytic reaction.
In addition, the gas combustion decomposition apparatus of the present invention using the structure of the present invention has high pressure loss and high performance, and can be arbitrarily designed from a small apparatus to a large apparatus as required. The application range is extremely wide.
[0035]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this.
Example 1.
A commercial heat exchanger (see FIG. 1) having a size of 10 cm × 10 cm × 10 cm, in which corrugated fins are made of plate fin type aluminum plates, was washed for 3 minutes in a 20 wt% sodium hydroxide solution. Thereafter, a pretreatment was performed for neutralizing in a 30% by weight aqueous nitric acid solution for 1 minute. Subsequently, anodization was performed for 8 hours in an aqueous solution of oxalic acid at 20 ° C. and a current density of 100 A / m ² under the condition that the electrolyte flowed into the heat exchanger. Next, the heat exchanger was cut, and the thickness of the anodized film formed on the corrugated fin surface was measured and found to be about 100 μm.
[0036]
As described above, the heat exchanger anodized inside as described above is immersed in an aqueous solution containing chloroplatinic acid, treated at 80 ° C. for 60 minutes, dried, baked at 500 ° C., and corrugated. A catalyst structure in which a platinum catalyst was supported on the anodic oxide film of the fin was obtained.
Next, a 50 W ribbon heater with insulation coating was provided around the outer wall to produce the catalyst structure of the present invention.
[0037]
The results of measuring the change in the catalyst surface temperature over time when the current was intermittently supplied to the electric heater (output 50 W) in the electric furnace at 238 ° C. in the produced catalyst structure are as shown in FIG. It is. From the results shown in FIG. 7, when an electric current is passed, a temperature increase of about 140 ° C. is recognized within 5 minutes, and when the electric current is cut off, the temperature returns quickly to the original temperature. Was confirmed to be extremely short. Incidentally, it took 30 minutes to increase the catalyst surface temperature by 140 ° C. by changing the temperature of the electric furnace itself.
Example 2
A catalyst structure of the same size was produced in the same manner as in Example 1 except that a commercially available heat exchanger with a corrugated fin of serrate type was used.
Using the obtained two catalyst structures, a regenerative catalytic combustion test apparatus shown in FIG. 8 was prepared, and 1.0 (m ³ / min) of air containing 200 ppm of toluene as a volatile organic compound was produced in this apparatus. ) And the catalyst structure was processed at a room temperature of 250 ° C., the result shown in FIG. 9 was obtained.
As can be seen from FIG. 9, the decomposition rate at a space velocity (SV) of 70,000 was 99%, which proved that the treatment performance of the combustion decomposition apparatus of the present invention was extremely high.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a catalyst structure of the present invention.
FIG. 2 is a schematic perspective view when two catalyst structures of the present invention are connected and used.
FIG. 3 is an enlarged schematic view of a partial cross section of a connection portion in which two catalyst structures are connected.
FIG. 4 is an example of a combustion flow for processing volatile organic gas and the like.
FIG. 5 is a conceptual diagram showing an example of a combustion decomposition apparatus according to the present invention.
FIG. 6 is a conceptual diagram of a combustion decomposition apparatus of the present invention that can reverse the flow direction of combustion gas.
FIG. 7 is a graph showing a change with time in the surface temperature of a catalyst body when an electric current is intermittently passed through an electric heater.
FIG. 8 is a conceptual diagram of a combustion decomposition apparatus according to the present invention, which is a heat storage type.
9 is a graph showing the decomposition rate with respect to the space velocity of the processing gas obtained in Example 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Catalyst structure 2 Corrugated fin 3 Separate sheet 4 Electric heater 5 Power supply outlet 6 L-shaped stopper 7 provided in the lower end part L-shape of the other structure provided in the lower end part of the catalyst structure A piece 8 to be fitted to the stopper 9 A connecting piece 9 provided at the upper end portion 10 A gas flow direction 10 A male edge 11 provided on the outer periphery of the opening at the end of the structure 11 A female edge 12 Packing 20 Gas introduction Port 21 Gas heating means 22 Reaction chamber 23 comprising the catalyst structure of the present invention Fan 24 Flow meter 25 Exhaust port 26 Central partition plate 27 Damper 28 Heat storage body 29 Thermocouple 30 Gas flow path

Claims (9)

It has an internal configuration in which separate sheets and corrugated fins are alternately stacked, and at least the corrugated fins are made of a metal having a surface that can be anodized. Next, a catalyst structure obtained by carrying out a catalyst carrying treatment after hydrothermal treatment or simultaneously with hydrothermal treatment, characterized in that it has an electric heating means with an insulation coating on its outer wall. The catalyst structure according to claim 1, wherein the corrugated fin is of a herringbone type. The catalyst structure according to claim 1, wherein the corrugated fin is of a serate type. The catalyst structure according to any one of claims 1 to 3, wherein a length between the gas inlet and the outlet is 50 to 200 mm. The catalyst structure according to any one of claims 1 to 4, which has a total weight of 25 kg or less and is portable. The catalyst structure according to any one of claims 1 to 5, wherein both end portions are formed so as to be connectable to other catalyst structures. Gas inlet (20), heating means (21) for heating the introduced gas, reaction chamber (22) for burning and decomposing the heated gas, and exhaust port (25) from the reaction chamber (22) A device having a fan (23) for letting gas flow out to the air and a flow meter (24) provided between the fan (23) and the exhaust port (25), wherein the reaction chamber (22) A gas combustion decomposition apparatus comprising the catalyst structure according to any one of claims 1 to 6. 8. The gas combustion decomposition apparatus has a compact box shape in which at least two catalyst structures are included in parallel, and each catalyst structure is arranged so that gas sequentially passes. The described gas combustion cracker. The gas combustion decomposition apparatus according to claim 8, wherein a damper device for reversing the flow method of the gas flowing through each catalyst structure is provided between the gas inlet (20) and the fan (26).

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