JPS59136140A - Catalyst body for combustion - Google Patents

Abstract

PURPOSE:To provide a catalyst body having catalysts for contact combustion on the wall surfaces of flow passages in which fuel-contg. gas flows and meeting the combustion condition for high load by arranging two kinds of flow passages having catalytic activity and having no catalytic activity so as to contact with each other via the wall surfaces. CONSTITUTION:The flow passages in a monolithic catalyst are formed by arranging flow passages 15 having catalyst layers on the surface and flow passages 16 having no catalyst layers adjacently with each other. The combustion heat generated on the layers 11 in the passages 15 flows therefore in the form of heat flow 12 in the flow passage direction and is used only for preheating of a gaseous mixture; at the same time, the layers 11 are cooled and the thermal deterioration thereof is prevented. The heat flow in the direction opposite to the inflow direction of the gas is decreased by the flow 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion catalyst, and more particularly to a catalyst for catalytic combustion suitable for high-load combustion, and a combustion apparatus using the catalyst.

In recent years, many attempts have been made to downsize boilers and various combustors by using the so-called catalytic combustion method, which promotes combustion reactions using catalysts.

In the catalytic combustion method, the volumetric combustion rate (k a L / ffI''h), which is the amount of heat generated per unit volume and time, is several ten times larger than that in the conventional flame combustion method. The catalytic combustion method also has the following advantages: (1) It is difficult to generate nitrogen oxides (NOT) (2) Complete combustion is possible at low oxygen concentrations. I have one, and the practical application of water washing is eagerly awaited.

However, in the above-mentioned catalytic combustion method, when the catalyst is used under high-load conditions, the catalyst deteriorates due to combustion heat, which is a major obstacle to practical application. For this reason, measures to avoid thermal deterioration of the catalyst are being considered by methods such as (1) recirculation of combustion gas and (2) dispensing of fuel.

That is, FIG. 1 shows an improved example of combustion gas recirculation, in which the air introduced from the air introduction pipe 3 is preheated by the heat exchanger 8, and then fuel is injected from the pipe 2. After being uniformly mixed in the mixer 5, the mixture is introduced into the catalyst device IA loaded with the catalyst body 1, and subjected to catalytic combustion. The combustion exhaust gas of the catalyst device IA is taken out through the heat recovery device 4, and a part of it passes through the pipe 6 and is sent to the fuel injection pipe 2 from the blower 7 trap.
The remaining exhaust gas is sent to the aforementioned heat exchanger 8, where the heat is recovered, and the remaining exhaust gas is then sent to the external K II through the piping 9.
Fig. 2 shows an example of improvement by dispensing fuel, in which the air introduced through the air introduction pipe 3 is preheated through the preheater 1o, and then is discharged from the pipe 2. After the fuel is injected and mixed in the trap mixer 5, the catalytic combustion unit IAK is introduced, and after catalytic combustion is performed, heat is recovered in the heat recovery device 4, and further compressed heat is recovered. After fuel is injected into the combustion exhaust gas from the pipe and the above-mentioned operation is repeated again in the mixer 5, the catalytic combustion device IA, and the heat recovery device 4,
Combustion exhaust gas is discharged from the pipe 9 to the outside.

However, method (1) (FIG. 1) has the disadvantage that the amount of gas to be handled for recirculation increases several times, which not only diminishes the advantages of catalytic combustion, but also complicates the device structure. Further, in the method (2) (FIG. 2), since the fuel is dispensed, the structure is complicated, and since the fuel is operated under conditions of low fuel concentration, the ignition temperature becomes high.

In order to eliminate the above-mentioned drawbacks, it is possible to divide the catalyst layer and perform partial combustion, but in this case, thermal runaway may cause partial shedding of the catalyst, or only a portion of the catalyst may be heated. There is a problem in that it is not possible to continue uniform combustion, and carbon monoxide and unburned carbon, which are partial combustion products, are produced.

An object of the present invention is to improve the drawbacks of the prior art described above, and to provide a catalyst body for melting and firing that can easily cope with high-load combustion conditions and is resistant to thermal deterioration.

The present invention tj: In a catalyst body having a catalyst for catalytic combustion on the wall surface of a channel through which a fuel-containing gas passes, the channel wall surface has a catalytic activity and a channel that does not have catalytic activity or has a catalytic activity higher than that of the channel. The present invention is characterized in that two types of channels, one with a small number of channels and the other with a small number of channels, are arranged so as to be in contact with each other through a wall surface.

The catalyst body of the present invention is preferably applied to a so-called monolith catalyst body, which has an opening shape such as a rectangular, circular, or hexagonal shape and has a flow path parallel to the gas flow.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

3 to 7 are diagrams schematically explaining the principle of the present invention. First of all, Fig. 4 schematically shows the combustion situation in a conventional monolithic catalyst.A mixed gas of air and fuel 1 flows into the catalyst from the direction of the arrow, and the PA medium 10
Burns in contact with the surface and generates heat. At that time, part of the combustion heat passes through the inside of the catalyst and becomes a heat flow 12 that is transmitted in the opposite direction to the gas flow, thereby preheating the air-fuel mixture.

Due to the temperature increase caused by this, the combustion reaction proceeds more rapidly, but as a result, the preheating of the mixed gas by the aforementioned reverse heat flow is strengthened, which further accelerates the combustion reaction. be done.

As a result, a narrow and extremely high temperature combustion zone 1 is created inside the catalyst body.
3 is formed, and combustion is almost completed in this part. Figure 4 shows the temperature distribution of the catalyst in this case, and the enthalpy of the mixed gas increases due to the heat flow 12 in the opposite direction, and the temperature of the combustion zone due to catalytic combustion (solid line A) ii. The temperature is not only higher than the non-catalytic flame combustion shown by the dotted line B, but also far exceeds the adiabatic flame temperature C, making it easier for the catalyst to undergo thermal deterioration.

As shown above, the width of the combustion zone formed in current catalysts is extremely narrow, and most combustion reactions proceed rapidly in that area. Therefore, shortening the catalyst layer can stabilize the combustion zone. Combustion is difficult in principle to carry out. Therefore, in the present invention, the gas flow path of the catalyst is made inhomogeneous, the heat flow is dispersed in the cross-sectional direction, the heat flow in the opposite direction is reduced, and stable partial combustion is made possible. In other words, schematically, the fifth
As shown in the figure, a channel 15 with a catalyst layer 11 on its surface and a channel 16 without a catalyst layer were bonded to each other in a monolithic catalyst. In this way, the combustion heat generated on the catalyst layer 11 in the rough passage 15 flows as a heat flow 12 in 6 directions of the passage, and is used only for preheating the mixed gas, and 1 catalyst layer 1.
1 is cooled to prevent thermal deterioration. Furthermore, the heat flow 12 reduces the heat flow in the opposite direction to the gas inflow direction, and as shown by DK in FIG. 6, an extreme temperature rise in the heating zone does not occur, and thermal deterioration of the catalyst is significantly reduced.

Furthermore, in the case of the present invention, the flow path 1 without the catalyst layer 11
6 structurally realizes partial combustion, so that unstable combustion phenomena and local heating that occur in the case of the method of separating narrow reaction zones do not occur. Moreover, the mixed gas flowing into the flow path 15 can be completely combusted by the contact layer 11 until it reaches the outlet of the flow path, and the generation of unburned carbon and carbon monoxide is also suppressed. Furthermore, unlike in the case of fuel dispensing, the air ratio of the inflowing gas can be selected to be close to 1, so there is an advantage that ignition can be started easily.

Note that the pressure of the flow PPr15 having the catalyst layer 11 shown in FIG. 5 and the flow path 16 having the catalyst layer 11 may be reversed as shown in FIG. 5A.

The catalyst body of the present invention is one in which flow passages 15 having catalyst components on the inner surface and flow passages 16 without catalyst components are provided alternately in a layered manner as shown in FIG. As shown in Fig. 1, an example is one in which the channels are arranged in a staggered manner in the cross section of the channel, but in short, two types of channels, channels 15 and 16, are arranged so that some or all of the outer surfaces are in contact with each other. In many cases, various variations can be considered. For example, channels 15 and 16 do not necessarily have to have the same cross-sectional area;
It is also within the range that can be easily inferred from the principle of this patent to cover the inner surface of the channel 6 with a catalyst layer having a lower activity than the catalyst on the inner surface of the flow path 15. Further, any combustion catalyst can be used as long as the material of the catalyst layer 11 or the carrier 14 is metal, gold halide oxide, etc.

Next, FIG. 9 shows an example of a combustion device using the combustion catalyst of the present invention. Jin's equipment is introduced from the piping 3.1. a preheater 1o, a fuel injection pipe 2 that supplies fuel to the preheated air, a mixer 5 that mixes the fuel and air, and a combustion device that combusts the fuel-air mixed gas from the mixer 5. The fuel fil'4 [IA consists of relatively short monolithic catalyst bodies 20 and heat recovery units 4 arranged alternately. This monolithic catalyst 2o is the seventh catalyst mentioned above.
It consists of those shown in FIG. 8 and FIG. By dividing the catalyst layers in this way and placing them alternately with heat transfer tubes, which serve as heat recovery units, and removing the combustion heat while partially combusting the fuel in each catalyst layer, the maximum temperature of the catalyst is limited. In each catalyst body 20, as shown in FIG. 5, combustion heat is dispersed in the cross-sectional direction of the flow path, so extremely stable split combustion is achieved in practice, and high-load combustion with an air-to-air ratio of nearly 1 is achieved. It is possible to construct a heat recovery device that can be fully applied to In addition,
The catalyst body of the present invention is applicable not only to the combustion apparatus shown in FIG. 9 but also to the winter combustion apparatus shown in FIGS. 1 and 2.

Hereinafter, the present invention will be explained in more detail with reference to specific examples.

Example A mullite carrier with a square channel shape of 2 mm on each side and a partition wall thickness of IC 5 m was cut into pieces with a fighting angle of 30 and a thread length of 30. Alumina (rAJtOs) was mixed with platinum Q and 5 wt%
A water slurry of the supported 350 mesh powder was poured into the channel so as to form the structure shown in FIG. After drying this at 140°C for 2 hours, it was fired at 500°C for 2 hours,
Catalyst powder was deposited to a thickness of about 0.1 on the mullite support.

Comparative Example The same carrier as in Example was cut into a shape of 30w square and 15 gates long, and the catalyst was deposited on the inner walls of all the channels in the same manner.

Examples Examples Trap Catalysts and Comparison Catalysts and Ic, 8 vol f
A catalytic combustion test was conducted by preheating the mixed gas of methane (remaining air) from No. 4 to 400° C. and contacting the mixture at a flow rate of 35 Nl/−.

Table 1 shows the performance of both catalysts immediately after the experiment and after 10 hours.

From the results in Table 1, it can be seen that the catalyst according to the present invention has no change in long-term catalyst performance and has little COL: r) generation, whereas the catalyst of the comparative example has high initial activity and However,
The generation of CO was significant, and a misfire occurred several hours later due to a decrease in activity.

As described above, according to the present invention, stable partial catalytic combustion becomes possible even when the air ratio is close to 1, and, for example, a high-load combustion-heat recovery system can be configured in combination with a heat recovery device. Therefore, the catalyst body of the present invention is particularly suitable for catalytic combustion boilers and the like.

[Brief explanation of drawings]

wc1 and 2 are device system diagrams showing a conventional catalytic combustion system, Fig. 3 is a model diagram showing the combustion situation inside the conventional catalyst body, Fig. 4 U is a diagram showing its temperature distribution, and Fig. 5 Figure 5A is a model diagram of a catalyst body showing the principle of the present invention, Figure 6 is a diagram showing its temperature distribution, and Figures 7 and 8 are configurations of catalyst bodies showing examples of the present invention, respectively. Figure 9 is
FIG. 1 is a system diagram of a high-load combustion-heat recovery system incorporating the catalyst of the present invention. 1.20... Catalyst body, 2... Combustion injection pipe, 3...
・Air introduction pipe, 4... Heat recovery device (heat transfer tube), 9...
Exhaust piping. Agent Patent Attorney Takenaga Kawakita Figure 1 Figure 2 Figure 3 Figure 5 Figure 5A ``Style 7 Figure 9 Procedure amendment writing method'' % formula % 1. Indication of the case 1988 Patent application No. 9418 2, Title of the invention Combustion catalyst 3, Relationship with the case of the person making the amendment Patent applicant 4, Agent 103 Address 11-8 Nihonbashi Kayaba-cho, Chuo-ku, Tokyo (
Shipping date: April 26, 1982) 6.? ili positive subject Full text of application and specification. 8. Contents of amendment: Copying of application and specification (no change in content)

Claims (1)

[Claims] (1) In a catalyst body having a catalyst for catalytic combustion on the wall surface of a channel through which fuel-containing gas passes, there is a channel whose wall surface has catalytic activity and a channel whose wall surface has no catalytic activity or whose catalytic activity is lower than that of the channel. A combustion catalyst body characterized in that two types of flow paths, one with a small number of flow paths and the other with a small number of flow paths, are arranged so as to be in contact with each other through a wall surface.