JPH04344006A - Catalyst combustion device - Google Patents

Abstract

PURPOSE:To prevent a reduction of activation of catalyst in an auxiliary catalyst layer under a coverage of sulfuric substance, prevent deterioration of combustion characteristics and maintain a production of clean discharged gas for a long period of time in a catalyst combustion device in which either gaseous fuel or liquid fuel is applied as fuel for a heater equipment or a drying equipment. CONSTITUTION:A combustion part is provided with a main catalyst layer 16 having many communication holes and an auxiliary catalyst layer 17 having many communication holes disposed at a downstream side of the main catalyst layer 16. An area of the auxiliary catalyst layer 17 is smaller than that of the main catalyst layer 16, thereby a flow speed of gas passing through the auxiliary catalyst layer 17 is faster than that of gas passing through the main catalyst layer 16. Accordingly, it is possible to cause combustion gas containing SOx generated at the main catalyst layer 16 to pass through the auxiliary catalyst 17 within a shirt period of time. It is also possible to provide a catalyst combustion device in which a reduction in activation of catalyst in the auxiliary catalyst layer 17 under a covering of sulfuric substance is prevented to improve deterioration of combustion characteristics and a production of clean discharging gas can be maintained for a long period of time.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic combustion device that uses gaseous or liquid fuel as fuel for heating, heating, drying, and other equipment.

0002

2. Description of the Related Art A conventional catalytic combustion apparatus has a configuration as shown in FIG.

As shown in the figure, fuel and air are supplied to a vaporization chamber 4 by a pump 2 and a fan 3 provided in a fuel tank 1, and the fuel is vaporized in the vaporization chamber 4 and mixed with air. The fuel enters the primary fuel section 5 and is ignited by the ignition device 6 to form a flame. The high-temperature combustion exhaust gas passes through the catalyst layer 7 and is discharged from the exhaust port 8, during which time the catalyst layer 7 is heated to rise in temperature. When it is detected that the catalyst layer 7 has reached a temperature sufficient for catalytic combustion (the detection part is not shown), the pump 2 is stopped and the flame in the primary combustion part 5 is extinguished. Thereafter, when the pump 2 is operated again to supply fuel, the fuel reaches the catalyst layer 7 as a premixed gas without forming a flame in the primary fuel section 5. Here, since the temperature of the catalyst layer 7 has risen to a temperature sufficient for catalytic combustion, catalytic combustion is started and complete combustion is performed. Since this catalytic combustion proceeds exclusively on the upstream surface of the catalyst layer 7, that portion becomes a radiant heat radiator, and the heat is radiated to the front surface through the glass window 9.

0004

A catalytic combustion device oxidizes fuel premixed with air in a catalyst layer, and uses the heat of the reaction for heating, space heating, and drying.

In catalytic combustion devices, the catalytic reaction proceeds at very high temperatures, so it is difficult to avoid thermal deterioration of the catalyst. It is common practice to prevent thermal deterioration of the catalyst by constructing the catalyst layer with a high-temperature main catalyst layer that burns the HC and CO that cannot be completely burned in the main catalyst layer.

[0006] However, in the fuel used in catalytic combustion devices, for example, city gas and LPG have sulfur-containing substances added as odorants, and kerosene contains several tens of parts of sulfur.
PM of sulfur content is included, and this trace amount of sulfur content is also burned during combustion, and the combustion gas comes to contain a trace amount of SOx. This SOx reacts with the catalyst metal of the auxiliary catalyst layer to reduce the catalytic activity of the auxiliary catalyst layer. therefore,
When a catalytic combustor is used for a long period of time, there is a problem in that the catalytic activity of the auxiliary catalyst layer gradually decreases and the combustion characteristics deteriorate.

The present invention solves the above-mentioned problems, and provides catalytic combustion that prevents the deterioration of the catalytic activity of the auxiliary catalyst layer, improves the deterioration of combustion characteristics, and maintains the production of clean exhaust gas for a long period of time. The purpose is to provide equipment.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention is such that the area or porosity of the auxiliary catalyst layer is smaller than the area or porosity of the main catalyst layer.

[0009]

[Operation] With the above-described configuration, the present invention has a flow rate of gas that passes through the auxiliary catalyst layer that burns HC and CO that have not been completely burned in the main catalyst layer, which is faster than the flow rate of gas that passes through the main catalyst layer that performs most of the combustion. Since the flow rate becomes faster, the combustion gas containing SOx generated in the main catalyst layer can be passed through the auxiliary catalyst layer in a short time.

Since the catalytic reaction is affected by the time during which the catalytic metal and gas are in contact with each other, the above-mentioned structure can make it difficult for the catalytic metal in the auxiliary catalyst layer to react with the sulfur content, and prevent poisoning caused by the sulfur content. A decrease in the catalytic activity of the auxiliary catalyst layer can be prevented.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

In FIG. 1, 10 is a fuel tank, 11 is a fuel supply pump, and 12 is a ventilation fan, both of which are communicated with a vaporization chamber 13. The vaporization chamber 13 is equipped with a heating heater (
(not shown) is provided. A primary fuel section 14 is provided on the downstream side of the vaporization chamber 13 via a mixing chamber for mixing fuel and air, and an ignition device 15 is provided in the vicinity thereof. A fuel cell 2 having catalyst layers 16 and 17 is downstream of the primary fuel part 14.
A secondary combustion section 18 is provided. The secondary combustion section 18 includes a high-temperature main catalyst layer 16 that performs most of the combustion, and the main catalyst layer 16 provided on the downstream side of the main catalyst layer 16.
and a low-temperature auxiliary catalyst layer 17 that burns the fuel, and communicates with an exhaust port 19.

The area of this auxiliary catalyst layer 17 is larger than that of the main catalyst layer 16.
In other words, it is formed so that the flow rate of gas passing through the auxiliary catalyst layer 17 is faster than the flow rate of gas passing through the main catalyst layer 16.

In the above configuration, fuel and air are supplied to the vaporization chamber 13 by the fuel supply pump 11 and the ventilation fan 12, and the fuel is vaporized in the vaporization chamber 13 and mixed with air, and then sent to the primary combustion section 14. and is ignited by the igniter 15 to form a flame. The high temperature combustion exhaust gas heats the main catalyst layer 16 and raises its temperature. When it is detected that the main catalyst layer 16 has reached a temperature sufficient for catalytic combustion (the detection part is not shown), the fuel supply pump 11 is stopped and the flame in the primary combustion part 14 is extinguished. . After that, when the fuel supply pump 11 is operated again to supply fuel to the vaporization chamber 13, the premixed gas reaches the main catalyst layer 16 without forming a flame in the primary combustion section 14, and the main catalyst layer At 16, catalytic combustion is started.

During this combustion, the premixture is not completely combusted in low-temperature areas such as the periphery of the main catalyst layer 16 or in areas that come into contact with overly rich or overly lean areas of the premixture, so HC and C
O is generated, but the generated HC and CO are transferred to the auxiliary catalyst layer 17.
It is completely reacted and purified, and is discharged from the discharge port 19.

By the way, in the fuel used in catalytic combustion equipment, city gas and LPG have sulfur-containing substances added as odorants, and kerosene contains about several tens of ppm of sulfur. It is generally known that there are Therefore, the combustion gas of the catalytic combustion device contains SOx, albeit in a small amount. This SOx reacts with the catalytic metal to reduce the activity of the auxiliary catalyst layer, but it is known that the catalytic reaction is affected by the time during which the catalytic metal and gas are in contact.

The present invention focuses on this, and the main catalyst layer 16 is supplied with a premixture of fuel and air that is supplied from the fuel tank 10 and vaporized in the vaporization chamber 13, and the main catalyst layer 1
6, most of this premixture is catalytically burned, but since the premixture supplied to the main catalyst layer 16 is a gas before combustion, it does not contain SOx, and therefore the main catalyst layer 16 does not contain SOx. The catalytic metal of layer 16 is not poisoned by sulfur.

The combustion gas containing HC and CO that has not been completely combusted in the main catalyst layer 16 flows into the auxiliary catalyst layer 17 .

Here, the area of the auxiliary catalyst layer 17 is smaller than the area of the main catalyst layer 16. Therefore, the auxiliary catalyst layer 1
The flow rate of the gas passing through the main catalyst layer 16 is faster than the flow rate passing through the main catalyst layer 16 . This causes a difference in the contact time between the catalyst metal and the gas, and in the auxiliary catalyst layer 17, the contact time between the catalyst metal and the gas becomes shorter, making it difficult for the catalyst metal to be poisoned by sulfur content. Although the catalytic reaction time is not shortened in the auxiliary catalyst layer 17, since the amount of HC and CO contained in the gas reacted in the auxiliary catalyst layer 17 is small, the HC and CO that could not be treated in the main catalyst layer 16 are assisted. The catalyst layer 17 can reliably purify the water.

As described above, according to the catalytic combustion apparatus of the embodiment of the present invention, when the gas for performing the catalytic reaction contains SOx, the flow rate of the gas passing through the auxiliary catalyst layer 17 is controlled by the main catalyst layer 16. By making the flow rate faster than the gas passing through the auxiliary catalyst layer 17, the deterioration of combustion characteristics is prevented by preventing a decrease in the catalytic activity of the auxiliary catalyst layer 17 due to sulfur poisoning, and maintaining clean exhaust gas generation for a long period of time. can do.

In order to change the gas flow rate, as shown in FIGS. 2 and 3, the porosity (see FIG. 3) of the catalyst used in the auxiliary catalyst layer 17 is changed from that of the catalyst used in the main catalyst layer 16. By forming the pores smaller than the pore size of the catalyst (see FIG. 2), the flow rate of gas passing through the auxiliary catalyst layer 17 can be made faster than the flow rate of gas passing through the main catalyst layer 16.

Furthermore, in order to prevent thermal deterioration of the main catalyst layer 16, as shown in FIG. After the coating layer 20 is made to support a catalyst metal 21 such as platinum or palladium in advance, the coating layer 20 is attached to a base 2 such as a ceramic honeycomb body.
2, the catalyst metal 21 is uniformly dispersed and supported on the coating layer 20, so that the main catalyst layer 16 can prevent grain growth of the catalyst metal 21 even when burned at high temperatures. This makes it possible to prevent thermal deterioration of the main catalyst layer 16.

Furthermore, in order to improve the catalytic activity of the auxiliary catalyst layer 17, as shown in FIG.
If the coating layer 20 is coated on the base 22 in advance and then supported with the catalyst metal 21, the catalyst metal 21
is now supported near the channel surface of the coating layer 20,
Since the amount of catalyst metal 21 is increased on the flow path surface of the auxiliary catalyst layer 17, the catalytic activity can be improved, and the flow rate of the auxiliary catalyst layer 17 is higher than that passing through the main catalyst layer 16.
The auxiliary catalyst layer 17 can further reliably purify HC and CO passing through.

The auxiliary catalyst layer 17 has poorer heat resistance than the main catalyst layer 16 because the dispersibility of the catalyst metal 21 is poorer, but the auxiliary catalyst layer 17 needs to burn at a high temperature like the main catalyst layer 16. Since there is no heat resistance required for the main catalyst layer 16, there is no problem.

[0025] Although the above-mentioned example describes a catalytic combustion device using petroleum as fuel, similar results have been obtained with devices using gas as fuel, and the type of fuel is not limited. .

[0026] Furthermore, there is no major difference depending on the material, shape, etc. of the catalyst body, and similar results have been obtained even when a ceramic fiber braided body or a metal honeycomb body is used.

[0027]

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, by making the area or porosity of the auxiliary catalyst layer smaller than the area or porosity of the main catalyst layer, the combustion Since the flow rate of gas passing through the auxiliary catalyst layer, which burns HC and CO that were not completely burned in the main catalyst layer, is faster than the flow rate of gas passing through the main catalyst layer, where most of the This allows combustion gas containing SOx to pass through the auxiliary catalyst layer in a short period of time, preventing a decrease in the catalytic activity of the auxiliary catalyst layer due to sulfur poisoning, improving deterioration of combustion characteristics, and improving long-term combustion performance. A catalytic combustion device that can maintain clean exhaust gas generation over a period of time can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a catalytic combustion device according to an embodiment of the present invention.

[Fig. 2] Plan view of another example of the same main catalyst layer

[Fig. 3] Plan view of another example of the same auxiliary catalyst layer

[Figure 4] Side sectional view of another example of the same main catalyst layer

[Figure 5] Side sectional view of another example of the same auxiliary catalyst layer

[Fig. 6] Side sectional view of a conventional catalytic combustion device

[Explanation of symbols]

16 Main catalyst layer 17 Auxiliary catalyst layer 20 Catalytic metal 21 Coating layer 22 Base

Claims (3)

[Claims] 1. A mixing chamber for mixing fuel and air, a main catalyst layer having a plurality of communication holes arranged downstream of the mixing chamber, and a plurality of communication holes arranged downstream of the main catalyst layer. and an auxiliary catalyst layer having communicating holes, the area of the auxiliary catalyst layer being smaller than the area of the catalyst layer. 2. A mixing chamber for mixing fuel and air, a main catalyst layer having a plurality of communication holes arranged downstream of the mixing chamber, and a plurality of communication holes arranged downstream of the main catalyst layer. and an auxiliary catalyst layer having communicating holes, wherein the porosity of the auxiliary catalyst layer is smaller than the porosity of the main catalyst layer. 3. The main catalyst layer consists of a substrate and a coating layer that uniformly supports a catalyst metal, and the auxiliary catalyst layer consists of a substrate,
3. The catalytic combustion device according to claim 1, further comprising a coating layer supporting a catalytic metal near the surface of the flow path.