JPS61173010A - Catalytic combustion equipment - Google Patents

Abstract

PURPOSE:To lower the ignition temp., or to miniaturize the size of a preheating unit, by replacing part of fuel or all of it by the fuel which is easy to start combustion at the starting time or during a steady combustion. CONSTITUTION:Both lines 8 and 9 are provided as fuel injection pipe lines. A catalyst layer is divided into two parts of a catalyst layer A5 and a catalyst layer B6. A fuel to be injected through the fuel injection line 9 and a catalyst which is to be charged to the catalyst layer A5 are chosen so as to make the best combination to enable to lower the ignition point. Fuel can be ignited at low temperature at the starting time, by injection fuel through the fuel injection line 9. Another method is to lower the preheating temperature for gas by adding an auxiliary fuel to a main fuel at a predetermined rate.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a combustion device, and particularly to a catalytic combustion device that can reduce the amount of heat for preheating.

<Prior Art and its Problems> In recent years, a catalytic combustion method in which combustion is performed using a catalyst, that is, a catalytic combustion method, has been attracting attention. The advantages of the catalytic combustion method are (1) that it is possible to burn low-calorie gases that do not self-combust, (2) that stable combustion is possible over a wide air-fuel ratio range, and (3) that the combustor has a large volumetric combustion rate. becomes more compact. However, the reality is that combustors employing this method have not been widely put into practical use due to the following reasons.

In other words, in the case of catalytic combustion, it is necessary to mix air and fuel in advance and to preheat them to the combustion start temperature determined by the type of catalyst. There is. For this reason, it is necessary to install a preheating device in conjunction with the catalytic combustion device, which complicates the device and poses a major obstacle to its practical application.

For this reason, research has been conducted into simplifying the preheating device in order to improve the catalytic activity and the ignition device, and many inventions have been made. However, none of these methods has been able to significantly lower the preheating temperature, and have not achieved an outstanding effect of lowering the preheating temperature by several hundred degrees Celsius, for example. This is because the combustion start temperature varies in a complex manner depending on the catalyst components and the type of fuel, and cannot be determined unambiguously. A catalyst that exhibits high performance with a specific fuel does not necessarily have high performance with other fuels. This stems from the inability to fully demonstrate one's abilities.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a combustion device that eliminates the drawbacks of the prior art described above, lowers the combustion start temperature, and allows the preheating device to be made smaller.

Summary of the Invention In short, the present invention focuses on the fact that the combustion start temperature differs depending on the combination K of catalyst components and fuel types, and makes it easy to start combustion of part or all of the fuel during startup and steady combustion. This device is designed to lower the ignition temperature or downsize the preheating equipment by replacing it with the previous one.

Example) Examples of the present invention will be described below.

In FIG. 1, reference numeral 1 is a fan, 2 is a heat exchanger for exchanging heat with combustion exhaust gas, 3 is a preheater, 4 is a catalytic combustor, and the A layer 5.8 is a catalyst layer with different properties inside. Layer 6 is arranged. 13 is a fuel (
and combustion air), and connected to this line are fuel lines 8 and 9 that supply different fuels, respectively. Reference numeral 7 denotes a heat recovery device for recovering heat from the combustion gas, and the exhaust gas leaving the device 7 is connected to the heat exchanger 2 via a line 15.

Note that 10, 11, and 12 in the figure are lines that supply combustion air. 14 is a line for passing exhaust gas.

In the above apparatus, air is taken in through line 10, pressurized by fan 1, and sent to heat exchanger 2 where it is heated. Further, the air led to the preheater B is further heated if necessary to raise the temperature to the combustion start temperature, and fuel is injected through the fuel injection line 8 or another fuel injection line 9. Thereafter, it is sent to the catalyst layers 5 and 6 and burned, and most of the combustion heat is recovered in the heat recovery device 7. The combustion exhaust gas is further sent to the heat exchanger 2 and used as an air preheating source.

In this device, the combination of fuel with different properties supplied from line 8 or 9 and the composition of catalyst layers 5 and 6 is specified to reduce the combustion start temperature at startup or the preheating temperature during steady combustion. It is configured to achieve this goal.

In Figure 2, an alumina catalyst carrying A1wt of platinum (PC) as an active component is used, and methane (OH4
) Shows the relationship between preheating temperature and combustion rate when propane (03HI) and kerosene are used. In addition, Figure 3 shows the relationship between preheating temperature and combustion rate when using propane (03HI) and kerosene. This shows the results of a test conducted using a similar method.

Incidentally, the reaction conditions are as shown below.

(1) Catalyst shape: Honeycomb shape of L + m + N2: Balance As is clear from the above, the combustion start temperature is determined by the catalyst, for example, the catalyst shown in Figure 2 can reduce the propane gas preheating temperature, and the catalyst shown in Figure 3 can reduce the kerosene gas preheating temperature. It varies greatly depending on the combination of components and fuel type.

By skillfully utilizing this point, the preheating temperature of each fuel can be reduced. That is, in the present invention, 8 is used as the fuel injection line.
and 9, and are divided into two, catalyst layer A5 and catalyst layer B6, and the combination of the fuel injected from fuel injection line 9 and the catalyst type filled in catalyst A layer 5 increases the ignition temperature. (1) Fuel is injected through the fuel injection line 9 at startup to enable combustion at a low temperature. Alternatively, (2) the specification may be modified to reduce the gas preheating temperature by adding auxiliary fuel to the main fuel at a constant ratio; (no change in content). Specifically, the auxiliary fuel and the catalyst to be filled in the catalyst A layer are determined depending on the main fuel to be burned, and it is preferable to select the combinations shown in Table 1.

In particular, in the combustion of methane, which is the main component of LNG, by using a combination of propane-platinum supported catalyst or kerosene-palladium supported catalyst as the auxiliary fuel and catalyst A, the combustion temperature can be as low as about 200°C.

Not only will it be possible to ignite from heat, but
By injecting a fixed amount of auxiliary fuel during steady combustion, the preheating equipment including the preheater 3 can be significantly simplified.

In addition, when burning kerosene, if the outlet temperature of the heat exchanger 2 shown in Fig. 1 does not reach the temperature required for vaporizing the kerosene at startup, propane is used as an auxiliary fuel and the catalyst A is By using a platinum-supported catalyst, approximately 200
Low-temperature ignition is possible by starting combustion at ℃ and starting kerosene combustion when the aforementioned heat exchanger outlet temperature reaches a sufficiently high temperature.

In short, the present invention provides a catalyst A suitable for combusting the fuel in the fuel line 9 before the auxiliary fuel supply line 9 and the main catalyst layer B in order to achieve low-temperature startup or lower the preheating temperature. The combination is, for example, a propane-platinum supported catalyst or a kerosene-palladium supported catalyst. However, the main fuel type.

This combination is not limited depending on the type of catalyst B. In addition, the catalyst A layer 5 and the catalyst B layer 6 are each line 8
, 9 does not necessarily have to be different depending on the combination of fuels supplied from the layers 5 and 9; for example, if both the layers 5 and 6 are
It is also possible to implement a method in which a combustion device is started using an alumina catalyst supporting wt.

Further, the ratio of the catalyst packed in the catalyst A layer 5 and the catalyst packed in the catalyst B layer 6 depends on the type of catalyst, but the former should normally be selected to be 1/3 or less of the latter. This is because most of the combustion reaction occurs at the inlet of the catalyst, so by the time the unreacted fuel reaches the catalyst B layer, it has reached a sufficiently high temperature that the catalyst B can act. be.

In addition, when reducing the preheating temperature during steady combustion, the mixing ratio of the auxiliary fuel is set so that the gas temperature when the auxiliary fuel is combusted in the catalyst A layer is higher than the combustion start temperature of the main fuel in the catalyst B layer. Just choose. Further, the fuel injection lines 8 and 9 may be installed anywhere upstream of the catalytic combustor 4, and there is no need to specify the order in which they are installed.

Alternatively, both lines may be integrated into one system, and both fuels may be supplied in a mixed manner or in a switched manner.

Next, the results of experiments using the apparatus of the present invention will be explained.

Experiment 1 In the apparatus having 70- in FIG. 1, methane was used as the main fuel and propane was used as the auxiliary fuel.

Catalyst A was an alumina catalyst on which α1 wt % of platinum was supported, and catalyst B was an alumina catalyst on which α5 wt % palladium was supported, and the ratio of the two was 1:9 on a volume basis. Air is flowed through this device at a space velocity of 30,000 h, and the preheater 3 with an electric heater is operated to gradually raise the temperature of the catalytic combustor while discharging propane to 1.
．． The fuel was injected from the auxiliary fuel injection line 9 to a concentration of 2 vol %. Combustion began when the catalytic combustor temperature reached 230°C. In accordance with the rise in the outlet gas temperature of the heat exchanger 3, the load on the preheater 3 is lowered and the gas temperature in the line 13 is increased to 40°C.
The temperature was controlled to be 0°C, and at this point, methane was injected into the main fuel line 8 at a concentration of 5 vol %, and at the same time injection of propane was stopped, but combustion continued well.

In Comparative Example Experiment 1, propane was not used as an auxiliary fuel, but dimethane was used at startup to start operation. In this case, in order to start combustion, it was necessary to increase the load on the preheater and raise the outlet gas temperature to 410°C. A comparison of the present results and the results of Experiment 1 revealed that according to the present invention, the preheater capacity required for startup can be reduced to about 172.

Experiment 2 In an apparatus having the flow shown in Fig. 1, 0.5wt% palladium-supported alumina catalyst was used in the catalyst A layer 5 and the 8th layer 6, methane was used as the main fuel, kerosene was used as the auxiliary fuel, and air was used in each case. After mixing, it was added at a concentration of 3.1 vol%. When a test similar to Experiment 1 was conducted for this example, combustion started at about 200°C, and if the gas temperature in the combustor inlet pipe 13 was maintained at 210°C,
I was able to sustain the combustion.

Comparative Example 2 A test similar to Experiment 2 was conducted without adding kerosene. In this case, in order to start combustion, it was necessary to heat the fuel to 410° C. using a preheater, and if the temperature was lower than that, the combustion that had once started would misfire.

From the present results and the results of Experiment 2, it is clear that according to the combustion method of the present invention, not only can the capacity of the preheater be significantly reduced, but also
It has become clear that since the gas temperature required for sustained combustion can be reduced by about 200°C, the capacity of the heat exchanger 2 can also be reduced.

Effects> Since the present invention has the above configuration, fuel can be ignited at a low temperature, the capacity of the preheater, which has conventionally been a large piece of equipment, can be significantly reduced, the device can be simplified, and the operation can be simplified. Expenses can also be reduced. .

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a catalytic combustion device showing an embodiment of the present invention;
Figures 2 and 3 are diagrams showing the relationship between the combustion rate of the catalyst and the gas preheating temperature for each fuel.
In the case of using an alumina catalyst supporting 0.5 wt % of Pd, FIG. 3 shows the case of using an alumina catalyst supporting 0.5 wt % of Pd. 3... Preheater 4... Catalytic combustor 5... Catalyst A layer 6... Catalyst B Layer 8.9...Fuel injection line Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a device in which fuel preheated on the upstream side is combusted in a catalyst layer, another catalyst layer is separately provided upstream of this catalyst layer, and two or more catalyst layers are provided upstream of the separately provided catalyst layer. A line for supplying the following types of fuel is arranged, and one of the fuels to be supplied is combined with a separate catalyst layer such that the combustion start temperature can be reduced in accordance with the type of fuel. A catalytic combustion device featuring: 2. Catalytic combustion according to claim 1, characterized in that the separate catalyst is a catalyst supporting approximately 0.1 wt% of Pt, and the fuel combined with this catalyst is propane. Device. 3. Catalytic combustion according to claim 1, characterized in that the separate catalyst is a catalyst supporting about 0.5 wt% of Pd, and the fuel combined with this catalyst is kerosene. Device.