JPS60202224A - Catalyst burner - Google Patents

Abstract

PURPOSE:To create atmosphere where generated H2 is added, more H2 is generated, and hydrocarbon is susceptible to be catalytically burnt, by a method wherein an vaporizing element impregnated with a moisture content is installed in the midway of a fuel feed circuit. CONSTITUTION:A steam feed chamber 8 is located right below a spot where an oxidation catalyst body 3 is situated, and a vaporizing element 9, causing water to be vaporized, is positioned at the central part of the chamber. A part of the heat of the oxidation catalyst body 3 during constant catalytic combustion is conducted to the underlaying steam feed chamber 8, and is used as heat for vaporization of steam from the vaporizing element 9. Water proportions an amount of a decrease in a water amount present in the steam feed chamber 8, and is automatically fed from a water tank 12. It is well known that, generally, inorganic gas, such as H2 and CO, is easily reacted as compared with hydrocarbon, such as CH4, and it is also well known that, when H2 is mixed in CH4 which is difficult to burn for catalytic combustion, an oxidation reaction rate of CH4 is increased. Thus, pouring of water during a series of reaction enables increase of an H2 amount.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a catalytic combustor that uses hydrocarbons as fuel, burns them flamelessly on an oxidation catalyst, and uses the generated radiant heat for purposes such as heating or drying. .

Conventional configuration and its problems In the conventional catalytic combustor configuration, as shown in FIG. It is supposed to be done. However, the oxidation activity of catalytic combustion varies greatly depending on the type of fuel being combusted. In other words, if we take platinum-supported inorganic fiber catalysts as an example, they range from those like hydrogen that start burning even at subzero temperatures to those like methane that inevitably leak by some percentage even at temperatures close to 500℃. be.

In particular, when using 13A city gas whose main component is methane, one must be prepared for a considerable amount of leakage.

OBJECTS OF THE INVENTION The object of the present invention is to solve such conventional problems and to make the supplied hydrocarbons into a form that facilitates catalytic combustion as much as possible.

DESCRIPTION OF THE INVENTION To achieve this objective, the present invention uses some method to introduce moisture into the fuel before it reaches the catalyst body. That is, an evaporation element impregnated with moisture is installed in the middle of the fuel supply circuit. Generally, it is most preferable to use heat during catalyst combustion as the energy required for evaporation, but external energy such as an electric heater may also be used.

With this configuration, the catalytic combustor of the present invention has the following effects. In general, if we look at the process of catalytic combustion of hydrocarbons microscopically, we can see that hydrocarbons and a small amount of air diffused from the surface undergo a retorming reaction (Retorming reaction) near the back surface of the oxidation catalyst. Partial
oxidation), the generated hydrogen and -
The carbon oxide burns near the surface of the oxidation catalyst and is converted to formic acid gas and water (more details on this reaction are provided below). It is generally known that inorganic gases such as H2 and C○ react more easily than hydrocarbons such as CH4;
It is also well known that when H2 is mixed with H4 or the like and subjected to catalytic combustion, the oxidation reaction rate of CH4 increases. The present invention has focused on this point, and when even a small amount of moisture (water vapor) is mixed into the combustion gas, it causes raying (R) near the back surface of the oxidation catalyst.
e t o r m i n g ) reaction (SteamRe
f o rming) and perform the above Part
Add H2 generated by ialOxidation,
More H2 is generated, creating an atmosphere that facilitates catalytic combustion of hydrocarbons.

Description of examples Embodiments of the present invention will be described below with reference to FIG.

Note that the same components in the figures are given the same numbers.

As shown in Fig. 2, there is an oxidation catalyst 3 in which a platinum group metal such as Pt, Pd, or Rh is supported on the surface of a catalyst carrier made of a matte-shaped inorganic fiber with side-heating properties, and an oxidation catalyst 3 in which a platinum group metal such as Pt, Pd, or Rh is supported on the surface of the catalyst carrier, and a catalyst is not supported on the surface of the catalyst carrier. A diffusion pine l-2 made of heat-suppressing inorganic fibers formed into a mantle shape is brought into close contact with the heat-suppressing inorganic fiber body, and the front part is sandwiched between a wire mesh 4 and the rear part between a wire mesh 5 and the combustor body 6 is assembled. A flange 6' is provided at the front of the combustor body 6 to prevent the oxidation catalyst 3, etc. from detaching.
At the rear, a fuel dispersion pipe 7 is installed in a space opened through a wire mesh 5. Immediately below the location where the oxidation catalyst body 3 is placed is a water vapor supply chamber 8, and an evaporation element 9 for evaporating water is placed in the center thereof. The steam supply chamber 8 is connected to the fuel distribution pipe 7 by a connecting pipe 10, and is also connected to a fuel gas supply pipe 11. Water supplied to the steam supply chamber 8 flows from a water tank 12 installed on the back side of the catalytic combustor main body 6 through a water supply pipe 13, and a heater 14 for evaporating the water.
is in close contact with the lower part of the steam supply chamber 8. A spark electrode 15 for initial ignition is placed on the front surface of the oxidation catalyst body 3, and a thermocouple 16 is inserted into the oxidation catalyst body 3 from the outer wall of the catalytic combustor main body 6.

Next, the operation of the catalytic combustor with the above configuration will be explained.

First, the spark electrode 15 is energized to start discharging. During this time, the fuel gas passes through the fuel supply pipe 11, the steam supply chamber 8, the connecting pipe 10, and enters the fuel distribution pipe 7.

The fuel is uniformly dispersed in the fuel distribution tube 7, passes through the diffusion mat 3 and the oxidation catalyst 3, and is ignited on the surface thereof, forming a flame over the entire surface. After several tens of seconds, the oxidation catalyst body 3 itself is heated by the flame, and catalytic combustion naturally begins. Combustion air at this time is taken in from the outside and diffusion combustion continues. During steady catalytic combustion, the oxidation catalyst body 3 is transferred to the supply chamber 8 and used as heat for evaporating water vapor from the evaporation element 9. Water is automatically supplied from the water pump 12 in proportion to the decrease in the amount of water present in the steam supply chamber 8. Initial combustion steam supply chamber 8
The heater 14 can be turned on when sufficient heat is not supplied to the combustion chamber, or when there is insufficient heat even during steady combustion. Any structure other than the ceramic structure of the combustor may be used as long as it can receive radiant heat or conductive heat from the oxidation catalyst 3 and use it for water evaporation.

In the oxidation catalyst body 3 of the above embodiment, the alumina fiber aggregate supports rhodium (Rh) at a weight ratio of 0.5%. When methane (CH4) is catalytically burned using this catalyst, the combustion efficiency is 96-98 (2-4% leakage,
The oxidation catalyst body temperature is 400 to 500'C), but in the case of the catalytic combustor of this example, the combustion efficiency reaches 99% or more. The area around the catalyst body in the catalytic combustor of this embodiment has the following effects. II) When CH4 and a small amount of water vapor are supplied from the right side of the oxidation catalyst 3 as shown in FIG.
4 comes into contact with oxygen diffused from the left side of the oxidation catalyst 3, causing an oxidation reaction.

CH4+202 → CO2+2H20...(1
) The moisture generated by the above reaction diffuses through the oxidation catalyst 3 or is absorbed onto the alumina surface of the catalyst carrier.
Then, it comes into contact with CH4 and causes a Reforming reaction.

CH4+ H20→3H2+CO・・・2 At this point, if a small amount of moisture is supplied from the outside, 2
reaction takes place, and a large amount of H2 is generated. The H2 and CO generated by the reaction in step 2 move to the left surface of the oxidation catalyst 3 (there is a larger amount of diffused oxygen near the surface), causing the following reaction.

2H2+02 →2H20−-・・−G)2CO+0
2→2 CO2... ■Also, some of the C H4 itself moves to the left side of the oxidation catalyst 3, where it is directly oxidized and completely combusted.

CH4+202-)CO2-1-2H20-5) A part of the generated water is used again for reforming and is also discharged to the outside as it is.

The above is a general outline of the reaction mechanism, but it actually involves a fairly complex process. However, it is generally known that inorganic gases such as H2 and CO react more easily than hydrocarbons such as CH4, and if H2 is mixed with CH4, which is difficult to burn, and catalytically combusted, the oxidation reaction rate of CH4 may increase. well known. Therefore, by injecting water during this series of reactions, the amount of H2 can be increased. Also, like Rh shown in this example, even at 400 to 500°C, Refo
This effect can be more advantageously developed by using a catalyst that can sufficiently carry out the rming reaction.

However, Rh's other platinum group catalysts or transition metal oxide group metal oxides exhibit similar effects, although the catalytic effect is lower.

Effects of the Invention As described above, the catalytic combustor of the present invention provides the following effects.

(1) The combustion efficiency of hydrocarbons such as CH4 can be increased by simply introducing a small amount of moisture into the fuel gas.

In particular, methane is a gas that is difficult to catalytically burn, but the combustion efficiency of 9996 or higher, which has never been seen before, can be seen.

2. Water is introduced as an additive in a supplementary sense, so even if the water supply is cut off for some reason, combustion will not become impossible, and combustion will continue with only a slight decrease in combustion efficiency. Can be done.

■ Conventional catalytic combustion systems for home heaters use propane,
Although butane or inorganic gas was used, it can now be applied to other gases whose main component is methane.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional catalytic combustor, FIG. 2 is a sectional view showing an embodiment of the catalytic combustor of the present invention, and FIG. 3 is a conceptual diagram of a catalytic combustion mechanism. 3... Oxidation catalyst body, 9... Evaporation element, 14...
Heater, 12... Water tank. Name of agent: Patent attorney Toshio Nakao and 1 other person
1rlA 2 2nd □ Fig. 3

Claims (1)

[Claims] (1) An evaporation element impregnated with moisture is installed in the middle of the path for supplying fuel gas containing hydrocarbons, and the fuel gas that has passed through it is supplied onto the oxidation catalyst, and diffused air is taken in from the outside to oxidize it. A catalytic combustor that burns at a low temperature on a catalytic body. ■ A patent claim in which the oxidation catalyst is constructed by using an aggregate of heat-resistant ceramic fibers as a carrier and supporting platinum group metals such as Pt, Pd, and Rh or transition metal oxides such as Ni and CosMn on the surface of the carrier. The catalytic combustor according to item 1. (2) The catalytic combustor according to claim 1, wherein water in the evaporation element is evaporated by radiant heat or conduction heat from the oxidation catalyst.