JPH08587Y2 - Catalytic combustion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention supplies vaporized fuel onto an oxidation catalyst body, promotes an oxidation reaction on the surface, and utilizes far infrared rays or the like generated at that time, for example, The present invention relates to a catalytic combustion device for heating.

[Conventional technology]

In the kerosene vaporization type catalytic combustion apparatus, the far infrared rays radiated from the catalyst body are effectively used for heating, unless the area of the catalyst body is large, a sufficient radiation effect cannot be obtained. Therefore, it is an important issue to supply the premixed gas of vaporized kerosene and combustion air evenly to the catalyst surface during steady combustion, and to uniformly transfer the heat of the preheating heater to the catalyst surface during catalyst preheating.

The combustor disclosed in Japanese Utility Model Publication No. 61-35217 vaporizes kerosene, mixes it with air to generate a premixed gas, and supplies this to a relatively large catalyst body in a horizontal and vertical position, from the catalyst side. The direct radiant heat of is used for heating. Such a device has a structure in which an opening is provided on one side surface of the box-shaped premixed gas supply chamber and a catalyst body, a preheater heater, and the like are installed in the vicinity of the opening, and as described above, a relatively large catalyst surface is provided. It has a supply means for supplying premixed gas and hot air for preheating.

As the catalytic combustion apparatus having such a supply means, a first type having a means for pumping the premixed gas from the bottom of the box-shaped premixed gas supply chamber at a relatively low ejection speed, or
It has means for continuously expanding the cross-sectional area in a diffuser shape from a premixed gas supply pipe with a small cross-sectional area to a catalyst surface with a large area, and installing a resistance plate, punching metal, wire mesh, etc. in the middle to rectify. Two types are known.

[Problems to be solved by the device]

However, in both types described above, when the catalyst body is preheated, the air flow velocity on the upper side of the catalyst is low and the flow state is close to a laminar flow. Therefore, when the catalyst body is preheated, the heat of the preheating heater does not sufficiently diffuse and propagate the air before it reaches the catalyst body, and moreover, only the upper portion of the catalyst body is heated due to the influence of natural convection. As a result, a non-uniform temperature distribution occurs such that the lower part remains at a low temperature.
When preheating is completed in this state and premixed gas is supplied to ignite and burn, the H
There is a risk that toxic gases such as C and CO will be generated.

Furthermore, if the premixed gas is not sufficiently rectified as in the first type, the speed of the premixed gas passing through the catalyst body also varies, resulting in temperature unevenness even during steady combustion. Even when the premixed gas is rectified in the upstream portion of the catalyst body as in the second type, the temperature of the premixed gas gradually increases as it approaches the catalyst during steady combustion, and the temperature gradually rises due to natural convection. Therefore, the premixed gas concentration on the upper side becomes high and that on the lower side becomes low by the time it reaches the catalyst body. As a result, like the first type,
Even during combustion, the surface temperature of the catalyst body tends to increase toward the upper side. If temperature unevenness occurs on the catalyst body during combustion, deterioration of the high temperature portion rapidly progresses and the life of the catalyst body is shortened.

Further, both of the above types have a drawback that when the premixed gas is introduced into the premixed gas supply chamber by a pipe, the premixed gas is condensed in the pipe to tar and the ignition performance is deteriorated.

Further, in the second type, as a result of providing the rectifying mechanism, it is necessary to lengthen the distance in the gas flow direction of the premixed gas supply chamber, so that there is a drawback that the device becomes large.

[Means for solving the problem]

In order to solve the above problems, the catalytic combustion apparatus according to the present invention introduces a premixed gas, which is a mixture of combustion air and vaporized fuel, into a preheated catalyst body to promote an oxidation reaction. In a catalytic combustion device that is designed to burn,
It is characterized by including a heat exchange section for preheating combustion air with exhaust heat, and a swirling mixed gas supply chamber for supplying at least a swirling flow to the premixed gas and then supplying this to the catalyst body.

[Action]

According to the above configuration, the combustion air recovers the exhaust heat and is preheated, so that the premixed gas generated by the combustion air has a relatively high temperature. Therefore, the condensation of the premixed gas is prevented, and the deterioration of the ignition performance can be avoided.

Further, since the premixed gas is supplied to the catalyst body after being given a swirl flow, the influence of natural convection is eliminated, and the inflow velocity and the inflow concentration of the premixed gas to the catalyst body are made uniform regardless of the vertical position. Can be made. Therefore, temperature unevenness on the catalyst body during combustion can be prevented, deterioration of the high temperature portion can be suppressed, and the life of the catalyst body can be extended.

Further, in the pre-combustion stage where only the combustion air is supplied, that is, at the time of preheating the catalyst body, the natural convection can be eliminated by the swirling flow of the combustion air to prevent the lower temperature of the catalyst body from being lowered. When igniting and burning by finishing with the premixed gas, the situation where toxic gases such as HC and CO are generated from the low temperature part for a while after ignition is also eliminated.

Furthermore, by giving a swirl flow to the premixed gas, it is possible to diffuse the air and the vaporized fuel in the premixed gas itself to form a uniform mixed state.

Further, since the rectifying mechanism is unnecessary, the device can be downsized.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the catalytic combustion device according to the present invention, FIG.
As shown in (b), a substantially cylindrical swirling mixed gas supply chamber 2 is incorporated inside the housing 1. On the front side of the swirling mixed gas supply chamber 2, a noble metal oxidation catalyst body 3 having excellent far infrared radiation efficiency is arranged. In the noble metal oxidation catalyst body 3, the catalyst carrier is Al ₂ O ₃ (alumina),
A honeycomb-shaped heat-resistant inorganic material such as cordierite, mullite, silicon carbide, silicon nitride, or zirconia.
Alternatively, the surface of the foam metal is sprayed with Al and Al ₂ O _3, etc., and at least one or more of the platinum group metals such as Pt, Pd, Rh, Ru, and Ir is loaded on the catalyst carrier of the previous period as an oxidation catalyst. I am letting you. The noble metal oxidation catalyst body 3 is formed in a rectangular shape, and a frame-shaped catalyst support body 4 made of a heat insulating material such as a ceramic fiber is mounted around the square body. Further, on the front side of the noble metal oxidation catalyst body 3, a guard net 5 is provided for protecting the catalyst surface and ensuring safety.

A gas opening 6a of the blower pipe 6 is communicated with a rectangular opening 2a formed at the bottom of the swirling mixed gas supply chamber 2, and only the combustion air or the premixed gas is discharged from the gas opening 6a. It is designed to come in tangentially.
An evaporative mixing section 7 is provided upstream of the gas ejection port 6a so as to vaporize kerosene from the oil pump and mix the vaporized fuel with the air from the blower pipe 6. The blower pipe 6 on the upstream side of the vaporizing and mixing section 7 is connected to the fan 8 through the space above the precious metal oxidation catalyst body 3. The fan 8 takes in air from the outside and sends it into the blower pipe 6. Further, fins 10a, which are made of a material having high thermal conductivity, are arranged on the outer peripheral portion of the blower pipe 6 located above the noble metal oxidation catalyst body 3 to form the heat exchange portion 10. Further, the part of the blower pipe 6 other than the heat exchange part 10 is covered with a heat insulating material such as glass wool which is not shown.

When the premixed gas blows in from the gas ejection port 6a in the tangential direction, a turbulent swirl flow is formed in the swirl mixed gas supply chamber 2, and the intensity of the turbulent flow of this turbulent swirl flow is increased and diffused. In order to improve efficiency, diffusion plates 11 ... Are arranged on the inner peripheral wall of the swirling mixed gas supply chamber 2. Further, in the swirling mixed gas supply chamber 2, a catalyst preheating heater 12 for heating the precious metal oxidation catalyst body 3 prior to ignition is arranged. The terminals 12a and 12a of the preheater 12 are connected to the control unit 13. In the vicinity of the noble metal oxidation catalyst body 3, a temperature sensing element 14 for sensing the radiant heat from the back side of the noble metal oxidation catalyst body 3 is arranged. The terminal portion 14a of the temperature sensing element 14 is connected to the control unit 13.

The control unit 13 detects the surface temperature of the noble metal oxidation catalyst body 3 based on the output of the temperature sensing element 14,
The fan 8, the catalyst preheater 12, the oil feed pump, and the like are automatically controlled.

The operation of the catalytic combustion apparatus having the above-described configuration is made up of a combustion operation for burning the premixed gas and a preheating operation performed prior to this combustion operation.

In the preheating operation, the catalyst preheating heater 12 is energized to generate heat and the temperature in the swirling mixed gas supply chamber 2 is raised. When the internal temperature of the swirling mixed gas supply chamber 2 reaches about 300 ° C., the heater (not shown) and the fan 8 in the vaporizing and mixing section 7 are activated to supply combustion air into the blower pipe 6. While the supplied air passes through the inside of the heat exchange section 10, it takes up the heat discharged to the upper side of the catalyst preheating heater 12 to be heated in advance and then the swirling mixed gas supply chamber 2
It is blown inward in the tangential direction. The preheated combustion air blown tangentially from the gas outlet 6a is
The turbulent swirling flow is formed by flowing along the inner wall of the swirling mixed gas supply chamber 2, and at the same time, the turbulent flow intensity is further increased by the diffusion plates 11 ... In such a turbulent swirling flow state, there is almost no effect of natural convection and diffusion is performed efficiently, so that the noble metal oxidation catalyst body 3 can be heated uniformly. The combustion air that has completed this preheating is discharged from the warm air outlet 1a formed above the catalyst preheating heater 12. In addition, the amount of air blown for combustion is kept constant until the subsequent steady combustion → extinction → cooling.

When the control unit 13 determines based on the output of the temperature sensing element 14 that the temperature of the noble metal oxidation catalyst body 3 has reached about 250 to 300 ° C., the operation of the catalyst preheating heater 12 is stopped, and at the same time, the oil transfer is performed. Operate the pump. That is, the combustion operation of the premixed gas is started.

The kerosene is delivered to the vaporizing and mixing section 7 by the oil feeding pump. Since the vaporizing section in the vaporizing and mixing section 7 is heated and held at about 300 ° C. by the heater (not shown), it passes through the vaporizing section. During that time, kerosene is heated and vaporized. Then, this vaporized kerosene is sprayed into the blower pipe 6,
A premixed gas is produced by mixing with the preheated combustion air. The premixed gas is blown out into the swirling mixed gas supply chamber 2 through the blower pipe 6, but has a relatively high temperature and therefore reaches the swirling mixed gas supply chamber 2 without dew condensation in the middle of the pipe. The flow velocity of the premixed gas is higher than the burning velocity, and is set to, for example, 2 m / s or more.

The premixed gas forms a turbulent swirling flow in the swirling mixed gas supply chamber 2, and is further efficiently diffused and mixed by the diffusion plates 11. Then, as described above, when passing through the uniformly preheated precious metal oxidation catalyst body 3, it is ignited and burned. As described above, since the temperature of the noble metal oxidation catalyst body 3 is uniform and there is no low-temperature portion, no toxic gas such as HC or CO is generated. Furthermore, since the noble metal oxidation catalyst body 3 is designed to give a sufficient space velocity for complete combustion of the premixed gas, ignition is performed while more efficiently preventing the emission of toxic gases such as CO and HC. Temperature rise → Transition to steady combustion state. During steady combustion, control the amount of kerosene delivered while maintaining a constant amount of air blow,
The volume ratio of premixed gas to air is always 2 for 1 air.
By controlling the backside temperature of the noble metal oxidation catalyst body 3 between 500 and 700 ° C., it is possible to increase or decrease the combustion amount while preventing flashback and incomplete combustion of the premixed gas. it can. In the unlikely event that the volume ratio of the premixed gas deviates from the set range and flashback or incomplete combustion occurs, the control unit is based on the output of the temperature sensing element 14 described above.
13 determines that the combustion is abnormal, so the combustion is stopped immediately.
The generation of NO _x is surely prevented.

The completely burned high-temperature exhaust gas rises after passing through the precious metal oxidation catalyst body 3 and imparts heat to the air in the blower pipe 6 in the heat exchange section 10 to become warm air of about 150 ° C. or less and the hot air outlet 1a.
Emitted from. On the other hand, far infrared rays are radiated from the noble metal oxidation catalyst body 3 directly or through the reflecting plate 17.
Therefore, the convection heating by the warm air and the far infrared radiation heating are simultaneously performed.

At the time of extinguishing the fire, the power supply to other devices except the fan 8 is cut off, and only the fan 8 is operated for several tens of seconds to blow air, thereby cooling the system including the precious metal oxidation catalyst body 3. At this time, since the precious metal oxidation catalyst body 3 has a certain heat capacity, even if the supply of the premixed gas is stopped, it does not emit odorous gas such as unburned HC and CO like combustion with ordinary flames. ,
It is completely oxidized on the noble metal oxidation catalyst body 3.

FIG. 2 (a) is a graph showing the temperature distribution in the vertical position on the back side of the noble metal oxidation catalyst body 5 five minutes after the energization of the catalyst preheater 12 is started, that is, in the preheating stage. The case of forming a swirl flow (the present invention) and the case of a non-swirl flow (conventional) are shown together. The air flow rates are set to be the same as each other, and the catalyst preheater 12
I am using 1kW. FIG. 2B is a graph showing the temperature distribution at the upper and lower positions on the back side of the noble metal oxidation catalyst body 3 in the steady combustion stage, and shows both the present invention and the conventional one. The fuel load was 850 kcal / h and the premixed gas with an air ratio of 4.3 was used.

As is clear from these figures, it is understood that the present invention is superior in uniformizing the catalyst surface temperature in both cases of catalyst preheating and steady combustion.

In the present embodiment, the noble metal oxidation catalyst body 3 is applied in the horizontal and vertical postures, but it is also applicable to the noble metal oxidation catalyst body 3 in the vertical and horizontal postures.

[Effect of device]

As described above, the catalytic combustion apparatus according to the present invention burns the premixed gas prepared by mixing the combustion air and the vaporized fuel by flowing into the preheated catalyst body to promote the oxidation reaction. In the above catalytic combustion apparatus, a heat exchange section for preheating combustion air with exhaust heat and a swirling mixed gas supply chamber for applying at least a swirling flow to the premixed gas and then supplying the swirling mixed gas to the catalyst body are provided. It is a composition.

 As a result, the following various effects are achieved.

(1) It is possible to prevent the premixed gas (vaporized fuel) from condensing in the pre-blowing pipe and avoid the deterioration of the ignition performance.

(2) Since the inflow velocity and the inflow concentration of the premixed gas with respect to the catalyst body can be made uniform regardless of the vertical position, temperature unevenness on the catalyst body during combustion is prevented, and deterioration of the high temperature portion is suppressed. Thus, the life of the catalyst body can be extended.

(3) Pre-combustion stage where only combustion air is supplied, that is,
Even during preheating of the catalyst body, natural convection can be eliminated by the swirling flow of combustion air to prevent lowering of the temperature on the lower side of the catalyst body, so preheating is terminated and premixed gas is supplied for ignition and combustion. In this case, it is possible to eliminate the situation where toxic gases such as HC and CO are generated from the low temperature part for a while after ignition.

(4) By imparting a swirl flow to the premixed gas, the premixed gas itself can diffuse air and vaporized fuel to form a uniform mixed state.

(5) Since the rectifying mechanism for the combustion air and the premixed gas is not required, the thickness of the gas inflow direction can be reduced to reduce the thickness of the device and increase the area of the catalyst body.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 (a) is a front view showing the internal structure of the catalytic combustion device,
FIG. 3B is a side view of the same. FIG. 2 (a) is a graph showing the temperature distribution at the upper and lower positions on the back side of the noble metal oxidation catalyst in the preheating stage, and FIG. 2 (b).
[Fig. 4] is a graph showing temperature distributions at upper and lower positions on the back side of the noble metal oxidation catalyst in the steady combustion stage. 2 is a swirling mixed gas supply chamber, 3 is a noble metal oxidation catalyst body (catalyst body), 6 is a blast pipe, 7 is a vaporizing and mixing section, 8 is a fan,
Reference numeral 10 is a heat exchange section, and 12 is a catalyst preheating heater.

Claims (1)

[Scope of utility model registration request] 1. A catalytic combustion apparatus in which a premixed gas, which is a mixture of combustion air and vaporized fuel, flows into a preheated catalyst body to promote an oxidation reaction to burn the premixed gas. A catalytic combustion apparatus comprising: a heat exchange section for preheating air with exhaust heat; and a swirling mixed gas supply chamber for supplying at least a swirling flow to the premixed gas and then supplying this to the catalyst body. .