JPH0362970B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a combustion type fluid heating device such as a water heater or a hot air heater.

[Conventional technology]

Conventionally, in combustion type fluid heating equipment,
To reduce CO, HC, and NO _x , in the combustion gas path from the burner, install an oxidation catalyst layer immediately after the burner and upstream of the fluid heating heat exchanger, or
Alternatively, an oxidation catalyst layer was provided in the exhaust gas path downstream of the fluid heating heat exchanger (I cannot provide any literature).

[Problem that the invention seeks to solve]

However, in the type where the oxidation catalyst layer is installed immediately after the burner, the temperature of the combustion gas passing through the oxidation catalyst layer is
Due to the high temperature of 1000℃ or more, ordinary oxidation catalysts deteriorate quickly, and if you try to suppress the deterioration, you need a special and expensive oxidation catalyst, or the temperature of the oxidation catalyst In order to lower the combustion load, the combustion load on the burner had to be limited, which resulted in the problem of hindering the ability to increase the performance of the device.

On the other hand, in the type in which an oxidation catalyst layer is provided in the exhaust gas path downstream of the fluid heating heat exchanger, it is not possible to secure a temperature (usually 200°C or higher) that can sufficiently activate the oxidation catalyst. CO, H.C.
There is a problem that NO _x cannot be sufficiently reduced, and if the exhaust gas temperature is raised by reducing the amount of heat exchanged in the heat exchanger to activate the oxidation catalyst, this will lead to a decrease in the performance of the equipment and , a problem arises that causes a decrease in thermal efficiency due to exhaust gas heat loss.

The purpose of the present invention is to improve the equipment capacity and thermal efficiency, suppress deterioration of the oxidation catalyst, and improve the efficiency of the oxidation catalyst by rationally improving the layout of the fluid heating heat exchanger and the oxidation catalyst layer in the combustion gas path from the burner. The aim is to achieve both of the three functions of active activation, and also to suppress and prevent deterioration and damage to the oxidation catalyst caused by drainage generated when moisture in the combustion gas condenses in the heat exchanger. It is in.

[Means for solving problems]

A characteristic configuration of the combustion type fluid heating device according to the present invention is that a first heat exchanger and a second heat exchanger for heating the fluid are provided in the combustion gas path from the burner in parallel in the combustion gas flow direction, and the combustion gas between the first heat exchanger and the second heat exchanger in the path;
The second heat exchanger is provided with an oxidation catalyst layer that acts on the combustion gas passing between the two heat exchangers, and is located upstream of the first heat exchanger in the heated fluid path to recover latent heat from the combustion gas. The exchanger is disposed on the downstream side of the oxidation catalyst layer in the flow direction of the combustion gas, and its operation and operation are as follows.
The effects are as follows.

[Effect]

In other words, in the above-described configuration, the amount of heat exchanged by the first heat exchanger located upstream of the combustion gas path than the oxidation catalyst layer is appropriately limited in terms of thermal design, and the high-temperature combustion gas from the burner is first By passing the combustion gas through the first heat exchanger, the temperature of the combustion gas is lowered to a temperature suitable for the oxidation catalyst, that is, a temperature that is sufficiently activated and does not accelerate deterioration. By passing the combustion gas after passing through the oxidation catalyst layer to the second heat exchanger on the downstream side, the amount of heat held by the combustion gas after passing through the oxidation catalyst layer, that is, the amount of heat held by the combustion gas after passing through the oxidation catalyst layer, is reduced by the first heat exchanger. Taking into account the activation of the oxidation catalyst during heat recovery, the amount of heat left behind is sufficiently recovered in the second heat exchanger.

In addition, in order to sufficiently recover heat in the second heat exchanger, in the heated fluid path, the temperature of the passing heated fluid is lower than that of the first heat exchanger. In a configuration in which the second heat exchanger is located on the side where the combustion gas is located and the latent heat of the combustion gas is also recovered by the second heat exchanger, drainage due to condensation of moisture in the combustion gas occurs in the second heat exchanger. In the above characteristic configuration, the second heat exchanger is disposed on the downstream side of the oxidation catalyst layer in the flow direction of the combustion gas, so that the drain generated in the second heat exchanger is blown away by the combustion gas. Even if something like this happens, there is no risk that the drain will be sprayed onto the oxidation catalyst layer.

〔Effect of the invention〕

As a result, the following effects are achieved.

(b) Since deterioration of the oxidation catalyst can be suppressed, it is possible to increase the load on the burner, and it is possible to use a normal oxidation catalyst instead of using a special and expensive oxidation catalyst with excellent thermal durability. Function can be maintained for a long time.

(b) Since the oxidation catalyst can be sufficiently activated, CO, HC, and NO _x in exhaust gas can be effectively reduced.
It is possible to prevent not only exhaust gas pollution but also equipment corrosion and wastewater pollution caused by the acidification of condensate caused by NO _x and the like melting into the condensate generated in the heat exchanger.

(c) Sufficient heat recovery in the second heat exchanger improves thermal efficiency and reduces running costs.
Furthermore, the combination of sufficient heat recovery in the second heat exchanger and the high load of the burner allows for a compact device with a large heating capacity.

(d) It is possible to prevent deterioration and damage to the catalyst due to drainage generated in the heat exchanger being blown onto the oxidation catalyst layer by combustion gas.

In short, it is possible to improve the equipment capacity and thermal efficiency, suppress the deterioration of the oxidation catalyst, and sufficiently activate the oxidation catalyst, thereby improving heating performance, durability, safety (environmental conservation), and economic efficiency. A combustion-type fluid heating device with high added value, which is excellent in all properties and also excellent in avoiding the adverse effects of drain on the oxidation catalyst, has been created.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

The drawing shows a gas instantaneous water heater as an example of a combustion-type fluid heating device, in which a gas burner 1 that is operated by combustion in a downward direction is installed on the upper end side of a casing 2 for forming a combustion gas path, and a fan 3 supplies combustion air. With this forced supply, the combustion gas produced by the burner 1 is made to flow downward within the casing 2, and the exhaust gas is discharged through an exhaust air passage 4 connected to the lower end side of the casing 2.

In the figure, V is a fuel valve.

In the combustion gas path F in the casing 2,
A first heat exchanger 5 and a second heat exchanger of Finch-Eube type, respectively.
The heat exchangers 6 are arranged in order from the upstream side in the flow direction of the combustion gas, and the water supply channel 7 is connected to the second heat exchanger 6.
In addition, a hot water supply path 9 for the tap 8 is connected to the first heat exchanger 5, and the first heat exchanger 5 and the second heat exchanger 6 are connected in series via an intermediate waterway 10. In other words, the water supplied from the water supply channel 7 is preheated in the second heat exchanger 6, then heated at a high temperature in the first heat exchanger 5, and then supplied to the tap 8. In the passage 7 the first heat exchanger 5
During preheating in the second heat exchanger 6 located upstream of the combustion gas (that is, on the side where the feed water temperature is lower than that of the first heat exchanger 5), latent heat is also recovered from the combustion gas. be.

A drain pan 11 is provided at the bottom of the casing 2 so as to connect the exhaust air passage 4 to the side wall of the casing 2, and the drain pan 11 receives the dripped condensate generated by the heat exchanger 6.
It is designed to be discharged from 2.

Incidentally, by arranging the burner 1 in a downward facing position on the upper end side of the casing 2, inhibition of the combustion operation of the burner 1 due to dripping of condensate can be reliably avoided. Drain is generated in the second heat exchanger 6, but since the drain pan 11 is located directly below the second heat exchanger 6 in the above-described configuration, drain discharge is extremely efficient.

Inside the casing 2, the first heat exchanger 5 and the second
An oxidation catalyst layer 1 is provided between the heat exchanger 6 and acts on the combustion gas passing between the heat exchangers 5 and 6.
3 is provided over the entire cross section of the combustion gas path F, and the catalytic action of the oxidation catalyst layer 13 reduces CO, HC, _NOx , etc. in the exhaust gas, and the first heat exchange The heat exchange efficiency of the heat exchanger 5 is limited to about 60% to 75% by design, and the combustion gas temperature after passing through the first heat exchanger 5 is set at 200°C to 400°C.
It is designed to maintain a temperature of approximately ℃.

In other words, by disposing the oxidation catalyst layer 13 between the two heat exchangers 5 and 6 and allowing the oxidation catalyst to act on the combustion gas whose temperature has decreased as it passes through the first heat exchanger 5, the oxidation catalyst layer 13 can be oxidized. The thermal deterioration of the catalyst is suppressed, and the burner 1 can be subjected to a high load based on the suppression of the deterioration. In other words, the downstream catalyst layer 13 oxidizes and detoxifies unburned components (CO, HC, NO _x , etc.) that increase as the load on the combustion chamber of the burner 1 increases, so the combustion chamber including the burner 1 can be made extremely small. This makes it possible to downsize the entire device.

Furthermore, even if the temperature of the combustion gas is lowered as it passes through the first heat exchanger 5, the heat exchange efficiency of the first heat exchanger 5 is deliberately limited to about 60% to 75%. By ensuring a combustion gas temperature of 200°C to 400°C, the oxidation catalyst can be sufficiently activated to effectively reduce CH, HC, NO _x , etc. while suppressing deterioration.

On the other hand, the second heat exchanger 6 is designed to obtain as high heat exchange efficiency as possible, and the amount of heat held by the combustion gas after passing through the oxidation catalyst layer 13 is recovered by the first heat exchanger 5. In consideration of the activation of the oxidation catalyst, the amount of heat left behind due to the limitation of heat exchange efficiency is sufficiently recovered in the second heat exchanger 6 to the latent heat as described above.

In other words, sufficient heat recovery in the second heat exchanger 6 improves the thermal efficiency of the device, and in addition to the above-mentioned high burner load, a large heating capacity can be obtained.

Further, there is a possibility that the drain generated in the second heat exchanger 6 is blown away by the combustion gas, but even if such drain is blown away,
Since the second heat exchanger 6 is located downstream of the oxidation catalyst layer 13 in the flow direction of the combustion gas, there is no risk of blown drain hitting the oxidation catalyst layer 13 and causing deterioration or damage to the oxidation catalyst. .

The heat exchange efficiency setting of each heat exchanger 5, 6 includes adjusting the combustion gas bypass rate and fin efficiency in the heat exchanger, and using the second heat exchanger 6 for preheating and the first heat exchanger 5. This is done by using for post-heating.

The oxidation catalyst layer 13 is constructed by forming an oxidation catalyst coating of palladium, platinum, or the like on a porous plate-like base material of cordierite.

[Another example]

Next, another embodiment of the present invention will be described.

In the above-mentioned embodiment, the burner 1 was arranged downward and the combustion gas path F was directed downward in order to prevent drainage. In other words, the drain generated in the second heat exchanger 6 dripped onto the oxidation catalyst layer 13 In order to prevent the second heat exchanger 6 from falling upward, it is preferable to arrange the second heat exchanger 6 below the oxidation catalyst layer 13, but there are particular restrictions on the direction of the burner 1 and the direction of the combustion gas path F. Instead, the burner 1 and the combustion gas path F may be oriented upward or sideways.

The fluid to be heated by the first and second heat exchangers 5 and 6 is not limited to water; for example, a hot air heater may be configured such that the heat exchangers 5 and 6 heat air. You can also do it.

Various improvements can be made to the specific shape and structure of each of the heat exchangers 5 and 6, and three or more heat exchangers may be arranged in parallel in the flow direction of the combustion gas.

The specific shape and structure of the oxidation catalyst layer 13 can be modified in various ways, such as forming it into a perforated plate shape, a wire mesh shape, or a packed bed structure of granular oxidation catalyst. On the other hand, instead of the type in which the oxidation catalyst is attached, a type in which the oxidation catalyst itself is formed into a porous plate shape, a wire mesh shape, etc. may be used.

Furthermore, the oxidation catalysts used include palladium, platinum, rhodium, chromium, cobalt, etc.
Various methods can be applied.

If the heat exchanger 5 is designed so that the temperature of the fuel gas passing through the heat exchanger 5 located upstream of the oxidation catalyst layer 13 in the flow direction of the combustion gas is 200°C or higher, the oxidation catalyst can be sufficiently absorbed. However, normally, the oxidation catalyst is rapidly activated at around 200°C, and the activation reaches equilibrium at a slightly higher temperature than 200°C, so the oxidation catalyst is activated upstream of the oxidation catalyst layer 13. It is preferable to adjust the temperature of the combustion gas after passing through the heat exchanger 5 located at about 200°C to 400°C.

Also, the temperature of the combustion gas after passing through the heat exchanger 5 located upstream of the oxidation catalyst layer 13 is specifically determined at what temperature.
Whether the adjustment should be made can be determined as appropriate depending on the oxidation catalyst used and the specific configuration of the apparatus, and furthermore, the specific design means adopted for the adjustment is not limited.

The fuel supplied to the burner 1 is not limited to gas fuel.

The present invention provides a water heater, a bath heating device, or
It can be applied to combustion type heating devices for various purposes, such as hot air heaters and hot air dryers.

[Brief explanation of drawings]

The drawing is a block diagram of a water heater showing an embodiment of the present invention. 1... Burner, 5... First heat exchanger, 6... Second heat exchanger, 13... Oxidation catalyst layer, F... Combustion gas path.

Claims (1)

[Scope of Claims] 1. A first exchanger 5 and a second heat exchanger 6 for heating fluid are provided in the combustion gas path F from the burner 1 in parallel in the combustion gas flow direction, and the combustion gas path F
An oxidation catalyst layer 13 is provided between the first heat exchanger 5 and the second heat exchanger 6, which acts on the combustion gas in the passage between the two heat exchangers, and the oxidation catalyst layer 13 acts on the combustion gas in the passage between the two heat exchangers. The second exchanger 6, which is located upstream of the first heat exchanger 5 and recovers latent heat from the combustion gas, is arranged downstream of the oxidation catalyst layer 13 in the direction of flow of the combustion gas. . 2. The combustion type fluid heating device according to claim 1, wherein the second heat exchanger 6 for recovering latent heat from combustion gas is arranged below the oxidation catalyst layer 13. Device.