JP2000146299A - Latent heat recovery mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent or retard acid corrosion of a heat transfer tube constituting a latent heat recovery unit due to drain water by supplying an alkaline liquid over a range where steam at least in the exhaust gas is condensed and covering the range with the alkaline liquid. SOLUTION: A latent heat recovery unit 8 arranged with a heat transfer tube 10 is constituted in the exhaust passage 7 of a combustor and the surface of the heat transfer tube is coated with an alkaline liquid by supplying the alkaline liquid thereto. In the case that the combustor is a boiler, boiler water can be used as the alkaline liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent heat recovery mechanism for a combustion device such as a boiler or a water heater.

[0002]

2. Description of the Related Art Since many fuels contain a hydrogen component, combustion generates steam. The volume ratio of steam in the exhaust gas is, for example, about 18% for natural gas and about 12% for heavy fuel oil A. On the other hand, the latent heat of the steam in the exhaust gas is very large, and the calorific value is about 10% of the total calorific value for the city gas 13A and about 6% for the heavy fuel oil A. Therefore, the exhaust gas temperature is reduced to about 50 ° C. by heat exchange to condense the vapor in the exhaust gas, and the latent heat is recovered, thereby significantly increasing the efficiency of the combustion equipment. Equipment such as a boiler and a water heater, which is widely used and whose efficiency is severly pursued, is particularly required to increase the efficiency by this technology.

FIG. 9 schematically shows a conventional mechanism for recovering latent heat in a boiler as an example of such a conventional technique. Reference numeral 1 denotes a burner installed on the upper part of the boiler main body 2, and a water pipe 6 is installed between an upper header 4 and a lower header 5 in a combustion chamber 3 in the boiler main body 2. Reference numeral 7 denotes an exhaust path from the upper part of the combustion chamber 3 to the chimney, and the exhaust path 7 is provided with a path 7 d for exhaust to descend, as a path for installing a latent heat recovery unit 8 described later. From the lower end to the chimney via a path 7u where the exhaust rises. A latent heat recovery unit 8 having a heat transfer pipe 10 for supplying water is arranged in the exhaust path 7d, and heat exchange is performed between the supply water supplied from the water supply unit to the lower header 5 and the exhaust flowing through the exhaust path 7d in the heat transfer pipe 10. It is configured to preheat. At this time, the steam in the exhaust is condensed and the latent heat is recovered in the feedwater.

[0004]

However, such a latent heat recovery device has not been widely used yet. The main factor is acid corrosion. That is, since a large amount of carbon dioxide is contained in the exhaust gas, the drain water becomes acidic with a pH of 3 to 4, whereby the heat transfer tube 10 of the latent heat recovery unit is corroded by acid and has a hole. In this case, as shown in FIG. 10, when the heat transfer tube 10 is installed in a path where the exhaust gas rises, the drain water 11 condensed in the heat transfer tube 10 does not fall due to the rising flow of the exhaust gas. Since it accumulates between the twelve, there is a disadvantage that corrosion is accelerated. For this reason, conventionally, the heat transfer tube 10 is provided in the path 7d where the exhaust gas descends as described above. That is, FIG. 11 shows a case in which the heat transfer tube 10 is provided in the path 7 d where the exhaust gas descends. In this case, the drain water 11 condensed in the heat transfer tube 10 drops due to the flow of the exhaust gas, and Does not accumulate. However, the provision of the path 7d for descending the exhaust increases the length of the exhaust path 7, which leads to an increase in the size of the latent heat recovery unit 8, and the drawback that the wind power must be increased in order to flow the warm exhaust downward. Connect.
An object of the present invention is to solve the above problems.

[0005]

According to the present invention, there is provided a latent heat recovery device in which a heat transfer tube for supplying water is disposed in an exhaust path of a combustion device, and a heat transfer tube of the latent heat recovery device. A latent heat recovery mechanism is proposed in which an alkaline liquid is caused to flow over the surface of the heat transfer tube and the surface of the heat transfer tube is covered with the alkaline liquid.

In the present invention, it is proposed in the above configuration that the latent heat recovery device is provided in an exhaust path in which the exhaust gas rises, and the alkaline liquid flows from the top of the heat transfer tube.

According to the present invention, in the above-described structure, the latent heat recovery device is provided in an exhaust path in which exhaust gas descends, and the temperature of the alkaline liquid is higher than a temperature at which vapor in the exhaust gas condenses by a predetermined amount or more. It is proposed to flow downward from the position of the heat transfer tube corresponding to.

When the combustion apparatus to which the present invention is applied is a water heater, the alkaline liquid may be an aqueous solution of an alkaline neutralizing agent.

When the combustion equipment to which the present invention is applied is a boiler, boiler blow water can be used as an alkaline liquid.

Further, in the present invention, when the combustion equipment is a boiler and boiler blow water is used as an alkaline liquid, the heat transfer tube has a double tube structure provided with fins on the outside, and feed water is supplied to the outer tube portion. It is proposed to supply boiler blow water to the inner pipe.

Further, in the present invention, in the above-described double pipe structure, a sprinkler pipe communicating with the inner pipe portion is provided outside the heat transfer pipe.
It is proposed that the boiler blow water flowing through the inner pipe part be drained from the sprinkler pipe and flow to the surface of the heat transfer pipe.

Further, in the present invention, in the above-mentioned double pipe structure, a communication portion is formed from the inner pipe portion to an outer periphery of the outer pipe portion, and boiler blow water flowing through the inner pipe portion flows out from the communication portion. It is proposed to adopt a configuration in which flow is made to flow to the surface of the heat transfer tube.

According to the present invention, since the surface of the heat transfer tube of the latent heat recovery unit is covered with the alkaline liquid, acid corrosion due to drain water can be prevented or delayed. In addition, since the drain water is flowed by the alkaline liquid, it does not accumulate between the fins, and the latent heat recovery device can be installed in the exhaust path where the exhaust rises. When the combustion equipment is a boiler and the boiler blow water is used as an alkaline liquid, the sensible heat of the boiler blow water can be recovered.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of a latent heat recovery mechanism of a boiler to which the present invention is applied. In this embodiment, a heat transfer tube 10 constituting a latent heat recovery device 10 is similar to that of FIG. The same components as those of the mechanism shown in FIG. 9 are denoted by the same reference numerals and are not described repeatedly. The heat transfer tube 10 is installed so that the upstream side of the water supply is on the lower side in the path 7d, and the water sprinkling section 13 is installed corresponding to the intermediate position. The sprinkler 13 is provided at the lower header 5 of the boiler body 2.
The boiler blow water is sprinkled by being connected to the blow water supply pipe 14. In such a configuration, the surface of the heat transfer tube 10 sprinkled by the sprinkler 13 is covered with the alkaline boiler blow water to neutralize the drain water, so that acid corrosion can be prevented or delayed. The range of the heat transfer tubes 10 covered by the boiler blow water sprinkled from the water sprinkling section 13 corresponds to a position where the exhaust gas temperature corresponds to a position higher than the temperature at which the steam in the exhaust gas condenses by a predetermined amount or more.
If the position of the heat transfer tube 10 is set to be lower than the position and the water is not sprayed above the heat transfer tube 10 in which the temperature of the exhaust gas is higher than the temperature at which the steam in the exhaust gas condenses by a predetermined amount or more,
The heat exchange between the exhaust gas and the feed water is performed more favorably than the portion covered with the boiler blow water. However, if this is not considered, the heat transfer tube 10 as shown in FIG.
In the configuration described above, the water sprinkling section 13 may be provided corresponding to the uppermost part of the heat transfer tube 10.

Next, FIG. 2 shows a second embodiment of a latent heat recovery mechanism for a boiler to which the present invention is applied. In this embodiment, unlike the one shown in FIG. Is provided only with a path 7u which rises, and a path with which the exhaust descends is not provided. However, the same components as those in FIG. 9 are denoted by the same reference numerals, and redundant description will be omitted. In this embodiment, the heat transfer tubes 10 constituting the latent heat recovery unit 8 are installed on the path 7u where the exhaust gas rises so that the upstream side of the water supply is upward. A sprinkling section 13 is provided. In the above configuration, since the surface of the heat transfer tube 10 is covered with boiler blow water from the uppermost portion where the exhaust gas temperature is lowest, the acidic drain water does not directly contact the surface of the heat transfer tube 10. , And is neutralized by alkaline boiler blow water, so that acid corrosion can be prevented or delayed. In this embodiment, the heat transfer tubes 10 constituting the latent heat recovery device 8 are
Is installed in the path 7u in which the exhaust gas rises, but the drain water flows down by the boiler blow water and falls, so that there is no accumulation between the fins 12. In such a configuration, the boiler blow water needs to be slightly larger than in the first embodiment.

Next, FIG. 3 shows a third embodiment of a latent heat recovery mechanism for a combustion apparatus to which the present invention is applied. In this embodiment, the combustion apparatus is a water heater. That is, reference numeral 15 denotes a water heater main body, and a burner 16 is provided in the water heater main body 15.
And a heat transfer tube 17 for boiling water. Reference numeral 19 denotes an exhaust path extending from the upper portion of the combustion chamber 18 to the chimney. The exhaust path 19 includes, similarly to the case of the boiler described above, a path 19d in which the exhaust descends and a path 19u in which the exhaust rises. I have. A latent heat recovery device 22 is provided in the exhaust path 19d. The latent heat recovery device 22 includes a heat recovery heat transfer tube 21 that communicates with the hot water heat transfer tube 17 to supply water.
7 is supplied to the heat transfer pipe 21 through the exhaust path 19.
It is configured to preheat by exchanging heat with the exhaust flowing through d. As in the first embodiment, the heat transfer tube 21 is
In d, the upstream side of the water supply is installed downward, and the water sprinkling section 23 is installed corresponding to the intermediate position. The sprinkling section 23 is connected to a neutralizing agent supply pipe 24 connected to a neutralizing agent supplying section (not shown). In the above configuration, as in the first embodiment, the water sprinkling section 23
Since the surface of the heat transfer tube 21 sprayed with water is covered with the neutralizing agent and the drain water is neutralized, acid corrosion can be prevented or delayed. As in the first embodiment, the range of the heat transfer tube 21 covered with the neutralizing agent sprinkled from the water sprinkling section 23 corresponds to a position where the exhaust gas temperature is higher than the temperature at which the vapor in the exhaust gas condenses by a predetermined amount or more. If water is not sprayed above the heat transfer tube 21 at a position lower than the position of the heat pipe 21 and the temperature of the exhaust gas is higher than the temperature at which the vapor in the exhaust gas condenses by a predetermined amount or more, the heat transfer tube 21 has a medium The heat exchange between the exhaust gas and the water supply is performed better as compared with the portion covered with the sump. However, if such a thing is not considered, the water sprinkling part 23 can be provided corresponding to the uppermost part of the heat transfer tube 21. In this embodiment, the latent heat recovery unit 2
2 is provided on the path 19d where the exhaust gas descends, but it is also possible to provide only the path 19u where the exhaust gas rises and install the latent heat recovery unit 22 on this path 19u.

FIGS. 4 and 5 show a fourth embodiment and a fifth embodiment, respectively. These embodiments are different from the first and second embodiments, respectively, in that the heat transfer tube 10 and the water spray Are different from each other, and the other configurations are the same. Therefore, the same reference numerals are given to the common components, and the duplicate description will be omitted. That is, in these fourth and fifth embodiments,
The heat transfer tube 10 in the latent heat recovery device 8 is configured as a double tube provided with fins 12 on the outside as shown in FIG.
Water is supplied to the outer pipe section 25 and boiler blow water is supplied to the inner pipe section 26.
It is what constituted. In this configuration, the outer tube 2
The feedwater flowing to the heat exchanger 5 exchanges heat with the exhaust gas flowing outside thereof, and also exchanges heat with the boiler blow water flowing through the inner pipe 26 on the inside, so that the heat retained in the boiler blow water as well as the heat retained in the exhaust gas can be recovered. Here, the watering unit 13
The heat transfer tube 10 is formed on the inner tube portion 26 or an extension thereof at the same position as the corresponding first and second embodiments. This embodiment will be described below.

FIG. 6 shows a first embodiment of the water sprinkling section. In the watering section of this embodiment, the inner pipe section 2
6, a communication part 27 which opens to the outer periphery of the outer pipe part 25 is formed. In this configuration, the boiler blow water flowing through the inner pipe part 26 exchanges heat with the feedwater flowing through the outer pipe part 25, The water flows out to the outer periphery of the outer tube portion 25 through the communication portion 27 and is sprayed on the surface of the heat transfer tube 10.

FIG. 7 shows a second embodiment of the water sprinkling section. In this embodiment, a water sprinkling pipe 27 communicating with the inner pipe section 26 is provided outside the heat transfer pipe 10, and this water sprinkling section is provided. 2
The boiler blow water flowing through the inner pipe part 26 exchanges heat with the water supply flowing through the outer pipe part 25, and is then sprayed to the surface of the heat transfer pipe 10 from the water spray hole 28 of the water spray pipe 27. You.

As shown in the first, second, fourth and fifth embodiments of the latent heat recovery mechanism according to the present invention,
When the combustion equipment to be applied is a boiler, boiler blow water can be used as an alkaline liquid.Therefore, in addition to using a neutralizing agent separately, neutralize the boiler blow water itself with acidic drain water. It has the advantage that it can be discharged.

[0021]

As described above, the present invention has the following effects. a. In the heat transfer tube constituting the latent heat recovery device, an alkaline liquid is flown and covers at least a region where the vapor in the exhaust gas condenses, so that acid corrosion due to drain water can be prevented or delayed. b. Since the heat transfer tubes constituting the latent heat recovery device can be installed in the exhaust path where the exhaust rises, the size of the latent heat recovery device and the size of the ventilator can be reduced. c. If the combustion equipment to be applied is a boiler and boiler blow water is used as the alkaline liquid,
Separately, in addition to using no neutralizing agent, the boiler blow water itself can be neutralized and discharged with acidic drain water.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a first embodiment of a latent heat recovery mechanism of the present invention.

FIG. 2 is a schematic explanatory view showing a second embodiment of the latent heat recovery mechanism of the present invention.

FIG. 3 is a schematic explanatory view showing a third embodiment of the latent heat recovery mechanism of the present invention.

FIG. 4 is a schematic explanatory view showing a fourth embodiment of the latent heat recovery mechanism of the present invention.

FIG. 5 is a schematic explanatory view showing a fifth embodiment of the latent heat recovery mechanism of the present invention.

FIG. 6 is a schematic explanatory view showing an embodiment of a configuration of a heat transfer tube according to the present invention, and FIG.

FIG. 7 is a schematic explanatory view showing a first embodiment of the structure of a water sprinkling section according to the present invention, and FIG. 7 (b) is a cross-sectional view taken along line AA of FIG. 7 (a).

FIG. 8 is a schematic explanatory view showing a second embodiment of the configuration of the water sprinkling section according to the present invention.

FIG. 9 is a schematic explanatory view showing an example of a conventional latent heat recovery mechanism.

FIG. 10 is a schematic explanatory view for explaining the reason why the exhaust heat recovery device is not conventionally provided on the path where the exhaust gas rises, and FIG. 10B is a cross-sectional view taken along the line CC of FIG.

11 is a schematic explanatory view showing a latent heat recovery operation in the latent heat recovery mechanism of FIG. 9, and (b) is a cross-sectional view taken along the line CC of (a).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Burner 2 Boiler main body 3 Combustion chamber 4 Upper header 5 Lower header 6 Water pipe 7 Exhaust path 7d Exhaust descending path 7u Exhaust rising path 8 Latent heat recovery device 10 Heat transfer tube 11 Drain water 12 Fin 13 Sprinkler part 14 Blow water supply Pipe 15 Water heater body 16 Burner 17 Heat transfer pipe for boiling water 18 Combustion chamber 19 Exhaust path 19d Exhaust descending path 19u Exhaust rising path 21 Heat transfer tube 22 Latent heat recovery unit 23 Water sprinkling unit 24 Neutralizing agent supply tube 25 Outside Pipe part 26 Inner pipe part 27 Communication part

Claims (8)

[Claims] 1. A latent heat recovery device in which a heat transfer tube for supplying water is disposed in an exhaust path of a combustion device, wherein an alkaline liquid is caused to flow on the surface of the heat transfer tube of the latent heat recovery device to make the surface of the heat transfer tube alkaline. Latent heat recovery mechanism characterized by being covered with a liquid 2. The latent heat recovery mechanism according to claim 1, wherein the latent heat recovery device is provided in an exhaust path in which exhaust gas rises, and the alkaline liquid flows from an uppermost portion of the heat transfer tube. 3. The latent heat recovery device is installed in an exhaust path in which exhaust gas descends, and a position of the heat transfer tube corresponding to a position where the temperature of the alkaline liquid is higher than a temperature at which the vapor in the exhaust gas condenses by a predetermined amount or more. 2. The method according to claim 1, wherein the liquid flows downward.
Latent heat recovery mechanism described in 4. The latent heat recovery mechanism according to claim 1, wherein the combustion device is a water heater, and the alkaline liquid is an alkaline neutralizer. 5. The combustion device is a boiler, and the alkaline liquid is boiler blow water.
4. The latent heat recovery mechanism according to any one of items 1 to 3. 6. The latent heat according to claim 5, wherein the heat transfer tube has a double-tube structure having fins on the outside, and feeds water to the outer tube and boiler blow water to the inner tube. Collection mechanism 7. A structure in which a sprinkler tube communicating with the inner tube portion is provided outside the heat transfer tube, and boiler blow water flowing through the inner tube portion flows out of the sprinkler tube and flows to the surface of the heat transfer tube. The latent heat recovery mechanism according to claim 6, 8. A communication portion that opens from the inner tube portion to the outer periphery of the outer tube portion, so that boiler blow water flowing through the inner tube portion flows out from the communication portion and flows to the surface of the heat transfer tube. The latent heat recovery mechanism according to claim 6, wherein: