JP2000055317A - Liquid heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To start a catalytic combustion in a short time without exhausting a harmful combustion product by providing a flame combustion unit for burning primary pre-mixed gas, a catalytic combustion unit for catalytically burning mixed gas obtained by mixing the exhaust gas with secondary pre-mixed gas by a gas mixer, and a heat recovering unit. SOLUTION: In starting, a flame combustion unit 3 flame burns primary pre-mixed gas. The flame temperature by the flame combustion is lowered by heat recovering by a first heat recovering unit 4 to suppress generation of an NOx. A catalyst of a catalytic combustion unit 6 is heated by exhaust gas of the flame combustion set to a catalytic combustible state, and the exhaust gas of the unit 3 is mixed with secondary pre-mixed gas by a gas mixer 5 to generate mixed gas. After unburned hydrocarbon of a large quantity generated by the combustion of the primary gas is mixed with the secondary gas, then the NOx is decomposed as a reducing agent when it is reburned by the unit 6. Accordingly, the mixed gas is completely burned, the exhaust gas is heat recovered by a second heat recovering unit 7, and then exhausted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid heating device.

[0002]

2. Description of the Related Art With the rise of environmental problems in recent years, social demands for reducing the emission of air pollutants from automobiles, industrial machines, and the like have become even more severe.
For, reduction of emissions is required. Various measures for reducing air pollutants have been proposed in the past, and as one of them, the catalytic combustion method has been spotlighted. This catalytic combustion method has the advantage that the combustion temperature can be lowered without increasing the amount of generated CO and the amount of generated NOx can be reduced.

In an apparatus utilizing such a catalytic combustion method, in order to start a catalytic reaction, it is necessary to raise the temperature to a temperature at which the catalyst is activated. At that time, the catalyst (including the carrier) itself is directly heated or heated by supplying a high-temperature gas (hereinafter, referred to as a high-temperature gas). In the former case, a suitable preheating means such as an electric heater is arranged near the catalyst portion to heat the catalyst itself. on the other hand,
In the latter case, a high-temperature gas is obtained by providing a heating means such as an electric heater or a burner as described above in a supply path of combustion air or an air-fuel mixture. Here, when an electric heater is used, a high-temperature gas is obtained by heating air. However, when a high-temperature gas is obtained by a burner, first, an air-fuel mixture is supplied to the preheating burner to burn it. The high-temperature combustion gas generated at that time is directly supplied to the catalyst and heated.

By the way, in performing the above-mentioned catalytic combustion,
If the air is preheated by an electric heating means such as an electric heater, the specific heat of the air is small, so the energy efficiency is poor,
Preheating takes time. Therefore, it is necessary to use a large-capacity electric heater, so that the required power becomes large. On the other hand, when preheating is performed using combustion gas (high-temperature gas) from a normal flame combustion type burner, preheating can be performed in a short time, but harmful combustion products such as CO and NOx are contained in the combustion gas. It is discharged as contained. Therefore, even in a catalytic combustion apparatus for achieving clean combustion, harmful combustion products are contained in the high-temperature gas used for preheating at the time of startup.

[0005]

The problem to be solved by the present invention is to eliminate harmful combustion products without discharging them.
It is an object of the present invention to provide a fluid heating device that can start catalytic combustion in a short time and that achieves energy saving when preheating a catalytic unit.

[0006]

Means for Solving the Problems The present invention has been made to solve the above problems, and the invention according to claim 1 has a flame combustion section for burning a primary premixed gas;
A first heat recovery section, a gas mixing section for mixing the exhaust gas from the flame combustion section and the secondary premixed gas, a catalytic combustion section for catalytically burning the mixed gas mixed in the gas mixing section, and a second heat recovery section And a part.

According to a second aspect of the present invention, a gas passage is formed outside the water pipe, a flame combustion portion for burning the primary premixed gas is provided in the gas passage, and a first heat generation portion is provided downstream of the flame combustion portion. A recovery section, a gas mixing section, a catalytic combustion section, and a second heat recovery section are provided, and a secondary premix gas is supplied to the first heat recovery section or the gas mixing section.

According to a third aspect of the present invention, a secondary premixed gas chamber is provided outside the gas passage, and the secondary premixed gas is supplied from the secondary premixed gas chamber to the first heat recovery section. It is characterized by having a configuration.

Further, the invention according to claim 4 is characterized in that a heat exchanger is provided in the secondary premixed gas chamber.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described. The present invention relates to a flame burning section for burning a primary premixed gas, a first heat recovery section, and the flame burning section. This is realized in a fluid heating device including a gas mixing unit that mixes the exhaust gas from the gas with the secondary premixed gas, a catalytic combustion unit that catalytically burns the mixed gas mixed in the gas mixing unit, and a second heat recovery unit. .

A primary premixed gas supply pipe for supplying a premixed gas obtained by mixing combustion air and fuel gas in advance is connected to the flame combustion section. In addition, a secondary premixed gas supply pipe branched from the primary premixed gas supply pipe is provided, and a tip of the secondary premixed gas supply pipe is connected to the gas mixing section.

The first heat recovery section and the second heat recovery section are formed, for example, in a helical shape with pipe members through which a fluid to be heated flows, and are disposed downstream of the flame combustion section and the catalyst combustion section, respectively. I have. That is, the fluid heating device of the present invention has a configuration in which the first heat recovery section, the gas mixing section, the catalytic combustion section, and the second heat recovery section are sequentially arranged downstream of the flame combustion section.

According to the fluid heating apparatus of the present invention, at the time of startup, a small amount of the primary premixed gas is flame-burned in the flame combustion section, and the temperature of the flame is lowered in the first heat recovery section provided in proximity. Thereby, generation of NOx is suppressed. Next, the catalyst is heated in a short time with the exhaust gas from the flame combustion. Then, transition to normal combustion, while supplying a normal amount of primary premixed gas and burning in the flame combustion unit, supplying a secondary premixed gas into the gas mixing unit, and the exhaust gas from the flame combustion unit Mix. This mixing lowers the NOx concentration in the exhaust gas. Next, the mixed gas is catalytically combusted in the catalytic combustion section. The unburned matter in the exhaust gas is completely burned by the catalytic combustion, and the NOx is reduced. That is, since the primary premixed gas is rapidly cooled during combustion, a large amount of unburned hydrocarbons is generated, but this hydrocarbon is mixed with the secondary premixed gas and then recombusted in the catalytic combustion section. NOx is decomposed as a reducing agent. And
The high-temperature exhaust gas after the catalytic combustion is heat-exchanged in the second heat recovery section, and is discharged after the exhaust gas temperature is lowered.

As described above, the fluid heating apparatus according to the present invention heats the catalyst with the exhaust gas from the flame combustion section in a short time, thereby saving energy. Also, the exhaust gas from the flame combustion section
The cooling of the flame, the dilution by mixing the secondary premixed gas, and the reduction with unburned hydrocarbons reduce the NOx concentration. Therefore, almost complete combustion can be achieved by catalytic combustion, and NOx can be further reduced.

Next, a second embodiment of the present invention will be described. In the second embodiment, the fluid heating device described in the first embodiment is a boiler in which a water pipe is erected, and a description overlapping with the first embodiment will be omitted. . That is, a gas passage is formed outside the water pipe, and a flame combustion unit for burning the primary premixed gas is provided in the gas passage, and a first heat recovery unit, a gas mixing unit, and a catalyst combustion unit are provided downstream of the flame combustion unit. And a second heat recovery unit, a secondary premix gas chamber is provided outside the gas passage, and a secondary premix gas is supplied from the secondary premix gas chamber to the first heat recovery unit. Is realized in the fluid heating device described above. Further, a configuration may be employed in which the secondary premixed gas is directly supplied to the gas mixing section.

In the second embodiment, the first heat recovery unit and the second heat recovery unit are configured such that metal fins are fixed to predetermined positions on the outer peripheral portion of the water pipe, for example. The metal fins function to recover heat of exhaust gas from the flame combustion unit and the catalyst combustion unit. In addition, a secondary premix gas supply pipe is connected to the secondary premix gas chamber, and supplies a secondary premix gas to the first heat recovery unit via the secondary premix gas chamber. .
Further, a heat exchanger may be provided in the secondary premixed gas chamber to exchange heat with the first heat recovery unit and heat the secondary premixed gas.

In the second embodiment, the first heat recovery section recovers the heat of the exhaust gas from the flame combustion section, raises the temperature of the secondary premixed gas and flows into the gas mixing section. Let it. Therefore, in the gas mixing section,
The exhaust gas and the secondary premixed gas are more uniformly mixed, and can be completely catalytically burned in the catalytic combustion unit. Except for the above, the configuration is the same as that of the first embodiment, and the description is omitted.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view schematically showing a configuration of a first embodiment of a fluid heating device embodying the present invention.

In FIG. 1, a fluid heating device 1 according to the present invention is shown.
Is provided with a flame combustion section 3 (for example, a burner) in the casing 2 and a first heat recovery section 4, a gas mixing section 5, a catalytic combustion section 6, and a second heat recovery section 7 downstream of the flame combustion section 3.
Are sequentially provided. A first premixed gas supply pipe 8 communicating with a premixed gas supply source (not shown) is connected to the flame combustion unit 3.
Is connected. Further, the first premixed gas supply pipe 8
A second premixed gas supply pipe 9 is provided, which is connected to the gas mixing section 5. Further, an exhaust gas pipe 10 is provided downstream of the second heat recovery unit 7.

The first and second heat recovery sections 4 and 7 each form one (or a plurality of) pipe members 11 through which the fluid to be heated flows in a spiral shape as shown in FIG. And, it is configured to be disposed downstream of the flame combustion unit 3 and the catalytic combustion unit 6.

The catalytic combustion section 6 has a structure in which a catalyst is supported on a ceramic structure, for example, and catalytically combusts a mixed gas containing unburned gas from the flame combustion section 3.

According to the fluid heating apparatus 1 having the above-described structure, a small amount of the primary premixed gas is flame-combusted in the flame combustion section 3 at the time of startup. The flame temperature due to the flame combustion is reduced by heat recovery (heat exchange) in the first heat recovery unit 4 to suppress generation of NOx. Next, the catalyst in the catalytic combustion section 6 is heated in a short time with the exhaust gas from the flame combustion, so that the catalytic combustion is enabled. Then, a transition is made to normal combustion, in which a normal amount of the primary premixed gas is supplied and burned in the flame combustion section 3, and a secondary premixed gas is supplied into the gas mixing section 5, and the flame combustion section 3 is supplied. And mixed gas is generated. Due to this mixing, NOx in the exhaust gas
The concentration dilutes and becomes lower. In addition, since the primary premixed gas is quenched during combustion, a large amount of unburned hydrocarbons is generated. When the hydrocarbons are mixed with the secondary premixed gas and recombusted in the catalytic combustion unit 6, NOx as a reducing agent
Is decomposed. Accordingly, the mixed gas is completely burned, and the exhaust gas is recovered (heat exchanged) by the second heat recovery unit 7 and then discharged out of the system through the exhaust gas pipe 10.

As described above, the fluid heating device 1 of the present invention
Is the exhaust gas from the flame combustion unit 3 and the catalytic combustion unit 6
Heating the catalyst in a short time saves energy. Further, the exhaust gas from the flame combustion unit 3 is used for cooling the flame,
The dilution by mixing the secondary premixed gas and the reduction by the unburned hydrocarbon lower the NOx concentration.
Therefore, it is possible to perform almost complete combustion in the catalytic combustion section 6, and it is possible to lower the NOx concentration.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the fluid heating device described in the first embodiment is a boiler in which a water pipe is erected. Therefore, the embodiment shown in FIG. 2 is a sectional explanatory view schematically showing the configuration of the boiler. In addition, the same members as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 2, a fluid heating device 1 according to the present invention is shown.
A flame for providing a water pipe 14 in the first cover member 13, forming a gas passage 15 between the first cover member 13 and the water pipe 14, and burning a primary premixed gas in a lower portion of the gas passage 15 A combustion section 3 (for example, a burner) is provided. A first heat recovery section 4, a gas mixing section 5, a catalytic combustion section 6, and a second heat recovery section 7 are sequentially provided downstream of the flame combustion section 3. A second cover member 19 that forms a secondary premixed gas chamber 18 is provided outside the first cover member 13 corresponding to the first heat recovery unit 4. A plurality of gas circulation holes 20 communicating the premixed gas chamber 18 and the first heat recovery unit 4 are opened at predetermined positions of the first cover member 13. Further, a heat exchanger 21 is provided in the premixed gas chamber 18 on the upstream side of the gas inflow hole 20.

The flame burning section 3 includes a flame holding plate 22 and a primary premixed gas supply pipe 8 is connected to a lower portion of the first cover member 13 through the second cover member 19. . In the secondary premixed gas chamber 18,
A secondary premixed gas supply pipe 9 is connected. On the other hand, a water supply pipe 23 penetrating through the flame holding plate 22, the first cover member 13, and the second cover member 19 is connected to a lower end portion of the water pipe 14.

At the downstream end of the gas passage 15, an exhaust gas collecting chamber 24 is provided. An exhaust gas pipe 25 for discharging exhaust gas to the outside is connected to the exhaust gas collecting chamber 24. The upper end of the water pipe 14 penetrating the exhaust gas collecting chamber 24 is connected to a steam header 26. A steam pipe 27 is connected to the top of the steam header 26. Further, a heat insulating member 28 is provided outside the first cover member 13.

The first and second heat recovery sections 4 and 7 have a structure in which metal fins are fixed to predetermined positions on the outer peripheral portion of the water pipe 14, respectively. Also, as an example of the fin shape,
There is also a configuration in which a corrugated plate is wound around the water tube 14. The first and second heat recovery sections 4 and 7 function to recover heat of exhaust gas from the flame combustion section 3 and the catalytic combustion section 6. Further, the heat exchanger 21 has a configuration in which metal fins are fixed at predetermined positions on the outer peripheral portion of the first cover member 13. The heat exchanger 21 exchanges heat with the first heat recovery unit 4 and the secondary premixed gas. It works to heat the water.

The catalytic combustion section 6 has a structure in which a catalyst is supported on a ceramic structure, for example, and catalytically combusts a mixed gas containing unburned gas from the flame combustion section 3.

According to the fluid heating apparatus 1 having the above-described configuration, the primary premixed gas is flame-burned in the flame burning section 3. The high-temperature exhaust gas generated by the flame combustion is recovered by the first heat recovery unit 4 and the temperature of the exhaust gas is reduced. The exhaust gas heats the catalyst in the catalytic combustion section 6 in a short time, so that catalytic combustion becomes possible. On the other hand, the secondary premix gas supplied from the secondary premix gas supply pipe 8 is supplied to the secondary premix gas chamber 18.
And the heated secondary premixed gas flows into the first heat recovery unit 4 through the gas inlet hole 20. In the first heat recovery section 4, the exhaust gas and the heated secondary premixed gas are merged, uniformly mixed in the gas mixing section 5, and the mixed gas is mixed in the catalytic combustion section 6. Catalytic combustion. That is, the heat generated by the combustion in the flame combustion unit 3 and the catalytic combustion unit 6 is transferred to the water pipe 14 and the first,
The water in the water pipe 14 is heated via the second heat recovery units 4 and 7. Then, the heated water becomes steam and is supplied to the load side from the steam pipe 27 via the steam header 26. On the other hand, the exhaust gas after heat recovery in the second heat recovery unit 7 is discharged out of the system from the exhaust gas pipe 25 through the exhaust gas collecting chamber 24.

Further, in order to adjust the amount of catalytic combustion, the temperature of the catalyst during combustion, and the like, the catalytic combustion unit 6 and the second heat recovery unit 7 may be provided alternately to have a multistage configuration. .

[0032]

As described above, according to the present invention,
It is possible to start catalytic combustion in a short time without discharging harmful combustion products, and to save energy when preheating the catalyst section.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment schematically showing a configuration of a fluid heating device embodying the present invention.

FIG. 2 is an explanatory sectional view schematically showing the configuration of a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluid heating apparatus 3 Flame combustion part 4 First heat recovery part 5 Gas mixing part 6 Catalyst combustion part 7 Second heat recovery part 14 Water pipe 15 Gas passage 18 Primary premixed gas chamber 21 Heat exchanger

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K017 BA01 BB08 BD00 3K065 TC03 TD05 TF01 TG01 TK02 TM01

Claims (4)

[Claims] 1. A flame combustion section 3 for burning a primary premixed gas, a first heat recovery section 4, a gas mixing section 5 for mixing exhaust gas from the flame combustion section 3 and a secondary premixed gas, A fluid heating device, comprising: a catalytic combustion unit 6 for catalytically combusting a mixed gas mixed in a gas mixing unit 5; and a second heat recovery unit 7. 2. A gas passage 15 is formed outside the water pipe 14, a flame combustion unit 3 for burning a primary premixed gas is provided in the gas passage 15, and a first heat recovery unit is provided downstream of the flame combustion unit 3. 4, a gas mixing section 5, a catalytic combustion section 6, and a second heat recovery section 7 are provided, and a secondary premixed gas is supplied to the first heat recovery section 4 or the gas mixing section 5. Fluid heating device. 3. A secondary premix gas chamber (18) is provided outside the gas passage (15), and a secondary premix gas is supplied from the secondary premix gas chamber (18) to the first heat recovery unit (4). The fluid heating device according to claim 2, wherein: 4. The fluid heating device according to claim 3, wherein a heat exchanger is provided in the secondary premixed gas chamber.