KR20090025272A - Combustor - Google Patents

Abstract

A combustor comprising combustion unit (11) and, linked thereto, fuel supply unit (12) for supplying of a fuel/air mixture gas containing a fuel mixed with air, wherein the fuel supply unit consists of venturi tube type mixer (23) with fuel supply aperture (25) disposed along the inner circumferential surface at a throat portion; combustion air supply aperture (31) connected to the base end portion of the venturi tube type mixer; and an igniter disposed so as to generate spark at the distal end portion of the venturi tube type mixer, and wherein the combustion unit consists of frame (16) bonded to a boiler main body, etc. and, supported thereby via heat insulators (15a,15b,15c), ceramic combustion tube (14) with its one end communicating with the distal end portion of the venturi tube type mixer of the fuel supply unit and with its other end protruding into the interior of boiler main body, etc., and wherein the ceramic combustion tube is made of a ceramic functioning as an oxidation catalyst so that compact stable combustion is attained without NOx generation and without unburnt residue.

Description

Combustor {COMBUSTOR}

TECHNICAL FIELD This invention relates to the combustor for obtaining the hot gas for the combustion reformer of a small-sized combustion cell system, for example.

The combustion gas generated from this type of combustor is preferably free from pollutants, that is, NOx and unburned powder, and a small amount of residual oxygen due to complete combustion.

Conventionally, in this type of combustor, (1) air and fuel are mixed at concentrations within the explosive limits, and the mixed gas is ignited by ignition means such as an electric spark to form a flame. Combustor for continuously burning mixed gas, (2) Combustor for combusting preheated mixed gas formed by mixing fuel in preheated air by combustion catalyst, (3) Auxiliary combustor outside the heating tube of main combustor (4) Combustor which is always heated above the ignition temperature of the fuel, and in the main combustion chamber, the mixed gas of fuel and air is brought into contact with the heated heating tube to continue combustion. Combustor which U-turns the combustion gas made by contacting the mixed gas of fuel and air at the end of the tube to continue combustion by heating the tube (Japanese Patent Laid-Open) Japanese Patent Application Laid-Open No. 10-26309).

The conventional combustor has not been satisfactory as a combustor of a boiler for use in a fuel reformer of a domestic small fuel cell system currently being developed.

The reason for this is that a combustor used in this kind of apparatus is required to be small in size and small in the combustion chamber, and that the temperature of the surrounding wall needs to be as low as 110 to 180 ° C, which is very disadvantageous for combustion. This is because complete combustion with a low NOx concentration is required under the conditions.

In addition, the small volume of the combustion chamber means that it is susceptible to pressure fluctuations, and in the case of flame combustion, the flow of fuel temporarily stops due to the pressure fluctuations, and the flame is lost, so that combustion is stopped and steam is not generated. Because there is.

As a result, the ratio of S / C (water vapor / carbon) in the reforming catalyst portion becomes smaller than a suitable value, and precipitation of carbon occurs, causing the entire fuel reforming device to stop.

In addition, in the small household fuel cell system as described above, the use of gaseous fuel and liquid fuel is required. Although the auxiliary igniter cannot be used at the start of operation, it is necessary to adopt a method in which the auxiliary combustor is not necessary as soon as possible after the start of operation, and the combustion does not stop even if there is a disturbance such as pressure fluctuation. There is.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object thereof is to provide a combustor capable of stably obtaining combustion gas even when there is no generation of NOx that is a pollutant and residual of unburned dust, and small size and small disturbance.

1st invention is the combustor which arrange | positioned the ceramic combustion cylinder which has an oxidation catalyst function downstream of the venturi-type fuel-air mixture provided with an igniter.

2nd invention is the combustor which provided the vortex generator which makes a mixed gas vortex in a ceramic combustion cylinder at the front-end | tip of a venturi tube type fuel-air mixer in 1st invention.

According to the first or second invention, in the third invention, the tip of the downstream portion of the ceramic combustion cylinder is covered with a cylindrical cover member whose head is closed, and further a combustion chamber is formed around the tip of the ceramic combustion cylinder. It is a combustor provided with the combustion gas outlet hole in the cylindrical base end part of a member.

4th invention is the combustor which applied radiation promoting paint on the outer peripheral surface of a cover member in 3rd invention.

5th invention is the combustor which provided the oxidation catalyst layer between the ceramic combustion cylinder and the base end part of a cover member in 3rd invention or 4th invention.

According to the first invention, for example, a combustor having a small combustion chamber which is preferable as a combustor of a boiler for use in a fuel reformer of a small fuel cell system for home use, which is currently being developed, and at the same time has a high combustion efficiency and stable combustion. You can get it.

According to the second invention, since the mixed gas sufficiently contacts the oxidation catalyst, a combustor capable of burning more stably can be obtained.

According to the third invention, combustion is further promoted in the combustion chamber in which the combustion gas flowing out from the ceramic combustion cylinder is constituted by the lid member.

According to the fourth aspect of the invention, since the radiant heat can be radiated from the outer surface of the lid member to the portion to be heated, the heating of the portion to be heated can be promoted.

According to the fifth invention, since the combustion gas flowing out from the combustion chamber in the cover member to the outside through the through-hole passes through the catalyst layer having an oxidizing function, unburned dust remains in the combustion gas combusted in a ceramic combustion cylinder, for example. Even if it is, this fine powder can be completely burned while passing through this catalyst layer.

1 is a cross-sectional view showing the main parts of a first embodiment of a combustor according to the present invention.

2 is a cross-sectional view showing an embodiment of a boiler in which the combustor of the first embodiment of FIG. 1 is used.

3 is a cross-sectional view showing a second embodiment of the combustor according to the present invention and another embodiment of the boiler provided therewith.

A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the principal part of the combustor of this invention, and FIG. 2 is sectional drawing which shows an example of the boiler which used the combustor of this invention.

In Fig. 1, reference numeral 1 denotes a boiler body composed of an inner cylinder 2 and an outer cylinder 3 arranged in a concentric shape, and reference numeral 4 denotes a combustor according to the present invention installed at the lower end of the boiler body 1, which is a combustor. The high temperature combustion gas generated in (4) is supplied to the inner surface side of the inner cylinder 2 of the boiler main body 1 so that the inner surface of the inner cylinder 2 is heated, and the inner cylinder 2 and the outer cylinder 3 arranged concentrically. Water (evaporation medium) supplied in the heat medium jacket 5 formed therebetween is heated to generate hot steam. The boiler lower flange 6 which closes the heat medium jacket 5 for evaporation medium is integrated in the lower end of the boiler main body 1, and the combustor which is integrally installed in the outer peripheral part of the combustor 4 in this boiler lower flange 6 is integrated. The flange 7 is coupled to the bolt 8 and the nut 9 so that the combustor 4 is located at the lower end of the boiler body 1 and the lid member 10 located at the top of the combustor 4 is provided with the boiler body ( The inner cylinder 2 of 1) is joined in a rushed state.

The combustor 4 includes a combustion section 11 including a ceramic combustion cylinder 14 through which the combustion gas is ejected, and a fuel supplying a fuel / air mixture gas in which fuel and air are mixed to the combustion section 11. The supply part 12 is comprised.

The combustion part 11 is the combustion chamber formation cover member 10 which comprises the combustion chamber 13 inside as the uppermost part, and the ceramic combustion cylinder which was arrange | positioned at the axial center part of this cover member, and released the upper end in the combustion chamber 13. (14), heat insulators (15a, 15b, 15c) made of ceramics arranged to surround the lower outer side of the ceramic combustion cylinder, and frame members (16) surrounding the heat insulators. 16 is fixed to the combustor flange 7.

The cover member 10 has a bell shape (or a car body cover shape), and is provided in a state of being covered by the heat insulators 15a, 15b, and 15c. The through-slit (combustion gas outflow hole) 17 of the slit-shaped long direction is provided. A catalyst layer 18 made of ceramic small particles having an oxidizing function up to the height of the through hole 17 is provided inside the lid member 10. The upper end of the ceramic combustion cylinder 14 has a predetermined distance L between the ceiling inner surface of the lid member 10 in the combustion chamber 13 and at the same time with respect to the upper surface of the catalyst layer 18. H), and the combustion gas flowing out from the upper end of the ceramic combustion cylinder 14 passes between the combustion chamber 13 and the catalyst layer 18, from the through hole 17 into the inner cylinder 2 of the boiler body 1; It is supposed to spill.

The fuel supply unit 12 is fixed to the lower surface of the combustion unit 11 by packing with bolts 22 between the mounting flanges 21 provided at the upper end thereof.

The installation flange 21 is equipped with a venturi tubular mixer 23 so as to penetrate it. The outlet portion of the venturi tubular mixer 23 is concentric with the ceramic combustion cylinder 14 of the combustion section 11, and the outlet diameter thereof is approximately the same as the inner diameter of the ceramic combustion cylinder 14. The outlet end thereof is provided to serve as the lower end of the ceramic combustion cylinder 14. And the vortex generator 24 is provided in this welding part. The vortex generator 24 is shaped to direct the mixed air flow from the venturi tubular mixer 23 toward the circumferential direction, that is, to generate vortices along the inner circumferential surface of the ceramic combustion cylinder 14.

On the inner circumferential surface of the throat portion of the venturi tubular mixer 23, a plurality of fuel ejection holes 25 are provided. This fuel injection hole 25 is connected to the fuel supply port 26 via the fuel manifold 25a provided in the throat part of the venturi tubular mixer 23.

An ignition rod conduit 27 of the igniter is provided at the shaft portion of the venturi tubular mixer 23. The ignition rod conduit 27 is provided with its upper end mounted in the center of the vortex generator 24 and its lower end protruded below the venturi tubular mixer 23. The ignition rod 28 is inserted into the ignition rod conduit 27 so that its tip protrudes from the ignition rod conduit 27.

A cross-shaped pipe joint 29 is connected to the proximal end of the venturi tubular mixer 23, and the lower end of the ignition rod conduit 27 is located in the pipe joint 29. Then, one of the two connecting ports in the direction orthogonal to the extension line of the connecting port with the venturi tubular mixer 23 of the pipe joint 29 serves as an igniter power rod connecting port, and from there, the igniter power supply rod 30. Is inserted, and the tip thereof is electrically connected to the ignition rod 28 in the pipe joint 29. In addition, a combustion air supply port 31 is connected to the other of the two connection ports. In addition, a combustion state monitoring device 32 is provided which allows the inside of the venturi tubular mixer 23 to be visible to the joint on the extension line of the joint with the venturi tubular mixer 23 of the pipe joint 29.

The operation of the combustor 4 on the boiler body 1 shown in FIG. 1 will be described below.

While supplying combustion air from the air supply port 31 of the fuel supply unit 12, the fuel supplied from the fuel supply port 26 is supplied from the fuel outlet port 25 to the throat portion of the venturi tubular mixer 23. By blowing, this air and fuel are mixed during the passage from the throat to the outlet of the venturi tubular mixer 23 to form a fuel / air mixture gas (hereinafter referred to as a 'mixture gas'), thereby providing a venturi tube mixer 23. Into the ceramic combustion cylinder (14) from the outlet of At this time, the mixed gas flowing into the ceramic combustion cylinder 14 is vortexed along the inner circumferential surface of the ceramic combustion cylinder 14 by the vortex generator 24. In this state, the igniter power supply rod 30 is energized to form a spark at the tip of the ignition rod 28 to ignite the mixed gas.

Thereby, the mixer starts combustion. After the ignition, the mixing ratio of fuel and air of the mixed gas is also affected. The combustion is carried out if the ceramic combustion cylinder 14 is heated above the temperature functioning as an oxidation catalyst even if the flame is stopped within 2 minutes. Continues.

When liquid fuel (for example, kerosene) is used for the combustion, the fuel itself is supplied at room temperature, and the combustion air is preheated and supplied at about 200 to 250 ° C. Gas fuel can also be used in the structure of this embodiment.

The ignited mixed gas starts combustion, and the combustion gas flows upwardly along the inner circumferential wall of the ceramic combustion cylinder 14. As a result, the ceramic combustion cylinder 14 itself is heated up above the catalytically active temperature. As a result, even when ignition by the ignition rod 28 is stopped at the time when the ceramic combustion cylinder 14 is heated, the ceramic combustion cylinder in which the mixed gas from the venturi tubular mixer 23 is elevated above the catalytically active temperature ( By contacting the inner circumferential surface of 14), an oxidation reaction occurs immediately in this mixed gas, and combustion continues.

Such combustion is aggravated toward the upper side (downstream side) of the ceramic combustion cylinder 14, and most of the mixed gas is combusted at the upper end of the ceramic combustion cylinder 14. On the other hand, the combustion state at this time is affected by the length of the ceramic combustion cylinder 14. From this, the length of the ceramic communication 14 is designed to be the length at which most of the mixed gas supplied from the fuel supply 12 is combusted.

Since the mixed gas supplied to the ceramic combustion cylinder 14 is mixed in the same density | concentration, the combustion reaction in this ceramic combustion cylinder 14 is very fast. For example, when the theoretical combustion temperature of the mixed gas is about 1400 to 1600 ° C, the combustion rate is about 7/1000 seconds. Therefore, it is preferable that the material of the ceramic combustion cylinder 14 has the property shown below.

That is, the conditions necessary for the ceramic combustion cylinder 14 having the above-described oxidation function include (1) high thermal shock resistance, (2) low catalytic activity temperature, (3) high emissivity, and (4) high temperature. High mechanical strength at (5), high thermal conductivity.

As ceramics having such properties, those in which 5-20% of other metal oxides are added to SiC, Si ₃ N ₄ , ZrO _2, and ZrO ₂ are suitable.

The non-oxide ceramics of SiC and Si ₃ N ₄ Si have a relatively high catalytic activity temperature of 640 to 645 ° C. Other than that, the above conditions are satisfied, and therefore, they can be sufficiently used practically. In addition, ZrO ₂ alone shows a catalytic activity temperature of 465 ° C., which mixes CoO, Cr ₂ O ₃ , MnO ₂ , La ₂ O ₃ , SnO ₂ , Y ₂ O ₃ , TbO ₂ and MgO from 5% to 20%. It is possible to lower the catalytic activity temperature from 330 ° C to 497 ° C (see 'Catalysis of ZrO ₂ Composite Oxides', presented at the 9th Symposium on Catalytic Combustion (May 25, 1990)). .

The reason why the above-mentioned (1) heat shock resistance is necessary is because the combustion speed is high, and the change in the amount of heat received from the inside of the ceramic combustion cylinder 14 is large. That is, when the change in the amount of heat received by the ceramic combustion cylinder 14 is large, the temperature change of the ceramic combustion cylinder 14 itself is large, and when the thickness of the ceramic combustion cylinder 14 is increased, the temperature difference inside the ceramic combustion cylinder 14 becomes large. This is because the ceramic combustion cylinder 14 is destroyed by thermal shock. In order to prevent this, (5) high thermal conductivity is required. In addition, the high thermal conductivity is suitable for transferring heat received from the downstream side of the combustion gas to the upstream side, and (3) the high emissivity also has the same effect.

The combustion gas generated in the ceramic combustion cylinder 14 flows into the combustion chamber 13 from the front end of the ceramic combustion cylinder 14, and is turned downward in accordance with the inner surface of the lid member 10 constituting the combustion chamber 13. And flows out from the through hole 17 into the inner cylinder 2 of the boiler body 1 through the catalyst layer 18.

At this time, when the combustion gas to be burned has a small volume of the flow path through which it passes and is surrounded by a cold wall surface, combustion may be insufficient and unburned dust may remain in the combustion gas. Since the combustion gas from the communication 14 flows into the combustion chamber 13 which becomes the comparatively large space which consists of the cover member 10, combustion is continued continuously and it becomes a high temperature (1500-1700 degreeC), and the unburned powder of combustion gas Is almost completely burned.

Then, the combustion gas in the combustion chamber 13 flows downward along the inner surface of the cover member 10 constituting the combustion chamber 13 and passes through the catalyst layer 18, and then passes through the boiler 17 through the boiler. It flows into the inner cylinder 2 of the main body 1, and the inner surface of this inner cylinder 2 is heated. At this time, the combustion gas comes into contact with the ceramic small particles of the catalyst layer 18, whereby the unburnt in the combustion gas is completely burned. The presence of this catalyst layer 18 prevents the combustion from stopping due to pressure variations between the fuel and combustion air.

Ceramic small particles having an oxidation function constituting the catalyst layer 18 are advantageously hollow particles of SiC.

With respect to the combustor 4 shown in the above embodiment, the dimensions of each member as an example of the combustor for steam generation of the domestic fuel cell system are 20 mm, thickness 2.5 mm, and length 40 mm in the inner diameter of the ceramic combustion cylinder 14. In addition, the inner diameter of the cover member 10 is 50 mm, and the dimension of H shown in Fig. 1 is 10 mm, the dimension of L is 15 mm.

1 shows an example in which the combustor shown in FIG. 1 is applied to the boiler main body 1 for the steam generator of the domestic fuel cell system, and water filled in the thermal catalyst jacket 5 of the boiler main body 1 is boiled. The generated steam is derived from the steam pipe connected to the upper portion of the thermal catalyst jacket 5. In this case, in order to use the cover member 10 for a long time, it is necessary to heat the heat received from the hot gas to the heat catalyst jacket 5 side as much as possible. In this embodiment, the cover member 10 By applying a radiation-promoting paint, e.g., a radiation paint having an emissivity of 92% or more, on the outer circumferential surface, the temperature of the wall portion of the cover member 10 is increased to 950 even when combustion gas having a theoretical combustion temperature of 1600 ° C occurs in the combustion section 11. Since the temperature can be lowered or lower, the cover member 10 can withstand long-term use by applying the radiation-promoting paint.

Figure 2 shows an embodiment of a boiler using a combustor 4 according to the present invention, a plurality of water pipes 33, 33, in the inner cylinder (2) of the boiler body (1) and above the combustion section (11) The heat exchange part 34 which consists of…) is arrange | positioned. On the other hand, the exhaust pipe 40 is connected inside the inner cylinder 2.

A drip tank 35 is provided above the heat exchanger 34, and a water supply pipe 36 is connected to the drip tank 35. And the inlet part 33a of each water pipe 33 of the heat exchange part 34 is connected to the drip tank 35, and the outlet part is connected to the outlet chamber 37. As shown in FIG. The outlet chamber 37 is a space formed between the upper part of the support plate 39 supporting the heat exchange part 34 and the bottom part of the drip tank 35 and is gas-liquid mixed from the heat medium jacket 5 of the boiler body 1. Evaporated in the state and evaporated in the gas-liquid mixed state from the outlet of the heat exchange part 34 are separated by gas-liquid separation in the outlet chamber 37. And since the outlet chamber 37 is connected to the lower part of the heat medium jacket 5 by the conduit 38, the separated liquid medium (hot water) absorbs the heat to circulate and evaporate. On the other hand, the vapor of the gas-liquid mixture in which the liquid is mostly separated rises the space between the inner cylinder 2 of the boiler body 1 and the outer cylinder portion of the drip tank 35 to separate the gas-liquid separated from the top of the drip tank 35. Steam is sent out from the steam extraction pipe 41, the separated hot water is collected in the drip tank (35).

In such a boiler, the heat of the combustion gas which flowed into the inner cylinder 2 of the boiler main body 1 from the combustion part 11 of the combustor 4 acts directly on the heat medium jacket 5 from the inner surface of the inner cylinder 2. At the same time, the heat exchanger 34 can also preheat the water that is heat-exchanged and supplied to the heat medium jacket 5, and the heat of the combustion gas generated in the combustion unit 11 can be effectively used.

In the above embodiment, by adjusting the length of the ceramic combustion cylinder 14 in the combustion section 11 of the combustor 4, only the mixed gas supplied from the venturi tubular mixer 23 of the fuel supply section 12 is supplied therefrom. In the case where it can be burned to the state where there is little unburned powder, the lid member 10 for constituting the combustion chamber 13 can be omitted (the embodiment which omitted the lid member 10 is mentioned later).

Also, even when the lid member 10 is provided, the through-hole 17 of the lid member 10 is closed if combustion occurs in the combustion chamber configured in the lid member 10 so that the unburnt in the combustion gas is completely burned. There is no need for the catalyst layer 18 to be prevented from entering.

In the above embodiment, the cover member 10 is provided on the outlet side of the ceramic combustion cylinder 14, but as described above, the length of the ceramic combustion cylinder 14 is appropriately adjusted in the combustion section 11 of the combustion chamber 4. By doing so, the cover member 10 for constituting the combustion chamber 13 when the mixed gas supplied from the venturi tubular mixer 23 of the fuel supply unit 12 can be burned to a state where there is little unburned powder thereon. Can be omitted. This is shown in FIG. 3 as a second embodiment. In the second embodiment shown in FIG. 3, the outlet side of the ceramic combustion cylinder 14 is provided with a plurality of guide passages 19 for guiding the combustion gas from the ceramic combustion cylinder 14 radially outward. It is closed by the heat insulator 15d. The combustion gas drawn out from the heat insulator 15d in the circumferential direction is discharged upward in FIG. 3 so that a plurality of vertically descending pipes 42 are disposed in the space between the inner cylinder 2 and the outer cylinder 3. The inner cylinder 2 of the boiler main body 1 which is arrange | positioned at intervals in the circumferential direction, and each outer wall of the several water pipes 33 arrange | positioned at the center area | region of this boiler main body 1 are heated.

On the other hand, in the second embodiment of FIG. 3, unlike the first embodiment of FIG. 1, the upstream region of the combustion section 11 that cannot be expected to be at or above the temperature at which the ceramic combustion cylinder 14 functions as an oxidation catalyst is described. The ceramic combustion cylinder 14 was abbreviate | omitted, and instead, the combustion furnace whose heat insulating body 15a is the same diameter as the internal diameter of the ceramic combustion cylinder 14 was formed in the abbreviate | omitted part. Such a structure is advantageous in cost because it can save the material cost of the ceramic combustion cylinder. This structure can also be used for heating the reformer or for heating at the start of a fuel cell using a solid oxide.

Described herein.

Claims (5)

A combustor characterized by arranging a ceramic combustion cylinder having an oxidation catalyst function downstream of a venturi tube type fuel / air mixture equipped with an igniter. The method of claim 1, A combustor characterized in that a vortex generator is provided at the tip of a venturi tubular fuel / air mixture to cause the mixed gas to vortex in a ceramic combustion cylinder. The method according to claim 1 or 2, The front end portion of the downstream ceramic combustion cylinder is covered with a cylindrical cover member with a closed head, and a combustion chamber is formed around the front end of the ceramic combustion cylinder, and a combustion gas outlet hole is provided in the cylindrical base end of the lid member. Combustor made with. The method of claim 3, wherein A combustor characterized by coating a radiation promoting coating on the outer circumferential surface of the cover member. The method according to claim 3 or 4, A combustor characterized in that an oxide catalyst layer is provided between a ceramic combustion cylinder and a proximal end of a lid member.

Images