WO1992000490A1

WO1992000490A1 - Burner

Info

Publication number: WO1992000490A1
Application number: PCT/JP1990/000855
Authority: WO
Inventors: Saburo Maruko
Original assignee: Nippon Chemical Plant Consultant Co., Ltd.
Priority date: 1990-06-29
Filing date: 1990-06-29
Publication date: 1992-01-09

Abstract

A burner, wherein combustion is conducted in two steps to utilize a primary combustion gas for only radiant heat transfer and a secondary combustion gas obtained by reburning the primary combustion gas containing unburnt oxygen for radiant and convection heat transfer. The burner is provided with an inner pipe (2) having primary combustion means, an outer pipe (14) forming the passage (15) of the primary combustion gas and disposed concentrically with the inner pipe with a specified space provided therebetween for heating the inner pipe from outside, secondary combustion means (17, 22, 31) disposed in the vicinity of the primary combustion gas exit of the outer pipe for reburning the primary combustion gas, and heat receiving surfaces (24) extending along the inner side wall of an outer cylinder (1) comprising a heat insulating member coaxially surrounding the outer pipe with a specified space therebetween.

Description

Specification

Combustor

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a combustor used as a heating device such as a heating furnace or a once-through boiler, and particularly to a harmful substance (Νοχ) associated with combustion while enhancing heating efficiency. In order to suppress the generation of primary combustion gas, lower the temperature of the primary combustion gas while dissipating the heat from the primary combustion, and then mix the secondary fuel into the primary combustion gas. The present invention relates to a combustor in which heat generated by the secondary combustion performed by the secondary combustion is used as sensible heat.

BACKGROUND OF THE INVENTION

Conventionally, this type of combustor uses radiant heat from a flame obtained in a single combustion and sensible heat from a high-temperature combustion gas.

In the above-described conventional combustor, if the oxygen in the air supplied into the combustor is almost completely used for combustion, the combustion temperature rises and the combustion temperature rises. As a result, a large amount of NOx, a harmful substance, was generated, causing pollution.

On the other hand, in conventional combustors, in order to suppress the generation of Nox, the length of the flame is increased and the temperature of the combustion gas is determined based on the fuel Z air. There was no other alternative but to a temperature much lower than the theoretical value. Therefore, as the size of the combustor became larger, the heating efficiency was not good. Summary of the Invention

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to reduce the primary and secondary oxygen in the air supplied for combustion. By using the two-stage combustion, it can be almost completely used.In the primary combustion, heat is dissipated, and in the secondary combustion, the sensible heat of the combustion gas is used to increase the heating efficiency. An object of the present invention is to provide a combustor in which the generation of harmful substances NO X is minimized.

To achieve the above object, according to a first aspect of the present invention, there is provided a mixing method in which fuel is mixed with air so as to have a concentration corresponding to a required combustion gas temperature. An inner pipe made of ceramic having a primary combustion means for primary combustion of gas, and an outflow passage of the primary combustion gas by the primary combustion, and the inner pipe is formed. An outer pipe coaxially disposed with a predetermined space between the inner pipe and the inner pipe so as to heat the outer pipe from the outside, and the primary combustion gas is subjected to secondary combustion. A secondary combustion means provided in the vicinity of a primary combustion gas outlet of the outer tube, and an outer cylinder made of a heat insulating material surrounding the outer tube coaxially with a predetermined space. A heat receiving surface provided along the inner wall of the outer tube, and heat generated by the primary combustion is transferred to the outer tube by the outer tube. The heat is radiated from the outer surface toward the heat receiving surface, while the heat from the secondary combustion is applied to the heat receiving surface as sensible heat of the secondary combustion gas. An improved combustor is provided.

According to a second aspect of the present invention, the fuel according to the first aspect is provided. A burner, wherein the primary combustion means is coaxially inserted into one side (upstream side) of the inner pipe so as to introduce a mixed gas of main fuel and air into the inner pipe. And a pilot burner device provided on the upstream side of the mixed gas conduit, and the secondary combustion means includes the primary combustion device. A secondary mixer for mixing the combustion gas and the secondary fuel; and a downstream side of the secondary mixer, and between the front pipe and the heat receiving surface. And a honeycomb member provided substantially upstream of the outlet for discharging the secondary combustion gas into the space so as to be substantially orthogonal to the flow of the secondary combustion gas. A combustor including is provided.

Further, according to a third aspect of the present invention, there is provided the combustor according to the first aspect, wherein the primary combustion ignited by the pilot burner device. In the vicinity of the upstream side of the outlet formed at the other (downstream) end of the inner pipe, and so as to guide the gas to the outflow passage formed between the inner and outer pipes. There is provided a combustor further including another honeycomb member provided in a diametric direction.

Further, according to the fourth and fifth aspects of the present invention, there are provided the combustors according to the second and third aspects, respectively, wherein the pilot burner device is provided. A base end force projecting outward from the mixed gas conduit, an inner cylinder for a pilot burner inserted coaxially so as to communicate with each other; It has a double structure to have a space that communicates with the inner space of the inner cylinder, An outer cylinder for a pilot burner provided at the base end of the inner cylinder for the pilot partner via an insulating material, and provided at the center of the base end of the outer cylinder. To introduce a pilot gas mixture of the pilot fuel and the pilot primary air into the pilot burner inner cylinder. And a pilot inserted so as to reach the center of the inside of the inner tube for the pilot burner from one outer side of the outer tube for the pilot burner. The pilot heater is provided on the other outer side surface of the outer tube so as to communicate with the ignition heater and the space of the outer tube for the pilot burner. A sintering apparatus including a secondary air introduction pipe is provided.

According to the present invention having each of the above aspects, the primary combustion gas having a large unburned oxygen remaining amount is used only for radiant heat transfer, and the primary combustion gas is reburned and unburned. because it was because Shi not reduce the amount of oxygen secondary combustion gas is Ru are used in convective heat transfer to the radiation of al beauty. ing in the same manner as the theoretical combustion temperature 1 9 0 0 ^e C about combustion row Tsu Na . However, the amount of residual oxygen in the discharged combustion gas is also reduced, and the generation of harmful substance Nox can be reduced to 10 ρ.p.m. Become . In addition, the use of the combustor according to the present invention in almost all conventional heating furnaces utilizing conventional burners reduces the generation of NOX. It is possible to keep it below 110.

The above and other objects, embodiments, and advantages of the present invention will be described in detail with reference to preferred embodiments that conform to the principles of the present invention. It will be apparent to a person of ordinary skill in the art by describing it in conjunction with the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an overall schematic longitudinal sectional view showing a specific example of the present invention, and FIGS. 2, 3 and 4 are lines π-π and m-in in FIG. 1, respectively. Then, it is a cross-sectional view along the line IV-I.

Detailed description of preferred examples

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The specific example shown is a combustor used for a once-through boiler.

1 In Fig. 1, reference numeral 1 indicates the outer cylinder of a combustor made of a heat-insulating member, which was made of aluminum or virgin fiber as a heat-insulating member. The member is suitably used. The same is true not only for the outer cylinder, but also for the heat insulating member used in other parts of the combustor.

As shown in Fig. 1, an inner pipe 2 for performing primary combustion is provided upright at a substantially central position inside the outer cylinder 1, and a lower end of the inner pipe 2 is provided with an insulating member. It is fixed to the inner surface of the bottom of the outer cylinder 1 via An opening 1a is formed in the upper central part of the outer cylinder 1, and a gas mixture for primary combustion is introduced into the inner pipe 2 through the opening 1a. The mixed gas conduit 3 is provided through a lid 4 made of a heat insulating material. The lower part of the mixed gas conduit 3 is supported by the upper end of the inner pipe 2 via a heat insulating member 2a, and the lower end opening is located above and substantially in the center of the inner space of the inner pipe 2 serving as the primary combustion chamber. It is designed to be positioned. On the other hand, on one side above the mixed gas conduit 3, a mixed gas intake pipe 3a communicating with a main mixer 5 for mixing main fuel and air for primary combustion. The opening at the tip is connected. In the main mixer 5, the main fuel is mixed with air so as to have a concentration corresponding to the required temperature of the combustion gas, and the mixed gas is supplied to the inner pipe 2 as a mixed gas. It is introduced into the primary combustion chamber. Reference numerals 5a and 5b are conduits for introducing main fuel and air to the main mixer 5, respectively.

Next, the pilot burner required at the start of the combustion operation in the combustor will be described.

A flange portion 3b is provided at the upper end of the mixed gas conduit 3, and a double structure is formed through the flange portion 3b so as to have a space portion 6a. The formed outer cylinder for pilot burner 6 is fixed to the mixed gas conduit 3. An inner cylinder 7 for a pilot burner is provided at a central portion on the inner side of the outer cylinder 6 through a heat insulating member, and is formed at an upper end of the inner cylinder 7. The opening 7a communicates with the space 6a of the outer cylinder 6 for the pilot burner, and there is air and pilot fuel for the pilot burner. The tip of a nozzle 8 for ejecting the mixed gas into the inner cylinder 7 is placed. The nozzle The base end of 8 penetrates through the center top of the outer cylinder 6 for the pilot burner and protrudes outward to produce a gas mixture for the pilot burner. It is connected to the mixer 9 for one-to-one connection. The mixer 9 is connected with a pilot fuel inlet pipe 10 and a primary air inlet pipe 11 for a pilot burner. The inner tube 7 for the pilot burner extends almost coaxially along the axial direction of the mixed gas conduit 3, and its lower end opening is downstream from the mixed gas intake pipe 3a. It is located on the side.

At one side of the pie mouth burner outer cylinder 6, the double-structured side wall of the outer cylinder penetrates in a substantially orthogonal direction, and the tip thereof is the pipe mouth inner cylinder 7 for the burner. There is provided a pilot burner ignition heater 12 extending to the axis of the burner. The tip of the ignition heater 12 is located immediately below the jet nozzle 8 for jetting the gas mixture for the pilot burner. The ignition heater 12 shown in Fig. 1 is of the hot surface ignition type. You can also use the talk-type.

In addition, the other side of the outer cylinder 6 for the pilot burner is connected to the space 6a of the outer cylinder 6 so as to communicate with the pilot burner. The air introduction pipes 13 are connected. The secondary air for the pilot burner is introduced into the inner cylinder 7 through the space 6 a of the outer cylinder 6 and the upper opening 7 a of the inner cylinder 7. As a result, the temperature of the pilot combustion gas, which tends to be high, is cooled to about 130 to 140 ° C. Be

In addition to the components described above, the specific example shown in FIG. 1 further includes the components described below.

The outer circumference of the inner pipe 2 in the radial direction is such that an outer pipe 14 having a diameter smaller than that of the inner pipe 2 extends coaxially along the outer peripheral surface of the inner pipe 2. It is provided. Thus, a donut-ring-like space (primary combustion gas outflow passage) 15 is formed between the inner pipe 2 and the outer pipe 3 in a cross section, and the space 15 Is connected to the inside of the inner pipe 2 through a plurality of openings (primary combustion gas outlets) 2b formed in the lower part of the inner pipe 2.

The upper part of the outer tube 2 is open, and a cylindrical outer tube support 16 having an inverted truncated cone shape made of a heat insulating member is provided on the outer peripheral portion thereof through the inner peripheral surface at the lower end thereof. It is fixed almost coaxially with the outer tube 2. The upper end of the outer tube support 16 is supported by the upper opening 1a of the combustor.

Further, the upper surface of the heat insulating member 2a provided so as to close the upper end opening of the inner pipe 2 except for the introduced mixed gas conduit 3 has an outer surface of the inner pipe 2. A ring-shaped secondary fuel jet nozzle 17 having an outer diameter substantially the same as the diameter is provided so as to surround the mixed gas conduit 3. Secondary fuel is ejected in the radial direction from port 17 toward the outlet of primary combustion gas outlet passage 15. Thus, at the outlet of the next combustion gas outlet passage 15, the primary combustion gas and the secondary combustion gas, which are created in the inner pipe 2 and contain unburned oxygen, And the ingredients are mixed.

Nozzle unit 17 has a secondary fuel conduit 18 for introducing secondary fuel from the outside, and a cooling water inlet pipe 19 for cooling the nozzle unit 17. It is connected to the cooling water discharge pipe 20 by force. The reason for cooling the nozzle unit 17 is that if the nozzle unit 17 is not maintained at about 500 ° C. or less, the introduced secondary fuel is kept inside the nozzle. This is the force that causes coking to close the nozzle hole and prevent secondary fuel from being ejected.

A truncated cone-shaped covering 21 whose diameter is reduced upward is formed coaxially with the support 16 of the outer tube 2 on the upper part of the nozzle lug 17. A ring-shaped space 22 extending upward is formed between the inner peripheral surface of the support 16 and the outer peripheral surface of the cover 21. Since the flow rate of the primary combustion gas containing the secondary fuel gradually decreases after flowing into this ring-shaped space, the secondary fuel is sufficiently mixed with the primary combustion gas during this time. Then, the secondary combustion by the gas phase combustion is caused.

The side wall of the outer tube support 16 extends along the circumferential direction of the outer tube support 16 so that the secondary combustion gas from the secondary combustion is guided to the inner chamber of the combustor surrounded by the outer cylinder 1. A plurality of openings (secondary combustion gas outlets) 23 are formed at equal intervals from each other.

In the inner chamber of the combustor, there is formed a heat receiving surface 24 composed of a plurality of metal tubes or a single ring-shaped cylinder continuous in the circumferential direction along the side wall of the outer cylinder 1. It has been done. (In the specific example shown in the figure, In some cases, the heat receiving surfaces are coaxially arranged in two rows in parallel. Inside the heat receiving surface 24, a heated fluid (eg, water) inlet 25 provided at the lower end of one side of the outer cylinder 1 and the inner bottom surface of the outer cylinder 1 are disposed. The fluid to be heated is allowed to flow through the communication pipe 26.

The fluid heated through the heat receiving surface is supplied to the communication pipe 27 arranged above the inside of the outer cylinder 1 (combustor inner chamber) and the heating fluid provided at the upper end on one side of the outer cylinder 1. From the outlet, it is sent to an external predetermined heat utilization device.

Reference numeral 29 indicates an exhaust pipe for secondary combustion gas.

If the residence time of each of the primary combustion gas and the secondary combustion gas in the primary combustion and the secondary combustion described above is 0.03 seconds or less, the combustion reaction takes place. In order to promote the combustion, it is necessary to provide the honeycombs 30 and 31 shown in the primary combustion chamber and the secondary combustion chamber, respectively. The honeycomb 30 in the primary combustion chamber inside the inner pipe 2 is located at the lower end of the inner pipe 2 and is located near the upstream side of the primary combustion gas outlet 2b. It is installed via a heat insulating member in the radial direction of the device. On the other hand, the honeycomb 31 is located downstream of the secondary fuel jet nozzle unit 17, and is formed only on the support 16 of the outer tube 14. It is installed in the vicinity of the upstream side of the outflow port 23 through the heat insulating member along the diametrical direction of the outer pipe support 16. Thus, either of the primary combustion gas and the secondary combustion gas is used. The flow should also be orthogonal to the honeycomb surfaces 30 and 31 respectively. What is it.

Most preferably, the honeycombs 30 and 31 and the inner and outer pipes 214 are formed of a sintering reaction type silicon carbide material.

Next, the operation of the embodiment of the present invention configured as described above will be described below.

At the start of the combustion action, the inner pipe 2, outer pipe 14 and / or both pipes 30 and 31 are preheated by the pilot burner device. . This preheating operation is completed when the primary combustion in the inner pipe 2 is started.

Since the inner surface of the inner tube 2 becomes a hot wall surface due to preheating, the mixed gas flowing from the mixed gas conduit 3 comes into contact with the hot wall surface—starts the next combustion, and the honeycomb 30 If installed, combustion is further enhanced here by about 140,000. As the primary combustion gas of C, it flows into the primary combustion outflow passage 15 from the primary combustion gas outlet 2b.

While the primary combustion gas flows through the primary combustion outflow passage 15, heat is radiated from the outer surface of the outer pipe 14 to the heat receiving surface 24, and the radiant heat transfer causes the outflow passage to be discharged. The temperature of the primary combustion gas that reached the outlet of No. 15 was lowered to about 900, and then flowed into the secondary combustion chamber where the nozzle unit 17 for secondary fuel injection was provided. You

The primary combustion gas mixed with the secondary fuel by the nozzle lut 17 is a ring-shaped gas formed inside the outer pipe support 16. The flow velocity is reduced in the secondary combustion chamber in the space 22, and secondary combustion by gas phase combustion occurs because of containing unburned oxygen.

When the honeycomb 31 is provided, the secondary combustion gas is completely burned in the honeycomb and is about 400 mm. The secondary combustion gas of C flows into the combustor inner chamber from the secondary combustion gas outlet 23 formed in the outer pipe support 16, and the heat receiving surface 24 is exposed by the secondary combustion gas. Heated by heat. The secondary combustion gas that has finished heating the heat receiving surface 24 is discharged out of the combustor through the gas discharge port 29.

Claims

The scope of the claims

1. An inner pipe made of ceramic having a primary combustion means for primary combustion of an air-fuel mixture in which fuel is mixed in air, and an outflow of primary combustion gas by the primary combustion An outer tube disposed coaxially with a predetermined space between the inner tube and the inner tube so as to heat the inner tube from the outside thereof while forming a passage; Secondary combustion means provided in the vicinity of the primary combustion gas outlet of the outer tube so as to cause the primary combustion gas to undergo secondary combustion; and A heat receiving surface provided along the inner wall of the outer cylinder made of heat insulating material is surrounded by the heat, and the heat generated by the primary combustion is transferred to the outer pipe by the heat receiving surface. The heat is radiated from the outer surface toward the heat receiving surface, while the heat from the secondary combustion is sensible heat of the secondary combustion gas. Combustor to jar by Ru is because we Shi not act on the heat receiving surface.

2. The combustor according to claim 1, wherein said primary combustion means is provided on one side of said inner tube for introducing a gaseous mixture of main fuel and air into said inner tube. A mixed gas conduit coaxially inserted into the (upstream) side, and a pilot burner device provided on the upstream side of the mixed gas conduit. A secondary combustion means for mixing the primary combustion gas and the secondary fuel with a secondary mixer; and a downstream side of the secondary mixer, and a front pipe and the heat receiving surface. Upstream of the outlet for letting out the secondary combustion gas into the space formed between them, on the side thereof so as to be substantially orthogonal to the flow of the secondary combustion gas. A combustor including the separated honeycomb member.

3. The combustor according to claim 2, wherein the primary combustion gas ignited by the pilot burner device is formed between the inner and outer pipes. It is provided near the upstream side of the outflow port formed at the other (downstream) end of the inner pipe so as to lead to the outflow passage, and extends in the diameter direction of the inner pipe. A combustor that further includes another honeycomb member.

4. The combustor according to claim 2, wherein said pilot burner device communicates with a proximal end force projecting outward of said gas mixture conduit. It has a double structure so as to have an inner cylinder for pilot partner inserted coaxially and a space communicating with the inner space of the inner cylinder. An outer cylinder for pilot pilot provided at the base end of the inner cylinder for the pilot nozzle via a member, and an outer cylinder provided at the center of the base end of the outer cylinder. And a pipe for introducing a gaseous mixture of the fuel and the primary air of the pilot into the inner cylinder of the pilot burner. The mixer for the pilot burner and the outer side of the outer cylinder for the pilot outlet burner reach the center of the inner cylinder for the pilot burner from the outer side. Introduced, An outer side of the outer cylinder is provided so as to communicate with the pilot ignition heater and the space of the outer cylinder for the pilot binder. A combustor including a pilot air inlet pipe.

5. The combustor according to claim 3, wherein the pyrol For a pilot burner which is coaxially inserted so that a bottom burner device communicates with the mixed gas conduit from a base end protruding outward from the mixed gas conduit. A base end portion of the pilot burner inner cylinder having a dual structure having an inner cylinder and a space communicating with the inner space of the inner cylinder, and a heat insulating member interposed therebetween. An outer cylinder for a pilot burner provided in the outer cylinder, and a pipe port fuel provided in the center of the base end of the outer cylinder and into the inner cylinder for the pilot burner. A pilot burner mixer for introducing a pilot gas mixture with the pilot primary air, and a pilot burner outer cylinder as described above A pilot ignition plug inserted so as to reach the center of the inside of the pilot burner inner cylinder from one outer side of the pilot ignition burner And a pilot secondary air introduction pipe provided on the other outer side of the outer cylinder so as to communicate with the space of the outer cylinder for the iron. And including a combustor.