WO2003006880A1

WO2003006880A1 - Method and burner element for burning gas by void combustion system

Info

Publication number: WO2003006880A1
Application number: PCT/JP2002/006969
Authority: WO
Inventors: Kenji Suzuki; Masahito Ishihara
Original assignee: Sun Frontier Technology Co., Ltd; Asahi Sesakusyo Co., Ltd.
Priority date: 2001-07-10
Filing date: 2002-07-10
Publication date: 2003-01-23

Abstract

A method for burning a gas, characterized in that a pre-mixed gas is fed to a burner element which comprises laminated Si-C-M-O type continuous fibers containing, in atomic %, 30 to 60 % of Si, 30 to 70 % of carbon, not more than 5.0 % of M, and not more than 30 % of O, and has a void volume percentage of 60 to 98%, wherein M represents one or more metal elements selected from among alkali metals, alkaline earth metals, multi-valent metals, transition metals, noble metals, rare earth metals and actinide metals which form a stable oxide, carbide or silicide, and the pre-mixed gas undergoes void combustion directly under the surface of the burner element to thereby emit radiant heat; and a burner element for use in the method. The method can be advantageously used for carrying out radiant heating by means of a void combustion system using a liquefied petroleum gas, a liquefied natural gas, a city gas, or the like as a fuel.

Description

Gas combustion method by crevice combustion method and Pana 1 'element

Technical field

The present invention relates to a method for burning gas using liquefied petroleum gas, liquefied natural gas, city gas, or the like as a fuel, and more particularly to a gas burning method advantageous for performing radiant heating by a gap combustion method and a burner element used therefor.

Background art

As a heating method using a gas perch, there is a radiant heating method in addition to a convection heating method using a blue flame by diffusion combustion. The latter radiant heating method is widely used industrially because of its advantages such as high heat transfer efficiency at high temperatures and the possibility of heating an arbitrary atmosphere when burning in a radiant tube, for example. In this radiant heating method, as shown in FIG. 4, a premixed gas in which gas fuel substantially contains theoretical combustion oxygen is introduced through a header 12 through a header 12 through a ceramic harder having a large number of pores 37. In this system, the gas is burned in or near the outlet of the pores 37 to heat the ceramic honeycomb plate 36 to a high temperature to dissipate the radiant heat, or as shown in Fig. 5, the theoretical combustion The gaseous fuel mixed with oxygen was introduced from the introduction pipe 11 to the header 21 and was burned while ejecting gas from a large number of horns 39 attached to the header, and the fuel was provided facing the nozzle surface by the heat of combustion. There is a method of radiating radiant heat by heating the ceramic plate 38 to a high temperature.

Japanese Patent Application Laid-Open No. 2002-22120 proposes a technique in which a burner mat made of a heat-resistant fiber of Si-C-0 system is used to burn the premixed gas supplied from the back surface to the surface. . Furthermore, Japanese Patent Application Laid-Open No. 2001-296005, Japanese Patent Application Publication No. 2001-519519 (W099 / 18393), and the like disclose techniques using metal fibers as burner'mats. However, among these conventional radiant heating methods, those using the former ceramic honeycomb or ceramic plate as a heating element have a risk of diffusion combustion, in which case the radiant heating efficiency is inevitably reduced. . Furthermore, the radiant heating type gas burner shown in FIG. 4, since PANA one 'element Ha second cam ceramic Itaa Rui is constituted by a laminate such as a metal net, CO, harmful combustion exhaust such NO _x There are limits to controlling the generation of substances.

On the other hand, in the case of using a Pana mat made of heat-resistant fiber of Si-C-0 series as the combustion element disclosed in JP-A-2002-22120, there is no such problem, but the fiber Due to its high quality, hardness, brittleness, and short strength, the strength of the burning mat cannot be increased sufficiently. Therefore, when flashback or internal ignition occurs, there is a danger that the burner will break due to the induced explosive wind pressure. In addition, the Si-C-0 fibers used in these burners and mats achieve ideal black body conditions by coating SiC on the surface. The coating may be lost due to repeated heat history, for example, and the radiation heat transfer efficiency may be reduced. In addition, such short fiber burner mats can cause discomfort during assembly or burning, with broken fiber ends scattered around and piercing the skin.

On the other hand, those using metal fibers disclosed in JP-A-2001-296005, JP-T-2001-519519 (W099 / 18393), etc., have a structure in which the metal fibers are made of a metal having a large specific heat, and Due to its high conductivity, the surface temperature of the burner made of metal fibers during surface combustion becomes higher than the ignition temperature of premixed gas, and there is a risk of internal ignition or flashback. In addition, there is you it is also the NO _x in the combustion gas is increased.

Disclosure of the invention

The present invention provides a gas combustion method comprising laminating Si-CM-0 filaments containing 30 to 60% Si, 30 to 70% C, 5.0% or less, and 0: 30% or less in atomic ratio. The premixed gas is supplied to the burner element having a void volume ratio of 60 to 98%, and the burner element The premixed gas is burned by crevice immediately below the surface to radiate radiant heat from the surface of the planar element. Here, M is one or more selected from alkali metals, alkaline earth metals, polyvalent metals, transition metals, precious metals, rare earth metals, and actinide metals that form stable oxides, carbides, and silicides. It is a metal element. Here, it is assumed that the void volume ratio on the supply surface side of the premixed gas is larger than the void volume ratio on the combustion surface side, or conversely, the void volume ratio on the supply surface side of the premixed gas is It can be smaller than the void volume ratio on the surface side. Further, it is preferable that the void volume ratio of the Pana 1 ′ element be 90 to 98%.

In the above gas combustion method, the gas combustion zone should be within 2 mm from the surface of the burner element, but in addition, the gas combustion zone should also be present on the surface of the burner element. Can also.

In the above gas combustion method, the mixed gas may contain oxygen gas in an amount of 0.90 to L10 times the theoretical combustion oxygen amount with respect to the combustion gas.

In order to carry out the above gas combustion method, it is necessary to include Si: 30 to 60%, C: 30 to 70%, M: 5.0% or less, and 0: 30% or less in atomic ratio. Uses a gap-burning burner element that is formed in a mat shape with a void volume ratio of 60 to 98% and a thickness of 1 to 20 mm (preferably 1 to 10 mm) formed by laminating CM-0 type long fibers. Is good. Here, M is one or more metals selected from the group consisting of alkali metals, alkaline earth metals, polyvalent metals, transition metals, noble metals, rare earth metals, and actinide metals that form stable oxides, carbides, and silicides. Element.

The burner-element may have a different void volume ratio between the combustion surface side and the supply surface side of the premixed gas. The void volume ratio is preferably set to 90 to 98%. '

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of a gas combustion device incorporating a burner element according to the present invention. FIG. 2 is a conceptual diagram showing a structure of a wrench element according to the present invention.

FIG. 3 is an explanatory diagram showing a heating state by a gas combustion device incorporating a parner element according to the present invention.

FIG. 4 is a schematic diagram showing an example of a conventional gas combustion device using a radiant heating method. FIG. 5 is a schematic diagram showing another example of a conventional gas heating device using a radiant heating method.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention employs a known gap combustion method. Here, the gap combustion method means that the premixed gas that has passed through the inside of a porous solid such as a black body material burns in a layer very close to the outlet surface, and the solid itself is heated by the energy to form a radiant heat radiator. Combustion method. In this combustion system, the floating of the flame is not apparently observed, and it is attached to the surface.

FIG. 1 is a schematic view of a gas combustion device incorporating a burner element according to the present invention. That is, the premixed gas is supplied to the burner element 31 through the introduction pipe 11, the header 12, and the flow straightening plate 21, and the gap is burned immediately below the surface to radiate radiant heat from the surface. By doing so, the premixed gas is guided into the parner element 31 while maintaining a substantially laminar flow state without substantially causing a pressure loss, and is ignited from the surface thereof so that the premixed gas is reduced. Continue burning in the gap just below the element surface. Note that, as the premixed gas, for example, a hydrocarbon-based gas such as propane or butane, or a gas containing oxygen necessary for combustion of a hydrogen gas can be used. The oxygen content of this premixed gas may be in the range of 0.90 to 1.10 of the theoretical combustion oxygen content.

In the present invention, the burner 'element 31 in which the above-mentioned crevice combustion is performed has an atomic ratio of Si: 30 to 60%, C: 30 to 70%, M: 5.0% or less (0 is not included), 0: 30% or less ( It does not include 0). It is composed of mats with a void volume ratio of 60 to 98% by laminating Si-CM-0 type long fibers having the composition Here, M is an alkali metal, alkaline earth metal, polyvalent metal, transition metal, noble metal, rare earth metal, which forms stable oxides, carbides, and silicides. It is one or more metal elements selected from octinide metals. Such a fibrous substance can be produced, for example, by an organic-inorganic conversion process using polycarbosilane as a precursor, and is known as a Tyranno fiber of Ube Industries, Ltd. The present invention utilizes this effectively. In addition, this fiber substance can appropriately contain B, N and the like as skeletal elements in addition to the above basic components.

In the above, the metal element M is an alkali metal such as Li, Na, K, Rb, and Cs; an alkaline earth metal such as Mg, Ca, Sr, and Ba; a polyvalent metal such as Al, Ge, and Sn; 3d transition metals such as Ti, V, Cr, Mn, Fe, Co, Ni, 4d transition metals such as Y, Zr, Nb, Mo, Ru, Rh, etc., 5d transition metals such as W, Re, Os, Ir , Pd, Ag, Pt, Au etc., Noble metals, La ヽ Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu etc., rare earth metals and Th, U Etc., and not only one kind but also several kinds of metal elements can be simultaneously contained at an appropriate ratio.

Since the Si-CMO filament-made burner element emits an almost ideal, ideal blackbody staple, it is heated by the crevice combustion of the premixed gas and becomes hot from the surface of the burner. Ideal radiant heat is dissipated. In addition, since fuel gas, for example, propane and butane contains oxygen which is substantially equivalent to the theoretical combustion amount in advance, secondary air is not required for crevice combustion. As a result, diffusion combustion is practically eliminated, and radiant heating efficiency is improved. In addition, the specific heat is extremely small, about 0.7 J / gK, so that the surface of the parner instantly glows red by ignition, and strong radiant heating is obtained.

The Si-CM-0 type long fiber is amorphous and has a uniform component over the entire cross section. Also, its strength reaches 3000MPa, so it does not break when it is spread and molded into a mat. In addition, since it has a thermal conductivity of 3 W / mK or less, even if the front surface is heated to a high temperature, for example, 1000 ° C, the back surface remains at a low temperature, at most about 100 ° C. Furthermore, even if heating and cooling are repeated, surface peeling does not occur. Further, even when a saline during use, when the Zr, A1 or the like is present as a Si-CM-0-based long fiber in the metal component (M) is dense hot containing Zr0 _{_2,} A1 ₂ 0 _3, etc. Heat resistant glass is formed on the surface and does not cause fiber deterioration over a long period of time. W

In order to take advantage of the excellent characteristics of Si-C-M-O long fiber and to perform crevice combustion ideally, it is desirable to pay attention to the following points regarding the structure of the wrench element. First, it is preferable that the Si-C-M-0 system constituting the Pana 'element is a long fiber having a diameter of 8 to 100 / m. Reducing the fiber diameter in this way makes it easier for the fiber to bend freely, burns it into a matte shape, reduces the generation of cut pieces when it is used as an element, and cuts the fiber during combustion. Solves the problem of flying around. In addition, by increasing the fiber length, the burner element can be formed as a long, laminated fiber in a folded or entangled mat shape. This allows the parner element to have a desired void volume ratio while not easily breaking even if the gas pressure fluctuates during combustion. In addition, the free ends of the fibers are small, and the shape of the burner element can be maintained stably even during combustion. In this sense, it is preferable that the fiber length has at least the span length of the burner 'element. Considering that the burner element is manufactured in a square having a side of about 150 mm as will be described later in the examples, the fiber length is preferably at least 150 mm.

The void volume ratio of the PANA-1 'element is not particularly limited, and may be about 60% to 90% which is generally used. However, the void volume ratio is preferably 90 to 98%, particularly 93 to 98%. As a result, the premixed gas is introduced into the burner element なく without substantially causing a pressure loss, and the crevice combustion is performed smoothly.

At this time, the void volume ratio of the Pana 'element may be within the above-mentioned range on the average of the entire Pana' element, but this is closer to the supply surface side than the premixed gas combustion surface side. Can be increased. By changing the void volume ratio in this way, the premixed gas burns most strongly under the surface of the burner 'element, and the combustion decreases rapidly toward the inside.

The method of changing the void volume ratio may not be uniform.For example, only the vicinity of the combustion surface is reduced, that is, the Si-C-M-0 fiber which is a black body is clogged. It can also be in the state of being left. These may be appropriately determined empirically so as to optimize the condition of crevice combustion. Most typically, the porosity can be 70-95% on the combustion side and 95-98% on the supply side.

The above void volume ratio is determined by, for example, linearly injecting a resin into the manufactured PANA-MAT and solidifying the resin, and then observing the cross section with an optical microscope to determine the area ratio occupied by the fiber. 'It can be determined by asking by analysis. In the gap combustion method using the above-described PANER 'element, it is preferable that the gas combustion zone be within a range of 2 mm or less from the surface of the PANER' element. Such adjustment of the gas combustion zone can be performed by adjusting the lamination state of the Si-C-M-0-based fibers described above. The above porosity of 70-95% on the combustion side and 95-98% on the supply side is desirable for such combustion.

The surface temperature of the burner's element reaches 800 to 900 ° C by the above gap combustion method. Further, as shown in FIG. 3, a part of the radiant heat energy radiated from the surface of the burner element 31 is reflected from the bottom surface of the heating element 41 to make the surface of the burner element 31 hotter, thereby further increasing the temperature. High radiant heating is possible.

However, the temperature on the bottom side of the burner element 31 is at most several tens of degrees Celsius due to the large void volume ratio of the burner element 31 and the low thermal conductivity of the material that composes it. It only rises up to. This has the advantage that flashback is effectively prevented and that the Pana 'element can be manufactured in any shape, such as flat, cylindrical or spherical.

Further, in the burner element of the present invention, the porosity is sufficiently small on the combustion surface side, that is, the fiber density is sufficiently high, because the premixed gas introduced into the parner element in a laminar flow state is turbulent in the combustion zone. It mixes the gas and increases the combustion rate by mixing the gas. As a result, the turndown ratio can be increased, for example, as large as 1:10, and combustion with a relatively small load density can be performed. This allows for efficient extraction of far-infrared radiation.

In the gas combustion method according to the present invention, the premixed gas is mostly Crevice combustion occurs just below the surface, causing virtually no flames and radiating heat from the ideal blackbody radiation from the surface of the burner 'element. In the combustion method of the present invention, the secondary air is practically unnecessary, and there is no need for a flame outlet as in the conventional burner element. '

However, the gas combustion zone need not be limited to just below the Pana 'element. A gas combustion zone exists on the element surface, even if the air volume of the premixed gas is small, for example, containing oxygen gas that is about 0.90 times the theoretical combustion oxygen amount with respect to the combustion gas. You can also do so.

FIG. 2 (a) is a conceptual diagram showing an example of the entire structure of a wrench element according to the present invention. FIG. 2 (b) is a partially enlarged schematic view showing the state of entanglement of the fiber by its cross section. As shown in FIG. 2 (b), the Pana 'element 31 is formed by vertically and horizontally tangling and stacking Si-C-M-0 type long fibers 32 represented by Tyranno fibers. The fiber diameter of the Si-C-M-O type long fiber is 8 to 100 μπι, and the length is, for example, 150 mm or more. This allows the shape to be kept constant while maintaining a higher void volume ratio (90 to 98%). In addition, as shown in Fig. 2 (a), the portion A near the surface has a relatively low void volume ratio, and the void volume ratio increases as it enters the interiors B and C. As a result, as already described, the gas flow force S is guided into the burner's element while being maintained almost laminar, and becomes turbulent immediately below the surface and burns rapidly. However, the heat of combustion is not transmitted to the interior of the perforation, due to the characteristics of the black body fiber, and the temperature of the rear surface is almost room temperature.

Note that the above-mentioned PARNER 'element may be manufactured as a so-called integral element, but is divided into' polygonal ',' circular 'and' elliptical 'unit shapes in consideration of safety during use. It is desirable. The area of one division unit is, for example, about 10 to 300 cm ^{2 in} consideration of the spread of the flame when used for household gas stoves.

Assemble the combustion apparatus by incorporating the burner 'element, when the normal fuel primary air premixed gas is a gap burning, 20 ppm of CO concentration in the combustion exhaust gas combustion load Te range odor 10~30W / cm ² hereinafter, to make the concentration of NO _x in 20ppm or less it can.

In the present invention, the premixed gas is preferably sent in a laminar flow into the burner element 31. For this purpose, as shown in FIG. 1, the burner element 31 and a header for introducing gas are used. It is good to arrange the current plate 21 between 12. Example 1

Hereinafter, the case where the present invention is applied to a household cassette gas stove will be specifically described. Void volume ratio made of Si-C-Ti-0 fiber (Tyranno fiber) with a mean fiber diameter of 10 μπι and a length of 1000 mm, which was made by an organic-inorganic conversion process using polycarbosilane as a precursor ( supply side: 98%, firing side: mat 95%) (thickness: 10 mm) was cut out circular burner 'element of the area 180cm ² from. This burner element is attached to the burner section of the cassette inlet, and a premixed gas of liquefied butane gas and air is supplied from the back of the burner element, and the gap is burned in a combustion zone with a thickness of 0.6 to 1.0 mm just below the surface. I let it.

When the secondary pressure of butane gas as fuel is controlled to about 70 hPa with respect to the atmospheric pressure by a pressure regulator, and the liquid regulator butane can kept at 30 ° C without the pressure regulator

(Internal pressure: 200-300 kPa) Combustion experiments were performed when the gas was directly introduced into a venturi tube of the con- trol opening. After the combustion reaches a steady state, the amount of butane gas consumed to raise the temperature of 2000 ml of water placed in an aluminum metal pan with an inner diameter of 200 mm and a depth of 100 mm from 20 ° C to 50 ° C according to JIS standards is measured. To determine the thermal efficiency. The distance between the combustion surface of the element and the bottom of the pan, which is the heating element, is 7 mm. Combustion exhaust is sampled along the side of the pan at a position 50 mm above the combustion surface, and if CO, NO _x A concentration measurement was performed. As a result, the combustion output 3,000kca] / h, combustion efficiency 57%, or less CO concentration 20ppm in the combustion exhaust gas, NO _x concentration 20ppm following data was obtained. As described above, according to the present invention, a large energy-saving effect is obtained, and clean combustion exhaust is realized. Example 2 Burner with Si-C-Zr-0 fibers laminated area: 150mm X 150mm, thickness: 6mm (two 3mm thick mats), volume porosity: 95% * Element size of opening The same combustion test as described above was conducted by mounting on the opening side of a steel potter with a size of 150 mm X 150 mm and a depth of 20 mm. The fuel gas was liquefied butane gas, and its secondary pressure was controlled to 200 hPa with respect to atmospheric pressure. As a result, combustion efficiency of 58%, or less CO concentration 20ppm in the combustion exhaust gas, NO _x concentration 20ppm following data was obtained. As in this example, the burner element is thin and the burner is a steel box that houses the burner element.The secondary pressure is sufficiently large even when the space behind the element is narrow. As a result, high combustion efficiency and clean combustion exhaust are realized.

As described above, the basic embodiment of the present invention has been described. However, the present invention can be applied to household gas stoves as in the above embodiment, and can be applied to industrial heating furnaces such as ceramics, steel, paint baking, and the like. Can be widely applied. Further, in this embodiment, in addition to using the parner in a naked state, the parner can be used by being wrapped with a suitable infrared transmitting means.

Claims

The scope of the claims

1. Laminated Si-C-M-0 filaments containing 30 to 60% Si, 30 to 70% C, 5.0% or less, and O: 30% or less in atomic ratio. A premixed gas is supplied to a burner element having a volume ratio of 60 to 98%, and the premixed gas is combusted immediately below the surface of the burner element to radiate radiant heat from the surface of the burner element. A gas combustion method using a gap combustion method, characterized by the following. Here, M is one or more metal elements selected from alkali metals, alkaline earth metals, polyvalent metals, transition metals, noble metals, rare earth metals, and actinide metals that form stable oxides, carbides, and silicides. It is.

2. The gas combustion method using the gap combustion method according to claim 1, wherein the porner element has a larger void volume ratio on the supply surface side of the premixed gas than on the combustion surface side. .

3. The gas combustion method according to claim 1, wherein the burner element has a void volume ratio on a supply surface side of the premixed gas smaller than a void volume ratio on a combustion surface side.

4. The gas burning method according to claim 1, wherein the burner element has a void volume ratio of 90 to 98%.

5. The gas burning method according to claim 1, wherein the gas burning zone is within 2 mm from the surface of the burner element.

6. The gas combustion method using the gap combustion method according to claim 4, wherein the gas combustion zone is within 2 mm from the surface of the pruner element.

7. The gas combustion method according to claim 1, wherein the gas combustion zone is also present on the surface of the Pana 'element.

8. The gas according to claim 1, wherein the premixed gas contains oxygen gas of 0.90 to L.10 times the theoretical combustion oxygen amount with respect to the combustion gas. The burning method.

9. Laminated 8 to 100 μm diameter Si-CM-0 long fibers including Si: 30 to 60%, C: 30 to 70%, M: 5.0% or less, 0: 30% or less in atomic ratio A burner element for crevice combustion formed in a mat shape with a void volume ratio of 60 to 98% and a thickness of l to 20 mm. Here, M is one or more selected from alkali metals, alkaline earth metals, polyvalent metals, transition metals, noble metals, rare earth metals, and actinide metals that form stable oxides, carbides, and silicides. It is a metal element. '

10. The gap combustion perch element according to claim 9, wherein a void volume ratio is different between a combustion surface side and a supply surface side of the premixed gas.

11. The gap combustion partner element according to claim 9 or 10, wherein the void volume ratio is 90 to 98%.