JPS61184319A - Method of generating hot blast by catalytic combustion - Google Patents

Abstract

PURPOSE:To provide a method of generating hot blast by catalytic combustion in small size and of large calorific value with increased heat generation per unit surface area of catalyst by premixing a fuel gas a gas containing molecular oxygen or a required amount and burning the premix in contact with the catalyst through a catalyst layer into which the premix is diffused and supplying an inert gas for cooling and diluting to the other faces of the catalyst layer to be mixed there with the combustion gas. CONSTITUTION:A laminated ceramic fibre body consisting of fibres of about 3mu average diameter, silica of 5% and alumina of 95% by weight is impregnated with platinum of 1% by weight. A catalyst of 0.5 grams is filled in a basket of about 20mm outer diameter, the basket being formed with stainless steel net of about 30 mesh. Further, in the center of the basket a stainless steel pipe with a great many small holes pierced through it is inserted to obtain a catalyst body for complete combustion with its catalyst portion being 50mm long and outer surface area about 31cm<2>. A combustion test device of 40mm inner diameter is provided with the combustion catalyst body and combustion is made by changing amounts of supplied fuel and air. Calorific value per unit area of catalyst in 10-17kcal/cm<2>.hr was obtained.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a method for generating hot air using a catalytic combustor.

More specifically, the present invention relates to a catalytic combustor suitable for the purpose of combusting fuel on a catalyst and extracting the resulting heat as hot air.

[Prior art]

Attempts to burn fuel on a catalyst and utilize the resulting heat have been known for a long time. Taking advantage of its characteristics of not causing any danger or anxiety, it has been applied to portable consumer devices such as hand warmers, small heaters, and small hair beauty devices.

However, in order to simplify the equipment and take into consideration risks such as backfire, the above-mentioned prior art does not premix combustion and air as an oxidizing agent, and the fuel that has diffused from inside the catalyst layer is naturally diffused to the surface. The diffusion combustion method is mainly adopted, which involves catalytic combustion in contact with air that diffuses into the catalyst layer.In this case, the combustion-supporting air as an oxidizer is supplied by natural diffusion, The diffusion rate is slow and this is the rate limiting factor, and the combustible amount per unit surface area of the catalyst, that is, the calorific value, is as small as 1.5 kcal/ct/1-hr, and if more fuel is supplied, unburned hydrocarbons and It has the disadvantage that carbon monoxide emissions increase rapidly.

Of course, in this case, if a premix combustion method is adopted in which fuel and air are premixed and introduced into the catalyst layer for catalytic combustion, the air volume would be too large, making it impossible to start and maintain combustion with a small amount of catalyst. be.

In this way, it has been difficult to apply the prior art to equipment that requires a larger calorific value because the amount of catalyst increases and the equipment becomes larger. Furthermore, with the exception of a few attempts, there have been few attempts to utilize the heat generated by catalytic combustion as hot air.

[Purpose of the invention]

The present invention solves the problems of the prior art described above, and provides a method for generating hot air using a small-sized catalytic combustor that increases the calorific value (combustible amount) per unit surface area of the catalyst and has a large calorific value. The purpose is to enable application to hair beauty devices, simple dryers, hot air heaters, flameless torches, or small power generators in combination with thermoelectric conversion elements.

[Structure of the invention]

In the present invention, a catalyst layer having a certain thickness is provided, and the entire amount of fuel and the amount of molecular oxygen-containing gas, such as air (hereinafter referred to as air, etc.) necessary for complete combustion, are mixed in advance from one side of the catalyst layer. A lean air-fuel mixture with a composition that does not fall within the flammable range is introduced into the catalytic converter to cause catalytic combustion, and an inert gas, such as air, is introduced onto the other side so that the diffused combustion gas is immediately absorbed at the surface layer of the catalytic layer. It consists of cooling and diluting to obtain the desired temperature and amount of hot air.

Unlike surface diffusion type catalysts, the present invention enables the entire catalyst layer to be heated by premixing the entire amount of fuel and the amount of molecular oxygen-containing gas such as air required for its complete combustion and introducing the mixture into the catalyst layer. As a result of making effective use of catalytic combustion and premixing only the necessary amount of air, etc., it is possible to control the space velocity passing through the catalyst layer low and to maintain a temperature of the catalyst layer that is sufficient for catalytic combustion to be self-sustaining. can.

Furthermore, by introducing an inert gas such as air to the other side of the catalyst layer to cool and dilute the hot combustion gas that diffuses from the catalyst layer, the hot gas generated by catalytic combustion can be immediately cooled. It can be diluted to obtain hot air at the desired temperature and amount.

As a result, it is possible to obtain a large amount of hot air with a small volume of catalyst layer, and the calorific value per unit surface area of the catalyst is 10~
It can reach up to 50kcal/crl-hr.

Furthermore, the hot air contains unburned hydrocarbons (UHC), -carbon oxides (
-CO), nitrogen oxides (NOx), and there is no flame that makes the user feel uneasy, and the catalyst layer does not become red hot. has.

Of the required amount of molecular oxygen-containing gas, the amount of the molecular oxygen-containing gas used for premixing, preferably air, etc., is determined based on the amount of catalyst, the amount of fuel and its calorific value, and the temperature and amount of the intended hot air. Although the optimum amount is determined by the following, it is preferable that the amount is such that the obtained air-fuel mixture is a lean air-fuel mixture outside the combustible range and the combustion gas temperature is from 400°C to 1200°C. If the temperature does not reach 400℃, the temperature will be low and the air volume will be large, making it difficult for catalytic combustion to become independent.
If the temperature exceeds 1,200°C, the temperature approaches the flammable range, making it difficult to generate flames and shortening the durability of the catalyst.

In order to embody the present invention more effectively, it is preferable that the catalyst has a cylindrical shape with one end closed, as shown in FIG. The present invention can be more effectively realized by ventilating the remaining amount of air, etc. in the outer peripheral portion. Alternatively, as shown in FIG. 2, it is also possible to supply premixed gas from the outer circumferential side and forcefully ventilate air into the inner cylinder, thereby achieving the present objective.

The shape of the tube is selected depending on its intended use, such as a cylinder or a rectangular tube, but it is also possible to have a 7-reare shape for the purpose of increasing the surface area.

A catalyst carrier with a large void ratio and low specific gravity and specific heat is suitable for the purpose of facilitating and uniform diffusion of fuel and molecular oxygen-containing gas, and allowing independent catalytic combustion outside the plate during ignition. Furthermore, in order to ensure uniform diffusion and prevent fuel from blowing through, a one-piece laminate or molded body is suitable.

As a carrier that satisfies these requirements, inorganic fiber laminates or molded bodies such as alumina, silica, and silica-alumina having a filling specific gravity of 0.02 to 0.6 (1'/ee) are preferable; A three-dimensional network structure made of metal or ceramic such as cordierite or mullite is also suitable.

The catalytic active component is optimally selected depending on the type of fuel, but platinum group elements such as platinum, palladium, and rhodium are usually suitable, and these can be supported on the above carrier alone or in combination of two or more. The catalyst is molded into a cylindrical shape or filled into a cylindrical wire mesh or the like to obtain a completed catalyst.

It is also possible to obtain a finished catalyst by molding it into a cylindrical shape in advance and supporting a catalytically active component on the voice carrier.Alumina or alumina stabilized with an oxide of alkaline earth, rare earth, etc. can be added to the molded body or structure. A finished catalyst can also be obtained by coating and supporting a platinum group element on the coating layer.

The larger the size of the catalyst layer is, the better, in order to reduce the passing space velocity of the premixed gas and ensure stable combustion.As long as the catalyst surface area is the same, the thicker the catalyst layer is, the larger the amount per unit catalyst surface area. This is preferable because it can increase the calorific value, but on the other hand, an increase in the amount of catalyst or the thickness of the catalyst layer leads to an increase in ventilation resistance and an increase in the size of the combustor as a whole.
Therefore, the amount of catalyst used in the present invention is such that the space velocity of the premixed gas passing through the catalyst layer is r-1 to, ooo ~ 500,000, preferably 30
,000 to 300,000 (STP), and the catalyst layer thickness is such that the average linear velocity of the premixed gas at room temperature is 1 to 100 cIIL/sec, preferably 5 to 50 cm/sec. The suitable thickness is usually 1 to 200 m, and depending on the size of the intended hot air generator and its use, the catalyst shape and design are optimally selected and designed to be within the above range. be done.

The total flow rate of molecular oxygen-containing gas such as air is determined by the temperature and flow rate of the hot air to be obtained, and is optimally selected depending on the purpose of use of the hot air as well as the size of the catalyst or the amount of fuel supplied. However, as mentioned above, the proportion of the total flow rate used for premixing is such that the resulting gas mixture is a lean gas mixture outside the combustion range, and the combustion gas temperature is 400 to 1260°C. The amount is determined to be equivalent to .

Air is suitable as the molecular oxygen-containing gas to be supplied, but for portable purposes, air can be supplied by incorporating a small fan, using batteries, or using electric power generated by a thermoelectric conversion element. This is possible by rotating the small fan. A part of the air flow thus generated may be supplied to the catalyst layer for premixing, or the air flow may be separately injected using a venturi system and used for premixing.

In the present invention, gaseous fuels such as methane, propane, butane, and natural gas, and liquid fuels such as methanol are suitable as the fuel used, but especially when used for portable purposes, small liquefied propane or butane cylinders are preferred. It is preferable to use methanol, and methanol is excellent in that it can perform catalytic combustion independently without any preheating.

Ignition is made possible by heating the catalyst layer using an electric heater or a separately prepared gas lighter, thereby allowing catalytic combustion to continue on its own.

The present invention is usually used at normal pressure, but depending on the application, it may also be used under pressure to increase the calorific value per unit surface area of the catalyst and make the combustor more compact. It is possible.

The catalytic combustion hot air generation method described above has made it possible to create a catalytic combustion hot air generator that can generate a large amount of heat with a small capacity catalyst, a large portable hair beauty device, and a simple dryer. The present invention can be suitably applied to a small power generator using a combination K with a heater, a hot air heater, a flameless torch, or a thermoelectric conversion element.

[Specific effects of the invention]

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 5 wt% silica, 95 wt% with average fiber diameter of about 3μ
A laminate of ceramic fibers made of alumina (filling specific gravity: 0.04 (1/cc)) was loaded with platinum at a weight ratio of 1%.

Next, 0.6 p of the catalyst was filled in a cage with an outer diameter of 20 mm made of about 30 mesh stainless steel wire mesh, and a stainless steel pipe with an outer diameter of 6 mm with numerous small holes was inserted into the center of the cage. As shown in Figure 3, the length of the catalyst section is 50tgN.
A completed combustion catalyst body A having an outer surface area of 31d was obtained.

Subsequently, the combustion catalyst A was installed in a combustion test device with an inner diameter of 4011x as shown in FIG. Hydrogen, carbon oxide, and nitrogen compound concentrations were measured.

The fuel was commercially available liquefied butane (calorific value: 29,600 kcal).
/Nm), and at the time of ignition, the combustion catalyst was preheated using a commercially available gas lighter, and then fuel and air were introduced to make the catalytic combustion independent.

As a result, as shown in Table 1, under the conditions within the scope of the present invention, a calorific value of 10 to 17 kcal/a+lhr was obtained per unit surface area of the catalyst, which was capable of substantially complete combustion.

The results of experiments/I61-4 in this example can be suitably applied to large portable hair beauty devices, simple dryers, hot air heaters, etc. that require large amounts of relatively low-temperature hot air. In addition, the results of Experiments 5 and 6 make it possible to apply the method to flameless torches that require medium-temperature hot air of about 350°C to 600°C, and small power generators in combination with thermoelectric conversion elements. .

Comparative Example 1 Using combustion catalyst A, a combustion experiment was conducted in the same manner as in Example 1 under conditions outside the scope of the present invention.

If this happens, UHC and CO emissions will increase, and the calorific value per unit surface area will be approximately 7. s kca1//cit・hr
It was possible to obtain only a certain degree.

In addition, by increasing the proportion of premixed air, HC in the premixed gas
If the concentration is low, the rate of passage through the catalyst layer is fast, and the temperature rise in the catalyst layer due to combustion is calculated to be less than 400°C, so catalytic combustion is no longer independent and a misfire occurs, or conversely, the temperature rise in the catalyst layer due to combustion is less than 400°C. Although combustion is stable when the proportion of mixed air is reduced, the catalyst layer becomes red hot and some flames are generated, giving the user a sense of uneasiness, and the temperature of the catalyst layer is calculated to exceed 1200℃. The durability of the catalyst was poor.

Example 2 The same ceramic fibers used in Example 1 were mixed with alumina sol and formed into an outer diameter of 2 as shown in Figure 4 by suction molding.
A cylinder with an inner diameter of 61111 mm and a length of 70 nm sealed at one end was manufactured.

Next, 0.5% of platinum and 0.2% by weight of platinum were added to the molded body.
% of palladium was supported to obtain a completed combustion catalyst body B.

Subsequently, a combustion test was conducted in the same manner as in Example 1, and as shown in Table 1, the calorific value per unit surface area of the catalyst was approximately 14 kcal/cit.
hr was obtained.

Example 3 A three-dimensional metal network structure made of Ni-Cr alloy (manufactured by Sumitomo Electric, Celmet) was used, and the outer diameter was 30 mm as shown in Fig. 5.
We made a cylinder with an inner diameter of 20tK and a length of 40m sealed at one end.

Next, alumina stabilized with 5 inches by weight of lanthana was coated, and 0.5% by weight of platinum was supported to obtain a completed combustion catalyst Ct-.

Subsequently, a combustion test was conducted in the same manner as in Example 1, and as shown in Table 1, a calorific value of approximately 12 kcal/hr per unit surface area of the catalyst was obtained, which enabled substantially complete combustion.

Example 4 Same as Example 3, outer diameter 401ErIL, inner diameter 30n
A cylindrical combustion catalyst body with a length of 50 nm was obtained, and it was installed in a stainless steel pipe with an inner diameter of 50 m as shown in Fig. 2. Fuel and premixed air were introduced from the outer circumferential side, and the remaining amount of air was poured into the inner cylinder. We installed it and conducted a combustion test.

As a result, as shown in Table 1, the calorific value per unit surface area of the catalyst capable of substantially complete combustion was approximately 19 kcal/(1i1
-hr was obtained.

[Brief explanation of the drawing]

FIG. 1 shows an outline of the combustion test apparatus used in Example 1, and FIG. 2 shows an outline of the combustion test apparatus used in Example 4. In addition, FIG. 3 is a schematic diagram of the catalyst body obtained in Example 1, FIG. 4 is a schematic diagram of the catalyst body B obtained in Example 2, and
The figure shows a schematic diagram of the catalyst body C seen in Example 3. Patent applicant Nippon Shokubai Chemical Co., Ltd. Figure 5

Claims (6)

[Claims] (1) From one side of a catalyst layer of a constant thickness, fuel gas and the amount of molecular oxygen-containing gas necessary for its complete combustion are premixed so that the composition is less than the lower limit of the flammability range. The fuel is diffused into the catalyst layer and catalytically combusted by supplying a raw material gas of A catalytic combustion hot air generation method characterized by mixing with combustion gas. (2) Claims characterized in that the premixed raw material gas is premixed with a molecular oxygen-containing gas so that the temperature raised by combustion is in the range of 400 to 1200°C. 1) The method described. (3) The method according to claim (1) or (2), wherein the catalyst is formed by supporting a platinum group metal on an inorganic fiber laminate or molded body as a carrier. (4) The method according to claim (1) or (2), wherein the catalyst is formed by supporting a platinum group metal on a ceramic foam or metal foam as a carrier. (5) The catalyst is prepared by coating and supporting alumina or alumina stabilized with an alkaline earth or rare earth element oxide on an inorganic fiber laminate, a molded body thereof, a ceramic foam, or a metal foam as a carrier; The method according to claim (1) or (2), characterized in that a platinum group metal is supported on a coated carrier. (6) Claims characterized in that the catalyst layer is formed into a cylindrical shape with one end closed on the fuel supply side, and substantially all of the supplied fuel is diffused and combusted ( The method described in 1), (2), (3), (4) or (5).