DE1751246A1 - Katalyt heater - Google Patents

Description

DR.-ING. WALTER ABITZ DR. DIETER MORF

Patent attorneys

8 Mönchen 27, Pienzenauerstraße 28 Telephone 483225 and ^ 86415 Telegrams: Chemlndus Munich

April 26, 1968 B-967

ENGELHARD MINERALS 4 CHEMICALS CORPORATION

113 Astor Street, Newark, N.J. 07114, V. St. A.

Katalyt - radiant heater

The invention relates to heating devices in which a bronze, which is usually gaseous, and an oxygen-containing gas, such as air, are used. The fuel and oxidising gas are combined and catalytically burning without Flanmenbildung on the surface Ainet _w non-flammable, ceramic skeletal block one-piece old Gasströaungskanälen, Such devices can

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used for heating when the temperature of this The surface area due to the combustion is high enough to allow the emission of significant amounts of heat through radiation cause.

The invention is directed to new types of radiation heat dissipation devices. In particular are The subject of the invention heating devices with precious metal catalysts, which result in flameless combustion and provide infrared radiant energy. These heaters use one-piece, channeled ceramic blocks to aid in oxidation, such devices can be used for removing paint, varnish and the like, laying and removing asphalt tiles, the Burning and drying of painted surfaces, heating and irradiating greenhouses and for others Purposes

Catalytic radiant heaters that use a noble metal catalyst, such as platinum black, on a substrate such as asbestos fiber or fabric or cloth, are known per se. Such heating devices are generally bulky, hanging of secondary or additional air for combustion and require a large flame for ignition. They also have

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Combustion gases have a tendency to be uneven to the surface such heaters to flow. This has an unevenly wet ige s result in burning and hot spots, which lead to a reduction in the life of the catalytic converter. Furthermore, such uneven combustion also has unoxidized or partially oxidized combustion products result, thereby keeping ineffective operation and toxic carbon monoxide. There are other heating devices as well known that generate an infrared radiation energy and use! ceramis cheGas flow channels, however A wide range of air-fuel mixtures cannot be used with these heaters. Furthermore let They also do not have a high turn-down ratio. Here is the option under throttling ratio to understand how to decrease the rate of fuel consumption by decreasing the fuel flow will. This reduction automatically reduces the air supply. Hin throttling ratio of loo: 1 means that a fuel with a maximum speed in a burner and with 1/100 of this maximum Speed can be consumed. This throttling ratio is very desirable when using the catalytic heater

to be used for different purposes of which each causes very different heating needs.

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The invention relates to catalytic radiant heaters, which simple Venturi tubes for the supply of 4 combustion air and use a one-piece ceramic to aid in the distribution of the combustion mixture Carrier block with a large number of gas channels on which Surface is a platinum group metal and preferably a refractory metal oxide is deposited. The catalyst carrier contributes to the oxidation of the fuel to catalyze, to prevent a flantom backlash and Heat off the object to be heated! Radiate.

The object of the invention is to create a catalytic heater with complete combustion of the fuel. Furthermore, losses in the catalyst life should be due to prevents hot spots from developing during operation will. A simple structure is also to be created that has a wide range of useful air-fuel ratios as well as a high risk ratio and enables a change in the amount of heat emitted. Further objects of the invention emerge from the following more detailed description.

Description of preferred execution formats.

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The inventive catalytic heater has a Housing designed to have a larger opening or area as well as a smaller one used as a gas inlet duct Has opening. The cross-sectional area within the Housing generally increases from the smaller to the larger Close the opening so that it expands the hot Permits gases in the housing. An essentially smooth transition from the smaller to the larger opening is preferred, E.g. a conical shape, so that an effective expansion and an even distribution of the fuel mixture inside * half of the housing can take place. The fuel and the oxygen-containing gas are attached to the housing at the inlet port fed through a Venturiano / dilution. This combustible mixture can optionally be taken through the interior of the housing Use of an inverted cone, a sieve or the like. be distributed. The gas mixture is preferably introduced axially into the housing. It can be either air or the Fuel can be supplied to the venturi for sucking in the other component. Compressed air is preferred to achieve combustion noises which are more than that Contains twice the stoichiometric amount of air.

Experience has shown that when a conical Housing is used, special apex angles preferred

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in order to achieve the lowest possible amount of irregular heating of the supported catalyst and an extended service life of the catalyst. The apex angle here is to be understood as the angle between the conical surface and the perpendicular to the axis of the cone in the plane containing the axis of the cone and the normal to it. A vertex angle of about 20 ° by 80 ° is preferred.

The one-piece used for the purposes of the invention ceramic support block is in the cross-sectional area of the Arranged front side of the housing and can occupy approximately the entire area. The ceramic block can come in many different shapes can be used, e.g. round, square, conical, spherical and can be used for the surface of the Housing raised or partially raised or recessed.

The one-piece, inert, refractory, skeletal The carrier for the catalyst differs in that it has a large number of unobstructed gas flow channels or -Vege, which extends through the carrier in the direction of the Extend gas flow. The gas flow channels can be a

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or more of a variety of cross-sectional shapes and large have _o The cross-sectional shape of the channels may, for example the shape of a trapezoid _c of a rectangle _s a square, a sinusoid or a circle to be such that the cross sections of the support representing a pattern, like the corrugated honeycomb as or lattice structure can be described «

The ceramic carrier is made of a chemically and catalytically essentially inert, porous, rigid, solid, fire-resistant material which can maintain its shape and strength at high temperatures of, for example, up to about 1,000 ° C. and higher. It has a low coefficient of thermal expansion which is between 3o ° C and 7oo ° C less _s betrögt than 6 χ Io ⁰ depending C "what a good impact strength of importance preferably. This refractory material has a bulk density of about o _e 4 to 2, o grams per cubic centimeter, preferably about 0.5-1.5 grams per cubic centimeter, and is unglazed and essentially completely crystalline in the form and is characterized by the lack of a substantial amount of glassy or amorphous matrices "as they are, for example, in porcelain Furthermore, the skeletal structure has considerable porosity accessible to the body

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Difference from the essentially non-porous porcelain used for electrical purposes, e.g. for manufacture of spark plugs, which are characterized by a relatively low accessible porosity. The accessible pore volume without taking into account the volume of the gas flow channels is generally over about 0.01 cubic centimeters each Grams of the skeletal structure, preferably between about 0.03 and 0.3 cc / g.

The walls of the channels of the one-piece ceramic support structures that use according to the invention *. contain a large number of surface macropores which are in communication with the channels, whereby a considerably increased accessible catalyst surface and practically the absence of small pores for high temperature stability and strength is obtained. While the F3 ächesibereir-h on the surface of such structures iron the order of magnitude of about ο, οοΐ l »ir o, ol Bi ² Zg including d, r cannula is de? Total curses are typically many. Times larger so that a large part of the catalytic reaction can take place in the large pores. Usually the total accessible area of the carrier is between about 0.1 and 2.0 om ² / g. The skeletal structure has such a macropoion distribution that over 95 I

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of the pore volume are in pores with a diameter greater than about 200 Angstrom units »

The total geometric or seemingly rigid surface area of the carrier, including the walls of the gas flow channels, is often about 0.5 to 12, preferably 1-7 square meters per liter of the carrier. The channels through the ceramic carrier can be of any shape and size that is compatible with the desired area on the surface and should be sufficiently large to allow the combustible gas mixture to pass freely. The channels can be parallel or essentially parallel and extend through the support from one side to an opposite side, which openings are separated by preferably thin walls that delimit the opening A network of channels penetrate the body and form an unused gas path through the ceramic material. The channels and outlet openings are distributed over the entire end face or the entire cross section of the support. The preferred ones used in the catalytic radiators according to the invention MuIlIt ceramic carrier are made of zircon, ₀ Mnllit "silicic acid, _alpha-D Alurainiuaoxyd Alueiniuraoxyd-Siliciumdioxrd-magnesium oxide and zirconium silicate, examples of other

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refractory crystalline ceramic materials "which instead of the preferred materials used as a carrier are sillimanite, magnesium silicate, zircon, Petalite, spun, cordierite and aluminum silicates. '

The refractory metal oxide is deposited on the porous one-piece ceramic carrier as a continuous thin deposit or as a discontinuous thin deposit, preferably with a thickness of about, ο, οΐο mis to «, o2S m (about o _t ooo4 '* to o, oo1 **) deposited. This catalytic material is a calcined refractory metal oxide, which in turn is characterized by a porous structure and has a large internal pore volume and a large total surface area. Generally, the total surface area of the refractory metal oxide is at least about 10 square meters / g, preferably at least about 100 square meters / g. Such oxides can n by a preferably substantially complete dehydration d t hydrate £ pra wsji'd of the oxide prepared by Kaisinieron usually at Temperature "from about ⁰ C to ISo 8oo ° C ^. The preferred active metal oxides contain members of the poailio des gamma or activated aluminum oxide, which, for example, by precipitation of a water-containing aluminum oxide gel and

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followed by drying and calcining can be made to drive out the water of hydration and active gamma-aluminum oxide produces "Bin particularly preferred active refractory metal oxide is obtained by drying and calcining at temperatures of about 3oo ° C to 800 ⁰ C a mixture of output phases of hydrated aluminum oxide in the form of of a crystalline trihydrate, ie containing more than about 50 t of the total aluminum oxide hydrate mass, preferably about 65 t to 95%, of the trihydrate forms gibbsite, bayerite and north strandite by X-ray diffraction. The essential residue of the hydrate preferably, about 35 t • SI may amorphous hydrate "or monohydrate boehmite alumina be _0. The calcination of the hydrous output aluminum oxide is preferably ro regulated that the obtained Gamna-alumina monohydrate alumina contains * in an amount which is essentially equivalent to that originally present in the mixture of the high trihydrate starting phases of hydrous alumina. Other suitable catalytic refractory metal oxides, for example, active or calcined beryllium oxide, zirconium oxide, Magnesiuaoxyd _p Siliciuradioxyd etc., and combinations of metal oxides such as boron oxide-aluminum ". minium oxide, silicon dioxide-aluminum oxide, thorium oxide-aluminum oxide etc. Preferably, the activated fire-

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solid oxide composed predominantly of oxides one or several metals of groups II, III and IV with atomic numbers, do not exceed the 4o. The precipitate of active refractory metal oxide can be about Io - 300 g per liter of the ceramic carrier, preferably about 3o "- 12o g per liter.

The active refractory metal oxide can be deposited on the support in a number of ways. A procedure consists in immersing the support in a solution of the salt of the refractory metal su and calcining it to to decompose the salt into the oxide form. Even more preferred is a method in which. which the carrier in oine aqueous Suspension, dispersion or slurry of the refractory Oxydes itself is dipped and then dried and calcined. In this process suspensions, «the Dispersions with a solids content in the range of, ** wa Io - 7ο wt. I used to make a suitable amount., of a refractory metal oxide on the carrier for a single Knock down application. For the production of a., Catalyst with Io I activated aluminum oxide on a Eirkon-Mullite structure will be about 2o I to 4o I solids Used in suspension. The percentage of solids (content is based on the weight after firing (Hai

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HoO ⁰ C) determined. Generally werder. Kalzinievungstemporaturen used that are within the range of about 15o ° C to 800 ⁰ C. The calciner is low in air, for example in flowing dry air _c carried out or may be in contact with other gases such as oxygen "nitrogen, hydrogen, flue gas, etc. or under vacuum condition. The fiery oxide is deposited on the surfaces. skeletal structure including the ksinal surfaces and the surfaces of the surface mocropores, which are in connection with the canal surfaces, in the form of thin precipitates with an amount of about 1%! and preferably cut off 5 - 30% by weight of the skeletal structure.

The gas ventilation ducts on a one-piece ceramic carrier deposited on the catalyst are thin-walled ducts in the present case, which give a large surface area. The walls of the cellular channels are generally of the minimum thickness required for a tough one-piece body . This Wanddickc is usually in the range of about o, o5 to o, 25 mm (about o _f oo2 up ο, οΐο **) · With this wall thickness contained the structures of about 25 - or very 2Soo gas or Ströaungskanal-BIII, Bottle openings 6.45 cm ² (J square inches) and a corresponding one

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Number of gas flow tubes, preferably about 100 - 2,000 inlet and flow channels, each 6.45 cm ² (per square inch). The open area should be greater than 60 l of the total area. The size and dimensions of the ceramic carrier according to the invention can be changed in the desired manner within wide limits.

The catalyst supports which make up the plurality of gas flow channels can be made from any of the aforementioned refractory ceramic materials. A method of making such supports is by spray application. Dipping or brushing? "Lner suspension of the powder £ örmigon ceramic material uad an organic Binöemitt ^ ls, eg Guwrai arabic, Koio ~ phonium, acrylate, Methncrylathane, Alkylh" rze _t phenolic resins or "in chlorinated ·· paraffin, on each side of a plurality of flexible organic film, for example made of cellulose, acrylic paper, flounder, nylon cloth or polyethylene film. Several of the door foils coated in this way are then corrugated, for example by curling, filling or multiple folding of the foils, while the remaining sized carrier foils are in their original flat shape

State to be left. The coated corrugated and

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flat foils are then alternately laid one on top of the other. The multilayer structure obtained is then Burned in a furnace at a great speed, to prevent breakage from thermal shock, and on a temperature sufficiently high to sinter the ceramic particles into an integral structure.

During the Brennans, the organic binders are used

removed by decomposition or volatilization. Am such

Manufacturing process is In the British patent

882,484 described · The porous, inert ·, one-piece, solid and refractory supports of ikelet-like structure with the

A large number of Gasströmvaigskaaäle is also on the market

from Minnesota Mining Manufacturing Company eel time regards "bsr _e which the carriers with seven to eleven" Wellunfen "

each linearΐ »inch (25.4 mm) delivers. The platinum group (

tall, s.B, platinum or palladium, can * on the carrier be so depressed that the amf stored kata «w lysator about 0.1 to Io t metal and preferably Q * 4 £ 2 I metal based on the total weight of the catalyst plus the carrier may contain. The catalytic ^

Metal is preferably applied immediately to ¹ den

Refractory metal oxide activated carrier knocked down.

Bas precipitation of the catalytically active metal

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The ceramic carrier can be done by immersing the skeletal structure, preferably with the refractory metal oxide deposited thereon, in an aqueous solution of a water-soluble inorganic salt or water-soluble inorganic string of the particular metal or metal, whereupon the mixture is left unmoved and the metal or metals, usually in a chemically combined state and xB as oxide, are deposited on the skeletal structure acting gas, eg, K _2, is contacted at an elevated temperature of between about loo ° and U00 ⁰ C in Xontakt.

The catalvt hot jets with radiating catalyst surfaces are manufactured sweckmtsslg with about 11 to zoo mm ("tws 1 ** to 8 ^N ) in their largest dimension, although froer units can also be used using a large number of olatolligen trig". For most purposes, and to avoid the need for internal space, dimensions of about ^{1 to} 2 (about 2 to 4) are preferred. The depth of the BieMmvabemkatalysato **

can carry about 25 mn (1 ") or more, however

Lows "/ ob less than 12.7 ram (1/2") and more than 1.6 in

(1/16 ^M ) in more detail & position end. Oils depths of about 6.35 to hiiben ice especially on aufrieinsteilend (1/4 ") proved

and are usually preferred · |

The fuels used by the invented catalytic radiant heaters can be a gas, a vapor, atomized liquid or the like and can be replaced by volatile hydrocarbons, including straight-chain hydrocarbons, such as lower alkanes, for example xthane, propane, butane, heptane and the like. Other usable fuels are aromatic hydrocarbons such as benzene, cycloparaffins "as cyclohexane, acetylene, alcohols," such as lower alkynol, for example, methanol, ethanol _D Isopropanel u. Like. ..

These fuels can be old air or tine »containing oxygen Gas with a wide range of oxygen-fuel ratio se are mixed up. In general, at least stoichiometric amounts of oxygen are preferred - and quantities of 4 # m o, 2 - to 2o times the stoichioaetrischti Quantities are also effectively used. Preferably been about I, o5 or 3 times the stoichlometric amount, Oxygen desired. This is particularly beneficial BATH ORIGINAL

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Feature of the invention. Amount of oxidizing agent for example air, can be used according to the invention in which the known etalyt radiant heaters oin flashback would occur if little oxy chemical agent is used, and the flames are drawn up or extinguished when large amounts of oxidant are used be used, g.B. twice the stoichiometric Amount, especially when the oxidizing surface is exposed to a light cross wind. The described hot radiators according to the invention were air velocities from 40 mph (64.5 km / h) across the surface of the ceramic Blocks exposed without flamxing blows.

The erfiftdungsgoafissen radiant heaters are best used in the way set in motion that less than normal Operating quantities of oxidizing agent are used. this makes possible a very rapid increase in the temperature of the cold catalyst. After approaching the operating temperature the amount of oxidizing agent can be adjusted so that the desired oxidizing agent-fuel ratio is obtained.

The new flammenloee catalytic heater according to Finding has another desirable feature

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times, namely the auto-ignition, wean a flammable Mixture is supplied even up to about 4 minutes after the heater has been switched off »This is done the heat retention by the catalyst support and by the very high activity of the catalyst required. This feature applies to the use of the radiant heater according to the invention very simple and useful in applications that his require intermittent use

As mentioned, the throttling ratio (turn-down ratio) of the radiant heaters described is very broad in the range of about 100: 1. This range is considerably larger than that for other flameless heating devices. The mentioned feature enables the use of a single heating device for the one application * case which requires heating with one device using only about 586o kcal / m ² (about 15 BTO / in ² ), as well as for a second application, the one Radiant heater capacity of 586,000 kcal / m ^{2 (15oo BTÜ / in 2} ) is necessary.

Brief description of the drawing. Fig. 1 is a side view of the inventive catalytic

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B-967

Radiant heater. A genic of fuel like propane and from an oxygen-containing gas, such as air, becomes in introduced a Gan inlet channel 1 of the housing 2 and takes its way to the opening or face 3, on which a catalyst and a ceramic carrier is arranged. This catalyst and the carrier practically fill them entire cross-sectional area of the opening and have the * usually the shape of this surface accordingly. Flg. 2 and

3 show two of the different shapes that make up the cross-section surface on the front of the housing and the ceramic carrier in this. The parallel channels

4 of the carrier and the catalyst 5 are in the direction the gas flow arranged. The one-piece ceramic support block mounts within the front opening of the housing held by suitable means, for which purpose a metal ring loading against the inner wall of the housing is, is satisfactory.

4 shows a side view of a preferred embodiment One of the inventors' principles of catalytics. In the venturi 6, the fuel and the oxidizing agent, e.g. air, are mixed and the combustible mixture is taken its way into the housing 7, whereupon it is ignited on the catalyst carrier 8. The carrier 8 is made by a metal ring

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stand in his position. Openings Io and 11 that are in Housings are provided, serve to suck in air · A pin 12 can be provided to the slide ring which is shown in Fig. 5 in side view and in Fig. 6 in plan view. When the cold burner ignited is, the sliding ring 13 is preferably arranged on the pin, over the inflow of oxidizing agent to restrict the openings 11.

The invention is of course not limited to the embodiments shown and described, but rather can experience various changes within its framework «,

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Claims (1)

■ ·· tt *. I ·. ι B-967 April 26, 1968 Claims { 1.jXatal / t-Hei «strahler xur emission of radiant heat, characterized by (a) a housing with a gas inlet duct and an end face, . , Cb) a Venturi tube adjacent to the gas inlet channel fOr. . the supply of a mixture of a fuel and an oxygen-containing gas into the housing, (c) a catalytically acting burner-emitter block, ..... which is arranged within the end face and. . is essentially formed by 1) a one-piece ceramic carrier block nit. 1 Channels that prevent gas flow through the Blocjc. direct through and 2) a platinum group metal deposited on the support iit. 2. Katalft hot radiator for the emission of radiant heat, -22- 10982A / 0A0 Γ «AO original denotes by (a) a housing with a gas inlet channel and an end face, (b) a venturi adjacent the gas inlet duct for the supply of a mixture of a fuel and an »oxygen-containing gas into the housing, (c) a catalytic burner-radiator block, which is arranged within the end face and in the essential is formed by (1) A one-piece ceramic support block with channels that velcho the gas straining through Direct the carrier through, (2) a refractory metal oxide deposited on the support and (3) a platinum group metal resting on the refractory Metal oxide is knocked down. 3. Radiant heater according to claim 2, characterized in that the one-piece ceramic carrier block contains 25 × 25oo flow channel binlafi openings each 6.45 cm ² (per square inch), BAÖ " ^2S ~ 109824/0401 4. Radiant heater according to claim 3, characterized in that » that the refractory metal oxide is aluminum oxide and the platinum group metal is platinum, 5. Radiant heater according to claim 4, characterized in that the catalytically active Bremer radiator block is formed by a one-piece > m ceramic support block of about 25 x 200 mm (about t "to 8 ^w ) in its largest dimension and 1.6 mm - 25 mm (1/16 "to 1") in depth, whereby the block enables easy self-ignition of the fuel and counteracts a flame retardation. 6. Radiant heater according to claim S _9, characterized in that the housing has a substantially truncated cone shape » 7. Radiant heater according to claim 6, characterized in that that the apex angle of the housing is about 2o ° - 8o °. litt, ¹⁰⁹⁸ 2A / 0401 BATH ORIGINAL 8ο radiant heater according to claim 7, characterized in that the platinum with an amount of o, o5 to Io GeWol based on the total weight of the catalyst plus the like the wearer is depressed " 9. Catalytic heater for emitting radiant heat with a turn-dcwn ratio of about loo to 1 and the possibility of using the 0.2 to 20 times the stoichiometric amount of oxygen, marked by (a) a housing with a »gas inlet feature and an end face, ( (b) a venturi adjacent the G is inlet channel for the supply of a mixture of a fuel and an oxygen-containing gas into the housing, (c) a catalytically active burner radiator block, which is arranged within the end face and is formed by (1) a one-piece ceramic support block nit Channels that allow gas to flow through the block pass through, BATH ORIGINAL -24- 10982Λ / 0Α01 B-967 (2) a refractory metal oxide deposited on the support and (3) a platinum group metal deposited on the refractory metal oxide. Io. Heat radiator according to Claim 9, characterized by Means for limiting the flow of oxygen In the case during the initial ignition. BAO ORIGINAL