DE3311953A1 - Process for making a reactor cylinder for a radiant heater, and reactor cylinder - Google Patents

Abstract

The invention relates to a process for making a reactor cylinder for use in a radiant heater and to a reactor cylinder made by the process. A liquid transport agent is first prepared, which comprises an alumina dispersion, magnesium sulphate, colloidal silica and powdered talc. An antifoam can be added. The alumina dispersion comprises dispersible alumina in a quantity of between about 1 and about 5% by weight, an acid in a quantity of up to about 0.2% by weight and water between about 10 to about 30% by weight, all percentages by weight being based on the weight of the liquid transport agent. The alumina dispersion is then diluted by further addition of water to between about 40 and about 80% by weight. Up to about 4% by weight of magnesium sulphate, colloidal silica in a quantity of up to about 10% by weight and powdered talc in a quantity of between about 0.0001 and about 0.1% by weight are added to the diluted alumina dispersion. A composition of solid alumina fibres and silica fibres is then added to the transport agent in a ratio of about 2.64 g of solid fibre per litre of transport agent (10 g of fibre/ gallon of transport agent). The mixture or suspension is then comminuted, mixed and formed in vacuo on a mandrel to form the reactor cylinder.

Description

Laurence B. Craig, 116 Duck Pond Road, Glen Cove, Ν.Υ., υΐ Alfred J. Farina, 1939 Anita Court, Baldwin, N.Y., USA

Process for producing a reactor cylinder for radiant heating, as well as reactor cylinder

The invention relates to a method for producing a reactor cylinder for radiant heating as well as a reactor cylinder for use in a.r Radiant heating.

The present invention thus relates generally to a thermocatalytic reactor of the type shown in Radiant heating units is used and a method to manufacture the same.

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Hiiro Bremen / Bremen Office:

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llullcrallee 3Λ D-2800 Bremen 1
Telephone: (04 21) 34 90 71
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Accounts Bremen:
Bremer Bank. Bremen
(BLZ 29080010) 100144900
Deutsche Bank. Bremen
(BLZ 29070050) 1112002

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P.O. Box / P. O. Box 22 OI37 *

Schlotthauerstraße 3, D-8000 Munich 22; Telephone: (089) 22 33 U!

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The reactor of the present invention is particularly for use in a radiant heating furnace of the flameless gas combustion type. In such heaters, a thermocatalytic reaction occurs on or near the outer surface of a maintaining the thermocatalytic reactor cylinder, which causes it to glow and, accordingly, to give off - radiant energy ".

An example of such a flameless radiant heater that uses a thermocatalytic The reactor is included in U.S. Patent No. 3,275,497, entitled "Method of Shaping a Combustion Element made of ceramic fibers on a porous carrier ", which on September 25, 1966 Gerhard Weiss et al, the contents of which are expressly incorporated into the present description and by Reference to it is incorporated.

In the case of such radiant heating systems, the thermocatalytic reactor typically forms a fireproof one Cylinder enclosed at one end. A multitude of individual, amorphous-inorganic fibers' are usually arranged in the homogeneous, porous wall structure of the reactor cylinder. The open one The end of the reactor cylinder is usually placed on a hollow fitting - which extends through a Metal reflector extends. A combustible air / gas mixture is then passed through the center of the cylinder passed, the pores of the reactor cylinder wall, the outer surface of the same when burned to glow cause. Reactors of this type typically remain thermally stable at relatively long periods of time high operating temperatures.

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The aforementioned combustion reaction is flameless and due to the relatively low thermal The conductivity of the reactor cylinder does not find any flashback of the reaction into the interior of the reactor cylinder instead of. There is a relatively high percentage of thermal energy given off by the reactor cylinder Radiant energy.

Heretofore, combustion reactor cylinders of this type have been manufactured by a process which includes the addition a filling or binding material,

included during manufacture to bind the reactive components together. For example, as described in U.S. Patent No. 3,275,496, the components of the cylinders, including alumina and colloidal silica, were mixed in a molding bath and then dispersed in water. An aqueous solution of aluminum nitrate was then added to form a gel which was then further diluted in water. Chopped fibers made from a melt of aluminum oxide Al ₃ O ₃ and silicon dioxide SiO were then added to form a slurry. A preferred fiber has been obtained from kaolin. A filler or binder, such as methyl methacrylate, was then added to chemically bond the aluminum fibers and silica.

The slurry was then formed into a reactor cylinder by gluing it onto a mesh mounted on a stretcher which became the inner tube of the reactor cylinder. This inner tube would typically be connected to the suction line of a pump during the shaping of the cylinder and be inserted into the gel mold ¹ for a sufficiently long time.

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• immersed to a suitable

Deposit amount of gel on the mesh to form the reactor cylinder-shaped. After removal from the bath of the cylinder at a temperature between about 60 ⁰ C (140 ⁰ F) and about 65.5 ⁰ C was dried (150 ⁰ F) between about 10 and about 60 minutes. After drying, the reactor cylinder was then placed in a furnace at relatively high temperatures baked namely above 593.5 ° C (1100 ° F) _f to the methyl methacrylate to sublimate binder. In this prior art process, the oven heating process was a necessary step because the binder had to be sublimed. However, heating to such temperatures had adverse effects on the aluminum oxide fibers located in the reactor cylinder. At temperatures below about 982.2 ° C (1800 ⁰ F), the Alumxniumoxidfasern were generally either the gamma or Thetaphase or a combination thereof. At temperatures above 982.2 ⁰ C (1800 ⁰ F) the Alumxniumoxidfasern undergo a further phase conversion step in the alpha phase. As alumina changes from gamma to theta and then to alpha, there is a tendency for the aluminum fibers to condense, reducing the porosity and available surface area of the resulting reactor cylinder.

It was recognized in Patent No. 3,275,497 that usually the phase of alumina fiber in the reactor cylinder had little, if any, effect on its operating characteristics. In certain cases Nevertheless, the gamma phase of aluminum oxide is preferred, especially when catalytic agents to the bath to deposit on the surface of the fibers

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were added due to its generally higher surface area to mass * ratio.

As previously mentioned, it is preferred that the reactor cylinder be porous and have as large a surface area as possible in order that it will serve as a very efficient source of combustion. Accordingly, it is preferred that whenever possible, the alumina in the reactor cylinder be primarily in the gamma or theta phase rather than the denser alpha phase. This has hitherto been impossible, whereby a reactor originated cylinder due to the fact that the binder at temperatures above 593.3 ⁰ C (110o F ⁰⁾ to be sublimated, the more dense and less porous than was optimal than preferred.

It is therefore a main object of the invention to use a binderless thermocatalytic reactor cylinder in a radiant heater of the flameless gas combustion type. It's another goal of the Invention of providing such a reactor cylinder, which has powdered talc as a component.

It is another object of the invention to provide such a reactor cylinder which is more porous and which is one has a larger surface area than the previously used binder-containing reactor cylinders.

It is another object of the present invention to achieve a reactor cylinder containing alumina fibers mainly in the gamma phase.

It is a further object of the present invention to provide a method for producing such a reactor

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To create cylinder.

The object of the invention is achieved by a method which is characterized in that the Cylinder is formed by the following process:

Prepare a liquid vehicle that is an alumina dispersion comprised between about 1 to about 5% by weight of the total vehicle encloses dispersible alumina; up to about 0.2% by weight of all means of transport acid; and between about 10 to about 30 weight percent of the total transportation means Has water;

Dilute the dispersion by adding between about 40 to about 80 percent by weight of the total vehicle Water to form the vehicle;

Adding the following material to the means of transport, the amounts being in% by weight of the total carrier material specified are:

Colloidal silica up to about 10% by weight; and powdered talc between about 1,0001 and 0.1 weight percent;

Blending a combination of solid alumina and silica fibers in a proportion of grams Fibers to liters of liquid from between about 2.1: 1 to about 3.2: 1 (2.1g / gallon to 12g / gallon)

Mixing the solid fibers and liquid vehicle to form a slurry and

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Vacuum forming the slurry around a mandrel to to shape the reactor cylinder.

The process of the invention thus seeks to create a better reactor cylinder that is molded without a binder. This allows elimination of the step of heating the cylinder in a furnace at temperatures above 593.3 ⁰ C (1100 ⁰ F), heating to sublimate the binder, whereby a denser and less porous than the reactor preferably in the best case, is produced. This was achieved by adding powdered talc. The resulting binderless reactor cylinder, molded at ambient temperature, therefore, includes alumina fiber in the less dense gamma phase. Accordingly, the reactor cylinder of the present invention is more porous and has a greater surface area to weight ratio than the previously used reactor cylinders.

Further features and advantages of the invention emerge from the claims and from the following Description in which exemplary embodiments are explained.

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The thermocatalytic reactor according to the invention is for use as a burner in a flameless radiant heater of the type described, for example, in U.S. Patent No. 3,275,497, and is accordingly as a combustion or reactor cylinder for installation in such a heater.

The present reactor cylinder is made by by using a liquid transport medium, which is an aluminum oxide dispersion, magnesium sulfate, colloidal silicon dioxide, water, powdered talc and preferably tributyl sulfate is produced as an anti-foaming agent. The means of transport is then marked with " a composition of alumina and silica fibers mixed together to form a slurry, which is formed around a net mandrel · Vacuum, around the reactor cylinder to build.

The aluminum oxide dispersion is first prepared by mixing dispersible aluminum oxide with water and an acid. A preferred dispersible alumina is sold by the Remet Corporation of Chadwicks, New Youk under the trademark "Dispal ¹ * -". A preferred acid "is hydrochloric acid, most preferably at 37% concentration.

During the production of the aluminum oxide dispersion, Water in an amount between about 10 and about 30% by weight, calculated on the weight of the total transport liquid, mixed with an amount of acid sufficient to maintain a desired pH in the resultant to obtain liquid means of transport. It is preferred that the pH of the vehicle is between about 4 and about 6, preferably about

For example, it has been found that it is necessary to add 37% hydrochloric acid to the water in an amount between about 0.1 and about 0.2% by weight _; calculated on the basis of the weight of the total transport liquid to be added to the water. A particularly preferred amount of 37% hydrochloric acid is between about 0.15 and about 0.2% by weight.

The dispersible alumina is then added to this water / acid mixture in an amount up to about 5% by weight based on the weight of the total means of transport and preferably in an amount between about 1 and 5% by weight added. A particularly preferred amount of dispersible alumina is about 2%, which is sufficient to produce a 10% alumina dispersion.

The alumina dispersion is then prepared by adding water in an amount between about 40 and about 80%, calculated on the total weight of the means of transport, diluted. . "

The aluminum oxide dispersion is preferably diluted in water in an amount between about 60 and 70% by weight and more preferably in an amount between about 65 and about 70 weight percent.

After dilution of the aluminum oxide dispersion, magnesium sulfate is added in an amount of up to about 4% by weight, calculated on the basis of the total weight of the means of transport, added. A preferred amount of magnesium sulfate is between about 1 and 2 percent by weight, and a particularly preferred amount is between about 1 and about 1.5% by weight.

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The mixture is then stabilized for some time, preferably overnight, after which it is thixotropic will.

After stabilization, colloidal silicon dioxide is used in an amount up to about 10% by weight, calculated on the Weight of total vehicle added to the mixture, followed by vigorous stirring.

A preferred colloidal silica is made by E.I. DuPont de Nemours of Wilmington, Delaware under under the trademark "Ludox AG". Preferably the colloidal silica is used in an amount between about 5 and about 8 wt .-% added, and particularly preferably in an amount between about 6 and about 7 wt .-%

Powdered talc is then added in an amount sufficient to cause the solid fiber portion to stick together to cause added to the mixture. Powdered talc is preferred in an amount between about 0.0001 and about 0.1% by weight, calculated on the basis of the weight of the entire transport medium, are added. A particularly preferred amount of powdered talc is between about 0.0001 and about 0.0002%. It is found that the addition of powdered talc in the above-mentioned amount molding the reactor cylinder made possible without adding the previously required methyl methacrylate filler or binder. Much more if the filler or the binder is omitted, it becomes unnecessary to use the filler or the binder at increased levels To sublime or decompose temperatures, whereby a phase change of the aluminum oxide takes place.

BOEHMEET & BOEHMERT

After addition of powdered the talc and vigorous stirring, the liquid vehicle may be an undesirable amount of entrapped air containing _If it may therefore be desirable to vent the means of transport by the addition of a defoaming agent 3 such as tributyl phosphate in sufficient quantity to eliminate the trapped air, preferably in an amount up to about 5ccm / 3.7 8543 liters (gallons) of the liquid vehicle. A preferred amount of defoamer. - "is about 2ccm per 3.78543 1 (gallon) After adding the" defoamer, the transport agent is mixed further until the remaining bubbles are eliminated. The transport agent, which is then ready to take up the solid aluminum oxide and the silicon dioxide fibers, should have a pH of between about 4 and about 6, preferably of about 5, and a specific gravity above about 1.00.

The proportion of solid fibers consists of a mixture of aluminum oxide and silicon dioxide fibers, which are approximately 2% aluminum. A preferred source of the alumina and silica fibers is an im Commercially available product sold by the Johns Manville Corporation under the tradename "Cerachrome" is distributed.

The solid fiber portion is added to the liquid means of transport and mixed. Approximately 2.252362 1 (2/3 gallon) of the liquid vehicle becomes about 10g of the alumina and silica solid fiber ' portion given. The mixture is then mixed and chopped for a time, followed by the addition of a

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additional liquid transport to the total amount of the resulting slurry to about 3.7543 1 (1 gallon). A preferred relationship Gram of solid fiber to liter of liquid vehicle is between about 2.1 to 1 and about 3 to 1 and preferably about 2.6 to 1 (between about 8g to a gallon and about 12g to a. gallon and preferably around 10g to 1 gallon). '

The reactor cylinder - is molded from the slurry prepared above in a manner similar to the vacuum molding process described in U.S. Patent No. 3,275,497. A vacuum tank and a vacuum pump are required. A preferred vacuum pump is the Gast 1022-103-G272X model or equivalent, and a preferred vacuum tank is a 37.85 1 modal stainless steel (10 gallon) equipped with a vacuum gauge that measures 0 to 762mm of mercury (0 -30 inches), a sight tube for the liquid level, a check valve and a drain valve. What is also needed is a tank for forming the slurry, preferably having a "capacity of at least 26.5 liters (7 gallons), two pieces of vacuum tubing, and a ketz-arm door that is closed at one end and with a gas / air supply tube at the." The mesh is preferably formed around a mandrel 1> 59cm in diameter and is preferably made of stainless steel with a mesh of 0.4064cm (0.61 inches) 20x20 inches _/ the gas / air supply tube is preferably 1 , 59cm in diameter (0.625 inches) and made of stainless steel.

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To carry out the procedure, one of the hoses is inserted into the outlet of the vacuum tank to the inlet of the vacuum pump and the other hose to the inlet of the Connect the vacuum tank to the gas / air supply pipe at the end of the network fitting. Approximately 18.93 1 (5 gallons) of the slurry is poured into the slurry forming tank. After starting the Vacuum pump, the mains fitting in the tank is approximated vertically and approximately within 5.08cm (2 inches) of the bottom of the tank. The sieve fitting is held in the tank in the position until the vacuum gauge reaches 609.6mm (24 inches) of mercury, at which point it will pulled out while maintaining the vacuum. In this way the slurry becomes formed around the Siebarmatur, and so the shaped Reactor cylinder manufactured.

The vacuum pump is kept in operation until the vacuum measuring device measures about 100 mm of mercury (4th inches), whereupon it is disconnected and the reactor cylinder is disconnected from the vacuum hose. The reactor cylinder is then stored, the check valve opened, and the depleted slurry . ■ drained. '

For subsequent manufacture of reactor cylinders fresh network fittings are used.

While the reactor cylinder is still wet and relatively soft, its surface is broken up into small areas.

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splits to break lines of thermal stress during combustion that can cause it to fall off the surface. This can be achieved, for example, by pressing a mold into the reactor cylinder surface. It can also be achieved by inserting the gas / air supply tube of the reactor cylinder into the chuck of a lathe and using a standard suture thread in a continuous spiral with a pitch of about 0.3175 cm (0.125 inches) and pretensioned to make a cut of about zero , 0762cm (0.030 inches) is wound. The free end of the thread can be secured by conventional means such as tying, tying, or adhesive tape, after which the reactor cylinder is removed from the lathe. The thread will burn off during the first ignition, with its pattern remaining permanently imprinted on the surface of the reactor cylinder.

The reactor cylinder is then placed on a shelf support and allowed to dry, after which it is ready for use is. Heating up in an oven, as was previously necessary, is unnecessary. ,

The following examples serve to and are intended to describe the process according to the invention in more detail should not be understood to limit the scope of protection.

example 1

The reactor cylinder of the present invention was made produced by first making a 10% strength aluminum oxide dispersion by mixing 3500 g of water with 30g of 37% hydrochloric acid was prepared, followed by

Addition of 392g "Dispal" ®, the dispersible one Alumina. 4000 g of the resulting 10% strength alumina dispersion were then converted into 1200 g Diluted water and added 200g magnesium sulfate. After stabilizing overnight, a thixotropic gel. 1200g "Ludox AG" colloidal silicon dioxide was added to the gel and mixed thoroughly, followed by the addition of 0.0793g powdered talc per liter of gel (0.3g talc per gallon of gel). 2ccm Tributyl phosphate was added as a defoamer, and the liquid means of transport was produced in this way.

2.52 liters (2/3 gallon) of the liquid vehicle was transferred to a Waring blender, followed by the addition of 10g "Cerachrome" aluminum oxide and silicon oxide fiber .. · The mixture was at-- lower Speed 15 seconds chopped and 90 seconds at high speed .. Additional Liquid vehicle was added to bring the total to 3.785 liters (1 gallon) ^ followed by vigorous mixing to form a slurry. . .

18.93 liters (5 gallons) of the slurry was placed in a 26.5 liters (7 gallons) slurry form tank. The reactor cylinder was closed at one end around a fitting made of stainless steel wire mesh of 0.04 cm, 20x20 mesh, formed _r -4md to a gas / air-

1.5875cm (0.625 inches) outside diameter feed tube connected. Inside the gas / air supply tube that was immersed in the slurry, Vacuum pulled until a pressure of 636mm (25 inches) was achieved. At this point the pipe was pulled out, the vacuum turned off and the reactor cylinder from the

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Vacuum pump removed. The resulting reactor cylinder was allowed to dry, whereupon this was ready to use. It showed all of the properties of a commercially acceptable reactor cylinder .

Example 2

The procedure of Example 1 was followed except that no powdered talc was added to the liquid Carrier was given. The resulting reactor cylinder was not commercially acceptable as it could not be formed around the air / gas mandrel.

Although the above examples have certain features of the novel product and method according to the invention describe, it is of course to be assumed that the teaching of the invention is broader and different Combinations than those listed in the examples includes. Accordingly, it is intended that the present invention be determined only by the scope of the appended claims be limited. .

Claims (14)

CM 1840 Expectations M J Method of making a reactor cylinder
for radiant heating, characterized in that it has the following steps: Manufacture of a liquid means of transport that
an alumina dispersion containing between about 1 to
about 5% by weight of the total vehicle encloses dispersible alumina; up to about 0.2% by weight of the total vehicle acid; and between about 10 to about 30 weight percent of the total transportation means
Has water; Dilute the dispersion by adding between about 40 to about 80 percent by weight of the total vehicle
Water to form the vehicle; Adding the following material to the means of transport, wherein the amounts are in% by weight of the total carrier material ■ specified are: Colloidal silica up to about 10% by weight; and
powdered talc between about 0.0001 and 0.1 weight percent; Mixing a combination of solid alumina-813 BOEHMERi & ßÖEHMERT ^: -. ^: ^? 1 1 Q ^ and silica fibers in a ratio of Grams of fiber to liter of liquid of between about 2.1: 1 to about 3.2: 1 (2.1 g / gallon to 12 g / gallon); Mixing the solid fibers and the liquid vehicle to make a slurry ^ and Vacuum forming the slurry around a mandrel around the Shaping reactor cylinder. 2. The method according to claim 1, characterized in that the aluminum oxide dispersion is about 10% Alumina dispersion is. 3. The method of claim 2, wherein dispersible alumina in an amount between about 1 and about 3 wt .-% is added. 4. The method according to claim 1, characterized in that the acid is hydrochloric acid in a sufficient amount is to lower the pH of the liquid vehicle to between about 4 and about 6. 5. The method according to claim 1, characterized in that magnesium sulfate in an amount between about 1 and about 1.5% by weight is added. 6. The method according to claim 1, characterized in that powdered talc in an amount between about 0.0001 and about 0.0002 wt% is added. 7. The method according to claim 1, characterized in that that a defoaming agent is added to the liquid transport means in '■ sufficient amount to prevent any to eliminate entrained air. 8. Reactor cylinder for use in radiant heating ., Characterized in that the cylinder is shaped by the following process: Prepare a liquid vehicle that is an alumina dispersion comprised between about 1 to about 5% by weight of the total vehicle encloses dispersible alumina; up to about 0.2% by weight of all means of transport acid; and between about 10 to about 30 weight percent of the total transportation means Has water; Dilute the dispersion by adding between about 40 to about 80 percent by weight of the total vehicle Water to form the means of transport; Adding the following material to the means of transport, the amounts being in% by weight of the total carrier material ■ | specified are: Colloidal silica up to about 10% by weight; and powdered talc between about 0.0001 and 0.1 weight percent; Blending a combination of solid alumina and silica fibers in a proportion of grams of fibers to liters of liquid of between about 2.1: 1 to about 3.2: 1 (2.1 g / gallon to 12 g / gallon); Mixing the solid fibers and the liquid transport means to make a slurry and BOEMiMER :! & BOEHMEST -. ^: Ί Ί 1 1 9 ^ Vacuum forming the slurry around a mandrel around the Shaping reactor cylinder. 9. reactor cylinder according to claim 8, characterized in that that the alumina dispersion is an approximately 10% alumina dispersion. ..1O. Reactor cylinder according to Claim 9 ', characterized in that that the dispersible alumina is added in an amount between about 1 and about 3 percent by weight. 11. Reactor cylinder according to claim 8, characterized in that the acid is hydrochloric acid, which is sufficient in a Amount is added to lower the pH of the liquid vehicle to between about 4 and about 6. 12. Reactor cylinder according to claim 8, characterized in that the magnesium sulfate in an amount 'between about 1 and about 1.5 weight percent is added. 13. Reactor cylinder according to claim 8, characterized in that the powdered talc in an amount between about 0.0001 and about 0.0002 weight percent is added. , "· -; ■ '.-' ■ - 14. Reactor cylinder according to claim "8", characterized in that the defoaming agent is added to the liquid vehicle in an amount sufficient to prevent any To eliminate air.