SE436024B - Reactor cylinder for use in a radiator and method for manufacture of the reactor cylinder - Google Patents

Abstract

The invention is a method for manufacturing a reactor cylinder for use in a radiant heater and the reactor cylinder produced by said method. To start, a liquid-state medium is prepared that includes an alumina dispersion, magnesium sulphate, colloidal silica and powdered talc. An anti-foam agent can also be added. The alumina dispersion includes approx. 1 to 5 percent by weight of alumina, up to approx. 0.2 percent by weight of an acid and approx. 10 to 30 percent by weight of water. All percentages are calculated as percent by weight based on the weight of the liquid-state medium. The alumina dispersion is further diluted by adding approx. 40 to 80 percent by weight of water. The following is then added to the diluted alumina dispersion: approx. 4 percent by weight of magnesium sulphate, approx. 10 percent by weight of colloidal silica, and approx. 0.0001 to 0.1 percent by weight of powdered talc. A solid alumina and silica fibre composition is then added to the medium at a ratio of approx. 10 g solid fibre per 3.785 L medium. The mixture or sludge is processed or chopped and then mixed and vacuum-shaped around a drift to form the reactor cylinder.

Description

Combustion reactor cylinders of this type were previously manufactured by a process which included the addition of a filler or binder added during the treatment to chemically bond the reactive components together. As described in, for example, U.S. Patent No. 3,275,496, the components of the cylinders including alumina and colloidal silica were mixed together in a forming 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, formed from a melt of alumina Al 2 O 3 and silica SiO 2, were then added to form a slurry. A preferred fiber was obtained from kaolin. A filler or binder, such as methyl methacrylate, was then added to chemically bond the alumina fibers and silica together.

The slurry was then formed into a reactor cylinder by adhering around a screen cloth, mounted on a substrate, which became the inner tube of the reactor cylinder. This inner tube would normally be connected during the formation of the cylinder to the suction line of a pump and immersed in the gel-forming bath for a sufficient time to deposit an appropriate amount of the gel on the screen to form the formed reactor cylinder. After removal from the bath, the cylinder was dried at a temperature between about 60 ° C and about 66 ° C for a period of time between about 10 and about 60 minutes. After drying, the reactor cylinder was then baked in a kiln at a relatively high temperature, i.e. in excess of 590 ° C, to sublimate the methyl methacrylate binder.

In this prior art process, the furnace heating step was a necessary process step, since the binder must be sublimated. However, heating to such high temperatures had a detrimental effect on the alumina fibers placed in the reactor cylinder. At temperatures below about 980 ° C, the alumina fibers were usually in either the gamma or theta phase or in a combination thereof.

However, at temperatures above 980 ° C, the alumina fibers undergo a continuous phase conversion to the alpha phase. In connection with the conversion of the alumina from gamma to theta and then to alpha, there is a tendency for the alumina fibers to be compressed, thereby reducing the porosity and available surface area of the obtained reactor cylinder. azo17a9-7 U.S. Pat. No. 3,275,497 discloses that the phase of the alumina fibers in the reactor cylinder normally has little, if any, effect on its operating properties. However, in some situations, especially when catalytic agents were added to the bath for deposition on the surface of the fibers, the gamma phase of the alumina was preferred due to its generally higher surface / mass ratio.

As previously pointed out, it is preferred that the reactor cylinder be porous and provide as large a surface area as possible in order to function as a fuel source in the most efficient and conceivable manner. Thus, when possible, it is preferred that the alumina in the reactor cylinder be present primarily in the gamma or theta phases rather than in the denser alpha phase. This has hitherto been impossible due to the fact that the binder had to be sublimated at temperatures above 60 DEG C., which resulted in a reactor cylinder which was denser and less porous than is optimally preferred.

The process of the present invention seeks to provide a more optimal reactor cylinder designed without any binder.

This allows the elimination of the step of heating the cylinder in a kiln to a temperature exceeding 590 ° C to sublimate the binder, which thus produced a denser and less porous reactor than is optimally preferred. This has been achieved by the addition of powdered talc. The resulting binder-free reactor cylinder, designed at ambient temperature, therefore includes alumina fibers in the less dense gamma phase. The reactor cylinder according to the present invention is thus more porous and has a larger surface / weight ratio than reactor cylinders used hitherto.

It is therefore a primary object of the present invention to provide a binder-free, thermocatalytic reactor cylinder for use in a radiant heater of the low operating gas combustion type.

Another object of the present invention is to provide such a reactor cylinder which includes powdered talc as a component therein.

A further object of the present invention is to provide such a reactor cylinder which is more porous and has a larger surface area than the binder-containing reactor cylinders used hitherto.

Furthermore, it is a further object of the present invention to provide such a reactor cylinder which includes alumina fibers primarily in the gamma phase.

Finally, it is yet another object of the present invention to provide a method of manufacturing such a reactor cylinder.

More particularly, the invention relates to a reactor cylinder for use in a radiant heater which is characterized by being shaped; prepares a liquid vehicle, which includes an alumina dispersion, comprising dispersible alumina in an amount between about 1% and about 5%, by weight of the vehicle as a whole, hydrochloric acid in an amount between about 0.1 and about 0.2 weight % and water in an amount between about 10 and about 30% by weight, dilute the dispersion by adding water in an amount between about 40 and about 80% by weight, add the following materials to the diluted dispersion, magnesium sulfate in a amount between about 1% and about 4% by weight, colloidal silica in an amount between about 5 and about 10% by weight, and powdered talc in an amount between about 0.000l and about 0.1% by weight, with said liquid vehicle a combination of solid alumina and silica fibers in a ratio of g solid fibers to 1 liquid vehicle of between about 2, 11: 1 and about 3,17: 1, mix the solid fibers and the liquid vehicle to form a slurry and vacuum forms the slurry around a mandrel to form the reactor cylinder.

The thermocatalytic reactor cylinder of the present invention is intended for use as the combustion source in a low-intensity radiant heater of the type described, for example, in U.S. Pat. in such a heater.

Furthermore, the present invention relates to a method of manufacturing a reactor cylinder as above, thus first preparing a liquid vehicle according to the above-described procedure and then mixing with the liquid vehicle a combination of solid alumina and silica fibers. in a ratio of g fibers to 1 liquid vehicle of between about 2.11: 1 and about 3.17: 1 (g solid fibers = gallons of liquid vehicle about 8: 1 to about 12: 1), the solid fibers and the the liquid vehicle during the formation of a slurry and the vacuum former slurry around a mandrel to form the reactor cylinder.

The actual reactor cylinder is thus formed by preparing a liquid vehicle, including an alumina dispersion, magnesium sulphate, colloidal silica, water, powdered talc and preferably tributyl sulphate as a defoamer. The vehicle is then mixed with a composition of alumina and silica fibers to form a slurry which is vacuum formed around a herring mandrel to form the reactor cylinder.

The alumina dispersion is initially prepared by mixing dispersible alumina with water and hydrochloric acid. A preferred dispersible alumina is marketed by the Remet Corporation of Chadwicks, New York, USA, under the tradename "Dispal".

The hydrochloric acid is preferably used in the form of 37% acid.

In preparing the alumina dispersion, water is mixed in an amount between about 10% and about 30% by weight, based on the weight of the liquid vehicle as a whole, together with a sufficiently large amount of hydrochloric acid to obtain a desired pH in the resulting the liquid vehicle. It is preferred that the pH of the vehicle be between about 4 and about 6, preferably about 5.

For example, to prepare a vehicle having a pH within this range, it has been found necessary to provide the water with a 37% concentration of hydrochloric acid in an amount between about 0.1 and about 0.2% by weight. -%, calculated on the weight of the vehicle as a whole. A particularly preferred amount of a 37% concentration of hydrochloric acid is between about 0.15 and 0.2% by weight.

To this water and acid mixture is then added the dispersible alumina in an amount between about 1% and about 5% by weight, based on the weight of the vehicle as a whole. A special amount of dispersible alumina is about 2%, which is a sufficiently large amount to prepare a 10% dispersion of alumina.

The alumina dispersion is then substantially diluted by adding water in an amount between about 40% and about 80%, based on the weight of the vehicle as a whole. Preferably, the alumina dispersion is diluted in water in an amount between 60 and 70% by weight and most preferably in an amount between about 65 and about 70% by weight.

After diluting the alumina dispersion, magnesium sulphate is added in an amount of between about 1% and about 4% by weight, based on the weight of the vehicle as a whole. A preferred amount of magnesium sulfate is between about 1 and about 2% by weight and a particularly preferred amount is between about 1 and about 1.5% by weight.

The mixture is then stabilized for a certain time, preferably overnight, during which time it becomes thixotropic.

After stabilization, colloidal silica is added to the mixture in an amount between about 5% and about 10% by weight, based on the weight of the vehicle as a whole, after which it is mixed vigorously. A preferred colloidal silica is marketed by E.I. DuPont de Nemours of Wilmington, Delaware, USA under the trade name "Ludox AG".

Preferably, the colloidal silica is added in an amount between about 5 and about 8% by weight and most preferably in an amount between about 6 and about 7% by weight.

Powdered talc in an amount sufficient to cause the solid fiber portion to adhere together is added to the mixture.

In other words, powdered talc is added in an amount between about 0.000 l and about 0.1% by weight, based on the weight of the vehicle as a whole. A particularly preferred amount of powdered talc is between about 0.000l% and about 0.0002%. It has been found that the addition of the powdered talc in the above quantity allows the formation of the reactor cylinder without any addition of the methyl methacrylate filler or binder hitherto required. In addition, due to the elimination of the filler or binder, it no longer becomes necessary to sublimate or degrade the filler or binder at elevated temperatures, which results in a phase conversion of the alumina.

After the introduction of the powdered talc and after vigorous mixing, the liquid vehicle may contain an undesirable amount of entrapped air. It may therefore be desirable to deaerate the vehicle by applying a defoamer, such as tributyl phosphate in an amount sufficient to eliminate the entrapped air, generally in an amount of up to about 5 cm 3 per 3.785 l of liquid vehicle. A preferred amount of defoamer is about 2 cm 3 per 3.785 L. After addition of the defoamer, the vehicle is further mixed until the remaining bubbles are removed. The vehicle, which is then ready to receive the solid alumina and silica fibers, should have a pH between about 4 and about 6, preferably about 5, and a density in excess of about 1.00.

The solid fiber component consists of a mixture of alumina and silica fibers, containing about 2% aluminum. A preferred raw material of the alumina and silica fibers is a commercially available product, which is marketed by Johns Manville Corporation under the tradename "Cerachrome".

The solid fiber portion is added to the liquid vehicle and mixed. About 2.52 l of the liquid vehicle is added to about 10 g of the solid alumina and silica fiber portion.

The mixture is then mixed and chopped for a period of time, after which additional liquid vehicle is added to achieve a total quantity of the resulting slurry of about 3.785 l. A preferred ratio of solid fiber to 1 liquid vehicle is between about 8: 3.785 and about 12: 3,785 and preferably about 10: 3,785, i.e. from about 2,11: 1 to about 3,17: 1 and preferably about 2,64: 1.

The reactor cylinder is formed from the slurry prepared as above in a manner similar to the vacuum forming process described in U.S. Pat. No. 3,275,497. A vacuum tank and a vacuum pump are required. A preferred vacuum pump is the Gast pump model 1022-103-G272X or an equivalent pump and a preferred vacuum tank is a 38 l 8-301789-7 stainless steel tank model, equipped with a vacuum gauge indicating 0 - 760 mm Hg , an inspection pipe for expelling the liquid level, a vacuum shut-off valve and a drain valve. Furthermore, a slurry forming tank is required, preferably with a capacity of 27 l, two lengths of vacuum hose and a strainer fitting around which the reactor cylinder is formed. The strainer fitting is closed at one end and equipped with a gas / air supply pipe at the other end. The screen is preferably formed around a 15.9 mm mandrel and is preferably a stainless steel screen with a mesh size of 4.1 mm, 20 x 20. The gas / air feed pipe is preferably a 15.9 mm outer diameter stainless steel pipe.

To carry out the process, one of the hoses is used to connect the outlet of the vacuum tank to the inlet of the vacuum pump and the other hose is used to connect the inlet of the vacuum tank to the gas / air supply pipe at the end of the strainer.

Approximately 19 l of the slurry is poured into the slurry forming tank. After starting up the vacuum pump, the strainer fitting is inserted into the tank in approximately vertical position and down to a position within approximately 5 cm from the bottom of the tank. The strainer fitting is kept in position in the tank until the vacuum meter reaches 610 mm Hg, at which time it is picked up at the same time as a vacuum is maintained. In this way, the slurry is formed around the strainer fitting, whereby the formed reactor cylinder is produced.

The vacuum pump is maintained in operation until the vacuum meter drops to approximately 102 mm Hg, after which it is switched off and the reactor cylinder is disconnected from the vacuum hose. The reactor cylinder is then stored and the vacuum shut-off valve is opened and the depleted slurry is allowed to drain. New filter fittings are used for subsequent designs of reactor cylinders.

While the reactor cylinder is still wet and relatively soft, its surface is divided into small areas in order to interrupt thermal voltage lines during combustion, which can result in surface flaking. This can be achieved, for example, by forcing a mold into the surface of the reactor cylinder.

It can also be accomplished by placing the gas / air feed pipe of the reactor cylinder in the chuck turn and on this a common sewing thread is wound in a continuous spiral with a pitch of about 8301789-7 3.18 mm and tensioned to achieve a dent of about 0 The free end of the wire can be fixed in a conventional manner, i.e. by tying or taping, and the reactor cylinder is then removed from the lathe. The wire will be burned off during initial ignition, leaving its pattern permanently pressed into the surface of the reactor cylinder.

The reactor cylinder is then placed on a support stand and allowed to dry, after which it is ready for use. No heating step in the kiln, which has hitherto been necessary, is required here.

The following examples are intended to further illustrate the process of the present invention and are not to be construed as limiting the scope of the invention.

Example 1 The reactor cylinder according to the present invention was designed by first preparing a 10% alumina dispersion by mixing 3500 g of water with 30 g of 37% hydrochloric acid with subsequent addition of 392 g of dispersible alumina of the "Dispal" type. 4000 g of the resulting 10% alumina dispersion were then diluted in 12000 <3 water and 200 g of magnesium sulfate was added. After stabilization overnight, a thixotropic gel was obtained. 1200 g of colloidal silica of the "Ludox AG" type were added to the gel and mixed thoroughly, after which 0.3 g of powdered talc per 3.785 l of gel were added with rapid stirring. 2 cm 3 of tributyl phosphate were added as a defoamer, thereby terminating the formation of the liquid vehicle. 2.52 l of the liquid vehicle was introduced into a Waring blender type mixer, after which 10 g of Cerachrome alumina and silica fibers were added. The mixture was chopped at low speed for 15 seconds and at high speed in An additional liquid vehicle was added to achieve a total amount of 3.785 l, after which vigorous mixing was carried out to form a slurry, 19 l of the slurry was placed in a 27 l slurry forming tank. , 20 x 20 mesh, closed at one end, and equipped with a 15.9 mm outer diameter gas / air inlet tube A vacuum was created in the gas / air inlet tube lowered into the slurry and retained therein until At this time, the tube was removed, the vacuum pressure was switched off and the reactor cylinder was separated from the vacuum pump. The resulting reactor cylinder was then allowed to dry and then r ready for use. It exhibited all 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 vehicle. The resulting reactor cylinder formed was not commercially acceptable as it could not be formed around the air / gas mandrel.

Although the foregoing examples illustrate certain features of the novel product and process of the present invention, it will be appreciated, of course, that the tasks in the present application encompass more extensive and other combinations than those set forth in the examples.

Thus, the present invention is to be limited only by the scope of the appended claims.

Claims (14)

10 15 20 25 30 35 Patent claim A reactor cylinder for use in a radiant heater, characterized in that it is designed by: preparing a liquid vehicle, which includes an alumina dispersion, which comprises dispersible alumina in an amount between about 1% and about 5%. % by weight of the vehicle as a whole, hydrochloric acid in an amount between about 0.1 and about 0.2% by weight and water in an amount between about 10 and about 30% by weight, dilute the dispersion by adding water in an amount between about 40 and about 80% by weight, the following materials add to the dilute dispersion magnesium sulphate in an amount between about 1 and about 4% by weight of colloidal silica in an amount between about 5 and about 10% by weight, and powdered talc in an amount between about 0.0001 and about 0.1% by weight, with said liquid vehicle mixing together a combination of solid alumina and silica fibers in a ratio of g solid fibers to 1 liquid vehicle of between about 2, 11: 1 and about 3.17: 1, the solid fibers and the liquid vehicle mix to form a slurry and vacuum form the slurry around a mandrel to form the reactor cylinder. 2. A reactor cylinder according to claim 1, characterized in that the alumina dispersion is an approximately 10% alumina dispersion. A reactor cylinder according to claim 2, characterized in that dispersible alumina is added in an amount between about 1 and about 3% by weight. The reactor cylinder of claim 1, characterized in that the hydrochloric acid is added in an amount sufficient to lower the pH of the liquid vehicle to a value between about 4 and about 6. A reactor cylinder according to claim 1, characterized in that the magnesium sulphate is added in an amount between about 1 and about 1.5% by weight. The reactor cylinder of claim 1, characterized in that the powdered talc is added in an amount between about 0.0001 and about 0.0002% by weight. The reactor cylinder of claim 1, characterized in that a defoamer is added to the liquid vehicle in an amount sufficient to eliminate all trapped air. A method of manufacturing a reactor cylinder according to claim 1 for use in a radiant heater, characterized in that: 111811: preparing a liquid vehicle, which includes an alumina dispersion, comprising dispersible alumina in an amount between about 1% and about 5% , by weight of the vehicle as a whole, hydrochloric acid in an amount of between about 0.1 and about 0.2%, by weight of the vehicle as a whole, and water in an amount of between about 10% and about 30%, based on the weight of the vehicle as a whole, dilute the dispersion by adding water in an amount between about 40% and about 80%, based on the weight of the vehicle as a whole, so that the vehicle formed, add the following materials to the vehicle, based on% by weight of the vehicle as a whole: magnesium sulphate in an amount of between about 1.0 and about 4% by weight of colloidal silica in an amount of between about 5 and about 10% by weight and powdered talc in an amount between about 0.00 01 and about 0.1% by weight, with the liquid vehicle mixing together a combination of solid alumina and silica fibers in a ratio of g fibers to 1 liquid vehicle of between about 2.11: 1 and about 3.17: 1, the solid fibers and the liquid vehicle mix to form a slurry and vacuum form the slurry around a mandrel to form the reactor cylinder. 9. A method according to claim 8, characterized in that the alumina dispersion is about 10% alumina dispersion. 10. A method according to claim 9, characterized in that dispersible alumina is added in an amount between about 1 and about 3% by weight. 11. The method of claim 8, wherein the hydrochloric acid is added in an amount sufficient to lower the pH of the liquid vehicle to between about 4 and about 6. 12. The method of claim 8, wherein the magnesium sulfate is added in an amount between about 1% and about 1.5% by weight. 13. The method of claim 8, wherein the powdered talc is added in an amount between about 0.0001 and about 0.0002% by weight. A method according to claim 8, characterized in that a defoamer is added to the liquid vehicle in an amount sufficient to eliminate all trapped air. The invention relates to a process for the manufacture of a reactor cylinder for use in a radiant heater and to the reactor cylinder produced by this process. Initially, a liquid vehicle is prepared which includes an alumina dispersion, magnesium sulfate, colloidal silica and powdered talc. A defoamer may be added. The alumina dispersion includes dispersible alumina in an amount between about 1% and about 5% by weight, an acid in an amount of up to about 0.2% by weight and water in an amount between about 10% and about 30% by weight. , all concentrations calculated as% by weight based on the weight of the liquid vehicle. The alumina dispersion is then further diluted by adding water in an amount between about 40% and about 80% by weight. To the dilute alumina dispersion is added magnesium sulfate in an amount of up to about 4% by weight, colloidal silica in an amount of up to about 10% by weight and powdered talc in an amount of between about 0.000l and about 0.1% by weight. -%. A solid alumina and silica fiber composition is then added to the vehicle in a ratio of about 10 grams of solid fiber per 3.785 liters of vehicle. The mixture or slurry is processed or chopped then mixed and vacuum formed around a mandrel to form the reactor cylinder.