US2578707A

US2578707A - Method and apparatus for producing fibrous material

Info

Publication number: US2578707A
Application number: US776905A
Authority: US
Inventors: Daniel W Kocher
Original assignee: Armstrong Cork Co
Current assignee: Armstrong World Industries Inc
Priority date: 1947-09-30
Filing date: 1947-09-30
Publication date: 1951-12-18
Anticipated expiration: 1968-12-18

Description

Dec. 18, 1951 w, KQCHER 2,578,707

METHOD AND APPARATUS FOR PRODUCING FIBROUS MATERIAL Filed Sept. 50, 1947 n 2 SHEETSSHEET l Dec. 18, 1951 w, KOCHER 2,578,707

METHOD AND APPARATUS FOR PRODUCING FIBROUS MATERIAL Filed Sept. 50, 1947 2 SHEETS-SHEET 2 Patented Dec. 18, 1951 METHOD AND APPARATUS FOR. PRODUCING FEBROUS MATERIAL Daniel W. Kocher, Columbus, Ohio, assignor, by

mesne assignments, to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsylvania Application September 30, 1947, Serial No. 776,905

Claims.

This invention relates to a method and apparatus for producing fibrous material and, more particularly, to a method and apparatus for producing mineral wool in which the molten stream from which the fibers are to be attenuated is disposed in the center of the blast of hot gas used to attenuate the fibers.

The term mineral wool is used generically throughout to include slag wool, rock wool, and glass wool, as well as other inorganic wools. The term raw material is used generically to include blast furnace slag, rock, glass, and other inorganic materials used in the manufacture of mineral wool. The term molten material is used generically to include molten wool-forming raw materials. The term shot as used herein refers to the small globules of materials which have not been attenuated by the attenuating blast. The term short dustlike fibers refers to the extremely short and extremely fine fibers present in blown mineral wools and which create objectionable dustiness when such wools are handled.

The invention disclosed in this application is an improvement adapted to be practiced in conjunction with a pressure type furnace for the production of mineral wool similar to that described in the copending patent application of Chester R. Austin, Serial No. 776,894, filed September 30, 1947, now Patent No. 2,554,486, in which there is disclosed a method and apparatus in which the molten material is attenuated by the hot gases resulting from the combustion of fuel under pressure in a furnace.

In the conventional method of producing mineral wool, the raw material is melted in a suitable receptacle, and a stream of molten material is allowed to intersect, an attenuating blast of steam or air which is at a temperature substantially lower than that of the molten material. This cooling effect of the attenuating blast striking the molten stream has a tendency to shatter the stream at the point of attenuation and produce fibrous material containing a large amount of shot and short dustlike fibers which have very little insulating value and which are further objectionable in that, they continue to sift out when the mineral wool is handled.

In the manufacture of fibrous material from a molten stream, it has been found highly desirable to maintain a constant temperature throughout the stream so that the temperature on the surface will be substantially the same as the temperature in the center of the stream. This cannot be accomplished where the stream is allowed to drop through the atmosphere, because the ambient atmosphere has a much greater cooling effect on the exterior of the stream than it has on the interior, making the molten material in the exterior region of the stream much more viscous than the interior. Experiments have shown that a wool-forming composition cannot be attenuated properly when the viscosity is above a certain range, and the quality of wool blown from molten streams which are allowed to fall through air clearly reveals that much of the mass of resulting product has not been attenuated properly. It is believed that the cooler outer surface of the stream of molten material is responsible for a large percentage of this improperly attenuated material.

Furthermore, it has been found that when attenuating fibers by a blast which is at temperature substantially lower than the temperature of the molten material, the blast has a tendency to increase the viscosity of the material very rapidly during attenuation and, of course, when the viscosity is increased to a point above the attenuation range, shot are formed. By using a blast at substantially the same temperature as the temperature of the material being attenuated, the fiber is maintained at attenuation viscosity for a greater period of time and, consequently, longer fibers and less shot are formed.

An object of this invention is to provide a method of producing mineral wool which is extremely fine, tough, and has a good average fiber length, a relatively low shot content, and a relatively small amount of short dustlike fibers by attenuation with hot gases from a pressure furnace.

A further object of this invention is to provide an apparatus for producin mineral wool in which the molten stream is disposed in the center of the blast of hot exhaust gases escaping through an orifice in the wall of a raw material melting furnace.

Another object of this invention is to provide a method of producing mineral wool in which the stream of molten material is completely surrounded by hot exhaust gases escaping through a small orifice in a furnace wall.

A still further object of this invention is to provide a method of producing fibrous material from a molten stream in which the temperature differential between the center of the stream and the outer surface of the stream is reduced to a minimum.

It is also an object of this invention to provide a method of producing fibrous material from molten material in which the gas used to attenuate the fibrous material ls also utilized to assist 3 in keeping the molten material at the proper viscosity for attenuation.

In order that my invention may be more readily understood, it will be described in connection with the accompanying drawing in which:

Figure 1 is a longitudinal cross-sectional view of a furnace suitable for carrying out my invention,

Figure 2 is a plan view of the discharge end of the furnace showing the orifice through which the gas escapes and the molten stream is attenuated, and

Figure 3 is a modification of the furnace of my invention showing a platinum alloy tube leading from a preliminary heating chamber, not shown, to the secondary heating chamber from which the mineral wool is blown.

In the drawing, the numeral 2 designates a cylindrical furnace shell having a lining of insulating brick 3 and an inner layer of rammed high temperature refractory material 4. This refractory material defines a cylindrical chamber 5 which is closed at one end by a refractory element 6 having an orifice l passing therethrough. This refractory element 6 is held in place by a metal ring 8 secured by bolts 9 to the plate iii. The metal plate It which forms the front of the furnace housing is secured by means of bolts H to a collar l2 which is secured to the furnace housing 2. In the forward section of the furnace, there is shown a refractory dam [3 which closes the lower part of the chamber 5, thus preventing the molten material from coming in contact with the refractory element 6. A tube i4 is provided, the one end of which is located close to the bottom of the cylindrical chamber 5 at a point to the rear of the refractory dam i3. This tube passes through and is afiixed to the refractory dam and then passes through the orifice 'i in the end of the furnace. The outside diameter of this tube M is less than the diameter of the orifice 1 leaving a passage [5 around the tube to permit the escape of hot gases around the outer circumference of the tube.

While in the embodiment illustrated a circular orifice and circular tube are shown, it will be understood that orifices and tubes of other geometrical shapes may be used, and it has also been found that the cross-sectional shape of the tube does not have to conform to the crosssectional shape of the orifice.

The best results have been obtained with a tube made of platinum alloy comprising 90% of platinum and 10% of rhodium; however, it will be understood a tube made of any material which will be satisfactory for conveying molten material at a high temperature may be used.

The granular raw material is charged through a double-lock feeding mechanism 56 into the furnace chamber 5 through the passage I! from any suitable source of supply not shown. The gas or other fuel used in the operation of the furnace is supplied from a suitable source, not shown, through the pipe l8, and the oxidant is supplied through the pipe 19 into the pipe 20 which surrounds the fuel supply pipe IS. The fuel and oxidant are mixed in the chamber 2!, and this mixture is then forced through the opening or nozzle 22 into the rear of the furnace chamber 5 in which it is ignited and burned. Suitable adjusting valves may be positioned in the fuel and oxidant lines to control the ratio of fuel to oxidant which, in turn, controls the temperature in the combustion chamber.

In the operation of the furnace, the raw material is fed into the furnace chamber 5 through the downwardly directed passage H. A mixture of fuel and oxidant is fed into the furnace under pressure through the nozzle 22 and is burned in the rear of the furnace chamber 5. This mixture of fuel and oxidant is preferably adjusted to produce a furnace temperature of between 2200 F. and 3000 F. and a pressure in the furnace of between 25 pounds per square inch and 50 pounds per square inch. This temperature converts the granular raw material to a fluid consistency and forms a pool of molten material in the bottom of the cylindrical chamber 5. During the initial heating period the furnace is tipped with the burner end lower than the orifice end to prevent the material from being forced through the tube. When the molten material has been heated to the proper state for attenuation, the furnace is leveled so that the inner end of the tube l4 dips into the pool of molten material in the bottom of the furnace chamber 5, and the pressure exerted upon the pool by the hot gases forces the molten material through the tube. Since the dam l3 does not completely close the forward end in the furnace chamber, the hot gases escaping through the orifice 1 completely surround the tube I4 and are traveling in a direction substantially parallel to the direction of flow of material through the tube. The passage of these hot gases past the end of the tube has an aspirating effect at the end of the tube 14, tending to aid the flow of molten material therethrough. These hot gases escaping from the furnace through the passage !5 and coming in contact with the stream of molten material attenuate it into fibers of a very fine, tough character.

In another embodiment of my invention, the furnace chamber described may be used as a secondary heating or conditioning chamber in the production of fibrous material from molten material. In using my invention in this type process, the raw material is melted in a suitable furnace, and the molten material is fed down through the passage H into the furnace chamber 5. During this feeding, the burner is shut off temporarily to prevent the pressure from impeding the flow of molten material into the furnace chamber. In this embodiment of my invention, the hot gases in the furnace chamber 5 are used to maintain or to assist in maintaining the molten material at the proper viscosity.

Since the furnace temperature is maintained between 2200 F. and 3000 F., the combustion gases are at substantially this same temperature. These hot gases keep the pool of molten material at a high temperature and, also, heat the platinum alloy tube to such an extent that it is at substantially the same temperature as the molten material. It will be obvious from this disclosure that, since the platinum alloy tube is at a temperature substantially the same as the stream of molten material, there is practically no temperature differential between the center of the stream and the outer surface thereof.

Furthermore, since the hot gases escaping past the end of the tube are at substantially the same temperature as the stream of molten material, they aid in keeping the material at the proper viscosity during attenuation and, thereby, produce longer fibers containing less shot.

In the modification of my invention shown in Figure 3, the raw material is melted in any suitable melting furnace having a heated platinum alloy tube passing from the melting furnace through the top of the furnace 2 and curving in such a manner as to pass through the orifice I. In this embodiment, the hot gases resulting from the combustion of fuel in the furnace chamber 5 pass through the orifice 'i surrounding the platinum alloy tube and have an attenuating effect on the molten material passing through the tube. In this embodiment, the type of fibrous material produced is similar to that produced by the other method disclosed in this application.

In this embodiment of my invention, the pressure furnace is maintained at substantially the same temperature as that of the vessel in which the raw material is melted, and the hot gases within the pressure furnace heat the platinum alloy tube to substantially the same temperature as the temperature of the molten stream, allowing substantially no temperature differential throughout the molten stream.

In the modification described above, it is possible to have one large melting vessel supplying molten material through platinum alloy tubes to a plurality of pressure furnaces surrounding or in the vicinity of the melting vessel; A setup of this kind could be operated continuously for long periods of time.

It has been found through experiment that, all other factors being constant, the diameter of the fiber produced varies with the viscosity of the molten material and with the pressure maintained in the pressure furnace. At a preferred viscosity, as for example 28 poises, and a pressure of 26 pounds per square inch, the fibers are fine and tough, and, as the viscosity is increased say to 1000 poises, a coarser fiber is produced. If the viscosity is decreased below 28 poises, an extremely fine, tough fiber is produced. Likewise, all other factors being equal, low pressures produce coarse fibers and high pressures produce fine fibers. The preferred pressure range is between 25 to 50 pounds per square inch. However, lower or higher pressures may be used if desired. Thus, by varying the viscosity or pressure, it is possible to produce mineral Wool of the various fiber sizes necessary for different commercial uses. It has been found through experiment that a viscosity 1,

range of 1000 poises to poises is satisfactory for the production of mineral Wool by the pressure furnace method, although, for the usual commercial wools, for insulating purposes a viscosity range of from 100 poises to poises is preferred.

The following is a specific example of the method of producing mineral wool by my invention: A cylindrical furnace 9 in diameter and 33" long having a circular orifice of a diameter of 0.56" in its front Wall was used. A platinum alloy tube comprising 90% of platinum and 10% of rhodium was placed in the front of the furnace and held in place by a refractory dam. This platinum alloy tube was '7 long, 3 in inside diameter with a wall thickness of This tube was bent so that the discharge end was horizontal and the other end dipped into the molten slag bath when the furnace was in a horizontal position.

A cold raw material charge was placed in the tilted furnace, and the furnace was heated to 2550 F. while tipped to prevent the premature flow of the material from the tube. When the molten material was melted to the proper state for attenuation, the furnace was placed in a horizontal position and the temperature held at 2550 F. to maintain the molten material at the proper viscosity of approximately 28 poises. During this trial run a pressure of approximately 26 pounds per square inch was maintained in the furnace.

The rate of flow of molten material through the platinum alloy tube was found to be approximately 10 pounds per hour. The mineral wool produced during this experimental run was extremely long, fine, and tough, containing substantially less shot and short dustlike fibers than occurs in commercial mineral wool produced by the conventional method.

It will be clear from the above that I have developed a new method and apparatus for producing fibrous material in which the hot gases resulting from the combustion of fuel in a pressure type furnace are used to attenuate fibers from a stream of molten material disposed in the center of the stream of gases. It will be obvious, too, that in a system of this type the path of the attenuating blast is substantially parallel to the path of travel of th: molten stream, avoiding the disadvantages arising from the stream being shattered by a blast at a low temperature directed at an angle to the path of the molten stream. It will also be obvious that, in this method, the possibility of a temperature differential in the molten stream has been reduced to a minimum.

While I have illustrated and described certain preferred embodiments of my invention, it will be understood that the same is not limited thereto, but may be otherwise embodied and practiced Within the scope of the following claims.

I claim:

1. A furnace including a chamber to contain a pool of molten material, said chamber having an orifice in one of its walls, a dam positioned so as to prevent the molten material from coming in contact with the wall having the orifice therein, and a tube passing through the center of the orifice and bein affixed to the dam, the one end of said tube being positioned to extend beneath the surface of the molten material and the other end extending beyond the exterior of the furnace.

2. A furnace including a chamber to contain a pool of molten material, fuel-supplyin means passing through one wall of the furnace, the opposite wall having an orifice serving as the only means of escape for the high temperature gases resulting from the combustion of fuel in the furnace chamber, a dam positioned so as to prevent the molten material from coming in contact with the wall havin the orifice therein, and a tube passing through the center of the orifice and being affixed to the dam, one end of said tube being positioned to extend beneath the surface of the molten material and the other end extending beyond the exterior of the furnace wall.

3. A furnace including a chamber to contain a pool of molten material, said chamber having an orifice in one of its walls, a dam positioned so as to prevent the molten material from coming in contact with the wall having the orifice therein, and a tube passing through the center of the orifice but not engaging the Walls of the orifice, said tube being affixed to the dam, one end of said tube being positioned to extend beneath the surface of the molten material.

4. A furnace including a chamber to contain a pool of molten material, said chamber having an orifice in one of its walls, said orifice being the only means of escape for gases generated within the furnace, a dam positioned so as to prevent the molten material from coming in con- 7 5 tact with the wall having the orifice therein, and

a tube passing through the center of the orifice and bein afiixed to the dam, the one end of said tube being positioned to extend beneath the surface of the molten material and the other end extending beyond the exterior of the furnace wall.

5. The method of producing fibrous material from a molten mass, the steps comprising charging a mass of material capable of attenuation into a pressure-tight combustion chamber, heating the mass in said chamber by the combustion of a fuel-oxidant mixture, forming a pool of molten material, delivering molten material from the pool into the path of the combustion gases escaping from the chamber, and attenuatin said mass solely by the application thereto under pressure of the combustion gases resulting from the combustion of the fuel-oxidant mixture, said combustion gases surrounding a stream of said heated mass during the attenuation thereof.

6. The method of producing fibrous material from a molten mass, the steps comprising charging a mass of material capable of attenuation into a pressure-tight combustion chamber, heating the mass in said chamber by the combustion of a fuel-oxidant mixture to a temperature ranging between 2200 F. and 3000 F., forming a pool of molten material, delivering molten material from the pool into the path of the combustion gases escaping from the chamber, and attenuatin said mass solely by the application thereto under pressure of the combustion gases resulting from the combustion of the fuel-oxidant mixture, said combustion gases surrounding a stream of said heated mass during the attenuation thereof.

'7. The method of producing fibrous material from a molten mass, the steps comprisin char ing a. mass of material capable of attenuation into a pressure-tight combustion chamber, heating the mass in said chamber by the combustion of a fuel-oxidant mixture, forming a pool of molten material, delivering molten material from the pool into the path of the com-bustion gases escaping from the chamber, and attenuating said mass solely by the application thereto under pressure of the combustion gases resulting from the combustion of the fuel-oxidant mixture, said combustion gases surrounding a stream of said heated mass and being under pressure of between 25 pounds per square inch and -0 pounds per square inch.

8. The method of producing fibrous material from a molten mass, the steps comprising charging a mass of material capable of attenuation into a pressure-tight combustion chamber, heating the mass in said chamber by the combustion of a fuel-oxidant mixture to produce a molten mass havin a viscosity ranging between 1,000 poises and 10 poises, forming a pool of molten material, delivering molten material from the pool into the path of the combustion gases escoping from the chamber, and attenuating said ass solely by the application thereto under pressure of the combustion gases resulting from the combustion of the fuel-oxidant mixture, said combustion gases surrounding a stream of said heated mass during the attenuation thereof.

9. The method of producing fibrous material from a molten mass, the steps comprising charging a mass of material capable of attenuation into a pressure-tight combustion chamber, heating the mass in said chamber by the combustion of a fuel-oxidant mixture to produce a molten mass having a viscosity ranging between poises and 25 poises, forming a pool of molten material, delivering molten material from the pool into the path of the combustion gases escaping from the chamber, and attenuating said mass solely by the application thereto under pressure of the combustion gases resulting from the combustion of the fuel-oxidant mixture, said combustion gases surrounding a stream of said heated mass during the attenuation thereof.

10. The method of producing fibrous material from a molten mass, the steps comprising charging a granular mass of material into a pressuretight combustion chamber, heating the mass in said chamber by the combustion of a fuel-oxidant mixture, forming a pool of molten material, delivering molten material from the pool into the path of the combustion gases escaping from the chamber, and attenuating said mass solely by the application thereto under pressure of the combustion gases resulting from the combustion of the fuel-oxidant mixture, said combustion gases surrounding a stream of said heated mass during the attenuation thereof.

11. The method of producing fibrous material from a molten mass, the steps comprising charging a mass of material capable of attenuation into a pressure-tight combustion chamber, heating the mass in said chamber by the combustion of a fuel-oxidant mixture, formin a pool of molten material, delivering molten material from the pool into the path of the combustion gases escaping from the chamber, and attenuating said mass solely by the application thereto under pressure of the combustion gases resulting from the combustion of the fuel-oxidant mixture, said combustion gases surrounding a stream of said heated mass during the attenuation thereof, the temperature of the combustion gases and the temperature of the molten material being substantially the same during the attenuating process.

12. The method of producing fibrous material from a molten mass, the steps comprising charging a mass of material capable of attenuation into a pressure-tight combustion chamber having an exhaust orifice in one of its walls, heating the mass in said chamber by the combustion of a fuel-oxidant mixture supplied under pressure, forming a pool of molten material, forcing the heated mass through a tube passing through said orifice, and attenuating said mass as it leaves the end of the tube by the application thereto under pressure of the combustion gases resulting from the combustion of the fuel-oxidant mixture, said combustion gases surrounding the stream of molten material while it is being attenuated.

13. A furnace including a chamber to contain a pool of molten material, said chamber having an orifice in one of its walls, a dam positioned so as to prevent the molten material from coming in contact with the wall having the orifice therein, and a tube passing through the orifice and bein afiixed to the furnace structure, said tube being spaced away from the walls of the orifice to permit the escape of combustion gases therearound, and the other end of said tube being positioned to extend beneath the surface of the molten material.

14. A furnace including a chamber to contain a pool of molten material, said chamber having an orifice in one of its walls, a dam positioned so as to prevent the molten material from coming in contact with the wall having the orifice therein, and a tube aflixed to the furnace structure having one end thereof disposed below the upper portion of the dam to bring the open end beneath the surface of the molten material, the other end of the tube passing through said oriflce'to the exterior of. the furnace, said tube being spaced away from the walls of the orifice to permit the escape of combustion ases therearound.

15. A furnace including a chamber to contain a pool of molten material, said chamber having an orifice in one of its walls, and a tube aflixed to the furnace structure having one end thereof extending beneath the pool of molten material, the other end of the tube passing through said orifice 10 to the exterior of the furnace, said tube being spaced away from the walls of the orifice to permit the escape of combustion gases therearound.

DANIEL W. KOCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

Claims

5. THE METHOD OF PRODUCING FIBROUS MATERIAL FROM A MOLTEN MASS, THE STEPS COMPRISING CHARGING A MASS OF MATERIAL CAPABLE OF ATTENUATION INTO A PRESSURE-TIGHT COMBUSTION CHAMBER, HEATING THE MASS IN SAID CHAMBER BY THE COMBUSTION OF A FUEL-OXIDANT MIXTURE, FORMING A POOL OF MOLTEN MATERIAL, DELIVERING MOLTEN MATERIAL FROM THE POOL INTO THE PATH OF THE COMBUSTION GASES ESCAPING FROM THE CHAMBER, AND ATTENUATING SAID MASS SOLELY BY THE APPLICATION THERETO UNDER PRESSURE OF THE COMBUSTION GASES RESULTING FROM THE COMBUSTION OF THE FUEL-OXIDANT MIXTURE, SAID COMBUSTION GASES SURROUNDING A STREAM OF SAID HEATED MASS DURING THE ATTENUATION THEREOF.