US3008701A

US3008701A - Improved cooling means on a rotating cylinder

Info

Publication number: US3008701A
Application number: US801092A
Authority: US
Inventors: Russell M Wiseman
Original assignee: Diamond Alkali Co
Current assignee: Diamond Shamrock Corp
Priority date: 1959-03-23
Filing date: 1959-03-23
Publication date: 1961-11-14
Anticipated expiration: 1978-11-14
Also published as: DK104632C; GB927549A; DE1295759B

Description

Nov. 14', 1961 R. M. WlSEMAN 3,008,701

IMPROVED COOLING MEANS ON A ROTATING CYLINDER Filed March 23, 1959 3 Sheets-Sheet 1 INVENTOR RUSSELL M. WISEMAN AT'TORNEY Nov. 14, 1961 R. M. WISEMAN 9 7 IMPROVED COOLING MEANS ON A ROTATING CYLINDER Filed March 23, 1959 3 Sheets-Sheet 2 INVENTOR RUSSELL M. WISEMAN' ya/thonim@ Cuna ATTORNEY Nov. 14, 1961 R. M. wsEMAN 3,008,701

IMPROVED COOLING MEANS ON A ROTATING CYLINDER Filed March 23, 1959 3 Sheets-Sheet 3 INVENTOR RUSSELL M. WISEMAN w/Mwa f ATTORNEY;

States ice 3,008,7 01 e IMPROVED COOLING MEANS ON A ROTATING CYLINDER Russell M. Wiseman, Mentor, Ohio, assignor to Diamond Alkali Company, Cleveland, Ohio, a Corporation of Delaware Filed Mar. 23, 1959, Ser. No. 801,092 20 Claims. (Cl. 266-38) This invention relates to improvements in an apparatus for the treatment of molten metals maintained under conditions providing for turbulent fiow in a generally spiral path under the influence of super gravitatonal forces, and more particularly to improvemerts in the cooling means of apparatus of the above type.

The term "turbulent flow" is used herein in the engineering sense for turbulent flow of fluids, as opposed to streamline flow.

It has heretofore been proposed to treat metals in the molten state with various chemical agents to remove undesirable impurities, such as sulfur, phosphorous, silicon and the like. In all of these methods, the primary diffculty encountered is that of securing an adequate admixture of the Chemical agent in the molten metal. In light of this it has been proposed to treat the molten metal in a rotating drum or cylinder thereby utilizing the rotation of the cylinder to sec-ure an adequate dispersion of the treating agent in the molten metal.

Generally, in practicing this method, the molten metal is charged into the drum or cylinder and the Chemical treating agent is charged into the cylinder as a separate layer on top of the molten metal. The rotating drum or cylinder is designed to rotate at a speed which is less than that at which the centrifugal and centrpetal forces upon the molten metal are in balance. At this speed, the molten metal cascades or cataracts from the sides of the rotating cylinder, i.e., the molten metal travels through an arc in which it is in a substantially continuous cascading body adjacent the inner surfaces of the rotating cylinder, and thereafter falls away from the irer surfaces of the cylinder due to the influence of the force of gravity. It is this cascading or cataractng which effects the uniform dispersion of the chemcal treating agent in the molten metal.

However, where the treating agent is a strongly alkaline material, such as caustic soda, by leaving portions of the refractories in the lining of the rotating cylinder exposed to such treating agents, the cascading or cataracting accelerates the corrosion and erosion of the refractories. Hence, with such method and apparatus, it has not been possible to utilize the more eflicient, strongly alkaline treating agents.

In light of this, it has been proposed to utilize a cylinder which may be rotated at high speeds, thereby producing a force on the molten metal 6 to 8 times the force of gravity. This force is suicient to form a substantially continuous layer of metal over the inner surface of the rotating cylinder, thus eliminating the cascading or cataracting of the metal which occurs in rotating cylinders designed to rotate at slower speeds. The Chemical treating agent is added to the molten metal at the point at which the metal enters the rotating cylinder. The molten metal may be introduced either simultaneously and in conjunction with the introduction of the molten metal or independently thereof. At the temperature of the molten metal, as it enters the cylinder, the treating agent is reacted immediately and taken up by the molten metal so that the impurtes are removed from the molten metal within 30 seconds. The molten metal may thus be passed rapidly through the rotating cylinder to the discharge end thereof where the metal is tangentially dscharged from the cylinder into a collecting zone. It is at this point that difliculty has been encountered' in providing adequate cooling means for the discharge end of the cylinder as well as adequate means for preventing the molten metal from collecting in the area between the rotating cylinder and the stationary collecting means.

It is therefore an object of this invention to provide an effective heat exchange means for the discharge end of an apparatus of the type described.

Another object of this invention is to provide a heat exchange means for :apparatus of the type described, which heat exchange means will dissipate the heat from the main body of the apparatus.

A further object of this invention is to provide a heat exchange means for apparatus of the type described, which heat exchange means will prevent flame or hot gases in the reactor from flowing back between the stationary and moving parts of the apparatus.

Still another object of this invention is to provide a heat exchange means for apparatus of the type described, which heat exchange means will help to form a protec tive coating on the molten metal receiving portions of the apparatus.

These and other objects will become apparent to those skilled in the art from the description and drawings of the invention which follows.

Pursuant to the above objects, the present invention is directed to the combinaton of a rotating cylinder apparatus of the type described above, which cylinder is designed to be rotated at speeds which are sufiicient to exert a force of at least 6 times the force of gravity on the molten metal and heat exchange means for this apparatus. The heat exchange means include -a water jacket, extending around the discharge end of the cylinder as well as air cooling means designed to prevent flame or hot gases from flowing back between the rotating and stationary parts of the apparatus and in addition may include cooling means by which the heat may be dissipated from the exterior of a portion of the main body of the cylinder itself.

Referring now to the drawings, attached hereto and made a part hereof:

FIG. 1 is a vertical longitudnal section of an apparatus of the type described above.

FIG. 2 is an enlarged, vertical longitudinal section of the discharge end of the apparatus shown in FIG. 1 with the molten metal collecting means removed.

FIG. 3 is an end view of the apparatus shown in FIG. 1 with portions thereof removed so as to show more clearly the appparatus of the present invention.

FIG. 4 is a plane view of the apparatus as shown in FIG. 2.

In the drawings, 2 is a hollow cylinder adapted for rotation about its axis, and constituting the metal-storage, metal-advancin:g zone 6 of the apparatus into which has been incorporated cooling means of the present invention. The feed end of the cylinder is generally indicated at 4, and the discharge end thereof ast 8.

At the discharge end 8 of the metal-storage, metal-advancng zone 6, is collection means 10 for collecting molten metal discharge from the metal-storage, metal-advancing Zone 6. Thecollection means 10 also has means such as spout 12 for releasing metal colleeted in the collection zone.

The metal-storage, metal-advancing zone 6, constituted by cylinder 2, is sutably mounted upon bearings 14 by means of tires 16, which adapt the cylinder for rotation about its axis. The cylinder 2 is suitably constituted by a steel shell 18 adjacent to which is a layer of insulating material .20 for the conservation of heat in order to maintain the temperature .of the molten metal in traversing the metal-storage, metal-advancing zone. Overlaying the insulating layer 20 is a refractory layer 22 which is directly in contact with the metal.

At each end of the cylinder 2,

dams

24 and 26 are formed by the refractory layer 22, the dam 26 being at the feed end of the metal-storage, metal-advancing zone and the dam 24 being at the discharge end thereof. The dam 26 is of greater height, i.e., extends radially inwardly a greater distance than does dam 24.

At the discharge end of the metal-storage, metal-advancing zone, the collection means 'is also preferably constructed of a steel shell 28, over which is placed a suitable insulatng material 30 which is in turn overlaid with a suitable refractory material 32. This refractory material 32 is capable of withstanding the effects of the high temperatures of the molten metal as well as providing insulaton against heat transfer to the surrounding atmosphere. Collection means 10 is also provided With an exhaust stack 34 to allow for the escape of fumes of the treating agent, where necessary, as well as port 36 for observing action taking place within the metal-storage, metal-advancing zone. Encircling the discharge end 8 of the cylinder 2 and spaced therefrom is an annular heat exchange means 38. The heat exchange means 38 is secured to the metal shell 28 in any suitable manner as for example by welding to the outer shell 28 of the collecting means 12.

As shown in FIG. 2, the annular heat exchanger 38 comprises four segments each having coo-lant inlets 39 and discharge pipes 40. The inlets 39 are located at the lowest point on each segment and the outlets 40 are at the opposite end of the segment. The coolant enters each segment at its lowest point and fiows upwardly through the segment and out the top, thus eliminating the chance of air binding in the segment. The heat exchanger 38 which is secured to the stationary metal collection means 28, is likewise stationary and hence is spaced outwardly from the outer surface of notating cylinder 2 so that the latter is free to rotate without interference.

Although the heat exchanger 38 may be only one continuous member instead of several segments of an annulus as shown, it has been found that a more even heat exchange at the discharge end of cylinder 2 is achieved when several segments are used. Moreover, in the event of a leak or obstruction in one segment, the remaining segments will still furnish sufiicient heat exchange to permit the continued operation of the apparatus.

Behind the heat exchanger 38 is an annular chamber 42, which chamber is spaced slightly outwardly from the rotating cylinder 2 and is likewise secured to the shell 28 of metal collection means 10. As shown in FIGS. 1 and 2, the chamber 42 is secured to the shell 28 by means of a bracket 44 and bolts 46. As shown in FIGS. 3 and 4, the chamber 42 has a projecting corner 45 on which is mounted the intake duet 47. Air is `drawn into the duct 47 by means of a pump or compressor (not shown) which is connected thereto. As shown in the cutaway portion of FIG. 4, the duct 47 is divided into two sections by a partition 49 thereby assuring an equal distribution of coolant throughout the chamber 42.

As shown in FIGS. l and 2, coolant, such as air, is blown into the chamber 42 and passes out of the chamber 42 through a slot 48 in the bottom thereof. The coolant passes through the annular space 64 which surrounds the rotatng cylinder 2, between the outer wall 18 thereof and the jacket 28. The force of this air is suflicient to prevent flame or hot gases, which are discharged from the cylinder 2, from fiowng back into the space 64 between the rotating cylinder and the stationary collection means where it would attack the metal and cause corrosion thereof. Additionally, the air in passing over the surface of the heat exchanger 38 increases the normal heat transfer, efiected thereby.

It has been found that the size of the slot in the bottom of chamber 42, will depend upon the Volume of chamber 42 and the velocity of the air entering the chamber. To insure that a constant Volume of air s discharged equally to all parts of annular space 64, slot 48 must be of such a size, with respect to the Volume of air chamber 42 and the velocity of the air entering therein, as to maintain an equal positive pressure on the air in chamber 42 at all times. When the pressure of the air in chamber 42 is unequal, the discharge of this air into space 64 will likewise be unequal, thus allowing flame or hot gases from cylinder 2 to flow back into space 64 at the points of low pressure.

To insure that the air will be directed out through the space 64, an annular baflie plate 66 is secured to the outer shell of the cylinder 2. As this baffle plate is rotating with the cylinder 2, the air Currents which it sets up help to direct the air from the chamber 42 outwardly through the space 64 and prevents the air from passing rearwardly along the length of cylinder 2.

The heat exchanger 38 not only cools the air from the air chamber 42 thereby making it more effective in preventing the hot gases from flowing into the space 64, but it also provides a cool area adjacent the discharge end of cylinder 2. In this` cool area, the molten metal tends to solidify thereby forming a coating which serves to protect the refractory lining of the collecting means 10 from the Corrosive action of the molten metal as it is discharged.

In order to increase the air circulation around the cylinder 2 itself, a plurality of vanes 68 are secured to the outer shell 18 of the cylinder 2. As the cylinder 2 rotates, these vanes 68 act as a fan, setting up air currents which help to dissipate the heat which is formed around the rotating cylinder 2. Although the total number of vanes 68 has not proved to be critical, it has been found that extremely good results are obtained when twelve vanes, mounted an equal distance apart, i.e., 30, are secured to the outer shell of the cylinder 2.

In operation, molten metal is introduced into the rotating cylinder 2, through the loading end 4, from a tundish or other suitable means. The cylinder 2 is rotated at a speed sufiicient to form a continuous layer of molten metal over the entire inner surface of the cylinder adjacent the refractory layer 24. The chemical treating agent is likewise introduced into the loading end 4 of the cylinder 2 either simultaneously or independently of the molten metal, from any suitable means. The molten metal is discharged tangentially from the discharge end 6 of cylinder 2 into the collection means 12 from which it is removed through spout 14.

As set forth above, air under pressure blown by means of a pump or compressor into the air duct passage 42, passes out through slot 48 into the space 64 and is cooled by the water jacket 38 as it is discharged from space 64. The force of this air prevents the flame and hot gases which are discharged from rotating cylinder 2 from flowing back into the space 64. In addition, a thin film of metal is formed adjacent to discharge end 8 of cylinder 2, on the area which is cooled by the water jacket 38. This thin metal layer affords very nearly ideal protection for the wall of collection means 12 against erosion, as well as mechanical shock by impact of the metal ejected from the cylinder 2. In addition, the vanes 68 on the outer shell of cylinder 2 set up a current of air which serves to dissipate the heat from around the main body of cylinder 2 thereby preventing an undesirable build-up in the external temperature of the cylinder.

From the above, it can be seen that a very effective cooling means and means for preventing erosion in the metal collecting portion of the present apparatus has been presented. Additionally, this cooling means serves to prevent a back flow of hot gases into the space between the rotary and stationary parts of the apparatus, as well as increasing the normal heat transfer of the heat exchange means.

While there have been illustrated and described in detal an embodiment of the invention, the described structure is not intended to be understood as limiting the scope of the invention as it is realized that changes therein are possible, and it is further intended that each element or instrumentality recited in any of the following claims is to be understood as referring to all equivalent elements or instrumentalities for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. In an apparatus for treating molten metal including a hollow cylinder constituting a metal-storage, metaladvancng zone adapted for rotation about its axis, means for introducing molten metal into said cylinder, means for introducing a treating a gent into said cylinder, means including a dam within said cylinder for retaining a continuous shallow body of molten metal coextensive with the inner surface thereof, means for imparting rotational motion to said cylinder suicient to form said continuous body of molten metal, and means for collecting molten metal discharged tangentially from said cylinder, which latter means is spaced from said cylinder to allow rotation thereof, the improvement comprising, first cooling means surrounding the discharge end of said hollow cylinder and spaced therefrom a distance sufiicient to permit the rotation of said cylinder, said cooling means being secured to the metal collecting means and including means to prevent the flowback of hot gases and molten metal between said molten metal collecting means and said cylinder and a second cooling means Secured to said hollow cylinder and designed to rotate therewith, thereby effectin-g cooling of the exterior of said cylinder.

2. The apparatus as claimed in claim 1 in which said first cooling means comprises the combination of a cooling means through which a liquid cooling fluid is directed and a cooling means through which a gaseous cooling fluid is directed.

3. The apparatus as claimed in claim 1 in which said first cooling means comprises a water jacket, which water jacket is contiguous to the space between said cylinder and said molten metal collecting means and an air chamber, which air chamber is in communication with the space between said cylinder and said molten metal collecting means.

4. The apparatus as claimed in claim 3 in which the side of the air chamber in closest proximity to the rotating cylinder has a continuous slot formed therein, which slot is the means of communication between the air chamber and the space between the cylinder and the molten metal collecting means.

5. The apparatus as claimed in claim 1 in which the second cooling means comprises a plurality of vanes, which vanes are generally parallel to the longitudinal axis of said cylinder.

6. The apparatus as claimed in claim 2 in which the second cooling means comprises a plurality of vanes, which vanes are generally parallel to the longitudinal axis of said cylinder.

7. The apparatus as claimed in claim 3 in which the second cooling means comprises a plurality of vanes, which vanes are generally parallel to the longtudinal axis of said cylinder.

8. The apparatus as claimed in claim 4 in which the second cooling means comprises a plurality of vanes, which vanes are generally parallel to the longitudinal axis of said cylinder.

9. The apparatus as claimed in claim 3 in which said water jacket is formed of a plurality of sections, each section having its own inlet and discharge pipe.

10. The apparatus as claimed in claim 4 in which said water jacket is formed of a plurality of sections, each section having its own inlet and discharge pipe.

11. The apparatus as claimed in claim 9 in which the second cooling means comprises a plurality of vanes,

which vanes are generally parallel to the longitudinal axis of said cylinder.

12. The apparatus as claimed in claim 10 in which the second cooling means comprises a plurality of vanes, which vanes are generally parallel to the longitudinal axis of said cylinder.

13. The apparatus as claimed in claim 4 in which the cylinder has a baflie plate Secured thereto adjacent the slot in said air chamber, which baflie plate is perpendicular to the longitudinal axis of said cylinder.

14. The apparatus as claimed in claim 4 in which the air chamber has an inlet duet, which inlet duct is partioned so as to direct the incoming air into both sides of the air chamber.

15. The apparatus as claimed in claim 4 in which the width of the continuous slot is such as to maintain the air in the air chamber under an equal positive pressu'e.

16. The apparatus as claimed in claim 13 in which the width of the continuous slot is such as to maintain the air in the air chamber under an equal positive pressure.

17. The apparatus as claimed in claim 14 in which the width of the continuous slot is such as to maintain the air in the air chamber under an equal positive pressure.

18. In an apparatus for treating molten metal including a hollow cylinder constituting a metal-storage, metaladvancing zone adapted for rotation about its axis, means for introducing molten metal into said cylinder, means for introducing a treating agent into said cylinder, means including a dam within said cylinder for retaiing a continuous shallow body of molten metal coextensive with the nner surface thereof, means for imparting rotational motion to said cylinder suflicient to form said continuous body of molten metal, and means for collecting molten metal discharged tangentially from said cylinder, which latter means is spaced from said cylinder to allow rotation thereof, the improvement comprising cooling means surrounding the discharge end of said hollow cylinder and spaced therefrom a distance sufiicient to permit the rotation of said cylinder, said cooling means compn'sing the combination of a cooling means through which a liquid cooling fluid is directed and a cooling means through which a gaseous cooling fluid is directed, said latter cooling means including means for preventing the flowback of hot gases and molten metal between said molten metal collecting means and said cylinder, which means efiect direction of gaseous cooling fluid under a pressure above atmospherc pressure into the space between the molten metal collecting means and the cylinder.

19. The apparatus as claimed in claim 18 in which said cooling means comprises a water jacket, which water jacket is contiguous to the space between said cylinder and said molten metal collecting means and an air chamber, which air chamber is in communication with the space between said cylinder and said molten metal collecting means.

20. The apparatus as claimed in claim 19 in which the side of the air chamber in closest proximity to the rotating cylinder has a continuous slot formed therein, which slot is the means of communication between the air chamber and the space between the cylinder and the molten metal collecting means.

References Cited in the file of this patent UNITED STATES PATENTS i FOREIGN PATENTS Germany, Serial No. N5600IVc/`c (Class Gruppe 1401), printed Sept. 6, 1956.