US2789945A

US2789945A - Thermal diffusion apparatus

Info

Publication number: US2789945A
Application number: US373807A
Authority: US
Inventors: John W Thomas
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1953-08-12
Filing date: 1953-08-12
Publication date: 1957-04-23
Anticipated expiration: 1974-04-23

Description

April 23, 1957 J. w. THOMAS THERMAL DIFFUSION APPARATUS Filed Aug. l2, 1955 Z M Z I INVENTOR. JOHN W. THoMns HTTORNE Y5 United States Patent The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio Application August 12, 1953, Serial No. 373,807

5 Claims. (Cl. 210- -176) The present invention relates to apparatus for the separation or concentration of fluids by thermal diffusion and more particularly to constructions designed to compensate for the difference in thermal expansion and contraction of the wall members of such apparatus and to facilitate their assembly.

In subjecting fluids, i. e., mixtures of materials that are gaseous or liquid under the conditions of operation 'or liquids containing one or more components dissolved or suspended therein, to thermal diffusion for the purpose of separating the components thereof or obtainirig fractions containing concentrations of one or more of the components that vary from those present in the original fluid, the fluid is passed through or confined Within a thermal diffusion separation chamber defined by closely and substantially equidistan'tly spaced surfaces, one of which is maintained at a relatively higher temperature than the other in order to impose a temperature gradient across the chamber. The width of the chamber, i. e., the spacing between the chamber-forming surfaces, is of the order of about 0.15 inch or less, preferably less than-about 0.06 or 0.08 inch in apparatus designed to subjeet liquid to thermal diffusion. For the thermal diffusion of gaseous mixtures, the width of the chamber may be considerably greater but is still preferably of the order of a small fraction of an inch.

The construction and assembly of thermal diffusion apparatus meeting these requirements ha heretofore been attended with considerable difliculty, particularly where the apparatus comprises a considerable number of fiat wall members, the exterior surfaces of which form a series of thermal diffusion separation chamber when they are bolted together with gaskets disposed between them. One of these difiiculties has been due to the fact thatwhen the apparatus is assembled, all of the wall members are at approximately room temperature, and

pansion and contraction, of the wall members promotes leakage of fluid past the gasket or gaskets due to-differences in pressures applied to the gaskets and to relative movement, small but appreciable in view of the extremely small width of the separation chamber, of the gasket contacting portions of the wall members. In :instances where such apparatus is assembled in the vertical position, considerable difliculty has also been experienced in maintaining the gaskets in their proper position until suflicient .pressure is applied thereto by adjacent wall members.

Similar difliculties have been encountered in the concentric tube type of thermal diifusionapparatus. In view of the extremely small width of the thermal diffusion chamber, it is manifest that it is almost impossible -to provide a cylindrical gasket'which at one and the same time will have a sufficient wall'thickness and compressibility to facilitate insertioninto the ends of the annular spacebetween two concentric tubes, and once having been inserted, exert sufficient pressure against the inner surface of the outer. tube and the outer surface of the inner tube to provide a seal that is leakproof when the temperature conditions vary between conditions of equal temperature of both tubes and relatively high and low temperatures of the inner and outer tubes, respectively, or vise versa, during operation. This difliculty is further aggravated by the fact that when a temperature gradient is applied across the annular separation chamher, i. e., when one of the tubes is heated to a temperature considerably higher than the other, the. relatively highly heated tube will expand and thus give rise to leakage of fluids in the chamber past the gasket unless the gasket is prefabricated and fitted with extreme accuracy.

The present invention is directed to constructions designed to obviate these problems.

In accordance with the present invention, thermal diffusion apparatus is provided which comprises two or more wall members subject to differential thermal expansion and contraction and having closely and substantially equidistantly spaced surfaces that define one or more thermal diffusion separation chambers. One or more gaskets are disposed between and in contact with portions of the wall members to confine fluid within the chamber or chambers. The gasket-contacting portion or portions of one or more of the wall members are recessed relative to the chamber-defining surface or surfaces thereof to facilitate retention of the gasket or gaskets in the desired position or positions during assembly of the apparatus and preferably also to compensate for dimensional changes in the wall member during operation and, in preferred embodiments, make possible the use of one or more gaskets having a thickness considerably in excess of the spacing between the chamberforming surface of the wall members.

The term recessed, as applied to a wall member herein, is intended to meanthat the portion of the wall member referred to has an indentation in its surface which departs from the chamber-defining surface of said wall member. Thus, for example, the recess of a wall member having a plane chamber-defining surface may be a surface portion below and parallel to, or at an obtuse angle to, the plane of the chamber-defining surface, and the recess of a wall member having a cylindrical chamher-defining surface may be a cylindrical or conical surface portion, the diameter, or mean diameter, of which is greater than the diameter of said cylindrical chamberdefining surface.

Where the wall members are fiat and the chamber-defining surfaces are substantially parallel to one another, the gasket-contacting portion may be recessed at an angle, preferably obtuse, to the surface thereof defining one side of the chamber, or the recessed gasket-contacting portion of said Wall member may be substantially parallel to the chamber-defining surface. Where the gasket-contacting portion of a first wall member is recessed at an obtuse angle, the gasket-contacting portion of the adjacent Wall member, i. e., the member having a surface defining the other side of the chamber, maybe parallel to the recessed gasket-contacting portion of the first wall member, or substantially parallel to its own chamberforming surface. Where the recessed gasket-contacting portion of the first wall member is substantially parallel to its chamber-forming surface, the gasket-contacting portion of the other Wall member may be similarly recessed or lie in the same plane as the chamber-formin surface of its own wall member.

Where apparatus comprises inner and outer wall members, the chamber-defining surfaces of which are cylindrical and concentric to form an annular separation chamher, the gasket-contacting portion of the outer wall member may be provided, at one or both ends, with a conical or cylindrical recess having a diameter greater than the diameter of its chamber-forming surface. The corresponding end or ends of the inner wall member may be of the same diameter as the chamber-forming surface thereof, have a radially protruding conical surface complementary to the recessed conical surface of the outer wall member, or have a radially protruding cylindrical surface of lesser diameter than the diameter of the cylindrical recess of the outer wall member.v

The advantages and utility of the apparatus of the invention will become further apparent from the following detailed description made with reference to the accompanying drawing wherein:

Figure 1 is a cross-sectional view in elevation through one preferred embodiment of the apparatus of the invention;

Figure 2 is a similar view through another preferred embodiment of the invention;

Figures 3, 4 and 5 are fragmentary views of similar apparatus, on a somewhat larger scale, illustrating several of the alternative embodiments of the invention;

Figure 6 is a cross-sectional view in elevation of a tubular type thermal diffusion apparatus employing the principles of the invention; and

Figures 7, 8 and 9 are fragmentary views, on a some what larger scale, illustrating several alternative embodiments of the invention illustrated in Figure 6.

The apparatus illustrated in Figure 1 comprises two wall members It and 11 having closely and substantially equidistantly spaced

surfaces

12 and 14 defining a thermal diffusion separation chamber 16, and a gasket 17 between and in contact with the

portions

19 and 20 thereof for sealing the chamber around its periphery and maintaining the

surfaces

12 and 14 in spaced relation. The wall members are provided with coils 21 or other suitable means for maintaining the

surfaces

12 and 14 at different temperatures and one or both of the wall members are provided with ports 22 for introducing the fluid into the chamber and withdrawing separated fractions thereof.

In this embodiment the gasket-contacting portion 19 of the wall member is at an obtuse angle (180-6) to the chamber-forming surface 12 and the gasket-contacting portion 2b of the wall member 11 is substantially parallel to the portion 19. The gasket 17 is substantially thicker than the width of the separation chamber 16. It is preferred, in this embodiment, that the wall member 19 be the wall member that is maintained at the relatively higher temperature during operation of the thermal diffusion separation chamber 16 inasmuch. as such a choice involves a minimum possibility of leakage past the gasket 17 during operation or during any interruptions in operation. It is further preferred that the angle 0 be an angle having a tangent equal or close to the ratio of the chamber thickness to the chamber width. If the resiliency of the gasket is fairly large, the angle 0 may be varied over a range greater than would be possible if the gasket were not too resilient, such as i50%.

To illustrate the manner in which this construction compensates for the differential expansion and contraction of the wall members 10 and 11, the contraction of the wall member 10 upon cooling from the operating temperature is illustrated, on an exaggerated scale, by dashed

lines

24 and 26 which shows an increase in chamber thickness. It will be noted that upon contraction of the wall member 10, which shows a decrease in chamher width, the gasket-contacting portion 19 thereof will tend to creep inwardly along the surface of the gasket 17 rather than to reduce the pressure thereon. This means that even with fluctuating temperatures the spacing between gasket surfaces 19 and will remain constant.

The gasket load will, therefore, remain constant, thereby assuring a leakproof seal. In addition, the recessing of the gasket-contacting portion 29 of the wall member 11 assists in maintaining the gasket 17 in the desired position during assembly of the wall members into the position shown.

The embodiment illustrated in Figure 2 likewise comprises wall members ltla and 11a having surfaces 12a and 14a forming a separation chamber 16a and a gasket 17a. In this embodiment the wall member 11a is recessed at 26a to form a gasket-contacting portion that is substantially parallel to its chamber-forming surface 14a. The gasket-contacting surface 19a of the wall member is in substantially. the same plane as its chamber-forming surface 120.

In this embodiment it is preferred that the wall member 10a be the wall member that is maintained at a relatively higher temperature than the wall member 11a for the reason that less gasket material makes contact with the portion 19a of the relatively hot wall member 10a than with the recessed portion 20a of the wall member 11a and is, therefore, less subject to deterioration by heat or to transfer of heat through the gasket to the wall member 11a. This embodiment is also preferred from the point of view of simplicity of the wall member 10a inasmuch as it contains no ports, all ports 22 being in the wall member 11a.

Figure 3 illustrates an embodiment wherein both

wall members

10b and 11b are recessed at the gasket-contacting portion 19b and 20b in order to accommodate a gasket 17!) having a thickness several times the width of the separation chamber 16b.

In another embodiment shown in Figure 4, one wall member 11c is recessed at an angle that is obtuse to its surface forming one wall of the separation chamber 16c, and the other wall member 100 is substantially plane, the gasket-contacting portion thereof being in the same plane with its chamber-forming surface 12c.

Figure 5 illustrates an embodiment similar to that of Figure 1 in which the spacing between the recessed gasketcontacting portion 20d of the wall member 11d and the gasket-contacting portion 19d of the wall member 10d, and therefore also the operative thickness of the gasket 17d, are substantially equal to the width of the chamber 16d. While this embodiment does not have the advantage !of utilizing a gasket substantially thicker than the width of the chamber, it possesses all of the thermal expansion and contraction compensating features of the embodiment illustrated in Figure 1.

Figure 6 illustrates a tubular type of thermal diffusion apparatus comprising an inner wall member 30, an outer wall member 31, the outer surface 32 of the inner member 39 and the inner surface 34 of the outer member 31 being concentric and forming an annular separation chamber 36. The upper end of the outer member 31 is shown as having a conically recessed gasket-contacting portion 37 for receiving a gasket 39, and the inner member 30 is provided, at the corresponding end, with a radially protruding conical surface 4i) that is complementary to the recessed conical surface 37 of the outer member 31. At the lower end, the separation chamber 36 is sealed by a cylindrical gasket 41 having a thickness approximately equal to the width of the separation chamber 36. It is to he understood, of course, that the apparatus illustrated in Figure 6 is further provided with suitable ports, such as shown at 42, for the introduction of a fluid into the separation chamber 36 and the removal therefrom of separated fractions, as well as with any desired means for maintaining the chamber-forming surfaces 32 and 34 at different temperatures to impose a temperature gradient across the chamber.

In this embodiment of the invention it will be apparent that it is necessary to provide for relative expansion and contraction of the wall members 30 and 31 at only one end if the wall members are more or less rigidly joined at the other end. It will be apparent, for example, that if Figure 6 represents the relative positions of the various elements of the structure during operation, e. g., when the inner wall member 34) is relatively hot and the outer wall member 31 is relatively cold, the inner wall member 3? will contract when the operation is interrupted or stopped and the upper end thereof will consequently tend to move downward relative to the outer wall member 31. In the construction illustrated in Figure 6 this will result, for the most part, in a slight sliding of the gasket-contacting portion 40 over the surface of the gasket 39 and to a minor extent in applying somewhat greater pressure to the gasket 39. In any event, the necessity of providing a gasket of such extremely small thickness as that of gasket 41; is avoided inasmuch as the thickness of the gasket 39 may be several times the width of the chamber 36.

Figures 7, 8 and 9 illustrate several alternative embodinents of the invention illustrated in Figure 6. In Figure 7 the construction of the outer wall member 310 is identi cal to that shown in Figure 6 but the inner wall member 30a has a gasket-contacting surface 40a of the same diameter as the chamber-forming surface 32a and the shape of the gasket 39:: is correspondingly altered. In Figure 8 the inner wall member 3042 is substantially simb lar to that illustrated in Figure 7 but the outer wall member 3115 is pr vided with a cylindrical recess 37a designed to accommodate a cylindrical gasket 3912 having a thickness substantially greater than the width of the annular separation chamber 36. In order to limit the upward movement of the

gasket material

39a and 39b as a result of the contraction of the outer tube 31, an annular ring 43 may be placed at the top of the inner tube 30a.

In Figure 9, the outer wall member 31a is substantially similar to that illustrated in Figure 8 and the inner wall member 30]) is provided with a radially protruding cylindrical surface having adiameter smaller than the diameter of the cylindrical recessed portion 37a of the outer wall member and a gasket 390 is interposed between the portions 4% and 37a of the members 30]) and 31a, respectively.

It is to be understood, of course, that any two of the embodiments illustrated in Figures 6, 7, 8 and 9 may be combined in a single apparatus. Thus, the structures shown in Figures 7 and 8 may replace the structure shown in the lower end of Figure 6, and the structures shown in Figures 7, 8 and 9 may replace the structure shown at the top of the apparatus in Figure 6.

It is further to be understood that innumerable modifications will at once become apparent to those skilled in the art upon reading this description. All such modifications are intended to be included within the scope of the invention as defined in the appended claims.

I claim:

1. Thermal diffusion apparatus comprising two wall members subject to differential thermal expansion and contraction and having closely and substantially equidistantly spaced surfaces defining a thermal diffusion separation chamber, means associated with each of said wall members for maintaining one of said surfaces at a higher temperature than'the other to maintain a temperature gradient across said chamber, and a gasket having a portion thicker than the spacing between said surfaces and being positioned between and in contact with portions of said wall members for confining fluid within said chamber, the gasket-contacting portion of one of the wall members having a recess in its chamber-defining surface to admit said gasket, the gasket contacting portion of said other of the wall members being aligned with the chamber defining surface of said other of the wall members.

2. The apparatus defined in claim 1 wherein the wall members and chamber-defining wall surfaces are cylindrical and concentric and form an annular separation chamber.

3. The apparatus defined in claim 2 wherein one end of the outer wall member having an inner cylindrical surface defining one side of the annular separation chamber is provided with a cylindrical recess of greater diameter than the diameter of said inner cylindrical surface, said outer wall member adapted to be maintained at a relatively lower temperature than the inner wall member, the gasket-contacting portion of the inner wall member being a cylindrical surface coaxial with the chamberclefining wall surface of the inner wall member.

4. The apparatus defined in claim 2 wherein one end of the outer wall member having an inner cylindrical surface defining one side of the annular separation chamber is provided with a cylindrical recess of greater diameter than the diameter of said inner cylindricm surface and the corresponding end of the inner wall member having an outer cylindrical surface defining the other side of the annular separation chamber has a diameter substantially equal to the diameter of said outer cylindrical surface, said outer wall member adapted to be maintained at a relatively lower temperature than said inner wall member, the gasket-contacting portion of the inner wall member being a cylindrical surface coaxial with said outer cylindrical surface of said inner wall member.

5. The apparatus defined in claim 2 wherein one end of the outer wall member having an inner cylindrical surface defining one side of the annular separation chamber is provided with a cylindrical recess of greater diameter than the diameter of said inner cylindrical surface and the corresponding end of the inner wall member having an outer cylindrical surface defining the other side of the annular separation chamber is provided with a radially'protruding cylindrical surface having a diameter smaller than the diameter of the cylindrically recessed portion of the outer wall member, said outer wall member adapted to be maintained at a relatively lower temperature than said inner wall member, the gasket-contacting portion of the inner wall member being a cylindrical surface coaxial with said outer cylindrical surface of the inner wall member.

References Cited in the file of this patent UNITED STATES PATENTS Debye Sept. 11, 1951

Claims

1. THERMAL DIFFUSION APPARATUS COMPRISING TWO WALL MEMBERS SUBJECT TO DIFFERENTIAL THERMAL EXPANSION AND CONTRACTION AND HAVING CLOSELY AND SUBSTANTIALLY EQUIDISTANTLY SPACED SURFACES DEFINING A THERMAL DIFFUSION SEPARATION CHAMBER, MEANS ASSOCIATED WITH EACH OF SAID WALL MEMBERRS FOR MAINTAINING ONE OF SAID SURFACES AT A HIGHER TEMPERATURE THAN THE OTHER TO MAINTAIN A TEMPERATURE GRADIENT ACROSS SAID CHAMBER, AND A GASKET HAVING A PORTION THICKER THAN THE SPACING BETWEEN SAID SURFACES AND BEING POSITIONED BETWEEN AND IN CONTACT WITH PORTIONS OF SAID WALL MEMBERS FOR CONFINING FLUID WITHIN SAID CHAMBER, THE GASKET-CONTACTING PORTION OF ONE OF THE WALL MEMBERS HAVING A RECESS IN ITS CHAMBER-DEFINING SURFACE TO ADMIT SAID GASKET, THE GASKET CONTACTING PORTION OF SAID OTHER OF THE WALL MEMBER BEING ALIGNED WITH THE CHAMBER DEFINING SURFACE OF SAID OTHER OF THE WALL MEMBERS.