GB2040723A

GB2040723A - Permeator apparatus

Info

Publication number: GB2040723A
Application number: GB7943106A
Authority: GB
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1978-12-22
Filing date: 1979-12-14
Publication date: 1980-09-03
Also published as: DE2950426C2; AU5384679A; IT1126063B; SU1069603A3; JPS5586503A; IT7941682A0; CA1124185A; AU525429B2; MX149501A; SE7910321L; SE430654B; BE880629A; DE2950426A1; NL7909027A; FR2444485A1; ZA796819B; GB2040723B

Abstract

In a permeator containing hollow fiber membranes, a resilient means 126 cooperates between a tubular shell 102 containing the hollow fiber membranes 116 and at least one tube sheet 118 through which bores of the hollow fiber membranes communicate wherein a force directing the tube sheet longitudinally outward from the shell is provided. An end closure cap 128 is adapted to be removably fastened to the end of the shell proximate to the tube sheet. A first sealing means 130 is positioned between the end closure cap and the shell to provide an essentially fluid-tight relationship, and a second sealing means 134 is positioned between the end closure cap and the tube sheet wherein the resilient means provides a sufficient force on the tube sheet that the second sealing means provides an essentially fluid-tight seal. <IMAGE>

Description

SPECIFICATION Permeator apparatus This invention pertains to end closures and also to apparatus for separating at least one fluid from a fluid mixture containing at least one other component by selective permeation of the at least one fluid through membranes which apparatus utilize an end closure of this invention. More advantageously, this invention relates to improved separation apparatus utilizing hollow fiber membranes in which the hollow fiber membranes are embedded in a tube sheet and the bores of the hollow fibers extend in a fluid communication relationship through the tube sheet.

The use of membranes for separating at least one fluid from a fluid mixture containing at least one other component has long been suggested. In these membrane separations, permeable fluids in the fluid mixture (feed mixture) pass, under the influence of a driving force such as concentration, partial pressure, total pressure, etc., (depending on the nature of the membrane separation operation) from a feed side of the membrane to a permeate exit side of the membrane. The fluid may pass through the membrane by interaction with the material of the membrane or by flow in the interstices or pores present in the membrane. Separations effected by membranes can include gas-gas, gas-liquid, and liquid-liquid (including liquid-dissolved solids) separations.

The viability of the use of membranes for fluid separations as compared to other separation procedures such as absorption, adsorption, distillation, and liquifaction often depends upon the cost (including installation and operating cost) of the apparatus for conducting separation procedure, the degree of selectivity of separation which is desired, the total pressure losses caused by such apparatus which can be tolerated, the useful life of such apparatus, and the size and ease of use of such apparatus. Film membranes may frequently not be as attractive as other separation apparatus due to the need for film membranes to be supported to withstand operating conditions and the overall complexity of apparatus containing film membranes. Membranes in the configuration of hollow fibres, or hollow filaments, may overcome some of the deficiencies of film membranes for many separation operations in that the hollow fibres are generally self-supporting, even during operating conditions, and provide a greater amount of membrane surface area per unit volume of separation apparatus than that which may be provided by film membranes. Thus, separation apparatus containing hollow fibers may be attractive from the standpoint of convenience and size and reduced complexity of design.

Separation apparatus (permeators) utilizing hollow fiber membranes generally comprise an essentially fluid impermeable tubular shell containing a plurality of hollow fibers which may be arranged in one or more bundles. In order to separate the exterior side of the hollow fibers (shell side) from the bore side of the hollow fibers such that the only fluid communication across the walls of the hollow fibers is through the walls of the hollow fibers which walls effect the desired separation, the hollow fibers are generally embedded in an essentially fluid impermeable tube sheet in which essentially only the bores of the hollow fibers extend through the tube sheet in a fluid communication relationship. While the hollow fibers may be embedded in the material to the tube sheet in an essentially fluid-tight manner, it is also necessary that the tube sheet be in an essentially fluid-tight relationship in the permeator such that fluid does not pass between the shell side and bore side of the hollow fibers except by passage through the walls of the hollow fibers. Even small leakages around the tube sheet can have serious effects on the performance of the permeator.

More advantageously, the tube sheet and bundle assembly should be capable of being facilely installed and removed from the shell. In many instances, especially for permeators utilized to separate fluids at high pressures, the shell represents a significant capital expenditure and thus is preferably capable of being re-used upon expiration of the useful life of the hollow fiber membranes. Accordingly, the tube sheet and bundle assembly should be capable of being quickly and easily removed from the permeator, and the new tube sheet and bundle assembly should be capable of being readily installed in a shell without difficulties in obtaining the desired fluid-tight relationship of the tube sheet in the permeator.

One of the often disclosed means for providing the desired fluid-tight relationship between the tube sheet and the shell involves the use of O-rings which surround the tube sheet and are positioned between the tube sheet and the interior surface of the shell.

The use of sucn O-rings are disclosed, for instance, by McLain in United States patent 3,422,008; MacNamara, et al., in United States patent 3,702,658; and Clark in United States patent 4,061,574. The presence of O-rings between the side of the tube sheet and the interior side of the shell can provide undue difficulties in the insertion and removal of the tube sheet and hollow fiber membrane assembly from the shell. Moreover, the interior surface of the shell and the lateral surface of the tube sheet must be machined to sufficiently close tolerances such that the desired fluid-tight relationship can be achieved.

Furthermore, since the achievement of the fluid-tight relationship may be dependent upon close toleranc- ing, unavoidable differentials in expansions of the tube sheet and shell, e.g., due to changes in temperature, swelling agents in the fluids being processed, etc., may result in substantial difficulties.

By this invention permeators containing hollow fiber membranes and utilizing essentially fluid impermeable tube sheets are provided wherein substantially the only fluid communication between the shell side and bore side of the hollow fiber membranes is through the walls of the hollow fibers.

Advantageously, the permeators of this invention can permit facile installation and removal (including replacement) of the tube sheet and hollow fiber membrane assembly. Moreover, the advantages provided by this invention can be obtained without undue machining of the interior surface of the shell or the tube sheet, yet an essentially fluid-tight relationship can be obtained. The permeators of this invention are able to employ high pressure differentials between the shell and the bore sides of the hollow fiber membranes. Furthermore, all sealing members can be readily exposed such that imperfections, dirt, or other debris which may adversely affect the fluid-tight relationship can be easily obviated. Additionaily, differentials in expansions of the tube sheet or shell can be tolerated without deleterious effect to the fluid-tight relationship, even when the expansions occur during use of the permeator.

The highly desirable benefits provided by the permeators of this invention can readily be achieved without undue fabrication efforts, and in many instances, the fabrication of the permeators of this invention may be facilitated as compared to previously suggested permeator designs. While substantial advantages with respect to permeators are provided by this invention, it is clear that other apparatus comprising an external container and at least one internal container, e.g., tube-in-shell heat exchangers, vessels holding two separate fluids, etc., can also be significantly benefited.

An apparatus comprising an end closure of this invention comprises an external container having at least one opening; and an end closure cap removably fastened to and covering a said opening of the external container in a fluid-tight relationship; at least one internal container having at least one opening, a said lateral container being positioned within said external container with the internal container being adapted to contact said end closure cap to cover a said opening of the internal container; and at least one resilient means cooperating between the external container and a said internal container to provide a sufficient force on a said internal container to provide an essentially fluidtight relationship between the end closure cap and a said internal container.

In an aspect of this invention, a permeator comprises an elongated tubular shell having at least one open end; and essentially fluid impermeable end closure cap removably fastened to and covering said elongated tubular shell at said open end, said end closure cap having at least one fluid communication port; a plurality of hollow fibers, which hollow fibers exhibit selectivity to the permeation of at least one fluid in a fluid mixture containing at least one another component, said hollow fibers being generally parallel and extending longitudinally to form at least one bundle in the elongated tubular shell; an essentially fluid-impermeable tube sheet having an outside face wherein the hollow fibers in said at least one bundle are embedded in the tube sheet such that the bores of the hollow fibers provide fluid communication through the tube sheet, wherein said outside face extends laterally beyond the periphery of said at least one bundle embedded in the tube sheet and is proximate to the end closure cap; at least one resilient member cooperating between the shell and tube sheet and being adapted to provide a force on the tube sheet, which force is generally directed longitudinally outward from said open end of the shell to said end closure cap; a first sealing means between the end closure cap and the shell which is adapted to provide an essentially fluid-tight seal between the end closure cap and the shell; and a second sealing means between the end closure cap and the outside face of the tube sheet, said second sealing means substantially surrounding said at least one bundle embedded in said tube sheet, wherein said at least one resilient member provides sufficient force on the tube sheet such that said second sealing means provides an essentially fluid-tight seal between the outside face of the tube sheet and the end closure cap. Conveniently, the fastening of the end closure cap to the shell can simultaneously effect the fluid-tight relationship between the end closure cap and the shell as well as the end closure cap and the tube sheet.

The permeator of this invention may be any suitable design for effecting fluid separations and may be a single-ended or double-ended permeator.

A single-ended permeator has a tube sheet at only one end, and one or both ends of the hollow fibers are embedded in the tube sheet. When only one end of each of the hollow fibers is embedded in the tube sheet, the other end must be plugged or otherwise closed. In a double-ended module, a tube sheet is provided at each end of the shell and the hollow fibers may extend from one tube sheet to the other tube sheet, or the permeators may contain at least two distinct bundles of hollow fibers where at least one bundle extends into only one tube sheet. One or both tube sheets of a double ended module may be in a fluid-tight relationship in accordance with this invention. The tubular shell of the permeator may have any suitable cross-sectional configuration and sufficient volume to provide a desired amount of membrane surface area in the permeator. Generally shells having a circular cross-sectional configuration are employed because of their availability, handling convenience, and strength; however, shells of other cross-sectional configurations e.g., rectangular, may be highly suitable for many permeators. Often, shells have a major cross-sectional dimension of at least about 0.02 or preferably at least about 0.05 meter, say, up to about 1 or 2 or more meters. The length of the shell containing the hollow fibers is frequently at least about 0.2 or 0.3, say, at least about 0.5, meter, up to 10 or more meters.

The permeator may be operated in any desired manner, e.g., the fluid feed mixture may be introduced into the shell and initially contact the shell side of the hollow fibers, or it may be introduced into the bores of the hollow fibers. The flow patterns of fluid on the shell side of the hollow fibers may be primarily transverse to the longitudinal orientation of the hollow fibers or may be primarily axial to the orientation of the hollow fibers. When the flow on the shell side of the hollow fibres is axial, it may be generally concurrent or countercurrent with the flow in the bores of the hollow fibers. In an advantageous mode of operation of the permeator, the fluid feed mixture is introduced to the shell side of the hollow fibers. Since often the fluid feed mixture is at a higher total pressure than the pressure of the permeating fluid, the pressure differential from the shell side to bore side assists in maintaining the desired fluid-tight relationship between the tube sheet and the end closure cap. Also, this mode of operation can provide a safety valve to protect the hollow fiber membranes. For example, if the shell side total pressure were decreased without a decrease in bore side total pressure, a substantially higher pressure may exist inside the bores of the hollow fibers which could deleteriously affect the hollow fiber membranes. However, this higher pressure may be sufficient to force the tube sheet from its fluid-tight relationship when the end closure cap and thereby release the pressure on the bore side of the hollow fibers prior to any undue deleterious effects on the hollow fiber membranes.

The hollow fiber membranes may be fabricated from any suitable synthetic or natural material suitable for fluid separations or as supports for materials which effect the fluid separations. The selection of the material for the hollow fiber may be based on heat resistance, chemical resistance, and/ or mechanical strength of the hollow fiber as well as other factors dictated by the intended fluid separation for which it will be used and the operating conditions to which it will be subjected. The material forforming the hollow fibers may be inorganic, organic or mixed inorganic and organic. Typical inorganic materials include glasses, ceramics, cermets, metals and the like. The organic materials are usually polymers. The hollow fiber diameters may be selected over a wide range; however, the hollow fiber should have sufficient wall thickness to provide adequate strength to the hollow fiber. Frequently, the outside diameter of the hollow fiber is at least about 20, say, at least about 30 microns, and the same or different outside diameter fibers may be contained in a bundle. Often, the outside diameter of the hollow fibers do not exceed about 800 or 1000 microns since larger diameter hollow fibers may provide less desirable ratios of hollow fiber surface area per unit volume of permeator. Preferably, the outside diameter of the hollow fibers is about 50 to 800 microns. Generally, the wall thickness of the hollow fibers is at least about 5 microns, and in some hollow fibers, the wall thickness may be up to about 200 or 300 microns, say, about 50 to 200 microns.

With hollow fibers fabricated from materials having lesser strength it may be necessary to employ larger hollow fiber diameters and wall thicknesses to impart sufficient strength to the hollow fiber. The walls of the hollow fibers may be essentially solid or may contain a substantial void volume. When voids are desired, the density of the hollow fiber can be essentially the same throughout its wall thickness, i.e., the hollow fiber is isotropic, or the hollow fiber can be characterized by having at least one relatively dense region within its wall thickness in barrierflow relationship in the wall of the hollow fiber, i.e., the hollow fiber is anisotropic.

The hollow fibers are generally parallelly arranged in the form of one or more bundles in the shell.

Generally, at least about 10,000 and often substantially greater numbers, e.g., up to 1 million or more hollow fibers are contained in a permeator. The fibers in the bundle, for instance, may be relatively straight, or they may be spirally wound as disclosed by McLain in United States patent No. 3,422,008. In many instances, a single bundle of hollow fibers employed in a permeator and at least one end of the hollow fibers in the bundle is embedded in a tube sheet. The opposite end of the hollow fibers may be looped back, i.e., the bundle is generally in a U shape, and embedded in the same tube sheet, or the opposite end of the hollow fibers may be plugged or embedded in another tube sheet. When the hollow fibers in the bundle are in a "U" shape, the ends may be segmented such that different regions on the tube sheet contain each end of the hollow fibers. Each of these regions on a tube sheet can be maintained in an essentially fluid impermeable relationship such that fluid communication between the regions can only occur by passage of fluid through the bores of the hollow fibers.

The tube sheet containing at least one end of at least one bundle of hollow fibers may be in any suitable configuration for assembly in the permeator. Sufficient surface area should be provided on the outside face of the tube sheet which surface surrounds at least one bundle embedded in the tube sheet, such that the surface can receive a sealing means and provide an essentially fluid-tight contact with the sealing means. Preferably, sufficient surface area is provided such that fluid communication with the bores of the hollow fibers in the bundle is substantially unhindered. For example, in a permeator containing a single bundle of hollow fibers having a generally circular transverse cross-section, the tube sheet may have a generally circular crosssection with a larger diameter than that of the bundle such that a sealing means can contact the outside face of the tube sheet without substantially blocking fluid communication to or from the bores of the embedded hollow fibers. In permeators in which more than one bundle of hollow fibers extends through the tube sheet, a sealing means may surround all of the bundles at the outside face of the tube sheet, or a sealing means can extend around a portion of the bundles at the outside face. Frequently, the zone to be contacted by the sealing means is at least about 0.005, e.g., at least about 0.01, meter in width. The outside face may be continuous or non-continuous, i.e., the tube sheet surface may be unitary or the tube sheet may have a separate lateral extension which can provide area for contact with the sealing means. Of course any lateral extension which is in contact with the sealing means should itself be in a fluid-tight relationship with the tube sheet. The outside face of the tube sheet may be substantially perpendicular to the orientation of the hollow fibers; however, it is clear that the benefits of this invention can be achieved utilizing outside faces which are, e.g., bevelled, curved, uneven (e.g., indented, stepped, etc.) or the like. The hollow fibers may extend through the outside face of the tube sheet, or more frequently, the hollow fibers are flush with the outside face of the tube sheet.

The tube sheet may extend at least partially into the shell, or, if desired, it may reside outside the shell at the open end. When the tube sheet is intended to at least partially be placed inside the shell, it is preferred that the cross-sectional dimensions of the tube sheet be sufficiently less than the crosssectional dimensions of the shell that the tube sheet can be slidably positioned within the shell. Since a fluid-tight relationship need not exist between the interior of the shell and the lateral wall of the tube sheet, close tolerancing of the dimensions of the shell and the tube sheet need not be provided.

Hence, if the tube sheet needs to be severed to expose open hollow fiber bores, the severing operation can be conducted to provide desirable openness to the bores of the hollow fibers without undue concern to the dimension of the the tube sheet. The tube sheet containing at least one end of at least one bundle of hollow fibers may be formed in any suitable manner, e.g., by casting a potting material around the end of the bundle such as disclosed in United States patent Nos. 3,339,341 (Maxwell, et al.) and 3,442,389 (McLain) or by impregnating the ends of the fibers with potting material while assembling the hollow fibers to form a bundle such as disclosed in United States patent Nos. 3,455,460 (Mahon) and 3,690,465 (McGinnis, et al.).

Suitable potting materials include settable liquid polymeric compositions (such as epoxies, urethanes, etc.), solders, cements, waxes and the like. The thickness of the tube sheet is generally sufficient to provide suitable strength for withstanding the total pressure differentials to which the tube sheet may be subjected in separation operations.

Thus, the thickness employed may depend upon the strength of the potting material. Also, the tube sheet should be sufficiently thick that ample contact is provided between the hollow fibers and the potting material such that they are in an essentially fluidtight relationship. Often, tube sheets are at least about 0.01, e.g., about 0.01 to 0.25 meter in thickness.

At least one resilient member cooperates between the shell and the tube sheet to provide a force on the tube sheet generally directed longitudinally outward from the open end of the shell and toward the end closure cap. The resilient member may, for example, be a spring, such as a coil spring, leaf spring, wave spring, metal strip spring, ball spring plunger, etc., or a resiliently deformable material such as flexible plastics, and the like. Sufficient force is preferably generated by the resilient member that the second sealing means positioned between the outside face of the tube sheet and the end closure cap can provide an essentially fluid-tight relationship between the end closure and the outside face of the tube sheet under expected operating conditions. In many instances, the resilient means generates a pressure of at least about 5, more frequently at least about 10, or even 100 or more, kilograms per square centimeter on the second sealing means. Preferably the shell side of the hollow fibers is at a higher total pressure than the total pressure on the bore side of the hollow fibers. Thus, the total pressure differential across the tube sheet can assist in providing the essentially fluid-tight relationship between the tube sheet and end closure. Advantageously, the pressure generated by the resilient means is below a pressure differential which could deleteriously affect the hollow fiber membrane when the higher pressure is on the bore side of the hollow fibers such that a safety valve can be provided by the end closure structure.

The resilient member cooperates between the shell and the tube sheet. Advantageously the resilient means has sufficient flexibility that the desired fluid-tight seal can be maintained even though the dimensions of, for instance, the second sealing means or the tube sheet or the shell may change over a period of time due to mechanical fatigue, deleterious effects by constitutents in the feed and/or permeate streams from the permeator, temperature changes, and the like. Moreover, it is particularly desirable that the resilient means has sufficient resiliency such that the tube sheet need not be precisely machined to fit within the permeator. Accordingly, in a given permeator and in accordance with this invention, tube sheets having dimensions varying by, e.g., up to several millimeters or more, may be employed while still providing the desired force to provide the fluid-tight contact. The resilient member may be in contact with the interior of the shell or the surface at the open end of the shell. The point of contact of the resilient member with the shell may also be variable such that tube sheets having larger variations and dimensions can be accommodated. The resilient means may contact the tube sheet in any suitable manner such that the desired forces on the tube sheet are provided. For instance, the resilient means may contact the inner face of the tube sheet or may contact a protrusion extending generally outward from the sides of the tube sheet. Preferably, the resilient means is easily removed from the tube sheet such that replacement of the tube sheet and hollow fiber membrane assembly is facilitated.

The first sealing means and the second sealing means may be comprised of the same or different material and each may be in a suitable configuration to effect desired fluid-tight relationships. Often the sealing are composed of natural or synthetic polymeric material which may, if desired, contain organic or inorganic fillers. The material of the sealing means should be sufficiently inert to the fluids to which it may become contacted such that it is not deleteriously effected during the separation operations. Preferably, the material of the sealing means has sufficient flexibility that a suitable fluidtight seal can be obtained even in the presence of minor imperfections in the surfaces to which it is contacted. Suitable sealing means thus often include gaskets, O-rings, and the like.

The end closure cap is adapted to be removably attached to the shell. A particularly convenient means for attaching the end closure to the shell includes the use of flanges attached by bolts.

Advantageously, the first sealing means is positioned between the shell and the end closure cap such that when the end closure cap is securely tightened to the shell a sealing contact is made by both the end closure cap and the shell with the sealing means. Also, when the end closure cap is securely fastened to the shell, the resilient member provides sufficient force on the tube sheet that the second sealing means maintains as essentially fluid tight seal between the outside face of the tube sheet and the end closure cap. It should be understood that the first sealing means and the second sealing means may be composed of, e.g., a single gasket.

One surface of the gasket partially contacts the shell and the other part of that surface of the gasket contacts the outer face of the tube sheet. Of course, the first sealing means and the second sealing means may be comprised of more than one, e.g., gasket or O-ring.

In the drawings Figure 1 is a schematic representation of a longitudinal cross-section of a permeator in accordance with this invention wherein the resilient means is positioned at the open end of the shell.

Figure 2 is a schematic representation of a partial view of a longitudinal cross-section of a permeator in accordance with this invention wherein the tube sheet is positioned outside of the longitudinal shell.

Figure 3 is a schematic representation of a partial view of a longitudinal cross-section of a permeator in accordance with this invention wherein the resilient member is positioned within the shell.

Figure 4 is a schematic representation of a partial view of a longitudinal cross-section of a permeator in accordance with this invention wherein a spacer is employed between the end closure cap and the tube sheet.

The permeator depicted in Figure 1 is generally designated by the numeral 100. Permeator 100 comprises shell 102 (only the head and tail ends are depicted) which is adapted to receive a tube sheet at one end. Shell 102 may be comprised of any suitable, fluid impervious material such as metals and plastics. In many permeators, metals such as steel are employed due to their ease of fabrication, durability, and strength. The shell may be in any suitable cross-sectional configurations; however, generally circular cross-sections are preferred. Shell 102 has head flange 104 at the end adapted to receive the tube sheet and tail flange 106 at the opposite end. As shown, shell 102 is provided with port 108 adjacent to the head flange 104. Port 108 can provide for fluid communication with the interior of the shell. While only a single port 108 is depicted, it should be understood that a plurality of ports 108 may be positioned around the periphery of shell 102.

End cap 110 is positioned at the tail end of shell 102 and is fastened by bolts (not shown) to tail flange 106. Gasket 112 is positioned between end cap 110 and tail flange 106 to provide an essentially fluid impermeable seal. End cap 110 is provided with port 1 14 for fluid communication through the end cap.

Bundle 116 (not shown in cross-section) is composed of a plurality of hollow fibers is positioned within shell 102. Often the bundle comprises over 10,000 hollow fibers, and with smaller diameter hollow fibers and larger diameter shells, there may be an excess of 100,000 or even an excess of 1,000,000 fibers. As depicted, the bundle has essentially the same cross-sectional configuration as that of the shell. One endxof each of the hollow fibers in bundle 116 is embedded in tube sheet 118 (not shown in cross-section). The bores of the hollow fibers communicate through tube sheet 118 to the open end of shell 102. The other end of each of the hollow fibers is embedded in plug 120 (not shown in cross-section). The bores of the hollow fibers do not communicate through plug 120. The tube sheet and plug may be formed in any suitable manner, e.g., by casting a potting material or by impregnating the ends of the fibers with potting material while assembling the hollow fibers to form the bundle.

As shown in Figure 1 t concentric central portion extends beyond the surrounding annular portion. Wave spring 226 is positioned between the end of shell 202 and the inside face of tube sheet 218. Wave spring 226 provides a resilient force adapted to direct tube sheet 218 longitudinally outward from shell 202. Head end closure cap 228 is adapted to be securely fastened to shell 202 by use of bolts (not shown). Gasket 230 is positioned between head end closure cap 228 and head flange 204 of shell 202 such that when head end closure cap 228 is securely attached to shell 202 a fluid-tight relationship is achieved. O-ring 234 contacts the outside face oftube sheet 218 at the annular portion and is maintained in a fluid-tight relationship with head end closure 223 when head end closure cap 228 and shell 202 are fastened due to the longitudinally outward forces exerted by a wave spring 226. Head end closure cap 228 is provided with port 236 for fluid communication through permeator 200 with the bores of the hollow fiber membranes.

Figure 3 illustrates the head portion of a permeator generally designated by the numeral 300. Permeator 300 comprises shell 302. Shell 302 comprises head flange 304 and bundle restraining tube 303 which extends therefrom. Head flange 304 has a large central bore and the end portion of bundle constraining tube 303 extends into the bore such that an annular region exists between the exterior surface of tube 303 and the surface of the bore in head flange 304. Spacing member 305 is positioned within the bore and head flange 304 in order to secure tube 303 therein. Spacing member 305 has a longitudinal extending portion which is adapted to be affixed to tube 303 and extends longitudinally beyond tube 303. At the end of spacing member 305 distant from tube 303, a laterally extending portion is provided which contacts the surface defining the bore in head flange 304. Head flange 304 is provided with port 308 for fluid communication into the annular region surrounding tube 303. The longitudinal surface of spacing member 305 has fluid entry ports 307 for communication of gases between the interior of tube 303 and the annular region surrounding tube 303, and thus spacing member 305 serves as a fluid distribution plenum.

Bundle 316 (not shown in cross-section), which is composed of a plurality of hollow fiber membranes, is positioned within tube 303 and extends beyond tube 303 and spacing member 307 into tube sheet 318 (not shown in cross-section). Tube sheet 318 is positioned within the bore of head flange 304 and wave spring 326 is positioned between the inside face of tube sheet 318 and the laterally extending surface of spacing member 305.

The end closure cap of permeator 300 comprises two members the first being tube sheet sealing member 335 which is adjacent to head flange 304, and fluid distribution member 329 which is positioned on the other side of sealing member 335.

Sealing member 335 has a sufficiently small concentric bore such that ample surface is provided to contact O-ring 334 in a fluid-tight manner which in turn contacts the outside face of tube sheet 318. The bore of sealing member 335 is sufficiently large in diameter that no undue restriction to flow from the bores of the hollow fibers occurs. Fluid distribution member 329 is provided with port 336 for fluid communication from the permeator. Gasket 330 is positioned between head flange 304 and sealing member 335, and gasket 331 is positioned between sealing member 335 and fluid distribution member 329. The gaskets are adapted to provide a fluid-tight relationship between the members when the members are secured together, e.g., by the use of bolts (not shown).

Figure 4 illustrates the head portion of a permeator generally designated by the numeral 400. Permeator 400 comprises shell 402 having a head end of increased diameter and head flange 404 and fluid communication port 408. Within shell 402 is positioned bundle 416 (not shown in cross-section) which is composed of a plurality of hollow fiber membranes. The bundle has the same general transverse cross-sectional configuration as the interior of the shell. Bundle 416 passes through plenum 405 having fluid distribution ports (not shown). Plenum 405 is positioned within the head end of shell 402 and serves to distribute fluid passing to or from fluid communication port 408. Bundle 416 is terminated at the head end with tubes sheet 418 (not shown in cross-section). Wave springs 426a and 426b are separated by washer 427 and serve to provide the resilient member between plenum 405 and tube sheet 418. By utilizing alternating wave springs and washers, a desired spacing and flexibility can be achieved. Accordingly, suitably forces can be obtained without concern for close tolerancing of the thickness of the tube sheet. At the face of tube sheet 418 is positioned annular sealing spacer 435.

Annular sealing spacer has 0-ring 437 positioned on its face adjacent the face of tube sheet 418 and 0-ring 439 positioned on its opposite face. Head end closure cap 428 is adapted to be securely fastened to shell 402 by the use of bolts (not shown) and cover the bore in the shell. 0-ring 430 is positioned between head end closure cap 428 and head flange 404 such that when head end closure cap 428 having fluid communication port 436 is securely attached to the shell a fluid-tight relationship is achieved. 0-ring 439 contacts head end closure cap 428 when attached to the shell. A fluid-tight relationship is provided by the forces exerted on tube sheet 418 by wave washers 426a and 426b. These forces also provide a fluid-tight seal of 0-ring 437 with the face of tube sheet 418. The width of annular sealing spacer 435 can be chosen to provide the desired compression of wave springs 426a and 426b and thus enable desired pressures to be provided by the wave springs.

Claims

1. A permeator comprising an elongated tubular shell having at least one open end; an essentially fluid impermeable end closure cap removably fastened to and covering said elongated tubular shell at said open end, said end closure cap having at least one fluid communication port; a plurality of hollow fibers exhibiting selectivity to the permeation of at least one fluid in a fluid mixture containing at least one another component which hollow fibers are generally parallel and extend longitudinally to form at least one bundle in the elongated tubular shell, an essentially fluid impermeable tube sheet having an outside face wherein the hollow fibers in said at least one bundle are embedded in the tube sheet such that the bores of the hollow fibers provide fluid communication thrugh the tube sheet, wherein said outside face extends beyond the periphery of said at least one bundle embedded in the tube sheet and is proximate to the end closure cap; at least one resilient member cooperating between the shell and the tube sheet and being adapted to provide a force on the tube sheet, which force is generally directed longitudinally outward from said open end of the shell; a first sealing means between the end closure cap and the shell which is adapted to provide an essentially fluid-tight seal between the end closure cap and the shell; and a second sealing means between the end closure cap and the outside face of the tube sheet, said second sealing means substantially surrounding said at least one bundle embedded in said tube sheet, wherein said at least one resilient member provides sufficient force on the tube sheet such that said second sealing means provides an essentially fluid-tight seal between the outside face of the tube sheet and the end closure cap.

2. The permeatorof claim 1 in which the tube sheet is at least partially within the shell and is longitudinally slideably positioned within the shell.

3. The permeator of claim 1 or 2 in which the resilient member contacts the interior surface of the shell and contacts the tube sheet.

4. The permeator of any of claims 1 to 3 in which the resilient member contacts the end surface of the shell and contacts the tube sheet.

5. The permeator of any of claims 1 to 4 in which the tube sheet is adapted to be removed from the permeator.

6. The permeator of claim 1 in which the tube sheet is outside of the shell.

7. The permeator of any of claims 1 to 5 in which the resilient means is a spring.

8. The permeator of any of claims 1 to 7 in which the outside face of the tube sheet is substantially perpendicular to the orientation of the hollow fibers.

9. The permeator of any of claims 1 to 8 having a single open end.

10. The permeator of any of claims 1 to 9 having a single bundle.