CA2030303C - Hollow fiber bundle element - Google Patents

Abstract

A hollow fiber bundle element is provided comprising a bundle of microporous hollow fibers disposed in a cylindrical impermeable casing. with respect to each fiber, its wall is selected to provide a permeability in the microfiltration range (0.05 to 5 micrometers). The bundle forms two longitudinal passageways, being the lumina of the fibers and the other being the void space between the fibers. A first of these passageways is densely and uniformly packed with minute solid particles. No binder is used to fix the particles - they maintain their distribution in the passageway as a result of having been densely packed under pressure. The ends of the first passageway are sealed and the fiber wall pores are smaller than the particles, whereby the particles are immobilized therein. The hollow fiber module packed with minute adsorbent particles in the first passageway provides an adsorber. A fluid mixture comprising a carrier and an adsorbate is introduced into the second passageway. The adsorbate diffuses through the fiber walls and is collected by the adsorbent particles. By way of result, the particles used in this adsorber can be of much smaller size than those used in a conventional fixed bed column. The use of small adsorbent particles enhances adsorption rate, and availability of a separate longitudinal flow passageway reduces pressure drop across the adsorber. Alternatively, the hollow fiber module may be packed with minute catalyst particles to provide an effective catalytic reactor with improved mass transfer between the catalyst particles in the first passageway and surrounding fluid containing the reactants, in the second passageway.

Description

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2 This invention relates to a hollow fiber bundle element

3 which may be packed in a first passageway with minute solid

4 particles, such that the particles may interact with fluid components in a second passageway.

7 Adsorption processes are widely used in industry for 8 separation of fluid mixtures (gas or liquid). The separation is 9 based on preferential adsorption of selective components on the surface of solid adsorbents. For efficient separation, the 11 adsorbent material must have large surface areas to provide 12 reasonable adsorptive capacities. The commonly used adsorbents, 13 such as molecular sieve zeolites, activated carbon, alumina and 14 silica gel, have surface areas of at least 200 m2/g.
Most industrial adsorption processes are carried out 16 in f fixed-bed type columns . The adsorbent granules are packed and 17 immobilized in a cylindrical vessel. As the fluid mixture to be 18 separated is passed through the packing via the void spaces among 19 the granules, the adsorbable components in the mixture are taken up and retained by the adsorbent.
21 Since the adsorbent has a limited adsorption capacity, 22 it will become gradually saturated with adsorbate, and periodic ,.~. ~~z.3 1 ~ adsorbent regeneration is required. For continuous processing 2 of a feed mixture, a multi-bed system is used in which each bed 3 goes through the adsorption/regeneration cycle in sequence.
4 Several different regeneration methods have been used commercially. Chief among them are the thermal swing adsorption 6 (TSA) and pressure swing adsorption (PSA) processes. In the TSA
7 process, the saturated adsorbent is regenerated by purging with 8 a hot gas. Each heating/cooling cycle usually requires a few 9 hours to over a day. In the PSA process, the adsorbent regeneration is effected by purging with a portion of the 11 purified product gas at reduced pressure. The throughput is 12 higher than that of the TSA since faster cycles, usually in 13 minutes, are possible.
14 Apart from the adsorptive capacity of the adsorbent, the adsorption rate and pressure drop are two important factors 16 that must be considered in adsorber design.
17 Pressure drop through the adsorber column should be 18 minimized, because high fluid pressure drop can cause movement 19 or fluidization of the adsorbent particles, resulting in serious attrition and loss of the adsorbent.
21 The adsorption rate has a significant bearing on the 22 efficiency of the adsorption process. This rate is usually 23 determined by the mass transfer resistance to adsorbate transport 24 from the bulk fluid phase to the internal surfaces of the adsorbent particles. Slow adsorption rate due to large mass 26 transfer resistance will result in a long mass transfer zone 27 (MTZ) within which the adsorbent is only partially saturated with 28 adsorbate. The adsorbent in the region upstream of the MTZ is 29 substantially saturated with adsorbate, while that downstream of 1 the MTZ is essentially free of adsorbate. As the fluid continues 2 to flow, the MTZ advances through the adsorber column in the 3 direction of the fluid stream. The adsorption step must be 4 terminated before the MTZ reaches the adsorber outlet in order to avoid the breakthrough of adsorbate in the effluent stream.
6 A long mass transfer zone, which contains a large quantity of 7 partially utilized adsorbent, will, therefore, result in a short 8 adsorption step and inefficient use of the adsorbent capacity.
9 These effects are especially serious for the pressure swing adsorption process.
11 Both the pressure drop and the mass transfer resistance 12 are strongly influenced by the size of the adsorbent particles.
13 Changing the particle size, unfortunately, has opposite effects 14 on these two important factors. This is elaborated below:
(1) The pore sizes of the void spaces among the 16 adsorbent particles in the fixed-bed are 17 proportional to the size of the particles. Since 18 the resistance to the fluid flow through the 19 adsorber is inversely proportional to the pore size of the packed bed, the use of small adsorbent 21 particles will cause high pressure drop. For this 22 reason, the sizes of particles of commercial 23 adsorbents for fixed-bed operation are generally 24 larger than 2 mm in equivalent diameter.
Adsorbent of smaller particle sizes, such as 26 zeolite crystals (less than 10 microns), are 27 pelletized using binding material to suitable 28 sizes.
29 (2) Almost all the surface areas of commercial adsorbents are located at the interior of the 2~
1 ~ adsorbent particle. For adsorption to occur, the 2 adsorbate needs to be transported from the 3 external fluid phase to the interior surface of 4 the particle. The transport rate is dominated by two mass transfer mechanisms in series: (a) 6 interfacial mass transfer - diffusion through the 7 fluid boundary layer surrounding the external 8 surface of the adsorbent particle; and (b) 9 intraparticle mass transfer - diffusion through the internal pore space (micropores and 11 macropores) of the particle to its interior 12 surface where adsorption takes place. The size 13 of the particle has significant effects on the 14 rates of these two diffusion processes. Small particles offer large fluid/solid contact areas 16 in the fixed bed for interfacial mass transfer and 17 reduce the path length for the intraparticle 18 diffusion. Hence, small adsorbent particles will 19 increase adsorption rate and result in a narrow mass transfer zone for fast and efficient 21 operation of adsorption/desorption cycles.
22 The above discussions and analysis show that small 23 adsorbent particles are desirable for efficient adsorption 24 processes, but the minimum particle size is limited by acceptable hydrodynamic operating conditions of the fixed bed ads,orber.
26 That is, one wants to avoid fluidization and excessive pressure 27 drop. Such a concept also applies to a heterogeneous catalytic 28 reaction process, which involves an adsorption step in the 29 reaction mechanism. The use of small catalyst particles will

5 1 enhance mass transfer between the catalyst and surrounding fluid 2 carrying the reactants, but it will also increase pressure drop 3 through the reactor bed.
4 It would therefore be desirable to provide an adsorber or catalytic reactor containing adsorbent or catalyst

6 characterized by a relatively small particle size and yet still

7 able to operate with an acceptable pressure drop.

8 At this point, it is appropriate to shortly describe

9 the structure and operation of a known separation device used for permeation and absorption and referred to as a hollow fiber 11 module. As will become clear below, this module is similar in 12 many respects to a shell and tube heat exchanger. The device is 13 used to separate at least one component (e. g. C02) from a second 14 'carrier' component (e.g. natural gas) with which it forms a feed mixture. A typical module comprises a cylindrical vessel 16 encapsulating a bundle of small-diameter, elongated, hollow 17 fibers. The fibers are formed of a material having a 18 permeability which, in the case of a permeation module, is 19 selected to allow the component to be extracted to diffuse therethrough but to substantially reject the carrier component.
21 In the case of an absorption module, the entire feed mixture may 22 readily diffuse through the fiber wall. The fibers are "potted"
23 at their ends in closure means, such as epoxy tube sheets, so 24 that the ends of the fibers project therethrough, leaving their bores or "lumina" open. The tube sheets function to seal the 26 void space between the fibers at the two ends. The tube sheets 27 further seal or are sealed by means, such as an O-ring, against 28 the inside surface of the vessel. The vessel is provided with 29 a first inlet and first outlet communicating with the ends of the 2~~~~
1 ~ fiber lumina. It further has a second inlet and second outlet 2 communicating with the ends of the void space. In operation, the 3 feed mixture of gases is fed through the second inlet into the 4 void space. In the case of an absorption module, absorbent fluid is fed into the lumina. The absorbate (C02) diffuses through the 6 fiber walls from the void space, is coJ.lected by the absorbent 7 fluid, and exits through the first outlet. The carrier gas, 8 reduced in C02, leaves through the second outlet.
9 With this background in mind, it is now appropriate to describe the present invention.

12 The present inven tion involves use of a known article, 13 namely a module comprising a bundle of hollow fibers contained 14 in an impermeable casing. The bundle may be used to provide interaction between minute solid particles and a feed stream 16 component or components. The fibers each have a microporous 17 permeable wall having pore openings in the range of about 0.05 -18 5 micrometers (known as the "microfiltration range"). The minute 19 solid particles are emplaced in a first of two passageways, either the lumina of the fibers or the void space between the 21 fibers. The particles are sufficiently densely packed 22 substantially throughout the length and breadth of the 23 passageway) so as to have density equal to or greater than a the 24 free-standing bulk density of the particles. The particles are sufficiently small or minut e so as to provide fast mass transfer 26 of the feedstream component or components to the particles where 27 interaction takes place.
They are "free" particles, not being 28 bonded together by binder or the like. The first passageway 1 ,NM~ containing the particles is sealed at its ends, for example by 2 an epoxy tube sheet. The pore openings of the fiber wall are 3 smaller than the particles involved. These openings, however, 4 are large enough to permit the fluid to diffuse therethrough.
The particles are emplaced in the module in a unique 6 fashion. More particularly, a suspension of the particles in a 7 liquid or gas carrier is pumped under pressure into one of the 8 passageways. The carrier filters through the fiber walls into 9 the other passageway and exits the module, leaving the particles trapped in the original passageway. By this process, a dense il uniform dispersion of particles is emplaced in the original 12 passageway throughout its length. The particles are individually 13 free but are collectively immobilized in the original passageway 14 due to the completeness of the packing.
The final product, comprising the casing, the hollow 16 fibers, the end closures, and the charge of particles, is 17 hereafter referred to as the "element".
18 As a result of assembling the foregoing, minute solid 19 particles having fast mass transfer rate are immobilized in the sealed first passageway of the element. Yet feedstream 21 components of a fluid stream that is introduced into the other 22 or second passageway, can still reach and interact with the 23 particles by diffusing through a fiber wall to enter the first 24 passageway.
The pore openings of the fiber wall are sufficiently 26 large to enable the carrier liquid or gas to filter readily 27 therethrough during the fabrication step of emplacing the packing 28 of particles in one of the passageways.

_ 2~0 1 ~ In this fashion, it is feasible to fabricate the 2 element without high expense and it is possible to use very small 3 particles having a very high mass transfer rate, in connection 4 with a pressure-driven fluid mixture to be processed, without having fluidization occur. And the availability of the second 6 passageway, for the passage therethrough of the fluid mixture, 7 has ensured that only a relatively low pressure drop will occur 8 across the element.
9 In one embodiment, the element may be an adsorber. The feedstream then contains an adsorbate. The particles packed in 11 the first passageway are adapted to adsorb the adsorbate from the 12 fluid stream as it flows through the element. An adsorbate-13 depleted stream is the result.
14 In another embodiment, the element may be a catalytic reactor. In this case the feedstream contains reactants. The 16 particles packed in the first passageway are adapted to catalyze 17 reaction between the reactants in the feedstream as it flows 18 through the element. Reaction products in the end stream is the 19 result.
DESCRIPTION OF THE DRAWINGS
21 Figure 1 is a schematic showing the arrangement used 22 to emplace particles in the lumina of an element;
23 Figure 2 is a schematic showing the arrangement used 24 to emplace particles in the void space between the fibers;
Figure 3 is a schematic showing an element, having the 26 particles in the lumina, being used to provide interaction 27 between the particles and a feedstream; and ~~~~
1 ~ Figure 4 is a schematic showing an element, having the 2 particles in the void space between the fibers, being used in 3 conjunction with a vessel to provide interaction between the 4 particles and a feedstream.
nFS~RIpTION OF THE PREFERRED EMBODIMENT
6 The element A can take one of two forms, shown in 7 Figures 3 and 4 (which are not to scale).
8 In Figure 3 the element A is the element itself and 9 comprises a bundle of f fibers 1, each fiber having a bore or lumen 2. The plurality of fibers form a void space 3 between them.
11 An impermeable cylindrical casing 4 contains the bundle. The 12 bundle has top and bottom closures 5, 6 which seal the lumina 2 13 and void space 3. An inlet 7 is provided at one end of the 14 casing 4, for introducing the feed mixture, and an outlet 8 is provided at the opposite end of the casing for exhausting a 16 stream after interaction with the particles. Particles 9 are 17 packed in the lumina 2. The fiber walls have sub-micron sized 18 pores which enable the feedstream components to diffuse readily 19 therethrough but the pores are smaller than the particles 9. As a result of providing fiber walls that prevent the particles 9 21 from moving therethrough and sealing the ends of the lumina 2 22 with the closures 5, 6, the particles 9 are immobilized in the 23 lumina 2.
24 In Figure 4, the element B has the particles 9 disposed in the void space 3 between the fibers 1. Closures 5a, 6a are 26 provided and leave the ends of the lumina 2 open but seal the 27 ends of the void space 3. The element 10 of Figure 4, comprising 28 the bundle of fibers 1, closures 5a, 6a and casing 4, is 2~
1 positioned in a vessel 11 having a top inlet 12 and bottom outlet 2 13. The inlet 12 and outlet 13 communicate with the ends of the 3 lumina 2.
4 From the foregoing, it will be noted that each of the elements provides a continuous longitudinal flow passageway. In 6 the case of the element A, the passageway is the void space 3.
7 In the case of the element B, the passageway is provided by the 8 lumina 2. For separation of fluid mixtures, the feed is directed 9 to flow through the flow passageway. Since the thin and porous fiber wall has negligible mass transfer resistance, the fluid is 11 always in intimate and substantially uniform contact with the 12 particles 9. The elements A, B when used as adsorbers are 13 adapted for use with PSA and TSA systems in accordance with known 14 technology.
Typically the hollow fibers will have a lumen diameter 16 less than 2 mm. The fiber wall will typically have pore openings 17 of about 0.5 micrometer in equivalent diameter.
18 The solid particles or crystals (referred to 19 collectively as "particles") can be packed into the lumina 2 or void space 3 using one of several techniques. More particularly, 21 in the case of non-soluble particles, they are first suspended 22 by agitation in a liquid or gas carrier, such as alcohol, water 23 or air. The suspension is then pumped into the lumina 2 or void 24 space 3, as shown in Figures 1 or 2. The liquid or gas carrier is able to permeate readily through the microporous fiber wall.
26 In the case of pumping the slurry into the lumina 2 (Figure 1), 27 the top ends of the lumina are open, to receive the feed and the 28 bottom ends are sealed. The particles 9 become trapped in the 29 lumina while the carrier diffuses through the fiber walls and 1 p exits through an outlet 8 in the casing 4. In this fashion, a 2 charge of densely packed particles may be accumulated to fill 3 the lumina substantially throughout its length. The top ends of 4 the lumina can then be sealed to immobilize the particles.
Similarly, in the case of pumping the slurry into the void space 6 3 (Figure 2), the top ends of the lumina 2 and the void space 3 7 are closed and the bottom ends of the lumina are left open. The 8 slurry enters the void space, the carrier passes through the 9 fiber walls and exits out the bottom of the lumina, and the particles 9 remain trapped in the void space 3. In both cases, 11 loading may be facilitated by vibration by immersing the module 12 in an ultrasonic bath.
13 In the case of soluble materials, the element, having 14 fibers that will not be wetted by the solvent, can be packed by filling a first passageway of the module with the solution and 16 then drying or leaching out the solvent by circulating air or 17 non-solvent through the second passageway of the module.
18 When the element is used as an adsorber, the particles 19 will be adsorbent particles, preferably selected from the group consisting of molecular sieve zeolites, silica gel, activated 21 alumina, carbon black, and activated carbon. The particle size 22 preferably will be less than 30 microns, most preferably 1 - 30 23 microns. The surface area preferably should be at least about 24 200 m2/g.
Still another class of materials that can be used as 26 the adsorbent are those that can be cast in-situ to form a 27 microporous structure by the sol-gel phase inversion techniques.
28 (See Example 2 and Robert E. Kesting, "Synthetic Polymeric 29 Membrane", 2nd Edition, John Wiley, N.Y., 1985). A typical sol-1 gel process for forming porous structure comprises: preparing 2 a solution of polymeric material, solvent, non-solvent and 3 swelling agent; evaporating or leaching the solvent with non-4 solvent; and drying the non-solvent.
The present hollow fiber element has certain advantages 6 over conventional packed bed elements, namely:
7 (1) In the hollow fiber element, the fluid pressure 8 drop through the element is independent of the 9 size of the particles, because the fluid flow path is separated from the particles by the microporous 11 fiber walls;
12 (2) The hollow fiber element can use very fine 13 particles. This will reduce mass transfer 14 resistance, because the use of small particles increases the fluid/solid interfacial mass 16 transfer areas and reduces the intraparticle 17 diffusion path length. In addition, for adsorbers 18 the binder materials contained in the larger 19 pelletized adsorbents used in conventional adsorbers is eliminated, resulting in higher 21 adsorptive capacities;
22 (3) The hollow fiber element broadens the choice of 23 materials for the particles. It can use a wide 24 range of powder materials. If the particle size is small enough, the particles need not be of 26 porous material, because small particles have 27 large external surface areas;
28 (4) The hollow fiber adsorber can use microporous and 29 adsorptive structure that can be cast into either 1 ~ the lumina or void space of the module. Many 2 plastic materials can be converted to microporous 3 matrices by the so-called phase inversion 4 technique (see Example 2). The fiber wall provides a partition between the matrix and the 6 flow passageway in the fiber module;

7 (5) The microporous hollow fibers provide efficient 8 and uniform contact between the particles and the 9 fluid mixture for a wide range of flow rates, thereby avoiding the channelling problems that can 11 affect conventional elements;

12 (6) The fast mass transfer and low pressure drop of 13 the hollow fiber adsorber enables the PSA process 14 to be operated efficiently at fast cycle and high feed rates.

16 The invention is illustrated by the following examples 17 ~xamy~le I
18 This example sets forth in detail an embodiment of the 19 best mode presently known to applicants for packing one of the passageways with a charge of particles. It further describes the 21 character of the charge so emplaced.
22 Three hollow fiber modules were made using microporous 23 polypropylene Celgardl hollow fibers manufactured by the Hoechst 24 Celanese Corporation (Charlotte, N.C.). The physical parameters of these modules are given in the following Table. Element 1 was 26 packed with molecular sieve zeolite crystals in the fiber lumina 27 (see Figure 1) using cyclohexane as the carrier fluid. Element 28 lTrade-Mark 1 '"'" 2 was packed with activated carbon powder in the void space 2 between fibers (see Figure 2) using methanol as the carrier 3 fluid. Both elements were packed using 20 psi slurry solution 4 of adsorbent particles suspended in the carrier fluid, driven by a diaphragm pump. The slurry pumping operation was then followed 6 by dry nitrogen circulation to dry out the carrier fluid from 7 adsorbent particles. Element 3 was packed with molecular sieve 8 zeolite crystals in the void space between the fibers, using 200 9 psi helium as the carrier fluid. As shown in the Table, the resulting hollow fiber elements have adsorbent particle packing 11 density considerably greater than the free standing particle bulk 12 density. The packing was uniform throughout the length and 13 breadth of the packing space.

2 Physical Parameters of Hollow ber AdsorberElements Fi 3 Hollow Fiber Module Element 1 Element 2 Element 3 4 casing, ID, cm .48 .45 .48 fiber type Celgard2 Celgard3 Celgard4 7 fiber number 60 132 150 8 active fiber length, cm 65 64 70 9 fiber ID, micrometer 400 200 200 fiber OD, micrometer 460 260 260 11 fiber wall porosity, ~ 40 40 40 12 fiber wall pore opening, 13 micrometer 14 (width x length) .0 65 x .19 .065 x .19 .065 x .19 Adsorbent Packings 16 packing location fiber outside outside 17 lumina fibers fibers 18 adsorbent type Union DarcoS Union 19 Carbide KB Carbide 5A Carbon 5A

22 particle size, micrometer <10 <30 <10 23 particle bulk density, g/cc 24 (free standing) .49 .25 .49 packing density, g/cc .53 .40 .64 26 total packing weight, g 2.6 2.3 4.6 27 2Trade-Mark 28 3Trade-Mark 29 4Trade-Mark STrade-Mark 1 ~ Example II
2 This example illustrates the use of very fine, non-3 soluble adsorbent particles in a hollow fiber adsorber for gas 4 separation.
Two hollow fiber modules were made containing 6 microporous polypropylene Celgard5 X10-400 hollow fibers. The 7 fiber had a 400 micron internal diameter lumen and 30 micron 8 thick wall. The fiber wall had 30~ porosity provided by .065 x 9 . 19 microns pore openings . Each of the test modules had 30 open-ended fibers of 50 cm length encased in a 3/16 inch OD stainless 11 steel tube ( . 375 cm ID) with both ends of the fiber bundle potted 12 in 3 cm long polyurethane tube sheets.
13 The previously described filtration technique was used 14 to pack a type Y zeolite powder (less than 10 micron size) into the modules. One module was packed with 1.3 g of powder in the 16 fiber lumen, and the other was loaded with 1.7 g of the same 17 powder in the void space between the fibers. The different modes 18 of adsorbent loading were chosen only to demonstrate the 19 workability of each version of the process.
The two modules were plumbed and instrumented to 21 operate as a cyclic pressure swing adsorption (PSA) system in 22 accordance with C. W. Skarstrom, U.S. patent 2,944,627. The 23 cyclic operation was automated with an 8 port valve directing 24 the gas to and from the inlets and outlets of the two adsorbers.
The valve was, in turn, driven by a solenoid controlled by a 26 programmable timer.
27 The PSA system was used to purify a feed stream 28 consisting of helium gas containing 1~ C02. In the first step of 29 5 Trade-Mark s 1 ~ the PSA cycle, the feed gas, at 200 psig and 23°C, was fed to the 2 first adsorber for C02 removal at a rate of 200cc (STP)/min.
3 Simultaneously a portion (25cc/min.) of the purified helium was 4 throttled down to about 6 psig and supplied to the second adsorber to purge previously adsorbed C02. The remainder, still 6 at high pressure, was taken off as purified helium product.
7 After 3.5 minutes, the timer switched the system into 8 the second step of operation. At the beginning of this step, the 9 first adsorber was de-pressurized to atmospheric pressure and the second adsorber was pressurized with feed gas. It then started 11 the adsorption and purging operations for the second and first 12 adsorbers, respectively. The duration of the second step was the 13 same as the first step, and the system was alternated between 14 these two steps in cyclic fashion. The gas flow direction in each adsorber for adsorption and pressurization cycles was 16 countercurrent to that for purging and de-pressurization cycles .
17 A thermal conductivity gas analyzer was used to measure 18 the C02 concentration in helium. The test results showed that 19 the microporous hollow fiber module, packed with minute adsorbent particles, in both versions, was effective for gas purification 21 by pressure swing adsorption, because no C02 could be detected in 22 the purified effluent helium.
23 Examsle III
24 This example illustrates the use of the sol-gel phase inversion technique for casting a microporous matrix into the 26 hollow fiber module for use as an adsorbent.
27 A hollow fiber module was made using microporous 28 polypropylene Celgard hollow fibers of 240 micron ID and 30 1 '""' micron wall thickness. The fiber wall had 30% porosity with .065 2 x .19 micron pore openings. The module had 60 50-cm long fibers 3 encased in a 3/16 inch OD nylon tube, with both ends of the fiber 4 bundle potted in 3 cm long polyurethane tube sheets.
A microporous cellulose acetate matrix structure was 6 cast into the void space between the fibers by first filling it 7 with a cellulose acetate solution (made of 22 g cellulose 8 acetate, 132 g acetone, 30 g Water and 10 g ZnCl2), and then 9 circulating water through the fiber lumina to leach out the acetone, followed by dry air circulation to remove water.
11 The element was tested for gas dehydration. The water 12 content in the gas was measured using a hygrometer. An air 13 containing .04% water vapour at 80 psig and 23°C was fed to the 14 module through the lumina at a rate of about 400 cc ( STP ) /min and dry air, containing only 20 ppm of water, was obtained from the 16 element outlet.
17 The moist air started to break through the element 18 outlet only after about 20 minutes of operation. The water 19 saturated cellulose acetate was able to be regenerated by purging the element with 6 psig dry air at 100 cc/min for about 20 21 minutes.
22 Example IV
23 This example illustrates the use of non-porous soluble 24 particles as an adsorbent in the hollow fiber adsorber. A hollow fiber module similar to the one described in Example 2 was packed 26 with CuCl2 powder by filling the void space between the fibers 27 with a 60°C concentrated aqueous CuCl2 solution (67% CuCl2 by 28 weight) followed by dry air circulation through the fiber lumina 1 o remove water. The module was tested for air dehydration, as 2 described in Example 2. An air containing .052% water vapour was 3 fed to the module through the fiber lumina at 80 psig, 23°C, and 4 500cc(STP)/min. Dry air containing 110 ppm of water was obtained from the outlet of the element. The moist air started to break 6 through the element outlet after about 24 hours of operation.
7 The water-saturated CuClZ was regenerated by purging the element 8 with 100 cc/min. dry air at 100°C for 12 hours.
9 Exaingle VV
This example illustrates the efficiency of the hollow 11 fiber adsorber in the fast-cycle pressure swing adsorption 12 process for high feed gas flow rates.
13 A hollow fiber module was made containing polypropylene 14 Celgard hollow fibers. The fiber had a 200 micron ID and 30 micron thick wall. The fiber wall had 40% porosity provided by 16 about .065 x .19 micron pore openings. The module had 132 open-17 ended fibers of about 70 cm length encased in a 1/4 inch OD nylon 18 tube (0.44 cm ID) with both ends of the fiber bundle potted in 19 3 cm long epoxy tube sheets.
The previously described filtration technique, with 21 the aid of ultrasonic vibration, was used to pack 2.3 g Darco KB6 22 activated carbon powder (particle size less than 30 microns) into 23 the void space between the fibers.
24 6 Trade-Mark ' Trade-Mark 20 i3 2~~~v 1 '~'' The element was plumbed and instrumented as a pressure 2 swing adsorber operating according to the following sequential 3 steps in cycle:

4 ( 1 ) Adsorbing adsorbate from a high pressure feed gas for a predetermined time period to obtain purified 6 gas from the adsorber outlet;

7 (2) Depressurizing the gas remaining in the adsorber 8 (after the adsorption step) through its outlet and 9 into a first gas storage vessel having an internal volume approximately equal to the internal void 11 volume of the adsorber;

12 (3) Further depressurizing the gas in the adsorber 13 into a second gas storage vessel having the same 14 internal volume;

(4) Venting the remaining gas in the adsorber through 16 its inlet;

17 (5) Purging the adsorber using the gas stored in the 18 second storage vessel; the purge gas flow 19 direction being countercurrent to the feed gas direction in the adsorption step;

21 (6) Pressurizing the adsorber using the gas stored in 22 the first storage vessel; the remaining gas in the 23 storage vessel is then removed as low pressure 24 product;

(7) Further pressurizing the adsorber to feed gas 26 pressure using a portion of the purified high 27 pressure product gas, and thus readying the 28 adsorber for the next adsorption cycle.

1 "'"'' The aforementioned hollow fiber adsorber containing 2 2.3g of minute activated carbon particles was used to purify a 3 314 psia hydrogen gas containing about 10% C02 using the above 4 pressure swing adsorption steps. In the tests, we varied the feed gas flow rate and determined the corresponding maximum 6 permissible adsorption step time without any C02 breakthrough 7 from the adsorber outlet. The following results were obtained:
8 Maximum Permissible 9 Feed Rate (Without Adsorption Step Time C02 Breakthrough) il Seconds cc (STP)/min.

36 1,000 16 17 2,000 17 10 3,600 18 It is seen that the maximum permissible feed gas rate 19 is inversely proportional to the adsorption step time. The corresponding hydrogen recovery for each of these flow rates is 21 virtually identical and equal to about 76%.
22 These test results clearly indicate that the feed gas 23 throughput of a hollow fiber adsorber can be effectively 24 increased without loss of separation efficiency by simply shortening the PSA cycle time. The high adsorption efficiency 26 at short adsorption cycle time and high feed rate is made 27 possible by the fast mass transfer rate and low gas pressure drop 28 in the hollow fiber adsorber using minute adsorbent particles.

2~~
1 ~"" Example VI
2 This example illustrates the use of the hollow fiber 3 module as a catalytic reactor having minute catalyst particles.
4 A hollow fiber module similar to the one described in Example III was packed according to the method in Example I with 6 1.17 g of minute catalyst particles in the void space between 7 fibers. The catalyst consists of 1% weight of palladium on 8 alumina powder of about 25 micron particle size (AP-4 9 heterogeneous catalyst manufactured by Engelhard Corporation of Newark, New Jersey, U.S.A.). The module was tested for room 11 temperature deoxygenation process for converting oxygen and 12 hydrogen into water. A hydrogen gas containing about 0.66%
13 oxygen at 10 psig was passed through the fiber lumina of the 14 module. A gas chromatographic instrument was used to measure oxygen content in the gas. At 700 cc (STP)/min. feed gas flow 16 rate, no oxygen content could be detected from the effluent 17 stream of the module, indicating complete conversion of oxygen 18 to water. This highly efficient deoxygenation process was due 19 mainly to the fast mass transfer between the gas stream and catalyst resulting from the use of small catalyst particles in 21 the hollow fiber module.
22 The scope of the invention is defined by the claims 23 now following.

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:

1. A hollow fiber element for use in a catalytic reactor adapted to catalyze a reaction between reactants in a feed mixture stream, comprising:
a bundle of hollow fibers, each fiber having a microporous wall that is permeable relative to the reactants, the fiber wall having pore openings whose effective pore diameters are in the range of about 0.05 to 5 micrometers, each fiber forming a lumen, said lumina and the void space between the fibers providing two longitudinal passageways extending through the bundle, said bundle having means at each end for sealing a first of the passageways;
an impermeable casing sealing the side periphery of the bundle; and a charge of individually free, minute, solid, catalytic particles packing the first passageway substantially throughout its length and breadth, said charge having a density substantially equal to or greater than the free-standing bulk density of the particles;
the pores of each fiber wall being smaller than the particles;
said particles being immobilized in the first passageway but being accessible to reactants introduced into the other passageway.

2. A hollow fiber catalytic reactor adapted to catalyze a reaction between reactants in a feed mixture stream, comprising:
a bundle of hollow fibers, each fiber having a microporous wall that is permeable relative to the reactants, the fiber wall having pore openings whose effective pore diameters are in the range of about 0.05 to 5 micrometers, each fiber forming a lumen, said lumina and the void space between the fibers providing two longitudinal passageways extending through the bundle, said bundle having means at each end for sealing a first of the passageways;
an impermeable casing sealing the side periphery of the bundle;
a vessel encapsulating the bundle;
means sealing the casing against the inside surface of the vessel;
first means for introducing the fluid mixture stream into one end of the first passageway and second means for removing the stream from the other end of the passageway;
a charge of individually free, minute, solid, catalytic particles, packing the other passageway substantially throughout its length and breadth, said charge having a density substantially equal to or greater than the free-standing bulk density of the particles;
the pores of each fiber wall being smaller than the particles;
said particles being immobilized in the other passageway but being accessible to the reactants introduced into the first passageway.

3. The element as set forth in claim 1 wherein:
the surface area of the particles is at least about 200 m2/g; and the particle size is less than about 30 microns.

4. The catalytic reactor as set forth in claim 2 wherein:
the surface area of the particles is at least about 200 m2/g; and the particle size is less than about 30 microns.

5. A process for packing a hollow fiber element used to provide interaction between minute solid catalytic particles and reactants contained in a feed mixture stream, comprising:
providing a bundle of hollow fibers, each fiber having a wall having pore openings whose effective diameters are in the range of about 0.05 to 5 micrometers, said openings being permeable relative to the reactants but not to the particles, each fiber forming a lumen, said lumina and the void space between the fibers providing two longitudinal passageways extending through the bundle, each passageway having corresponding first and second ends, said bundle having means at the second end of one of the passageways for sealing said passageway, said bundle having means at the first end of the other passageway for sealing said other passageway, said bundle having an impermeable casing sealing its side periphery;

pumping a suspension or solution of the minute solid particles in a carrier fluid, formed of liquid or gas, under pressure into the first end of the one passageway, said fiber walls being permeable to the carrier fluid, whereby the carrier fluid filters through the fiber walls into the other passageway and exits the element and the particles are retained in the one passageway and accumulate to form a dense, substantially uniform packing of individually free particles, said packing having a density substantially equal to or greater than the free-standing bulk density of the particles; and sealing the first end of the one passageway to immobilize the particles and opening the first end of the other passageway to remove the filtrate.

6. The process as set forth in claim 5 wherein it is a suspension of solid particles in a carrier fluid that is pumped under pressure into the first end of the one passageway.