MXPA97005553A - Adsorbent vessel for vacuum oscillation / bed pressure rad - Google Patents

Abstract

The present invention relates to a radial bed adsorbent vessel for air separation by vacuum / pressure oscillation adsorption containing a single fixed adsorbent chamber. The unique design of this vessel reduces empty volumes, improves flow distribution in multiple directions, and provides the bed restriction required for the cyclic operation

Description

ADSORBENT VESSEL FOR VACUUM OSCILLATION / RADIAL BED PRESSURE FIELD OF THE INVENTION This invention relates to a vessel used in a pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA) process, and more particularly, to an improved radial bed vessel for use in an adsorption process by vacuum / pressure oscillation.

BACKGROUND OF THE INVENTION Vacuum pressure / pressure swing adsorption and pressure swing adsorption processes employ a selective adsorbent to remove at least one component of a gas from a gas mixture. Both processes employ four basic steps of the process: adsorption, depressurization, purging and repressurization. The processes of adsorption by pressure oscillation and adsorption by vacuum / pressure oscillation are well known, and are widely used to selectively separate the components from the air, i.e., oxygen and nitrogen. The design of the adsorbent vessel is critical for efficient operation of an air separation system.

Improvements in the design of the adsorbent vessel contribute to lower energy consumption, lower capital cost, and increased plant capacity. Vacuum / pressure oscillation adsorption vessels are typically designed as axial flow adsorbents that have limited applicability when the capacity requirements of the plant produce a vessel diameter greater than 4-5 meters, thus exceeding the limits of economic boarding This results in a costly and difficult requirement to assemble axial flow vessels in the field. These large diameter containers also inherently have large percentages of void volume in the upper and lower spaces, and present flow distribution difficulties as a result of the large cross section. As a result, the economy of large-scale vacuum / pressure swing adsorption systems (ie,> 80 tons per day) is compromised when axial flow vessel designs are employed. The operation of the vacuum / pressure oscillation adsorption system is adversely affected by the pressure drop of the bed and the empty volume inside the container. The pressure drop of the bed represents a substantial source of inefficiency in a vacuum / pressure oscillation adsorption process. Large gas flows into and out of the adsorbents are required due to the relatively low operating pressures and recovery of these systems. This large gas flow results in high surface gas velocities through the bed, creating an undesired pressure drop, and contributing to a loss in efficiency. These losses due to the pressure drop of the bed typically comprise 10 to 15 percent of the energy consumption. In an axial flow bed, increasing the cross section of the adsorbent bed by enlarging the diameter and lowering the surface velocity requires larger inventories of adsorbent. This increases the cost of capital in order to improve energy consumption, resulting in little gain in the global economy. The voids in an adsorption vessel also create losses in an adsorption system by vacuum / pressure oscillation. The volume of gas remaining in a lower hydrostatic space is pressurized and depressurized during the cycle, ultimately resulting in losses by air disinflation. Similarly, the volume of gas remaining in a higher hydrostatic space that is enriched in oxygen after the step of manufacturing the product, subsequently evacuates in the waste passage, and acts as an inefficient oxygen purge. This inefficient use of the oxygen purge gas results in a decrease in the overall efficiency of the process.

Advanced vacuum / pressure oscillation adsorption cycles employ powerful adsorbents with a relatively short cycle, and the losses by disinflation and the losses by purge of hydrostatic oxygen superior can get to be very great. The use of adsorbents and advanced cycles drives the design of the adsorption process by vacuum / pressure oscillation towards a reduced length of the bed. Advanced adsorbents typically can operate in an efficient manner with a lower transfer length and, therefore, a container design that easily accommodates this feature is attractive. The use of shorter bed lengths with axial vessels is possible, but when larger sized plants are desired, the diameter of the vessel becomes prohibitively large. Most large pressure swing adsorption systems employ either parallel axial flow vessels with four bed versions of the two-bed cycle, or large horizontal vessels with conventional cycles. The use of the designs of four beds, of multiple containers, adds to the complexity and cost of the installation. The use of horizontal vessels adds to the inefficiency of a non-uniform bed geometry, and results in a higher energy consumption. The design is not considered to be optimized for the production of adsorption oxygen by large-scale vacuum / pressure oscillation. There are radial bed design configurations in the prior art, which originate primarily from the design of the reactor and prepurifier system. See U.S. Patent Nos. 5,232,479 to Poteau et al., 4,544,384 to Metschl et al., 4,541,851 to Bosquain et al., And 3,620,685 to Rogers. In some cases, it has been claimed that these radial bed designs can be used in pressure swing adsorption systems. Each of the radial bed designs of the prior art exhibits one or more of the following impediments: 1) Large empty volumes; 2) non-uniform flow paths; 3) the design is not dimensioned for a reverse flow operation; 4) the design incorporates multiple sections of adsorbent bed; 5) there are complicated internal structures that make loading of adsorbent difficult; 6) the high pressure drop; etc. In accordance with the foregoing, it is an object of the invention to provide an improved container for use in a vacuum swing / pressure adsorption process or pressure swing adsorption, employing only an adsorbent chamber with low void volumes. It is another object of the invention to provide an improved container for use in a vacuum / pressure swing adsorption process, which makes reversible flow direction possible, and a better flow distribution. It is a further object of the invention to provide an improved container for use in a vacuum / pressure swing adsorption process, using a densely packed adsorbent in a restricted adsorbent bed, and exhibiting a reduced adsorbent inventory. It is still a further object of the invention to provide an improved container for use in a vacuum / pressure oscillation adsorption process, which makes possible: a reduction in energy consumption, compared to conventional designs; an up scaling of the size of the plant by a factor better than that provided by the prior art designs; and a capacity of the plant that is not limited by the volume of the adsorbent vessel.

COMPENDIUM OF THE INVENTION A container for use in a pressure swing adsorption gas separation process includes a confinement wall defining an enclosed space having an upper region and a lower region. An annular adsorbent bed is placed inside the enclosed space, and has a porous outer wall, a porous inner wall, and adsorbent material placed between the walls. The porous outer wall is separated from the enclosing wall to create a gas feed channel therebetween, and the porous internal wall surrounds an internal tank, whose wall surface is separated from the porous inner wall, and creates a channel of product flow between them. An optional gas supply / distribution screen structure is placed in the lower region of the container, and in fluid communication with the gas supply channel to provide a gas feed thereto. The gas feed enters the gas feed channel and the adsorbent bed, via the porous outer wall, and in a generally radial direction towards the porous inner wall and the product flow channel. A product outlet is placed in fluid communication with the product flow channel to collect the gas product passing therethrough by means of the porous internal wall from the adsorbent bed. A flexible membrane extends between the porous outer wall and the porous inner wall, at its upper extremities, and is pressurized to rest on the upper surface of the adsorbent material to prevent its fluidization during gas flow.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram showing a vacuum / pressure oscillation adsorption vessel embodying the present invention. Figure 2 is a schematic sectional view showing the structural details of the internal and external mesh walls restricting an adsorbent bed that is included in the vacuum / pressure oscillation adsorption vessel of Figure 1. Figure 3 is a scheme showing an optional radial flow distribution screen, for distributing the inflow gas into the vacuum / pressure oscillation adsorption vessel of Figure 1. Figure 4 is a schematic showing the structural details of a U-shaped flow profile container, with the product duct 42 coming out at the bottom of the adsorbent.

DETAILED DESCRIPTION OF A PREFERRED MODE Initially, the overall structure of the vacuum / pressure swing adsorption vessel 10 will be described in relation to Figures 1 to 3, followed by a detailed consideration of each of the main components of the vessel. The vacuum / pressure oscillation adsorption vessel 10 (see Figure 1) comprises an outer vessel wall 12, inside which an annular radial bed 14 is placed. The radial bed 14 comprises a densely packed region of adsorbent granules which they are held in place by an external annular mesh wall 16 and an inner annular mesh wall 18. The region between the wall of the container 12 and the external mesh wall 16, defines an external annular channel 20. The region between the wall of inner mesh 18 and an outer wall 29 of inner tank 22, defines an internal annular channel 24. The radial bed 14 rests on a bed supporting structure 26. At its uppermost extremity, radial bed 14 is compressed downwardly by a pressurized bladder 28. A pressure inlet (not shown) pressurizes the region below the upper head 32, thereby causing an extension of the bladder 28 against it. adsorbent in the bed 14. In addition, the internal tank 22 is also maintained, by means of the opening 30, at the same pressure level as the bladder 28. The upper head 32 encloses the uppermost region of the adsorption vessel by oscillating the vacuum / pressure 10, and through the opening 34, makes possible the introduction of a removable feeding tube 36 for charging adsorbent granules in the adsorbent bed 14. At the lowermost end of the vacuum / pressure oscillation adsorption vessel 10, a duct resides Inlet and waste feed 40. Conduit 40 is connected to the lower distribution section 38, which distributes both the gas flowing inward and the one flowing outward. The lower distribution section 32 is connected to the radial flow channel 52, which carries the gas flow to the external annular flow channel 20. The channel 52 is defined by the walls of the lower external head 33 and the lower internal head. 35. Referring to Figure 3, details for an optional lower downstream flow distribution screen 38 are shown. The gas entering via the external conduit 40 is directed through the screens 46 along a generally radial direction. , towards the external annular feed channel 20. The screens 46 ensure a relatively uniform distribution of the inlet gas into the external annular feed channel 20. This lower distribution can also be made with a perforated plate (not shown) that replaces the the screens 46. As shown in Figures 1 and 2, the gas entering the external annular feed channel 20, travels upwards, and proceeds adially through the outer mesh wall 16, to the radial adsorbent bed 14. There, the less desirable gas in the feed is adsorbed, and the most desired gas exits through the internal mesh wall 18, and into the internal annular product channel 24. From there, the gas product flows downward and outwardly of the conduit 42 through the upper part of the container 10. Now the details of the vacuum / pressure swing adsorption vessel 10 will be discussed. The feed and waste gas is supplied through the conduit 40, and the process pipe is constructed with an internal straightening to provide an almost uniform flow profile into the container 10 with a minimum pressure drop. Then the feed gas passes through the radial flow distribution section 38, which evenly distributes the gas to the external annular feed channel 20 through the section 52. The radial flow distribution screens 46, shown in FIG. Figure 3, are used in the optional configuration. These screens impart a centrifugal flow pattern to the radially flowing gas. The gas comes out with a centrifugal flow pattern, and in addition it is mixed and the pressure is equalized in an open lower hydrostatic area 52. A perforated straight wall screen can also be used instead of the radial screens 46. The perforated screen of the the same way it will have a higher pressure drop, compared to the radial screens 46. These configurations of operating screens are used when the inlet gas in the duct 40 is not of a uniform profile, and further straightening is required. The gas, which is now evenly distributed in the lower head at 52, is supplied to the radial adsorption bed 14 by means of the external external annular feed channel 20. The gas flows through the adsorbent bed 14 in an inward and radial manner . The gas exiting at the product end of the adsorbent bed 14 is collected in the inner annular product channel 24 and flows downward. This flow configuration forms a "U" shaped flow pattern. The gas product is collected in the collection region of the hydrostatic space 54 at the bottom of the adsorption vessel by vacuum / pressure oscillation 10. The collected gas product leaves the vessel through the conduit 42, exiting at the top of the vessel. container 10. The gas product conduit 42 can also be designed to exit from the bottom of the container. Figure 4 shows a configuration wherein the product conduit 42 is contained within the feed conduit 40, and it comes out from the bottom. The flow distribution of the vessel is critical for a successful operation of a vacuum / pressure oscillation adsorption process. A major contributor to the flow distribution is the channel pressure differential between the feed and product ends of the radial adsorbent bed 14. The pressure differential is a combination of friction pressure losses and head recovery or loss. of speed of the gases that flow. These effects tend to be canceled when the flow is entering a channel, and they are additive when the flow is leaving a channel. The degree of cancellation and addition is affected by the internal geometry of the camera (ie, straight walls, straight thinning, or parabolic thinning). In addition, all vacuum / pressure oscillation adsorption processes reverse the direction of the gas flow, periodically, to perform steps of the subsequent adsorption and desorption process. Therefore, the impact of a poor flow distribution introduced in each step must be measured in accordance with the foregoing. The orientation of the gas flow in a "U" shape, and the geometry of the thin wall vertical flow chamber 20, are the answers to the previous considerations. It has been found that thinned flow channels improve the flow distribution in the reverse flow application. The thinned flow channel is effective in allowing larger inlet areas at the lower end, or in the gas outlet / inlet of channel 20. These large areas substantially reduce the pressure loss in the feed and waste streams, improving in this way the efficiency of the process. The thinning of channel 20 reduces the undesired void of this channel. This vacuum results in a loss by disinflation when the pressure levels are reversed. The thinning of the channel balances the empty volume and the loss by the pressure drop. The U-shaped flow path, in combination with the thin-walled flow channels, maximizes the process efficiency of the vacuum / pressure swing adsorption vessel 10, while also minimizing the effects of associated maldistribution of flow with a reverse flow pattern in a minimum empty space. Although the outlet channel 24 is shown without thinning, it could also be thinned from the top to the bottom. Some maldistribution of flow in a radial bed design is inevitable, with the requirements of vacuum / pressure oscillation adsorption. The selection of the global flow path and the internal geometry of the flow path shown in Figures 1 to 3, balance the losses by friction and dynamic pressure in the flow channels over the entire cycle, and result in an equilibrium acceptable between flow distribution, pressure drop, and vacuum. Each channel width is selected based on an average between the losses due to pressure drop, empty volume and flow distribution for the given process. The preferred width of the entrance of the external annular feed channel 20 is 4.5% of the vertical length of the adsorbent bed 14, within a preferred scale of 4 percent to 5 percent, and within an overall scale of 2 percent to 8 percent. The preferred width of the inner annular product channel 24 is 9 percent of the vertical length of the adsorbent bed 14, within a preferred range of 7 to 11 percent, and within a general scale of 5 to 13 percent. The supply area of the external annular feed channel 20, as a proportion to the area of the inner annular product channel 24, is selected to correspond to the gas flows of the process, and is preferably 2.4, within a preferred scale of 1.25-3.

Bed Support Structure 26 t Vacuum / pressure oscillation adsorption vessel 10 is designed to minimize unnecessary empty regions. The vacuum at the feed end of the adsorbent bed 14 is minimized by the bed support structure 26. The bed support structure 26 is constructed as an internal tank. The design thus eliminates the void volume associated with this area. The lower head volume in a conventional container is left unoccupied, and represents an unnecessary loss in the system. These voids are cycled during the operation, and are pressurized and depressurized in an alternating manner, creating losses due to disinflation. The vacuum / pressure oscillation adsorption vessel 10 has, on the feed side, an empty volume percentage typically between 10 and 25 percent of the volume of the adsorbent bed 14. The bed support system of the inner tank is it can design as a closed pressure vessel capable of withstanding the cyclic pressure stresses, or as a tank filled with a solid material, thus being left open at the lower pressure of the container.

Vacuum Volume, Product Side: The empty volume on the product side of the radial adsorbent bed 14, is minimized by the internal tank 22, located in the center of the adsorption vessel by vacuum / pressure oscillation 10. The internal tank 22 is opens at the top 30, and is pressurized to the same pressure as the disinflation bladder 28. The lower section of the tank 22 is closed by a head, thereby reducing unnecessary vacuum, and distributing the oxygen reflux gas from entry. The empty volume on the product side is cycled during the operation, and the oxygen product in these channels is pressurized and depressurized, acting as an inefficient oxygen purge in the evacuation step. This inefficient use of the oxygen purge causes an elongation of the oxygen / nitrogen desorption front, with a subsequent loss of oxygen during the waste removal step. This results in a decrease in oxygen recovery. To reduce these losses, the vacuum / pressure oscillation adsorption vessel 10 has an empty product-side percentage typically between 3 and 10 percent of the volume of the adsorbent bed 14.

Uniform Profile of the Adsorbent Bed 1 t The internal flow path of the bed is critical in vacuum / pressure oscillation adsorption operations. A uniform bed profile is necessary to promote and maintain a gas flow distribution. This is particularly acute at the upper and lower corners of the bed, where the adjacent surfaces are located. The internal design of the bed and the flow path are shown in Figure 2. The adsorbent bed 14 is completely symmetrical, with no discontinuities in the adjoining surfaces, and the internal flow path is completely uniform, with no areas of the bed not swept. The interconnection between the mesh walls 16 and 18 and the bladder 28 is shown in the dotted circles 60. The mesh walls extend above the adsorbent bed 14, and the adsorbent granules are covered and sealed by the bladder 28. This height is between 2 and 4 percent of the vertical length of the bed, and allows a variation in the level of adsorbent in the initial load, or due to a variation caused by the settlement, and does not allow areas to remain unwashed. The meshes are sealed to the perforated support plates 64 by seal rings 66, which are designed to accept the mesh without creating large obstructions that can not be covered by the bladder 28. This system provides a positive seal of adsorbent and bladder. The mesh walls extend below the bed support plate 68, and are connected in this area using a seal ring or filler material that is inserted into a groove (not shown). This area is completely filled with sealant, resulting in a uniform flow path.

Pressurized Bladder 28: The adsorbent bed 14 is restricted by the sealing action of the flexible bladder 28. Bladder 28 provides both a bed restriction, and an integral part of the flow assembly that provides a uniform bed flow profile. The radial flow path in the container 10 creates a differential pressure of the bed that would lift the upper corner sections of the bed if restriction was not provided. Bladder 28 is designed to provide this restriction, without voids or non-uniform flow paths. Bladder 28 is placed on top of the adsorbent bed 14, only covering the area of the bed formed inside the two concentric circles of the inner and outer edges of the bed. The bladder 28 is then sealed on the edges by compression clamps, and pressurized by pressurizing the region of the upper head 27 to a pressure higher than the maximum cycle pressure. A compressible sponge material (not shown) is inserted above the adsorbent bed adjacent walls 18 and 16. Compression of this material by bladder 28 ensures restriction of the adsorbent at the upper corners of the bed. This ensures a grip in all process conditions. The structure of the container is designed to withstand this maximum clamping pressure.

Top Load Assembly: The vacuum / pressure swing adsorption vessel 10 is designed to provide space to accommodate the installation and operation of the dense adsorbent loading system shown in U.S. Patent No. 5,234,159, assigned to the same Assignee of this request. The disclosure of U.S. Patent No. 5,234,159 is incorporated herein by reference. The upper head space 27 (Figure 1) is left open to accommodate the rotary arm assembly 36. The vacuum bed pressure / vacuum pressure adsorption process relatively short and low pressure drop, performed in the adsorption vessel by oscillation of vacuum / pressure 10, requires a uniform dense charge adsorbent. This dense charge adsorbent provides a uniform pressure drop profile in the bed 14, which is necessary to maintain a uniform flow distribution. The arm assembly 36 is removed after loading the adsorbent. The application of this loading system is made specifically possible by the design of the removable top flange assembly / product pipe, with an internal connector, the tank with the empty top of internal low profile, and the removable bed disinflation bladder. .

Radial Flow Distribution Screen: The feed air stream passes through an optional radial flow distribution screen (Figure 3), which evenly distributes the gas circumferentially to the outer annular channel 20. The screens 46, in the optional configuration, they impart a centrifugal flow pattern to the radially flowing gas, which is then further mixed and the pressure is equalized in the open lower hydrostatic area 52. The screens 46 are shown straight, but may be curved to reduce the separation and the pressure drop. The inlet flow distribution system can also be designed with a perforated plate or other screen assembly to create a radial pressure drop.

Differential Temperature Effects: Although the vacuum / pressure oscillation adsorption processes are not designed to create large differential temperatures, the inlet and outlet temperatures are different. The design described above accommodates this by connecting internal mesh walls 18 of the adsorbent bed 14, only with the lower stationary bed support, leaving the upper part of the internal mesh walls 18 free to move with the changing process temperatures. Although a preferred modality has been described, a number of variations are possible. The pressurized section above the bladder 28 can be replaced by a dense material. This dense material may be metallic and ceramic balls, which would provide the required discharge over bladder 28 to restrict the adsorbent. The optional inlet gas flow distribution system can be designed in a different way. The structure described above induces a circumferential flow direction to the gas flowing radially outwards. Then this pressurized gas is equalized in the surrounding ring. The radial screens can be replaced by a perforated plate screen, producing essentially the same distribution, but with a slightly increased pressure drop. Step perforations could be used instead of uniform perforations on the perforated wall plates of the radial inlet and outlet bed. Although the container 10 is designed specifically for the operation of vacuum / pressure swing adsorption in an oxygen cycle, it can be used in other applications. These would include any adsorption process that does not require high-temperature thermal regeneration, such as pressure swing adsorption for the production of oxygen or nitrogen, and prepurification of air by pressure swing adsorption. The design parameters of the container would need to be altered to suit the specific flow requirements of the application. In summary, the invention provides a number of convenient features: Single Fiio Bed: The container 10 combines the adsorbent, the process and the design attributes of the container, in order to operate with an integral prepurifying section in the adsorbent bed 14. This feature is different from many other containers that employ a section Separate adsorbent to perform the previous purification. The container 10, therefore, contains only one section of adsorbent bed that includes both the prepurifying zone and the main separation zone, leading to a simplified construction. The container 10 makes possible the large-scale production of oxygen, employing vacuum / pressure oscillation adsorption technology with a fixed adsorbent bed. Other adsorbent vessel designs employ multiple adsorbent chambers that are rotated around internal gates inside the vessel to effect the switching of the process gas flow. This rotating bed technology is prohibitively complex to use in large sizes.

Flow Profile of Power from the Outside to the Inside: The supply air is adsorbed during the system cycle, and the container is configured with the feed gas flowing from the external side towards the center, taking advantage of the geometry that reduces the section cross-section of the bed in conjunction with the gas flow that is being reduced. The external feed side flow area, as a proportion to the lateral flow area of the internal product, corresponds to the gas flows of the process.

Fluid or Reversible Direction: (U-shaped flow path): The gas flow path is configured with the feed flow up along the external channel, and the product flow down into the channel central, creating a flow pattern in the form of "U". The vacuum / pressure oscillation adsorption process operates with a reversed gas flow direction during periods of the cyclic process, and the container 10 is designed to accommodate reverse flow directions.

Direction of Reversible Flow: Drills were conducted on passages of wall flow thinned against straight. The calculations show that the thinned flow paths offer the lowest pressure drop and the lowest empty volume, while maintaining an acceptable flow distribution. The container 10 is designed with vertical flow channels thinned.

Low Vacuum Volume - Short Cycle Application: The low void volume in the feed and product distribution channels is essential for efficient operation of an advanced vacuum / pressure swing adsorption system. Vacuum / pressure oscillation adsorption systems that use adsorbents and advanced cycles, operate with a short cycle time. This characteristic is a natural result of the high utilization of the adsorbent and the factors of low bed size. The volume of gas in the lower head is pressurized and depressurized during the cycle, resulting in a loss by disinflation. The volume of gas in the upper head is enriched in oxygen, and when the container 10 is evacuated, this gas is pulled through the bed, acting as an inefficient oxygen purge, and raising the oxygen content in the waste. This inefficient use of the oxygen purge results in a decrease in the overall recovery of the process. Losses due to disinflation and losses due to oxygen purge would be very large if specific measures were not taken to minimize the vacuum. This radial bed design of the container 10 minimizes voids in the feed end and the end of the product.

Uniform Bed Flow area: The container 10 includes a bed geometry that promotes and maintains a uniform movement of the separation front in the bed. The design of the internal flow path of the bed is critical in this regard. If these fronts were not uniform, there would be a premature breakage in different sectors of the bed at the end of the adsorption and desorption steps. This premature breaking of the local front, for example, would result in a mixture of the lower purity gases in the bulky product stream, thereby reducing overall efficiency. The discontinuities in the design of the bed are particularly acute in the upper and lower corners of the bed, where the adjacent surfaces are located. This requires a container design with a completely uninterrupted and symmetric geometry that has no discontinuities at either end. The side wall mesh assemblies of the container 10 meet this requirement.

Limited Bed Fixing System: Vacuum oscillation / radial bed pressure adsorption vessels should be designed with a limited bed fastening system to prevent fluidization of the adsorbent. The gas velocity in certain adsorption cycles by vacuum / pressure oscillation is high, resulting in velocities exceeding the fluidization levels during parts of the cycle. There is also the possibility of an alteration caused by a malfunction of the equipment, which could cause a fluidization of the bed on a large scale in an unrestricted bed. Since the container 10 includes a uniform and densely packed adsorbent, any fluidization of the adsorbent that alters this density is detrimental. The aforementioned bladder holding system provides the holding requirement, while creating a uniform flow path within the variable height adsorbent bed. The length of the adsorbent may vary, due to the settlement of the adsorbent during the operation.

Distribution of the Flow of Entry: The distribution of the flow is an important element of the container 10. The design pressure drop in the entrance and exit gates must be kept small to minimize the energy consumption. This results in the requirement to maintain a uniform flow distribution of the incoming gas without creating an unnecessary pressure drop or empty spaces. If the pipe system can not be designed to provide a uniform flow in this inlet, the inlet port of the container 10 is designed to distribute the inlet gas in a uniform circumferential manner through the use of a radial screen configuration. The flow channel connecting the inlet gate 40 with the thinned outlet channel 20, is also a designed flow channel. The channel 52 is formed by the lower head 33 and the lower empty tank 35. This passage 52 is thinned to provide a smooth transition between the area of the inlet 40 and the channel 20, and to minimize the empty volume and the pressure drop. .

Uniform Bed Packing Density: As previously reported, the bed length in adsorption adsorbents by advanced vacuum / pressure oscillation is short, and the surface velocities of the gas are large. This results in a front advancing rapidly during the container cycle, with the need to keep the front as uniform as possible. If these fronts are not uniform, premature breaking can occur in different sectors of the bed, reducing the efficiency of the separation. The pressure drop through a packed bed structure is a function of the packing density, and the flow is a function of the pressure drop. Accordingly, a uniform packing density of the adsorbent becomes critical if a uniform frontal movement is desired. The container 10 accommodates a dense packing loading system which makes it possible to load the entire adsorbent bed to a uniform density. The upper head section of the container 10 is left intentionally unobstructed, and the details of the head space and bed location are selected to allow the installation of the loader. It should be understood that the foregoing description only illustrates the invention. The experts in this field can devise different alternatives and modifications without departing from the invention. In accordance with the foregoing, the present invention is intended to encompass all alternatives, modifications and variations that fall within the scope of the appended claims.

Claims (11)

1. A container for use in a pressure swing adsorption gas separation process, which comprises: an enclosing wall element defining an enclosed space having an upper region and a lower region; an annular adsorbent bed positioned between the upper region and the lower region within the enclosed space, having a porous external wall, a porous internal wall, and adsorbent material placed therebetween, the porous external wall being separated from the enclosing wall element , to create a gas feed channel therebetween, surrounding the porous inner wall to a chamber; an internal wall element placed in the chamber, and separated from the porous internal wall to create a product flow channel therebetween; a gas feed inlet element positioned in the lower region and in fluid communication with the gas feed channel, to provide a gas supply thereto, thereby entering the gas supply in the gas supply channel and in the adsorbing bed by means of the porous outer wall and in a generally radial direction towards the internal porous wall and the product flow channel; and a product outlet element positioned in the lower region and in fluid communication with the product flow channel, to collect the gas product that passes into it through the porous internal wall, and which provides a flow of outlet thereof, and wherein the product outlet member includes an outlet conduit in fluid communication with the lower region, and extending upwardly through the upper region. The container as described in claim 1, further comprising: a movable restraining element extending between the porous outer wall and the porous internal wall at its upper extremities; and an element for pressurizing at least a portion of the upper region to cause the movable restraining element to rest on a top surface of the adsorbent material, the upper region being maintained at a pressure that is greater than any pressure experienced within the adsorbent bed, wherein the movable restraining element comprises a flexible membrane that adheres to both the porous outer wall and the porous inner wall, in a manner that prevents any region from being swept into an upper portion of the annular adsorbent bed. The container as described in claim 2, wherein the internal wall element is configured as a tank having an opening in communication with the portion of the upper region that is pressurized, thereby making it possible for the tank to reach a similar level of pressurization. The container as described in claim 1, wherein the gas feed inlet element comprises: an inlet duct; and a distribution element coupled between the inlet conduit and the gas supply channel, for imparting a generally radial flow pattern to the gas feed, to achieve a substantially uniform distribution of the feed gas in the gas supply channel , wherein the distribution element comprises a closed tank having an upper portion that serves as a mechanical support for the annular adsorbent bed, and a lower portion defining an entrance channel, extending from an entrance of the entrance element of the Gas supply to the gas supply channel. The container as described in claim 1, wherein the enclosing wall element is separated from the porous outer wall, such that a thinned gas feed channel is created, and wherein the internal wall element it is separated from the porous inner wall by a substantially fixed distance to create a product feed channel of substantially constant cross-section. 6. The container as described in claim 5, wherein the gas feed channel exhibits a cross-sectional width between the enclosing wall element and the porous outer wall, which carries a ratio in the range of 2 percent to 8 percent of a height of the annular adsorbent bed . The container as described in claim 5, wherein the product flow channel exhibits a cross-sectional width between the inner wall element and the inner porous wall, which carries a ratio in the 5 percent scale to the 13 percent of a height of the annular adsorbent bed. 8. The container as described in claim 5, wherein the void volume within the gas feed channel and the gas feed inlet element is on a scale of 10 percent to 25 percent of the volume of the bed annular adsorbent. The container as described in claim 8, wherein the void volume within the product flow channel and the product exit element is on a scale of 3 percent to 10 percent of the volume of the annular adsorbent bed. The container as described in claim 2, wherein the upper ends of the porous outer wall and the internal porous wall are positioned within the enclosing wall element, to accommodate the relative movement therebetween under different temperature conditions. . The container as described in claim 1, wherein the upper region is constructed to make possible the introduction therein of a rotating conduit extending in a generally radial manner, to enable dense filling of the annular adsorbent bed .