WO2010059156A1

WO2010059156A1 - Sorptive fractionator system with combined temperature and pressure swing

Info

Publication number: WO2010059156A1
Application number: PCT/US2008/084058
Authority: WO
Inventors: Donald H. White; Brian G. Mcgill; Cullen G. Chrivia; Michael Schweer
Original assignee: Donaldson Company, Inc.
Priority date: 2008-11-19
Filing date: 2008-11-19
Publication date: 2010-05-27

Abstract

Example embodiments of a fractionator system for reducing sorbate concentration a dirty gas stream include a vessel bed configured to remove (e.g., adsorb, absorb, chemisorb, etc.) sorbate from the dirty gas stream. The vessel bed is regenerated via application of a purge stream. A heater assembly can be arranged at a purge exhaust output of the vessel bed. The heater assembly includes at least one heating element configured to heat the purge stream at the purge exhaust region sufficiently to increase a sorbate saturation pressure of the purge stream without aiding desorption within the vessel bed.

Description

COMBINATION TEMPERATURE AND PRESSURE SWING FRACTIONATOR SYSTEM

This application is being filed on November 19, 2008, as a PCT International Patent application in the name of Donaldson Company, Inc., a U.S. national corporation, applicant for the designation of all countries except the US, and Donald H. White, Brian G. McGiIl, Cullen G. Chrivia, and Michael Schweer, all citizens of the United States, applicants for the designation of the US only.

Field of the Invention The present invention relates to regenerable fractionator systems and methods for reducing sorbate in air or other gases.

Background

Fractionator systems for reducing sorbate concentration in air or other gases include one or more vessel beds. Each bed contains an sorbent (e.g., a desiccant, a deliquescent salt, etc.) configured to remove (e.g., adsorb, absorb, chemisorb, etc.) one or more sorbates (e.g., moisture, oil vapor, or other contaminants) from a gas stream fed through the vessel bed in a feed direction. The vessel bed can be regenerated (e.g., via a desorption process) by passing a purge stream through the vessel bed counter-current to the feed direction. In general, each vessel bed of a fractionator system cycles between a reduction phase, in which the vessel bed removes sorbate from the gas stream, and a regeneration phase, in which a purge stream removes sorbate from the vessel bed off-stream. In fractionator systems having two or more vessel beds, the reduction and regeneration phases of the vessel beds can be staggered. For example, a first vessel bed removes sorbate while a second vessel bed regenerates and vice versa.

A temperature swing (TS) reduction process is one conventional process by which a vessel bed alternately removes sorbate and regenerates during a fractionator cycle. In general, the TS reduction process facilitates desorption during the regeneration cycle by sufficiently heating the vessel bed to promote desorption of sorbate from the vessel bed and into a purge stream that is exhausted from the vessel. In some cases, the TS reduction process heats the entire vessel bed. hi other cases, the TS reduction process preheats the purge stream, which produces a heat pulse that travels through the vessel bed during the regeneration cycle. Each phase of the TS reduction process typically lasts for a period of time on the order of hours.

The pressure swing (PS) reduction process is another conventional process by which a vessel bed alternately removes sorbate and regenerates during a fractionator cycle. The PS reduction process also introduces a purge stream into the bed to desorb the sorbate. However, the PS reduction process has a shortened fractionator cycle (i.e., each phase of the fractionator cycle typically lasts for a period of time on the order of minutes or seconds). Shortening the duration of the reduction phase enables each vessel bed to retain heat produced by the reduction process (e.g., adsorption). Accordingly, heating the vessel bed during the regeneration phase is unnecessary to promote desorption of the sorbate. Rather, the heat retained from the reduction process promotes sufficient desorbtion of sorbate to regenerate the vessel bed.

Summary A regenerable fractionator system, a vessel bed assembly, a method of regenerating the vessel bed assembly, and a method of reducing sorbate concentration of a gas stream are described. The regenerable fractionator system includes one or more vessel beds, each bed containing a heater assembly at a purge exhaust outlet of the bed. The heater assembly heats the purge stream sufficient to increase a sorbate saturation pressure of the purge stream (i.e., the amount of sorbate the purge stream is capable of holding). Typically, the heater assembly does not produce sufficient heat to affect the rate of desorption of sorbate from the vessel bed. According to some aspects of the disclosure, a fractionator system for reducing sorbate concentration of an input gas stream includes a first vessel bed configured to reduce sorbate concentration of a gas stream; and a second vessel bed configured to reduce sorbate concentration of the gas stream. Each bed includes a gas flow input; a gas flow output; a purge flow input; a purge exhaust output; and a heater assembly operably positioned at the purge exhaust output. The heater assembly includes at least one heater element configured to heat a purge gas stream at or adjacent the purge exhaust output. A sorbate saturation pressure of the heated purge gas stream is increased prior to exiting the first vessel bed through the purge exhaust output. According to other aspects of the disclosure, a method for regenerating a vessel bed containing sorbate includes sealing the vessel bed from a gas stream. The method also includes providing an ambient temperature purge gas stream substantially free of sorbate to the vessel bed; receiving the purge gas stream at a purge exhaust output, the purge gas stream removing sorbate from the vessel bed when passing through the vessel bed; and heating the purge gas stream at the purge exhaust output to increase a sorbate saturation pressure of the purge gas stream prior to the purge gas flow exiting the vessel bed through the purge exhaust output.

Brief Description of the Drawings

FIG. 1 is a schematic diagram of flow paths for one example regenerable fractionator system configured in accordance with the principles of the present disclosure;

FIG. 2 is a flowchart illustrating an operational flow for an example regeneration process by which one or more vessel beds of an sorbent system can be regenerated in accordance with the principles of the present disclosure;

FIG. 3 is a schematic diagram of an example regeneration system including a first vessel, a second vessel, and a control assembly in accordance with the principles of the present disclosure; FIG. 4 is a schematic block diagram of one example control assembly that can be used to operate the heater assemblies and valve assemblies of a fractionator system in accordance with the principles of the present disclosure;

FIG. 5 is a flowchart illustrating an operational flow for an example control process by which a control assembly may operate one of the vessels of a fractionator system in accordance with the principles of the present disclosure; and

FIG. 6 is a schematic diagram showing one example heater assembly that can be used in the fractionator systems disclosed herein in accordance with the principles of the present disclosure. Detailed Description

As the terms are used herein, a "dirty" gas stream is a gas stream containing sorbate and a "clean" gas stream is a gas stream from which at least some sorbate has been removed. As the term is used herein, elements that are "operationally coupled" are arranged together with suitable intermediate components to enable the elements to perform a specified function.

The present disclosure is directed to a new fractionator process by which sorbate can be removed from a dirty gas stream and fractionator systems configured to implement the new fractionator process. The new fractionator process includes a new regeneration process by which sorbate can be removed from vessel beds of the fractionator system. In general, the new regeneration process utilizes less heat than the conventional temperature swing process and less purge flow than the conventional pressure swing process described above for a given gas flow rate and bed size.

FIG. 1 is a schematic diagram of flow paths for one example regenerable fractionator system 100 configured in accordance with the principles of the present disclosure. The fractionator system 100 shown in FIG. 1 includes a first fractionator vessel 110 and a second fractionator vessel 120. hi other embodiments, however, the fractionator system 100 can include greater or fewer fractionator vessels. Each fractionator vessel 110, 120 contains a vessel bed 115, 125, respectively, configured to remove (e.g., adsorb, absorb, chemisorb, etc.) sorbate from a dirty gas stream fed into the vessel to produce a clean gas stream having a reduced sorbate concentration level as compared to the dirty gas stream. The vessel bed 125 of the second fractionator vessel 120 has a length L. Typically, the vessel beds 115, 125 have the same length.

In general, each fractionator vessel 110, 120 cycles between a reduction configuration and a regeneration configuration during a fractionator cycle of the fractionator system 100. When arranged in the reduction configuration, a fractionator vessel reduces a sorbate concentration of a dirty gas stream passing through the vessel bed. When the fractionator vessel is arranged in the regeneration configuration, sorbate desorbs from the vessel bed and exits the vessel via a purge stream. In the example shown, when one of the vessels 110, 120 is arranged in the reduction configuration, the other of the vessels 110, 120 is arranged in the regeneration configuration. Accordingly, the fractionator system 100 can operate continuously. hi some embodiments, each phase of the fractionator cycle lasts for a period of time on the order of minutes. Indeed, in some embodiments, each phase of the fractionator cycle lasts for a period of time on the order of seconds, hi other embodiments, however, each phase can last for a longer or shorter period of time. Limiting the duration of each phase to shorter time periods enables the regeneration phase to use the heat produced by the reduction process to desorb the sorbate. Limiting the duration of each phase also reduces the distance into the vessel bed the sorbate can travel. Accordingly, the sorbate removed from the dirty gas flow is substantially contained in the portion of the vessel bed at or adjacent the gas flow inlet.

The disclosure recognizes that adding sufficient heat to the purge stream to increase a sorbate saturation pressure, but not enough to facilitate desorption, can enable greater amounts of sorbate to be removed from the vessel for a given flow rate of purge stream. Accordingly, the flow rate of the purge stream can be decreased as compared to a purge stream flow rate used in conventional PS reduction process. Furthermore, because the heat applied to the purge stream is not intended to effect or aid in desorption of the sorbate from the vessel bed, significantly less thermal energy can be generated as compared to the thermal energy necessary to heat the vessel beds in a conventional TS reduction process.

FIG. 1 shows the gas flow paths along which gas and purge streams are routed through the system 100 during the fractionator cycle. During a first phase of the fractionator cycle, the first vessel 110 is arranged in the reduction configuration and the second vessel 120 is arranged in the regeneration configuration. The first vessel 110 has at least a first port 135 and a second port 145 through which gas streams and purge streams enter and exit the vessel. The second vessel 120 also has at least a first port 165 and a second port 155 through which gas streams and purge streams enter and exit the vessel, hi one embodiment, the second ports 145, 155 are arranged opposite the respective first ports 135, 165.

A dirty gas stream 130 containing sorbate to be removed is fed into the first port 135 of the first vessel 110 in a feed direction FD. When the dirty gas stream 130 passes through the vessel bed 115, the vessel bed 115 removes (e.g., adsorbs) sorbate from the dirty gas stream 130 to produce a clean gas output stream 140 having a reduced sorbate concentration level. In one embodiment, the clean gas output stream 140 is substantially free of sorbate. The clean gas output stream 140 exits the first vessel 110 at the second port 145 and is routed to one or more downstream applications. For example, the clean, compressed air can be used to cool equipment, dry liquid containing reservoirs, or in other applications.

In general, each phase of the fractionator cycle of the regenerable fractionator system 100 is sufficiently short to enable the vessels 110, 120 to retain the heat of sorption produced when the vessel beds 115, 125 remove (e.g., adsorbs, absorbs, chemisorbs, etc.) sorbate from a gas stream 130. In some embodiments, the fractionator cycle of the regenerable fractionator system 100 has approximately the same duration as the fractionator cycle of a conventional PS regeneration process. For example, in some embodiments, each phase of the fractionator cycle has a duration on the order of hours. In some embodiments, each phase of the fractionator cycle has a duration on the order of minutes. Indeed, in some embodiments, each phase has a duration on the order of seconds.

In one example embodiment, the sorbate to be removed from the dirty gas stream 130 includes water vapor. In such an embodiment, the vessel bed 115 can include a desiccant configured to remove moisture from the dirty gas stream 130 to produce a dried gas stream 140. In other embodiments, however, the sorbate to be removed can include other contaminants (e.g., oil vapor). In one embodiment, the dirty gas stream 130 includes compressed (i.e., pressurized) air. Use of alternative compressed gases (e.g., nitrogen, carbon dioxide, biogas, or natural gas), however, is consistent with the scope of the disclosure.

During the same phase of the fractionator cycle, a purge gas stream 150 is fed into the second vessel 120 at the second port 155. In some embodiments, a portion 142 of the gas output stream 140 is directed to the second vessel 120 as the purge gas stream 150 or a portion thereof. In other embodiments, however, the purge gas stream 150 is produced separately from the gas output stream 140. The purge gas stream 150 travels through the second vessel 120 in a purge direction PD, which runs at least partially counter-current to the feed direction FD, to regenerate the vessel bed 125 of the second vessel 120. The purge gas stream 150 accumulates sorbate from the vessel bed 125 as the purge gas stream 150 passes through the vessel bed 125 to produce a purge exhaust stream 160. The purge exhaust stream 160 exits the second vessel 120 through the first port 165 of the second vessel 120. In general, prior to being introduced into the second vessel 120, the purge gas stream 150 is not heated sufficiently to affect the regeneration process significantly (e.g., to effect desorption of sorbate from the vessel bed). Typically, the purge stream 150 is not heated above an ambient operating temperature prior to being introduced into the vessel 120. The purge stream 150 also is not heated sufficiently within the vessel 120 to promote desorption significantly. Rather, desorption of the sorbate is at least significantly aided by heat generated during a previous phase of the fractionator process (i.e., when the second vessel was configured in the reduction configuration).

Prior to reaching the first port 165 of the second vessel 120, the purge exhaust stream 160 passes through a purge exhaust region 127 of the second vessel 120. The purge exhaust region 127 is a region of the second vessel 120 that is located adjacent to the first port 165 and that is heated by a heat source. In certain embodiments, the purge exhaust region 127 includes the first port 165. For example, in one embodiment, the purge exhaust region 127 can extend at least partially along a length of the first port 165. In one embodiment, the first port 165 of the second vessel 120 also functions as an input for a dirty gas stream when the second vessel 120 is configured in the reduction configuration. In other embodiments, a separate port enables ingress of a dirty gas stream. In such embodiments, the purge exhaust region 127 can include or be adjacent to the separate port. The purge exhaust region 127 of the second vessel 120 has a length

L'. Typically, the length L' of the purge exhaust region 127 extends over about 50% or less of the length L of the vessel bed 125 starting at the first port 165. hi some embodiments, the length L' of the purge exhaust region 127 extends over about 30% or less of the length L of the vessel bed 125 starting at the first port 165. Indeed, in some embodiments, the length L' of the purge exhaust region 127 extends over about 20% or less of the length L of the vessel bed 125 starting at the first port 165. In certain embodiments, the length L' of the purge exhaust region 127 extends over about 15% of less of the length L of the vessel bed 125 starting at the first port 165. In general, the fractionator system 100 is configured to heat the purge exhaust region 127 of the vessel 120 during the regeneration phase of the fractionator cycle to increase the temperature of the purge stream. For example, the vessel 120 can include a heat source arranged at or adjacent the purge exhaust region 127. IQ general, the purge exhaust region 127 is heated sufficiently to create a temperature differential between the purge gas stream 150 and the purge exhaust stream 160. Typically, the purge exhaust region 127 is heated to a higher temperature than the remainder of the vessel 120. hi one embodiment, only the purge exhaust region 127 of the vessel 120 is heated. Heating the purge exhaust region 127 heats the purge exhaust stream

160 sufficiently to increase a sorbate saturation threshold of the purge exhaust stream 160. Increasing the sorbate saturation threshold enables the purge exhaust stream 160 to hold a greater amount of sorbate per unit volume. Accordingly, the volume flow rate necessary to remove a threshold level of sorbate from the vessel 120 is reduced as compared to a PS regeneration system configured to regenerate a corresponding vessel by removing a similar amount of sorbate. However, the amount of energy used to heat the purge exhaust region 127 to a temperature sufficient only to increase the sorbate saturation threshold is generally less than the amount of energy used to preheat the purge gas stream or to heat the vessel bed in a TS regeneration system configured to regenerate a corresponding vessel by removing a similar amount of sorbate.

In certain embodiments, the purge exhaust stream 160 is heated sufficiently to increase a temperature of the purge stream 160 by no more than about 100°F (56°C). In some embodiments, the temperature of the incoming purge stream 150 is about 100°F (38°C) and the purge exhaust stream 160 is heated sufficiently to increase the temperature of the purge exhaust stream 160 to less than about 200°F (94⁰C). For example, in certain embodiments, the temperature of the purge exhaust stream 160 is elevated by a differential amount ranging from about 1O⁰F (6⁰C) to about 100°F (56⁰C). In one embodiment, the temperature of the incoming purge stream 150 is about 100⁰F (38⁰C) and the purge exhaust stream 160 is heated only sufficiently to elevate the temperature of the purge exhaust stream 160 to be about 20⁰F (11°C) above the temperature of the purge stream 150. In some embodiments, about 100 watts to about 200 watts of power are used to heat the purge exhaust stream 160. In other embodiments, greater or lesser power can be used.

When the fractionator cycle proceeds to a second phase, each vessel 110, 120 switches configurations. Accordingly, the vessel bed 115 of the first vessel 110 switches from a reduction configuration to a regeneration configuration and the vessel bed 125 of the second vessel 120 switches from a regeneration configuration to a reduction configuration. The gas flow paths of the second phase are shown in dashed lines in FIG. 1.

In summary, during the second phase, a gas input stream 130' is fed into the second vessel 120 (e.g., through the first port 165), passed through the vessel bed 125, and output from the second vessel 120 (e.g., through the second port 155) as gas output stream 140'. In some embodiments, a portion 142' of the gas output stream 140' can be directed to the first vessel 110 as a purge gas stream 150' or a portion thereof. In other embodiments, the gas output stream 140' is directed to other applications and the purge gas stream 150' is produced separately from the gas output stream 140'. The purge gas stream 150' is directed into the first vessel 110 (e.g., through the second port 145) to regenerate the vessel bed 115. Also during the second phase, a purge exhaust region 117 of the first vessel 110 is heated to raise the temperature of the purge exhaust stream 160' by a threshold level before the purge exhaust stream 160' exits the vessel 110 (e.g., at the first port 135). In other embodiments, each vessel 110, 120 can have separate ports for dirty gas ingress and purge exhaust egress. Accordingly, each vessel 110, 120 can have separate ports for clean gas egess and purge stream ingress.

FIG. 2 is a flowchart illustrating an operational flow for an example regeneration process 200 by which one or more vessel beds of a fractionator system, such as vessel beds 115, 125 of fractionator system 100 of FIG. 1, can be regenerated. The regeneration process 200 begins at a start module 202, performs any appropriate initialization operations, and proceeds to a heat operation 204. The heat operation 204 increases a temperature of a purge exhaust region of a vessel. In certain embodiments, the heat operation 204 is performed prior to introduction of a purge gas stream into the vessel.

In general, the heat operation 204 is implemented by a low power heat source operably positioned in the purge exhaust region of the vessel. In some embodiments, the heat operation 204 increases the temperature of the purge exhaust region by a threshold amount to heat a purge gas stream flowing within the purge exhaust region. Typically, the heat operation 204 increases the temperature of the purge exhaust region by a differential amount ranging between about 5°F (about 2⁰C) and about 100°F (about 55⁰C). hi one embodiment, the heat operation 204 increases the temperature of the purge stream in the purge exhaust region by a differential amount ranging between about 20⁰F (about 11°C) and about 60⁰F (about 33°C). hi another embodiment, the heat operation 204 increases the temperature of the purge stream in the purge exhaust region by about 40°F (about 22°C). In certain embodiments, the heat operation 204 heats the purge exhaust region at periodic intervals during the regeneration phase to maintain a consistent temperature or temperature range within the vessel, hi some embodiments, the heat operation 204 stops heating the purge exhaust region when a temperature of the purge exhaust region or another region of the vessel bed reaches or exceeds a predetermined threshold temperature. For example, in some embodiments, the heat operation 204 can cease applying heat to the purge exhaust region of a vessel in response to the fractionator system determining a temperature sensor located within the vessel has measured a temperature during the regeneration phase equal to or exceeding about 300⁰F. hi other embodiments, the threshold temperature can be higher or lower as appropriate to the application.

An input operation 206 introduces the purge gas stream into the vessel at a purge input of the vessel. Li general, the input operation 206 introduces the purge gas stream into the vessel at least partially counter-current to a feed direction of a gas input stream. In one embodiment, the input operation 206 introduces the purge gas stream into the vessel at a purge input located opposite a gas input of the vessel. Typically, the heat operation 204 continues to be implemented during implementation of the input operation 206. hi some embodiments, the input operation 206 is initiated a predetermined amount of time after beginning the heat operation 204 to enable sufficient thermal energy to be produced to sufficiently heat the purge stream within the purge exhaust region, hi one embodiment, the input operation 206 is initiated about 10 to about 60 seconds after beginning the heat operation 204. In another embodiment, the input operation 206 is initiated about 40 to about 50 seconds after beginning the heat operation 204. In another embodiment, the input operation 206 is initiated about 45 seconds after beginning the heat operation 204. In other embodiments, the input operation 206 can be initiated when the temperature of the purge exhaust region reaches a predetermined threshold. A cool operation 208 discontinues the application of heat to the purge exhaust region of the vessel to enable the purge exhaust region to cool. Cooling the purge exhaust region facilitates the sorption process within this region during the reduction phase. In some embodiments, the cool operation 208 mitigates the temperature differential across the vessel. In other embodiments, the cool operation 208 reduces the temperature of the purge exhaust region to at or below a threshold temperature. In one embodiment, the cool operation 208 enables the purge exhaust region to return to an ambient operating temperature. For example, the cool operation 208 can enable the purge exhaust region to cool to match the temperature of an input gas stream that will be introduced into the vessel during the reduction phase of the fractionator cycle.

In some embodiments, the cool operation 208 discontinues the application of heat a predetermined amount of time before beginning the next phase of the fractionator cycle. In one embodiment, the cool operation 208 is implemented about 10 to about 60 seconds before arranging the vessel in the reduction configuration for the start of the next phase. In another embodiment, the cool operation 208 is implemented about 40 to about 50 seconds before arranging the vessel in the reduction configuration. In another embodiment, the cool operation 208 is implemented about 45 seconds before the start of the next phase. hi other embodiments, the cool operation 208 discontinues the application of heat based on readings obtained at one or more sensors. For example, the cool operation 208 can be implemented when a threshold level of sorbate has been desorbed from the vessel bed. For example, the cool operation 208 can be implemented when one or more sensors provide readings indicating a sorbate concentration level of the operating environment has dropped below a predetermined threshold, m another embodiment, the cool operation 208 is implemented when a threshold temperature of the purge exhaust region or vessel is reached or exceeded. In certain embodiments, the cool operation 208 can be implemented when a threshold level of sorbate has been sorbed by another vessel bed arranged in the reduction configuration. In one such embodiment, the cool operation 208 is implemented when a threshold level of sorbate is met or exceeded in the operating environment of the vessel arranged in the reduction configuration. In another embodiment, the cool operation 208 is implemented when a threshold level of sorbate is met or exceeded in the clean gas output stream of the vessel arranged in the reduction configuration.

A close operation 210 stops the flow of the purge gas stream into the vessel. For example, the close operation 210 can shut the purge input of the vessel to the purge gas stream. In one embodiment, the close operation 210 is implemented a predetermined period of time after initiation of the input operation 206 or the cool operation 208. hi another embodiment, the close operation 210 is implemented based on readings obtained at one or more sensors. The regeneration process 200 completes and ends at a stop module 212.

FIG. 3 is a schematic diagram of an example sorption system 300 including a first vessel 310, a second vessel 310', and a control assembly 370. Other embodiments of the sorption system 300 can include greater or fewer vessels. The control assembly 370 can selectively configure each vessel 310, 310' into a reduction configuration, in which a vessel bed 315, 315' of the vessel 310, 310', respectively, removes sorbate from an influent gas stream, and a regeneration configuration, in which the vessel bed 315 , 315 ' is regenerated off-stream.

Gas flow conduits 305 provide selective ingress and egress of a gas stream and a purge stream into and out of the vessels 310, 310'. The control assembly 370 manages the flow pathways of the gas and purge streams within the conduits 305. The gas stream enters the first vessel 310 through a first gas input conduit 335 and exits the first vessel 310 through a first gas output conduit 345. The purge stream enters the first vessel 310 through a first purge input conduit 355 and exits the first vessel 310 through a first purge exhaust conduit 365. hi some embodiments, two or more of these conduits can share a port defined by the vessel 310. For example, the gas input conduit 335 and purge exhaust conduit 365 can share a port into and out of the vessel 310. In other embodiments, however, each conduit 335, 345, 355, 365 can have a separate port into and/or out of the vessel. The second vessel 310' includes a second gas input 335', a second gas output 345', a second purge input 355', and a second purge exhaust 365' to perform the same functions.

In some embodiments, the gas stream exiting from one of the vessels 310, 310' is directed to downstream applications via a gas exhaust 347, 347'. In other embodiments, the gas output 345, 345' of each vessel 310, 310' is fluidly connected to the purge input 355', 355 of the other vessel 310', 310 by connecting conduits 342, 342', respectively. Accordingly, at least part of the gas stream exiting from one of the vessels can be directed to the purge input of the other vessel. It will be appreciated, however, that the principles of the disclosure can be practiced using other conduit configurations. For example, fractionator system consistent with the scope of the disclosure can include vessels having separate ports for each input and output conduit.

The control assembly 370 selectively operates one or more valve assemblies to manage the gas flow pathways within the conduits 305. The control assembly 370 is operationally coupled to the valve assemblies via connections 376, 376'. In one embodiment, connections 376, 376' are electrical connections enabling the control assembly 370 to send power and/or instructions to the valve assemblies. However, other suitable types of connections are within the scope of the disclosure. First valve assemblies 380, 380' selectively open and close the gas inputs 335, 335' of the vessels 310, 310', respectively. Second valve assemblies 385, 385' selectively open and close the purge inputs 355, 355' of the vessels 310, 310', respectively. In some embodiments, the first valve assemblies 380, 380' also can selectively open and close the purge exhausts 365, 365'. In other embodiments, the purge exhausts 365, 365' are controlled by separate valve assemblies. The control assembly 370 also selectively operates a heater assembly

312, 312' operably positioned at or adjacent a purge exhaust region 317, 317' of each vessel 310, 310', respectively. The control assembly 370 is operationally coupled to the heater assemblies 312, 312' via connections 375, 375' which enable the control assembly 370 to manage activation and deactivation of the heating elements of the heater assemblies 312, 312'. As the term is used herein, elements that are "operationally coupled" are arranged together with suitable intermediate components to enable the elements to perform a specified function. For example, in one embodiment, connections 375, 375' are electrical connections enabling the control assembly 370 to send power and/or instructions to the heater assemblies 312, 312'. However, other suitable types of connections are within the scope of the disclosure.

Typically, the heater assembly 312, 312' of each vessel 310, 310' extends over only a portion of the respective vessel bed 315, 315'. In some embodiments, the heater assembly 312, 312' extends over less than about 50% of the vessel bed 315, 315'. In some embodiments, the heater assembly 312, 312' extends over less than about 25% of the vessel bed 315, 315'. In certain embodiments, the heater assembly 312, 312' extends only within the purge exhaust region 317, 317' of each vessel 310, 310'. In other embodiments, the heater assembly 312, 312' extends partially within the vessel bed 315, 315' and partially within the purge exhaust 365, 365'. Embodiments in which the heater assembly 312, 312' is positioned only within the purge exhaust 365, 365' of the respective vessel 310, 310' also are consistent with the scope of the disclosure. Each heater assembly 312, 312' includes one or more heating elements for heating the purge stream upstream of the purge exhaust outlet 365, 365', but downstream of the purge input 355, 355'. Typically, the heating elements of each heater assembly 312, 312' are configured to heat the purge stream within the purge exhaust region 317, 317' of the vessel 310, 310'. In general, the heating elements of each vessel 310, 310' are configured to create a heat differential across the vessel bed 315, 315' of the vessel 310, 310' by heating the respective purge exhaust region 317, 317'.

In the example shown in FIG. 3, the heater assemblies 312, 312' each include a single heating element mounted centrally in the purge exhaust output 365, 365' of the vessel 310, 310'. In some embodiments, each heater assembly 312, 312' includes a cage 314, 314' installed around the heating element or elements to inhibit direct contact between the heating elements and the sorbent of the vessel bed 315, 315'. In one embodiment, the cage 314, 314' includes a perforated metal cage. In some embodiments, the heating element includes a zoned electrical heater. In some embodiments, the heater assemblies 312,312' include heating elements having multiple heating zones.

In other embodiment, each heater assembly 312, 312' includes multiple heating elements operably positioned within the purge exhaust region 317, 317' and/or purge exhaust 365, 365' of the vessel 310, 310'. For example, in some embodiments, the heater assembly 312, 312' includes multiple heating elements installed radially within the purge exhaust region 317, 317' of the vessel bed 315, 315'. In other embodiments, each heater assembly 312, 312' includes multiple heating elements installed axially through the purge exhaust 365, 365' of the vessel 310, 310' and/or through the purge exhaust region 317, 317' of the vessel 310, 310'.

Some non-limiting examples of a heating element include an electrical immersion heater installed within the vessel 310, 310', a steam coil installed within the vessel 310, 310', a steam jacket fitted outside the vessel 310, 310' at or adjacent the purge exhaust outlet 365, 365', or some combination thereof. In other embodiments, a heating element can include a conduit providing hot discharge air produced by a gas compressor (not shown), for example, the gas compressor that compresses the gas input stream. In other embodiments, the heating element can include hot oil from the gas compressor and/or hot flue gas from a fired furnace or boiler. An example heating element will be described in additional detail herein with respect to FIG. 6.

FIG. 4 is a schematic diagram of one example control assembly 400 that can be used to operate the heater assemblies and/or valve assemblies of a fractionator system. The control assembly 400 includes a housing 410 containing a clock 401, a processor 402, a power source 409, and a memory 405 electrically coupled to each other. The memory 405 stores instructions 406 for operating the fractionator system. For example, in one embodiment, the memory 405 can store instructions 406 indicating a duration length of each phase of the fractionator cycle. In another embodiment, the memory 405 can store instructions 406 indicating when to activate and deactivate the heater assemblies.

The control assembly 400 also includes a heater control module 403 and a valve control module 404 configured to implement the instructions 406 stored in the memory 405. The heater control module 403 is coupled to a first output line (e.g., electrical wire) 407 that connects the control assembly 400 to the heater assemblies (e.g., heater assemblies 312, 312' of FIG. 3) of the fractionator system. In one embodiment, the heater control module 403 supplies power to the heater assemblies, thereby enabling the heater assemblies to generate heat, hi such an embodiment, the first output line 407 can include electrical wire connections. In other embodiments, however, the control assembly 400, using any suitable type of connection, can provide instructions to the heater assemblies to draw power from separate power sources.

The valve control module 404 is coupled to a second output line (e.g., electrical wire) 408 that connects the control assembly 400 to the valve assemblies (e.g., valve assemblies 380, 385, 380', 385' of FIG. 3) of the fractionator system, hi one embodiment, the valve control module 404 supplies power to the valve assemblies, thereby enabling the valve assemblies to operate to route the gas flow through the fractionator system. In such an embodiment, the second output line 408 can include electrical wire connections, hi other embodiments, however, the valve assemblies may be coupled to separate power sources or mechanically operated. Accordingly, the control assembly 400 can provide operating instructions to the valve assemblies using any suitable connection type including a mechanical connection. FIG. 5 is a flowchart illustrating an operational flow for an example control process 500 by which a control assembly can operate a vessel of a sorption system during a fractionator cycle. For ease in understanding, the control process 500 will be described as being implemented by the control assembly 400 to operate the first vessel 310 of the sorption system 300 of FIG. 3. In this example, the first vessel 310 begins the fractionator cycle in the reduction configuration and the other vessel 310' begins in the regeneration configuration. Of course, it is within the scope of the disclosure for the first vessel 310 to begin the fractionator cycle in the regeneration configuration.

The control process 500 begins at a start module 502, performs any suitable initialization procedures, and proceeds to a first open operation 504. The first open operation 504 operates the valve assemblies 380, 385 to configure the first vessel 310 in the reduction configuration, hi one embodiment, the first open operation 504 operates the first valve assembly 380 to open the gas stream input 335 of the first vessel 310 and operates the second valve assembly 385 to open the gas stream output 345. Accordingly, a gas stream is fed into the first vessel 310 through the gas stream input 335, cleansed of sorbate by the vessel bed 315, and received at the gas stream output 345. In one embodiment of the first open operation 504, the processor 402 of the control assembly 400 determines the time is appropriate to configure the first vessel 310 in the reduction configuration. For example, the processor 402 can determine the time is appropriate based on phase duration instructions 406 stored in the memory 405 of the control assembly 400 and the pulses of the clock 401.

Accordingly, the processor 402 can provide instructions to the valve control module 404 to operate the first valve assembly 380 to open the gas stream input 335 and to operate the second valve assembly 385 to open the gas stream output 345. In one embodiment, the valve control module 404 also sends power from power source 409 to the first and/or second valve assemblies 380, 385.

A first close operation 506 operates the valve assemblies 380, 385 to take the first vessel 310 off the fractionating process line. In one embodiment, the first close operation 506 operates the first valve assembly 380 to close the gas stream input 335 of the first vessel 310 and operates the second valve assembly 385 to close the gas stream output 345. Accordingly, the gas stream is redirected away from the first vessel 310. For example, the gas stream can be redirected to another fractionator vessel of the sorption system 300.

In one embodiment of the first close operation 506, the processor 402 of the control assembly 400 determines the time is appropriate to end the first phase of the fractionator cycle. For example, the processor 402 may determine the time is appropriate based on phase duration instructions 406 stored in the memory 405 of the control assembly 400 and the pulses of the clock 401. In another embodiment, the processor 402 receives a sensor input signal from a sensor (not shown) indicating regeneration of the vessel bed of the vessel 310 is appropriate. For example, in one embodiment, the sensor input signal can indicate the gas stream (e.g., obtained mid- bed, obtained at the output port, etc.) contains unsuitable amounts of sorbate. In another embodiment, the sensor input signal can indicate the operating environment (e.g., the sorbent in the vessel bed) contains a threshold amount of sorbate. Accordingly, the processor 402 provides instructions to the valve control module 404 via the second output line 408 to configure the first valve assembly 380 to close the gas stream input 335 and to configure the second valve assembly 385 to close the gas stream output 345. An activate operation 508 triggers the operation of the heater assembly 312. In one embodiment, the activate operation 508 supplies power to the heater assembly 312 to begin heating a purge exhaust region of the first vessel 310. For example, the activate operation 508 can supply an electrical current to one or more heating elements within the heater assembly 312. hi another embodiment, the activate operation 508 sends instructions to the heater assembly 312 to activate. The activate operation 508 generates a heat differential within the vessel 310 in which the purge exhaust region 317 has a higher temperature than the gas input 335 of the vessel 310. In one embodiment, the heating elements of the heater assembly 312 heat the purge exhaust region to a temperature of about 150°F (about 66°C) or more while the gas input 335 remains at about 100°F (about 38⁰C). hi one embodiment of the activate operation 508, the processor 402 of the control assembly 400 activates the heater assembly 312 a predetermined length of time prior to providing a purge flow through the vessel 310. For example, the processor 402 can determine the time is appropriate to activate the heater assembly 312 based on heating instructions 406 stored in the memory 405 of the control assembly 400 and the pulses of the clock 401. The processor 402 provides instructions to the heater control module 403 to activate the heater assembly 312. In one embodiment, the heater control module 403 sends power from the power source 409 to the heater assembly 312 via the first output line 407. hi another embodiment, the heater control module 403 sends instructions to the heater assembly 312 to begin drawing power from a separate power source.

A second open operation 510 operates the valve assemblies 380, 385 to configure the first vessel 310 in the regeneration configuration during a second phase of the fractionator cycle. In one embodiment, the second open operation 510 operates the second valve assembly 385 to open the purge stream input 355 of the first vessel 310 and operates the first valve assembly 380 to open the purge exhaust output 365. Accordingly, a purge stream enters the first vessel 310 through the purge stream input 355, desorbs the sorbate from the vessel bed 315 to regenerate the vessel bed 315, and exits the first vessel 310 via the purge exhaust output 365. The purge stream increases in temperature as the purge stream progresses through the first vessel 310 and reaches the purge exhaust region 317. In one embodiment of the second open operation 510, the processor 402 of the control assembly 400 determines the time is appropriate to configure the first vessel 310 in the regeneration configuration. For example, the processor 402 may determine the time is appropriate based on phase duration instructions 406 stored in the memory 405 of the control assembly 400 and the pulses of the clock 401. Accordingly, the processor 402 provides instructions to the valve control module 404 to configure the first valve assembly 385 to open the purge exhaust output 365 and to configure the second valve assembly 385 to open the purge stream input 355. In some embodiments, the control assembly 400 implements the second open operation 510 a predetermined period of time after initiation of the activate operation 508. In one embodiment, the control assembly 400 initiates the second open operation 510 about 10 to about 60 seconds after beginning the activate operation 508. In another embodiment, the control assembly 400 initiates the second open operation 510 about 40 to about 50 seconds after beginning the activate operation 508. In another embodiment, the control assembly 400 initiates the second open operation 510 about 45 seconds after beginning the activate operation 508. In another embodiment, the control assembly 400 initiates the second open operation 510 when the temperature of the purge exhaust region 317 reaches a predetermined temperature threshold as measured by a temperature sensor (not shown). In another embodiment, the control assembly 400 initiates the second open operation 510 when the temperature differential of the vessel 310 reaches a predetermined differential threshold as measured by the temperature sensor.

A second close operation 512 operates the valve assemblies 380, 385 to take the first vessel 310 off the regeneration process line. In one embodiment, the second close operation 512 operates the second valve assembly 385 to close the purge input 355 and operates the first valve assembly 380 to close the purge exhaust output 365. Accordingly, no purge or gas stream is provided to the vessel 310.

In one embodiment of the second close operation 512, the processor 402 of the control assembly 400 determines the time is appropriate to end the second phase of the fractionator cycle. For example, the processor 402 may determine the time is appropriate based on phase duration instructions 406 stored in the memory 405 of the control assembly 400 and the pulses of the clock 401. hi another embodiment, the processor 402 may determine the time is appropriate based on comparisons between an input signal from a sensor (not shown) and threshold values stored in the memory 405. For example, in one embodiment, the sensor signal can indicate sorbate concentration levels in the operating environment (e.g., the vessel bed) have reached or dropped below a predetermined threshold. In another embodiment, the sensor input signal can indicate sorbate concentration levels in the purge exhaust stream have reached or dropped below a predetermined threshold. Accordingly, the processor 402 provides instructions to the valve control module 404 to operate the first valve assembly 385 to close the purge exhaust 365 and to operate the second valve assembly 385 to close the purge input 355.

A deactivate operation 514 terminates the operation of the heater assembly 312. In one embodiment, the deactivate operation 514 stops supplying power to the heater assembly 312. For example, the processor 402 of the control assembly 400 can instruct the heater control module 403 to cease sending power from the power source 409 to the heater assembly 312. In another embodiment, the deactivate operation 514 sends instructions to the heater assembly 312 to toggle off. For example, the processor 402 can instruct the heater control module 403 to send a toggle command to the heater assembly 312. hi different embodiments, the deactivate operation 514 can be implemented after completion of the second close operation 512, prior to beginning the second close operation 512, or anytime in between. The control process 500 completes and ends at a stop module 516.

FIG. 6 is a schematic diagram showing one example heater assembly 600 that can be used in the fractionator systems disclosed herein. The heater assembly 600 includes a heater body 610 having a length A. The heater body 610 is configured to operably connect to a control assembly. For example, the heater body 610 can operably couple to the heater control module 403 of the control assembly 400 of FIG. 4. In general, the heater body 610 includes at least one heat generating section 612 and a mounting section 616. hi one embodiment, the heater assembly 600 includes one or more FIREBAR® immersion heaters produced by Watlow Electric Manufacturing Company of Hannibal, Missouri.

The heat generating section 612, which has a length B, produces and emits heat when power is supplied to the heater assembly 600, for example, by a control assembly. Li some embodiments, the heater body 610 includes at least one spacer section 614 arranged between the heat generating section 612 and the mounting section 616. The spacer section 614, which has a length C, does not produce heat. In some embodiments, the length B of the heat generating section 612 is less than the length C of the spacer section. Li some embodiments, the heater body 610 includes multiple heat generating sections 612 and spacer sections 614 arranged to provide heating zones along the length A of the heater body 610. hi general, the length A of the heater body 610 can range from about 1 inch to about 25 inches. Li some embodiments, the length A of the heater body 610 can range from about 10 inches to about 20 inches. In one embodiment, the length A of the heater body 610 is about 18 inches. Li another embodiment, the length A of the heater body 610 is about 16.5 inches. Li some embodiments, the length B of the heat generating section 612 is about one-third of the length A of the heater body 610 and the length C of the spacer section 614 is about two-thirds the length A of the heater body 610. Li one embodiment, the length B of the heat generating section 612 can be about 6 inches and the length C of the spacer section 614 can be about 12 inches. In another embodiment, the length B of the heat generating section 612 can be about 6 inches and the length C of the spacer section can be about 10.5 inches.

The mounting section 616 is configured to mount the heater body 610 to a fractionator vessel, such as fractionator vessel 310 of FIG. 3. Li one embodiment, the mounting section 616 includes a threaded region enabling the heater body 610 to threadably mount to the fractionator vessel. For example, in one embodiment, the heater body 610 can be threadably mounted to a peripheral wall of the fractionator vessel. In another embodiment, the heater body 610 can mount within an output port or conduit of the fractionator vessel (e.g., within the purge exhaust 365 of vessel 310). In other embodiments, however, the mounting section 616 can be otherwise configured to secure the heater body 610 to the fractionator vessel.

Connection lines 618 protrude from the mounting section 616 to operably connect the heater body 610 to a control assembly. In one embodiment, the connection lines 618 have sufficient length to be routed to the control assembly. Li another embodiment, the connection lines 618 couple to intermediate connection lines routed from the fractionator vessel to the control assembly. For example, the connection lines 618 can include wires configured to electrically couple the heat generating section 612 of the heater body 610 to the control assembly, hi some embodiments, an insulating sheath 619 surrounds the wires 618. In one embodiment, the insulating sheath 619 is formed from fiberglass. hi some embodiments, the heater assembly 600 receives power from the control assembly, hi other embodiments, the heater assembly 600 receives power from a separate power source (not shown) or from an internal power source (not shown), hi general, the heater assembly 600 receives sufficient power to enable the heat generating section 612 to produce sufficient heat to cause a predetermined threshold heat differential within the fractionator vessel, hi one embodiment, the heat generating section 612 heats to a temperature of at least about 150°F (about 66⁰C). hi one embodiment, the heater assembly 600 can be fed a voltage of about 120 volts and wattage of about 100 watts to enable the heat generating section 612 to produce sufficient heat, hi another embodiment, the heater assembly 600 can be fed a voltage of about 120 volts and wattage of about 300 watts to enable the heat generation section 612 to produce sufficient heat.

The principles of the present disclosure will now be further explored by walking through a hypothetical engineered example, hi particular, the costs of a TSA regeneration process, a PSA regeneration process, and a hybrid process implemented in accordance with the principles of the present disclosure are compared herein based on a hypothetical numerical simulation. For the purposes of this comparison, the regeneration processes are assumed to be performed for a 1,000 scfrn (standard cubic feet per minute) compressed air dryer operating at 100°F (38°C) and 100 psig (pound-force per square inch gauge) furnished with 600 to 800 pounds of sorbent (e.g., activated alumina) per vessel. Typically, this type of dryer provides about 5 to 10 years of continuous purification service using a conventional regeneration process.

If the gas input stream is fed into the dryer vessel at a temperature of about 100°F (38°C), then the gas output stream will leave the vessel at about 100°F (38°C) since the sorption process is isentropic and at 80% relative humidity in equilibrium with the moisture laden sorbent at the exhaust end of the vessel bed. hi a PSA regeneration system, both the purge gas stream and the purge exhaust would have a temperature of about 100⁰F (38°C). In such a case, the partial pressure of water vapor in the purge stream exhaust would be about 0.76 psia (pounds-force per square inch absolute). In a TSA regeneration system, the purge gas stream is heated, for example, to about 400°F (205°C), prior to entering the vessel.

One conventional TSA regeneration process operates on an 8 hour NEMA cycle (e.g., 4 hours sorbing and 4 hours regenerating). As the term is used herein, a NEMA cycle is a purification cycle implemented by a compressed air dryer and includes a drying phase and a regeneration phase. If the vessels of the sorbent system each include a 27 KW heater to heat the purge gas stream fed to the off- stream vessel bed and if the heater heats the bed for 3 hours and cools for 1 hour, then the average energy consumption per vessel will be about 20 KW (i.e., 0.020

KW/scfm) of compressed air. At $0.05/KW-hr, the average energy consumption per vessel can cost about $8,760 per year to implement such a TSA process (i.e., 0.020 x 1000 x 24 x 365 x 0.05).

In comparison, one conventional PSA regeneration process operates on a 10 minute NEMA cycle (e.g., 5 minutes sorbing and 5 minutes regenerating), hi the PSA process, the flow rate of the gas stream to be purified is increased to provide sufficient purified gas to produce a purge stream and a repressurization stream. For example, about 15% of the purified gas stream output from the vessel can be diverted to form the purge stream and about 1.6% of the purified gas stream can be diverted to form a repressurization stream. Accordingly, to maintain a purified gas output flow of about 1000 scfm, the gas stream input flow is raised to about 1200 scfm, about 180 scfm of which is consumed as the purge stream and about 20 scfm of which is consumed as the repressurization stream. If the energy consumption rate for air compression based on a single-stage compressor is about 1 KW per 5 scfm (i.e., about 40 KW for 200 scfm), then the energy consumption cost of compressing the additional 200 scfm of the gas input stream utilized in the PSA system is about $17,520 per year (i.e., 200 x (1/5) x 24 x 365 x 0.05).

Advantageously, the energy consumption costs can be dramatically reduced by regenerating the vessel beds in accordance with the principles of the hybrid regeneration process disclosed herein as shown by the following hypothetical numerical model. The cycle time of the hybrid regeneration process is on the same order of magnitude as the PSA process. Accordingly, the vessel bed need not be heated to the same extent as the vessel bed in a TSA system to enable desorption. In an example hybrid regeneration system operating on a 10 minute NEMA cycle, the temperature rise in an on-stream vessel bed of the above described air dryer resulting from the heat of sorption of water vapor would be about 21.6°F (12⁰C) based on an 80% inlet relative humidity (i.e., 1250 (BTU/lb water vapor) x 0.80 x 0.00519 (Ib water vapor/lb air) / 0.24 (BTU/°F-lb air)). This heat of sorption added to the vessel bed during the drying of the compressed air is retained and applied to desorption of the moisture during the regeneration process. Accordingly, the hybrid regeneration process does not require the energy consumption of the TSA process to heat the vessel bed.

For example, the hybrid regeneration process is expected to utilize about 0.6 KW of energy to provide sufficient heat to operate the system instead of the about 27 KW necessary for a conventional 1000 scfm temperature swing system. The hybrid regeneration process also is expected to utilize about 7% of the effluent gas as purge flow instead of the about 15% effluent gas used in conventional pressure swing systems.

In a hybrid regeneration system implemented in accordance with the principles of the present disclosure, the water vapor partial pressure in the purge stream exhaust is elevated by heating the purge stream in the purge exhaust region of the vessel only. Heating only the purge stream traveling through the purge exhaust region of the vessel decreases the cost of heating the purge stream as will be shown herein. Heating the purge stream only at the purge exhaust region of the vessel also is expected to increase the vapor pressure of the purge stream in accordance with the following table, Table 1 :

Increasing the vapor pressure of the purge stream enables the purge stream to hold more sorbate. Accordingly, increasing the temperature of the purge

¹ Based on 80% inlet relative humidity times 0.9496 psia. stream time at the purge exhaust region of the vessel enables a greater amount of sorbate to be exhausted from the vessel using the same amount of purge flow. Therefore, a vessel can be regenerated using the hybrid regeneration process by a purge stream having a decreased flow rate as compared to the purge stream in a conventional PSA system. Since less purge flow is used, the total flow of the gas stream need not be increased as much for the hybrid regeneration process as for the conventional PSA process.

In general, the total gas stream flow from which sorbate is to be removed is sufficient produce a predetermined amount of clean gas flow, sufficient purge inlet flow, and sufficient repressurization flow. Accordingly, the total gas stream flow is determined according to the following equation (1):

wherein Qj_n is the total gas stream flow, Qo is the desired amount of clean gas flow, and R is the amount by which the total flow of the gas stream inlet must be increased to provide a predetermined amount of purified gas flow, a sufficient purge inlet flow, and a sufficient repressurization flow.

In general, the amount R by which the total flow of the gas stream inlet must be increased is determined by the following equation (2):

(2) R = Q_p (Avg. purge) + Q_r (Avg. Repress. Air) wherein Q_p is the purge stream inlet flow and Q_r is the repressurization stream inlet flow.

It is expected a repressurization stream inlet flow of about 1.6% of the gas stream inlet flow is sufficient to repressurize the vessel after regeneration.

When the purge stream has a temperature of about 100°F at the purge exhaust region, it is expected that a purge stream inlet flow of approximately 15% of the gas stream inlet flow will support adequate regeneration the vessel bed. Accordingly, equation (2) becomes equation (3):

(3) R = (0.76/p) 0.15 Q_in + 0.016 Q_in which becomes equation (4): (4) Q_in = Qo + (0.76/p) 0.15 Q_1n + 0.016 Q_in

Accordingly, the amount R by which the gas stream inlet flow must be increased to provide a purified gas outlet flow Qo of 1000 scfm is provided in the following table, Table 2:

The heat energy consumption rate KW needed to operate the heater assembly that heats the purge stream at the purge exhaust region can be determined with the following equation:

(5) KW = Q_p x 0.075 ( ) x ΔT°F x 0.24 (BTU/°F-lb of air) x 0.017576 KW/BTU/min scf wherein KW refers to the amount of thermal energy provided to the heater assembly. The annual cost of producing sufficient thermal energy KW to heat the purge exhaust region of the sorption vessel is determined with the following equation:

(6) Cost = KW x 24 x 365 x $0.05/KW-hr

The following table, Table 3, shows how the annular cost of heating the purge exhaust region of each vessel varies based on temperature in accordance with equations 5 and 6.

The following table, Table 4, shows how the annual cost of compressing the additional flow amount R of the total gas stream input changes based on the purge exhaust temperature. For the purposes of this example, the compressor energy consumption rate to compress both the purge stream flow and the repressurization stream flow is estimated at 1 kw per 5 scfm.

² Based on 80% inlet relative humidity times 0.9496 psia.

The total annual energy consumption rate and cost of operation for the hybrid regeneration process can be determined by totaling annular cost of heating the purge exhaust region of each vessel as shown in Table 4 and the annual cost of compressing the additional flow amount R of the total gas stream input. Table 5 shows how this total cost varies according to the temperature to which the purge exhaust region is heated.

Accordingly, the application of a small amount of thermal energy into the purge stream at the purge exhaust end of the vessel bed of a pressure swing sorption system can dramatically reduce the dry purge consumption rate (and thereby the annular compression costs) and the thermal energy consumption rate (and thereby the heat energy costs), and thereby lower the annular operating cost of the sorption system.

The above specification provides examples of how certain aspects of the disclosure may be put into practice. It will be appreciated that the aspects can be practiced in other ways than those specifically shown and described herein without departing from the spirit and scope of the disclosure.

Claims

WE CLAM:

1. A fractionator system comprising: at least one vessel bed, each vessel bed being configured to be alternately arranged in a reduction configuration and a regeneration configuration, wherein each vessel bed removes sorbate from a dirty gas stream when arranged in the reduction configuration and releases sorbate obtained from the dirty gas stream into a purge stream when arranged in the regeneration configuration, each vessel bed having a purge exhaust region extending over less than 50% of a length of the vessel bed; a valve assembly operationally coupled to each of the vessel beds, the valve assembly being configured to selectively route the dirty gas stream and the purge stream to each vessel bed; and a heater assembly arranged within the purge exhaust region of each vessel bed, each heater assembly including at least one heater element configured to heat the purge stream sufficiently to increase a sorbate saturation pressure of the purge stream without significantly aiding desorption of the sorbate from the vessel bed.

2. The fractionator system of claim 1 , wherein the heater element is configured to heat the purge stream to raise a temperature of the purge stream by a differential amount ranging between about 10°F (5°C) and about 100⁰F (55°C).

3. The fractionator system of claim 2, wherein the heater element is configured to heat the purge stream to raise the temperature of the purge stream by a differential amount of about 20⁰F (H⁰C).

4. The fractionator system of claim 1, further comprising a control arrangement operationally coupled to the valve assembly, the control arrangement being configured to operate the valve assembly to route the dirty gas stream and purge stream to the vessel bed in accordance with a predetermined fractionator cycle.

5. The fractionator system of claim 4, wherein the control arrangement also is operationally coupled to the heater assembly and is configured to selectively operate the heater assembly according to the predetermined fractionator cycle.

6. The fractionator system of claim 5, wherein the control arrangement activates the heater element of the vessel bed at about 10 to 60 seconds prior to routing the purge stream into the vessel bed.

7. The fractionator system of claim 1, wherein each heater element comprises an immersion heater installed centrally within the purge exhaust region of the vessel bed.

8. The fractionator system of claim 1 , wherein each heater assembly comprises a plurality of heater elements installed radially within the purge exhaust region of the vessel bed.

9. The fractionator system of claim 1, wherein each heater assembly comprises a plurality of heater elements installed axially within the purge exhaust region of the vessel bed.

10. The fractionator system of claim 1, wherein each heater assembly also includes a perforated metal cage installed around the heater element to inhibit direct contact between the heater element and the vessel bed.

11. The fractionator system of claim 1 , wherein the sorbate is water vapor.

12. The fractionator system of claim 1 , further comprising a second vessel bed arranged in the regeneration configuration when the first vessel bed is arranged in the reduction configuration.

13. A method for regenerating a vessel bed after passing a dirty gas stream through the vessel bed, the method comprising: sealing the vessel bed from the dirty gas stream; providing an ambient temperature purge stream to the vessel bed, the purge stream being substantially free of sorbate, wherein the purge stream passes through the vessel bed counter-current to the dirty gas stream; heating the purge stream at a purge exhaust region of the vessel bed to increase a sorbate saturation pressure of the purge stream, the purge stream being heated to increase a temperature of the purge stream by a differential ranging from about 1O⁰F (5°C) to about 100⁰F (55⁰C); and outputting the purge stream at the purge exhaust output, the purge stream having desorbed sorbate from the vessel bed when passing through the vessel bed to produce a regenerated vessel bed.

14. The method of claim 13 , wherein heating the purge stream comprises providing at least one heater element at the purge exhaust output and selectively operating the heater element to heat the purge stream.

15. The method of claim 14, wherein selectively operating the heater element comprises activating the heater element about 10 to about 60 seconds prior to providing the ambient temperature purge stream to the vessel bed.

16. The method of claim 14, wherein selectively operating the heater element comprises activating the heater element about 45 seconds prior to providing an ambient temperature purge gas stream to the vessel bed.

17. The method of claim 14, further comprising: sealing the vessel bed from the purge stream; deactivating the heater element; and providing the dirty gas stream to the regenerated vessel bed to remove sorbate from the dirty gas stream to produce a clean gas stream.

18. The method of claim 17, wherein deactivating the heater element comprises deactivating the heater element about 10 to about 60 seconds prior to providing the dirty gas stream to the regenerated vessel bed.

19. The method of claim 17, wherein deactivating the heater element comprises deactivating the heater element about 45 seconds prior to providing the dirty gas stream to the regenerated vessel bed.

20. The method of claim 17, deactivating the heater element comprises deactivating the heater element when a temperature of the vessel bed rises above a predetermined threshold.

21. The method of claim 17, wherein a duration of time between sealing the vessel bed from the dirty gas stream and sealing the vessel bed from the purge stream is on the order of minutes.