A vacuum regeneration system for improving overall performance of a PSA unit and process thereof

Abstract

The present invention relates to implementing vacuum regeneration technology for improving overall performance of a pressure swing adsorption (PSA) unit. The present invention provides a vacuum regeneration system integrated with the PSA unit for enhancing the product recovery and improving the feed rate of the PSA unit. The present invention also provides a process for improving the overall performance of the PSA unit by integrating with the vacuum regeneration system.

Description

[0001] A VACUUM REGENERATION SYSTEM FOR IMPROVING OVERALL PERFORMANCE OF A PSA UNIT AND PROCESS THEREOF

[0002] FIELD OF THE INVENTION:

[0003] The present invention relates to implementing vacuum regeneration technology for improving overall performance of a pressure swing adsorption (PSA) unit. Specifically, the present invention provides a vacuum regeneration system integrated with the PSA unit for enhancing the product recovery and improving the feed rate of the PSA unit. The present invention also provides a process for improving the overall performance of the PSA unit by integrating with the vacuum regeneration system.

[0004] BACKGROUND OF THE INVENTION:

[0005] Vacuum pressure swing adsorption processes or VPSA processes are well known from the state of the art. This process is distinguished from a pressure swing adsorption process or a PSA process in that the regeneration of the loaded adsorber takes place at a pressure below atmospheric pressure. In order to achieve a pressure below this atmospheric pressure, the adsorber to be regenerated is regenerated using a vacuum pump. Adsorption is often performed at overpressure.

[0006] Application of vacuum pressure swing adsorption is increasing currently in hydrogen production because of its high productivity and high H2 purity compared with PSA process. A fast-cycling VS A method has been used for hydrogen production from a binary mixture of H2 / C02:70 / 30 (Lopes et al. Fuel, Volume 93, March 2012, Pages 510-523), and they purified hydrogen with purity of 99.99% and recovery of about 61.8%. Another work was conducted (Lopes et al. Chemical Engineering Science, Volume 66, Issue 3, 1 February 2011, Pages 303- 317) on VSA process and they produced hydrogen with purity of 99.981%, CO concentration of 63 ppm and recovery of 81.6% from a syngas source. Some of the prior art disclosing the use of vacuum pressure swing adsorption method for separating mixture of gases have been given below.

[0007] W02002094417A1 discloses a method and a device for separating components of a gas by adsorption, vacuum pressure swing adsorption (VPSA), with two reactors lined with adsorbents selected on the basis of the gas to be adsorbed, and operating in accordance with a four-phase cycle comprising pressure variations at room temperature; adsorption under pressure in a first reactor and purified gas production, vacuum desorption of the second reactor and rinsing the purified gas, further adsorption and purified gas production to the first reactor and re-pressurising the second reactor, adsorption to the second reactor and purified gas production, desorption of the first reactor with rinsing, adsorption to the second reactor with purified gas production and re -pressurising the first reactor, repeating the cycle; and use of a rotary gas dispenser for carrying out said four phases with radial circulation mode of the gases in the adsorbent masses at constant speed and with inverse rinsing of the masses with purified gas during desorption,

[0008] CN109529533A discloses the optimizations and control method of a kind of dual reflux pressure-swing absorption apparatus, in order to improve the product gas concentration and yield of oxygen and nitrogen, increase intermediate gas holding vessel between two absorption bed bodies, second adsorption will be carried out after gas boosting after flushing, utilize the oxygen in nitrogen " displacement " adsorbent bed, on the one hand make oxygen and nitrogen separation, on the other hand improve the product gas concentration of oxygen and nitrogen ; It is desorbed after absorption using vacuum pump-down, extracts nitrogen-rich gas therein out, also make the flushing recycled next time more thorough, improve the product gas concentration of oxygen.

[0009] CN110052114A discloses a kind of vacuum pressure swing adsorption system of band backwash. The present invention include vacuum pump P-01 A, vacuum pump P-0 IB, raw material gas transmission pipe line, inverse put decompression pipeline, vacuum clean-up line, clean-up line, along put pipeline, product gas external transport pipeline, along putting surge tank D-01 and six adsorption towers (being illustrated by taking six tower processes as an example) ; Adsorbent reactivation vacuumizes progress synchronous with two ways is rinsed using vacuumizing and rinsing two ways combination, middle and later periods in adsorbent reactivation stage, and adsorbent reactivation is more thorough, and impurity content is lower, and adsorbent regeneration effect is more preferable. When vacuum system breaks down, it can be achieved that vacuum process and flushing process switchover operation. When full factory's operating condition changes, it can also realize vacuum process and rinse the switchover operation of process.

[0010] Despite advances in the prior art, VPS A processes remain less efficient in respect of the product recovery and feed rate than desired. Thus, there is a need for further improvements to increase the product recovery and feed rate that will result in increased productivity, to make the use of the highly desirable VPSA technology in commercial plants efficient and more economical. SUMMARY OF THE INVENTION:

[0011] In an aspect, the present invention provides a vacuum regeneration system to enhance the product recovery and to improve the feed rate of a PSA unit. The system comprises a vacuum unit (8) having an inlet opening and an outlet opening, wherein the inlet opening is connected to a tail gas header (5) of the PSA unit and the outlet opening is connected with a separate Safety Instrumented System (SIS) comprising an oxygen analyzer (11),

[0012] In an embodiment of the present invention, there is provided a system, wherein the oxygen analyzer (11) is configured with an interlock to switch the PSA unit from vacuum pressure swing adsorption mode to pressure swing adsorption mode.

[0013] In an embodiment of the present invention, there is provided a system, wherein the tail gas header (5) of the PSA unit has two separate blowdown headers forming a closed assembly, wherein the first blowdown header acts as an Atmospheric blowdown header (6) and the second blowdown header acts as a Vacuum blow down header (7), wherein the second blowdown header is connected to the vacuum unit (8).

[0014] In an embodiment of the present invention, there is provided a system, wherein the vacuum unit (8) has a pressure in a range of -0.7 to -0.9 kg / cm2g.

[0015] In an embodiment of the present invention, there is provided a system, wherein the vacuum unit (8) is selected from a dry root blower, liquid ring vacuum pump (LRVP) and ejector system, preferably LRVP system.

[0016] In another aspect, the present invention provides a process to enhance the product recovery and to improve the feed rate of a PSA unit through a vacuum regeneration system connected to a tail gas header (5) of the PSA unit. The process includes steps of de-pressuring the PSA unit by reducing a desorption pressure for desorbing impurities in a blowdown mode of a PSA cycle sequence.

[0017] The next step includes passing desorbed impurities through a tail gas header (5), wherein the tail gas header (5) of the PSA unit has two separate blowdown headers forming a closed assembly, wherein the first blowdown header acts as an Atmospheric blowdown header (6) and the second blowdown header acts as a Vacuum blow down header (7), wherein the closed assembly works as an ABD mode, a VBD mode and a combination thereof.

[0018] In an embodiment of the present invention, there is provided a process, wherein reducing the desorption pressure for desorbing impurities in the blowdown mode of the PSA cycle sequence is performed through a vacuum unit (8) of the vacuum regeneration system, wherein the vacuum unit (8) is connected to the tail gas header (5) of the PSA unit.

[0019] In an embodiment of the present invention, there is provided a process, wherein the desorption pressure is in a range of -0.7 to -0.9 kg / cm2g.

[0020] In an embodiment of the present invention, there is provided a process, wherein the feed rate of the PSA unit increases by up to 50%.

[0021] In another embodiment of the present invention, there is provided a process, wherein the product recovery is in a range of 90 to 95%, wherein the impurity in the product gas is up to 3 ppm.

[0022] BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

[0023] The following figures form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the figures in combination with the detailed description of the specific embodiments presented herein.

[0024] Figure 1 illustrates a conventional PSA unit.

[0025] Figure 2 illustrates PSA unit integrated to a vacuum regeneration system.

[0026] DETAILED DESCRIPTION OF THE INVENTION:

[0027] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are delineated here. These definitions should be read in light of the remainder of the disclosure and understood as by a person of skill in the art.

[0028] The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below. The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”. The term "at least one" is used to mean one or more and thus includes individual components as well as mixtures / combinations.

[0029] Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps. The term “including” is used to mean “including but not limited to”, “including” and “including but not limited to” are used interchangeably.

[0030] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods and materials are now described.

[0031] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally equivalent products, compositions, and methods are clearly within the scope of the disclosure, as described herein.

[0032] In an aspect, the present invention provides a vacuum regeneration system to enhance the product recovery and to improve the feed rate of a PSA unit. The system comprises a vacuum unit (8) having an inlet opening and an outlet opening, wherein the inlet opening is connected to a tail gas header (5) of the PSA unit and the outlet opening is connected with a separate Safety Instrumented System (SIS) comprising an oxygen analyzer (11),

[0033] In an embodiment of the present invention, there is provided a system, wherein the oxygen analyzer (11) is configured with an interlock to switch the PSA unit from vacuum pressure swing adsorption mode to pressure swing adsorption mode.

[0034] In an embodiment of the present invention, there is provided a system, wherein the tail gas header (5) of the PSA unit has two separate blowdown headers forming a closed assembly, wherein the first blowdown header acts as an Atmospheric blowdown header (6) and the second blowdown header acts as a Vacuum blow down header (7), wherein the second blowdown header is connected to the vacuum unit (8).

[0035] In an embodiment of the present invention, there is provided a system, wherein the vacuum unit (8) has a pressure in a range of -0.7 to -0.9 kg / cm2g.

[0036] In an embodiment of the present invention, there is provided a system, wherein the vacuum unit has a pressure of -0.7 kg / cm2g. In an embodiment of the present invention, there is provided a system, wherein the vacuum unit (8) is selected from a dry root blower, liquid ring vacuum pump (LRVP) and ejector system, preferably LRVP system.

[0037] In another aspect, the present invention provides a process to enhance the product recovery and to improve the feed rate of a PSA unit through a vacuum regeneration system connected to a tail gas header (5) of the PSA unit. The process includes steps of de-pressuring the PSA unit by reducing a desorption pressure for desorbing impurities in a blowdown mode of a PSA cycle sequence.

[0038] The next step includes passing desorbed impurities through a tail gas header (5), wherein the tail gas header (5) of the PSA unit has two separate blowdown headers forming a closed assembly, wherein the first blowdown header acts as an Atmospheric blowdown header (6) and the second blowdown header acts as a Vacuum blow down header (7), wherein the closed assembly works as an ABD mode, a VBD mode and a combination thereof.

[0039] In an embodiment of the present invention, there is provided a process, wherein reducing the desorption pressure for desorbing impurities in the blowdown mode of the PSA cycle sequence is performed through a vacuum unit (8) of the vacuum regeneration system, wherein the vacuum unit (8) is connected to the tail gas header (5) of the PSA unit.

[0040] In an embodiment of the present invention, there is provided a process, wherein the desorption pressure is in a range of -0.7 to -0.9 kg / cm2g.

[0041] In an embodiment of the present invention, there is provided a process, wherein the desorption pressure is -0.7 kg / cm2g.

[0042] In an embodiment of the present invention, there is provided a process, wherein the feed rate of the PSA unit increases by up to 50%.

[0043] In another embodiment of the present invention, there is provided a process, wherein the product recovery is in a range of 90 to 95%, wherein the impurity in the product gas is up to 3 ppm.

[0044] By splitting the blow down mode, the size of the vacuum pump can be reduced by at least 30% in comparison to a normal vacuum pressure swing adsorption. The vacuum regeneration system has two headers, one to remove all the gas present in the interstitial space (pressure above 1.5 kg / cm2) and another for evacuating the rest of the gas and induce vacuum inside the bed which is connected through the vacuum pump.

[0045] Addition of vacuum pump will decrease the regeneration pressure to sub-atmospheric pressures which increases the net- working capacity of the adsorbents.

[0046] Addition of vacuum regeneration helps in achieving higher product recovery as well as improving feed flow rate thereby improving the overall productivity of the PSA.

[0047] The increase in adsorption capacity allows to load more impurity i.e. increased feed rate or cycle time.

[0048] EXAMPLES:

[0049] The disclosure will now be illustrated with working examples, which are intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure.

[0050] Example 1: PSA unit without vacuum.

[0051] The regeneration of the PSA unit with five adsorbers is carried out without vacuum (figure 1).

[0052] The PSA process cycle sequence is given in table 1. Various process parameters have been tabulated in table 2.

[0053] Table 1. PSA cycle sequence Table 2. Process parameters

[0054] Example 2: PSA unit integrated to a vacuum regeneration system.

[0055] The regeneration of the PSA unit with five adsorbers is carried out with vacuum (figure 2). The

[0056] PSA process cycle sequence is given in table 3. Various process parameters have been tabulated in table 4.

[0057] Table 3. PSA cycle sequence Table 4. Process parameters

Claims

CLAIMS:

1. A vacuum regeneration system to enhance the product recovery and to improve the feed rate of a PSA unit, wherein the system comprises: a vacuum unit (8) having an inlet opening and an outlet opening, wherein the inlet opening is connected to a tail gas header (5) of the PSA unit and the outlet opening is connected with a separate Safety Instrumented System (SIS) comprising an oxygen analyzer (11).

2. The system as claimed in claim 1, wherein the oxygen analyser (11) is configured with an interlock to switch the PSA unit from vacuum pressure swing adsorption mode to pressure swing adsorption mode.

3. The system as claimed in claim 1, wherein the tail gas header (5) of the PSA unit has two separate blowdown headers forming a closed assembly, wherein the first blowdown header acts as an Atmospheric blowdown header (6) and the second blowdown header acts as a Vacuum blow down header (7), wherein the second blowdown header is connected to the vacuum unit (8).

4. The system as claimed in claim 1, wherein the vacuum unit (8) has a pressure in a range of -0.7 to -0.9 kg / cm2g.

5. The system as claimed in claim 1, wherein the vacuum unit (8) is selected from a dry root blower, liquid ring vacuum pump (LRVP) and ejector system, preferably LRVP system.

6. A process to enhance the product recovery and to improve the feed rate of a PSA unit through a vacuum regeneration system connected to a tail gas header (5) of the PSA unit, wherein the process comprises steps of: de-pressuring the PSA unit by reducing a desorption pressure for desorbing impurities in a blowdown mode of a PSA cycle sequence; and passing desorbed impurities through a tail gas header (5), wherein the tail gas header (5) of the PSA unit has two separate blowdown headers forming a closed assembly, wherein the first blowdown header acts as an Atmospheric blowdown header (6) and the second blowdown header acts as a Vacuum blow down header(7), wherein the closed assembly works as an ABD mode, a VBD mode and a combination thereof.

7. The process as claimed in claim 6, wherein reducing the desorption pressure for desorbing impurities in the blowdown mode of the PSA cycle sequence is performed through a vacuum unit (8) of the vacuum regeneration system, wherein the vacuum unit (8) is connected to the tail gas header (5) of the PSA unit.

8. The process as claimed in claim 6, wherein the desorption pressure is in a range of -0.7 to -0.9 kg / cm2g.

9. The process as claimed in claim 6, wherein feed rate of the PSA unit increases by up to 50%.

10. The process as claimed in claim 6, wherein the product recovery is in a range of 90 to95%, wherein the impurity in the product gas is up to 3 ppm.

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