(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`(19) World Intellectual Property
`Organization
`International Bureau
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`UOUTA ATTA AARA
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`(43) International Publication Date
`3 March 2016 (03.03.2016)
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`WIPO!IPCT
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`\=
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`(10) International Publication Number
`WO 2016/033447 Al
`
`GD)
`
`International Patent Classification:
`BOLD 53/047 (2006.01)
`BOID 53/26 (2006.01)
`
`(21)
`
`International Application Number:
`
`PCT/US2015/047409
`
`(22)
`
`International Filing Date:
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`28 August 2015 (28.08.2015)
`
`(25)
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`(26)
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`(30)
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`(71)
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`(72)
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`(74)
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`(81)
`
`Filing Language:
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`Publication Language:
`
`English
`
`English
`
`Priority Data:
`62/043,692
`
`29 August 2014 (29.08.2014)
`
`US
`
`Applicant: NUVERA FUEL CELLS, INC. [US/US]; 129
`Concord Road, Building 1, Billerica, MA 01821 (US).
`
`Inventors: LI, Zhijiang; 9 Meetinghouse Lane, Franklin,
`MA 02038 (US). VANZANDT, Kyle; 9 Gordon Street,
`Allston, MA 02134 (US). BLANCHET, Scott; 43 Chest-
`nut Hill Road, Chelmsford, MA 01824 (US).
`
`Agents: CHAPMAN,Ernest F. et al.; Finnegan, Hender-
`son, Farabow, Garrett & Dunner, LLP, 901 New York Av-
`enue, N.W., Washington, D.C. 20001-4413 (US).
`
`Designated States (unless otherwise indicated, for every
`kind of national protection available). AE, AG, AL, AM,
`
`AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW,BY,
`BZ, CA, CII, CL, CN, CO, CR, CU, CZ, DE, DK, DM,
`DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM,GT,
`IIN,IIR, ITU, ID,IL, IN, IR, IS, JP, KE, KG, KN, KP, KR,
`KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, MG,
`MK, MN, MW, MX, MY, MZ, NA, NG, NIL, NO, NZ, OM,
`PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW,SA, SC,
`SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN,
`TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW.
`
`(84)
`
`Designated States (unless otherwise indicated, for every
`kind of regional protection available): ARIPO (BW, GH,
`GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ,
`TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU,
`TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE,
`DK,EE, ES, FI, FR, GB, GR, HR, HU,IE,IS, IT, LT, LU,
`LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK,
`SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ,
`GW, KM,ML, MR,NE, SN, TD, TG).
`Published:
`
`with international search report (Art. 21(3))
`
`before the expiration of the time limit for amending the
`claims and to be republished in the event of receipt of
`amendments (Rule 48.2(h))
`
`(54) Title: METHODS OF OPERATING PRESSURE SWING ADSORPTION PURIFIERS WITH ELECTROCHEMICAL HY-
`DROGEN COMPRESSORS
`
`
`
`
`
`wo2016/033447A[INITIUMIIMTANIIMTITTVNTTATTAEMTA
`
`(57) Abstract: In accordance with one embodiment, a method of drying a hydrogen gas mixture is disclosed. The method may in-
`clude determining a mass flow rate of water m0 in a hydrogen gas mixture stream and an adsorbent capacity of one or more adsorb-
`ent beds; determiningafirst period of time based on the determined mass flow rate of water mmo in the hydrogen gas mixture stream
`and the adsorbent capacity; directing the hydrogen gas mixture stream through a first adsorbent bed of the one or more adsorbent
`bedsfor the first period oftime; adsorbing a quantity of water from the hydrogen gas mixture stream into the first adsorbent bed; and
`regenerating the first adsorbent bed.
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`METHODS OF OPERATING PRESSURE SWING ADSORPTION PURIFIERS
`WITH ELECTROCHEMICAL HYDROGEN COMPRESSORS
`
`i001] This application claims the benefit of U.S. Provisional Application No.
`
`62/043,692, filed August 29, 2014, which is incorporated by reference in its entirety.
`
`fOO2] Embodiments of the present disclosure relate to a pressure swing
`
`adsorption (PSA) based purification device, and more particularly, to methods of
`utilizing a PSA device fer drying a wet hydrogen stream from an electrachemical
`
`hydrogen compressor (EHC),
`{063] An EHC, for example, may selectively transfer hydrogen ions across a
`
`membrane within an electrochemical cell An EHC may include a proton exchange
`
`membrane positioned between two electrodes, Le., an anode and a cathode.
`Hydrogen gas in cantact the anode may be oxidized by applying a vollage potential
`across the electrodes. Oxidation of a hydrogen molecule produces two electrons
`
`and two protons. The two protons are electrochemically driven through the
`membrane to the cathode, wherein the protons rejoin the two rerouted electrons and
`
`reduce back to a hydragen molecule. The transfer of charge or current within the
`cell is commonly referred to as the stack current. The reactions taking place at the
`
`glectrodes can be expressed as oxication-reduction half-reactions, as shown below.
`Anode oxidation reaction: H2-> 2H" + 3e
`
`Cathode reduction reaction: 2H’ + 26 —+ He
`
`Overall electrachemica] reaction: H2—-> He
`
`[004] EHCs operating in this manner are sometimes referred to as a
`hydrogen pumps. When the hydrogen accurnulated at the cathode is restricted to a
`confined space, the cell compresses the hydrogen, and thus raises the pressure
`within that space. Multiple celis may be linked in series to form a multi-stage EHC.
`ina multi-stage EHC, for example, the gas flow path, may be configured such that
`the compressed output gas of the first cell becomes the input gas of the second ceil.
`Alternatively, single-stage cells may be linked in parallel fo increase the throughput
`capacity (.e., total gas flow rate) of an EHC.
`[O05] The output of an EHC may include liquid water and water vapar in
`addition to hydrogen gas. Liquid water may be rernoved from the output stream by
`passing the stream through a phase separator. After liquid water has been removed
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`from the output stream, water vapar may be removed from the gas stream.
`Conventional methods for removing water vapor from a gas stream may ental
`
`adsorbing water vapor onto adsorbent materiais at certain pressures and
`
`temperatures. Examples of these methods include PSA and ternperature swing
`
`adsorption.
`
`[O08]
`
`in a conventional PSA process, a hydrogen gas sirearn containing
`
`impurity species may be passed through an adsorbent bed at elevated pressures for
`
`a duration of time known as an adsorption time. Elevating the partial pressures of
`
`the impurities may cause the impurities to adsorb onto adsorbent materials within the
`
`adsorbent bed. After the adsorption time has heen reached, the adsorbent bed may
`
`be depressurized and purged to remove the impurities and regenerate the
`
`adsorption capacity of the adsorbent materials. Typically, the adsorption time is
`
`fixed,
`
`[OO7]
`
`In consideration of the aforernentioned factars, the preseni disclosure
`
`is directed toward methods of utilizing a PSA device for drying a wet hydragen
`
`stream.
`
`in addition, an EHC may supply the wet hydrogen strearn to the PSA
`
`device, and the feeding (adsorption)/regeneration cycle time of the PSA device may
`
`be optimized or controlied based on operating parameters of the EHC,
`
`igo8] PSA devices may separate gas fractions fromm gas mixtures by
`coordinating pressure cycling and flow reversal over an adsorbent material in an
`adsorbent bed. The adsorbent material may have a pressure sensitive affinity to at
`
`least one component in the gas mixture, and may more readily adsorb this gas
`
`cemponent compared to at least one other component of the gas. During operation,
`
`a component of the gas stream can adsorb onto the adsorbent bsd as the gas
`
`pressure in the bed is increased. A “light” product, Le., the gas stream without the
`
`adsorbed gas, can be removed from the bed. The materials in an adsorbent bed can
`
`adsorb a finite mass of the gas component. The adsorbent bed may be regenerated
`
`by decreasing its pressure, such that the adsorbed gas desorbs back inte a gas
`
`phase. The desorbed gas, Le., the “heavy” product is then exhausted from the
`
`adsorbent bed. The process of increasing the pressure in the adsorbent bed and
`
`adsorbing a gas component is considered “feeding,” whereas the process of
`
`decreasing the pressure in the adsorbent bed and desorbing the gas camponent is
`»
`considered “regeneration.” For example, an adsorbent bed may adsorb a maximum
`
`quantity of molecules of a gas component when it reaches a saturation limit. The
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`adsorbent bed must be regenerated before adsorbing more of this gas cornponent,
`
`while itis af the saturation limit. The adsorbent beds can be cycled through feeding
`
`and regeneration processes for equal periods of time: this is referred te as a
`
`constant switching time.
`
`{O09] The applicant has discovered that when a mass flow rate of a gas
`
`component into a PSA device is not constant, using a constant switching time may
`
`resuit in inefficiencies with the PSA device. This may also cause unnecessary rapid
`
`switching, which may resull in increased wear on some of the camponents of the
`
`PSA device, such as the valves. The applicant has discovered that by adjusting the
`
`switch time for a PSA device as a function of the operating parameters of the PSA
`
`device and the EHC, the size of the adsorbent beds may be reduced and the
`
`efficiency of the PSA device may be increased.
`
`{O10]
`
`in accordance with one embodiment, a method of drying a hydrogen
`
`gas mixture is disclosed. The method may include determining a mass flowrate of
`
`water tiyeq in a hydrogen gas mixture stream and an adsorbent capacity of one or
`
`more adsorbent beds; determining a4 first period of adsorption time based on the
`
`determined mass flow rate of water Mu2o in the hydrogen gas mixture stream and ihe
`
`adsorbent capacity; directing the hydrogen gas mixture stream through a first
`
`adsorbent bed of the ane or more adsorbent beds for the first period of time;
`
`adsorbing a quantity of water from the hydrogen gas mixture stream into the first
`
`adsorbent bed: and regenerating the first adsorbent bed.
`
`[Olt] Various embodiments of the disclosure may include one or more of the
`
`following aspects: determining a second period of adsorption time based on the
`
`determined mass flow rate of water Muzo in the hydrogen gas mixture stream and ihe
`
`adsorbent capacity, and directing the hydrogen gas mixture stream through the first
`
`acisorbent bed fer a second period of time, wherein the first period of time is different
`
`than the second period of time; directing the hydrogen gas mixture stream through a
`
`second adsorbent bed of the one or more adsorbent beds during the second period of
`
`time, and adsorbing a quantity of water from the hydrogen gas mixture stream into the
`
`second adsorbent bedthe quantily of water adsorbed by the first adsorbent bed during
`
`the first time period may be substantially the same as the quantiy of water adsorbed
`
`by the second adsorbent bed during the second time period; each of the quantity of
`
`water adsorbed by the first adsorbent bed during the first time period and the quantity
`
`of water adsorbed by the second adsorbent bed during the second time period may
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`be less than the maximum quantity of water that can be adsorbed by the respective
`
`first and second adsorbent beds; regenerating the first adsorbent bed may include
`
`directing a different gas stream through the first adsorbent bed, and desorbing a
`
`quantity of water from the first adsorbent bed into the different gas stream: the
`
`hydrogen gas mixture stream may be supplied by an electrochemical hydrogen
`
`compressor or electrolyzer; the different gas stream may be a dry hydrogen gas
`
`stream: atleast a portion of the different gas stream may include a portion of the
`
`hydrogen gas mixture stream after the hydrogen gas mixture strearn passes through
`
`the first adsorbent bed; the mass flow rate of water rhiueo may be determined at least
`
`by measuring the amount of water in the hydrogen gas mixture stream) and
`
`determining an electrochemical hydragen cornpressor or electrolyzer stack current i,
`
`an electrochemical hydrogen compressor or electroiyzer outlet temperature T, an
`
`electrochemical hydrogen compressor or electrolyzer outlet pressure P,oi, and a
`constant k, wherein the mass flowrate of water muzo may be determined at least by
`calculating the amount of water in the hydrogen gas mixture stream according fo an
`equation Mz = Kk “1 * T/Pot
`[O12]
`In another embodiment of the disclosure, a method of operating a
`pressure swing adsorption purifier is disclosed. The method may include supplying 2
`hydrogen gas mixture stream from an electrochemical hydrogen compressor to the
`pressure swing adsorption purifier, supplying a different gas stream to the pressure
`swing adsorption purifier. The pressure swing adsorption purifier may include at least
`ane first adsorbent bed and at least one second adsorbent bed. Further, the method
`
`may include feeding the at least one first adsorbent bed, which may include adsorbing
`water from the hydrogen gas mixture stream inte the at least one first adsorbent bed;
`regenerating the atleast one second adsorbent bed, which may include desorbing
`water from the at least one second adsorbent bed into the different gas stream;
`
`feeding the at least one second adsorbent bed, which may include adsorbing water
`
`fram the hydrogen gas mixture stream into the at least one second adsorbent bed,
`
`regenerating the at least one first adsorbent bed, which may include desorbing water
`from the atleast one first adsorbent bed into the different gas stream; and switching
`
`between feeding the at ieast one first adsorbent bed and regenerating the al least one
`
`second adsorbent bed according to a switching time.
`
`[013] Various embodiments of the disclosure ray include one or more of the
`
`following aspects: repeating swiiching between feeding the al least one first
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`adsorbent beci and regenerating the af least one second adsorbent bed according to
`
`a different switching time: determining a mass flow rate of water theo in the hydrogen
`
`gas mixture stream, wherein the switching time may be determined ai least on the
`
`determined mass flow rate of water muzo) the mass flow rate of water Muze may be
`
`determined at least by measuring the amount of water in the hydrogen gas mixture
`
`stream; and the hydrogen gas mixture stream may be supplied by an electrochemical
`
`hydrogen compressor or electralyzer and the method may further comprise:
`
`determining the electrochemical hydrogen compressor or electrolyzer stack current 1,
`
`the electrochemical hydrogen compressor or electrolyzer outlet temperature T, the
`
`electrochemical hydrogen compressor or electrolyzer outlet pressure Pig, and a
`
`constant k, wherein the mass flow rate of water Mizo may be determined at least by
`
`calculating the amount of water in the hydrogen gas mixture siream according toe an
`
`equation MHZO = k *i* T/Piot.
`[O14]
`In another embodiment, a controller for operating one or more
`downstream valves of an electrochemical hydrogen compressor or an electrolyzer is
`
`disclosed. The controller may include a temperature sensor configured fo measure
`
`the outlet temperature of the electrochemical hydrogen compressor or the
`electrolyzer, a circuit configured to determine the stack current of the electrochemical
`hydrogen compressor or the electrolyzer; and a pressure sensor configured to
`measure the outlet pressure of the electrochemical hydrogen compressor or the
`
`glectrolyzer. The controller may be configured to determine an outlet mass flow rate
`of water in a hydrogen gas mixture strearn based on the outlet ternperaiure, the stack
`
`current, and the outlet pressure.
`
`In addition, the one or more valves may include a
`
`first valve and the controller may be configured te epen and close the first valve
`
`based at least on the determined outlet mass flow rate of water.
`
`i075] Various embodiments of the disclosure may include one or more of the
`
`following aspects: the controller may be configured to determine a switching time
`
`based at least on the outlet mass flow rate of water for opening and closing the first
`
`vaive, and the first valve may be opened and closed based on the switching time; the
`
`electrochemical hydrogen cornpressor or the electrolyzer may be in fluid
`communication a pressure swing adsorption purifier having a first adsorbent bed, and
`
`the controler may be configured to open and close the first valve based atleast on an
`
`adsorbent capacity of the adsorbent bed; the pressure swing adsorption purifier may
`
`include a second adsorbent bed, and the controller may be configured fo determine a
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`switching time for opening and closing the first valve based at least on the determined
`
`outlel mass flow rate of water, the adsorbent capacity of the first adsorbent bed, and
`
`an adsorbent capacity of the secand adsorbent bed, and the first vaive may be
`
`opened and closed based on the switching time; and the one or more vaives may
`
`include a second valve and the controller may be configured to open and close the
`
`second valve based atleast on the determined outlet mass flow rate of water, and the
`
`first valve and the second valve may be opened asynchronously or closed
`
`asynchronously.
`
`[016] Additional objects and advantages of the embodiments will be set forth
`
`in part in the description that follows, and in part will be obvious from the description,
`
`or may be learned by practice of the embodiments. The objects and advantages of
`
`the embodiments will be realized and attained by means of the elements and
`
`combinations particularly pointed out in the appended claims.
`
`[017]
`
`itis to be understeod that both the foregoing general description and
`
`the following detailed description are exemplary and explanatory only and are not
`
`restrictive of the invention, as claimed.
`
`jOiS8}] The accompanying drawings, which are incorporated in and constitute
`
`a part of this specification, illustrate embodiments of the disciosure, and together
`
`with the description, serve to explain the principles of the disclosure.
`
`[019] Figure (1 illustrates a diagram of a pressure swing adsorption based
`
`purification device, according fo an embodiment of the present disclosure.
`
`[020] Figure 2 illustrates a diagram of a pressure swing adsorption based
`
`purification device, according to an embadiment of the present disclosure.
`
`[O21] Figure 3 illustrates a diagrarn of a pressure swing adsorption based
`
`purification device, according to an embodiment of the present disclosure.
`[022] Figure 4 ilustrates a diagram of a pressure swing adsorption based
`
`purification device, according to an embodiment of the present disclosure.
`[023] Reference will new be made in detail to the exemplary embodiments of
`
`the present disclosure described below and illustrated in the accompanying
`
`drawings. Wherever possible, the same reference nurmbers will be used throughout
`
`the drawings to refer to same orlike parts.
`
`fo24) While the present disclosure is described herein with reference to
`
`illustrative embcdimenis of a pressure swing adsorption based purification device, it
`
`is understood that the devices and methods of the present disclosure may be
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`employed with various types of electrochemical cells, including, but not limited to any
`
`suitable hydrogen compressors, fuel cells, electrolysis cells, hydrogen purifiers, and
`
`hydrogen expanders. Those having ordinary skillin the art and access to the
`
`teachings provided herein will recognize additional modifications, applications,
`
`embodiments, and substitution of equivalents that all fall within the scope of the
`
`disclosure. Accordingly, the disclosure is not to be considered as limited by the
`
`foregoing or following descriptions.
`
`O25) Other features and advantages and potential uses of the present
`
`disclosure will become apparent to semeone skilled in the art from the following
`
`description of the disclosure, which refers to the accompanying drawings.
`{026}
`Figure 1 depicts a schematic of a PSA device 8 in a first configuration,
`according ta an exemplary embodiment of the present disclosure. The PSA device 9
`
`includes a first adsorbent bed 1, a second adsorbent bed 2, a first four-way vaive 7
`
`having first and second configurable positions, and a second four-wayvalve 8, also
`
`having first and second configurable positions. Similarly, figure 2 depicts the PSA
`
`device 9 in a second configuration.
`
`In the first configuration, the four-way valves 7
`
`and § are in the first position, whereas in the second configuration, the four-way
`
`valves 7 and 8 are in the second position.
`
`{027]
`
`in an adsorption or feeding operation, according to an exemplary
`
`embodiment, an EHC 10 (or an electrolyzer) may receive and pressurize a hydrogen
`
`gas mixture 12 and supply a hydrogen gas mixture 3 (e.g., a stream of wet hydrogen
`gas that includes hydrogen gas and water vapor) to the four-way vaive 7. VWhen the
`four-way valve 7 is in the first position, the hydrogen gas mixture 3 may be routed to
`
`the first adsorbent bed 1. The hydrogen gas mixture 3 may establish a pressure
`
`gradient across the first adsorbent bed 7 in the direction from the four-way vaive 7
`towards the four-way valve 8. The first adsorbent bed 1 may comprise 4 material
`
`having an affinity to water that increase with increasing pressure. As a non-limiting
`example, the first adsorbent bed 1 may comprise one or more of a desiccant, such as
`
`silica, carbon or silicon nanoparticles, surface treated particles, aluminum oxide, and
`
`zeolites. Due to the pressure of the hydrogen gas mixture 3, the first adsorbent bed 14
`
`may adsorb a fraction of the water vapor from the hydrogen gas mixture 3, such that
`the gas becomes dryer. This dryer gas is represented as dry hydrogen gas 6 in figure
`
`4. After the removal of a portion or all of the water vapor from the hydrogen gas
`
`mixture 3, the dry hydrogen gas 6 may exit through the four-way vaive 8.
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`[O28] Simultaneously, a regeneration operation may take place in the second
`
`adsorbent bed 2 as the adsorption operation takes place in the first adsorbent bed 1.
`
`During this regeneration operation, dry hydrogen gas 5 may be supplied te the four-
`
`way valve 8. During this operation, the dry hydrogen gas 5 may be af a lower
`
`pressure than the dry hydrogen gas 6. Dry hydrogen gas 5 may be supplied from a
`
`discrete hydrogen gas source (not shown), or it may be shunted from the dry
`
`hydrogen gas 6 to a lower pressure. VVhen the four-way valve 8 is in the first position,
`
`the dry hydrogen gas 5 may be routed to the secand adsorbent bed 2. Due to the
`
`lower pressure of the dry hydrogen gas 5 compared to the pressure of sither the
`
`hydrogen gas mixture 3 or the dry hydrogen gas 6, the dry hydrogen gas 5 may
`
`desorb a fraction of adsorbed water in the second adsorbent bed 2, such that the gas
`
`becomes hurnid. This humid gas is represented as wet hydrogen gas 4. After the
`
`addition of water to the dry hydrogen gas 5, the wet hydrogen gas 4 may exit through
`
`the four-way valve 7.
`
`[O29] Figure 2 shows the adsorption and regeneration cycie of the PSA
`
`device 9 in a second configuration. The second configuration differs from the first
`
`configuration in that the four-way valves 7 and 8 are in their second positions instead
`
`of their first positions. During the adsorption cycle, the first adsorbent bed 1 may
`
`adsorb water until it reaches a maximum capacity, or a saturation limit. To prevent
`
`the first adsorbent bed 7 from becoming fully saturated, or to allow the first aclsorbent
`
`bed i to be ahle to remove a quantity of water that would otherwise exceed the
`
`quantity of water at its saturation limit, the PSA device 9 may reverse its adsorption
`
`and regeneration cycles, iLe., the first adsorbent bed 1 regenerates and the second
`
`adsorbent bed 2 removes water vapor from the hydrogen gas mixture 3.
`
`i030] After the four-way valves 7 and 8 have switched from the first position to
`
`the second pasition, the EHC 10 may continue to supply the hydrogen gas mixture 3
`
`to the four-way vaive 7. The hydrogen gas mixture 3 may be routed to the second
`
`adserbent bed 2, due to the four-way vaive 7 being in the second position. The
`
`hydrogen gas mixture 3 may establish a pressure gradient across the second
`
`adsorbent bed 2 in the direction from the four-way valve 7 towards the four-way valve
`8. The second adsorbent bed 2 may also comprise adsorbing materials, similarly fo
`the first adsorbent bed 1.
`In some embodiments, the adserbing materials in the
`
`second adsorbing bed 2 may be different the adsorbing materials in the first
`
`adsorbing bed 1. Due fo the pressure of the hydragen gas mixture 3, the second
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`adsorbent bed 2 may adsorb a fraction of the water vapor from the hydrogen gas
`
`mixture 3, such that the gas becomes dryer. This dryer gas is represented as dry
`
`hydrogen gas G in figure 2. After the removal of water vapor from the hydrogen gas
`
`mixture 3, the dry hydragen gas 6 may exit through the four-way vaive 8.
`
`O31] Simultaneously, a regeneration operation may take place in the first
`
`adsorbent bed 1 as the adsorption operation takes place in the second adsorbent bed
`
`2. During this regeneration operation, dry hydrogen gas 5 may be supplied to the
`
`four-way valve 8. The dry hydrogen gas 5 may be routed to the first adsorbent bed 4
`
`due to the four-way valve & being In the second pasition. Due to the lower pressure
`
`of the dry hydrogen gas 5 compared to pressure of either the hydrogen gas mixture 3
`
`or the dry hydrogen gas &, the dry hydrogen gas 5 may desorb a fraction of adsorbed
`
`water in the first adsorbent bed 1, such that the gas becomes humid. This humid gas
`
`is represented as wei hydrogen gas 4. After the addition of water to the dry hydrogen
`
`gas 5, the wet hydrogen gas 4 may exit through the four-way valve 7. After exiting
`
`the PSA device 9, the wet hydrogen gas 4 may be recycled back fo the EHC 10, ar it
`
`may be used in other processes. For example, the wet hydrogen gas 4 may be
`
`routed to a burner to generate heat for other processes.
`
`[032] The PSA device 9 may switch frorn the first configuration to the secand
`
`configuration before the first adsorbent bed 1 becomes fully saturated. Likewise, the
`
`PSA device 9 may switch from the second configuration to the first configuration
`
`before the second adsorbent bed 2 becomes fully saturated. To determine the
`
`operational switch times, a contrailer 17 may actuate the four-way valves 7 and 8,
`
`é.g., in the form of sclenaids, based on operational parameters of the PSA device 8
`
`and/or the EHC 10.
`
`[O33] For example, the mass flow rate of hydrogen gas and water vapor of the
`
`hydrogen gas mixture 3 may be determined based on the measurements from the
`
`EHC 10, such as stack current, termperature, pressure, relative humidity, and
`
`volumetric fow rates. The controller 11 may perform an integral control by integrating
`
`the mass flow rate of water to calculate the mass of water in the hydrogen gas
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`mixture 3 over a given period of ime. The mass flow rate of hydrogen and water may
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`be determined by calculating partial pressures for each of the hydrogen and water in
`
`the hydrogen gas mixture 3. For example, the mass flow rate of water ray be
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`determined by solving equation 1, wherein thiues is the mass flow rate of water, Mus is
`
`the mass flow raise of hydrogen, Mfigsy is the molecular weight of water, Myo, is the
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`WO 2016/033447
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`PCT/US2015/047409
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`molecular weight of hydrogen, Pyso is the partial pressure of water, and Pio is the
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`outlet pressure of the EHC (or electrolyzer).
`
`fuze | Puzo
`Buz
`Prot
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`i034] Equation 1: thyzo = Myo
`
`[O35] Moreover, equation 1 can be rewritten in terms of water concentration
`
`Gueo 88 equation 2, wherein kK, is a constant.
`
`[O36] Equation 2: thas = ty. ky + Causa
`
`i037] Thus, the mass flow rate of water can be determined by directly
`
`measuring the mass flowrate of hydrogen and the concentration of water.
`
`{038}
`
`in addition, the applicant nas found that the mass flow raie of hydrogen
`
`ig proportional to the EHC stack current i, and the mass flow rate of hydrogen is
`
`oroportional to EHC outlet temperature T. Therefore, the mass flow rate of hydrogen
`
`may be expressed by equation 3, wherein kz is a constant.
`(O39} Equation 3: musg = k2:h- —
`jO40] Further, a partial pressure of any impurity in the hydrogen gas mixture 3
`may calculated.
`in addition, the maximum amount of water that the adsorbent beds 4
`ang 2 may adsorb can be calculated based on the volume of the adsorbent beds 7
`
`and 2, the adsorbent density of the adsorbent material, and the adsorbent capacity of
`
`the adsorbent material. The adsorbent density and adsorbent capacity of the
`
`adsorbent materials may be known quaniities.
`
`[fo41] The controller 11 may switch between the adsorbing and regeneration
`
`operations of the PSA device 9 when the calculated mass of water in the hydrogen
`
`gas mixture 3 equals or exceeds the saturation limit of the adsorbent beds 7 and 2.
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`In addition, a safety factor may be applied tc this cornparison, such that switching
`
`may occur when the mass of water in the hydrogen gas mixture 3 equals a
`
`predetermined percentage of the saturation lirnit of the adsorbent beds 7 and 2. For
`
`example, if a safety factor of 2 is selected, switching may occur when the mass of
`
`water adsorbed in the adsorbent beds 1 and 2 reaches 50% ofIts saturation limit. A
`
`safety factor between 1 and 10 may be selected, although a safety factor higher than
`
`10 may be selected as well. Switching may occur when the controller 11 sends a
`
`control signal to the valves 7 and 8.
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`{O42} The mass flow rate of water in the hydrogen gas mixture 3 may vary
`
`during operation. Thus, the adsorbing and regeneration operations of the PSA device
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`10
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`9 may be optimized by adjusting the switch time based on the mass of water inputted
`
`into the adsorbent beds 1 and 2 during the respective adsorbing cperations.
`
`{043] Although only adsorbent beds 1 and 2 are depicted in figures 1 and 2,
`
`the PSA device 9 may include additional adsorbent becis N. Any of the adsorbent
`
`beds N may have the same capacity of either adsorbent beds 1 or 2, or it may have a
`
`different capacity. Furthermore, any of the adsorbent beds N may operate ait the
`
`same phase as adsorbent beds 1 or 2, or it may operate at different phase (or
`
`asynchronously). For example, an additional adsorbent bed N1 may operate in an
`
`adsorbing operation, such that a vaive controlling the Input of the hydrogen gas
`
`mixture 3 opens at some time period after the four-way vaive 7 is switched to the first
`
`position. Likewise, a different valve controlling the input of a dry hydrogen gas 5 to
`
`the adsorbent bed Ni may open at some time period after the four-way valve is
`
`switched to the second position, thus switiching the operation of adsorbent bed N1 to
`
`a regenerating operation.
`
`[044]
`
`In other embodiments, switching times of the feeding and regeneration
`
`operations of the PSA device 9 may he initially predetermined.
`
`In addition, the mass
`
`flow rate of water in the hydrogen gas mixture 3 may be calculated, and when this
`
`value increases by a predetermined amount, the switching time may temporarily
`
`increase to accommodate an increase in water that the adsorbent beds 1 and 2 may
`
`remove. After the mass flow rate of water in the hydrogen gas mixture 3 drops below
`
`a predetermined value, the switching time may return to its initial value.
`
`{045}
`
`In other embodiments, feedback control of the switching time may alse
`
`be employed. For exampis, the amount of water in the dry hydrogen gas 6, the wet
`
`hydrogen gas 5, and/orthe first and second adsorbent beds 1 and 2 may be directly
`
`measured by hurnidity and/or chemical sensors (not shown). The controller 11 may
`
`receive feedback from humidity and/or chemical sensors and may adjust the
`
`switching times that were previously calculated from the parameters of the EHC 10
`
`and PSA device 9 based on these measurements.
`
`O46)
`
`in other embodimenis, only one adsorbent bed may be used. For this
`
`process, the flow of a hydrogen gas mixture may be supplied to a first two-way valve.
`
`Vnen the first two-way valve is opened, the hydrogen gas mixture may flow to the
`
`adsorbent bed.
`
`in the adsorbent bed, water may be adsorbed in a similar manner as
`
`adsorbent beds 1 and 2 described above. The light gas mayexit the adsorbent bed
`
`through a second two-way valve.
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`i047] Next, the adsorbent bed may be regenerated. For this process, the first
`
`and second two-way vaives may close at substantially the same time.
`
`in some
`
`embodiments, the second two-way vaive may close prior to the first fwo-way valve
`
`closing. At this point, flow of the hydrogen gas mixture into the adsorbent bed may be
`
`temporarily stopped. To accommodate a potential increase in pressure, a tank
`
`positioned in series with and between the ECH and