WO2024226689A1

WO2024226689A1 - Multi vessel adsorption desorption system and methods

Info

Publication number: WO2024226689A1
Application number: PCT/US2024/026112
Authority: WO
Inventors: Henrik F. Bernheim; Michael Morgan; Alex BERNACCHI; Jonathan D. KINTNER; Cole Davis; Brian MEDEMA; Marco ACEVEDO
Original assignee: Starfire Energy Inc
Current assignee: Starfire Energy Inc
Priority date: 2023-04-24
Filing date: 2024-04-24
Publication date: 2024-10-31
Anticipated expiration: 2025-10-24

Abstract

Systems and methods for transforming the cyclic batch process of adsorption and desorption of a polar molecule to a nearly continuous process through utilization of step function emulation is described.

Description

MULTI VESSEL ADSORPTION DESORPTION SYSTEM AND METHODS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63/497,960, filed April 24, 2023, and entitled “MULTI VESSEL ADSORPTION DESORPTION SYSTEM”, the entirety of which is incorporated by reference herein.

TECHNICAL FIELD

[0002] The technology described herein generally relates to systems and methods for introducing and adsorbing polar molecules in an adsorbent material and then removing the same polar molecules from the adsorbent material by exposing the adsorbent material to radio frequency (RF) energy and recovering the released (desorbed) polar molecules in a manner that emulates a continuous process that better matches the continuous (or nearly continuous) polar molecule synthesis process. Polar molecules recovered in this manner can be used directly or stored for later use. One such type of polar molecule of particular interest is anhydrous ammonia (NH3), although other types of polar molecules are also useful and can be recovered by the technology described herein.

BACKGROUND

[0003] Human-caused emissions of carbon dioxide (CO2) are causing global warming, climate changes, and ocean acidification. These threaten humanity’s continued health, life, economic development and security. To counter this threat, energy sources that are substantially free of CO2 emissions are highly sought after in both industrialized and developing countries. While several CO2-free energy generation options have been extensively developed, none presently include a practicable carbon-free energy carrier.

[0004] Ammonia (NH3) can be burned with oxygen (O2) as a fuel yielding nitrogen (N2) and water (H2O) according to the following reaction equation (1 ):

4 NH₃ + 3 O2 2 N2 + 6 H2O + heat (1 ) [0005] NHs can be used directly as a carbon-free fuel or as a hydrogen source if it is reformed into hydrogen and nitrogen gases. It can also be used in a mixture of NH3, H2, and N2 to tailor its combustion characteristics to specific processes or equipment. It has a higher energy density, easier storage conditions, and cheaper long-term storage and distribution than gaseous hydrogen, liquid hydrogen, or batteries.

[0006] The main industrial process for the production of ammonia is the Haber-Bosch process, illustrated in the following reaction equation (2):

N₂ (g) + 3 H₂ (g) ^ 2 NH3 (g) (AH = -92.2 kJ/mol) (2)

[0007] In 2005, Haber-Bosch ammonia synthesis produced an average of about 2.1 tonnes of CO2, per tonne of NH3 produced. About two thirds of the CO2 production derives from steam reforming of hydrocarbons to produce hydrogen gas, while the remaining third derives from hydrocarbon fuel combustion to provide energy to the synthesis plant. As of 2005, about 75% of Haber-Bosch NH3 plants used natural gas as feed and fuel, while the remainder used coal or petroleum. Haber-Bosch NH3 synthesis consumed about 3% to 5% of global natural gas production and about 1 % to 2% of global energy production.

[0008] The Haber-Bosch reaction is generally carried out in a reactor containing an iron oxide or a ruthenium catalyst at a temperature of between about 300 °C and about 550 °C and at a pressure of between about 90 bar and about 180 bar. The elevated temperature is required to achieve a reasonable reaction rate. The reaction is equilibrium limited, which can be counteracted by the high pressure. Conversion rates per pass are typically 15% (although this varies based upon plant design and implementation). To extract the produced NH3, the Haber-Bosch process takes advantage of the high operating pressure to remove the NH3 through condensation.

[0009] Recent advances in NH3 synthesis have yielded reactors that can operate at temperatures between about 300 °C and about 650 °C and pressures ranging from 1 bar up to the practical limits of pressure vessel and compressor design. When designed for lower operating pressures, effectively marrying the operating pressure of the reactor to that of the output of commercially available H2 electrolyzers (typically < 35 bar), this newer generation of reactors can reduce equipment costs and gas compression costs, but they also reduce the fraction of the N₂ and H₂ reactants converted to NH₃ during each pass through the reactor. The conversion of NH3 per pass is therefore typically in the single digits percentage range (< 9% NH3 per pass at reactor temperatures of > 425 °C).

[0010] The lower conversion rate increases the number of recirculations required to make a given quantity of NH₃, which must be efficiently extracted. Given that the operating pressure is too low for particle separation via condensation, molecular sieve capture using zeolites, activated carbon, and other molecular sieve materials (adsorbents) is utilized to adsorb NH3 or other such polar molecules.

[0011] Typically, the adsorbent is contained in a pressure vessel that is placed within the synthesis process loop in such a way that the adsorbent removes 100% of the NH3 generated by the reactor. When the adsorbent contained within the pressure vessel cannot adsorb any additional NH3, the pressure vessel is switched out and replaced by another pressure vessel containing adsorbent that is devoid, or nearly devoid, of NH3.

[0012] The pressure vessel containing the NH3 bearing adsorbent is then subjected to a desorption process that typically increases the temperature of the adsorbent until the NH3 is released. The molecular sieve material is then cooled either by active or passive cooling mechanisms, until the adsorbent can again adsorb NH3. As this heating/cooling cycle takes a long time, the pressure vessels containing the adsorbent are typically large, operate in batch mode rather than continuous mode, tend to utilize high temperatures to drive as much NH3 from the adsorbent as possible, and are not suitable for small, compact, modular NH3 synthesis systems.

[0013] Notwithstanding the above, low pressure synthesis utilizing adsorbents to extract the NH3 have a number of advantages over that of Haber-Bosch systems, including, but not limited to, rapid start (measured in hours rather than days) and the ability to operate on variable power (ideal for powering the system using variable, excess or dispatchable power). [0014] Therefore, there is a need in the art for a polar molecule extraction system that overcomes scaling issues raised by batch processing of lower operating pressure polar molecule synthesis by emulation of a continuous process that better matches the continuous (or nearly continuous) polar molecule synthesis process, that can be operational in a short time period, and which is capable of utilizing variable, excess, or dispatchable power sources.

SUMMARY

[0015] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary, and the foregoing Background, is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter.

[0016] In the simplest form, the technology described herein transforms the cyclic batch process of adsorption followed by desorption, of at least one pressure vessel containing an adsorbent material, with the adsorption/desorption process repeated over and over again, into a step function emulation of a continuous process by the use of at least one additional pressure vessel and operating the at least one additional pressure vessel in opposition to the first at least one pressure vessel. Therefore, while the at least one pressure vessel containing an adsorbent material is adsorbing, the at least one additional pressure vessel containing an adsorbent material is desorbing. This use of oppositional operating pressure vessels is subsequently referenced herein as a vessel pair.

[0017] For this process to work efficiently, the adsorption time and the desorption time ideally need to be matched, or nearly matched. As the time for adsorption is driven largely by the material properties of the adsorbent, absorbent temperature, system pressure, and the properties of the polar molecule being adsorbed, the desorption time can be matched to the adsorption time by the amount of energy applied to the adsorbent material during the desorption cycle. Traditional methods of desorption utilize heat to desorb polar molecules from an adsorbent, making the process of desorption too slow for use in this application. Therefore, the application of radio frequency (RF) energy as the driving function of desorption is utilized herein. Further detail regarding the application of RF energy as the driving function of desorption is provided in International Patent Application No, PCT/US2023/60785, entitled SYSTEMS AND METHODS FOR RAPID DESORPTION OF POLAR MOLECULES BEARING ADSORBENT MATERIAL USING RF ENERGY, the entirety of which is hereby incorporated by reference.

[0018] Desorption of a polar molecule from adsorbent material is a complex process. Sufficient energy must be applied to the adsorbent material for sufficient time so that the cumulative energy exceeds the cumulative heat of adsorption of the polar molecule. As a result, the release of polar molecules held in an adsorbent material more resembles a time- driven pulse release rather than a continuous release. In order to emulate a continuous process, the pulse output of desorption in the step function emulation must be smoothed in some manner to reduce the dynamic range of the output stream.

[0019] To reduce the dynamic range of the output stream, the technology described herein employs a multiplicity of vessel pairs operating in parallel in sequential timed offset operation to thereby assure that the peak production output of a given vessel pair does not occur in phase with the peak production output of another vessel pair. Furthermore, utilizing a multiplicity of parallel operating vessel pairs in which the output of a given vessel pair is 1/N of the total desired output (wherein N is the number of vessel pairs), and the time offset of operation of vessel pairs is T/N (wherein T is the time allocated for adsorption or desorption, whichever is greater, plus the time to switch the functions of the at least two (2) vessel of each vessel pair) allows smaller values of T as N increases. Thus, the pressure vessels containing the adsorbent are reduced in size and the magnitude of the dynamic range of the output is likewise reduced, resulting in an average value equal to the desired output with minimal amplitude in variable product flow.

[0020] These and other aspects of the technology described herein will be apparent after consideration of the Detailed Description and Figures herein. It is to be understood, however, that the scope of the claimed subject matter shall be determined by the claims as issued and not by whether given subject matter addresses any or all issues noted in the Background or includes any features or aspects recited in the Summary. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Non-limiting and non-exhaustive embodiments of the disclosed technology, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0022] Figure 1 is a graph showing the effect of three different pressures on the equilibrium concentration of NH3, in a 3:1 mixture of H2:N2 as a function of temperature.

[0023] Figure 2 is a graph showing the percentage of expected NH3 driven from an adsorbent material over time when subjected to a radio frequency (RF) signal of a fixed intensity.

[0024] Figure 3 is a graph showing the time-based adsorption of NH3 by an adsorbent material followed by the time-based desorption of NH3 when the adsorbent material is subjected to an RF signal of a fixed intensity.

[0025] Figure 4 is a set of two time-based curves illustrating an embodiment of the operation scheme employable by the technology described herein, with the upper curve showing alternating adsorption cycles of a pair of pressure vessels each containing an adsorbent material and the lower curve showing offset alternating desorption cycles of the same pair of pressure vessels.

[0026] Figure 5 is a schematic illustration of a system configured in accordance with various embodiments described herein, the system comprising at least one pair of pressure vessels, each containing adsorbent material, combined with at least two valves, at least two RF generators, at least one system controller, and at least one back pressure regulator, wherein the system can simultaneously adsorb gaseous polar molecules in at least one pressure vessel while desorbing gaseous polar molecules from the at least one other pressure vessel, and when these operations are complete, can swap the functions of the pressure vessels and continue both adsorption and desorption.

[0027] Figure 6 is a state table that shows the state-based operation of valves and RF generators contained in the system shown in Figure 5. [0028] Figure 7 is a set of two time-based curves illustrating an embodiment of the operation scheme employable by the technology described herein, with the upper curve showing alternating adsorption desorption cycles of at least one pressure vessel shown in Figure 5 and the lower curve showing an offset of alternating desorption adsorption cycles of at least one other pressure vessel shown in Figure 5.

[0029] Figure 8 is a schematic illustration of a composite system configured in accordance with various embodiments described herein, the composite system comprising eight (8) sets of at least two pressure vessels, wherein each set comprises the system shown in Figure 5 and wherein each set is operating with sequentially offset adsorption/desorption timing.

[0030] Figure 9 is a schematic illustration of a master controller configured in accordance with various embodiments described herein, where at least one master controller is connected to each of the controllers of the eight (8) sets of systems shown on Figure 8.

[0031] Figure 10 is a graph showing a set of curves showing the output of each of the eight (8) systems illustrated in Figure 8, the sum of the outputs of the eight (8) systems, and the curve of an equivalent single pressure vessel system’s output.

DETAILED DESCRIPTION

[0032] Embodiments are described more fully below with reference to the accompanying Figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense.

[0033] Figure 1 is a graph showing the effect of three different pressures on the equilibrium concentration of NH3, in a 3:1 mixture of H2:N2 as a function of temperature. Vertical axis 101 shows the potential equilibrium concentration and ranges from zero (0) to 16 %. Horizontal axis 102 shows potential reaction temperature ranging from 400 °C to 600 °C. Curve 103 demonstrates equilibrium concentration at 10 bar, curve 104 is at 20 bar, and curve 105 is at 30 bar. State of the art for the output pressure of H2 production via electrolyzers is approximately 30 bar. Current state of the art of catalysts limits the lower end of the range of operation to 425 °C, at which point the equilibrium concentration of NH3, at the electrolyzer output pressure is approximately 8.5%, as shown by the circled point 106. Therefore, as direct condensation of NH3 at 30 bar is not practical, molecular sieve adsorbents must be utilized to concentrate the NH3 prior to condensation.

[0034] Figure 2 is a graph showing a curve, 202, demonstrating the percentage of expected NH3 desorbed from an adsorbent material over time when subjected to a radio frequency (RF) signal of a fixed intensity. The vertical axis, 201 , is measured in percent of expected NH3 output from a given adsorbent that is saturated with NH3 molecules. Therefore, if is it expected that 35% of the NH3 molecules will be driven from the adsorbent, 100% on the vertical axis, 201 , is equivalent to that amount. The horizontal axis, 202, is measured in time. Note that the initial output of desorption is zero for approximately half a minute and then proceeds approximately linearly. In a preferred embodiment, the time allocated for desorption (and adsorption) is 10 minutes.

[0035] Figure 3 is a graph showing the time-based adsorption of NH3 by an adsorbent material followed by the time-based desorption of NH3 when the adsorbent material is subjected to an RF signal of a fixed intensity during the desorption period. Curve 302 represents adsorption and curve 303 represents desorption. As the period of adsorption of NH3, 304, from a starting point of 308 (approximately 35% in a preferred embodiment) to an ending point of 307 (approximately 70% in a preferred embodiment) is not easily adjusted, the level of RF energy provided for desorption is adjusted so that time-period 305 equals time-period 304. In a preferred embodiment, the selected adsorbent of Zeolite 13X will adsorb the desired amount of NH3 in 10 minutes, thus setting the ideal desorption period to 10 minutes.

[0036] Figure 4 is a set of two time-based curves, 401 and 402, illustrating an embodiment of the operation scheme employable by the technology described herein, with the upper curve, 401 , showing alternating adsorption cycles of a pair of pressure vessels contained in a vessel pair system and the lower curve, 402, showing offset alternating desorption cycles of the same pair of pressure vessels. In operation, one pressure vessel adsorbs NH3 during curve 405, is then desorbs during curve 405, adsorbs again during curve 406 and desorbs again during curve 407. Simultaneously, the other pressure vessel desorbs NH3 during curve 408, is then adsorbs during curve 409, desorbs again during curve 410 and adsorbs again during curve 411. The periods indicated by 403 correspond to the switchover of the vessel pairs from adsorption to desorption and back again. The points 415 and 417 of both curves represents the lower end point of the adsorption/desorption cycle, and the points 416 and 418 represent the upper end points. 412 and 413 demonstrate the cycle time of adsorption or desorption in the preferred embodiment, wherein 412 is one (1 ) minute and 413 is 10 minutes, thus creating a total adsorption/desorption cycle time for a vessel pair of 11 minutes.

[0037] Figure 5 illustrates a system 500 comprising at least one pair of pressure vessels 505, 506, each containing adsorbent material, combined with at least two valves, at least two RF generators 516, 519, at least one system controller 522, and at least one back pressure regulator 511 , wherein the system 500 can simultaneously adsorb gaseous polar molecules in at least one pressure vessel while desorbing gaseous polar molecules from the at least one other pressure vessel, and when these operations are complete, can swap the functions of the pressure vessels and continue both adsorption and desorption.

[0038] To accomplish the simultaneous adsorption and desorption operations, the system operates in a set of States as outlined in the state table shown in Figure 6 under the control of the system controller shown in Figure 5. It is important to note that the adsorption/desorption cycles operate in the rapid adsorption and desorption regions of the selected adsorbent, or combination of adsorbents. Thus, at the start of the adsorption cycle, the adsorbent contains a minimal quantity (not zero) of polar molecules. At the end of the adsorption cycle, the adsorbent is not saturated, but at a maximum quantity point of polar molecules. In a preferred embodiment, the difference between the minimum and maximum quantity of polar molecules contained within the adsorbent is approximately 35% of the total capacity of polar molecules that can be adsorbed by the adsorbent, and ranges approximately between the 35% capacity point and the 70% capacity point. [0039] Therefore, at the initial conditions, the system 500 is at State 1 , wherein the adsorbent in pressure vessel 505 is at the minimal quantity point of polar molecules, and the adsorbent in pressure vessel 506 is at maximum quantity point of polar molecules. The pressure in pressure vessel 505 is at maximum system pressure as measured by pressure transducer 518 and the pressure in pressure vessel 506 is at minimum system pressure as measured by pressure transducer 521. For reference, the maximum system pressure is limited by the output pressure of H2 electrolyzers unless increased by one or more compressors and the minimum system pressure is defined by Passion’s Curve to prevent arcing between RF electrodes within both pressure vessels 505 and 506. For a more detailed description of Passion’s Curve and the factors that set the minimum system pressure, reference is made to International Patent Application No. PCT/US2023/60785, entitled SYSTEMS AND METHODS FOR RAPID DESORPTION OF POLAR MOLECULES BEARING ADSORBENT MATERIAL USING RF ENERGY.

[0040] Process gases comprising H2, N2, and NH3, enter via port 501 from a synthesis reactor (not shown), feeding the gases to automated valves 502 and 504. In State 1 , automated valve 502 is open, allowing the gases to enter pressure vessel 505. Pressure vessel 505 contains a molecular sieve adsorbent material, such as Zeolite 13X. As the gases enter and pass through pressure vessel 505, and exit through the open automated valve 507, NH3 is adsorbed by the adsorbent material. After the gases exit via valve 507, they exit via port 523 and are returned to the synthesis reactor via a compressor (not shown). Also at State 1 , the automated equalization valve 503 is closed, as is automated valve 508. RF generator 516 (and matching circuit) measures the impedance of the adsorbent contained in pressure vessel 505 as a proxy of the measure of quantity of polar molecules contained within the adsorbent, and no RF energy is flowing into pressure vessel 505.

[0041] In State 1 , automated valve 504 is closed, preventing the process gases from flowing into pressure vessel 506. Automated valves 509 and 510 are closed, preventing gases from flowing from pressure vessel 506. RF generator 519 (and matching circuit) is disabled, and no RF energy is flowing into pressure vessel 506. [0042] Also, at initial condition State 1 , automated valve 512 is closed, isolating the flare/vent 513, and automated valve 514 is closed, isolating the system from the polar molecule output port 515.

[0043] The next step in the process is State 2, in which the quantity of polar molecules contained in the adsorbent in pressure vessel 505 continues to increase, while the adsorbent in pressure vessel 506 is placed into desorption (thus removing polar molecules from the adsorbent) by enabling the RF generator 519 and simultaneously opening automated valves 510 and 514. Back pressure regulator 511 prevents the pressure in pressure vessel 506 from increasing by allowing the resultant polar molecules to exit in gaseous form through the polar molecule output port 515.

[0044] All other automated valves and the RF generator 516 remain in their previous configurations.

[0045] The impedance of the adsorbent in pressure vessel 506 is monitored by the RF generator 519 to determine when the minimum quantity of polar molecules contained within the adsorbent in pressure vessel 506 is reached. Likewise, RF generator 516 measures the impedance of the adsorbent contained in pressure vessel 505 to determine when the maximum quantity of polar molecules contained within the adsorbent in pressure vessel 505 is reached. The first of either of these events starts the transition into State 3. State 3 cannot be exited until both events have occurred.

[0046] For purpose of explanation, assume the first event occurs when the minimum quantity of polar molecules contained within the adsorbent in pressure vessel 506 is reached as measured by the RF generator 519. In this scenario, the RF generator 519 is disabled, and automated valves 510 and 514 are closed. The pressure in pressure vessel 506 is at minimum system pressure as measured by pressure transducer 521. When the second event, the maximum quantity of polar molecules contained within the adsorbent in pressure vessel 505, is reached as measured by RF generator, automated valves 502 and 507 are closed. This stops the flow of process gases through the vessel pair and it is desirable to minimize the time spent in this condition. No other changes are affected with the automated valves and RF generators and associated matching circuits. [0047] This now completes the conditions of State 3, and the process advances to State 4, in which the flow of process gases remains blocked, and the pressure equalization automated valve 503 is opened. As a result, the pressure in pressure vessel 505 begins to fall and the pressure in pressure vessel 506 begins to climb, until the pressure in both pressure vessels equalizes at a value equal to the midpoint of the State 3 pressures of the two (2) vessels. This process transfers approximately half of the process gases contained in pressure vessel 505 to pressure vessel 506, preserving some of the process gases to improve system operational efficiency. When the pressure is balanced between the two (2) pressure vessels 505 and 506 as measured by pressure transducers 518 and 521 , State 4 is complete and the system advances to State 5.

[0048] State 5 closes automated valve 503 and the system advances to State 6.

[0049] In State 6, automated valves 504 and 509 open, placing pressure vessel 506 in the restored process gases flow, beginning the adsorption process and quickly increasing the pressure within pressure vessel 506 to that of maximum system pressure. At the same time, automated valves 508 and 512 open, allowing the gases in pressure vessel 505 to transit through the back pressure regulator 511 to the vent/flare 513. This reduces the pressure in pressure vessel 505 to the minimum system pressure. When the pressure in pressure vessel 506 is at maximum system pressure as measured by pressure transducer 521 and the pressure in pressure vessel 505 is at minimum system pressure as measured by pressure transducer 518, the system advances to State 7.

[0050] Upon entering State 7, the system closes automated valves 508 and 512, isolating pressure vessel 505 in preparation for desorption, and the system advances to State 8.

[0051] In State 8, the system puts the adsorbent in pressure vessel 505 into desorption (thus removing polar molecules from the adsorbent) by enabling the RF generator 516 and simultaneously opening automated valves 508 and 514. Back pressure regulator 511 prevents the pressure in pressure vessel 505 from increasing by allowing the resultant polar molecules to exit in gaseous form through the polar molecule output port 515. Pressure vessel 504 remains in adsorption mode through this state. [0052] The impedance of the adsorbent in pressure vessel 505 is monitored by the RF generator 516 to determine when the minimum quantity of polar molecules contained within the adsorbent in pressure vessel 505 is reached. Likewise, RF generator 519 measures the impedance of the adsorbent contained in pressure vessel 506 to determine when the maximum quantity of polar molecules contained within the adsorbent in pressure vessel 506 is reached. The first of either of these events starts the transition into State 9. State 9 cannot be exited until both events have occurred.

[0053] Again, for purpose of explanation, assume the first event occurs when the maximum quantity of polar molecules contained within the adsorbent in pressure vessel 506 is reached as measured by RF generator 519. At this point, automated valves 504 and 509 are closed. This stops the flow of process gases through the vessel pair and it is desirable to minimize the time spent in this condition.

[0054] When the second event, the minimum quantity of polar molecules contained within the adsorbent in pressure vessel 505, is reached as measured by the RF generator 516, the RF generator 516 is disabled, and automated valves 508 and 514 are closed. The pressure in pressure vessel 505 is at minimum system pressure as measured by pressure transducer 518. No other changes are affected with the automated valves and RF generators and associated matching circuits.

[0055] This now completes the conditions of State 9, and the process advances to State 10, in which the flow of process gases remains blocked, and the pressure equalization automated valve 503 is opened. As a result, the pressure in pressure vessel 506 begins to fall and the pressure in pressure vessel 505 begins to climb, until the pressure in both pressure vessels equalizes at a value equal to the midpoint of the State 9 pressures of the two (2) vessels. This process transfers approximately half of the process gases contained in pressure vessel 506 to pressure vessel 505, preserving more of the process gases to improve system operational efficiency. When the pressure is balanced between the two (2) pressure vessels 505 and 506 as measured by pressure transducers 518 and 521 , State 10 is complete and the system advances to State 11 .

[0056] Statel 1 closes automated valve 503 and the system advances to State 12. [0057] In State 12, automated valves 502 and 507 open, placing pressure vessel 505 in the restored process gases flow, beginning the adsorption process and quickly increasing the pressure within pressure vessel 505 to that of maximum system pressure. At the same time, automated valves 510 and 512 open, allowing the gases in pressure vessel 506 to transit through the back pressure regulator 511 to the vent/flare 513. This reduces the pressure in pressure vessel 506 to the minimum system pressure. When the pressure in pressure vessel 505 is at maximum system pressure as measured by pressure transducer 521 and the pressure in pressure vessel 506 is at minimum system pressure as measured by pressure transducer 518, the system advances to State 13.

[0058] Upon entering State 13, the system closes automated valves 510 and 512, isolating pressure vessel 506 in preparation for desorption, and the system advances to State 14.

[0059] In State 14, the system puts the adsorbent in pressure vessel 506 into desorption (thus removing polar molecules from the adsorbent) by enabling the RF generator 519 and simultaneously opening automated valves 510 and 514. Back pressure regulator 511 prevents the pressure in pressure vessel 506 from increasing by allowing the resultant polar molecules to exit in gaseous form through the polar molecule output port 515. Pressure vessel 505 remains in adsorption mode through this state.

[0060] The impedance of the adsorbent in pressure vessel 506 is monitored by the RF generator 519 to determine when the minimum quantity of polar molecules contained within the adsorbent in pressure vessel 506 is reached. Likewise, RF generator 516 measures the impedance of the adsorbent contained in pressure vessel 505 to determine when the maximum quantity of polar molecules contained within the adsorbent in pressure vessel 505 is reached. The first of either of these events starts the transition back into State 3. As discussed previously, State 3 cannot be exited until both events have occurred.

[0061] The aforementioned vessel pair process cycle from State 3 through State 14 can be repeated endlessly during system operation.

[0062] It should be noted that the aforementioned detailed description of a single vessel pair uses the RF generator and coupling circuit to determine the impedance of the adsorbent as a proxy of the amount of polar molecules contained within the adsorbent. This can be facilitated in desorption mode by determining the relative adjustment required to match the generator to the load presented by the adsorbent. Dynamic measurement of load impedance is state of the art in radio frequency engineering and design and is therefore excluded from this description. In a like manner, the impedance of the adsorbent can be facilitated in adsorbing mode by commanding the radio frequency generator to transmit at an energy level too low to cause desorption, but will still support dynamic measurement of load impedance. This concept is also state of the art in radio frequency engineering and design and is therefore excluded from this description.

[0063] There are other methods to determine the amount of polar molecules during both adsorption and desorption, including, but not limited to, breakthrough detection, and mass flow measurement both prior to the pressure vessel and after the pressure vessel.

[0064] Likewise, the technology described herein utilizes a pair of RF generators and matching circuits. This could also be accomplished with a single RF generator and matching circuit and the use of automated RF switches.

[0065] System switchover time, i.e., the time to switch the vessel pair from adsorption/desorption to desorption/adsorption, should be held to the lowest time possible, ideally limited by the impact of the rate of the change of pressure on the adsorbent.

[0066] The technology described herein discloses a sequential process in which the RF energy utilized for desorption starts after the pressure vessel’s pressure is at the minimum system pressure. Due to the time lag from the application of RF energy to the first detectable release of polar molecules, it is possible to initiate the RF energy as the pressure is dropping in the pressure vessel, but is not yet at minimum system pressure. This will reduce the system switchover time.

[0067] Active cooling of the adsorbent is not discussed herein, and is not needed if the power applied to the adsorbent is limited so as to not cause the adsorbent to excessively heat. However, the use of active cooling is well known state of the art and inclusion does not deviate from the spirit of the technology described herein. [0068] It is recognized that dropping the pressure within a pressure vessel without evacuating the pressure vessel to 0 bar and then repressurizing with another gas, such as NH3, will result in small amounts of H2 and N2 being passed through the system to the point of condensation, resulting in H2 and N2 present in the head space of the condenser. H2 and N2 can be removed from the head space gases and recycled in the system process gases using state of the art techniques which are not described herein. Note that by not evacuating the pressure vessel to 0 bar the switchover time is significantly reduced.

[0069] Using the RF impedance measurement and pressure sensors, or other means as described above, the system can learn the amount of RF energy to apply during the desorption process to match the desorption time to the adsorption time.

[0070] At this point, the detailed description has focused on a single vessel pair. It should be noted that it is advantageous to operate more than one vessel pair in a parallel configuration in sequential timed offset operation, as discussed in the summary section. Figure 8 is a schematic illustration of one such configuration in which eight (8) vessel pairs are utilized.

[0071] For a given product flow output, the size of the pressure vessels is inversely proportional to the number of vessel pairs. Thus, the adsorption/desorption time of each vessel pair is correspondingly reduced. This allows for faster operation and results in minimal amplitude variance in the resulting product flow.

[0072] As there are time periods in the operation of each vessel pair when the process flow is momentarily paused, a larger number of vessel pairs minimizes the variance in flow and pressure drop across the composite system.

[0073] It should be noted that the number of vessel pairs utilized is limited only by the cost, space, and complexity of the composite system.

[0074] Figure 7 shows the actions of a pair of vessels operating in opposition. The actions of the first pressure vessel are shown by curve 701 and the actions of the second pressure vessel are shown by curve 715. Curves 701 and 715 are shown aligned over time so that the simultaneous actions of the respective pressure vessels can be compared. [0075] Marks 705 and 719 represent the maximum system pressure, marks 707 and 721 represent the minimum system pressure, and marks 706 and 720 represent the middle system pressure (the average of 705 and 707, and the average of 719 and 721 , respectively). In a preferred embodiment, the maximum system pressure is 30 bar, the minimum system pressure is 1.5 bar, and the middle system pressure is 15.75 bar. The marks 708 and 722 represent zero (0) bar.

[0076] The periods 709, 710, 712, 714, 723, 725, 726, and 728 represent the system switchover time. In a preferred embodiment, all of these periods are one (1) minute in duration. The diagonal lines 729, 731 , 734, and 736 represent decreasing pressure during switchover, while diagonal lines 730, 732, 733, and 735 represent increasing pressure during switchover.

[0077] The periods of 702, 704, and 717 represent periods in which the pressure of the respective pressure vessel is at minimum system pressure, which occurs during desorption. The duration of these periods is shown as 737, 713, and 711. In a preferred embodiment,

737, 713, and 711 are each 10 minutes in duration.

[0078] The periods of 703, 716, and 718 represent periods in which the pressure of the respective pressure vessel is at maximum system pressure, which occurs during adsorption. The duration of these periods is shown as 738, 724, and 727. In a preferred embodiment,

738, 724, and 727 are each 10 minutes in duration.

[0079] To facilitate the proper time for the sequential timed offset operation, a master controller 808, shown in Figure 8 and again in Figure 9, synchronizes each of the vessel pairs. As the master controller communicates with each of the vessel pair system controllers (e.g., 522A, 522B, 522C, etc.), as shown in Figure 9, the master controller can adjust the overall timing of the composite system to pair the adsorption/desorption process to that of the NH3 synthesis reactor and thus match the constraints imposed by the availability of power. In system implementations of only one (1 ) vessel pair, the aforementioned adjustment can be implemented by the system controller of the single vessel pair.

[0080] Figure 10 shows the benefits of a multiple vessel pair configuration. The outputs of each of the vessel pairs over time are the curves 1003 at the bottom of the graph. The summation of their outputs is shown in curve 1004 and curve 1001 demonstrates the required output of a single vessel pair to achieve the same process output over the same time period. The amplitude of the pulse resulting from a single vessel pair, 1002, can be compared to that of the composite output, shown in Figure 10 as 1005.

[0081] As can be seen in Figure 10, curve 1004 demonstrates an improved transformation of a cyclic batch process into that of a pseudo continuous process through the process of step function emulation.

[0082] From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

[0083] Although the technology has been described in language that is specific to certain structures and materials, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures and materials described. Rather, the specific aspects are described as forms of implementing the claimed invention. Because many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.

[0084] Unless otherwise indicated, all number or expressions, such as those expressing dimensions, physical characteristics, etc., used in the specification (other than the claims) are understood as modified in all instances by the term "approximately". At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter recited in the specification or claims which is modified by the term "approximately" should at least be construed in light of the number of recited significant digits and by applying rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass and provide support for claims that recite any and all sub-ranges or any and all individual values subsumed therein. For example, a stated range of 1 to 10 should be considered to include and provide support for claims that recite any and all sub-ranges or individual values that are between and/or inclusive of the minimum value of 1 and the maximum value of 10; that is, all sub-ranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth).

Claims

CLAIMS I/We claim:

1 . A method of controlling adsorption and desorption of polar molecules in a pair of pressure vessels, comprising:

(1) flowing a gas stream comprising polar molecules through a first pressure vessel having adsorbent material disposed therein such that polar molecules are adsorbed by the adsorbent material;

(2) while the amount of polar molecules adsorbed by the adsorbent material in the first pressure vessel increases, delivering radio frequency (RF) energy to a second pressure vessel having adsorbent material disposed therein such that polar molecules contained within the adsorbent material are desorbed from the adsorbent material and flow out of the second pressure vessel;

(3) upon reaching a maximum amount of polar molecules in the adsorbent material in the first pressure vessel and reaching minimum amount of polar molecules in the adsorbent material in the second pressure vessel, equalizing the pressure in the first pressure vessel and the second pressure vessel;

(4) simultaneously flowing a gas stream comprising polar molecules through the second pressure vessel such that polar molecules are adsorbed by the adsorbent material disposed in the second pressure vessel and venting the first pressure vessel;

(5) while the amount of polar molecules adsorbed by the adsorbent material in the second pressure vessel increases, delivering radio frequency (RF) energy to the first pressure vessel such that polar molecules contained within the adsorbent material are desorbed from the adsorbent material and flow out of the first pressure vessel; and

(6) upon reaching a maximum amount of polar molecules in the adsorbent material in the second pressure vessel and reaching minimum amount of polar molecules in the adsorbent material in the first pressure vessel, equalizing the pressure in the first pressure vessel and the second pressure vessel.

2. The method of claim 1 , wherein prior to pressure equalization at step (3), the pressure in the first pressure vessel is at a maximum system pressure and the pressure in the second pressure vessel is at a minimum system pressure.

3. The method of claim 1 , wherein after pressure equalization at step (3), the pressure in the first pressure vessel and the second pressure vessel is the average of the maximum system pressure and the minimum system pressure.

4. The method of claim 1 , wherein at the start of step (2), the adsorbent material in the second pressure vessel is at a maximum amount of polar molecules.

5. The method of claim 1 , further comprising:

(7) simultaneously flowing a gas stream comprising polar molecules through the first pressure vessel such that polar molecules are adsorbed by the adsorbent material disposed in the second pressure vessel and venting the second pressure vessel.

6. The method of claim 5, wherein step (7) results in the pressure in the first pressure vessel being at a maximum system pressure and the pressure in the second pressure vessel being at a minimum system pressure.

7. The method of claim 1 , wherein venting in step (4) reduces the pressure in the first pressure vessel to the minimum system pressure.

8. The method of claim 1 , wherein the gas stream comprises nitrogen, hydrogen and ammonia.

9. The method of claim 1 , wherein the adsorbent material disposed in the first pressure vessel and the second pressure vessel is configured to adsorb ammonia.

10. A method of controlling adsorption and desorption of polar molecules in a multiplicity of pairs of pressure vessels, comprising: executing a first routine with respect to a first pressure vessel and a second pressure vessel serving as a first pair of pressure vessels, the first routine comprising:

(3) upon reaching a maximum amount of polar molecules in the adsorbent material in the first pressure vessel and reaching a minimum amount of polar molecules in the adsorbent material in the second pressure vessel, equalizing the pressure in the first pressure vessel and the second pressure vessel;

(6) upon reaching a maximum amount of polar molecules in the adsorbent material in the second pressure vessel and reaching a minimum amount of polar molecules in the adsorbent material in the first pressure vessel, equalizing the pressure in the first pressure vessel and the second pressure vessel; and executing a second routine with respect to a third pressure vessel and a fourth pressure vessel serving as a second pair of pressure vessels, the second routine comprising: (7) flowing a gas stream comprising polar molecules through a third pressure vessel having adsorbent material disposed therein such that polar molecules are adsorbed by the adsorbent material;

(8) while the amount of polar molecules adsorbed by the adsorbent material in the third pressure vessel increases, delivering radio frequency (RF) energy to a fourth pressure vessel having adsorbent material disposed therein such that polar molecules contained within the adsorbent material are desorbed from the adsorbent material and flow out of the fourth pressure vessel;

(9) upon reaching a maximum amount of polar molecules in the adsorbent material in the third pressure vessel and reaching a minimum amount of polar molecules in the adsorbent material in the fourth pressure vessel, equalizing the pressure in the third pressure vessel and the fourth pressure vessel;

(10) simultaneously flowing a gas stream comprising polar molecules through the fourth pressure vessel such that polar molecules are adsorbed by the adsorbent material disposed in the fourth pressure vessel and venting the third pressure vessel;

(11 ) while the amount of polar molecules adsorbed by the adsorbent material in the fourth pressure vessel increases, delivering radio frequency (RF) energy to the third pressure vessel such that polar molecules contained within the adsorbent material are desorbed from the adsorbent material and flow out of the third pressure vessel; and

(12) upon reaching a maximum amount of polar molecules in the adsorbent material in the fourth pressure vessel and reaching a minimum amount of polar molecules in the adsorbent material in the third pressure vessel, equalizing the pressure in the third pressure vessel and the fourth pressure vessel; wherein initiation of the second routine commences after a set time period from initiation of the first routine.

11. The method of claim 10, wherein the first routine is controlled independently of the second routine.

12. The method of claim 10, wherein a master controller independently controls the first routine and the second routine.

13. The method of claim 10, wherein the gas stream comprises nitrogen, hydrogen and ammonia.

14. The method of claim 10, wherein the adsorbent material disposed in the first pressure, the second pressure vessel, the third pressure vessel, and the fourth pressure vessel is configured to adsorb ammonia.