Ammonia-based photocatalytic reactor system and method

Abstract

An improved ammonia-based photocatalytic reactor system and method is provided. Ammonia-based photocatalytic reactor systems and methods are provided, including example features such as a coolant circulation system that utilizes water and / or ammonia as a coolant for removal of heat generated by LEDs that are part of the photocatalytic reactor; compression of ammonia gas to anywhere from room temperature to 132.4°C and 1 to 113.4 Bar, eliminating the need for a second compressor and selecting an optimized reactor conversion, where temperature and pressure are selected to maintain the gas phase at suitable conditions for downstream separation; storage of ammonia at anywhere from -33°C to room temperature and atmospheric pressure to 113.4 bar, eliminating either the need for a single compressor prior to the photoreactor inlet, one or both downstream compressors, and / or the need to store liquid ammonia at negative temperatures, thereby allowing room temperature storage; a product stream provided substantially directly to an ammonia scrubber to produce ammonium hydroxide as a by-product, and ammonia storage that can be used in-house or for consumer applications. replacement of the PSA system with a membrane H2 and N2 separator; elimination of the reactor downstream compressor, condenser, two-phase separator, and scrubber and replacing it with two PSA systems including a first PSA to separate ammonia as a backflush and a second PSA to separate H2 and N2, in one example including a compressor between the first and second PSA systems; and a PDA reactor with a combined membrane separation and substantially only one gas cooler and PSA system downstream of the PDA reactor, thereby eliminating multiple downstream components such as one or more compressors, condensers, separators, scrubbers, and / or dryers.

Description

[Technical Field]

[0001] Related Applications

[0001] This international application claims the benefit of U.S. Provisional Patent Application No. 63 / 271,337, filed October 25, 2021, and specifically incorporates by reference the entirety of U.S. Provisional Patent Application No. 63 / 271,337, including the features illustrated in the color drawings of that application at the time of filing.

[0002] Field FIELD OF THE DISCLOSURE

[0002] The present disclosure relates to the field of industrial chemical production, and specifically to ammonia-based photocatalytic reactor systems and methods. [Background technology]

[0003] background Photocatalytic reactors (also referred to herein as "photoreactors"), such as those developed by Syzygy Plasmonics Inc., may include light-emitting diodes (LEDs) to enable photocatalysis and chemical conversion. The LEDs convert electrical energy into light energy and thermal energy. While the light energy is utilized by the photocatalyst, the thermal energy is typically considered waste and must be constantly removed to maintain the temperature of the LED below a specified LED operating temperature, such as approximately 100°C. Summary of the Invention [Problem to be solved by the invention]

[0004]

[0004] What is needed are improved ammonia-based photocatalytic reactor systems and methods, including improved LED cooling mechanisms for such photocatalytic reactor systems and methods. [Means for solving the problem]

[0005] overview

[0005] One embodiment presented in this specification relates to a system including an ammonia decomposition photocatalytic reactor and a coolant circulation system that utilizes liquid ammonia as a coolant for cooling LEDs in the photocatalytic reactor, with the liquid ammonia being recovered from the product stream from the photocatalytic reactor.

[0006]

[0006] Another embodiment presented in this specification relates to a system including an ammonia decomposition photocatalytic reactor and a coolant circulation system that utilizes water as a coolant to cool LEDs in the photocatalytic reactor, with thermal energy being removed from the coolant via cold liquid ammonia.

[0007]

[0007] Some disclosed embodiments may include only a single compressor positioned in the feed stream prior to the inlet of the photocatalytic reactor, and the compressor compresses ammonia gas to a pressure in the range of approximately 1 Bar to the critical pressure of 113.4 Bar at a temperature in the range of approximately 20°C to the critical temperature of 132.4°C, thereby eliminating the need for a second compressor.

[0008]

[0008] Some disclosed embodiments may include a single-walled tank for storage of feed ammonia at elevated temperatures and pressures, the elevated temperatures being within a range that includes ambient temperature at its upper end and the elevated pressure being up to a critical pressure of 113.4 bar, the elevated temperatures and pressures thereby eliminating the need to chill the circulating coolant used to cool the LEDs in the photoreactor, the elevated temperatures and pressures also thereby eliminating the need to double-wall the tank, and the elevated temperatures and pressures reducing compressor duty by generating a reduced amount of ammonia vapor in the tank, thereby allowing an overhead compression system to be omitted from the system.

[0009]

[0009] Some disclosed embodiments may include a multi-stage compressor with interstage cooling positioned in the product stream after the photoreactor.

[0010]

[0010] Some disclosed embodiments may eliminate the need for one or both downstream compressors by including a tank for storing feed ammonia at a temperature range of approximately -33°C to 20°C and a pressure range of approximately atmospheric pressure to the critical pressure of 113.4 bar, and the feed ammonia is supplied to the photocatalytic reactor.

[0011]

[0011] Some disclosed embodiments may include a photocatalytic reactor product stream that is provided directly to an ammonia scrubber without the need for a compressor, condenser, or two-phase separator, thereby producing ammonium hydroxide as a by-product of ammonia decomposition.

[0012]

[0012] Some disclosed embodiments may include an ammonia scrubber that receives the product stream directly from the photocatalytic reactor without the application of any compressor, condenser, or scrubber, thereby producing ammonium hydroxide as a by-product.

[0013] Some disclosed embodiments may include a pressure swing adsorber (PSA) system at the output of the system.

[0014] Some disclosed embodiments may include a membrane H2 and N2 separator at the output of the system.

[0015] Some disclosed embodiments may include a first pressure swing adsorber (PSA) system that separates ammonia as a backflush and a second PSA system that separates H2 and N2. For example, the first and second PSA systems may replace the compressor, condenser, two-phase separator, and ammonia scrubber. In another example, a compressor is provided between the first PSA system and the second PSA system.

[0016] Another embodiment presented herein relates to a method for cooling a plurality of LEDs in an ammonia decomposition photocatalytic reactor system, the method including circulating liquid ammonia in proximity to a plurality of LEDs to remove heat generated by the LEDs, the liquid ammonia being recovered from a product stream from the photocatalytic reactor.

[0017] Yet another embodiment presented herein relates to a method for cooling a plurality of LEDs in an ammonia decomposition photocatalytic reactor system, the method including circulating water in proximity to a plurality of LEDs to remove heat generated by the LEDs.

[0018]

[0018] Some disclosed embodiments may include storing feed ammonia at a temperature range of approximately -33°C to 20°C and a pressure range of approximately atmospheric pressure to a critical pressure of 113.4 bar, eliminating the need for one or both downstream compressors, and the feed ammonia is supplied to a photocatalytic reactor.

[0019] Some disclosed embodiments may include producing separate H2 and N2 product streams by separating the product streams from the photocatalytic reactor via membrane H2 and N2 separators.

[0020] Another embodiment presented herein relates to a photocatalytic ammonia decomposition reactor system including a membrane separator at the product stream outlet of the reactor system, a product stream gas cooler, and a PSA system for separation of ammonia and nitrogen.

[0021] Yet another embodiment described herein relates to a photocatalytic reactor system including a photocatalytic ammonia decomposition (P-DA) reactor having multiple LEDs to catalyze an ammonia decomposition reaction in which a feed ammonia stream is converted into a product gas containing hydrogen, nitrogen, and unconverted ammonia. The multiple LEDs are cooled by a cooling block heat exchanger through which a coolant is circulated. The system further includes an ammonia tank storing liquid ammonia at atmospheric pressure, the tank supplying the feed ammonia stream to the P-DA reactor, and the feed ammonia stream supplied by the tank being vaporized using thermal energy from the coolant so that the feed ammonia stream is supplied to the P-DA reactor in a gaseous state. The system further includes a turboexpander that cools the product gas from the P-DA reactor after the product gas has been compressed and cooled via an ammonia recycle loop including the ammonia tank, an ammonia cooler, a first ammonia condenser, and a recycle compressor. The system further includes a second ammonia condenser that reduces the product gas cooled by the turboexpander, a preheater that heats the reduced product gas by removing thermal energy from a coolant circulating through the cooling block heat exchanger, and a PSA system that receives the heated product gas from the preheater and outputs a tail gas that includes hydrogen and a mixture of unrecovered hydrogen and nitrogen. The coolant may be water in some example embodiments.

[0022]

[0022] Some embodiments further include multiple knockout separators that remove liquid ammonia from the product gas, which is returned to the ammonia recycle loop.

[0023]

[0023] These and other embodiments, aspects, advantages, and alternatives will become apparent to those skilled in the art upon reading the following detailed description, with appropriate reference to the accompanying drawings. Moreover, this summary and other descriptions and figures provided herein are intended to illustrate embodiments by way of example only, and as such, numerous variations are possible. For example, structural elements and process steps can be rearranged, combined, distributed, eliminated, or otherwise changed while remaining within the scope of the claimed embodiments.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding of the systems, apparatus, devices, and / or methods of the present disclosure, and are incorporated into and constitute a part of this specification. The drawings are not necessarily to scale, and sizes of various elements may be distorted for clarity and / or illustrated in overly simplified representations to facilitate understanding. The drawings illustrate one or more embodiments of the present disclosure and, together with the description, serve to clarify the principles and operation of the present disclosure.

[0025] This international application specifically incorporates by reference the features illustrated in color in the color drawings at the time of filing of U.S. Provisional Patent Application No. 63 / 271,337. While not necessarily required for a thorough understanding of applicant's claimed invention, the above-described coloring may serve as a helpful complement to the black-and-white drawings and accompanying specification text. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a process flow diagram illustrating an ammonia-based photocatalytic reactor system according to a first example embodiment. [Figure 2]

[0027] FIG. 1 is a process flow diagram illustrating an ammonia-based photocatalytic reactor system in accordance with a second example embodiment. [Figure 3]

[0028] 1A-1C are cross-sectional views illustrating two cooling block geometries in accordance with example embodiments. [Figure 4]

[0029] FIG. 2 is a phase diagram illustrating example temperature-pressure design zones for an ammonia-based photocatalytic reactor system in accordance with at least one example embodiment. [Figure 5]

[0030] FIG. 1 is a phase change diagram illustrating an example simulated phase transition between two phases as a function of temperature. [Figure 6]

[0031] 10A-10C are color gradient diagrams illustrating modeled temperature field simulation results and mass fraction simulation results according to example embodiments utilizing an ammonia cooling block. [Figure 7]

[0032] FIG. 10 is a process flow diagram illustrating an ammonia-based photocatalytic reactor system in accordance with a third example embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0027] Detailed Description

[0033] Examples of systems, apparatus, devices, and / or methods are described herein. It should be understood that the word "example" is used to mean "serving as an example, instance, or exemplary serving." Any embodiment or feature described herein as being "example" should not necessarily be construed as preferred or advantageous over other embodiments or features, unless expressly stated as such. Accordingly, other embodiments may be utilized, and other changes may be made, without departing from the scope of the subject matter presented herein. The aspects described herein are not limited to specific embodiments, apparatus, or configurations, which may, of course, vary. It should be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, unless specifically defined herein.

[0028]

[0034] Throughout this specification, unless the context otherwise requires, the words "comprise" and "include" and variations thereof (e.g., "comprises," "comprising," "includes," "including," "has," and "having") will be understood to imply the inclusion of the specified component, feature, element, or step, or group of components, features, elements, or steps, but not the exclusion of any other component, feature, element, or step, or group of components, features, elements, or steps.

[0029]

[0035] Furthermore, unless the context indicates otherwise, the features illustrated in each of the figures may be used in combination with one another, and as such, the figures should be generally considered as component aspects of one or more overall embodiments, with the understanding that not all illustrated features are required for each embodiment.

[0030]

[0036] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0031]

[0037] Ranges can be expressed herein as from "about" one particular value and / or to another particular value. When such a range is expressed, another aspect includes from the one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0032]

[0038] Any counting of elements, blocks, or steps in this specification or claims is for clarity and, as such, should not be construed as requiring or implying that these elements, blocks, or steps adhere to a particular arrangement or be performed in a particular order.

[0033] I. Overview

[0039] One LED cooling mechanism available for photocatalytic reactor systems is a water-cooled LED heat exchanger. Such a heat exchanger, which may be in the form of a cooling block, for example, can be configured to remove heat energy generated by the LEDs. During this heat removal process, the incoming water increases in temperature as it passes through and exits the LED heat exchanger (removing the heat generated by the LEDs). In a system with a full balance of plant, the energy contained in this heated water can be used elsewhere in the plant to improve the overall energy efficiency of the plant or system.

[0034]

[0040] In addition to water, the same principles can be applied to other cooling fluids, such as liquid ammonia. In particular, the use of liquid ammonia in LED heat exchangers creates new opportunities for process design using novel waste heat management routes and techniques. These heat management routes and techniques can be utilized in ammonia-based photocatalytic reactor systems, including plants that use ammonia as a feed (or process gas), such as ammonia splitting (i.e., photocatalytic decomposition of ammonia), or plants that produce ammonia as a product (e.g., photocatalytic ammonia synthesis).

[0035]

[0041] Several example ammonia-based photocatalytic reactor systems and methods are presented. Exemplary features of such systems and methods include: (1) a coolant circulation system that utilizes water and / or ammonia as a coolant for removing heat generated by LEDs that are part of the photocatalytic reactor; (2) a single compressor prior to the photoreactor inlet that compresses ammonia gas to anywhere from room temperature (e.g., approximately 20°C) to 132.4°C (ammonia's critical temperature) and 1 to 113.4 bar (ammonia's critical pressure), eliminating the need for a second compressor and providing an opportunity for optimized reactor conversion (i.e., temperature and pressure are selected to maintain the gas phase in a state suitable for downstream separation); (3) ammonia storage at anywhere from -33°C to room temperature and atmospheric pressure to 113.4 bar (ammonia's critical pressure), eliminating the typical need that may be required for one or both downstream compressors and / or the need to store liquid ammonia at negative temperatures, thereby allowing room temperature storage; and (4) a product stream that is provided substantially directly to an ammonia scrubber to remove ammonia as a by-product. (5) replacing the pressure swing adsorber (PSA) with a membrane H2 and N2 separator to produce ammonium hydroxide for use either in-house or as a consumer product; (6) eliminating the reactor downstream compressor, condenser, two-phase separator, and scrubber and replacing them with two PSA systems, including a first PSA to separate ammonia as a backflush and a second PSA to separate H2 and N2, in one example including a compressor between the first and second PSA systems; and (7) a PDA reactor (photocatalytic ammonia decomposition reactor) with combined membrane separation and essentially only one gas cooler and PSA system downstream of the PDA reactor, thereby allowing for the elimination of multiple downstream components, such as one or more compressors, condensers, separators, scrubbers, and / or dryers.

[0036] II. Ammonia-based Photocatalytic Reactor System Example

[0042] 1 and 2 utilize flow lines (routes or paths) depicted in different patterns to indicate their general function: solid lines (generally on the left side of FIGS. 1 and 2, including before the inlet to photoreactor 102) refer to feed lines and, in the case of system 100 (liquid ammonia refrigeration), ammonia refrigeration lines; dashed lines (generally on the bottom left and top right of FIGS. 1 and 2) refer to product lines; and lines with alternating dashes and dots refer to utility lines (e.g., water refrigeration lines). Similarly, in incorporated U.S. Provisional Patent Application No. 63 / 271,337, FIGS. 1 and 2 are process flow diagrams in which the flow lines (routes) are colored according to the following color scheme: That is, orange colored lines (generally on the left side of Figures 1 and 2, including before the inlet to photoreactor 102) represent feed lines and, in the case of system 100 (liquid ammonia cooled), ammonia cooling lines, green colored lines (generally on the bottom left and top right of Figures 1 and 2) represent product lines, and black lines represent utility lines (e.g., water cooling lines). The function of each of these lines can also be identified from the components in the process flow diagram to which they are connected.

[0037]

[0043] FIG. 1 is a process flow diagram illustrating a liquid ammonia-cooled photocatalytic reactor system 100 according to a first example embodiment. The system 100 includes an ammonia decomposition photocatalytic (P-DA) reactor 102 having the following components: a cylindrical or annular reactor cell 104, an annular cooling block 106, and end caps 108a-b through which feed ammonia 110 enters and product stream 112 (also referred to herein as PDA product) exits. The example P-DA reactor 102 has the following operating ranges: 30-100% conversion for optimal plant efficiency; a 300-600°C temperature range for optimal plant efficiency; and 15-2000 PSIA (for a rectangular reactor). The P-DA reactor 102 is merely one example reactor configuration; other shapes, sizes, configurations, phases, and / or other modifications may be made depending on the particular desired application and operating environment. The following applications provide further description of photoreactors and related systems and are hereby incorporated by reference in their entirety: International Application No. PCT / US2018 / 039470, International Application No. PCT / US2018 / 039476, International Application No. PCT / US2020 / 013190, International Application No. PCT / US2020 / 013206, International Application No. PCT / US2021 / 042448, and International Application No. PCT / US2022 / 031444.

[0038]

[0044] System 100 also includes atmospheric ammonia tank 101, product cooler 114, product compressor 116, ammonia condenser 118, two-phase separator 120, NH3 scrubber 122, vapor recovery compressor 124, vapor recovery chiller 126, dryer cooler 128, pressure swing adsorber (PSA) system 130, and cold ammonia pump 132, some or all of which are described in further detail herein. In the illustrative example of system 100, atmospheric ammonia tank 101 and ammonia condenser 118 have the following operating ranges: 15 to 2000 PSIA at a temperature range of -33°C to room temperature.

[0039]

[0045] In system 100, the P-DA reactor 102 is cooled with liquid ammonia. In the following discussion, an ammonia decomposition plant configured to produce 5 kg H / day is assumed.

[0040]

[0046] The product stream 112 from the P-DA reactor 102 typically does not comprise pure components but rather is a ternary system (N + H + NH). Therefore, the ammonia dew point in such a system depends on (i) the concentration of ammonia in the product stream and (ii) the system pressure. Lower pressures lower the ammonia dew point, while higher pressures increase it. Therefore, for practical purposes, it is recommended to pressurize the PDA product so that ammonia condenses under practically achievable conditions. To reduce the compression work, it is recommended to reduce the PDA product temperature from 400°C to approximately 35°C using a product cooler 114 (e.g., a water cooler), such as one with a cooling duty of approximately 0.5 kW. The product compressor 116 increases the pressure of the PDA product, for example, from 50 PSIA to 400 PSIA. The compressed product from the product compressor 116 is sent directly to the ammonia condenser 118. High pressure is provided by product compressor 116 so that approximately 95% of the ammonia (in the PDA product) can be condensed by evaporating pure ammonia at atmospheric pressure and saturation temperature (-32°C) in the shell side of ammonia condenser 118.

[0041]

[0047] Condensed ammonia from the ammonia condenser 118 is recovered in a two-phase separator 120, while leftover trace ammonia is separated in a scrubber 122. According to one example, near-ambient water is used for scrubbing. A water flow rate of 5 kg / hr has been found to be effective for heating the incoming scrubber gaseous feed from -32°C to approximately 30°C-35°C, suitable for subsequent PSA system operation. Ammonia dissolves in water and reacts to form NH3 + HO in an exothermic reaction, releasing some heat, while equilibrating the system at 30°C-35°C. Liquid ammonia from the two-phase separator 120 is transferred to an atmospheric tank 101, which serves as the primary ammonia reservoir. The pressure in the atmospheric tank 101 is maintained near atmospheric conditions by exporting overhead vapor to a recovery system. The vapor recovery system uses (i) a vapor recovery compressor 124 to compress the vapor to nearly 50 PSIA with an expected adiabatic temperature rise of approximately 70°C to 75°C upon compression, and (ii) a vapor recovery chiller system 126 to liquefy the vapor and return it to the PDA reactor 102. Additionally, a portion of the compressed vapor is supplied to the reactor as feed ammonia 110, while a steady supply of feed liquid is maintained in a reservoir.

[0042]

[0048] Cooling of the LEDs in the P-DA reactor 102 is via a cold liquid ammonia circulation circuit. A cold ammonia pump 132 receives ammonia from the atmospheric ammonia tank 101 and provides cold liquid ammonia to the cooling block 106 of the P-DA reactor 102. The cold liquid ammonia in the cooling block 106 absorbs heat from the LEDs in the P-DA reactor 102, and the heated ammonia is fed along with the product stream 112 to the product cooler 114, which then follows the same route as the product stream 112 (i.e., via the compressor 116, the ammonia condenser 118, etc.). Note that the dryer cooler 128 only cools off any exothermic heat generated in the scrubber 120 and does not otherwise act as a heat sink.

[0043]

[0049] Liquid ammonia (Cp=80.8 J / mol / K) has a slightly higher heat capacity compared to water (Cp=75.38 J / mol / K), making it an efficient fluid for extracting waste heat generated by LEDs. In addition to cooling with recycled liquid ammonia, the system 100 shown in Figure 1 produces additional ammonia gas that can be fed as feed 110 to the P-DA reactor 102. This can result in improved reactor energy efficiency over non-optimized photocatalytic reactors.

[0044]

[0050] For a photoreactor system such as reactor system 100 illustrated in Figure 1, but without ammonia recycling, reactor efficiency (liquid ammonia cooling): = (thermal energy generated by LEDs + energy stored in hydrogen produced (lower heating value (LHV) used)) / (light energy in + thermal energy in + energy in as ammonia (both reacted and unreacted)). This can be expressed as (wall power x driver efficiency x (1 - LED efficiency) + hydrogen produced in g LHV) / (light energy in + thermal energy in + energy in as ammonia (both reacted and unreacted)). Substituting the example values ​​gives the following efficiency result for a reactor system cooled by liquid ammonia with no ammonia recycling: (0.25 x 0.88 x 3487 + 0.33 x 0.88 x 4029 + 6385) / (3487 + 4029 + 7995) = (767 + 1170 + 6385) / 15511 = 8322 / 15511 = 53.6%.

[0045]

[0051] 1, with ammonia recycling, the reactor efficiency is (liquid ammonia cooling + ammonia recycling): = (thermal energy generated by LEDs + energy stored in hydrogen produced (LHV used)) / (light energy in + thermal energy in + energy in as ammonia (reacted)). This can be expressed as (wall power x driver efficiency x (1 - LED efficiency) + hydrogen produced in g LHV) / (light energy in + thermal energy in + ammonia conversion x ammonia energy in). Substituting example values ​​gives the following efficiency result for a reactor system cooled by liquid ammonia and ammonia recycle = (0.25 x 0.88 x 3487 + 0.33 x 0.88 x 4029 + 6385) / (3487 + 4029 + 0.67 x 7995) = (767 + 1170 + 6385) / 12873 = 8322 / 12873 = 64.7%.

[0046]

[0052] In a reactor system utilizing both LEDs and IR lamps (e.g., IR lamps in the annulus of the reactor cells 104 or immersed in the reactor bed of the reactor cells 104 (see, e.g., Applicant's International Application No. PCT / US2022 / 031444)), the reactor efficiency is calculated to improve from 55.5% to 57.3% when using liquid ammonia for LED cooling (without ammonia recycling), increasing to 66.7% when ammonia recycling is also incorporated. Using the equations set forth in the previous paragraph, the calculated efficiencies of a photoreactor system utilizing both LEDs and IR lamps are as follows: (1) reactor efficiency (liquid ammonia cooling without ammonia recycling) = (0.25 x 0.88 x 10 + 7174) / (10 + 3892 + 7995) = 7397 / 12900 = 57.26%, (2) reactor efficiency (liquid ammonia cooling with ammonia recycling) = (0.25 x 0.88 x 10 + 7174) / (10 + 3892 + 0.78 x 7995) = 7397 / 11141 = 66.4%.

[0047]

[0053] FIG. 2 is a process flow diagram illustrating an ammonia-based photocatalytic reactor system 200 according to a second example embodiment. System 200 includes the ammonia decomposition photocatalytic (P-DA) reactor 102 illustrated in FIG. 1 along with its components, which may be the same or similar in both systems 100 and 200. Similarly, many of the other components illustrated in system 200 in FIG. 2 are similar or identical to those illustrated in system 100 in FIG. 1 and are therefore numbered identically in both figures. The description of each individual component associated with FIG. 1 is incorporated by reference for the identically numbered components in FIG. 2, unless otherwise used. System 200 is designed for an ammonia decomposition plant configured to produce 5 kg H2 / day over a reactor operating range characterized as follows: 30-100% conversion suitable for optimized plant efficiency; a 300-600°C temperature range suitable for optimized plant efficiency; and 15-2000 PSIA (for a rectangular reactor). The ammonia storage tank and condenser have an operating range of 15 to 2000 PSIA at temperatures ranging from -33°C to room temperature.

[0048]

[0054] In the embodiment of Figure 2, the P-DA reactor 102 is cooled by a closed-loop water circuit as illustrated. Hot water heated by the LEDs in the P-DA reactor 102 is combined with hot water used to cool the PDA reactor product. This combined heat stream is cooled using a saturated ammonia stream in an atmospheric pressure water cooler 134. The ammonia liquid / vapor mixture is sent to the atmospheric pressure ammonia tank 101. The entire process has only one major heat sink, which is the chiller 126. Note that the dryer cooler 128 only cools off any exothermic heat generated in the scrubber and does not otherwise act as a heat sink.

[0049]

[0055] FIG. 3 is a cross-sectional view illustrating two cooling block geometries according to an example embodiment used in modeling and simulation (see the discussion below and FIG. 6 for a helical channel implementation similar to geometry 300a). Both illustrated cooling block geometries 300a and 300b may be used as heat exchanger components in systems 100 and 200 shown in FIGS. 1 and 2, such as in photoreactor cells having cylindrical or annular shapes. Specifically, cooling block geometry 300a or 300b may position the cooling block 106 in close proximity to the LED array in the reactor 102 so that a circulating coolant (e.g., water or ammonia) can remove heat generated by the LEDs. Cooling block geometry 300a is shown as having a helical channel that wraps around the entire inner circumference of the cooling block shell. Cooling block geometry 300b is shown as having a vertical channel that oscillates vertically back and forth along the inner circumference of the cooling block shell. Other cooling block geometries may be used besides the example illustrated in FIG. 3.

[0050]

[0056] FIG. 4 is a phase diagram illustrating example temperature-pressure design zones for an ammonia-based photocatalytic reactor system in accordance with at least one example embodiment.

[0051]

[0057] In the ammonia-based photoreactor design presented herein, the following example design parameters apply: First, an inlet pressure of 1-5 bar (absolute) may be utilized, which allows the liquid room to exchange heat before vaporizing due to the increased pressure. Second, a lower inlet temperature (just below saturation) may be utilized, which also allows the liquid room to exchange heat well at a lower temperature.

[0052]

[0058] Figure 5 is a phase diagram illustrating an example of a simulated phase transition between two phases as a function of temperature. Simulating the phase change of ammonia requires a smooth transition as illustrated in Figure 5. The temperature interval affects the smoothness and mesh size required. Effective material properties are calculated based on the phases (mass fractions), i.e.

number

[0053]

[0059] 6 is a modeling simulation result illustrating temperature field simulation results and mass fraction simulation results according to an example embodiment utilizing an ammonia cooling block. The shading (or color) of the simulation results in FIG. 6 illustrates how the temperature and mass fraction, respectively, change as the coolant is circulated in a helical bottom-to-top configuration starting at the bottom right of each example simulation and delivered at the bottom left of each example simulation (after traveling top-to-bottom through the inside of the helix). As shown, the coolant temperature starts below −40° C. and is heated to approximately −15° C. before delivery, while the mass fraction starts below 0.3 and reaches a mass fraction approaching 0.89 before delivery.

[0054]

[0060] Figure 7 is a process flow diagram illustrating an ammonia-based photocatalytic reactor system 700 according to a third example embodiment, which differs somewhat from the systems 100 and 200 illustrated in Figures 1 and 2, respectively. System 700 includes a P-DA reactor 102, which may be similar to or identical to the P-DA reactor 102 described above in connection with Figures 1 and 2, for example.

[0055]

[0061] System 700 also includes atmospheric ammonia tank 101, product cooler 114, product compressor 116, first ammonia condenser 118, and pressure swing adsorber (PSA) system 130, similar to those described above for systems 100 and 200. Moreover, like-numbered components in system 700 may have similar or identical operating ranges to those in systems 100 and 200, for example. In addition to the components described above, system 700 additionally includes a product / effluent heat exchanger 706, a water cooler 708, a reactor control valve 710 (for controlling the flow of ammonia to heat exchanger 706), a recycle control valve 712 (for controlling the flow of cooled ammonia to first ammonia condenser 118), a vaporizer 714, an ammonia cooler 716, an ammonia recycle compressor 718, a first knockout separator 720, a second knockout separator 722, a third knockout separator 724, a second ammonia condenser 726, a PSA preheater 728, and a turboexpander 730.

[0056]

[0062] System 700 may be utilized in a plant designed to use a P-DA reactor 102 to convert ammonia feedstock to fuel cell-grade hydrogen. Feed ammonia 110 is fed into P-DA reactor 102 and converted to product stream 112, consisting of hydrogen, nitrogen, and unconverted ammonia. Product stream 112 is cooled via product cooler 114 using a recycle loop taken from an ammonia tank. The cooled product stream 112 is compressed via product gas compressor 116. After knocking out liquid ammonia via first and second knockout separators 720 and 722, the product gas is further cooled via the outlet of turboexpander 730 to knock out more liquid ammonia (via third knockout separator 724), resulting in an ammonia concentration of less than 50 ppm in the product stream (which is fed back via second ammonia condenser 726). The product gas (output from the second ammonia condenser 726) is then heated via a PSA preheater 728 and sent through a PSA system 130 to produce fuel cell grade hydrogen 702 and tail gas 704, which in the illustrated example is a mixture of unrecovered hydrogen and nitrogen.

[0057]

[0063] System 700 differs from other system designs in several ways. First, system 700 utilizes the heat integration of energy removed by the LED coolant (e.g., water). Second, system 700 replaces the ammonia scrubber 122 of systems 100 and 200 with a turboexpander 730. Third, system 700 eliminates the need for a dedicated vaporizer in or associated with ammonia tank 101. Each of these distinctive features is now described in further detail.

[0058]

[0064] First, system 700 utilizes the heat integration of energy removed by the LED coolant (e.g., water). The P-DA reactor 102 uses light generated by LEDs to power the reaction. The LEDs must be kept cool to operate. To accomplish this, the LEDs are mounted in an in-house designed water-cooled cooling block / heat exchanger. Water circulation through the cooling block removes heat energy from the LEDs, thereby capturing it. Instead of wasting the heat energy removed by the water, the heat energy is partially utilized to vaporize the liquid ammonia feed into the reactor (via vaporizer 714). Additionally, cold product gas from the outlets of turboexpander 730 and third knockout separator 724 is used to cool down the water (feedback to ammonia cooler 716). This allows operation without a traditional chiller unit before returning the water to the cooling block.

[0059]

[0065] Second, system 700 replaces the ammonia scrubber 122 of systems 100 and 200 with a turboexpander 730. Unconverted ammonia in the product stream is typically scrubbed from the system using water. In system 700, the scrubber 122 of systems 100 and 200 is replaced with a turboexpander. This provides at least four potential advantages. The first of these potential advantages is a reduction in the total amount of water required for the system, since water is not required to operate the scrubber. The second potential advantage is a reduction in waste generation. Because turboexpander 730 replaces scrubber 122, the ammonium hydroxide waste that scrubber 122 could generate is removed from the system. As a result, the plant does not need to provide safe storage and disposal of the hazardous ammonium hydroxide waste stream, thereby reducing costs and providing other potential benefits. A third potential advantage is that low concentration ammonia can be knocked off the product stream to bring it below 50 ppm by cooling the product stream through turboexpander 730. Finally, a fourth potential advantage is the use of the cooled product stream to remove heat from the LED cooling water, eliminating the need for a chiller unit for that purpose.

[0060]

[0066] A third distinguishing feature between system 700 and systems 100 and 200 is that system 700 does not require a dedicated vaporizer in or associated with ammonia tank 101. Conventional ammonia tanks store ammonia under pressure and room temperature such that the chemical is stored in liquid form. Liquid ammonia must be supplied to P-DA reactor 102 at above atmospheric pressure and temperature in gas form. A feed ammonia tank from other designs is typically connected to a vaporizer to supply gaseous ammonia to the reactor at the required pressure and temperature. In the present system 700, instead of using a dedicated vaporizer in ammonia tank 101, the process is integrated to utilize water from the LED cooling block for ammonia vaporization (in vaporizer 714), which is then further integrated with the reactor product gas to achieve the desired reaction pressure and temperature.

[0061]

[0067] Each of the above plant design changes results in better thermal integration and potentially reduces plant capital and operating costs, which in turn provides higher plant efficiency and reduces hazardous waste generation.

[0062] III. Conclusion

[0068] The above detailed description, together with reference to the accompanying figures, sets forth various features and operations of the systems, apparatus, devices, and / or methods of the present disclosure. The example embodiments described herein and in the figures are not meant to be limiting, with the true scope being indicated by the following claims. As will be apparent to those skilled in the art, many modifications and variations can be made without departing from the scope thereof. Functionally equivalent systems, apparatus, devices, and / or methods within the scope of the present disclosure, in addition to those described herein, will become apparent to those skilled in the art from the foregoing description. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations. All such modifications and variations are intended to be encompassed by the scope of the appended claims. Finally, all publications, patents, and patent applications cited herein are hereby incorporated by reference for all purposes.

Claims

1. an ammonia decomposition photocatalytic reactor; and a coolant circulation system that utilizes liquid ammonia as a coolant for cooling LEDs in the ammonia decomposition photocatalytic reactor, the liquid ammonia being recovered from a product stream from the ammonia decomposition photocatalytic reactor; A system including:

2. an ammonia decomposition photocatalytic reactor; and a coolant circulation system that utilizes water as a coolant to cool LEDs in the ammonia decomposition photocatalytic reactor, wherein thermal energy is removed from the coolant via cold liquid ammonia; A system including:

3. 3. The system of claim 1 or 2, comprising only a single compressor positioned in the feedstream prior to the inlet of the ammonia decomposition photocatalytic reactor, said compressor compressing ammonia gas to a pressure in the range of approximately 1 bar to 113.4 bar critical pressure at a temperature in the range of approximately 20°C to 132.4°C critical temperature, thereby eliminating the need for a second compressor.

4. 3. The system of claim 1 or 2, further comprising a single-walled storage tank for feed ammonia at elevated temperature and pressure, wherein the elevated temperature is within a range that includes ambient temperature at its upper end and the elevated pressure is up to a critical pressure of 113.4 bar, wherein the elevated temperature and pressure thereby eliminates the need to chill circulating coolant used to cool LEDs in the photoreactor, wherein the elevated temperature and pressure also thereby eliminates the need to double-wall the single-walled storage tank, and wherein the elevated temperature and pressure reduces compressor duty by generating a reduced amount of ammonia vapor in the single-walled storage tank.

5. The system of claim 4 , wherein the reduced compressor duty allows for the elimination of an overhead compression system.

6. 6. The system of claim 5, further comprising a multi-stage compressor with interstage cooling positioned in the product stream after the photoreactor.

7. 3. The system of claim 1 or 2, further comprising a tank for storage of feed ammonia at a temperature range of approximately -33°C to 20°C and a pressure range of approximately atmospheric pressure to a critical pressure of 113.4 bar, thereby eliminating the need for one or both downstream compressors, wherein the feed ammonia is supplied to the ammonia decomposition photocatalytic reactor.

8. 3. The system of claim 1 or 2, wherein the product stream from the ammonia decomposition photocatalytic reactor is provided directly to an ammonia scrubber without the aid of a compressor, condenser, or two-phase separator, thereby producing ammonium hydroxide as a by-product of ammonia decomposition.

9. 3. The system of claim 1 or 2, further comprising an ammonia scrubber that directly receives the product stream from the ammonia decomposition photocatalytic reactor without the application of any compressor, condenser or scrubber, thereby producing ammonium hydroxide as a by-product.

10. 3. The system of claim 1 or 2, further comprising a pressure swing adsorber (PSA) system at the output of the system.

11. 3. The system of claim 1 or 2, further comprising a membrane H2 and N2 separator at the output of the system.

12. a first pressure swing adsorber (PSA) system for separating ammonia as a backflush; and a second PSA system for separating H2 and N2; The system of claim 1 or 2, further comprising:

13. 13. The system of claim 12, wherein the first and second PSA systems are in place of a compressor, a condenser, a two-phase separator, and an ammonia scrubber.

14. The system of claim 12 further comprising a compressor between the first PSA system and the second PSA system.

15. 1. A method for cooling a plurality of LEDs in an ammonia decomposition photocatalytic reactor system, the method comprising circulating liquid ammonia in proximity to the plurality of LEDs to remove heat generated by the plurality of LEDs, the liquid ammonia being recovered from a product stream from the ammonia decomposition photocatalytic reactor.

16. 1. A method for cooling a plurality of LEDs in an ammonia decomposition photocatalytic reactor system, the method comprising circulating water adjacent to the plurality of LEDs to remove heat generated by the plurality of LEDs.

17. 17. The method of claim 15 or 16, further comprising storing feed ammonia at a temperature range of approximately -33°C to 20°C and a pressure range of approximately atmospheric pressure to a critical pressure of 113.4 bar, thereby eliminating the need for one or both downstream compressors, and wherein the feed ammonia is supplied to the ammonia decomposition photocatalytic reactor.

18. 17. The method of claim 15 or 16, further comprising producing separate H2 and N2 product streams by separating the product streams from the ammonia decomposition photocatalytic reactor through membrane H2 and N2 separators.

19. a photocatalytic ammonia decomposition (P-DA) reactor having a plurality of LEDs that catalyze an ammonia decomposition reaction in which a feed ammonia stream is converted into a product gas comprising hydrogen, nitrogen, and unconverted ammonia, the plurality of LEDs being cooled by a cooling block heat exchanger through which a coolant is circulated; an ammonia tank for storing liquid ammonia at atmospheric pressure, the ammonia tank supplying the feed ammonia stream to the P-DA reactor, the feed ammonia stream supplied by the ammonia tank being vaporized using thermal energy from the coolant so that the feed ammonia stream is supplied to the P-DA reactor in a gaseous state; a turboexpander that cools the product gas from the P-DA reactor after the product gas has been compressed and cooled via an ammonia recycle loop that includes the ammonia tank, an ammonia cooler, a first ammonia condenser, and a recycle compressor; a second ammonia condenser for reducing the product gas cooled by the turboexpander; a preheater that heats the reduced product gas by removing thermal energy from the coolant circulating through the cooling block heat exchanger; and a pressure swing adsorber (PSA) system receiving the heated product gas from the preheater and outputting a tail gas comprising hydrogen and a mixture of unrecovered hydrogen and nitrogen; 1. A photocatalytic reactor system comprising:

20. 20. The photocatalytic reactor system of claim 19, wherein the coolant is water.

21. 21. The photocatalytic reactor system of claim 19 or 20, further comprising a plurality of knockout separators for removing liquid ammonia from said product gas, said liquid ammonia being returned to said ammonia recycle loop.

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