Systems and methods for producing renewable ammonia

Abstract

A method for producing renewable ammonia is disclosed. A system for carrying out the method is also disclosed. In one embodiment, a method for producing ammonia (NH3) is provided, comprising: a. producing hydrogen (H2) using electrolysis; b. enriching nitrogen (N2) to a concentration of at least about 95%; c. combining and deoxygenating H2 and N2 to produce a feed stream; and d. synthesizing NH3 from the feed stream in a synthesis reactor at a pressure of less than about 80 bar.

Description

[Technical field]

[0001] background Technical Field The present disclosure relates generally to methods and associated systems for producing renewable ammonia. [Background technology]

[0002] 2. Description of Related Art Approximately 175 million metric tons of ammonia (NH3) were produced worldwide in 2018, of which approximately 88% was used as fertilizer. The remainder is primarily used as a precursor for the production of nitrogen compounds. Ammonia is typically produced using the Haber-Bosch process, which involves the exothermic gas-phase reaction of hydrogen (H2) and nitrogen (N2) at approximately 450°C and high pressure (about 100 bar). H2 for this process is typically produced from fossil fuels, for example, by steam reforming of natural gas, partial oxidation of methane, or coal gasification. By some measurements, the production of ammonia and its derivatives accounts for approximately 3-5% of global greenhouse gas (GHG) emissions. Thus, there exists a critical need for sustainable (i.e., with reduced or negligible GHG emissions) production of ammonia. The present disclosure provides this and related technical advantages. Summary of the Invention [Means for solving the problem]

[0003] A quick overview Current technologies for the production of ammonia are not well suited for sustainable production (e.g., from hydrogen produced by electrolysis). World-scale ammonia plants can produce up to approximately 5,000 tons per day and are located in areas of cheap natural gas, with the product being transported significant distances. In contrast, the systems described herein are designed to produce up to about 100,000 tons per year and are located in areas of cheap renewable electricity (e.g., from solar or wind), ideally close to the end consumer of the product.

[0004] The inventors of the present disclosure have recognized that simply scaling down the traditional Haber-Bosch process and using H2 produced from the electrolysis of water is not a practical and ideal solution for a number of reasons. First, the rate of ammonia production from such a design cannot be accelerated and decelerated (i.e., load-followed) to match the variability of renewable energy generation from wind and solar due to the nature of the compressors required to achieve the high operating pressures of the traditional process. Second, operation at these high pressures (above about 80 bar) requires complex reactor units with cold shells (where the catalyst is not in direct contact with the pressure vessel) and expensive special purpose materials that are not weakened by hydrogen embrittlement, hot hydrogen attack and nitridation. These materials are not practical or economical at smaller scales.

[0005] Counterintuitively, the systems described herein operate at lower pressures (below about 80 bar, below about 60 bar, or below about 40 bar). At these pressures, the reaction N2+3H2→2NH3 is not as favorable as at higher pressures. However, this disadvantage is more than compensated for by other benefits. That is, the systems described herein can be operated at pressures that more closely match the outlet pressure of the electrolysis unit, thereby eliminating the compressors required to reach reaction pressures above 80 bar. This eliminated compressor was typically a multi-stage centrifugal compressor, which is expensive and prevents the process from accelerating and decelerating quickly. Second, the lower pressure allows for simpler reactor designs (e.g., hot shell axial type reactors), which are much less expensive than conventional cold shell ammonia synthesis converters. At lower pressures, the synthesis reactors can also use quasi-isothermal designs. For example, tubular reactors made of conventional materials (e.g., carbon steel or stainless steel) can be used without incurring metallurgical decomposition due to hot hydrogen attack. Alternatively, plate-cooled reactors can also be used for ammonia synthesis at low pressures. Furthermore, lower pressures reduce the severity of hydrogen embrittlement, hot hydrogen attack and nitridation, and allow for construction of lower cost materials throughout the thermal section of the ammonia synthesis loop. Furthermore, a single deoxygenation reactor can be used to purify the reactant gas stream, eliminating the shift reactors, CO2 removal and methanation units of traditional designs based on hydrocarbon reforming. Furthermore, the ammonia product can be condensed at temperatures below about -20°C, which can be achieved by a closed-loop refrigeration cycle using a screw compressor rather than the multi-stage centrifugal compressor of the traditional open-loop design.

[0006] Synergistically, the modules of the system described herein work to realize unexpected benefits. The system can be modular (i.e., designed once, built and deployed multiple times) to match scale and realize the economics required for renewable power production, electrolyzer output, and ammonia consumption. Thus, in one embodiment, a method for producing ammonia (NH3) is provided, comprising: a. Producing hydrogen (H2) using electrolysis; b. enriching the nitrogen (N2) to a concentration of at least about 95%; c. combining and deoxygenating the H2 and N2 to produce a feed stream; d. synthesizing NH3 from the feed stream in a synthesis reactor at a pressure less than about 80 bar; A method is provided, comprising:

[0007] In some embodiments, the method further comprises condensing NH3 at a temperature below about -20 °C, such as below about -25 °C.

[0008] In a different embodiment, NH3 is condensed using a screw compressor that uses ammonia as the cooling medium.

[0009] In other embodiments, the NH3 is condensed using an economizer. For example, in some cases, the condensed ammonia is heated by cooling a refrigerant stream.

[0010] In other different embodiments, the NH3 is condensed using a closed-loop cooling module, which in one particular embodiment uses propane or propylene as the cooling fluid.

[0011] In others of the foregoing embodiments, the method further includes storing the condensed NH3 at ambient temperature and a pressure between about 15 bar and about 25 bar.

[0012] In more of the foregoing embodiments, the method further includes recycling the unreacted H2 and N2 to the synthesis reactor. For example, the recycled H2 and N2 may be compressed to the pressure of the synthesis reactor using a single stage compressor.

[0013] In a further embodiment, the electrolysis is powered using renewable energy.

[0014] In certain embodiments, N2 is enriched from air. In different embodiments, N2 is enriched using pressure swing adsorption (PSA). In some other embodiments, N2 is enriched using an air separation unit (ASU). In other different embodiments, N2 is enriched using a membrane.

[0015] In some embodiments, the N2 contains between about 1% and about 2% oxygen (O2) prior to deoxygenation.

[0016] In certain embodiments, H2 and / or N2 are deoxygenated by reacting H2 with O2.

[0017] In various embodiments, the electrolyzer used to generate H2 is integrated with a deoxygenation module.

[0018] In yet further embodiments, H2 and N2 are deoxygenated in a single reactor. In some of these embodiments, H2 and / or N2 are deoxygenated using a catalyst comprising a platinum group metal. In other embodiments, H2 and / or N2 are deoxygenated at a temperature less than about 400°C.

[0019] In different embodiments, the synthesis reactor has a hot shell. For example, in some embodiments, the catalyst is in direct contact with the pressure vessel. In other embodiments, the pressure vessel can safely contain hydrogen at the equilibrium temperature of the ammonia synthesis reaction.

[0020] In some further embodiments, the synthesis reactor is an axial reactor, for example, in some embodiments, the gas flows downward relative to the catalyst bed.

[0021] In other different embodiments, the synthesis reactor is a tubular reactor. For example, the synthesis reactor may have the catalyst in a shell or multiple tubes. In other embodiments, the synthesis reactor uses a cooling medium, thermal oil, boiler feed water (BFW), or steam, which is a gas feed to the reactor.

[0022] In some other embodiments, the synthesis reactor is a plate-cooled reactor with the catalyst housed in a shell. For example, in some embodiments, the synthesis reactor uses a cooling medium that is a gas feed to the reactor, thermal oil, boiler feed water (BFW), or steam.

[0023] In other embodiments, the synthesis reactor includes a catalyst having a pellet diameter of less than about 3 millimeters (mm). For example, in some embodiments, the catalyst includes iron oxide, such as iron oxide including wustite or magnetite. In other embodiments, the catalyst includes ruthenium or cobalt. In yet other embodiments, the catalyst is nanostructured and includes nanotubes or nanofibers.

[0024] In some embodiments, the method can produce NH3 at an approximately constant ratio of power consumption per unit mass of NH3 produced. For example, the ratio can be approximately constant when the NH3 production rate is reduced by at least about 30%, at least about 50%, or at least about 70% from the maximum production rate.

[0025] In different embodiments, the rate of production of NH3 may increase or decrease by at least about 10% per minute.

[0026] In other embodiments, the synthesis reactor is operated at a pressure of less than about 60 bar.

[0027] In some other embodiments, the synthesis reactor is operated at a pressure of about 40 bar.

[0028] In yet a further embodiment, the present disclosure provides a system for producing ammonia (NH3), comprising: a. an air separation module configured to separate air into a first stream comprising oxygen (O2) and a second stream comprising nitrogen (N2); b. an electrolysis module configured to split water (H2O) using electrical power into a third stream comprising O2 and a fourth stream comprising hydrogen (H2); c. a deoxygenation module configured to remove oxygen from the second stream, the fourth stream, or any combination thereof; d. an ammonia synthesis module configured to react N2 from the second stream with H2 from the fourth stream to produce NH3, the ammonia synthesis module comprising a synthesis reactor configured to operate at a pressure less than about 80 bar; The present invention provides a system comprising:

[0029] In some embodiments, the system further comprises a condensing module configured to condense the NH3 at a temperature below about -20°C. In some embodiments, the condensing module uses a screw compressor that uses ammonia as a cooling medium. In other embodiments, the condensing module includes an economizer. For example, the condensed ammonia may be heated by cooling a refrigerant stream. In others of the foregoing embodiments, the condensing module comprises a closed-loop refrigeration unit.

[0030] In some embodiments, the system further comprises a storage module configured to store the condensed NH3 at ambient temperature and a pressure between about 15 and about 25 bar.

[0031] In some different embodiments, the system further comprises a single stage compressor configured to recycle unreacted H2 and N2 to the synthesis reactor.

[0032] In some embodiments, the electrolysis module is powered using renewable energy.

[0033] In other embodiments, the air separation module uses pressure swing adsorption (PSA). In some other embodiments, the air separation module uses membranes. In yet other embodiments, the air separation module produces N2 containing between about 1% and about 2% oxygen (O2).

[0034] In some embodiments, the deoxygenation module is configured to react H2 with O2.

[0035] In another embodiment, the electrolysis module is integrated with the deoxygenation module.

[0036] In some embodiments, the deoxygenation module comprises a single reactor. In some other embodiments, the deoxygenation module comprises a catalyst comprising a platinum group metal.

[0037] In a different embodiment, the deoxidization module is configured to operate at a temperature less than about 400°C.

[0038] In some embodiments, the synthesis reactor has a hot shell. For example, in some such embodiments, the catalyst is in direct contact with the pressure vessel. In an exemplary embodiment, the pressure vessel can safely contain hydrogen at the equilibrium temperature of the ammonia synthesis reaction.

[0039] In some embodiments, the synthesis reactor is an axial reactor. In some of these examples, the gas flows downward relative to the catalyst bed.

[0040] In other embodiments, the synthesis reactor comprises a catalyst having a pellet diameter of less than about 3 millimeters (mm). In some of these embodiments, the catalyst comprises an iron oxide, such as an iron oxide comprising wustite or magnetite.

[0041] In different embodiments, the system can produce NH3 at an approximately constant rate of power consumption per unit mass of NH3 produced, e.g., a rate that is approximately constant when the NH3 production rate is reduced by at least about 30%, at least about 50%, or at least about 70% from the maximum production rate.

[0042] In some embodiments, the rate of NH3 production may increase or decrease by at least about 10% per minute.

[0043] In some different embodiments, the system consumes less than about 50 megawatts (MW) of power per year.

[0044] In yet other embodiments, the system has a production capacity of at least about 1,000 metric tons of NH3 per year.

[0045] In yet a further embodiment, the system has a production capacity of less than about 100,000 metric tons of NH3 per year.

[0046] In a different embodiment, the system further comprises a boost compressor to increase the pressure of the second stream and / or the fourth stream.

[0047] It should be appreciated that all combinations of the foregoing concepts, and additional concepts discussed in more detail below (provided that such concepts are not mutually inconsistent), are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of subject matter within this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

[0048] Still other aspects, examples, and advantages of these exemplary aspects and examples are discussed in detail below. Furthermore, it should be understood that both the preceding information and the following detailed description are merely illustrative examples of various aspects and examples, and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed aspects and examples. Any example disclosed herein may be combined with any other example in any manner consistent with at least one of the objects, purposes, and needs disclosed herein, and references to "examples," "some examples," "alternative examples," "various examples," "one example," "at least one example," or "this and other examples" are not necessarily mutually exclusive, but are intended to indicate that a particular feature, structure, or characteristic described in connection with the example may be included in at least one example. Appearances of such terms in this specification do not necessarily all refer to the same example. [Brief description of the drawings]

[0049] [Figure 1] FIG. 1 illustrates an example of the systems and methods described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Detailed Description The production of synthetic ammonia and its derivatives is one of the key enabling factors for the global development of intensive agriculture. It is estimated that the world would need three to four times more arable land to maintain current food production demands without synthetic nitrogen fertilizers.

[0051] The commercial production of synthetic ammonia was made possible by the discovery of iron-based catalysts capable of reacting hydrogen with nitrogen under industrially feasible conditions, typically pressures of several hundred atmospheres and temperatures above 400 °C. In this traditional process, the hydrogen feed is produced via steam reforming of hydrocarbons, with natural gas being the most commonly utilized hydrocarbon. Nitrogen is introduced into the process in the form of air, and oxygen is combusted along with a fraction of the hydrocarbons to generate some of the heat required for steam reforming.

[0052] The basic process described above has not changed significantly since the first commercial production of synthetic ammonia many decades ago. Over the years, technology development has progressed in two main directions: (a) continuous optimization to achieve step-by-step improvements in utilization of the energy contained in the hydrocarbon feed through increasingly sophisticated heat and mass integration; and (b) continuous scale-up efforts to increase the maximum single train size to current global production capacities of over 3,500 metric tons per day (MTD).

[0053] The commercial production processes resulting from these two development strategies cannot be easily adapted and deployed for renewable ammonia production, especially when the hydrogen feed is produced via renewable energy powered water electrolysis. Indeed, ammonia production from renewable electricity does not involve a hydrocarbon feed and is typically highly distributed in nature.

[0054] In contrast, the process described herein uses electrolysis to produce hydrogen (H2), enrich nitrogen (N2) to a concentration of at least about 95%, deoxygenate and combine the H2 and N2 to produce a feed stream, and synthesize NH3 from the feed stream in a synthesis reactor at a pressure less than about 80 bar.

[0055] With reference to FIG. 1, an embodiment of a system described herein for producing ammonia (NH3) may include an air separation module 100 configured to separate air 102 into a first stream 104 comprising oxygen (O2) and a second stream 106 comprising nitrogen (N2). The system may include an electrolysis module 108 configured to split water (H2O) 112 into a third stream 114 comprising O2 and a fourth stream 116 comprising hydrogen (H2), using power 110. The system may further include a deoxygenation module 118 configured to remove oxygen from the second stream and / or the fourth stream, and an ammonia synthesis module 120 configured to react N2 from the second stream with H2 from the fourth stream to produce NH3. The ammonia synthesis module includes a synthesis reactor 122 configured to operate at a pressure less than about 80 bar.

[0056] The system may further include a condensation module 124 configured to condense the NH3 at a temperature below about -20°C. The condensation module may use a screw compressor 126 that uses ammonia as a cooling medium (e.g., to evaporate and recompress the ammonia). The storage module 128 may be configured to store the condensed NH3 at a pressure between about 15 and about 25 bar and at ambient temperature. In some cases, the single stage compressor 130 is configured to recycle unreacted H2 and N2 to the synthesis reactor 122.

[0057] In some cases, the electrolyzer outlet pressure is less than the ammonia synthesis module pressure. In such cases, a boost compressor can be used to increase the pressure before the ammonia synthesis module. The electrolyzer outlet pressure can be any suitable pressure, for example, about 15 bar, about 20 bar, about 25 bar, about 30 bar, about 35 bar, about 40 bar, about 50 bar, about 60 bar, or about 80 bar. In some cases, the electrolyzer outlet pressure is between about 20 and about 30 bar. The electrolyzer can be a polymer electrolyte membrane (PEM) or alkaline electrolyzer.

[0058] The hydrogen required for ammonia synthesis can be provided by an electrolyzer that utilizes electrical power to convert water into hydrogen and oxygen. The ammonia product can be considered renewable if some of the electrical power supplied to the electrolyzer comes in whole or in part from renewable or carbon-free resources, such as nuclear power, or if such electrical power is supplied from the grid or any other source in combination with the acquisition of renewable power certificates or similar financial instruments. For the systems and methods described herein, the electrolyzer does not require a hydrogen purification unit to remove oxygen impurities, since the final oxygen removal is performed in a deoxygenation (aka hydrogenation) reactor. However, in some embodiments, a hydrogen purification unit may be beneficial.

[0059] The nitrogen required for ammonia synthesis can be produced from the separation of nitrogen from air or from the enrichment of nitrogen in air. For example, such enrichment can be obtained through the use of membranes, which can produce a stream containing more than 80% molar nitrogen. Alternatively, a pressure swing adsorbent (PSA) or vacuum PSA (VPSA) can be utilized to produce a nitrogen-enriched stream with a nitrogen concentration of more than 80% molar. Alternatively, an air separation unit (ASU) can be utilized to separate nitrogen from air via liquefaction and / or distillation of air. Any other means of separating nitrogen from air or enriching nitrogen in air can be utilized in this process to achieve a nitrogen concentration in the resulting stream of more than 80% molar.

[0060] In some cases, the nitrogen concentration is about 80%, about 85%, about 90%, about 95%, about 97%, about 99%, about 99.5%, about 99.9%, about 99.95%, or about 99.99%. In some cases, the nitrogen concentration is at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 97%, at least about 99%, at least about 99.5%, at least about 99.9%, at least about 99.95%, or at least about 99.99%.

[0061] The hydrogen and nitrogen streams can be mixed together to produce a raw synthesis gas ("syngas") stream, which contains oxygen in addition to hydrogen, nitrogen and other trace impurities. As used herein, the term "syngas" describes the gas stream used to make ammonia. Syngas, as used herein, typically does not contain appreciable amounts of carbon monoxide (CO). The raw synthesis gas is preheated to a temperature between ambient and 300°C depending on the required inlet temperature for the deoxygenation reactor, usually the exact type and composition of the hydrogenation catalyst employed. Preheating can be accomplished either with an external energy source (e.g., an electric heater) or by recovering heat from a suitable stream in the process via heat exchange.

[0062] The deoxygenation reactor can be a fixed bed reactor using a standard hydrogenation catalyst, such as those used for hydrogen purification from electrolyzers. For example, platinum or palladium containing catalysts are conventionally used for these applications. The reactor design can be single stage adiabatic, e.g., a vessel containing one type of catalyst. Alternatively, the reactor can be a multi-stage adiabatic reactor with multiple sections of catalyst (same catalyst or different catalysts optimized for each section of the reactor, as needed), e.g., in series with a heat exchanger between each catalyst bed. The reactor can also be an isothermal or quasi-isothermal reactor, including any means of providing heat exchange within the catalyst bed. In some embodiments, the reactor can also be a combination of such designs.

[0063] The output from the deoxygenation reactor can be a wet syngas stream, which contains hydrogen, nitrogen, trace impurities, and water produced by the combination of hydrogen and oxygen in the reactor. The wet syngas stream can be cooled to ambient temperature via heat exchange with other process streams, water cooling, air cooling, direct quenching with water, or even below ambient temperature by heat exchange with another cold fluid (e.g., ammonia or any ammonia-containing stream), or any combination thereof. The wet syngas stream can be dried.

[0064] Water can be removed from the wet syngas. In some cases, the syngas is dried in a dehydration unit, which is operated in a temperature swing adsorption (TSA) cycle. Two or more vessels can be filled with an adsorbent material (e.g., molecular sieves) that has a high affinity for water. One or more vessels can be operated in an adsorption mode, where the water in the wet syngas is adsorbed by the adsorbent while the gas stream flows through the bed. Once the adsorbent is saturated with water, the vessels can be switched to a regeneration mode. While some vessels are operated in an adsorption mode, the rest are operated in a regeneration mode, where a purge gas stream is heated to a suitable temperature (usually between 150-350°C) and passed through the saturated adsorbent material to evaporate the water contained in the adsorbent. The arrangement of the purge extraction of the synthesis loop can vary depending on the particular design and operating conditions. For example, the purge can be extracted from the downstream discharge of the main condenser or from the dry syngas produced by the dehydration unit itself.

[0065] The dry synthesis gas stream can be fed to the ammonia synthesis reactor without risk of damage or poisoning of catalysts that may be sensitive to ammonia synthesis and / or oxygenates. Several designs can be adapted for the ammonia synthesis reactor. In some cases, a multi-stage adiabatic reactor with multiple layers of catalyst can be separated by a heat exchanger. The catalyst beds can be housed in separate vessels or in a single vessel, and the heat exchanger can be external or can be housed inside the vessel. The catalyst beds can have an axial, axial-radial, or radial design. In some cases, the reactor is an axial reactor.

[0066] In some cases, the reactor is a quasi-isothermal reactor having one or more layers of catalyst characterized by heat exchange elements, such as tubes or plates, inserted into the catalyst bed. The catalyst beds may be contained in separate vessels or in a single vessel and may have an axial, axial-radial, or radial design. In some cases, the reactor is an axial reactor.

[0067] The synthesis reactor used in the methods described herein may have a hot shell. In a hot shell reactor, the catalyst is in direct contact with the pressure vessel. This may be achieved here by operating the ammonia synthesis module at lower pressure (and lower temperature). This is in contrast to the more expensive cold shell reactor, which separates the catalyst from the pressure vessel. The pressure vessel can safely accommodate hydrogen at the equilibrium temperature of the ammonia synthesis reaction. The synthesis reactor may be an axial type reactor. In an axial type reactor, the gas may flow downwards relative to the catalyst bed.

[0068] The synthesis reactor used in the methods described herein may include heat exchange elements (e.g., tubes or plates) made of conventional metallurgy (e.g., carbon or stainless steel) placed in direct contact with the catalyst. This may be achieved by operation of the ammonia synthesis module at lower pressures (and lower temperatures).

[0069] The ammonia synthesis catalyst may include iron oxide. In some cases, the iron oxide includes wustite or magnetite. The catalyst may contain any suitable promoter, diluent, binder, excipient, and may be formed into any suitable form. In some cases, the catalyst has a pellet diameter of about 10 millimeters (mm), about 7 mm, about 5 mm, about 3 mm, about 2 mm, or about 1 mm. In some cases, the catalyst has a pellet diameter of less than about 10 millimeters (mm), less than about 7 mm, less than about 5 mm, less than about 3 mm, less than about 2 mm, or less than about 1 mm. In contrast, global designs typically use radial reactors to achieve high cross-sectional areas. The reactor designs described herein are uniquely applicable to use these small catalyst forms.

[0070] Ammonia synthesis catalysts may also be based on formulations optimized for operation at low pressure. For example, the catalyst may contain highly active materials such as ruthenium (Ru) or promoters such as cobalt (Co). These low pressure catalysts may also be based on nanostructures with very large effective surface areas, such as nanotubes or nanofibers (e.g., nanostructures obtained by precipitation of lanthanum oxide).

[0071] The synthesis of NH3 can be carried out at any suitable pressure. In some cases, the synthesis reactor is operated at a pressure of about 100 bar, about 80 bar, about 70 bar, about 60 bar, about 50 bar, about 40 bar, or about 30 bar. In some cases, the synthesis reactor is operated at a pressure of less than about 100 bar, less than about 80 bar, less than about 70 bar, less than about 60 bar, less than about 50 bar, less than about 40 bar, or less than about 30 bar.

[0072] The ammonia synthesis reactor effluent may be cooled via heat exchange with another process stream or an external stream, such as water or air, or any combination thereof. Further cooling may be provided by direct injection of cold ammonia into the reactor effluent (i.e., direct quench) or via an ammonia chiller (e.g., indirect cooling produced by ammonia evaporation with steam).

[0073] Depending on the operating pressure and temperature of the main condenser of the ammonia synthesis, a portion ranging between 0% and 80% of the ammonia contained in the reactor effluent condenses to form a liquid stream of anhydrous ammonia, which is separated from the synthesis gas stream in a gas-liquid separator.

[0074] The pressure of the anhydrous ammonia may be reduced by one or more adiabatic expansions, typically performed with suitably designed valves and gas-liquid separators. In some embodiments, the pressure reduction may be performed by an expander, or any combination of an expander and an adiabatic flash. The final anhydrous ammonia product may be stored either (i) at pressures above ambient temperature and corresponding vapor pressure (typically 15-20 atm), or (ii) at ambient pressure under cryogenic conditions (-33°C), or (iii) at any intermediate pressure between ambient and 15-20 atm.

[0075] The recovery module may be capable of recovering NH3 and utilizing an economizer. If the final ammonia product is stored and / or utilized at a higher temperature than the condensation temperature accommodated in the synthesis loop (e.g., ambient temperature), an economizer can be used. In the economizer, the condensed ammonia product stream is heated by further cooling the refrigerant stream.

[0076] The process can be operated with a recycle loop, for example by recycling unreacted H2 and N2 to the synthesis reactor. The recycled H2 and N2 can be compressed to the synthesis reactor pressure using a single stage compressor.

[0077] In some cases, the process has only air, water, and power inputs, and the end product is aqueous and anhydrous ammonia, which can be produced in any combination depending on the design and operating parameters selected for the process.

[0078] The method can produce NH3 at an approximately constant ratio of power consumption per unit mass of NH3 produced, the ratio being approximately constant when the NH3 production rate is reduced by at least about 20%, at least about 50%, or at least about 70% from the maximum production rate.

[0079] The process can be rapidly accelerated or decelerated (e.g., to accommodate fluctuating production of renewable energy). The rate of NH3 production can increase or decrease by at least about 10% per minute.

[0080] The system may consume about 300 megawatts (MW), about 200 MW, about 100 MW, about 80 MW, about 80 MW, about 60 MW, about 40 MW, about 20 MW, or about 10 MW of power per year. In some cases, the system consumes less than about 300 megawatts (MW), less than about 200 MW, less than about 100 MW, less than about 80 MW, less than about 80 MW, less than about 60 MW, less than about 40 MW, less than about 20 MW, or less than about 10 MW of power per year.

[0081] The systems described herein may have any suitable production capacity for producing NH3. In some cases, the systems have a production capacity for producing about 1,000, about 5,000, about 10,000, about 50,000, or about 100,000 metric tons of NH3 per year. In some embodiments, the systems have a production capacity for producing at least about 1,000, at least about 5,000, at least about 10,000, at least about 50,000, or at least about 100,000 metric tons of NH3 per year. In some cases, the systems have a production capacity for producing up to about 1,000, up to about 5,000, up to about 10,000, up to about 50,000, or up to about 100,000 metric tons of NH3 per year.

[0082] In summary, the systems and methods described herein are designed for scale, discontinuous operation (e.g., it allows for the use of non-standard units), and process integration. Without limitation, certain design factors minimize specific capital expenditures ($ / metric ton) at production capacities below 200 metric tons per day (equivalent to less than 100 megawatts). These design parameters are technically and economically impossible at traditional scales above 1,000 metric tons per day.

[0083] First, low pressure operation can nearly match the delivery pressure of a polymer electrolyte membrane (PEM) electrolyzer without the need for a custom two-barrel syngas compressor, a major component of the capital expenditure of traditional designs. In some cases, no compressor is required, or a smaller, simpler compressor can be used. This option is not possible above 1,000 metric tons per day (MTD) because the volumetric circulation flow rates in the synthesis loop are too high.

[0084] Second, the use of inexpensive and simple hot shell axial reactors eliminates the need for millions of cold shell converters with internal radial cartridges and exchangers. This option is not practical above about 1,000 MTD because (i) the operating pressures preclude the use of a hot shell (due to the high equilibrium T) and (ii) the axial design requires impractical vessel diameters (due to the cross-sectional area required to accommodate the recycle flow).

[0085] Third, the recycler can be inexpensive (e.g., Sundyne™) equipment that eliminates the need for a custom centrifugal stage integrated with the syngas compressor, a factor that is not possible at >1,000 MTD because standard equipment is insufficiently sized and cannot handle the operating pressures.

[0086] Fourth, the systems and methods described herein may use cooled screw compressors, which eliminate the need for custom multi-stage centrifuges. This option is not practical for >1,000 MTD because these machines are not large enough. In fact, two at 100 MW would be needed to fit them.

[0087] Fifth, in some cases there is no heat recovery anywhere in the system, including the synthesis loop, which may eliminate the need for a steam system, which is a large contributor to capital expenditures.

[0088] Sixth, the systems and methods described herein have the option to produce and store ammonia at about 20 bar and ambient temperature. This can result in capital expenditure and operational cost savings versus cryogenic ammonia production. This design feature is not possible with >1,000 MTD because such volumetric storage and logistics are only possible with cryogenic ammonia.

[0089] The above embodiments can be implemented in any of a number of ways. For example, the embodiments can be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed across multiple computers. It should be appreciated that any component or collection of components for implementing the above functions can be generally considered as one or more controllers that control the functions discussed above. The one or more controllers can be implemented in a number of ways, for example, by dedicated hardware, or one or more processors programmed with microcode or software to implement the functions enumerated above.

[0090] In this regard, it should be appreciated that one implementation of an embodiment of the present invention includes at least one non-transitory computer-readable storage medium (e.g., computer memory, portable memory, compact disk, etc.) coded with a computer program (i.e., a plurality of instructions), which, when executed by a processor, performs the above-discussed functions of the embodiments of the present invention. The computer-readable storage medium may be portable such that the program stored thereon may be loaded into any computer resource that performs the aspects of the present invention discussed herein. Furthermore, it should be appreciated that reference to a computer program that, when executed, performs the functions discussed above is not limited to an application program running on a host computer. Rather, the term computer program is used herein in a general sense to refer to any type of computer code (e.g., software or microcode) that may be used to program a processor to perform the above-discussed aspects of the present invention.

[0091] Various aspects of the invention may be used alone, in combination, or in various arrangements not specifically discussed in the embodiments described above, and therefore their application is not limited to the details and arrangements of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0092] Also, embodiments of the invention may be implemented as one or more methods for which examples are provided. The operations performed as part of the method(s) may be ordered in any suitable manner. Thus, embodiments may be constructed in which operations are performed in an order different from that illustrated, which may include performing some operations simultaneously even though shown as sequential operations in the example embodiments.

[0093] The use of ordinal terms such as "first," "second," "third," etc. to modify claim elements in the claims does not, by itself, imply a priority, precedence, or ordering of one claim element over another, or the temporal order in which method operations are performed. Such terms are used merely as a label to distinguish one claim element having a particular name from other elements having the same name (absent the use of ordinal terms).

[0094] The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," "containing," "involving," and variations thereof are meant to encompass the items listed thereafter as well as additional items.

[0095] Although several embodiments of the present invention have been described in detail, various modifications and improvements will occur to those skilled in the art. Such modifications and improvements are intended to be within the spirit and scope of the present invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited only as defined by the following claims and equivalents thereof.

[0096] U.S. Provisional Patent Application No. 63 / 290,945, filed December 17, 2021, from which this application claims priority, and No. 63 / 328,632, filed April 7, 2022, are hereby incorporated by reference in their entireties herein.

Claims

[Claim 1] The invention described in the present specification.

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