Ammonia synthesis plant and method

Abstract

The ammonia production system comprises a hydrogen source and a hydrogen compression unit adapted to compress hydrogen from the hydrogen source. The system further comprises a nitrogen source and a syngas compressor adapted to receive nitrogen from the nitrogen source and hydrogen from the hydrogen compression unit, and further adapted to compress a syngas comprising a mixture of hydrogen and nitrogen and deliver the compressed gas mixture to the ammonia synthesis module. The nitrogen source is fluidly coupled to the hydrogen compression unit such that, in use, the hydrogen compression unit compresses a blend containing hydrogen and nitrogen.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to ammonia synthesis plants and methods. In particular, a novel compression train configuration and associated method for an ammonia synthesis system is disclosed herein. [Background technology]

[0002] Ammonia (NH3) is a gas that is highly soluble in water and is often used in aqueous solutions. Ammonia is used in several industrial applications, particularly for the production of nitric acid, urea, and other ammonia salts such as nitrates and phosphates. Ammonia derivatives are widely used in agriculture. Approximately 80% of ammonia production is used for the production of fertilizers.

[0003] Generally, ammonia is produced by the synthesis of nitrogen and hydrogen according to the following exothermic reaction (i.e., a reaction that releases heat):

[0004] [ka] where ΔH is the heat released by the reaction.

[0005] According to widely used methods, ammonia production usually starts with a feed gas, such as methane, that provides a source of hydrogen. Nitrogen is obtained from air.

[0006] An alternative method for ammonia synthesis uses hydrogen obtained by electrolysis. In recent years, so-called green ammonia production processes and systems have been intensively researched in an attempt to reduce greenhouse gas production and avoid the use of hydrocarbons. In green ammonia production, the process for making ammonia is 100% renewable and carbon-free. One way to make green ammonia is by using nitrogen separated from air and hydrogen from water electrolysis powered by renewable energy sources. The nitrogen and hydrogen are then fed into the Haber process (also known as the Haber-Bosch process), where the hydrogen and nitrogen react together at high temperature and pressure to produce ammonia.

[0007] The Haber process is usually carried out under high pressure and high temperature conditions, which requires a large amount of energy. However, more recently, research has been conducted into synthesis methods under lower temperature conditions using suitable catalysts to promote the synthesis reaction.

[0008] Regardless of the synthesis process used, one important aspect of ammonia production using hydrogen produced by electrolysis at ambient pressure is the need to compress the hydrogen at the high pressures required for the synthesis reaction.

[0009] Compressing gases with low molecular weight (Mw) can be challenging because the lower the molecular weight of the gas, the higher the compressor impeller rotational speed and / or the number of compressor stages and compressor casings required to achieve a desired compression ratio. Long compressor trains containing many compressor stages, sometimes spread across several compressor casings, present difficult problems to the designer, particularly with regard to rotor dynamic issues.

[0010] Hydrogen is the gas with the lowest molecular weight, and therefore its compression is particularly demanding in terms of compressor performance.

[0011] Although catalysts can reduce the temperature at which the reaction is carried out, high pressures of the gases involved in the synthesis reaction are necessary to improve the efficiency of the synthesis process in terms of ammonia yield.

[0012] The need to compress hydrogen from the ambient pressure produced by electrolysis to the pressure required for an efficient ammonia synthesis reaction makes the design of the hydrogen compressor particularly demanding, both in terms of the number of compressor stages, but also in terms of their rotational speed, if a dynamic compressor, such as a centrifugal compressor, is used. Summary of the Invention [Problem to be solved by the invention]

[0013] Therefore, it would be beneficial to simplify the construction, manufacture, and control of hydrogen compressors in ammonia production systems, particularly green ammonia synthesis systems.

[0014] According to one aspect, disclosed herein is an ammonia production system including a hydrogen source and a hydrogen compression unit adapted to compress hydrogen from the hydrogen source. The system further includes a nitrogen source. The synthesis gas compressor is adapted to receive nitrogen from the nitrogen source and hydrogen from the hydrogen compression unit, and is further adapted to compress a synthesis gas comprising a mixture of hydrogen and nitrogen for delivery to an ammonia synthesis module fluidly coupled to the synthesis gas compressor. The nitrogen source is fluidly coupled to the hydrogen compression unit such that, in use, the hydrogen compression unit compresses the blend containing hydrogen and nitrogen. Thus, the molecular weight of the gas blend processed by the hydrogen compression unit is higher relative to the molecular weight of pure hydrogen, improving the compression process and simplifying the hydrogen compression unit.

[0015] The hydrogen compression unit includes at least one dynamic compressor, such as a centrifugal compressor. In embodiments, the hydrogen compression unit includes multiple dynamic compressors in series to achieve the desired compression ratio.

[0016] According to a further aspect, a method for producing ammonia from hydrogen and nitrogen is disclosed. The method includes delivering a nitrogen stream to the suction side of a syngas compressor at syngas suction pressure. The method further includes delivering a hydrogen stream to the suction side of a hydrogen compression unit at a hydrogen inlet pressure lower than the syngas suction pressure. A further step includes increasing the pressure of the hydrogen stream from the hydrogen inlet pressure to the syngas suction pressure in the hydrogen compression unit and delivering the compressed hydrogen to the syngas compressor. Additionally, the method also includes delivering the compressed syngas from the syngas compressor to an ammonia synthesis module and producing ammonia from the compressed syngas. According to embodiments disclosed herein, the method further includes adding nitrogen to the hydrogen in the hydrogen compression unit to increase the molecular weight of the gas processed by the hydrogen compression unit. [Brief explanation of the drawings]

[0017] Reference will now be made briefly to the accompanying drawings, in which: [Figure 1] FIG. 1 is a schematic diagram of a system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram of a system according to a further embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic diagram of a system according to a further embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic diagram of a system according to a further embodiment of the present disclosure. [Figure 5] FIG. 5 is a schematic diagram of a system according to a further embodiment of the present disclosure. [Figure 6] FIG. 6 is a schematic diagram of a system according to a further embodiment of the present disclosure. [Figure 7] FIG. 7 is a schematic diagram of a system of the present disclosure in a still further embodiment. [Figure 8] FIG. 8 is a flowchart summarizing a method according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] In general terms, disclosed herein is a system for ammonia synthesis that includes novel features adapted to simplify the construction or design of a hydrogen compression unit.

[0019] Briefly, the system is configured so that an amount of nitrogen is added to a low-pressure hydrogen stream before achieving the required final hydrogen pressure at the suction side of the synthesis gas compressor, where the partially compressed hydrogen is mixed with nitrogen from a nitrogen source. In some embodiments, the nitrogen stream is reduced in pressure before being blended with hydrogen in the hydrogen compression unit.

[0020] The hydrogen and nitrogen blend processed by the hydrogen compression unit has a higher molecular weight than pure hydrogen. When at least a portion of the hydrogen compression is performed with hydrogen mixed with nitrogen, the hydrogen compressor stages can be reduced and / or its rotational speed can be lower than that of current technology hydrogen compressors. This reduces the demands on the compressor design and allows the overall size of the hydrogen compression unit to be reduced.

[0021] Separation of the nitrogen and hydrogen after compression is not required, as the nitrogen and hydrogen are mixed to form synthesis gas which is then delivered to the ammonia synthesis module.

[0022] Referring now to the drawings, FIG. 1 illustrates a schematic diagram of an ammonia production system 1 according to the present disclosure in one embodiment. The ammonia production system 1 includes a hydrogen source 3 and a nitrogen source 5. In the exemplary embodiment of FIG. 1, the hydrogen source 3 may include an electrolyzer 7. The electrolyzer 7 may be powered by electrical energy from an electrical grid 8. In some embodiments, the electrical energy may be provided, at least in part, by one or more renewable energy sources. As a non-limiting example, in the schematic of FIG. 1, the renewable energy is solar energy. Energy from the renewable resource may be collected and converted to electrical energy by an electrical converter 9. In FIG. 1, the electrical converter 9 includes a photovoltaic panel 9A and a solar inverter 9B electrically coupled to the photovoltaic panel 9A and the electrical grid 8.

[0023] In other embodiments not shown, other renewable energy sources can be used instead of or in addition to solar energy, such as wind, geothermal, wave, and tidal energy.

[0024] In some embodiments, the power grid 8 may be connected to a public power grid, which is adapted to supply power when there is a shortage of power from the renewable energy source and / or to receive power from the electrical converter 9 when the power obtained from the renewable energy source exceeds the power demand of the electrolyzer 7. Alternatively, or in combination, surplus power from the electrical converter 9 may be used by other modules of the system 1 and / or may be stored in a suitable storage unit, not shown.

[0025] Nitrogen source 5 may include any configuration adapted to provide nitrogen, for example, by separation from ambient air. In the embodiment of Figure 1, nitrogen source 5 includes air compressor 5A and nitrogen separation module 5B. Nitrogen separation module 5B may include, for example, a membrane separator, a fractionation system, or any other device adapted to separate nitrogen from other air components, specifically oxygen and carbon dioxide.

[0026] The ammonia production system 1 further comprises an ammonia synthesis unit generally labeled 11. The ammonia synthesis unit 11 may include a compressor 11A and an ammonia synthesis module 11B. While a single compressor 11A is shown in the schematic diagram of Figure 1 for simplicity, it should be understood that the compressor 11A may in turn include a single compressor or multiple compressors, typically centrifugal compressors, arranged in parallel and / or series, for example along the shaft line of a compressor train.

[0027] Ammonia synthesis module 11B may include any configuration adapted to synthesize ammonia from a blend or mixture of hydrogen and nitrogen in gaseous form, delivered to ammonia synthesis module 11B at a suitable pressure by compressor 11A. Compressor 11A is referred to herein as a synthesis gas compressor because it is adapted to compress the gas mixture containing nitrogen and hydrogen required for ammonia synthesis.

[0028] Hydrogen is delivered by hydrogen source 3 at a low hydrogen pressure P1, e.g., near ambient pressure. Nitrogen source 5 delivers nitrogen at a low nitrogen pressure P2 through nitrogen delivery line 12 towards ammonia synthesis unit 11. Low nitrogen pressure P2 is higher than low hydrogen pressure P1 due to the nature of the separation process performed by nitrogen separation module 5B, which is supplied with air pressurized by air compressor 5A.

[0029] Nitrogen from nitrogen source 5 flows through main nitrogen delivery duct 12 to the suction side of syngas compressor 11A, where the nitrogen is at syngas suction pressure P3, which is substantially equal to or slightly lower than low nitrogen pressure P2 due to head losses along main nitrogen delivery duct 12.

[0030] Ammonia production system 1 further comprises a hydrogen compression unit 15, the inlet of which is fluidly coupled to hydrogen source 3 and the outlet of which is fluidly coupled to the suction side of syngas compressor 11A. Because low hydrogen pressure P1 is substantially lower than syngas suction pressure P3, hydrogen from hydrogen source 3 is compressed in hydrogen compression unit 15 from low hydrogen pressure P1 to syngas suction pressure P3, or to a slightly higher pressure P3′, taking into account head losses along connecting duct 17 that fluidly couples the delivery side of hydrogen compression unit 15 to syngas compressor 11A.

[0031] 1, the hydrogen compression unit 15 is represented as a single compressor. However, it should be understood that, generally speaking, the hydrogen compression unit 15 may include one or more compressors, typically centrifugal compressors, which may form a single compressor train, with multiple compressors usually arranged in series and along a common shaft line driven by a driver, not shown. Each compressor of the hydrogen compression unit 15 may in turn include multiple compressor stages.

[0032] The gases delivered by the hydrogen compression unit 15 and the nitrogen source 5 flow together in the synthesis gas compressor 11A, which thus processes the blend of hydrogen and nitrogen and raises the pressure of the gas mixture from the synthesis gas suction pressure P3 to the final pressure P4 required for the synthesis reaction carried out in the ammonia synthesis module 11B.

[0033] To increase the molecular weight of the gas processed by hydrogen compression unit 15 and to ease the difficulty of designing the hydrogen compressor, for example to reduce the rotational speed or number of compressor impellers required to boost the hydrogen pressure from the low hydrogen pressure P1 to the synthesis gas suction pressure P3, a certain amount of nitrogen is added to the hydrogen before or during compression in hydrogen compression unit 15. The nitrogen is provided by nitrogen source 5.

[0034] 1 , the majority of the nitrogen provided by nitrogen source 5 is delivered to the suction side of syngas compressor 11A through main nitrogen delivery duct 12. A secondary nitrogen stream is diverted from main nitrogen delivery duct 12 through secondary nitrogen delivery line 21, which fluidly connects nitrogen source 5 to hydrogen compression unit 15. In the embodiment of FIG. 1 , secondary nitrogen delivery line 21 is connected to hydrogen delivery line 25 upstream of the inlet of hydrogen compression unit 15. Therefore, the nitrogen supplied through secondary nitrogen delivery line 21 must be reduced in pressure to low hydrogen pressure P1 before being blended with hydrogen from hydrogen source 3.

[0035] Because the low nitrogen pressure P 2 in the main nitrogen delivery duct 12 is typically higher than the low hydrogen pressure P 1 on the inlet side of the hydrogen compression unit 15 , a pressure reducing device 23 is positioned along the secondary nitrogen delivery line 21 .

[0036] In some embodiments, pressure reducing device 23 comprises a throttle valve 26. As used herein, the term "throttle valve" includes any valve adapted to reduce the pressure of gas flowing therethrough.

[0037] In the embodiment of Figure 1, the pressure reduction device 23 is controlled to regulate the nitrogen pressure and flow rate. For such purposes, a control unit 27 may be operatively connected to the pressure reduction device 23.

[0038] In some embodiments, the control unit 27 is further operatively connected to a flow detection arrangement. In the embodiment of Figure 1, the flow detection arrangement is adapted to detect the flow rate of hydrogen along the hydrogen delivery line 25 and further to detect the flow rate of nitrogen in the secondary nitrogen delivery line 21. Schematically, the flow detection arrangement includes a hydrogen flow meter 29A in the hydrogen delivery line 25 and a nitrogen flow meter 29B in the secondary nitrogen supply line 21 upstream of the pressure reducing device 23. Generally speaking, the flow detection arrangement is adapted to detect mass flow. In some embodiments, this can be obtained using, for example, an orifice in combination with temperature and pressure measurements.

[0039] Based on the flow meter signal, control unit 27 is adapted to adjust the percentage of nitrogen blended with the hydrogen delivered by hydrogen source 3. The greater the amount of nitrogen added to the hydrogen stream, the higher the molecular weight of the gas mixture processed by hydrogen compression unit 15. Because higher molecular weight gas blends are easier to process in hydrogen compression unit 15 than pure hydrogen, increasing the mole percentage of nitrogen in the gas mixture processed by hydrogen compression unit 15 may result in a reduction in the tip speed of the compressor impellers in hydrogen compression unit 15 and / or a reduction in the number of impellers, and therefore a reduction in the number of compressors in hydrogen compression unit 15.

[0040] The control unit 27 may be adapted to adjust the pressure reduction device 23 when the flow rate processed by the syngas compressor 11A changes. The control unit 27 may, for example, be adapted to maintain the ratio between the nitrogen flow rate and the hydrogen flow rate within a predetermined range when the total flow rate processed by the syngas compressor changes over time.

[0041] As mentioned above, the nitrogen pressure in the secondary nitrogen delivery line 21 must be reduced from a pressure value P2 (low nitrogen pressure P2) to a pressure P1 (low hydrogen pressure P1) lower than P2. The resulting hydrogen and nitrogen mixture must then be repressurized to a pressure P3' substantially equal to P2. Thus, nitrogen expansion in the pressure reduction device 23 causes some energy loss that is directly proportional to the percentage of blended nitrogen in the hydrogen stream.

[0042] Therefore, a compromise must be reached between the costs in terms of energy and power losses and the benefits in terms of reducing the speed of the hydrogen compression unit and / or the number of impellers and their stages.

[0043] By way of example, but not limitation, the mole percentage of nitrogen in the gas stream processed by hydrogen compression unit 15 can vary from 2% to 20%, preferably from 4% to 15%. More preferably, the mole percentage of nitrogen in the hydrogen-nitrogen blend can range from 4% to 10%.

[0044] 1, the secondary nitrogen stream delivered through secondary nitrogen delivery line 21 is supplied upstream of hydrogen compression unit 15 such that the nitrogen pressure must be reduced from low nitrogen pressure P2 to low hydrogen pressure P1. This approach maximizes the pressure drop and therefore the amount of additional power required to recompress the percentage of the secondary nitrogen stream delivered through secondary nitrogen delivery line 21. However, it maximizes the beneficial effect of mixing the nitrogen and hydrogen in terms of easier compression in hydrogen compression unit 15.

[0045] In other embodiments, a compromise between the energy penalty and the benefits associated with hydrogen-nitrogen blend compression can be achieved by adding a secondary nitrogen stream at an intermediate stage of hydrogen compression. In such cases, the benefit of molecular weight increase is reduced, but so is the power penalty caused by the need to expand part of the nitrogen stream.

[0046] Continuing with reference to Figure 1, Figure 2 illustrates an embodiment in which nitrogen is added to the hydrogen stream once it is partially compressed. Like numbers refer to the same or equivalent components already shown in Figure 1 and described above. These components and their functions will not be described again.

[0047] The embodiment of Figure 2 differs from the embodiment of Figure 1 primarily in that the hydrogen compression is split into two phases and nitrogen is added to the hydrogen stream between the first and second compression phases.

[0048] In the embodiment of Figure 2, the hydrogen compression unit 15 is shown as including two hydrogen compressors 15A and 15B. The two hydrogen compressors 15A and 15B are arranged in series, with the first hydrogen compressor 15A being located upstream of the second hydrogen compressor 15B relative to the direction of hydrogen flow through the hydrogen compression unit 15. The suction side of the first hydrogen compressor 15A receives hydrogen from the hydrogen source 3 at a low hydrogen pressure P1. Hydrogen at an intermediate hydrogen pressure P5 is delivered from the delivery side of the first hydrogen compressor 15A to the suction side of the second hydrogen compressor 15B. The hydrogen pressure is increased from the intermediate hydrogen pressure P5 to a synthesis gas pressure P3 or a slightly higher pressure P3' by the second hydrogen compressor 15B.

[0049] The secondary nitrogen delivery line 21 is fluidly coupled to the hydrogen compression unit 15 between the delivery side of the first hydrogen compressor 15A and the suction side of the second hydrogen compressor 15B. The pressure reducing device 23 thereby reduces the nitrogen pressure from the low nitrogen pressure P2 to an intermediate hydrogen pressure P5 that is higher than the low hydrogen pressure P1. Therefore, the power loss required to reach the required pressure in the secondary nitrogen delivery line 21 is lower. While this is beneficial in terms of reducing the power consumption of the system 1, it reduces the benefit in terms of hydrogen compression, since the molecular weight of the gas stream processed in the hydrogen compression unit 15 is increased only in the second hydrogen compressor 15B, not in the first hydrogen compressor 15A.

[0050] In a further embodiment, the enthalpy drop of the secondary nitrogen stream through pressure reduction device 23 may be at least partially recovered to produce useful power. To this end, pressure reduction device 23 may comprise at least one expander instead of or in combination with throttle valve 26.

[0051] Continuing with reference to Figures 1 and 2, Figure 3 illustrates an embodiment similar to Figure 1 in which the throttle valve 26 is replaced by an expander 24. Components of the system shown in Figure 3 that were already disclosed in connection with Figure 1 are labeled with the same reference numerals and will not be described again.

[0052] The primary difference between the embodiment of FIG. 3 and the embodiment of FIG. 1 is that the pressure of the nitrogen from the nitrogen source 5 is reduced by expansion in the expander 24 of the pressure reducing device 23 rather than by a throttle valve. In the embodiment of FIG. 3, the expander 24 is drivingly coupled to a generator 31. Thus, the enthalpy reduction of the secondary nitrogen stream in the expander 24 is at least partially converted to electrical power by the generator 31. The electrical power is delivered to an electrical power grid, labeled 8A. The electrical power grid 8A may be part of or electrically connected to the electrical power grid 8. Thus, the power recovered by the expander 24 from the nitrogen expansion can be used to produce hydrogen. Alternatively, or in combination, the electrical power generated by the generator 31 can be used to power other components of the system 1, such as an electric motor driving one or more of the compressors in the system 1. In further embodiments, the expander 24 can be drivingly coupled to the shafts of one or more of the hydrogen compressor, air compressor, and syngas compressor. In this embodiment, the expander 24 is used as a mechanical driver (helper) to assist the main driver of each compressor, thus reducing the external power supply and the size of the main driver.

[0053] The expander 24 may also be used in place of or in combination with the throttle valve 26 of the embodiment of Figure 2, as shown in the embodiment of Figure 4. The power generated by the expander 24 may be utilized or converted to electricity, as described above.

[0054] In a currently preferred embodiment, the secondary nitrogen stream is diverted from the main nitrogen delivery line 12, but the option of diverting the secondary nitrogen stream from an additional nitrogen source component independent of the nitrogen separation module 5B is not excluded. Such an option is illustrated in FIG. 5, where the same reference numerals used in FIGS. 1 to 4 indicate the same or equivalent components, which will not be described again. In FIG. 5, the nitrogen source 5 includes an additional nitrogen source 5C, e.g., a nitrogen delivery line from a separate plant or system. A duct 32 connects the additional nitrogen source 5C of the nitrogen source 5 to the suction side of the hydrogen compression unit 15. A control valve 33 can be arranged along the duct 32 to regulate the amount of nitrogen flow. A flow meter 29 interfaced to a control unit 27 is further foreseen, the control unit 27 being adapted to control the valve 33.

[0055] An additional nitrogen source 5C can also be envisaged in the embodiment according to Figure 2, where a secondary nitrogen stream is injected between the first upstream hydrogen compressor and the second downstream hydrogen compressor. This embodiment is shown in Figure 6, where the same reference numerals are used to denote the same or corresponding components already described in relation to Figures 2 and 5 and will not be described again.

[0056] In the embodiments described above, the secondary nitrogen stream is delivered entirely upstream of the hydrogen compression unit 15 (FIGS. 1, 3, and 5), or entirely between the upstream hydrogen compressor 15A and the downstream hydrogen compressor 15B of the hydrogen compression unit 15. In other embodiments, the secondary nitrogen stream can be split, with part delivered upstream of the hydrogen compression unit 15 and part delivered to an intermediate location between the serially arranged hydrogen compressors 15A, 15B. Alternatively, the secondary nitrogen stream can be split into two or more streams and delivered at different pressure levels to different points in the hydrogen compression unit 15, for example to the suction sides of different compressors or different compressor stages.

[0057] For example, the same reference numerals are used to indicate the same or corresponding components as those already disclosed in connection with Figures 1, 2, 3, 4, 5, and 6, and will not be described again. In Figure 7, the secondary nitrogen stream is diverted from the main nitrogen delivery duct 12 at pressure P2 and divided into a first secondary nitrogen stream delivered at pressure P1 upstream of the hydrogen compression unit 15 and a second secondary nitrogen stream delivered at pressure P5 between the first hydrogen compressor 15A and the second hydrogen compressor 15B. Two pressure reducing valves, such as two controlled throttle valves 26A and 26B, can be interfaced to the control unit 27. Alternatively, one or both of the throttle valves 26A and 26B can be replaced by an expander. Three flow detection devices 29A, 29B, and 29C are used to detect the hydrogen flow rate delivered by the hydrogen source 3 to the hydrogen compression unit 15 and the flow rates of the first and second secondary nitrogen streams.

[0058] In the above description of some embodiments, reference is made to a first upstream hydrogen compressor 15A and a second downstream hydrogen compressor 15B, and a secondary nitrogen stream can be delivered therebetween at an intermediate pressure P5. However, it should be understood that the hydrogen compression unit 15 can include three or more serially arranged hydrogen compressors 15A, 15B, and that more than one secondary nitrogen stream can be delivered between more than one pair of serially arranged hydrogen compressors, provided that the secondary nitrogen stream is delivered at the correct intermediate pressure.

[0059] Further, as understood herein, the first and second serially arranged hydrogen compressors may also be embodied by two serially arranged compressor stages of the same compressor device. For example, one or more secondary nitrogen streams may be injected as side streams at one or more intermediate locations along one or more multi-stage hydrogen compressors.

[0060] Furthermore, while some of the embodiments disclosed above provide a secondary nitrogen stream diverted from the main nitrogen stream delivered from nitrogen separation module 5B, and some other embodiments provide a secondary nitrogen stream delivered by additional nitrogen source 5C, other embodiments not shown may include a combination of both a secondary nitrogen stream diverted from main nitrogen delivery duct 12 and an additional nitrogen source 5C delivering the additional secondary nitrogen stream. In such cases, the two secondary nitrogen streams may either be combined and fed at the same point in hydrogen compression unit 15, or maintained separately and delivered to different points in hydrogen compression unit 15 at appropriate nitrogen pressures.

[0061] 8 illustrates a flowchart summarizing the method performed by the ammonia production system disclosed thus far. Briefly, the method includes the following: In step 101, nitrogen is delivered to the suction side of syngas compressor 11A. In step 102, a low-pressure hydrogen stream is delivered to the suction side of hydrogen compression unit 15. In step 103, nitrogen is added to hydrogen in hydrogen compression unit 15, either upstream of its suction side and / or at an intermediate location between the suction side at pressure P1 and the delivery side at pressure P3'. In step 104, the pressure of the hydrogen and nitrogen blend is increased in hydrogen compression unit 15 from low hydrogen pressure P1 to syngas suction pressure P3, or slightly higher. The compressed hydrogen and nitrogen blend is delivered to syngas compressor 11A (see step 105). The compressed synthesis gas from the synthesis gas compressor 11A is delivered to the ammonia synthesis module 11B (step 106), and ultimately, ammonia is synthesized from the compressed synthesis gas in the ammonia synthesis module 11B (step 107).

[0062] Certain exemplary embodiments have been described to provide a general understanding of the principles of the structure, function, and use of the systems, devices, and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the systems, devices, and methods expressly described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments, and that the scope of the present invention is defined only by the claims. Features described or illustrated in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be within the scope of the present invention.

Claims

1. 1. An ammonia production system comprising: a hydrogen source; and a hydrogen compression unit adapted to compress hydrogen from the hydrogen source; a nitrogen source; a synthesis gas compressor adapted to receive nitrogen from the nitrogen source and hydrogen from the hydrogen compression unit, and further adapted to compress a synthesis gas comprising a mixture of hydrogen and nitrogen; an ammonia synthesis module fluidly coupled to the synthesis gas compressor; the nitrogen source is fluidly coupled to the hydrogen compression unit such that, in use, the hydrogen compression unit compresses a blend containing hydrogen and nitrogen; The system for producing ammonia, wherein the nitrogen of the nitrogen source is delivered unmixed with the hydrogen of the hydrogen source to the suction side of the synthesis gas compressor and to the suction side of the hydrogen compression unit.

2. 2. The system of claim 1, wherein the hydrogen compression unit comprises an inlet fluidly coupled to the hydrogen source and adapted to receive hydrogen from the hydrogen source, and an outlet fluidly coupled to the synthesis gas compressor, and wherein the nitrogen source is fluidly coupled to the inlet of the hydrogen compression unit.

3. 3. The system of claim 1, wherein the hydrogen compression unit comprises at least a first hydrogen compressor and a second hydrogen compressor arranged in series, and the nitrogen source is fluidly coupled to the hydrogen compression unit between a delivery side of the first hydrogen compressor and a suction side of the second hydrogen compressor.

4. 10. The system of claim 1, comprising a nitrogen delivery line fluidly coupling the nitrogen source to the hydrogen compression unit, and a pressure reduction device along the nitrogen delivery line between the nitrogen source and the hydrogen compression unit.

5. The system of claim 4 , wherein the pressure reducing device comprises a throttle valve.

6. The system of claim 4 or 5, wherein the pressure reducing device comprises an expander.

7. The system of claim 6 , wherein the expander is drivingly coupled to one of a generator and a compressor.

8. The system of claim 4 , wherein the pressure reducing device is controlled by a control unit operatively coupled to a flow sensing arrangement.

9. 9. The system of claim 8, wherein the flow detection arrangement comprises: a hydrogen flow detection device adapted to detect a hydrogen flow rate supplied to the hydrogen compression unit; and a nitrogen flow detection device adapted to detect a nitrogen flow rate supplied to the hydrogen compression unit.

10. 10. The system of claim 9, further comprising a control unit operatively coupled to the hydrogen flow detection device and the nitrogen flow detection device, the control unit adapted to control the pressure reduction device to maintain a ratio between the nitrogen flow rate and the hydrogen flow rate within a desired range as flow rates through the syngas compressor vary.

11. The system of claim 1 , wherein the hydrogen source comprises an electrolyzer.

12. 12. The system of claim 11, wherein the electrolyzer is electrically coupled to an energy conversion facility adapted to convert energy from a renewable energy source into electrical energy.

13. The system of claim 1 , wherein the nitrogen source is adapted to separate nitrogen from air.

14. 1. A method for producing ammonia from hydrogen and nitrogen, said method comprising the steps of: delivering a nitrogen stream to the suction side of a syngas compressor at syngas suction pressure; delivering a hydrogen stream to the suction side of a hydrogen compression unit at a hydrogen inlet pressure less than said synthesis gas suction pressure; increasing the pressure of the hydrogen stream from the hydrogen inlet pressure to the synthesis gas suction pressure in the hydrogen compression unit and delivering the compressed hydrogen to the synthesis gas compressor; delivering compressed synthesis gas from the synthesis gas compressor to an ammonia synthesis module and producing ammonia from the compressed synthesis gas; the method further comprising adding nitrogen to the hydrogen in the hydrogen compression unit; The method wherein the nitrogen stream from a nitrogen source is delivered to the suction side of the synthesis gas compressor and to the suction side of the hydrogen compression unit unmixed with the hydrogen stream from a hydrogen source.

15. The method of claim 14, further comprising the steps of: delivering a main nitrogen stream from said nitrogen source at said synthesis gas suction pressure; diverting a secondary nitrogen stream from the primary nitrogen stream; reducing the pressure of the secondary nitrogen stream to a reduced nitrogen pressure; and delivering the secondary nitrogen stream at the reduced nitrogen pressure to the hydrogen compression unit.

16. 16. The method of claim 15, wherein the step of reducing the pressure of the secondary nitrogen stream comprises flowing the secondary nitrogen stream through a throttling valve.

17. 17. The method of claim 15 or 16, wherein the step of reducing the pressure of the secondary nitrogen stream comprises expanding the secondary nitrogen stream in an expander to produce useful power in the expander.

18. Steps below: converting the power generated by the expander into electricity; and transferring mechanical power produced by the expander to at least one of the hydrogen compression unit, an air compressor, and the syngas compressor.

19. 15. The method of claim 14, wherein the hydrogen compression unit comprises a first hydrogen compressor and a second hydrogen compressor arranged in series, the first hydrogen compressor being disposed upstream of the second hydrogen compressor with respect to the hydrogen flow within the hydrogen compression unit, and nitrogen being added to the hydrogen within the hydrogen compression unit upstream of the first hydrogen compressor.

20. 15. The method of claim 14, wherein the hydrogen compression unit comprises a first hydrogen compressor and a second hydrogen compressor arranged in series, the first hydrogen compressor being disposed upstream of the second hydrogen compressor with respect to the hydrogen flow within the hydrogen compression unit, and nitrogen being added to the hydrogen between a delivery side of the first hydrogen compressor and a suction side of the second hydrogen compressor.

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