Multiple compression units for ammonia production.

Abstract

A compression unit for ammonia comprises a multi-stage compressor including a first set of compressor stages adapted to compress a synthesis gas containing hydrogen and nitrogen and a second set of compressor stages adapted to compress a refrigerant of a refrigerant circuit. Also described herein are ammonia production systems and methods including such an ammonia compression unit.

Description

[Technical field]

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

[0002] Ammonia is a gas that is highly soluble in water and is often used in aqueous solutions. Ammonia (NH 3 ) is used in several industrial applications, among others for the production of nitric acid, urea, and other ammonia salts such as nitrates and phosphates. Ammonia derivatives are widely used in agriculture. About 80% of ammonia production is used for the manufacture 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] Ammonia production usually starts with a feed gas that provides a hydrogen source, for example methane. Nitrogen is obtained from air. The details of the ammonia production process are known to those skilled in the art, and some features of the plant and process may be recalled later for a better understanding of the novel aspects of the system disclosed herein, as well as for a better appreciation of its various advantages and beneficial effects over plants of the current technology.

[0006] Generally, the various process steps carried out to produce ammonia from air and feed gas require several compression trains. As understood herein, the term "compression train" refers to a machine assembly comprising at least one drive and one or more compressors driven by the drive to process one or more gaseous fluids. A gaseous fluid or gas as understood herein is any compressible fluid.

[0007] More specifically, in current technology ammonia production plants, a first compression train may be required to compress a feed gas such as methane and deliver the compressed feed gas to the primary and secondary steam reformers when the feed gas is not available at sufficient pressure. A second compression train is provided to compress process air and deliver the compressed process air to the second compression train. Raw synthesis gas (syngas) obtained from the shift conversion is compressed by a third compression train. A further fourth compression train is required to process the refrigerant fluid, which cools the ammonia produced from the synthesis gas in the ammonia converter.

[0008] 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 studied in an attempt to reduce the production of greenhouse gases and avoid the use of hydrocarbons. In green ammonia production, the process of making ammonia is 100% renewable and carbon-free. One way of making green ammonia is by using nitrogen separated from the air and hydrogen produced by water electrolysis powered by renewable energy sources. The nitrogen and hydrogen are then fed as synthesis gas to an ammonia converter, which synthesizes ammonia from the synthesis gas. The ammonia thus obtained is cooled by heat exchange with a refrigerant fluid in a refrigerant circuit. Summary of the Invention [Problem to be solved by the invention]

[0009] The production of green ammonia also requires expensive and cumbersome compression units, driven by respective drive units, inter alia to compress the synthesis gas and the refrigerant in the refrigeration circuit.

[0010] The need for several compression trains makes an ammonia production plant complex and expensive, therefore it is desirable to simplify the general layout of an ammonia production plant.

[0011] According to one aspect, disclosed herein is an ammonia production compression unit including a multi-stage compressor. The multi-stage compressor includes a first set of compressor stages adapted to compress a synthesis gas containing hydrogen and nitrogen, and a second set of compressor stages adapted to compress a refrigerant of a refrigerant circuit. A synthesis gas inlet is fluidly connected to the most upstream compressor stage of the first set of compressor stages, and a synthesis gas outlet is fluidly connected to the most downstream compressor stage of the first set of compressor stages. Similarly, a refrigerant inlet is fluidly connected to the most upstream compressor stage of the second set of compressor stages, and a refrigerant outlet is fluidly connected to the most downstream compressor stage of the second set of compressor stages.

[0012] The terms "upstream" and "downstream" refer to the direction of flow of process gas through an associated set of compressor stages.

[0013] The first set of compressor stages and some of the second set of compressor stages may be contained within a single casing of the multi-stage compressor.

[0014] In a particularly advantageous embodiment, the compressor is a reciprocating compressor. The reciprocating compressor includes a common crankshaft rotatably housed in a single frame. The crankshaft imparts motion to the connecting rods, crossheads, piston rods and pistons of each of the multiple cylinders of the multi-stage reciprocating compressor. A first set of cylinder / piston systems processes the synthesis gas and a second set of cylinder / piston systems processes the refrigerant. Thus, the two process gases are separated from each other despite being processed by the same compressor. The reciprocating compressor offers a simple construction with fewer problems regarding leakage and contamination between the two gases processed in the same compressor.

[0015] Thus, a compact arrangement is obtained adapted to process two process fluids, namely refrigerant and synthesis gas, in a single compressor.

[0016] According to a further aspect, disclosed herein is an ammonia production system including a syngas compression unit, an ammonia converter, and an ammonia chiller, the ammonia chiller having a hot side fluidly connected to the ammonia converter and a cold side fluidly coupled to an ammonia refrigeration circuit comprising a refrigerant compression unit adapted to circulate a refrigerant within the refrigeration circuit.

[0017] In embodiments disclosed herein, the synthesis gas compression unit and the refrigerant compression unit are characterized by a single multi-stage compressor. In embodiments disclosed herein, the synthesis gas compression unit comprises a first set of compressor stages of the multi-stage compressor and the refrigerant compression unit comprises a second set of compressor stages of the multi-stage compressor.

[0018] According to yet another aspect, disclosed herein is a method of producing ammonia using the ammonia production system generally described above, comprising: compressing a synthesis gas in a first set of compressor stages of a multi-stage compressor; feeding the compressed synthesis gas to an ammonia converter where ammonia is produced therein; feeding ammonia from the ammonia converter through an ammonia chiller in heat exchange relationship with a refrigerant circulating in a refrigeration circuit; removing heat from the refrigerant and compressing the cooled refrigerant in a second set of compressor stages of the multi-stage compressor.

[0019] Further features and embodiments of the compressors, systems, and methods according to the present disclosure are described below and claimed in the accompanying claims. [Brief description of the drawings]

[0020] Reference will now be made briefly to the accompanying drawings, in which: [Figure 1] FIG. 1 is a diagram showing a green ammonia production system according to one embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram showing a green ammonia production system in a further embodiment of the present disclosure. [Diagram 3] FIG. 3 is a diagram showing a green ammonia production system in a further embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram showing a green ammonia production system in a further embodiment of the present disclosure. [Diagram 5] FIG. 5 illustrates an ammonia production system according to the present disclosure using a hydrocarbon feed gas. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] To reduce the complexity of an ammonia production system, the present disclosure proposes combining the syngas and refrigerant compression functions in a single multi-stage compressor, with the stages of the multi-stage compressor being divided into a first set of compressor stages adapted to compress the syngas and a second set of compressor stages adapted to compress a refrigerant used to chill the ammonia delivered by the ammonia converter.

[0022] In the following description and the accompanying drawings, particular reference is made to the green ammonia process and system. However, it will be understood that the novel features of the present disclosure can also be used with similar beneficial effect in more conventional ammonia production facilities that use feed gases such as methane or any other hydrocarbon as a hydrogen source. The novel features disclosed herein are in fact intended to improve the ammonia synthesis section of the system, starting from the synthesis gas compressor. How the nitrogen and hydrogen are produced is not particularly important. Thus, in this specification and the appended claims, the terms "hydrogen source" and "nitrogen source" can include any structure, system, unit, apparatus, or equipment adapted to produce hydrogen-containing and nitrogen-containing fluids, respectively. The term "synthesis gas production section" as understood in this specification includes any structure, system, unit, apparatus, or equipment adapted to produce a gas stream that includes or consists mainly of hydrogen and nitrogen.

[0023] An "ammonia synthesis section" as understood herein is any system, unit, apparatus, facility, or structure adapted to synthesize ammonia from synthesis gas.

[0024] Referring now to the drawings, FIG. 1 illustrates a schematic diagram of a first ammonia production system 1.

[0025] The ammonia production system 1 includes a synthesis gas production section 3 and an ammonia synthesis section 5. As mentioned above, by way of non-limiting example, the ammonia production system 1 of Figure 1 is a green ammonia system in which hydrogen is produced by electrolysis, preferably using electricity from renewable energy sources.

[0026] In the exemplary embodiment of FIG. 1, the synthesis gas production section 3 includes a hydrogen source 4. The hydrogen source 4 can use power generated by a power source 6 including a solar photovoltaic panel 7 and an associated inverter 9 for the electrolysis of water. Power from the power source 6 is supplied to an electrolyzer 11, which produces water (H 2 O to Hydrogen (H 2 ) is generated.

[0027] Alternative renewable energy resources can be used to power the hydrogen source 4, such as wind energy from wind farms, tidal energy, etc., as well as combinations thereof.

[0028] The hydrogen source 4 further includes a hydrogen compressor 13 driven by a first drive device 15, such as an electric motor or a turbine (such as a gas turbine or steam turbine). The hydrogen compressor 13 delivers hydrogen at a pressure suitable for mixing with nitrogen from a nitrogen source 17.

[0029] The nitrogen source 17 may include an air compressor 19 driven by a second drive unit 21, such as an electric motor or a turbine (e.g. a gas turbine or a steam turbine). It is not excluded to use a single train including the air compressor and the hydrogen compressor, driven by a single drive unit.

[0030] The compressed air is delivered by the air compressor 19 to the nitrogen separation unit 23, from which compressed nitrogen (N 2) is delivered to ammonia synthesis section 5. Nitrogen separation unit 23 may include, for example, a membrane separator, a fractionation system, or any other device, unit, or system adapted to separate nitrogen from other air components (specifically oxygen and carbon dioxide).

[0031] The ammonia synthesis section 5 comprises a multi-stage compressor 31, which can be driven by a third drive 33, for example an electric motor or a turbine, such as a gas turbine or steam turbine. The possibility of using the same drive of the air compressor or the hydrogen compressor is not excluded.

[0032] In the embodiment of Figure 1, the multi-stage compressor 31 is an integrally geared compressor including a bull gear 311 drivingly coupled to a third driver 33 via a shaft 35. A plurality of pinions 313 mesh with the bull gear 311. Each pinion gear 313 transmits rotation from the bull gear 311 to a respective shaft 315. In the embodiment of Figure 1, by way of non-limiting example, the multi-stage compressor 31 includes four shafts 315. In other embodiments, the number of shafts 315 may be more or less than four.

[0033] Each shaft 315 drives and rotates at least one, and preferably two, compressor stages 317. In the exemplary embodiment of Figure 1, each shaft 315 drives and rotates two compressor stages 317. The eight compressor stages are labeled starting with 317A, followed by 317B, 317C, 317D, 317E, 317F, 317G, and 317H.

[0034] In the embodiment of FIG. 1, each compressor stage 317A-317H includes a rotating impeller extending from an end of a respective shaft 315, and more specifically, from each end.

[0035] Integral gear compressors can be particularly beneficial in the systems disclosed herein because the bull gear and pinion gear combination allows different compressor impellers to rotate at different rotational speeds.

[0036] The compressor stages 317A-317H are grouped into a first set of compressor stages including compressor stages 317A, 317B, 317C, 317D, and 317E, and a second set of compressor stages including compressor stages 317F, 317G, and 317H. As will be explained in more detail below, the first set of compressor stages is characterized by a syngas compression unit and is adapted to process a syngas. The second set of compressor stages is characterized by a refrigerant compressor and is adapted to compress a refrigerant. The number of compressor stages in each set may be different from the number of compressor stages shown in FIG. 1. However, in a preferred embodiment, the number of compressor stages in the first set is greater than the number of compressor stages in the second set. This takes into account the fact that syngas is of low molecular weight due to the large amount of hydrogen it contains. The low molecular weight process gas processed by the syngas compression section requires a relatively large number of compressor stages to achieve the required compression ratio without requiring too high a rotational speed.

[0037] The compressor stages 317A, 317B, 317C, and 317D of the first set of compressor stages are arranged in sequence, with compressor stage 317A being the most upstream compressor stage of the first set and compressor stage 317D being the most downstream compressor stage. The suction side of the first compressor stage 317A is fluidly connected to the delivery side of the hydrogen compressor 13 and the nitrogen separation unit 23 to receive a synthesis gas stream comprising hydrogen delivered by the hydrogen compressor 13 and nitrogen delivered by the nitrogen separation unit 23. The synthesis gas stream is then compressed sequentially to higher and higher pressure values ​​in compressor stages 317A, 317B, 317C, and 317D. The delivery side of compressor stage 317D is fluidly connected to the ammonia converter 37.

[0038] In the embodiment of Figure 1, the multi-stage compressor 31 is an intercooled or interrefrigerated compressor that includes one or more intercoolers 39 between one or more pairs of sequentially arranged compressor stages 317A-317H. In the embodiment of Figure 1, the multi-stage compressor 31 includes an intercooler 39 between each pair of sequentially arranged and fluidly connected compressor stages.

[0039] The compressed synthesis gas delivered by compressor stage 317D is processed in ammonia converter 37, where the following synthesis reactions occur:

[0040] [ka] is carried out under suitable pressure and temperature conditions to produce an ammonia rich stream that is delivered to chiller 41.

[0041] In the chiller 41, the ammonia rich stream flows through the hot side of the chiller 41 in heat exchange relationship with the refrigerant fluid circulating in the refrigeration circuit 43. The refrigerant circulating in the refrigeration circuit may be ammonia or other suitable refrigerant.

[0042] The refrigerant fluid removes heat from the ammonia-rich stream and the cooled ammonia-rich stream is then sent to an ammonia separator 45 where liquid ammonia is separated from unreacted syngas (line 47). The unreacted syngas is recycled in syngas recovery and recycle line 49. A third line 48 can be provided to discharge other gaseous residues, if any.

[0043] A syngas recovery and recycle line 49 delivers the recycled unreacted syngas to the multi-stage compressor 31. Specifically, in the embodiment of Figure 1, one of the compressor stages of the first set of compressor stages, namely compressor stage 317E, is dedicated to compressing the recirculated syngas. The recompressed syngas delivered by compressor stage 317E is returned to the ammonia converter 37 along with the main syngas stream delivered by compressor stage 317G.

[0044] As shown in the schematic diagram of FIG. 1, the refrigeration circuit 43 includes a refrigerant compression unit that compresses and circulates the refrigerant in the refrigeration circuit 43; an expander, throttle valve, or stacked valve 51; a low-temperature side of the ammonia chiller 41; and a heat exchanger 53, in which heat Q is removed from the refrigerant circulating in the refrigeration circuit 43 prior to compression in the refrigerant compression unit.

[0045] 1 and described above, the refrigerant compression unit is characterized by a second set of compressor stages 317F, 317G, and 317H. More specifically, the expanded and heated refrigerant discharged from the hot side of the ammonia chiller 41 is delivered via heat exchanger 53 to the suction side of compressor stage 317F where it is partially compressed and delivered sequentially through compressor stage 317G and finally through compressor stage 317H. The delivery side of compressor stage 317H is fluidly connected to an expander or valve 51.

[0046] In summary, the refrigerant compression unit and the syngas compression unit are combined in the same multi-stage compressor 31, with some of the compressor stages (stages 317A, 317B, 317C, 317D, and 317E) being dedicated to syngas compression and the remaining compression stages (stages 317F, 317G, and 317H) being dedicated to refrigerant compression.

[0047] This layout results in a significant reduction in System 1 capital expenditures (CAPEX), System 1 footprint, and architectural complexity.

[0048] With continuing reference to FIG. 1, reference is now made to FIG. 2, which illustrates a modified embodiment of an ammonia production system 1. The same reference numbers indicate the same or equivalent parts of the system 1 illustrated in FIG. 1 and described above with reference thereto. These parts will not be described again. The system of FIG. 2 differs from that of FIG. 1 in that the main syngas stream entering the first compressor stage 317A is processed sequentially through all compressor stages 317A, 317B, 317C, 317D, and 317E of the first set of compressor stages. The synthesis gas recovered from the ammonia separator 45 is combined with the main synthesis gas stream from compressor stage 317D, and the main synthesis gas stream and the synthesis gas stream recovered from the ammonia separator 45 are subjected to final compression in the most downstream compressor stage 317E of the first set of compressor stages 317A-317E.

[0049] With continuing reference to Figures 1 and 2, reference is now made to Figure 3, which illustrates a further embodiment of a system according to the present disclosure, in which like reference numbers indicate the same elements or components shown in Figures 1 and 2 and described above, or elements and features having similar or equivalent functionality in system 1.

[0050] The main difference between the embodiment of Figure 3 and the embodiment of Figures 1 and 2 is that the system 1 of Figure 3 includes a multi-stage reciprocating compressor (again designated with reference number 31) instead of an integrally geared compressor as shown in Figures 1 and 2. Reference number 33 again denotes a drive for the multi-stage compressor 31. The drive 33 is drivingly connected to a crankshaft 61 rotatably housed in a frame 63. The crankshaft 61 transmits rotational motion to the connecting rods, crossheads, piston rods and pistons of each of the multiple cylinders of the multi-stage reciprocating compressor 31. The connecting rods, crossheads, piston rods and pistons are not shown in the schematic diagram of Figure 3.

[0051] The multi-stage reciprocating compressor 31 includes a first set of compressor stages 317A, 317B, 317C, and 317E and a second set of compressor stages 317G and 317H. Each compressor stage is characterized by a respective compressor cylinder housing a piston that slides reciprocally therein. The first set of compressor stages 317A, 317B, 317C, and 317E process the synthesis gas, and the second set of compressor stages 317G and 317H process the refrigerant fluid circulating in the refrigerant circuit. As in the embodiment of FIG. 1, the multi-stage compressor 31 of FIG. 3 includes a compressor stage 317E that processes the synthesis gas recovered and recycled from the ammonia separator 45, while the compressor stages 317A, 317B, and 317C are arranged in sequence to process the synthesis gas consisting of nitrogen from the nitrogen source 17 and hydrogen from the hydrogen source 4.

[0052] In the embodiment of FIG. 3, an intercooler may be provided between each pair of sequentially arranged compressor stages, except between stages 317C and 317E, and between stages 317E and 317G, which are not directly fluidly connected to each other.

[0053] The system of FIG. 3 operates in exactly the same way as the systems of FIGS.

[0054] With continuing reference to Figures 1, 2 and 3, reference is now made to Figure 4, which illustrates a further embodiment of the ammonia production system 1. The system of Figure 4 differs from the system of Figure 3 primarily in that the delivery side of compressor stage 317C is fluidly connected to the suction side of the most downstream compressor stage 317E of the first set of compressor stages, which compressor stage 317E is adapted to process the synthesis gas recycled through recovery and recycle line 49 and the synthesis gas partially compressed by the first compressor stage 317A, the second compressor stage 317B and the third compressor stage 317C.

[0055] While Figures 1-4 show schematic diagrams of a green ammonia system, Figure 5 shows a schematic diagram of an exemplary embodiment of the system, in which a multi-stage compressor for processing synthesis gas and refrigerant gas in its different compressor stages is used to produce methane (CH) as a hydrogen source for the production of synthesis gas. 4 ) or another feed gas.

[0056] In FIG. 5, a feed gas, e.g., methane (CH 4 ) or another gaseous hydrocarbon or gaseous hydrocarbon blend is delivered to a primary catalytic steam reformer 105 through a feed gas compression train 103. The feed gas compression train 103 includes a first drive 107 and a feed gas compression section 108. The feed gas compression section 108 may include a compressor 109. Process steam is delivered in line 111 to the primary catalytic steam reformer 105 where the feed gas reacts with the steam to produce carbon monoxide and hydrogen according to the following reactions:

[0057] [ka]

[0058] The primary reformer 105 is fluidly connected to a secondary steam reformer 115 which receives reaction products from the primary reformer 105 as well as process air from a process air inlet line 117. The process air is compressed by a process air compression train 119.

[0059] The process air compression train 119 includes a second drive 121 capable of driving a process air compression section 122. The process air compression section 122 may include, for example, a first process air compressor 123 and a second process air compressor 125 arranged in series. An intercooler 127 may be disposed between the delivery of the first process air compressor 123 and the second process air compressor 125.

[0060] In the secondary steam reformer 115, unreacted methane (CH 4 ) is converted into carbon monoxide (CO) and carbon dioxide (CO 2 ). The resulting gas mixture is raw syngas, which is delivered to a shift conversion unit 129.

[0061] In the shift conversion unit 129, carbon monoxide is converted to carbon dioxide according to the following reaction:

[0062] [ka]

[0063] The resulting gas mixture is sent to a scrubber 131 where carbon dioxide is removed and the resulting gas mixture is delivered to a methanation section 133. Residual carbon monoxide contained in the gas stream from the scrubber 131 is converted by hydrogenation in the methanation section 133 to methane (CH), according to the following reaction: 4 ) and water (H2 O).

[0064] [ka]

[0065] The gas mixture thus obtained is fed through a dryer 135 and the resulting pure synthesis gas containing mainly nitrogen and hydrogen is delivered to a multi-stage compressor 31 which may be configured as shown in any of Figures 1, 2, 3 or 4 above.

[0066] In Figure 5, the multi-stage compressor 31 and the remainder of the system 1, i.e., the ammonia converter 37, the ammonia separator 45, the chiller 4, and the refrigerant circuit 43, are configured similarly to Figure 1. In other embodiments, the multi-stage compressor 31 and other portions of the system downstream thereof may be configured as shown in any one of Figures 2, 3, and 4 above.

[0067] By combining synthesis gas compression and refrigerant compression in a single multi-stage compressor, the number of compressor casings and the number of compressor units of the ammonia production system can be reduced. By appropriately selecting the number of compressor stages in each of the first and second sets of compressor stages and by providing an appropriate compression ratio, a particularly compact configuration can be obtained, which has beneficial effects, for example, in terms of reducing the installation area. In a preferred embodiment, the first set of compressor stages compressing the synthesis gas can include 3 to 5 compressor stages. In an embodiment, the second set of compressor stages can include 2 to 4 compressor stages.

[0068] In a currently preferred embodiment, the first set of compressor stages may be adapted to provide a compression ratio of from 4 to 7, and the second set of compressor stages may be adapted to provide a compression ratio of from 12 to 17.

[0069] Exemplary embodiments are disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various modifications, omissions, and additions may be made to what is specifically disclosed herein without departing from the scope of the invention as defined in the following claims.

Claims

1. 1. An ammonia production compression unit comprising a multi-stage compressor, the multi-stage compressor comprising: a first set of compressor stages adapted to compress a synthesis gas containing hydrogen and nitrogen; a second set of compressor stages adapted to compress refrigerant in the refrigerant circuit; 1. An ammonia production compression unit comprising:

2. 2. The compression unit of claim 1, wherein the multi-stage compressor is a reciprocating compressor including a plurality of cylinders, a first set of cylinders compressing a synthesis gas and a second set of cylinders compressing the refrigerant, and a single crankshaft drives the pistons of the first set of cylinders and the pistons of the second set of cylinders.

3. 3. A compression unit according to claim 1 or 2, wherein the first set of compressor stages comprises 3 to 5 compressor stages and the second set of compressor stages comprises 2 to 4 compressor stages, the first set of compressor stages being adapted to provide a compression ratio of between 4 and 7 and the second set of compressor stages being adapted to provide a compression ratio of between 12 and 17.

4. 4. The compression unit of claim 1, wherein the multi-stage compressor comprises at least one of an intercooler between two successively arranged stages of the first set of compressor stages and an intercooler between two successively arranged stages of the second set of compressor stages.

5. 1. An ammonia production system comprising: a synthesis gas compression unit; an ammonia converter; an ammonia chiller having a hot side fluidly coupled to the ammonia converter and a cold side fluidly connected to an ammonia refrigeration circuit, the ammonia refrigeration circuit comprising a refrigerant compression unit adapted to circulate a refrigerant within the refrigeration circuit; 1. The ammonia production system, wherein the synthesis gas compression unit and the refrigerant compression unit are characterized by multi-stage compressors, the synthesis gas compression unit comprising a first set of compressor stages of the multi-stage compressor, and the refrigerant compression unit comprising a second set of compressor stages of the multi-stage compressor.

6. 6. The ammonia producing system of claim 5, wherein the refrigerant is ammonia.

7. 7. The ammonia production system of claim 5 or 6, further comprising an ammonia separator downstream of the ammonia chiller, a synthesis gas recycle line fluidly connecting the ammonia separator to the downstream-most stage of the first set of stages.

8. 8. The system for producing ammonia as described in claim 7, wherein the most downstream stage of the first set of stages is adapted to process only recirculated synthesis gas from the ammonia separator.

9. 8. The ammonia production system of claim 7, wherein a downstream-most stage of the first set of stages is further fluidly connected to a delivery side of an upstream stage of the first set of stages.

10. 10. The ammonium production system of claim 5, wherein the multi-stage compressor is a reciprocating compressor including a plurality of cylinders, a first set of cylinders compressing the synthesis gas and a second set of cylinders compressing the refrigerant, and a single crankshaft drives the pistons of the first set of cylinders and the pistons of the second set of cylinders.

11. 11. The ammonium production system according to any one of claims 5 to 10, wherein the first set of compressor stages comprises 3 to 5 compressor stages and the second set of compressor stages comprises between 2 and 4 compressor stages, the first set of compressor stages being adapted to provide a compression ratio of between 4 and 7 and the second set of compressor stages being adapted to provide a compression ratio of between 12 and 17.

12. 12. The ammonia production system according to any one of claims 5 to 11, wherein the multi-stage compressor comprises at least one of an intercooler between two consecutively arranged stages of the first set of compressor stages and an intercooler between two consecutively arranged stages of the second set of compressor stages.

13. A method for producing ammonia using the ammonia production system according to any one of claims 5 to 12, comprising: compressing a synthesis gas in the first set of compressor stages of the multi-stage compressor; supplying the compressed synthesis gas to the ammonia converter and producing ammonia therein; supplying ammonia from the ammonia converter through an ammonia chiller in heat exchange relationship with a refrigerant circulating in the refrigeration circuit; removing heat from the refrigerant and compressing the cooled refrigerant in the second set of compressor stages of the multi-stage compressor.

14. processing the cooled ammonia in an ammonia separator; 14. The method of claim 13, further comprising recovering a synthesis gas from the ammonia separator and recirculating the recovered synthesis gas through one of the compressor stages of the second set of the multi-stage compressor.

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