Green ammonia absorption cooling

Abstract

1. An ammonia synthesis process and plant comprising an ammonia synthesis converter and a downstream ammonia cooling system, the ammonia synthesis converter being arranged to receive an ammonia synthesis gas comprising hydrogen and nitrogen and produce an ammonia product gas stream and an off-gas ammonia stream; the ammonia cooling system comprising: an ammonia evaporator for evaporating an ammonia liquid stream and producing an ammonia vapor stream; an off-gas scrubbing unit for scrubbing the off-gas ammonia stream with the addition of water as a scrubbing agent and producing a water stream and an ammonia-depleted off-gas stream; an absorption cooling unit comprising water for cooling the ammonia vapor stream and collecting a condensed ammonia-water stream; a regeneration unit for producing from the condensed ammonia-water stream a purified water stream, the ammonia liquid stream, and an overhead ammonia gas stream.

Description

[Technical Field]

[0001] The present invention relates to an ammonia cooling (refrigeration) apparatus for cooling ammonia product gas from an ammonia synthesis converter in an ammonia synthesis plant or ammonia synthesis process. The present invention also relates to an ammonia synthesis plant and method comprising an ammonia cooling system, wherein ammonia is produced from hydrogen by electrolysis using electricity from a renewable energy source. [Background technology]

[0002] Conventional, or traditional, ammonia synthesis plants, as is well known in the art, typically include a reforming section comprising a steam methane reforming unit and / or a self-thermal reforming unit for catalytic steam reforming of hydrocarbon feedstock, typically derived from natural gas or renewable sources, thereby producing a hydrogen-rich feedstock synthesis gas combined with nitrogen to produce ammonia synthesis gas. The ammonia synthesis plant has a downstream ammonia synthesis section, such as an ammonia synthesis loop, which includes an ammonia synthesis converter into which the ammonia synthesis gas is converted into an ammonia product gas stream.

[0003] In conventional ammonia synthesis plants, the so-called turndown ratio is approximately 100%. The turndown ratio, also hereafter referred to as "turndown," is the ratio of operation at the normal load, such as the upstream hydrocarbon supply used to produce ammonia synthesis gas and, consequently, ammonia product gas, typically natural gas, to the amount that the ammonia synthesis plant can tolerate. Therefore, in conventional ammonia synthesis plants, the natural gas supply is steady, and thus the normal load, i.e., the turndown, is 100%, so a turndown of, for example, 10%, is not considered. However, in dynamic ammonia synthesis plants, such as green ammonia synthesis plants where the hydrogen for ammonia synthesis gas is produced by water electrolysis or steam electrolysis powered by electricity from renewable energy sources such as solar, wind, and hydroelectric power, the power input from these power sources can fluctuate significantly throughout the day and between seasons, so a turndown of, for example, 10%, occurs frequently, and therefore, addressing this becomes a very important issue.

[0004] Conventional natural gas-based ammonia synthesis plants or processes typically employ an ammonia cooling circuit to condense the ammonia produced. Thus, the produced ammonia is separated from the circulating ammonia synthesis gas by cooling / condensation. To avoid the accumulation of inert substances within the plant, a small amount of ammonia-containing gas, or off-gas ammonia flow, is released from the plant. This flow is treated in a scrubbing tower for environmental reasons, and the absorbed ammonia is recovered by distillation.

[0005] The well-known operating principle in ammonia cooling circuits is the use of so-called mechanical refrigeration, which causes ammonia to evaporate at low pressure, generating a low temperature that is then used to cool the main process flow in the upstream ammonia synthesis plant. The released ammonia vapor is compressed in a multistage ammonia compressor, such as a multistage centrifugal compressor driven by a steam turbine, and the compressed vapor is condensed with cooling water or air in an ammonia condenser. As a result, liquid ammonia is collected and reused for cooling. For example, a standard, i.e., conventional natural gas-based ammonia synthesis plant typically includes an ammonia refrigeration compressor and an ammonia recovery unit consisting of two off-gas scrubbers and a distillation column.

[0006] Traditionally, cooling has been performed by multi-stage cooling compressors operating at multiple pressure levels. While this results in high energy efficiency at high loads, the ammonia cooling circuit has a complex layout and, due to compressor limitations, low efficiency at low loads (or low turndown ratios). This becomes problematic when plant loads fluctuate significantly and the compressors are steam-driven. At full plant load, the steam produced as a byproduct in the ammonia plant is sufficient to power the cooling compressors, but this becomes impossible when the load decreases. Therefore, the heat generated from the ammonia synthesis converter in conventional ammonia synthesis plants is typically removed by a steam boiler, and the resulting superheated steam can be used to drive the multi-stage compressors in the ammonia cooling circuit with a steam turbine, or to drive AC generators for power generation. However, the turndown of the steam turbine is lower than that of the ammonia synthesis plant, for example, its ammonia synthesis loop. Therefore, when the load on the ammonia synthesis plant is low (e.g., below 50%), an imbalance occurs between the steam produced in the ammonia synthesis plant and the steam used in the downstream ammonia refrigeration circuit, which changes how this steam is utilized by the steam turbine. This necessitates stopping the steam turbine and using extra power to condense the steam. Conventional steam turbines operate on superheated steam, requiring the inclusion of a steam superheater as part of the steam generation section, resulting in increased capital expenditures (CAPEX) and more complex operation.

[0007] WO2020057818A1 discloses an aqua / ammonia absorption refrigeration system and methods for improving the same. Preferred applications relate to absorption refrigeration systems for refrigerating process gases in ammonia synthesis plants.

[0008] US4376758 discloses a method for synthesizing ammonia from hydrocarbons, including cooling and purification. An off-gas containing a low ammonia content of 0.48% is drawn at the top of an ammonia absorption tower. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] WO2020057818A1 [Patent Document 2] US4376758 [Overview of the project] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide a robust ammonia cooling system that can withstand fluctuating loads in an ammonia synthesis plant with a fluctuating power supply, particularly a green ammonia synthesis plant, where the hydrogen required for the production of ammonia synthesis gas is obtained from the electrolysis of water or steam powered by electricity from renewable energy sources.

[0011] Another objective of the present invention is to provide an improved ammonia recovery method for off-gas ammonia streams generated in ammonia synthesis plants. [Means for solving the problem]

[0012] These and other objectives are addressed by the present invention.

[0013] Accordingly, in a first embodiment, the present invention relates to an ammonia synthesis plant including an ammonia synthesis converter and a downstream ammonia cooling system, wherein the ammonia synthesis converter is configured to receive ammonia synthesis gas containing hydrogen and nitrogen and to produce an ammonia product gas stream. Here, the ammonia synthesis plant is configured to generate an off-gas ammonia stream, The ammonia cooling system includes the following: - An ammonia evaporator that evaporates a liquid ammonia stream to produce a vapor ammonia stream; - An off-gas cleaning unit that cleans the off-gas ammonia stream with the addition of water as a scrubbing agent (absorbent) to generate a water stream and an ammonia-depleted off-gas stream; - An absorption cooling unit containing water for cooling the ammonia vapor stream and collecting the condensed ammonia-water stream; -From the condensed ammonia-water flow purified water stream, The ammonia liquid flow, and, Ammonia gas flow at the top of the tower; A regeneration unit for generating: Furthermore, here, - The ammonia evaporator is arranged to receive the ammonia liquid flow and the heat exchange medium for evaporating the ammonia liquid flow, and to generate the ammonia vapor flow; - The off-gas cleaning unit, preferably an off-gas scrubbing unit, is configured to receive the purified water stream and the off-gas ammonia stream from the regeneration unit as scrubbing agents to generate the ammonia-depleted off-gas stream and the water stream; -The absorption cooling unit is preferably a mixing container containing water, and is arranged to receive the water flow and the ammonia vapor flow, thereby generating and collecting the condensed ammonia-water flow. The absorption cooling unit further includes a cooling device such as a coil arranged to receive a cooling medium, for example, water, and an outlet for extracting the condensed ammonia-water flow; - The regeneration unit is a distillation column, i.e., an ammonia recovery distillation column, which is arranged to receive the condensed ammonia-water flow. The regeneration unit includes an outlet for taking out the purified water flow as a bottom flow, an outlet for taking out the ammonia flow at the top of the column, and a separation unit, such as a drum at the top of the ammonia recovery column, for separating the ammonia gas flow at the top of the column from the ammonia liquid flow at the top of the column.

[0014] As used herein, the term "comprising" includes "consisting only of", i.e., "consisting of". As used herein, the term "preferably" means "optionally", i.e., any embodiment. As used herein, the term "first aspect" or "the first aspect of the present invention" means a plant (system, apparatus). The term "second aspect" or "the second aspect of the present invention" means a method (process). As used herein, the terms "the present invention" or simply "invention" can be used interchangeably with the terms "the present application" or simply "application".

[0015] Other definitions are provided in connection with one or more of the following embodiments.

[0016] In one embodiment, the ammonia synthesis plant comprises a water or steam electrolysis unit for producing the hydrogen. Preferably, the electrolysis unit is driven by electric power from a renewable energy source such as sunlight, wind power or hydraulic power. Optionally, the electrolysis unit is driven by electric power from thermonuclear power.

[0017] The water electrolysis unit is an alkaline / polymer electrolyte membrane electrolysis unit, i.e., an alkaline / PEM electrolysis unit (alkaline battery or polymer battery unit). For the purposes of the present invention, the term "alkaline / PEM electrolysis unit" means an alkaline and / or PEM electrolysis unit. The steam electrolysis unit is a solid oxide electrolysis cell unit (SOEC unit). Operation by the SOEC unit is usually carried out at a high temperature (700 - 800 °C), and the latter operates at a much lower temperature, i.e., in the range of 60 - 160 °C, so it often has advantages over alkaline / PEM electrolysis. It will be understood that water is used for alkaline / PEM electrolysis and steam is used for SOEC.

[0018] The term "green ammonia absorption cooling" should be understood as referring to the cooling of ammonia product gases in an ammonia cooling system where electrolysis of water or steam is performed to produce hydrogen.

[0019] Furthermore, the terms “green ammonia plant” or “green ammonia synthesis plant” are also understood to mean an ammonia synthesis plant equipped with water or steam electrolysis units for producing hydrogen for ammonia synthesis gas, wherein the electrolysis units are powered by electricity from renewable energy sources such as solar, wind, or hydropower. Optionally, the electrolysis units may also be powered by electricity from thermonuclear power generation.

[0020] It will be understood that an ammonia cooling system encompasses a closed circuit and therefore can also be interpreted as, for example, an ammonia cooling circuit. The term "ammonia cooling circuit" can be used interchangeably with the term "ammonia refrigeration circuit."

[0021] The term "mechanical refrigeration" can be used interchangeably with the terms "compressor-driven cooling circuit" or "compressor-driven ammonia cooling."

[0022] The term "ammonia evaporator" is used interchangeably with the term "ammonia cooler" or simply "cooler." It should also be understood that the terms "ammonia evaporator" or "cooler" refer to one or more ammonia evaporators, i.e., one or more coolers.

[0023] A similar interpretation can apply to other units. For example, the term "absorption cooling unit" means one or more absorption cooling units.

[0024] Preferably, the ammonia cooling system consists of multiple ammonia evaporators, i.e., multiple coolers, for example, two coolers, arranged in series. The coolers can condense the ammonia in the ammonia product gas, and by providing multiple coolers, the energy efficiency of the plant or process can be increased.

[0025] An "off-gas cleaning system" refers to a device that removes ammonia from off-gas. Preferably, an off-gas cleaning system is a cleaning tower or scrubbing tower, and a scrubbing agent is used to wash away the ammonia present in the off-gas. It should be understood that "scrubbing agent" is synonymous with "absorbent."

[0026] The term "regeneration unit" is used interchangeably with the term "regeneration device."

[0027] The term "load" refers to the percentage of hydrogen supply used for ammonia synthesis in an ammonia synthesis plant relative to the load during normal operation (100% load). The plant's ammonia production capacity is assumed to be directly proportional to the hydrogen supply used. Therefore, a 10% load means that 10% of the hydrogen used for ammonia synthesis is relative to normal operation. The hydrogen used is obtained through water (steam) electrolysis, as is well known in the art. 100% load corresponds to the normal operation of an ammonia synthesis plant with a stable natural gas supply.

[0028] As described above, the term "turndown ratio," also simply called "turndown," refers to the ratio of the normal load of the upstream hydrocarbon feedstock, typically natural gas, used to produce ammonia synthesis gas and the resulting ammonia product gas, to the normal load that the ammonia synthesis plant can withstand. The terms "normal load" or "normal operation" may also be understood as meaning a state where the load is 100%. Thus, a 100% load, i.e., normal load, corresponds to a 100% turndown, and a 10% load corresponds to a 10% turndown.

[0029] The term "turndown" also applies to parts of an ammonia synthesis plant, such as units or equipment. Therefore, the term "turndown" also applies, for example, to steam turbines used to drive compressors in conventional ammonia refrigeration circuits. A 50% turndown of a steam turbine, for instance, refers to the ratio of operation at normal load to the amount the steam turbine can handle.

[0030] Currently, in ammonia plants operating under vastly different loads and rapid load fluctuations, such as green ammonia plants powered solely by renewable energy, absorption cooling has proven to be advantageous over mechanical refrigeration because ammonia cooling systems can be designed with better turndown ratios than those available in compressor-operated cooling units, and therefore can adapt to the fluctuations of a typical plant.

[0031] The absorption cooling according to the present invention is combined with off-gas cleaning, such as off-gas absorption, resulting in a cooling system layout that has considerably fewer device units than a conventional compressor-driven cooling circuit and a conventional off-gas cleaning unit.

[0032] While the use of absorption cooling for refrigeration in conventional ammonia synthesis plants is known, for energy-saving reasons, it has typically only been used to produce ammonia-aqueous solutions of the required concentration for the absorber. This invention differs in that at least ammonia and water are separated into nearly pure components. Thus, the ammonia cooling system is suitable for both the production of purified water, i.e., ammonia-free water, and the production of ammonia solution, some of which can be recovered as an additional ammonia product.

[0033] Therefore, the present invention makes it possible to replace conventional compressor-driven cooling circuits (i.e., mechanical refrigeration) and conventional off-gas absorption with a single system.

[0034] As used herein, the term “integration” means achieving synergistic effects when combining conventional standalone units or systems, such as significantly reducing the number of resulting device units.

[0035] In one embodiment, the off-gas cleaning unit (132) is an off-gas scrubbing unit, and it will be understood that the off-gas cleaning unit (132) is also configured to receive the ammonia gas flow (139) at the top of the tower from the regeneration unit (126), for example, mixed with the off-gas ammonia flow (143).

[0036] As described above, preferably, the off-gas ammonia flow also includes the top-of-stack ammonia gas flow from the regeneration unit. Accordingly, in certain embodiments, means such as a junction unit or mixing unit are also provided for adding and mixing the top-of-stack ammonia gas flow with the off-gas ammonia flow. The thus mixed flow is supplied to the off-gas cleaning unit. For the purposes of this application, the term “junction” means “joint.”

[0037] This achieves further integration. For environmental reasons, off-gases containing ammonia, such as slip gases from upstream ammonia synthesis plants and the ammonia cooling system itself, need to be cleaned. The off-gases containing ammonia are scrubbed with pure water produced in the bottom flow of the ammonia cooling system, more specifically the regenerator, to recover ammonia and minimize ammonia leakage into the atmosphere. The water flow from the off-gas cleaning unit thus produced is added to an absorption cooler, such as a mixing vessel, to recover ammonia as a product downstream and send the purified water back to the off-gas cleaning unit.

[0038] Therefore, in one embodiment, the absorption cooling unit is a mixing container containing water.

[0039] The ammonia present in the off-gas ammonia stream and the ammonia gas stream at the top of the column is reduced to levels unattainable in conventional plants or processes, resulting in ammonia-containing streams being discarded to the end user, which is highly undesirable. The present invention reduces the ammonia content in the ammonia-depleted off-gas stream from the off-gas cleaning unit to less than 10 ppmv, for example, 7 or 5 ppmv. The off-gas ammonia stream entering the off-gas cleaning unit may contain, for example, 10-15% (mol%) ammonia, and the ammonia gas stream at the top of the column may contain, for example, 80-90% ammonia.

[0040] In a first aspect of the present invention, in the ammonia cooling system, the heat exchange medium of the ammonia evaporator is the ammonia product gas flow.

[0041] This allows the ammonia cooling system to be fully integrated within the ammonia synthesis plant. Apart from green ammonia synthesis plants that inherently have fluctuating power supplies due to the intermittent nature of renewable energy sources such as wind, solar, and hydroelectric power, the present invention is also suitable for cooling ammonia product gases in any ammonia synthesis plant having a fluctuating power supply or a fluctuating hydrocarbon supply.

[0042] In an embodiment according to a first aspect of the present invention, the ammonia cooling system comprises an upper section (I) and a lower section (II) in the regeneration unit; The aforementioned lower section (II) A power-driven heating device and / or a reboiling unit arranged to receive a heat exchange medium; and, An outlet for extracting the purified water flow as a bottom flow; Equipped with, The aforementioned upper section (I) -Concentrated ammonia-Inlet for receiving water flow, -The top of the tower includes the following: An outlet for extracting the ammonia flow from the top of the aforementioned tower; An ammonia condensation unit positioned to receive the ammonia flow at the top of the tower and a cooling medium such as water to generate the condensed ammonia flow at the top of the tower; A separation unit, preferably an ammonia recovery drum, is positioned to receive the condensed ammonia flow from the top of the column, the separation unit comprising an outlet for removing a liquid ammonia fraction and an outlet for removing a gaseous ammonia flow from the top of the column; A reflux pump is positioned to receive the aforementioned ammonia liquid fraction and guide a portion of it to the top of the column as reflux at the top of the column; Means for extracting the remaining portion of the ammonia liquid fraction as the ammonia liquid stream.

[0043] The term "reboiling unit" can be used interchangeably with the term "reboiler."

[0044] The term "ammonia condensation unit" can be used interchangeably with the term "ammonia condenser."

[0045] The term "power-driven heating device" refers to a heating element that uses electricity as its power source, thereby converting electricity or electrical energy into heat, for example, through a process such as Joule heating.

[0046] Unlike conventional ammonia absorption systems, such as those shown in Figure 1, where the ammonia-water mixture is sent to a distillation column, the ammonia at the top of the column is condensed and used for cooling in an ammonia evaporator (chiller), and therefore there is no reflux at the top of the column, the present invention, as shown in Figure 2, enables reflux at the top of the column, thereby realizing a distillation column with fewer trays, and at the same time, the purified water stream from the bottom of the distillation column can be used as a scrubbing agent (e.g., an absorbent) in an off-gas washing unit.

[0047] Furthermore, conventional ammonia absorption systems required the addition of a considerable amount of demineralized water, but the present invention significantly reduces such required amounts.

[0048] In a first embodiment of the present invention, the ammonia synthesis plant further comprises one or more steam boilers positioned upstream of the ammonia cooling system to receive the ammonia product gas stream, recover heat therefrom, and generate steam, and the plant further comprises supplying at least a portion of the steam as a heat exchange medium to the reboiling unit i.e., the reboiler.

[0049] A reboiler is, as is well known in the art, a heat exchanger, such as a tube-and-shell heat exchanger, which supplies the heat necessary to boil a liquid from the bottom of the reboiler, and the reboiler is preferably a distillation column, which generates steam that is returned to the distillation column to drive the separation of ammonia.

[0050] As a result, in this invention, the reboiler load follows the load of ammonia production, and therefore, balanced use of steam is possible even at any turndown level, particularly well below 100%, for example, 10%, i.e., when the load of the ammonia synthesis plant is 10%. In other words, it is possible to balance the steam produced in the ammonia synthesis plant with the steam used in the ammonia cooling system at any operating load, for example, between 10% and 100%.

[0051] The steam generated in the ammonia synthesis plant can preferably be supplied at a pressure level that matches the pressure level required by the reboiler, thereby enabling thermal efficiency at least as high as that of mechanical refrigeration. Preferably, the steam is medium-pressure steam, for example, steam at 50 bar (264°C).

[0052] Furthermore, when operating at a low turndown rate of less than 50%, such as 30% or 10%, the availability of the steam generated by ammonia synthesis to external users is limited, if possible. The present invention also solves this problem by linking an ammonia cooling system adapted for absorption cooling with a dynamic ammonia synthesis gas plant having fluctuating ammonia and steam production, such as a green ammonia synthesis plant.

[0053] Furthermore, the present invention eliminates the use of a steam turbine connected to the operation of conventional ammonia cooling circuits. More specifically, since ammonia cooling systems do not have a centrifugal compressor and are usually driven by such a steam turbine, the steam turbine is absent.

[0054] A power-driven heating device is provided instead of, or in combination with, a reboiler. This heating device is preferably fitted into the regenerator at its bottom. This achieves greater flexibility, as the power required for the heating device can be supplied from a renewable energy source, as described above, and if for any reason the steam reboiler requirements cannot be met, the power-driven heating device will supply the necessary heat within the regenerator. Furthermore, under transient conditions such as during startup, the regenerator can be operated solely by the power-driven heating device.

[0055] In an embodiment according to a first aspect of the present invention, the ammonia cooling system further comprises an ammonia evaporator for taking out a purge ammonia flow, and the ammonia cooling system further comprises, upstream of the regeneration unit, means such as a joining unit or mixing unit for combining the purge ammonia flow with the condensed ammonia-water flow.

[0056] Because an outlet for extracting the purge ammonia flow, i.e., a liquid blowdown outlet, is provided, water does not accumulate inside the cooler.

[0057] Preferably, an ammonia recovery and circulation pump guides the combined flow to a regeneration unit.

[0058] For example, the condensed ammonia-water flow after adding a purge flow from a cooler contains, for example, 30-50% by mass of ammonia, or 35, 40, or 45% by mass of ammonia, with the remainder being water.

[0059] In conventional systems, as shown in Figure 1, for example, the purge ammonia stream from the cooler is sent directly to the distillation column. As in the present invention, by combining the purge ammonia stream with the condensed ammonia-water stream, a single pump is used to supply ammonia-water to the regenerator, thereby improving energy efficiency. The purge stream from the ammonia evaporator, instead of being discarded as acidic water, contains not only ammonia but also water, which is then recovered.

[0060] In an embodiment according to a first aspect of the present invention, the ammonia cooling system further comprises: A heat exchanger, also referred to below as an aftercooler, is located upstream of the ammonia evaporator and is positioned to receive the ammonia liquid flow and a cooling medium such as water as the heat exchange medium, in order to cool the ammonia liquid flow before it enters the ammonia evaporator.

[0061] In an embodiment according to a first aspect of the present invention, the regeneration unit of the ammonia cooling system further comprises a feed / e heat exchanger (F / E HEX) arranged to receive a flow resulting from combining the condensed ammonia-water flow or the purge ammonia flow with the condensed ammonia-water flow, which is arranged to receive the purified water flow as a heat exchange medium to preheat the condensed ammonia-water flow before it enters the regeneration unit, or to preheat the flow resulting from combining the condensed ammonia-water flow and the purge ammonia flow.

[0062] Preferably, the purified water stream thus cooled is further cooled in an additional heat exchanger (hereinafter also referred to as an ammonia recovery cooler). This additional unit is preferably arranged to receive the purified water stream and a cooling medium such as water as a heat exchange medium in order to further cool the purified water stream before it enters the off-gas cleaning unit.

[0063] By providing F / E HEX and preferably an ammonia recovery cooler, it is possible to maintain energy efficiency at least comparable to that obtained when mechanical refrigeration is used instead, where such a heat exchanger is not typically required.

[0064] In a first embodiment of the present invention, the ammonia cooling system further comprises a conduit for taking out a portion of the purge ammonia flow or the liquid ammonia flow as additional ammonia products suitable for discharge as excess ammonia products.

[0065] Preferably, the remaining portion of the ammonia liquid fraction at the top of the regeneration unit is taken out as the ammonia liquid stream.

[0066] While known (conventional) ammonia cooling circuits using ammonia absorption generate ammonia at the top of the column from a regenerator, which is condensed and collected in a drum at the top of the column and then used for cooling, and the relatively water-rich bottom flow of the regenerator is then used for absorption as a recycled flow (see, for example, Figure 1), the present invention makes it possible to use the ammonia flow at the top of the column from the regenerator, which is then condensed and collected in a drum at the top of the column, not only for cooling, i.e., not only for use as ammonia, but also in the drum at the top of the column. The present invention makes it possible to use the ammonia flow at the top of the column from the regenerator, which is condensed and recovered in a drum at the top of the column, not only for cooling, i.e., for use in an ammonia evaporator, but also as part of the ammonia product pool, and at the same time, it mitigates problems related to load fluctuations and turndown, particularly in green ammonia synthesis plants, below 100% (see Figure 2).

[0067] Furthermore, in conventional ammonia cooling circuits using ammonia absorption, a bottom flow typically rich in about 25% by mass of ammonia and 75% water is generated in the regenerator, and this bottom flow is recycled to the absorber by combining with the ammonia vapor flow from the ammonia cooler. However, with the present invention, the purified water bottom flow from the regenerator according to the present invention has far more than 75% water, for example, at least 99%, i.e., pure water. The pure water is advantageously used in the off-gas scrubber, avoiding the need to rely on an external source of pure water, such as the use of demineralized water.

[0068] In a second embodiment, the present invention relates to a method for producing ammonia product gas from an ammonia synthesis gas stream containing hydrogen and nitrogen, wherein the method also produces an off-gas ammonia stream, and the method comprises the following steps: a) Any electrolysis of water or steam for producing the hydrogen; the electrolysis is preferably powered by electricity from a renewable energy source such as solar, wind, or hydroelectric power; b) A step of converting ammonia synthesis gas into ammonia product gas in an ammonia synthesis converter; The step further includes cooling the ammonia product gas according to the following steps: c) Evaporating a liquid ammonia stream in an ammonia evaporator and supplying the ammonia product gas as a heat exchange medium to generate an ammonia vapor stream; d) A step of supplying the off-gas ammonia stream to an off-gas cleaning unit with the addition of a water stream and a purified water stream as a scrubbing agent (absorbent) to generate an ammonia-depleted off-gas stream; e) Steps of taking the water stream from the off-gas cleaning device and supplying it, together with the ammonia vapor stream, to an absorption cooling unit under the supply of a cooling medium such as water to generate and collect a condensed ammonia-water stream; f) The step of taking the condensed ammonia-water flow from the absorption cooling unit and supplying it to a regeneration unit such as a distillation column to generate the ammonia liquid flow, the ammonia gas flow at the top of the column, and the purified water flow.

[0069] Compared to conventional compressor-driven ammonia cooling circuits and conventional off-gas absorption units, this combination of absorption cooling and off-gas absorption, as related to the first aspect of the present invention, results in a much simpler process layout with significantly fewer equipment units and fewer process steps. This achieves a high degree of process and plant integration.

[0070] In ammonia production methods operating under vastly different loads and rapid load fluctuations, such as green ammonia plants powered solely by renewable energy, providing absorption cooling instead of conventional, more efficient compressor-driven ammonia cooling (mechanical refrigeration) has been found to offer a better turn-town ratio than mechanical refrigeration and to keep pace with typical plant fluctuations.

[0071] In a second embodiment of the present invention, the method further includes the following steps: g) A step of supplying the ammonia gas flow from the top of the tower to the off-gas cleaning device.

[0072] Slip flows within processes and plants containing ammonia, such as off-gas ammonia flows generated upstream to avoid the accumulation of inert substances during the conversion of ammonia synthesis gas to ammonia product gases, and top-of-the-stack ammonia gas flows now generated in regeneration units, are advantageously treated in off-gas cleaning units. This also relieves end-users of the burden of finding a way to treat top-of-the-stack ammonia flows.

[0073] In an embodiment according to a second aspect of the present invention, prior to step c), the ammonia product gas is cooled first by passing it through one or more steam boilers for generating steam, preferably medium-pressure steam, and in step f), the regeneration unit comprises a power-driven heating device or a reboiling unit, and the method further comprises supplying the steam to the reboiling unit.

[0074] Conventionally, when ammonia product gas cooling is provided by a multi-stage cooling compressor operating at multiple pressure levels, ammonia cooling can be provided with high energy efficiency at high loads, but at low loads, it has been found that a complex process and plant layout arise due to compressor limitations, including low efficiency at low loads. This is problematic when the plant load fluctuates greatly and the compressor is steam-driven. At full plant load, enough steam produced as a byproduct in the ammonia plant is generated to power the compressor for ammonia cooling, but this is not possible at low loads.

[0075] Now, with this invention, the generated steam can be adjusted to the steam needed for use as a heat exchange medium in, for example, a reboiler in a regenerator. The use of a steam turbine required for cooling the compressor drive can be avoided.

[0076] Furthermore, greater flexibility in the method is achieved by providing a power-driven heating device suitably fitted to the bottom of the regenerator. The power required for the heating device can be supplied from renewable resources, and if for any reason the steam reboiler requirements cannot be met, the power-driven heating device supplies the necessary heat to the regenerator. Moreover, as relating to the first aspect of the present invention, under transient conditions such as startup, the regenerator can be operated solely by the power-driven heating device.

[0077] In an embodiment according to a second aspect of the present invention, in step c), a purge ammonia flow (liquid blowdown) is generated, and the method further includes taking out the purge ammonia flow and combining it with the condensed ammonia-water flow.

[0078] The purge flow from the ammonia evaporator contains not only ammonia but also water, and is recovered instead of being discarded as acidic water. Furthermore, by removing the purge ammonia flow, water does not accumulate in the cooler.

[0079] In a second embodiment of the present invention, the method further includes diverting a portion of the liquid ammonia stream or the purged ammonia stream (i.e., liquid blowdown from the cooler) as an additional ammonia product. Thus, either stream is utilized as an excess ammonia effluent.

[0080] This method allows for the generation of additional valuable ammonia products, in addition to cooling the ammonia product gas, instead of simply having a closed ammonia cooling circuit. For example, the liquid ammonia stream, some of which is diverted as additional ammonia products, has a purity of at least 99.5% by mass of NH3.

[0081] It will be understood that any embodiment of the first aspect of the present invention and any related advantages can be used in conjunction with the second aspect of the present invention, and vice versa. [Brief explanation of the drawing]

[0082] Figure 1 shows an ammonia cooling system according to prior art, more specifically, an ammonia cooling circuit with absorption cooling according to prior art.

[0083] Figure 2 shows an absorption-type ammonia cooling system according to one embodiment of the present invention. [Modes for carrying out the invention]

[0084] Referring to both figures, absorption cooling is used in the ammonia cooling circuit. The basic principle is to absorb ammonia vapor from the ammonia cooler into a liquid ammonia-water mixture and remove the heat of absorption by water cooling. The resulting condensed ammonia-water mixture is sent to a regenerator (distillation column), where the ammonia at the top of the column is condensed and used for cooling (Figures 1 and 2), and optionally used as an additional ammonia product (Figure 2). Meanwhile, the bottom product from the regenerator is either used directly for ammonia absorption (Figure 1) or used as a pure water stream in an off-gas washing unit (Figure 2).

[0085] Referring specifically to Figure 1 from the prior art, an ammonia cooling circuit 10 is shown. A liquid ammonia flow 1 from an ammonia recovery drum 12 passes through a first exchanger 14 located upstream of an ammonia evaporator (chiller) 16, using an ammonia vapor flow 7 as the heat exchange medium. The resulting liquid ammonia flow 1' is then evaporated in the cooler 16 using an ammonia product gas 5 from an ammonia synthesis converter (not shown) of an ammonia synthesis plant, thereby producing an ammonia vapor flow 7. After being supplied for cooling in the heat exchanger 14, the ammonia vapor flow 7' is combined with a water-heavy bottom flow 25' from a regenerator (distillation column) 26, which has numerous trays 26' arranged in its upper section I, such as 25% ammonia by mass / 75% water by mass. The ammonia-water mixture flow is then led to an absorber 18, which consists of a cooler 18' and a mixing vessel 18''. The cooling water 39 in the cooling unit 18'' removes absorbed heat, thereby producing a condensed ammonia-water flow 15, which is supplied to the mixing vessel 18''. The condensed ammonia-water flow 19 is drawn out of the mixing vessel 18'', transported via pump 22, heated in heat exchanger 24 using the bottom flow 25 from the regenerator 26 as a heat exchange medium, and supplied to the regenerator 26 as flow 21. The purged ammonia flow (liquid blowdown) 29 is transported to the top of the regenerator 26 via a separate pump 20.

[0086] The regenerator 26 includes an upper section I and a lower section II. The lower section is equipped with a reboiler 28 that boils the bottom liquid 33 and generates steam 35 to drive distillation separation. The reboiler 28 is typically driven by steam 37 generated by a steam turbine (not shown). The ammonia flow 23 at the top of the column is drawn out and guided to the ammonia condenser 30 using a cooling medium 41 such as water. The condensed ammonia flow 27 is then guided to the ammonia recovery drum 12, from which the liquid ammonia flow 1 is drawn out, thereby closing the ammonia cooling circuit.

[0087] When mechanical refrigeration is used under the same load, a centrifugal compressor driven by a condensing steam turbine is required. The compressor replaces the absorber 18 with a heat exchanger 14, a cooling unit 18'' and a mixing vessel 18'', a heat exchanger 24, a reboiler 28, a regenerator 26, pumps 22 and 20.

[0088] In this invention, in a condenser for processing nearly pure ammonia, ammonia vapor boils at low pressure, thereby cooling and partially condensing the ammonia product gas (optionally ammonia synthesis gas) on the tubular side. The ammonia vapor is sent to an absorber, preferably a mixing vessel containing mostly water, where it is absorbed by the water. The condensed mixture of ammonia and water is then sent to a regenerator, preferably a distillation column. Pure ammonia, i.e., 99% by mass or more of ammonia, for example, 99.5% by mass or more of ammonia, is recycled back to the condenser as a liquid ammonia stream. Excess ammonia is preferably also removed by a condenser purge stream, i.e., a liquid blowdown from the condenser. The purified water from the regenerator is sent to an off-gas scrubbing unit to remove ammonia from the off-gas to a very low level, for example, less than 10 ppm ammonia. From the bottom of the off-gas scrubbing unit, the water is sent to a mixing vessel.

[0089] Therefore, with specific reference to Figure 2 according to an embodiment of the present invention, an ammonia cooling system 100 is shown. The liquid ammonia flow 101'', separated from the reflux flow 101' at the top of the tower in the downstream regenerator 126, passes through a heat exchanger 114 (for example, an aftercooler using cooling water 131 as a heat exchange medium) and is placed in the upstream ammonia evaporator (chiller) 116. The liquid ammonia flow 101'' thus cooled iv Next, using the ammonia product gas 105 from the ammonia synthesis converter of an ammonia synthesis plant (not shown), it is evaporated in the cooler 116. This generates an ammonia vapor stream 107, which is led to the absorber 118, which includes the cooling unit 118' and the mixing vessel 118''. Cooling water in the cooler 118' 140 The absorber removes the heat of absorption, thereby generating a condensed ammonia-water stream 119, which is drawn from the mixing vessel 118'', transported via pump 122, heated by the supply / discharge heat exchanger 124 using the bottom stream 125 from the regenerator 126 as the heat exchange medium, and supplied to the regenerator 126 as stream 121. The thus cooled generated stream 125' is further cooled in the ammonia recovery cooler 144, for example using cooling water 147, to become stream 125''. The purged ammonia stream (liquid blowdown) 129 is preferably appropriately combined with the condensed ammonia-water stream 119 from the absorber 118 before being transported to the regenerator 126 via pump 122. Excess ammonia 129' is preferably also discharged from the cooler purge stream 129.

[0090] The regenerator 126 includes an upper section I containing a number of trays 126' and a lower section II. The lower section is provided with a reboiler 128 that boils the bottom liquid 133 and generates steam 135 to drive the distillation separation. The reboiler 128 is driven by steam 137, which is preferably generated in a steam boiler for cooling the ammonia product gas coming out of the ammonia converter and thus supplied to the ammonia product gas 105. The lower section II of the regenerator 126 may also include a power-driven heating device (not shown) that is adapted, for example, to the bottom of the column. The upper section I includes a top section: the top ammonia stream 123 is drawn out and led to an ammonia condenser 130 using a cooling medium 141 such as water. The thus condensed top ammonia stream 127 is led to a separation unit 112, preferably an ammonia recovery drum, from which the ammonia liquid fraction 101 is taken out, as well as the top ammonia gas stream 139. A reflux pump 134 is positioned to transport the liquid ammonia fractions 101 and 101' and direct a portion of them to the top of the regenerator 126 as a reflux flow 101'' at the top of the column. The remaining portion of the liquid ammonia fraction is reused as a liquid ammonia flow 101''.

[0091] In the lower section II of the regenerator 126, the reboiler 128 is driven by steam 137 produced by one or more steam boilers (not shown) that recover heat from the ammonia product gas stream. This makes it possible to balance the steam produced in the ammonia synthesis plant, for example, the upstream ammonia synthesis loop, with the steam used in the ammonia cooling system 100 at any operating load between 10 and 100%, or with any corresponding turndown. A steam turbine is not required. Furthermore, from the separation unit 112 at the top of the regenerator 126, the liquid ammonia streams 101''', 101 used in the ammonia cooler 16 are supplied. iv Separately, flow 101 is used as additional ammonia product, such as for the discharge of excess ammonia. v You can obtain this.

[0092] Furthermore, instead of recycling the bottom flow 25 from the regenerator 26 to the absorber 18 in Figure 1, bottom purified water flows 125, 125', and 125'' containing at least 99% by mass of water, for example 99.98 mol% or more of H2O, or 100 mol% H2O with NH3 less than 50 ppmv, are preferably led together with the top ammonia gas flow 139 to the off-gas scrubbing unit 132 to remove ammonia from the off-gas ammonia flow 143 produced in the ammonia synthesis plant. Thus, the purified water flow 125'' is used as a scrubbing agent. From the off-gas scrubbing unit 132, for example, the off-gas scrubber, the water flow 117 is taken out as the bottom flow and then sent to the absorber 118 together with the ammonia vapor flow 107 from the cooler 116. From the off-gas scrubbing unit 132, a clean off-gas flow, i.e., an ammonia-depleted off-gas flow 145 with NH3 less than 10 ppmv, for example, less than 7 ppmv, is taken out. This invention includes the following items. [Item 1] An ammonia synthesis plant comprising an ammonia synthesis converter and a downstream ammonia cooling system (100), Here, the ammonia synthesis converter is configured to receive ammonia synthesis gas containing hydrogen and nitrogen and produce an ammonia product gas stream (105), and the ammonia synthesis plant is configured to generate an off-gas ammonia stream (143). Here, the ammonia cooling system (100) is - Ammonia liquid flow (101, 101', 101''', 101 iv An ammonia evaporator (116) for evaporating (105) and generating an ammonia vapor stream (107), wherein the heat exchange medium of the ammonia evaporator (116) is the ammonia product gas stream (105); - An off-gas scrubbing unit (132) for scrubbing the off-gas ammonia stream (143) with the addition of water as a scrubbing agent to generate a water stream (117) and an ammonia-depleted off-gas stream (145); - An absorption cooling unit (118) containing water for cooling the ammonia vapor stream (107) and collecting the condensed ammonia-water stream (119); -From the condensed ammonia-water stream (119, 121) Purified water stream (125, 125', 125''), The ammonia liquid flow (101, 101', 101''', 101 iv )and Ammonia gas flow at the top of the tower (139); A regeneration unit (126) for generating the output; Includes, Furthermore, here, - The ammonia evaporator (116) is the ammonia liquid flow (101, 101', 101''', 101 iv ) and the ammonia liquid flow (101, 101', 101''', 101 iv The device is arranged to receive the heat exchange medium (105) for evaporating the ammonia vapor and generate the ammonia vapor flow (107); - The off-gas cleaning unit (132), preferably the off-gas scrubbing unit, is configured to receive the purified water stream (125, 125', 125'') and the off-gas ammonia stream (143) from the regeneration unit as a scrubbing agent to generate the ammonia-depleted off-gas stream (145) and the water stream (117); -The absorption cooling unit (118), preferably a mixing vessel (118'') containing water, is arranged to receive the water flow (117) and the ammonia vapor flow (107), thereby generating and collecting the condensed ammonia-water flow (119), and the absorption cooling unit further includes a cooling device (118'), e.g., a coil, arranged to receive a cooling medium (139), e.g., water, and an outlet for taking out the condensed ammonia-water flow (119); - The regeneration unit (126) is a distillation column arranged to receive the condensed ammonia-water stream (119, 121), and the regeneration unit (126) comprises an outlet for taking out the purified water stream (125) as a bottom stream, an outlet for taking out the ammonia stream (123) at the top of the column, and a separation unit (112) for separating the ammonia gas stream (139) and the ammonia liquid stream (101) at the top of the column from the ammonia stream (123). The aforementioned ammonia synthesis plant. [Item 2] The ammonia synthesis plant according to item 1, comprising a water or steam electrolysis unit for producing the hydrogen, wherein the electrolysis unit is powered by electricity from a renewable energy source, such as solar, wind, or hydroelectric power. [Item 3] The ammonia synthesis plant according to any one of items 1 to 2, wherein the off-gas cleaning unit (132) is an off-gas scrubbing unit, and the off-gas cleaning unit (132) is further configured to receive the ammonia gas stream (139) from the top of the tower from the regeneration unit (126), for example, mixed with the off-gas ammonia stream (143). [Item 4] The ammonia synthesis plant according to item 3, wherein the ammonia cooling system (100) further comprises means for adding and mixing the ammonia gas flow (139) at the top of the tower with the off-gas ammonia flow (143), for example, a joining unit or a mixing unit. [Item 5] The ammonia synthesis plant according to any one of items 1 to 4, wherein the absorption cooling unit (118) is a mixing vessel (118'') containing water. [Item 6] In the ammonia cooling device (100), the regeneration unit (126) comprises an upper section (I) and a lower section (II), The aforementioned lower section (II) is, A power-driven heating device and / or reboiling unit (128) arranged to receive a heat exchange medium (137); and An outlet for extracting the purified water flow (125) as a bottom flow; Equipped with, The aforementioned upper section (I) -Inlet for receiving condensed ammonia-water flow (119, 121), -The top of the tower includes the following: • An outlet for extracting the ammonia flow (123) from the top of the tower; - An ammonia condensation unit (130) positioned to receive the ammonia flow (123) at the top of the tower and a cooling medium (141), such as water, for generating a condensed ammonia flow (127) at the top of the tower; A separation unit (112), preferably an ammonia recovery drum, is positioned to receive the condensed ammonia flow (127) from the top of the column, and comprises an outlet for removing ammonia liquid fraction (101) and an outlet for removing ammonia gas flow (139) from the top of the column; A reflux pump (134) is positioned to receive the ammonia liquid fraction (101) and direct a portion of it to the top of the column as reflux flow (101''); • Means for extracting the remaining portion of the ammonia liquid fraction as the ammonia liquid stream (101'''), Equipped with, An ammonia synthesis plant as described in any of items 1-5. [Item 7] An ammonia synthesis plant as described in item 6, further comprising one or more steam boilers positioned upstream of the ammonia cooling system (100) to receive the ammonia product gas stream (105) and to recover heat therefrom and generate steam, wherein the plant is further configured to supply at least a portion of the steam as a heat exchange medium (137) to the reboiling unit (128). [Item 8] An ammonia synthesis plant according to any one of items 1 to 7, wherein the ammonia cooling system (100) further comprises an outlet for taking out a purge ammonia flow (129), and the ammonia cooling system (100) further comprises, upstream of the regeneration unit (126), means for combining the purge ammonia flow (129) with the condensed ammonia-water flow (119), for example, a joining unit or a mixing unit. [Item 9] An ammonia synthesis plant according to any one of items 1 to 8, wherein the regeneration unit (126) of the ammonia cooling system (100) further comprises a feed / outlet heat exchanger (F / E HEX) 124 arranged to receive the condensed ammonia-water flow (119) or the flow (121) resulting from combining the condensed ammonia-water flow (129) with the condensed ammonia-water flow (119), the feed / outlet heat exchanger (F / E HEX) 124 for receiving the purified water flow (125) as a heat exchange medium for preheating the condensed ammonia-water flow (119) or the flow (121) resulting from combining the condensed ammonia-water flow (119) with the purged ammonia flow (129). [Item 10] The ammonia cooling system (100) discharges additional ammonia products (129', 101''') from the purge ammonia flow (129) or the liquid ammonia flow (101''') as excess ammonia products. v An ammonia synthesis plant as described in any of items 1 to 9, further comprising conduits for extracting a portion of it as an ammonia. [Item 11] A method for producing ammonia product gas (105) from an ammonia synthesis gas stream containing hydrogen and nitrogen, The above method also produces an off-gas ammonia stream (143), The aforementioned method, a) Any electrolysis step of water or steam for producing the hydrogen; the electrolysis preferably uses electricity from a renewable energy source, such as solar, wind, or hydroelectric power; b) A step of converting ammonia synthesis gas to the ammonia product gas (105) in an ammonia synthesis converter; Includes, The above method follows the next step: c) In an ammonia evaporator (116) for generating an ammonia vapor flow (107) while supplying the ammonia product gas (105) as a heat exchange medium, a liquid ammonia flow (101, 101', 101''', 101 iv ) step to evaporate; d) The step of supplying the off-gas ammonia stream (143) to the off-gas scrubbing unit (132) with the addition of purified water streams (125, 125', 125'') as a scrubbing agent in order to generate a water stream (117) and an ammonia-depleting off-gas stream (145); e) The step of taking the water stream (117) from the off-gas cleaning unit (132) and supplying it to an absorption cooling unit (118) together with the ammonia vapor stream (107) under the supply of a cooling medium (139), such as water, in order to generate and collect the condensed ammonia-water stream (119); f) The condensed ammonia-water flow (119) is taken from the absorption cooling unit (118) and supplied to the regeneration unit (126), and the ammonia liquid flow (101, 101', 101''', 101 iv ), a step of generating an ammonia gas stream (139) and a purified water stream (125) at the top of the column; The method further comprises cooling the ammonia product gas according to the following. [Item 12] g) The method according to item 11, further comprising the step of supplying the ammonia gas stream (139) at the top of the tower to the off-gas cleaning unit (132). [Item 13] A method according to any one of items 11 to 12, wherein, prior to step c), the ammonia product gas (105) is first cooled by passing it through one or more steam boilers to generate steam, and, in step f), the regeneration unit (126) includes a power-driven heating device or a reboiling unit (128), and the method further comprises supplying the steam (137) to the reboiling unit (128). [Item 14] A method according to any one of items 11 to 13, wherein in step c), a purge ammonia stream (129) is generated, and the method further comprises taking out the purge ammonia stream (129) and combining it with the condensed ammonia-water stream (119). [Item 15] A method according to any one of items 11 to 14, wherein a portion of the liquid ammonia flow (101'') or the purged ammonia flow (129) is used to produce additional ammonia products (101''). v A method that further includes repurposing it as ,129').

Claims

1. An ammonia synthesis plant comprising an ammonia synthesis converter and a downstream ammonia cooling system (100), Here, the ammonia synthesis converter is configured to receive ammonia synthesis gas containing hydrogen and nitrogen and produce an ammonia product gas stream (105), and the ammonia synthesis plant is configured to generate an off-gas ammonia stream (143). Here, the ammonia cooling system (100) is - Ammonia liquid flow (10¹, 10¹', 10¹'', 10¹ ｉｖ An ammonia evaporator (116) for evaporating (105) and generating an ammonia vapor stream (107), wherein the heat exchange medium of the ammonia evaporator (116) is the ammonia product gas stream (105); - Off-gas scrubbing unit (132) for scrubbing the off-gas ammonia stream (143) with the addition of water as a scrubbing agent to generate a water stream (117) and an ammonia-depleted off-gas stream (145); - An absorption cooling unit (118) containing water for cooling the ammonia vapor stream (107) and collecting the condensed ammonia-water stream (119); - The condensed ammonia - from the water stream (119, 121) Purified water stream (125, 125', 125''), The ammonia liquid flow (101, 101', 101'', 101 ｉｖ )and Ammonia gas flow at the top of the tower (139); A regeneration unit (126) for generating; Includes, Furthermore, here, - The ammonia evaporator (116) is the ammonia liquid flow (101, 101', 101''', 101 ｉｖ ) and the ammonia liquid flow (101, 101', 101''', 101 ｉｖ The heat exchange medium (105) for evaporating the ammonia vapor is arranged to receive the ammonia vapor flow (107); - The off-gas scrubbing unit (132) is configured to receive the purified water streams (125, 125', 125'') and the off-gas ammonia stream (143) from the regeneration unit as scrubbing agents to generate the ammonia-depleted off-gas stream (145) and the water stream (117); - The absorption cooling unit (118) is arranged to receive the water flow (117) and the ammonia vapor flow (107), thereby generating and collecting the condensed ammonia-water flow (119), and the absorption cooling unit further includes a cooling device (118') arranged to receive a cooling medium (140), and an outlet for taking out the condensed ammonia-water flow (119); - The regeneration unit (126) is a distillation column arranged to receive the condensed ammonia-water stream (119, 121), and the regeneration unit (126) comprises an outlet for taking out the purified water stream (125) as a bottom stream, an outlet for taking out the ammonia stream (123) at the top of the column, and a separation unit (112) for separating the ammonia gas stream (139) and the liquid ammonia stream (101) at the top of the column from the ammonia stream (123) at the top of the column. The aforementioned ammonia synthesis plant.

2. The ammonia synthesis plant according to claim 1, comprising a water or steam electrolysis unit for producing the hydrogen, wherein the electrolysis unit is powered by electricity from a renewable energy source.

3. The ammonia synthesis plant according to claim 1 or 2, wherein the off-gas cleaning unit (132) is an off-gas scrubbing unit, and the off-gas cleaning unit (132) is further configured to receive the ammonia gas stream (139) from the top of the tower from the regeneration unit (126) and mix it with the off-gas ammonia stream (143).

4. The ammonia synthesis plant according to claim 3, wherein the ammonia cooling system (100) further comprises means for adding and mixing the ammonia gas flow (139) at the top of the tower with the off-gas ammonia flow (143).

5. The ammonia synthesis plant according to claim 1 or 2, wherein the absorption cooling unit (118) is a mixing container (118'') containing water.

6. In the ammonia cooling system (100), the regeneration unit (126) comprises an upper section (I) and a lower section (II), The aforementioned lower section (II) is, A power-driven heating device and / or reboiling unit (128) arranged to receive a heat exchange medium (137); and An outlet for extracting the purified water flow (125) as a bottom flow; Equipped with, The aforementioned upper section (I) -Condensed ammonia-Inlet for receiving water flow (119, 121), - The top of the tower includes the following: - An outlet for extracting the ammonia flow (123) from the top of the tower; - Ammonia condensation unit (130) positioned to receive the ammonia flow (123) and cooling medium (141) at the top of the column, for generating a condensed ammonia flow (127) at the top of the column; - A separation unit (112) positioned to receive the condensed ammonia flow (127) at the top of the column, comprising an outlet for extracting a liquid ammonia fraction (101) and an outlet for extracting a gaseous ammonia flow (139) at the top of the column; - A reflux pump (134) positioned to receive the ammonia liquid fraction (101) and direct a portion of it to the top of the column as reflux flow (101''); - Means for extracting the remaining portion of the ammonia liquid fraction as the ammonia liquid stream (101'''), Equipped with, The ammonia synthesis plant according to claim 1 or 2.

7. An ammonia synthesis plant according to claim 6, further comprising one or more steam boilers positioned upstream of the ammonia cooling system (100) to receive the ammonia product gas stream (105) and to recover heat therefrom and generate steam, wherein the plant is further configured to supply at least a portion of the steam as a heat exchange medium (137) to the reboiling unit (128).

8. The ammonia synthesis plant according to claim 1 or 2, wherein the ammonia cooling system (100) further comprises an outlet for taking out a purge ammonia flow (129), and the ammonia cooling system (100) further comprises, upstream of the regeneration unit (126), means for combining the purge ammonia flow (129) with the condensed ammonia-water flow (119).

9. The ammonia synthesis plant according to claim 1 or 2, wherein the regeneration unit (126) of the ammonia cooling system (100) further comprises a feed / outlet heat exchanger (F / E HEX) 124 arranged to receive the condensed ammonia-water flow (119) or a flow (121) resulting from combining the condensed ammonia-water flow (129) with the condensed ammonia-water flow (119), the feed / outlet heat exchanger (F / E HEX) 124 for receiving the purified water flow (125) as a heat exchange medium for preheating the condensed ammonia-water flow (119) or for preheating the flow (121) resulting from combining the condensed ammonia-water flow (119) with the purged ammonia flow (129).

10. The ammonia cooling system (100) discharges additional ammonia products (129', 101''') from the purged ammonia flow (129) or from the liquid ammonia flow (101''') as excess ammonia products. ｖ The ammonia synthesis plant according to claim 1 or 2, further comprising a conduit for extracting a portion of it as an ammonia.

11. A method for producing ammonia product gas (105) from an ammonia synthesis gas stream containing hydrogen and nitrogen, The above method also produces an off-gas ammonia stream (143), The aforementioned method, a) Any step of electrolysis of water or steam for producing the hydrogen; the electrolysis is powered by electricity from a renewable energy source; b) A step of converting the ammonia synthesis gas to the ammonia product gas (105) in an ammonia synthesis converter; Includes, The above method follows these steps: c) In an ammonia evaporator (116) for generating an ammonia vapor flow (107) while supplying the ammonia product gas (105) as a heat exchange medium, a liquid ammonia flow (101, 101', 101''', 101 ｉｖ ) step to evaporate; d) The step of supplying the off-gas ammonia stream (143) to the off-gas scrubbing unit (132) with the addition of purified water streams (125, 125', 125'') as a scrubbing agent in order to generate a water stream (117) and an ammonia-depleting off-gas stream (145); e) The step of taking the water stream (117) from the off-gas cleaning unit (132) and supplying it to an absorption cooling unit (118) together with the ammonia vapor stream (107) under the supply of a cooling medium (140) in order to generate and collect a condensed ammonia-water stream (119); f) The condensed ammonia-water flow (119) is taken out from the absorption cooling unit (118) and supplied to the regeneration unit (126), and the ammonia liquid flow (101, 101', 101''', 101 ｉｖ ), a step of generating an ammonia gas stream (139) and a purified water stream (125) at the top of the column; The method further comprises cooling the ammonia product gas according to the following.

12. g) The method according to claim 11, further comprising the step of supplying the ammonia gas flow (139) at the top of the tower to the off-gas cleaning unit (132).

13. A method according to claim 11 or 12, wherein, prior to step c), the ammonia product gas (105) is first cooled by passing it through one or more steam boilers to generate steam, and, in step f), the regeneration unit (126) includes a power-driven heating device or a reboiling unit (128), and the method further comprises supplying the steam (137) to the reboiling unit (128).

14. A method according to claim 11 or 12, wherein in step c), a purge ammonia stream (129) is generated, and the method further comprises taking out the purge ammonia stream (129) and combining it with the condensed ammonia-water stream (119).

15. A method according to claim 11 or 12, wherein a portion of the liquid ammonia flow (101'') or purged ammonia flow (129) is used to produce additional ammonia products (101''). ｖ A method that further includes repurposing it as 129'.

16. The ammonia synthesis plant according to claim 1, wherein the off-gas cleaning unit (132) is an off-gas scrubbing unit.

17. The ammonia synthesis plant according to claim 1, wherein the absorption cooling unit (118) is a mixing container (118'') containing water.

18. The ammonia synthesis plant according to claim 1, wherein the cooling device (118') is a coil.

19. The ammonia synthesis plant according to claim 1, wherein the cooling medium (140) is water.

20. The ammonia synthesis plant according to claim 2, wherein the renewable energy source is electricity from solar, wind, or hydroelectric power.

21. The ammonia synthesis plant according to claim 4, wherein the means for adding and mixing the ammonia gas stream (139) at the top of the tower with the off-gas ammonia stream (143) is a joining unit or a mixing unit.

22. The ammonia synthesis plant according to claim 6, wherein the cooling medium (141) is water.

23. The ammonia synthesis plant according to claim 6, wherein the separation unit (112) is an ammonia recovery drum.

24. The ammonia synthesis plant according to claim 8, wherein the means for combining the purged ammonia stream (129) with the condensed ammonia-water stream (119) is a joining unit or a mixing unit.

25. The method according to claim 11, wherein the renewable energy source is electricity from solar, wind, or hydroelectric power.

26. The method according to claim 11, wherein the cooling medium is water.

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