Liquid ammonia preparation method and liquid ammonia preparation system

Abstract

The invention aims to provide a liquid ammonia preparation method and system, nitrogen and hydrogen are mixed according to a preset proportion and then conveyed to a feed gas compressor to obtain first compressed mixed gas, and the first compressed mixed gas is used as fresh gas to be mixed with second compressed mixed gas conveyed by a recycle gas compressor to obtain unreacted gas; unreacted gas is divided into two streams after being subjected to heat exchange and temperature rise through the first heat exchanger, the two streams respectively enter the upper part and the lower part of the ammonia synthesis tower, the first stream of unreacted gas is further subjected to heat exchange and temperature rise by utilizing heat released by ammonia synthesis reaction, is led to the lower part of the ammonia synthesis tower, and is mixed with the second stream of unreacted gas entering the lower part of the ammonia synthesis tower to generate high-temperature gas; the liquid ammonia gas flows through a central pipe of the ammonia synthesis tower from bottom to top and then flows out through an interstitial space provided with a catalyst bed layer to obtain reaction gas, and the reaction gas is cooled and then introduced into a condensation separator to prepare a liquid ammonia product; according to the method and the system, a heating unit does not need to be independently provided for ammonia synthesis reaction, large operation energy consumption is prevented, heat energy in the system is fully utilized, and resources are saved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid ammonia preparation, and in particular to a liquid ammonia preparation method and a preparation system. Background Art

[0002] Ammonia (NH3) is a chemical energy storage carrier. Its raw materials are nitrogen and water, which are widely present on the earth. It has the natural advantage of ultra-low raw material cost. It is easy to liquefy. Ammonia gas can be converted into liquid ammonia by pressurizing at room temperature or cooling at normal pressure. Liquid ammonia, also known as anhydrous ammonia, is a colorless liquid with a strong pungent odor.

[0003] Liquid ammonia is usually produced by pressurizing or cooling gaseous ammonia. Some chemical products also produce some by-product ammonia during processing. However, in the existing production process, a separate heating unit is required during ammonia synthesis to meet the temperature conditions required for the ammonia synthesis reaction, which results in high operating energy consumption and high production costs. Summary of the invention

[0004] The present invention aims to provide a method and system for preparing liquid ammonia, so as to solve the problem in the existing production process that a heating unit needs to be provided separately during ammonia synthesis to meet the temperature conditions required for the ammonia synthesis reaction, i.e., there is a high operating energy consumption, which in turn leads to high production costs.

[0005] The technical solution adopted by the present invention is:

[0006] A method for preparing liquid ammonia comprises the following steps:

[0007] Step S100, mixing nitrogen and hydrogen in a preset ratio and conveying them to a first compression section for compression to obtain a first compressed mixed gas, wherein the pressure of the first compressed mixed gas is 7-13 MPa;

[0008] Step S200, mixing the first compressed mixed gas in step S100 as fresh gas with the second compressed mixed gas delivered from the second compression section to obtain unreacted gas, wherein the unreacted gas is divided into two streams after heat exchange and temperature increase, one of which enters the upper part of the ammonia synthesis tower, and the other enters the lower part of the ammonia synthesis tower, and the second compressed mixed gas is a mixed gas containing at least nitrogen, hydrogen, and ammonia;

[0009] Step S300, the first unreacted gas entering the upper part of the ammonia synthesis tower is further heated and then introduced to the lower part of the ammonia synthesis tower, mixed with the second unreacted gas entering the lower part of the ammonia synthesis tower to generate a gas with a temperature of 330° C.-440° C., and then flows from bottom to top through the central tube of the ammonia synthesis tower and then flows out through the gap space between the central tube and the tower body of the ammonia synthesis tower where the catalyst bed is provided, to obtain a reaction gas;

[0010] Step S400, cooling the reaction gas and passing it into a condensation separator to obtain a liquid ammonia product.

[0011] Preferably, in the step S100, the mixing ratio of the nitrogen and the hydrogen is 1:3.

[0012] A liquid ammonia preparation system, comprising:

[0013] A raw gas compressor, used for compressing the raw gas containing nitrogen and hydrogen to a first pressure;

[0014] A circulating gas compressor, used for compressing a mixed gas containing at least nitrogen, hydrogen and ammonia to a second pressure;

[0015] A first heat exchanger is used to perform a temperature raising operation on unreacted gas formed by mixing the raw gas having the first pressure and the mixed gas having the second pressure;

[0016] an ammonia synthesis tower, arranged on the downstream path of the first heat exchanger, for receiving the unreacted gas after the temperature is increased by the first heat exchanger and performing a catalytic reaction operation on the unreacted gas to produce a reaction gas;

[0017] The condensation separator is connected to the reaction gas outlet of the ammonia synthesis tower, and is used for receiving the reaction gas produced by the ammonia synthesis tower and condensing the reaction gas to separate the liquid ammonia product.

[0018] Preferably, the ammonia synthesis tower has at least:

[0019] a first flow-through channel, a second flow-through channel, and a third flow-through channel;

[0020] One end of the first flow passage is connected to the upper end of the ammonia synthesis tower to transport the first unreacted gas into the upper part of the ammonia synthesis tower;

[0021] One end of the second flow passage is connected to the lower end of the ammonia synthesis tower to transport the second stream of unreacted gas into the lower part of the ammonia synthesis tower;

[0022] The third flow passage is used to transport the reaction gas produced by the ammonia synthesis tower to the condensation separator;

[0023] in,

[0024] The other ends of the first flow channel and the second flow channel merge into a total flow channel, and the total flow channel is connected to the first heat exchanger;

[0025] The first heat exchanger is arranged at the intersection of the total flow channel and the third flow channel.

[0026] Preferably, an air cooler and a second heat exchanger are sequentially arranged on the third flow passage on a path downstream of the first heat exchanger;

[0027] The first heat exchanger is also used to cool the reaction gas produced by the ammonia synthesis tower;

[0028] The air cooler is used to cool the reaction gas after the temperature is reduced by the first heat exchanger;

[0029] The second heat exchanger is used to exchange heat between the reaction gas cooled by the air cooler and the mixed gas drawn out from the condensation separator to achieve further cooling.

[0030] Preferably, the ammonia synthesis tower comprises:

[0031] The central tube has a gas outlet at its upper portion for conveying an unreacted mixed gas formed by mixing the first unreacted gas and the second unreacted gas;

[0032] An outer cylinder is sleeved on the outer side of the central tube, a gap space is formed between the central tube and the outer cylinder, and a catalyst bed is arranged in the gap space;

[0033] a heat exchange tube, located in the interstitial space and passing through the catalyst bed;

[0034] in,

[0035] The lower end of the heat exchange tube is connected to the lower part of the central tube;

[0036] The upper side portion of the central tube is communicated with the gap space by means of the air outlet hole.

[0037] Preferably, the ammonia synthesis tower further comprises:

[0038] A heater, wherein a heating portion of the heater is disposed in the central tube and is used to heat the unreacted mixed gas flowing through the central tube under a specific situation;

[0039] An insulating layer is disposed on the outer wall of the central tube to isolate the central tube from the catalyst bed;

[0040] An upper tube plate is arranged at the upper end of the outer tube to block the upper end portion of the gap space, and a first air inlet for a first stream of unreacted gas to enter the heat exchange tube is opened on the upper tube plate;

[0041] A tube sheet cover is arranged at the upper end of the upper tube sheet to seal the upper end of the central tube, and the heating part of the heater extends through the tube sheet cover and the upper tube sheet to the lower end of the central tube;

[0042] The lower tube plate is arranged at the lower end of the outer tube to block the gap space and the lower end of the central tube. The lower tube plate is provided with a second air inlet for a second stream of unreacted gas to enter the central tube, and is also provided with a reaction gas outlet connected to the lower end of the gap space for the reaction gas to be sent out.

[0043] Preferably, it also includes a liquid ammonia storage tank;

[0044] The liquid ammonia storage tank is connected to the bottom outlet of the condensation separator and is used to store the liquid ammonia after the gas-liquid separation is completed by the condensation separator.

[0045] Preferably, the liquid ammonia storage tank is also connected to the circulating gas compressor.

[0046] Preferably, the condensation separator comprises a condensation part and a separation part, and the separation part is located at the lower end of the condensation part;

[0047] The condensation part inputs a cold source to condense the ammonia in the reaction gas into liquid;

[0048] The separation part is used to separate the condensed gas-liquid mixture into gas-liquid to obtain a liquid ammonia product.

[0049] The beneficial effects of the present invention are:

[0050] 1. The liquid ammonia preparation method and preparation system pressurize the mixed gas of hydrogen and nitrogen and mix it with the mixed gas discharged from the circulating gas compressor as unreacted gas, and exchange heat between the unreacted gas and the reaction gas produced by the ammonia synthesis tower through the first heat exchanger. The heated unreacted gas is introduced into the ammonia synthesis tower in two streams, one of which is further heated by exchanging heat with the heat released by the ammonia synthesis reaction through the heat exchange tube in the ammonia synthesis tower to achieve the temperature condition required for the ammonia synthesis reaction. After the two unreacted gases are combined, ammonia is generated under the action of the catalyst bed, and the ammonia is introduced into the condensation separator to obtain liquid ammonia. The liquid ammonia preparation method and preparation system have low difficulty in preparation and operation, and no heating unit is required to be provided for the ammonia synthesis reaction separately, thereby avoiding the problem of high operating energy consumption, thereby reducing production costs, and making full use of the heat energy in the system, saving resources;

[0051] 2. The condensation separator can complete the two operations of condensation and gas-liquid separation at the same time, which improves the system integration and saves equipment investment;

[0052] 3. The introduction of a condensation separator can realize the liquefaction of ammonia and return the mixed gas containing hydrogen and nitrogen to the circulating gas compressor to participate in ammonia synthesis again. The mixed gas separated by the condensation separator is recycled to obtain a green liquid ammonia preparation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 Schematic diagram of the process for preparing liquid ammonia of the present invention;

[0055] Figure 2 It is a structural schematic diagram of the liquid ammonia preparation system of the present invention;

[0056] Figure 3 It is a schematic diagram of the structure of an ammonia synthesis tower according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] 10. Circulating gas compressor;

[0058] 20. A first heat exchanger;

[0059] 30. Air cooler;

[0060] 40. Second heat exchanger;

[0061] 50. ammonia synthesis tower; 500. central tube; 5001. gas outlet; 501. outer tube; 502. gap space; 503. catalyst bed; 504. heat exchange tube; 505. insulation layer; 506. heater; 5061. heating part; 507. upper tube sheet; 5071. first air inlet; 508. lower tube sheet; 5081. second air inlet; 5082. reaction gas outlet; 509. tube sheet cover;

[0062] 60. condensation separator; 61. condensation section; 62. separation section;

[0063] 70. Liquid ammonia storage tank. DETAILED DESCRIPTION

[0064] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0065] The term "comprise" and any variation thereof in this application is intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products or devices.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for describing specific embodiments and are not intended to limit this application. The term "or" used herein includes any and all combinations of one or more related listed items.

[0067] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0068] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0069] In order to reduce operating energy consumption and production costs, such as Figure 1 As shown, an embodiment of the present invention provides a method for preparing liquid ammonia, comprising the following steps:

[0070] Step S100, mixing nitrogen and hydrogen in a preset ratio and conveying them to a first compression section for compression to obtain a first compressed mixed gas, wherein the pressure of the first compressed mixed gas is 7-13 MPa;

[0071] Step S200, mixing the first compressed mixed gas in step S100 as fresh gas with the second compressed mixed gas delivered from the second compression section to obtain unreacted gas, wherein the unreacted gas is divided into two streams after heat exchange and temperature increase, one of which enters the upper part of the ammonia synthesis tower, and the other enters the lower part of the ammonia synthesis tower, and the second compressed mixed gas is a mixed gas containing at least nitrogen, hydrogen, and ammonia;

[0072] Step S300, the first unreacted gas entering the upper part of the ammonia synthesis tower is further heated and then introduced to the lower part of the ammonia synthesis tower, mixed with the second unreacted gas entering the lower part of the ammonia synthesis tower to generate a gas with a temperature of 330° C.-440° C., and then flows from bottom to top through the central tube of the ammonia synthesis tower and then flows out through the gap space between the central tube and the tower body of the ammonia synthesis tower where the catalyst bed is provided, to obtain a reaction gas;

[0073] Step S400, cooling the reaction gas and passing it into a condensation separator to obtain a liquid ammonia product.

[0074] The ammonia synthesis reaction is an exothermic and shrinking reaction. From the perspective of chemical equilibrium, low temperature is conducive to the reaction equilibrium moving toward the direction of ammonia production, corresponding to a high equilibrium ammonia concentration; but at the same time, from the perspective of reaction kinetics, the ammonia synthesis reaction rate is very low at a lower temperature. Under the condition of limited catalyst volume, the actual ammonia concentration obtained will be much lower than the equilibrium concentration. Industrial production needs to take into account both chemical equilibrium and reaction rate. Preferably, the pressure of the first compressed mixed gas is 7-10MPa, and the temperature of the gas generated by the mixing of the first unreacted gas and the second unreacted gas at the lower part of the ammonia synthesis tower can be preferably 330°C, or 360°C, or 400°C, or 440°C.

[0075] The above technical solution increases the temperature of the unreacted gas by exchanging heat with the heat generated in the production process. There is no need to provide a heating unit for the ammonia synthesis reaction separately, thus avoiding the problem of high operating energy consumption, thereby reducing production costs and making full use of the heat energy generated in the production process, saving resources.

[0076] Specifically, in step S100, the mixing ratio of the nitrogen and the hydrogen is 1:3.

[0077] Based on the same purpose, an embodiment of the present invention further provides a liquid ammonia preparation system, and the synthetic ammonia system is suitable for the liquid ammonia preparation method described above.

[0078] like Figure 2 As shown, the liquid ammonia preparation system comprises:

[0079] A raw gas compressor, used for compressing the raw gas containing nitrogen and hydrogen to a first pressure;

[0080] A circulating gas compressor 10, for compressing a mixed gas containing at least nitrogen, hydrogen and ammonia to a second pressure;

[0081] The first heat exchanger 20 is used to perform a temperature raising operation on the unreacted gas formed by mixing the raw gas having the first pressure and the mixed gas having the second pressure;

[0082] an ammonia synthesis tower 50, disposed on the downstream path of the first heat exchanger 20, for receiving the unreacted gas heated by the first heat exchanger 20 and performing a catalytic reaction operation on the unreacted gas to produce a reaction gas;

[0083] The condensation separator 60 is connected to the reaction gas outlet of the ammonia synthesis tower 50, and is used to receive the reaction gas produced by the ammonia synthesis tower 50 and condense the reaction gas to separate the liquid ammonia product.

[0084] When in use, the mixed gas of hydrogen and nitrogen is pressurized by the raw gas compressor and mixed with the mixed gas discharged from the circulating gas compressor 10 as unreacted gas, and the unreacted gas is heat-exchanged with the reaction gas produced by the ammonia synthesis tower 50 through the first heat exchanger 20. The heated unreacted gas is divided into two streams and introduced into the ammonia synthesis tower 50, one of which is further heat-exchanged and heated in the ammonia synthesis tower 50 to reach the temperature condition required for the ammonia synthesis reaction. After the two streams of unreacted gas are merged, ammonia is generated under the action of the catalyst bed 503, and then the ammonia is introduced into the condensation separator 60 to obtain liquid ammonia. The liquid ammonia preparation system has a simple structure and low difficulty in preparation operation, and is suitable for popularization and use.

[0085] Specifically, the ammonia synthesis tower 50 at least has:

[0086] a first flow-through channel, a second flow-through channel, and a third flow-through channel;

[0087] One end of the first flow passage is connected to the upper end of the ammonia synthesis tower 50 to transport the first unreacted gas into the upper part of the ammonia synthesis tower 50;

[0088] One end of the second flow passage is connected to the lower end of the ammonia synthesis tower 50 to transport the second stream of unreacted gas into the lower part of the ammonia synthesis tower 50;

[0089] The third flow passage is used to transport the reaction gas produced by the ammonia synthesis tower 50 to the condensation separator 60;

[0090] in,

[0091] The other ends of the first flow channel and the second flow channel merge into a total flow channel, and the total flow channel is connected to the first heat exchanger 20;

[0092] The first heat exchanger 20 is disposed at the intersection of the total flow channel and the third flow channel, so that the reaction gas and the unreacted gas can exchange heat.

[0093] More specifically, an air cooler 30 and a second heat exchanger 40 are sequentially arranged on the third flow passage on a path downstream of the first heat exchanger 20;

[0094] The first heat exchanger 20 is also used to cool the reaction gas produced by the ammonia synthesis tower 50;

[0095] The air cooler 30 is used to cool the reaction gas after the temperature is reduced by the first heat exchanger 20;

[0096] The second heat exchanger 40 is used to exchange heat between the reaction gas cooled by the air cooler 30 and the mixed gas drawn out of the condensation separator 60 to achieve further cooling.

[0097] When in use, the first unreacted gas after pressurization and heat exchange and temperature increase enters the upper part of the ammonia synthesis tower 50 through the first flow-through channel, further exchanges heat and heats up in the ammonia synthesis tower 50 and flows to the lower part of the ammonia synthesis tower 50, and mixes with the second unreacted gas entering the lower part of the ammonia synthesis tower 50 through the second flow-through channel, and generates reaction gas, i.e., ammonia, under high temperature and catalytic action; the reaction gas flows to the top inlet of the condensation separator 60 through the third flow-through channel and passes through the first heat exchanger 20, the air cooler 30 and the second heat exchanger 40 in sequence, the reaction gas exchanges heat with the unreacted gas in the first heat exchanger 20, the reaction gas after cooling is cooled in the air cooler 30, and then passes through the second heat exchanger 40 to exchange heat with the mixed gas drawn out of the condensation separator 60, the reaction gas enters the condensation separator 60 after further cooling, and the mixed gas after reheating enters the circulating gas compressor 10 for pressurization circulation to participate in ammonia synthesis again, thereby maintaining the environmental protection of the system.

[0098] like Figure 3 As shown, in order to promote the occurrence of ammonia synthesis reaction, the ammonia synthesis tower 50 includes:

[0099] The central tube 500 has a gas outlet 5001 at its upper side for conveying an unreacted mixed gas formed by mixing the first unreacted gas and the second unreacted gas;

[0100] The outer cylinder 501 is sleeved on the outer side of the central tube 500, and a gap space 502 is formed between the central tube 500 and the outer cylinder 501. A catalyst bed 503 is arranged in the gap space 502 to catalyze the unreacted mixed gas;

[0101] A heat exchange tube 504, located in the gap space 502 and passing through the catalyst bed 503, for performing a temperature increase operation on the first unreacted gas;

[0102] in,

[0103] The lower end of the heat exchange tube 504 is connected to the lower part of the central tube 500;

[0104] The upper portion of the central tube 500 is connected to the gap space 502 via the air outlet hole 5001 .

[0105] When in use, the first stream of unreacted gas can take away the heat released from the ammonia synthesis reaction when flowing through the heat exchange tube 504, thereby obtaining a high-temperature gas after further heating. The heat exchange tube 504 leads the high-temperature gas to the bottom space of the gap space 502, and mixes it with the second stream of unreacted gas also led to the bottom space of the gap space 502. The mixed gas flows from bottom to top in the central tube 500, rises to the top of the gap space 502, and is led out from the gas outlet 5001 to the upper part of the catalyst bed 503, and undergoes an ammonia synthesis reaction under the action of the catalyst bed 503. The heat released by the reaction is removed by the first stream of unreacted gas in the heat exchange tube 504 buried in the catalyst bed 503, so that the reaction can continue. Such a cycle not only realizes the recovery and utilization of heat energy and saves resources, but also makes full use of the heat energy in the system to make the ammonia synthesis reaction reach the required temperature conditions, avoids the problem of high operating energy consumption, and thus reduces production costs.

[0106] It should be noted that the activation energy of the ammonia synthesis reaction is very high. When there is no catalyst, the reaction hardly occurs, and industrial production of ammonia is impossible. The present invention changes the reaction process through the catalyst bed 503, reduces the activation energy of the reaction, and allows the reaction to proceed at a significant rate.

[0107] Specifically, the ammonia synthesis tower 50 further includes:

[0108] A heater 506, wherein a heating portion 5061 of the heater 506 is disposed in the central tube 500, and is used to heat the unreacted mixed gas flowing through the central tube 500 under a specific situation;

[0109] The heat insulating layer 505 is disposed on the outer wall of the central tube 500 to isolate the central tube 500 from the catalyst bed 503;

[0110] An upper tube plate 507 is provided at the upper end of the outer tube 501 to block the upper end of the gap space 502. A first air inlet 5071 is provided on the upper tube plate 507 for the first unreacted gas to enter the heat exchange tube 504.

[0111] A tube sheet cover 509 is provided at the upper end of the upper tube sheet 507 to seal the upper end of the central tube 500. The heating portion 5061 of the heater 506 extends through the tube sheet cover 509 and the upper tube sheet 507 toward the lower end of the central tube 500.

[0112] The lower tube plate 508 is arranged at the lower end of the outer tube 501 to seal the gap space 502 and the lower end portion of the central tube 500. The lower tube plate 508 is provided with a second air inlet 5081 for a second stream of unreacted gas to enter the central tube 500, and is also provided with a reaction gas outlet 5082 connected to the lower end of the gap space 502 for the reaction gas to be delivered out.

[0113] In the above technical solution, when the temperature of the unreacted gas cannot meet the temperature conditions required for the ammonia synthesis reaction for some reason, the heater 506 can heat the unreacted mixed gas flowing through the central tube 500 to ensure the occurrence of the ammonia synthesis reaction; the insulation layer 505 isolates the central tube 500 from the catalyst bed 503, and the height of the insulation layer 505 is not less than the filling height of the catalyst bed 503 to prevent the heat released by the ammonia synthesis reaction from being lost through the central tube 500 and affecting the heat exchange; the upper tube sheet 507, the tube sheet cover 509 and the lower tube sheet 508 ensure the sealed environment between the central tube 500 and the gap space 502 to prevent gas and / or heat leakage.

[0114] Furthermore, it also includes a liquid ammonia storage tank 70;

[0115] The liquid ammonia storage tank 70 is connected to the bottom outlet of the condensation separator 60 to store the liquid ammonia after gas-liquid separation by the condensation separator 70 .

[0116] In order to discharge the impure liquid ammonia in the liquid ammonia storage tank 70, a filter layer is provided in the liquid ammonia storage tank 70, and the liquid ammonia storage tank 70 is also connected to the circulating gas compressor 10, and the impure liquid ammonia after filtration is discharged into the circulating gas compressor 10 to be compressed into high-pressure gas, and re-participate in ammonia synthesis, thereby ensuring the purity of the liquid ammonia in the liquid ammonia storage tank 70.

[0117] From the perspective of system integration and to save equipment investment, the condensation separator 60 includes a condensation section 61 and a separation section 62, wherein the separation section 62 is located at the lower end of the condensation section 61; wherein the condensation section 61 inputs a cold source to condense the ammonia in the reaction gas into liquid, and the separation section 62 is used to perform gas-liquid separation on the condensed gas-liquid mixture to obtain a liquid ammonia product.

[0118] In addition, in order to ensure the source of hydrogen and nitrogen, an air separation module and a water electrolysis hydrogen production module are also included; the air separation module and the water electrolysis hydrogen production module are both connected to the raw gas compressor; the air separation module is used to obtain nitrogen from the air; the water electrolysis hydrogen production module is used to electrolyze water to obtain hydrogen.

[0119] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing liquid ammonia, characterized in that: The steps include: Step S100, mixing nitrogen and hydrogen in a preset ratio and conveying them to a first compression section for compression to obtain a first compressed mixed gas, wherein the pressure of the first compressed mixed gas is 7-13 MPa; Step S200, mixing the first compressed mixed gas in step S100 as fresh gas with the second compressed mixed gas delivered from the second compression section to obtain unreacted gas, wherein the unreacted gas is divided into two streams after heat exchange and temperature increase, one of which enters the upper part of the ammonia synthesis tower, and the other enters the lower part of the ammonia synthesis tower, and the second compressed mixed gas is a mixed gas containing at least nitrogen, hydrogen, and ammonia; Step S300, the first unreacted gas entering the upper part of the ammonia synthesis tower is further heated and then introduced to the lower part of the ammonia synthesis tower, mixed with the second unreacted gas entering the lower part of the ammonia synthesis tower to generate a gas with a temperature of 330° C.-440° C., and then flows from bottom to top through the central tube of the ammonia synthesis tower and then flows out through the gap space between the central tube and the tower body of the ammonia synthesis tower where the catalyst bed is provided, to obtain a reaction gas; Step S400, cooling the reaction gas and passing it into a condensation separator to obtain a liquid ammonia product.

2. The method for preparing liquid ammonia according to claim 1, characterized in that: In the step S100, the mixing ratio of the nitrogen gas and the hydrogen gas is 1:

3.

3. A liquid ammonia preparation system, characterized in that: include: A raw gas compressor, used for compressing the raw gas containing nitrogen and hydrogen to a first pressure; A circulating gas compressor, used for compressing a mixed gas containing at least nitrogen, hydrogen and ammonia to a second pressure; A first heat exchanger is used to perform a temperature raising operation on unreacted gas formed by mixing the raw gas having the first pressure and the mixed gas having the second pressure; an ammonia synthesis tower, arranged on the downstream path of the first heat exchanger, for receiving the unreacted gas after the temperature is increased by the first heat exchanger and performing a catalytic reaction operation on the unreacted gas to produce a reaction gas; The condensation separator is connected to the reaction gas outlet of the ammonia synthesis tower, and is used for receiving the reaction gas produced by the ammonia synthesis tower and condensing the reaction gas to separate the liquid ammonia product.

4. The liquid ammonia preparation system according to claim 3, characterized in that: The ammonia synthesis tower at least has: a first flow-through channel, a second flow-through channel, and a third flow-through channel; One end of the first flow passage is connected to the upper end of the ammonia synthesis tower to transport the first unreacted gas into the upper part of the ammonia synthesis tower; One end of the second flow passage is connected to the lower end of the ammonia synthesis tower to transport the second stream of unreacted gas into the lower part of the ammonia synthesis tower; The third flow passage is used to transport the reaction gas produced by the ammonia synthesis tower to the condensation separator; in, The other ends of the first flow channel and the second flow channel merge into a total flow channel, and the total flow channel is connected to the first heat exchanger; The first heat exchanger is arranged at the intersection of the total flow channel and the third flow channel.

5. The liquid ammonia preparation system according to claim 4, characterized in that: An air cooler and a second heat exchanger are sequentially arranged on the third flow passage on a path downstream of the first heat exchanger; The first heat exchanger is also used to cool the reaction gas produced by the ammonia synthesis tower; The air cooler is used to cool the reaction gas after the temperature is reduced by the first heat exchanger; The second heat exchanger is used to exchange heat between the reaction gas cooled by the air cooler and the mixed gas drawn out from the condensation separator to achieve further cooling.

6. The liquid ammonia preparation system according to claim 4, characterized in that: The ammonia synthesis tower comprises: The central tube has a gas outlet at its upper portion for conveying an unreacted mixed gas formed by mixing the first unreacted gas and the second unreacted gas; An outer cylinder is sleeved on the outer side of the central tube, a gap space is formed between the central tube and the outer cylinder, and a catalyst bed is arranged in the gap space; a heat exchange tube, located in the interstitial space and passing through the catalyst bed; in, The lower end of the heat exchange tube is connected to the lower part of the central tube; The upper side portion of the central tube is communicated with the gap space by means of the air outlet hole.

7. The liquid ammonia preparation system according to claim 6, characterized in that: The ammonia synthesis tower also includes: A heater, wherein a heating portion of the heater is disposed in the central tube and is used to heat the unreacted mixed gas flowing through the central tube under a specific situation; An insulating layer is disposed on the outer wall of the central tube to isolate the central tube from the catalyst bed; An upper tube plate is arranged at the upper end of the outer tube to block the upper end portion of the gap space, and a first air inlet for a first stream of unreacted gas to enter the heat exchange tube is opened on the upper tube plate; A tube sheet cover is arranged at the upper end of the upper tube sheet to seal the upper end of the central tube, and the heating part of the heater extends through the tube sheet cover and the upper tube sheet to the lower end of the central tube; The lower tube plate is arranged at the lower end of the outer tube to block the gap space and the lower end of the central tube. The lower tube plate is provided with a second air inlet for a second stream of unreacted gas to enter the central tube, and is also provided with a reaction gas outlet connected to the lower end of the gap space for the reaction gas to be sent out.

8. The liquid ammonia preparation system according to claim 3, characterized in that: It also includes liquid ammonia storage tanks; The liquid ammonia storage tank is connected to the bottom outlet of the condensation separator and is used to store the liquid ammonia after the gas-liquid separation is completed by the condensation separator.

9. The liquid ammonia preparation system according to claim 8, characterized in that: The liquid ammonia storage tank is also connected to the circulating gas compressor.

10. The liquid ammonia preparation system according to claim 3, characterized in that: The condensation separator comprises a condensation part and a separation part, wherein the separation part is located at the lower end of the condensation part; The condensation part inputs a cold source to condense the ammonia in the reaction gas into liquid; The separation part is used to separate the condensed gas-liquid mixture into gas-liquid to obtain a liquid ammonia product.

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