Green ammonia synthesis method and system taking renewable energy as power

Abstract

The invention relates to a green ammonia synthesis method and system taking renewable energy as power. The method comprises the following steps: S1, providing high-temperature reaction gas; s2, raw material gas is heated through at least part of the high-temperature reaction gas, and heated raw material gas and first cooled mixed gas are obtained; s3, carrying out heating treatment on the adsorbent adsorbing the ammonia gas through the first cooling mixed gas to desorb the ammonia gas, so as to obtain desorbed gas containing the ammonia gas; s4, the desorption gas is subjected to cooling treatment and flash evaporation treatment, and liquid ammonia and first flash evaporation gas are obtained; and S5, carrying out ammonia gas adsorption on the first flash steam through the adsorbent. According to the green ammonia synthesis method taking the renewable energy source as the power, the generated ammonia gas is subjected to low-temperature adsorption and high-temperature desorption, so that efficient recovery of ammonia can be realized; and the energy utilization of the system is reasonable, the energy consumption is reduced, the operation difficulty of device operation is simplified, and the device is more suitable for application in green ammonia scenes.

Description

Technical Field

[0001] The present invention relates to the synthesis of ammonia, and in particular to a green ammonia synthesis process and system which can reduce energy consumption and take renewable energy as power. Background Art

[0002] Ammonia is one of the most basic chemical raw materials for modern industrial and agricultural production. It has the advantages of easy liquefaction, high volume energy density, no carbon emissions, non-flammability, and high safety. It has obvious advantages in storage and transportation. Recently, green ammonia has become the focus of global attention. Ammonia is expanding from the field of traditional agricultural fertilizers to the field of new energy sources.

[0003] The energy consumption of the traditional synthetic ammonia industry is mainly electricity, including compressor power consumption, refrigerator power consumption and circulation machine power consumption. Among them, the power consumption of the compressor and circulation machine increases with the increase of synthetic ammonia pressure, and the power consumption of the refrigerator decreases with the increase of synthetic ammonia pressure. In the ammonia synthesis process, limited by the reaction balance, the net value of ammonia in the synthesis gas is about 20% (the inlet ammonia content is about 3%). At present, the liquid ammonia condensation method is generally used in the industry to liquefy and separate ammonia from the synthesis gas, and the remaining gas is mixed with fresh raw gas as circulating gas and sent back to the synthesis tower for further reaction. However, about 3% of ammonia will still remain in the circulating gas of the physical condensation separation process, which wastes a large amount of ammonia products, reduces the net value of ammonia, and increases the circulation volume of the circulation machine. In addition, the residual ammonia returned to the synthesis tower with the circulating gas is not conducive to the balanced conversion of the raw gas.

[0004] In addition, in the traditional ammonia synthesis process, more than 80% of the hydrogen and nitrogen mixture is cooled from a high temperature of about 400°C to -15°C while condensing ammonia. The cooled hydrogen and nitrogen mixture will be circulated to the ammonia synthesis tower again and heated up to the reaction temperature again. On the one hand, the high and low temperature operation of such a large amount of gas will cause very high energy consumption. On the other hand, the condensing equipment requires many auxiliary facilities and is complex to operate, which is not suitable for flexible, small-scale green ammonia scenarios. Summary of the invention

[0005] In order to overcome at least one defect of the above-mentioned prior art, in a first aspect, an embodiment of the present invention provides a method for synthesizing green ammonia using renewable energy as power, comprising the following steps:

[0006] S1: providing high temperature reaction gas, wherein the temperature of the high temperature reaction gas is 400-460° C.;

[0007] S2: heating the raw gas by at least part of the high-temperature reaction gas to obtain heated raw gas and a first cooled mixed gas;

[0008] S3: heating the adsorbent adsorbed with ammonia by the first cooled mixed gas to desorb the ammonia to obtain a desorbed gas containing ammonia;

[0009] S4: subjecting the desorbed gas to a cooling treatment and a flash vaporization treatment to obtain liquid ammonia and a first flash vapor; and

[0010] S5: Adsorbing ammonia gas on the first flash gas by the adsorbent;

[0011] Wherein, the high-temperature reaction gas includes hydrogen, nitrogen and ammonia; the raw material gas includes hydrogen and nitrogen, which are used to form the high-temperature reaction gas through reaction.

[0012] In a second aspect, an embodiment of the present invention provides a green ammonia synthesis system powered by renewable energy, comprising:

[0013] A synthesis device for reacting hydrogen and nitrogen to obtain a high-temperature reaction gas containing ammonia;

[0014] A heat exchange device connected to the synthesis device, through which at least part of the high-temperature reaction gas can be heated to produce the raw gas for the high-temperature reaction gas;

[0015] An adsorption device, used for adsorbing or desorbing the ammonia;

[0016] Cooling device;

[0017] Flash evaporation device;

[0018] A water electrolysis hydrogen production device, used to provide the hydrogen for the synthesis device;

[0019] a buffer device, disposed between the water electrolysis hydrogen production device and the synthesis device, for storing the hydrogen or the hydrogen and the nitrogen; and

[0020] Renewable energy generation devices for providing electrical energy;

[0021] The cooling device and the flash evaporation device are capable of cooling and flash evaporating the ammonia-containing gas discharged from the adsorption device or the synthesis device to obtain liquid ammonia.

[0022] A green ammonia synthesis method powered by renewable energy according to one embodiment of the present invention can achieve efficient recovery of ammonia by low-temperature adsorption and high-temperature desorption of the generated ammonia gas; and the energy utilization of the system is reasonable, which reduces energy consumption, simplifies the operating difficulty of the device, and is more suitable for application in green ammonia scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

[0024] Figure 1 A process flow chart of green ammonia synthesis using renewable energy as power according to one embodiment of the present invention;

[0025] Figure 2 A process flow chart of green ammonia synthesis using renewable energy as power according to another embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the structure of a system for synthesizing green ammonia using renewable energy as power according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially used as illustrations rather than to limit the present invention.

[0028] Reference Figure 1 , 2 As shown, one embodiment of the present invention provides a method for synthesizing green ammonia using renewable energy as power, comprising the following steps:

[0029] S1: providing high temperature reaction gas, the temperature of which is 400-460°C;

[0030] S2: heating the raw gas by at least part of the high-temperature reaction gas to obtain a heated raw gas and a first cooled mixed gas;

[0031] S3: heating the adsorbent containing ammonia in the adsorption tower by the first cooling mixed gas to desorb the ammonia in the adsorbent to obtain a desorbed gas containing ammonia;

[0032] S4: cooling and flashing the desorbed gas to obtain liquid ammonia and first flash gas; and

[0033] S5: passing the first flash gas into an adsorption tower, and adsorbing ammonia gas on the first flash gas by an adsorbent;

[0034] The high-temperature reaction gas includes hydrogen, nitrogen and ammonia; the raw material gas includes hydrogen and nitrogen, which are used to form the high-temperature reaction gas through reaction.

[0035] In one embodiment, a method for synthesizing green ammonia powered by renewable energy comprises the following steps:

[0036] Providing a raw gas, the raw gas comprising hydrogen and nitrogen;

[0037] The raw gas is subjected to an ammonia synthesis reaction to obtain a high-temperature reaction gas having a temperature of 400 to 460°C;

[0038] Heating the raw gas by at least part of the high-temperature reaction gas to obtain heated raw gas and a first cooled mixed gas;

[0039] Cooling the first cooled mixed gas to obtain a second cooled mixed gas;

[0040] The second cooled mixed gas is subjected to a cooling treatment and a flash vaporization treatment to obtain liquid ammonia and a second flash vapor;

[0041] Adsorbing ammonia gas on the second flash gas by an adsorbent to obtain a deammoniation gas;

[0042] A portion of the deammoniation gas is subjected to a temperature treatment and then used as a desorption circulating gas, and an adsorbent adsorbed with ammonia is subjected to a temperature treatment by the desorption circulating gas to desorb the ammonia and obtain a desorption gas containing ammonia;

[0043] performing a temperature reduction treatment and a flash vaporization treatment on the desorbed gas containing ammonia to obtain a first flash gas and liquid ammonia; and

[0044] The first flash gas is subjected to ammonia adsorption by the adsorbent.

[0045] In one embodiment, hydrogen can be produced by electrolysis of water and nitrogen can be separated from air.

[0046] In one embodiment, hydrogen and nitrogen are mixed in proportion to form a raw gas, which is pressurized to 5-20 MPa (e.g., 14.9 MPa) by a compression device (e.g., a compressor) and then introduced into a synthesis device (e.g., a synthesis tower) for reaction. Furthermore, the raw gas may be preheated before being introduced into the synthesis tower for reaction.

[0047] In one embodiment, hydrogen and nitrogen in the raw gas react in a synthesis tower under the action of a catalyst to obtain a high-temperature reaction gas including hydrogen, nitrogen and ammonia. The temperature of the high-temperature reaction gas discharged from the synthesis tower may be 400-460°C; the pressure of the high-temperature reaction gas may be 10-15 MPa(G).

[0048] In one embodiment, the volume content of ammonia in the high-temperature reaction gas may be 19-25%; the sum of the volume contents of nitrogen and hydrogen in the high-temperature reaction gas may be 78-87%.

[0049] In one embodiment, the catalyst used for the reaction of hydrogen and nitrogen can be an iron-based or non-iron-based catalyst, preferably a low-temperature catalyst; the reaction of hydrogen and nitrogen can be carried out at a temperature of 360 to 500°C, and part or all of the high-temperature reaction gas can be used to heat the raw gas to save energy.

[0050] In one embodiment, reference Figure 1 As shown, in steps S2 and S3, the high-temperature reaction gas can be heat-exchanged with the raw gas to raise the temperature of the raw gas (preheating), and the heated raw gas and the cooled high-temperature reaction gas (first cooled mixed gas) can be obtained; then, the first cooled mixed gas and the desorption circulating gas can be heat-exchanged (for example, by heat-exchanging in a heat exchanger) to raise the temperature of the desorption circulating gas, and the second cooled mixed gas and the heated desorption circulating gas can be obtained; and the heated desorption circulating gas can be passed into the adsorption tower to heat the adsorbent. Among them, the composition of the first cooled mixed gas is the same as that of the high-temperature reaction gas, and the temperature is lower than that of the high-temperature reaction gas; the temperature of the first cooled mixed gas can be 340-360°C, for example, 350°C, 357°C. The second cooling mixed gas has the same composition as the first cooling mixed gas and the high temperature reaction gas, and its temperature is lower than that of the first cooling mixed gas and the high temperature reaction gas; the temperature of the second cooling mixed gas can be 130-150° C., for example, 132° C., 135° C., 138° C., 140° C., 143° C., 145° C., 148° C. The temperature of the heated desorption circulating gas can be 330-350° C., for example, 340° C., 350° C.

[0051] In one embodiment, the raw gas and the desorption circulating gas are heated by high-temperature reaction gas, so that the energy efficiency of the entire system is optimized and the energy consumption is reduced.

[0052] In one embodiment, the raw gas may be heated to 160-190°C, such as 170°C or 180°C, by exchanging heat between the high-temperature reaction gas and the raw gas.

[0053] In one embodiment, the second cooled mixed gas can be subjected to cooling treatment and flash evaporation treatment, and gas-liquid separation can be performed by flash evaporation treatment to obtain liquid ammonia and second flash gas; wherein, the second cooled mixed gas can be cooled by water cooling, and further, the second cooled mixed gas can be cooled to 32-45°C, for example, 35°C, 38°C, 40°C, 42°C.

[0054] In one embodiment, flash treatment can be performed in a flash tank (or a pressure reducing tank), and the obtained liquid ammonia can enter the storage tank as a product from the lower outlet of the flash tank, and the gas phase material after flashing (such as the second flash gas) can be discharged from the upper outlet of the flash tank. The second flash gas includes hydrogen, nitrogen and residual ammonia. Further, the second flash gas can be introduced into an adsorption tower, and ammonia is adsorbed on the second flash gas by an adsorbent to obtain a deammonified gas from which ammonia is further removed; the deammonified gas mainly includes hydrogen and nitrogen.

[0055] In one embodiment, the liquid ammonia obtained by flash evaporation can be directly stored in a storage tank or stored after decompression. For example, the pressure can be reduced to about 3 MPa, and the third flash gas generated by the decompression can enter the compression system through a pipeline.

[0056] In one embodiment, the adsorbent disposed in the adsorption tower may be an existing adsorbent for adsorbing ammonia; the temperature of the second flash gas may be 32 to 45° C., for example, 35° C., 38° C., 40° C., or 42° C. Thus, the adsorption process of ammonia may be carried out at a relatively low temperature of 32 to 45° C.

[0057] In one embodiment, at least part of the deammoniation gas can be used as the above-mentioned desorption circulation gas, for example, part of the deammoniation gas can be used as the desorption circulation gas, and the remaining deammoniation gas can be mixed with the raw gas to carry out the synthesis reaction of ammonia. Compared with the prior art (such as the traditional condensation method), the ammonia content in the deammoniation gas is less (for example, 0 to 0.1%), and recycling it as a raw material can promote the reversible reaction of synthetic ammonia to proceed in the forward direction, improve the conversion rate of synthetic ammonia, and also improve the recovery rate and output of ammonia.

[0058] In one embodiment, under the action of the heated desorption circulating gas, the adsorbent adsorbing ammonia can desorb ammonia at high temperature (high temperature desorption), and the high temperature condition is more conducive to desorption; the heated desorption circulating gas can make the average temperature of the adsorption tower reach 100-120° C., in other words, the temperature of high temperature desorption can be 100-120° C. Further, the desorption gas includes desorbed ammonia and desorption circulating gas (mainly including hydrogen and nitrogen).

[0059] In one embodiment, referring to Figure 2 As shown, the high temperature reaction gas includes a first high temperature reaction gas and a second high temperature reaction gas, and the raw material gas can be heated by the first high temperature reaction gas to obtain a first cooling mixed gas; the first cooling mixed gas and the second high temperature reaction gas are introduced into the adsorption tower, and the adsorbent adsorbed with ammonia in the adsorption tower is contacted with the adsorbent to heat it, so that the ammonia is desorbed (high temperature desorption) to obtain a desorbed gas containing ammonia. Further, the adsorbent can be heated to 200-250°C, for example, 217°C, by heating the first cooling mixed gas and the second high temperature reaction gas. In other words, the temperature of high temperature desorption is 200-250°C.

[0060] In one embodiment, the first high-temperature reaction gas may be introduced into a preheater to heat the raw gas. Further, the raw gas may be heated to 160-190°C, for example, 190°C.

[0061] In one embodiment, the first cooling mixed gas can be introduced into the adsorption tower from the upper part of the adsorption tower, and the second high-temperature reaction gas can be introduced from the middle and bottom of the adsorption tower. The adsorbent bed (or adsorbent) in the adsorption tower can be heated to 200-250°C by the action of the two mixed gases, so that the adsorbent adsorbed with ammonia desorbs ammonia at high temperature to obtain a desorbed gas containing ammonia. The desorbed gas may include hydrogen, nitrogen and ammonia. Further, the volume percentage of ammonia in the desorbed gas may be 28-32%, for example, 30%.

[0062] An embodiment of the present invention heats the adsorption tower by dividing the high-temperature reaction gas into two paths, thereby ensuring the uniformity of desorption and making full use of the heat of the high-temperature reaction gas. Compared with the traditional by-product steam solution, the system is simpler and the energy utilization is more thorough.

[0063] In one embodiment, the desorbed gas may be subjected to a cooling treatment and a flash vaporization treatment to obtain liquid ammonia and a first flash vapor; wherein the desorbed gas may be cooled by water cooling, and further, the desorbed gas may be cooled to 32-45°C, and further may be 35-45°C, for example, 35°C.

[0064] In one embodiment, flash evaporation can be performed in a flash tank, and the obtained liquid ammonia can enter the storage tank as a product from the lower outlet of the flash tank, and the gas phase material after flash evaporation (such as the first flash gas) can be discharged from the upper outlet of the flash tank. The first flash gas includes hydrogen and nitrogen, and the first flash gas can be mixed with the raw gas for recycling; if the first flash gas still contains residual ammonia, the first flash gas can be passed into an adsorption tower, and the first flash gas is adsorbed by the adsorbent, and the aforementioned adsorption→desorption→flash evaporation process is repeated until the ammonia is almost completely recovered.

[0065] exist Figure 2 In the embodiment shown, the desorbed gas can be separated and treated by a gas-solid separator (e.g., a cyclone separator) and then passed into a flash tank for treatment. Through the separation treatment of the gas-solid separator, a separated mixed gas and liquid ammonia (e.g., 35-38°C) are obtained; wherein, the temperature of the separated mixed gas can be 35-45°C, the volume content of ammonia can be 15-17%, and the volume content of hydrogen and nitrogen can be 83-85%; the separated mixed gas can be passed into an adsorption tower, and the ammonia therein can be adsorbed by an adsorbent. In addition, the liquid ammonia separated by the gas-solid separator can be passed into a flash tank for treatment, and the liquid ammonia after flashing can be sent to a 3MPa (G) storage tank for storage, and the obtained flash gas can be returned from the upper outlet of the flash tank (35-38°C, containing 50-60% ammonia) to a first inlet of the compression device for recycling.

[0066] In one embodiment, the desorbed gas can be cooled to 35-45° C. by water cooling and then passed into a gas-solid separator (such as a cyclone separator) for solid separation. After the adsorbent powder that is broken due to high temperature is separated, it is passed into a flash tank for gas-liquid separation.

[0067] In one embodiment, the adsorption and desorption of ammonia can be performed in the same adsorption tower by changing the conditions. The number of adsorption towers can be one or more, for example, two or three, and the setting of multiple adsorption towers can achieve continuous operation of the process.

[0068] Reference Figure 3 As shown, one embodiment of the present invention provides a green ammonia synthesis system powered by renewable energy, which can be used to implement the above method, and the system includes:

[0069] The synthesis device 20 is used to react the hydrogen and nitrogen in the raw gas to obtain a high-temperature reaction gas containing ammonia;

[0070] The heat exchange device 30 is connected to the synthesis device 20, and at least part of the high-temperature reaction gas can be heated by the heat exchange device 30 to treat the raw gas;

[0071] Adsorption device 40, used for adsorption or desorption of ammonia;

[0072] Cooling device 50;

[0073] Flash evaporation device 60;

[0074] The water electrolysis hydrogen production device 110 is used to provide hydrogen for the synthesis device 20;

[0075] The buffer device 130 is disposed between the water electrolysis hydrogen production device 110 and the synthesis device 20 and is used to store hydrogen or hydrogen and nitrogen;

[0076] The cooling device 50 and the flash evaporation device 60 can cool and flash the ammonia-containing gas discharged from the adsorption device 40 or the synthesis device 20 to obtain liquid ammonia.

[0077] In one embodiment, hydrogen and ammonia may be mixed in a certain volume ratio (eg, N2:H2=1:3) to form a raw gas.

[0078] In one embodiment, the green ammonia synthesis system includes a compression device 10, which may include a compressor. The compression device 10 may be connected to a synthesis device 20; the compression device is used to pressurize the raw gas containing hydrogen and nitrogen to, for example, 5 to 20 MPa (G) before passing it into the synthesis device 20 for reaction; further, the raw gas may be pressurized by three-stage compression. Further, the compression device 10 may be connected to a buffer device 130.

[0079] In one embodiment, the synthesis device 20 includes a synthesis tower, and the compression device 10 is connected to the synthesis device 20 to pass the mixed raw gas into the synthesis device 20 for ammonia synthesis reaction.

[0080] In one embodiment, the heat exchange device 30 includes a heat exchanger, and the gas discharged from the synthesis device 20 (such as high-temperature reaction gas) can be heat exchanged with the raw gas discharged from the compression device 10 through the heat exchange device 30, thereby preheating the raw gas, and the preheated raw gas can be introduced into the synthesis device 20 for synthesis reaction.

[0081] In one embodiment, the adsorption device 40 includes one or more adsorption / desorption towers, in which an adsorbent for adsorbing ammonia is disposed. The adsorbent may be disposed on an adsorbent bed. The adsorption device 40 may be connected to the heat exchange device 30 .

[0082] In one embodiment, the heat exchanger of the heat exchange device 30 can be connected with the adsorption tower as an integrated device, or can be operated independently as a heat exchanger.

[0083] In one embodiment, the cooling device 50 includes one or more water coolers to cool the gas by water; the cooling device 50 can be connected to the heat exchange device 30 and / or the adsorption device 40. Furthermore, the water cooler can be connected to the adsorption tower as an integrated device, or can be operated as a water cooler alone.

[0084] In one embodiment, the flash device 60 includes one or more flash tanks, and the flash device 60 may be connected to the cooling device 50 .

[0085] In one embodiment, the system for synthesizing ammonia further includes a gas-solid separation device, which is disposed between the cooling device 50 and the flash device 60. The gas-solid separation device may be, for example, a cyclone separator.

[0086] In one embodiment, a circulating gas pipeline 41 is provided outside the adsorption device 40, and the heat exchange device 30 is connected to the circulating gas pipeline 41. The gas discharged from the adsorption device 40 (for example, desorption circulating gas) can re-enter the adsorption device 40 after heat exchange with the gas in the heat exchange device 30 through the circulating gas pipeline 41.

[0087] In one embodiment, the green ammonia synthesis system includes a liquid ammonia storage tank 70 for storing the produced liquid ammonia, and the liquid ammonia storage tank 70 is connected to the flash evaporation device 60.

[0088] In one embodiment, the system for synthesizing ammonia further includes a renewable energy power generation device.

[0089] In one embodiment, the renewable energy power generation device is used to power other devices in the system (such as the water electrolysis hydrogen production device 110); for example, the renewable energy power generation device can electrically connect the intermittent "peak and valley" electricity generated by wind, light or solar energy to the external power grid through a power supply mechanism / inverter for use in the power consumption of electrical equipment in the system.

[0090] In one embodiment, the renewable energy power generation device can generate electricity through wind energy, light energy or solar energy, and it can be an existing device.

[0091] In one embodiment, the buffer device 130 is provided to continuously provide raw gas (especially hydrogen) to the synthesis device 20, thereby avoiding the interruption of raw gas due to intermittent power supply from the renewable energy power generation device.

[0092] In one embodiment, the green ammonia synthesis system further includes a nitrogen generator for providing nitrogen; the nitrogen generator may be an air separation unit 120.

[0093] In one embodiment, the green ammonia synthesis system further includes a drying device 111, which can be arranged between the water electrolysis hydrogen production device 110 and the buffer device 130, so as to dry the hydrogen discharged from the water electrolysis hydrogen production device 110 before passing it into the buffer device 130; further, the air separation device 120 is also connected to the drying device 111. During operation, the hydrogen produced by the water electrolysis hydrogen production device 110 and the nitrogen produced by the air separation device 120 can be passed into the drying device 111 at a ratio of 3:1 to remove the moisture in the hydrogen and nitrogen, and then the obtained mixed gas is passed into the buffer device 130 for storage; thereafter, the hydrogen and nitrogen mixed gas is passed into the compression device 10 for pressurization as needed, and then passed into the synthesis device 20 for reaction.

[0094] In one embodiment, the low-temperature gas (for example, 35-40°C) discharged from the adsorption tower can be directly returned to the compressor inlet to mix with the compressor second stage outlet gas to reduce the temperature of the second stage outlet gas. The second stage outlet of the raw gas compressor no longer needs to be equipped with a water cooler and directly enters the third stage of the compressor for compression.

[0095] Compared with the traditional condensation method, the green ammonia synthesis method powered by renewable energy in one embodiment of the present invention does not require liquid ammonia refrigeration, and the system has no ice machine linkage process / equipment, and only requires commonly used circulating water cooling, which greatly simplifies the process. The synthesis system used is simple in structure and reduces the difficulty of operation.

[0096] A green ammonia synthesis method powered by renewable energy according to one embodiment of the present invention can achieve efficient recovery of ammonia by low-temperature adsorption and high-temperature desorption of the generated ammonia gas; and the energy utilization of the system is reasonable, which reduces energy consumption, simplifies the operating difficulty of the device, and is more suitable for application in green ammonia scenarios.

[0097] In one embodiment of the present invention, the green ammonia synthesis method powered by renewable energy greatly reduces the ammonia content in the circulating gas through a temperature swing adsorption separation process compared to a traditional condensation separation process, promotes the forward direction of the synthetic ammonia reaction, and increases the synthetic ammonia yield.

[0098] A green ammonia synthesis method powered by renewable energy according to one embodiment of the present invention achieves zero-carbon emission hydrogen production while storing and transporting hydrogen energy in the form of liquid ammonia. At the same time, a temperature swing adsorption process utilizes the synthesized high-temperature reaction gas for temperature increase and desorption, thereby making full use of the heat release of the synthetic ammonia reaction, improving the energy utilization rate of the system, and the self-heat exchange ratio of the system can reach about 50%.

[0099] Compared with the traditional ammonia synthesis process, the green ammonia synthesis method powered by renewable energy according to one embodiment of the present invention can use the energy contained in the high-temperature reaction gas of 400 to 460°C discharged from the synthesis tower in subsequent processes, such as high-temperature desorption of the adsorption tower, without considering the energy gradient utilization of by-product steam and the raw gas for heating the synthetic ammonia; in addition, part of the deammoniation gas (for example, 38°C) discharged from the adsorption tower can be directly returned to the three-stage inlet of the compression device, and then directly enter the synthesis tower for reaction after being preheated by the high-temperature reaction gas (for example, 180°C). The second stage of compression of this compression device does not need to be water-cooled again and directly enters the third stage for recompression, saving the use of circulating water. As a result, all the high-level heat energy of the system is recovered, and the energy utilization rate can reach, for example, more than 49%. By optimizing the heat exchange inside the system, the energy consumption of synthetic ammonia is reduced.

[0100] Hereinafter, a method and system for synthesizing green ammonia using renewable energy as power according to an embodiment of the present invention will be further described in conjunction with the accompanying drawings and specific examples.

[0101] Example 1

[0102] (1) The hydrogen produced by the water electrolysis hydrogen production device 110 and the nitrogen produced by the air separation device 120 are mixed in a volume ratio of 3:1, and then introduced into the drying device 111 for drying, and the dried mixed gas is introduced into the buffer device 130; then, the hydrogen and nitrogen mixed gas (28° C., 2.8 MPa(G)) and the circulating gas are introduced into the compression device 10 as the raw gas, and the raw gas is pressurized to 14.9 MPa(G) after two-stage compression; the pressurized raw gas is introduced into the synthesis tower of the synthesis device 20, and ammonia synthesis reaction is carried out under the action of a catalyst to obtain a high-temperature reaction gas including hydrogen, nitrogen and ammonia; the outlet temperature of the high-temperature reaction gas is about 460° C., the pressure is about 14.7 MPa(G), and the volume content of ammonia is about 20-25%;

[0103] (2) The high-temperature reaction gas is heat exchanged with the raw gas through the heat exchange device 30, and the raw gas is preheated to 180° C. before being introduced into the synthesis tower. The temperature of the first cooled mixed gas obtained after the heat exchange is reduced to about 357° C.;

[0104] (3) exchanging heat between the first cooled mixed gas and the desorption circulating gas discharged from the adsorption tower to obtain a second cooled mixed gas at about 143° C. and a heated desorption circulating gas at about 357° C.;

[0105] (4) The second cooled mixed gas is water-cooled to 38° C. by a cooling device 50 (water cooler), and then introduced into a flash evaporation device 60; the liquid ammonia obtained after flash evaporation is sent to a liquid ammonia storage tank 70 from the lower outlet of the device, and the gas phase second flash gas (38° C., 14.5 MPa (G)) after flash evaporation is introduced into an adsorption device 40 through the upper outlet of the device;

[0106] (5) The second flash gas at about 38° C. is subjected to low-temperature adsorption of ammonia by the adsorption tower (provided with adsorbent) of the adsorption device 40 to obtain a deammoniation gas from which ammonia is removed; a portion of the deammoniation gas is returned to the compression device 10 as a circulating gas to be directly mixed with the feed gas and re-entered into the synthesis tower for reaction; another portion of the deammoniation gas is heated by the heat exchange device 30 and used as a desorption circulating gas for high-temperature desorption; the desorption circulating gas is heated as described in step (3) to obtain a heated desorption circulating gas;

[0107] (6) After the desorption circulating gas after heating enters the adsorption tower, the adsorbent adsorbed with ammonia will remove ammonia at a high temperature of about 110-120°C to obtain a desorbed gas (95°C, 14MPa(G)); the desorbed gas includes hydrogen, nitrogen and ammonia;

[0108] (7) The desorbed gas is cooled and flashed in the same manner as in step (4) to obtain liquid ammonia (38°C, 13.9 MPa(G)) and a first flash gas (38°C, 13.9 MPa(G)), and the first flash gas is returned to the adsorption tower for further adsorption.

[0109] (8) Liquid ammonia (38° C., 13.9 MPa (G)) is depressurized to 3 MPa and then introduced into a liquid ammonia storage tank. The third flash gas obtained in this process is returned to the first inlet of the compressor for recycling.

[0110] Example 2

[0111] (1) The hydrogen produced by the water electrolysis hydrogen production device 110 and the nitrogen produced by the air separation device 120 are mixed in a volume ratio of 3:1, and then introduced into the drying device 111 for drying, and the dried mixed gas is introduced into the buffer device 130; then, the hydrogen and nitrogen mixed gas and the circulating gas are introduced into the compression device 10 as the raw gas, and the raw gas is pressurized to 14.9 MPa (G) after two-stage compression; the pressurized raw gas is introduced into the synthesis tower of the synthesis device 20, and ammonia synthesis reaction is carried out under the action of a catalyst to obtain a high-temperature reaction gas including hydrogen, nitrogen and ammonia; the outlet temperature of the high-temperature reaction gas is about 450° C., and the volume content of ammonia is about 20-25%;

[0112] (2) a portion of the high-temperature reaction gas is heat exchanged with the raw gas through the heat exchange device 30, and the raw gas is preheated to 180° C. before being introduced into the synthesis tower, and the first cooled mixed gas obtained after the heat exchange is introduced into the upper part of the adsorption tower of the adsorption device 40; another portion of the high-temperature reaction gas is directly introduced into the middle and bottom of the adsorption tower, and the two high-temperature gases are heated to heat the adsorbent bed to 217° C.; the adsorbent removes ammonia at high temperature to obtain a desorbed gas; the desorbed gas includes hydrogen, nitrogen and ammonia, and the volume content of ammonia can reach 30%;

[0113] (3) The desorbed gas is cooled to 38° C. by water through a cooling device 50 (water cooler), and then passed into a cyclone separator for separation to obtain a separated mixed gas and liquid ammonia; the liquid ammonia is then passed into a flash evaporation device 60 for separation; the liquid ammonia obtained after flash evaporation is sent to a liquid ammonia storage tank 70 from the lower outlet of the device, and the first flash gas of the gas phase after flash evaporation is passed into the adsorption tower of the adsorption device 40 through the upper outlet of the device;

[0114] (4) The low-temperature first flash gas is subjected to low-temperature adsorption of ammonia by an adsorption tower to obtain a deammoniation gas from which ammonia is removed; the deammoniation gas is returned to the compression device 10 as a circulating gas and directly mixed with the raw gas to re-enter the synthesis tower for reaction.

[0115] Table 1 lists the relevant parameters and results of the condensation process of Example 1 and the prior art.

[0116] Table 1

[0117]

[0118] Based on a 15W ton / year scale, the circulation volume of hydrogen-nitrogen mixed gas is approximately 49943Nm 3 / h; Calculate the circulating gas energy consumption of Example 1 and the traditional condensation process. It can be seen from Table 1 that the power consumption per ton of ammonia in Example 1 is reduced by about 10% compared with the traditional separation process, the energy self-utilization ratio is increased to 49%, and there is no cold consumption, and the whole system has a wide requirement for circulating water. Compared with the circulating water temperature difference of 5-7°C in the traditional separation process, the temperature of the device in the embodiment of the present invention can be fully used with a temperature difference of >10°C, so the consumption of ammonia water (circulating water) per ton in Example 1 is reduced by 36% compared with the traditional separation process.

[0119] Therefore, compared with the traditional process / device, the process flow of green ammonia synthesis in Example 1 of the present invention is simple, with less equipment, convenient operation and low energy consumption. The energy consumption of a ton of ammonia in traditional coal chemical industry is 1150-1285 standard coal, and the system energy consumption of Example 1 can be reduced to about 800-900 standard coal.

[0120] Table 2 lists the relevant parameters and results of the condensation process of Example 2 and the prior art.

[0121] Table 2

[0122]

[0123] Based on a 15W ton / year scale, the circulating volume of hydrogen and nitrogen reaction gas is approximately 49943 Nm 3 / h; Calculate the circulating gas energy consumption of Example 2 and the traditional condensation process. The electricity consumption per ton of ammonia in Example 2 is reduced by about 23% compared with the traditional separation process, and the self-utilization ratio of the hot flow energy is increased to 58%. The entire system is cooled only by circulating water, and there is no cold consumption. A propylene refrigeration system is not required, which reduces energy consumption and simplifies the process.

[0124] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0125] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A method for synthesizing green ammonia using renewable energy as power, comprising the following steps: S1: providing high temperature reaction gas, wherein the temperature of the high temperature reaction gas is 400-460° C.; S2: heating the raw gas by at least part of the high-temperature reaction gas to obtain heated raw gas and a first cooled mixed gas; S3: heating the adsorbent adsorbed with ammonia by the first cooled mixed gas to desorb the ammonia to obtain a desorbed gas containing ammonia; S4: subjecting the desorbed gas to a cooling treatment and a flash vaporization treatment to obtain liquid ammonia and a first flash vapor; and S5: Adsorbing ammonia gas on the first flash gas by the adsorbent; in, The high-temperature reaction gas includes hydrogen, nitrogen and ammonia; the raw material gas includes hydrogen and nitrogen, which are used to form the high-temperature reaction gas through reaction.

2. The synthesis method according to claim 1, comprising the steps of: Providing a raw material gas, wherein the raw material gas comprises hydrogen and nitrogen; The raw gas is subjected to an ammonia synthesis reaction to obtain a high-temperature reaction gas having a temperature of 400 to 460° C.; The raw material gas is heated by at least a portion of the high-temperature reaction gas to obtain a heated raw material gas and a first cooled mixed gas; Cooling the first cooled mixed gas to obtain a second cooled mixed gas; The second cooled mixed gas is subjected to a cooling treatment and a flash vaporization treatment to obtain liquid ammonia and a second flash vapor; Adsorbing ammonia gas on the second flash gas by an adsorbent to obtain a deammoniation gas; A portion of the deammoniation gas is subjected to a temperature treatment and then used as a desorption circulating gas, and an adsorbent adsorbed with ammonia is subjected to a temperature treatment by the desorption circulating gas to desorb the ammonia, thereby obtaining a desorption gas containing ammonia; The desorbed gas is subjected to a temperature reduction treatment and a flash vaporization treatment to obtain a first flash vapor and liquid ammonia; and The first flash gas is subjected to ammonia adsorption by an adsorbent.

3. The synthesis method according to claim 1, wherein In step S3, the first cooling mixed gas is heat exchanged with the desorption circulating gas to increase the temperature of the desorption circulating gas to obtain a second cooling mixed gas and a heated desorption circulating gas; the adsorbent is heated by the heated desorption circulating gas; and / or, The hydrogen is produced by electrolysis of water.

4. The synthesis method according to claim 3, wherein The second cooled mixed gas is subjected to a cooling treatment and a flash vaporization treatment to obtain liquid ammonia and a second flash vapor; and Adsorbing ammonia gas on the second flash gas by the adsorbent to obtain deammoniation gas; and / or, The temperature of the second cooling mixed gas is 130-150° C., and the temperature of the heated desorption circulating gas is 330-350° C.; and / or, The desorption temperature is 100-120°C.

5. The synthesis method according to claim 4, wherein using at least part of the deamination gas as the desorption circulating gas; or, Using part of the deammoniation gas as the desorption circulating gas, and mixing the remaining deammoniation gas with the feed gas; and / or, In the cooling process, the second cooling mixed gas is cooled to 32-45°C.

6. The synthesis method according to claim 1, wherein The high-temperature reaction gas includes a first high-temperature reaction gas and a second high-temperature reaction gas. The first high-temperature reaction gas is used to heat the raw gas to obtain the first cooled mixed gas. The first cooled mixed gas and the second high-temperature reaction gas are brought into contact with an adsorbent adsorbed with ammonia and heated to desorb the ammonia to obtain a desorbed gas containing ammonia.

7. The synthesis method according to claim 6, wherein The desorption temperature is 200-250° C.; and / or, The desorbed gas is subjected to a temperature reduction treatment, a solid separation treatment and a flash evaporation treatment to obtain liquid ammonia.

8. The synthesis method according to claim 1, wherein The pressure of the high temperature reaction gas is 12-15 MPa; and / or, In step S4, the desorption gas is cooled to 32-45° C.; and / or, The temperature reduction treatment is performed by water cooling.

9. A green ammonia synthesis system powered by renewable energy, comprising: A synthesis device for reacting hydrogen and nitrogen to obtain a high-temperature reaction gas containing ammonia; A heat exchange device connected to the synthesis device, through which at least part of the high-temperature reaction gas can be heated to produce the raw gas for the high-temperature reaction gas; An adsorption device, used for adsorbing or desorbing the ammonia; Cooling device; Flash evaporation device; A water electrolysis hydrogen production device, used to provide the hydrogen for the synthesis device; A buffer device, disposed between the water electrolysis hydrogen production device and the synthesis device, for storing the hydrogen or the hydrogen and the nitrogen; as well as Renewable energy generation devices for providing electrical energy; The cooling device and the flash evaporation device are capable of cooling and flash evaporating the ammonia-containing gas discharged from the adsorption device or the synthesis device to obtain liquid ammonia.

10. The synthesis system according to claim 9, wherein: The system for synthesizing ammonia comprises a compression device for pressurizing the raw gas; the compression device is connected to the buffer device; A circulating gas pipeline is arranged outside the adsorption device, the heat exchange device is connected to the circulating gas pipeline, and the gas discharged from the adsorption device can re-enter the adsorption device after heat exchange with the gas in the heat exchange device through the circulating gas pipeline; or, The system for synthesizing ammonia further comprises a nitrogen generator for providing the nitrogen; or, The system for synthesizing ammonia further comprises a drying device for drying the hydrogen or the hydrogen and the nitrogen; the drying device is arranged between the water electrolysis hydrogen production device and the buffer device; or, The system for synthesizing ammonia further comprises a gas-solid separation device, which is arranged between the cooling device and the flash evaporation device.

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