Process for producing ammonia water and ammonia water production system

Abstract

The application provides an ammonia water preparation process and system, which comprises the following steps: deoxygenating raw gas to obtain deoxygenated raw gas; mixing the deoxygenated raw gas with cooled ammonia synthesis gas to obtain ammonia-rich gas; washing and absorbing the ammonia-rich gas in an ammonia absorption tower to obtain crude ammonia water and ammonia-removed circulating gas; after dehydration, compression and heat exchange, the circulating gas enters a catalyst bed for ammonia synthesis reaction to generate ammonia synthesis gas, which is cooled by heat exchange; and part of the crude ammonia water after cooling is recycled into the ammonia absorption tower, and the other part is used to prepare ammonia water products by flash evaporation. The system is suitable for the process, directly generates ammonia water products, does not need to be diluted, has no ammonia gas liquefaction and liquid ammonia storage links, has lower equipment process requirements, is suitable for small-scale green hydrogen green ammonia synthesis processes, has low application scene requirements and has a wide application range.

Description

Technical Field

[0001] This invention belongs to the field of ammonia production technology, specifically relating to a process and system for producing ammonia. Background Technology

[0002] Traditional ammonia synthesis processes involve liquefying and purifying ammonia gas into liquid ammonia as the product. This traditional process is widely used in large-scale chemical plants, but in smaller processes such as green hydrogen to green ammonia production, the liquid ammonia product typically needs to be diluted into ammonia water before use. However, ammonia liquefaction and liquid ammonia storage place high demands on equipment, processes, and application scenarios. Therefore, there is an urgent need to develop an ammonia water production process and system suitable for smaller processes and meeting the needs of more diverse applications. Summary of the Invention

[0003] To address the shortcomings of the existing technologies, this invention provides a process and system for producing ammonia water. This method and system directly generate ammonia water without dilution, ammonia liquefaction, or liquid ammonia storage. It has lower equipment and process requirements, is suitable for small-scale ammonia synthesis processes such as green hydrogen to green ammonia production, has low requirements for application scenarios, and has a wide range of applications.

[0004] The technical solution adopted in this invention is as follows: A process for producing ammonia water includes the following steps: S100 deoxygenates the raw material gas to obtain deoxygenated raw material gas; S200, the deoxygenated raw material gas is mixed with the cooled ammonia synthesis gas to obtain ammonia-rich gas; S300, the ammonia-rich gas is washed and absorbed by an ammonia absorption tower to obtain crude ammonia water and ammonia-free circulating gas; S400, the circulating gas, after being dehydrated, compressed, and heated by heat exchange, enters the catalyst bed to carry out the ammonia synthesis reaction, generating ammonia synthesis gas, which is then cooled by heat exchange. S500, after the crude ammonia water is discharged and cooled, part of it is recycled back into the ammonia absorption tower, and the other part is flash-distilled to obtain ammonia water product.

[0005] In one embodiment of this application, heat exchange heating in step S400 includes: The first stage of heat exchange heating involves exchanging heat with the outside of the catalyst bed for the ammonia synthesis reaction after the compressed circulating gas undergoes heat exchange heating. The second-stage heat exchange heating involves the circulating gas after the first-stage heat exchange heating being heated by heat exchange with the ammonia synthesis gas. The third stage of heat exchange heating involves the circulating gas, after being heated in the second stage, entering the catalyst bed of the ammonia synthesis reaction through a pipeline for further heat exchange heating.

[0006] In one embodiment of this application, the circulating gas is heated to 90°C~100°C via a first-stage heat exchanger, to 270°C~310°C via a second-stage heat exchanger, and to 350°C~480°C via a third-stage heat exchanger.

[0007] In one embodiment of this application, step S400 further includes a first temperature regulation process after heat exchange heating. The first temperature regulation process includes: dividing the circulating gas after secondary heat exchange heating into two parts, one part undergoing tertiary heat exchange heating, and the other part serving as temperature regulation gas, mixing with the circulating gas after tertiary heat exchange heating, and then entering the catalyst bed for ammonia synthesis reaction after temperature regulation.

[0008] In one embodiment of this application, step S400 further includes a second temperature adjustment process after heat exchange heating. The second temperature adjustment process includes: electrically heating the circulating gas after the third-stage heat exchange heating to adjust the temperature, and then entering the catalyst bed for ammonia synthesis reaction after temperature adjustment.

[0009] In one embodiment of this application, in step S400, the temperature of the circulating gas entering the catalyst bed for the ammonia synthesis reaction is 320°C to 360°C.

[0010] In one embodiment of this application, in step S400, the ammonia synthesis gas is cooled by heat exchange, which includes: the ammonia synthesis gas is cooled by heat exchange in a first heat exchanger, and then cooled by heat exchange in a second heat exchange cooler with the circulating gas heated by the first stage heat exchange. After cooling, it is mixed with the deoxygenated raw material gas to form ammonia-rich gas.

[0011] In one embodiment of this application, in step S400, the circulating gas is dehydrated until the water content in the gas is ≤5ppmv and compressed to a pressure of 7.0~8.0 MPaG; the ammonia content of the cooled ammonia synthesis gas is about 8.5%.

[0012] Based on the same inventive concept, the present invention also provides an ammonia-producing system, comprising: The deoxygenation tower has its inlet end connected to the raw gas pipeline and its outlet end connected to the first pipeline. The ammonia absorption tower has an air inlet at its lower part connected to the first pipeline. The ammonia absorption tower is provided with a circulating gas outlet at the top and an ammonia discharge outlet at the bottom. The ammonia synthesis tower has an inlet and a synthetic ammonia outlet. The dehydration and drying device and the compression device are connected in series via a second pipeline. The inlet end of the dehydration and drying device is connected to the outlet of the circulating gas via the second pipeline, and the outlet end of the compression device is connected to the inlet end of the ammonia synthesis tower via the second pipeline. The heat exchange component has its inlet end connected to the ammonia synthesis outlet via a third pipeline, and its outlet end connected to the first pipeline via a third pipeline. The ammonia synthesis gas and the deoxygenation feed gas are mixed in the first pipeline and sent into the ammonia absorption tower.

[0013] In one embodiment of this application, the heat exchange assembly includes a first heat exchanger and a second heat exchanger sequentially arranged via the third pipeline.

[0014] In one embodiment of this application, the ammonia synthesis tower is provided with a protective gas inlet and a synthetic ammonia outlet at the bottom, and a protective gas outlet, a circulating gas inlet and a temperature regulating gas inlet at the top. The protective gas inlet is connected to the outlet of the compression device via a second pipeline. Gas entering through the protective gas inlet is discharged through the protective gas outlet. The protective gas outlet is connected to the heating medium inlet of the second heat exchanger via a fourth pipeline. The heating medium outlet of the second heat exchanger is connected to the circulating gas inlet via a fifth pipeline and to the temperature regulating gas inlet via a sixth pipeline.

[0015] In one embodiment of this application, the ammonia synthesis tower includes a central pipe, a central pipe outer cylinder, an inner cylinder, and an outer shell arranged sequentially from the inside out; There is a first annular gap between the outer shell and the inner cylinder, the lower part of the first annular gap is connected to the protective gas inlet, and the upper part is connected to the protective gas outlet; There is a second annular gap between the inner cylinder and the outer cylinder of the central tube. A catalyst bed is provided in the second annular gap. The lower part of the second annular gap is connected to the ammonia synthesis outlet. There is a third annular gap between the central tube and the outer cylinder of the central tube. The upper outer wall of the central tube is sealed to the upper end of the outer cylinder of the central tube. A first vent is provided on the side wall of the central tube above the connection. The first vent communicates with the inside of the central tube and the second annular gap. The lower end of the central tube communicates with the third annular gap. The upper part of the third annular gap communicates with the temperature regulating gas inlet. The bottom of the outer cylinder of the central tube is sealed, and a second vent is provided on the lower side wall. It also includes a heat exchange tube, which is disposed in the catalyst bed, with its upper end connected to the circulating gas inlet and its lower end connected to the inner cylinder of the central tube through the second gas hole.

[0016] In one embodiment of this application, an electric heater is provided inside the central tube, and the electric heater is used to heat the gas inside the central tube; And / or, the outer wall of the central tube is provided with a heat insulation layer.

[0017] In one embodiment of this application, a support plate is provided in the lower part of the inner cylinder, the middle part of the support plate is sealed to the bottom of the outer cylinder of the central tube, and a plurality of third air holes are provided in the outer circumferential direction of the support plate, the third air holes connecting the second annular gap to the ammonia synthesis outlet.

[0018] In one embodiment of this application, the catalyst bed includes a first catalyst layer located in the upper part of the second annular space and a second catalyst layer located in the lower part of the second annular space.

[0019] In one embodiment of this application, the heat exchange tube includes a straight tube section at the upper part and a tube bundle assembly at the lower part; The upper end of the straight pipe section is connected to the circulating gas inlet; The tube bundle assembly includes an upper gas collecting pipe, several tube bundles, and a lower gas collecting pipe. The upper gas collecting pipe connects the lower end of the straight pipe section to the upper end of the tube bundles, and the lower gas collecting pipe connects the lower end of the tube bundles to the second air hole.

[0020] In one embodiment of this application, it further includes a circulating pump, a cooler, a flash tank, and an external pump connected in sequence. The inlet end of the circulating pump is connected to the ammonia discharge port via a pipeline, and the external pump outputs ammonia water product.

[0021] In one embodiment of this application, the ammonia absorption tower is provided with an upper packing section and a lower packing section. The ammonia absorption tower is provided with a demineralized water inlet above the upper packing section and a washing liquid circulation inlet between the upper packing section and the lower packing section. The washing liquid circulation inlet is connected to the outlet end of the cooler via a pipeline.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The ammonia production process and system of the present invention directly generate ammonia products without dilution, ammonia liquefaction and liquid ammonia storage, and has lower equipment and process requirements. It is suitable for small-scale synthetic ammonia processes such as green hydrogen to green ammonia, has low requirements for application scenarios, and has a wide range of applications.

[0023] 2. This method and system mix the deoxygenated raw gas with ammonia synthesis gas and then enter the ammonia absorption tower for washing and ammonia removal / ammonia water production. The washing process after diluting the ammonia synthesis gas with the raw gas allows for more thorough ammonia absorption, and the discharged circulating gas contains almost no ammonia. At the same time, the raw gas, after passing through the ammonia absorption tower, is used as circulating gas for dehydration, compression, and heat exchange before undergoing the ammonia synthesis reaction to generate ammonia synthesis gas. This effectively reduces the number of equipment, simplifies the system and process, and makes the production process easier to control.

[0024] 3. This method and system effectively utilize the heat released from the ammonia synthesis reaction to heat the circulating gas in multiple stages, heating the circulating gas to the inlet temperature required for the ammonia synthesis reaction. Simultaneously, it cools the catalyst bed inside the ammonia synthesis reaction, cools the discharged ammonia synthesis gas, and controls the cooling of the exterior of the ammonia synthesis tower. Once started, the ammonia synthesis reaction can continue without requiring additional heat energy. It can also provide heat energy for other media requiring heating in the system (such as demineralized water, steam, and heat transfer oil), resulting in high efficiency, low energy consumption, and high equipment safety.

[0025] 4. This invention provides a compact and reasonable ammonia synthesis tower, which can use circulating gas as a protective gas to effectively control the upper temperature limit of the ammonia synthesis tower and protect its safe and normal operation; it can effectively utilize the heat released by the ammonia synthesis reaction to heat the circulating gas, while controlling the temperature of the ammonia synthesis reaction, which is conducive to obtaining a better chemical equilibrium and reaction rate, and improving the efficiency of the ammonia synthesis reaction; and it can effectively adjust the inlet temperature of the ammonia synthesis reaction to ensure that the ammonia synthesis reaction proceeds stably and efficiently. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the ammonia production process in this invention.

[0028] Figure 2 This is a schematic diagram of the process route for the ammonia production system in this invention.

[0029] Figure 3 This is a schematic diagram of the ammonia synthesis tower in this invention.

[0030] Figure 4 This is a schematic diagram of the ammonia absorption tower in this invention.

[0031] Figure label: 1. Deoxygenation tower; 10. First pipeline; 2. Ammonia absorption tower; 201. Demineralized water pump; 202. Demineralized water inlet; 203. Washing liquid circulation inlet; 21. Upper packing section; 22. Lower packing section; 3. Ammonia Synthesis Tower; 301. Protective Gas Inlet; 302. Protective Gas Outlet; 303. Circulating Gas Inlet; 304. Temperature Control Gas Inlet; 305. Synthetic Ammonia Outlet; 306. Fourth Pipeline; 307. Fifth Pipeline; 308. Sixth Pipeline; 31. Central Pipe; 311. First Gas Hole; 32. Outer Cylinder of Central Pipe; 320. Third Annular Gap; 321. Second Gas Hole; 33. Inner Cylinder; 330. Second Annular Gap; 331. First Catalyst Layer; 332. Second Catalyst Layer; 34. Outer Shell; 340. First Annular Gap; 35. Support Plate; 351. Third Gas Hole; 36. Electric Heater; 4. Dehydration and drying device; 40. Second pipeline; 5. Compression device 60. Third pipeline; 61. First heat exchanger; 62. Second heat exchanger; 71. Straight pipe section; 72. Upper gas collecting pipe; 73. Tube bundle; 74. Lower gas collecting pipe; 8. Circulating pump; 81. Cooler; 9. Flash evaporator; 91. External pump. Detailed Implementation

[0032] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0033] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "vertical," "top," "bottom," "inner," "outer," "circumferential," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0034] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0035] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0036] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0037] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention.

[0038] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] like Figure 1 As shown in the figure, an embodiment of the present invention provides a process for producing ammonia water, which includes the following steps: S100 deoxygenates the raw gas to obtain deoxygenated raw gas.

[0040] The feed gas is a mixture of nitrogen and hydrogen in a certain proportion. Preferably, the feed gas is pressurized to 7.0~8.0 MPaG and then sent to a deoxygenation tower for deoxygenation treatment to remove oxygen impurities from the feed gas, prevent oxygen from entering the subsequent ammonia synthesis reaction section and causing catalyst poisoning, and ensure the continuous and efficient operation of the ammonia water production process.

[0041] S200 mixes the deoxygenated feed gas after deoxygenation treatment with the cooled ammonia synthesis gas to produce ammonia-rich gas.

[0042] S300, the above-mentioned ammonia-rich gas is sent from the lower part of the ammonia absorption tower into the ammonia absorption tower, where it is washed and absorbed to obtain crude ammonia water and ammonia-free circulating gas.

[0043] Specifically, ammonia-rich gas enters the ammonia absorption tower from the bottom. The gas rises within the tower, flowing through the lower packing layer, where it is washed by cooled circulating washing liquid (i.e., crude ammonia water) fed in from the top of this packing layer, as well as the liquid remaining from the upper packing layer. Most of the ammonia in the rich ammonia gas is absorbed. The gas continues upward through the upper packing layer, where it is washed by demineralized water fed in from the top of this packing layer. Almost all of the ammonia in the gas is absorbed. The washed gas is the ammonia-free circulating gas, discharged from the circulating gas outlet at the top of the ammonia absorption tower to the next process stage. The ammonia absorbed during washing enters the bottom of the tower with the washing liquid, where crude ammonia water is obtained. Preferably, the crude ammonia water has a mass concentration of approximately 20%.

[0044] In step S400, the circulating gas obtained in step S300 is successively dehydrated, compressed and pressurized, and then heated by heat exchange before being sent to the ammonia synthesis tower for ammonia synthesis reaction to generate ammonia synthesis gas. The ammonia synthesis gas is then cooled by heat exchange, and the cooled ammonia synthesis gas is then mixed with the deoxygenated raw material gas in step S200 to become ammonia-rich gas.

[0045] Specifically, the circulating gas discharged from the top of the ammonia absorber has a water content of approximately ~0.13 (V / V%). This water content is removed by a dehydration and drying unit to obtain dry circulating gas. Preferably, the water content in this dried circulating gas is controlled to ≤5 ppmv, and the oxygen content to ≤1 ppmv. This effectively ensures that the dehydrated circulating gas will not cause catalyst poisoning when it enters the subsequent ammonia synthesis process.

[0046] The dried circulating gas is compressed and pressurized by a compression device, preferably to a pressure of 7.0~8.0 MPaG, before being sent to subsequent heat exchange and heating treatment. After being heated to the temperature required for the ammonia synthesis reaction inlet gas, it comes into contact with the catalyst to carry out the ammonia synthesis reaction. After the ammonia synthesis reaction, ammonia synthesis gas is generated. This ammonia synthesis gas is cooled by heat exchange, preferably to a temperature below 100°C, and the ammonia content in the cooled ammonia synthesis gas is 8~10%, preferably controlled at around 8.5%. After cooling, it is mixed with the deoxygenated feed gas in the aforementioned step S200.

[0047] In S500, the crude ammonia water produced at the bottom of the ammonia synthesis tower is discharged and cooled. After cooling, part of the crude ammonia water is circulated into the ammonia absorption tower as a circulating washing liquid to wash and absorb ammonia in the ammonia-rich gas. The other part is treated by flash evaporation and depressurization to obtain the desired ammonia water product.

[0048] The amount of crude ammonia water that is circulated into the ammonia absorption tower as circulating washing liquid is greater than the amount of crude ammonia water sent to flash evaporation to prepare ammonia water products.

[0049] Specifically, the crude ammonia water at the bottom of the ammonia synthesis tower is pumped out and pressurized by a circulating pump and sent to a cooler for cooling. After cooling, most of the liquid is returned to the middle of the ammonia absorption tower as circulating washing liquid, and a small portion of the liquid is introduced into the ammonia water flash evaporation tank for flash evaporation and depressurization to atmospheric pressure. Non-condensable gases such as hydrogen, nitrogen, and argon dissolved in the crude ammonia water, as well as a small amount of ammonia gas and water vapor, are flash-separated from the liquid phase and discharged through the vent pipe. The liquid phase after flash evaporation and degassing is the ammonia water product with a mass concentration of about 20%.

[0050] The aforementioned ammonia water production process involves mixing the deoxygenated feed gas with ammonia synthesis gas and then feeding it into an ammonia absorption tower for washing and ammonia removal / production. The washing process after diluting the ammonia synthesis gas with the feed gas ensures more thorough ammonia absorption, resulting in exhaust recirculated gas that is almost ammonia-free. Simultaneously, the feed gas, after passing through the ammonia absorption tower, is used as recirculated gas for dehydration, compression, and heat exchange before entering the catalyst bed for ammonia synthesis. This effectively reduces the number of equipment units (e.g., reducing the need for dehydration and drying devices), simplifying the system and process, and making production easier to control. Furthermore, this process directly produces ammonia water without dilution, ammonia liquefaction, or liquid ammonia storage. It has lower equipment and process requirements, is suitable for small-scale ammonia synthesis processes such as green hydrogen to green ammonia production, has low application requirements, and a wide range of applicability.

[0051] Further, in step S400, the heat exchange heating includes: a first-stage heat exchange heating, where the compressed circulating gas exchanges heat with the outside of the catalyst bed for the ammonia synthesis reaction; a second-stage heat exchange heating, where the circulating gas after the first-stage heat exchange heating exchanges heat with the ammonia synthesis gas; and a third-stage heat exchange heating, where the circulating gas after the second-stage heat exchange heating enters the inside of the catalyst bed for the ammonia synthesis reaction through a pipeline for heat exchange heating. That is, in step S400, the compressed circulating gas undergoes three stages of heat exchange sequentially to achieve heating.

[0052] Specifically, the compressed circulating gas, acting as a protective flow, passes through the outer periphery of the catalyst bed in the ammonia synthesis reaction. It exchanges heat with the outer periphery of the catalyst bed where the ammonia synthesis reaction occurs, absorbing the heat generated by the reaction and achieving the first-stage heat exchange heating of the circulating gas. This heat exchange between the circulating gas and the outer periphery of the catalyst bed effectively lowers the upper temperature limit of the ammonia synthesis reaction, protecting the equipment and ensuring its normal operation. Preferably, the circulating gas is heated to 90℃~100℃ after the first-stage heat exchange.

[0053] The circulating gas, heated in the first stage of heat exchange, is heated again by the ammonia synthesis gas produced and discharged from the ammonia synthesis reaction. This second-stage heat exchange simultaneously cools the ammonia synthesis gas. In other words, the heat from the ammonia synthesis gas is recovered and utilized for the second-stage heat exchange heating of the circulating gas. Preferably, the circulating gas is heated to 270℃~310℃ in the second-stage heat exchange, while the ammonia synthesis gas is cooled to below 100℃.

[0054] The circulating gas, after being heated in the second stage of heat exchange, then enters the catalyst bed of the ammonia synthesis reaction through pipes (i.e., heat exchange tubes) for further heat exchange, achieving a third stage of heat exchange for the circulating gas while simultaneously cooling the catalyst bed. This utilizes the heat from the ammonia synthesis reaction to heat the circulating gas, effectively reducing and controlling the temperature inside the catalyst bed. This facilitates a shift in the equilibrium of the ammonia synthesis reaction towards ammonia production, resulting in a higher equilibrium concentration and improved ammonia synthesis efficiency. Preferably, the temperature of the circulating gas after the third stage of heat exchange is controlled between 350℃ and 480℃, and even more preferably, between 350℃ and 420℃.

[0055] In a further embodiment, step S400, after heat exchange heating, includes a first temperature regulation process. This first temperature regulation process includes: dividing the circulating gas after the second-stage heat exchange heating into two parts; one part undergoes the aforementioned third-stage heat exchange heating; and the other part serves as temperature regulation gas, which is mixed with the circulating gas after the third-stage heat exchange heating to regulate the temperature. The temperature-regulated mixed gas then enters the catalyst bed for the ammonia synthesis reaction. This first temperature regulation process effectively prevents excessively high circulating gas temperatures entering the catalyst bed from inhibiting the ammonia synthesis reaction.

[0056] Furthermore, in step S400, after heat exchange heating, a second temperature control process is included. This second temperature control process involves electrically heating the circulating gas after the third-stage heat exchange heating to adjust its temperature before it enters the catalyst bed for the ammonia synthesis reaction. This second temperature control process effectively prevents the circulating gas entering the catalyst bed from being too cold, ensuring the efficient conduct of the ammonia synthesis reaction.

[0057] By employing a first temperature control treatment and / or a second temperature control treatment, the temperature of the circulating gas entering the catalyst bed to participate in the ammonia synthesis reaction can be effectively ensured to be within a suitable range. Preferably, the temperature of the circulating gas entering the catalyst bed for the ammonia synthesis reaction is controlled to be 320℃~360℃.

[0058] In step S400, the ammonia synthesis gas undergoes heat exchange cooling, including: after being cooled by a first heat exchanger, the ammonia synthesis gas is further cooled by a second heat exchanger with the circulating gas heated in the first stage of heat exchange. The cooled ammonia synthesis gas is then mixed with the deoxygenated feed gas to produce ammonia-rich gas for ammonia water production. The other heat exchange medium in the first heat exchanger can be other media requiring heating in the ammonia water production system, such as demineralized water, steam, or heat transfer oil, to more fully recover and utilize the heat energy in the ammonia synthesis gas and reduce the energy consumption of the ammonia water production system. After being cooled to below 100°C, the ammonia synthesis gas is mixed with the deoxygenated feed gas to produce ammonia-rich gas for ammonia water production.

[0059] Based on the same inventive concept, embodiments of the present invention also provide an ammonia-producing system. For example... Figures 2 to 4As shown, the ammonia production system includes a deoxygenation tower 1, an ammonia absorption tower 2, an ammonia synthesis tower 3, a deoxygenation drying device 4, a compression device 5, and heat exchange components.

[0060] The deoxygenation tower 1 is used for deoxygenation treatment of the raw gas. Its inlet end is connected to the raw gas pipeline, and its outlet end is connected to the first pipeline 10. A highly efficient deoxygenation catalyst is installed inside the deoxygenation tower 1. Under the action of the catalyst, oxygen impurities in the nitrogen-hydrogen raw gas react with hydrogen to generate water, thereby achieving oxygen removal.

[0061] Preferably, a raw material gas buffer tank 101 and a raw material gas compression device 102 are also provided at the front end of the deoxygenation tower 1. The raw material gas buffer tank 101 and the raw material gas compression device 102 are connected to the deoxygenation tower 1 in sequence via the raw material gas pipeline. They are used to temporarily store the nitrogen and hydrogen raw material gas mixed in a certain proportion and to compress the raw material gas to 7.0~8.0 MPaG before sending it to the deoxygenation tower 1.

[0062] The ammonia absorption tower 2 is used to wash and absorb ammonia gas to prepare ammonia water. The ammonia absorption tower 2 is set vertically, and its lower part is provided with an air inlet for ammonia-rich gas to enter. The air inlet is connected to the first pipeline 10. The top of the ammonia absorption tower 2 is provided with a circulating gas outlet for discharging the washed gas (i.e., circulating gas). The bottom of the ammonia absorption tower 2 is provided with an ammonia discharge port for discharging the crude ammonia water and / or washing liquid that has been collected at the bottom of the ammonia absorption tower 2.

[0063] The ammonia synthesis tower 3 is used to catalyze the ammonia synthesis reaction to generate ammonia synthesis gas. The ammonia synthesis tower 3 is set vertically and has an inlet end and a synthetic ammonia outlet 305.

[0064] The dehydration drying device 4 and the compression device 5 are connected in series via a second pipeline 40. The inlet of the dehydration drying device 4 is connected to the circulating gas outlet at the top of the ammonia absorption tower 2 via the second pipeline 40, and the outlet of the dehydration drying device 4 is connected to the inlet of the compression device 5 via the second pipeline 40. The outlet of the compression device 5 is connected to the gas inlet of the ammonia synthesis tower 3 via the second pipeline 40. The circulating gas discharged from the top of the ammonia absorption tower 2 is dehydrated and dried by the dehydration drying device 4 to reduce the water content in the circulating gas to ≤5ppmv. Preferably, the dehydration drying device 4 is a temperature swing adsorption (TSA) gas dryer, but it can also be a device using cryogenic drying technology. The dried circulating gas is compressed and pressurized by the compression device 5, preferably to 7.0~8.0 MPaG, and then sent to the ammonia synthesis tower 3.

[0065] The heat exchange component performs heat exchange to cool the ammonia synthesis gas and recover its heat. Simultaneously, it can also be used to heat the circulating gas and other heat-requiring media in the system. The inlet end of the heat exchange component is connected to the ammonia synthesis outlet 305 of the ammonia synthesis tower 3 via a third pipeline 60, and the outlet end of the heat exchange component is connected to the first pipeline 10 via the third pipeline 60. In the first pipeline 10, the ammonia synthesis gas is mixed with the deoxygenated feed gas to form ammonia-rich gas, which is then sent to the ammonia absorption tower 2.

[0066] The system deoxygenates the raw material gas and mixes it with ammonia synthesis gas before entering the ammonia absorption tower for washing and ammonia removal / ammonia water production. The washing process after diluting the ammonia synthesis gas with the raw material gas allows for more thorough ammonia absorption, and the discharged circulating gas contains almost no ammonia. At the same time, the raw material gas, after passing through the ammonia absorption tower, is used as circulating gas for dehydration, compression and pressurization, and then undergoes an ammonia synthesis reaction to generate ammonia synthesis gas. This effectively reduces the number of equipment, simplifies the system and process, and makes the production process easier to control.

[0067] In one embodiment, the heat exchange assembly includes a first heat exchanger 61 and a second heat exchanger 62 connected sequentially via a third pipeline 60. The inlet end of the first heat exchanger 61 is connected to the ammonia synthesis outlet 305 via the third pipeline 60, the outlet end of the first heat exchanger 61 is connected to the inlet end of the second heat exchanger 62, and the outlet end of the second heat exchanger 62 is connected to the first pipeline 10 via the third pipeline 60. That is, the ammonia synthesis gas discharged from the ammonia synthesis tower 3 undergoes two-stage heat exchange and cooling (i.e., two-stage heat exchange and heat energy recovery) via the first heat exchanger 61 and the second heat exchanger 62.

[0068] In a further embodiment, the ammonia synthesis tower 3 has a protective gas inlet 301 and a synthetic ammonia outlet 305 at its lower part, and a protective gas outlet 302, a circulating gas inlet 303, and a temperature-regulating gas inlet 304 at its upper part. The protective gas inlet 301 is connected to the outlet of the compression device 5 via a second pipeline 40, and the compressed circulating gas enters the ammonia synthesis tower 3 as protective gas. The gas entering through the protective gas inlet 301 (protective gas) is discharged through the protective gas outlet 302; this outlet is connected to the heating medium inlet of the second heat exchanger 62 via a fourth pipeline 306, allowing the heated circulating gas (protective gas) to exchange heat with the ammonia synthesis gas in the second heat exchanger 62; the heating medium outlet of the second heat exchanger 62 is connected to the circulating gas inlet 303 at the upper part of the ammonia synthesis tower 3 via a fifth pipeline 307, and simultaneously, the heating medium outlet of the second heat exchanger 62 is connected to the temperature-regulating gas inlet 304 at the upper part of the ammonia synthesis tower 3 via a sixth pipeline 308. After being heated by the second heat exchanger 62, the circulating gas can enter the ammonia synthesis tower 3 through the fifth pipeline 307 and / or the sixth pipeline 308 to participate in the ammonia synthesis reaction.

[0069] Furthermore, such as Figure 3As shown, the ammonia synthesis tower 3 includes a central pipe 31, a central pipe outer cylinder 32, an inner cylinder 33, and an outer shell 34 arranged sequentially from the inside to the outside. Preferably, the ammonia synthesis tower 3 is a cylindrical tower body, and the central pipe 31, the central pipe outer cylinder 32, the inner cylinder 33, and the outer shell 34 are arranged coaxially.

[0070] There is a first annular gap 340 between the outer shell 34 and the inner cylinder 33. The lower part of the first annular gap 340 is connected to the protective gas inlet 301, and the upper part is connected to the protective gas outlet 302. The first annular gap 340 is a circulation channel for circulating gas as protective gas.

[0071] A second annular gap 330 is provided between the inner cylinder 33 and the outer cylinder 32 of the central tube. This second annular gap 330 is the ammonia synthesis reaction zone, and a catalyst bed is provided therein. The lower part of the second annular gap 330 is connected to the ammonia synthesis outlet 305.

[0072] There is a third annular gap 320 between the central tube 31 and the outer cylinder 32 of the central tube; the upper outer wall of the central tube 31 is sealed to the upper end of the outer cylinder 32 of the central tube, and a number of first vent holes 311 are opened on the side wall of the central tube 31 above the connection. The first vent holes 311 connect the interior of the central tube 31 with the second annular gap 330, that is, the gas in the central tube 31 enters the catalyst bed of the second annular gap 330 through the first vent holes 311. The lower end of the central tube 31 is suspended, connecting the inside of the central tube 31 with the third annular gap 320 on the outside. The upper part of the third annular gap 320 is connected to the temperature regulating gas inlet 304 via a pipeline. The bottom of the outer cylinder 32 of the central tube is a sealed end, and several second vents 321 are provided on the lower side wall of the outer cylinder 32 of the central tube. The temperature regulating gas enters from the upper part of the third annular gap 320 and moves downward, mixing with the gas entering through the second vents 321. It then enters the central tube 31 from the bottom and moves upward through the first vent 311 into the catalyst bed of the second annular gap 330.

[0073] It also includes a heat exchange tube, which is disposed within the catalyst bed. The upper end of the heat exchange tube is connected to the circulating gas inlet 303, and the lower end is connected to the interior of the outer cylinder 32 of the central tube through a second gas hole 321 at the lower part of the outer cylinder 32. The circulating gas entering through the circulating gas inlet 303 moves from top to bottom to exchange heat, and enters the outer cylinder 32 of the central tube through several second gas holes 321 to mix with the temperature regulating gas.

[0074] The third annular gap 320 is designed to work in conjunction with the temperature regulating gas inlet 304, allowing the temperature regulating gas to flow from top to bottom through the inner wall of the outer cylinder 32 of the central tube and then into the central tube 31. This effectively absorbs the heat of the catalyst bed on the outer cylinder 32 side of the central tube, ensuring uniform heat exchange in the catalyst bed and reducing heat leakage from the inner central tube 31. At the same time, the introduction of temperature regulating gas adjusts the temperature of the circulating gas entering from the heat exchange tube, effectively preventing the gas temperature entering the catalyst bed from being too high.

[0075] In one embodiment, an electric heater 36 is provided inside the central tube 31 to heat the gas inside the central tube 31. When the temperature of the circulating gas or the mixture of circulating gas and temperature-regulating gas entering the central tube 31 is too low, the electric heater 36 is activated to heat the circulating gas or the mixture of circulating gas and temperature-regulating gas to ensure that the temperature of the gas entering the catalyst bed is within the set range, thus ensuring the efficient catalytic ammonia synthesis reaction.

[0076] Preferably, the outer wall of the central tube 31 is provided with an insulation layer, which can effectively prevent the heat of the catalyst bed and circulating gas from being lost through the central tube 31.

[0077] In one embodiment, the catalyst bed is divided into two parts, including a first catalyst layer 331 located in the upper part of the second annular space 330 and a second catalyst layer 332 located in the lower part of the second annular space 330. The segmentation of the catalyst bed provides favorable conditions for the triggering and continuous conduct of the ammonia synthesis reaction.

[0078] The lower part of the inner cylinder 33 is provided with a support plate 35, the middle part of which is sealed to the bottom of the outer cylinder 32 of the central tube. The outer periphery of the support plate 35 is provided with several vertically penetrating third vent holes 351, which connect the second annular gap 330 to the ammonia synthesis outlet 305. Specifically, a partition is provided at the lower part of the support plate 35. The partition seals the bottom of the first annular gap 340 and forms a collecting cavity with the support plate 35 and the outer cylinder 32 of the central tube. The ammonia synthesis outlet 305 is connected to the collecting cavity through a pipeline. The ammonia synthesis gas after the catalytic reaction enters the collecting cavity through the third vent holes 351 and is then discharged from the ammonia synthesis outlet 305.

[0079] In one embodiment, the heat exchange tube includes an upper straight tube section 71 and a lower tube bundle assembly. The straight tube section 71 is vertically disposed in the region of the first catalyst layer 331, and its upper end communicates with the circulating gas inlet 303. The tube bundle assembly is disposed in the region of the second catalyst layer 332 and includes an upper gas collecting pipe 72, a plurality of tube bundles 73, and a lower gas collecting pipe 74. The upper gas collecting pipe 72 connects the lower end of the straight tube section 71 and the upper ends of all tube bundles 73, and the lower gas collecting pipe 74 connects the lower ends of all tube bundles 73 and all second vents 321. Preferably, the upper gas collecting pipe 72 and the lower gas collecting pipe 74 are annular pipes, and the plurality of tube bundles 73 are vertically arranged, which can be arranged in multiple layers inside and outside, and are evenly distributed circumferentially along the upper gas collecting pipe 72 and the lower gas collecting pipe 74. The segmented arrangement of the heat exchange tubes and catalyst bed allows for better heat exchange and control of the internal temperature of the catalyst bed. This enables the rapid initiation of the ammonia synthesis reaction under relatively higher temperature conditions and promotes the shift of the reaction equilibrium towards ammonia synthesis under relatively lower temperature conditions. This facilitates the rapid and efficient ammonia synthesis reaction, resulting in a better chemical equilibrium and reaction rate.

[0080] The ammonia production system also includes a circulating pump 8, a cooler 81, a flash evaporator 9, and an external pump 91 connected in sequence. The inlet of the circulating pump 8 is connected via a pipeline to the ammonia discharge port at the bottom of the ammonia absorption tower 2. The crude ammonia water exiting the bottom of the ammonia absorption tower 2 is pressurized by the circulating pump 8, flows through the cooler 81 where it is cooled by circulating water, and is then sent to the flash evaporator 9 or returned to the ammonia absorption tower 2. The external pump 91 is connected to the flash evaporator 9 and is used to output the ammonia water product obtained after flash evaporation.

[0081] The ammonia absorption tower 2 has an upper packing section 21 and a lower packing section 22. Above the upper packing section 21, the ammonia absorption tower 2 has a demineralized water inlet 202, which is connected to a demineralized water pump 201 via a pipeline. The demineralized water pump 201 delivers demineralized water to the top of the packing in the ammonia absorption tower 2 through the demineralized water inlet, allowing the demineralized water to flow downwards through the upper packing section 21 and the lower packing section 22, ensuring sufficient contact with the upward-moving gas for washing, adsorption, and ammonia removal. Furthermore, a washing liquid circulation inlet 203 is located between the upper packing section 21 and the lower packing section 22, and this inlet 203 is connected to the outlet of the cooler 81 via a pipeline. The crude ammonia water exiting the bottom of the ammonia absorption tower 2 is pressurized by the circulation pump 8 and flows through the cooler 81 where it is cooled by circulating water. Part of it is sent to the flash tank 9, and the other part is returned to the ammonia absorption tower 2 via the washing liquid circulation inlet 203.

[0082] In summary, the ammonia production process and system of the present invention, after deoxygenation of the raw material gas, mixes it with ammonia synthesis gas and enters the ammonia absorption tower for washing and ammonia removal / production. The washing of the raw material gas after diluting the ammonia synthesis gas allows for more thorough ammonia absorption, and the discharged circulating gas contains almost no ammonia. At the same time, the raw material gas, after passing through the ammonia absorption tower, is used as circulating gas for dehydration, compression, and heat exchange, and then undergoes an ammonia synthesis reaction to generate ammonia synthesis gas. This can effectively reduce the number of equipment, simplify the system and process, and make the production process easier to control.

[0083] This method and system effectively utilize the heat released from the ammonia synthesis reaction to heat the circulating gas in multiple stages, raising the circulating gas to the inlet temperature required for the ammonia synthesis reaction. Simultaneously, it cools the catalyst bed inside the ammonia synthesis reaction, cools the discharged ammonia synthesis gas, and controls the cooling of the exterior of the ammonia synthesis tower. Once started, the ammonia synthesis reaction can continue without requiring additional heat energy. It can also provide heat energy for other media requiring heating in the system (such as demineralized water, steam, and heat transfer oil), resulting in high efficiency, low energy consumption, and high equipment safety.

[0084] The ammonia synthesis tower of this invention has a compact and reasonable structure. It can use circulating gas as a protective gas to effectively control the upper temperature limit of the ammonia synthesis tower and protect its safe and efficient operation. It can effectively use the heat released by the ammonia synthesis reaction to heat the circulating gas, while controlling the temperature of the ammonia synthesis reaction, which is conducive to obtaining a better chemical equilibrium and reaction rate, and improving the efficiency of the ammonia synthesis reaction. It can also effectively adjust the inlet temperature of the ammonia synthesis reaction to ensure that the ammonia synthesis reaction proceeds stably and efficiently.

[0085] The ammonia production process and system of the present invention directly generate ammonia products without dilution, ammonia liquefaction, or liquid ammonia storage. It has lower equipment and process requirements, is suitable for small-scale ammonia synthesis processes such as green hydrogen to green ammonia, has low requirements for application scenarios, and has a wide range of applications.

Claims

1. A process for producing ammonia water, characterized in that, Includes the following steps: S100 deoxygenates the raw material gas to obtain deoxygenated raw material gas; S200, the deoxygenated raw material gas is mixed with the cooled ammonia synthesis gas to obtain ammonia-rich gas; S300, the ammonia-rich gas is washed and absorbed by an ammonia absorption tower to obtain crude ammonia water and ammonia-free circulating gas; S400, the circulating gas, after being dehydrated, compressed, and heated by heat exchange, enters the catalyst bed to carry out the ammonia synthesis reaction, generating ammonia synthesis gas, which is then cooled by heat exchange. S500, after the crude ammonia water is discharged and cooled, part of it is recycled back into the ammonia absorption tower, and the other part is flash-distilled to obtain ammonia water product.

2. The ammonia production process according to claim 1, characterized in that, In step S400, heat exchange heating includes: The first stage of heat exchange heating involves exchanging heat with the outside of the catalyst bed for the ammonia synthesis reaction after the compressed circulating gas undergoes heat exchange heating. The second-stage heat exchange heating involves the circulating gas after the first-stage heat exchange heating being heated by heat exchange with the ammonia synthesis gas. The third stage of heat exchange heating involves the circulating gas, after being heated in the second stage, entering the catalyst bed of the ammonia synthesis reaction through a pipeline for further heat exchange heating.

3. The ammonia production process according to claim 2, characterized in that, The circulating gas is heated to 90℃~100℃ through the first stage heat exchange, to 270℃~310℃ through the second stage heat exchange, and to 350℃~480℃ through the third stage heat exchange.

4. The ammonia production process according to claim 2, characterized in that, In step S400, after heat exchange heating, a first temperature regulation process is also included. The first temperature regulation process includes: dividing the circulating gas after the second stage heat exchange heating into two parts, one part being heated by the third stage heat exchange, and the other part being used as temperature regulation gas, which is mixed with the circulating gas after the third stage heat exchange heating, and then entering the catalyst bed for ammonia synthesis reaction after temperature regulation.

5. The ammonia production process according to claim 2, characterized in that, In step S400, after heat exchange heating, a second temperature adjustment process is also included. The second temperature adjustment process includes: electrically heating the circulating gas after the third-stage heat exchange heating to adjust the temperature, and then entering the catalyst bed for ammonia synthesis reaction.

6. The ammonia production process according to any one of claims 1 to 5, characterized in that, In step S400, the temperature of the circulating gas entering the catalyst bed for the ammonia synthesis reaction is 320℃~360℃.

7. The ammonia production process according to any one of claims 2 to 5, characterized in that, In step S400, the ammonia synthesis gas is cooled by heat exchange, which includes: the ammonia synthesis gas is cooled by heat exchange in a first heat exchanger, and then cooled by heat exchange in a second heat exchange cooler with the circulating gas heated by the first stage heat exchange. After cooling, it is mixed with the deoxygenated raw material gas to form ammonia-rich gas.

8. The ammonia production process according to claim 1, characterized in that, In step S400, the circulating gas is dehydrated until the water content in the gas is ≤5 ppmv and compressed to a pressure of 7.0~8.0 MPaG; the ammonia synthesis gas after cooling has an ammonia content of about 8.5%.

9. An ammonia production system, characterized in that, include: The deoxygenation tower has its inlet end connected to the raw gas pipeline and its outlet end connected to the first pipeline. The ammonia absorption tower has an air inlet at its lower part connected to the first pipeline. The ammonia absorption tower is provided with a circulating gas outlet at the top and an ammonia discharge outlet at the bottom. The ammonia synthesis tower has an inlet and a synthetic ammonia outlet. The dehydration and drying device and the compression device are connected in series via a second pipeline. The inlet end of the dehydration and drying device is connected to the outlet of the circulating gas via the second pipeline, and the outlet end of the compression device is connected to the inlet end of the ammonia synthesis tower via the second pipeline. The heat exchange component has its inlet end connected to the ammonia synthesis outlet via a third pipeline, and its outlet end connected to the first pipeline via a third pipeline. The ammonia synthesis gas and the deoxygenation feed gas are mixed in the first pipeline and sent into the ammonia absorption tower.

10. The ammonia production system according to claim 9, characterized in that, The heat exchange assembly includes a first heat exchanger and a second heat exchanger arranged sequentially through the third pipeline.

11. The ammonia production system according to claim 10, characterized in that, The ammonia synthesis tower is provided with a protective gas inlet and a synthetic ammonia outlet at the bottom, and a protective gas outlet, a circulating gas inlet and a temperature regulating gas inlet at the top. The protective gas inlet is connected to the outlet of the compression device via a second pipeline. Gas entering through the protective gas inlet is discharged through the protective gas outlet. The protective gas outlet is connected to the heating medium inlet of the second heat exchanger via a fourth pipeline. The heating medium outlet of the second heat exchanger is connected to the circulating gas inlet via a fifth pipeline and to the temperature regulating gas inlet via a sixth pipeline.

12. The ammonia production system according to claim 11, characterized in that, The ammonia synthesis tower includes a central pipe, a central pipe outer cylinder, an inner cylinder, and an outer shell arranged sequentially from the inside out. There is a first annular gap between the outer shell and the inner cylinder, the lower part of the first annular gap is connected to the protective gas inlet, and the upper part is connected to the protective gas outlet; There is a second annular gap between the inner cylinder and the outer cylinder of the central tube. A catalyst bed is provided in the second annular gap. The lower part of the second annular gap is connected to the ammonia synthesis outlet. There is a third annular gap between the central tube and the outer cylinder of the central tube. The upper outer wall of the central tube is sealed to the upper end of the outer cylinder of the central tube. A first vent is provided on the side wall of the central tube above the connection. The first vent communicates with the inside of the central tube and the second annular gap. The lower end of the central tube communicates with the third annular gap. The upper part of the third annular gap communicates with the temperature regulating gas inlet. The bottom of the outer cylinder of the central tube is sealed, and a second vent is provided on the lower side wall. It also includes a heat exchange tube, which is disposed in the catalyst bed, with its upper end connected to the circulating gas inlet and its lower end connected to the inner cylinder of the central tube through the second gas hole.

13. The ammonia production system according to claim 12, characterized in that, An electric heater is installed inside the central tube, and the electric heater is used to heat the gas inside the central tube. And / or, the outer wall of the central tube is provided with a heat insulation layer.

14. The ammonia production system according to claim 12, characterized in that, The lower part of the inner cylinder is provided with a support plate, the middle part of which is sealed to the bottom of the outer cylinder of the central tube. The outer circumference of the support plate is provided with several third air holes, which connect the second annular gap to the ammonia synthesis outlet.

15. The ammonia production system according to claim 12, characterized in that, The catalyst bed includes a first catalyst layer located in the upper part of the second annulus and a second catalyst layer located in the lower part of the second annulus.

16. The ammonia production system according to any one of claims 12 to 15, characterized in that, The heat exchange tube includes a straight tube section at the top and a tube bundle assembly at the bottom; The upper end of the straight pipe section is connected to the circulating gas inlet; The tube bundle assembly includes an upper gas collecting pipe, several tube bundles, and a lower gas collecting pipe. The upper gas collecting pipe connects the lower end of the straight pipe section to the upper end of the tube bundles, and the lower gas collecting pipe connects the lower end of the tube bundles to the second air hole.

17. The ammonia production system according to claim 9, characterized in that, It also includes a circulating pump, a cooler, a flash tank and an external pump connected in sequence. The inlet end of the circulating pump is connected to the ammonia discharge port via a pipeline, and the external pump outputs ammonia water product.

18. The ammonia production system according to claim 17, characterized in that, The ammonia absorption tower is provided with an upper packing section and a lower packing section. The ammonia absorption tower is provided with a demineralized water inlet above the upper packing section and a washing liquid circulation inlet between the upper packing section and the lower packing section. The washing liquid circulation inlet is connected to the outlet end of the cooler via a pipeline.

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