A low-pressure skid-mounted ammonia synthesis plant using an iron-based catalyst and a ruthenium-based catalyst in succession

Abstract

The utility model belongs to synthetic ammonia equipment technical field provides a low pressure prizing synthetic ammonia equipment of iron base catalyst, ruthenium base catalyst relay, including reaction unit, including iron base reactor and ruthenium base reactor that communicate in proper order, and the gas inlet end of iron base reactor is connected with feed unit through preheater, product recovery unit, including the condensation subassembly that is connected with the gas outlet end of ruthenium base reactor, the discharge end of condensation subassembly is connected with product tank, the gas outlet end of condensation subassembly is connected with gas -liquid recovery subassembly, and the liquid outlet end of gas -liquid recovery subassembly communicates with condensation subassembly, the booster unit including circulating compressor, and the gas inlet end of circulating compressor communicates with recovery subassembly, and the gas outlet end of circulating compressor communicates with the gas inlet end of preheater, the utility model discloses the form of iron base catalyst, ruthenium base catalyst relay can realize efficient synthesis ammonia under low pressure condition, and equipment arrangement is compact and has reduced reaction energy consumption significantly.

Description

Technical Field

[0001] This utility model belongs to the technical field of ammonia synthesis equipment, and in particular relates to a low-pressure skid-mounted ammonia synthesis equipment using iron-based catalysts and ruthenium-based catalysts in succession. Background Technology

[0002] Synthetic ammonia (NH3), as one of the core basic raw materials of modern chemical industry, plays an irreplaceable role in agricultural production (such as fertilizer manufacturing), clean energy, and the chemical industry chain.

[0003] Currently, the mainstream industrial ammonia synthesis process still employs the Haber-Bosch process, developed in the early 20th century. This method relies on stringent reaction conditions of high temperature (300–500℃) and high pressure (10–30 MPa). While it boasts high conversion efficiency, it suffers from a significant mismatch with the intermittent and fluctuating power supply characteristics of renewable energy sources such as wind and solar power, making effective coupling and synergistic operation with new energy systems difficult. Therefore, developing new processes and equipment for efficient catalytic ammonia synthesis under mild conditions (low temperature, low pressure), and promoting the development of ammonia synthesis processes towards flexible capacity control, small-scale modular equipment, and flexible and controllable operation, has become a cutting-edge issue of common concern to both academia and industry.

[0004] Among numerous novel catalyst systems, ruthenium (Ru)-based catalysts are widely recognized as the second-generation high-performance ammonia synthesis catalysts following traditional iron-based catalysts. In 1992, BP and Kellogg jointly developed a Ru / C catalyst supported on graphitized activated carbon. This catalyst exhibited extremely high catalytic activity even at significantly lower operating pressures than the traditional Haber-Bosch process, providing an important technological pathway for green, low-pressure ammonia synthesis. However, ruthenium atoms have a very strong adsorption affinity for hydrogen molecules. Under high hydrogen concentration reaction conditions, hydrogen species readily adsorb strongly onto ruthenium active sites, forming stable adsorbed states that are difficult to desorb and renew in a timely manner. This hinders the competitive adsorption of nitrogen molecules at the active sites, limiting the nitrogen dissociation process and ultimately suppressing the ammonia formation rate. Furthermore, ruthenium is extremely rare in the Earth's crust, making it a scarce and precious metal resource with high raw material costs. This significantly increases the catalyst preparation cost, severely restricting its widespread application in large-scale industrial production. Utility Model Content

[0005] The purpose of this invention is to provide a low-pressure skid-mounted ammonia synthesis equipment that uses iron-based and ruthenium-based catalysts in succession to solve the above-mentioned problems and overcome the issues of existing ammonia synthesis equipment being unable to effectively utilize renewable energy, having high costs and high energy consumption, and having its activity inhibited by excessively high hydrogen concentration.

[0006] To achieve the above objectives, this utility model provides the following solution: a low-pressure skid-mounted ammonia synthesis equipment using an iron-based catalyst and a ruthenium-based catalyst in succession, comprising: The reaction unit includes an iron-based reactor and a ruthenium-based reactor connected in sequence, wherein the air inlet of the iron-based reactor is connected to a feeding unit via a preheater; The product recovery unit includes a condensation assembly connected to the gas outlet of the ruthenium-based reactor, a product tank connected to the discharge end of the condensation assembly, a gas-liquid recovery assembly connected to the gas outlet of the condensation assembly, and a liquid outlet of the gas-liquid recovery assembly connected to the condensation assembly. The booster unit includes a circulating compressor, the inlet of which is connected to the recovery assembly, and the outlet of which is connected to the inlet of the preheater.

[0007] Preferably, the outlet of the iron-based reactor is connected to the inlet of the ruthenium-based reactor via a heat exchanger.

[0008] Preferably, the condensation assembly includes a coil condenser and a cryogenic tank connected in sequence. The top and bottom of the cryogenic tank are respectively provided with a discharge port and a gas outlet. The gas inlet of the coil condenser is connected to the gas outlet of the ruthenium-based reactor. The discharge port is connected to the product tank. The gas outlet is connected to the gas-liquid recovery assembly.

[0009] Preferably, the gas-liquid recovery assembly includes a tube condenser and a gas-liquid separator connected in sequence. The inlet of the tube condenser is connected to the outlet, the liquid outlet of the gas-liquid separator is connected to the cryogenic tank, and the outlet of the gas-liquid separator is connected to the pressurization unit.

[0010] Preferably, a branch pipe is connected to the connecting pipeline between the tube condenser and the gas-liquid separator, and a pressure safety regulating valve is connected to the branch pipe.

[0011] Preferably, the inlet and outlet of the circulating compressor are respectively connected to a front buffer tank and a rear buffer tank. The front buffer tank is connected to the outlet of the gas-liquid separator, and the outlet of the rear buffer tank is connected to the inlet of the preheater through a circulating gas control component.

[0012] Preferably, the front buffer tank and the rear buffer tank are interconnected via a pressure regulating valve.

[0013] Preferably, the feeding unit includes a nitrogen-hydrogen compressor and a nitrogen-hydrogen storage tank connected in sequence, and the outlet of the nitrogen-hydrogen storage tank is connected to the inlet of the preheater through a raw material gas control component.

[0014] Preferably, the circulating gas control component includes a second pressure reducing valve and a second flow meter connected between the rear buffer tank and the preheater.

[0015] Preferably, the raw material gas control component includes a first pressure reducing valve and a first flow meter connected between the preheater and the nitrogen-hydrogen gas storage tank.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: 1. This utility model, in conjunction with a novel ruthenium-based ammonia synthesis catalyst, enables efficient ammonia synthesis under low-pressure conditions. The equipment is compact, occupies a small area, and is easy to operate. Its intensive design facilitates transportation and significantly reduces reaction energy consumption and equipment costs. It is highly compatible with the trend of miniaturized and flexible ammonia production.

[0017] 2. This invention adopts a relay approach of iron-based catalyst and ruthenium-based catalyst. During the operation of the equipment, the high-hydrogen-concentration feed gas first contacts the iron-based catalyst, effectively leveraging the high catalytic activity of the iron-based catalyst at high temperature and high hydrogen concentration. This avoids the inhibitory effect of high-concentration hydrogen on the ruthenium-based catalyst while reducing the amount of ruthenium-based catalyst used.

[0018] 3. By setting up a circulating compressor and a recovery component, this utility model can repressurize and circulate unreacted gas back into the preheater, significantly improving the utilization rate of raw material gas. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the ammonia synthesis equipment of this utility model; The components include: 1. Nitrogen-hydrogen compressor; 2. Nitrogen-hydrogen storage tank; 3. First pressure reducing valve; 4. First flow meter; 5. Preheater; 6. Iron-based reactor; 7. Heat exchanger; 8. Ruthenium-based reactor; 9. Coil condenser; 10. Cryogenic tank; 11. Shell-and-tube condenser; 12. Pressure safety regulating valve; 13. Gas-liquid separator; 14. Liquid level regulating valve; 15. Product tank; 16. Pre-buffer tank; 17. Circulating compressor; 18. Post-buffer tank; 19. Pressure regulating valve; 20. Second pressure reducing valve; 21. Second flow meter; 22. Branch pipe. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Reference Figure 1 This utility model provides a low-pressure skid-mounted ammonia synthesis equipment using iron-based and ruthenium-based catalysts in succession, comprising: The reaction unit includes an iron-based reactor 6 and a ruthenium-based reactor 8 connected in sequence. The air inlet of the iron-based reactor 6 is connected to a feeding unit through a preheater 5. The product recovery unit includes a condensation assembly connected to the gas outlet of the ruthenium-based reactor 8, a product tank 15 connected to the discharge end of the condensation assembly, a gas-liquid recovery assembly connected to the gas outlet of the condensation assembly, and a liquid outlet of the gas-liquid recovery assembly connected to the condensation assembly. The booster unit includes a circulating compressor 17, the inlet of which is connected to the recovery assembly, and the outlet of which is connected to the inlet of the preheater 5.

[0024] Iron-based reactor 6 and ruthenium-based reactor 8 are connected in sequence, forming a relay combination of iron-based and ruthenium-based catalysts. This allows the high-hydrogen-concentration feed gas to preferentially contact the iron-based catalyst, fully utilizing its high activity under high-temperature, high-hydrogen conditions. This avoids the inhibitory effect of high-concentration hydrogen on the ruthenium-based catalyst and reduces the amount of ruthenium-based catalyst used. The main function of preheater 5 is to raise the temperature of the feed gas to the reaction temperature; the main function of condenser is to condense gaseous ammonia into liquid ammonia; the main function of gas-liquid recovery unit is to further recover ammonia entrained in the gas, allowing the recovered ammonia to re-enter the condenser in liquid form; the main function of circulating compressor 17 is to re-mix unreacted ammonia and hydrogen with the feed gas and reintroduce them into preheater 5 for further reaction. Overall, this invention, combined with a novel ruthenium-based ammonia synthesis catalyst, enables efficient ammonia synthesis under low-pressure conditions, significantly reducing reaction energy consumption and equipment costs. The equipment is compact in design, occupies a small area, is easy to operate, and has intensive characteristics that facilitate transportation, making it highly compatible with the trend of small-scale and flexible ammonia production.

[0025] In this further optimized embodiment, the preheated feed gas enters the iron-based reactor 6, where most of the nitrogen and hydrogen react to form ammonia under the high temperature and high activity of the iron-based catalyst. The reaction gas from the iron-based reactor 6 (containing the generated ammonia and unreacted nitrogen and hydrogen) then enters the ruthenium-based reactor 8 after its temperature is adjusted by the heat exchanger 7. After the initial reaction by the iron-based catalyst, the hydrogen concentration in the reaction gas is reduced, effectively avoiding the inhibitory effect of high-concentration hydrogen on the ruthenium-based catalyst. This allows the ruthenium-based catalyst to efficiently catalyze the remaining nitrogen and hydrogen to continue synthesizing ammonia at a lower pressure. This relay method fully utilizes the advantages of both catalysts, ensuring high conversion rates while reducing reliance on high-pressure equipment and the amount of expensive ruthenium-based catalyst required.

[0026] In a further optimized design, the outlet of the iron-based reactor 6 is connected to the inlet of the ruthenium-based reactor 8 via a heat exchanger 7.

[0027] like Figure 1 As shown, in this embodiment, the main function of the heat exchanger 7 is to transfer the heat from the gas discharged from the iron-based reactor 6, thereby lowering the temperature of the gas entering the ruthenium-based reactor 8, promoting the forward equilibrium of the ammonia synthesis reaction, increasing the net ammonia value, and facilitating efficient ammonia synthesis.

[0028] In this embodiment, the volume fraction of ammonia in the gas entering the iron-based reactor 6 is controlled to be 2%–5% by the feeding unit, and the volume fraction of ammonia in the outlet gas is approximately 6%–15%, with a pressure of 5–10 MPa and a space velocity of 6000–20000 h⁻¹. -1 The inlet gas temperature is 320–370℃, and the outlet gas temperature is 390–490℃.

[0029] The gas entering the ruthenium-based reactor 8 contains 6%–15% ammonia by volume, at a pressure of 5–10 MPa, and with a space velocity of 10,000–60,000 h⁻¹. -1 The inlet temperature is 320–450℃, and the outlet temperature is 390–470℃.

[0030] To further optimize the design, heaters are installed on the outside of the iron-based reactor 6 and the ruthenium-based reactor 8 to maintain the reaction temperature of the reactors.

[0031] The scheme is further optimized. The condensation assembly includes a coil condenser 9 and a cryogenic tank 10 connected in sequence. The top and bottom of the cryogenic tank 10 are respectively provided with a discharge port and a gas outlet. The gas inlet of the coil condenser 9 is connected to the gas outlet of the ruthenium-based reactor 8. The discharge port is connected to the product tank 15. The gas outlet is connected to the gas-liquid recovery assembly.

[0032] like Figure 1As shown, the reaction gas (mainly containing ammonia, nitrogen, hydrogen, and a small amount of inert gas) output from the ruthenium-based reactor 8 first enters the coil condenser 9 for preliminary cooling, causing most of the gaseous ammonia to condense into liquid ammonia. The gas-liquid mixture after preliminary condensation enters the cryogenic tank 10 for further separation and cryogenic cooling. The liquid ammonia accumulates in the cryogenic tank 10 and is transported to the product tank 15 for storage through the discharge port. The uncondensed gas (mainly unreacted nitrogen, hydrogen, and a small amount of ammonia) is discharged from the top outlet into the tube condenser 11.

[0033] In a further optimized design, a liquid level regulating valve 14 is connected between the cryogenic tank 10 and the product tank 15. When the liquid level in the cryogenic tank 10 exceeds the set value of the liquid level regulating valve 14, the liquid level regulating valve 14 controls the liquid level by discharging the liquid in the cryogenic tank 10 into the product tank 15, thereby maintaining a stable liquid level.

[0034] Further optimization of the scheme: the gas-liquid recovery component includes a tube condenser 11 and a gas-liquid separator 13 connected in sequence. The inlet end of the tube condenser 11 is connected to the outlet end, the liquid outlet end of the gas-liquid separator 13 is connected to the cryogenic tank 10, and the gas outlet end of the gas-liquid separator 13 is connected to the pressurization unit.

[0035] like Figure 1 As shown, the condensed gas is further deeply cooled in the tube condenser 11 to recover as much of the entrained ammonia as possible. The condensed liquid ammonia flows into the gas-liquid separator 13, and the liquid outlet of the gas-liquid separator 13 returns the recovered liquid ammonia to the cryogenic tank 10, where it is collected and sent to the product tank 15. The remaining non-condensable gas is discharged from the gas outlet of the gas-liquid separator 13 and flows to the circulating compressor 17.

[0036] In a further optimized design, a branch pipe 22 is connected to the connecting pipeline between the tube condenser 11 and the gas-liquid separator 13, and a pressure safety regulating valve 12 is connected to the branch pipe 22.

[0037] like Figure 1 As shown, when the pressure in the tube condenser 11 or the gas-liquid separator 13 exceeds the set value of the pressure safety regulating valve 12, the pressure safety regulating valve 12 controls the pressure by discharging gas into the branch pipe 22, thus maintaining a stable pressure.

[0038] In a further optimized design, the inlet and outlet of the circulating compressor 17 are connected to a front buffer tank 16 and a rear buffer tank 18, respectively. The front buffer tank 16 is connected to the outlet of the gas-liquid separator 13, and the outlet of the rear buffer tank 18 is connected to the inlet of the preheater 5 through a circulating gas control component.

[0039] like Figure 1 As shown, the recirculated gas, after being pressurized by the recirculating compressor 17, is mixed with the fresh raw material gas from the feeding unit before or inside the preheater 5, and then enters the reaction unit to participate in the reaction again.

[0040] The scheme was further optimized so that the front buffer tank 16 and the rear buffer tank 18 are interconnected through a pressure regulating valve 19.

[0041] like Figure 1 As shown, when the pressure in the rear buffer tank 18 of the circulating compressor exceeds the set value of the pressure regulating valve 19, the pressure regulating valve 19 controls the pressure by venting the gas in the rear buffer tank 18 of the circulating compressor into the front buffer tank 16 of the circulating compressor, thus maintaining a stable pressure.

[0042] The scheme is further optimized. The feeding unit includes a nitrogen-hydrogen compressor 1 and a nitrogen-hydrogen storage tank 2 connected in sequence. The outlet of the nitrogen-hydrogen storage tank 2 is connected to the inlet of the preheater 5 through the raw material gas control component.

[0043] The scheme is further optimized, and the circulating gas control components include a second pressure reducing valve 20 and a second flow meter 21 connected between the rear buffer tank 18 and the preheater 5.

[0044] The scheme is further optimized, and the raw material gas control components include a first pressure reducing valve 3 and a first flow meter 4 connected between the preheater 5 and the nitrogen-hydrogen gas storage tank 2.

[0045] The scheme has been further optimized so that the first flow meter 4, the second flow meter 21, the first pressure reducing valve 3, the second pressure reducing valve 20, and the liquid level regulating valve 14 are all connected to a computer control system (not shown in the figure).

[0046] A method for synthesizing ammonia using a low-pressure skid-mounted ammonia synthesis equipment employing a relay system of iron-based and ruthenium-based catalysts, as described in this embodiment, includes the following steps: (1) The pressure of the pressure safety regulating valve 12 is set to the working pressure of the equipment (5-10MPa) through the computer control system, and the pressure of the pressure regulating valve 19 is set to be slightly higher than the working pressure (0.5-1MPa higher than the working pressure). (2) The flow rates of the first flow meter 4 and the second flow meter 21 are set by the computer control system so that the total air intake of the reactor is 4-32 L / min, and the flow ratio between the first flow meter 4 and the second flow meter 21 is: The ratio of flow rate of the first flow meter 4 to flow rate of the second flow meter 21 is 1:1 to 1:4. (3) Adjust the first pressure reducing valve 3 to slightly higher than the working pressure (0.5-1 MPa higher than the working pressure) to allow the equipment to start intake air; (4) Start the circulating compressor 17 and set the oil discharge pressure slightly higher than the working pressure (0.5 to 1 MPa higher than the working pressure). (5) Adjust the second pressure reducing valve 20 to slightly higher than the working pressure (0.5 to 1 MPa higher than the working pressure); (6) The preheating temperature of the preheater 5 is set to 330-400℃ through the computer control system; (7) The reaction temperatures of the iron-based reactor 6 and the ruthenium-based reactor 8 are set to 310-350℃ and 310-430℃ respectively by the computer control system; (8) The liquid level of the liquid level regulating valve 14 is set to 20-50% by the computer control system. When the liquid ammonia level in the cryogenic tank 10 reaches the set liquid level, the produced liquid ammonia product is discharged from the cryogenic tank 10 into the product tank 15 for storage.

[0047] In the description of this utility model, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and do not 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 utility model.

[0048] The embodiments described above are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A low-pressure skid-mounted ammonia synthesis equipment using a successor of iron-based and ruthenium-based catalysts, characterized in that, include: The reaction unit includes an iron-based reactor (6) and a ruthenium-based reactor (8) connected in sequence. The inlet end of the iron-based reactor (6) is connected to a feeding unit through a preheater (5). The product recovery unit includes a condensation assembly connected to the gas outlet of the ruthenium-based reactor (8), a product tank (15) connected to the discharge end of the condensation assembly, a gas-liquid recovery assembly connected to the gas outlet of the condensation assembly, and a liquid outlet of the gas-liquid recovery assembly connected to the condensation assembly. The booster unit includes a circulating compressor (17), the inlet of which is connected to the recovery assembly, and the outlet of which is connected to the inlet of the preheater (5).

2. The low-pressure skid-mounted ammonia synthesis equipment using iron-based catalysts and ruthenium-based catalysts in succession as described in claim 1, characterized in that: The outlet of the iron-based reactor (6) is connected to the inlet of the ruthenium-based reactor (8) via a heat exchanger (7).

3. The low-pressure skid-mounted ammonia synthesis equipment using iron-based catalysts and ruthenium-based catalysts in succession as described in claim 1, characterized in that: The condensation assembly includes a coil condenser (9) and a cryogenic tank (10) connected in sequence. The top and bottom of the cryogenic tank (10) are respectively provided with a discharge port and a gas outlet. The gas inlet of the coil condenser (9) is connected to the gas outlet of the ruthenium-based reactor (8). The discharge port is connected to the product tank (15). The gas outlet is connected to the gas-liquid recovery assembly.

4. The low-pressure skid-mounted ammonia synthesis equipment using iron-based catalysts and ruthenium-based catalysts in succession as described in claim 3, characterized in that: The gas-liquid recovery assembly includes a tube condenser (11) and a gas-liquid separator (13) connected in sequence. The inlet of the tube condenser (11) is connected to the outlet, the liquid outlet of the gas-liquid separator (13) is connected to the cryogenic tank (10), and the outlet of the gas-liquid separator (13) is connected to the pressurization unit.

5. The low-pressure skid-mounted ammonia synthesis equipment using iron-based catalysts and ruthenium-based catalysts in succession as described in claim 4, characterized in that: A branch pipe (22) is connected to the connecting pipeline between the tube condenser (11) and the gas-liquid separator (13), and a pressure safety regulating valve (12) is connected to the branch pipe (22).

6. The low-pressure skid-mounted ammonia synthesis equipment using iron-based catalysts and ruthenium-based catalysts in succession as described in claim 4, characterized in that: The inlet and outlet of the circulating compressor (17) are respectively connected to the front buffer tank (16) and the rear buffer tank (18). The front buffer tank (16) is connected to the outlet of the gas-liquid separator (13), and the outlet of the rear buffer tank (18) is connected to the inlet of the preheater (5) through the circulating gas control component.

7. The low-pressure skid-mounted ammonia synthesis equipment using iron-based catalysts and ruthenium-based catalysts in succession as described in claim 6, characterized in that: The front buffer tank (16) and the rear buffer tank (18) are connected to each other through a pressure regulating valve (19).

8. The low-pressure skid-mounted ammonia synthesis equipment using iron-based catalysts and ruthenium-based catalysts in succession as described in claim 1, characterized in that: The feeding unit includes a nitrogen-hydrogen compressor (1) and a nitrogen-hydrogen storage tank (2) connected in sequence. The outlet of the nitrogen-hydrogen storage tank (2) is connected to the inlet of the preheater (5) through a raw material gas control component.

9. A low-pressure skid-mounted ammonia synthesis equipment using a relay of iron-based catalyst and ruthenium-based catalyst as described in claim 6, characterized in that: The circulating gas control unit includes a second pressure reducing valve (20) and a second flow meter (21) connected between the rear buffer tank (18) and the preheater (5).

10. A low-pressure skid-mounted ammonia synthesis equipment using a relay of iron-based catalyst and ruthenium-based catalyst as described in claim 8, characterized in that: The raw material gas control unit includes a first pressure reducing valve (3) and a first flow meter (4) connected between the preheater (5) and the nitrogen-hydrogen gas storage tank (2).

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