A composite U-shaped wall tubular ammonia synthesis reactor

Abstract

This utility model discloses a composite U-shaped wall tube type ammonia synthesis reactor, including a shell with an inner end cap that divides the shell cavity into an upper cavity and a lower cavity. The upper cavity contains a first gas distribution chamber and a first catalyst chamber. The first catalyst chamber contains an iron-based catalyst bed, a radial gas distributor, and an upper gas collection cylinder. No heat transfer tube is installed in the first catalyst chamber. The lower cavity contains a second gas distribution chamber and a second catalyst chamber. The second catalyst chamber contains a ruthenium-based catalyst bed, a water-cooled bundle tube, and a lower gas collection cylinder. The outer wall of the lower cavity contains an upper heat exchange chamber and a lower heat exchange chamber. The water-cooled bundle tube is located inside the ruthenium-based catalyst bed and surrounds the outer periphery of the lower gas collection cylinder. Its upper end is connected to the upper heat exchange chamber, and its lower end is connected to the lower heat exchange chamber. Compared with ammonia synthesis reaction systems using iron-based catalysts as catalytic coal, this invention can increase the net ammonia value of the total reaction by 5% to 9%; or, under the condition that the system circulation volume remains unchanged, the synthesis system output can be increased by 15% to 35% after increasing the amount of supplementary gas; or, under the condition that the output does not increase, the system operating pressure can be reduced by 3.0 MPa to 5.0 MPa.

Description

Technical Field

[0001] This utility model relates to the field of reactor technology, specifically to a composite U-shaped wall tube type ammonia synthesis reactor. Background Technology

[0002] The ammonia synthesis reactor is the core equipment in the ammonia synthesis industry, used to synthesize ammonia from nitrogen and hydrogen under high temperature, high pressure, and catalysis. Traditional catalysts for ammonia synthesis reactions are mainly iron-based, which have advantages such as high activity, low cost, and good stability. However, iron-based catalysts are sensitive to impurities such as sulfur, oxygen, and chlorine in the feed gas, and are easily poisoned and deactivated. Furthermore, the activity of iron-based catalysts decreases significantly at lower temperatures. To achieve higher reaction rates and ammonia yields, relatively high temperatures are required, increasing energy consumption and the occurrence of side reactions. Ruthenium-based catalysts are a new type of highly efficient catalyst with high low-temperature activity and strong adaptability to low pressure; however, ruthenium is expensive, approximately 10,000 times more expensive than iron. Iron-ruthenium composite catalysts can combine the advantages of both, optimizing reaction conditions, reducing energy consumption, and increasing ammonia yield. Therefore, developing a composite reactor combining iron-based and ruthenium-based catalysts is of great significance to the field of ammonia synthesis. Utility Model Content

[0003] To achieve the above objectives, this utility model provides a composite U-shaped wall tube type ammonia synthesis reactor.

[0004] The technical solution adopted in this utility model is:

[0005] A composite U-shaped wall-tube ammonia synthesis reactor includes a shell, which comprises an upper head, a lower head, and a cylindrical body. The upper head has an inlet at its top and an outlet at its bottom. An inner head divides the shell's interior into an upper cavity and a lower cavity. The upper cavity contains a first gas distribution chamber and a first catalyst chamber. The first catalyst chamber contains an iron-based catalyst bed, a radial gas distributor, and an upper gas collector. The radial gas distributor is located on the outer periphery of the iron-based catalyst bed, allowing gas to pass radially from the first gas distribution chamber through the iron-based catalyst bed. The upper gas collector is located at the center of the upper cavity, used to collect gas. Gas passes radially through the iron-based catalyst bed and is guided into the lower cavity; no heat transfer tube is installed in the first catalyst cavity; the lower cavity is provided with a second gas distribution cavity and a second catalyst cavity. The second catalyst cavity is provided with a ruthenium-based catalyst bed, a water-cooled bundle tube, and a lower gas collection cylinder. The lower gas collection cylinder is located in the center of the lower cavity and is used to collect gas passing axially through the ruthenium-based catalyst bed and guide it to be discharged from the gas outlet. The outer wall of the lower cavity is provided with an upper heat exchange cavity and a lower heat exchange cavity. The water-cooled bundle tube is located in the ruthenium-based catalyst bed and surrounds the outer periphery of the lower gas collection cylinder. Its upper end is connected to the upper heat exchange cavity, and its lower end is connected to the lower heat exchange cavity.

[0006] The "composite U-shaped tube wall tubular ammonia synthesis reactor" of this application operates at the optimal temperature for the iron-based catalyst reaction, which can further increase the ammonia content by 2% to 2.5% based on the original tower reaction. Because this temperature rise is not high, this section is designated as an "adiabatic section," eliminating the need for heat transfer. Instead, the heat is transferred to the lower U-shaped tube phase change heat transfer section, which also provides heat-assisted reaction heating for the lower ruthenium catalyst layer. Due to the phase change heat transfer effect and the low-temperature, high-reactivity ruthenium catalyst, the lower ruthenium catalyst layer can further increase the ammonia content by 3% to 6%, achieving a highly efficient effect of increasing the net ammonia content of the entire reactor by 5% to 9%.

[0007] Furthermore, the upper heat exchange chamber is equipped with an outlet pipe, and the lower heat exchange chamber is equipped with an inlet pipe. Both the inlet and outlet pipes are connected to the high-pressure steam drum, which generates high-pressure saturated steam.

[0008] This application utilizes the heat of reaction to generate high-pressure saturated steam, efficiently recovering the heat of reaction and improving energy utilization. The steam generation process in the high-pressure steam drum is itself an isothermal phase change (endothermic but with constant temperature), which can smoothly remove the heat of reaction, avoid local overheating, and extend catalyst life. The high-pressure saturated steam can be directly used for power generation (via a steam turbine) or to drive process compressors (such as hydrogen compressors), reducing external energy consumption, significantly lowering production costs, and even achieving "steam self-sufficiency." The high-pressure steam drum is directly connected to the reactor, eliminating the need for a complex cooling medium circulation system (such as water cooling + cooling tower), reducing equipment investment and operation and maintenance costs.

[0009] Furthermore, a second gas distribution chamber and a second catalyst chamber are formed between the bottom surface of the water-cooled bundle tube and the inner end cap, and a third catalyst chamber is formed between the bottom surface of the water-cooled bundle tube and the lower end cap; a pre-reduced iron-based catalyst bed is provided in the third catalyst chamber.

[0010] The pre-reduced iron-based catalyst bed can supplement the reaction, capture incompletely converted N2 / H2, and improve the overall yield.

[0011] Furthermore, an axial air distribution component is provided inside the air inlet. The axial air distribution component includes an insert part and an air distribution part. The axial air distribution component is fixedly installed inside the air inlet through its insert part. The air distribution part consists of several annular horizontal plates spaced apart along the axis of the housing and several vertical plates inclined at the same angle A between two annular horizontal plates. A swirling air outlet is formed between two adjacent vertical plates.

[0012] The structural features of the axial gas distributor allow the synthesis gas entering through the inlet to be evenly distributed into the radial gas distributor, and then evenly dispersed into the catalyst bed through the radial gas distributor. This ensures that the gas concentration and flow rate are consistent in each region of the catalyst bed, reduces the temperature gradient, maintains the uniformity of the catalyst bed temperature, avoids hot spots, and extends the catalyst life.

[0013] Furthermore, the upper air collecting cylinder includes a straight cylinder section and a conical diffuser section. The inner cavity of the upper air collecting cylinder forms a first air collecting chamber. The top of the first air collecting chamber is closed, and the bottom is connected to the lower cavity through a through hole opened in the center of the inner end cap. The side wall of the straight cylinder section is provided with a first vent hole that connects to the first catalyst chamber, and the side wall of the conical diffuser section is provided with a second vent hole that connects to the first catalyst chamber.

[0014] The straight-cylinder structure ensures that the gas maintains a certain axial flow direction when it enters, reducing turbulence and maintaining the uniformity of gas distribution. The conical bottom design (larger at the top and smaller at the bottom) reduces the gas velocity, preventing high-speed airflow from directly impacting the catalyst bed, reducing the risk of channeling and localized overheating; furthermore, the diffusion effect of the conical structure allows the gas entering the lower cavity to pass evenly through the ruthenium-based catalyst bed, thereby ensuring consistent gas concentration and velocity in all areas of the catalyst bed, reducing temperature gradients, maintaining uniform catalyst bed temperature, avoiding hot spots, and extending catalyst life.

[0015] Furthermore, there are several radial air distribution components, which are arranged around the inner side of the cylinder sidewall; each radial air distribution component includes a distribution cylinder extending in a vertical direction. The distribution cylinder includes an arc-shaped outer side plate and an arc-shaped inner side plate. The arc-shaped outer side plate protrudes towards the cylinder sidewall, and the arc-shaped inner side plate protrudes towards the center of the shell. The arc-shaped outer side plate and the arc-shaped inner side plate form a gas distribution cavity with a crescent-shaped cross-section. A gas distribution hole is opened on the inner side plate, and the gas distribution hole connects the gas distribution cavity and the first catalyst cavity; the bottom of the distribution cylinder is closed, and the upper end has an air inlet that connects to the first gas distribution cavity.

[0016] The radial gas distribution component adopts the applicant's patented technology, the first gas distribution component 100 structure disclosed in Chinese patent CN212348667U, which makes the reaction temperature in the second medium cavity more uniform.

[0017] Furthermore, the upper heat exchange cavity is formed by an annular upper tube sheet and an upper annular crown, and the lower heat exchange cavity is formed by an annular lower tube sheet and a lower annular crown. Both the annular upper tube sheet and the annular lower tube sheet are located on the side wall of the cylinder. The water-cooled bundle tubes are composed of several U-shaped heat exchange tubes. The upper ends of all U-shaped heat exchange tubes pass through the annular upper tube sheet and communicate with the upper heat exchange cavity, and their lower ends pass through the annular lower tube sheet and communicate with the lower heat exchange cavity.

[0018] The heat exchange chamber structure facilitates uniform water distribution and improves the temperature uniformity of the catalyst bed. Furthermore, the crown-shaped structure facilitates maintenance of the heat exchange tube sheet.

[0019] Furthermore, the U-shaped heat exchange tube is provided with a first horizontal section, a vertical section and a second horizontal section. The vertical section extends along the axial direction of the shell, and the first horizontal section and the second horizontal section extend along the radial direction of the shell. The U-shaped heat exchange tube is concentrically arranged around the lower gas collection cylinder.

[0020] Multiple U-shaped heat exchange tubes are arranged concentrically around the central gas collecting cylinder (or central tube), forming a multi-layered annular tube bundle. This fully utilizes the space within the reactor and increases the heat exchange area. Horizontal heat exchange tube sections cover the entire reaction cross-section, facilitating a radially uniform distribution of the tubes and improving overall heat exchange uniformity. Vertical heat exchange tube sections ensure coverage at different heights, promoting a uniform heat exchange area along the reactor's height. The combination of horizontal (radial) and vertical (axial) sections allows the cooling medium to flow in and out radially uniformly, avoiding "hot zones" or "cold zones" and achieving a uniform temperature field distribution.

[0021] Furthermore, the lower gas collection cylinder is straight, and a hemispherical gas collection hood is connected to the lower end of the straight cylinder. A third vent hole communicating with the second catalyst chamber is opened on the side wall of the part of the straight cylinder that extends into the lower end cap. The hemispherical gas collection hood is placed above the gas outlet, and a fourth vent hole communicating with the second catalyst chamber is opened on it.

[0022] The straight-cylinder structure ensures that the gas maintains a certain axial flow direction when it enters, reducing turbulence and maintaining the uniformity of gas distribution. The hemispherical gas collection hood can expand the collection area, reduce the gas flow velocity, prevent gas short-circuiting, and improve gas collection efficiency and reaction conversion rate; the second vent allows for multi-path gas intake, improving the uniformity of gas entering the gas collection cylinder.

[0023] Furthermore, the upper end cap is provided with a first manhole, which is connected to the first gas distribution chamber; the upper cavity has a third manhole on its cylindrical side wall, which is connected to the second gas distribution chamber; and the lower end cap is provided with a second manhole, which is connected to the second catalyst chamber.

[0024] The manhole design facilitates heat exchanger maintenance, and the second and third manholes also serve as catalyst loading and unloading ports.

[0025] The beneficial effects of this utility model are:

[0026] 1. Compared with ammonia synthesis reaction systems using iron-based catalysts as catalytic flux, the composite U-shaped tube-walled tubular ammonia synthesis reactor of this invention can increase the net ammonia value of the total reaction by 5% to 9%; or, under the condition that the system circulation volume remains unchanged, the synthesis system output can be increased by 15% to 35% after increasing the amount of supplementary gas; or, under the condition that the output does not increase, the system operating pressure can be reduced by 3.0 MPa to 5.0 MPa; and it can greatly save the amount of ruthenium catalyst used, save precious metals, and significantly improve the cost-effectiveness of investment.

[0027] 2. The lower chamber of the reactor does not contain internal components such as heat exchange tube sheets and gas distribution cylinders, which can realize axial flow and low height-to-diameter ratio catalyst loading, and make the reaction gas uniformly distributed in the catalyst bed, accurately control the temperature of the catalyst bed, and improve the ammonia synthesis efficiency. Furthermore, since the weld between the heat exchange tube and the tube sheet does not come into contact with the process gas, the corrosion problem of the weld is completely solved, ensuring the safety of the reactor. Attached Figure Description

[0028] Figure 1 This is a structural diagram of the composite U-shaped wall tube type ammonia synthesis reactor of this application.

[0029] Figure 2 This is a structural diagram of the upper cavity of the reactor.

[0030] Figure 3 This is a structural diagram of the lower chamber of the reactor.

[0031] Figure 4 This is a three-dimensional structural diagram of the axial air distribution component.

[0032] Figure 5 This is a cross-sectional view of the air distribution section of the axial air distribution unit.

[0033] Figure 6 This is a structural diagram of a single U-shaped heat exchange tube in a water-cooled bundled tube system. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below in conjunction with the accompanying drawings and preferred embodiments.

[0035] See Figure 1 This embodiment provides a composite U-shaped wall tube type ammonia synthesis reactor, including a shell. The shell includes a vertically extending cylindrical body 1, an upper end cap 2 installed at the top of the cylindrical body, and a lower end cap 3 installed at the bottom of the cylindrical body. In this embodiment, both the upper end cap 2 and the lower end cap 3 are spherical end caps. The bottom of the shell is provided with a skirt-type support, and the side wall of the support has a maintenance manhole and a through hole for the outlet pipe to pass through.

[0036] The upper head 2 is provided with an air inlet 21, a temperature measuring port 22, and a first manhole 23. The air inlet 21 is located at the top of the upper head and is connected to an inlet flange. Two temperature measuring ports 22 are symmetrically arranged on both sides of the air inlet 21, and the first manhole 23 is located below the temperature measuring ports 22. The lower head 3 is provided with an air outlet 31 and a second manhole 32. The air outlet 31 is located at the bottom of the lower head and is connected to an air outlet pipe. The second manhole 32 is located above the air outlet 31, and the lower end of the air outlet pipe extends out from the through hole of the skirt support.

[0037] Both the shell and the inner wall of the air inlet 21 are equipped with a thermal insulation layer. The shell material can be 12Cr2Mo1R, with 321 stainless steel overlay welded on. After the overlay weld, an inner lining insulation is applied. The insulation material is high-insulation aerosol insulation felt, rock wool, or aluminum silicate fiber insulation felt. The insulation skin material can be 321 stainless steel plate. Thermal plugs are installed at the openings of the first manhole 23 and the second manhole 32.

[0038] The shell has an inner end cap 4 with its opening facing downwards. In this embodiment, the inner end cap 4 is a butterfly-shaped end cap. In other embodiments, it can also be a spherical end cap, an elliptical end cap, etc. The inner end cap 4 divides the inner cavity of the shell into an upper cavity and a lower cavity.

[0039] See Figure 2 The upper cavity is equipped with an axial air distribution component 24, a radial air distribution component 25, and an upper air collection cylinder 26.

[0040] The inner wall of the upper cavity is provided with an upper fixing plate 251 and a lower fixing plate 252. Both the upper fixing plate 251 and the lower fixing plate 252 are annular flat plates, and the outer wall of the annular flat plate is sealed and fixedly connected to the inner wall of the upper cavity. The inner end cap 4 is fixedly installed on the inner ring of the lower fixing plate 252, and the inner ring of the upper fixing plate 251 is fixedly installed with a catalyst cover plate 27. The catalyst cover plate 27 divides the upper cavity into a first gas distribution chamber 101 and a first catalyst chamber 102. The center of the catalyst cover plate 27 is provided with a gas collector mounting hole, and a sleeve is fixedly installed in the gas collector mounting hole.

[0041] The upper gas collector 26 is axially positioned at the center of the upper cavity, and its inner cavity forms the first gas collecting chamber 103. The bottom of the upper gas collector 26 is detachably fixed and supported on the inner end cap 4 by bolts, and its top freely passes through the sleeve on the catalyst cover plate 27, with the sleeve slidingly engaging with the upper gas collector 26. The upper gas collector 26 can be lifted out of the reactor through the air inlet 21. The top of the first gas collecting chamber 103 is closed by the gas collector cover plate, and the bottom communicates with the lower cavity through a through hole opened in the center of the inner end cap. The side communicates with the first catalyst chamber 102 through first vent holes 26 evenly distributed from top to bottom on its sidewall. In this embodiment, the lower end of the upper gas collector 26 is detachably connected to a conical bottom by bolts, and the sidewall of the conical bottom has a second vent hole 262 connecting the first gas collecting chamber 103 and the first catalyst chamber 102. The conical bottom has a diffusion effect, which can make the reaction gas collected in the first gas collecting chamber 103 more evenly distributed axially into the lower chamber.

[0042] Several radial air distribution components 25 are arranged around the inner side of the cylinder sidewall between the upper fixed plate 251 and the lower fixed plate 252. The space enclosed by the radial air distribution components 25, the upper air collection cylinder 26, the catalyst cover plate 27, and the inner end cap 4 forms the first catalyst cavity 102. The radial air distribution components 25 adopt the first air distribution component 100 disclosed in patent CN212348667U. The bottom of the radial air distribution component 25 is fixedly supported on the lower air distribution component fixed plate 252, and the upper end is fixed on the upper air distribution component fixed plate 251. Its air inlet seal passes through the upper air distribution component fixed plate 251 and communicates with the first air distribution cavity 101.

[0043] See Figure 4 and Figure 5 An axial gas distributor 24 is disposed within the air inlet 21 and includes an insertion part and a gas distributor 242. The gas distributor 242 consists of several (five in this embodiment) annular horizontal plates 2421 spaced apart along the axis of the housing and several (sixteen in this embodiment) vertical plates 2422 inclined at the same angle A between two annular horizontal plates 2421. Angle A refers to the angle between the extension line of the surface of the horizontal plate 2421 and the tangent of the outer circle of the annular horizontal plate 2421. A swirling air outlet is formed between two adjacent vertical plates 2422. The insertion part consists of several (eight in this embodiment) long strips 241 vertically disposed on the top surface of the uppermost annular horizontal plate 2421. The eight long strips 241 are evenly distributed radially along the annular horizontal plate 2421, and the outer surface forms an insertion surface adapted to the inner diameter of the air inlet. The gas distributor 24 is fixed inside the air inlet through its insertion part.

[0044] See Figure 3 The lower cavity is provided with a water-cooled bundle pipe 33 and a lower air-collecting cylinder 34. The outer wall of the lower cavity is provided with an upper heat exchange cavity 35 and a lower heat exchange cavity 36. The upper heat exchange cavity 35 is provided with a water outlet pipe 37, and the lower heat exchange cavity 36 is provided with a water inlet pipe 38.

[0045] The lower cavity has a third manhole 11, a first annular through hole, and a second annular through hole sequentially opened from top to bottom on the side wall of the cylinder.

[0046] The upper heat exchange chamber 35 is installed in the first annular through hole, and the lower heat exchange chamber 36 is installed in the second annular through hole. The upper heat exchange chamber consists of an annular upper tube sheet 351 and an upper annular crown 352; the upper tube sheet 351 is inserted into the upper through hole and welded to the side wall of the cylinder, and the upper annular crown and the upper tube sheet form the upper heat exchange chamber 301. The lower heat exchange chamber 36 consists of an annular lower tube sheet 361 and a lower annular crown 362; the lower tube sheet 361 is inserted into the lower through hole and welded to the side wall of the cylinder, and the cavity formed by the lower annular crown and the lower tube sheet is the lower heat exchange chamber 302. A water outlet is provided on the upper side of the crown of the upper annular crown, and a water outlet pipe 37 is connected to the water outlet. A third manhole 363 is provided on the side of the crown. The lower spherical crown has a water inlet on its upper side, connected to a water inlet pipe 38. A fourth manhole 363 and a superheated steam inlet 365 are located on the side of the crown. Several drain outlets 364 are located at the bottom of the crown. In this embodiment, four water outlet pipes 37 and four water inlet pipes 38 are provided, which can be used as rising and falling pipes to connect to the high-pressure steam drum, respectively. Saturated water is introduced into the high-pressure steam drum. The saturated water at the bottom of the high-pressure steam drum enters the lower heat exchange chamber 302 through the water inlet pipe 38, undergoes phase change and heat transfer after flowing through the water-cooled bundled tubes, and then enters the upper heat exchange chamber 301. Finally, it returns to the high-pressure steam drum through the water outlet pipe 37.

[0047] The lower gas collecting cylinder 34 is axially positioned at the center of the lower cavity, and its inner cavity forms the second gas collecting chamber 104. In this embodiment, the lower end of the lower gas collecting cylinder 34 is connected to a hemispherical gas collecting hood. The lower gas collecting cylinder 34 is fixedly supported on the lower end cap by the hemispherical gas collecting hood and can be lifted out of the reactor through the air inlet 21. The upper end of the lower gas collecting cylinder 34 extends into the first annular through hole, and the lower end extends to the bottom of the lower end cap 3 and is connected to the hemispherical gas collecting hood; the hemispherical gas collecting hood covers the air outlet 31. The sidewall of the portion of the lower gas collecting cylinder 34 that extends into the lower end cap 3 is evenly distributed with third vent holes 341, and the hemispherical gas collecting hood is evenly distributed with fourth vent holes 342. The top of the second gas collecting chamber 104 is closed by an elliptical cover plate, and the bottom is connected to the air outlet 31 through the hemispherical gas collecting hood.

[0048] The water-cooled bundle tube 33 is installed in the annular cavity surrounded by the lower gas collecting cylinder 34 and the side wall of the cylinder body. Its upper end is connected to the upper heat exchange cavity 301, and its lower end is connected to the lower heat exchange cavity 302. The cavity between the top surface of the water-cooled bundle tube 33 and the inner end cap 4 forms the second gas distribution cavity 201. The space enclosed by the water-cooled bundle tube 33, the side wall of the shell, and the lower gas collecting cylinder 34 forms the second catalyst cavity 202. The cavity enclosed by the bottom surface of the water-cooled bundle tube 33 and the lower end cap 3 forms the third catalyst cavity 203. The third catalyst cavity 203 is connected to the second gas collecting cavity 104 through the third vent 341 and the fourth vent 342.

[0049] See Figure 3 and Figure 6The water-cooled bundled tubes 33 include several concentrically arranged U-shaped heat exchange tubes 331. Each U-shaped heat exchange tube 331 has a first horizontal section 3311, a vertical section 3312, and a second horizontal section 3313. The vertical section extends axially along the shell, and the first and second horizontal sections extend radially along the shell. The first horizontal section passes through the upper tube sheet 351 and communicates with the upper heat exchange cavity 301, and the second horizontal section passes through the lower tube sheet 361 and communicates with the lower heat exchange cavity 302. Figure 3 As shown, the U-shaped heat exchange tubes 331 are arranged in concentric rings around the lower gas collection cylinder 34, with the outermost U-shaped heat exchange tube being the shortest and the innermost heat exchange tube being the longest, and the inner layer encompassing the outer layer. The heat exchange tubes are made of materials with strong resistance to hydrogen and nitrogen corrosion under the operating temperature and pressure conditions, such as 12Cr2Mo1, SS321, and Alloy690. The heat exchange tubes are bonded to the tube sheet to eliminate gaps; 321 stainless steel or nickel-based alloy materials are welded to both the front and back of the tube sheet, and the back of the tube sheet is further sealed with an organic adhesive material.

[0050] When this application is used in ammonia synthesis reactions,

[0051] The first catalyst chamber 102 is filled with an iron-based catalyst, the second catalyst chamber 202 is filled with a ruthenium-based catalyst, and the lower part of the second gas distribution chamber and the third catalyst chamber 203 are filled with a pre-reduced iron-based catalyst; that is, the lower part of the second gas distribution chamber forms a first pre-reduced iron-based catalyst bed, the third catalyst chamber 203 forms a second pre-reduced iron-based catalyst bed, the first catalyst chamber 102 forms an iron-based catalyst bed, and the second catalyst chamber 202 forms a ruthenium-based catalyst bed.

[0052] High-temperature and high-pressure synthesis gas enters the first gas distribution chamber 101 through the gas inlet 21. Under the action of the axial gas distributor 24, it flows evenly to the surrounding area and enters the radial gas distributor 25. Under the action of the radial gas distributor 25, the synthesis gas flows radially through the iron-based catalyst bed and can react rapidly under high-temperature and high-pressure conditions to generate some NH3. For example, the reaction temperature is 400-500℃ and the reaction pressure is 15-30MPa.

[0053] The mixed gas enters the upper gas collection cylinder 26 through the first vent 261 and is introduced into the lower cavity through the upper gas collection cylinder 26. Under the action of the conical diffuser of the upper gas collection cylinder, the mixed gas flows axially and uniformly through the first pre-reduced iron-based catalyst bed, the ruthenium-based catalyst bed and the second pre-reduced iron-based catalyst bed in sequence to continue the reaction. The reaction gas is discharged through the gas outlet 31.

[0054] The first pre-reduced iron-based catalyst bed can pre-adsorb and convert some impurities (such as H2S and CO) to avoid poisoning of the ruthenium-based catalyst; and can rapidly activate unreacted N2 and H2 to generate initial NH3 under high temperature and pressure, thus alleviating the high temperature sensitivity of the ruthenium-based catalyst.

[0055] Ruthenium-based catalyst beds can achieve highly active and selective ammonia synthesis reactions at relatively low temperatures and pressures, such as reaction temperatures of 200-400℃ and reaction pressures of 5-15MPa.

[0056] The second pre-reduced iron-based catalyst bed can supplement the reaction, capture incompletely converted N2 / H2, and improve the overall yield.

[0057] During the above reaction process, saturated water in the high-pressure steam drum enters the lower heat exchange chamber 36 through the water inlet pipe 38, flows upward along the lumen of the water-cooled bundled tube, and exchanges heat with the reaction gas in a countercurrent manner. The temperature of the catalyst bed is reduced through phase change heat absorption. The steam-water mixture circulating in the pipe system flows out from the upper heat exchange chamber 35 through the water outlet pipe 37 and returns to the high-pressure steam drum. Saturated steam overflows from the upper part of the high-pressure steam drum. This saturated steam is sent into the pipeline network and then sent out as superheated steam for power generation, or directly sent to the steam turbine for power generation.

[0058] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and optimizations can be made without departing from the principle of the present utility model, and these improvements and optimizations are also within the protection scope of the present utility model.

Claims

1. A composite U-shaped wall tube type ammonia synthesis reactor, comprising a shell, the shell including an upper head (2), a lower head (3), and a straight cylinder (1), wherein the upper head is provided with an air inlet (21) at the top and the lower head is provided with an air outlet (31) at the bottom, characterized in that, The shell is provided with an inner end cap (4), which divides the inner cavity of the shell into an upper cavity and a lower cavity; The upper cavity is provided with a first gas distribution chamber (101) and a first catalyst chamber (102). The first catalyst chamber (102) is provided with an iron-based catalyst bed, a radial gas distributor (25), and an upper gas collector (26). The radial gas distributor (25) is located on the outer periphery of the iron-based catalyst bed and is used to allow gas to pass radially from the first gas distribution chamber (101) through the iron-based catalyst bed. The upper gas collector (26) is located in the center of the upper cavity and is used to collect the gas that passes radially through the iron-based catalyst bed and guide it into the lower cavity. No heat transfer tube is provided in the first catalyst chamber (102). The lower cavity is provided with a second gas distribution chamber (201) and a second catalyst chamber (202). The second catalyst chamber (202) is provided with a ruthenium-based catalyst bed, a water-cooled bundle tube (33) and a lower gas collection cylinder (34). The lower gas collection cylinder (34) is located in the center of the lower cavity and is used to collect the gas passing through the ruthenium-based catalyst bed axially and guide it to be discharged from the gas outlet (31). The outer wall of the lower cavity is provided with an upper heat exchange chamber (35) and a lower heat exchange chamber (36). The water-cooled bundle tube (33) is located in the ruthenium-based catalyst bed and surrounds the outer periphery of the lower gas collection cylinder (34). Its upper end is connected to the upper heat exchange chamber (35) and its lower end is connected to the lower heat exchange chamber (36).

2. The composite U-shaped wall tube type ammonia synthesis reactor according to claim 1, characterized in that, The upper heat exchange chamber (35) is provided with an outlet pipe (37), and the lower heat exchange chamber (36) is provided with an inlet pipe (38). Both the inlet pipe (38) and the outlet pipe (37) are connected to the high-pressure steam drum, and high-pressure saturated steam is generated through the high-pressure steam drum.

3. The composite U-shaped wall tube type ammonia synthesis reactor according to claim 1, characterized in that, A second gas distribution chamber (201) and a second catalyst chamber (202) are formed between the bottom surface of the water-cooled bundle tube (33) and the inner end cap (4), and a third catalyst chamber (203) is formed between the bottom surface of the water-cooled bundle tube (33) and the lower end cap (3); a pre-reduced iron-based catalyst bed is provided in the third catalyst chamber (203).

4. The composite U-shaped wall tube type ammonia synthesis reactor according to claim 1, characterized in that, An axial air distribution component (24) is provided inside the air inlet (21). The axial air distribution component (24) includes an insert part and an air distribution part (242). The axial air distribution component (24) is fixedly installed inside the air inlet (21) through its insert part. The air distribution part (242) consists of several annular horizontal plates (2421) spaced apart along the axis of the housing and several vertical plates (2422) inclined at the same angle A between two annular horizontal plates (2421). A swirling air outlet is formed between two adjacent vertical plates (2422).

5. A composite U-shaped wall tube ammonia synthesis reactor according to claim 1, characterized in that, The upper air collecting cylinder (26) includes a straight cylinder and a conical diffuser. The inner cavity of the upper air collecting cylinder (26) forms a first air collecting chamber (103). The top of the first air collecting chamber (103) is closed, and the bottom is connected to the lower cavity through a through hole opened in the center of the inner end cap. The side wall of the straight cylinder is provided with a first vent hole (261) that connects to the first catalyst chamber (102), and the side wall of the conical diffuser is provided with a second vent hole (262) that connects to the first catalyst chamber (102).

6. A composite U-shaped wall tube ammonia synthesis reactor according to claim 1, characterized in that, There are several radial gas distribution components (25), which are arranged around the inner side of the cylinder sidewall. Each radial gas distribution component includes a distribution cylinder extending in a vertical direction. The distribution cylinder includes an arc-shaped outer side plate and an arc-shaped inner side plate. The arc-shaped outer side plate protrudes towards the cylinder sidewall, and the arc-shaped inner side plate protrudes towards the center of the shell. The arc-shaped outer side plate and the arc-shaped inner side plate form a gas distribution cavity with a crescent-shaped cross-section. A gas distribution hole is opened on the inner side plate, and the gas distribution hole connects the gas distribution cavity with the first catalyst cavity (102). The bottom of the distribution cylinder is closed, and the upper end has an air inlet that connects to the first gas distribution cavity (101).

7. A composite U-shaped wall tube ammonia synthesis reactor according to claim 1, characterized in that, The upper heat exchange cavity (35) is formed by an annular upper tube sheet (351) and an upper annular crown (352), and the lower heat exchange cavity (36) is formed by an annular lower tube sheet (361) and a lower annular crown (362). The annular upper tube sheet (351) and the annular lower tube sheet (361) are both located on the side wall of the cylinder. The water-cooled bundle tube (33) is composed of several U-shaped heat exchange tubes (331). The upper end of all U-shaped heat exchange tubes passes through the annular upper tube sheet (351) and communicates with the upper heat exchange cavity (35), and the lower end passes through the annular lower tube sheet (361) and communicates with the lower heat exchange cavity (36).

8. A composite U-shaped wall tube ammonia synthesis reactor according to claim 7, characterized in that, The U-shaped heat exchange tube (331) is provided with a first horizontal section (3311), a vertical section (3312) and a second horizontal section (3313). The vertical section (3312) extends along the axial direction of the shell, and the first horizontal section (3311) and the second horizontal section (3313) extend along the radial direction of the shell. The U-shaped heat exchange tube (331) is concentrically arranged around the lower gas collection cylinder (34).

9. A composite U-shaped wall tube ammonia synthesis reactor according to claim 1, characterized in that, The lower gas collecting cylinder (34) has a straight cylinder body. The lower end of the straight cylinder body is connected to a hemispherical gas collecting hood. The side wall of the part of the straight cylinder body that extends into the lower end cap (4) is provided with a third vent (341) that connects to the second catalyst chamber (202). The hemispherical gas collecting hood is placed above the gas outlet (31), and a fourth vent (342) that connects to the second catalyst chamber (202) is provided on it.

10. A composite U-shaped wall tube ammonia synthesis reactor according to claim 1, characterized in that, The upper end cap (2) is provided with a first manhole (23), which is connected to the first air distribution chamber (101); the upper cavity is provided with a third manhole (11) on the side wall of the cylinder, which is connected to the second air distribution chamber (201); the lower end cap (3) is provided with a second manhole (32), which is connected to the second catalyst chamber (202).

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