Energy-saving double-tube-pass main heat exchanger for nitric acid production

Abstract

The invention discloses an energy-saving double-tube-pass main heat exchanger for nitric acid production, which comprises a main tank body, a water inlet shell and a return shell, the water inlet shell and the return shell are communicated with two ends of the main tank body, the inner surface of the main tank body is fixedly connected with a plurality of heat exchange tubes communicated with the water inlet shell and the return shell, and the inner surface of the water inlet shell is fixedly connected with a partition plate. The partition plate is used for dividing the heat exchange pipes into two groups; a flow gathering assembly is arranged in the water inlet shell and comprises a sealing plate, a first-order baffle, a second-order baffle and a third-order baffle, the sealing plate is movably connected to the lower portion of the water inlet position of the water inlet shell, and the first-order baffle, the second-order baffle and the third-order baffle are movably sealed at end openings of part of the heat exchange pipes. The flow gathering assembly can open a plurality of heat exchange pipes in sequence according to the opening degree of the sealing plate, through the components, according to the fluctuation pain point of the nitric acid production working condition, the sealing plate is in linkage with the three-order baffle to achieve graded operation of the heat exchange pipes, and therefore equipment can conduct efficient heat exchange under all working conditions, recycle high-temperature gas heat and save energy.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger technology, and in particular to an energy-saving double-pass main heat exchanger for nitric acid production. Background Technology

[0002] In the nitric acid production process, the double-pass main heat exchanger is the core heat exchange equipment, mainly used to recover high-temperature NO produced by the ammonia oxidation reaction. x Gas heat exchange, which enables heat exchange between the tube-side and shell-side fluids, is a key piece of equipment for improving the energy utilization rate and reducing energy consumption of the unit.

[0003] Existing two-pass heat exchangers mostly feature a fully open design for all operating conditions, lacking flow channel control structures. In nitric acid production, operating parameters such as raw material flow rate, ammonia oxidation rate, and hot fluid temperature easily fluctuate with production load. At low loads, the fluid velocity in the tubes decreases, turbulence weakens, and the thermal boundary layer thickens, resulting in a significant reduction in the heat transfer coefficient and poor heat recovery efficiency. At high loads, there is no room for control, and the heat exchange area cannot adapt to the load increase, failing to meet the requirements of nitric acid production for high efficiency, energy saving, and adaptability to variable operating conditions. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide an energy-saving double-pass main heat exchanger for nitric acid production. This solves the technical problems of traditional double-pass main heat exchangers for nitric acid production, which suffer from low heat transfer coefficient and poor heat recovery efficiency under fluctuating operating conditions due to the heat exchange tubes being fully open under all operating conditions and the lack of flow channel control structure, as well as the lack of control space under high load.

[0005] The present invention also provides an energy-saving double-pass main heat exchanger for nitric acid production, comprising: a main tank, an inlet shell and a return shell connected at both ends of the main tank, wherein a plurality of heat exchange tubes connected to the inlet shell and the return shell are fixedly connected to the inner surface of the main tank, and a baffle plate is fixedly connected to the inner surface of the inlet shell, the baffle plate being used to divide the plurality of heat exchange tubes into two groups; a flow-concentrating assembly is provided inside the inlet shell, the flow-concentrating assembly comprising: a sealing plate, a first-stage baffle, a second-stage baffle, and a third-stage baffle, wherein the sealing plate is movably connected below the water inlet of the inlet shell, and the first-stage baffle, the second-stage baffle, and the third-stage baffle are movably sealed at the ports of some of the heat exchange tubes; the flow-concentrating assembly can sequentially open the plurality of heat exchange tubes by adjusting the opening degree of the sealing plate.

[0006] According to the present invention, the energy-saving dual-pass main heat exchanger for nitric acid production is provided with a tube-side interface one and a tube-side interface two on the water inlet shell, and a shell-side interface one and a shell-side interface two on the main tank body; the tube-side interface one is located above the water inlet shell and is arranged opposite to the tube-side interface two, and the shell-side interface one is located above the main tank body and is arranged opposite to the shell-side interface two.

[0007] According to the present invention, the energy-saving double-pass main heat exchanger for nitric acid production has multiple baffles fixedly connected to the inner surface of the main tank in an alternating manner, and multiple heat exchange tubes are inserted through the baffles.

[0008] According to the present invention, an energy-saving double-pass main heat exchanger for nitric acid production has a plurality of sliding rods fixedly connected to the inner surface of the water inlet shell, a sealing plate slidably connected to the outer wall of the plurality of sliding rods, and a spring fixedly connected between the sealing plate and the tail end of the sliding rod; the sealing plate is provided with a through hole.

[0009] According to the present invention, the energy-saving double-pass main heat exchanger for nitric acid production further includes: a slide rail, a slider, and a crank. The slide rail is fixedly connected to the inner surface of the water inlet shell, the slider is slidably connected to the inside of the slide rail, one end of the crank is hinged to the upper surface of the slider, and the other end is hinged to the bottom of the sealing plate; a pull rod is fixedly connected to the side of the slider facing the tube sheet.

[0010] According to the present invention, the energy-saving double-pass main heat exchanger for nitric acid production further includes: a first support, a second support, and a third support. The first support is fixedly connected to the rear surface of a first-stage baffle, the second support is fixedly connected to the rear surface of a second-stage baffle, and the third support is fixedly connected to the rear surface of a third-stage baffle. One side of each of the first, second, and third supports is sleeved on the outer wall of a pull rod. The first support is located at the tail end of the pull rod, the second support is located in the middle section of the pull rod, and the third support is located at the head end of the pull rod.

[0011] According to the present invention, the energy-saving double-pass main heat exchanger for nitric acid production has multiple supports on the side of the first-stage baffle, second-stage baffle, and third-stage baffle facing the heat exchange tube, and the multiple supports are movably arranged inside the corresponding heat exchange tube; the outer wall of the pull rod is fixedly connected to three push plates, and the three push plates are movably abutting against the first support, the second support, and the third support, respectively.

[0012] Beneficial effects: This technical solution utilizes an energy-saving dual-tube heat exchanger for nitric acid production. Addressing the pain points of traditional dual-tube heat exchangers—namely, the decrease in heat transfer coefficient under low load and the lack of controllability under high load caused by fluctuations in nitric acid production conditions—this solution achieves graded operation of the heat exchange tubes by sequentially opening first- to third-stage baffles through the linkage of the sealing plate opening degree. Under low load, the flow velocity and turbulence intensity of the tube-side fluid are maintained; under medium and high loads, the heat exchange area is gradually expanded, ensuring high heat exchange efficiency across all operating conditions. This significantly improves the heat recovery efficiency of high-temperature gases, achieving energy-saving effects. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a front view of the energy-saving double-pass main heat exchanger for nitric acid production according to the present invention. Figure 2 This is a front cross-sectional view of the energy-saving double-pass main heat exchanger for nitric acid production according to the present invention. Figure 3 This is a partially enlarged structural view of the water inlet shell of the energy-saving double-pass main heat exchanger for nitric acid production according to the present invention; Figure 4 This is a left-side cross-sectional view of the energy-saving double-pass main heat exchanger for nitric acid production according to the present invention. Figure 5 This is a right-side cross-sectional view of the energy-saving double-pass main heat exchanger for nitric acid production according to the present invention.

[0014] Legend: 1. Shell-side interface 1; 2. Tube-side interface 1; 3. Water inlet shell; 4. Tube-side interface 2; 5. Main tank; 6. Return shell; 7. Shell-side interface 2; 8. Baffle; 9. Tube sheet; 10. Heat exchange tube; 11. Baffle plate; 12. Third-stage baffle; 13. Second-stage baffle; 14. First-stage baffle; 15. Support; 16. Spring; 17. Sealing plate; 18. Through hole; 19. Crank; 20. Slide rail; 21. Slider; 22. Push plate; 23. Tie rod; 24. Slide rod; 25. Third support; 26. Second support; 27. First support. Detailed Implementation

[0015] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0016] Reference Figure 1-5 This invention discloses an energy-saving double-pass heat exchanger for nitric acid production, comprising: considering the need to construct a basic double-pass heat exchange channel for the double-pass heat exchanger and to provide an installation carrier for the subsequent control structure, a main tank 5, an inlet shell 3 and a return shell 6 connected at both ends of the main tank 5 are designed, a plurality of heat exchange tubes 10 connected to the inlet shell 3 and the return shell 6 are fixedly connected to the inner surface of the main tank 5, and a partition 8 is fixedly connected to the inner surface of the inlet shell 3, the partition 8 being used to divide the plurality of heat exchange tubes 10 into two groups; The baffle 8 divides the heat exchange tube 10 into two independent flow channels. The tube-side fluid enters one group of heat exchange tubes 10 through the water inlet shell 3, and then enters the other group of heat exchange tubes 10 through the return shell 6, thus completing the double-pass flow. This structure not only realizes the basic heat exchange function of the double-pass flow, but also provides a structural basis for the graded control of the flow convergence component, ensuring the basic efficiency of the double-pass heat exchange. Considering the problem that traditional two-pass heat exchangers cannot achieve phased operation based on fluctuations in operating conditions when the heat exchange tubes are fully open under all operating conditions, a flow-concentrating assembly is installed inside the water inlet shell 3. The flow-concentrating assembly includes: a sealing plate 17, a first-stage baffle 14, a second-stage baffle 13, and a third-stage baffle 12. The sealing plate 17 is movably connected below the water inlet of the water inlet shell 3, and the first-stage baffle 14, second-stage baffle 13, and third-stage baffle 12 are movably sealed at the ports of some of the heat exchange tubes 10. The flow-concentrating assembly can sequentially open multiple heat exchange tubes 10 depending on the degree of opening of the sealing plate 17. The flow-concentrating assembly also includes: a slide rail 20, a slider 21, and a crank 19. The slide rail 20 is fixedly connected to the inner surface of the water inlet shell 3, and the slider 21 is slidably connected inside the slide rail 20. One end of the crank 19 is hinged to the upper surface of the slider 21, and the other end is hinged to the bottom of the sealing plate 17; a pull rod 23 is fixedly connected to the side of the slider 21 facing the tube sheet 9. The current-concentrating assembly also includes: a first bracket 27, a second bracket 26, and a third bracket 25. The first bracket 27 is fixedly connected to the rear surface of the first-stage baffle 14, the second bracket 26 is fixedly connected to the rear surface of the second-stage baffle 13, and the third bracket 25 is fixedly connected to the rear surface of the third-stage baffle 12. One side of the first bracket 27, the second bracket 26, and the third bracket 25 are all sleeved on the outer wall of the pull rod 23. The first bracket 27 is located at the tail end of the pull rod 23, the second bracket 26 is located in the middle section of the pull rod 23, and the third bracket 25 is located at the head end of the pull rod 23. The sliding of the sealing plate 17 drives the slider 21 to move along the slide rail 20 via the crank 19. The slider 21 drives the pull rod 23 to move synchronously. The pull rod 23, through the first bracket 27, the second bracket 26, and the third bracket 25, sequentially links the first-stage baffle 14, the second-stage baffle 13, and the third-stage baffle 12 to open or close the corresponding heat exchange tubes 10. This structure realizes the staged operation of the heat exchange tubes 10, enabling the equipment to adjust the number of tube groups participating in heat exchange according to the operating load, providing core support for efficient heat exchange under all operating conditions.

[0017] In summary, the improvement of this embodiment lies in: To address the pain points of traditional two-pass heat exchangers, such as decreased heat transfer coefficient under low load and lack of controllability under high load caused by fluctuations in nitric acid production conditions, the heat exchange tubes 10 are put into operation in stages by sequentially opening the first-stage baffle 14 to the third-stage baffle 12 in conjunction with the opening degree of the sealing plate 17. This ensures the flow velocity and turbulence intensity of the tube-side fluid at low loads, and gradually expands the heat exchange area at medium and high loads, so that the equipment maintains high heat exchange efficiency under all operating conditions, significantly improving the heat recovery efficiency of high-temperature gas and achieving energy-saving effects.

[0018] Based on the above, other structures also need to be disclosed in detail, such as: The inlet shell 3 is provided with a pipe-side interface 1 2 and a pipe-side interface 2 4, and the main tank 5 is provided with a shell-side interface 1 1 and a shell-side interface 2 7; the pipe-side interface 1 2 is located above the inlet shell 3 and is opposite to the pipe-side interface 2 4, and the shell-side interface 1 1 is located above the main tank 5 and is opposite to the shell-side interface 2 7. Tube-side interface 1 (2) is the tube-side fluid inlet, tube-side interface 2 (4) is the tube-side fluid outlet, shell-side interface 1 (1) is the shell-side fluid inlet, and shell-side interface 2 (7) is the shell-side fluid outlet.

[0019] To address the issue of increasing the travel distance of the shell-side fluid, multiple baffles 11 are fixedly connected to the inner surface of the main tank 5 in an alternating manner, and multiple heat exchange tubes 10 are inserted inside the baffles 11. The staggered baffles 11 force the shell-side fluid to change its flow direction multiple times, increasing its stroke and continuously passing through the gaps in the heat exchange tubes 10, thus enhancing the turbulence of the fluid.

[0020] Considering the connection and reset of the sealing plate 17, multiple sliding rods 24 are fixedly connected to the inner surface of the water inlet housing 3. The sealing plate 17 is slidably connected to the outer wall of the multiple sliding rods 24. A spring 16 is fixedly connected between the sealing plate 17 and the tail end of the sliding rod 24. A through hole 18 is provided on the sealing plate 17. The sealing plate 17 is set by the slide bar 24, and the sealing plate 17 can be reset under low load by the spring 16.

[0021] Considering the connection and sliding stability of the first-stage baffle 14, the second-stage baffle 13, and the third-stage baffle 12, multiple supports 15 are provided on the side of the first-stage baffle 14, the second-stage baffle 13, and the third-stage baffle 12 facing the heat exchange tube 10. The multiple supports 15 are movably arranged inside the corresponding heat exchange tube 10. Three push plates 22 are fixedly connected to the outer wall of the pull rod 23. The three push plates 22 are movably abutting against the first support 27, the second support 26, and the third support 25, respectively. The support frame 15 is placed inside the heat exchange tube 10 to provide support for the first-stage baffle 14, the second-stage baffle 13, and the third-stage baffle 12 and to ensure their smooth sliding. The push plate 22 is used to push the first-stage baffle 14, the second-stage baffle 13, and the third-stage baffle 12 back when the pull rod 23 is reset.

[0022] Working principle: When the equipment is working, the tube-side fluid enters the inlet shell 3 through tube-side interface 2, and the shell-side fluid enters the main tank 5 through shell-side interface 1, forming a heat exchange mode between the two.

[0023] The core of the tube side relies on the flow-concentrating component to achieve graded control: at low load, the spring 16 pushes the sealing plate 17 to reset along the slide rod 24. The flow area of ​​the through hole 18 is small. The pressure of the tube side fluid pushes the sealing plate 17 to slide slightly. The crank 19 drives the slider 21 to move along the slide rail 20. The slider 21 pulls the pull rod 23 to move synchronously. The pull rod 23 first pulls the first-stage baffle 14 to open the corresponding heat exchange tube 10, ensuring the tube side fluid velocity and turbulence intensity. As production load increases, the flow rate and pressure of fluid in the pipe increase, the sliding distance of the sealing plate 17 increases, and the distance that the pull rod 23 pulls the first-stage baffle 14 increases synchronously until it contacts and pulls the second-stage baffle 13 to open. As the load increases further, the movement distance of the lever 23 continues to increase, contacting and pulling the third-stage baffle 12 to open, gradually increasing the number of heat exchange tubes 10 in operation to match the heat exchange load.

[0024] After the tube-side fluid completes the first stage of flow through the staged heat exchange tubes 10, it enters another set of heat exchange tubes 10 divided by the baffle 8 through the return shell 6 to complete the second stage of flow, and finally exits from the tube-side interface 4. The shell-side fluid is guided by staggered baffles 11 within the main tank 5, changing its flow direction multiple times and increasing turbulence to improve heat exchange efficiency before being discharged from the shell-side interface 7.

[0025] When the load decreases, the spring 16 pushes the sealing plate 17 to reset, and the push plate 22 on the pull rod 23 pushes the third-stage baffle 12, the second-stage baffle 13, and the first-stage baffle 14 back to the sealed state in sequence. The support frame 15 ensures that each baffle slides smoothly throughout the process. The whole system achieves efficient heat exchange and high-temperature gas heat recovery under all working conditions through the dual-pass design and adaptive control of the flow-concentrating component, thus achieving energy-saving effect.

[0026] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. An energy-saving double-pass main heat exchanger for nitric acid production, characterized in that: include: The main tank (5) has an inlet shell (3) and a return shell (6) connected at both ends of the main tank (5). The inner surface of the main tank (5) is fixedly connected with a plurality of heat exchange tubes (10) that are connected to the inlet shell (3) and the return shell (6). The inner surface of the inlet shell (3) is fixedly connected with a partition (8). The partition (8) is used to divide the plurality of heat exchange tubes (10) into two groups. The water inlet shell (3) is provided with a flow-gathering component, which includes: a sealing plate (17), a first-stage baffle (14), a second-stage baffle (13), and a third-stage baffle (12). The sealing plate (17) is movably connected below the water inlet of the water inlet shell (3), and the first-stage baffle (14), the second-stage baffle (13), and the third-stage baffle (12) are movably sealed at the port of part of the heat exchange tube (10). The heat exchanger assembly can sequentially open multiple heat exchange tubes (10) by adjusting the opening degree of the sealing plate (17).

2. The energy-saving double-pass main heat exchanger for nitric acid production according to claim 1, characterized in that, The water inlet shell (3) is provided with a pipe side interface 1 (2) and a pipe side interface 2 (4), and the main tank (5) is provided with a shell side interface 1 (1) and a shell side interface 2 (7). The first pipe-side interface (2) is located above the water inlet shell (3) and is opposite to the second pipe-side interface (4). The first shell-side interface (1) is located above the main tank (5) and is opposite to the second shell-side interface (7).

3. The energy-saving double-pass main heat exchanger for nitric acid production according to claim 1, characterized in that, The inner surface of the main tank (5) is provided with multiple baffles (11) that are fixedly connected in an alternating manner, and multiple heat exchange tubes (10) are inserted inside the baffles (11).

4. The energy-saving double-pass main heat exchanger for nitric acid production according to claim 1, characterized in that, The inner surface of the water inlet shell (3) is fixedly connected with a plurality of sliding rods (24), the sealing plate (17) is slidably connected to the outer wall of the plurality of sliding rods (24), and a spring (16) is fixedly connected between the sealing plate (17) and the tail end of the sliding rod (24). The sealing plate (17) is provided with a through hole (18).

5. The energy-saving double-pass main heat exchanger for nitric acid production according to claim 1, characterized in that, The flow-gathering assembly also includes: a slide rail (20), a slider (21), and a crank (19). The slide rail (20) is fixedly connected to the inner surface of the water inlet housing (3). The slider (21) is slidably connected to the inside of the slide rail (20). One end of the crank (19) is hinged to the upper surface of the slider (21), and the other end is hinged to the bottom of the sealing plate (17). A pull rod (23) is fixedly connected to the side of the slider (21) facing the tube plate (9).

6. The energy-saving double-pass main heat exchanger for nitric acid production according to claim 5, characterized in that, The current-gathering assembly further includes: a first support (27), a second support (26), and a third support (25). The first support (27) is fixedly connected to the rear surface of the first-stage baffle (14), the second support (26) is fixedly connected to the rear surface of the second-stage baffle (13), and the third support (25) is fixedly connected to the rear surface of the third-stage baffle (12). One side of the first bracket (27), the second bracket (26), and the third bracket (25) are all sleeved on the outer wall of the pull rod (23). The first bracket (27) is located at the tail end of the pull rod (23), the second bracket (26) is located in the middle section of the pull rod (23), and the third bracket (25) is located at the head end of the pull rod (23).

7. The energy-saving double-pass main heat exchanger for nitric acid production according to claim 6, characterized in that, The first-stage baffle (14), the second-stage baffle (13), and the third-stage baffle (12) are provided with multiple supports (15) on the side facing the heat exchange tube (10), and the multiple supports (15) are movably arranged inside the corresponding heat exchange tube (10); the outer wall of the pull rod (23) is fixedly connected with three push plates (22), and the three push plates (22) are movably abutting against the first support (27), the second support (26), and the third support (25) respectively.

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