A molten salt heater

Abstract

The utility model discloses a kind of fused salt heaters, including vertical structure's shell and multiple groups of heat exchange tube bundle, heat exchange tube bundle includes heat exchange inner tube and sequentially coaxially cover heat insulation pipe in heat exchange inner tube outside, heat exchange outer tube, heat exchange outer tube free end seal, the free end of heat exchange inner tube and heat insulation pipe is open;The lower end opening of heat exchange inner tube is communicated f0 cold gas import through pipe box;The inner tube wall of heat insulation pipe and the outer tube wall of heat exchange inner tube interval form heat insulation dead air layer;The outer tube wall of heat insulation pipe and the inner tube wall of heat exchange outer tube interval lower end are communicated f0 hot gas export through pipe box, upper end opening is communicated with the free end of heat exchange inner tube and forms airflow heat exchange passage. Heat insulation dead air layer can effectively reduce the heat transfer between gas in different temperature difference section of pipe passage import and export.

Description

Technical Field

[0001] This utility model belongs to the field of process gas heating technology, and specifically relates to a molten salt heater. Background Technology

[0002] The process cold gas enters the low-pressure pipe box through the inlet guide pipe of the N1 port of the molten salt heater, and then enters the heat exchange inner tube. At the end of the heat exchange inner tube, it turns back and enters the annular gap between the heat exchange outer tube and the inner tube, where it exchanges heat with the high-temperature molten salt outside the heat exchange outer tube. After heat exchange, the process hot gas finally enters the high-pressure pipe box at the outlet of the heat exchange outer tube and leaves the molten salt heater through the N2 port. During operation, it was found that the temperature difference between the gas in the inner tube and the outer tube was small, that is, the heat exchange efficiency was relatively low. After repeated experiments, it was concluded that there was heat exchange between the cold gas in the inner tube and the outer tube inside the pipe, and the cold gas outlet temperature would be increased by 20-25℃, which also means that the temperature of the output hot gas would be reduced.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the overall background of this utility model and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Utility Model Content

[0004] The purpose of this invention is to provide a molten salt heater that overcomes the defects in the prior art.

[0005] To achieve the above objectives, this utility model provides a molten salt heater, comprising a vertically shaped shell; multiple sets of heat exchange tube bundles are installed inside the shell, one end of each heat exchange tube bundle being a free expansion end, and the other end being fixedly connected to eliminate thermal stress and adapt to heat load and temperature changes. Molten salt flows within the shell and forms indirect heat exchange with the flowing gas within the heat exchange tube bundles. The heat exchange tube bundles include an inner heat exchange tube and an insulating tube and an outer heat exchange tube sequentially and coaxially sleeved outside the inner heat exchange tube. The free end of the outer heat exchange tube is sealed, while the free ends of the inner heat exchange tube and the insulating tube are open. The fixed end of the inner heat exchange tube is connected to a cold gas inlet (f0) through a tube box.

[0006] The fixed end of the heat insulation tube is circumferentially sealed and fixed to the outer wall of the air inlet end of the heat exchange inner tube. The inner tube wall of the heat insulation tube and the outer tube wall of the heat exchange inner tube are spaced apart to form a first annular gap. One end of the first annular gap is closed to form a heat insulation dead air layer. The outer tube wall of the heat insulation tube and the inner tube wall of the heat exchange outer tube are spaced apart to form a second annular gap. The lower end opening of the second annular gap is connected to the hot gas outlet through the tube box. The upper end opening of the second annular gap is connected to the free end of the heat exchange inner tube to form an airflow heat exchange passage.

[0007] Preferably, in the above technical solution, insulation material is filled in or at the bottom of the heat-insulating dead air layer between the f0 cold gas inlet and the f0 hot gas outlet. This section is where the cold gas inlet and hot gas outlet overlap, where the temperature difference is greatest and heat damage is most significant. This is used to reduce the heat radiation and heat transfer from the high-temperature gas in the heat exchange outer tube to the low-temperature gas in the heat exchange inner tube. Airflow scouring can easily damage the fragile insulation layer, reducing the insulation effect and contaminating the process gas. The insulation material is located between the heat exchange inner tube and the insulation tube, and the insulation material does not directly contact the flowing airflow. Therefore, the insulation material is not subject to scouring by the flowing airflow, and there will be no problems of damage or contamination.

[0008] Preferably, in the above technical solution, the lower side wall of the shell is provided with a molten salt inlet, the top of the shell is provided with a molten salt outlet, the bottom of the shell is fixedly connected to a high-pressure tube box through a high-pressure tube sheet, a low-pressure tube box is provided between the high-pressure tube box and the high-pressure tube sheet, the bottom of the low-pressure tube box is connected to the f0 cold gas inlet through an inlet guide pipe passing through the side wall of the high-pressure tube box, and the side wall of the high-pressure tube box opposite to the f0 cold gas inlet is provided with an fO hot gas outlet; the low-pressure tube sheet of the low-pressure tube box is provided with a through hole that is fixedly connected to the bottom air inlet end of the heat exchange inner tube;

[0009] The high-pressure tube sheet of the high-pressure tube box is provided with a through hole for fixing and connecting the bottom outlet end of the heat exchange outer tube.

[0010] Preferably, in the above technical solution, thermal insulation material is filled in the thermal insulation dead air layer between the low-pressure tube sheet and the high-pressure tube sheet. This section is where the cold air inlet and hot air outlet are located, where the temperature difference is greatest. This is used to reduce the heat radiation and heat transfer from the high-temperature gas in the outer heat exchange tube to the low-temperature gas in the inner heat exchange tube. The thermal insulation material is only installed on the side extending to the high-pressure tube sheet where it contacts the shell-side medium, in the section where the temperature difference between the inlet and outlet of the tube-side fluid is greatest. Other components are insulated using the thermal insulation dead air layer between the inner heat exchange tube and the insulation tube.

[0011] Preferably, in the above technical solution, the heat exchange inner tube is fixedly connected to the through hole of the low-pressure tube sheet through a short section. The end faces of the heat exchange inner tube and the short section are fixedly sealed, and a heat insulation annular gap is left between the heat exchange inner tube and the short section. The heat insulation annular gap further reduces the heat exchange area. The end face fixing further isolates the heat exchange between the low-pressure tube sheet and the heat exchange inner tube by reducing the contact area. In addition, the design of the short section facilitates the disassembly, assembly, and maintenance of the heat exchange inner tube.

[0012] Preferably, in the above technical solution, the inlet guide pipe is connected to the low-pressure pipe box by means of a pressure ring to compress the packing, forming a free expansion structure to reduce thermal stress.

[0013] Preferably, in the above technical solution, the number and diameter of the short sections are the same as those of the heat exchange outer tubes; the short sections are used to drill holes with the high-pressure tube sheet to improve the concentricity of the heat exchange inner tubes, insulation tubes and heat exchange outer tubes; the short sections are welded to the inlet end of the heat exchange inner tubes to facilitate the maintenance of the heat exchange tube bundle.

[0014] Preferably, in the above technical solution, the heat exchange outer tube is inserted into the through hole of the high-pressure tube sheet and the heat exchange outer tube is welded and fixed to the end face of the high-pressure tube sheet.

[0015] Preferably, in the above technical solution, the thermal insulation material is ceramic fiber paper, which has a low thermal conductivity, typically between 0.03 and 0.05 W / mK, far lower than traditional thermal insulation materials such as asbestos and glass fiber. Furthermore, this material also possesses excellent high-temperature resistance, low thermal conductivity, and excellent corrosion resistance, oxidation resistance, and high-temperature stability, making it suitable for a wider range of applications.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] High-temperature difference zone insulation enhancement design: For areas with significant temperature differences between the inlet and outlet, a thermal barrier is constructed through the synergistic effect of setting up a thermally insulating dead gas layer and thermal insulation materials. This design can effectively reduce heat transfer between gases at different temperatures at the inlet and outlet of the pipe.

[0018] Energy-saving insulation solution for low temperature difference sections: For pipe sections with relatively small temperature differences, an innovative heat-insulating dead air layer structure is adopted. This structure utilizes the low thermal conductivity of non-flowing gases to suppress conductive heat transfer and reduce natural convection effects, significantly reducing material costs while ensuring insulation performance.

[0019] Optimization of high-performance thermal insulation material application: In view of the fragile nature of high thermal conductivity high-efficiency thermal insulation materials (such as ceramic fiber paper), this structure only sets a small section between the heat exchange inner tube and the thermal insulation tube, effectively avoiding the risk of breakage by high-speed airflow. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a molten salt heater;

[0021] Figure 2 for Figure 1 Enlarged schematic diagram of the middle section (Part I);

[0022] Figure 3 for Figure 1 Enlarged schematic diagram of section II;

[0023] Figure 4 for Figure 1 Enlarged schematic diagram of section III;

[0024] In the diagram: 1. High-pressure tube box; 2. Shell; 3. Heat exchanger tube bundle; 4. High-pressure tube sheet; 5. Low-pressure tube sheet; 6. Low-pressure tube box; 7. Inlet guide tube; 8. High-pressure flat cover; 9. Inner heat exchanger tube; 10. Insulation tube; 11. Outer heat exchanger tube; 12. Short section; 13. Insulation material; 14. Pressure ring; 15. Packing; N1, f0 cold gas inlet; N2, f0 hot gas outlet; N3, molten salt inlet; N4, molten salt outlet. Detailed Implementation

[0025] The specific embodiments of this utility model are described in detail below, but it should be understood that the scope of protection of this utility model is not limited to the specific embodiments.

[0026] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0027] (1) Molten salt heater process flow: f0 cold gas enters the low-pressure tube box 6 through the inlet guide pipe 7 of the N1 port of the molten salt heater, and then enters the heat exchange inner tube 9. At the end of the heat exchange inner tube 9, it turns back and enters the annular gap between the heat exchange outer tube 11 and the heat insulation tube 10, and exchanges heat with the high-temperature molten salt outside the heat exchange outer tube 11. After heat exchange, f1 hot gas finally enters the high-pressure tube box 1 at the outlet of the heat exchange outer tube 11, and leaves the molten salt heater through the N2 port.

[0028] (2) Structure of the molten salt heater: The molten salt heater adopts a vertical structure, which is mainly composed of three parts: high-pressure tube box 1, shell 2, and heat exchange tube bundle 3. Each heat exchange tube bundle 3 consists of heat exchange inner tube 9, heat insulation tube 10, and heat exchange outer tube 11. The heat insulation tube 10 is installed in the annular gap between the heat exchange inner tube 9 and the heat exchange outer tube 11, and one end of it is welded to the heat exchange inner tube 9, thereby forming a heat insulation dead air layer between the heat exchange inner tube 9 and the heat insulation tube 10, thereby reducing the heat transfer between f0 cold gas and f1 hot gas and improving the heat exchange effect; in order to further reduce the heat transfer between the low temperature zone of f0 cold gas and the high temperature zone of f0 hot gas, a section of heat insulation material 13 is set at the inlet of the heat insulation dead air layer between the heat exchange inner tube 9 and the heat insulation tube 10 to reduce the heat radiation of f0 hot gas to f0 cold gas through the heat insulation tube 10.

[0029] (3) Advantages and characteristics of molten salt heaters:

[0030] a. Heat exchanger tube bundle 3, one end of which is free to expand, without thermal stress, can withstand changes in heat load and temperature without causing equipment damage, and can adapt to industrial devices with large load fluctuations in green ammonia production from wind and solar power.

[0031] b. The heat exchange inner tube 9 is welded to the inlet of the heat insulation tube 10 to form a closed annular gap at one end. A section of heat insulation material 13 is set at the bottom of the annular gap to reduce the heat radiation and heat transfer from the high-temperature gas (f0 hot gas) after heat exchange to the low-temperature gas (f0 cold gas) before heat exchange, thereby improving the heat exchange effect of the heat exchanger.

[0032] c. The inlet guide tube 7 achieves free expansion at one end by pressing the packing 15 with the pressure ring 14, thereby reducing thermal stress and improving service life;

[0033] d. Short sections 12 are welded onto the low-pressure tube sheet 5. The number and diameter of the short sections 12 are the same as those of the heat exchange outer tube 11. On the one hand, this facilitates the drilling of tube holes between the low-pressure tube sheet 5 and the high-pressure tube sheet 4, and improves the concentricity of the heat exchange inner tube 9, the insulation tube 10, and the heat exchange outer tube 11. On the other hand, the short sections 12 are welded to the inlet end of the heat exchange inner tube 9, which is beneficial for the maintenance of the heat exchange tube bundle 3.

[0034] Maintenance procedure: Open the high-pressure flat cover 8 of the molten salt heater, remove the end caps and other components of the low-pressure tube box 6, then remove the weld between the short section 12 and the heat exchange inner tube 9, and pull out the heat exchange inner tube 9 and the insulation tube 10; after the heat exchange inner tube 9 and the insulation tube 10 are completely pulled out, remove the low-pressure tube sheet 5, and then inspect the heat exchange outer tube 11 welded to the high-pressure tube sheet 4 (Note: the heat exchange outer tube 11 can be replaced separately). After the inspection is completed, reassemble.

[0035] (4) Comparison between traditional three-tube heat exchangers and molten salt heaters:

[0036] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A molten salt heater, comprising a vertically oriented shell (2); wherein multiple sets of heat exchange tube bundles (3) are erected within the shell (2), and molten salt flows within the shell and forms indirect heat exchange with the flowing gas within the heat exchange tube bundles (3), characterized in that, The heat exchange tube bundle (3) includes an inner heat exchange tube (9) and an outer heat exchange tube (11) that are coaxially sleeved around the inner heat exchange tube (9). The free end of the outer heat exchange tube (11) is sealed, while the free ends of the inner heat exchange tube (9) and the outer heat exchange tube (10) are open. The fixed end of the inner heat exchange tube (9) is connected to the cold air inlet (N1) of f0 through the tube box. The fixed end of the heat insulation tube (10) is circumferentially sealed and fixed on the outer wall of the air inlet end of the heat exchange inner tube (9). The inner tube wall of the heat insulation tube (10) and the outer tube wall of the heat exchange inner tube (9) are spaced apart to form a first annular gap. One end of the first annular gap is closed to form a heat insulation dead air layer. The outer tube wall of the heat insulation tube (10) and the inner tube wall of the heat exchange outer tube (11) are spaced apart to form a second annular gap. The lower end of the second annular gap is connected to the hot gas outlet (N2) through the tube box. The upper end of the second annular gap is connected to the free end of the heat exchange inner tube (9) to form a gas flow heat exchange passage.

2. The molten salt heater according to claim 1, characterized in that, Insulating material (13) is filled in or at the bottom of the insulating dead air layer between the f0 cold air inlet (N1) and the f0 hot air outlet (N2).

3. The molten salt heater according to claim 1, characterized in that, The lower side wall of the shell (2) is provided with a molten salt inlet (N3), the top of the shell (2) is provided with a molten salt outlet (N4), the bottom of the shell (2) is fixedly connected to the high-pressure tube box (1) through the high-pressure tube plate (4), a low-pressure tube box (6) is provided between the high-pressure tube box (1) and the high-pressure tube plate (4), the bottom of the low-pressure tube box (6) is connected to the f0 cold air inlet (N1) through the inlet guide pipe (7) through the side wall of the high-pressure tube box (1), and the side wall of the high-pressure tube box (1) opposite to the f0 cold air inlet (N1) is provided with an fO hot gas outlet (N2); the low-pressure tube plate (5) of the low-pressure tube box (6) is provided with a through hole that is fixedly connected to the bottom air inlet end of the heat exchange inner tube (9); The high-pressure tube plate (4) of the high-pressure tube box (1) is provided with a through hole for fixed connection to the bottom outlet end of the heat exchange outer tube (11).

4. The molten salt heater according to claim 3, characterized in that, Insulating material (13) is filled in the thermal dead air layer between the low-pressure tube sheet (5) and the high-pressure tube sheet (4).

5. The molten salt heater according to claim 3, characterized in that, The heat exchange inner tube (9) is fixedly connected to the through hole of the low-pressure tube sheet (5) through the short section (12). The end faces of the heat exchange inner tube (9) and the short section (12) are fixedly sealed, and a heat insulation annular gap is left between the heat exchange inner tube (9) and the short section (12).

6. The molten salt heater according to claim 3, characterized in that, The inlet guide pipe (7) is connected to the low-pressure pipe box (6) by pressing the packing (15) with a pressure ring (14) to form a free expansion structure.

7. The molten salt heater according to claim 5, characterized in that, The number and diameter of the short sections (12) are the same as those of the outer heat exchange tube (11); the short sections (12) are used to drill holes with the high pressure tube sheet (4); the short sections (12) are welded to the inlet end of the inner heat exchange tube (9).

8. The molten salt heater according to claim 3, characterized in that, The heat exchange outer tube (11) is inserted into the through hole of the high pressure tube sheet (4) and the heat exchange outer tube (11) is welded and fixed to the end face of the high pressure tube sheet (4).

9. The molten salt heater according to claim 4, characterized in that, The heat insulation material (13) is ceramic fiber paper.

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