Silicon carbide heat exchanger for high-temperature working condition

Abstract

The utility model discloses a silicon carbide heat exchanger for a high-temperature working condition, which belongs to the field of chemical machinery, and adopts the technical scheme that the silicon carbide heat exchanger comprises a shell pass barrel and a plurality of silicon carbide heat exchange tubes positioned in the shell pass barrel, and two ends of each silicon carbide heat exchange tube are respectively communicated with the shell pass barrel through a polytetrafluoroethylene embedded steel plate type tube plate; a flexible expansion section is arranged on the shell pass barrel, flanges are further arranged at the two ends of the shell pass barrel, the flanges at the two ends of the shell pass barrel are connected through a pulling and supporting rod, the pulling and supporting rod comprises an upper rod and a lower rod, and the corresponding ends of the upper rod and the lower rod are in threaded connection through an elastic nut. The silicon carbide heat exchanger is extremely simple in structure and easy to manufacture and transform, and the thermal expansion coordination problem of the silicon carbide heat exchanger under the high-temperature working condition is effectively solved.

Description

Technical Field

[0001] The utility model discloses a heat exchanger, in particular to a silicon carbide heat exchanger used in high-temperature working conditions. Background Art

[0002] Some heat exchangers are used in hydrogen fluoride devices, such as mixed acid heaters, acid-acid heat exchangers, etc. Typical media of these heat exchangers are fluosilicic acid, sulfuric acid, hydrofluoric acid or a mixture of multiple media; the maximum operating temperature of the medium on the high-temperature side of the heat exchanger is ~180°C. High concentrations of sulfuric acid, fluosilicic acid and trace amounts of F-, Cl- and other ions are highly corrosive at high temperatures. The generated HF has a low evaporation temperature and is easy to volatilize. The concentration in the gas phase in the tank is much greater than that in the liquid phase. HF has a strong corrosive ability in a humid and high-temperature environment. The raw materials or reactants also contain a small amount of SiO 2 , has certain abrasiveness.

[0003] How to design a heat exchanger for a high temperature and high corrosion environment, so as to achieve the process heat exchange effect, carry out appropriate material selection and structural design, and be safe, reliable, economical and durable, is a technical problem that needs to be solved for heat exchangers used in hydrogen fluoride devices.

[0004] Silicon carbide heat exchanger, the main materials of contact materials are silicon carbide and PTFE, suitable for heat exchange of corrosive media. Silicon carbide heat exchange tubes have high corrosion resistance, oxidation resistance and abrasion resistance, and can withstand sulfuric acid, hydrofluoric acid, nitric acid, phosphoric acid, mixed acid, strong alkali, etc.; Silicon carbide has high thermal conductivity, and under the same heat exchange efficiency, the heat exchange area required by silicon carbide heat exchanger will be less; Silicon carbide heat exchange tube surface is smooth, not easy to scale, easy to clean; and the price is lower than precious metals such as tantalum, zirconium, Hastelloy, etc. Due to these unique advantages, silicon carbide heat exchangers are increasingly widely used in the chemical industry, and have been widely used in cooling, condensation or low-pressure steam heating and other working conditions with low operating temperatures.

[0005] For silicon carbide heat exchangers, during the operation of the equipment, as the temperature changes, the expansion and contraction of the silicon carbide heat exchange tube and the metal cylinder of the shell are different. The thermal expansion coefficient of silicon carbide is smaller than that of steel. At 180°C, the thermal expansion coefficient of the carbon steel cylinder is (~1.2×10 -5 / K) is a silicon carbide heat exchange tube (~4.2×10 -6 / k) thermal expansion coefficient is ~3 times that of the heat exchanger with a 4m long heat exchange tube. At 180℃, the difference in thermal expansion between the carbon steel cylinder and the silicon carbide heat exchange tube is ~5mm. On the other hand, after the PTFE steel plate tube sheet is enlarged, the deformation of the tube sheet (such as the bulge in the center of the tube sheet) increases the risk of sealing failure and may even break the silicon carbide heat exchange tube. Considering the deformation coordination measures of the two and appropriate thermal expansion compensation measures to reduce thermal stress is the key to reducing the damage of the silicon carbide heat exchange tube and increasing the reliability of the tube sheet and heat exchanger seal.

[0006] The document "A Shell and Tube Heat Exchanger for Corrosive Media" with patent number CN200620068354.0 discloses a heat exchanger for silicon carbide. Due to the different thermal expansion coefficients between silicon carbide and the metal shell, the connecting tube sheet will extend or shorten with the shell. At this time, relative displacement will occur between the silicon carbide tube and the tube sheet. Such repeated movement over a long period of time will cause abrasion of the sealing ring, or excessive deformation and cause sealing failure. It is not suitable for high temperature conditions or conditions with frequent hot and cold changes.

[0007] Therefore, there is an urgent need for a silicon carbide heat exchanger with a new structure to solve the thermal expansion coordination problem of the silicon carbide heat exchanger under high temperature conditions, so as to broaden the operating range of the silicon carbide heat exchanger. Summary of the invention

[0008] The purpose of the utility model is to solve the above technical problems and to provide a silicon carbide heat exchanger for high temperature working conditions which has a simple structure, is easy to manufacture and effectively solves the thermal expansion coordination problem of the silicon carbide heat exchanger under high temperature working conditions.

[0009] The utility model is a silicon carbide heat exchanger for high-temperature working conditions, comprising a shell-side cylinder and a plurality of silicon carbide heat exchange tubes located in the shell-side cylinder, the two ends of the silicon carbide heat exchange tubes are respectively connected to the tube-side cylinder through a polytetrafluoroethylene-lined steel plate tube sheet, a flexible expansion section is provided on the shell-side cylinder, and flanges are also provided at both ends of the shell-side cylinder, and the flanges at both ends of the shell-side cylinder are connected through a tension rod, and the tension rod comprises an upper rod and a lower rod, and the corresponding ends of the upper rod and the lower rod are threadedly connected through a loose nut.

[0010] The threads of the upper internal thread and the lower internal thread of the clamping nut 8 are opposite.

[0011] At least three tie rods are evenly arranged along the circumference of the shell side cylinder.

[0012] An annular clamping block is also provided between the PTFE inner steel plate tube sheet and the shell side cylinder, and the annular clamping block and the flange are connected by bolts to clamp the PTFE inner steel plate tube sheet.

[0013] The shell side cylinder, the annular clamping block and the flange are also connected by bolts.

[0014] The end of the silicon carbide heat exchange tube is connected to the PTFE steel plate-lined tube sheet by a sealing element.

[0015] The sealing element is a perfluoroether sealing ring sleeved on the end of the silicon carbide heat exchange tube.

[0016] In view of the thermal stress problem of the heat exchange tubes of the heat exchanger made of silicon carbide and the tube sheet made of PTFE steel plate, a flexible expansion section is set on the shell cylinder, and pre-stretching is performed during installation, so that the thermal expansion of the cylinder can be appropriately compensated under high-temperature operating conditions, reducing the stress of the cylinder and the expansion joint; a tension rod is set on the outside of the shell cylinder to limit the thermal expansion displacement of the cylinder and the tube sheet, and the sealing element is sealed with a small pre-compression force, which increases the rigidity of the shell and avoids the asymmetric deformation of the shell cylinder; at least three tension rods are evenly arranged along the circumference of the shell cylinder, which increases the rigidity of the shell and avoids the asymmetric deformation of the shell. Furthermore, the tension rod is composed of an upper rod and a lower rod, and the upper rod and the lower rod are threadedly connected by a loose nut. The length of the tension rod is adjusted by the loose nut, so as to adjust the pre-stretching amount of the shell cylinder under installation conditions, and compensate for the installation length deviation of the shell and the tube sheet by a small amount. Under high-temperature operating conditions, the length of the shell cylinder can also be adjusted at any time to reduce the thermal stress inside the equipment.

[0017] The end of the silicon carbide heat exchange tube is covered with a perfluoroether sealing ring to strengthen the sealing between the silicon carbide heat exchange and the PTFE steel plate tube sheet. Under high temperature conditions, the silicon carbide heat exchange tube expands thermally, further tightening the perfluoroether sealing ring, thereby better ensuring the sealing effect under high temperature conditions.

[0018] In view of the problem that the PTFE steel plate tube sheet is inconvenient to install and fix due to material limitations, an annular clamping block is added, and the annular clamping block is connected to the flange by bolts to achieve the clamping of the PTFE steel plate tube sheet, limit the tube sheet and strengthen it to prevent the tube sheet from deforming and protruding, resulting in failure of the seal between the heat exchange tube.

[0019] The utility model aims at the thermal expansion coordination problem of silicon carbide heat exchangers under high temperature conditions, has good sealing effect, and effectively reduces the relative displacement between silicon carbide tubes and tube sheets, such as the abrasion of the sealing ring, or excessive deformation that leads to sealing failure. It greatly extends the service life of the equipment and is suitable for high temperature conditions or conditions with frequent hot and cold changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the utility model.

[0021] Among them, 1. Tube side head; 2. Tube side cylinder; 3. Annular clamping block; 4. PTFE steel plate tube sheet; 5. Silicon carbide heat exchange tube; 6. Shell side cylinder; 7. Bracing rod; 7.1, upper rod, 7.2-lower rod; 8. Loose nut; 9. Flexible expansion section; 10.1, perfluoroether sealing ring; 10.2, fastening screw; 11, first material inlet; 12, first material outlet; 13, second material inlet; 14, second material outlet; 15, flange. DETAILED DESCRIPTION

[0022] The utility model is further explained below in conjunction with the accompanying drawings:

[0023] See also Figure 1 The utility model includes a shell-side cylinder 6 and a plurality of silicon carbide heat exchange tubes 5 located inside the shell-side cylinder 6. Both ends of the silicon carbide heat exchange tubes 5 are connected to the tube-side cylinder 2 through a PTFE steel plate tube sheet 4. A tube-side head 1 is provided at the end of the tube-side cylinder 2. The tube-side heads 1 at both ends are respectively a first material inlet 11 and a second material outlet 12. The tube-side cylinder 6 is respectively provided with a second material inlet 13 and a second material outlet 14. The shell-side cylinder 6 has a flexible expansion section 9.

[0024] The two ends of the shell cylinder 6 are also equipped with flanges 15, and the flanges 15 at the two ends of the shell cylinder 6 are connected by a tension rod 7. The tension rod 7 includes an upper rod 7.1 and a lower rod 7.2. The corresponding ends of the upper rod 7.1 and the lower rod 7.2 are threadedly connected by a loose nut 8. Specifically, the threads of the upper section internal thread and the lower section internal thread of the loose nut 8 are opposite, so that the positive or negative twisting of the loose nut 8 can realize the movement of the upper rod 7.1 and the lower rod 7.2 in the axial direction close or far, and realize the control of the elongation or shortening of the tension rod 7. At least three tension rods 7 are evenly arranged along the circumference of the shell cylinder 6 to increase the rigidity of the shell and prevent the asymmetric deformation of the shell cylinder 6.

[0025] Due to the material of the PTFE steel-lined tube sheet 4, it is not convenient to install the fixings, so an annular clamping block 3 is also provided between the PTFE steel-lined tube sheet 4 and the shell-side cylinder 6. The annular clamping block 3 and the flange 15 are connected by bolts to clamp the PTFE steel-lined tube sheet 4, limit the tube sheet, prevent the tube sheet from deforming and protruding, and cause the seal between the silicon carbide heat exchange tube 5 to fail, and ensure the connection and sealing performance. In order to further improve the connectivity, the shell-side cylinder 6, the annular clamping block 3 and the flange 15 are also connected by bolts.

[0026] Furthermore, the end of the silicon carbide heat exchange tube 5 is connected to the PTFE steel plate tube sheet 4 by a sealing element. Preferably, the sealing element 10 is a perfluoroether sealing ring 10.1 sleeved on the end of the silicon carbide heat exchange tube 4, which is tightened with a fastening screw 10.2 or bonded with an adhesive and then sintered.

[0027] The flexible expansion section 9 is pre-stretched during installation to compensate for the thermal expansion of the cylinder appropriately. The tension rod 7 should also be pre-stretched during installation so that it is not affected by the medium operating temperature during operation, thereby ensuring that the total length of the shell-side cylinder 6 remains unchanged, effectively reducing the thermal expansion difference between the shell-side cylinder 6 and the silicon carbide heat exchange tube 5. The silicon carbide heat exchange tube 5 only bears compressive stress, which can reduce the damage of the silicon carbide heat exchange tube 5, increase the sealing reliability of the tube sheet and the heat exchanger, reduce the maintenance frequency of the sealing components, extend the service life of the equipment, and achieve better long-term comprehensive economic benefits.

Claims

1. A silicon carbide heat exchanger for high temperature working conditions, comprising a shell-side cylinder and a plurality of silicon carbide heat exchange tubes located in the shell-side cylinder, wherein both ends of the silicon carbide heat exchange tubes are connected to the tube-side cylinder through a tetrafluoroethylene steel plate-lined tube sheet, characterized in that: The shell-side cylinder is provided with a flexible expansion section, and flanges are also installed at both ends of the shell-side cylinder. The flanges at both ends of the shell-side cylinder are connected via a tension rod. The tension rod includes an upper rod and a lower rod. The corresponding ends of the upper rod and the lower rod are threadedly connected via a loose nut.

2. The silicon carbide heat exchanger for high temperature conditions according to claim 1, characterized in that: The threads of the upper internal thread and the lower internal thread of the clamping nut are opposite.

3. The silicon carbide heat exchanger for high temperature working conditions according to claim 1 or 2, characterized in that: At least three tie rods are evenly arranged along the circumference of the shell side cylinder.

4. The silicon carbide heat exchanger for high temperature conditions according to claim 1, characterized in that: An annular clamping block is also provided between the PTFE steel plate lined tube sheet and the shell side cylinder, and the annular clamping block and the flange are connected by bolts to clamp the PTFE steel plate lined tube sheet.

5. The silicon carbide heat exchanger for high temperature working conditions according to claim 1 or 4, characterized in that: The shell side cylinder, the annular clamping block and the flange are also connected by bolts.

6. The silicon carbide heat exchanger for high temperature conditions according to claim 1, characterized in that: The end of the silicon carbide heat exchange tube is connected to the PTFE steel plate-lined tube sheet by a sealing element.

7. The silicon carbide heat exchanger for high temperature conditions according to claim 6, characterized in that: The sealing element is a perfluoroether sealing ring sleeved on the end of the silicon carbide heat exchange tube.

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