A falling film reboiler provided with a circumferential slotted overflow film distributor

Abstract

The application provides a falling film reboiler with a circumferential slotted overflow film distributor, the film distributor is connected with a part of a protruding tube sheet of heat exchange tubes and is aligned with the heat exchange tube mouth through spot welding connection, the film distributor is divided into two parts, the lower 1 / 3 part is a liquid storage space, the remaining upper part is a spiral slotted part, the spiral angle is 360° and is respectively formed by a plurality of notches. In the reboiler operation, when the material is accumulated on the tube sheet until overflowing the notch, the material is simultaneously overflowed into the inner wall of the film distributor along the axial direction and the circumferential direction from the notch, so that complete and uniform liquid films are formed on the inner wall of the heat exchange tubes, and because the high viscosity fluid has high viscosity, it can be considered as laminar flow, so the superposition between the liquid films does not affect the completeness of the liquid films. The novel film distributor has the advantages of excellent film distribution effect, easy installation, wide applicable viscosity range and the like.

Description

Technical Field

[0001] This application relates to the field of high-efficiency heat exchanger technology, and in particular to a falling film reboiler equipped with a circumferentially slotted overflow film distributor. Background Technology

[0002] Compared with ordinary evaporators, vertical tube falling film evaporators have advantages such as a large concentration ratio, wide viscosity range, low pressure drop, good heat transfer effect, and large throughput. They are suitable for processing heat-sensitive materials and can be used in multi-effect evaporation systems. Therefore, they are widely used in industries such as chemical, light industry, food, pharmaceutical, metallurgy, and seawater desalination.

[0003] The rationality of the liquid distribution device and the uniformity of the liquid film distribution on the corresponding inner wall surface directly affect the heat transfer efficiency and operational stability of the falling film evaporator. Uneven liquid film distribution directly leads to a phenomenon—local drying. A liquid film with a certain radial thickness, initially uniformly distributed circumferentially and falling along the heat exchange tube wall, becomes unstable once laminar flow transitions to turbulent flow. The resulting wavy flow at the gas-liquid interface causes localized drying at the troughs, leading to axial film breakage and the formation of stream-like liquid films. This deteriorates heat transfer and can even burn out the tubes. Furthermore, under current technology, film distributors suitable for high-viscosity materials (>1000cp) face limitations, significantly restricting the applicability and application scenarios of falling film reboilers.

[0004] To prevent "localized drying" and improve the application viscosity range of falling film reboilers, a reasonable liquid distribution device is designed in the falling film evaporator. A distribution device that can evenly distribute the liquid along the periphery of the downcomer is developed, and the applicable viscosity range is expanded to within 15000cp, which will greatly expand the application scenarios of falling film reboilers. Summary of the Invention

[0005] This application provides a falling film reboiler with a circumferentially slotted overflow film distributor, which can be used to solve the technical problem that falling film evaporators are easily burned dry.

[0006] This application provides a falling film reboiler equipped with a circumferentially slotted overflow film distributor, the falling film reboiler comprising:

[0007] Multiple film distributors are installed on the upper end of the tube sheet, and heat exchange tubes are installed at the lower end of the tube sheet at positions corresponding to the film distributors.

[0008] The film distributor is a cylinder with a radial dimension consistent with that of the heat exchange tube. The film distributor has multiple channels. The slots are distributed along both the axial and circumferential directions of the film distributor. The unslotted part of the film distributor is connected to the heat exchange tube by welding points.

[0009] Furthermore, the cross-section of the channel is fan-shaped.

[0010] Furthermore, the number of channels ranges from 2 to 5, and the channels are evenly distributed.

[0011] Furthermore, the number of channels is four.

[0012] Furthermore, the channel has circumferential spiral grooves distributed along the axial direction, with a spiral angle of 360°.

[0013] Furthermore, the central angle range corresponding to the sector shape of the channel cross-section is 10-16°.

[0014] Furthermore, the radii of the inner and outer arcs of the sector-shaped cross-section of the channel correspond to the inner and outer diameters of the cylindrical film distributor, respectively. The radial dimensions of the cylindrical film distributor are consistent with those of the heat exchange tube, allowing the film distributor to be aligned with the heat exchange tube and tightly connected by spot welding.

[0015] Furthermore, the axial length of the channel accounts for 2 / 3 of the total length of the cylindrical film applicator.

[0016] Furthermore, the surface of the channel is smoothed.

[0017] The liquid material accumulates on the tube sheet until it overflows the bottom slot and flows into the heat exchange tubes. As the liquid accumulation height increases, the liquid will continue to flow into the heat exchange tubes, and the liquid film will be evenly distributed along the circumference when viewed from above.

[0018] The channel has a fan-shaped cross-section, allowing the liquid to flow from the edge of the cylinder into the film distributor.

[0019] The central angle of the channel sector is related to the number of slots and the physical properties of the liquid.

[0020] The axially grooved overflow membrane distributor of this invention is a liquid membrane distribution device that features uniform membrane distribution, simple structure, is not prone to clogging, is applicable to a wide range of material viscosities, and is easy to arrange. It enables the liquid to form a stable laminar flow with uniform thickness in the circumferential direction along the heat exchange tube. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the installation of the circumferentially slotted overflow membrane device and heat exchange tube along the axial direction of this utility model.

[0022] Figure 2 This is a top view schematic diagram of the circumferentially slotted overflow membrane distribution device along the axial direction of this utility model.

[0023] Figure 3 This is a side view of the circumferentially slotted overflow membrane device of this utility model along the axial direction.

[0024] In the diagram: 1-channel, 2-weld point, 3-heat exchange tube, 4-tube sheet, 5-film distributor. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0026] The embodiments of this application will now be described in conjunction with the accompanying drawings.

[0027] like Figure 1 As shown, an axially slotted overflow membrane distributor is provided. The membrane distributor is spot-welded to the upper part of the heat exchange tube protruding from the tube sheet. The heat exchanger is a cylinder with the same radial dimension as the heat exchange tube. The lower part connected to the heat exchange tube is not slotted.

[0028] The processing method involves simultaneously opening several 360° spiral grooves along the axial and circumferential directions on the wall thickness of the cylinder. In a preferred embodiment, four grooves are selected, and the axial depth is processed from the top of the film applicator downwards to a depth of 2 / 3, 40 mm. The initial cross-sectional shape of the groove is a fan shape with a central angle of 12°. After the groove is processed, the surface of the groove must be polished to ensure the smoothness of the channel.

[0029] During installation, ensure the film distributor is perfectly aligned with the heat exchange tubes and connect via spot welding. Experiments and usage tests demonstrate that this novel structure is simple, provides excellent film distribution, and is suitable for low-viscosity silicone oil with a viscosity of 15000 cp. This novel structure is not only suitable for conventional low-viscosity materials (less than 1000 cp) but also for high-viscosity Newtonian fluids (less than 100000 cp). Under the Newtonian definition, higher viscosity results in lower turbulent kinetic energy, rendering film distributors that rely on inertial forces for uniform liquid distribution ineffective. During reboiler operation, as material accumulates on the tube sheet until it overflows the notch, it simultaneously spills into the inner wall of the film distributor axially and circumferentially from the slot, forming a complete and uniform liquid film on the inner wall of the heat exchange tubes. Because high-viscosity fluids are almost laminar, the superposition of liquid films does not affect their integrity. This modified film distributor offers advantages such as excellent film distribution, ease of installation, and a wide applicable viscosity range.

[0030] The embodiments described above do not constitute a limitation on the scope of protection of this application.

Claims

1. A falling film reboiler equipped with a circumferentially slotted overflow film distributor, characterized in that, The falling film reboiler includes: Multiple upper membrane distributors (5) are installed on the tube sheet (4), and heat exchange tubes (3) are installed at the lower end of the tube sheet (4) at positions corresponding to the membrane distributors (5). The membrane distributor (5) is a cylinder with radial dimensions consistent with those of the heat exchange tube (3). The membrane distributor (5) is provided with multiple channels (1). The slots of the channels (1) are distributed along both the axial and circumferential directions of the membrane distributor (5). The unslotted part of the membrane distributor (5) is connected to the heat exchange tube (3) by welding points (2).

2. The falling film reboiler according to claim 1, characterized in that, The channel (1) has a fan-shaped cross-section.

3. The falling film reboiler according to claim 1, characterized in that, The number of channels (1) ranges from 2 to 5, and the channels (1) are evenly distributed.

4. The falling film reboiler according to claim 3, characterized in that, The number of channels (1) is 4.

5. The falling film reboiler according to claim 1 or 3, characterized in that, The channel (1) is a circumferential spiral groove distributed along the axial direction, with a spiral angle of 360°.

6. The falling film reboiler according to claim 2, characterized in that, The central angle range corresponding to the sector shape of the cross section of the channel (1) is 10-16°.

7. The falling film reboiler according to claim 6, characterized in that, The radii of the inner and outer arcs of the fan-shaped cross-section of the channel (1) correspond to the inner and outer diameters of the cylindrical film applicator, respectively.

8. The falling film reboiler according to claim 1 or 4, characterized in that, The axial length of the channel (1) accounts for 2 / 3 of the total length of the cylindrical film applicator.

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