A low temperature gas-liquid distribution system

Abstract

The present invention discloses a low-temperature gas-liquid distribution system, which is arranged inside the head of a shell-and-tube liquid nitrogen heat exchanger. The low-temperature gas-liquid distribution system includes a liquid nitrogen inlet pipe and a distribution plate. The distribution plate includes a bottom plate and a cylindrical surrounding plate. The bottom plate is located below the liquid outlet end of the liquid nitrogen inlet pipe. A plurality of liquid distribution pipes arranged vertically are provided on the bottom plate. The upper end of each liquid distribution pipe is higher than the liquid outlet end of the liquid nitrogen inlet pipe and lower than the upper edge of the cylindrical surrounding plate. The lower end of each liquid distribution pipe penetrates through the bottom plate. A tube sheet of the shell-and-tube liquid nitrogen heat exchanger is located below the distribution plate. The liquid inlet ends of the heat exchange tubes connected to the tube sheet are all higher than the upper surface of the tube sheet, and the heat exchange tubes on the tube sheet and the liquid distribution tubes on the distribution plate are arranged in a staggered manner. The present invention realizes the distribution of N2 with gas-liquid two-phase mixing through two-stage overflow distribution, completely avoiding the rapid frost blockage and ice blockage caused by uneven liquid nitrogen distribution; and the second-stage overflow distribution is carried out without air flow disturbance, making the distribution more uniform.

Description

Technical Field

[0001] The invention relates to the technical field of liquid nitrogen heat exchange equipment, and in particular to a low-temperature gas-liquid distribution system. Background Art

[0002] During the production, storage and transportation of chemical, pharmaceutical and tank storage tanks, the emission of high-concentration VOCs process tail gas is inevitable due to the needs of the process. Before being discharged into the atmosphere, the process method of ultra-low temperature condensation of liquid nitrogen is often used to condense and precipitate the harmful components.

[0003] In the condensation purification process system, the condensation heat exchanger is the key equipment. The high-concentration VOCs process tail gas exchanges heat with low-temperature liquid nitrogen in the heat exchanger to achieve the purpose of low-temperature condensation purification. Normally, the temperature difference between the liquid nitrogen on the cold side and the medium on the hot side is as high as 150° or more. In this case, the harmful components on the hot side are very easy to frost and form blockage on the hot side surface of the heat exchanger. As a result, the heat exchanger cannot continue to operate for a long time. In this case, an important factor that aggravates the rapid blockage of the heat exchanger is that the uniformity of the distribution of liquid nitrogen in the heat exchanger tube has a decisive effect on the blockage time of the heat exchanger.

[0004] Normally, liquid nitrogen enters the heat exchanger from the top and is distributed in the pipe box of the heat exchanger. Before the liquid nitrogen enters the heat exchanger, the flow rate of the liquid nitrogen is generally adjusted by a control valve. There is a certain degree of throttling and pressure reduction in the liquid nitrogen at the regulating valve, which causes part of the liquid nitrogen to be vaporized. After a small mass proportion of the liquid nitrogen is vaporized, its volume is much larger than that of the unvaporized liquid nitrogen. After entering the liquid nitrogen heat exchanger, N 2 It exists in two phases: liquid and gas. 2 It is completely impossible to ensure that the gas enters the heat exchange tube evenly to exchange heat with the VOCs process exhaust gas.

[0005] A common practice is to Figure 1 As shown, a baffle 14 is set at the inlet when the two-phase mixed N 2 After entering, the liquid nitrogen N2 is intercepted by the baffle 14 and splashed back, then falls into the heat exchanger tube sheet 2, and flows into the heat exchange tube 9. The gaseous nitrogen enters the heat exchange tube in the form of gas.

[0006] It should be noted that: on the one hand, due to the existence of gas and liquid phases, full liquid distribution cannot be carried out. On the other hand, the reason is that the diameter of the liquid nitrogen heat exchanger tube is usually much larger than the actual need due to the requirements of the manufacturing process. Generally speaking, the minimum diameter of the heat exchange tube is φ8 and above. This size, while ensuring the heat exchange area, is much larger than the size required for liquid nitrogen distribution. Therefore, on the premise of satisfying the heat exchange area and heat exchange tube diameter of the heat exchanger, how to achieve uniform distribution of liquid nitrogen is a technical problem that needs to be solved urgently. Summary of the invention

[0007] The embodiment of the present invention provides a low-temperature gas-liquid distribution system for achieving pressure-loss-free distribution of liquid nitrogen and ensuring that the liquid nitrogen can evenly enter the heat exchange tube.

[0008] In order to achieve the above-mentioned invention object, the present invention provides a low-temperature gas-liquid distribution system, which is arranged in the head of a shell and tube liquid nitrogen heat exchanger, and the low-temperature gas-liquid distribution system includes a liquid nitrogen inlet pipe and a distribution plate. The liquid inlet end of the liquid nitrogen inlet pipe passes through the head and is located outside the head to connect the liquid nitrogen supply pipeline. The extension direction of the liquid nitrogen inlet pipe is the vertical direction, and the position of the liquid inlet end of the liquid nitrogen inlet pipe relative to its liquid outlet end is the top. The axis of the shell and tube liquid nitrogen heat exchanger extends in the vertical direction. The distribution plate includes a bottom plate arranged in the horizontal direction and a cylindrical enclosure formed by the edge of the bottom plate extending upward. The bottom plate is located at the lower part of the liquid outlet end of the liquid nitrogen inlet pipe. A plurality of liquid distributors arranged in the vertical direction are arranged on the bottom plate, and the upper end of each liquid distributor is higher than the liquid outlet end of the liquid nitrogen inlet pipe and lower than the upper edge of the cylindrical enclosure. The lower end of each liquid distributor passes through the bottom plate, and each liquid distributor is sealed and connected to the bottom plate.

[0009] The shell and tube liquid nitrogen heat exchanger generally includes a shell and a plurality of heat exchange tubes arranged in the shell. The shell includes a cylindrical shell and heads arranged at both ends of the cylindrical shell. Both ends of each heat exchange tube are connected to the tube sheet on the corresponding side. The two tube sheets are arranged on both sides of the shell and divide the internal space of the shell into three independent spaces.

[0010] A tube sheet of the shell and tube liquid nitrogen heat exchanger is located below the distribution plate. The liquid inlet ends of the heat exchange tubes connected to the tube sheet are higher than the upper surface of the tube sheet, and the heat exchange tubes on the tube sheet and the liquid distribution tubes on the distribution plate are staggered so that the liquid nitrogen falling from the liquid distribution tube cannot fall directly into the heat exchange tubes, but falls onto the upper surface of the tube sheet.

[0011] The present invention allows the gas-liquid two-phase N entering from the liquid nitrogen inlet pipe to 2 First enter the liquid separation plate, the gas phase and liquid phase are separated, and the gas phase N 2 The liquid phase N enters the heat exchange tube directly through the upper opening of the liquid separation plate and the air flow annular gap between the liquid separation plate and the head. 2It accumulates in the liquid separator. When the liquid nitrogen reaches the height of the separator, it begins to overflow through the separator by gravity and falls onto the tube sheet. 2 It cannot directly enter the heat exchange tube, and because the heat exchange tube is higher than the tube sheet by a certain height, the liquid N 2 Accumulate on the tube sheet; when the accumulation exceeds the liquid inlet end of the heat exchange tube, the liquid N 2 It also enters the heat exchange tube in the form of overflow to achieve overflow distribution again.

[0012] The liquid nitrogen inlet pipe is sealedly connected to the liquid nitrogen heat exchanger, for example, it can be welded, etc., which is not limited. The distribution plate is fixedly arranged in the shell and tube liquid nitrogen heat exchanger, and it can be fixedly connected to the shell and tube liquid nitrogen heat exchanger through a connector, or fixedly connected to the liquid nitrogen inlet pipe through a connector, or fixed in other ways, which is not limited.

[0013] The number of the dispensing tubes is designed according to needs. Preferably, the total flow area of ​​the dispensing tubes should not be less than the flow area of ​​the liquid nitrogen inlet tube.

[0014] Optionally, the height of the upper end of the liquid dispensing tube is 10 mm to 100 mm lower than the height of the upper edge of the cylindrical enclosure. Further preferably, the height of the upper end of the liquid dispensing tube is 20 to 50 mm lower than the height of the upper edge of the cylindrical enclosure.

[0015] Optionally, the height of the portion of the dispensing tube that exceeds the upper surface of the bottom plate is 30 mm to 100 mm. Further preferably, the height of the portion of the dispensing tube that exceeds the upper surface of the bottom plate is 40-60 mm.

[0016] Optionally, a baffle for splash prevention is provided at the end of the liquid nitrogen inlet pipe, and the area of ​​the baffle is generally 2-5 times the outer diameter of the liquid nitrogen inlet pipe, which can be adjusted according to the distance from the tube sheet. Optionally, the baffle is a flat plate; also optionally, the baffle is a downwardly concave arc plate or spherical plate, and preferably, the arc plate or spherical plate is provided with a leak hole, and the arc plate or spherical plate can store a certain amount of liquid inside while being able to seep liquid downward, so as to form a buffer effect on the liquid flowing out of the liquid nitrogen inlet pipe and enhance the splash prevention effect.

[0017] Optionally, the distance between the baffle and the bottom plate of the liquid separation plate is set to 10 to 50 mm.

[0018] Optionally, the height between the upper end of the heat exchange tube and the tube sheet is 5-20 mm.

[0019] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0020] The present invention adopts two overflow distribution to realize gas-liquid two-phase mixing N 2 The distribution is very uniform, completely avoiding the rapid frost and ice blockage caused by uneven liquid nitrogen distribution. The second overflow distribution is carried out without air flow disturbance, making the distribution more uniform.

[0021] During the entire distribution process, the pressure drop loss of conventional distributors can be effectively avoided, achieving pressure-loss-free distribution; at the same time, the diameter of the distributor tube is much larger than the aperture of the traditional pressure-reducing distributor, which can avoid blockage. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of an existing liquid nitrogen heat exchanger;

[0023] Figure 2 It is a structural schematic diagram of the present invention;

[0024] Figure 3 It is a schematic structural diagram of another embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The embodiment of the present invention provides a low temperature gas-liquid distribution system, such as Figure 2 , Figure 3 As shown, it is arranged in the head 3 of the shell and tube liquid nitrogen heat exchanger, and the low-temperature gas-liquid distribution system includes a liquid nitrogen inlet pipe 4 and a distribution plate 7. The liquid inlet end of the liquid nitrogen inlet pipe 4 passes through the head 3 and is located outside the head 3 to connect the liquid nitrogen supply pipeline. The extension direction of the liquid nitrogen inlet pipe 4 is the vertical direction, and the position of the liquid inlet end of the liquid nitrogen inlet pipe 4 relative to its liquid outlet end is the top. The axis of the shell and tube liquid nitrogen heat exchanger extends in the vertical direction. The distribution plate 7 includes a bottom plate arranged in the horizontal direction and a cylindrical enclosure formed by the edge of the bottom plate extending upward. The bottom plate is located at the lower part of the liquid outlet end of the liquid nitrogen inlet pipe 4. A plurality of liquid distributors 6 arranged in the vertical direction are arranged on the bottom plate. The upper end of each liquid distributor 6 is higher than the liquid outlet end of the liquid nitrogen inlet pipe 4 and lower than the upper edge of the cylindrical enclosure. The lower end of each liquid distributor 6 passes through the bottom plate, and each liquid distributor 6 is sealed and connected to the bottom plate.

[0027] The shell and tube liquid nitrogen heat exchanger generally includes a shell and a plurality of heat exchange tubes 8 arranged in the shell. The shell includes a cylindrical shell 1 and a head 3 arranged at both ends of the cylindrical shell 1. Both ends of each heat exchange tube 8 are connected to the tube sheet 2 on the corresponding side. The two tube sheets 2 are arranged on both sides of the shell and divide the internal space of the shell into three independent spaces.

[0028] A tube sheet 2 of the shell and tube liquid nitrogen heat exchanger is located below the distribution plate 7. The liquid inlet ends of the heat exchange tubes 8 connected to the tube sheet 2 are higher than the upper surface of the tube sheet 2, and the heat exchange tubes 8 on the tube sheet 2 and the liquid distributors 6 on the distribution plate 7 are staggered so that the liquid nitrogen falling from the liquid distributor 6 cannot fall directly into the heat exchange tubes 8, but falls onto the upper surface of the tube sheet 2.

[0029] The present invention makes the gas-liquid two-phase N entering from the liquid nitrogen inlet pipe 4 2 First enter the liquid separation plate, the gas phase and liquid phase are separated, and the gas phase N 2 The liquid phase N enters the heat exchange tube 8 directly through the upper opening of the liquid separation plate and the air flow annular gap 10 between the liquid separation plate and the head 3. 2 The liquid nitrogen accumulates in the liquid separator. When the liquid nitrogen reaches the height of the liquid separator 6, it begins to overflow through the liquid separator 6 by gravity and falls onto the tube sheet 2. Since the liquid separator 6 and the heat exchange tube 8 are arranged in a staggered manner, the falling liquid nitrogen 2 It cannot directly enter the heat exchange tube 8, and because the heat exchange tube 8 is higher than the tube sheet 2 by a certain height, the liquid N 2 Accumulate on the tube sheet 2; when the accumulation exceeds the liquid inlet end of the heat exchange tube 8, the liquid N 2 Then it also enters the heat exchange tube 8 in the form of overflow to achieve overflow distribution again.

[0030] The liquid nitrogen inlet pipe 4 is sealed and connected to the liquid nitrogen heat exchanger, for example, it can be welded, etc., which is not limited. The distribution plate 7 is fixedly arranged in the shell and tube liquid nitrogen heat exchanger, and it can be fixedly connected to the shell and tube liquid nitrogen heat exchanger through a connector, or fixedly connected to the liquid nitrogen inlet pipe 4 through a connector, or fixed in other ways, which is not limited.

[0031] The number of the liquid dispensing tubes 6 is designed according to needs. Preferably, the total flow area of ​​the liquid dispensing tubes 6 should not be less than the flow area of ​​the liquid nitrogen inlet tube 4 .

[0032] Optionally, the height of the upper end of the liquid dispensing tube 6 is 10 mm to 100 mm lower than the height of the upper edge of the cylindrical enclosure. Further preferably, the height of the upper end of the liquid dispensing tube 6 is 20 to 50 mm lower than the height of the upper edge of the cylindrical enclosure.

[0033] Optionally, the height of the portion of the liquid dispensing tube 6 that exceeds the upper surface of the bottom plate is 30 mm to 100 mm. Further preferably, the height of the portion of the liquid dispensing tube 6 that exceeds the upper surface of the bottom plate is 40-60 mm.

[0034] Optionally, the liquid outlet of the liquid nitrogen inlet pipe 4 is provided with a baffle 5 for splash prevention, and the area of ​​the baffle 5 is generally 2-5 times the outer diameter of the liquid nitrogen inlet pipe, and can be adjusted according to the distance from the tube sheet 2. The baffle can be fixedly connected to the liquid nitrogen inlet pipe 4 through a connecting rod, or fixedly connected to the distribution plate through a connecting piece, or fixedly connected to other components through a connecting piece, and there is no limitation on this, as long as it is fixedly placed below the liquid outlet of the liquid nitrogen inlet pipe 4. Optionally, as Figure 2 As shown, the baffle 5 is a flat plate; alternatively, Figure 3 As shown, the baffle plate 5 is a downwardly concave arc plate or spherical plate, and preferably, a water leakage hole is provided on the arc plate or spherical plate. While the arc plate or spherical plate can seep liquid downward, a certain amount of liquid can be stored inside, thereby forming a buffering effect on the liquid flowing out of the liquid nitrogen inlet pipe 4 and improving the splash-proof effect.

[0035] Optionally, the distance between the baffle 5 and the bottom plate of the liquid separation plate is set to 10-50 mm.

[0036] Optionally, the upper end of the heat exchange tube 8 is 5-20 mm away from the tube sheet 2.

[0037] It should be noted that the above embodiments illustrate the present invention rather than limit it, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets should not be constructed as a limitation to the claims. The words "comprise" or "include" do not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of a plurality of such elements. The use of the words first, second, and third, etc., does not indicate any order, and these words may be interpreted as names.

[0038] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0039] The present invention adopts two overflow distribution to realize gas-liquid two-phase mixing N 2 The distribution is very uniform, completely avoiding the rapid frost and ice blockage caused by uneven liquid nitrogen distribution. The second overflow distribution is carried out without air flow disturbance, making the distribution more uniform.

[0040] During the entire distribution process, the pressure drop loss of conventional distributors can be effectively avoided, achieving pressure-loss-free distribution; at the same time, the diameter of the distributor tube is much larger than the aperture of the traditional pressure-reducing distributor, which can avoid blockage.

[0041] All features disclosed in this specification, except mutually exclusive features, can be combined in any way.

[0042] Any feature disclosed in this specification (including any additional claims, abstract and drawings), unless otherwise stated, may be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0043] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A low temperature gas-liquid distribution system, characterized in that: It is arranged in the head of the shell and tube liquid nitrogen heat exchanger. The low-temperature gas-liquid distribution system includes a liquid nitrogen inlet pipe and a distribution plate. The liquid inlet end of the liquid nitrogen inlet pipe passes through the head and is located outside the head. The extension direction of the liquid nitrogen inlet pipe is the vertical direction, and the position of the liquid inlet end of the liquid nitrogen inlet pipe relative to its liquid outlet end is the top. The axis of the shell and tube liquid nitrogen heat exchanger extends in the vertical direction. The distribution plate includes a bottom plate arranged in the horizontal direction and a cylindrical enclosure formed by the edge of the bottom plate extending upward. The bottom plate is located at the lower part of the liquid outlet end of the liquid nitrogen inlet pipe. A plurality of liquid distributors arranged in the vertical direction are arranged on the bottom plate. The upper end of each liquid distributor is higher than the liquid outlet end of the liquid nitrogen inlet pipe and lower than the upper edge of the cylindrical enclosure. The lower end of each liquid distributor passes through the bottom plate, and each liquid distributor is sealed and connected to the bottom plate. A tube sheet of the shell and tube liquid nitrogen heat exchanger is located below the distribution plate, the liquid inlet ends of the heat exchange tubes connected to the tube sheet are higher than the upper surface of the tube sheet, and the heat exchange tubes on the tube sheet and the liquid distribution tubes on the distribution plate are staggered.

2. A cryogenic gas-liquid distribution system according to claim 1, characterized in that: The total flow area of ​​the dispensing pipes should not be less than the flow area of ​​the liquid nitrogen inlet pipe.

3. A cryogenic gas-liquid distribution system according to claim 1, characterized in that: The height of the upper end of the liquid dispensing pipe is 10 mm to 100 mm lower than the height of the upper edge of the cylindrical enclosure.

4. A cryogenic gas-liquid distribution system according to claim 1, characterized in that: The height of the portion of the dispensing tube that exceeds the upper surface of the bottom plate is 30 mm to 100 mm.

5. A cryogenic gas-liquid distribution system according to claim 1, characterized in that: The end of the liquid nitrogen inlet pipe is provided with a baffle for preventing splashing, and the area of ​​the baffle is 2-5 times the outer diameter of the liquid nitrogen inlet pipe.

6. A cryogenic gas-liquid distribution system according to claim 5, characterized in that: The baffle is a flat plate.

7. A cryogenic gas-liquid distribution system according to claim 5, characterized in that: The baffle is a downwardly concave arc plate or a spherical plate, and a water leakage hole is arranged on the arc plate or the spherical plate.

8. A cryogenic gas-liquid distribution system according to any one of claims 5 to 7, characterized in that: The distance between the baffle and the bottom plate of the liquid separation plate is set to 10~50mm.

9. A cryogenic gas-liquid distribution system according to claim 1, characterized in that: The height of the portion of the dispensing tube that exceeds the upper surface of the base plate is 40-60 mm.

10. A cryogenic gas-liquid distribution system according to claim 1, characterized in that: The height of the upper end of the liquid separation pipe is 20-50 mm lower than the height of the upper edge of the cylindrical enclosure, and the height of the upper end of the heat exchange tube from the tube sheet is 5-20 mm.

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