Cooling liquid nitrogen energy-saving device of rectifying tower

Abstract

The invention discloses a liquid nitrogen cold supply energy-saving device for krypton and xenon separation and purification. The liquid nitrogen cold supply energy-saving device comprises a liquid nitrogen supply unit, a low-temperature nitrogen supply unit, a first rectifying tower, a liquid nitrogen gasification tank, a low-temperature nitrogen buffer tank, a second rectifying tower and a tail gas emission unit. The liquid nitrogen supply unit supplies liquid nitrogen to the first rectifying tower and the liquid nitrogen gasification tank through two-way adjustment, low-temperature nitrogen generated by the first rectifying tower is divided and then partially enters the liquid nitrogen gasification tank to be adjusted, and gasified nitrogen is subjected to pressure stabilization through the low-temperature nitrogen buffer tank and then serves as an auxiliary cold source of the second rectifying tower. And gradient utilization of cooling capacity is realized through a multi-stage regulating valve. According to the device, low-temperature nitrogen discharged by the rectifying tower is subjected to secondary recycling innovatively, an auxiliary cold source system is constructed through the low-temperature nitrogen buffer tank, and liquid nitrogen consumption is effectively reduced; discharged low-temperature nitrogen is recycled, and loss of liquid nitrogen is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of air temperature gas separation equipment, and more specifically, to an energy-saving device for supplying cooling liquid nitrogen for a rectification column. Background Art

[0002] Liquid nitrogen is significantly different from gaseous nitrogen in physical form, such as an increase in density and a decrease in volume. Although liquid nitrogen retains all the chemical properties of nitrogen in the liquid state, its extremely low temperature and chemical inertness have wide applications in scientific research, medical treatment, and industrial use. Liquid nitrogen can separate and stratify gases with different boiling points in the rectification column through a cooling effect. In addition, the pressure inside the column can be reduced through a pressure reduction effect, making the bottom product easy to volatilize and separate, thereby improving the purity and yield of the product.

[0003] The liquid nitrogen supply for the rectification column is usually achieved through heat exchange in a condensing evaporator, and the low-temperature nitrogen gas after heat exchange is discharged to a safe location. In the krypton-xenon separation rectification process, according to the difference in the boiling point temperatures of krypton and xenon (the boiling point of krypton is -153.3°C and the boiling point of xenon is -107.1°C under normal pressure), generally two towers or even multiple towers are used for purification and separation. During continuous production, each rectification column requires continuous low-temperature cooling, which results in a relatively large loss of liquid nitrogen.

[0004] Therefore, providing an energy-saving device for supplying cooling liquid nitrogen for a krypton-xenon separation and purification rectification column is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0005] To solve the above technical problems, the present application provides an energy-saving device for supplying cooling liquid nitrogen for a rectification column, aiming to save production costs by supplying cooling from a previous rectification column to a subsequent rectification column in the krypton-xenon separation rectification process.

[0006] An energy-saving device for supplying cooling liquid nitrogen for a rectification column provided by the present application has the following specific technical solutions, including: a liquid nitrogen supply unit, a low-temperature nitrogen gas supply unit, a first rectification column, a liquid nitrogen vaporization tank, a low-temperature nitrogen gas buffer tank, a second rectification column, and a tail gas discharge unit; The liquid nitrogen supply unit is connected to the first rectification column through a first liquid nitrogen regulating valve for providing an initial cold source; The low-temperature nitrogen gas supply unit includes: a low-temperature nitrogen gas discharge pipeline connected to the first rectification column, and this pipeline is also connected to the liquid nitrogen vaporization tank through a first nitrogen regulating valve; The liquid nitrogen supply unit is also connected to the liquid nitrogen vaporization tank through a second liquid nitrogen regulating valve; The liquid nitrogen vaporization tank is connected to the low-temperature nitrogen gas buffer tank through a second nitrogen regulating valve; The low-temperature nitrogen buffer tank is connected to the second rectification column, and the low-temperature nitrogen discharged from the first rectification column is used as an auxiliary cold source for the second rectification column; The tail gas discharge unit is connected to the second rectification column through a third nitrogen regulating valve for discharging excess gas.

[0007] Preferably, a first temperature sensor is further provided in the first rectification column for the first liquid nitrogen regulating valve and the first nitrogen regulating valve to adjust the temperature of the first rectification column.

[0008] Preferably, a first pressure sensor is further provided in the first rectification column for the first liquid nitrogen regulating valve and the first nitrogen regulating valve to adjust the pressure of the first rectification column.

[0009] Preferably, a second temperature sensor is further provided in the liquid nitrogen vaporization tank for the second liquid nitrogen regulating valve, the first nitrogen regulating valve, and the second nitrogen regulating valve to adjust the temperature of the liquid nitrogen vaporization tank.

[0010] Preferably, a second pressure sensor is further provided in the liquid nitrogen vaporization tank for the second liquid nitrogen regulating valve, the first nitrogen regulating valve, and the second nitrogen regulating valve to adjust the pressure of the liquid nitrogen vaporization tank.

[0011] Preferably, a third temperature sensor is further provided in the low-temperature nitrogen buffer tank for the second nitrogen regulating valve to adjust the temperature of the low-temperature nitrogen buffer tank.

[0012] Preferably, a third pressure sensor is further provided in the low-temperature nitrogen buffer tank for the second nitrogen regulating valve to adjust the pressure of the low-temperature nitrogen buffer tank.

[0013] Preferably, a fourth temperature sensor is further provided in the second rectification column for the third nitrogen regulating valve to adjust the temperature of the low-temperature nitrogen buffer tank.

[0014] Preferably, a fourth pressure sensor is further provided in the second rectification column for the third nitrogen regulating valve to adjust the pressure of the low-temperature nitrogen buffer tank.

[0015] Preferably, the low-temperature nitrogen discharge pipeline further includes a fourth nitrogen regulating valve for accelerating the vaporization of liquid nitrogen and improving the cooling efficiency during the pre-cooling stage of the first rectification column.

[0016] The cold nitrogen liquid energy-saving device for the rectification column provided by the present invention realizes multiple goals of reducing energy consumption, improving efficiency and optimizing costs through the recycling and reuse of cold sources. In practical applications, combined with the cascade cooling requirements in the krypton-xenon separation and purification rectification column process, the best benefits are achieved. It has a positive effect on carbon emission reduction and sustainable development in the industrial field. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a schematic diagram of the connection relationship of the cold nitrogen liquid energy-saving device for the rectification column.

[0019] Reference Signs Cold nitrogen liquid energy-saving device for the rectification column: 1. Liquid nitrogen supply unit; 2. Low-temperature nitrogen supply unit; 3. First rectification column; 4. Liquid nitrogen vaporization tank; 5. Low-temperature nitrogen buffer tank; 6. Second rectification column; 7. Tail gas emission unit; 8. First liquid nitrogen regulating valve; 9. First nitrogen regulating valve; 10. Second liquid nitrogen regulating valve; 11. Second nitrogen regulating valve; 12. Third nitrogen regulating valve; 13. First temperature sensor; 14. First pressure sensor; 15. Second temperature sensor; 16. Second pressure sensor; 17. Third temperature sensor; 18. Third pressure sensor; 19. Fourth temperature sensor; 20. Fourth pressure sensor; 21. Fourth nitrogen regulating valve. Detailed Embodiments

[0020] In order to enable those skilled in the art to better understand the technical solutions in the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0021] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly disposed on the other element; when an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0022] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0023] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, the meaning of "a plurality" and "several" is two or more, unless otherwise specifically defined.

[0024] It should be noted that the structures, proportions, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in the art to understand and read, and are not used to limit the implementation conditions of the present application. Therefore, they do not have a technical essence. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present application can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present application.

[0025] The specific embodiments of the present invention are written in a progressive manner.

[0026] As Figure 1 shown, in this embodiment, the cooling liquid nitrogen energy-saving device of the rectification column includes: a liquid nitrogen supply unit 1, a low-temperature nitrogen supply unit 2, a first rectification column 3, a liquid nitrogen vaporization tank 4, a low-temperature nitrogen buffer tank 5, a second rectification column 6, and a tail gas emission unit 7; The liquid nitrogen supply unit 1 is connected to the first rectification column 3 through a first liquid nitrogen regulating valve 8 and is used to provide an initial cold source to the first rectification column 3 for separating and purifying liquid nitrogen. In this embodiment, the first rectification column 3 is specifically a krypton-xenon separation column, and the second rectification column 6 is specifically a xenon purification column. While the liquid nitrogen flows into the first rectification column 3 for precooling, the tower temperature drops accordingly, and it enters the low-temperature separation and purification working state; After stabilizing the cooling working condition of the first rectification column 3, the low-temperature nitrogen discharged is used as a cold source or an auxiliary cold source again through the low-temperature nitrogen supply unit 2 for the second rectification column 6, i.e., the xenon purification column. The low-temperature nitrogen supply unit 2 includes: a low-temperature nitrogen discharge pipeline connected to the first rectification column 3, and this pipeline is also connected to the liquid nitrogen vaporization tank 4 through a first nitrogen regulating valve 9; The liquid nitrogen supply unit 1 is also connected to the liquid nitrogen vaporization tank 4 through a second liquid nitrogen regulating valve 10. When the low-temperature nitrogen gas provided by the first rectification tower 3 is insufficient, the liquid nitrogen supply unit 1 is directly used to supplement the liquid nitrogen vaporization tank 4. The liquid nitrogen vaporization tank 4 is connected to the low-temperature nitrogen buffer tank 5 through a second nitrogen regulating valve 11 to further adjust the process parameters of the low-temperature nitrogen gas. The low-temperature nitrogen buffer tank 5 is connected to the second rectification tower 6. By using the low-temperature nitrogen gas discharged from the first rectification tower 3 as the auxiliary cold source of the second rectification tower 6, the design of the low-temperature nitrogen buffer tank 5 ensures the process conditions of a stable cold source during the switching between the low-temperature nitrogen gas discharged from the first rectification tower 3 and the use of liquid nitrogen in the liquid nitrogen vaporization tank 4 to supplement the low-temperature nitrogen gas. The tail gas discharge unit 7 is connected to the second rectification tower 6 through a third nitrogen regulating valve 12 for discharging excess nitrogen gas.

[0027] Preferably, in order to better monitor the working state in the first rectification tower 3, in this embodiment, a first temperature sensor 13 is further provided in the first rectification tower 3 for the first liquid nitrogen regulating valve 8 and the first nitrogen regulating valve 9 to adjust the temperature of the first rectification tower 3. When the first rectification tower 3 starts the process production, first open the first liquid nitrogen regulating valve 8 of the liquid nitrogen supply unit 1 to supply liquid nitrogen cooling to the first rectification tower 3, and at the same time open the first nitrogen regulating valve 9 to provide low-temperature nitrogen gas to the liquid nitrogen vaporization tank 4.

[0028] Furthermore, in order to further monitor the working state in the first rectification tower 3, in this embodiment, a first pressure sensor 14 is further provided in the first rectification tower 3 for the first liquid nitrogen regulating valve 8 and the first nitrogen regulating valve 9 to adjust the pressure of the first rectification tower 3. According to the set value of the first pressure sensor 14, the first liquid nitrogen regulating valve 8 and the first nitrogen regulating valve 9 are put into use for discharge adjustment to synchronously stabilize the process conditions of the first rectification tower 3.

[0029] Preferably, in order to better monitor the working state inside the liquid nitrogen vaporization tank 4, in this embodiment, a second temperature sensor is further provided inside the liquid nitrogen vaporization tank 4 for the second liquid nitrogen regulating valve 10, the first nitrogen regulating valve 9, and the second nitrogen regulating valve 11 to adjust the temperature of the liquid nitrogen vaporization tank 4. Since this energy-saving device has a liquid nitrogen-assisted cooling design, during the early stage of cooling supply by the second rectification tower 6 and when the cooling capacity is insufficient during the rectification process, liquid nitrogen will be fed into the liquid nitrogen vaporization tank 4 for auxiliary cooling. The liquid nitrogen vaporization tank 4 is automatically fed according to the set value of the second temperature sensor. When the temperature detected by the second temperature sensor is lower than the set value, the second liquid nitrogen regulating valve 10 will be used for adjustment to perform liquid nitrogen-assisted cooling, and supply the cold source to the second rectification tower 6 simultaneously with the low-temperature nitrogen discharged from the first rectification tower 3.

[0030] Further, in order to further monitor the working state inside the liquid nitrogen vaporization tank 4, in this embodiment, a second pressure sensor 15 and a second temperature sensor 16 are further provided inside the liquid nitrogen vaporization tank 4 for the second liquid nitrogen regulating valve 10, the first nitrogen regulating valve 9, and the second nitrogen regulating valve 11 to adjust the pressure of the liquid nitrogen vaporization tank 4 to ensure stable adjustment of the pressure of the low-temperature nitrogen supplement under the switching of the cold source in the liquid nitrogen-assisted cooling design.

[0031] Preferably, in order to better monitor the working state inside the low-temperature nitrogen buffer tank 5, in this embodiment, a third temperature sensor 17 is further provided inside the low-temperature nitrogen buffer tank 5 for the second nitrogen regulating valve 11 to adjust the temperature of the low-temperature nitrogen buffer tank 5. In the solution of this application, the design of the low-temperature nitrogen buffer tank 5 is to provide stable and process-required low-temperature nitrogen for the second rectification tank. By detecting the temperature inside the low-temperature nitrogen buffer tank 5, the nitrogen temperature can be better detected and feedback-regulated.

[0032] Further, in order to further monitor the working state inside the low-temperature nitrogen buffer tank 5, in this embodiment, a third pressure sensor 18 is further provided inside the low-temperature nitrogen buffer tank 5 for the second nitrogen regulating valve 11 to adjust the pressure of the low-temperature nitrogen buffer tank 5. The design of the low-temperature nitrogen buffer tank 5 is to provide stable and process-required low-temperature nitrogen for the second rectification tank. By detecting the pressure inside the low-temperature nitrogen buffer tank 5, the nitrogen pressure can be better detected and feedback-regulated, especially to maintain the pressure stability under the switching of the cold source in the liquid nitrogen-assisted cooling design.

[0033] Preferably, in order to better monitor the working state in the second rectification column 6, in this embodiment, a fourth temperature sensor 19 is further provided in the second rectification column 6 for the third nitrogen gas regulating valve 12 to adjust the temperature of the low-temperature nitrogen buffer tank 5, so as to better purify xenon in the low-temperature nitrogen to meet the process temperature requirements for xenon purification.

[0034] Furthermore, in order to further monitor the working state in the second rectification column 6, in this embodiment, a fourth pressure sensor 20 is further provided in the second rectification column 6 for the third nitrogen gas regulating valve 12 to adjust the pressure of the low-temperature nitrogen buffer tank 5. When the pressure in the second rectification column 6 is higher than the set value, the opening of the third nitrogen gas regulating valve 12 is adjusted to be set to the tail gas discharge unit 7, so as to better purify xenon in the low-temperature nitrogen to meet the process pressure requirements for xenon purification.

[0035] Preferably, in the initial cooling stage of the first rectification column 3, in order to accelerate the cooling of the first rectification column 3, in this embodiment, the low-temperature nitrogen discharge pipeline further includes a fourth nitrogen gas regulating valve 21. The fourth nitrogen gas regulating valve 21 can be opened in the initial stage of cooling the tower to accelerate the flow rate of the low-temperature nitrogen gas after the liquid nitrogen is vaporized, and can quickly achieve the cooling effect for accelerating the vaporization of the liquid nitrogen in the pre-cooling stage of the first rectification column 3 and improving the cooling efficiency.

[0036] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A liquid nitrogen energy-saving device for cooling a distillation tower, characterized in that: include: Liquid nitrogen supply unit, cryogenic nitrogen supply unit, first distillation tower, liquid nitrogen vaporization tank, cryogenic nitrogen buffer tank, second distillation tower, tail gas discharge unit; The liquid nitrogen supply unit is connected to the first distillation tower through a first liquid nitrogen regulating valve to provide an initial cold source; The cryogenic nitrogen supply unit comprises: a cryogenic nitrogen discharge pipeline connected to the first distillation tower, the pipeline also being connected to the liquid nitrogen gasification tank via a first nitrogen regulating valve; The liquid nitrogen supply unit is also connected to the liquid nitrogen gasification tank by a second liquid nitrogen regulating valve; The liquid nitrogen gasification tank is connected to the low-temperature nitrogen buffer tank through a second nitrogen regulating valve; The low-temperature nitrogen buffer tank is connected to the second distillation tower, and the low-temperature nitrogen discharged from the first distillation tower is used as an auxiliary cold source for the second distillation tower; The tail gas discharge unit is connected to the second distillation tower through a third nitrogen regulating valve for discharging excess gas.

2. The cooling liquid nitrogen energy-saving device for a distillation tower according to claim 1, characterized in that: A first temperature sensor is further provided in the first distillation tower, so that the first liquid nitrogen regulating valve and the first nitrogen regulating valve can regulate the temperature of the first distillation tower.

3. The cooling liquid nitrogen energy-saving device for a distillation tower according to claim 2, characterized in that: A first pressure sensor is further provided in the first distillation tower, so that the first liquid nitrogen regulating valve and the first nitrogen regulating valve can regulate the pressure of the first distillation tower.

4. The cooling liquid nitrogen energy-saving device for a distillation tower according to claim 1, characterized in that: A second temperature sensor is also provided in the liquid nitrogen gasification tank, so as to enable the second liquid nitrogen regulating valve, the first nitrogen regulating valve and the second nitrogen regulating valve to regulate the temperature of the liquid nitrogen gasification tank.

5. The cooling liquid nitrogen energy-saving device for a distillation tower according to claim 4, characterized in that: A second pressure sensor is also provided in the liquid nitrogen gasification tank to enable the second liquid nitrogen regulating valve, the first nitrogen regulating valve and the second nitrogen regulating valve to regulate the pressure of the liquid nitrogen gasification tank.

6. The cooling liquid nitrogen energy-saving device for a distillation tower according to claim 1, characterized in that: A third temperature sensor is also provided in the cryogenic nitrogen buffer tank, so that the second nitrogen regulating valve can regulate the temperature of the cryogenic nitrogen buffer tank.

7. The cooling liquid nitrogen energy-saving device for a distillation tower according to claim 6, characterized in that: A third pressure sensor is also provided in the cryogenic nitrogen buffer tank, so that the second nitrogen regulating valve can regulate the pressure of the cryogenic nitrogen buffer tank.

8. The cooling liquid nitrogen energy-saving device for a distillation tower according to claim 1, characterized in that: A fourth temperature sensor is also provided in the second distillation tower so that the third nitrogen regulating valve can regulate the temperature of the low-temperature nitrogen buffer tank.

9. The cooling liquid nitrogen energy-saving device for a distillation tower according to claim 8, characterized in that: A fourth pressure sensor is also provided in the second distillation tower for the third nitrogen regulating valve to regulate the pressure of the low-temperature nitrogen buffer tank.

10. The cooling liquid nitrogen energy-saving device for a distillation tower according to any one of claims 1 to 9, characterized in that: The low-temperature nitrogen discharge pipeline also includes a fourth nitrogen regulating valve, which is used to accelerate the gasification of liquid nitrogen in the precooling stage of the first distillation tower to improve the cooling efficiency.

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