Nitrogen cycle refrigeration system for cryogenic separation plant

Abstract

The utility model belongs to refrigeration technical field, specifically disclose a kind of nitrogen circulation refrigeration system for cryogenic separation device, including fractionating column, nitrogen compressor, plate heat exchanger and intake pipe;Raw gas is connected to fractionating column by intake pipe after passing plate heat exchanger, can carry out preliminary cooling to raw gas;The inside top of fractionating column is equipped with tubular heat exchanger, and the top of fractionating column is connected with first gas outlet pipe, and first gas outlet pipe is connected with second gas outlet pipe after passing plate heat exchanger, reheats and exports process gas;Tubular heat exchanger is connected by first pipeline and is connected to nitrogen compressor again by the internal pipeline of plate heat exchanger, and after passing nitrogen compressor, the high-pressure normal-temperature nitrogen gas generated by it is connected back to plate heat exchanger by third pipeline, and after preliminary cooling by plate heat exchanger, it is connected back to tubular heat exchanger by fourth pipeline to provide cold quantity, can realize the rapid cooling of fractionating column overhead, shorten driving cycle.

Description

Technical Field

[0001] This utility model belongs to the field of refrigeration technology, specifically relating to a nitrogen cycle refrigeration system for cryogenic separation devices. Background Technology

[0002] The basic principle of cryogenic separation is the Joule-Thomson throttling cooling effect. Gas at a certain pressure can be reduced in temperature and throttled to produce a lower temperature. After the gas is cooled and liquefied, the gas is separated by distillation based on the difference in boiling points of different gases. Among these methods, gas throttling and adiabatic expansion of the gas by doing external work are the main methods used in cryogenic industry.

[0003] As a key component, the nitrogen cycle refrigeration system needs to maintain a low-temperature environment through efficient heat exchange and cold energy circulation to meet the requirements of cryogenic separation processes. However, existing traditional nitrogen cycle refrigeration systems suffer from uneven cold energy distribution and slow cooling rates. Specifically, insufficient synergy between plate and tubular heat exchangers makes it difficult to maintain the low-temperature environment at the top of the fractionation column. At the same time, the high compressor discharge temperature affects equipment lifespan, and poor pressure control stability further limits the efficiency of cold energy recovery. Utility Model Content

[0004] To address the problems of low cold energy recovery efficiency and long cooling cycles caused by unstable pressure control in existing technologies, a nitrogen cycle refrigeration system for cryogenic separation devices is proposed. This invention provides the following technical solution: A nitrogen cycle refrigeration system for a cryogenic separation device includes a fractionation tower, a nitrogen compressor, a plate heat exchanger, and an inlet pipe. The feed gas passes through the plate heat exchanger and is connected to the fractionation tower via the inlet pipe. A tubular heat exchanger is installed on the inner top of the fractionation tower, and a first outlet pipe is connected to the top of the fractionation tower. The first outlet pipe passes through the plate heat exchanger and is connected to a second outlet pipe. The tubular heat exchanger is connected via a first pipe and, after passing through the internal piping of the plate heat exchanger, is connected to the nitrogen compressor via a second pipe. After passing through the nitrogen compressor, it is connected back to the plate heat exchanger via a third pipe, and then, after passing through the plate heat exchanger, it is connected back to the tubular heat exchanger via a fourth pipe.

[0005] Preferably, the nitrogen compressor is a four-stage compressor.

[0006] Preferably, a first throttle valve is installed on the fourth pipe.

[0007] Preferably, a fifth pipe is connected to the fourth pipe, and the fifth pipe is connected in parallel with the first pipe.

[0008] Preferably, a second throttle valve is installed on the fifth pipe.

[0009] Preferably, the tubular heat exchanger is connected via a sixth pipe to a liquid nitrogen storage tank for injecting liquid nitrogen into the tubular heat exchanger for auxiliary cooling.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. By constructing a complementary heat exchange network using plate heat exchangers and tubular heat exchangers, heat exchange efficiency is improved, the ability to maintain a low-temperature environment is enhanced, and the top of the distillation column is ensured to quickly reach the required low-temperature conditions, providing a stable supply of cooling capacity for cryogenic separation processes. 2. The fourth and fifth pipes are connected in parallel to form a two-stage pressure regulating system with the first and second throttle valves, which optimizes the distribution of cooling capacity, improves the stability of pressure control and cooling efficiency, and enhances the dynamic adjustment capability of the system. 3. The tubular heat exchanger is connected to the liquid nitrogen storage tank through the sixth pipe, and liquid nitrogen is injected from the bottom to assist in cooling, which directly accelerates the condensation process, significantly shortens the start-up cycle of the cryogenic separation unit, and improves the process start-up efficiency. Attached Figure Description

[0011] Figure 1 This is a structural schematic diagram of a specific embodiment of the present invention.

[0012] In the attached diagram, 1 is a distillation tower; 2 is a tubular heat exchanger; 3 is a plate heat exchanger; 4 is a nitrogen compressor; 5 is a liquid nitrogen storage tank; 6 is an inlet pipe; 7 is a first outlet pipe; 8 is a second outlet pipe; 9 is a first throttle valve; 10 is a second throttle valve; 11 is a first pipeline; 12 is a second pipeline; 13 is a third pipeline; 14 is a fourth pipeline; 15 is a fifth pipeline; and 16 is a sixth pipeline. Detailed Implementation

[0013] To enable those skilled in the art to better understand the technical solution of this utility model, the technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as "up", "down", "left", and "right", are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for illustration and not for limiting the creation of this utility model.

[0014] like Figure 1As shown, a nitrogen cycle refrigeration system for a cryogenic separation unit includes a fractionating tower 1, a nitrogen compressor 4, a plate heat exchanger 3, and an inlet pipe 6. The feed gas passes through the plate heat exchanger 3 and is connected to the fractionating tower 1 via the inlet pipe 6 for preliminary cooling. The cooled feed gas then undergoes fractionation within the fractionating tower 1. A tubular heat exchanger 2 is installed at the top inner side of the fractionating tower 1. A first outlet pipe 7 is connected to the top of the fractionating tower 1. The first outlet pipe 7 passes through the plate heat exchanger 3 and is then connected to a second outlet pipe 8 for reheating and output of the process gas. The tubular heat exchanger 2 connects to the first... Pipe 11 connects to and passes through the internal piping of plate heat exchanger 3, and then connects to nitrogen compressor 4 through second pipe 12, providing reheated room temperature nitrogen to nitrogen compressor 4. After passing through nitrogen compressor 4, the high-pressure room temperature nitrogen generated therefrom is connected back to plate heat exchanger 3 through third pipe 13. After preliminary cooling by plate heat exchanger 3, it is connected back to tubular heat exchanger 2 through fourth pipe 14 to provide cooling capacity. Plate heat exchanger 3 and tubular heat exchanger 2 form a complementary heat exchange network, which enhances the ability to maintain a low temperature environment and enables rapid cooling of the top of distillation column 1, shortening the start-up cycle.

[0015] Furthermore, the nitrogen compressor adopts a four-stage compressor, which has high compression efficiency, energy saving and low cost.

[0016] Furthermore, a first throttle valve 9 is installed on the fourth pipe 14, which can throttle and cool the pipe.

[0017] Furthermore, a fifth pipe 15 is connected to the fourth pipe 14. The fifth pipe 15 is connected in parallel with the first pipe 11 and can circulate and cool the nitrogen from the nitrogen compressor 4. This generates a partial loop of plate heat exchanger 3 – fourth pipe 14 – fifth pipe 15 – plate heat exchanger 3 – fourth pipe 14 – fifth pipe 15. The third pipe 13 serves as the input to this partial loop, and the rear part of the fifth pipe 15 of the fourth pipe 14 forms the output of this partial loop, which can improve the cooling efficiency.

[0018] Furthermore, a second throttle valve 10 is installed on the fifth pipe 15 to further throttle and cool it.

[0019] Furthermore, the tubular heat exchanger 2 is connected to a liquid nitrogen storage tank 5 via a sixth pipe 16, which injects liquid nitrogen into the tubular heat exchanger 2 from the bottom for auxiliary cooling, thereby improving cooling efficiency and further shortening the start-up cycle.

[0020] Among them, the first pipe 11, the second pipe 12, the third pipe 13, the fourth pipe 14, the fifth pipe 15 and the sixth pipe 16 can all be formed by connecting two or more pipes, and are not limited to a single pipe.

[0021] Working principle: Part of the high-pressure, ambient-temperature nitrogen from nitrogen compressor 4 is first pre-cooled by plate heat exchanger 3 and throttled by first throttle valve 9 before entering the tubular condenser at the top of fractionation tower 1 to provide cooling. Another part is circulated and cooled between plate heat exchanger 3, fourth pipe 14, and fifth pipe 15. The remaining liquid nitrogen is throttled and returned to plate heat exchanger 3 through first pipe 11 to provide cooling. After fractionation in the tubular condenser, the nitrogen in fractionation tower 1 is reheated and returned to nitrogen compressor 4. During reheating, it passes through first pipe 11, plate heat exchanger 3, and second pipe 12, and returns to the nitrogen compressor inlet to complete the cycle. At the same time, liquid nitrogen storage tank 5 is connected to tubular heat exchanger 2 at the top of fractionation tower 1, and liquid nitrogen is injected from the bottom of the top condenser of fractionation tower 1 to cool it and accelerate the condensation process in cryogenic separation. The process gas after condensation and fractionation is reheated and discharged through first outlet pipe 7, plate heat exchanger 3, and second outlet pipe 8.

Claims

1. A nitrogen cycle refrigeration system for a cryogenic separation device, characterized in that, It includes a fractionation tower (1), a nitrogen compressor (4), a plate heat exchanger (3), and an inlet pipe (6); the raw gas passes through the plate heat exchanger (3) and is connected to the fractionation tower (1) through the inlet pipe (6); a tubular heat exchanger (2) is installed on the inner top of the fractionation tower (1), and a first outlet pipe (7) is connected to the top of the fractionation tower (1). The first outlet pipe (7) passes through the plate heat exchanger (3) and is connected to a second outlet pipe (8); the tubular heat exchanger (2) is connected through a first pipe (11) and through the internal pipeline of the plate heat exchanger (3), and then through a second pipe (12) to the nitrogen compressor (4). After passing through the nitrogen compressor (4), it is connected back to the plate heat exchanger (3) through a third pipe (13), and then through the plate heat exchanger (3) and through a fourth pipe (14) to the tubular heat exchanger (2).

2. The nitrogen cycle refrigeration system for a cryogenic separation device according to claim 1, characterized in that, The nitrogen compressor (4) is a four-stage compressor.

3. The nitrogen cycle refrigeration system for a cryogenic separation device according to claim 1, characterized in that, The fourth pipe (14) is equipped with a first throttle valve (9).

4. The nitrogen cycle refrigeration system for a cryogenic separation device according to claim 3, characterized in that, The fourth pipe (14) is connected to a fifth pipe (15), which is connected in parallel with the first pipe (11).

5. The nitrogen cycle refrigeration system for a cryogenic separation device according to claim 4, characterized in that, A second throttle valve (10) is installed on the fifth pipe (15).

6. The nitrogen cycle refrigeration system for a cryogenic separation device according to claim 1, characterized in that, The tubular heat exchanger (2) is connected to a liquid nitrogen storage tank (5) via a sixth pipe (16) for injecting liquid nitrogen into the tubular heat exchanger (2) for auxiliary cooling.

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