Air separation plant liquid nitrogen gas extraction device

Abstract

The utility model discloses a kind of air separation equipment liquid nitrogen gas stripping devices, it relates to air separation equipment field, it includes liquid tank, adsorption tank, pressure reducing valve, automatic regulating valve, buffer tank and gasifier.Liquid tank is connected with the input of gasifier by delivery pump;The output of gasifier is connected with the input of adsorption tank and buffer tank respectively;The output of adsorption tank and buffer tank is connected with the liquid nitrogen pipeline that rectifying column lower tower is transported to rectifying column upper tower by automatic regulating valve;The output of gasifier is equipped with pressure reducing valve between the input pipeline of adsorption tank and buffer tank;Pressure detection point is equipped on the pipeline before the outlet of pressure reducing valve, and on the buffer tank and the pipeline before the outlet of buffer tank.The utility model can solve the problem that existing air separation device is not designed with gas stripping device, and has gas stripping device, but because of low pressure or temperature fluctuation leads to the problem that rectifying column cannot work stably, and simultaneously solve the problem that cold box maintenance is inconvenient, maintenance cycle is long, difficult, and maintenance cost is high.

Description

Technical Field

[0001] This utility model relates to the field of air separation equipment technology, and in particular to a device for liquid nitrogen stripping in air separation equipment. Background Technology

[0002] In the air separation distillation process, liquid needs to be drawn from the lower column to the upper column as reflux. To get the liquid from the lower column to the upper column, work must be done to overcome the weight of the liquid and the height of the column. The main driving force for transporting the liquid is the pressure in the lower column. Therefore, the pressure in the lower column is crucial, as it determines how high the liquid can be drawn to the upper column. However, with the development of air separation units, in order to achieve higher product purity, the number of theoretical plates and the packing height are constantly increasing, and the height of the distillation column is also getting higher and higher.

[0003] Due to the increased height of the distillation column, during the air separation unit's production process, a situation arises where the liquid from the lower column cannot be smoothly transferred to the upper column. If the reflux from the upper column is interrupted, the distillation process is disrupted, product purity immediately deteriorates, and production must be halted, significantly impacting production. To address this issue, the designers added a stripping device after the liquid pipeline valve connecting the lower and upper columns. The purpose is to create airflow at the throttling valve, generating negative pressure to facilitate smoother liquid transfer to the upper column.

[0004] In actual production, other situations may arise. For example, older air separation units, which were not originally designed with such a stripping device, may not have problems during normal production. However, when the pressure at the bottom of the distillation column is low, such as during molecular sieve pressurization or depressurization, the amount of air entering the column decreases, and the pressure fluctuates, the liquid at the bottom of the distillation column may not be able to reach the top of the distillation column. Another example is that some air separation units are designed with a stripping device for the liquid at the bottom of the distillation column, but due to the relatively high column height, the pressure at the bottom of the distillation column cannot be stabilized to ensure a stable supply of liquid to the top of the distillation column, leading to fluctuations in operating conditions. The usual solution to these two types of problems is a cold box (…). Figure 1 The overhaul within the section marked in the middle (the area within the dashed box) involves removing all the insulation material (perlite) from the cold box of the air separation unit, modifying the liquid piping from the lower to the upper distillation column, reinstalling the perlite, and then restarting the unit. This approach has two drawbacks: first, it is expensive; for example, a 40,000 kilowatt-class air separation unit would require approximately 1 million yuan for such a project. Second, it is time-consuming, requiring about one month for such an overhaul.

[0005] This invention involves installing a gas stripping device outside the cold box, avoiding the need for major overhauls of the cold box in the two similar situations mentioned above. It addresses both the issue of air separation units not originally designed with a gas stripping device and the problem of unstable operation due to low pressure in units with designed gas stripping devices. Furthermore, it is quick, taking approximately one week, and the maintenance cost is low, around 100,000-150,000 yuan. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide a liquid nitrogen stripping device for air separation equipment. It can solve the problems of existing air separation equipment that does not have a stripping device or that the distillation column cannot work stably due to low pressure or temperature fluctuations. At the same time, it solves the problems of inconvenient maintenance of cold box, long maintenance cycle, high difficulty and maintenance cost.

[0007] To solve the above problems, the technical solution of this utility model is: this air separation equipment liquid nitrogen stripping device includes a liquid tank, an adsorption tank, a buffer tank, and a vaporizer; The liquid tank is connected to the inlet of the vaporizer via a delivery pump; the outlet of the vaporizer is connected to the inlets of the adsorption tank and the buffer tank after being depressurized by a pressure reducing valve; the outlets of the adsorption tank and the buffer tank are connected to the liquid nitrogen pipeline from the lower column of the distillation column to the upper column of the distillation column via an automatic regulating valve.

[0008] A more specific embodiment of the above technical solution is that pressure detection points are provided on the pipeline in front of the outlet of the pressure reducing valve, as well as on the buffer tank and the pipeline in front of the outlet of the buffer tank.

[0009] Furthermore, a pressure reducing valve is provided between the output port of the vaporizer and the input port of the adsorption tank and the buffer tank.

[0010] Furthermore, control valves are provided on the outlet and inlet pipes of the adsorption tank and the buffer tank, as well as on the connecting pipe between the inlet of the adsorption tank and the buffer tank.

[0011] Furthermore, the suction pressure detection point is connected to the DCS system via a transmitter for remote control and real-time monitoring to control the flow rate and pressure of nitrogen in the liquid nitrogen pipeline that supplies nitrogen from the lower column to the upper column of the distillation column.

[0012] By adopting the above technical solution, this utility model has the following beneficial effects compared with the prior art: 1. This utility model effectively solves the problem of excessively high gas source temperature causing disturbance to distillation after being sent into the distillation column by using nitrogen gas after liquid nitrogen vaporization outside the cold box as a gas source.

[0013] 2. This utility model directly introduces nitrogen gas after liquid nitrogen vaporization into the outside of the cold box, forming an airflow at the valve. This flow process generates a certain negative pressure, which helps the liquid after the valve to be more smoothly led to the upper column of the distillation column. It can effectively solve the problem that liquid nitrogen in the lower column of the distillation column cannot be smoothly sent to the upper column of the distillation column. Moreover, it does not require major overhaul of the cold box. The modification can be achieved by carrying out construction in the valve box of the throttling valve during a short shutdown (about one week). It can effectively reduce maintenance time and costs, and save costs significantly.

[0014] 3. The buffer tank of this utility model can effectively ensure the stability of the gas stripping pressure and avoid the impact of pressure fluctuations on production after nitrogen enters the distillation column.

[0015] 4. This utility model can be remotely controlled through a DCS system, which can monitor and control the pressure and process of the gas stripping device in real time, meet the adjustment requirements under different distillation conditions, and achieve precise control of nitrogen pressure and process under adjustment. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the main structure of this utility model.

[0017] The labels in the diagram represent: 1. Liquid tank; 2. Adsorption tank; 3. Buffer tank; 4. Automatic regulating valve; 5. Upper column of distillation column; 6. Throttling valve; 7. Lower column of distillation column; 8. Control valve; 9. Pressure reducing valve; 10. Vaporizer. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: Figure 1 The air separation equipment liquid nitrogen stripping device includes a liquid tank 1, an adsorption tank 2, a buffer tank 3, and a vaporizer 10.

[0019] Liquid nitrogen, contained in liquid tank 1, is pumped into vaporizer 10 by a transfer pump and vaporized into cryogenic nitrogen gas. The nitrogen gas then passes through pressure reducing valve 9 and enters adsorption tank 2 and buffer tank 3 respectively. Adsorption tank 2 adsorbs impurities from the vaporized nitrogen gas to ensure its purity. Buffer tank 3 stores a certain amount of gas to maintain stable pressure when the nitrogen flow rate fluctuates. After adsorption and buffering, the nitrogen gas converges at the outlets of adsorption tank 2 and buffer tank 3 and then passes through an automatic regulating valve 4 with the nitrogen gas in the cold chamber. Figure 1 The section within the dashed box (part of the distillation column) is connected to the liquid nitrogen pipeline from the lower column 7 to the upper column 5. The nitrogen gas entering the pipeline forms an airflow at the valve, generating a negative pressure that helps the liquid downstream of the valve to flow more smoothly into the upper column. The liquid nitrogen in the lower column 7, driven by the stripping device, flows directly from the upper part of the lower column into the upper column 5 through the pipeline and throttle valve 6. The nitrogen's path is as follows: Figure 1As shown by the arrow in the image.

[0020] A pressure monitoring point PI is installed on the pipeline before the outlet of pressure reducing valve 9, as well as on buffer tank 3 and the pipeline before the outlet of buffer tank 3, to monitor the pressure of the gas at the location. These pressure monitoring points PI are connected to the DCS system through transmitters for remote control and real-time monitoring, as well as control of the flow and pressure of the gas lifting device.

[0021] Control valves 8 are installed on the outlet and inlet pipes of adsorption tank 2 and buffer tank 3, as well as on the connecting pipe between adsorption tank 2 and buffer tank 3, to control the gas entering and exiting adsorption tank 2 and buffer tank 3.

Claims

1. A liquid nitrogen gas stripping apparatus for a space division plant, characterized by: It includes a liquid tank (1), an adsorption tank (2), a buffer tank (3), a pressure reducing valve (9), an automatic regulating valve (4), and a vaporizer (10); The liquid tank (1) is connected to the inlet of the vaporizer (10); the outlet of the vaporizer (10) is connected to the inlet of the adsorption tank (2) and the buffer tank (3) respectively after being depressurized by the pressure reducing valve (9); the outlets of the adsorption tank (2) and the buffer tank (3) are connected to the liquid nitrogen pipeline from the lower column of the distillation column to the upper column of the distillation column through the automatic regulating valve (4).

2. The apparatus of claim 1, wherein: Pressure detection points are provided on the pipe in front of the outlet of the pressure reducing valve (9), as well as on the buffer tank (3) and the pipe in front of the outlet of the buffer tank (3).

3. The apparatus according to claim 1 or 2, wherein: A pressure reducing valve (9) is provided between the outlet of the vaporizer (10) and the inlet pipes of the adsorption tank (2) and the buffer tank (3).

4. The apparatus of claim 3, wherein: Control valves (8) are provided on the outlet and inlet pipes of the adsorption tank (2) and the buffer tank (3), as well as on the connecting pipes at the inlets of the adsorption tank (2) and the buffer tank (3).

5. The apparatus of claim 2, wherein: The suction pressure detection point is connected to the DCS system via a transmitter for remote control and real-time monitoring to control the flow rate and pressure of nitrogen in the liquid nitrogen pipeline that supplies nitrogen from the lower column to the upper column of the distillation column.

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