Device for stably measuring liquid level of low-temperature liquid

Abstract

The utility model discloses a device for stably measuring the liquid level of low-temperature liquid, and particularly relates to the technical field of stable measurement of the liquid level of the low-temperature liquid, the device comprises a lower tower, an inlet above the lower tower is fixedly communicated with a first needle valve pipeline, and a first outlet below the lower tower is fixedly connected with a second needle valve pipeline; the positive pressure side of the differential pressure type liquid level transmitter is communicated with the second needle valve through a pipeline, and the negative pressure side of the differential pressure type liquid level transmitter is communicated with the first needle valve through a pipeline; and the first nitrogen access pipe is communicated with the second needle valve pipeline in parallel. According to the utility model, through introduction of nitrogen, heat tracing is carried out on the second needle valve pipeline equivalently, and reheating of the pressure guide pipe on the positive pressure side of the differential pressure type liquid level transmitter is accelerated, so that the gasification pressure is kept stable, and finally, the pressure difference between the positive pressure side and the negative pressure side is stabilized.

Description

Technical Field

[0001] The utility model relates to the technical field of stable measurement of cryogenic liquid levels, in particular to a device for stable measurement of cryogenic liquid levels. Background Art

[0002] In the air separation cryogenic device, the liquid level of the lower tower of the main distillation tower is measured by a differential pressure level transmitter. The high and low pressure sides of the lower tower level gauge are measured through the pressure pipe to enter the differential pressure level transmitter for differential pressure conversion and finally converted into a liquid level signal to enter the DCS system for monitoring. The low pressure side of the differential pressure level transmitter of this device is a single pressure point, and the high pressure side is a two-way pressure point. The latter two ways are combined into one way to enter the transmitter positive pressure chamber. Figure 1 As shown in the figure, during operation, all the valves mentioned above were open, and there were no leaks from the pressure pipe joints or valves. However, after a period of operation, the DCS monitoring screen showed that the liquid level in the lower column would slowly rise for about six minutes before suddenly dropping by approximately 60-70 mm. The PID control of the corresponding valve (the oxygen-enriched liquid air throttle valve) would activate in response to the sudden change in liquid level, opening by approximately 1.8% with a relatively regular cycle. This frequent valve activation resulted in an unstable liquid flow into the upper column, ultimately affecting the temperature stability of the upper column and the distillation process. In severe cases, nitrogen plugging could occur. This failure is caused by insufficient reheating of the pressure pipe in the transmitter's positive pressure chamber. Once the liquid in the positive pressure chamber has reheated, bubbles flow back into the lower column. This process, pushed back into the lower column by the bubbles, caused the static pressure differential to drop briefly, resulting in a sudden drop in the liquid level. The liquid then slowly began to flow downward again, increasing the static pressure differential and causing the valve (the oxygen-enriched liquid air throttle valve) to fluctuate in a repetitive pattern with the sudden change in liquid level. Utility Model Content

[0003] The purpose of the utility model is to provide a device for stable measurement of cryogenic liquid level, which is used to solve the problem that the liquid level measurement data jumps periodically due to insufficient reheating of the pressure taking tube of the differential pressure liquid level transmitter in the cryogenic deep freezing device.

[0004] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0005] A device for stable measurement of cryogenic liquid level, comprising a lower tower, wherein an inlet above the lower tower is fixedly connected to a first needle valve pipeline, and a first outlet below the lower tower is fixedly connected to a second needle valve pipeline;

[0006] Also included is a differential pressure liquid level transmitter, the positive pressure side of which is in communication with the second needle valve pipeline, and the negative pressure side of which is in communication with the first needle valve pipeline;

[0007] It also includes a first nitrogen inlet pipe, which is connected in parallel with the second needle valve pipeline.

[0008] Preferably, a first filter pressure reducing valve, a first float flowmeter and a first check valve arranged along the flow direction of nitrogen are connected in series on the pipeline of the first nitrogen inlet pipe.

[0009] Preferably, the second needle valve pipeline includes a needle valve, and the parallel connection point between the first nitrogen inlet pipe and the second needle valve pipeline is located at the output port of the needle valve.

[0010] Preferably, a second nitrogen inlet pipe is further included, the inlet end of which is connected in parallel to the nitrogen inlet end of the first nitrogen inlet pipe and is arranged at the input end of the first filter pressure reducing valve on the first nitrogen inlet pipe.

[0011] Preferably, the second nitrogen inlet pipe is connected in series with a second filter pressure reducing valve, a second float flowmeter and a second check valve arranged along the flow direction of nitrogen.

[0012] Preferably, a third needle valve pipeline is fixedly connected to the second outlet below the lower tower, and the third needle valve pipeline includes a needle valve. The nitrogen outlet of the second nitrogen inlet pipe is connected in parallel with the third needle valve pipeline and is arranged at the output end of the needle valve.

[0013] Preferably, the output end of the third needle valve pipeline is connected in parallel with the output end of the first nitrogen inlet pipe.

[0014] In the above-mentioned technical solution, the present invention provides a device for stable measurement of cryogenic liquid levels, which has the following beneficial effects: a small flow of nitrogen gas is introduced into the second needle valve line on the positive pressure side of a differential pressure level transmitter to vaporize the liquid within the second needle valve line. The pressure after the pressure reducing valve in the second needle valve line is controlled at 0.5 MPa, and the flow rate is controlled at 20-30 L / H. The introduction of nitrogen acts as a heat tracer in the second needle valve line, accelerating the reheating of the pressure pipe on the positive pressure side of the differential pressure level transmitter, thereby maintaining a stable vaporization pressure and ultimately stabilizing the pressure differential between the positive and negative pressure sides. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0016] Figure 1 This is a structural diagram provided for an embodiment of the present utility model.

[0017] Description of reference numerals:

[0018] 1. Lower tower; 2. First needle valve pipeline; 3. Second needle valve pipeline; 4. Differential pressure level transmitter; 5. First nitrogen inlet pipe; 51. First filter-pressure reducing valve; 52. First float flowmeter; 53. First check valve; 6. Second nitrogen inlet pipe; 61. Second filter-pressure reducing valve; 62. Second float flowmeter; 63. Second check valve; 7. Third needle valve pipeline. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] like Figure 1 The device shown here is for stable cryogenic liquid level measurement. This device addresses the issue of periodic jumps in liquid level measurement data caused by insufficient reheating of the pressure-sensing pipe in the differential pressure level transmitter in the lower tower. In this embodiment, a first needle valve pipeline 2 is fixedly connected to the inlet at the top of the lower tower 1, while a second needle valve pipeline 3 is fixedly connected to the first outlet at the bottom, and a third needle valve pipeline 7 is fixedly connected to the second outlet.

[0021] The outlets of the third needle valve pipeline 7 and the second needle valve pipeline 3 are connected in parallel to the positive pressure side of the differential pressure liquid level transmitter 4 , while the negative pressure side is connected to the first needle valve pipeline 2 .

[0022] Furthermore, in the above embodiment, a small flow of nitrogen gas is introduced into the second needle valve pipeline 3 and the third needle valve pipeline 7 to vaporize the liquid in the second needle valve pipeline 3 and the third needle valve pipeline 7. The pressure after the pressure reducing valve of the second needle valve pipeline 3 is controlled at 0.5 MPa, and the flow rate is controlled at 20-30 L / H. The introduction of nitrogen is equivalent to heating the second needle valve pipeline 3 and the third needle valve pipeline 7, accelerating the reheating of the pressure pipe of the differential pressure liquid level transmitter 4, thereby maintaining the vaporization pressure stable and ultimately stabilizing the pressure difference between the positive and negative pressure sides. Specifically:

[0023] Combine Figure 1 It can be seen that the introduction of nitrogen is achieved through the first nitrogen inlet pipe 5 and the second nitrogen inlet pipe 6.

[0024] The first nitrogen inlet pipe 5 is connected in series with a first filter pressure reducing valve 51, a first float flowmeter 52, and a first check valve 53, arranged along the nitrogen flow direction. The second needle valve pipe 3 includes a needle valve, and the parallel connection between the first nitrogen inlet pipe 5 and the second needle valve pipe 3 is located at the output port of the needle valve.

[0025] The inlet of the second nitrogen inlet pipe 6 is connected in parallel to the nitrogen inlet of the first nitrogen inlet pipe 5 and is located at the input of the first filter-pressure reducing valve 51 on the first nitrogen inlet pipe 5. A second filter-pressure reducing valve 61, a second float flowmeter 62, and a second check valve 63 are connected in series along the nitrogen flow direction. The third needle valve line 7 includes a needle valve, and the nitrogen outlet of the second nitrogen inlet pipe 6 is connected in parallel to the third needle valve line 7 and located at the output of the needle valve.

[0026] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A device for stable measurement of cryogenic liquid level, comprising a lower tower (1), characterized in that: The inlet above the lower tower (1) is fixedly connected to a first needle valve pipeline (2), and the first outlet below the lower tower (1) is fixedly connected to a second needle valve pipeline (3); It also includes a differential pressure liquid level transmitter (4), the positive pressure side of which is in communication with the second needle valve pipeline (3), and the negative pressure side of which is in communication with the first needle valve pipeline (2); It also includes a first nitrogen inlet pipe (5), which is connected in parallel with the second needle valve pipeline (3).

2. The device for stable measurement of cryogenic liquid level according to claim 1, characterized in that: The first nitrogen inlet pipe (5) is connected in series with a first filter pressure reducing valve (51), a first float flowmeter (52) and a first check valve (53) arranged along the flow direction of nitrogen.

3. The device for stable measurement of cryogenic liquid level according to claim 1, characterized in that: The second needle valve pipeline (3) comprises a needle valve, and the first nitrogen inlet pipe (5) and the second needle valve pipeline (3) are connected in parallel at an output port of the needle valve.

4. The device for stable measurement of cryogenic liquid level according to claim 1, characterized in that: It also includes a second nitrogen inlet pipe (6), the inlet end of which is connected in parallel to the nitrogen inlet end of the first nitrogen inlet pipe (5) and is arranged at the input end of the first filter pressure reducing valve (51) on the first nitrogen inlet pipe (5).

5. The device for stable measurement of cryogenic liquid level according to claim 4, characterized in that: The second nitrogen inlet pipe (6) is connected in series with a second filter pressure reducing valve (61), a second float flowmeter (62) and a second check valve (63) arranged along the flow direction of nitrogen.

6. The device for stable measurement of cryogenic liquid level according to claim 1, characterized in that: A third needle valve pipeline (7) is fixedly connected to the second outlet below the lower tower (1), and the third needle valve pipeline (7) includes a needle valve. The nitrogen outlet of the second nitrogen inlet pipe (6) is connected in parallel with the third needle valve pipeline (7) and is arranged at the output end of the needle valve.

7. The device for stable measurement of cryogenic liquid level according to claim 6, characterized in that: The output end of the third needle valve pipeline (7) is connected in parallel with the output end of the first nitrogen inlet pipe (5).

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