A nitrogen backup system

Abstract

This utility model relates to a nitrogen backup system, including a liquid nitrogen storage tank. A main liquid nitrogen delivery pipe is installed on the liquid nitrogen storage tank, and a nitrogen vaporizer is installed on the main liquid nitrogen delivery pipe. The nitrogen vaporizer includes a shell, a demineralized water delivery main pipe, a spiral coil, a guide cone, a connecting column, spiral blades, and a demineralized water return main pipe. The spiral coil is connected to the main liquid nitrogen delivery pipe, and a vaporized nitrogen delivery pipe is installed on the spiral coil. A buffer tank is installed on the vaporized nitrogen delivery pipe, and a supplementary nitrogen supply pipe is installed on the buffer tank. An air-cooled heat exchanger, a first regulating valve, and a first pressure sensor are installed on the supplementary nitrogen supply pipe. This system can reduce localized supercooling of the demineralized water, which serves as a heat source, thus preventing frost or ice formation on the coil of the heat exchanger. This utility model is easy to use and has broad market prospects.

Description

Technical Field

[0001] This utility model relates to the field of nitrogen backup equipment, and specifically to a nitrogen backup system. Background Technology

[0002] A nitrogen backup system is a system used in conjunction with other gas supply systems (such as the instrument dry air system in a high-purity nitrogen unit) to provide nitrogen supply when the main gas source fails. In this type of nitrogen backup system within a high-purity nitrogen unit, it is connected in parallel with the instrument dry air system via a shared pipeline. Both the instrument dry air system supply pipeline and the instrument nitrogen backup system supply pipeline are equipped with check valves and pressure regulating valves. A pressure sensor and a pressure regulating relief valve are located on the shared pipeline; the pressure sensor is positioned downstream of the pressure regulating relief valve and close to the actuator. The check valve and pressure regulating valve reduce the risk of air contamination from the high pressure in the air pipeline during system failures. Furthermore, when the regulating valve fails, it can be isolated and replaced without disturbance, ensuring normal and reliable online system pressure and guaranteeing a reliable nitrogen supply when needed.

[0003] In existing technologies, nitrogen backup systems often utilize nitrogen formed from the vaporization of liquid nitrogen to supplement the nitrogen supply network, which then supplies it to the instrument gas supply network or downstream customers to meet nitrogen supply needs after an emergency trip of the main nitrogen supply system. The common process for liquid nitrogen vaporization involves heat exchange between a heat source and liquid nitrogen. Specifically, this involves counter-current heat exchange between the heated demineralized water supplied to the heat source channel and the continuously supplied liquid nitrogen to the cold source channel of the heat exchanger. However, extensive practical experience has shown that when the heat exchanger return water temperature is below 49°C, frost forms on the outer surface of the coils serving as the cold source channel. When the heat exchanger return water temperature rises to 55°C, the frost formation on the outer surface of the coils is alleviated, and the thin layer of ice adhering to the coil surface begins to melt. When the heat exchanger return water temperature rises to 70°C, no frost or ice forms on the outer surface of the coils. When frost or even ice forms on the outer surface of the coil, it affects the heat exchange between the demineralized water (heat source) and the liquid nitrogen (cold source). Some of the heat carried by the demineralized water is absorbed by the frost or ice adhering to the outer surface of the coil, thus affecting the vaporization of the liquid nitrogen. Analysis reveals that the excessively intense local heat exchange of the demineralized water (heat source) causes that portion of the demineralized water to become too cold, resulting in frost or ice formation. Therefore, there is room for improvement in the existing technology to reduce the occurrence of ice formation on the cold source channels of the heat exchanger due to localized overcooling of the demineralized water during indirect heat exchange with liquid nitrogen, thereby affecting the heat exchange between the demineralized water and liquid nitrogen and ensuring the normal operation of the equipment. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a nitrogen backup system that can reduce localized supercooling of demineralized water as a heat source, thereby preventing frost or ice buildup on the coils of the heat exchanger, thus overcoming the deficiencies in existing technologies.

[0005] The technical solution adopted by this utility model is as follows: a nitrogen backup system, including a liquid nitrogen storage tank, wherein the liquid nitrogen storage tank is provided with an inlet end of a liquid nitrogen delivery main pipe, and a nitrogen vaporizer is provided with an outlet end of the liquid nitrogen delivery main pipe. The nitrogen vaporizer includes a shell, an outlet end of a demineralized water delivery main pipe provided at the bottom of the shell, a spiral coil provided inside the shell, a guide cone provided inside the shell between the spiral coil and the outlet end of the demineralized water delivery main pipe, a connecting column provided at the end of the guide cone near the spiral coil, a spiral blade provided on the connecting column and the shell, and an inlet end of a demineralized water return main pipe provided on the shell above the spiral coil. The inlet end of the spiral coil is connected to the outlet end of the liquid nitrogen delivery main pipe, and an inlet end of a vaporized nitrogen delivery pipe is provided at the outlet end of the spiral coil. A buffer tank is provided at the outlet end of the vaporized nitrogen delivery pipe, and an inlet end of a supplementary nitrogen supply pipe is provided on the buffer tank. An air-cooled heat exchanger, a first regulating valve, and a first pressure sensor are sequentially provided on the supplementary nitrogen supply pipe from the direction near the buffer tank to the direction away from the buffer tank.

[0006] Preferably, the liquid nitrogen delivery main pipe is provided with a liquid nitrogen pump, a second regulating valve, an inlet end of a liquid nitrogen return pipe and a first shut-off valve in sequence along the direction from near the liquid nitrogen storage tank to far away from the liquid nitrogen storage tank. The liquid nitrogen return pipe is provided with a second shut-off valve, and the outlet end of the liquid nitrogen return pipe is connected to the liquid nitrogen storage tank.

[0007] Preferably, a demineralized water storage tank is provided at the outlet end of the demineralized water delivery main pipe and the inlet end of the demineralized water return main pipe, and a filter, a water pump, a third regulating valve, a flow sensor and a cold source channel of a tubular heat exchanger are sequentially arranged on the demineralized water delivery main pipe from the direction closest to the demineralized water storage tank to the direction furthest away from the demineralized water storage tank.

[0008] Preferably, a first temperature sensor is installed on the demineralized water return main pipe, and a second temperature sensor is installed on the demineralized water delivery main pipe between the tubular heat exchanger and the shell.

[0009] Preferably, the inlet end of the heat source channel of the tubular heat exchanger is provided with the outlet end of a high-pressure steam conveying pipe, the outlet end of the heat source channel of the tubular heat exchanger is provided with the inlet end of a mixed liquid conveying pipe, the outlet end of the mixed liquid conveying pipe is provided with a gas-liquid separator, a wire mesh coalescer is provided in the gas-liquid separator above the outlet end of the mixed liquid conveying pipe, a low-pressure steam conveying pipe is provided on the gas-liquid separator above the wire mesh coalescer, the bottom end of the gas-liquid separator and the inlet end of the demineralized water storage tank are connected through a condensate conveying pipe, and the gas-liquid separator is located above the demineralized water storage tank.

[0010] Preferably, a second pressure sensor is installed on the top of the liquid nitrogen storage tank, a third pressure sensor and a pressure relief valve are installed on the top of the buffer tank, a first pressure regulating pipe and a second pressure regulating pipe are installed on the top of the liquid nitrogen storage tank and the buffer tank, a fourth regulating valve is installed on the first pressure regulating pipe, and the second pressure regulating pipe is provided with an inlet end of a bypass branch pipe, a self-regulating valve and an outlet end of the bypass branch pipe in sequence along the direction from the liquid nitrogen storage tank to the buffer tank, and a fifth regulating valve is installed on the bypass branch pipe.

[0011] The beneficial effects of this utility model are as follows: First, this utility model enables the heated demineralized water to rotate after entering the shell and being guided by the guide cone and spiral blades, thereby improving the fluidity of the demineralized water during the heat exchange process between the demineralized water and the spiral coil. This reduces the phenomenon of frost or ice forming on the outer surface of the spiral coil due to insufficient fluidity of the demineralized water and local overcooling after heat exchange between the demineralized water and the spiral coil.

[0012] Secondly, the demineralized water conveying main pipe of this utility model is provided with a filter, a water pump, a third regulating valve, a flow sensor and a cold source channel of a tubular heat exchanger in sequence along the direction from the demineralized water storage tank to the distance from the demineralized water storage tank. The installation of the flow sensor facilitates the feedback of flow parameters.

[0013] Furthermore, liquid level sensors are installed on both the gas-liquid separation tank below the wire mesh coalescer and the demineralized water storage tank of this utility model. Installing liquid level sensors facilitates the feedback of liquid level parameters.

[0014] This utility model has a simple structure, is easy to operate, and has a clever design, which greatly improves work efficiency and has good social and economic benefits. It is a product that is easy to promote and use. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model.

[0016] Figure 2 for Figure 1 A magnified view of detail A. Detailed Implementation

[0017] like Figure 1 and Figure 2As shown, a nitrogen backup system includes a liquid nitrogen storage tank 1. The liquid nitrogen storage tank 1 has an inlet end of a liquid nitrogen delivery main pipe 2, and a nitrogen vaporizer is installed at the outlet end of the liquid nitrogen delivery main pipe 2. The nitrogen vaporizer includes a shell 3, an outlet end of a demineralized water delivery main pipe 4 located at the bottom of the shell 3, a spiral coil 5 installed inside the shell 3, a guide cone 6 installed inside the shell 3 between the spiral coil 5 and the outlet end of the demineralized water delivery main pipe 4, a connecting column 7 installed at the end of the guide cone 6 near the spiral coil 5, a spiral blade 8 installed on the shell 3, and a section above the spiral coil 5. The inlet end of the demineralized water return main pipe 9 is provided on the shell 3; the inlet end of the spiral coil 5 is connected to the outlet end of the liquid nitrogen delivery main pipe 2. The inlet end of the vaporized nitrogen delivery pipe 10 is provided on the outlet end of the spiral coil 5. A one-way valve 48 is provided on the vaporized nitrogen delivery pipe 10. A buffer tank 11 is provided on the outlet end of the vaporized nitrogen delivery pipe 10. The inlet end of the supplementary nitrogen supply pipe 12 is provided on the buffer tank 11. An air-cooled heat exchanger 13, a first regulating valve 14, and a first pressure sensor 15 are arranged sequentially along the direction from near the buffer tank 11 to away from the buffer tank 11. A demineralized water storage tank 21 is provided on the outlet end of the demineralized water delivery main pipe 4 and the inlet end of the demineralized water return main pipe 9. A filter 22, a water pump 23, a third regulating valve 24, a flow sensor 25, and a cold source channel of a tubular heat exchanger 26 are arranged sequentially along the direction from near the demineralized water storage tank 21 to away from the demineralized water storage tank 21. A venting valve 27 is installed at the top of the demineralized water storage tank 21 to facilitate the balance of gas pressure above the liquid layer inside the tank. A drain pipe 28 with a drain valve 29 is installed at the bottom of the tank. A first temperature sensor 30 is installed on the demineralized water return main pipe 9, and a second temperature sensor 31 is installed on the demineralized water delivery main pipe 4 between the tubular heat exchanger 26 and the shell 3. Furthermore, the installation of the first and second temperature sensors 30 on the demineralized water return main pipe 9 and the second temperature sensor 31 on the demineralized water delivery main pipe 4 between the tubular heat exchanger 26 and the shell 3 facilitates the feedback of temperature parameters.

[0018] The liquid nitrogen delivery main pipe 2 is sequentially equipped with a liquid nitrogen pump 16, a second regulating valve 17, the inlet end of a liquid nitrogen return pipe 18, and a first shut-off valve 19 along the direction from near to far from the liquid nitrogen storage tank 1. A second shut-off valve 20 is installed on the liquid nitrogen return pipe 18, and the outlet end of the liquid nitrogen return pipe 18 is connected to the liquid nitrogen storage tank 1. It is worth mentioning that when the parameter fed back by the first temperature sensor 30 is too low, the liquid nitrogen pressurized by the liquid nitrogen pump 16 can be returned to the liquid nitrogen storage tank 1 by switching the states of the first shut-off valve 19 and the second shut-off valve 20. This avoids the need for re-cooling after the liquid nitrogen pump 16 stops working, and also avoids further exacerbating the frost or ice buildup on the spiral coil 5 by continuing to deliver liquid nitrogen into the already frosted or frozen spiral coil 5.

[0019] The inlet end of the heat source channel of the tubular heat exchanger 26 is provided with the outlet end of the high-pressure steam conveying pipe 32, the outlet end of the heat source channel of the tubular heat exchanger 26 is provided with the inlet end of the mixed liquid conveying pipe 33, the outlet end of the mixed liquid conveying pipe 33 is provided with the gas-liquid separator 34, the gas-liquid separator 34 above the outlet end of the mixed liquid conveying pipe 33 is provided with the wire mesh coalescer 35, the gas-liquid separator 34 above the wire mesh coalescer 35 is provided with the low-pressure steam conveying pipe 36, the bottom end of the gas-liquid separator 34 and the inlet end of the demineralized water storage tank 21 are connected through the condensate conveying pipe 37, and the gas-liquid separator 34 is located above the demineralized water storage tank 21. After high-pressure steam, delivered to the heat source channel of the tubular heat exchanger 26 via the high-pressure steam delivery pipe 32, and the medium continuously delivered to the cold source channel of the tubular heat exchanger 26 undergo countercurrent heat exchange, the high-pressure steam is partially liquefied to form a gas-liquid mixture, and the pressure of the gas-liquid mixture decreases. After separation by the wire mesh coalescer 35, the liquid phase is temporarily stored in the demineralized water storage tank 21 below the wire mesh coalescer 35 and continuously delivered to the demineralized water storage tank 21 via the condensate delivery pipe 37. The gas phase is discharged externally via the low-pressure steam delivery pipe 36 for further delivery to low-pressure steam users. Furthermore, level sensors 38 are respectively installed on the gas-liquid separation tank 34 below the wire mesh coalescer 35 and on the demineralized water storage tank 21, facilitating feedback of liquid level parameters.

[0020] Furthermore, since the vaporization of nitrogen stored in liquid nitrogen storage tank 1 causes an increase in pressure above the liquid layer inside liquid nitrogen storage tank 1, and the process of liquid nitrogen storage tank 1 transferring liquid nitrogen outward causes a decrease in pressure above the liquid layer inside liquid nitrogen storage tank 1, in order to facilitate the balance of pressure above the liquid layer inside liquid nitrogen storage tank 1, this product is equipped with a second pressure sensor 39 on the top of liquid nitrogen storage tank 1, and a third pressure sensor 40 and a pressure relief valve 41 are equipped on the top of buffer tank 11. The installation of the second pressure sensor 39 and the third pressure sensor 40... The pressure relief valve 41 is installed to facilitate pressure parameter feedback, thereby maintaining the safe operating pressure of the buffer tank 11. A first pressure regulating pipe 42 and a second pressure regulating pipe 43 are installed on the top of the liquid nitrogen storage tank 1 and on the buffer tank 11. A fourth regulating valve 44 is installed on the first pressure regulating pipe 42. The second pressure regulating pipe 43, along the direction from the liquid nitrogen storage tank 1 to the buffer tank 11, is sequentially provided with the inlet end of a bypass branch pipe 45, a self-regulating valve 46, and the outlet end of the bypass branch pipe 45. A fifth regulating valve 47 is installed on the bypass branch pipe 45. The self-regulating valve 46 includes a regulating valve body and a pressure tapping pipe. The second pressure regulating pipe 43 between the regulating valve body and the liquid nitrogen storage tank 1 is connected to the pressure tapping pipe. When the pressure inside the liquid nitrogen storage tank 1 is higher than the preset value, the self-regulating regulating valve 46 opens, and part of the nitrogen above the liquid layer in the liquid nitrogen storage tank 1 is transported to the buffer tank 11 through the second pressure regulating pipe 43. If the self-regulating regulating valve 46 does not open when the pressure inside the liquid nitrogen storage tank 1 is higher than the preset value, the operator needs to manually open the fifth regulating valve 47. At this time, part of the nitrogen above the liquid layer in the liquid nitrogen storage tank 1 is transported to the buffer tank 11 through the second pressure regulating pipe 43 and the bypass branch pipe 45. When the liquid nitrogen storage tank 1 is supplying liquid nitrogen outward, the pressure above the liquid layer in the liquid nitrogen storage tank 1 continues to drop. When the pressure above the liquid layer in the liquid nitrogen storage tank 1 drops to the preset range, the fourth regulating valve 44 needs to be opened. At this time, the nitrogen temporarily stored in the buffer tank 11 is replenished to the liquid nitrogen storage tank 1 through the first pressure regulating pipe 42, thereby maintaining the pressure above the liquid layer in the liquid nitrogen storage tank 1 within the preset range.

[0021] The usage instructions for this product are as follows: Figure 1 and Figure 2 As shown, it includes the following steps:

[0022] After being pre-cooled to the operating temperature, the liquid nitrogen pump 16 is turned on. The liquid nitrogen stored in the liquid nitrogen storage tank 1 enters the liquid nitrogen delivery main pipe 2 and is driven by the liquid nitrogen pump 16 to be delivered to the spiral coil 5 and continuously delivered to the demineralized water in the shell 3 for heat exchange. As the liquid nitrogen continues to move forward in the spiral coil 5, it is continuously vaporized to form high-pressure nitrogen gas, which is delivered to the buffer tank 11 through the outlet end of the spiral coil 5 and the vaporized nitrogen delivery pipe 10. The high-pressure nitrogen gas in the buffer tank 11 is then delivered to the supplementary nitrogen supply pipe 12, which exchanges heat with the air through the cold source channel of the air-cooled heat exchanger 13 and is then delivered to the low-pressure nitrogen pipeline network.

[0023] Meanwhile, the demineralized water temporarily stored in the demineralized water storage tank 21 is filtered by the filter 22 and then pressurized by the water pump 23 and transported to the cold source channel of the tubular heat exchanger 26 for heat exchange with the medium continuously supplied to the heat source channel of the tubular heat exchanger 26, forming heated demineralized water. The heated demineralized water enters the shell 3 from the bottom after the temperature is fed back by the second temperature sensor 31, and then is guided by the guide cone 6 and the spiral blade 8 in sequence to form a rotating liquid flow. The rotating liquid flow moves towards the top of the shell 3, and during this process, the spiral coil 5 continuously exchanges heat, thereby causing the liquid nitrogen in the spiral coil 5 to vaporize. When the rotating liquid flow is transported to the demineralized water return main pipe 9, it forms a reflux liquid. The reflux liquid is sent back to the demineralized water storage tank 21 after the temperature is fed back by the first temperature sensor 30, thus forming a demineralized water circulation. During this period, the high-pressure steam conveying pipe 32 continuously receives high-pressure steam and continuously conveys high-pressure steam to the heat source channel of the tubular heat exchanger 26 through the outlet end of the high-pressure steam conveying pipe 32. The high-pressure steam continuously exchanges heat with the medium in the cold source channel of the tubular heat exchanger 26 in a countercurrent manner. When the high-pressure steam is discharged from the outlet end of the heat source channel of the tubular heat exchanger 26, a gas-liquid mixture is formed. The gas-liquid mixture is conveyed to the gas-liquid separator 34 through the mixed liquid conveying pipe 33. After gas-liquid separation by the wire mesh coalescer 35, the gas phase is conveyed to the high-pressure steam conveying pipe 32 as low-pressure steam and delivered to the user end of the low-pressure steam. The liquid phase is temporarily stored in the gas-liquid separator 34 below the wire mesh coalescer 35 and is replenished and conveyed to the demineralized water storage tank 21 through the condensate conveying pipe 37 to participate in the demineralized water circulation.

[0024] This embodiment achieves the goal that after the heated demineralized water enters the shell 3, it rotates after being guided by the guide cone 6 and the spiral blade 8, which improves the fluidity of the demineralized water during the heat exchange process between the demineralized water and the spiral coil 5. This reduces the phenomenon of frost or ice forming on the outer surface of the spiral coil 5 due to insufficient fluidity of the demineralized water and local overcooling after heat exchange with the spiral coil 5.

[0025] The embodiments described above are merely preferred embodiments of this utility model and are not intended to limit the scope of implementation of this utility model. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the patent claims of this utility model should be included within the scope of the patent application of this utility model.

Claims

1. A nitrogen backup system, characterized in that: The system includes a liquid nitrogen storage tank (1), on which the inlet end of a liquid nitrogen delivery main pipe (2) is provided, and a nitrogen vaporizer is provided at the outlet end of the liquid nitrogen delivery main pipe (2). The nitrogen vaporizer includes a shell (3), the outlet end of a demineralized water delivery main pipe (4) provided at the bottom of the shell (3), a spiral coil (5) provided inside the shell (3), a guide cone (6) provided inside the shell (3) between the spiral coil (5) and the outlet end of the demineralized water delivery main pipe (4), a connecting column (7) provided at the end of the guide cone (6) near the spiral coil (5), a spiral blade (8) provided on the connecting column (7) and the shell (3), and a spiral disc. The inlet end of the demineralized water return main pipe (9) is provided on the shell (3) above the pipe (5); the inlet end of the spiral coil (5) is connected to the outlet end of the liquid nitrogen delivery main pipe (2); the inlet end of the vaporized nitrogen delivery pipe (10) is provided on the outlet end of the spiral coil (5); the buffer tank (11) is provided on the outlet end of the vaporized nitrogen delivery pipe (10); the inlet end of the supplementary nitrogen supply pipe (12) is provided on the buffer tank (11); the supplementary nitrogen supply pipe (12) is provided with an air-cooled heat exchanger (13), a first regulating valve (14) and a first pressure sensor (15) in sequence along the direction from near the buffer tank (11) to away from the buffer tank (11).

2. The nitrogen backup system according to claim 1, characterized in that: The liquid nitrogen delivery main pipe (2) is provided with a liquid nitrogen pump (16), a second regulating valve (17), the inlet end of the liquid nitrogen return pipe (18) and a first shut-off valve (19) in sequence along the direction from near the liquid nitrogen storage tank (1) to far away from the liquid nitrogen storage tank (1). The liquid nitrogen return pipe (18) is provided with a second shut-off valve (20), and the outlet end of the liquid nitrogen return pipe (18) is connected to the liquid nitrogen storage tank (1).

3. The nitrogen backup system according to claim 1, characterized in that: A demineralized water storage tank (21) is installed at the outlet end of the demineralized water conveying main pipe (4) and the inlet end of the demineralized water return main pipe (9). A filter (22), a water pump (23), a third regulating valve (24), a flow sensor (25), and a cold source channel for a tubular heat exchanger (26) are sequentially arranged on the demineralized water conveying main pipe (4) from the direction close to the demineralized water storage tank (21) to the direction far away from the demineralized water storage tank (21).

4. The nitrogen backup system according to claim 3, characterized in that: A first temperature sensor (30) is installed on the demineralized water return main pipe (9), and a second temperature sensor (31) is installed on the demineralized water delivery main pipe (4) between the tubular heat exchanger (26) and the shell (3).

5. The nitrogen backup system according to claim 3, characterized in that: The inlet end of the heat source channel of the tubular heat exchanger (26) is provided with the outlet end of the high-pressure steam conveying pipe (32), the outlet end of the heat source channel of the tubular heat exchanger (26) is provided with the inlet end of the mixed liquid conveying pipe (33), the outlet end of the mixed liquid conveying pipe (33) is provided with the gas-liquid separator (34), the gas-liquid separator (34) above the outlet end of the mixed liquid conveying pipe (33) is provided with the wire mesh coalescer (35), the gas-liquid separator (34) above the wire mesh coalescer (35) is provided with the low-pressure steam conveying pipe (36), the bottom end of the gas-liquid separator (34) and the inlet end of the demineralized water storage tank (21) are connected through the condensate conveying pipe (37), and the gas-liquid separator (34) is located above the demineralized water storage tank (21).

6. The nitrogen backup system according to claim 1, characterized in that: The liquid nitrogen storage tank (1) is equipped with a second pressure sensor (39) at the top, and the buffer tank (11) is equipped with a third pressure sensor (40) and a pressure relief valve (41) at the top. The liquid nitrogen storage tank (1) and the buffer tank (11) are equipped with a first pressure regulating pipe (42) and a second pressure regulating pipe (43). The first pressure regulating pipe (42) is equipped with a fourth regulating valve (44). The second pressure regulating pipe (43) is equipped with the inlet end of the bypass branch pipe (45), a self-regulating valve (46) and the outlet end of the bypass branch pipe (45) in sequence along the direction from the liquid nitrogen storage tank (1) to the buffer tank (11). The bypass branch pipe (45) is equipped with a fifth regulating valve (47).

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