CN-122003561-A - Closed loop net positive suction pressure control for cryogenic liquid pump

Abstract

Systems and methods for reducing cavitation of a pump in a liquid delivery system including the pump and a liquid storage tank. More specifically, a system and method for maintaining and adjusting a Net Positive Suction Pressure (NPSP) is provided to a pump.

Inventors

• J. Stephen
• P. Drube
• L. GASPERIN

Assignees

• 查特股份有限公司

Dates

Publication Date

20260508

Application Date

20240808

Priority Date

20230809

Claims (20)

1. 1. A cryogenic liquid transfer system comprising: a tank configured to hold a cryogenic liquid; a pump in fluid communication with the reservoir, wherein the pump is configured to pump liquid out of the reservoir; A temperature sensor and a pressure sensor configured to measure the temperature and pressure of the cryogenic liquid upstream of the pump; a boost circuit including a boost valve, and A controller, wherein the controller is configured to: the net positive suction pressure provided to the pump is determined based on measurements from the temperature sensor and the pressure sensor, and the determined net positive suction pressure is adjusted by operating the pressure increasing valve to provide a target net positive suction pressure to the pump.
2. 2. The liquid delivery system of claim 1, wherein the controller is configured to open the pressurization valve to increase the net positive suction pressure provided to the pump.
3. 3. The liquid delivery system of claim 1, wherein the controller is configured to close the pressurization valve to reduce or maintain the net positive suction pressure provided to the pump.
4. 4. The liquid delivery system of claim 1, wherein the controller is configured to store the target net positive suction pressure.
5. 5. The liquid delivery system of claim 1, wherein the pump includes an outlet in fluid communication with a discharge line.
6. 6. The liquid delivery system of claim 1, wherein the pump is a centrifugal pump.
7. 7. The liquid delivery system of claim 1, wherein the pump is a reciprocating pump.
8. 8. The liquid delivery system of claim 1, wherein the pressurization circuit is in direct fluid communication with the storage tank.
9. 9. The liquid delivery system of claim 8, wherein the boost circuit comprises an inlet line in fluid communication with the tank and configured to receive liquid from the tank, wherein the inlet line comprises the boost circuit valve, a boost coil in fluid communication with the inlet line downstream of the valve, and an outlet line in direct fluid communication with the boost coil and configured to return vapor flow to a headspace of the tank.
10. 10. The liquid delivery system of claim 8, wherein the temperature sensor and the pressure sensor are located near or at an inlet of the pump.
11. 11. The liquid delivery system of claim 1, wherein the pump is submerged in the cryogenic liquid in the sump.
12. 12. The liquid delivery system of claim 11, wherein the sump comprises a liquid supply line in direct fluid communication with the reservoir and a vapor return line in direct fluid communication with the reservoir.
13. 13. The liquid delivery system of claim 11, wherein the sump is filled with liquid from the reservoir.
14. 14. The liquid delivery system of claim 11, wherein the temperature sensor and the pressure sensor are associated with the sump and are configured to measure the temperature and pressure of the cryogenic liquid within the sump.
15. 15. The liquid delivery system of claim 11, wherein the pressurization circuit comprises a pressurization line including the pressurization valve, the pressurization line being in direct flow communication with the sump and high pressure tank.
16. 16. The liquid delivery system of claim 15, wherein the high pressure reservoir contains a high pressure fluid.
17. 17. The liquid delivery system of claim 16, wherein the high pressure tank is in direct flow communication with the pump and is filled with cryogenic liquid from the pump.
18. 18. The liquid delivery system of claim 17, wherein the drain line comprises a drain valve, and the controller is configured to close the drain valve to direct pumped cryogenic liquid from the pump to the high pressure tank.
19. 19. The liquid delivery system of claim 16, wherein the high pressure tank is filled with high pressure fluid from an external high pressure fluid source.
20. 20. The liquid delivery system of claim 11, further comprising a liquid isolation valve in the liquid supply line and a vapor isolation valve in the vapor return line, and wherein the controller is further configured to operate the liquid isolation valve and the vapor isolation valve.

Description

Closed loop net positive suction pressure control for cryogenic liquid pump Priority claim The application claims the benefit of U.S. provisional application No.63/518,470, filed 8/9 at 2023, the contents of which are incorporated herein by reference. Technical Field The present disclosure relates to systems and methods for preventing cavitation (cavitation) of a liquid in a pump in a liquid delivery system. More specifically, the present disclosure relates to closed loop systems and methods for maintaining and/or adjusting a Net Positive Suction Pressure (NPSP) provided to a pump in a cryogenic liquid delivery system. Background When operating a cryogenic pump, whether a centrifugal or reciprocating pump, a certain amount of Net Positive Suction Head (NPSH) is required to ensure that the pump does not cause the liquid to boil as it enters the pump. This is sometimes referred to as cavitation or "loss of perfusion". If NPSH is listed in pressure units rather than head height, it is referred to as Net Positive Suction Pressure (NPSP). NPSP is the amount of pressure above the saturation pressure of the liquid at a given temperature. The standard industry practice for pump manufacturers is to specify on their data sheet what NPSP is needed for the pump to operate without cavitation. In this case, the abbreviation may be changed to NPSHr or NPSPr, where r represents "required". In some pump applications, simply satisfying NPSPr may not be sufficient to achieve the desired result. Some refrigerants, particularly liquid hydrogen (LH 2), are more susceptible to the NPSPr problem. In these cases, the pump flow rate may increase as NPSP increases beyond the minimum required level. Without the method of controlling NPSP, the pump results may change dramatically and be unpredictable, which may interfere with downstream processes or customers. Another related problem is that the traditional method of adding NPSP to the pump to prevent cavitation is to pressurize the tank that is fed to the pump. This is accomplished by taking a small amount of the liquid stored in the tank and passing it through a heater (typically an ambient air heat exchanger or vaporizer) and returning the warmed fluid (now vapor) to the headspace of the liquid collection tank. This increases the pressure of the tank, as shown in the phase diagram of fig. 1, while not warming much of the liquid so that it is no longer on the saturation curve. One problem with this is that the extra heat added to build up pressure in the tank will eventually be transferred through the fluid and cause the liquid to warm up faster than normal. This results in the liquid eventually returning to the saturation curve, but at a higher pressure than before. In many processes, this may require venting the tank to return it to the desired pressure, wasting some of the stored fluid in the process. Therefore, if pressure build-up is to be performed, it is desirable to limit it to only the pressure build-up required. Accordingly, there is a need for improved methods and systems for control NPSP. Disclosure of Invention There are several aspects of the present subject matter, which may be embodied separately or together in the methods, apparatus, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein and the description of these aspects together is not intended to exclude the use of these aspects alone or the claims in various combinations as recited in the claims appended hereto. In one aspect, a cryogenic liquid transfer system includes a tank configured to hold a cryogenic liquid. A pump is in fluid communication with the tank and is configured to pump the liquid out of the tank. The temperature sensor and the pressure sensor are configured to measure the temperature and pressure of the cryogenic liquid upstream of the pump. The pressurization circuit includes a pressurization (pressurization-pressurization) valve. The controller is configured to determine a net positive suction pressure provided to the pump based on measurements from the temperature sensor and the pressure sensor, and adjust the determined net positive suction pressure by manipulating the pressure increasing valve to provide a target net positive suction pressure to the pump. In another aspect, a method for preventing cavitation in a cryogenic liquid delivery system that includes a storage tank and a pump includes determining a net positive suction pressure provided to the pump by measuring a temperature and a pressure of the cryogenic liquid upstream of the pump and adjusting the net positive suction pressure to a target net positive suction pressure based on the measured temperature and pressure. Drawings Fig. 1 is a phase diagram illustrating the generation of NPSP for a pump by directing vapor to the headspace of a tank for supplying liquid to the pump. Fig. 2 is a schematic diagram of a first embodiment of a clo