CN115751180A - Method and system for detecting, regulating and controlling net positive pressure head of LNG immersed pump - Google Patents
Method and system for detecting, regulating and controlling net positive pressure head of LNG immersed pump Download PDFInfo
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- CN115751180A CN115751180A CN202211421268.3A CN202211421268A CN115751180A CN 115751180 A CN115751180 A CN 115751180A CN 202211421268 A CN202211421268 A CN 202211421268A CN 115751180 A CN115751180 A CN 115751180A
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Abstract
The invention provides a net positive pressure head detection regulation and control method and system of an LNG immersed pump, wherein the regulation and control method comprises the following steps: after the liquid source components of the gas station are stable, measuring an LNG saturation temperature-pressure curve; obtaining the net positive pressure head P required by the normal operation of the immersed pump N (ii) a After precooling of the LNG immersed pump is completed, acquiring real-time temperature of a pump inlet and real-time pressure P in the immersed pump tank before starting the pump Fruit of Chinese wolfberry Obtaining the saturation pressure P at the saturation temperature according to the saturation temperature-pressure curve Full of (ii) a Obtaining a real-time net positive head of LNG: p Fruit of N ＝P Fruit of Chinese wolfberry ‑P Full of (ii) a Judgment of P N And P Fruit of N The size relationship of (1): if P N shi > P N When the LNG immersed pump runs, the required net positive pressure head is enough; if P N is less than or equal to P N And meanwhile, the clean positive pressure head required by the operation of the LNG immersed pump is insufficient. The invention detects and adjusts the net positive pressure head of the LNG immersed pump, so that the net positive pressure head always accurately meets the working requirement, cavitation is prevented, the immersed pump is protected, the service life of the immersed pump is prolonged, and the LNG immersed pump is liftedThe filling efficiency is improved.
Description
Technical Field
The invention belongs to the technical field of filling devices of marine and vehicular LNG filling stations, and particularly relates to a method and a system for detecting and regulating a net positive pressure head of an LNG immersed pump.
Background
An LNG (liquefied natural Gas) station takes an LNG immersed pump as a pressurizing device, pressurizes LNG with the pressure of 0-1.2MPa in an LNG storage tank to the maximum pressure of 1.6MPa, and fills the LNG to an LNG fuel vehicle after being metered by an LNG dispenser.
When LNG is stored in a closed insulated container, it is usually present as a boiling liquid and is in a temperature-pressure equilibrium state, and when the LNG pressure drops below the boiling point pressure or the LNG absorbs heat from the outside, a certain amount of the liquid is vaporized into a gas (LNG flash), and the temperature of the liquid is reduced to its boiling point at that pressure until a new equilibrium is established. When the LNG pressure rises above the boiling point pressure or lower temperature LNG is replenished from the outside, vaporization of LNG is suppressed and liquefaction of BOG (boil Off Gas, boil Off Gas of LNG) is promoted until a new equilibrium is formed.
The LNG gas station adopts the immersed pump as LNG transport pressure equipment, and the immersed pump is a centrifugal pump, and when the centrifugal pump works, a certain pressure drop is generated at the inlet of the impeller due to the suction force of the pump, and LNG is locally evaporated to generate cavitation. In order to avoid cavitation, the LNG at the suction inlet needs to have a certain net positive head when the pump is operating to prevent the pressure from dropping below the boiling point pressure to generate flash vapor, thereby causing cavitation.
When the immersed pump of the existing LNG gas station runs, whether cavitation occurs is judged according to the phenomenon in running in control, and the pump is stopped to protect the pump after the cavitation occurs, and the pump is damaged more or less. In addition, due to the difference of gas sources, the LNG components of the gas station have large differences, and before operation, whether the net positive pressure head required by the immersed pump is enough or not is difficult to judge, and the net positive pressure head can only be judged according to long-term accumulated experience of operators, so that large errors can occur.
Disclosure of Invention
The invention aims to solve the technical problems in the prior art and provides a method and a system for detecting and regulating a net positive pressure head of an LNG immersed pump.
According to a first aspect of the invention, the invention provides a method for detecting and regulating net positive pressure head of an LNG immersed pump, which comprises the following steps:
s1, after liquid source components of a gas station are stable, measuring an LNG saturation temperature-pressure curve when LNG in a storage tank reaches 50% -90%;
s2, acquiring a net positive pressure head P required by normal operation of the immersed pump N ；
S3, after precooling of the LNG immersed pump is completed, collecting the real-time temperature of the pump inlet and the real-time pressure P in the immersed pump tank before starting the pump Fruit of Chinese wolfberry Obtaining the saturation pressure P at the saturation temperature according to the saturation temperature-pressure curve obtained in the step S1 Full of food ；
S4, obtaining a real-time net positive pressure head of the LNG: p is Fruit of N ＝P Fruit of Chinese wolfberry -P Full of ；
S5, judging P N And P Fruit of N The size relationship of (1):
if P "N Shi > P N When the LNG immersed pump needs enough net positive pressure head, the immersed pump can run and exit;
if P N is less than or equal to P N And (3) when the clean positive pressure head required by the operation of the LNG immersed pump is insufficient and the immersed pump cannot operate, starting a pressurization program by the system, and returning to the step S3 until the requirement of the clean positive pressure head is met.
The method and the device detect and adjust the net positive pressure head of the LNG immersed pump, enable the net positive pressure head to accurately meet working requirements all the time, prevent cavitation, protect the immersed pump, prolong the service life of the immersed pump and improve the filling efficiency.
In the prior art, it was determined empirically that the actual net positive head could not be measured. The invention detects the relation between the temperature and the saturation pressure of the natural gas with unknown components, and tests to obtain the real-time net positive pressure head, so that the result is more accurate.
According to a preferred embodiment of the present invention, the method for determining the saturation temperature-pressure curve of the LNG comprises:
conveying LNG in an LNG storage tank through an immersed pump, then sending the LNG into a liquid inlet at the top of the LNG storage tank, operating for t1 time, standing for t2 time, wherein t1 is less than t2, and collecting the temperature and pressure of the LNG in the storage tank through a temperature transmitter and a pressure transmitter;
adjusting saturation pressure of a storage tank, operating at a low speed by using an immersed pump, wherein the low-speed operation frequency is not more than 30Hz, conveying LNG in the storage tank to an LNG vaporizer for heating, then feeding liquid from the bottom of the storage tank into the LNG storage tank for heating the LNG, and collecting the pressure of the storage tank once when the temperature rises by 1 ℃ in the heating process until the pressure of the storage tank reaches 0.8 MPa;
and (4) putting the collected temperature and pressure data of the storage tank into a controller for immersed pump control, and calculating other parameters which are not collected by adopting an interpolation method.
The invention detects the relation between the temperature and the saturation pressure of the natural gas with unknown components, and obtains a real-time net positive pressure head through testing, thereby obtaining a more accurate result.
According to a second aspect of the present invention, the present invention provides a system for detecting and regulating a net positive pressure head of an LNG immersed pump, wherein a temperature transmitter and a pressure transmitter are arranged in an LNG storage tank, the LNG immersed pump is arranged on an external pipeline of the LNG storage tank, the temperature transmitter and the pressure transmitter collect a temperature signal and a pressure signal in the LNG storage tank and transmit the temperature signal and the pressure signal to a controller, the controller performs LNG saturation temperature-pressure curve measurement, and the method for detecting and regulating a net positive pressure head of the LNG immersed pump according to claim 1 is used for detecting and regulating a net positive pressure head.
The method and the device detect and adjust the net positive pressure head of the LNG immersed pump, enable the net positive pressure head to accurately meet working requirements all the time, prevent cavitation, protect the immersed pump, prolong the service life of the immersed pump and improve the filling efficiency.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Detailed Description
The following detailed description of embodiments of the invention is intended to be illustrative, and is not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "vertical", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present invention.
In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "mounted," "connected," and "connected" are to be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, a communication between two elements, a direct connection, or an indirect connection through an intermediate medium, and those skilled in the art will understand the specific meaning of the terms as they are used in the specific case.
The invention provides a net positive pressure head detection regulation and control method of an LNG immersed pump, which comprises the following steps:
s1, after liquid source components of a gas station are stable, unloading a vehicle of liquid with saturation pressure close to 0 (gauge pressure), and measuring an LNG saturation temperature-pressure curve when LNG in a storage tank reaches 50% -90% (preferably 80% -90%), wherein a specific gas source is stable as a default when the gas source is from the same factory;
s2, acquiring a net positive pressure head P required by normal operation of the immersed pump N ；
S3, after precooling of the LNG immersed pump is completed, collecting the real-time temperature of the pump inlet and the real-time pressure P in the immersed pump tank before starting the pump Fruit of Chinese wolfberry Obtaining the saturation pressure P at the saturation temperature according to the saturation temperature-pressure curve obtained in the step S1 Full of ；
S4, obtaining a real-time net positive pressure head of the LNG: p Fruit of N ＝P Fruit of Chinese wolfberry -P Full of ；
S5, judging P N And P Fruit of N The size relationship of (1):
if P "N Shi > P N When the LNG immersed pump needs enough net positive pressure head for operation, the immersed pump can operate and exit;
if P N is less than or equal to P N And (3) when the clean positive pressure head required by the operation of the LNG immersed pump is insufficient and the immersed pump cannot operate, starting a pressurization program by the system, and returning to the step S3 until the requirement of the clean positive pressure head is met.
In the present embodiment, the method for measuring the LNG saturation temperature-pressure curve includes:
delivering LNG in the LNG storage tank into a liquid inlet at the top of the LNG storage tank after the LNG storage tank is delivered by an immersed pump, standing for t2 time after t1 time, wherein t1 is less than t2, preferably t1 is 2 minutes, and t2 is 30 minutes. The LNG temperature and pressure in the storage tank are collected through the temperature transmitter and the pressure transmitter.
Adjusting saturation pressure of a storage tank, operating at a low speed by using an immersed pump, wherein the low-speed operating frequency is not more than 30Hz, conveying LNG in the storage tank to an LNG vaporizer for heating, then feeding the LNG into an LNG storage tank through liquid inlet at the bottom of the storage tank to heat the LNG, and collecting the pressure of the storage tank once when the temperature rises by 1 ℃ in the heating process until the pressure of the storage tank reaches an operating pressure threshold value (such as 0.8 MPa) of the storage tank. As the pressure of the storage tank is actually in the range of 0-1.2MPa, the pressure is generally maintained between 0.1-0.8MPa during operation, and if the pressure exceeds 0.1-0.8MPa, an approximate value can be obtained by a curve fitting mode.
And (4) putting the collected temperature and pressure data of the storage tank into a controller for immersed pump control, and calculating other parameters which are not collected by adopting an interpolation method.
The invention also provides a system for detecting, regulating and controlling the net positive pressure head of the LNG immersed pump, wherein a temperature transmitter and a pressure transmitter are arranged in the LNG storage tank, the LNG immersed pump is arranged on an external pipeline of the LNG storage tank, the temperature transmitter and the pressure transmitter collect temperature signals and pressure signals in the LNG storage tank and transmit the temperature signals and the pressure signals to the controller, the controller measures an LNG saturated temperature-pressure curve, and the method for detecting, regulating and controlling the net positive pressure head of the LNG immersed pump is utilized to detect, regulate and control the net positive pressure head of the LNG immersed pump.
In the description herein, reference to the description of the terms "preferred embodiment," "one embodiment," "some embodiments," "an example," "a specific example" or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims (4)
1. A net positive pressure head detection regulation and control method of an LNG immersed pump is characterized by comprising the following steps:
s1, after liquid source components of a gas station are stable, measuring an LNG saturation temperature-pressure curve when LNG in a storage tank reaches 50% -90%;
s2, acquiring a net positive pressure head P required by normal operation of the immersed pump N ；
S3, after precooling of the LNG immersed pump is completed, collecting the real-time temperature of the pump inlet and the real-time pressure P in the immersed pump tank before starting the pump Fruit of Chinese wolfberry Obtaining the saturation pressure P at the saturation temperature according to the saturation temperature-pressure curve obtained in the step S1 Full of ；
S4, obtaining a real-time net positive pressure head of the LNG: p Fruit of N ＝P Fruit of Chinese wolfberry -P Full of ；
S5, judging P N And P Fruit of N The size relationship of (1):
if P N shi > P N When the LNG immersed pump needs enough net positive pressure head for operation, the immersed pump can operate and exit;
if P N is less than or equal to P N And (3) when the clean positive pressure head required by the operation of the LNG immersed pump is insufficient and the immersed pump cannot operate, starting a pressurization program by the system, and returning to the step S3 until the requirement of the clean positive pressure head is met.
2. The method for detecting, regulating and controlling the net positive pressure head of the LNG immersed pump according to claim 1, wherein the method for measuring the LNG saturation temperature-pressure curve comprises the following steps:
conveying LNG in an LNG storage tank through an immersed pump, then sending the LNG into a liquid inlet at the top of the LNG storage tank, operating for t1 time, standing for t2 time, wherein t1 is less than t2, and collecting the temperature and pressure of the LNG in the storage tank through a temperature transmitter and a pressure transmitter;
adjusting saturation pressure of a storage tank, operating at a low speed by using an immersed pump, wherein the low-speed operation frequency is not more than 30Hz, conveying LNG in the storage tank to an LNG vaporizer for heating, then feeding liquid from the bottom of the storage tank into the LNG storage tank for heating the LNG, and collecting the pressure of the storage tank once when the temperature rises by 1 ℃ in the heating process until the pressure of the storage tank reaches the operation pressure threshold of the storage tank;
and (4) putting the collected temperature and pressure data of the storage tank into a controller for immersed pump control, and calculating other parameters which are not collected by adopting an interpolation method.
3. The method for detecting and controlling the net positive head of the LNG immersed pump according to claim 2, wherein t1 is 2 minutes, and t2 is 30 minutes.
4. A net positive pressure head detection regulation and control system of an LNG immersed pump is characterized in that a temperature transmitter and a pressure transmitter are arranged in an LNG storage tank, the LNG immersed pump is arranged on an external pipeline of the LNG storage tank, the temperature transmitter and the pressure transmitter collect temperature signals and pressure signals in the LNG storage tank and transmit the temperature signals and the pressure signals to a controller, the controller carries out LNG saturation temperature-pressure curve determination, and the net positive pressure head detection regulation and control method of claim 1 is utilized to carry out detection regulation and control on the net positive pressure head of the LNG immersed pump.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211421268.3A CN115751180A (en) | 2022-11-14 | 2022-11-14 | Method and system for detecting, regulating and controlling net positive pressure head of LNG immersed pump |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211421268.3A CN115751180A (en) | 2022-11-14 | 2022-11-14 | Method and system for detecting, regulating and controlling net positive pressure head of LNG immersed pump |
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| Publication Number | Publication Date |
|---|---|
| CN115751180A true CN115751180A (en) | 2023-03-07 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211421268.3A Pending CN115751180A (en) | 2022-11-14 | 2022-11-14 | Method and system for detecting, regulating and controlling net positive pressure head of LNG immersed pump |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115751180A (en) |
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2022
- 2022-11-14 CN CN202211421268.3A patent/CN115751180A/en active Pending
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