CN107514541B - Floating liquefied natural gas storage and gasification device, control system and control method - Google Patents

Floating liquefied natural gas storage and gasification device, control system and control method Download PDF

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Publication number
CN107514541B
CN107514541B CN201710878057.5A CN201710878057A CN107514541B CN 107514541 B CN107514541 B CN 107514541B CN 201710878057 A CN201710878057 A CN 201710878057A CN 107514541 B CN107514541 B CN 107514541B
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pressure
medium
pressure area
tank
low
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CN107514541A (en
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庞维龙
侯晓羽
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Beijing Gte Global Combustion Gas Equipment Technology Co ltd
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Beijing Gte Global Combustion Gas Equipment Technology Co ltd
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Priority to PCT/CN2018/114233 priority patent/WO2019063025A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C13/00—Details of vessels or of the filling or discharging of vessels
    • F17C13/002—Details of vessels or of the filling or discharging of vessels for vessels under pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C13/00—Details of vessels or of the filling or discharging of vessels
    • F17C13/02—Special adaptations of indicating, measuring, or monitoring equipment
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C13/00—Details of vessels or of the filling or discharging of vessels
    • F17C13/02—Special adaptations of indicating, measuring, or monitoring equipment
    • F17C13/025—Special adaptations of indicating, measuring, or monitoring equipment having the pressure as the parameter
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C13/00—Details of vessels or of the filling or discharging of vessels
    • F17C13/04—Arrangement or mounting of valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C7/00—Methods or apparatus for discharging liquefied, solidified, or compressed gases from pressure vessels, not covered by another subclass
    • F17C7/02—Discharging liquefied gases
    • F17C7/04—Discharging liquefied gases with change of state, e.g. vaporisation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2205/00—Vessel construction, in particular mounting arrangements, attachments or identifications means
    • F17C2205/03—Fluid connections, filters, valves, closure means or other attachments
    • F17C2205/0302—Fittings, valves, filters, or components in connection with the gas storage device
    • F17C2205/0323—Valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2205/00—Vessel construction, in particular mounting arrangements, attachments or identifications means
    • F17C2205/03—Fluid connections, filters, valves, closure means or other attachments
    • F17C2205/0302—Fittings, valves, filters, or components in connection with the gas storage device
    • F17C2205/0323—Valves
    • F17C2205/0332—Safety valves or pressure relief valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2221/00—Handled fluid, in particular type of fluid
    • F17C2221/03—Mixtures
    • F17C2221/032—Hydrocarbons
    • F17C2221/033—Methane, e.g. natural gas, CNG, LNG, GNL, GNC, PLNG
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
    • F17C2223/01—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the phase
    • F17C2223/0146—Two-phase
    • F17C2223/0153—Liquefied gas, e.g. LPG, GPL
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2225/00—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel
    • F17C2225/01—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel characterised by the phase
    • F17C2225/0107—Single phase
    • F17C2225/0123—Single phase gaseous, e.g. CNG, GNC
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/01—Propulsion of the fluid
    • F17C2227/0121—Propulsion of the fluid by gravity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/01—Propulsion of the fluid
    • F17C2227/0128—Propulsion of the fluid with pumps or compressors
    • F17C2227/0135—Pumps
    • F17C2227/0142—Pumps with specified pump type, e.g. piston or impulsive type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/04—Methods for emptying or filling
    • F17C2227/043—Methods for emptying or filling by pressure cascade
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2250/00—Accessories; Control means; Indicating, measuring or monitoring of parameters
    • F17C2250/03—Control means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2250/00—Accessories; Control means; Indicating, measuring or monitoring of parameters
    • F17C2250/04—Indicating or measuring of parameters as input values
    • F17C2250/0404—Parameters indicated or measured
    • F17C2250/043—Pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2270/00—Applications
    • F17C2270/01—Applications for fluid transport or storage
    • F17C2270/0102—Applications for fluid transport or storage on or in the water
    • F17C2270/0105—Ships

Abstract

The invention belongs to the technical field of LNG storage and gasification, and relates to a floating storage and gasification device for continuously and uninterruptedly providing natural gas fuel for port natural gas users and power plants. The floating liquefied natural gas storage and gasification device has the advantages of convenient parking, low manufacturing cost, continuous gas supply, simple control and the like.

Description

Floating liquefied natural gas storage and gasification device, control system and control method
Technical Field
The invention belongs to the technical field of LNG storage, transportation and gasification, and particularly relates to a floating storage and gasification device for continuously and uninterruptedly providing natural gas fuel for port natural gas users and power plants, and a control system and a control method of the storage and gasification device.
Background
LNG is an abbreviation for liquefied natural gas (Liquefied Natural Gas), the main component of which is methane. LNG is cooled to-162 ℃ by gaseous natural gas under normal pressure, so that the LNG is condensed into liquid, and after the natural gas is liquefied, the storage and transportation space can be greatly saved, and the LNG has the characteristics of large heat value, high performance and the like.
LNG is a clean and efficient energy source, and LNG is listed as the preferred fuel in many countries, and the proportion of natural gas in the energy supply is rapidly increasing, so that LNG will become a hot energy commodity for the next global competition after petroleum.
The waterway transportation of LNG can greatly reduce the transportation cost, however, the existing LNG transportation ship has large tonnage, can only enter various ports, can not stop at the coast at a short distance, and can not be directly docked and matched with a user. The existing LNG storage device needs to occupy a certain land, and has the problems of long construction period, poor mobility, high land use cost and the like in practical application.
Disclosure of Invention
In view of the above, the invention aims to provide a floating liquefied natural gas storage and gasification device, a control system and a control method, which are used for solving the problems of land occupation, long construction period, poor mobility, higher energy cost and the like when the existing users and power plants use LNG.
In order to achieve the above purpose, the technical scheme of the invention is realized as follows:
the floating liquefied natural gas storage and gasification device comprises a ship body, wherein at least one medium-pressure area storage tank is arranged on the ship body, and the medium-pressure area storage tank is sequentially connected with a low-pressure area buffer tank, a submersible pump tank and an LNG gasification device;
the liquid outlet of the medium-pressure area storage tank is positioned at the top of the tank body, the liquid outlet of the low-pressure area buffer tank is positioned at the bottom of the LNG, one end of the liquid output pipeline extends from the liquid outlet of the medium-pressure area storage tank to the bottom of the LNG, and the other end of the liquid output pipeline is connected with the low-pressure area buffer tank;
the medium-pressure area storage tank and the low-pressure area buffer tank are internally provided with air supplementing pipes, the working air pressure in the tank body is controlled through the air supplementing pipes, the lower limit of the working air pressure of the medium-pressure area storage tank is higher than the upper limit of the working air pressure of the low-pressure area buffer tank, and the medium-pressure area storage tank provides continuous LNG for the low-pressure area buffer tank through the pressure difference of the working air pressure;
the bottom of the buffer tank in the low pressure area is connected with a liquid inlet of the immersed pump box through a liquid output pipeline, a cavity of the buffer tank in the low pressure area is communicated with the cavity of the immersed pump box through a ventilation pipeline, the ventilation pipeline enables the working air pressure of the buffer tank in the low pressure area to be always the same as the working air pressure of the immersed pump box, and LNG flowing into the buffer tank in the low pressure area continuously flows into the immersed pump box;
the immersed pump tank provides continuous LNG to the LNG gasification device through the immersed pump, and the LNG gasification device provides continuous high-pressure gaseous natural gas to the gas utilization equipment.
Further, the medium-pressure area storage tank is a vacuum double-layer liquid storage tank or a single-layer pressure-bearing liquid storage tank, and the low-pressure area buffer tank is a vacuum double-layer buffer tank or a single-layer pressure-bearing buffer tank.
Further, the outer tank body of the vacuum double-layer liquid storage tank is made of carbon steel, and the inner tank body of the vacuum double-layer liquid storage tank is made of stainless steel; the tank body of the single-layer pressure-bearing liquid storage tank is made of stainless steel, the periphery of the tank body is wound with heat-insulating materials, and the tank body of the single-layer pressure-bearing buffer tank is made of stainless steel, and the periphery of the tank body is wound with heat-insulating materials; the outer layer tank body of the vacuum double-layer buffer tank is made of stainless steel, and the inner layer tank body of the vacuum double-layer buffer tank is made of stainless steel.
Further, the vacuum double-layer liquid storage tank, the vacuum double-layer buffer tank, the single-layer pressure-bearing liquid storage tank and the single-layer pressure-bearing buffer tank are all C-shaped storage tanks.
Further, at least two medium-pressure area storage tanks are arranged on the ship body, liquid inlets of the medium-pressure area storage tanks are positioned at the top of the tank body, each medium-pressure area storage tank is connected with a total liquid inlet in parallel through a liquid input pipeline, the total liquid inlet provides LNG for the medium-pressure area storage tanks through the liquid input pipeline, and each medium-pressure area storage tank is connected with a low-pressure area buffer tank in parallel through a liquid output pipeline.
Further, the liquid input pipeline is a steel pipe or a hose, and the liquid output pipeline is a steel pipe or a hose.
Further, an upper liquid inlet spray header is arranged on a liquid inlet of the medium-pressure area storage tank.
Further, a first switch valve for controlling whether the medium-pressure area storage tank supplies liquid to the low-pressure area buffer tank or not is arranged at the liquid outlet of each medium-pressure area storage tank; a second switch valve for controlling whether the total liquid inlet supplies liquid to the medium-pressure area storage tank is arranged at the liquid inlet of each medium-pressure area storage tank; the air compensating pipe of each medium-pressure area storage tank is provided with a medium-pressure air compensating valve, and the air compensating pipe of the low-pressure area buffer tank is provided with a low-pressure air compensating valve.
Further, the middle pressure area storage tank and the low pressure area buffer tank are internally provided with air pressure detectors.
Furthermore, a safety relief valve is also arranged in the medium-pressure area storage tank and the low-pressure area buffer tank.
The control system of the floating liquefied natural gas storage and gasification device comprises a switch control unit, a gas pressure detection unit and a processing unit;
the switch control unit comprises a first switch valve for controlling whether each medium-pressure area storage tank supplies liquid to the low-pressure area buffer tank, a second switch valve for controlling whether the total liquid inlet supplies liquid to the medium-pressure area storage tank, a medium-pressure air compensating valve for controlling the working air pressure in each medium-pressure area storage tank and a low-pressure air compensating valve for controlling the working air pressure in the low-pressure area buffer tank;
the air pressure detection unit comprises air pressure detectors arranged in each medium-pressure area storage tank and each low-pressure area buffer tank, and the air pressure detectors detect working air pressure values in each medium-pressure area storage tank and each low-pressure area buffer tank in real time;
the processing unit comprises a PLC controller for controlling the switching actions of each first switching valve, each second switching valve, each medium-pressure air compensating valve and each low-pressure air compensating valve;
the air pressure detection unit sends the working air pressure value in each medium-pressure area storage tank and the working air pressure value in the low-pressure area buffer tank to the processing unit;
the processing unit selects one medium-pressure area storage tank to be communicated with the low-pressure area buffer tank by controlling the first switch valve, and the processing unit controls the working air pressure P1 of the medium-pressure area storage tank to be always larger than the working air pressure P2 of the low-pressure area storage tank by the medium-pressure air compensating valve of the selected medium-pressure area storage tank.
Further, the processing unit controls the working air pressure P1 in the medium-pressure zone storage tank to be kept within the working air pressure range: pa < P1< Pb; pa is the lower limit of working gas of the medium-pressure area storage tank, when P1 is lower than Pa, the medium-pressure air compensating valve is opened, and the air compensating pipe supplements gas into the medium-pressure area storage tank; pb is the upper limit of the working gas of the medium-pressure area storage tank, and when P1 is higher than Pb, the medium-pressure gas supplementing valve is closed, and the gas supplementing pipe stops supplementing gas.
Further, the working air pressure P2 of the low-pressure zone buffer tank is maintained within the working air pressure range: pc < P2< Pd; pc is the lower limit of working gas of the buffer tank in the low-pressure area, when P2 is lower than Pc, the low-pressure air supplementing valve is opened, and the air supplementing pipe supplements gas into the buffer tank in the low-pressure area; pd is the upper limit of the working gas of the buffer tank in the low pressure area, and when P2 is higher than Pd, the low pressure gas supplementing valve is closed, and the gas supplementing pipe stops supplementing gas.
Further, the medium-pressure air compensating valve and the low-pressure air compensating valve are pneumatic switch valves.
Further, the first switch valve, the second switch valve, the medium-pressure air compensating valve and the low-pressure air compensating valve are normally closed switch valves.
Further, the processing unit further comprises a wireless communication module, the processing unit is connected with a remote server through the wireless communication module, the remote server is connected with an intelligent terminal, the intelligent terminal obtains data in the processing unit through the remote server and the wireless communication module, and the intelligent terminal controls the switching action of the switching control unit through the remote server, the wireless communication module and the processing unit.
A method of controlling a floating lng storage and gasification unit comprising the steps of:
s1, connecting an LNG transport ship with a general liquid inlet of a ship body, connecting a high-pressure natural gas outlet of the ship body with gas equipment, sequentially opening a second switching valve by a processing unit to input LNG into storage tanks in each medium-pressure area, and controlling the working air pressure P1 of the storage tanks in the medium-pressure area to be within the range: the working air pressure P2 range of the Pa-Pb buffer tank in the low pressure area is as follows: pc-Pd, wherein Pb > Pa > Pd > Pc;
s2, the processing unit selects one medium-pressure area storage tank as a working storage tank by controlling the switching action of each first switching valve, and LNG flows into a low-pressure area buffer tank from the working storage tank under the action of working air pressure difference;
s3, enabling the working air pressure of the buffer tank in the low-pressure area to be always the same as the working air pressure of the immersed pump tank through the ventilation pipeline, and enabling LNG flowing into the buffer tank in the low-pressure area to continuously flow into the immersed pump tank;
s4, continuously conveying LNG in the immersed pump box into the LNG gasification device by the immersed pump;
s5, continuously providing high-pressure gaseous natural gas to gas utilization equipment by the LNG gasification device;
s6, when the working air pressure P1 of the working storage tank is lower than Pa, the medium-pressure air compensating valve is opened, the air compensating pipe supplements air into the storage tank in the medium-pressure area, and when the working air pressure P1 of the storage tank in the medium-pressure area is higher than Pb, the medium-pressure air compensating valve is closed, and the air compensating pipe stops air compensating;
when the working air pressure P2 of the low-pressure area buffer tank is lower than Pc, the low-pressure air compensating valve is opened, the air compensating pipe supplements air into the low-pressure area buffer tank, and when the working air pressure P2 of the low-pressure area buffer tank is higher than Pd, the low-pressure air compensating valve is closed, and the air compensating pipe stops air compensating.
Further, step S7 is further included, wherein the processing unit closes the first switch valves of the working storage tanks, and the processing unit selects another medium-pressure storage tank as a new working storage tank by controlling the switching actions of the first switch valves.
Further, the processing unit selects the working storage tank in the following manner: the first on-off valve of the target intermediate-pressure zone storage tank is opened and the first on-off valves of the remaining intermediate-pressure zone storage tanks are closed.
Compared with the prior art, the floating liquefied natural gas storage and gasification device, the control system and the control method have the following advantages:
(1) According to the floating liquefied natural gas storage and gasification device, the plurality of medium-pressure area storage tanks are arranged on the ship, the medium-pressure area storage tanks are vacuum double-layer liquid storage tanks, the design is reasonable, the ship body can be stopped at the bank side with smaller water depth, the draft is at least 3-4 meters, the floating liquefied natural gas storage and gasification device is convenient to dock with users and power plants, the problem that large-scale transport ships can only be stopped at deep water areas such as ports is solved, and the problem that the natural gas storage and gasification device needs to occupy land is avoided;
in order to meet the requirements of industry standard IGC, a liquid outlet of a liquid storage tank is required to be positioned at the upper part, and in order to continuously supply liquid to a submerged pump tank by the liquid storage tank with the liquid outlet positioned at the upper part, a vacuum double-layer buffer tank is arranged, and the tank body of the vacuum double-layer buffer tank is smaller, so that the cost control of the whole equipment is reasonable, the continuous liquid supply of the equipment to the submerged pump tank and an LNG gasification device is realized by the vacuum double-layer buffer tank, and further, the continuous high-pressure gaseous natural gas is provided for users or power plants;
the adoption of the upper liquid inlet spraying mode can reduce the generation of a medium-pressure area storage tank BOG (Boil Off Gas) and increase the storage time of LNG;
the external immersed pump has low manufacturing, installation and maintenance cost, low power consumption and stable operation; the C-shaped storage tank is convenient to manufacture, durable and good in heat preservation.
(2) The control system of the floating liquefied natural gas storage and gasification device can control the air pressure of each medium-pressure area storage tank and each low-pressure area buffer tank and the flow of LNG through each switch valve and each air compensating valve, and has the advantages of convenient control and realization of remote control and automatic control.
(3) The control method of the floating liquefied natural gas storage and gasification device can realize that the floating liquefied natural gas storage and regasification system provides continuous high-pressure gaseous natural gas for users and power plants.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute an undue limitation on the invention. In the drawings:
FIG. 1 is a schematic diagram of a floating liquefied natural gas storage and gasification unit according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the pressure zoning of a floating lng storage and gasification unit according to an embodiment of the present invention.
Reference numerals illustrate:
10-a medium-pressure area storage tank; 11-a liquid output line; 121-a first switching valve; 122-a second switching valve; 13-upper liquid inlet spray header; 14-a liquid input line; 151-medium pressure air compensating valve; 152-a low pressure air make-up valve; 16-an air supplementing pipe; 17-total liquid inlet; 18-a low pressure zone buffer tank; 19-immersed pump; 20-a submersible pump tank; a 21-LNG vaporization unit; 22-high pressure natural gas outlet; 23-hull; 24-a vent line; 25-safety relief valve.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
In the description of the invention, it should be understood that the terms "center," "longitudinal," "transverse," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships that are based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the invention and simplify the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be configured and operate in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the creation of the present invention can be understood by those of ordinary skill in the art in a specific case.
The invention will be described in detail below with reference to the drawings in connection with embodiments.
The technical problems to be solved by the technical scheme are mainly as follows:
1, the existing LNG transport ship is large in tonnage, can only enter a port, cannot stop at the coast with shallow water depth, cannot be directly connected with gas equipment, needs transfer equipment, and increases the gas cost of natural gas;
2, besides equipment cost, the natural gas transfer equipment needs to occupy land, so that the cost of the natural gas is further increased;
3, the existing equipment such as LNG transport ships, turnover ships and the like is limited and required by industry standards, a vacuum double-layer liquid storage tank or a single-layer pressure-bearing liquid storage tank is needed, and particularly, the vacuum double-layer liquid storage tank loaded on offshore facilities such as ships and the like has specific requirements on a liquid outlet mode of the storage tank:
when the vacuum double-layer liquid storage tank with the inner layer and the outer layer being made of stainless steel is adopted, a liquid discharging mode can be adopted, the liquid discharging mode can utilize the gravity of LNG to realize that the medium-pressure area storage tank 10 provides continuous LNG for the immersed pump tank 20, however, when the inner layer and the outer layer of the vacuum double-layer liquid storage tank are made of stainless steel, the cost of the liquid storage tank is very high, and particularly, the cost is multiplied along with the volume increase of the vacuum double-layer liquid storage tank.
When the vacuum double-layer liquid storage tank with the inner layer made of stainless steel and the outer layer made of carbon steel and other heat-insulating materials is adopted, the cost of the liquid storage tank can be effectively controlled, the cost of the heat-insulating materials such as carbon steel and the like is far lower than that of the stainless steel materials, but according to the requirement of an industry standard IGC, the liquid outlet of the vacuum double-layer liquid storage tank in the form is required to be arranged at the top of the tank body, and LNG needs to be pumped out from the top. How to pump out LNG and continuously supply the LNG vaporization device 21 with liquid is one of the core problems to be solved by the present invention. The industry standard is specifically the IGC requirement (IGC MSC.370 (93) _ the latest version of IGC Code).
In order to provide continuous high-pressure gaseous natural gas for users such as power plants on the coast, the invention provides a floating liquefied natural gas storage and gasification device which does not occupy the land, as shown in figure 1, the system comprises a hull 23, the minimum draft of the hull 23 is between 3 and 4 meters, the hull 23 can conveniently rest on most coasts, the problem that large ships cannot be directly docked with users is solved, the problem that natural gas transfer equipment needs to occupy the land is also solved, and the gas cost of the high-pressure natural gas is greatly reduced;
the ship body 23 is provided with at least one medium-pressure area storage tank 10, the medium-pressure area storage tank 10 is a vacuum double-layer liquid storage tank, the vacuum double-layer liquid storage tank is universal equipment for storing and transporting liquefied natural gas, the manufacturing cost of the large vacuum double-layer liquid storage tank is extremely high, the use cost of the storage tank is reduced by using a plurality of smaller vacuum double-layer liquid storage tanks to store LNG respectively, 4-8 vacuum double-layer liquid storage tanks are arranged on the ship body 23 generally, and the number of the vacuum double-layer liquid storage tanks is not limited by the technical scheme. The ship body 23 is provided with a plurality of vacuum double-layer liquid storage tanks, and the design is reasonable, so that the ship body 23 carrying the vacuum double-layer liquid storage tanks can be stopped at the bank with smaller water depth, and is convenient to dock with a power plant.
The core problem of how to pump LNG out and continuously supply liquid to the LNG vaporizing device 21, which is to be solved by the present technical solution, can be further disassembled into a plurality of continuous small problems, firstly how to pump LNG out continuously from the medium-pressure storage tank 10; second, how the withdrawn LNG is continuously supplied to the LNG vaporization unit; thirdly, when the external immersed pump 19 and the immersed pump tank 20 are adopted, how to ensure the normal operation of the immersed pump 19, namely, the control of the liquid level of the immersed pump tank 20 and the control of the working air pressure of the immersed pump tank 20, if the speed of LNG entering the immersed pump tank 20 is too high, the liquid level of the immersed pump tank 20 rises too fast, the LNG can not flow into the immersed pump tank 20 or the operation of the immersed pump 19 is abnormal, if the speed of the flowing LNG is too slow, the liquid level of the immersed pump tank 20 drops to expose the immersed pump 19, and the immersed pump 19 is damaged, namely, the liquid supply cooperation of the medium-pressure area storage tank 10 and the immersed pump tank 20 is a problem which is difficult to solve; fourth, the cavity in the immersed pump tank 20 is usually required to be communicated with a liquid storage cavity for discharging BOG, if the intermediate pressure area storage tank 10 is matched with the immersed pump tank 20, the proper liquid storage cavity matching is not found in the cavity of the immersed pump tank 20, and if the liquid storage cavity is independently configured, the cost is unnecessarily increased; fifth, a simple and automatic control of LNG liquid flow between the intermediate pressure zone storage tank 10, the low pressure zone buffer tank 18, and the immersed pump tank 20 is achieved.
When the existing large-scale LNG liquid storage tank adopts the upper liquid outlet type, the LNG is pumped out by adopting the immersed pump 19 generally, but because the LNG is light in specific gravity and low in temperature, the immersed pump 19 has very high requirements, the cost of one immersed pump 19 device is often millions, and the control of the gas consumption cost of natural gas is very unfavorable. In particular, in the vacuum double-layer liquid storage tank used in the scheme, carbon steel is used as the outer layer, stainless steel is used as the inner layer, and because the tank body wall is relatively thin, the immersed pump 19, a matched bracket and other devices are difficult to be arranged in the tank, the scheme is not prone to selecting a mode of extracting LNG by the embedded immersed pump 19 from the cost and practical technical point of view.
In the technical scheme, at least one medium-pressure area storage tank 10 is arranged on a ship body 23, and the medium-pressure area storage tank 10 is sequentially connected with a low-pressure area buffer tank 18, a immersed pump tank 20 and an LNG vaporizing device 21; the liquid outlet of the medium-pressure area storage tank 10 is positioned at the top of the tank body, the liquid outlet of the low-pressure area buffer tank 18 is positioned at the bottom of LNG, one end of the liquid output pipeline 11 extends from the liquid outlet of the medium-pressure area storage tank 10 to the bottom of LNG, and the other end of the liquid output pipeline 11 is connected with the low-pressure area buffer tank 18;
in this technical scheme, set up low pressure district buffer tank 18, this low pressure district buffer tank 18 is the double-deck buffer tank of vacuum, and the inside and outside bilayer of vacuum double-deck buffer tank is stainless steel material, in order to control the higher storage tank of this kind of cost, the double-deck buffer tank of vacuum only sets up one, and the double-deck buffer tank volume of vacuum is less, and its cost is lower relatively.
Because certain working air pressure is set in all the vacuum double-layer liquid storage tanks, the vacuum double-layer buffer tank also has certain working air pressure range, and the working air pressure of the vacuum double-layer liquid storage tank is always higher than that of the vacuum double-layer buffer tank, and LNG is conveyed into the vacuum double-layer buffer tank by utilizing pressure difference. The pressure difference is utilized to pump LNG out of the vacuum double-layer liquid storage tank.
After LNG is pumped from the intermediate-pressure tank 10 to the low-pressure buffer tank 18, if the immersed pump 19 is disposed inside the low-pressure buffer tank 18, there are still problems such as cost, maintenance, and repair of the immersed pump 19, and particularly, if the immersed pump 19 is replaced with a problem, it is necessary to stop the continuous supply of LNG, and thus it is necessary to use a separate immersed pump tank 20, that is, to form continuous connection between the intermediate-pressure tank 10, the low-pressure buffer tank 18, and the immersed pump tank 20. The external immersed pump 19 has low manufacturing, installation and maintenance cost, low power consumption and stable operation.
Further, the external immersed pump 19 has a great problem that it is difficult to normally operate and achieve the purpose of continuously supplying LNG in actual operation, and the problems mainly include control of the liquid level of the immersed pump tank 20, control of the working air pressure of the immersed pump tank 20, and discharge of BOG from the immersed pump tank 20, but the series of problems are perfectly solved by providing a vacuum double-layer buffer tank and conducting the vacuum double-layer buffer tank and the hollow cavity of the immersed pump tank 20.
The functions of the vacuum double-layer buffer tank include: 1, pumping LNG forward by matching with a vacuum double-layer liquid storage tank; 2, the liquid outlet of the vacuum double-layer buffer tank is arranged at the bottom of the LNG, so that the conventional gravity-based continuous LNG liquid supply is recovered, and the liquid level and the working air pressure of the immersed pump tank 20 can be simultaneously regulated by the vacuum double-layer buffer tank because the vacuum double-layer buffer tank is communicated with the immersed pump tank 20 through the ventilation pipeline 24. For example, when LNG flows into the vacuum double-layer buffer tank quickly, the liquid level rising speed is relatively slow, and the liquid level rising speed in the immersed pump tank 20 is also relatively slow, which solves the problems that the immersed pump tank 20 is small in volume, very sensitive to the flow rate of LNG and difficult to control; 3, the BOG in the immersed pump tank 20 can be discharged as the vacuum double-layer buffer tank is provided with a safety relief valve 25.
The functions of the vent line 24 include: 1, a vacuum double-layer buffer tank and a immersed pump tank 20 are conducted, so that the vacuum double-layer buffer tank can utilize the dead weight of LNG to realize that the LNG automatically flows into the immersed pump tank 20;2, the three-level pressure is formed between the vacuum double-layer liquid storage tank, the vacuum double-layer buffer tank and the immersed pump tank 20 from high to low, the design method causes the working air pressure range of equipment in each pressure range to be too narrow, the equipment needs to be frequently switched on and switched off, the design cost is high, and the facility loss is large. 3, the BOG in the immersed pump tank 20 can be led out to the vacuum double buffer tank, and the BOG can be discharged by the safety relief valve 25 of the vacuum double buffer tank.
From this point, the complete LNG continuous feed scheme is completed, in a preferred embodiment:
as shown in fig. 2, the floating liquefied natural gas storage and gasification device comprises a ship body 23, wherein at least one vacuum double-layer liquid storage tank is arranged on the ship body 23, each vacuum double-layer liquid storage tank is connected with a vacuum double-layer buffer tank, the vacuum double-layer buffer tank is connected with a immersed pump tank 20, and the immersed pump tank 20 is connected with an LNG gasification device 21; the liquid outlet of the vacuum double-layer liquid storage tank is positioned at the top of the tank body, the liquid outlet of the vacuum double-layer buffer tank is positioned at the bottom of LNG, one end of the liquid output pipeline 11 extends from the liquid outlet of the vacuum double-layer liquid storage tank to the bottom of LNG, and the other end of the liquid output pipeline is connected with the vacuum double-layer buffer tank; the vacuum double-layer liquid storage tank and the vacuum double-layer buffer tank are both provided with an air supplementing pipe 16, the working air pressure of the vacuum double-layer liquid storage tank is controlled to be always larger than that of the vacuum double-layer buffer tank through the air supplementing pipe 16, and the vacuum double-layer liquid storage tank provides continuous LNG for the vacuum double-layer buffer tank through a liquid output pipeline 11 by utilizing the pressure difference; the ventilation pipeline 24 conducts the vacuum double-layer buffer tank and the immersed pump tank 20 to ensure that the working air pressure of the vacuum double-layer buffer tank and the immersed pump tank is always the same, and LNG flowing into the vacuum double-layer buffer tank continuously flows into the immersed pump tank 20; the immersed pump tank 20 supplies continuous LNG to the LNG vaporizing device 21 through the immersed pump 19, and the LNG vaporizing device 21 supplies continuous high-pressure gaseous natural gas to the gas consuming equipment.
The pressure of each intermediate pressure zone tank 10 is in the intermediate pressure zone and the vacuum double buffer tank and immersed pump tank 20 is in the low pressure zone.
The technical scheme of the embodiment has the following advantages: the ship is provided with a plurality of medium-pressure area storage tanks 10, the medium-pressure area storage tanks 10 are vacuum double-layer liquid storage tanks, and the design is reasonable, so that the ship body 23 can be stopped at the bank with smaller water depth, the draft is at least 3-4 meters, the ship is convenient to dock with users and power plants, the problem that large-scale transport ships can only be stopped at deep water areas such as ports is solved, and the problem that the natural gas storage and gasification devices need to occupy land is avoided; the vacuum double-layer liquid storage tank adopts a tank body with a lower cost and a stainless steel inner layer, wherein the outer layer is made of carbon steel or other heat-insulating materials, and under the same volume, the cost of the carbon steel tank body is far lower than that of the stainless steel tank body, so that the scheme avoids using a large-sized and high-price large-sized liquid storage tank, and under the condition of bearing the same LNG weight, the cost of the device is about 10 percent of that of a ship body 23 of the stainless steel large-sized liquid storage tank; continuous liquid supply of equipment to the immersed pump tank 20 and the LNG gasification device 21 is realized through the vacuum double-layer buffer tank, and continuous high-pressure gaseous natural gas is further provided for users or power plants.
The vacuum double-layer liquid storage tank and the vacuum double-layer buffer tank can also be arranged into a single-layer pressure-bearing liquid storage tank and a single-layer pressure-bearing buffer tank, and specifically, the tank body of the single-layer pressure-bearing liquid storage tank is made of stainless steel, the heat-insulating material is wound on the periphery of the tank body, and the tank body of the single-layer pressure-bearing buffer tank is made of stainless steel, and the heat-insulating material is wound on the periphery of the tank body.
The vacuum double-layer liquid storage tank, the vacuum double-layer buffer tank, the single-layer pressure-bearing liquid storage tank and the single-layer pressure-bearing buffer tank are all C-shaped storage tanks. The C-shaped storage tank is convenient to manufacture, durable and good in heat preservation.
The hull 23 is provided with at least two medium-pressure area storage tanks 10, the liquid inlet of each medium-pressure area storage tank 10 is positioned at the top of the tank body, each medium-pressure area storage tank 10 is connected with a total liquid inlet 17 in parallel through a liquid input pipeline 14, the total liquid inlet 17 supplies LNG to the medium-pressure area storage tanks 10 through the liquid input pipeline 14, the total liquid inlet 17 can simultaneously supply LNG to a plurality of medium-pressure area storage tanks 10 or can supply LNG to individual medium-pressure area storage tanks 10, each medium-pressure area storage tank 10 is connected with a low-pressure area buffer tank 18 in parallel through a liquid output pipeline 11, and each medium-pressure area storage tank 10 is selected to supply LNG to the low-pressure area buffer tank 18 each time.
The liquid input pipeline 14 is a steel pipe or a hose, and the liquid output pipeline 11 is a steel pipe or a hose.
As shown in fig. 2, the liquid inlet of the medium-pressure area storage tank 10 is provided with an upper liquid inlet spray header 13. The adoption of the upper liquid inlet spraying mode can reduce the generation of BOG of the medium-pressure area storage tank 10 and increase the storage time of LNG.
A first switch valve 121 for controlling whether the medium-pressure zone storage tank 10 supplies liquid to the low-pressure zone buffer tank 18 is arranged at the liquid outlet of each medium-pressure zone storage tank 10; a second switch valve 122 for controlling whether the total liquid inlet 17 supplies liquid to the medium-pressure area storage tank 10 is arranged at the liquid inlet of each medium-pressure area storage tank 10; the air supply pipe 16 of each medium-pressure area storage tank 10 is provided with a medium-pressure air supply valve 151, and the air supply pipe 16 of the low-pressure area buffer tank 18 is provided with a low-pressure air supply valve 152.
Barometers are provided in both the intermediate pressure zone tank 10 and the low pressure zone buffer tank 18. The air pressure detector detects the working air pressure value in the tank body in real time.
The middle pressure area storage tank 10 and the low pressure area buffer tank 18 are also internally provided with a safety relief valve 25. When LNG flows into the medium-pressure area storage tank 10 or the low-pressure area buffer tank 18, the safety relief valve 25 can timely discharge the protective gas or the gaseous natural gas containing BOG, so that the excessive high gas pressure in the tank body is avoided, and the safety relief valve 25 can also filter and recycle the BOG or the gaseous natural gas, so that the pollution to the environment and the resource waste are avoided.
The control system of the floating liquefied natural gas storage and gasification device is used for controlling the floating liquefied natural gas storage and gasification device to continuously supply high-pressure gaseous natural gas to the gas utilization equipment, and comprises a switch control unit, a gas pressure detection unit and a processing unit; a switch control unit including a first switch valve 121 for controlling whether each intermediate-pressure zone tank 10 supplies liquid to the low-pressure zone buffer tank 18, a second switch valve 122 for controlling whether the total liquid inlet 17 supplies liquid to the intermediate-pressure zone tank 10, an intermediate-pressure air-compensating valve 151 for controlling the operating air pressure in each intermediate-pressure zone tank 10, and a low-pressure air-compensating valve 152 for controlling the operating air pressure in the low-pressure zone buffer tank 18; the air pressure detection unit comprises air pressure detectors arranged in the storage tanks 10 and the buffer tanks 18 of the medium-pressure areas, and the air pressure detectors detect working air pressure values in the storage tanks 10 and the buffer tanks 18 of the low-pressure areas in real time; the air pressure detection unit further includes a signal transmission unit that transmits the operating air pressure value to the processing unit.
A processing unit including a PLC controller for controlling the switching operation of each of the first switching valve 121, the second switching valve 122, the medium pressure air compensating valve 151 and the low pressure air compensating valve 152; the air pressure detection unit sends the working air pressure value in each medium-pressure area storage tank 10 and the working air pressure value in the low-pressure area buffer tank 18 to the processing unit; the processing unit selects one medium-pressure area storage tank 10 to be communicated with the low-pressure area buffer tank 18 by controlling the first switch valve 121, and controls the working air pressure P1 of the medium-pressure area storage tank 10 to be always larger than the working air pressure P2 of the low-pressure area storage tank by controlling the medium-pressure air compensating valve 151 of the selected medium-pressure area storage tank 10.
The control system controls the air pressure of each medium-pressure area storage tank 10 and the low-pressure area buffer tank 18 and the flow of LNG through each switch valve and the air compensating valve, and has the advantages of convenient control and realization of remote control and automatic control.
The processing unit controls the operating air pressure P1 in the intermediate-pressure zone tank 10 to remain within the operating air pressure range: pa < P1< Pb; pa is the lower limit of the working gas of the medium-pressure area storage tank 10, when P1 is lower than Pa, the medium-pressure air compensating valve 151 is opened, and the air compensating pipe 16 supplements gas into the medium-pressure area storage tank 10; pb is the upper limit of the working gas pressure of the medium-pressure tank 10, and when P1 is higher than Pb, the medium-pressure gas make-up valve 151 is closed, and the gas make-up pipe 16 stops the gas make-up.
The operating pressure P2 of the low-pressure zone buffer tank 18 is maintained within the operating pressure range: pc < P2< Pd; pc is the lower limit of the working gas of the low-pressure zone buffer tank 18, when P2 is lower than Pc, the low-pressure gas supplementing valve 152 is opened, and the gas supplementing pipe 16 supplements gas into the low-pressure zone buffer tank 18; pd is the upper limit of the working gas pressure of the buffer tank 18 in the low pressure area, and when P2 is higher than Pd, the low pressure gas compensating valve 152 is closed, and the gas compensating pipe 16 stops gas compensation.
The medium-pressure air compensating valve 151 and the low-pressure air compensating valve 152 are pneumatic switch valves.
The first switch valve 121, the second switch valve 122, the medium-pressure air compensating valve 151 and the low-pressure air compensating valve 152 are all normally closed switch valves. When the processing unit selects the target medium-pressure zone storage tank 10, the corresponding operation of the target medium-pressure zone storage tank 10 can be realized only by opening the first switch valve 121, the second switch valve 122 or the medium-pressure air compensating valve 151.
The processing unit further comprises a wireless communication module, the processing unit is connected with a remote server through the wireless communication module, the remote server is connected with an intelligent terminal, the intelligent terminal obtains data in the processing unit through the remote server and the wireless communication module, and the intelligent terminal controls the switching action of the switching control unit through the remote server, the wireless communication module and the processing unit. The floating liquefied natural gas storage and gasification device is remotely controlled through an intelligent terminal such as a mobile phone, a portable computer and the like.
A method of controlling a floating lng storage and gasification unit comprising the steps of:
s1, connecting an LNG carrier with a total liquid inlet 17 of a ship body 23, connecting a high-pressure natural gas outlet 22 of the ship body 23 with gas utilization equipment, sequentially opening a second switch valve 122 by a processing unit to input LNG into each medium-pressure area storage tank 10, wherein the working air pressure P1 range of the medium-pressure area storage tanks 10 is as follows: the operating pressure P2 of the low pressure zone buffer tank 18 ranges from Pa-Pb: pc-Pd, wherein Pb > Pa > Pd > Pc;
s2, the processing unit selects one medium-pressure area storage tank 10 as a working storage tank by controlling the switching action of each first switching valve 121, and LNG flows into the low-pressure area buffer tank 18 from the working storage tank under the action of working air pressure difference;
s3, the working air pressure of the low-pressure zone buffer tank 18 is always the same as the working air pressure of the immersed pump tank 20 through the ventilation pipeline 24, and the LNG flowing into the low-pressure zone buffer tank 18 continuously flows into the immersed pump tank 20;
s4, continuously conveying the LNG in the immersed pump tank 20 into the LNG vaporizing device 21 by the immersed pump 19;
s5, continuously providing high-pressure gaseous natural gas to gas utilization equipment by the LNG gasification device 21;
s6, when the working air pressure P1 of the working storage tank is lower than Pa, the medium-pressure air compensating valve 151 is opened, the air compensating pipe 16 supplements air into the medium-pressure area storage tank 10, and when the working air pressure P1 of the medium-pressure area storage tank 10 is higher than Pb, the medium-pressure air compensating valve 151 is closed, and the air compensating pipe 16 stops air compensating;
when the operating pressure P2 of the low-pressure buffer tank 18 is lower than Pc, the low-pressure air compensating valve 152 is opened, the air compensating pipe 16 compensates air in the low-pressure buffer tank 18, and when the operating pressure P2 of the low-pressure buffer tank 18 is higher than Pd, the low-pressure air compensating valve 152 is closed, and the air compensating pipe 16 stops compensating air.
Further comprising step S7, the processing unit closes the first switch valves 121 of the working storage tanks, and the processing unit selects another intermediate-pressure zone storage tank 10 as a new working storage tank by controlling the switching action of each first switch valve 121.
The control method can realize that the floating liquefied natural gas storage and regasification system provides continuous high-pressure gaseous natural gas for users and power plants.
The mode of the processing unit selecting the working storage tank is as follows: the first on-off valve 121 of the target intermediate-pressure zone storage tank 10 is opened and the first on-off valves 121 of the remaining intermediate-pressure zone storage tanks 10 are closed.
The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The floating liquefied natural gas storage and gasification device is characterized in that: the LNG gasification device comprises a ship body (23), wherein the draft of the ship body is 3-4 meters, at least one medium-pressure area storage tank (10) is arranged on the ship body (23), and the medium-pressure area storage tank (10) is sequentially connected with a low-pressure area buffer tank (18), a submerged pump tank (20) and an LNG gasification device (21);
the liquid outlet of the medium-pressure area storage tank (10) is positioned at the top of the tank body, the liquid outlet of the low-pressure area buffer tank (18) is positioned at the bottom of LNG, one end of the liquid output pipeline (11) extends from the liquid outlet of the medium-pressure area storage tank (10) to the bottom of LNG, and the other end of the liquid output pipeline (11) is connected with the low-pressure area buffer tank (18);
the medium-pressure area storage tank (10) and the low-pressure area buffer tank (18) are internally provided with air supplementing pipes (16), working air pressure in the tank body is controlled through the air supplementing pipes (16), the lower limit of the working air pressure of the medium-pressure area storage tank (10) is higher than the upper limit of the working air pressure of the low-pressure area buffer tank (18), and the medium-pressure area storage tank (10) provides continuous LNG for the low-pressure area buffer tank (18) through the pressure difference of the working air pressure;
the bottom of the low-pressure area buffer tank (18) is connected with a liquid inlet of the immersed pump tank (20) through a liquid output pipeline (11), a cavity of the low-pressure area buffer tank (18) is communicated with a cavity of the immersed pump tank (20) through a ventilation pipeline (24), and the ventilation pipeline (24) enables the working air pressure of the low-pressure area buffer tank (18) to be always the same as the working air pressure of the immersed pump tank (20), and LNG flowing into the low-pressure area buffer tank (18) continuously flows into the immersed pump tank (20);
the immersed pump box (20) provides continuous LNG for the LNG gasification device (21) through the immersed pump (19), and the LNG gasification device (21) provides continuous high-pressure gaseous natural gas for gas utilization equipment;
the medium-pressure area storage tank (10) is a vacuum double-layer liquid storage tank, the low-pressure area buffer tank (18) is a vacuum double-layer buffer tank, the working air pressure of the vacuum double-layer liquid storage tank is always higher than that of the vacuum double-layer buffer tank, and LNG is conveyed into the vacuum double-layer buffer tank by utilizing the pressure difference;
the LNG is pumped out by the forward direction of the vacuum double-layer buffer tank and the cooperation of the vacuum double-layer liquid storage tank; the liquid outlet of the vacuum double-layer buffer tank is arranged at the bottom of LNG (liquefied Natural gas) and is communicated with the immersed pump tank (20) through the ventilation pipeline (24), the liquid level and the working air pressure of the immersed pump tank (20) can be adjusted simultaneously by the vacuum double-layer buffer tank, and the BOG in the immersed pump tank (20) is discharged by the vacuum double-layer buffer tank with the safety relief valve (25).
2. The floating lng storage and gasification unit of claim 1, wherein: the ship body (23) is provided with at least two medium-pressure area storage tanks (10), liquid inlets of the medium-pressure area storage tanks (10) are positioned at the top of the tank body, each medium-pressure area storage tank (10) is connected with a total liquid inlet (17) in parallel through a liquid input pipeline (14), the total liquid inlet (17) provides LNG for the medium-pressure area storage tanks (10) through the liquid input pipeline (14), and each medium-pressure area storage tank (10) is connected with a low-pressure area buffer tank (18) in parallel through a liquid output pipeline (11); an upper liquid inlet spray header (13) is arranged on a liquid inlet of the medium-pressure area storage tank (10).
3. The floating lng storage and gasification unit of claim 2, wherein:
a first switch valve (121) for controlling whether the medium-pressure area storage tank (10) supplies liquid to the low-pressure area buffer tank (18) or not is arranged at the liquid outlet of each medium-pressure area storage tank (10);
a second switch valve (122) for controlling whether the total liquid inlet (17) supplies liquid to the medium-pressure area storage tank (10) is arranged at the liquid inlet of each medium-pressure area storage tank (10);
a medium-pressure air compensating valve (151) is arranged on the air compensating pipe (16) of each medium-pressure area storage tank (10), and a low-pressure air compensating valve (152) is arranged on the air compensating pipe (16) of the low-pressure area buffer tank (18).
4. The floating lng storage and gasification unit of claim 1, wherein: barometer is arranged in the medium-pressure area storage tank (10) and the low-pressure area buffer tank (18).
5. The floating lng storage and gasification unit of claim 1, wherein: a safety relief valve (25) is also arranged in the medium-pressure area storage tank (10) and the low-pressure area buffer tank (18).
6. The control system of the floating liquefied natural gas storage and gasification device is characterized in that: the device comprises a switch control unit, an air pressure detection unit and a processing unit;
the switch control unit comprises a first switch valve (121) for controlling whether each medium-pressure area storage tank (10) supplies liquid to the low-pressure area buffer tank (18), a second switch valve (122) for controlling whether the total liquid inlet (17) supplies liquid to the medium-pressure area storage tank (10), a medium-pressure air compensating valve (151) for controlling the working air pressure in each medium-pressure area storage tank (10) and a low-pressure air compensating valve (152) for controlling the working air pressure in the low-pressure area buffer tank (18);
the air pressure detection unit comprises air pressure detectors arranged in each medium-pressure area storage tank (10) and each low-pressure area buffer tank (18), and the air pressure detectors detect working air pressure values in each medium-pressure area storage tank (10) and each low-pressure area buffer tank (18) in real time;
the processing unit comprises a PLC controller for controlling the switching actions of each first switching valve (121), each second switching valve (122), each medium-pressure air compensating valve (151) and each low-pressure air compensating valve (152);
the air pressure detection unit sends the working air pressure value in each medium-pressure area storage tank (10) and the working air pressure value in the low-pressure area buffer tank (18) to the processing unit;
the processing unit selects one medium-pressure area storage tank (10) to be communicated with the low-pressure area buffer tank (18) by controlling the first switch valve (121), and controls the working air pressure P1 of the medium-pressure area storage tank (10) to be always larger than the working air pressure P2 of the low-pressure area storage tank by controlling the medium-pressure air compensating valve (151) of the selected medium-pressure area storage tank (10);
the processing unit controls the working air pressure P1 in the medium-pressure zone storage tank (10) to be kept within the working air pressure range: pa is less than P1 and less than pb; pa is the lower limit of working gas of the medium-pressure area storage tank (10), when P1 is lower than Pa, the medium-pressure air supplementing valve (151) is opened, and the air supplementing pipe (16) supplements gas into the medium-pressure area storage tank (10);
pb is the upper limit of the working gas of the medium-pressure area storage tank (10), when P1 is higher than Pb, the medium-pressure air supplementing valve (151) is closed, and the air supplementing pipe (16) stops supplementing air;
the operating pressure P2 of the low-pressure zone buffer tank (18) is maintained within the operating pressure range: pc is more than P2 and less than pd;
pc is the lower limit of the working gas of the low-pressure area buffer tank (18), when P2 is lower than Pc, the low-pressure air supplementing valve (152) is opened, and the air supplementing pipe (16) supplements gas into the low-pressure area buffer tank (18);
pd is the upper limit of the working gas of the buffer tank (18) in the low pressure area, and when P2 is higher than Pd, the low pressure gas supplementing valve (152) is closed, and the gas supplementing pipe (16) stops supplementing gas.
7. The control system of a floating lng storage and gasification unit of claim 6 wherein: the medium-pressure air compensating valve (151) and the low-pressure air compensating valve (152) are pneumatic switch valves;
the first switch valve (121), the second switch valve (122), the medium-pressure air compensating valve (151) and the low-pressure air compensating valve (152) are normally closed switch valves.
8. The control system of a floating lng storage and gasification unit of claim 6 wherein: the processing unit further comprises a wireless communication module, the processing unit is connected with a remote server through the wireless communication module, the remote server is connected with the intelligent terminal, the intelligent terminal obtains data in the processing unit through the remote server and the wireless communication module, and the intelligent terminal controls the switching action of the switching control unit through the remote server, the wireless communication module and the processing unit.
9. The control method of the floating liquefied natural gas storage and gasification device is characterized by comprising the following steps of: the method comprises the following steps:
s1, the LNG carrier is connected with a total liquid inlet (17) of a ship body (23), a high-pressure natural gas outlet (22) of the ship body (23) is connected with gas utilization equipment, a processing unit sequentially opens a second switching valve (122) to input LNG into each medium-pressure area storage tank (10), and the working air pressure P1 range of the medium-pressure area storage tanks (10) is as follows: the working air pressure P2 range of the Pa-Pb low pressure area buffer tank (18) is as follows: pc-Pd, wherein Pb > Pa > Pd > Pc;
s2, the processing unit selects one medium-pressure area storage tank (10) as a working storage tank by controlling the switching action of each first switching valve (121), and LNG flows into a low-pressure area buffer tank (18) from the working storage tank under the action of working air pressure difference;
s3, enabling the working air pressure of the low-pressure zone buffer tank (18) to be always the same as the working air pressure of the immersed pump tank (20) through the ventilation pipeline (24), and enabling LNG flowing into the low-pressure zone buffer tank (18) to continuously flow into the immersed pump tank (20);
s4, continuously conveying LNG in the immersed pump box (20) to the LNG gasification device (21) by the immersed pump (19);
s5, continuously providing high-pressure gaseous natural gas to gas utilization equipment by the LNG gasification device (21);
s6, when the working air pressure P1 of the working storage tank is lower than Pa, the medium-pressure air compensating valve (151) is opened, the air compensating pipe (16) supplements air into the medium-pressure area storage tank (10), and when the working air pressure P1 of the medium-pressure area storage tank (10) is higher than Pb, the medium-pressure air compensating valve (151) is closed, and the air compensating pipe (16) stops air compensating;
when the working air pressure P2 of the low-pressure area buffer tank (18) is lower than Pc, the low-pressure air compensating valve (152) is opened, the air compensating pipe (16) supplements air into the low-pressure area buffer tank (18), and when the working air pressure P2 of the low-pressure area buffer tank (18) is higher than Pd, the low-pressure air compensating valve (152) is closed, and the air compensating pipe (16) stops supplementing air;
the method also comprises the steps of:
s7, the processing unit closes the first switch valves (121) of the working storage tanks, and the processing unit selects the other medium-pressure area storage tank (10) as a new working storage tank by controlling the switch action of each first switch valve (121).
10. The method of controlling a floating lng storage and gasification unit according to claim 9, wherein: the mode of the processing unit selecting the working storage tank is as follows: the first switch valve (121) of the target intermediate-pressure zone storage tank (10) is opened and the first switch valves (121) of the remaining intermediate-pressure zone storage tanks (10) are closed.
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