CN117146180A

CN117146180A - BOG condensing system and operation method thereof

Info

Publication number: CN117146180A
Application number: CN202311002073.XA
Authority: CN
Inventors: 严旭忱; 吕慰华; 刘秋均; 高志林; 余斌
Original assignee: Yuehai Panyu Petrochemical Storage And Transportation Development Co ltd
Current assignee: Yuehai Panyu Petrochemical Storage And Transportation Development Co ltd
Priority date: 2023-08-09
Filing date: 2023-08-09
Publication date: 2023-12-01

Abstract

The invention discloses a BOG condensing system and an operation method of the BOG condensing system. The operation method of the BOG condensation system comprises the steps that LNG in the LNG heat exchange component exchanges heat with a cold storage medium; the BOG in the first BOG heat exchange assembly exchanges heat with the cold accumulation medium to precool the BOG; and (3) the precooled BOG enters a second BOG heat exchange assembly and exchanges heat with a cold accumulation medium to liquefy the BOG. The BOG condensing system can reduce the energy consumption required by BOG liquefaction. The invention is used in the technical field of natural gas liquefaction.

Description

BOG condensing system and operation method thereof

Technical Field

The invention relates to the technical field of natural gas liquefaction, in particular to a BOG condensing system and an operation method of the BOG condensing system.

Background

Natural gas is a clean and efficient fossil fuel, and compared with traditional fossil fuels such as coal, petroleum and the like, the natural gas has the advantages of low carbon content, clean combustion products and the like, so that the natural gas is widely applied to modern industrial production and resident living energy supply. The volume of the liquefied natural gas can be reduced by about 600 times, which is beneficial to long-distance transportation. However, liquefied natural Gas (Liquefied Natural Gas, LNG) has a low boiling point (-162.6 ℃) and is vaporized during daily storage and transportation to produce boil-off Gas (BOG). The BOG can cause the rising of LNG storage tank pressure, causes the influence of certain degree to the safe operation of LNG storage tank.

The BOG treatment modes generally include direct pressurization and output, re-liquefaction and pressurization and output, direct combustion of a torch and re-liquefaction and return to a storage tank. The method for re-liquefying BOG and returning the BOG to the storage tank mainly comprises a medium cooling method, a jet cooling method and an active cooling method, wherein a large amount of refrigeration medium (such as liquid nitrogen) is generally added in the medium cooling method, and the temperature of the BOG is reduced by utilizing the heat absorption of heating or the latent heat of gasification of the refrigeration medium, so that a large amount of refrigeration medium is consumed in the method. The jet flow method generally absorbs the heat of the BOG through gasification of the high-pressure LNG through the Venturi jet pipe so as to achieve the purpose of liquefying the BOG. The active cooling method generally reduces the temperature of the BOG by a refrigerator, so as to liquefy the BOG, thus consuming a large amount of electricity, saving no energy and generating extremely high running cost.

Disclosure of Invention

The present invention aims to solve, at least to some extent, one of the above technical problems in the prior art. Therefore, the embodiment of the first aspect of the invention provides a BOG condensing system, which has a simple structure and can reduce the running cost and the medium consumption required by BOG liquefaction.

An embodiment of the second aspect of the present invention provides a method for operating a BOG condensation system.

A BOG condensing system according to an embodiment of the first aspect of the present invention includes: the precooler is internally provided with an LNG heat exchange assembly, a first BOG heat exchange assembly and a cold storage medium, the LNG heat exchange assembly is provided with an LNG inlet and an LNG outlet, LNG in the LNG heat exchange assembly can exchange heat with the cold storage medium in the precooler so as to reduce the temperature of the cold storage medium in the precooler, the first BOG heat exchange assembly is provided with a first BOG inlet and a first BOG outlet, and BOG in the first BOG heat exchange assembly can exchange heat with the cold storage medium in the precooler so as to precool the BOG; the condenser, be provided with second BOG heat transfer subassembly and cold-storage medium in the condenser, second BOG heat transfer subassembly is provided with second BOG entry and product export, second BOG entry with BOG export intercommunication, precooled BOG pass through second BOG heat transfer subassembly can with cold-storage medium in the condenser exchanges heat to liquefaction BOG and form the liquefaction product.

Based on the above technical solution, the embodiment of the first aspect of the present invention has at least the following beneficial effects: the LNG in the outward transportation process is utilized to absorb the heat of the cold accumulation medium in the precooler, so that the temperature of the cold accumulation medium in the precooler is reduced, the cooled cold accumulation medium is used for precooling the BOG, the precooled BOG is input into the condenser for liquefaction, the energy consumed for liquefying the BOG is effectively reduced, and the running cost required for liquefying the BOG is also reduced.

According to the BOG condensation system provided by the embodiment of the first aspect of the invention, the LNG heat exchange assembly comprises a liquid inlet main pipe, a liquid outlet main pipe and a plurality of LNG heat exchange pipes, one end of each LNG heat exchange pipe is communicated with the liquid inlet main pipe, the other end of each LNG heat exchange pipe is communicated with the liquid outlet main pipe, the LNG inlet is arranged at one end of the liquid inlet main pipe far away from the LNG heat exchange pipes, and the LNG outlet is arranged at one end of the liquid outlet main pipe far away from the LNG heat exchange pipes; the first BOG heat exchange assembly comprises a first air inlet main pipe, a first air outlet main pipe and a plurality of first BOG heat exchange pipes, one end of each first BOG heat exchange pipe is communicated with the first air inlet main pipe, the other end of each first BOG heat exchange pipe is communicated with the first air outlet main pipe, the first BOG inlet is arranged at one end, far away from the first BOG heat exchange pipes, of the first air inlet main pipe, and the BOG outlet is arranged at one end, far away from the first BOG heat exchange pipes, of the first air outlet main pipe; the LNG heat exchange pipes and the first BOG heat exchange pipes are arranged in a crossing mode.

According to the BOG condensation system provided by the embodiment of the first aspect of the invention, the precooler is provided with a first cold storage medium inlet, a first dispersing component is arranged in the precooler and is positioned above the LNG heat exchange tube and the first BOG heat exchange tube, the first dispersing component is communicated with the first cold storage medium inlet, the first dispersing component comprises a plurality of first nozzles, a first cold storage medium outlet is arranged at the bottom of the precooler, and a first temperature sensor is also arranged in the precooler.

According to the BOG condensation system provided by the embodiment of the first aspect of the invention, the second BOG heat exchange assembly comprises a second air inlet main pipe, an outlet main pipe and a plurality of second BOG heat exchange pipes, wherein the second air inlet main pipe and the outlet main pipe are respectively and vertically arranged at two sides of the second BOG heat exchange pipes, the second BOG inlet is arranged at the upper end of the second air inlet main pipe, the product outlet is arranged at the lower end of the outlet main pipe, one end of each second BOG heat exchange pipe is communicated with the lower end of the second air inlet main pipe, and the other end of each second BOG heat exchange pipe is communicated with the upper end of the outlet main pipe.

According to the BOG condensation system provided by the embodiment of the first aspect of the invention, the condenser is provided with a second cold storage medium inlet, a second dispersion assembly is arranged above the second BOG heat exchange tube, the second dispersion assembly is communicated with the second cold storage medium inlet, the second dispersion assembly comprises a plurality of second nozzles, the bottom of the condenser is provided with a second cold storage medium outlet, and a second temperature sensor is also arranged in the condenser.

According to the BOG condensation system disclosed by the embodiment of the first aspect of the invention, the BOG condensation system further comprises a cold storage medium circulation line, the cold storage medium circulation line comprises a first pipeline and a second pipeline, the cold storage medium in the precooler enters the condenser through the first pipeline, the cold storage medium in the condenser enters the precooler through the second pipeline, a refrigerator is arranged on the first pipeline to reduce the temperature of the cold storage medium, a first node is arranged between the precooler and the refrigerator in the first pipeline, a second node is arranged on the second pipeline, the first node is communicated with the second node through a third pipeline, a first one-way valve is arranged between the precooler and the first node in the first pipeline, a conveying pump is arranged between the condenser and the second node in the second pipeline, and a second one-way valve is arranged on the third pipeline.

According to an embodiment of the first aspect of the present invention, the BOG condensing system further comprises an LNG storage tank and a liquid separation tank, wherein the LNG storage tank is communicated with the LNG inlet of the precooler, the liquid separation tank comprises a product inlet, a liquid phase outlet and a gas phase outlet, the product outlet of the condenser is communicated with the product inlet of the liquid separation tank, the gas phase outlet of the liquid separation tank is communicated with the BOG inlet of the precooler, and the liquid phase outlet of the liquid separation tank is communicated with the LNG storage tank.

A method of operating a BOG condensing system according to an embodiment of the second aspect of the present invention includes the steps of: LNG in the LNG storage tank enters an LNG heat exchange assembly in the precooler from an LNG inlet and exchanges heat with a cold storage medium in the precooler so as to reduce the temperature of the cold storage medium; the BOG enters a first BOG heat exchange component in the precooler from a BOG inlet and exchanges heat with a cold accumulation medium in the precooler so as to precool the BOG; the precooled BOG enters a second BOG heat exchange component in the condenser and exchanges heat with a cold accumulation medium in the condenser to liquefy the BOG and form a liquefied product; and the liquefied product enters a liquid separation tank to carry out gas-liquid separation, LNG formed by BOG liquefaction enters an LNG storage tank, and if the liquefied BOG exists, the liquefied BOG is conveyed back to the first BOG heat exchange component of the precooler.

According to the operation method of the BOG condensation system provided by the embodiment of the second aspect of the invention, LNG in the LNG storage tank is pumped by the low-pressure pump, enters the liquid inlet manifold from the LNG inlet through the first LNG pipeline and is then split to each LNG heat exchange tube, BOG enters the first air inlet manifold through the first BOG inlet and is then split to each first BOG heat exchange tube, the first nozzles of the first dispersion branch tubes spray cold storage medium, the LNG in the LNG heat exchange tubes exchanges heat with the cold storage medium in the precooler so as to reduce the temperature of the cold storage medium in the precooler, and the BOG in the first BOG heat exchange tubes exchanges heat with the cold storage medium in the precooler so as to pre-cool the BOG in the first BOG heat exchange tubes, wherein the LNG heat exchange tubes and the first BOG heat exchange tubes are arranged in a crossing way.

According to the operation method of the BOG condensation system of the embodiment of the second aspect of the invention, after the cold storage medium in the precooler exchanges heat, the cold storage medium enters the second dispersion branch pipe of the condenser after being cooled further by the refrigerator, the cold storage medium is sprayed out from the second nozzle of the second dispersion branch pipe to exchange heat with the BOG in the second BOG heat exchange pipe so as to liquefy the BOG, and the cold storage medium after heat exchange is conveyed back to the precooler so as to form a cold storage medium circulation loop; in the process of exchanging heat between the cold storage medium in the condenser and the BOG in the second BOG heat exchange tube, when the second temperature sensor in the condenser detects that the cold storage medium in the condenser is higher than a second preset value, the conveying pump is started, the second one-way valve is started, the cold storage medium in the condenser is conveyed into the refrigerator for refrigeration, and the cooled cold storage medium is conveyed back into the second dispersion assembly of the condenser.

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.

Drawings

The invention is further described below with reference to the drawings and examples;

FIG. 1 is a schematic diagram of a BOG condensing system according to an embodiment of the first aspect of the present invention;

FIG. 2 is a schematic circuit diagram of a BOG condensing system according to an embodiment of the present invention;

FIG. 3 is a schematic view of a precooler according to an embodiment of the first aspect of the present invention;

FIG. 4 is a schematic view showing an internal structure of a precooler according to an embodiment of the first aspect of the present invention;

fig. 5 is a schematic structural view of an LNG heat exchange tube according to an embodiment of the first aspect of the present invention;

FIG. 6 is a schematic structural diagram of a first BOG heat exchange tube according to an embodiment of the first aspect of the present invention;

fig. 7 is a schematic structural view of a condenser according to an embodiment of the first aspect of the present invention.

Reference numerals: an LNG storage tank 100, a low pressure pump 110; precooler 200, first shell 210, first cold storage medium outlet 211, liquid inlet manifold 221, lng inlet 2211, first cross pipe 222, first branch pipe 223, liquid outlet manifold 224, lng outlet 2241, second cross pipe 225, second branch pipe 226, lng heat exchange pipe 227, lng heat exchange pipe body 2271, second heat exchange fin 2272, first air inlet manifold 231, first BOG inlet 2311, third cross pipe 232, third branch pipe 233, first air outlet manifold 234, BOG outlet 2341, fourth cross pipe 235, fourth branch pipe 236, first BOG heat exchange pipe 237, first BOG heat exchange pipe body 2371, first heat exchange fin 2372, first dispersion manifold 241, first cold storage medium inlet 2411, first dispersion branch pipe 242; a refrigerator 300; condenser 400, second shell 410, second cold storage medium outlet 411, second intake manifold 421, second BOG inlet 4211, fifth cross pipe 422, fifth branch pipe 423, outlet manifold 424, product outlet 4241, sixth cross pipe 425, sixth branch pipe 426, second BOG heat exchange pipe 427, second distribution manifold 431, second cold storage medium inlet 4311, seventh cross pipe 432, second distribution branch pipe 433; a liquid separation tank 500; a first LNG line 610, a second LNG line 620; a first BOG line 710, a product line 720, a third LNG line 730, a second BOG line 740, a third check valve 741; a first line 810, a first check valve 811, a first node 812, a second line 820, a transfer pump 821, a second node 822, a third line 830, and a second check valve 831.

Detailed Description

Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the accompanying drawings are used to supplement the description of the written description so that one can intuitively and intuitively understand each technical feature and overall technical scheme of the present invention, but not to limit the scope of the present invention.

In the description of the present invention, it should be understood that references to orientation descriptions such as upper, lower, front, rear, left, right, etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description of the present invention and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.

In the description of the present invention, a number means one or more, a number means two or more, and greater than, less than, exceeding, etc. are understood to not include the present number, and above, below, within, etc. are understood to include the present number. The description of the first and second is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless explicitly defined otherwise, terms such as arrangement, connection, etc. should be construed broadly and the specific meaning of the terms in the present invention can be reasonably determined by a person skilled in the art in combination with the specific contents of the technical solution.

Referring to fig. 1, an embodiment of the first aspect of the present invention provides a BOG condensing system, which can pre-cool BOG and liquefy the BOG into LNG to be returned to an LNG storage tank 100, without frequent filling and consumption of other refrigeration media, and can effectively reduce the running cost required for liquefying BOG. Wherein, LNG is liquefied natural gas, BOG is the vaporization gas that liquefied natural gas LNG gasification produced.

The BOG condensing system comprises an LNG storage tank 100, a precooler 200, a refrigerator 300, a condenser 400, a liquid separation tank 500, an LNG transfer line, a BOG condensing line and a cold storage medium circulation line.

Referring to fig. 2, the LNG transfer line includes a first LNG line 610 and a second LNG line 620, LNG in the LNG tank 100 is transferred to the precooler 200 through the first LNG line 610, and LNG in the precooler 200 is introduced to the external transfer system through the second LNG line 620.

Specifically, referring to fig. 3 and 4, the precooler 200 includes a first housing 210, an LNG heat exchange assembly, a first BOG heat exchange assembly and a cold storage medium are disposed in the first housing 210, the LNG heat exchange assembly is provided with an LNG inlet 2211 and an LNG outlet 2241, the LNG storage tank 100 can be communicated with the LNG inlet 2211 through a first LNG line 610, a low pressure pump 110 is disposed in the LNG storage tank 100, LNG in the LNG storage tank 100 is pumped by the low pressure pump 110, the LNG enters the LNG heat exchange assembly from the LNG inlet 2211 through the first LNG line 610, the LNG in the LNG heat exchange assembly can exchange heat with the cold storage medium in the precooler 200 to reduce the temperature of the cold storage medium in the precooler 200, and the LNG in the LNG heat exchange assembly after heat exchange exits from the LNG outlet 2241 and enters the external transmission system through a second LNG line 620.

The LNG in the process of output is utilized to absorb the heat of the cold accumulation medium in the precooler 200, so that the temperature of the cold accumulation medium in the precooler 200 is reduced, the BOG is precooled through the cooled cold accumulation medium, the energy consumed by liquefying the BOG is effectively reduced, the energy-saving effect can be achieved, and the running cost required by liquefying the BOG is also reduced.

Referring to fig. 2, the BOG condensing circuit includes a first BOG line 710, a product line 720, a third LNG line 730 and a second BOG line 740, the BOG in the precooler 200 is precooled and then enters the condenser 400 through the first BOG line 710 to be liquefied, liquefied products are generated, the liquefied products enter the liquid separation tank 500 through the product line 720, and if the liquefied products are LNG, the generated LNG enters the LNG storage tank 100 through the third LNG line 730; if the liquefied product is a mixture of LNG and BOG, after gas-liquid separation in the knockout drum 500, the produced LNG enters the LNG tank 100 through the third LNG line 730, and BOG that has not been liquefied is returned to the precooler 200 through the second BOG line 740.

The first BOG heat exchange assembly is provided with a first BOG inlet 2311 and a BOG outlet 2341, and BOG generated in the process area enters the first BOG heat exchange assembly from the first BOG inlet 2311 and exchanges heat with the cold storage medium in the precooler 200 to precool the BOG.

It will be appreciated that in precooler 200, LNG is the lowest temperature medium, and the temperature of the cold storage medium is higher than the temperature of LNG and lower than the temperature of BOG, which is insufficient to liquefy BOG, and only BOG can be precooled.

Further, the LNG heat exchange assembly comprises a liquid inlet main pipe 221, a liquid outlet main pipe 224 and a plurality of LNG heat exchange pipes 227, one end of each LNG heat exchange pipe 227 is communicated with the liquid inlet main pipe 221, the other end of each LNG heat exchange pipe 227 is communicated with the liquid outlet main pipe 224, an LNG inlet 2211 is formed in one end, far away from each LNG heat exchange pipe 227, of the liquid inlet main pipe 221, and an LNG outlet 2241 is formed in one end, far away from each LNG heat exchange pipe 227, of the liquid outlet main pipe 224.

The first BOG heat exchange assembly comprises a first air inlet main pipe 231, a first air outlet main pipe 234 and a plurality of first BOG heat exchange tubes 237, one end of each first BOG heat exchange tube 237 is communicated with the first air inlet main pipe 231, the other end of each first BOG heat exchange tube 237 is communicated with the first air outlet main pipe 234, a first BOG inlet 2311 is formed in one end, far away from the first BOG heat exchange tubes 237, of the first air inlet main pipe 231, and a BOG outlet 2341 is formed in one end, far away from the first BOG heat exchange tubes 237, of the first air outlet main pipe 234.

The LNG heat exchange tubes 227 are disposed intersecting the first BOG heat exchange tubes 237, which is more beneficial to the simultaneous heat exchange between the cold storage medium in the precooler 200 and the LNG in the LNG heat exchange tubes 227 and the BOG in the first BOG heat exchange tubes 237, and improves the heat exchange efficiency.

Further, referring to fig. 3 and 4, the LNG heat exchange assembly and the first BOG heat exchange assembly are inserted together, the liquid inlet main pipe 221 is vertically disposed on the upper right side, the upper end of the liquid inlet main pipe 221 extends out of the first housing 210, the upper port of the liquid inlet main pipe 221 is an LNG inlet 2211, the lower end of the liquid inlet main pipe 221 is communicated with a first transverse pipe 222, and three first branch pipes 223 are disposed at intervals along the length direction of the bottom of the first transverse pipe 222. The liquid outlet main 224 is vertically arranged at the left lower side, the lower end of the liquid outlet main 224 extends out of the first shell 210 to be arranged, the lower port of the liquid outlet main 224 is an LNG outlet 2241, the upper end of the liquid outlet main 224 is communicated with a second transverse pipe 225, three second branch pipes 226 are arranged at intervals along the length direction of the top of the second transverse pipe 225, the first branch pipes 223 and the second branch pipes 226 are vertically arranged and correspond to each other one by one, six LNG heat exchange pipes 227 are arranged between each first branch pipe 223 and the corresponding second branch pipe 226 along the vertical direction at intervals, one ends of the LNG heat exchange pipes 227 are horizontally arranged, and the LNG heat exchange pipes 227 are communicated with the first branch pipes 223 and the second branch pipes 226.

Similarly, the first air intake manifold 231 is vertically disposed on the upper left side, the upper end of the first air intake manifold 231 extends out of the first housing 210, the upper port of the first air intake manifold 231 is a first BOG inlet 2311, the lower end of the first air intake manifold 231 is communicated with a third transverse pipe 232, and three third branched pipes 233 are disposed at intervals along the length direction of the bottom of the third transverse pipe 232. The first main 234 of giving vent to anger is vertical to be set up in the lower right side, the lower extreme of first main 234 of giving vent to anger stretches out first shell 210 setting, the lower port of first main 234 of giving vent to anger is BOG export 2341, the upper end of first main 234 of giving vent to anger communicates with a fourth violently pipe 235, the top of fourth violently pipe 235 is provided with three fourth branch pipes 236 along its length direction interval, third branch pipe 233 and fourth branch pipe 236 are vertical to be set up and the one-to-one, be provided with six first BOG heat transfer pipe 237 along vertical direction interval between every third branch pipe 233 and the corresponding fourth branch pipe 236, first BOG heat transfer pipe 237 level sets up, and the one end and the third branch pipe 233 intercommunication of first BOG heat transfer pipe 237, the other end and fourth branch pipe 236 intercommunication. Wherein the first branch pipe 223 and the fourth branch pipe 236 are connected in an up-and-down manner, and the second branch pipe 226 and the third branch pipe 233 are connected in an up-and-down manner.

Referring to fig. 5, the LNG heat exchange tube 227 includes an LNG heat exchange tube body 2271, the LNG heat exchange tube body 2271 is of a single tube structure, and a second heat exchange fin 2272 is provided at the outer circumference of the LNG heat exchange tube body 2271. Referring to fig. 6, the first BOG heat exchange tube 237 includes a first BOG heat exchange tube body 2371, the first BOG heat exchange tube body 2371 includes a plurality of heat exchange sub-tubes, the plurality of heat exchange sub-tubes are arranged at intervals, and the outer circumference of the first BOG heat exchange tube body 2371 is also provided with first heat exchange fins 2372. The multi-tube structure of the first BOG heat exchange tube 237 and the arrangement of the first heat exchange fins 2372 can effectively improve heat exchange efficiency.

It is easily expected that decreasing the diameter of the heat exchange tubes and/or increasing the number of the heat exchange tubes may effectively increase the heat exchange area, thereby further improving the heat exchange efficiency.

Referring to fig. 3 and 4, the precooler 200 is provided with a first cold storage medium inlet 2411, a first dispersion assembly is disposed in the first casing 210 of the precooler 200, the first dispersion assembly is located above the LNG heat exchange tube 227 and the first BOG heat exchange tube 237, and the first dispersion assembly is in communication with the first cold storage medium inlet 2411, so that the first dispersion assembly can release cold storage medium in the first casing 210 of the precooler 200, a first cold storage medium outlet 211 is disposed at the bottom of the first casing 210, and a first temperature sensor is further disposed in the first casing 210, for detecting the temperature of the cold storage medium in the first casing 210, so as to keep the temperature below a first preset temperature.

In some embodiments, the first dispersion assembly includes a first dispersion manifold 241 and a plurality of first dispersion branches 242. Referring to fig. 4, a first distribution header pipe 241 is horizontally disposed above the LNG heat exchange pipe 227 and the first BOG heat exchange pipe 237, the right end of the first distribution header pipe 241 extends out of the first housing 210, the right end of the first distribution header pipe 241 is a first cold storage medium inlet 2411, the first distribution header pipe 241 is horizontally disposed along the length direction thereof with five first distribution branch pipes 242, the bottom of each first distribution branch pipe 242 is provided with a plurality of first nozzles along the length direction thereof, cold storage medium is sprayed from the first nozzles, and sprayed cold storage medium is distributed in a gap between the LNG heat exchange pipe 227 and the first BOG heat exchange pipe 237, and disturbance is formed to improve heat exchange efficiency.

Condenser 400 includes a second housing 410, a second BOG heat exchange assembly and a cold storage medium are disposed in second housing 410, the second BOG heat exchange assembly is provided with a second BOG inlet 4211 and a product outlet 4241, BOG outlet 2341 of precooler 200 is communicated with second BOG inlet 4211 of condenser 400 through first BOG line 710, and precooled BOG enters the second BOG heat exchange assembly of condenser 400 and exchanges heat with the cold storage medium in condenser 400 to liquefy BOG and form liquefied product.

Specifically, the second BOG heat exchange assembly includes a second air inlet manifold 421, an outlet manifold 424 and a plurality of second BOG heat exchange tubes 427, the second air inlet manifold 421 and the outlet manifold 424 are respectively vertically arranged at two sides of the second BOG heat exchange tubes 427, a second BOG inlet 4211 is arranged at the upper end of the second air inlet manifold 421, a product outlet 4241 is arranged at the lower end of the outlet manifold 424, one end of each second BOG heat exchange tube 427 is communicated with the lower end of the second air inlet manifold 421, and the other end is communicated with the upper end of the outlet manifold 424.

Referring to fig. 7, the second intake manifold 421 is vertically disposed at an upper left side, an upper end of the second intake manifold 421 is disposed to extend out of the second housing 410, an upper port of the second intake manifold 421 is a second BOG inlet 4211, a lower end of the second intake manifold 421 is communicated with a fifth transverse pipe 422, and a plurality of fifth branched pipes 423 are disposed at intervals along a length direction of the bottom of the fifth transverse pipe 422. The outlet main pipe 424 is vertically arranged at the lower right side, the lower end of the outlet main pipe 424 extends out of the second shell 410 to be arranged, the lower port of the outlet main pipe 424 is a product outlet 4241, the upper end of the outlet main pipe 424 is communicated with a sixth transverse pipe 425, a plurality of sixth branch pipes 426 are arranged at intervals on the top of the sixth transverse pipe 425 along the length direction of the sixth transverse pipe, the fifth branch pipes 423 and the sixth branch pipes 426 are vertically arranged in one-to-one correspondence, three second BOG heat exchange pipes 427 are arranged between each fifth branch pipe 423 and the corresponding sixth branch pipe 426 along the vertical direction at intervals, the second BOG heat exchange pipes 427 are horizontally arranged, one end of each second BOG heat exchange pipe 427 is communicated with the fifth branch pipe 423, and the other end of each second BOG heat exchange pipe 427 is communicated with the sixth branch pipes 426.

It is easily conceivable that the structure of the second BOG heat exchange tube 427 may be selected to have a multi-tube structure identical or similar to that of the first BOG heat exchange tube 237 or a single-tube structure identical or similar to that of the LNG heat exchange tube 227 according to practical situations, so as to achieve an optimal condensing effect.

The condenser 400 is provided with a second dispersion assembly above the second BOG heat exchange tube 427, which communicates with the second cool storage medium inlet 4311, so that the second dispersion assembly can release cool storage medium in the second casing 410 of the condenser 400, the bottom of the second casing 410 is provided with a second cool storage medium outlet 411, and a second temperature sensor is further provided in the second casing 410 to detect the temperature of the cool storage medium in the second casing 410.

In some embodiments, the second dispersion assembly includes a second dispersion manifold 431 and a plurality of second dispersion branches 433. Referring to fig. 7, a second distributing main pipe 431 is vertically disposed above the second BOG heat exchange pipes 427, an upper end of the second distributing main pipe 431 extends out of the second housing 410 to be disposed, an upper port of the second distributing main pipe 431 is a second cold storage medium inlet 4311, a seventh transverse pipe 432 is horizontally disposed at a lower end of the second distributing main pipe 431, the seventh transverse pipe 432 is vertically disposed with the second BOG heat exchange pipes 427, a plurality of second distributing branch pipes 433 are disposed at intervals along a length direction of the seventh transverse pipe 432, the second distributing branch pipes 433 are disposed in parallel with the second BOG heat exchange pipes 427, a plurality of second nozzles are disposed at a bottom of each second distributing branch pipe 433 along a length direction of the second distributing branch pipes, cold storage medium is sprayed out of the second nozzles, the sprayed cold storage medium is dispersed in gaps among the second BOG heat exchange pipes 427, and disturbance is formed to improve heat exchange efficiency.

Referring to fig. 2, the cold storage medium circulation line includes a first line 810, a second line 820, and a third line 830, the cold storage medium in the precooler 200 enters the condenser 400 through the first line 810, and the cold storage medium in the condenser 400 enters the precooler 200 through the second line 820, so that a first cold storage medium circuit is formed between the precooler 200 and the condenser 400. The refrigerator 300 is disposed on the first line 810 to reduce the temperature of the cold storage medium, the first line 810 is provided with the first node 812 between the precooler 200 and the refrigerator 300, the second line 820 is provided with the second node 822, and the first node 812 is communicated with the second node 822 through the third line 830, so that a second cold storage medium loop is formed between the condenser 400 and the refrigerator 300. The first cold accumulation medium loop and the second cold accumulation medium loop enable the cold accumulation medium to flow and be recycled, and consumption of the cold accumulation medium is effectively reduced.

The first cold storage medium outlet 211 of the precooler 200 is communicated with the second cold storage medium inlet 4311 of the condenser 400 through a first pipeline 810, the second cold storage medium outlet 411 of the condenser 400 is communicated with the first cold storage medium inlet 2411 of the precooler 200 through a second pipeline 820, the first pipeline 810 is provided with a first check valve 811 between the precooler 200 and the first node 812, the second pipeline 820 is provided with a delivery pump 821 between the condenser 400 and the second node 822, the delivery pump is arranged close to the second cold storage medium outlet 411, and the third pipeline 830 is provided with a second check valve 831.

The cold storage medium exchanges heat with LNG in the first housing 210 of the precooler 200 to reduce the temperature of the cold storage medium and maintain the temperature of the cold storage medium below a first preset temperature, and also exchanges heat with BOG in the first housing 210 to reduce the temperature of BOG to precool it. The temperature of the cold storage medium at this time is higher than the temperature of LNG and lower than the temperature of BOG, and is insufficient to liquefy BOG. The cold storage medium in the precooler 200 is delivered from the first cold storage medium outlet 211 at the bottom of the first shell 210, reaches the refrigerator 300 through the first pipeline 810, enters the second dispersion branch 433 through the second cold storage medium inlet 4311 at the upper end of the second dispersion main 431 after being cooled by the refrigerator 300, and is sprayed out of the second dispersion branch 433, so that the cold storage medium can exchange heat with the BOG in the second BOG heat exchange tube 427 in the second shell 410 of the condenser 400, and the temperature of the cold storage medium in the condenser 400 is lower than the condensation temperature of the BOG, and therefore the BOG can be liquefied and liquefied products can be generated. After the cold storage medium in the condenser 400 exchanges heat with the BOG, the cold storage medium is delivered from the second cold storage medium outlet 411 at the bottom of the second housing 410, the second check valve 831 is closed, and the cold storage medium is delivered to the first cold storage medium inlet 2411 at the upper end of the first dispersion manifold 241 through the delivery pump 821, enters the first dispersion branch pipe 242, and the first dispersion branch pipe 242 ejects the cold storage medium, so that the cold storage medium can exchange heat with the LNG in the LNG heat exchange pipe 227 in the first housing 210 of the precooler 200, and the temperature storage amount is reduced again.

In the process of exchanging heat between the cold storage medium in the condenser 400 and the BOG in the second BOG heat exchange tube 427, when the second temperature sensor in the condenser 400 detects that the cold storage medium in the condenser 400 is higher than the second preset value, the cold storage medium cannot liquefy the BOG, the delivery pump 821 is started, the second one-way valve 831 is opened, the cold storage medium in the condenser 400 is delivered into the refrigerator 300 for refrigeration, and the cooled cold storage medium is delivered back into the second dispersion assembly of the condenser 400 for continuing to exchange heat with the BOG in the second BOG heat exchange tube 427, so that the BOG is liquefied and liquefied products are generated.

It will be readily appreciated that the liquefied product may be LNG liquid or may be a mixture of LNG liquid and BOG gas. When the liquefied product is a mixture of LNG liquid and BOG gas, the mixture needs to be subjected to gas-liquid separation, and thus, the BOG condensing system further includes a knock-out tank 500. The knock out drum 500 is provided with a product inlet, a liquid phase outlet, which communicates with the LNG storage tank 100 through a third LNG line 730, and a gas phase outlet, which communicates with the BOG inlet of the precooler 200 through a second BOG line 740, the product outlet 4241 of the condenser 400 communicates with the product inlet of the knock out drum 500 through a product line 720. The second BOG line 740 is provided with a third one-way valve 741 at an end near the BOG inlet.

Liquefied product formed in condenser 400 is externally delivered from second BOG outlet 2341 and enters liquid separation tank 500 from the inlet for gas-liquid separation, LNG formed by BOG liquefaction enters LNG storage tank 100 from the liquid phase outlet, and BOG which has not been liquefied is returned to the first BOG heat exchange assembly of precooler 200.

It is readily understood that the cold storage medium employs a substance having a good cold storage capacity in a low temperature environment and being capable of flowing after exchanging heat with LNG while having a boiling point temperature higher than the BOG temperature in the precooler 200. The heat exchange device still has the capability of carrying out circulating heat exchange in a cold storage medium circulating line after heat exchange with LNG reduces the temperature or precools BOG to raise the temperature. For example, wax-based petroleum hydrocarbons are used as the cold storage medium.

The BOG condensing system further includes a controller electrically connected to the first temperature sensor, the second temperature sensor, the first check valve 811, the second check valve 831, the third check valve 741, the transfer pump 821 and the refrigerator 300 to control the opening and closing of the first check valve 811, the second check valve 831, the third check valve 741, the transfer pump 821 and the refrigerator 300 according to an electric signal transmitted from the first temperature sensor or the second temperature sensor.

Other components and operation of the BOG condensing system according to the embodiment of the first aspect of the present invention are known to those of ordinary skill in the art and will not be described in detail herein.

An embodiment of the second aspect of the present invention provides a method for operating a BOG condensing system, comprising the following steps.

LNG in the LNG storage tank 100 enters the LNG heat exchange assembly in the precooler 200 from the LNG inlet 2211 and exchanges heat with the cold storage medium in the precooler 200 to reduce the temperature of the cold storage medium, and LNG in the LNG heat exchange assembly is transported out from the LNG outlet 2241 after heat exchange. BOG enters the first BOG heat exchange assembly in the precooler 200 from a BOG inlet and exchanges heat with the cold storage medium in the precooler 200 to precool the BOG.

Specifically, LNG in LNG storage tank 100 is pumped by low pressure pump 110, enters feed header 221 from LNG inlet 2211 via first LNG line 610, and is split to LNG heat exchange tubes 227.BOG enters the first intake manifold 231 from the first BOG inlet 2311 and is split to each first BOG heat exchange tube 237. The first nozzles of the first dispersion branch pipes 242 spray cold storage medium, and LNG in the LNG heat exchange pipe 227 exchanges heat with the cold storage medium to reduce the temperature of the cold storage medium, and the LNG after the heat exchange is externally delivered through the LNG outlet 2241. The BOG in the first BOG heat exchange tube 237 exchanges heat with the cold storage medium to pre-cool the BOG. Wherein the LNG heat exchange tubes 227 are disposed intersecting the first BOG heat exchange tubes 237.

It will be readily appreciated that the temperature of the cold storage medium in precooler 200 is higher than LNG and lower than BOG, and is insufficient to liquefy BOG, and only to precool BOG.

The pre-cooled BOG is output from BOG outlet 2341, enters the second BOG heat exchange assembly in condenser 400 from second BOG inlet 4211 via first BOG line 710, and exchanges heat with the cold storage medium in condenser 400 to liquefy BOG and form liquefied product.

It will be appreciated that the liquefied product may be LNG liquid or may be a mixture of LNG liquid and BOG gas.

The liquefied product enters the liquid separation tank 500 for gas-liquid separation, the LNG formed by the BOG liquefaction enters the LNG storage tank 100, and if the liquefied BOG is still present, the non-liquefied BOG is conveyed back to the first BOG heat exchange assembly of the precooler 200, and the above steps are repeated to liquefy the BOG again.

After heat exchange, the cold storage medium in the precooler 200 is cooled further by the refrigerator 300 and then enters the second dispersion branch pipe 433 of the condenser 400, the cold storage medium is ejected from the second nozzle of the second dispersion branch pipe 433 to exchange heat with the BOG in the second BOG heat exchange pipe 427 so as to liquefy the BOG, and the cold storage medium after heat exchange is conveyed back to the precooler 200 so as to form a cold storage medium circulation loop.

Specifically, the cold storage medium exchanges heat with LNG in the first shell 210 of the precooler 200 to reduce the temperature of the cold storage medium, and keeps the temperature of the cold storage medium below a first preset temperature, and exchanges heat with BOG in the first shell 210 to reduce the temperature of BOG, so as to precool the BOG. The temperature of the cold storage medium at this time is higher than the temperature of LNG and lower than the temperature of BOG, and is insufficient to liquefy BOG. The cold storage medium in the precooler 200 is delivered from the first cold storage medium outlet 211 at the bottom of the first shell 210, reaches the refrigerator 300 through the first pipeline 810, enters the second dispersion branch 433 through the second cold storage medium inlet 4311 at the upper end of the second dispersion main 431 after being cooled by the refrigerator 300, and is sprayed out of the second dispersion branch 433, so that the cold storage medium can exchange heat with the BOG in the second BOG heat exchange tube 427 in the second shell 410 of the condenser 400, and the temperature of the cold storage medium in the condenser 400 is lower than the condensation temperature of the BOG, and therefore the BOG can be liquefied and liquefied products can be generated. After the cold storage medium in the condenser 400 exchanges heat with the BOG, the cold storage medium is delivered from the second cold storage medium outlet 411 at the bottom of the second housing 410, the second check valve 831 is closed, and the cold storage medium is delivered to the first cold storage medium inlet 2411 at the upper end of the first dispersion manifold 241 through the delivery pump 821, enters the first dispersion branch pipe 242, and the first dispersion branch pipe 242 ejects the cold storage medium, so that the cold storage medium can exchange heat with the LNG in the LNG heat exchange pipe 227 in the first housing 210 of the precooler 200, and the temperature storage amount is reduced again.

In some embodiments, the LNG export amount is smaller, that is, the LNG import amount into the LNG heat exchange assembly is smaller, so that when the temperature of the cold storage medium in the precooler 200 is lower than the first preset value, the first temperature sensor transmits a signal to the controller, and the controller controls the transfer pump 821, the second check valve 831 and the refrigerator 300 to start, so that the cold storage medium in the condenser 400 enters the second pipeline 820 from the second cold storage medium outlet 411, then enters the first shell 210 of the precooler 200 through the first cold storage medium inlet 2411, the cold storage medium in the precooler 200 enters the refrigerator 300 from the first cold storage medium outlet 211 to reduce the temperature, and then enters the condenser 400 from the second cold storage medium inlet 4311. Through the circulation, the temperature of the cold accumulation medium in the system can be effectively controlled when the LNG output is smaller, and the stability of the system is maintained.

Other configurations and operations of the method of operation of the BOG condensing system according to the second aspect of the embodiments of the present invention are known to those of ordinary skill in the art and will not be described in detail herein.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention.

Claims

A bog condensing system, comprising:

the precooler is internally provided with an LNG heat exchange assembly, a first BOG heat exchange assembly and a cold storage medium, the LNG heat exchange assembly is provided with an LNG inlet and an LNG outlet, LNG in the LNG heat exchange assembly can exchange heat with the cold storage medium in the precooler so as to reduce the temperature of the cold storage medium in the precooler, the first BOG heat exchange assembly is provided with a first BOG inlet and a first BOG outlet, and BOG in the first BOG heat exchange assembly can exchange heat with the cold storage medium in the precooler so as to precool the BOG;

the condenser, be provided with second BOG heat transfer subassembly and cold-storage medium in the condenser, second BOG heat transfer subassembly is provided with second BOG entry and product export, second BOG entry with BOG export intercommunication, precooled BOG pass through second BOG heat transfer subassembly can with cold-storage medium in the condenser exchanges heat to liquefaction BOG and form the liquefaction product.
2. The BOG condensation system according to claim 1, wherein: the LNG heat exchange assembly comprises a liquid inlet main pipe, a liquid outlet main pipe and a plurality of LNG heat exchange pipes, one end of each LNG heat exchange pipe is communicated with the liquid inlet main pipe, the other end of each LNG heat exchange pipe is communicated with the liquid outlet main pipe, the LNG inlet is arranged at one end, far away from the LNG heat exchange pipes, of the liquid inlet main pipe, and the LNG outlet is arranged at one end, far away from the LNG heat exchange pipes, of the liquid outlet main pipe; the first BOG heat exchange assembly comprises a first air inlet main pipe, a first air outlet main pipe and a plurality of first BOG heat exchange pipes, one end of each first BOG heat exchange pipe is communicated with the first air inlet main pipe, the other end of each first BOG heat exchange pipe is communicated with the first air outlet main pipe, the first BOG inlet is arranged at one end, far away from the first BOG heat exchange pipes, of the first air inlet main pipe, and the BOG outlet is arranged at one end, far away from the first BOG heat exchange pipes, of the first air outlet main pipe; the LNG heat exchange pipes and the first BOG heat exchange pipes are arranged in a crossing mode.
3. The BOG condensation system according to claim 2, wherein: the precooler is provided with a first cold storage medium inlet, a first dispersing component is arranged in the precooler and positioned above the LNG heat exchange tube and the first BOG heat exchange tube, the first dispersing component is communicated with the first cold storage medium inlet and comprises a plurality of first nozzles, a first cold storage medium outlet is arranged at the bottom of the precooler, and a first temperature sensor is further arranged in the precooler.
4. The BOG condensation system according to claim 1, wherein: the second BOG heat exchange assembly comprises a second air inlet main pipe, an outlet main pipe and a plurality of second BOG heat exchange pipes, wherein the second air inlet main pipe and the outlet main pipe are respectively and vertically arranged on two sides of the second BOG heat exchange pipes, a second BOG inlet is formed in the upper end of the second air inlet main pipe, a product outlet is formed in the lower end of the outlet main pipe, one end of each second BOG heat exchange pipe is communicated with the lower end of the second air inlet main pipe, and the other end of each second BOG heat exchange pipe is communicated with the upper end of the outlet main pipe.
5. The BOG condensation system of claim 4, wherein: the condenser is provided with the second cold-storage medium entry, the condenser is in the top of second BOG heat exchange tube is provided with second dispersion subassembly, second dispersion subassembly and second cold-storage medium entry intercommunication, just second dispersion subassembly includes a plurality of second spouts, the bottom of condenser is provided with the second cold-storage medium export, still be provided with second temperature sensor in the condenser.
6. The BOG condensation system according to claim 1, wherein: the cooling medium cooling device comprises a condenser, and is characterized by further comprising a cooling medium circulation line, wherein the cooling medium circulation line comprises a first pipeline and a second pipeline, the cooling medium in the precooler enters the condenser through the first pipeline, the cooling medium in the condenser enters the precooler through the second pipeline, a refrigerator is arranged on the first pipeline to reduce the temperature of the cooling medium, a first node is arranged between the precooler and the refrigerator, a second node is arranged on the second pipeline, the first node is communicated with the second node through a third pipeline, a first one-way valve is arranged between the precooler and the first node, a conveying pump is arranged between the condenser and the second node through the second pipeline, and a second one-way valve is arranged on the third pipeline.
7. The BOG condensation system according to claim 1, wherein: the LNG storage tank is communicated with the LNG inlet of the precooler, the liquid separation tank comprises a product inlet, a liquid phase outlet and a gas phase outlet, the product outlet of the condenser is communicated with the product inlet of the liquid separation tank, the gas phase outlet of the liquid separation tank is communicated with the BOG inlet of the precooler, and the liquid phase outlet of the liquid separation tank is communicated with the LNG storage tank.
A method of operating a bog condensing system comprising the steps of:

LNG in the LNG storage tank enters an LNG heat exchange assembly in the precooler from an LNG inlet and exchanges heat with a cold storage medium in the precooler so as to reduce the temperature of the cold storage medium;

the BOG enters a first BOG heat exchange component in the precooler from a BOG inlet and exchanges heat with a cold accumulation medium in the precooler so as to precool the BOG;

the precooled BOG enters a second BOG heat exchange component in the condenser and exchanges heat with a cold accumulation medium in the condenser to liquefy the BOG and form a liquefied product;

and the liquefied product enters a liquid separation tank to carry out gas-liquid separation, LNG formed by BOG liquefaction enters an LNG storage tank, and if the liquefied BOG exists, the liquefied BOG is conveyed back to the first BOG heat exchange component of the precooler.
9. The method of operating a BOG condensing system of claim 8, wherein: LNG in an LNG storage tank is pumped by a low-pressure pump, enters a liquid inlet header pipe from an LNG inlet through a first LNG pipeline, then is split into each LNG heat exchange tube, BOG enters a first air inlet header pipe through a first BOG inlet, then is split into each first BOG heat exchange tube, cold storage media are sprayed out from first nozzles of first dispersing branch pipes, LNG in the LNG heat exchange tubes exchanges heat with the cold storage media in the precooler so as to reduce the temperature of the cold storage media in the precooler, and BOG in the first BOG heat exchange tubes exchanges heat with the cold storage media in the precooler so as to precool BOG in the first BOG heat exchange tubes, wherein the LNG heat exchange tubes and the first BOG heat exchange tubes are arranged in a crossing manner.
10. The method of operating a BOG condensing system of claim 8, wherein: after heat exchange, the cold storage medium in the precooler is cooled further by a refrigerator and then enters a second dispersion branch pipe of the condenser, cold storage medium is sprayed out from a second nozzle of the second dispersion branch pipe to exchange heat with BOG in a second BOG heat exchange pipe so as to liquefy the BOG, and the cold storage medium after heat exchange is conveyed back to the precooler so as to form a cold storage medium circulation loop;

in the process of exchanging heat between the cold storage medium in the condenser and the BOG in the second BOG heat exchange tube, when the second temperature sensor in the condenser detects that the cold storage medium in the condenser is higher than a second preset value, the conveying pump is started, the second one-way valve is started, the cold storage medium in the condenser is conveyed into the refrigerator for refrigeration, and the cooled cold storage medium is conveyed back into the second dispersion assembly of the condenser.