CN102182919B - Device and method for recovery and reliquefaction of boil-off gas of liquefied natural gas - Google Patents
Device and method for recovery and reliquefaction of boil-off gas of liquefied natural gas Download PDFInfo
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Abstract
The invention relates to a device for the recovery and reliquefaction of boil-off gas of liquefied natural gas, which comprises a storage tank with a safety valve and a low-temperature pump, wherein a first interface is formed between the storage tank and the safety valve and is connected with a recovery pipe; the low-temperature pump is provided with a second interface; the other end of the recovery pipe is communicated with a recovery compressor; an outlet of the recovery compressor is connected with a cooler, an oil-gas separator and a boil-off gas distributor, and first boil-off gas and second boil-off gas are respectively discharged from the boil-off gas distributor; the first boil-off gas is communicated with a screw expansion machine and enters a heat exchanger and a second screw compressor; the second boil-off gas is connected with the second interface of the low-temperature pump by the heat exchanger, a throttling valve and a gas-liquid separator; and the liquefied natural gas enters the storage tank. The device has the advantages that by using a screw expansion-compressor set refrigerating reliquefaction method of recovering the boil-off gas directly by the screw compressors and taking the boil-off gas as a refrigerant directly, system flow equipment is simplified, energy waste is avoided, and peripheral environmental pollution and potential safety hazards are avoided, so obvious economic and social benefits are created; and a system runs automatically, continuously and circularly, and has the excellent running work condition and high using efficiency and running reliability.
Description
Technical field
The present invention relates to liquefied gas at low temp storaging and transport technology field; Specifically refer to a kind of boil-off gas (BOG) recovery of the LNG Liquefied natural gas (LNG) in storage tank and the apparatus and method field of liquefying again thereof; It can extensively be suitable for the recovery of boil-off gas in various types of LNG Liquefied natural gas storage facilities and the application of liquefying again.
Background technique
LNG Liquefied natural gas (LNG) is current a kind of desirable clean fuel; This LNG Liquefied natural gas propagation and employment is very important task of current raising energy utilization rate and social benefit.
This LNG Liquefied natural gas (LNG) is the cryogenic liquide that rock gas forms through being cooled to dew point temperature after purifying, and the temperature under normal pressure is-163 ℃; It can be stored in the low-temperature storage tank that double-deck centre vacuumizes, so that transportation and loading and unloading.
Because the ambient temperature of this storage tank is usually above the LNG Liquefied natural gas temperature in this storage tank, under the action of thermal difference of the LNG Liquefied natural gas temperature in ambient temperature and storage tank, boil-off gas (BOG) can be evaporated and form to the LNG Liquefied natural gas (LNG) in the storage tank; In addition, in the liquefied natural gas process of packing in this storage tank, the LNG Liquefied natural gas in this storage tank also can be evaporated the formation boil-off gas; And As time goes on, it is more and more that the boil-off gas in this storage tank gathers, and the temperature and pressure in the described storage tank is raise gradually; When this pressure surpassed described storage tank opening pressure of safety valve, this safety valve was namely opened, and described boil-off gas is released, thereby make described tank inner pressure be down to rating value, to guarantee the safety of described storage tank.
The boil-off gas that described natural gas vaporization produces belongs to greenhouse gases, and these greenhouse effect are 20 times of carbon dioxide, and boil-off gas is directly released in the atmosphere, will cause the heavy damage to environment.
At present, in large-scale liquefied natural gas (LNG) tank, be provided with torch and emptying delivery system, be used for collecting and processing releasing of described boil-off gas; And small-sized liquefied natural gas (LNG) tank, in the atmosphere of normally described boil-off gas directly being released.
The boil-off gas day vaporization rate of existing liquefied natural gas (LNG) tank design is generally 0.05% of total cubical content; The factor that produces boil-off gas in this storage tank has: one, charge and discharge operations can produce a large amount of described boil-off gas; Its two, the cold cycle facilities of described storage tank has heat input also can produce described boil-off gas; Its three, high-pressure service pump and pipeline also have heat input, also can produce described boil-off gas; Its four, because the rolling that causes of described LNG Liquefied natural gas layering also can bring violent evaporation, and produce thus described boil-off gas in the storage tank; In sum, these boil-off gas are directly released in the atmosphere, perhaps burn by flare system, not only waste a large amount of energy and cause direct economic loss, also can surrounding enviroment be polluted simultaneously, and safety of surrounding environment is caused a hidden trouble.
Current, traditional natural gas liquefaction is the method that adopts low-temperature liquefaction, wherein have Cascade, mix refrigerant liquefaction flow path with the liquefaction flow path of decompressor etc., the method flow system is complicated, be suitable for mass production, every kind of flow process all will be set up a LNG plant; Yet the boil-off gas liquefaction for described storage tank and tank area also is provided with corresponding this boil-off gas recovery and reliquefaction installation and method at present.
Summary of the invention
Technical problem to be solved by this invention is the situation for prior art, provides a kind of and not only can stop energy waste but also can avoid liquefied natural gas boiloff gas surrounding enviroment pollution and potential safety hazard thereof, system flow equipment advantages of simple is reclaimed the again apparatus and method of liquefaction.
The present invention solves the problems of the technologies described above the technological scheme that adopts: a kind of liquefied natural gas boiloff gas reclaims the again device of liquefaction, comprise a liquefied natural gas (LNG) tank group, this tank battery is by liquefied natural gas (LNG) tank and be located at the safety valve on its top and the loading valve of bottom forms, be provided with the latent liquid type cryopump between this storage tank and the loading valve, it is characterized in that:
A. be provided with first interface between described liquefied natural gas (LNG) tank and the described safety valve, described latent liquid type cryopump is provided with the second interface; Described first interface is connected with recovery tube, and the other end of this recovery tube is by the first boil-off gas convergence device and the entrance UNICOM that reclaims compressor; Pressure controlled valve is equipped with in this recovery suction port of compressor; Described the first boil-off gas convergence device entrance point also with the described recovery tube second boil-off gas convergence device that is connected in parallel;
B. described recovery compressor is Singe stage screw compressor, this Singe stage screw compressor outlet connects cooler, deaerator and boil-off gas distributor successively by pipeline, this boil-off gas distributor distributes the first boil-off gas and the second boil-off gas, this first boil-off gas with the screw expander entrance UNICOM of rotating speed control valve;
C. the outlet of described screw expander enters heat exchanger by pipeline, then the entrance UNICOM by pipeline and the second helical-lobe compressor; The outlet of this second helical-lobe compressor is by pipeline and described the second boil-off gas convergence device UNICOM;
D. the second boil-off gas of described boil-off gas distributor shunting enters heat exchanger by pipeline, then connects successively throttle valve and gas-liquid separator; This gas-liquid separator lower end is connected with described the second interface by pipeline; This gas-liquid separator upper end enters described heat exchanger by pipeline, again by pipeline and described the second boil-off gas convergence device of described the second screw compressor exit pipeline access in parallel;
E. described Singe stage screw compressor, described the second helical-lobe compressor and described screw expander arrange a cooling and lubricating oil system jointly.
Adopt boil-off gas relieving pressure in the above control liquefied natural gas (LNG) tank device, and directly reclaim with screw expander and realize the boil-off gas method of re-liquefaction as the refrigerator throttling refrigeration, simplified widely that boil-off gas reclaims and the equipment of liquefaction system flow process, realized simultaneously stopping energy waste and avoid surrounding enviroment are polluted and huge economic benefit and the social benefit of potential safety hazard.
In order to regulate the boil-off gas flow of this screw expander, as preferably, described rotating speed control valve can be controlled the rotating speed of described screw expander, thereby regulates the boil-off gas flow of this screw expander; As further preferred, this screw expander is by coupling and described the second helical-lobe compressor Driven by Coaxial; Its effect is to simplify set structure, and helps to make and installation.
For the bearing lubrication that realizes above-described three SCREW COMPRESSOR and the engagement process that screw pair in this compressor is provided form good working oil membrane and its frictional behavior; As preferably, described cooling and lubricating oil system comprises Oil gallery distributor, Singe stage screw compressor oil dispenser, the second screw compression oil distributing box and screw expansion oil distributing box; The lubricant oil of described Singe stage screw compressor oil dispenser is divided into three the tunnel, enters respectively entry end bearing, the outlet end bearing of described Singe stage screw compressor and sprays in the compression chamber of this compressor; Above-mentioned three road lubricant oil are mixed in company with described boil-off gas, enter described cooler and deaerator from the outlet end of described compressor.Its effect is the bearing cooling and lubrication to above three described compressors, and good working oil membrane and the frictional behavior thereof of engagement formation in service that this compressor screw pair is provided.
Above-mentioned three road lubricant oil in company with described boil-off gas together, enter cooler from the outlet of reclaiming compressor, enter deaerator after temperature is down to 40 ℃, the lubricant oil of separating enters the Oil gallery distributor more again, makes lubricant oil continuously circular flow and use.
As further preferred, the lubricant oil of described screw expansion oil distributing box is divided into two the tunnel, enters respectively its entrance and outlet end bearing, is mixed with described boil-off gas again, enter described heat exchanger from the outlet end of described screw expander, and then enter described the second helical-lobe compressor.
As further preferred, the lubricant oil of described the second screw compression oil distributing box is divided into three the tunnel, and left and right sides two-way enters respectively this second helical-lobe compressor entrance and outlet end bearing, is used for the Cooling and Lubricator of bearing; The Third Road hydrojet is cooled off in the described boil-off gas in this compression chamber, makes described screw rod form oil film in joggleword.The boil-off gas that described the second helical-lobe compressor entrance of described three road lubricant oil companion comes together, after compressing, outlet from this second helical-lobe compressor, enter described the second boil-off gas convergence device, after entering described the first boil-off gas convergence device, described pressure controlled valve, described Singe stage screw compressor, described cooler by pipeline again, enter described deaerator, the lubricant oil that this deaerator is separated enters described Oil gallery distributor again.
In order to realize installation of the present invention, debugging, O﹠M is convenient, as preferably, described the first boil-off gas convergence device, described pressure controlled valve and described Singe stage screw compressor, described cooler, described deaerator, described boil-off gas distributor, described the second boil-off gas convergence device, described heat exchanger, described screw expander, described the second helical-lobe compressor, described throttle valve, described gas-liquid separator, described cooling and lubricating oil system and connecting tube thereof, and the electrical source of power that matches and control system, all be contained on the same skid gantry base; As long as described first and second two interfaces are set, use that can be on existing liquefied gas storage or tank area original equipment; Thereby form the liquefied natural gas (LNG) tank boil-off gas that automatically to control of the present invention and reclaim reliquefaction installation.
Boil-off gas recovery method for alternative tank area occasion for having a plurality of liquefied natural gas (LNG) tank, as preferably, can be that outlet with a plurality of liquefied natural gas (LNG) tank is connected in one and discharges on the house steward, this release house steward the other end connects a torch knockout drum, this release house steward is in the front portion that is positioned at described torch knockout drum, connect a total recovery tube, this total recovery tube passes through described the first boil-off gas convergence device and described pressure controlled valve, described Singe stage screw compressor entrance UNICOM.When the pressure of boil-off gas in this release house steward was higher than the 0.015MPa left and right sides of pilot pressure in the torch knockout drum, pressure controlled valve was opened, and the unit starting work of described recovery compressor begins to reclaim boil-off gas; When the pressure of boil-off gas was lower than pilot pressure in the knockout drum in discharging house steward, described pressure controlled valve just cut out, and described recovery compressor stops the recovery of boil-off gas; Like this, the boil-off gas of described tank area constantly automatic cycle reclaims, and can not destroy the normal function of described flare system.
Method and step that described recovery is liquefied again are:
The first step, reclaim with compression when the boil-off gas pressure in the storage tank is lower than the 0.05MPa of opening pressure of safety valve, pressure controlled valve is opened Singe stage screw compressor and is started, and will rise to about 4MPa approximately 180 ℃ of adiabatic compression temperatures from the compression of boil-off gas described in the recovery tube and pressure; But the oil owing to spraying in the compression chamber makes its temperature be down to 70 ℃.
Second step, cooling enters cooler cooling with the described rear boil-off gas that boosts of Oil-gas Separation, then enters deaerator and carries out lubricating oil separation in boil-off gas and the described helical-lobe compressor, enters the boil-off gas distributor again;
In the 3rd step, refrigeration is divided into two-way by pipeline with boil-off gas with the described boil-off gas distributor that liquefies again; First via boil-off gas is as refrigerant, enters screw expander by the rotating speed control valve; The the second road boil-off gas enters gas-liquid separator behind heat exchanger and throttle valve; Boil-off gas after described decompressor expands enters heat exchanger as the first cold flow of refrigeration agent, and described the second road boil-off gas is freezed; Meanwhile, described gas-liquid separator separates low-temperature evaporation gas out, enter described heat exchanger through pipeline, cool off for the second time described the second road boil-off gas as the second cold flow, then after described throttle valve throttling, drop to dew point temperature, and the cryogenic liquide that forms, and enter described gas-liquid separator;
The 4th step, gas-liquid separation and liquefaction are reclaimed and to be carried out boil-off gas in the described gas-liquid separator and separate with described LNG Liquefied natural gas, the liquid that this is separated, be exactly the LNG Liquefied natural gas that reclaims after liquefying again, the LNG Liquefied natural gas after this separation is continuously sent into described liquefied natural gas (LNG) tank by cryopump.
The 5th step, boil-off gas after the described decompressor of boil-off gas circular flow after the expansion expands, enter the second helical-lobe compressor entrance by described heat exchanger, after compression is boosted, from this second screw compressor exit enter second boil-off gas convergence device in parallel with described gas-liquid separator separates low-temperature evaporation gas out, enter again the first boil-off gas convergence device boil-off gas in described recovery tube, reclaim compression and circular flow by described Singe stage screw compressor;
The 6th step, when the reclaiming system boil-off gas pressure in described storage tank out of service is lower than the 0.15MPa of described opening pressure of safety valve, described pressure controlled valve cuts out described Singe stage screw compressor and shuts down, so that it is automatically out of service to reclaim the complete unit of again liquefaction.
The workflow of above step is continuously circular flow process all the time.
The present invention compared with prior art, its advantage is: the employing helical-lobe compressor directly reclaims boil-off gas and directly uses boil-off gas as the screw expansion one compressor bank refrigeration method of re-liquefaction of refrigeration agent, simplified widely the equipment of boil-off gas recovery and liquefaction system flow process, realized simultaneously as stopping energy waste and avoiding significant economic benefit and the social benefit of surrounding enviroment pollution with potential safety hazard; Secondly, system's operation is the continuously circular flow process of automation all the time, thereby has realized reclaiming the operating conditions of reliquefaction installation excellence and utilization efficiency is high, operational reliability is good.
Description of drawings
Fig. 1 is the first embodiment of the invention structural representation;
Fig. 2 is the partial structurtes schematic diagram of second embodiment of the invention;
Fig. 3 is that the present invention is contained in a structural representation on the public skid gantry base;
Embodiment
Embodiment is described in further detail the present invention below in conjunction with accompanying drawing.
Fig. 1 to Fig. 3 illustrates two mode of executions of the present invention, it comprises liquefied natural gas (LNG) tank device 14 (or liquefied natural gas (LNG) tank zone device 17), the first boil-off gas (BOG) convergence device 1, with the recovery compressor 3 of pressure controlled valve 2, this recovery compressor is Singe stage screw compressor, cooler 4, deaerator 5, boil-off gas (BOG) distributor 6, the second boil-off gas (BOG) convergence device 7, plate-fin heat exchanger 8, butterfly rotating speed control valve 9, by screw expander 10 and the second helical-lobe compressor 11 coaxial linkages cooling machine set, throttle valve 12, gas-liquid separator 13 and cooling and lubricating system 15; , except liquefied natural gas (LNG) tank device 14, all be contained on the public skid gantry base 16 by the package unit that forms with upper-part, so that installation of the present invention, debugging, accumulating, O﹠M.
The present invention is the pressure that boil-off gas is released in the described liquefied natural gas (LNG) tank device 14 of control to LNG Liquefied natural gas recovery method of boil-off gas in storage tank, and directly reclaims with reclaiming compressor 3; For different occasions, address the method for direct recovery by following two embodiments;
First embodiment is aimed at boil-off gas recovering device and the method for single storage tank, it adopts and connect a recovery tube 145 below storage tank safety valve 141, the other end of this recovery tube 145 and entrance 31 UNICOMs that reclaim compressor 3, butterfly type pressure controlled valve 2 is equipped with in this ingress; When the pressure of boil-off gas in the storage tank (BOG) was lower than the 0.05MPa left and right sides of safety valve 141 cracking pressures, this pressure controlled valve 2 was opened, and reclaimed compressor 3 startups; The unit of this recovery compressor 3 is started working, and namely begins the recovery of boil-off gas (BOG) in the storage tank.
When the pressure of BOG in the storage tank was lower than the 0.15MPa of described opening pressure of safety valve, pressure controlled valve 2 cut out, and the unit of this recovery compressor 3 quits work, and boil-off gas (BOG) reclaims and just stops in the storage tank.Said process is automatic cycle constantly, just can all reclaim boil-off gas (BOG) in the storage tank.
Recovery boil-off gas method of re-liquefaction of the present invention is: directly use boil-off gas (BOG) in the storage tank 142 as refrigeration agent, with Singe stage screw compressor as after reclaiming compressor 3 compressions, make the pressure of this boil-off gas rise to 4～4.5MPa, use again screw expander 10 as the method for refrigerator throttling refrigeration, make described boil-off gas (BOG) reach the temperature of liquefaction, liquefy with realization.
Among Fig. 1, liquefied natural gas (LNG) tank group 14 is existing equipments, it comprise liquefied natural gas (LNG) tank 142 with and top be provided with safety valve 141, bottom and be provided with loading valve 143 and latent liquid type cryopump 144.
The below of safety valve 141 arranges an interface A, and interface A connects a BOG recovery tube 145, and the other end of this recovery tube 145 is connected with a BOG convergence device 1; The one BOG convergence device 1 is connected with the second convergence device 7 by managing 113 again.
After the BOG of BOG and the 2nd BOG convergence device 7 merges in a BOG convergence device from recovery tube 145, enter pressure controlled valve 2; The outlet of this pressure controlled valve is connected with the entrance 31 of Singe stage screw compressor 3.When the pressure of storage tank 142 interior BOG is lower than the 0.05MPa left and right sides of safety valve 141 cracking pressures, compressor start and pressure controlled valve 2 are opened, BOG enters the entrance 31 of Singe stage screw compressor 3 and compressed, when the pressure after BOG is compressed is increased to 4～4.5MPa, enter cooler 4 from compressor outlet by pipeline 101, make the temperature cooling of BOG, enter deaerator 5 by pipeline 102, with the lubricating oil separation in pressurized gas and the compressor.
BOG out enters BOG distributor 6 from oil separator 5, and this distributor is divided into two the tunnel with BOG: first via BOG enters butterfly rotating speed control valve 9 by pipeline 104, and the outlet of rotating speed control valve 9 is connected with the entrance of screw expander 10; When the pressure of pipeline 104 interior BOG reached 4MPa, rotating speed control valve 9 was opened, and BOG enters decompressor 10, and the pressure and temperature of BOG all reduces after expanding, and it enters finned heat exchanger 8 by pipeline 106 again as the cold flow of the first refrigerant; At this moment, from BOG distributor 6 the second road BOG out, enter finned heat exchanger 8 by pipeline 103, this second road BOG is for the first time by described the first cold flow cooling.
After BOG after the process decompressor expands enters plate-fin heat exchanger 8 as cold flow by pipeline 106, entering the second helical-lobe compressor 11 by pipeline 108 again compresses, after pressure raises, enter the 2nd BOG convergence device 7 from the second screw compressor exit and by pipeline 110.
By the adjusting to rotating speed control valve 9 open amounts, can obtain the required rotating speed of described screw expander 10, thereby realize the BOG flow control that enters this screw expander.This screw expander is by described the second helical-lobe compressor 11 of coupling 20 Driven by Coaxial.
Low temperature BOG out enters heat exchanger 8 by pipeline 109 from gas-liquid separator 13, and this low temperature BOG is as the cold flow of the second refrigerant, and cooling is from the second road BOG that enters finned heat exchanger of BOG distributor 6 for the second time; After this second road BOG is cooled, pressure is about 4MPa, temperature is down to about-85 ℃ from heat exchanger 8 out, by pipeline 105 after throttle valve 12 throttlings, this the second road BOG Pressure Drop to the 0.8MPa, temperature is down to about-130 ℃, enter by pipeline 107 and to carry out BOG in the gas-liquid separator 13 and separate with LNG, LNG Liquefied natural gas after the separation (LNG) is sent into liquefied natural gas (LNG) tank 142 by pipeline 131 and the interface (B) divided into through latent liquid type cryopump 144; Boil-off gas after the separation (BOG) enters plate-fin heat exchanger 8 as cold flow by pipeline 109, and cooling is from the second road BOG of BOG distributor 6 for the second time.
Continuous circulation running in sum just can continuously be reclaimed BOG and make it be liquefied as LNG, and be entered liquefied natural gas (LNG) tank 142.
When liquefied natural gas (LNG) tank 142 interior BOG pressure were lower than the 0.15MPa left and right sides of safety valve 141 cracking pressures, pressure controlled valve 2 cut out, and Singe stage screw compressor 3 shuts down, and whole unit is just out of service.
Cooling and lubricating oil system 15 of the present invention is comprised of Oil gallery distributor 151, recovery compressor oil distributor 152, the second screw compression oil dispenser 153, screw expansion oil distributing box 154 and respective lines; This cooling and lubricating oil system conduct independently parts is installed on the skid base 16; Lubricating oil temperature is 40 ℃, pressure is that the lubricant oil of 4～4.5MPa is from deaerator 5, enter Oil gallery distributor 151, divide three the tunnel to enter respectively recovery compressor oil distributor 152, the second screw compression oil distributing box 153 and screw expansion oil distributing box 154 after the decompression.Enter the lubricant oil that reclaims compressor oil distributor 152 and be divided into three the tunnel again, enter respectively entry end bearing, the outlet end bearing that reclaims compressor and spray in the compression chamber of this compressor, the cooling and lubrication that is used for bearing, and compressor screw forms working oil membrane in the operation engagement.
Above-mentioned three road lubricant oil enter cooler 4 from the outlet of reclaiming compressor 3 in company with BOG together, enter deaerator 5 after temperature is down to 40 ℃ again, and the lubricant oil of separating enters Oil gallery distributor 151 again, and lubricant oil is continuously recycled.
The lubricant oil that enters screw expansion oil distributing box 154 is divided into two the tunnel again, enters respectively decompressor entry end and outlet end bearing, is used for the Cooling and Lubricator of bearing.This two road binders enters finned heat exchanger 8 with BOG from the outlet end of screw expander, enters the entrance of the second helical-lobe compressor 11 again.
The lubricant oil that enters the second screw compression oil distributing box 153 is divided into three the tunnel again, and left and right sides two-way enters respectively the second helical-lobe compressor entry end and outlet end bearing, is used for the Cooling and Lubricator of bearing; The Third Road hydrojet is cooled off in the BOG in compression chamber, makes the second helical-lobe compressor screw rod form working oil membrane in the operation engagement.The BOG that these three road binders companion the second helical-lobe compressor, 11 entrances come and oil are together, after compressing, outlet from the second helical-lobe compressor 11, enter the 2nd BOG convergence device 7, enter by pipeline 113 again first converge BOG device 1, pressure controlled valve 2, reclaim compressor 3 and cooler 4 after, enter deaerator 5, the lubricant oil of separating enters Oil gallery distributor 151 again, makes continuously periodic duty of lubricant oil.
Fig. 3 illustrates all parts of the present invention (except existing liquefied natural gas (LNG) tank device 14) and all can be contained on the public skid gantry base 16, forms a complete skid unit.This unit only has two interfaces: namely one is and the connecting port A of existing LNG storage tank 142, and this connecting port A is below safety valve 141, and links by pipeline 145 and a BOG convergence device 1; Another is LNG outlet B, and this outlet B is below existing latent liquid type cryopump 144, and links by the liquid outlet of pipeline 131 with gas-liquid separator 13.
The supporting electrical source of power of described unit and control system 191 with existing liquefied natural gas (LNG) tank device 14, form the liquefied natural gas (LNG) tank boil-off gas that can automatically control of the present invention and reclaim reliquefaction installation.
Second embodiment of the invention is the boil-off gas recovery method for the tank area 17 with a plurality of liquefied natural gas (LNG) tank, its difference is to adopt respectively outlet with described a plurality of liquefied natural gas (LNG) tank 142 to be connected in to discharge on the house steward 147, this release house steward 147 the other ends connect a torch knockout drum 148, this release house steward 147 connects a total recovery tube 149 in the front portion that is positioned at torch gas liquid knockout drum 148, this total recovery tube 149 and entrance 31 UNICOMs that reclaim compressor 3, pressure controlled valve 2 is equipped with in this ingress; When the pressure of boil-off gas (BOG) was higher than the 0.015MPa left and right sides of pilot pressure in the torch knockout drum in discharging house steward, pressure controlled valve 2 was opened, and reclaims the unit starting work of compressor, begins to reclaim BOG; When the pressure of boil-off gas (BOG) was lower than pilot pressure knockout drum in discharging house steward, pressure controlled valve 3 just cut out, and reclaims compressor and does not work, and the BOG recovery also stops; Like this, constantly automatic circulating operation just can reclaim to maximum flow the BOG of tank area, does not also destroy the normal function of flare system.
Below be the operation overall process (wherein opening pressure of safety valve is set as 0.95MPa) of first embodiment of the invention:
When the boil-off gas pressure in the storage tank 142 is lower than the 0.05MPa of safety valve 141 cracking pressures, namely during (0.95-0.05)=0.9MPa, reclaiming compressor 3 starts, after spending 20 seconds, pressure controlled valve 2 is opened, boil-off gas pressure is risen to about 4MPa, and approximately 180 ℃ of adiabatic compression temperatures enter pipeline 101; Owing to spray into the compression chamber that reclaims compressor 3 from the lubricant oil that reclaims compressor oil distributor 152, because this lubricant oil cooling action is down to about 70 ℃ the boil-off gas true temperature in the pipeline 101; After cooler 4 coolings, enter deaerator 5 from pipeline 102, enter again boil-off gas distributor 6, the temperature of boil-off gas is down to 40 ℃ again in the pipeline 102.
Boil-off gas distributor 6 is divided into two-way by 103 and 104 pipelines with boil-off gas; First via boil-off gas is to enter rotating speed control valve 9 from pipeline 104, and when the pressure in the pipeline 104 reached 4MPa, this rotating speed control valve 9 was opened, and first via boil-off gas enters decompressor 10; The the second road boil-off gas be from pipeline 103 behind heat exchanger 8 and throttle valve 13, enter gas-liquid separator 13; Boil-off gas after described decompressor expands enters finned heat exchanger 8 as the first cold flow of refrigeration agent, and described first via BOG103 is freezed, and the pressure in the pipeline 106 is 0.2982MPa, temperature-77.32 ℃;
Control the rotating speed of decompressor 10 by adjusting rotary speed control valve 9 about 1200 rev/mins; This decompressor directly with the 11 coaxial runnings of the second helical-lobe compressor, first via boil-off gas after will the expansion from pipeline 106 enters finned heat exchanger 8, it as the first cold flow boil-off gas behind pipeline 108, enter the second helical-lobe compressor 11 entrances, enter pipeline 110 after boosting, its pressure is about 0.8MPa, and temperature is about 102 ℃.Owing to spraying into the compression chamber of the second helical-lobe compressor from the lubricant oil of the second screw compression oil dispenser 153, the BOG true temperature in the pipeline 110 be down to about 50 ℃.
From gas-liquid separator 13 low temperature BOG out, enter finned heat exchanger 8 through pipeline 109, cool off for the second time the first via boil-off gas that from pipeline 103, enters heat exchanger 8 as the second cold flow, then through pipeline 105 (at this moment, temperature reaches about-87 ℃, pressure reaches about 4MPa) enter throttle valve 12, after the throttle valve throttling, the boil-off gas of throttling expansion enters gas-liquid separator 13 through pipeline 107.This gas-liquid separator separates liquid out is exactly the LNG Liquefied natural gas that reclaims after liquefying again, and its mass flow rate is about about 22kg/h.This LNG Liquefied natural gas is delivered to described storage tank 142 through latent liquid type cryopump 144 again.The quality that reclaims the LNG after BOG and described recovery are liquefied again is equal to, and also is about 22kg/h.
When the pressure of the BOG in the storage tank 142 is lower than 0.8MPa, reclaim compressor 3 by pressure controlled valve 2 controls and shut down, this pressure controlled valve cuts out immediately.Whole reclaiming system is just automatically out of service.Namely realize AutoPlay function of the present invention according to said process.
The present invention adopts helical-lobe compressor and screw expansion compressor combination structure liquifying method, simplified widely the equipment of described boil-off gas (BOG) recovery and liquefaction flow path, and can realize that whole unit is made on the public skid gantry base 16, make installation, debugging, the O﹠M of its unit all very convenient; Also do not affect simultaneously the use function of former liquefaction gas storage tank and tank area original equipment.
Claims (8)
1. a liquefied natural gas boiloff gas reclaims the again device of liquefaction, comprise a liquefied natural gas (LNG) tank group (14), this tank battery is comprised of liquefied natural gas (LNG) tank (142) and the safety valve (141) that is located at its top loading valve (143) with the bottom, be provided with latent liquid type cryopump (144) between this storage tank (142) and the loading valve (143), it is characterized in that:
A. be provided with first interface (A) between described liquefied natural gas (LNG) tank (142) and the described safety valve (141), described latent liquid type cryopump (144) is provided with the second interface (B); Described first interface (A) is connected with recovery tube (145), and the other end of this recovery tube is by the first boil-off gas convergence device (1) and entrance (31) UNICOM that reclaims compressor; Pressure controlled valve (2) is equipped with in this recovery suction port of compressor (31); Described the first boil-off gas convergence device (1) entrance point also with described recovery tube (145) the second boil-off gas convergence device (7) that is connected in parallel;
B. described recovery compressor is Singe stage screw compressor (3), this Singe stage screw compressor (3) outlet connects cooler (4), deaerator (5) and boil-off gas distributor (6) successively by pipeline, this boil-off gas distributor (6) distributes the first boil-off gas (104) and the second boil-off gas (103), this first boil-off gas (104) and screw expander (10) the entrance UNICOM that is with rotating speed control valve (9);
C. the outlet of described screw expander (10) enters heat exchanger (8) by pipeline, then the entrance UNICOM by pipeline and the second helical-lobe compressor (11); The outlet of this second helical-lobe compressor (11) is by pipeline and described the second boil-off gas convergence device (7) UNICOM;
D. second boil-off gas (103) of described boil-off gas distributor shunting enters heat exchanger (8) by pipeline, then connects successively throttle valve (12) and gas-liquid separator (13); This gas-liquid separator (13) lower end is connected with described the second interface by pipeline; This gas-liquid separator (13) upper end enters described heat exchanger (8) by pipeline, again by pipeline and described the second boil-off gas convergence device (7) of described the second helical-lobe compressor (11) outlet conduit access in parallel;
E. described Singe stage screw compressor (3), described the second helical-lobe compressor (11) arrange a cooling and lubricating oil system (15) jointly with described screw expander (10).
2. described liquefied natural gas boiloff gas reclaims the again device of liquefaction according to claim 1, it is characterized in that: described rotating speed control valve (9) can be controlled the rotating speed of described screw expander (10), thereby regulates the boil-off gas flow of this screw expander; This screw expander is by coupling (20) described the second helical-lobe compressor of Driven by Coaxial (11).
3. described liquefied natural gas boiloff gas reclaims the again device of liquefaction according to claim 1, and it is characterized in that: described cooling and lubricating oil system (15) comprises Oil gallery distributor (151), Singe stage screw compressor oil dispenser (152), the second screw compression oil distributing box (153), screw expansion oil distributing box (154); The lubricant oil of described Singe stage screw compressor oil dispenser (152) is divided into three the tunnel, enters respectively entry end bearing, the outlet end bearing of described Singe stage screw compressor and sprays in the compression chamber of Singe stage screw compressor; Above-mentioned three road lubricant oil are mixed in company with described boil-off gas, enter described cooler (4) and deaerator (5) from the outlet end of described Singe stage screw compressor.
4. described liquefied natural gas boiloff gas reclaims the again device of liquefaction according to claim 3, it is characterized in that: the lubricant oil of described screw expansion oil distributing box (154) is divided into two the tunnel, enter respectively its entrance and outlet end bearing, be mixed with described boil-off gas again, enter described heat exchanger (8) from the outlet end of described screw expander, and then enter described the second helical-lobe compressor (11).
5. described liquefied natural gas boiloff gas reclaims the again device of liquefaction according to claim 3, it is characterized in that: the lubricant oil of described the second screw compression oil distributing box (153) is divided into three the tunnel, left and right sides two-way enters respectively this second helical-lobe compressor entrance and outlet end bearing, is used for the Cooling and Lubricator of bearing; The Third Road hydrojet is cooled off in the described boil-off gas in the compression chamber of this second helical-lobe compressor, makes described screw rod form oil film in joggleword; The described boil-off gas that described the second helical-lobe compressor entrance of described three road lubricant oil companion comes together, after compressing, outlet from this second helical-lobe compressor, enter described the second boil-off gas convergence device (7), after entering described the first boil-off gas convergence device (1), described pressure controlled valve (2), described Singe stage screw compressor (3), described cooler (4) by pipeline again, enter described deaerator (5), the lubricant oil that this deaerator is separated enters described Oil gallery distributor (151) again.
6. described liquefied natural gas boiloff gas reclaims the again device of liquefaction according to claim 1, it is characterized in that: described the first boil-off gas convergence device (1), described pressure controlled valve (2) and described Singe stage screw compressor (3), described cooler (4), described deaerator (5), described boil-off gas distributor (6), described the second boil-off gas convergence device (7), described heat exchanger (8), the described screw expander (10) of described band rotating speed control valve (9), described the second helical-lobe compressor (11), described throttle valve (12), described gas-liquid separator (13), described cooling and lubricating oil system (15) and connecting tube thereof, and the supporting electrical source of power of described device and control system (191), all be contained on the same skid gantry base (16).
7. described liquefied natural gas boiloff gas reclaims the again device of liquefaction according to claim 1, it is characterized in that: the outlet of a plurality of described liquefied natural gas (LNG) tank (142) is connected in and discharges on the house steward (147), this release house steward the other end connects a torch knockout drum (148), the front portion that this release house steward (147) is positioned at described torch knockout drum connects a total recovery tube (149), and this total recovery tube is by described the first boil-off gas convergence device (1) and described pressure controlled valve (2) and described recovery suction port of compressor (31) UNICOM.
8. a liquefied natural gas boiloff gas reclaims the again method of liquefaction, it is characterized in that: the workflow of described recovery method of re-liquefaction system operation is as follows:
The first step, reclaim and compression: when the boil-off gas pressure in the storage tank (142) is lower than the 0.05MPa of safety valve (141) cracking pressure, pressure controlled valve (2) is opened, Singe stage screw compressor (3) starts, to compress from boil-off gas described in the recovery tube (145), and pressure rises to about 4MPa approximately 180 ℃ of adiabatic compression temperatures, but the oil owing in the compression chamber that sprays into Singe stage screw compressor makes described boil-off gas temperature be down to 70 ℃;
Second step, cooling and Oil-gas Separation: the described rear boil-off gas that boosts enters cooler (4) cooling, then enter deaerator (5) and carry out lubricating oil separation in described gas and the described Singe stage screw compressor, enter again boil-off gas distributor (6);
In the 3rd step, refrigeration and again liquefaction: described boil-off gas distributor (6) is divided into two-way by pipeline with boil-off gas; First via boil-off gas (104) is as refrigerant, enters decompressor (10) by rotating speed control valve (9); The the second road boil-off gas (103) enters gas-liquid separator (13) behind heat exchanger (8) and throttle valve (12); Boil-off gas after described decompressor (10) expands enters heat exchanger (8) as the first cold flow of refrigeration agent, and the second road boil-off gas (103) is freezed; Meanwhile, the low-temperature evaporation gas that described gas-liquid separator (13) is separated, enter described heat exchanger (8) through pipeline, cool off for the second time this second road boil-off gas (103) as the second cold flow, then the second road boil-off gas is after described throttle valve throttling, drops to dew point temperature and the cryogenic liquide that forms enters described gas-liquid separator (13);
The 4th step, gas-liquid separation is reclaimed with liquefaction: carry out boil-off gas in the described gas-liquid separator (13) and separate with LNG Liquefied natural gas, the liquid that this is separated, be exactly the LNG Liquefied natural gas that reclaims after liquefying again, the LNG Liquefied natural gas after this separation is sent into described liquefied natural gas (LNG) tank (142) by described cryopump (144);
The 5th step, boil-off gas circular flow after the expansion: the boil-off gas after described decompressor (10) expands, enter the second helical-lobe compressor (11) entrance by described heat exchanger (8), after compression is boosted, the low-temperature evaporation gas second boil-off gas convergence device (7) that enters in parallel of separating from this second screw compressor exit and described gas-liquid separator (13), then, enter the first boil-off gas convergence device (1) and reclaim compression with boil-off gas in the described recovery tube (145) by described Singe stage screw compressor (3);
The 6th step, reclaiming system is out of service: when the boil-off gas pressure in the described storage tank (142) is lower than the 0.15MPa of described safety valve (141) cracking pressure, described pressure controlled valve (2) cuts out, described Singe stage screw compressor (3) shuts down, and the complete unit that reclaims again liquefaction is automatically out of service;
Above system operation workflow is continuously circular flow process all the time.
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| CN102425725B (en) * | 2011-12-05 | 2013-07-24 | 四川金星压缩机制造有限公司 | System and method for reclaiming boil off gas (BOG) in liquefied natural gas (LNG) storage tank |
| CN103398288B (en) * | 2013-08-12 | 2015-12-23 | 广西新天德能源有限公司 | carbon dioxide storage tank |
| CN103697327B (en) * | 2013-12-13 | 2016-05-18 | 江苏克劳特低温技术有限公司 | A kind of zero-emission liquid feeding system and method thereof |
| CN105020583A (en) * | 2014-04-24 | 2015-11-04 | 陕西重型汽车有限公司 | Overpressure exhaust recycling device of automotive LNG supply system |
| CN104073309B (en) * | 2014-07-14 | 2015-12-16 | 北京海珍志阔科技有限公司 | The method of bio-natural gas preparation facilities and preparation thereof |
| CN104792114B (en) * | 2015-04-10 | 2017-11-07 | 四川金科深冷设备工程有限公司 | The re-liquefied techniques of BOG and its re-liquefied recovery system |
| CN104806879A (en) * | 2015-04-22 | 2015-07-29 | 四川金科深冷设备工程有限公司 | BOG recovery system for LNG (Liquefied Natural Gas) gas station |
| CN106838605B (en) * | 2017-02-09 | 2018-09-28 | 中国海洋石油集团有限公司 | A kind of process and device for LNG receiving stations BOG systems |
| CN106705569A (en) * | 2017-03-28 | 2017-05-24 | 北京工业大学 | Volumetric combustible gas liquefying device utilizing compression-expansion refrigeration and using method thereof |
| CN108799823A (en) * | 2017-05-02 | 2018-11-13 | 中国石油化工股份有限公司 | A kind of recycling of On Lng Leakage and boil-off gas retracting device |
| CN108317391A (en) * | 2018-03-22 | 2018-07-24 | 上海华林工业气体有限公司 | A kind of CO supply systems optimized based on CO compressor output pressure differences |
| CN108506726B (en) * | 2018-04-11 | 2024-01-19 | 青岛乐戈新能源科技有限公司 | Unloading system and unloading method of low-temperature liquid tank car |
| CN109798439A (en) * | 2019-03-05 | 2019-05-24 | 江苏鼎程新能源科技有限公司 | A kind of re-liquefied system of BOG |
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| DE4417106A1 (en) * | 1994-05-16 | 1995-11-23 | Hermeling Werner Dipl Ing | Gas compression process for gases kept in liquefied form under low pressure in tank |
| DE59600717D1 (en) * | 1995-05-02 | 1998-11-26 | Linde Ag | HIGH PRESSURE GAS SUPPLY |
| JP2000018499A (en) * | 1998-07-06 | 2000-01-18 | Nec Corp | Liquefied gas storage installation |
| CN101943163B (en) * | 2010-09-10 | 2011-12-07 | 宁波鲍斯能源装备股份有限公司 | Two-stage medium-pressure screw-type air compressor set |
| CN202012731U (en) * | 2011-03-26 | 2011-10-19 | 宁波鲍斯能源装备股份有限公司 | Device for recovering LNG (liquefied natural gas) evaporated gas and liquefying again |
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Inventor after: Jia Anquan Inventor after: Lu Xuesheng Inventor after: Zhu Shiming Inventor after: Zhang Jiongyan Inventor after: Luo Jiangen Inventor before: Jia Anquan Inventor before: Lu Xuesheng Inventor before: Cheng Junfeng Inventor before: Zhang Jiongyan Inventor before: Luo Jiangen |
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Address after: 315505 Zhejiang Province, Ningbo city Fenghua District streets Xiwu Shang Qiao Road No. 18 Patentee after: NINGBO BAOSI ENERGY EQUIPMENT Co.,Ltd. Address before: 315505 Zhejiang province Fenghua city streets Xiwu Shang Qiao Road No. 18 Patentee before: NINGBO BAOSI ENERGY EQUIPMENT Co.,Ltd. |