CN105240064A - LNG (Liquefied Natural Gas) energy recovery process - Google Patents

Abstract

The invention relates to the technical field of natural gas low temperature equipment, in particular to an LNG energy recovery process. By an LNG hydraulic turbine device (or expanding machinery in other forms), high pressure and low temperature LNG converts pressure energy to mechanical energy which is output by a supercharging end of the LNG hydraulic turbine device. Depressurized LNG is further cooled, a gas phase and a liquid phase generated in a depressurizing process are separated by a gas-liquid separation tank, the liquid LNG is charged to an LNG storage tank, and the gas phase BOG and BOG of the LNG storage tank are supercharged together by the supercharging end, namely, a BOG supercharger, of the LNG hydraulic turbine device. The LNG hydraulic turbine device replaces a J-T valve of the LNG product for expanding throttling, as the LNG is lower in temperature, output of the BOG is reduced, LNG yield is improved, and mechanical energy can be recovered by BOG supercharging of the BOG supercharging end.

Description

A kind of LNG energy recovery process

Technical field

The present invention relates to natural gas in low temperature equipment technical field, particularly a kind of LNG energy recovery process.

Background technique

LNG Liquefied natural gas (LiquefiedNaturalGas is called for short LNG), main component is methane, and being recognized is the energy the cleanest on the earth.Colourless, tasteless, nontoxic and non-corrosiveness, its volume is about with amount gaseous natural gas volume 1/625, and the weight of LNG Liquefied natural gas is only about 45% of consubstantiality ponding.Very little to atmospheric pollution after LNG Liquefied natural gas burning, and liberated heat is large, so LNG Liquefied natural gas is a kind of more advanced energy.

The manufacture process that LNG Liquefied natural gas is general is the LNG first rock gas after purification being liquefied as high pressure, low temperature through various refrigeration process, then enter normal pressure or low pressure tank by the LNG of Joule-Thomson (J-T) valve further reducing pressure by regulating flow formation low pressure, low temperature, the significant losses that this process causes high-grade energy causes waste.Meanwhile, the BOG amount that the flash distillation of LNG produces is comparatively large, adds the cost of BOG process.

Summary of the invention

The present invention is directed to prior art Problems existing, a kind of LNG energy recovery process is provided.

Technological scheme of the present invention is:

A kind of LNG energy recovery process, comprises the steps:

1) rock gas through pre-treater purification enters ice chest, through the LNG of precooling, cryogenic technology liquefaction formation high pressure low temperature;

2) LNG of described high pressure low temperature reduces pressure through the inflating end of expansion machinery device, while the pressure energy of self is converted into mechanical energy, exports low temperature, low pressure LNG;

3) described low temperature, low pressure LNG carry out after gas-liquid separation through knockout drum, liquid phase LNG send LNG storage tank to store, and gas phase BOG converges, by the pressurized end of LNG hydraulic turbine installation with the BOG from LNG storage tank 4, enter the supercharging of BOG pressure-increasing machine to export, realize the recovery of energy.LNG temperature after step-down is lower, contributes to the generation reducing BOG.

Wherein, BOG pressure-increasing machine, the supercharging of the BOG produced for LNG expansion decompression and the BOG of LNG storage tank.

Preferably, described expansion machinery device is LNG hydraulic turbine installation.

Preferably, the inflating end of described LNG hydraulic turbine installation is preferably centrifugal, also can be axial flow, screw type or reciprocating.

Preferably, the inflating end of described LNG hydraulic turbine installation is main driving, and the motor of described LNG hydraulic turbine installation is auxiliary drive; Drive pattern COMM communication is provided with between described LNG hydraulic turbine installation inflating end and motor 7.

Preferably, described drive pattern COMM communication is overrunning cluth or hydraulic couplers.For overrunning cluth: when without LNG hydraulic turbine installation (or other expansion machinery) inflating end power stage or power stage too small, motor can drive separately BOG pressure-increasing machine.When rotating speed higher than motor of the rotating speed of LNG hydraulic turbine or other expansion machinery, overrunning cluth closes, and realizes the recovery of energy.When the rotating speed of LNG hydraulic turbine (or other expansion machinery) inflating end is lower than the rotating speed of main motor or when not exporting, overrunning cluth is thrown off, and the driving of BOG pressure-increasing machine is by motoring.

Preferably, the rated power of described motor, under the driving without described LNG hydraulic turbine inflating end, can drive separately BOG pressure-increasing machine.

Preferably, when rotating speed higher than described motor of the rotating speed of described LNG hydraulic turbine inflating end, overrunning cluth closes, and realizes the recovery of energy; When rotating speed lower than described motor of the rotating speed of described LNG hydraulic turbine inflating end, described overrunning cluth is thrown off, and the driving of described BOG pressure-increasing machine is by described motoring.

Preferably, inflating end and the BOG pressure-increasing machine of described LNG hydraulic turbine installation are coaxially installed, and also can adopt other kind of drive.

Preferably, Dual Drive pattern is adopted between the pressurized end of described LNG hydraulic turbine installation and the input end of BOG pressure-increasing machine.

The invention has the beneficial effects as follows:

(1) the J-T valve using the inflating end of LNG hydraulic turbine installation (or expansion machinery of other form) to substitute LNG product carries out the expansion decompression of LNG, and because post-decompression LNG temperature is lower, therefore LNG output increased, BOG measures minimizing.

(2) inflating end of LNG hydraulic turbine installation (or expansion machinery of other form) transforms gained mechanical energy and exports to power take-off for BOG supercharging, can realize effective recovery of energy, save the power consumption of BOG supercharging.

(3) driving of BOG pressure-increasing machine adopts Energy transmission and motor two kinds of drive patterns of LNG hydraulic turbine installation (or expansion machinery of other form), powershift is carried out by overrunning cluth or hydraulic couplers, avoid technological fluctuation comparatively large, the shortcoming of outer defeated power instability.

Accompanying drawing explanation

Accompanying drawing 1 is the schematic flow sheet of LNG energy recovery process;

Wherein, 1 is ice chest; 2 is the inflating end of LNG hydraulic turbine installation (or expansion machinery of other form); 3 is knockout drum; 4 is LNG storage tank; 5 is pressurized end---the BOG pressure-increasing machine of LNG hydraulic turbine installation (or expansion machinery of other form); 6 is drive pattern COMM communication; 7 is motor.

Embodiment

The specific embodiment of the present invention is as follows,

Embodiment 1:

LNG hydraulic turbine installation (or expansion machinery of other form) is for LNG hydraulic turbine installation:

As shown in Figure 1, be a kind of schematic flow sheet of LNG energy recovery process, comprise:

Rock gas through pre-treater purification enters ice chest 1, in ice chest in heat exchanger with cryogen heat exchange, through the LNG of precooling, cryogenic technology liquefaction formation high pressure low temperature, this LNG reduces pressure through the inflating end 2 of LNG hydraulic turbine installation, the pressure energy of self is converted into mechanical energy, exports low temperature, low pressure LNG; Described low temperature, low pressure LNG are after knockout drum 3 carries out gas-liquid separation, liquid phase LNG send LNG storage tank 4 to store, gas phase BOG converges with the BOG from LNG storage tank 4, by the pressurized end of LNG hydraulic turbine installation---BOG pressure-increasing machine 5 carries out supercharging, enter BOG pressure-increasing machine to export, realize the recovery of energy.LNG temperature after step-down is lower, contributes to the generation reducing BOG.

The inflating end 2 of LNG hydraulic turbine installation is centrifugal, and LNG hydraulic turbine installation expansion pressure reduction can carry out in the simple liquid phase that pressure is higher, also can carry out at the Gas-liquid phase region that pressure is lower.

BOG both can direct supercharging under low-temperature condition, also can be reclaimed after cold or other mode of heating re-heat to normal temperature again through the supercharging of BOG pressure-increasing machine by ice chest or other heat exchange.For the LNG device of 2,000,000 sides/d scale, LNG hydraulic turbine installation output shaft power can reach 170 ~ 190kW.

The energy input end of the pressurized end of LNG hydraulic turbine installation---BOG pressure-increasing machine 5 adopts Dual Drive pattern, LNG hydraulic turbine installation inflating end 2 is main driving, motor 7 is auxiliary drive, be provided with drive pattern COMM communication 6 between LNG hydraulic turbine installation inflating end 2 and motor 7, drive pattern COMM communication 6 adopts overrunning cluth; LNG hydraulic turbine installation inflating end 2 can coaxially be installed with BOG pressure-increasing machine 5, also can pass through alternate manner transmission.The rated power of motor 7 can drive separately BOG pressure-increasing machine 5 under the assistance without LNG hydraulic turbine inflating end 2; When rotating speed higher than motor of the rotating speed of LNG hydraulic turbine inflating end 2, overrunning cluth 6 closes, and realizes the recovery of energy; When rotating speed lower than motor of the rotating speed of LNG hydraulic turbine inflating end 2, overrunning cluth 6 is thrown off, and the driving of BOG pressure-increasing machine 5 is driven by motor 7.

Through a large amount of tests, adopt technique of the present invention, can about 1% ~ 3% be improved than the LNG output of former LNG output (adopting Joule-Thomson (J-T) valve).

Embodiment 2:

LNG hydraulic turbine installation inflating end 2 is axial flow.

Be provided with drive pattern COMM communication 6 between LNG hydraulic turbine installation inflating end 2 and motor 7, drive pattern COMM communication 6 adopts hydraulic couplers.

Other parts such as embodiment 1 arranges identical.

Through a large amount of tests, adopt technique of the present invention, can about 1% ~ 3% be improved than the LNG output of former LNG output (adopting Joule-Thomson (J-T) valve).

Embodiment 3:

LNG hydraulic turbine installation inflating end 2 is screw type.

Be provided with drive pattern COMM communication 6 between LNG hydraulic turbine installation inflating end 2 and motor 7, drive pattern COMM communication 6 adopts overrunning cluth.

Other parts such as embodiment 1 arranges identical.

Through a large amount of tests, adopt technique of the present invention, can about 1% ~ 3% be improved than the LNG output of former LNG output (adopting Joule-Thomson (J-T) valve).

Claims (9)

1. a LNG energy recovery process, is characterized in that, comprises the steps:

Rock gas through pre-treater purification enters ice chest, through the LNG of precooling, cryogenic technology liquefaction formation high pressure low temperature,

The LNG of described high pressure low temperature reduces pressure through the inflating end of expansion machinery device, while the pressure energy of self is converted into mechanical energy, exports low temperature, low pressure LNG;

Described low temperature, low pressure LNG carry out after gas-liquid separation through knockout drum, liquid phase LNG send LNG storage tank to store, and gas phase BOG converges, by the pressurized end of LNG hydraulic turbine installation with the BOG from LNG storage tank, enter the supercharging of BOG pressure-increasing machine to export, realize the recovery of energy.

2. LNG energy recovery process according to claim 1, is characterized in that, described expansion machinery device is LNG hydraulic turbine installation.

3. LNG energy recovery process according to claim 2, is characterized in that, the inflating end of described LNG hydraulic turbine installation is preferably centrifugal, also can be axial flow, screw type or reciprocating.

4. LNG energy recovery process according to claim 3, is characterized in that, the inflating end of described LNG hydraulic turbine installation is main driving, and the motor of described LNG hydraulic turbine installation is auxiliary drive; Drive pattern COMM communication is provided with between described LNG hydraulic turbine installation inflating end and motor 7.

5. LNG energy recovery process according to claim 4, is characterized in that, described drive pattern COMM communication is overrunning cluth or hydraulic couplers.

6. LNG energy recovery process according to claim 5, is characterized in that, described motor, under the assistance without described LNG hydraulic turbine inflating end, can drive separately BOG pressure-increasing machine.

7. the LNG energy recovery process according to claim 5 or 6, is characterized in that, when rotating speed higher than described motor of the rotating speed of described LNG hydraulic turbine inflating end, overrunning cluth closes, and realizes the recovery of energy; When rotating speed lower than described motor of the rotating speed of described LNG hydraulic turbine inflating end, described overrunning cluth is thrown off, and the driving of described BOG pressure-increasing machine is by described motoring.

8. the LNG energy recovery process according to Claims 2 or 3, is characterized in that, inflating end and the BOG pressure-increasing machine of described LNG hydraulic turbine installation are coaxially installed.

9. the LNG energy recovery process according to Claims 2 or 3, is characterized in that, adopts Dual Drive pattern between the pressurized end of described LNG hydraulic turbine installation and the input end of BOG pressure-increasing machine.