System for purifying helium gas, method, and application

1 . A system for purifying helium gas comprising: a first gas-liquid separation device, a primary helium extraction tower ( 11 ), a second gas-liquid separation device, a secondary helium extraction tower ( 27 ), and a nitrogen removal tower ( 33 ) which are in sequential communication;

the first gas-liquid separation device is used for performing the first treatment to convert helium-containing natural gas ( 1 ) into a first gas phase and a first liquid phase;

the primary helium extraction tower ( 11 ) is used for performing the first distillation on the first gas phase and the first liquid phase to obtain a second gas phase and a second liquid phase;

the second gas-liquid separation device is used for performing the second treatment to convert the second gas phase to a third gas phase and a third liquid phase;

the secondary helium extraction tower ( 27 ) is used for performing second distillation on the third gas phase and the third liquid phase to obtain crude helium and a fourth liquid phase;

the nitrogen removal tower ( 33 ) is used for performing nitrogen removal on the fourth liquid phase to obtain nitrogen gas and LNG products.

2 . The system according to claim 1 , wherein the first gas-liquid separation device comprises at least one primary cold box ( 5 ) and at least one primary low-temperature separator ( 6 );

and/or, the first gas-liquid separation device comprises a primary cold box ( 5 ) and a primary low-temperature separator ( 6 ) which is in sequential communication;

wherein the primary cold box ( 5 ) is used for pre-cooling the helium-containing natural gas ( 1 ) to obtain a low-temperature helium-containing natural gas; the primary low-temperature separator ( 6 ) is used for performing a first low-temperature separation on the low-temperature helium-containing natural gas to obtain a first gas phase and a first liquid phase;

and/or, at least one primary tower bottom reboiler ( 7 ) is further arranged between the primary cold box ( 5 ) and the primary low-temperature separator ( 6 ) for cooling the low-temperature helium-containing natural gas, and then feeding it to the primary low-temperature separator ( 6 );

and/or, a gas-phase outlet of the primary low-temperature separator ( 6 ) is connected to the middle part of the primary helium extraction tower ( 11 ), and a liquid-phase outlet of the primary low-temperature separator ( 6 ) is connected to the middle and lower parts of the primary helium extraction tower ( 11 );

and/or, the primary helium extraction tower ( 11 ) is connected to the primary tower bottom reboiler ( 7 ) for performing a reboiled liquid in the bottom of the primary helium extraction tower ( 11 ) to a heat exchange in the primary tower bottom reboiler ( 7 ), and feeding the reboiled liquid to a gas-phase space at the bottom of the primary helium extraction tower ( 11 ) for supplying heat to the primary helium extraction tower ( 11 ).

3 . The system according to claim 1 , wherein the second gas-liquid separation device comprises at least one primary helium extraction tower reflux drum ( 13 ) and at least one second low-temperature separator ( 24 );

and/or, the second gas-liquid separation device comprises a primary helium extraction tower reflux drum ( 13 ) and a second low-temperature separator ( 24 ) which is in sequential communication;

wherein the primary helium extraction tower reflux drum ( 13 ) is used for separating the second gas phase to obtain a gas phase material flow and a liquid phase material flow; the second low-temperature separator ( 24 ) is used for performing a second low-temperature separation on the gas phase material flow to obtain a third gas phase and a third liquid phase;

and/or, at least one primary helium extraction tower overhead condenser ( 12 ) is further arranged between the primary helium extraction tower ( 11 ) and the primary helium extraction tower reflux drum ( 13 ) for condensing the second gas phase, and then feeding the second gas phase to the primary helium extraction tower reflux drum ( 13 );

and/or, at least a second tower bottom reboiler ( 29 ) is further arranged between the primary helium extraction tower reflux drum ( 13 ) and the second low-temperature separator ( 24 ) for cooling the gas phase material flow, and then feeding the gas phase material flow to the second low-temperature separator ( 24 );

and/or, a gas-phase outlet of the second low-temperature separator ( 24 ) is connected to the middle part of the secondary helium extraction tower ( 27 ), and the liquid-phase outlet of the second low-temperature separator ( 24 ) is connected to the middle and lower parts of the secondary helium extraction tower ( 27 );

and/or, at least one second cold box ( 22 ) is further arranged between the second low-temperature separator ( 24 ) and the secondary helium extraction tower ( 27 ) for supercooling the third gas phase, and then feeding the third gas phase to the secondary helium extraction tower ( 27 );

and/or, a gas-phase outlet of the secondary helium extraction tower ( 27 ) is connected to the second cold box ( 22 ) for performing a gas phase discharged from the top of said secondary helium extraction tower ( 27 ) to a heat exchange via the second cold box ( 22 ) to obtain a crude helium product;

and/or, the secondary helium extraction tower ( 27 ) is connected to the second tower bottom reboiler ( 29 ) for performing a reboiled liquid in the bottom of the secondary helium extraction tower ( 27 ) to a heat exchange in the second tower bottom reboiler ( 29 ), and feeding the reboiled liquid to a gas-phase space at the bottom of the secondary helium extraction tower ( 27 ) for supplying heat to the secondary helium extraction tower ( 27 ).

4 . The system according to claim 3 , wherein a nitrogen removal tower overhead condenser ( 32 ) is arranged in an upper part of the nitrogen removal tower ( 33 );

and/or, the nitrogen removal tower overhead condenser ( 32 ) is connected to the second cold box ( 22 ) for cooling and liquefying a high-pressure refrigerant ( 18 ) in the second cold box ( 22 ), and then feeding the high-pressure refrigerant ( 18 ) to the nitrogen removal tower overhead condenser ( 32 ) for supplying a cooling capacity to the nitrogen removal tower ( 33 ) and returning to the second cold box ( 22 ) to obtain a low-pressure gaseous phase refrigerant ( 19 );

and/or, a liquid-phase outlet at the bottom of the nitrogen removal tower ( 33 ) is connected to the second cold box ( 22 ) for supercooling the liquid phase from the bottom of the nitrogen removal tower ( 33 ) via the second cold box ( 22 ) to obtain an LNG product.

5 . The system according to claim 3 , wherein a nitrogen removal tower bottom reboiler ( 34 ) is arranged in a lower part of the nitrogen removal tower ( 33 );

and/or, the nitrogen removal tower bottom reboiler ( 34 ) is connected to the primary helium extraction tower ( 11 ) and the primary helium extraction tower overhead condenser ( 12 ) for performing a portion of the second liquid phase discharged by the primary helium extraction tower ( 11 ) to a heat exchange in the nitrogen removal tower bottom reboiler ( 34 ) and supplying heat to the nitrogen removal tower ( 33 ), and then feeding the second liquid phase to the primary helium extraction tower overhead condenser ( 12 ) for supplying a cooling capacity to the primary helium extraction tower overhead condenser ( 12 ), and converting the second liquid phase to a crude natural gas;

and/or, the primary helium extraction tower overhead condenser ( 12 ) is connected to the primary cold box ( 5 ) for feeding the crude natural gas to the primary cold box ( 5 ) for reheating to obtain low-pressure lean natural gas ( 3 ).

6 . The system according to claim 3 , wherein a liquid-phase outlet of the primary helium extraction tower reflux drum ( 13 ) is connected to an upper part of the primary helium extraction tower ( 11 ) for feeding the liquid phase material flow of the primary helium extraction tower reflux drum ( 13 ) to the upper part of the primary helium extraction tower ( 11 ) as a reflux liquid at the top of the primary helium extraction tower ( 11 ).

7 . The system according to claim 1 , wherein the bottom of the primary helium extraction tower ( 11 ) is connected to the primary cold box ( 5 ) for recovering the cooling capacity of the remainder of the second liquid phase to obtain a medium-pressure lean natural gas ( 2 ).

8 . A method for extracting helium from natural gas employing the system according to claim 1 .

9 . A method for purifying helium gas comprising the following steps:

(1) performing the first treatment on the helium-containing natural gas to convert it into a first gas phase and a first liquid phase;

(2) performing first distillation on the first gas phase and the first liquid phase to obtain a second gas phase and a second liquid phase;

(3) performing the second treatment on the second gas phase to obtain a third gas phase and a third liquid phase;

(4) performing second distillation on the third gas phase and the third liquid phase to obtain crude helium and a fourth liquid phase;

(5) performing nitrogen removal on the fourth liquid phase to obtain nitrogen gas and LNG product.

10 . The method according to claim 9 , wherein the first treatment in step (1) comprises: pre-cooling the helium-containing natural gas to obtain a low-temperature helium-containing natural gas;

and/or the first treatment comprises: performing the helium-containing natural gas and/or the low-temperature helium-containing natural gas to a first low-temperature separation to obtain the first gas phase and the first liquid phase;

and/or, the first treatment further comprises: cooling the helium-containing natural gas and/or the low-temperature helium-containing natural gas prior to the first low-temperature separation.

11 . The method according to claim 9 , wherein the conditions of the first distillation in step (2) comprise a temperature from −95° C. to −80° C. and a pressure from 3.5 MPa to 4.5 MPa;

and/or, the method further comprises a step of supercooling the first gas phase and the first liquid phase prior to the first distillation;

and/or, the method further comprises a step of performing the reboiled liquid obtained from the first distillation to a heat exchange.

12 . The method according to claim 9 , wherein the second treatment in step (3) comprises: separating the second gas phase to obtain a gas phase material flow and a liquid phase material flow;

and/or the second treatment comprises performing the second gas phase and/or the gas phase material flow to a second low-temperature separation to obtain a third gas phase and a third liquid phase;

and/or, the second treatment further comprises condensing the second gas phase prior to the separation;

and/or, the second treatment further comprises cooling the second gas phase and/or the gas phase material flow prior to the second low-temperature separation;

and/or, the method further comprises recycling the liquid phase material flow obtained from the separation as a reflux liquid for the first distillation.

13 . The method according to claim 9 , wherein the conditions of the second distillation in step (4) comprise a temperature from −185° C. to −110° C. and a pressure from 2 MPa to 3 MPa;

and/or the method further comprises a step of supercooling the third gas phase prior to the second distillation;

and/or, the method further comprises a step of performing the reboiled liquid obtained from the second distillation to a heat exchange;

and/or, the method further comprises a step of performing the gas phase obtained from the second distillation to a heat exchange to obtain a crude helium product.

14 . The method according to claim 9 , wherein the conditions of the nitrogen removal in step (5) comprise a temperature from −160° C. to −110° C. and pressure from 1.5 MPa to 2.5 MPa;

and/or, the method further comprises a step of cooling and liquefying the high-pressure refrigerant to obtain a low-pressure gaseous phase refrigerant;

and/or, the method further comprises a step of supercooling the liquid phase obtained from the nitrogen removal to obtain LNG product;

and/or the method further comprises performing a part of the second liquid phase to a heat exchange for converting it to crude natural gas;

and/or, the method further comprises reheating the crude natural gas to obtain low-pressure lean natural gas;

and/or the method further comprises recovering the cooling capacity of the remainder of the second liquid phase to obtain medium-pressure lean natural gas.

15 . The method according to claim 9 , wherein the helium-containing natural gas comprises the following ingredients in volume fraction: 98-99% of CH 4 , 0.1-0.5% of C 2 H 6 , 0.2-0.6% of N 2 , 0.3-0.8% of CO 2 , 0.01-0.1% of He, and 0.005-0.3% of H 2 ;

and/or, the crude helium comprises the following ingredients in volume fraction: 0.2-0.8% of CH 4 , 6-12% of N 2 , 60-70% of He, and 15-25% of H 2 .

16 . A method for extracting helium from natural gas employing the method according to claim 9 .