Mixed refrigerant distributed chilling scheme
Processes and systems are provided for recovering a liquid natural gas (“LNG”) from a hydrocarbon-containing gas. More particularly, the present invention is generally related to processes and systems that optimize the chilling efficiencies of an LNG facility through the utilization of an auxiliary refrigeration cycle. Additionally, the present invention is also generally related to the rerouting of mixed refrigerants in a closed-loop refrigeration cycle in order to optimize the chilling efficiencies of the LNG facility.
1. A process for producing liquid natural gas (LNG) from a natural gas stream in an LNG liquefaction plant, the process comprising:
(a) compressing a mixed refrigerant in a refrigerant compressor using a combustion gas turbine having an inlet air stream as the compressor driver, thereby forming a compressed mixed refrigerant stream;
(b) cooling and at least partially condensing the compressed mixed refrigerant stream, thereby forming a first two-phase mixed refrigerant stream;
(c) separating the first two-phase mixed refrigerant stream, thereby forming a vapor mixed refrigerant stream and a liquid mixed refrigerant stream;
(d) combining the vapor mixed refrigerant stream and a first portion of the liquid mixed refrigerant stream, thereby forming a second two-phase mixed refrigerant stream;
(e) condensing the two-phase mixed refrigerant stream via indirect heat exchange with an expanded mixed refrigerant stream, thereby forming a condensed mixed refrigerant stream;
(f) expanding the condensed mixed refrigerant stream, thereby forming the expanded mixed refrigerant stream in step (e);
(g) liquefying the natural gas stream via indirect heat exchange with the expanded mixed refrigerant stream, thereby forming the liquid natural gas and a first warmed mixed refrigerant stream;
(h) expanding a second portion of the liquid mixed refrigerant stream, thereby forming a third two-phase mixed refrigerant stream;
(i) cooling a heat transfer fluid via indirect heat exchange with the third two-phase mixed refrigerant stream, thereby forming a cooled heat transfer fluid and a second warmed mixed refrigerant stream; and
(j) cooling the combustion gas turbine inlet air stream in step (a) via indirect heat exchange with the cooled heat transfer fluid,
wherein the first warmed mixed refrigerant stream and the second warmed mixed refrigerant stream are returned to the compressor in step (a).
2. The process of claim 1 , wherein the cooling and partial condensation of step (b) is performed via indirect heat exchange with a cooling medium comprising water or air.
3. The process of claim 1 , wherein the first warmed mixed refrigerant stream is returned to a suction inlet of the refrigerant compressor.
4. The process of claim 1 , wherein the second warmed mixed refrigerant stream is returned to a suction inlet of the refrigerant compressor.
5. The process of claim 1 , wherein prior to step (b), further compressing the mixed refrigerant in a second refrigerant compressor using the combustion gas turbine as the compressor driver, thereby forming the compressed mixed refrigerant that is cooled in step (b).
6. The process of claim 5 , wherein the second warmed mixed refrigerant stream is returned to a second suction inlet of the second refrigerant compressor.
7. The process of claim 1 , wherein the heat transfer fluid comprises water, a glycol, or combinations thereof.
8. A process for producing liquid natural gas (LNG) from a natural gas stream in an LNG liquefaction plant, the process comprising:
(a) compressing a mixed refrigerant in a compressor using a combustion gas turbine having an inlet air stream as the compressor driver, thereby forming a compressed mixed refrigerant stream;
(b) cooling and at least partially condensing the compressed mixed refrigerant stream, thereby forming a first two-phase mixed refrigerant stream;
(c) separating the first two-phase mixed refrigerant stream, thereby forming a vapor mixed refrigerant stream and a liquid mixed refrigerant stream;
(d) combining the vapor stream and the liquid stream, thereby forming a second two-phase mixed refrigerant stream;
(e) condensing the two-phase mixed refrigerant stream via indirect heat exchange with an expanded mixed refrigerant stream, thereby forming a condensed mixed refrigerant stream;
(f) expanding a first portion of the condensed mixed refrigerant stream, thereby forming the expanded mixed refrigerant stream in step (e);
(g) liquefying the natural gas stream via indirect heat exchange with the expanded mixed refrigerant stream, thereby forming the liquid natural gas and a first warmed mixed refrigerant stream;
(h) expanding a second portion of the condensed mixed refrigerant stream, thereby forming a third two-phase mixed refrigerant stream;
(i) cooling a heat transfer fluid via indirect heat exchange with the third two-phase mixed refrigerant stream, thereby forming a cooled heat transfer fluid and a second warmed mixed refrigerant stream; and
(j) cooling the combustion gas turbine inlet air stream in step (a) via indirect heat exchange with the cooled heat transfer fluid,
wherein the first warmed mixed refrigerant stream and the second warmed mixed refrigerant stream are returned to the compressor in step (a).
9. The process of claim 8 , wherein the cooling and partial condensation of step (b) is performed via indirect heat exchange with a cooling medium comprising water or air.
10. The process of claim 8 , wherein the first warmed mixed refrigerant stream is returned to a suction inlet of the refrigerant compressor.
11. The process of claim 8 , wherein the second warmed mixed refrigerant stream is returned to a suction inlet of the refrigerant compressor.
12. The process of claim 8 , wherein prior to step (b), further compressing the mixed refrigerant in a second refrigerant compressor using the combustion gas turbine as the compressor driver, thereby forming the compressed mixed refrigerant that is cooled in step (b).
13. The process of claim 12 , wherein the second warmed mixed refrigerant stream is returned to a second suction inlet of the second refrigerant compressor.
14. The process of claim 8 , wherein the heat transfer fluid comprises water, a glycol, or combinations thereof.
15. The process of claim 8 , wherein at least a portion of the liquid stream is pressurized in a pump prior to the combining in step (d).