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US 6,289,692 B1Granted
Efficiency improvement of open-cycle cascaded refrigeration process for LNG production
AssigneePhillips Petroleum Company
InventorsClarence G. Houser, Rong-Jwyn Lee, Ned Baudat
Life of this patent
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Abstract
This invention concerns a method and an apparatus for improving the efficiency of an open-cycle refrigeration process for LNG production by the employment of a liquid expander to recover energy associated with the flashing of a pressurized liquid stream and employing said recovered energy to compress the flashed vapor streams in the open cycle.
Claims56
In a process wherein a LNG-bearing stream is produced at an elevated pressure and said stream is flashed in an open methane refrigeration cycle employing a multi-stage compressor via multiple stages of pressure reduction to a near-atmospheric pressure and employing a multi-stage compression step, the improvement comprising in at least one of said pressure reduction stages:
- (a) flashing a pressurized LNG-bearing stream in an expander thereby generating a two-phase stream and energy;
- (b) separating said two-phase stream into a gas stream and lower pressure predominantly LNG-bearing stream;
- (c) compressing said gas stream in a compressor thereby producing a pressurized gas stream and wherein said compressor is powered at least in part by the energy of step (a);
- and
- (d) returning said pressurized gas stream to the multi-stage compression step employed in the open methane refrigeration cycle.
2 more elements
In a process wherein a LNG-bearing stream at elevated pressure is flashed in an open methane refrigeration cycle via multiple stages of pressure reduction to a near-atmospheric pressure, the improvement comprising:
- (a) cooling via indirect heat exchange said LNG-bearing stream at elevated pressure thereby producing a cooled LNG-bearing stream;
- (b) flashing said cooled LNG-bearing stream in an expander thereby generating a first pressure reduction two-phase stream and energy;
- (c) separating said first pressure reduction two-phase stream into a first gas stream and a second LNG-bearing stream;
- (d) warming said first gas stream via indirect heat exchange with the stream of step (a) thereby producing a warmed first gas stream;
- (e) compressing said warmed gas stream via a compressor thereby producing a compressed first gas stream and wherein said compressor is powered at least in part by energy of step (a);
- (f) returning said compressed first gas stream to the high stage inlet port of the multi-stage compressor employed in the open methane refrigeration cycle;
- (g) cooling via indirect heat exchange the second LNG-bearing stream thereby producing a cooled second LNG-bearing stream;
- (h) flashing said cooled LNG-bearing stream via an expansion valve thereby generating a second pressure reduction two-phase stream;
- (i) separating said second pressure reduction two-phase stream into a second gas stream and a third LNG-bearing stream;
- (j) warming said second gas stream via indirect heat exchange with the stream of step (g) thereby producing a warmed second gas stream;
- (k) returning said warmed second gas stream to the intermediate stage inlet port of the multi-stage compressor employed in the open methane refrigeration cycle;
- (l) cooling via indirect heat exchange the third LNG-bearing stream thereby producing a cooled third LNG-bearing stream;
- (m) flashing said cooled LNG-bearing stream via an expansion valve thereby generating a third pressure reduction two-phase stream;
- (n) separating said third pressure reduction two-phase stream into a third gas stream and a fourth LNG-bearing stream;
- (o) flowing said fourth LNG-bearing stream to storage;
- (p) warming said third gas stream via indirect heat exchange with the stream of step (l) thereby producing a warmed third gas stream;
- (q) returning said warmed third gas stream to the low stage inlet port of the multi-stage compressor employed in the open methane refrigeration cycle.
14 more elements
In a process wherein a LNG-bearing stream at elevated pressure is flashed in an open methane refrigeration cycle via multiple stages of pressure reduction to a near-atmospheric pressure, the improvement comprising:
- (a) cooling via indirect heat exchange the LNG-bearing stream at elevated pressure thereby producing a cooled LNG-bearing stream;
- (b) flashing said cooled LNG-bearing stream in an expander thereby generating a first pressure reduction two-phase stream and energy;
- (c) separating said first pressure reduction two-phase stream into a first gas stream and a second LNG-bearing stream;
- (d) warming said first gas stream via indirect heat exchange with the stream of step (a) thereby producing a warmed first gas stream;
- (e) compressing said warmed gas stream via a compressor thereby producing a compressed first gas stream and wherein said compressor is powered at least in part by energy of step (a);
- (f) returning said compressed first gas stream to the high stage inlet port of the multi-stage compressor employed in the open methane refrigeration cycle;
- (g) cooling via indirect heat exchange the second LNG-bearing stream thereby producing a cooled second LNG-bearing stream;
- (h) flashing said cooled LNG-bearing stream in an expander thereby generating a second pressure reduction two-phase stream and energy;
- (i) separating said second pressure reduction two-phase stream into a second gas stream and a third LNG-bearing stream;
- (j) warming said second gas stream via indirect heat exchange with the stream of step (g) thereby producing a warmed second gas stream;
- (k) compressing said warmed second gas stream via a compressor thereby producing a compressed second gas stream and wherein said compressor is powered at least in part by energy of step (h);
- (l) returning said warmed second gas stream to the intermediate stage inlet port of the multi-stage compressor employed in the open methane refrigeration cycle;
- (m) cooling via indirect heat exchange the third LNG-bearing stream thereby producing a cooled third LNG-bearing stream;
- (n) flashing said cooled LNG-bearing stream via an expansion valve thereby generating a third pressure reduction two-phase stream;
- (o) separating said third pressure reduction two-phase stream into a third gas stream and a fourth LNG-bearing stream;
- (p) flowing said fourth LNG-bearing stream to storage;
- (q) warming said third gas stream via indirect heat exchange with the stream of step (m) thereby producing a warmed third gas stream;
- and
- (r) returning said warmed third gas stream to the low stage inlet port of the multi-stage compressor employed in the open methane refrigeration cycle.
16 more elements
An apparatus comprising
- (a) a first indirect heat exchange means;
- (b) a first directional flow control means;
- (c) a first junction means;
- (d) a liquid expander;
- (e) an expansion valve;
- (f) a gas liquid separator;
- (g) a second indirect heat exchange means situated in close proximity to the first indirect heat exchange means and situated such that fluids flowing though such means flow generally countercurrent to one another;
- (h) a single-stage compressor;
- (i) a mechanical or hydraulic coupling between the liquid expander of (d) and the compressor of (h);
- (j) a second directional flow control means;
- (k) a second junction means;
- (l) a multi-stage compressor;
- (m) a conduit connected to the inlet of the first indirect heat exchange means;
- (n) a conduit connected to the outlet of the first indirect heat exchange means and the inlet to the first directional flow control means;
- (o) a conduit connected to an outlet of the first directional flow control means and to the liquid expander;
- (p) a conduit connected to the liquid expander and to the first junction means;
- (q) a conduit connected to an outlet of the first direction flow control means and to the expansion valve;
- (r) a conduit connected to the expansion valve and the first junction means;
- (s) a conduit connected to the first junction means and the gas-liquid separator;
- (t) a conduit connected to the upper section of the gas-liquid separator and the inlet to the second indirect heat exchange means;
- (u) a conduit connected to the outlet to the second indirect heat exchange means and the inlet to the second directional flow control means;
- (v) a conduit connected to the outlet of the second directional flow control means and the single-stage compressor;
- (w) a conduit connected to the single-stage compressor and the second junction means;
- (x) a conduit connected to an outlet of the second directional flow control means and the second junction means;
- and
- (y) a conduit between the second junction means and the high-stage inlet port of the multi-stage compressor.
23 more elements
Dependencies are inferred from the claim text.