Patent Abstract:
The present invention provides a power and regasification system based on liquefied natural gas (LNG), comprising a vaporizer by which liquid working fluid is vaporized, said liquid working fluid being LNG or a working fluid liquefied by means of LNG; a turbine for expanding the vaporized working fluid and producing power; heat exchanger means to which expanded working fluid vapor is supplied, said heat exchanger means also being supplied with LNG for receiving heat from said expanded fluid vapor, whereby the temperature of the LNG increases as it flows through the heat exchanger means; a conduit through which said working fluid is circulated from at least the inlet of said vaporizer to the outlet of said heat exchanger means; and a line for transmitting regasified LNG.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of power generation. More particularly, the invention relates to a system which both utilizes liquefied natural gas for power generation and re-gasifies the liquefied natural gas. 
     BACKGROUND OF THE INVENTION 
     In some regions of the world, the transportation of natural gas through pipelines is uneconomic. The natural gas is therefore cooled to a temperature below its boiling point, e.g. −160° C., until becoming liquid and the liquefied natural gas (LNG) is subsequently stored in tanks. Since the volume of natural gas is considerably less in liquid phase than in gaseous phase, the LNG can be conveniently and economically transported by ship to a destination port. 
     In the vicinity of the destination port, the LNG is transported to a regasification terminal, whereat it is reheated by heat exchange with sea water or with the exhaust gas of gas turbines and converted into gas. Each regasification terminal is usually connected with a distribution network of pipelines so that the regasified natural gas may be transmitted to an end user. While a regasification terminal is efficient in terms of the ability to vaporize the LNG so that it may be transmitted to end users, there is a need for an efficient method for harnessing the cold potential of the LNG as a cold sink for a condenser to generate power. 
     Use of Rankine cycles for power generation from evaporating LNG are considered in “Design of Rankine Cycles for power generation from evaporating LNG”, Maertens, J., International Journal of Refrigeration, 1986, Vol. 9, May. In addition, further power: cycles using LNG/LPG (liquefied petroleum gas) are considered in U.S. Pat. No. 6,367,258. Another power cycle utilizing LNG is considered in U.S. Pat. No. 6,336,816. More power cycles using LNG are described in “Energy recovery on LNG import terminals ERoS RT project” by Snecma Moteurs, made available at the Gastech 2005, The 21 st  International Conference &amp; Exhibition for the LNG, LPG and Natural Gas Industries,—14/17 Mar., 2005 Bilbao, Spain. 
     On the other hand, a power cycle including a combined cycle power plant and an organic Rankine cycle power plant using the condenser of the steam turbine as its heat source is disclosed in U.S. Pat. No. 5,687,570, the disclosure of which is hereby included by reference. 
     It is an object of the present invention to provide an LNG-based power and regasification system, which utilizes the low temperature of the LNG as a cold sink for the condenser of the power system in order to generate electricity or produce power for direct use. 
     Other objects and advantages of the invention will become apparent as the description proceeds. 
     SUMMARY OF THE INVENTION 
     The present invention provides a power and regasification system based on liquefied natural gas (LNG), comprising a vaporizer by which liquid working fluid is vaporized, said liquid working fluid being LNG or a working fluid liquefied by means of LNG; a turbine for expanding the vaporized working fluid and producing power; heat exchanger means to which expanded working fluid vapor is supplied, said heat exchanger means also being supplied with LNG for receiving heat from said expanded fluid vapor, whereby the temperature of the LNG increases as it flows through the heat exchanger means; a conduit through which said working fluid is circulated from at least the inlet of said vaporizer to the outlet of said heat exchanger means; and a line for transmitting regasified LNG. 
     Power is generated due to the large temperature differential between cold LNG, e.g. approximately −160° C., and the heat source of the vaporizer. The heat source of the vaporizer may be sea water at a temperature ranging between approximately 5° C. to 20° C. or heat such as an exhaust gas discharged from a gas turbine or low pressure steam exiting a condensing steam turbine. 
     The system further comprises a pump for delivering liquid working fluid to the vaporizer. 
     The system may further comprise a compressor for compressing regasified LNG and transmitting said compressed regasified LNG along a pipeline to end users. The compressor may be coupled to the turbine. The regasified LNG may also be transmitted via the line to storage. 
     In one embodiment of the invention, the power system is a closed Rankine cycle power system such that the conduit further extends from the outlet of the heat-exchanger means to the inlet of the vaporizer and the heat exchanger means is a condenser by which the LNG condenses the working fluid exhausted from the turbine to a temperature ranging from approximately −100° C. to −120° C. The working fluid is preferably organic fluid such as ethane, ethene or methane or equivalents, or a mixture of propane and ethane or equivalents. The temperature of the LNG heated by the turbine exhaust is preferably further increased by means of a heater. 
     In another embodiment of the invention, the power system is an open cycle power system, the working fluid is LNG, and the heat exchanger means is a heater for re-gasifying the LNG exhausted from the turbine. 
     The heat source of the heater may be sea water at a temperature ranging between approximately 5° C. to 20° C. or waste heat such as an exhaust gas discharged from a gas turbine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic arrangement of a closed cycle power system in accordance with one embodiment of the invention; 
         FIG. 2  is a temperature-entropy diagram of the closed cycle power system of  FIG. 1 ; 
         FIG. 3  is a schematic arrangement of an open cycle power system in accordance with another embodiment of the invention; 
         FIG. 4  is a temperature-entropy diagram of the open cycle power system of  FIG. 3 . 
         FIG. 5  is a schematic arrangement of a closed cycle power system in accordance with a further embodiment of the invention; 
         FIG. 6  is a temperature-entropy diagram of the closed cycle power system of  FIG. 5 ; 
         FIG. 7  is a schematic arrangement of a two pressure level closed cycle power system in accordance with a further embodiment of the invention; 
         FIG. 7A  is a schematic arrangement of an alternative version of the two pressure level closed cycle power system in accordance with the embodiment of the invention shown in  FIG. 7 ; 
         FIG. 7B  is a schematic arrangement of a further alternative version of the two pressure level closed cycle power system in accordance with the embodiment of the invention shown in  FIG. 7 ; 
         FIG. 7C  is a schematic arrangement of further alternative versions of the two pressure level closed cycle power system in accordance with the embodiment of the invention shown in  FIG. 7 ; 
         FIG. 7D  is a schematic arrangement of a further alternative version of the two pressure level closed cycle power system in accordance with the embodiment of the invention shown in  FIG. 7 ; 
         FIG. 7E  is a schematic arrangement of a further alternative version of the two pressure level closed cycle power system in accordance with the embodiment of the invention shown in  FIG. 7 ; 
         FIG. 7F  is a schematic arrangement of a further embodiment of a two pressure level open cycle power system in accordance with the present invention; 
         FIG. 7G  is a schematic arrangement of a further alternative version of the two pressure level open cycle power system in accordance with the embodiment of the invention shown in  FIG. 7F ; 
         FIG. 7H  is a schematic arrangement of a further alternative version of the two pressure level open cycle power system in accordance with the embodiment of the invention shown in  FIG. 7F ; 
         FIG. 7I  is a schematic arrangement of a further alternative version of the two pressure level open cycle power system in accordance with the embodiment of the invention shown in  FIG. 7F ; 
         FIG. 7J  is a schematic arrangement of a further alternative version of the two pressure level open cycle power system in accordance with the embodiment of the invention shown in  FIG. 7F ; 
         FIG. 7K  is a schematic arrangement of a further alternative version of the two pressure level open cycle power system in accordance with the embodiment of the invention shown in  FIG. 7F ; 
         FIG. 7L  is a schematic arrangement of further embodiments of an open cycle power system in accordance with the present invention; 
         FIG. 7M  is a schematic arrangement of a further embodiment of the present invention including an closed cycle power plant and an open cycle power plant; 
         FIG. 8  is a schematic arrangement of a closed cycle power system in accordance with a further embodiment of the invention; and 
         FIG. 9  is a schematic arrangement of a closed cycle power system in accordance with a still further embodiment of the invention. Similar reference numerals and symbols refer to similar components. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention is a power and regasification system based on liquid natural gas (LNG). While transported LNG, e.g. mostly methane, is vaporized in the prior art at a regasification terminal by being passed through a heat exchanger, wherein sea water or another heat source e.g. the exhaust of a gas turbine heats the LNG above its boiling point, an efficient method for utilizing the cold LNG to produce power is needed. By employing the power system of the present invention, the cold temperature potential of the LNG serves as a cold sink of a power cycle. Electricity or power is generated due to the large temperature differential between the cold LNG and the heat source, e.g. sea water. 
       FIGS. 1 and 2  illustrate one embodiment of the invention, wherein cold LNG serves as the cold sink medium in the condenser of a closed Rankine cycle power plant.  FIG. 1  is a schematic arrangement of the power system and  FIG. 2  is a temperature-entropy diagram of the closed cycle. 
     The power system of a closed Rankine cycle is generally designated as numeral  10 . Organic fluid such as ethane, ethene or methane or an equivalent, is the preferred working fluid for power system  10  and circulates through conduits  8 . Pump  15  delivers liquid organic fluid at state A, the temperature of which ranges from about −80° C. to −120° C., to vaporizer  20  at state B. Sea water in line  18  at an average temperature of approximately 5-20° C. introduced to vaporizer  20  serves to transfer heat to the working fluid passing therethrough (i.e. from state B to state C). The temperature of the working fluid consequently rises above its boiling point to a temperature of approximately −10 to 0° C., and the vaporized working fluid produced is supplied to turbine  25 . The sea water discharged from vaporizer  20  via line  19  is returned to the ocean. As the vaporized working fluid is expanded in turbine  25  (i.e. from state C to state D), power or preferably electricity is produced by generator  28  operated to turbine  25 . Preferably, turbine  25  rotates at about 1500 RPM or 1800 RPM. LNG in line  32  at an average temperature of approximately −160° C. introduced to condenser  30  (i.e. at state E) serves to condense the working fluid exiting turbine  25  (i.e. from state D to state A) corresponding to a liquid phase, so that pump  15  delivers the liquid working fluid to vaporizer  20 . Since the LNG lowers the temperature of the working fluid to a considerably low temperature of about −80° C. to −120° C., the recoverable energy available by expanding the vaporized working fluid in turbine  25  is relatively high. 
     The temperature of LNG in line  32  (i.e. at state F) increases after heat is transferred thereto within condenser  80  by the expanded working fluid exiting turbine  25 , and is further increased by sea water, which is passed through heater  36  via line  37 . Sea water discharged from heater  36  via line  38  is returned to the ocean. The temperature of the sea water introduced into heater  36  is usually sufficient to re-gasify the LNG, which may held in storage vessel  42  or, alternatively, be compressed and delivered by compressor  46  through line  43  to a pipeline for distribution of vaporized LNG to end users. Compressor  40  for re-gasifying the natural gas prior to transmission may be driven by the power generated by turbine  25  or, if preferred driven by electricity produced by electric generator  25 . 
     When sea water is not available or not used or not suitable for use, heat such as that contained in the exhaust gas of a gas turbine may be used to transfer heat to the working fluid in vaporizer  20  or to the natural gas directly or via a secondary heat transfer fluid (in heater  36 ). 
       FIGS. 3 and 4  illustrate another embodiment of the invention, wherein LNG is the working fluid of an open cycle power plant.  FIG. 3  is a schematic arrangement of the power system and  FIG. 4  is a temperature-entropy diagram of the open cycle. 
     The power system of an open turbine-based cycle is generally designated as numeral  50 . LNG  72 , e.g. transported by ship to a selected destination, is the working fluid for power system  50  and circulates through conduits  48 . Pump  56  delivers cold LNG at state G, the temperature of which is approximately −160° C., to vaporizer  60  at state H. Sea water at an average temperature of approximately 5-20° C. introduced via line  18  to vaporizer  60  serves to transfer heat to the LNG passing therethrough from state H to state I. The temperature of the LNG consequently rises above its boiling point to a temperature of approximately −10 to 0° C., and the vaporized LNG produced is supplied to turbine  65 . The sea water is discharged via line  19  from vaporizer  60  is returned to the ocean. As the vaporized LNG is expanded in turbine  65  from state I to state J, power or preferably electricity is produced by generator  68  coupled to turbine  65 . Preferably, turbine  65  rotates at 1500 RPM or 1800 RPM. Since the LNG at state G has a considerably low temperature of −160° C. and is subsequently pressurized by pump  65  from state G to state H so that high pressure vapor is produced in vaporizer  60 , the energy in the vaporized LNG is relatively high and is utilized via expansion in turbine  65 . 
     The temperature of LNG vapor at state J, after expansion within turbine  65 , is increased by transferring heat thereto from sea water, which is supplied to, via line  76 , and passes through heater  75 . The sea water discharged from heater  75  via line  77  and returned to the ocean The temperature of sea water introduced to heater  75  is sufficient to heat the LNG vapor, which may held in storage  82  or, alternatively, be compressed and delivered by compressor  86  through line  83  to a pipeline for distribution of vaporized LNG to end users. Compressor  80  which compresses the natural gas prior to transmission may be driven by the power generated by turbine  65  or, if preferred, driven by electricity produced by electric generator  68 . Alternatively, the pressure of the vaporized natural gas discharged from turbine  65  may be sufficiently high so that the natural gas which is heated in heater  75  can be transmitted through a pipeline without need of a compressor. 
     When sea water is not available or not used, heat such as heat contained in the exhaust gas of a gas turbine may be used to transfer heat to the natural gas in vaporizer  60  or in heater  75  or via a secondary heat transfer fluid. 
     Turning to  FIG. 5 , a further embodiment designated  10 B of a closed cycle power system (similar to the embodiment described with reference to  FIG. 1 ) is shown, wherein LNG pump  40 A is used to pressurize the LNG prior to supplying it to condenser  30 A to a pressure, e.g. about 80 bar, for producing a pressure for the re-gasified LNG suitable for supply via line  43  to a pipeline for distribution of vaporized LNG to end users. Pump  40 B is used rather than compressor in the embodiment shown in  FIG. 1 . Basically, the operation of the present embodiment is similar to the operation of the embodiment of the present invention described with reference to  FIGS. 1 and 2 . Consequently, this embodiment is more efficient. Preferably, turbine  25 B included in this embodiment, rotates at 1500 RPM or 1800 RPM. Furthermore, a mixture of propane and ethane or equivalents is the preferred working fluid for closed organic Rankine power system in this embodiment. However, ethane, ethene or other suitable organic working fluids can also be used in this embodiment. This is because the cooling curve of the propane/ethane mixture organic working fluid in the condenser  30 A is more suited to the heating curve of LNG at such high pressures enabling the LNG cooling source to be used more effectively (see  FIG. 6 ). However, if preferred, a dual pressure organic Rankine cycle using a single organic working fluid e.g. preferably ethane, ethene or an equivalent, can be used here wherein two different expansion levels and also two condensers can be used (see  FIG. 7 ). As can be seen, expanded organic vapors are extracted from turbine  25 B in an intermediate stage via line  26 B and supplied to condenser  31 B wherein organic working fluid condensate is produced. In addition, further expanded organic vapors exit turbine  25 B via line  27 B and are supplied to further condenser  30 B wherein further organic working fluid condensate is produced. Preferably, turbine  25 B rotates at 1500 RPM or 1800 RPM. Condensate produced in condensers  30 B and  31 B is supplied to vaporizer  20 B using cycle pump II,  16 B and cycle pump I,  15 B, respectively where sea water (or other equivalent heating) is supplied thereto via line  18 B for providing heat to the liquid working fluid present in vaporizer  20 B and producing vaporized working fluid. Condensers  30 B and  31 B are also supplied with LNG using pump  40 B so that the LNG is pressurized to a relatively high pressure e.g. about 80 bars. As can be seen from  FIG. 7 , the LNG is supplied first of all to condenser  30 B for condensing the relatively low pressure organic working fluid vapor exiting turbine  25 B and thereafter, the heated LNG exiting condenser  30 B is supplied to condenser  31 B for condensing the relatively higher pressure organic working fluid vapor extracted from turbine  25 B. Thus, in accordance with this embodiment of the present invention, the supply rate or mass flow of the working fluid in the bleed cycle, i.e. line  26 , condenser  31 B and cycle pump I,  15 B, can be increased so that additional power can be produced. Thereafter, the further heated LNG exiting condenser  31 B is preferably supplied to heater  36 B for producing LNG vapor which may held in storage  42 B or, alternatively, be delivered by through line  43 B to a pipeline for distribution of vaporized LNG to end users. While only one turbine is shown in  FIG. 7 , if preferred, two separate turbine modules, i.e. a high pressure turbine module and a low pressure turbine module, can be used. 
     In an alternative version (see  FIG. 7A ) of the last mentioned embodiment, direct-contact condenser/heater  32 B′ can be used together with condensers  30 B′ and  31 B′. By using direct-contact condenser/heater  32 B′, it is ensured that the working fluid supplied to vaporizer  20 B′ will not be cold and thus there will be little danger of freezing sea water or heating medium in the vaporizer. In addition, the mass flow of the working fluid in the power cycle can be further increased thereby permitting an increase in the power produced. Furthermore, thereby, the dimensions of the turbine at e.g. its first stage can be improved, e.g. permit the use of blades having a larger size. Consequently, the turbine efficiency is increased. 
     In a still further alternative version (see  FIG. 7B ) of the embodiment described with reference to  FIG. 7 , reheater  22 B″ is included and used in conjunction with direct-contact condenser/heater  32 B″ and condensers  30 B″ and  31 B″. By including the reheater, the wetness of the vapors exiting high-pressure turbine module  24 B″ will be substantially reduced or eliminated thus ensuring that the vapors supplied to low-pressure turbine module  25 B are substantially dry so that effective expansion and power production can be achieved. If preferred, one heat source can be used for providing heat for the vaporizer while another heat source can be provided for supplying for the reheater. 
     In both alternatives described with reference to  FIG. 7A  or  7 B, the position of direct contact condenser/heaters  32 B′ and  82 B″ can be changed such that the inlet of direct contact condenser/heaters  32 B′ can receive working fluid condensate exiting intermediate pressure condenser  31 B′ (see  FIG. 7A ) while direct contact condenser/heaters  32 B″ can receive pressurized working fluid condensate exiting cycle pump  16 B″ (see  FIG. 7B ). 
     In an additional alternative version (see  FIG. 7C ) of the embodiment described with reference to  FIG. 7 , condensate produced in low pressure condenser  30 B′″ (or low pressure condenser  30 B″″) can also be supplied to intermediate pressure condenser  31 B′″ (intermediate pressure condenser  31 B″″) to produce condensate from intermediate pressure vapor extracted from an intermediate stage of the turbine by indirect or direct contact respectively. 
       FIG. 7D  shows a still further alternative version of the embodiment described with reference to  FIG. 7  wherein rather than using a direct contact condenser/heater, an indirect condenser/heater is used. In this alternative, only one cycle pump can be used wherein suitable valves can be used in the intermediate pressure condensate lines. 
     In an alternative shown in  FIG. 7E , only one indirect condenser using LNG is used while a direct contact condenser/heater is also used. 
     In an additional embodiment of the present invention (see  FIG. 7F ), numeral  50 A designates an open cycle power plant wherein portion of the LNG is drawn off the main line  61 A of the LNG via line  62 A and cycled through a turbine for producing power. In this embodiment, two direct contact condenser/heaters are used for condensing vapor extracted and exiting the turbine respectively using pressurized LNG pressurized by pump  65 A prior to supply to the direct contact condenser/heaters. 
     In an alternative version, designated  50 B in  FIG. 7G , of the embodiment described with reference to  FIG. 7F  using an open cycle power plant, reheater  72 B is included and used in conjunction with direct-contact condenser/heaters  31 B and  33 B. By including the reheater, the wetness of the vapors exiting high-pressure turbine module  64 B will be substantially reduced or eliminated thus ensuring that the vapors supplied to low-pressure turbine module  65 B are substantially dry so that effective expansion and power production can be achieved. If preferred, one heat source can be used for providing heat for the vaporizer while another heat source can be provided for supplying for the reheater. 
     In a still further alternative option of the embodiment described with reference to  FIG. 7F  wherein an open cycle power plant is used, two indirect contact condensers can be used rather than the direct contact condensers used in the embodiment described with reference to  FIG. 7F . Two different configurations for the two indirect contact condensers can be used (see  FIGS. 7H and 7I ). 
     In an additional alternative option of the embodiment described with reference to  FIG. 7F  wherein an open cycle power plant is used, an additional direct contact condenser/heater can be used in addition to the two indirect contact condensers (see  FIG. 7J ). 
     Furthermore, if preferred, in a further alternative option, see  FIG. 7K , of the embodiment described with reference to  FIG. 7F  wherein an open cycle power plant is used, one direct contact condenser and one indirect contact condenser can be used. 
     Moreover, in a further embodiment, if preferred, in an open cycle power plant, one direct contact condenser or one indirect contact condenser can be used (see  FIG. 7L ). 
     In addition, in a further embodiment, if preferred, an open cycle power plant and closed cycle power plant can be combined (see  FIG. 7M ). In this embodiment, any of the described alternatives can be used as part of the open cycle power plant portion and/or closed cycle power plant portion. 
     Furthermore, it should be pointed out that, if preferred, the components of the various alternatives can be combined. Furthermore, also if preferred, certain components can be omitted from the alternatives. Additionally, an alternative used in a closed cycle power plant can be used in an open cycle power plant. E.g. the alternative described with reference to  FIG. 7C  (closed cycle power plant) can be used in an open cycle power plant (e.g. condensers  30 B′″ and  31 B′″ can be used in stead of condeners  33 B′ and  34 B′ shown in  FIG. 7H , condensers  30 B″″ and  31 B″″ can be used in stead of condeners  33 B′ and  34 B′ shown in  FIG. 7H ). 
     In addition, while two pressure levels are described herein, if preferred, several or a number of pressure levels can be used and, if preferred, an equivalent number of condensers can be used to provide effective use of the pressurized LNG as a cold sink or source for the power cycles. 
     In  FIG. 8 , a further embodiment of the present invention is shown wherein a closed organic Rankine cycle power system is used. Numeral  10 C designates a power plant system including steam turbine system  100  as well closed is used as well as organic Rankine cycle power system  35 C. Also here LNG pump  40 C is preferably used for pressurizing the LNG prior to supplying it to condenser  30 C to a pressure, e.g. about 80 bar, for producing a pressure for the re-gasified LNG suitable for supply via line  43 C to a pipeline for distribution of vaporized LNG to end users. In this embodiment, the preferred organic working fluid is ethane or equivalent. Preferably in this embodiment, power plant system  10 C includes, in addition, gas turbine unit  125  the exhaust gas of which providing the heat source for steam turbine system  100 . In such a case, as can be seen from  FIG. 8 , the exhaust gas of gas turbine  124  is supplied to vaporizer  120  for producing steam from water contained therein. The steam produced is supplied to steam turbine  105  where it expands and produces power and preferably drives electric generator  110  generating electricity. The expanded steam is supplied to steam condenser/vaporizer  120 C where steam condensate is produced and cycle pump  115  supplies the steam condensate to vaporizer  120  thus completing the steam turbine cycle. Condenser/vaporizer  120 C also acts as a vaporizer and vaporizes liquid organic working fluid present therein. The organic working fluid vapor produced is supplied to organic vapor turbine  25 C and expands therein and produces power and preferably drives electric generator  28 C that generates electricity. Preferably, turbine  25 C rotates at 1500 RPM or 1800 RPM. Expanded organic working fluid vapor exiting organic vapor turbine is supplied to condenser  30 C where organic working fluid condensate is produced by pressurized LNG supplied thereto by LNG pump  40 C. Cycle pump  15 C supplies the organic working fluid condensate from condenser  30 C to condenser/vaporizer  120 C. Pressurized LNG is heated in condenser  30 C and preferably heater  86 C further the pressurized LNG so that re-gasified LNG is produced for storage or supply via a pipeline for distribution of vaporized LNG to end users. Due to pressurizing of the LNG prior to supplied the LNG to the condenser, it can be advantageous to use a propane/ethane mixture as the organic working fluid of the organic Rankine cycle power system rather than ethane mentioned above. On the other hand, if preferred ethane, ethene or equivalent can be used as the working fluid while two condensers or other configurations mentioned above can be used in the organic Rankine cycle power system.
         1. Turning to  FIG. 9 , a further embodiment of the present invention is shown wherein a closed organic Rankine cycle power system is used. Numeral  10 D designates a power plant system including intermediate power cycle system  100 D as well as closed organic Rankine cycle power system  35 D. Also here LNG pump  40 D is preferably used for pressurizing the LNG prior to supplying it to condenser  30 D to a pressure, e.g. about 80 bar, for producing a pressure for the re-gasified LNG suitable for supply via line  43 D to a pipeline for distribution of vaporized LNG to end users. In this embodiment, the preferred organic working fluid is ethane, ethene or equivalent. Preferably, in this embodiment, power plant system  10 D includes gas turbine unit  125 D the exhaust gas of which providing the heat source for intermediate heat transfer cycle system  100 D. In such a case, as can be seen from  FIG. 9 , the exhaust gas of gas turbine  124 D is supplied to an intermediate cycle  100 D for transferring heat from the exhaust gas of the vaporizer  120 D for producing intermediate fluid vapor from intermediate fluid liquid contained therein. The vapor produced is supplied to intermediate vapor turbine  105 D where it expands and produces power and preferably drives electric generator  110 D generating electricity. Preferably, turbine  25 D rotates at 1500 RPM or 1800 RPM. The expanded vapor is supplied to vapor condenser/vaporizer  120 D where intermediate fluid condensate is produced and cycle pump  115 D supplies the intermediate fluid condensate to vaporizer  120  thus completing the intermediate fluid turbine cycle. Several working fluids are suitable for use in the intermediate cycle. An example of such a working fluid is pentane, i.e. n-pentane or iso-pentane. Condenser/vaporizer  120 D also acts as an vaporizer and vaporizes liquid organic working fluid present therein. The organic working fluid vapor produced is supplied to organic vapor turbine  25 D and expands therein and produces power and preferably drives electric generator  28 D that generates electricity. Expanded organic working fluid vapor exiting organic vapor turbine is supplied to condenser  30 D where organic working fluid condensate is produced by pressurized LNG supplied thereto by LNG pump  40 D. Cycle pump  15 D supplies the organic working fluid condensate from condenser  30 D to condenser/vaporizer  120 D. Pressurized LNG is heated in condenser  30 D and preferably heater  36 D further the pressurized LNG so that re-gasified LNG is produced for storage or supply via a pipeline for distribution of vaporized LNG to end users. Due to pressurizing of the LNG prior to supplied the LNG to the condenser, it can be advantageous to use a propane/ethane mixture as the organic working fluid of the organic Rankine cycle power system rather than ethane mentioned above. On the other hand, if preferred ethane, ethene or equivalent can be used as the working fluid while two condensers or other configurations mentioned above can be used in the organic Rankine cycle power system. Furthermore, a heat transfer fluid such as thermal oil or other suitable heat transfer fluid can be used for transferring heat from the hot gas to the intermediate fluid and, if preferred, a heat transfer fluid such as an organic, alkylated heat transfer fluid e.g. a synthetic alkylated aromatic heat transfer fluid. Examples can be an alkyl substituted aromatic fluid, Therminol LT, of the Solutia company having a center in Belgium or a mixture of isomers of an alkylated aromatic fluid, Dowterm J, of the Dow Chemical Company. Also other fluids such as hydrocarbons having the formula C n H 2n+2  wherein n is between 8 and 20 can also be used for this purpose. Thus, iso-dodecane or 2,2,4,6,6-pentamethylheptane, iso-eicosane or 2,2,4,4,6,6,8,10,10-nonamethylundecane, iso-hexadecane or 2,2,4,4,6,8,8-heptamethylnonane, iso-octane or 2,2,4 trimethylpentane, iso-nonane or 2,2,4,4 tetramethylpentane and a mixture of two or more of said compounds can be used for such a purpose, in accordance with U.S. patent application Ser. No. 11/067,710, the disclosure of which is hereby incorporated by reference. When an organic, alkylated heat transfer fluid is used as the heat transfer fluid, it can be used to also produce power or electricity by e.g. having vapors produced by heat in the hot gas expand in a turbine, with the expanded vapors exiting the turbine being condensed in a condenser which is cooled by intermediate fluid such that intermediate fluid vapor is produced which is supplied to the intermediate vapor turbine.       

     Furthermore, any of the alternatives described herein can be used in the embodiments described with reference to  FIG. 8  or  FIG. 9 . 
     While in the embodiments and alternatives described above it is stated that the preferred rotational speed of the turbine is 1500 or 1800 RPM, if preferred, in accordance with the present invention, other speeds can also be used, e.g. 3000 or 3600 RPM. 
     If preferred, the methods of the present invention can also be used to cool the inlet air of a gas turbine and/or to carry out intercooling in an intermediate stage or stages of the compressor of a gas turbine. Furthermore, if preferred, the methods of the present invention can be used such that LNG after cooling and condensing the working fluid can be used to cool the inlet air of a gas turbine and/or used to carry out intercooling in an intermediate stage or stages of the compressor of a gas turbine. 
     Furthermore, it should be pointed out that, if preferred, steam turbine system  100  described with reference to  FIG. 8  can be a condensing steam turbine system. 
     While methane, ethane, ethene or equivalents are mentioned above as the preferred working fluids for the organic Rankine cycle power plants they are to be taken as non-limiting examples of the preferred working fluids. Thus, other saturated or unsaturated aliphatic hydrocarbons can also be used as the working fluid for the organic Rankine cycle power plants. In addition, substituted saturated or unsaturated hydrocarbons can also be used as the working fluids for the organic Rankine cycle power plants. Trifluromethane (CHF 3 ), fluromethane (CH 3 F), tetrafluroethane (C 2 F 4  and hexafluroethane (C 2 F 6 ) are also preferred working fluids for the organic Rankine cycle power plants described herein. Furthermore, such Chlorine (Cl) substituted saturated or unsaturated hydrocarbons can also be used as the working fluids for the organic Rankine cycle power plants but would not be used due to their negative environmental impact. 
     Auxiliary equipment (e.g. values, controls, etc.) are not shown in the figures for sake of simplicity. 
     While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.

Technology Classification (CPC): 5