MX2008000503A

MX2008000503A - Configurations and methods for power generation in lng regasification terminals.

Info

Publication number: MX2008000503A
Application number: MX2008000503A
Authority: MX
Inventors: John Mak
Original assignee: Fluor Tech Corp
Priority date: 2005-07-18
Filing date: 2006-07-17
Publication date: 2008-03-07
Also published as: CA2615850A1; WO2007011921A2; WO2007011921B1; EP1904782A4; WO2007011921A3; CA2615850C; CN101238322B; CN101238322A; EP1904782A2

Abstract

Contemplated power producing configurations and methods use refrigeration cold of LNG to condense expanded vaporized natural gas produced in an expansion turbine, wherein the expansion turbine is driven by heated vaporized natural gas drawn from a vaporizer. Most typically, condensed expanded vaporized natural gas is combined with the LNG and fed to the vaporizer.

Description

CONFIGURATIONS AND PROCEDURES FOR THE GENERATION OF ENERGY IN LNG REGASIFICATION TERMINALS Field of the Invention The field of the invention is the generation of energy using LNG, and in particular it refers to the generation of energy in LNG regasification facilities, and / or the integration to a power plant. Background of the Invention The importation of liquefied natural gas (L? G) is expected to accelerate, mainly due to the growing and technological use and economic advantages over crude oil. While some of the existing existing L? G regasification facilities are extended, the new regasification facilities must still be added to meet the future demand for natural gas. Conventional LNG regasification facilities typically require an external heat source such as an open seawater vaporizer, a submerged combustion vaporizer, an intermediate fluid vaporizer (by e., using a water-glycol mixture), and / or room air vaporizers. However, vaporization L? G is an energy intensive process and typically requires a working heat equivalent of about 3% of the energy content in L? G. More REF. : 188332 recently, attempts have been made to reduce the energy requirement for regasification by coupling the heat of the production processes with the LNG regasification. For example, power plants can be coupled with regasification of LNG, as described in U.S. Pat. Do not . 4,036,028 and 4,231,226 of Mandrin and Griepentrog, respectively. Similar configurations are reported in the U.S. Patent application publication. ? o? 2003/0005698 by Keller, EP 0 683 847 by Johnson et al., And WO 02/097252 by Keller. In such known configurations, the heat for regasification L? G is provided by a heat exchange fluid, which is in thermal exchange with the low pressure turbine or with a combined cycle power plant. While some of these configurations provide for the reduction in energy consumption, the increase in power generation efficiencies are often not significant, mainly due to the inability of these methods to effectively use the same low L? G temperature. (typically between -255 ° F to -150 ° F) as the heat sink. Still further, and among all other difficulties still, the heat transfer in some of these configurations is limited by the relatively high freezing point of the heat transfer medium. Due to these and other limitations, the efficiency of power generation is generally low. In other known configurations, as described in EP 0 496 283, the power is generated by a steam expansion turbine that is driven by a working fluid (here: water) which is heated by a low pressure gas turbine and cooled by a LNG regasification circuit. While such a configuration increases the efficiency of a plant at least at a certain level, several problems remain. For example, the use of the cryogenic cooling content of the L? G is often restricted due to the high freezing point of the water. To overcome at least some of the difficulties associated with high freezing temperatures, non-aqueous fluids can be used as working fluid in a typical Rankine cycle of power generation. An illustrative configuration for such an approach is disclosed in U.S. Pat. ?or. 4,388,092 from Matsumoto and Aoki, in which a mui-component hydrocarbon stream from a distillation column is used to improve generation efficiency. However, the operation of these systems and the monitoring and control of the working fluid component is expensive and complex. Therefore, while numerous processes and configurations for the use of LNG and regasification are known in the art, almost all of them suffer from one or more disadvantages. Thus, there is still a need to provide improved configurations and procedures for the utilization and regasification of LNG. BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to the configurations and methods for power generation in a LNG regasification operation in which the L? G is used as the working fluid, wherein the L? G in the state liquefied is used upstream of a vaporizer to condense the expanded working fluid, while a fraction of L? G in the vaporized state (vaporized natural gas) is used downstream of the vaporizer to drive an expansion turbine. More advantageously, the L? G is vaporized at the pressure of the pipe, while the condensed expanded working fluid is pumped back into the pressure pipe and combined with the LNG in a position upstream of the vaporizer. Therefore, in one aspect of the inventive matter, a L? G regasification plant is considered to include a heat exchanger that is configured to condense the expanded vaporized natural gas using the refrigerated content of the liquefied natural gas. A vaporizer in such plants is configured to produce vaporized natural gas from liquefied natural gas, and an extender is fluidly coupled to the vaporizer and configured to expand at least a fraction of the natural gas vaporized thereby to produce the expanded vaporized natural gas . Preferably, the contemplated plants will further include a pump that is configured to receive the condensed natural gas from the heat exchanger and a conduit fluidly coupled to the pump and configured to combine the condensed natural gas with the liquefied natural gas, and / or a second exchanger of heat that is configured to heat at least the vaporized natural gas fraction of the vaporizer using heat from the expanded vaporized natural gas. In more preferred aspects, the plant includes a third heat exchanger that is configured to heat at least the vaporized natural gas fraction of the vaporizer to a temperature of at least 300 ° F (e.g., using combustion gas from a gas turbine, a residual heat recovery unit, and / or a burning heater as a heat source). Additionally, or alternatively, a heat transfer fluid circuit may be included that is thermally coupled to the vaporizer and to a fourth heat exchanger (which is typically configured to heat the fraction of vaporized natural gas from the vaporizer to a position upstream of the extender. ). In particular the plants considered include a second pump that pumps the liquefied natural gas at a storage pressure to a pipe pressure, where the storage pressure is between 1 psig and 100 psig, and where the pipe pressure is between 700 psig and 2000 psig. Therefore, the extender is typically configured to expand the vaporized natural gas fraction from about 1000 to 2000 psig at a pressure of between about 1 psig and 100 psig. It is also considered that the plant includes a flow control unit that controls the volume flow of the vaporized natural gas fraction from the vaporizer to the extender. In another aspect of the inventive matter, a method of producing energy using natural gas as a working fluid will include an expansion step of at least a fraction of vaporized natural gas in a turbine to produce energy (typically at a pressure of between 1 and 2). at 100 psig) and expanded vaporized natural gas. In yet another stage, the expanded vaporized natural gas is condensed using refrigeration from the liquefied natural gas refrigeration, and combining the condensed natural gas with the liquefied natural gas, and at another stage still, the combined liquidity and condensed natural gas are vaporized to produce vaporized natural gas. In particular, preferred methods include a step of heating the vaporized natural gas fraction in one or more heat exchangers using heat from the gas of a gas turbine., of a residual heat recovery unit, of a burn-in heater, and / or of expanded vaporized natural gas. Other preferred methods include a step of pumping the liquefied natural gas at least to the pipe pressure in a position upstream of a vaporizer that produces the vaporized natural gas. More typically, the vaporizer uses seawater, a heat exchange medium, and / or a submerged burner as a heat source. In preferred aspects of the inventive matter, the vaporized natural gas fraction is between about 1% and 50% of the total vaporized natural gas. Thus, and viewed from a different perspective, the inventors contemplate the use of the LNG sent from a position upstream of a vaporizer to condense the expanded vaporized working fluid of natural gas from an open cycle of energy wherein the vaporized working fluid of the Natural gas is sent from a downstream location of the vaporizer. Typically, the open energy cycles considered include an expansion turbine and a heater that heats the vaporized working fluid of the natural gas, while both the condensed working fluid of the natural gas and the LNG sent from the position upstream of the vaporizer are combined and fed to the vaporizer. As in the plants and methods considered above, it is typically preferred that the LNG in the upstream situation of the vaporizer is close to the pipe pressure and the expanded vaporized working fluid of the natural gas is at a pressure of between 1 to 100 psig . Various objects, features, aspects and advantages of the present invention become more apparent from the detailed description of the preferred embodiments of the invention, together with the attached drawing. Brief Description of the Figures Figure 1 is an illustrative configuration of an energy production scheme coupled to a regasification operation of the LNG according to the inventive matter. Figure 2 is another illustrative configuration of an energy production scheme together with a regasification operation of L? G according to the inventive matter. Detailed Description of the Invention The inventor has discovered that the refrigeration content in L? G can be used successfully in the production of energy in a regasification facility using at least a fraction of the LNG regasified gas as the working fluid in a cycle open, where the L? G after the expansion using the cryogenic cooling content of the L? G fed to the installation. Depending on the configuration of the vaporizer, an intermediate heat transfer medium can be used in considered configurations. It should be particularly appreciated that L? G is pumped at a desired pressure to the refrigeration supply in an open cycle of energy using LNG as the working fluid. In such plants, the working fluid of the LNG is condensed using the cryogenic temperatures of the LNG that is supplied to the plant. Therefore, it must be recognized that regasification of ING and / or power generation can be achieved with that of ambient air vaporizers, seawater vaporizers, and / or waste heat from turbine gas. combustion gas or burning heaters, which significantly reduces fuel consumption in power generation. On the other hand, since the LNG is used as a working fluid, no external working fluid is required. Seen from a different perspective, a substantially increasing amount of the refrigeration content is recoverable as working fluid will not cool to cryogenic temperatures. An example of an open-cycle LNG energy is schematically represented in Figure 1, in which the power generation is operationally coupled to a LNG regasification plant that has a delivery speed of around 350 MMscfd. However, it should be noted that the inventive material is not limited to a specific shipping velocity, and the appropriate plants may have higher or lower velocities. Table 1 below shows a typical composition of typical LNG in Figure 1. Table 1 COMPONENT MOL% Ci 86 to 95% C2 4 to 14% C3 to C5 3 to 7% C6 + 0.5 to 1% N2 + C02 0.1 to 1% Current 1 of the LNG from the storage tank of the LNG or from different sources is typically at a pressure between 70 psig to 100 psig and at a temperature around -260 ° F to -250 ° F. The stream 1 is pumped by the ING pump 51 to a suitable pressure, typically about 1200 to 1600 psig of LNG to form the pressurized stream 2 of the LNG, as needed to meet the requirement of the pipe. As used herein, the term "around" in conjunction with a number refers to a range of that number from 20% below the number to 20% of the number, inclusive. For example, the term "about -150 ° F" refers to a range of -180 ° F to -120 ° F, and the term "about 1400 psig" refers to a range of 1372 psig to 1680 psig. A fraction of the stream 2 of the LNG is divided as stream 3 and sent to the exchanger 54 using the bypass valve 52. The stream 3 is heated in the exchanger about -250 ° F to about -170 ° F to form the stream 4, while the expanded vaporized working fluid 8 of the natural gas cools and condenses around 40 ° F to about -215 ° F. The condensed working fluid 9 of the LNG is at a pressure of about 80 psig and a temperature of about -215 ° F and pumped by the pump 55 at a pressure of around 1400 psig, forming the stream 10 which is combined with the fraction remaining current 2 of the LNG to form the combined current 5. The stream 5 is then heated in the vaporizer 53 to around 40 ° F with heat provided by environmental heat sources (eg, ambient air or sea water). The vaporized stream of natural gas 6 is then divided into a first fraction (about 85%, stream 7) and a second fraction (about 15%, stream 30) using a flow control apparatus (not shown). It should be noted that, among different factors, the proportion of the vaporized natural gas division usually depends on the composition of the LNG and the desirable output signal of the power generation. The stream 7 is sent to the consuming pipe, while current 30 is used in the feed cycle as described below. The stream 30 is first heated in the exchanger 56 about 155 ° F which forms the stream 11 using the heat content of the stream 13 of the extender discharge. The heated vaporized natural gas is further heated in the heater 57 with an external source around 450 ° F (or higher) forming the current 12. It should be appreciated that numerous external heat sources are suitable (eg, gas from combustion of a gas turbine, the waste heat recovery unit, and / or a burn-in heater). The resulting stream 12 of the high pressure high temperature working fluid is then expanded in the extender 58 around 75 psig to form the stream 13, generating energy that can be used to drive an electrical generator. The heat content of the discharge in the extender is recovered in the exchanger 56 by forming a stream 8 which is subsequently condensed in the exchanger 54 forming the stream 9 to repeat the energy cycle. In the illustrative configuration of Figure 1, the open cycle of energy circulates around 550 GPM of the working fluid of the LNG, generating about 5,000 kilowatts. The efficiency of power generation, as calculated by the heat equivalent of the net energy output of the cycle divided by the heat input to exchanger 57, is about 68%. The efficiency can also be increased with a higher operating temperature and pressure, which must be balanced with high equipment costs and a heat requirement. With respect to the quantities of streams 3 and 30 that are moved from currents 2 and 6 of the LNG, respectively, it must be recognized that the specific quantities are at least partly determined by the amount of energy that must be generated. For example, where relatively large amounts of energy is desired, current 30 may be more than 15% (eg, 16 to 20%, 20 to 25%, or even higher) of current 6. Therefore, and depending on the temperature of the cooled discharge of the extender 8, the amounts of stream 3 can vary considerably. More typically, the stream 3 will be at least an effective amount to condense the expanded stream 8 of the natural gas. Thus, it should be recognized that a first fraction of the cryogenic content of the cooling of stream 2 of the LNG is used as a heat sink for the working fluid of the LNG, and that at least a fraction of the LNG in at least one partially forms Vaporized is heated and expanded to produce work in an open cycle of energy. Another illustrated illustrative energy cycle of the LNG is schematically represented in Figure 2, in which energy generation is operationally coupled to a LNG regasification plant using an intermediate heat transfer fluid (eg, water-glycol). , alcohol, or the very high boiling temperature chemical, etc.) to provide heat to the LNG vaporizer. Here, the intermediate fluid stream 14 is pumped by the pump 59 about 120 psig forming the stream 15 which is preferably heated with ambient air in the vaporizer 60 which forms the stream 16. A first fraction of the stream 16 is additionally heated via stream 17 with waste heat 22 in exchanger 61 about 480 ° F or higher, forming a hot stream 19 which heats the preheated stream 11 of the LNG. The stream 19 leaves the heat exchanger 57 as stream 20 and is combined with the second stream fraction 16. (stream 18) to form stream 21 that is used in vaporizer 53. With respect to the remaining components of Figure 2, the same considerations apply for similar components with similar numbers as depicted in Figure 1. The sources of Suitable heat for exchangers 22 and 57 include the combustion air of the gas turbine, the cooling water to the surface of the condensers, the combustion gas of a gas turbine, and / or the combustion gas of a heater burner. However, numerous alternative sources of heat are also considered, including the units found in plants other than a combined cycle plant. Similarly, containers suitable for cold LNG may also include numerous cryogenic processes (eg, air separation plants) in which the LNG cools the air or other gas, the processes providing combustion gas (e.g., gases). of reformed combustion, etc.), and other procedures act as a heat sink (eg, plants producing liquid carbon dioxide, desalination plants, or food freezing facilities). Therefore, it should be appreciated that the LNG sent from an upstream placement of a vaporizer can be used to condense the expanded vaporized working fluid of natural gas from a preferably open cycle of energy wherein the vaporized working fluid of natural gas it is sent from a position downstream of the vaporizer. In a further considered aspect of the inventive subject, it is generally preferred that the energy production be operationally coupled with the LNG regasification facilities and / or the LNG receiving terminals, and the particularly preferred configurations include those in which the LNG is regasified in a procedure in which at least a part of the LNG is used to generate electric power (more preferably with integration to a combined energy cycle). For example, suitable plants and methods are described in our international patent application and co-dependent with serial numbers PCT / US03 / 25372 and PCT / US03 / 26805, which are incorporated by reference mode. Accordingly, and depending on the particular heat source, it must be recognized that the energies necessary for regasification of the LNG may be entirely, or only partially provided by, heat sources considered. Where the heat source provides insufficient amounts of heat to completely gasify the LNG, it must be recognized that supplemental heating can be provided. Suitable supplemental heat sources include waste heat from the steam turbine discharge, condensation due to combustion gas, environmental heating with air (eg, providing air conditioning to buildings), with seawater, or fuel gas. Therefore, it should be appreciated that the considered configuration and procedures can be used to adapt existing regasification plants to improve efficiencies and flexibility of power generation, or can be used in new installations. It should be appreciated in particular that numerous of the advantages can be achieved by using the configurations according to the inventive matter. Among other things, the configurations considered provide very efficient cycles of power generation of the LNG without the external working fluid, such as water vapor, or the hydrocarbons with a composition different from that of LNG. The considered procedures can be coupled with any type of power plant and still provide the benefit or improved efficiency. In particular the preferred configurations use the cold of the LNG in the cryogenic region and the LNG as the working fluid to achieve the thermally high efficiency, typically in the range of about 70% or higher. In the most preferred plants, the sent LNG is pumped at supercritical pressure and regasified using conventional vaporizers while a fraction of the regasified product is divided as the working fluid of the LNG (vaporized natural gas) to the open energy cycle. The working fluid of the LNG is additionally superheated and expanded to a lower pressure in such a way as to generate the energy, where the expanded working fluid is condensed using the cryogenic temperatures of the LNG sent in a range of -250 ° F to - 150 ° F. Alternatively, the working fluid of the LNG is pumped to a supercritical pressure (here: above cricondenbar pressure), and heated with an external heat source, and then expanded to a lower pressure for power generation with a heat source integral with or thermally coupled to the energy cycle. The expanded working fluid is condensed using the LNG sent, pumped and mixed with the LNG sent and heated in the vaporizers. According to the simple conceptual configuration of considered plants, it must be recognized that energy generation according to the inventive matter can be implemented as a modification to existing facilities or in facilities built from starting lines. Thus, specific embodiments and applications for configurations and procedures for power generation with integrated LNG regasification have been disclosed. It should be evident, however, to those skilled in the art that those many more modifications besides that are already described possible without leaving the inventive concepts attached. The inventive matter, therefore, should not be restricted except in the spirit of the present description. On the other hand, in interpreting the description, all denominations should be interpreted in the widest possible form consistent with the context. In particular the terms "comprises" and "comprising" must be interpreted refers to elements, constructive elements, or stages in a non-exclusive manner, indicating that elements, components, or referenced steps may be present, or used, or combined with different elements, components, or stages are not expressly referenced. In addition, where a definition or an application of a term in a reference mode is incorporated by the reference mode attached here as a reference is inconsistent with or contrary to the definition of the term provided herein, the definition of the term provided herein applies and the definition of the term in the reference does not apply. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

Claims Having described the invention as above, the content of the following claims is claimed as property: 1. - A LNG regasification plant with an open energy cycle, characterized in that it comprises: a heat exchanger that is configured to condense the vaporized natural gas in such a way as to form an expanded condensed natural gas using the liquefied natural gas refrigeration content; a vaporizer that is configured to produce vaporized natural gas from liquefied natural gas and condensed natural gas; an expander fluidly coupled to the vaporizer and configured to expand at least a fraction of the vaporized natural gas in such a way as to produce energy and the expanded vaporized natural gas; and wherein a pipe is configured to receive another fraction of vaporized natural gas, and in which the other fraction and at least the vaporized natural gas fraction have the same pressure. 2. The regasification plant according to claim 1, characterized in that it also comprises a pump configured to receive natural gas condensed from the heat exchanger and a pipe fluidly coupled to the pump and configured to combine natural gas condensed with natural gas smoothie. 3. The regasification plant according to claim 1, characterized in that it further comprises a second heat exchanger that is configured to heat at least the vaporized natural gas fraction of the vaporizer using heat from the expanded vaporized natural gas. The regasification plant according to claim 1, characterized in that it further comprises a third heat exchanger which is configured to heat at least the vaporized natural gas fraction of the vaporizer at a temperature of at least 300 ° F. 5. The regasification plant according to claim 4, characterized in that the third heat exchanger is configured to use a heat source selected from the group consisting of a gas turbine combustion gas, a gas recovery unit, and waste heat, and from a burn-in heater. 6. The regasification plant according to claim 1, characterized in that it further comprises a second pump that is configured to pump the liquefied natural gas from a storage pressure to a pipe pressure. 7. The regasification plant according to claim 6 characterized in the storage pressure is between 1 psig and 100 psig, and in which the pressure of the pipeline is between 700 psig and 2000 psig. The regasification plant according to claim 1, characterized in that the extender is configured to expand at least the vaporized natural gas fraction from about 1000 to 2000 psig at a pressure between about 1 psig and 100 psig. psig The regasification plant according to claim 1, characterized in that it further comprises a flow control unit that controls the flow volume of at least the fraction of vaporized natural gas from the vaporizer to the extender. 10. The regasification plant according to claim 1, characterized in that it further comprises a circuit of heat transfer fluid that is thermally coupled to the vaporizer and a fourth heat exchanger that is configured to heat at least the fraction of the natural gas vaporized from the vaporizer in a countercurrent position of the extender. 11. A process for producing energy using natural gas as a working fluid, characterized in that it comprises: expanding at least a fraction of vaporized natural gas in a turbine to produce energy and the expanded vaporized natural gas; feed another fraction of vaporized natural gas to the pipeline, in which the other fraction of vaporized natural gas have the same pressure; condensing the expanded vaporized natural gas using cold refrigeration of the liquefied natural gas, and combining the condensed natural gas with the liquefied natural gas; and vaporizing the combined liquefied natural gas and condensed natural gas to produce the vaporized natural gas. 12. The method according to claim 11, further comprising a step of heating the vaporized natural gas fraction in at least one heat exchanger using heat from a source selected from the group consisting of a combustion gas of a gas turbine, a waste heat recovery unit, burn heater, and expanded vaporized natural gas. 13. The method according to claim 11, characterized in that it further comprises a step of pumping the liquefied natural gas at least to the pressure of the pipe in a countercurrent placement of a vaporizer that produces the vaporized natural gas. 14. The method according to claim 13, characterized in that the vaporizer used is at least one of sea water, a heat exchange medium, a submerged burner as a source of heat. The method according to claim 11, characterized in that the step of expanding the fraction of vaporized natural gas comprises expansion at a pressure of between 1 to 100 psig. 16. The method according to claim 11, characterized in that the vaporized natural gas is between 1% and 50% of the total vaporized natural gas. 17. The use of the LNG sent from a countercurrent placement of a vaporizer to condense the expanded vaporized working fluid of natural gas from an open cycle of energy in which the vaporized working fluid of the natural gas is sent from a downstream location of the vaporizer and has a pressure that is close to the vaporized natural gas pressure is sent from the vaporizer to the pipeline. 18. The use according to claim 17, wherein the open energy cycle comprises an expansion turbine and a heater that heats the vaporized working fluid of the natural gas. 19. The use according to claim 17, wherein the condensed working fluid of the natural gas and the LNG sent from the upstream setting of the vaporizer are fed to the vaporizer. 20. The use according to claim 17, wherein the LNG in the countercurrent placement of the vaporizer is close to the pipeline pressure and in which the expanded vaporized working fluid of the natural gas is at a pressure of between 1 to 100 psig.