JP2016519277A - Gear coupled compressor for precooling in LNG applications - Google Patents

Abstract

A natural gas liquefaction system is disclosed that includes at least a pre-cooling loop (103) configured to circulate a first refrigerant. The precooling loop removes heat from the first refrigerant, at least one compressor (109) for pressurizing the first refrigerant, at least one prime mover (111) for driving the compressor (109). At least one condenser (115) for the expansion, at least a first expansion element (119A-119D) for expanding the first refrigerant, and at least for transferring heat from the natural gas to the first refrigerant A first heat exchanger (123A to 123D). The system further comprises at least a cooling loop (105) downstream of the precooling loop for circulating the second refrigerant. Natural gas is configured to be sequentially cooled in the pre-cooling loop and the cooling loop. The precooling loop compressor is a gear-coupled turbocompressor comprising a plurality of compressor stages (109A-109D). [Selection] Figure 2

Description

  Embodiments disclosed herein relate to processes and systems for liquefying natural gas.

  Natural gas has become an increasingly important energy source. In order to be able to transport natural gas from the source to the point of use, the gas volume needs to be reduced. Cryogenic liquefaction has become a routine process for converting natural gas into a liquid that can be stored and transported more conveniently, cheaper and more safely. Transportation of liquefied natural gas (LNG) by pipeline or ship is possible at ambient pressure by keeping the cooled and liquefied gas at a temperature below the liquefaction temperature at ambient pressure.

  In order to store and transport natural gas in a liquid state, the natural gas is preferably cooled to about −150 to −170 ° C., where the gas has a vapor pressure of approximately atmospheric.

  For natural gas liquefaction, several processes and systems that sequentially pass high pressure natural gas through multiple cooling stages to cool the gas to lower temperatures in sequential cooling cycles until the liquefaction temperature is achieved Exists in the prior art.

  Prior to passing the natural gas through the cooling stage, the natural gas is pretreated to remove unwanted impurities in the final product that may interfere with processing, damage the equipment, or in the final product. Impurities include acid gases, sulfur compounds, carbon dioxide, mercaptans, water, and mercury. Then, the pretreated gas from which impurities have been removed is cooled by the refrigerant flow, and heavier hydrocarbons are separated. The remaining gas is mainly composed of methane, and the content of high molecular weight hydrocarbons such as propane or heavier hydrocarbons is usually less than 0.1 mol%. The natural gas purified by removing impurities in this way is cooled to the final temperature in the cryogenic part. The resulting LNG can be stored and transported at approximately atmospheric pressure.

  Cryogenic liquefaction is usually performed by a multi-cycle process, ie a process that uses several different cooling cycles. Depending on the type of process, each cycle can use a different cooling fluid, or the same cooling fluid can be used in more than one cycle.

  FIG. 1 schematically shows a diagram of a cryogenic natural gas liquefaction system using a so-called APCI process. This known process uses two cooling cycles. The first cycle uses propane as the cooling medium, and the second cycle uses a mixed refrigerant usually made of nitrogen, methane, ethane, and propane. The system (shown generally as 1) comprises a first cycle 2 that includes a line formed by a gas turbine 3 that drives a compressor train. The compressor row includes a first compressor 5 and a second compressor 7 in series for compressing the mixed refrigerant. An interstage cooler (intercooler) 9 cools the mixed refrigerant provided by the first compressor 5, lowers the temperature of the mixed refrigerant before entering the second compressor 7, and reduces the volume. The compressed mixed refrigerant provided by the second compressor 7 is condensed in the heat exchanger 11 against air or water. The mixed refrigerant is further cooled and partially liquefied by the propane cycle 12, as disclosed below.

  Propane is processed in the second cycle or precooling cycle. The second cycle includes a line including a gas turbine 13 that drives the multistage compressor 15. The compressed propane provided by the compressor 15 is condensed in the condenser 17 against water or air. Condensed propane is used to precool natural gas to −40 ° C. and to cool and partially liquefy the mixed refrigerant. The natural gas precooling and the partial liquefaction of the mixed refrigerant are performed in a multi-pressure process, and in the illustrated example, are performed at four stages of pressure.

  The condensed propane stream from condenser 17 is brought into a first set of four in-line heat exchangers to cool and partially liquefy the mixed refrigerant, while a second set of It is brought into four pre-cooled heat exchangers arranged in series to cool the natural gas. A first portion of the compressed propane stream from condenser 17 is brought through line 19 to a first set of heat exchangers, and expanders 21, 23, 25, and 27 arranged in series. At 4 different progressively lower pressure levels. Downstream of each expander 21, 23, and 25, a portion of the expanded propane stream is passed to a respective heat exchanger 29, 31, 33. Propane flowing through the last expander 27 is passed to the heat exchanger 35.

  The compressed mixed refrigerant provided from the heat exchanger 11 flows through the pipe 37 toward the main cryogenic heat exchanger 38. The pipe 37 sequentially passes through the heat exchangers 29, 31, 33, and 35 so that the mixed refrigerant is gradually cooled against the expanded propane and partially liquefied.

  A second portion of the condensed propane stream from the condenser 17 is brought to the second line 39 and expanded in sequence in four in-line expanders 41, 43, 45 and 47. It is done. A portion of the propane expanded in each expander 41, 43, and 45 and the propane flowing from the last expander 47 flow toward the corresponding precooling heat exchangers 49, 51, 53, and 55, respectively. It is. The main natural gas line 61 flows through the precooling heat exchangers 49, 51, 53, and 55 sequentially so that the natural gas is precooled before entering the main cryogenic heat exchanger 38. The heated propane exiting the pre-cooling heat exchangers 49, 51, 53, and 55 is collected with the propane exiting the heat exchangers 29, 31, 33, and 35 to recover four vaporized propane tributaries. The steam is again fed to the compressor 15 which compresses it to, for example, 15-25 bar so that it can be condensed again in the condenser 17.

JP 2013-36375 A

  The subject matter disclosed herein relates to an improved natural gas liquefaction system comprising at least a precooling circuit or loop for circulating a first refrigerant and at least one cooling or liquefaction loop for circulating a second refrigerant. The natural gas in the gaseous state passes through the heat exchanger apparatus of the precooling loop and then flows into the heat exchanger apparatus of the cooling or liquefaction loop. Natural gas is pre-cooled by heat exchange with the first refrigerant and at least the second refrigerant, cooled, and finally liquefied. An additional third cooling and / or liquefaction circuit or loop (or further cooling and / or liquefaction circuit or loop) can be placed in a cascade or continuous arrangement to gradually cool the natural gas and eventually liquefy it. Can be arranged. The loop includes a respective compressor device for processing a respective refrigerant, at least one condenser, and one or more expansion elements such as turbo expanders and / or throttle valves. At least the pre-cooling loop includes a gear-coupled turbo compressor for processing the first refrigerant. The first refrigerant may be divided into two or more tributaries that are used to exchange heat at progressively lower pressure values with natural gas and / or refrigerant circulating in the subsequent cooling or liquefaction loop.

According to some embodiments,
Configured to circulate the first refrigerant;
At least one compressor for pressurizing the first refrigerant;
At least one prime mover for driving the compressor;
At least one condenser for removing heat from the first refrigerant;
At least a first expansion element for expanding the first refrigerant;
A precooling loop comprising at least a first heat exchanger for transferring heat from natural gas to the first refrigerant, and a cooling loop located downstream of the precooling loop and circulating the second refrigerant At least,
The natural gas is configured to be sequentially cooled in the pre-cooling loop and the cooling loop,
The compressor is a gear-coupled turbo compressor comprising a plurality of compressor stages, each compressor stage having an independent movable inlet guide vane for independently adjusting the flow entering the compressor stage. A natural gas liquefaction system comprising the set is provided.

  According to some embodiments, an additional compressor stage may be provided that does not include a movable inlet guide vane. When multiple compressor stages are arranged in series, one set of movable inlet guide vanes is sufficient because the downstream stage is regulated by the set of movable inlet vanes in the upstream stage. Compressor stages arranged in series are each movable when the flow of the first refrigerant is divided into two or more tributaries and sequentially rejoins at an intermediate position between two subsequent compressor stages. A set of entrance vanes can be provided.

  According to another aspect, the natural gas stream is cooled and liquefied by heat exchange with at least a first refrigerant circulating in the precooling loop and a second refrigerant circulating in the cooling and / or liquefaction loop. A liquefaction method is provided. The first refrigerant is divided into a plurality of tributaries having pressure values that gradually decrease. The tributary exchanges heat with the flow of natural gas and / or the second refrigerant. The tributaries are returned to the respective compressor stages of the gear-coupled turbo compressor.

According to one embodiment,
Providing a pre-cooling loop comprising a gear coupled turbo compressor having a plurality of compressor stages, at least one condenser, at least one expansion element, and at least one heat exchanger;
Driving the gear-coupled turbo compressor with a prime mover;
Circulating a first refrigerant through the gear-coupled turbo compressor;
Condensing in the condenser the first refrigerant provided by the gear-coupled turbo compressor;
Dividing the first refrigerant into a plurality of partial flows; expanding the condensed first refrigerant in the expansion element;
Circulating the expanded refrigerant through the heat exchanger, removing heat from the natural gas and precooling the natural gas;
Individually controlling movable inlet guide vanes to regulate the partial flow on the suction side of the compressor stage;
Providing at least one cooling loop;
Circulating a second refrigerant in the at least one cooling loop;
Removing heat from the pre-cooled natural gas by heat exchange with the second refrigerant.

  Features and embodiments are disclosed herein below and are further described in the appended claims forming an integral part of this specification. The foregoing brief description sets forth features of various embodiments of the present invention so that the detailed description that follows may be better understood, and this technical contribution may be better appreciated. There are, of course, other features of the invention that will be described later in this specification and set forth in the appended claims. In this regard, before describing some embodiments of the present invention in detail, various embodiments of the present invention, in their application, will be described in the following description or illustrated in detail in the drawings and in the drawings. It should be understood that the arrangement is not limited to the components. The invention is capable of other embodiments and of being practiced and carried out in various ways. It should also be understood that the expressions and terms used herein are for illustrative purposes and should not be construed as limiting.

  The flow rate of the first refrigerant provided by the present system and method can be controlled without depending on the rotational speed of the compressor stage. This provides a more efficient and reliable LNG circuit.

  Thus, one of ordinary skill in the art can readily use the concepts underlying the present invention as a basis for designing other structures, methods, and / or systems for carrying out some of the objectives of the present invention. Can be understood. It is important, therefore, that the claims be understood as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

  A more thorough evaluation of many of the disclosed embodiments of the invention and their attendant advantages will be better understood by reference to the following detailed description and considered in conjunction with the accompanying drawings. It will be easy to obtain.

It shows a system for natural gas liquefaction with current technology. 1 shows an overview of a first embodiment of a system for the production of LNG according to the invention. Fig. 3 illustrates an exemplary embodiment of a gear coupled compressor used in the configuration of Fig. 2; 2 shows an overview of a system for manufacturing LNG according to the present invention in a second embodiment. 2 shows a cross section of two compressor stages of a gear-coupled turbo compressor used in the LNG system according to the invention.

  Exemplary embodiments are described in detail below with reference to the accompanying drawings. In the various figures, the same reference numbers refer to the same or analogous elements. Further, the figures are not necessarily drawn to scale. Also, the following detailed description does not limit the invention. Rather, the scope of the invention is defined by the appended claims.

  Throughout the specification, references to “one embodiment” or “embodiments” or “some embodiments” refer to particular features, structures, or characteristics described in connection with an embodiment. It is meant to be included in at least one embodiment of the disclosed subject matter. Thus, the phrases “in one embodiment” or “in an embodiment” or “in some embodiments” appearing in various places in the specification do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

  FIG. 2 schematically shows a diagram of a cryogenic natural gas liquefaction system based on an APCI process that embodies the subject matter disclosed herein. This process uses two cooling cycles or loops in which the first refrigerant and the second refrigerant are each processed. The first loop is a pre-cooling loop in which natural gas and a second refrigerant circulating through the second loop are cooled by exchanging heat with the first refrigerant. In the present specification, the first loop is referred to as a pre-cooling loop or cycle, so the second loop is referred to as a cooling or liquefaction loop or cycle.

  In some embodiments, the first refrigerant circulating in the pre-cooling loop can include propane or can consist of propane. The first refrigerant can have an average molecular weight of at least 35, such as an average molecular weight between 35 and 41. In some embodiments, the second refrigerant circulating in the second loop can include a mixed refrigerant including, for example, nitrogen, methane, ethane, and propane.

  More specifically, in the embodiment of FIG. 2, the system is generally designated 101, the first loop or precooling loop is labeled 103 and the second liquefaction cycle or loop is labeled 105. Natural gas is brought into the system 101 by piping 107 and is sequentially cooled and finally liquefied by flowing through a plurality of serially arranged heat exchangers in each of the pre-cooling loop 103 and the cooling loop 105.

  The precooling loop 103 includes a multistage gear-coupled turbo compressor 109. The gear-coupled turbo compressor may be configured as shown in more detail in FIG. 4 and will be described in more detail below with reference to this figure.

  At least one stage, some stages, or preferably all stages of the gear-coupled turbocompressor may adjust the operating conditions of these (these) stages as needed in the actual operation of the system 101. With movable entrance guide vanes. Each set of movable inlet guide vanes can be adjusted independently of the other sets, for example to account for different flow rates in one stage and the other.

  In some embodiments, the gear-coupled turbo compressor comprises a number of stages comprised between 2-8. For example, a gear-coupled turbo compressor can include 3 to 6 stages. As will be described in more detail below, one or more intercoolers may be provided between one or more pairs of consecutively arranged stages of a gear-coupled turbo compressor. Further, in some embodiments, in some embodiments, the multi-gear coupled turbo compressor 109 is driven by a prime mover that can include an internal combustion engine such as a gas turbine (eg, an aeroderivative gas turbine). Can do. In an advantageous embodiment, the gear-coupled turbo compressor 109 is driven by an electric motor 111.

  An exemplary embodiment is shown in FIG. 2, where the gear-coupled turbo compressor 109 is composed of four stages (designated 109A, 109B, 109C, and 109D, respectively) arranged in sequence, and stage 109D. Is the lowest pressure stage, and stage 109A is the highest pressure stage.

  A compressed first refrigerant stream is provided to the condenser 115 by a gear-coupled turbo compressor 109. The flow of the first refrigerant brought through the condenser 115 is cooled and condensed with water or air, for example.

  In some embodiments, the condensed first refrigerant circulates through the precooling loop 103 to precool the natural gas and cools the second refrigerant circulating through the cooling loop 105, optionally partially. Allow to liquefy.

  In some embodiments, the process is divided into four pressure levels. The number of pressure levels can correspond to the number of stages of the gear-coupled turbo compressor 109. In a preferred embodiment, the first refrigerant stream brought through the condenser 115 is divided into several partial streams, which are then expanded sequentially at progressively lower pressure levels. Each partial stream of refrigerant circulates through the sub-cycle and is returned as a tributary to a gear-coupled turbo compressor at the inlet of a corresponding one of the plurality of compressor stages.

  Delivery line 117 provides a first portion of the condensed first refrigerant flow to a plurality of serially arranged first expansion elements 119A-119D. A second delivery line 118 branched from delivery line 117 provides a second portion of the condensed first refrigerant flow to a plurality of second expansion elements 121A-121D arranged in series.

  The first portion of the condensed first refrigerant from the condenser 115 is expanded in sequence in four expansion elements 119A-119D at four different progressively lower pressure levels. Downstream of each expansion element 119A-119D, a portion of the partially expanded first refrigerant flow is channeled to the corresponding one of the first precooling heat exchangers 123A-123D. . The remaining portion of the partially expanded first refrigerant is flowed through the next expansion element 119A-119D, and so on. The remaining first refrigerant flowing through the most downstream expansion element (119D) of the first expansion elements 119A-119D is brought to the most downstream precooling heat exchanger 123D.

  In each of the first heat exchangers 123A to 123D, the first refrigerant exchanges heat with the natural gas flowing through the pipe 107, and thus precools the natural gas and optionally partially liquefies.

  A part of the first refrigerant expanded in each of the second expansion elements 121A, 121B, 121C, and 121D is caused to flow to a corresponding one of the plurality of second heat exchangers 125A to 125D. . Of the refrigerant flow provided by each of the second expansion elements 121A-121D, the portion that is not flowed to the respective heat exchangers 125A-125D is routed through subsequent expansion elements. The remaining downstream portion of the first refrigerant in which the most downstream heat exchanger (125D) of the second heat exchanger expands in the most downstream (121D) of the second expansion elements 121A to 121D. Receive. In each of the second heat exchangers 125A to 125D, the first refrigerant exchanges heat with the second refrigerant circulating in the cooling or liquefaction loop 105, and as a result, the delivery side of the heat exchanger 125D The second refrigerant is cooled and at least partially liquefied.

  The heated first refrigerant exiting the first precooling heat exchangers 123A-123D is collected with the heated first refrigerant exiting the second heat exchangers 125A-125D and sent to the gear-coupled turbo compressor 109. And will be supplied again.

  In some embodiments, the heated first refrigerant exiting each of the second heat exchangers 125A-125D is approximately the same as the heated first refrigerant exiting the corresponding first heat exchanger 123A-123D. At the same pressure. The refrigerant collected at the corresponding pressure level is brought to the inlet of the corresponding stage of the gear-coupled turbo compressor 109. In this way, the multiple tributaries of refrigerant are returned to the inlets of the stages arranged in series of the gear-coupled turbo compressor 109 with progressively lower pressure.

  In FIG. 2, reference numbers 130A-130D indicate return lines that return the expanded and used tributaries resulting from heat exchangers 123A-123D and 125A-125D to the corresponding stages 109A-109D of the gear-coupled turbo compressor. Show.

  In some embodiments, the cooling or liquefaction loop 105 comprises a compressor train. In some embodiments, the compressor row may be composed of a first compressor 131 and a second compressor 133 arranged in series. In other embodiments, only one compressor may be provided. Each compressor may be a multi-stage compressor, such as a multi-stage centrifugal compressor.

  In some embodiments, the compressor of the cooling loop 105 is driven by a prime mover that can include an internal combustion engine. The prime mover may be a gas turbine 135, such as an aeroderivative gas turbine.

  To reduce the temperature and reduce the volume of the interstage cooler (intercooler) 137 before entering the second compressor 133 for the second refrigerant provided by the first compressor 131, It can be arranged between the compressor 131 and the second compressor 133. The compressed second refrigerant provided by the second compressor 133 is condensed in the condenser 139. The condenser 139 may be an air condenser or a water condenser that condenses the second refrigerant by exchanging heat with air or water. As described above, the condensed second refrigerant is then sent through the second heat exchangers 125A to 125D sequentially arranged by the delivery line 141, and in the second heat exchangers 125A to 125D. The second refrigerant is cooled by heat exchange with the first refrigerant circulating in the pre-cooling loop 103 and possibly liquefied.

  The cooled and optionally partially liquefied second refrigerant from heat exchangers 125A-125D flows through piping 143 to main cryogenic heat exchanger 145 where main cryogenic heat exchanger 145. The second refrigerant removes additional heat from the pre-cooled and optionally partially liquefied natural gas to complete the liquefaction process. While fully liquefied natural gas exits the system at 149, the heated second refrigerant is returned to the compressor or compressor row 131, 133 through line 151.

  In FIG. 2, the gear-coupled turbo compressor 109 is only schematically shown. The main components of a typical gear-coupled turbo compressor 109 are shown in more detail in FIG. 2A. FIG. 4 shows in more detail a longitudinal section of the two compressor stages supported on a common rotating shaft of the gear-coupled turbo compressor 109. More specifically, FIG. 4 shows the first and second stages 109D and 109C as an example.

  Preferably, each stage 109A-109D of the compressor comprises a movable inlet guide vane conceptually shown at 110A-110D for the four stages 109A-109D. In other embodiments, the movable inlet guide vanes are provided only at the inlet of some of the compressor stages, or not at any stage. As can be seen from FIG. 4, an inlet guide vane can be placed at the axial inlet of the compressor stage. Each set of movable inlet guide vanes can be controlled independently of the other sets in order to autonomously regulate the flow entering the compressor stage. An intercooler can be provided between two consecutively arranged compressor stages 109A-109D. As shown in FIG. 2A, the first intercooler 153 can be disposed between the delivery side of the first compressor stage 109D and the suction side of the second compressor stage 109C. A second intercooler 155 can be disposed between the delivery side of the second compressor stage 109C and the suction side of the third compressor stage 109B. A third intercooler 157 can be disposed between the delivery side of the third compressor stage 109B and the suction side of the fourth compressor stage 109A.

  Each compressor stage 109A-109D comprises at least one impeller supported on a rotating shaft. FIG. 4 shows two impellers 112D, 112C in each of the two most upstream compressor stages 109D, 109C. Each impeller may be a centrifugal impeller having an axial inlet and a radial outlet. The fluid processed by the impeller is collected in respective volutes, such as the volutes 114D, 114C of the compressor stages 109D, 109C.

  The impellers may be paired and each pair of impellers is supported by a common axis of rotation. In the embodiment of FIG. 2A, two rotating shafts 159 and 161 are provided. The impellers of the first and second compressor stages 109D and 109C are rotatably attached to the first rotary shaft 159, and the impellers of the third and fourth compressor stages 109B and 109A are the second rotary shaft. 161 is rotatably attached. Another number of rotating shafts and respective compressor stages and impellers can be provided. In some embodiments, the number of stages provided may be odd, in which case one of the rotating shafts may support only one impeller rather than a paired impeller. it can.

  Each rotating shaft 159, 161 includes a pinion 159A, 161A keyed to each rotating shaft 159, 161. The pinions 159A and 161A mesh with a central gear or crown 163 that is rotationally driven by the electric motor 111 via the drive shaft 165. The two rotary shafts 159, 161 and thus the respective impellers attached to the two rotary shafts 159, 161 can rotate at different rotational speeds.

  The configuration of the gear coupled turbo compressor 109 is particularly suitable for treating different tributaries of the first refrigerant circulating in the precooling loop 103. The state of each set of movable inlet guide vanes 110A-110D located at the inlet of the compressor stage is matched to the operating conditions of the compressor stage to the temperature conditions and flow rates in the various heat exchangers 123A-123D, 125A-125D Can be tailored to the flow conditions of each tributary (i.e. each refrigerant flow brought to the respective suction side of the compressor stage). Therefore, the efficiency and operability of the compressor can be maximized. One or more intercoolers, such as intercoolers 153, 155, 157, which can be easily integrated into the structure of the gear coupled turbocompressor 109, further improve the efficiency of the compressor and thus the overall LNG system.

  A further embodiment of the subject matter disclosed herein is shown in FIG. 3 and described below. The LNG system 200 shown in FIG. 3 includes three closed loops (single or plural) 201, 203, and 205. Three different refrigerants are processed in three loops. The first refrigerant processed in the loop 201 may be propane. The first loop 201 is hereinafter referred to as a precooling loop. The second refrigerant processed in the loop 203 may be ethylene, and the third refrigerant circulating in the loop 205 may be methane. Natural gas line 207 flows through three consecutively arranged heat exchangers 209, 211, and 213 in three loops 201, 203, 205. Natural gas enters the first heat exchanger 209 in the gaseous state and exits the last heat exchanger 213 in the liquid state.

  The system of FIG. 3 is represented in a somewhat simplified manner. The first precooling loop or cycle 201 comprises a gear coupled turbo compressor 229 that includes a plurality of compressor stages. In some embodiments, three compressor stages 229A-229C may be provided, as shown by way of example in the schematic diagram of FIG. In other embodiments, a different number of compressor stages can be provided. In general, the number of compressor stages can depend on the number of tributaries provided in the precooling loop 201 in a manner similar to that disclosed in connection with FIGS. 2 and 2A.

  Inlet guide vanes 228C, 228B, 228A may be provided at the inlet of some compressor stages (preferably each compressor stage). An intercooler can be placed between a pair of consecutively arranged compressor stages, for example, the first intercooler 230 can be connected to the delivery side of the first compressor stage 229C and to the second compressor. It can arrange | position between the suction side of the step 229B. A further intercooler 231 can be arranged between the delivery side of the compressor stage 229B and the suction side of the compressor stage 229A.

  The last compressor stage 229A, ie, the delivery side of the most downstream compressor stage in the direction of increasing pressure, is connected to the condenser 233. The first refrigerant circulating through the gear-coupled turbo compressor 229 is condensed in the condenser 233 and brought to the first heat exchanger 209 through the line 235. The compressed and condensed refrigerant stream can be expanded through one or more expansion elements, one of which is indicated at 237. In a manner similar to FIG. 2, the main refrigerant stream flowing through the delivery line 235 can be divided into progressively decreasing pressure and temperature tributaries. The heat exchanger 209 can be composed of a plurality of heat exchanger parts arranged in series, with a portion of the refrigerant gradually decreasing in a manner very similar to that described in connection with FIGS. 2 and 2A. In these heat exchanger sections. In this way, a plurality of tributaries are formed and each tributary is returned to the corresponding one of the compressor stages 229A, 229B, 229C.

  Thus, each compressor stage handles a variable and progressively different flow rate of refrigerant from the most upstream compressor stage 229C to the most downstream compressor stage 229A.

  The gear coupled turbo compressor 229 can be driven by a prime mover. In some embodiments, the prime mover may be an electric motor (not shown) similar to the motor 111 described with reference to FIG. In other embodiments, the prime mover may comprise a gas turbine, such as an aeroderivative gas turbine.

  The second loop 203 includes a compressor device 241. The compressor device 241 can comprise one compressor or a plurality of sequentially arranged compressors. One or more of the compressors of the compressor device 241 may be a multistage compressor, such as a multistage centrifugal compressor. The compressor device 241 can be driven by the second prime mover 243. In some embodiments, the second prime mover 243 can comprise a gas turbine, such as an aeroderivative gas turbine. In other embodiments, the power source may comprise an electric motor. Combinations of different engines or motors are also conceivable.

  The second loop 203 includes a condenser 245 that condenses the compressed second refrigerant provided by the compressor device 241. A delivery line 247 brings the compressed and condensed second refrigerant to the first heat exchanger 209 and the second heat exchanger 211. In the first heat exchanger 209, the condensed second refrigerant is cooled by heat exchange with the first refrigerant circulating in the first loop 201. In the second heat exchanger 211, the second refrigerant is expanded in one or more continuously arranged expansion elements, one of which is indicated by 249. In this way, the said flow of the second refrigerant of different pressures which gradually decreases can be generated in a manner known per se, and these tributaries pass through the lower pressure return lines 251, 253, 255. Returned to the second compressor unit 241. In some embodiments, each tributary is injected into the inlet of the corresponding compressor of the plurality of consecutively arranged compressors that make up the compressor unit 241. A movable inlet guide vane can be provided at the inlet of each such compressor. In the second heat exchanger 211, the second refrigerant cools and / or partially liquefies the natural gas flowing through the gas line 207.

  The third loop 205 comprises a further compressor device 261. The compressor device 261 may be composed of one compressor or a plurality of continuously arranged compressors. The compressor of the compressor device 261 may be a centrifugal compressor such as a multistage centrifugal compressor. In order to drive and rotate the compressor device 261, a further prime mover 263 is provided. In some embodiments, prime mover 263 may comprise a gas turbine, such as an aeroderivative gas turbine. In other embodiments, prime mover 263 can include an electric motor. Different motor and engine combinations may be provided.

  The compressed third refrigerant provided by the compressor device 261 is condensed in the condenser 265 and liquids through the delivery line 267 to the first, second and third heat exchangers 209, 211, 213. Brought on in the state. In the first and second heat exchangers 209 and 211, the third refrigerant flows in a liquid state and is cooled by heat exchange with the first refrigerant and the second refrigerant, respectively. In the last part of the loop, the third refrigerant is expanded in one or more continuously arranged expansion elements 269. The vaporized third refrigerant performs heat exchange with the natural gas in the third heat exchanger 213 until the natural gas is liquefied when the natural gas comes from the third heat exchanger 213. In some embodiments, the third refrigerant can be divided into tributaries at progressively decreasing pressures, each tributary being connected to the compressor unit 261 via a respective return line 271, 273, 275. Returned to. Again, the tributaries can be injected into the inlets of continuously arranged compressors that form part of the compressor unit, each compressor possibly having a movable inlet guide vane.

  The LNG process described above and shown in FIG. 3 is known as a cascade process. As described above, unlike known cascade processes and systems, in the present embodiment, at least the first precooling loop 201 comprises a multi-stage gear-coupled turbo compressor.

  The treatment of the first refrigerant in the precooling loop through the gear-coupled turbo compressor has several advantages, as already described in connection with the embodiment of FIGS. The gear-coupled turbo compressor 229 of the embodiment of FIG. 3 can be conceptually similar to the gear-coupled turbo compressor described in relation to the embodiment of FIGS. 2 and 2A and shown in more detail in FIG. By way of example only, the number of compressor stages of the gear coupled turbo compressor 229 shown in FIG. 3 differs from the number of stages in the embodiment of FIGS. This number may vary based on design considerations, for example, based on the number of divisions of the main refrigerant mainstream into the tributaries downstream of the condenser.

  In some embodiments, the gear coupled turbocompressor can be driven with a power in the range of about 12 MW to about 40 MW. In some embodiments, the gear-coupled turbo compressor may have a rated power in the range of between about 14 MW to 40 MW, more specifically between about 25 MW to 30 MW.

In some embodiments, the flow rate of the first refrigerant in the range of about 10,000 m ³ / h to about 70,000 ³ / h, can be processed by the geared turbo compressor.

  As disclosed above, the first refrigerant in an LNG system is usually expanded at progressively lower pressure values and divided into tributaries, each flow being several compressors of a gear-coupled turbocompressor. Return to the appropriate one of the stages. In some embodiments, the delivery pressure of the most downstream compressor stage, ie, the highest pressure compressor stage, ranges from about 45 bar (absolute pressure) to about 65 bar (absolute pressure), in some embodiments The delivery pressure may range between about 52 bar (absolute pressure) to about 56 bar (absolute pressure). In some embodiments, each suction pressure, i.e., the pressure at the inlet of the most upstream compressor stage, may range between about 2.5 and about 15 bar (absolute pressure), more specifically. May range, for example, from about 3 to about 10 bar (absolute pressure), such as around 3 to 3.5 bar (absolute pressure).

  In other embodiments, the final stage delivery pressure (discharge pressure) of the gear-coupled turbocompressor may range between about 10 bar (absolute pressure) to 30 bar (absolute pressure), some specific implementations. In form, it may be in the range between 15 and 25 bar (absolute pressure). Each suction pressure in the most upstream compressor stage may range between about 1 and about 2.5 bar (absolute pressure), more specifically between about 1.5 and about 2 bar (absolute pressure). For example, it may be in the vicinity of 1.6 to 1.9 bar (absolute pressure).

  The use of a gear-coupled turbo compressor in the precooling cycle improves the efficiency of the compressor and therefore consumes less power compared to current technology centrifugal multistage compressors, resulting in significant cost savings .

  In order to fully appreciate the significant benefits associated with the efficiency gains and energy consumption and cost reductions achieved by this, the following comparative examples should be considered.

In the system according to FIG. 1, a beam centrifugal compressor with “100%” efficiency, such as 3MCL804 manufactured by GE Oil & Gas, for example, Florence, Italy, is connected to this compressor in Florence, Italy. In a standard configuration driven and used by an aeroderivative gas turbine called PGT25 + G4 available from GE Oil & Gas, the following operating conditions are: • Inlet pressure 1.13 bar (absolute pressure),
・ Inlet volume flow rate 56,000m ³ / h and ・ Rotation speed 6,100rpm
The compressor is considered to consume 21,108 kW in the design conditions. 2, 2A comprising a gear-coupled turbocompressor such as SRL 804 manufactured by GE Oil & Gas, Florence, Italy, driven by an equivalent gas turbine and having an efficiency of 102.4% It is considered to consume 20,493 kW under the same operating conditions, which means a 3% reduction in power consumption.

  The total cost reduction in the configuration with gear coupling is 5%.

  The use of a gear-coupled compressor is thus even more attractive because of the omission of a gearbox when considering a configuration in which an electric motor is used instead of a gas turbine. In a standard technical solution according to the prior art using an electric motor as the power source, a fixed speed electric motor is connected to the compressor via a gearbox and drives the compressor. In contrast, when using a gear-coupled compressor, the compressor can be designed for optimum speed without the need for an additional gearbox. The compressor can reach an efficiency of up to 104.1%. As a result, under the above operating conditions, power consumption is 20,102 kW, which is thought to result in a reduction of power consumption of 1006 kW. In terms of cost, the technical solution comprising a gear-coupled compressor and electric motor is 14% less expensive than the standard technical solution comprising an electric motor, gearbox and compressor, mainly due to the omission of the gearbox. is there.

  While the embodiments disclosed for the subject matter described herein have been fully described above in the drawings, together with details and details regarding some exemplary embodiments, the novel teachings, principles, It will be apparent to those skilled in the art that numerous modifications, variations, and omissions can be made without departing substantially from the advantages of the subject matter recited in the appended claims and in the appended claims. Accordingly, the proper scope of the disclosed invention should be determined only by the broadest interpretation of the appended claims, including all such changes, modifications, and omissions. Furthermore, the order and order of the steps of the process or method can be changed or rearranged according to other embodiments.

2 First cycle 3 Gas turbine 5 First compressor 7 Second compressor 11 Heat exchanger 12 Propane cycle 13 Gas turbine 15 Multistage compressor 17 Condenser 19 Pipes 21, 23, 25, 27 Expander 29, 31, 33, 35 Heat exchanger 37 Pipe 38 Main cryogenic heat exchanger 39 Second pipe 41, 43, 45, 47 Expander 49, 51, 53 Precooling heat exchanger 61 Main natural gas line 101 System 103 Precooling loop 105 Cooling or liquefaction loop 107 Piping 109 Multi-stage gear-coupled turbo compressor 109A-109D Compressor stage 110A-110D Entrance guide vane 111 Electric motor 112C, 112D Impeller 114C, 114D Volute 115 Condenser 117, 118 Delivery line 119A-119D First Expansion elements 121A to 121D of the second expansion element 12 A to 123D First heat exchangers 125A to 125D Second heat exchangers 130A to 130D Reference number 131 First compressor 133 Second compressor 135 Gas turbine 139 Condenser 141 Delivery line 143 Piping 145 Main pole low Heat exchanger 151 Pipe 153 First intercooler 155 Second intercooler 157 Third intercooler 159 First rotation shaft 159A Rotation shaft 159A Pinion 161 Second rotation shaft 161A Pinion 163 Crown 165 Drive shaft 200 LNG system 201 1st loop 203 2nd loop 205 3rd loop 207 Line 209 1st heat exchanger 211 2nd heat exchanger 213 3rd heat exchangers 228A-228C Inlet guide vane 229 Gear coupled turbo compressor 229A-229C Compressor stage 230 1st interque 231 Intercooler 233, 245, 265 Condenser 235, 247, 267 Delivery line 241, 261 Compressor unit 243, 263 Motor 251, 253, 255 line 269 Expansion element 271, 273, 275 line

Claims (23)

Configured to circulate the first refrigerant;
At least one compressor (109) for pressurizing the first refrigerant;
At least one prime mover (111) for driving the compressor (109);
At least one condenser (115) for removing heat from the first refrigerant;
At least first expansion elements (119A-119D) for expanding the first refrigerant;
At least a first heat exchanger (123A-123D) for transferring heat from natural gas to the first refrigerant;
A pre-cooling loop (103) comprising: a cooling loop (105) that is located downstream of the pre-cooling loop (103) and circulates the second refrigerant
At least,
The natural gas is configured to be sequentially cooled in the pre-cooling loop (103) and the cooling loop (105),
The compressor (109) is a gear-coupled turbo compressor (109) comprising a plurality of compressor stages (109A-109D), each compressor stage independently adjusting the flow entering the compressor stage. Natural gas liquefaction system with a set of independent movable entrance guide vanes to do.   The pre-cooling loop (109) is configured to divide the first refrigerant into two or more tributaries that are returned to respective compressor stages (109A-109D) of the gear-coupled turbo compressor (109). The system of claim 1.   The system according to claim 1 or 2, wherein the prime mover (111) comprises an electric motor.   The system according to claim 1 or 2, wherein the prime mover (111) comprises a gas turbine.   The pre-cooling loop (103) includes a plurality of sequentially arranged first expansion elements (119A-119D) configured to expand the first refrigerant at a plurality of lower pressure levels, and the plurality Receive respective portions of the first refrigerant expanded through first continuously arranged expansion elements (119A-119D) and transfer heat from the natural gas to the first refrigerant A plurality of first heat exchangers (123A-123D) arranged and configured to cause each of the gear-coupled turbo compressors (109) from each of the first heat exchangers (123A-123D). 5. The system according to claim 1, further comprising a plurality of return paths (130 </ b> A to 130 </ b> D) for returning a tributary of the first refrigerant to the compressor stage.   The precooling loop (103) receives at least a first auxiliary expansion element (121A-121D) and a portion of the first refrigerant expanded through the first auxiliary expansion element (121A-121D). At least a first auxiliary heat exchanger configured to transfer heat from the second refrigerant circulating in the cooling loop (105) to the first refrigerant circulating in the precooling loop (103). 125A-125D). The system of any one of claims 1-5.   The pre-cooling loop (103) includes a plurality of continuously arranged second expansion elements configured to expand the first refrigerant at a plurality of lower pressure levels, and the first auxiliary expansion element. A plurality of second heat exchanges arranged and configured to receive respective portions of the first refrigerant expanded through and transfer heat from the second refrigerant to the first refrigerant And a plurality of return paths for returning portions of the first refrigerant from each of the second heat exchangers to the respective compressor stages (109A-109D) of the gear-coupled turbo compressor (109). The system according to any one of claims 1 to 6, further comprising:   The system according to any one of claims 1 to 7, wherein the first refrigerant includes a gas having a molecular weight greater than 35.   The system according to any one of claims 1 to 8, wherein the second refrigerant is a mixed refrigerant, ethylene, or methane.   The gear-coupled turbo compressor (109) is driven by the prime mover (111) and is rotated by a central gear (163) that is meshed with the central gear (163) and driven by the central gear (163). A plurality of driven shafts (159, 161) with pinions (159A, 161A) rotating in rotation and at least one respective compressor impeller mounted on each shaft (159, 161). The system according to any one of 1 to 9.   System according to claim 10, wherein two respective compressor impellers are mounted on at least one of the shafts (159, 161). The system according to any one of the preceding claims, further comprising at least one intercooler between at least two consecutively arranged compressor stages of the gear-coupled turbo compressor (109).   The gear-coupled turbo compressor (109) is configured such that the pressurized first refrigerant is at a pressure in the range of about 45 to about 65 bar (absolute pressure), preferably between about 50 and about 60 bar (absolute pressure). The first refrigerant is compressed as provided from the last stage of the gear-coupled turbo compressor (109) and the pressure of the first refrigerant at the inlet of the first stage of the gear-coupled turbo compressor (109) 13. A system according to any one of the preceding claims, in the range from about 2.5 to about 10, preferably from about 3 to about 5 bar (absolute pressure).   The gear-coupled turbo compressor (109) is configured such that the pressurized first refrigerant is at a pressure in the range of about 10 to about 30 bar (absolute pressure), preferably between about 15 and about 25 bar (absolute pressure). The first refrigerant is compressed as provided from the last stage of the gear-coupled turbo compressor (109) and the pressure of the first refrigerant at the inlet of the first stage of the gear-coupled turbo compressor (109) 13. The system according to any one of the preceding claims, wherein is in the range of about 1 to about 2.5, preferably about 1.5 to about 2 bar (absolute pressure). The geared turbo compressor (109) according to any one of claims 1 to 14 results in a first refrigerant in the actual flow rate in the range of about 10,000 m ³ / h to about 70,000 ³ / h System.   The system according to any of the preceding claims, wherein the gear-coupled turbo compressor (109) consumes power in the range of about 12 MW to about 40 MW, preferably in the range of about 14 MW to about 30 MW.   The system according to any of the preceding claims, wherein the gear-coupled turbo compressor (109) comprises at least four stages, each stage comprising at least one impeller. A method for liquefying natural gas,
A gear-coupled turbo compressor (109) having a plurality of compressor stages, each stage having a movable inlet guide vane, at least one condenser (115), and at least one expansion element ( 119A-119D) and providing a pre-cooling loop (103) comprising at least one heat exchanger (123A-123D);
Driving the gear-coupled turbo compressor (109) with a prime mover (111);
Circulating a first refrigerant through the gear-coupled turbo compressor (109);
Condensing in the condenser (115) the first refrigerant provided by the gear-coupled turbo compressor (109);
Dividing the first refrigerant into a plurality of partial flows;
Expanding the condensed first refrigerant in the expansion element (119A to 119D);
Circulating the expanded refrigerant through the heat exchangers (123A-123D), removing heat from the natural gas and precooling the natural gas;
Individually controlling movable inlet guide vanes to regulate the partial flow on the suction side of the compressor stage;
Providing at least one cooling loop (105);
Circulating a second refrigerant through the at least one cooling loop (105);
Removing heat from the precooled natural gas by heat exchange with the second refrigerant.   The method of claim 18, wherein the prime mover (111) comprises an electric motor.   The method of claim 18, wherein the prime mover (111) comprises a gas turbine.   21. A method according to any one of claims 18 to 20, wherein the movable inlet guide vanes are controlled as a function of the partial flow conditions. Providing a plurality of continuously disposed first expansion elements (119A-119D) in the precooling loop (103);
Expanding the condensed first refrigerant through the first expansion elements (119A-119D) at a plurality of lower pressure levels;
A portion of the expanded first refrigerant from each of the first expansion elements (119A-119D) is circulated through a plurality of first heat exchangers (123A-123D) from the natural gas. Removing heat,
A portion of the expanded first refrigerant from the first heat exchanger (123A-123D) passes through a respective return path (130A-130D) and each compressor stage of the plurality of compressor stages. Step back to
The method according to any one of claims 18 to 21, further comprising: Providing a plurality of continuously arranged second expansion elements (121A-121D) in the precooling loop (103);
Expanding the condensed first refrigerant through the second expansion elements (121A-121D) at a plurality of lower pressure levels;
Circulating a portion of the expanded first refrigerant through a plurality of second heat exchangers (125A-125D) of the precooling loop (103) to remove heat from the second refrigerant;
Returning a portion of the first refrigerant from each of the second heat exchangers (125A-125D) to a respective compressor stage of the gear-coupled turbo compressor (109). The method of any one of thru | or 21.