KR102188435B1 - Integrally-geared compressors for precooling in lng applications - Google Patents

Abstract

A natural gas liquefaction system is disclosed comprising at least a precooling loop 103 adapted to circulate a first refrigerant. The precooling loop includes at least one compressor 109 for compressing 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 to 119D for expanding the first refrigerant; And at least first heat exchangers 123A to 123D for transferring heat from natural gas to the first refrigerant. The system includes at least a cooling loop 105 downstream of the precooling loop, through which the second refrigerant circulates. Natural gas is intended to be cooled sequentially in the precooling loop and in the cooling loop. The compressor of the precooling loop is a gear-integrated turbocompressor including a plurality of compressor stages 109A to 109D.

Description

Integrated gear compressor for precooling in LNG applications{INTEGRALLY-GEARED COMPRESSORS FOR PRECOOLING IN LNG APPLICATIONS}

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

Natural gas is becoming increasingly important as an energy source. In order to allow the transport of natural gas from the supply source to the place of use, the volume of natural gas must be reduced. Cryogenic liquefaction has become a routinely practiced process to convert natural gas into a liquid that is more convenient, less expensive and safer for storage and transport. Transportation of liquefied natural gas (LNG) by pipeline or ship is made possible at atmospheric pressure by maintaining the cooled and liquefied gas at a temperature lower than the liquefaction temperature at atmospheric pressure.

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

In the prior art for natural gas liquefaction, the natural gas at an elevated pressure, until the liquefaction temperature is achieved, a number of sequentially passing a plurality of cooling stages in which the natural gas is continuously cooled to a lower temperature in a sequential cooling cycle. Of processes and systems exist.

Before passing the natural gas through the cooling stage, it is pretreated to remove any impurities that may interfere with processing, damage machinery, or undesirable in the final product. Impurities include acid gases, sulfur compounds, carbon dioxide, mercaptan, water and mercury. The pretreatment gas from which impurities have been removed is cooled by a refrigerant stream to separate the heavier hydrocarbons. The residual gas consists mainly of methane and usually contains less than 0.1 mol% of higher molecular weight hydrocarbons such as propane or heavier hydrocarbons. The natural gas thus cleaned and purified is cooled to its final temperature in the cryogenic section. The resulting LNG can be stored and transported at near atmospheric pressure.

Cryogenic liquefaction is usually carried out by a multicycle process, ie by a process using different cooling cycles. Depending on the type of process, each cycle may use a different cooling fluid, and in addition, the same cooling fluid may be used in two or more cycles.

1 schematically shows a diagram of a cryogenic natural gas liquefaction system using the so-called APCI process. This known process uses two cooling cycles. The first cycle uses propane as the cooling fluid, and the second cycle uses a mixed refrigerant usually formed of nitrogen, methane, ethane and propane. The system, labeled 1 as a whole, includes a first cycle 2 comprising a line formed by a gas turbine 3 driving a compressor train. The compressor train includes a first compressor 5 and a second compressor 7 in series for compressing the mixed refrigerant. The intermediate stage cooler (intermediate cooler) 9 cools the mixed refrigerant delivered by the first compressor 5 to reduce its temperature and volume before the mixed refrigerant enters the second compressor 7. The compressed mixed refrigerant delivered by the second compressor 7 is condensed with respect to air or water in the heat exchanger 11. The mixed refrigerant is further cooled and partially liquefied by the propane cycle 12 as disclosed below here.

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

The condensed propane stream from the condenser 17 is transferred to a first set of four sequentially arranged heat exchangers to cool and partially liquefy the mixed refrigerant and a second set of four sequentially arranged precooled heat exchangers to cool the natural gas. It is transmitted by the energy. The first portion of the compressed propane stream from the condenser 17 is passed through a pipe 19 to a first set of heat exchangers, and four different diminishing pressures in the sequentially arranged expanders 21, 23, 25, 27 It expands sequentially in levels. Downstream of each expander (21, 23, 25), a portion of the expanded propane flow is directed to each of the heat exchangers (29, 31, 33). The propane flowing through the last expander 27 is transferred to the heat exchanger 35.

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

A second portion of the condensed propane flow from the condenser 17 is transferred to the second pipe 39 and is sequentially expanded in the four sequentially arranged expanders 41, 43, 45, 47. Part of the propane expanded in each expander 41, 43, 45, as well as the propane flowing out of the last expander 47, are also directed toward the corresponding precooled heat exchangers 49, 51, 53, 55, respectively. The main natural gas line 61 sequentially flows through the precooling heat exchangers 49, 51, 53, 55, and the natural gas is precooled before entering the main cryogenic heat exchanger 38. The heated propane exiting the pre-cooled heat exchanger (49, 51, 53, 55) is collected together with the propane exiting the heat exchanger (29, 31, 33, 35), and again compressor (15)-4 evaporated propane The side stream is recovered and the vapor is compressed to, for example, 15 to 25 bar and fed back to condensation in condenser 17 -.

The subject of protection disclosed herein relates to an improved natural gas liquefaction system comprising at least a precooling circuit or loop for allowing a first refrigerant to circulate, and at least one cooling or liquefaction loop for allowing a second refrigerant to circulate. The gaseous natural gas flows sequentially through the heat exchanger device of the precooling loop and subsequently cooling also in the heat exchanger device of the liquefaction loop. Natural gas is precooled, cooled, and finally liquefied by exchanging heat for the first refrigerant and at least the second refrigerant. To gradually cool and finally liquefy the natural gas, additional third or other cooling and/or liquefaction circuits or loops may be arranged in the cascade or sequential device. The loop comprises a respective compressor device for processing each refrigerant, at least one condenser, and one or more expansion elements, such as a turboexpander and/or throttle valve. At least the precooling loop includes an integrally geared turbocompressor for processing the first refrigerant. The first refrigerant is divided into two or more side streams and is used to exchange heat at decreasing pressure values for the natural gas and/or refrigerant circulating in a subsequent cooling or liquefaction loop.

According to some embodiments,

At least a precooling loop, wherein the first refrigerant passes and circulates,

At least one compressor compressing the first refrigerant;

At least one prime mover 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;

At least a first heat exchanger that transfers heat from natural gas to the first refrigerant

Precooling loop comprising a; And

At least a cooling loop which is located downstream of the precooling loop and circulates through the second refrigerant

Including, the natural gas is to be cooled sequentially in the precooling loop and in the cooling loop,

The compressor is provided with a gear-integrated turbocompressor including a plurality of compressor stages each provided with an independent movable inlet guide vane set for self-regulating the flow entering the compressor stage.

According to some embodiments, an additional compressor stage may be provided in which no moving inlet guide vanes are provided. When a plurality of compressor stages are arranged in succession, a single set of movable inlet vanes is sufficient, because the downstream stages are controlled by a set of movable inlet vanes of the further upstream stage. In the continuously arranged compressor stages, each set of movable inlet vanes may be equipped in the case where the first refrigerant stream is divided into two or more side streams and recombined continuously at an intermediate position between two subsequent compressor stages.

According to another aspect, a natural gas liquefaction method is provided in which the natural gas flow is cooled and liquefied by heat exchange for at least a first catalyst circulating in a precooling loop and a second refrigerant circulating in the cooling and/or liquefaction loop. The first refrigerant is divided into a plurality of side streams of decreasing pressure values. The side stream exchanges heat for the natural gas stream and/or for the second refrigerant. The side stream is returned at each compressor stage of the integral gear turbocompressor.

According to one embodiment,

Providing a precooling loop including a geared turbocompressor having a plurality of compressor stages, at least one condenser, at least one expansion element, and at least one heat exchanger;

Driving the integrated gear turbocompressor using a prime mover;

Circulating the first refrigerant through the integrated gear turbocompressor;

Condensing the first refrigerant delivered by the integrated gear turbocompressor in the condenser;

Dividing the first refrigerant into a plurality of partial flows;

Expanding the first refrigerant condensed in the expansion element;

Circulating the expanded refrigerant through a heat exchanger to precool the natural gas by removing heat from the natural gas;

Independently controlling the movable inlet guide vanes to regulate the partial flow at the suction side of the compressor stage;

Providing at least one cooling loop;

Circulating a second refrigerant in the at least one cooling loop; And

Removing heat from the precooled natural gas by heat exchange for the second refrigerant

A method comprising a is provided.

Features and embodiments are disclosed herein below, and are further described in the appended claims forming an integral part of this description. The above brief description describes features of various embodiments of the present invention to enable a better understanding of the following detailed description and a better understanding of the contribution of the invention to the art. It goes without saying that there are also other features of the invention that are described hereinafter and described in the appended claims. In this respect, prior to describing a number of embodiments of the present invention in detail, various embodiments of the present invention are not limited to the details or arrangement of the configurations of the components described in the following description and illustrated in the drawings in their application. It is understood that it does not. Other embodiments of the present invention are possible and implemented and implemented in various ways. In addition, it is understood that the terminology and technical terms employed herein are for the purpose of description and should not be considered limiting.

The flow rate of the first refrigerant generated by the system and the invention of the present invention is controllable and does not affect only the rotation speed of the compressor stage. In this way, a more efficient and reliable LNG circuit is provided.

As such, those skilled in the art will appreciate that the concepts on which the present disclosure is based may be readily utilized as a basis for designing other structures, methods, and/or systems for carrying out the various purposes of the present invention. Accordingly, it is important that the claims are considered to include such equivalent configurations without departing from the spirit and scope of the invention.

A more complete understanding of the disclosed embodiment and its various advantages will be readily obtained when the above disclosed embodiment and its various advantages are better understood by referring to the detailed description below, which is considered together with the accompanying drawings. .
1 illustrates a system for liquefying natural gas according to the prior art,
2 is a schematic diagram of a first embodiment of a system for LNG generation according to the present disclosure,
2A is a diagram illustrating an exemplary embodiment of a gear-integrated compressor used in the configuration of FIG. 2,
3 is a schematic diagram of a system for LNG generation in a second embodiment according to the present disclosure,
4 is a cross-sectional view of two compressor stages of an integral gear turbocompressor for use in an LNG system according to the present disclosure.

For the following detailed description of exemplary embodiments, refer to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Additionally, the drawings are not necessarily drawn to scale. Further, the detailed description below does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout this specification to “one embodiment”, “an embodiment” or “several embodiments” refers to at least one embodiment of a particular feature, structure, or characteristic described in connection with the embodiment with respect to the disclosed subject of protection. Means to be included. Accordingly, the appearances of the phrases "in one embodiment", "in an embodiment" or "in some embodiments" in various places throughout this specification are not necessarily all referring to the same embodiment(s). Moreover, certain features, structures or features 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 the APCI process implementing the protected object disclosed herein. The APCI process uses two cooling cycles or loops in which the first refrigerant and the second refrigerant are each treated. The first loop is a precooling loop in which the second refrigerant and natural gas circulating in the second loop are cooled by exchanging heat with the first refrigerant. Hereinafter, the first loop will be referred to as a precooling loop or cycle, and the second loop will be referred to as a cooling or liquefaction loop or cycle.

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

More specifically, in the embodiment of Figure 2, the system is labeled 101 as a whole, the first or precooling loop is labeled 103 , and the second liquefaction cycle or loop is labeled 105 . The natural gas is delivered to the system 101 along the pipe 107, and is sequentially cooled by flowing through each of the plurality of sequentially arranged heat exchangers of the precooling loop 103 and the cooling loop 105 and finally cooled. Liquefied.

The precooling roof 103 includes a multi-stage geared turbocompressor 109. The integrated gear turbocompressor may be configured as shown in more detail in FIG. 4, and will be described in more detail later with reference to the drawings.

At least one, some or preferably all stages of the integrally geared turbocompressor are configured with movable inlet guide vanes to adjust the operating conditions of the stage(s) according to the actual operating requirements of the system 101. Each set of movable inlet guide vanes can be adjusted independently of each other, for example to account for different flow rates from stage to stage.

In some embodiments, the integral gear turbocompressor consists of a number of stages comprising from 2 to 8. For example, an integral gear turbocompressor may include 3 to 6 stages. As will be explained in more detail below, one or more intermediate coolers may be provided between the sequentially arranged stages of one or more pairs of the integrally geared turbocompressor.

In some embodiments, the multi-gear integral turbocompressor 109 may be driven by a prime mover, and the prime mover may include an internal combustion motor such as a gas turbine, such as an aeroderivative gas turbine. In an advantageous embodiment, the integrally geared turbocompressor 109 is driven by an electric motor 111.

In Figure 2, four stages in which the gear-integrated turbocompressor 109 is sequentially arranged-each labeled 109A, 109B, 109C, 109D, 109D is the minimum pressure stage, and 109A is the maximum pressure stage- An exemplary embodiment is shown.

The compressed first refrigerant flow is transmitted to the condenser 115 by the integrated gear turbocompressor 109. The flow of the first refrigerant delivered through the condenser 115 is cooled and condensed, for example with water or air.

In some embodiments, the condensed first refrigerant is circulated in the precooling loop 103, which precools the natural gas, cools the second refrigerant circulating in the cooling loop 105, and optionally partially liquefies.

In some embodiments, the process is divided into four pressure levels. The number of pressure levels may correspond to the number of stages of the integrated gear turbocompressor 109. In a preferred embodiment, the flow of first refrigerant delivered through condenser 115 is divided into a plurality of partial flows, and the plurality of partial flows are then expanded sequentially to a number of progressively decreasing pressure levels. Each partial refrigerant flow circulates in a sub-cycle, and returns to the integrated gear turbocompressor at the inlet of a corresponding compressor stage among the plurality of compressor stages as a side flow.

The conveying line 117 delivers a first portion of the condensed first refrigerant flow to a plurality of sequentially arranged first expansion elements 119A to 119D. The second delivery line 118 branching from the delivery line 117 delivers a second portion of the condensed first refrigerant flow to the plurality of sequentially arranged second expansion elements 121A-121D.

The first portion of the condensed first refrigerant coming out of the condenser 115 is expanded sequentially within the four expansion elements 119A-119B of four different diminishing pressure levels. Downstream of each expansion element 119A-119C, a portion of the flow of the partially expanded first refrigerant is directed to each of the first precooling heat exchangers 123A-123C. The remainder of the partially expanded first refrigerant flows through the next expansion elements 119A to 119C or the like. The remaining first refrigerant flowing through the most downstream expansion element 119D among the first expansion elements 119A to 119D is delivered to the most downstream precooling heat exchanger 123D.

In each of the first heat exchangers 123A to 123D, the first refrigerant exchanges heat for the natural gas flowing in the pipe 107, thereby precooling the natural gas and selectively partially liquefying the natural gas.

A portion of the first refrigerant expanded in each of the second expansion elements 121A, 121B, 121C is transferred to a corresponding second heat exchanger among the plurality of second heat exchangers 125A to 125D. A portion of the refrigerant flow that is transmitted by each of the second expansion elements 121A to 121C and does not flow through each heat exchanger 125A to 125C is transmitted through a subsequent expansion element. The heat exchanger 125D at the most downstream of the second heat exchangers accommodates all of the entire remaining portion of the second refrigerant that expands in the expansion element 121D at the most downstream of the second expansion elements 121A to 121D. do. 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, so that the second refrigerant is transferred from the transfer side of the heat exchanger 125D. Cooled and at least partially liquefied.

The heated first refrigerant exiting the first precooling heat exchangers 123A to 123D is collected together with the heated first refrigerant exiting the second heat exchangers 125A to 125D, and a gear-integrated turbocompressor ( 109).

In some embodiments, the heated first refrigerant exiting each of the second heat exchangers 125A-125D is at approximately the same pressure as the heated first refrigerant exiting the corresponding first heat exchangers 123A-123D. The refrigerant collected at the corresponding pressure level is delivered to the inlet of the corresponding stage of the integrally geared turbocompressor 109. The plurality of refrigerant side streams are thus returned to the pressure diminishing at the inlet of the sequentially arranged stages of the integrally geared turbocompressor 109.

In FIG. 2, reference numerals 130A to 130D denote a return line, and a side stream of the expanded and discharged refrigerant fluid delivered from the heat exchangers 123A to 123D and 125A to 125D through the return line is a gear-integrated turbocompressor. It returns to the corresponding stages 109A to 109D.

In some embodiments, the cooling or liquefaction loop 105 includes a compressor train. In some embodiments, the compressor train may consist of a first compressor 131 and a second compressor 133 arranged in series. In other embodiments, a single compressor may be provided. Each compressor may be a multistage compressor, such as a multistage centrifugal compressor.

In some embodiments, the compressor(s) of the cooling loop 105 are driven by a prime mover, which may include an internal combustion engine. The prime mover may be a gas turbine 135, such as an aviation-only gas turbine.

An intermediate stage cooler (intermediate cooler) 137 is disposed between the first compressor 131 and the second compressor 133, and is delivered by the first compressor 131 before entering the second compressor 133. 2 Reduce the temperature and volume of refrigerant. The compressed second refrigerant delivered by the second compressor 133 is condensed in the condenser 139. The condenser 139 is condensed by exchanging heat with air or water. The condensed second refrigerant is cooled by exchanging heat with respect to the second heat exchangers 125A to 125D sequentially arranged-the first refrigerant circulating in the precooling loop 103 as described above, and the second refrigerant is cooled. , Possibly liquefied-passed through and sequentially delivered by the transfer line 141.

The cooled and optionally partially liquefied second refrigerant delivered from the heat exchangers 125A to 125D is the main cryogenic heat exchanger 145 through a pipe 143-natural gas in which the second refrigerant is precooled and optionally partially liquefied Further heat is removed from and flows to the-side to complete the liquefaction process. The fully liquefied natural gas exits the system at 149 and the heated second refrigerant is returned to the compressor(s) or compressor trains 131, 133 via line 151.

In Fig. 2 only schematically the integrated gear turbocompressor 109 is shown. The main components of an exemplary integrated gear turbocompressor 109 are illustrated in more detail in FIG. 2A. 4 illustrates in more detail the axial cross section of two compressor stages supported on a common rotating shaft of an integral gear turbocompressor 109. More specifically, Fig. 4 illustrates, for example, the first end 109D and the second end 109D.

Preferably, each compressor stage 109A-109D is provided with a movable inlet guide vane, schematically denoted 110A- 110D , for the four stages 109A-109D. In other embodiments, the movable inlet guide vanes are provided at or at the inlets of only some of the compressor stages, or not provided at any of the compressor stages. As can be understood from Fig. 4, the inlet guide vanes can be arranged at the axial inlet of the compressor stage. Each set of movable inlet guide vanes can be controlled independently of the other sets to self-regulate the flow entering the compressor stage. An intermediate cooler may be provided between the two sequentially arranged compressor stages 109A to 109D. As shown in FIG. 2A, the first intermediate cooler 153 may be disposed between the transmission side of the first compressor stage 109D and the suction side of the second compressor stage 109D. The second intermediate cooler 155 may be disposed between the delivery side of the second compressor stage 109C and the suction side of the third compressor stage 109B. A third intermediate cooler 157 may 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 includes at least one impeller supported on a rotating shaft. In Fig. 4 two impellers 112D and 112C of each of the two upstream compressor stages 109D and 109C are shown. Each impeller may be a radial impeller having an axial inlet and a radial outlet. The fluid processed through the impeller is collected in each of the volutes, such as the volutes 114D and 114C of the compressor stages 109D and 109C.

The impellers can be paired, and each impeller pair is supported by a common rotating shaft. 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 mounted to rotate on the first rotary shaft 159, and the impellers of the third and fourth compressor stages 109B and 109A are the second rotary shaft 161 It is mounted to rotate on the top. Different numbers of rotating shafts and respective compressor stages and impellers may be provided. In some embodiments, an odd number of stages may be provided, in which case one of the rotating shafts may support a single impeller instead of a paired impeller.

Each of the rotary shafts (159, 161) includes pinions (159A, 161A) fixed in a key manner on the top. The pinions 159A and 161A are engaged with a central toothed wheel or crown 163 which is rotationally driven by an electric motor 111 via a drive shaft 165. The two rotating shafts 159A and 161A and each impeller mounted on the rotating shaft can rotate at different rotational speeds.

The structure of the integrated gear turbocompressor 109 is very suitable for processing the different side streams of the first refrigerant circulating in the precooling loop 103. The position of each set of movable inlet guide vanes at the inlet of the compressor stage can be tailored to the flow conditions of each side stream, i.e., each refrigerant stream delivered to each suction side of the compressor stage, so that the operating conditions of the compressor stage are It can be tailored to temperature conditions and flow rates through different heat exchangers 123A to 123D and 125A to 125D. Compressor efficiency and operability can be maximized accordingly. One or more intermediate coolers, such as intermediate coolers 153, 155, 157, which are easily included in the structure of the integrated gear turbocompressor 109, further increase the efficiency of the compressor and thus the efficiency of the entire LNF system.

Another embodiment of the object to be protected disclosed herein is illustrated in FIG. 3 and will be described below here. The LNG system 200 of FIG. 3 includes three closed loops or cycles-labeled 201 , 203 and 205 respectively. Three different refrigerants are processed in three loops. The first refrigerant processed in the loop 201 may be propane. The first loop 201 will be referred to as a precooling loop below. The second refrigerant processed in the loop 203 may be ethylene, and the third refrigerant circulating in the loop 205 may be methane. The natural gas line 207 flows through three sequentially arranged heat exchangers 209, 211, 213 in three loops 201, 203, 205. Natural gas enters the first heat exchanger 209 in a gaseous state and exits the last heat exchanger 213 in a liquid state.

The system of Figure 3 is shown in a rather simple manner. The first precooling loop or cycle 201 includes a geared turbocompressor 229 comprising a plurality of compressor stages. In some embodiments, three compressor stages 229A-229C may be provided as shown in the schematic diagram of FIG. 3 as an example. In other embodiments, different numbers of compressor stages may be provided. In general, the number of compressor stages may depend on the number of side streams provided to the precooling loop 201 in a manner similar to that disclosed in connection with FIGS. 2 and 2A.

Inlet guide vanes 228C, 228B, 228A can be provided at the inlet of several compressor stages, preferably each compressor stage. An intermediate cooler may be disposed between pairs of sequentially arranged compressor stages, for example, the first intermediate cooler 230 is disposed between the transmission side of the first compressor stage 229C and the suction side of the second compressor stage 229B. Can be. Another intermediate cooler 231 may be disposed between the delivery side of the compressor stage 229B and the suction side of the compressor stage 229A.

The delivery side of the last compressor stage 229A, that is, the one most downstream in the pressure increasing direction is connected to the condenser 233. The first refrigerant circulating through the gear-integrated turbocompressor 229 is condensed in the condenser 233 and transferred to the first heat exchanger 209 through the line 235. The compressed and condensed refrigerant flow can be expanded through one or more expansion elements, one of which is shown at 237 . In a manner similar to FIG. 2, the main refrigerant stream flowing in the transfer line 235 can be divided into side streams of diminishing pressure and temperature. The heat exchanger 209 may be composed of a plurality of heat exchanger sections arranged in sequence, and through the heat exchanger section, a portion of the refrigerant flows at a decreasing pressure in a manner very similar to that described in connection with FIGS. 2 and 2A. do. Accordingly, a plurality of side streams returning to the respective compressor stages 229A, 229B, 229C are formed.

In each compressor stage process, a different refrigerant flow rate of thus increasing pressure passes from the upstream compressor stage 229C to the variable and downstream compressor stage 229A.

The integrated gear turbocompressor 229 may be driven by a prime mover. In some embodiments, the prime mover may be an electric motor and, although not shown, is similar to the motor 111 described with reference to FIG. 2. In another embodiment, the prime mover may comprise a gas turbine, such as an aviation-only gas turbine.

The second loop 203 includes a compressor device 241. The compressor arrangement 241 may comprise a single compressor or a plurality of compressors arranged in sequence. 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 may be driven by the second prime mover 243. In some embodiments, the second prime mover 243 may comprise a gas turbine, such as an aviation-only gas turbine. In another embodiment, the prime mover may comprise an electric motor. Different engines or combinations of motors may also be considered.

The second loop 203 includes a condenser 245 in which the compressed second refrigerant delivered by the compressor device 241 is condensed. The delivery line 247 delivers the compressed and condensed second refrigerant through the first heat exchanger 209 and through the second heat exchanger 211. In the first heat exchanger 209, the condensed second refrigerant is cooled by exchanging heat for the first refrigerant circulating in the first loop 201. In the second heat exchanger 211, the second refrigerant is expanded in one or more sequentially arranged expansion elements, one of which is shown at 249 . In a manner known per se, the stream of a second refrigerant of different and diminishing pressure can thus be produced, the side stream being a second compressor with a decreasing pressure via return lines 251, 253, 255. Return to device 241. In some embodiments, each side stream is injected at an inlet of each of a plurality of sequentially arranged compressors forming a compressor arrangement 241. A movable inlet guide vane may be provided at the inlet of each of the above compressors. 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 includes another compressor device 261. The compressor device 261 may be composed of a single compressor or a plurality of compressors arranged in sequence. The compressor(s) of the compressor device 216 may be a centrifugal compressor, such as a multistage centrifugal compressor. Another prime mover 263 is provided to drive the compressor device 261 in rotation. In some embodiments, the prime mover 263 may comprise a gas turbine, such as an aviation-only gas turbine. In another embodiment, the prime mover 263 may comprise an electric motor. Combinations of different motors and engines may also be provided.

The compressed third refrigerant delivered by the compressor device 261 is condensed in the condenser 265, and in a liquid state, the first, second and third heat exchangers 209, 211, 213 through the delivery line 267 Is passed through. In the first and second heat exchangers 209 and 211, the third refrigerant flows in a liquid state and is cooled by exchanging heat for the first refrigerant and the second refrigerant, respectively. In the last section of the loop, the third refrigerant is expanded in one or more sequentially arranged expansion elements 269. The evaporated third refrigerant exchanges heat for natural gas in the third heat exchanger 213 until liquefied when the natural gas is transferred from the third heat exchanger 213. In some embodiments, the third refrigerant may be subdivided into side streams at a declining pressure, with each side stream being returned to the compressor unit 261 via a respective return line 271, 273, 275. Also in this case, the side stream can be injected at the inlets of sequentially arranged compressors forming part of the compressor arrangement, each compressor being provided with variable inlet guide vanes, if possible.

The LNG process described so far and illustrated in FIG. 3 is known as a cascade process. As mentioned above, unlike known cascade processes and systems, in this embodiment at least the first precooling loop 201 comprises a multi-gear integral turbocompressor.

Treatment of the first refrigerant in the precooling loop through a gear-integrated turbocompressor has several advantages, as already described in connection with the embodiments of FIGS. 2 and 2A. The gear-integrated turbocompressor 229 of the embodiment of FIG. 3 may be conceptually similar to the gear-integrated turbocompressor shown in more detail in FIG. 4 and described with respect to the embodiments of FIGS. 2 and 2A. As only one example, the number of compressor stages of the gear-integrated turbocompressor 229 shown in FIG. 3 is different from the number of stages of the embodiment of FIGS. 2 and 2A, and this is the number of stages of the integrated gear turbocompressor. For example, it indicates that the main stream of the first refrigerant can be varied based on design considerations that depend on the number of side streams that are split at the bottom of the condenser.

In some embodiments, the integral gear turbocompressor may be driven with an output power ranging from about 12 MW to about 40 MW. In some embodiments, the integral gear turbocompressor may have a rated power in the range of about 14 MW to 40 MW, more specifically about 25 MW to 30 MW.

In some embodiments, a first refrigerant flow rate in the range of about 10,000 m ³ /h to 70,000 m ³ /h may be processed by an integral gear turbocompressor.

As previously disclosed, the first refrigerant in the LNG system is expanded to a pressure value that normally decreases and is divided into side streams that are each returned to each of the plurality of compressor stages of the integrated gear turbocompressor. In some embodiments, the delivery pressure of the most downstream compressor stage, ie the maximum pressure compressor stage, ranges from about 45 bar absolute to about 65 bar (absolute pressure), and in some embodiments the delivery pressure is about It may range from 52 bar (absolute pressure) to about 56 bar (absolute pressure). In some embodiments, the respective suction pressure, i.e. the pressure at the inlet of the most upstream compressor stage, is about 2.5 to about 15 bar (absolute pressure), more specifically, such as about 3 to 10 bar (absolute pressure), such as about 3 To 3.5 bar (absolute pressure).

In other embodiments, the delivery pressure (discharge pressure) of the last stage in an integral gear turbocompressor may range from about 10 bar (absolute pressure) to about 30 bar (absolute pressure), and in some specific embodiments 15 bar (absolute pressure). To 25 bar (absolute pressure). Each suction pressure at the most upstream compressor stage may range from about 1 to about 2.5 bar (absolute pressure), more specifically about 1.5 to 2 bar (absolute pressure), such as about 1.6 to 1.9 bar (absolute pressure).

The use of an integral gear turbocompressor in the precooling cycle increases the efficiency of the compressor, thereby reducing power consumption, and ultimately, significantly reducing the cost compared to the centrifugal multistage compressor of the prior art.

In order to fully understand the important advantages in terms of increased efficiency and reduced energy consumption and cost reduction achieved in this way, the following comparative examples should be considered.

In the system according to FIG. 1, a beam centrifugal compressor, for example a PGT25+G4 aviation-only gas turbine manufactured by GE Oil & Gas of Florence, Italy and coupled directly to the compressor-GE Oil, Florence, Italy Available from & Gas Co.-The operating conditions of the standard configuration using the 3MCL804 with an efficiency "100%" driven by are as follows.

-Inlet pressure: 1.13 bar (absolute pressure)

-Inflow volume flow: 56,000 m ³ /h

-Rotation speed: 6,1OO rpm

The compressor will absorb 21,108 kW under design conditions. Gear-integrated compressor-manufactured by GE Oil & Gas, located in Florence, Italy, driven by an equivalent gas turbine and has an efficiency of 102.4%-the configuration according to Fig. 2 and Fig. 2a including the same operating conditions It will absorb 20,493 kW, which entails a 3% reduction in power consumption.

The total cost savings due to the integrated gear configuration is 5%.

The use of an integrally geared compressor receives even more attention due to the removal of the gearbox when considering a configuration in which an electric motor is used instead of a gas turbine. In the standard solution according to the prior art using an electric motor as a driver, a fixed speed electric motor is driveably connected to the compressor via a gearbox. Conversely, when an integral gear compressor is used, the compressor can be designed at an optimum speed without an additional gear box. The compressor will achieve an efficiency of up to 104.1%. Under the aforementioned operating conditions, this will result in a power absorption of 20,102 kW, which results in a power consumption reduction of 1006 kW. In terms of cost, solutions using an integral gear compressor and electric motor are 14% cheaper than standard solutions using electric motors, gearboxes and compressors, mainly due to the removal of the gearbox.

While the disclosed embodiments of the subject of protection disclosed herein are shown in the drawings and have been sufficiently described above in particular and in detail in connection with a number of several embodiments, the novel teachings, principles and concepts described herein and the protection cited in the appended claims. It will be apparent to those skilled in the art that various modifications, variations and omissions are possible without actually departing from the merits of the subject. Accordingly, the appropriate scope of the disclosed innovations should be determined only by broad interpretation of the appended claims, covering all of the foregoing modifications, variations and omissions. In addition, the order or order of steps in any process or method may be changed or redefined according to variations.

Claims (23)

As a natural gas liquefaction system,
At least a precooling loop through which the first refrigerant is circulated,
At least one compressor compressing the first refrigerant;
At least one prime mover 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;
At least a first heat exchanger that transfers heat from natural gas to the first refrigerant
Precooling loop comprising a; And
At least a cooling loop downstream of the precooling loop through which the second refrigerant passes and circulates
Including, the natural gas is to be cooled sequentially in the precooling loop and in the cooling loop,
The compressor is an integrally-geared turbo-compressor including a plurality of compressor stages, and each of the plurality of compressor stages has a set of independent movable inlet guide vanes for self-regulating the flow entering the compressor stage. Is prepared,
The precooling loop is
A plurality of sequentially arranged first expansion elements configured to expand the first refrigerant to a plurality of decreasing pressure levels;
A plurality of first heat exchangers arranged and configured to receive each portion of the first refrigerant expanded through the plurality of sequentially arranged first expansion elements, and to transfer heat from natural gas to the first refrigerant; And
A plurality of return paths for returning the side stream of the first refrigerant from each of the first heat exchangers to each compressor stage of the integrated gear turbocompressor
It further includes,
The first refrigerant contains a gas having a molecular weight of more than 35,
The integrated gear turbocompressor further comprises at least one intermediate cooler between at least two sequentially arranged compressor stages,
A natural gas liquefaction system, characterized in that the side stream of the first refrigerant returned from each compressor stage is mixed with the refrigerant in the intermediate cooler and supplied to each compressor stage. The natural gas liquefaction system of claim 1, wherein the precooling loop is configured to divide the first refrigerant into two or more side streams that are returned at each compressor stage of the integral gear turbocompressor. The natural gas liquefaction system of claim 1 or 2, wherein the prime mover comprises an electric motor. 3. The natural gas liquefaction system according to claim 1 or 2, wherein the prime mover comprises a gas turbine. The second precooling loop according to claim 1 or 2, wherein the precooling loop receives at least a first auxiliary expansion element and a part of the first refrigerant expanded through the first auxiliary expansion element, and circulates in the cooling loop. The natural gas liquefaction system further comprising at least a first auxiliary heat exchanger configured to transfer heat from the refrigerant to the first refrigerant circulating in the precooling loop. The method of claim 5, wherein the precooling loop
A plurality of sequentially arranged second expansion elements configured to expand the first refrigerant to a plurality of decreasing pressure levels;
A plurality of second heat exchangers arranged and configured to receive each portion of the first refrigerant expanded through the first auxiliary expansion element, and to 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 each compressor stage of the integrated gear turbocompressor
The natural gas liquefaction system further comprising a. The natural gas liquefaction system according to claim 1 or 2, wherein the second refrigerant is a mixed refrigerant, ethylene or methane. The method of claim 1 or 2, wherein the integrated gear turbocompressor,
A central gear rotationally driven by a prime mover;
A plurality of driven shafts each including a pinion engaged with the central gear and driven to rotate by the central gear; And
At least one respective compressor impeller mounted on each shaft
Natural gas liquefaction system comprising a. 9. The natural gas liquefaction system of claim 8, wherein two respective compressor impellers are mounted on at least one of the shafts. The gear-integrated turbocompressor of claim 1 or 2, wherein the gear-integrated turbocompressor compresses the first refrigerant, and the compressed first refrigerant is a gear-integrated type at a pressure in the range of 45 to 65 bar (bar absolute). The natural gas liquefaction system that is transmitted from the last stage of the turbocompressor, and the pressure of the first refrigerant at the inlet of the first stage of the gear-integrated turbocompressor is in the range of 2.5 to 10 bar (absolute pressure). The gear-integrated turbocompressor of claim 1 or 2, wherein the gear-integrated turbocompressor compresses the first refrigerant, and the compressed first refrigerant is at a pressure in the range of 10 to 30 bar (absolute pressure). The natural gas liquefaction system that is transmitted from the stage, and the pressure of the first refrigerant at the inlet of the first stage of the integrated gear turbocompressor is in the range of 1 to 2.5 bar (absolute pressure). The natural gas liquefaction system according to claim 1 or 2, wherein the integrated gear turbocompressor delivers the first refrigerant flow at an actual flow rate ranging from 10,000 m ³ /h to 70,000 m ³ /h. The natural gas liquefaction system according to claim 1 or 2, wherein the integrated gear turbocompressor absorbs power in the range of 12 MW to 40 MW. The natural gas liquefaction system according to claim 1 or 2, wherein the integral gear turbocompressor comprises at least four stages each comprising at least one impeller. As a natural gas liquefaction method,
Driving a gear-integrated turbocompressor of a precooling loop using a prime mover, wherein the gear-integrated turbocompressor includes a plurality of compressor stages each provided with a movable inlet guide vane;
Circulating the first refrigerant through the integrated gear turbocompressor;
Condensing the first refrigerant delivered by the integrated gear turbocompressor in the condenser of the precooling loop;
Dividing the first refrigerant into a plurality of partial flows;
Expanding the first refrigerant condensed in the expansion element of the precooling loop;
Circulating the expanded refrigerant through a heat exchanger of the precooling loop to precool the natural gas by removing heat from the natural gas;
Independently controlling the movable inlet guide vanes to regulate the partial flow at the suction side of the compressor stage;
Circulating a second refrigerant in at least one cooling loop;
Removing heat from the pre-cooled natural gas by heat exchange for the second refrigerant;
Expanding the condensed first refrigerant to a plurality of decreasing pressure levels through a plurality of first expansion elements sequentially arranged in the precooling loop;
Circulating portions of the expanded first refrigerant from each of the first expansion elements through a plurality of first heat exchangers to remove heat from the natural gas; And
Returning portions of the expanded first refrigerant from the first heat exchanger to each of the plurality of compressor stages through respective return paths
Including,
The first refrigerant contains a gas having a molecular weight of more than 35,
The integrally geared turbocompressor further comprises at least one intermediate cooler between at least two sequentially arranged compressor stages,
The side stream of the first refrigerant returned from each compressor stage is mixed with the refrigerant in the intermediate cooler and supplied to each compressor stage. 16. The method of claim 15, wherein the prime mover comprises an electric motor. The method of claim 15 wherein the prime mover comprises a gas turbine. 18. The natural gas liquefaction method according to any one of claims 15 to 17, wherein the movable inlet guide vane is controlled according to the flow condition of the partial flow. The method according to any one of claims 15 to 17,
Expanding the condensed first refrigerant to a plurality of decreasing pressure levels through a plurality of second expansion elements sequentially arranged in the precooling loop;
Circulating the expanded portions of the first refrigerant through a plurality of second heat exchangers in the precooling loop to remove heat from the second refrigerant; And
Returning portions of the first refrigerant from each of the second heat exchangers to each compressor stage of the integrated gear turbocompressor
Natural gas liquefaction method further comprising a. delete delete delete delete

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