KR20190015743A - An LNG plant comprising a compression train comprising two centrifugal compressors and two centrifugal compressors - Google Patents

Abstract

The compression train 200 includes an engine 210, a first centrifugal compressor 220 driven by the engine 210 and a second centrifugal compressor 230 driven by the engine 210; The first centrifugal compressor (220) is housed in one case; The second centrifugal compressor 230 is housed in one case; The first centrifugal compressor 220 has a first inlet which is fluidly connected to a line of high molecular weight gas, in particular a gas of molecular weight greater than 40; The second centrifugal compressor 230 has a second inlet fluidly connected to a line of low molecular weight gas, in particular a gas of molecular weight 20 to 30; The second centrifugal compressor 230 is configured to provide a compression ratio of greater than 10: 1, preferably greater than 15: 1.

Description

An LNG plant comprising a compression train comprising two centrifugal compressors and two centrifugal compressors

An embodiment of the subject matter disclosed herein includes a compression train comprising two centrifugal compressors and a LNG (= Liquefied Natural Gas; Liquefied natural gas] plant.

1 is a schematic diagram of a plant implementing a well known liquefaction technique with a LNG plant 100 according to the prior art, in particular an APCI process, i.e. a first cycle using one net refrigerant and a second cycle using one mixed refrigerant to be.

The plant 100 includes a first compression train including a centrifugal compressor 130 and a centrifugal compressor 160 having a first common shaft and a centrifugal compressor 140 and a centrifugal compressor 150 having a second common shaft And the second compression train. Compressor 130 is used to compress the propane; The inlet 131 of the compressor 130 is fluidly connected to the line of propane; The outlet 132 of the compressor 130 provides compressed propane. Compressors (140, 150, 160) are used to compress the mixed refrigerant gas; The inlet (141) of the compressor (140) is fluidly connected to the line of mixed refrigerant; The outlet 142 of the compressor 140 is fluidly connected to the inlet 151 of the compressor 150; The outlet 152 of the compressor 150 is fluidly connected to the inlet 161 of the compressor 160; The outlet (162) of the compressor (160) provides a compressed mixed refrigerant.

The first compression train is driven by the first engine 110 and the second compression train is driven by the second engine 120. [ The first engine 110 and the second engine 120 are low speed engines and may be, for example, electric engines rotating at a speed of 1500 RPM or gas turbines rotating at a speed of, for example, 3000 or 3600 RPM.

Each of the compressors 130, 140, 150, 160 is housed in a separate case.

LNG plants are known from WO 2008/015224, where there is a first compression configuration for the propane and a second compression configuration for the so-called " mixed refrigerant " (i.e., a hydrocarbon mixture having a different molecular weight). According to the exemplary process of Figure 2, the mixed refrigerant is subjected to a compression of 18.5. On the priority date of WO 2008/015224, the compression of the mixed refrigerant was usually carried out through two compressors in two separate cases; This is also the case in WO 2008/1/1, which reflects the solution shown in Figures 2 and 3 of the paper by Perez, whose title is "The 4.5 MMTBA LNG Train - A Cost Effective Design" (cited by WO 2008/015224) 015224; It should therefore be noted that Figures 1 and 2 of WO 2008/015224 correspond to three compressors in three cases. Furthermore, according to WO 2008/015224, the first compression configuration and the second compression configuration rotate at the same speed (i.e., no gearbox is provided), but the output ratios of these compression configurations can be freely selected.

It would be desirable to provide a LNG plant with a reduced number of compressor cases for prior art solutions; This is also advantageous in terms of footprint.

In general, it is advantageous to increase the efficiency, availability or modularity of the LNG plant and to reduce the CAPEX for the LNG plant.

The above objects and advantages are particularly applicable to LNG plants implementing APCI processes.

The first embodiment of the protection object disclosed herein relates to a compression train.

According to the first embodiment described above, the compressor train comprises an engine, a first centrifugal compressor driven by the engine and a second centrifugal compressor driven by the engine; The first centrifugal compressor is housed in one case; The second centrifugal compressor is housed in one case; The first centrifugal compressor has a first inlet fluidly connected to a line of high molecular weight gas, in particular a gas of molecular weight greater than 40; The second centrifugal compressor has a second inlet fluidly connected to a line of low molecular weight gas, in particular a gas of molecular weight 20 to 30; The second centrifugal compressor is configured to provide a compression ratio of greater than 10: 1, preferably greater than 15: 1.

A second embodiment of the protection object disclosed herein relates to an LNG plant.

According to the second embodiment described above, the LNG plant includes a compression train; The compression train includes an engine, a first centrifugal compressor driven by the engine, and a second centrifugal compressor driven by the engine; The first centrifugal compressor is housed in one case; The second centrifugal compressor is housed in one case; The first centrifugal compressor has a first inlet fluidly connected to a line of high molecular weight gas, in particular a gas of molecular weight greater than 40; The second centrifugal compressor has a second inlet fluidly connected to a line of low molecular weight gas, in particular a gas of molecular weight 20 to 30; The second centrifugal compressor is configured to provide a compression ratio of greater than 10: 1, preferably greater than 15: 1.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with the description, serve to illustrate these embodiments.
1 is a schematic view of a conventional LNG plant,
Figure 2 is a schematic view of an embodiment of a compression train,
Figure 3 is a schematic view of an embodiment of a compressor which may be a component of the compressed gear train of Figure 2,
Figure 4 is a schematic diagram of an embodiment of an LNG plant.

The following description of an exemplary embodiment refers to the accompanying drawings.

The following description does not limit the present invention. Instead, the scope of the invention is defined in the appended claims.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosed protected subject matter . Accordingly, the appearances of the phrases " in one embodiment " or " in an embodiment " in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any suitable manner in one or more embodiments.

Below (and according to its mathematical meaning), the term " set " means a group of one or more items.

The compression train 200 of Figure 2 includes an engine 210, a first centrifugal (i.e., centrifugal) compressor 220 driven by the engine 210, and a second centrifugal , Centrifugal flow) compressors 230. The first centrifugal compressor (220) is housed in one case; The second centrifugal compressor (230) is housed in one case. The first centrifugal compressor 220 has a first inlet which is fluidly connected to a line of high molecular weight gas, in particular a gas of molecular weight greater than 40; The second centrifugal compressor 230 has a second inlet fluidly connected to a line of low molecular weight gas, particularly a gas of molecular weight 20-30. Thus, after being processed by the compressor 220, the gas provided to the first outlet 222 is processed by the compressor 230 and then differs from the gas provided to the second outlet 232.

The second centrifugal compressor 230 is a high compression ratio compressor; In particular, it is configured to provide a compression ratio higher than 10: 1, preferably higher than 15: 1.

A train the same or similar to that shown in Figure 2 is particularly advantageous when it is configured to provide both compressed propane and compressed mixed refrigerant to implement the APCI process. In this case, the above-mentioned high molecular weight gas is propane, and the aforementioned low molecular weight gas is a mixed refrigerant gas, particularly a mixture of propane, ethylene or ethane and methane.

The train of Figure 2 includes only two centrifugal compressors.

Figure 2 shows two sets of embodiments. According to the first set, there is one shaft, and the second compressor 230 is mechanically connected directly to the one compressor 220. According to the second set, there are two shafts, and the second compressor 230 is mechanically connected indirectly to the first compressor 220 via the gearbox 250. In Figure 2, the gearbox is shown as a dotted line because it is optional.

The following description applies to the first set of embodiments.

The compression train has a single shaft.

The engine 210 may be an electric motor, a steam turbine or a gas turbine, particularly an airborne gas turbine.

The engine 210 is preferably a high speed engine having a maximum rotational speed in the range of 5000-9000 RPM, and more preferably a maximum rotational speed in the range of 6000-9000 RPM.

The following description applies to the second set of embodiments.

The compression train has two shafts.

The second centrifugal compressor 230 is mechanically connected to the first centrifugal compressor 220 through a gear box 250 having a transmission ratio preferably greater than 2: 1.

The engine 210 may be an electric motor, a steam turbine or a gas turbine, particularly an airborne gas turbine.

Engine 210 is preferably a low speed engine having a maximum rotational speed in the range of 1500-5000 RPM, more preferably a maximum rotational speed in the range of 1500-4000 RPM.

The following description applies to both sets of embodiments.

The train may further include an auxiliary engine, such as the engine 240 of FIG. 2, preferably an electric motor. In Fig. 2, the engine 240 is connected directly to, for example, the second compressor 230.

It is noted that the auxiliary engine may be used at start-up of the train and / or may be used to assist the main engine when the output absorbed by the compressor or compressors exceeds a certain threshold value; Such auxiliary engines are often referred to as " helpers. &Quot;

According to the embodiment of Figure 3, the high compression ratio compressor 230 is a high compression ratio centrifugal (i.e., centrifugal) compressor and comprises a first set of impellers (i.e., one or more impellers), a second set of impellers A second set of impellers (i.e., one or more impellers) disposed at a downstream (preferably downstream) position.

As shown in FIG. 3, the first set includes two impellers 311, 312, but an impeller of any number from one to twenty, for example, is suitable. According to the present embodiment, the second set includes three impellers 321, 322, 323, but an impeller of any number from one to twenty, for example, is suitable. The first set of impellers 311 and 312 are both centrifugal and unshrouded. As shown in Fig. 3, the second set of impellers 321, 322 and 323 are of the centrifugal and shroud type. At least the impellers (311, 312, 321, 322, 323) of the first set and the second set are housed in one case (300). The first set and the second set of impellers 311, 312, 321, 322, 323 are coupled to each other via a mechanical connection.

According to a variant, the entire impeller is of the centrifugal and shroud type.

The axial compression set may be more than two, for example three or four.

One or more auxiliary inlets may be provided.

One or more auxiliary outlets may be provided.

Advantageously, as in the embodiment of FIG. 3, at least some of the impellers of the high compression ratio centrifugal compressor are stacked up and down and mechanically coupled by a Hirth joint. The stacked and coupled impellers are tightened together by a tie rod, and in this way a very stable and reliable mechanical connection is achieved. Each of the impellers has, for example, a through hole at its rotary shaft, and is configured so that the tie rod passes through the through hole. The rotor is achieved when the impellers are stacked together and tightened.

3, all of the two sets of impellers 311, 312, 321, 322 and 323 are stacked and coupled by hose joints 340A, 340B, 340C and 340D, Respectively.

The compressor 230 includes a main inlet 301 (labeled 231 in FIG. 2), a main outlet 302 (labeled 232 in FIG. 2), and a main outlet 302 from the main inlet 310. [ Has at least one auxiliary inlet and / or at least one auxiliary outlet at an intermediate position along the flow path to the auxiliary outlet; FIG. 3 shows a common case for one intermediate tab 303, which in some embodiments is a secondary inlet (see upward arrow), and in some embodiments is a secondary outlet (see downward arrow).

Advantageously, as in the embodiment of FIG. 3, the second set of impellers 321, 322, 323 are located downstream of the first set of impellers 311, 312 and the second set of impellers 321, 322, May have a smaller diameter than the first set of impellers 311, 312.

According to the embodiment of Figure 3, the impellers of the first set of impellers 311, 312 are of the unshrouded type and have a diameter greater than the diameter of the second set of impellers 321, 322, 323.

Unshrouded impellers can rotate faster than shrouded impellers due to the absence of shrouds; In fact, when the impeller rotates, the shroud is pulled outward by the centrifugal force acting on the shroud, and the shroud may pull the impeller over a predetermined rotational speed.

Due to the rotor configuration of the previously defined high compression ratio centrifugal compressor, the compressor can rotate faster than conventional centrifugal compressors, thereby achieving a larger compression ratio.

It should be noted that the unshrouded impeller and the shrouded impeller may be interchangeable; This occurs in particular when there is more than one auxiliary inlet and / or outlet.

A centrifugal compressor which is the same as or similar to that shown in Fig. 3 can rotate very quickly, and thus can reach a very high compression ratio. Thus, one innovative centrifugal compressor in one (and small) case can replace two or three or more conventional centrifugal compressors in a separate case.

Moreover, due to the high rotational speed of the impeller, a high flow coefficient can be obtained.

By using the same or similar trains as those shown in FIG. 2 (especially with compressors identical or similar to those shown in FIG. 3), a smaller space and / or a smaller footprint and a smaller number of devices can be used for high LNG Production can be obtained.

It should be noted that it is advantageous to have only one case instead of two or more cases from several perspectives:

Easy to install and maintain,

Reduced maintenance time,

Increased reliability (fewer components and fewer failures)

Reducing machine footprint and weight,

Reducing gas leakage,

Reduces the complexity and size of lubricating oil systems.

A train identical or similar to that shown in Figure 2 is configured to be used primarily in an LNG plant.

Figure 4 shows a schematic view of an embodiment of an LNG plant comprising two said trains; A gearbox may be present although not shown.

In this embodiment, advantageously both trains are the same.

In the above embodiment, both trains implement the APCI process.

In the above embodiment, both of the trains include compressors which are the same as or similar to those shown in Fig.

A plant such as that shown in Fig. 4 may have substantially the same output as the plant of Fig. In any case, one of the advantages of the plant of Figure 4 with respect to the plant of Figure 1 is that if one component of the plant fails, the plant of Figure 1 can no longer produce LNG, Of the total production.

Claims (13)

A compression train (200) comprising an engine (210), a first centrifugal compressor (220) driven by an engine (210) and a second centrifugal compressor (230) driven by an engine
The first centrifugal compressor 220 is housed in one case,
The second centrifugal compressor 230 is housed in one case,
The first centrifugal compressor 220 has a first inlet fluidly connected to a line of high molecular weight gas, in particular a gas of molecular weight greater than 40,
The second centrifugal compressor 230 has a second inlet fluidly connected to a line of low molecular weight gas, particularly a gas having a molecular weight of 20 to 30,
The second centrifugal compressor (230) is configured to provide a compression ratio of greater than 10: 1, preferably greater than 15: 1. The method according to claim 1,
The high molecular weight gas is propane,
Wherein the low molecular weight gas is a mixed refrigerant gas, particularly a mixture of propane, ethylene or ethane and methane. 3. Compressed train according to claim 1 or 2, wherein the engine (210) is an electric motor, a steam turbine or a gas turbine, in particular an airborne gas turbine. 4. The compression train of claim 3, wherein the engine (210) is a high speed engine. 3. The centrifugal compressor of claim 1 or 2, wherein the second centrifugal compressor (230) is mechanically coupled to the first centrifugal compressor (220) through a gear box (250) having a transmission ratio preferably greater than 2: Compressed train to be connected. The compression train according to claim 5, wherein the engine (210) is an electric motor, a steam turbine or a gas turbine, in particular an airborne gas turbine. The compression train according to claim 5 or 6, wherein the engine (210) is a low speed engine. 8. A compression train as claimed in any one of the preceding claims, further comprising an auxiliary engine (240). 9. The method according to any one of claims 1 to 8,
The second centrifugal compressor 230 includes a first set of impellers 411 and 412 and a second set of impellers 421, 422, and 423,
The first set of impellers 411 and 412 are centrifugal and unshrouded,
The second set of impellers (421, 422, 423) are centrifugal and unshrouded. 9. The method according to any one of claims 1 to 8,
The second centrifugal compressor 230 includes a first set of impellers and a second set of impellers,
The first set of impellers are of the centrifugal and shroud type,
The second set of impellers being of centrifugal and shroud type. An LNG plant (100) comprising a compression train (200) according to any one of the preceding claims. 11. An LNG plant according to claim 10, comprising two compression trains (200, 300) according to one of the preceding claims. 13. A method according to claim 11 or 12, wherein said or each first centrifugal compressor (220, 320) is configured to compress high molecular weight gas,
The or each second centrifugal compressor (230, 330) is configured to compress a low molecular weight gas,
Wherein said or each first centrifugal compressor (220, 320) and said or each second centrifugal compressor (230, 330) cooperate to liquefy natural gas flow.

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