U.S. patent application number 16/305090 was filed with the patent office on 2020-10-08 for compression train including two centrifugal compressors and lng plant including two centrifugal compressors.
The applicant listed for this patent is Nuovo Pignone Tecnologie Srl. Invention is credited to Davide BECHERUCCI, Antonio PELAGOTTI, Emanuele RIZZO.
Application Number | 20200318641 16/305090 |
Document ID | / |
Family ID | 1000004941950 |
Filed Date | 2020-10-08 |
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United States Patent
Application |
20200318641 |
Kind Code |
A1 |
PELAGOTTI; Antonio ; et
al. |
October 8, 2020 |
COMPRESSION TRAIN INCLUDING TWO CENTRIFUGAL COMPRESSORS AND LNG
PLANT INCLUDING TWO CENTRIFUGAL COMPRESSORS
Abstract
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
inside one case; the second centrifugal compressor is housed inside
one case; the first centrifugal compressor has a first inlet
fluidly connected to a line of high molecular weight gas, in
particular higher than 40; the second centrifugal compressor has a
second inlet fluidly connected to a line of low molecular weight
gas, in particular between 20 and 30; the second centrifugal
compressor is arranged to provide a compression ratio higher than
10:1.
Inventors: |
PELAGOTTI; Antonio;
(Florence, IT) ; RIZZO; Emanuele; (Florence,
IT) ; BECHERUCCI; Davide; (Florence, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nuovo Pignone Tecnologie Srl |
Florence |
|
IT |
|
|
Family ID: |
1000004941950 |
Appl. No.: |
16/305090 |
Filed: |
June 7, 2017 |
PCT Filed: |
June 7, 2017 |
PCT NO: |
PCT/EP2017/063790 |
371 Date: |
November 28, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25J 1/02 20130101; F04D
17/12 20130101; F04D 25/16 20130101; F04D 25/04 20130101 |
International
Class: |
F04D 17/12 20060101
F04D017/12; F04D 25/04 20060101 F04D025/04; F04D 25/16 20060101
F04D025/16; F25J 1/02 20060101 F25J001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 2016 |
IT |
102016000058269 |
Claims
1. A compression train comprising an engine, a first centrifugal
compressor driven by the engine and a second centrifugal compressor
driven by the engine; wherein the first centrifugal compressor is
housed inside one case; wherein the second centrifugal compressor
is housed inside one case; wherein the first centrifugal compressor
has a first inlet fluidly connected to a line of high molecular
weight gas; wherein the second centrifugal compressor has a second
inlet fluidly connected to a line of low molecular weight gas; and
wherein the second centrifugal compressor is arranged to provide a
compression ratio higher than 10:1.
2. The compression train of claim 1, wherein the high molecular
weight gas is propane, wherein the low molecular weight gas is a
mixed-refrigerant gas.
3. The compression train of claim 1, wherein the engine is an
electric motor or a steam turbine or a gas turbine.
4. The compression train of claim 3, wherein the engine is a high
speed engine.
5. The compression train of claim 1, wherein the second centrifugal
compressor is mechanically connected to the first centrifugal
compressor through a gear box having a transmission ratio higher
than 2:1.
6. The compression train of claim 5, wherein the engine is an
electric motor or a steam turbine or a gas turbine, in particular
an aeroderivative gas turbine.
7. The compression train of claim 5, wherein the engine is a low
speed engine.
8. The compression train of claim 1, comprising further an
auxiliary engine.
9. The compression train of claim 1, wherein the second centrifugal
compressor comprises a first set of impellers and a second set of
impellers; the impellers of the first set being centrifugal and
unshrouded; and the impellers of the second set being centrifugal
and shrouded.
10. The compression train of claim 1, wherein the second
centrifugal compressor comprises a first set of impellers and a
second set of impellers; the impellers of the first set being
centrifugal and shrouded; and the impellers of the second set being
centrifugal and shrouded.
11. An LNG plant comprising a compression train according to claim
1.
12. The LNG plant of claim 10, further comprising two compression
trains.
13. The LNG plant of claim 11, wherein the or each first
centrifugal compressor is arranged to compress a high molecular
weight gas, wherein the or each second centrifugal compressor is
arranged to compress a low molecular weight gas; the or each first
centrifugal compressor and the or each second centrifugal
compressor cooperating to liquefy a flow of natural gas.
14. The compression train of claim 1, wherein the high molecular
weight gas is higher than 40.
15. The compression train of claim 1, wherein the low molecular
weight gas is between 20 and 30.
16. The compression train of claim 1, wherein the compression ratio
is higher than 15:1.
17. The compression train of claim 2, wherein the mixed-refrigerant
gas is a mixture of propane, ethylene or ethane, and methane.
18. The compression train of claim 3, wherein the engine is an
aeroderivative gas turbine
Description
TECHNICAL FIELD
[0001] Embodiments of the subject matter disclosed herein
correspond to compression trains including two centrifugal
compressors and LNG [=Liquefied Natural Gas] plants including two
centrifugal compressors.
BACKGROUND OF THE INVENTION
[0002] FIG. 1 shows a schematic diagram of an LNG plant 100
according to the prior art, in particular a plant implementing an
APCI process, i.e. a well-known liquefaction technology with a
first cycle using one pure-refrigerant and a second cycle using one
mixed-refrigerant.
[0003] The plant 100 consists of a first compression train with a
centrifugal compressor 130 and a centrifugal compressor 160, having
a first common shaft, and a second compression train with a
centrifugal compressor 140 and a centrifugal compressor 150, having
a second common shaft. The compressor 130 is used for compressing
propane; an inlet 131 of compressor 130 is fluidly connected to a
line of propane; an outlet 132 of compressor 130 provides
compressed propane. The compressors 140, 150 and 160 are used for
compressing a mixed-refrigerant gas; an inlet 141 of compressor 140
is fluidly connected to a line of mixed refrigerant; an outlet 142
of compressor 140 is fluidly connected to an inlet 151 of
compressor 150; an outlet 152 of compressor 150 is fluidly
connected to an inlet 161 of compressor 160; an outlet 162 of
compressor 160 provides compressed mixed refrigerant.
[0004] The first compression train is driven by a first engine 110,
and the second compression train is driven by a second engine 120.
The first engine 110 and the second engine 120 are low speed
engines and may be for example an electric engine rotating at a
speed of e.g. 1500 RPM or a gas turbine rotating at a speed of e.g.
3000 or 3600 RPM.
[0005] Each of the compressors 130, 140, 150 and 160 is housed
inside a distinct case.
[0006] An LNG plant is known from WO 2008/015224 wherein there is a
first compression arrangement for propane and a second compression
arrangement for a so-called "mixed refrigerant" (i.e. a mixture of
hydrocarbons having different molecular weights). According to the
example process of FIG. 2, the mixed refrigerant is subject to a
compression of 18.5. At the priority date of WO 2008/015224,
compression of a mixed refrigerant was typically carried out
through three compressors inside three distinct cases; this also
applies to the solution of WO 2008/015224 that reflects the
solution shown in FIGS. 2 and 3 of the article by Perez entitled
"The 4.5 MMTBA LNG Train--A Cost Effective Design" (cited by WO
2008/015224); therefore, it is to be noted that block 122 in FIGS.
1 and 2 of WO 2008/015224 corresponds to three compressors in three
cases. Furthermore, according to WO 2008/015224 the first
compression arrangement and the second compression arrangement
rotate at the same speed (i.e. there is no gearbox provided), while
the power ratio of these compression arrangements can be freely
chosen.
SUMMARY OF THE INVENTION
[0007] It would be desirable to provide an LNG plant with a reduced
number of compressor cases with respect to the prior art solutions;
this is also advantageous from the footprint point of view.
[0008] In general, it is advantageous to increase efficiency,
availability and modularity of LNG plants and to reduce CAPEX for
LNG plants.
[0009] The above-mentioned objects and advantages apply in
particular to LNG plants implementing an APCI process.
[0010] Some embodiments of the subject matter disclosed herein
relate to compression trains.
[0011] According to such embodiments, the compression 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 inside one case; the
second centrifugal compressor is housed inside one case; the first
centrifugal compressor has a first inlet fluidly connected to a
line of high molecular weight gas, in particular higher than 40;
the second centrifugal compressor has a second inlet fluidly
connected to a line of low molecular weight gas, in particular
between 20 and 30; the second centrifugal compressor is arranged to
provide a compression ratio higher than 10:1, in an embodiment,
higher than 15:1.
[0012] Additional embodiments of the subject matter disclosed
herein relate to LNG plants.
[0013] According to such embodiments, the LNG plant comprises a
compression train; the compression 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 inside one case; the second centrifugal
compressor is housed inside one case; the first centrifugal
compressor has a first inlet fluidly connected to a line of high
molecular weight gas, in particular higher than 40; the second
centrifugal compressor has a second inlet fluidly connected to a
line of low molecular weight gas, in particular between 20 and 30;
the second centrifugal compressor is arranged to provide a
compression ratio higher than 10:1, in an embodiment, higher than
15:1.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings, which are incorporated herein and
constitute an integral part of the present specification,
illustrate exemplary embodiments of the present invention and,
together with the detailed description, explain these embodiments.
In the drawings:
[0015] FIG. 1 shows a schematic diagram of an LNG plant according
to the prior art;
[0016] FIG. 2 shows a schematic diagram of embodiments of a
compression train;
[0017] FIG. 3 shows a schematic diagram of an embodiment of a
compressor that may be a component of the compression train of FIG.
2; and
[0018] FIG. 4 shows a schematic diagram of an embodiment of a LNG
plant.
DETAILED DESCRIPTION
[0019] The following description of exemplary embodiments refers to
the accompanying drawings.
[0020] The following description does not limit embodiments of the
invention. Instead, the scope of embodiments of the invention is
defined by the appended claims.
[0021] Reference throughout the specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter
disclosed. Thus, the appearance of the phrases "in one embodiment"
or "in an embodiment" in various places throughout the
specification is not necessarily referring to the same embodiment.
Further, the particular features, structures or characteristics may
be combined in any suitable manner in one or more embodiments.
[0022] In the following (and according to its mathematical meaning)
the term "set" means a group of one or more items.
[0023] The compression train 200 of FIG. 2 comprises an engine 210,
a first centrifugal (i.e. centrifugal flow) compressor 220 driven
by the engine 210 and a second centrifugal (i.e. centrifugal flow)
compressor 230 driven by the engine 210. The first centrifugal
compressor 220 is housed inside one case; the second centrifugal
compressor 230 is housed inside one case. The first centrifugal
compressor 220 has a first inlet fluidly connected to a line of
high molecular weight gas, in particular higher than 40; the second
centrifugal compressor 230 has a second inlet fluidly connected to
a line of low molecular weight gas, in particular between 20 and
30. Therefore, the gas processed by the compressor 220 and then
provided at a first outlet 222 is different from the gas processed
by the compressor 230 and then provided at a second outlet 232.
[0024] The second centrifugal compressor 230 is a
high-compression-ratio compressor; in particular, it is arranged to
provide a compression ratio higher than 10:1, in an embodiment,
higher than 15:1.
[0025] A train identical or similar to the one shown in FIG. 2 is
arranged to provide both compressed propane and compressed mixed
refrigerant for implementing an APCI process. In this case,
[0026] the high molecular weight gas mentioned above is propane,
and
[0027] the low molecular weight gas mentioned above is a
mixed-refrigerant gas, in particular mixture of propane, ethylene
or ethane, and methane.
[0028] The train of FIG. 2 comprises only two centrifugal
compressors.
[0029] FIG. 2 shows two sets of embodiments. According a first set,
there is one shaft and the second compressor 230 is directly
mechanically connected to the first compressor 220. According a
second set, there two shafts and the second compressor 230 is
indirectly mechanically connected to the first compressor 220
through a gear box 250. In FIG. 2, the gear box is drawn with
dashed lines as it is optional.
[0030] The following applies to the first set of embodiments.
[0031] The compression train has a single shaft.
[0032] The engine 210 may be an electric motor or a steam turbine
or a gas turbine, in particular an aeroderivative gas turbine.
[0033] The engine 210 is a high speed engine having, in an
embodiment, a maximum rotation speed in the range of 5000-9000 RPM,
more particularly a maximum rotation speed in the range of
6000-9000 RPM.
[0034] The following applies to the second set of embodiments.
[0035] The compression train has two shafts.
[0036] The second centrifugal compressor 230 is mechanically
connected to the first centrifugal compressor 220 through a gear
box 250 having a transmission ratio, in an embodiment, higher than
2:1.
[0037] The engine 210 is an electric motor or a steam turbine or a
gas turbine, in particular an aeroderivative gas turbine.
[0038] The engine 210 is a low speed engine having, in an
embodiment, a maximum rotation speed in the range of 1500-5000 RPM,
more particularly a maximum rotation speed in the range of
1500-4000 RPM.
[0039] The following applies to both sets of embodiments.
[0040] The train may comprise further an auxiliary engine, in an
embodiment, electric motor, such as the engine 240 in FIG. 2. In
FIG. 2, the engine 240 is directly connected, for example, to the
second compressor 230.
[0041] It is to be noted that the auxiliary engine may be used at
start-up of the train and/or to help the main engine when the power
absorbed by the compressor or compressors exceeds certain
thresholds; such auxiliary engine is sometimes called "helper".
[0042] According to the embodiment of FIG. 3, the
high-compression-ratio compressor 230 is a high-compression-ratio
centrifugal (i.e. centrifugal flow) compressor and comprises a
first set of impellers (i.e. one or more impellers) and a second
set of impellers (i.e. one or more impellers) arranged downstream
or upstream (in an embodiment, downstream) the first set of
impellers.
[0043] As shown in FIG. 3, the first set includes two impellers 311
and 312, but any number of impellers from 1 to e.g. 20 is suitable.
According to this embodiment, the second set includes three
impellers 321 and 322 and 323, but any number of impellers from 1
to e.g. 20 is suitable. The impellers 311 and 312 of the first set
are centrifugal and unshrouded. As shown in FIG. 3, the impellers
321 and 322 and 323 of the second set are centrifugal and shrouded.
At least impellers 311 and 312 and 321 and 322 and 323 of the first
set and of the second set are housed inside one case 300. The
impellers 311 and 312 and 321 and 322 and 323 of the first set and
of the second set are coupled to each other through mechanical
connections.
[0044] According to an alternative embodiment, all the impellers
are centrifugal and shrouded.
[0045] The sets of axial compression stages may be more than two,
for example three or four.
[0046] There may be one or more auxiliary inlets.
[0047] There may be one or more auxiliary outlets.
[0048] In an embodiment, as in the embodiment of FIG. 3, at least
some of the impellers of said high-compression-ratio centrifugal
compressor are stacked on each other and mechanically coupled by
means Hirth joint. The stacked and coupled impellers are tightened
together by means of a tie rod, in this way, a very stable and
reliable mechanical connection is achieved. Each impeller has for
example a passing hole at its rotational axis and is configured so
that the tie rod can pass through it. A rotor is achieved when the
impellers are stacked and tightened together.
[0049] In the embodiment of FIG. 3 all impellers 311, 312, 321,
322, 323 of the two sets are stacked, coupled by Hirth joints 340A,
340B, 340C, 340D, and tightened together by a tie rod 330.
[0050] Compressor 230 has a main inlet 301 (labelled 231 in FIG.
2), a main outlet 302 (labelled 232 in FIG. 2), and at least one
auxiliary inlet and/or at least one auxiliary outlet at an
intermediate position along the flow path from the main inlet 301
to the main outlet 302; FIG. 3 shows the general case of one
intermediate tap 303, being in some embodiments an auxiliary inlet
(see upward arrow) and being in some embodiments an auxiliary
outlet (see downward arrow).
[0051] In an embodiment, as in the embodiment of FIG. 3, the second
set of impellers (321 and 322 and 323) are downstream the first set
of impellers (311 and 312), and the impellers (321 and 322 and 323)
of the second set may have a smaller diameter than the impellers
(311 and 312) of the first set.
[0052] According to the embodiment of FIG. 3, the impellers of the
first set of impellers (311 and 312) are unshrouded and with a
larger diameter than those of the second set of impellers (321 and
322 and 323).
[0053] Unshrouded impellers can rotate faster than shrouded
impellers, due to the absence of the shroud; in fact, when the
impeller rotates the shroud is pull outwardly by the centrifugal
force acting on it and over a certain rotary speed the shroud risks
to pull out the impeller.
[0054] Thanks to the rotor configuration of the
high-compression-ratio centrifugal compressor defined above, the
compressor can rotate faster than traditional centrifugal
compressors thus achieving a greater compression ratio.
[0055] It is to be noted that unshrouded impellers and shrouded
impellers may alternate between each other; this happens, in
particular, when there is one or more auxiliary inlets and/or
outlets.
[0056] Centrifugal compressors identical or similar to the one
shown in FIG. 3 may rotate very quickly and so they can reach a
very high compression ratio. Therefore, a single innovative
centrifugal compressor in a single (and small) case may replace two
or three or more traditional centrifugal compressors in distinct
cases.
[0057] Furthermore, thanks to high rotation speeds of the
impellers, high flow coefficients may be obtained.
[0058] By using a train identical or similar to the one shown in
FIG. 2 (in particular with a compressor identical or similar to the
one shown in FIG. 3), a high LNG production may be obtained in a
smaller space and/or in a smaller footprint and with a lesser
number of machines.
[0059] It is to be noted that having only one case instead of two
or more cases is advantageous from many points of view:
[0060] it simplifies installation and maintenance,
[0061] it reduces maintenance time,
[0062] it increases reliability (less components and less
likelihood of failure),
[0063] it reduces footprint and weight of machines,
[0064] it reduces leakages of gasses,
[0065] it reduces the complexity and size of the lubricant oil
system.
[0066] A train identical or similar to the one shown in FIG. 2 is
mainly designed to be used in a LNG plant.
[0067] FIG. 4 shows a schematic diagram of an embodiment of a LNG
plant comprising two such trains; gear boxes are not shown but may
be present.
[0068] In such embodiment, both trains are identical.
[0069] In such embodiment, both trains implement an APCI
process.
[0070] In such embodiment, both trains comprises a compressor
identical or similar to the one shown in FIG. 3.
[0071] A plant such as the one shown in FIG. 4 may have a power
substantially equal to the plant of FIG. 1. Anyway, one of the
advantages of the plant of FIG. 4 with respect to the plant of FIG.
1 is that if one component of the plant breaks the plant of FIG. 1
is not able to produce any LNG while the plant of FIG. 4 will be
able to produce 50% of the rated production.
[0072] This written description uses examples to disclose the
invention, including the preferred embodiments, and also to enable
any person skilled in the art to practice the invention, including
making and using any devices or systems and performing any
incorporated methods. The patentable scope of the invention is
defined by the claims, and may include other examples that occur to
those skilled in the art. Such other examples are intended to be
within the scope of the claims if they have structural elements
that do not differ from the literal language of the claims, or if
they include equivalent structural elements with insubstantial
differences from the literal languages of the claims.
* * * * *