U.S. patent application number 16/348230 was filed with the patent office on 2019-09-12 for bath-type vaporiser-condenser for a method of cryogenically separating a natural gas stream.
The applicant listed for this patent is L'Air Liquide, Societe Anonyme pour I'Etude et I'Exploitation des Procedes Georges Claude. Invention is credited to Paul TERRIEN.
Application Number | 20190277565 16/348230 |
Document ID | / |
Family ID | 60582615 |
Filed Date | 2019-09-12 |
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United States Patent
Application |
20190277565 |
Kind Code |
A1 |
TERRIEN; Paul |
September 12, 2019 |
BATH-TYPE VAPORISER-CONDENSER FOR A METHOD OF CRYOGENICALLY
SEPARATING A NATURAL GAS STREAM
Abstract
A method of cryogenically separating a natural gas supply stream
into a gas which contains the most volatile compounds of the supply
stream, and a liquid product which contains the heaviest compounds
of the supply stream, including the following steps: at least
partially condensing a natural gas supply stream in a first heat
exchanger system; introducing the liquid product into a
fractionation column in order to obtain, in the bottom of the
fractionation column, a liquid produce that contains the heaviest
compounds of the supply stream and, at the top of the fractionation
column, a distillate that is at least partially condensed;
introducing, at a stage in the upper part of the absorption column,
the gaseous phase of the condensed distillate as a supply stream
for the absorption column; where the distillate is condensed in a
bath-type vaporizer-condenser installed in a casing mounted on the
fractionation column.
Inventors: |
TERRIEN; Paul; (Paris,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
L'Air Liquide, Societe Anonyme pour I'Etude et I'Exploitation des
Procedes Georges Claude |
Paris |
|
FR |
|
|
Family ID: |
60582615 |
Appl. No.: |
16/348230 |
Filed: |
November 8, 2017 |
PCT Filed: |
November 8, 2017 |
PCT NO: |
PCT/FR2017/053046 |
371 Date: |
May 8, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25J 2205/04 20130101;
F25J 2200/78 20130101; F25J 3/0209 20130101; F25J 2200/74 20130101;
F25J 2240/02 20130101; F25J 3/0233 20130101; F25J 3/0242 20130101;
F25J 2215/04 20130101; F25J 2235/60 20130101; F25J 2250/02
20130101; F25J 2200/04 20130101 |
International
Class: |
F25J 3/02 20060101
F25J003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2016 |
FR |
1660780 |
Claims
1.-5. (canceled)
6. A process for the cryogenic separation of a natural gas feed
stream into a gas containing the most volatile compounds of the
feed stream and into a liquid product containing the heaviest
compounds of the feed stream, comprising at least the following
stages: Stage a): at least partial condensation of a natural gas
feed stream in a first heat-exchange system; Stage b): introduction
of the at least partially condensed stream resulting from stage a)
into an absorption column at an introduction level located in the
lower part of said absorption column, said absorption column
producing, at the top, a gas stream containing the most volatile
compounds and, at the bottom, a liquid product; Stage c):
introduction of the liquid product resulting from stage b) into a
fractionation column in order to obtain, in the fractionation
column bottom, a liquid product containing the heaviest compounds
of the feed stream and, at the fractionation column top, an at
least partially condensed distillate; Stage d): introduction, at a
level located in the upper part of the absorption column, of the
gas phase of the condensed distillate resulting from stage c) as
feed stream of the absorption column; wherein the distillate
resulting from stage c) is condensed in a bath vaporizer-condenser
installed in a shell surrounding the fractionation column.
7. The process as claimed in claim 6, wherein the bath
vaporizer-condenser contains at least one heat exchanger fed with
refrigerating fluid by the liquid product resulting from stage
b).
8. The process as claimed in claim 6, wherein the liquid phase of
the condensed distillate resulting from stage c) is used as reflux
at the top of the fractionation column.
9. The process as claimed in claim 6, wherein no pump is necessary
for setting up said reflux.
10. A unit for the cryogenic separation of a natural gas feed
stream utilizing the process as defined in claim 6, wherein a pipe
connects the top of the fractionation column to a heat exchanger
surmounting said fractionation column, which heat exchanger is
itself placed in a shell provided for a bath formed predominantly
of hydrocarbons.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a 371 of International PCT Application
PCT/FR017/053046, filed Nov. 8, 2017, which claims priority to
French Patent Application No. 1660780, filed Nov. 8, 2016, the
entire contents of which are incorporated herein by reference.
BACKGROUND
[0002] The present invention relates to a process for the cryogenic
separation of a natural gas feed stream into a gas containing the
most volatile compounds of the feed stream and into a liquid
product containing the heaviest compounds of the feed stream.
[0003] During the exploitation of natural gas deposits, numerous
stages may be provided. A relatively conventional stage after the
drying and the withdrawal of the impurities is the separation of
the liquids associated with the natural gas (NGLs).
[0004] It is often desirable to separate the heavy hydrocarbons, or
more generally the NGL (Natural Gas Liquids), from the natural gas,
for example such as ethane, butane, propane or C5+ and C6+(that is
to say, having at least five carbon atoms and having more than six
carbon atoms) hydrocarbons.
[0005] This stage can have many advantages but often it is a matter
of upgrading various products (ethane, propane, and the like) which
are generally sold at a much higher price than the natural gas
product. It is in particular common to sell hydrocarbons having a
least three carbon atoms as propane, butane and condensate
products.
[0006] Many industrial installations have been described which make
it possible to fractionate gas feedstocks into a residual gas
containing the most volatile compounds of the feedstock and into a
liquid product containing the heaviest compounds of the feedstock,
this being done for the purpose of obtaining, in said liquid
product, a given component of the feedstock with a high degree of
recovery.
[0007] In this regard, mention may be made, for example, of the
recovery of liquefied petroleum gas (hydrocarbons therein having
three or four carbon atoms) from natural or refinery gas, the
recovery of ethane intended in particular to feed steam cracking
units, or the desulfurization and the gasoline extraction of
natural gases by recovery of the sulfur-comprising compounds, such
as carbon oxysulfide and mercaptains
[0008] Several technologies exist for producing hydrocarbons having
at least three carbon atoms from natural gas.
[0009] One of the most effective is a process employing a
two-column turbo-expander in which the first column is an absorber
dedicated to forcing the recovery of as much propane as possible
and the second column is a de-ethanizer.
[0010] The condensation of the de-ethanizer top stream is often
carried out in part with the fluid coming from the absorber
bottom.
[0011] Such a process is described in the documents U.S. Pat. Nos.
4,690,702 and 5,114,450.
[0012] Such processes can prove to be complicated to control and
require investment in fairly expensive components, such as
pumps.
SUMMARY OF THE INVENTION
[0013] The inventors of the present invention have thus developed a
solution which makes it possible to solve the problems raised
above.
[0014] A subject matter of the present invention is a process as
defined in claims 1 to 4.
[0015] According to another embodiment, another subject-matter of
the invention is an apparatus as defined in claim 5.
[0016] The stream of hydrocarbons to be liquefied is generally a
stream of natural gas obtained from natural gas fields, oil
reservoirs or a domestic gas network in which the gas is
distributed via pipelines.
[0017] Generally, the natural gas stream is essentially composed of
methane. Preferably, the feed stream comprises at least 80 mol % of
methane. Depending on the source, the natural gas contains
quantities of hydrocarbons heavier than methane, such as, for
example, ethane, propane, butane and pentane and also certain
aromatic hydrocarbons. The natural gas stream also contains
nonhydrocarbon products, such as H.sub.2O, N.sub.2, CO.sub.2,
H.sub.2S and other sulfur-comprising compounds, mercury and
others.
[0018] The feed stream containing the natural gas is thus
pretreated before being introduced into the heat exchanger making
possible the first stage of cooling of the process which is a
subject matter of the present invention. This pretreatment
comprises the reduction and/or the removal of the undesirable
components, such as CO.sub.2 and H.sub.2S, or other stages, such as
the precooling and/or the pressurization.
[0019] Given that these measures are well known to a person skilled
in the art, they are not described in further detail here.
[0020] The expression "natural gas" as used in the present patent
application relates to any composition containing hydrocarbons,
including at least methane.
[0021] This comprises a "crude" composition (prior to any treatment
or scrubbing) and also any composition which has been partially,
substantially or completely treated for the reduction and/or
removal of one or more compounds, including, but without being
limited thereto, sulfur, carbon dioxide, water, mercury and certain
heavy and aromatic hydrocarbons.
[0022] The heat exchanger can be any heat exchanger, any unit or
other arrangement suitable for making possible the passage of a
certain number of streams, and thus making possible at least one
system for direct or indirect exchange of heat between one or more
liquid coolant lines and one or more feed streams.
[0023] A bath vaporizer-condenser is, for example, of the type as
described in the patent application EP 1 087 194.
[0024] The invention will be described in a more detailed manner
with reference to the FIGURE.
BRIEF DESCRIPTION OF THE DRAWING
[0025] For a further understanding of the nature and objects for
the present invention, reference should be made to the following
detailed description, taken in conjunction with the accompanying
drawings, in which like elements are given the same or analogous
reference numbers and wherein:
[0026] FIG. 1 illustrates a schematic representation of one
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] In the FIGURE, a feed stream of natural gas 1 is introduced
into a main heat exchanger 2 in order to be cooled. The gas thus
cooled 3 is partially condensed and introduced into a phase
separator 4. The gas phase 5 at the phase separator 4 top is
introduced into a turbine 6 in order to recover the expansion
energy and to condense a portion of the stream 5, and is then
introduced into an absorption column 7 comprising a lower part 7'
and an upper part 7''. The liquid phase 8 at the phase separator 4
bottom is introduced after expansion 9 into the absorption column
7. The absorption column produces a liquid 10 at the column bottom
and a residual gas 11 at the column top. The liquid 10 is reheated
in a heat exchanger 12 in which it is partially evaporated. The
stream thus reheated 13 is subsequently introduced into the main
exchanger 2; this introduction 13 is thus strongly a two-phase
introduction.
[0028] At the absorption column 7 top, the residual gas 11, which
contains only the products more volatile than ethane, is reheated
in the main heat exchanger 2; the stream which results therefrom 14
is subsequently compressed and sent to a treatment unit A.
[0029] The stream 13' at the heat exchanger 2 outlet resulting from
the bottom of the absorption column 7 is introduced into a
fractionation column 15.
[0030] This column 15 produces, at the bottom 16, a reboiled liquid
product 18 using a reboiler 17 in order to obtain a liquid rich in
propane and depleted in ethane.
[0031] A gas 20 is produced at the fractionation column 15 top 19.
This gas 20 is condensed in the heat exchanger 12 and the product
21 which exits from this exchanger 12 is introduced into a phase
separator 22. The gas phase 23 at the top of the phase separator 22
acts as reflux in the absorption column 7. The liquid 25 at the
bottom of the phase separator 22 acts as reflux 26 at the top of
the fractionation column 15. A pump is not necessary to pump the
liquid 25. This arrangement with the use of a bath
vaporizer-condenser exhibits the advantage of being very easy to
control while integrating the exchanger and the fractionation
column and without using a pump (thermosiphon scheme).
[0032] It will be understood that many additional changes in the
details, materials, steps and arrangement of parts, which have been
herein described in order to explain the nature of the invention,
may be made by those skilled in the art within the principle and
scope of the invention as expressed in the appended claims. Thus,
the present invention is not intended to be limited to the specific
embodiments in the examples given above.
* * * * *