U.S. patent application number 10/504525 was filed with the patent office on 2005-09-29 for method for liquefying a flow rich in hydrocarbons.
This patent application is currently assigned to Linde Aktiengesellschaft. Invention is credited to Paurola, Pentti, Prietzel, Werner, Stockmann, Rudolf.
Application Number | 20050210915 10/504525 |
Document ID | / |
Family ID | 27635008 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050210915 |
Kind Code |
A1 |
Paurola, Pentti ; et
al. |
September 29, 2005 |
Method for liquefying a flow rich in hydrocarbons
Abstract
A process is described for liquefaction of a hydrocarbon-rich
stream, especially a natural gas stream, at least indirect heat
exchange taking place between the hydrocarbon-rich stream to be
liquefied and the refrigerant mixture of at least one refrigerant
mixture circuit, and the refrigerant mixture being separated after
completed supercooling into a gaseous fraction and a liquid
fraction and these fractions being recombined before and/or during
the reheating of the refrigerant mixture. According to the
invention, a gas fraction (9) that is identical or similar in
composition is added at least from time to time to the gas fraction
(4) that has been obtained in the separation (D). In doing so, the
addition of the gas fraction (9) that is identical or similar in
composition takes place when a minimum amount of the gas fraction
(4) obtained in the separation (D) of the refrigerant mixture is
not reached.
Inventors: |
Paurola, Pentti; (Solln,
DE) ; Stockmann, Rudolf; (Buchloe, DE) ;
Prietzel, Werner; (Muenchen, DE) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Assignee: |
Linde Aktiengesellschaft
Abraham-Lincoln-Strasse-21
Wiesbaden
DE
65189
|
Family ID: |
27635008 |
Appl. No.: |
10/504525 |
Filed: |
May 6, 2005 |
PCT Filed: |
February 14, 2003 |
PCT NO: |
PCT/EP03/01498 |
Current U.S.
Class: |
62/613 |
Current CPC
Class: |
F25J 1/0022 20130101;
F25J 2290/32 20130101; F25J 1/0245 20130101; F25J 2245/02 20130101;
F25J 1/0052 20130101; F25J 2290/62 20130101; F25J 1/0262 20130101;
F25J 2205/02 20130101; F25J 1/0248 20130101 |
Class at
Publication: |
062/613 |
International
Class: |
F25J 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2002 |
DE |
102 06 388.5 |
Claims
1. Process for liquefaction of a hydrocarbon-rich stream,
especially a natural gas stream, at least indirect heat exchange
taking place between the hydrocarbon-rich stream to be liquefied
and the refrigerant mixture of at least one refrigerant mixture
circuit, and the refrigerant mixture being separated after
completed supercooling into a gaseous fraction and a liquid
fraction and these fractions being recombined before and/or during
the reheating of the refrigerant mixture, characterized in that a
gas fraction (9) that is identical or similar in composition is
added at least from time to time to the gas fraction (4) that has
been obtained in the separation (D).
2. Process for liquefaction of a hydrocarbon-rich stream according
to claim 1, wherein the addition of the gas fraction (9) that is
identical or similar in composition takes place when a minimum
amount of the gas fraction (4) obtained in the separation (D) of
the refrigerant mixture is not reached.
3. Process for liquefaction of a hydrocarbon-rich stream according
to claim 1, wherein the gas fraction (9) that is identical or
similar in composition is withdrawn at a point of the refrigerant
mixture circuit that is suitable for this purpose and that has a
refrigerant mixture that is separated into a gaseous fraction (4)
and a liquid fraction (3).
Description
[0001] The invention relates to a process for liquefaction of a
hydrocarbon-rich stream, especially a natural gas stream, at least
indirect heat exchange taking place between the hydrocarbon-rich
stream to be liquefied and the refrigerant mixture of at least one
refrigerant mixture circuit, and the refrigerant mixture being
separated after completed supercooling into a gaseous fraction and
a liquid fraction and these fractions being recombined before
and/or during the reheating of the refrigerant mixture.
[0002] The most varied processes for liquefaction of a
hydrocarbon-rich stream, especially a natural gas stream, are
known. Here, in a host of these liquefaction processes, indirect
heat exchange takes place between the hydrocarbon-rich stream to be
liquefied and the refrigerant mixture of at least one refrigerant
mixture circuit. In doing so, often after completed supercooling of
the refrigerant mixture, separation of the refrigerant mixture into
a gaseous fraction and a liquid fraction takes place. The
aforementioned fractions are then combined before and/or during
reheating of the refrigerant mixture; reheating of the refrigerant
mixture generally takes place against the hydrocarbon-rich stream
that is to be cooled and liquefied and optionally other
processes--especially refrigerant (mixture) streams.
[0003] The above-described separation of the supercooled
refrigerant mixture into a gaseous fraction and a liquid fraction
and the subsequent recombination of the two fractions results in
improved heat transfer between the refrigerant mixture and the
other process stream(s) in the reheating of the refrigerant
mixture.
[0004] Generally, a liquefaction process is run such that after
completed supercooling of the refrigerant mixture, separation into
a gaseous fraction and a liquid fraction is possible. Under certain
boundary conditions--which can vary in the course of the
liquefaction process--it can, however, happen that the refrigerant
mixture is supercooled to the extent that it has no more gaseous
portion. This results in that the aforementioned heat transfer
between the now liquid refrigerant mixture and the other process
stream(s) is adversely affected.
[0005] The object of this invention is to devise a generic process
that makes it possible for heat exchange between one or more
process streams to take place at any instant and under all process
conditions, especially between the hydrocarbon-rich stream to be
liquefied and the refrigerant mixture in which the subsequently
supercooled refrigerant mixture has both liquid and also gaseous
components.
[0006] This is achieved by a gas fraction that is identical or
similar in composition being added at least from time to time to
the gas fraction that has been obtained in the separation.
[0007] By means of the procedure according to the invention, it is
thus ensured that at any instant in the heat exchange between the
refrigerant mixture and at least one other process stream, the
refrigerant mixture also has gaseous components.
[0008] If the supercooled refrigerant mixture does not have any
more gaseous components, the formulation "addition of a gas
fraction that is similar or identical in composition" is defined as
feed of this gas fraction into the line(s) via which during normal
operation, the gas fraction withdrawn from the separation is
routed.
[0009] One advantageous configuration of the process according to
the invention is characterized in that the addition of the gas
fraction that is identical or similar in composition takes place
when a minimum amount of the gas fraction obtained in the
separation of the refrigerant mixture is not reached.
[0010] It is not absolutely necessary for a gas fraction that is
identical or similar in composition to be permanently added to the
gas fraction that has been obtained in the separation since it is
adjusted in a regular process sequence to a sufficient quantitative
volume. If at this point only a preset minimum amount of the gas
fraction obtained in the separation of the refrigerant mixture is
not reached, it is sufficient if addition of the gas fraction that
is identical or similar in composition takes place at these times.
The control mechanisms required for this purpose are familiar to
one skilled in the art.
[0011] Another advantageous embodiment of the process according to
the invention is characterized in that the gas fraction that is
identical or similar in composition is withdrawn at a point of the
refrigerant mixture circuit that is suitable for this purpose and
that has a refrigerant mixture that is separated into a gaseous
fraction and a liquid fraction.
[0012] Fundamentally, the gas fraction that is identical or similar
in composition can, however, originate from any "source."
[0013] The process according to the invention as well as other
configurations thereof that constitute the subject matters of the
dependent claims are detailed below using the embodiment shown in
the figure.
[0014] The figure shows an extract from a liquefaction process, in
a heat exchanger E four process streams being brought into thermal
contact with one another. They are: a first refrigerant mixture
stream that is delivered via the line 1, a second refrigerant
(mixture) stream that is routed via the line 7 through the heat
exchanger E, the hydrocarbon-rich stream that is to be liquefied
and that is routed through the heat exchanger E by means of line 8,
and the first refrigerant mixture stream that is to be heated,
which is supplied via the line 5 to the heat exchanger E and which
after completed heating is withdrawn against the aforementioned
three process streams via the line 6 from the heat exchanger E.
[0015] The refrigerant mixture stream that is supplied to the heat
exchanger E via the line 1 is supercooled in the heat exchanger E
and then supplied via the line 2 to the expansion valve a and
subjected to Joule-Thomson expansion in it. Instead of the
expansion valve a shown in the figure, there can also be an
expansion turbine.
[0016] Then, the refrigerant mixture stream is separated in the
separator D into a liquid fraction and into a gaseous fraction. The
liquid fraction is withdrawn via the line 3 in which there is a
control valve b from the bottom of the separator d and is supplied
to the aforementioned line 5.
[0017] The gas fraction that is formed in the separator D is
withdrawn via the line 4 at the top of the separator D and is
combined with the liquid fraction in the line 3. There is also
generally a control valve c in the line 4.
[0018] The proportion of the gas fraction that is present after
expansion in the expansion valve a is determined by the degree of
supercooling of the refrigerant mixture stream in the line 2.
[0019] The mixing of the fractions obtained in the separator D
upstream from the heat exchanger E and in the entry area of the
heat exchanger E--the way this process is performed is not shown in
the figure--results in a good distribution of the liquid and
gaseous portions of the refrigerant mixture stream in the heat
exchanger E; this leads to improved heat transfer in the heat
exchanger E; this applies especially when the heat exchanger E is a
so-called plate-fine-type heat exchanger.
[0020] The separator D is optionally used not only for separation
of the refrigerant mixture stream into a liquid fraction and into a
gaseous fraction, but, moreover, in the case of plant shutdown as a
storage tank in which the refrigerant mixture is intermediately
stored during plant shutdown. This storage of the refrigerant
mixture at the coldest point of a refrigerant mixture circuit makes
it possible to implement a start-up procedure that is as short as
possible during restart. The separator D should therefore be
dimensioned such that it can accommodate the entire amount of
refrigerant mixture of the refrigerant circuit.
[0021] If the refrigerant mixture stream in the line 2 is now
supercooled to such an extent that after expansion in the expansion
valve a it has an overly low proportion of gaseous components or
even no gaseous components at all, at this point according to the
invention, a gas fraction that is identical or similar in
composition is supplied to the line 4 via a side line 9 in which
there is likewise a control valve d. Here, the control of the
control valve d can take place automatically and/or manually.
* * * * *