U.S. patent application number 11/205035 was filed with the patent office on 2006-02-23 for process and system for obtaining a gaseous pressure product by the cryogenic separation of air.
This patent application is currently assigned to Linde Aktiengesellschaft. Invention is credited to Ulrich Ewert, Gerhard Pompl.
Application Number | 20060037357 11/205035 |
Document ID | / |
Family ID | 35768639 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060037357 |
Kind Code |
A1 |
Ewert; Ulrich ; et
al. |
February 23, 2006 |
Process and system for obtaining a gaseous pressure product by the
cryogenic separation of air
Abstract
A process and system are used for obtaining a gaseous pressure
product by cryogenic separation of air. In the normal operation,
charge air is condensed, cooled and fed to a distillation column
system; a product fraction is withdrawn-in a liquid condition from
the distillation column system, and is introduced into a liquid
tank; product liquid is removed from the liquid tank, is
pressurized in a pump set in the liquid condition to an increased
pressure, is evaporated in an indirect heat exchange with a first
heat transfer medium flow, and is withdrawn as a gaseous pressure
product. In an emergency operation, product liquid is removed from
the liquid tank, is brought in the liquid condition to an increased
pressure, is evaporated in an indirect heat exchange with a second
heat transfer medium flow, and is withdrawn as a gaseous pressure
product. In a bypass operation, the product fraction withdrawn in
the liquid condition from the distillation column system is guided
past the liquid tank; is brought via the pump set is brought in the
liquid condition to an increased pressure; is evaporated in an
indirect heat exchange, and is withdrawn as a gaseous pressure
product.
Inventors: |
Ewert; Ulrich; (Bichl,
DE) ; Pompl; Gerhard; (Beilngries, DE) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Linde Aktiengesellschaft
Muenchen
DE
|
Family ID: |
35768639 |
Appl. No.: |
11/205035 |
Filed: |
August 17, 2005 |
Current U.S.
Class: |
62/656 ;
62/643 |
Current CPC
Class: |
F25J 2245/50 20130101;
F25J 2290/62 20130101; F25J 3/04103 20130101; F25J 3/0409 20130101;
F25J 3/04781 20130101; F25J 3/04824 20130101; F25J 2235/50
20130101; F25J 3/04818 20130101 |
Class at
Publication: |
062/656 ;
062/643 |
International
Class: |
F25J 3/00 20060101
F25J003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 17, 2004 |
DE |
10 2004 039 839.9 |
Claims
1. Process for obtaining a gaseous pressure product by cryogenic
separation of air, wherein, in a normal operation: charge air is
condensed, cooled and fed to a distillation column system, a
product fraction is withdrawn in a liquid state from the
distillation column system and is introduced into a liquid tank,
product liquid is removed from the liquid tank, via a pump set
having one or more parallel-connected individual pumps, is brought
in the liquid condition to an increased pressure, is evaporated in
an indirect heat exchange with a first heat transfer medium flow,
and is withdrawn as a gaseous pressure product, wherein, in an
emergency operation: product liquid is removed from the liquid
tank, is brought in the liquid condition to an increased pressure,
is evaporated in an indirect heat exchange with a second heat
transfer medium flow and is withdrawn as a gaseous pressure
product, and wherein in a bypass operation: the product fraction
withdrawn in a liquid state from the distillation column system is
guided past the liquid tank, is pressurized in the pump set in the
liquid condition to an increased pressure, is evaporated in an
indirect heat exchange, and is withdrawn as a gaseous pressure
product.
2. Method according to claim 1, wherein at least one individual
pump of the pump set has a first pump bypass, by way of which, in
the normal operation, at least at times, a portion of the product
liquid exiting from the pump is expanded and is returned into the
liquid tank, and wherein at least one individual pump, in addition
to the first pump bypass, has a second pump bypass, by way of
which, in the bypass operation, at least at times, a portion of the
product liquid exiting from the pump is expanded, is guided past
the liquid tank, and is returned into the distillation column
system.
3. Process according to claim 1, wherein the distillation column
system is constructed with two or more branches, the product
fraction being introduced from the two or more branches of the
distillation column system into the liquid tank.
4. Process according to claim 2, wherein the distillation column
system is constructed with two or more branches, the product
fraction being introduced from the two or more branches of the
distillation column system into the liquid tank.
5. System for obtaining a gaseous pressure product by cryogenic
separation of air having a distillation column system, a liquid
tank, a pump set having one or more parallel-connected individual
pumps, a main heat exchanger and an emergency supply heat
exchanger, and a regulating device which regulates the operation of
the system in a normal operation and in an emergency operation,
wherein, in the normal operation: charge air is condensed, cooled
and fed to the distillation column system, a product fraction is
withdrawn in a liquid state from the distillation column system and
is introduced into the liquid tank, product liquid is removed from
the liquid tank via the pump set, is brought in the liquid
condition to an increased pressure, is evaporated in the indirect
heat exchange with a first heat transfer medium flow in the main
heat exchanger, and is withdrawn as a gaseous pressure product, and
in the emergency operation: product liquid is removed from the
liquid tank, is brought in the liquid condition to an increased
pressure via the pump set, is evaporated in an indirect heat
exchange with a second heat transfer medium flow in the emergency
supply heat exchanger and is withdrawn as a gaseous pressure
product, and wherein in addition, the regulating device regulates
the operation of the system in a bypass operation such that, in the
bypass operation: the product fraction withdrawn in a liquid state
from the distillation column system is guided past the liquid tank,
is brought in the liquid condition to an increased pressure, is
evaporated in an indirect heat exchange, and is withdrawn as a
gaseous pressure product.
6. A system according to claim 5, wherein at least one individual
pump of the pump set has a first pump bypass, by way of which, in
the normal operation, at least at times, a portion of the product
liquid exiting from the pump is expanded and is returned into the
liquid tank, and wherein at least one individual pump, in addition
to the first pump bypass, has a second pump bypass, by way of
which, in the bypass operation, at least at times, a portion of the
product liquid exiting from the pump is expanded, is guided past
the liquid tank, and is returned into the distillation column
system.
7. A system according to claim 5, wherein the distillation column
system is constructed with two or more branches, the product
fraction being introduced from the two or more branches of the
distillation column system into the liquid tank.
8. A system according to claim 6, wherein the distillation column
system is constructed with two or more branches, the product
fraction being introduced from the two or more branches of the
distillation column system into the liquid tank.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] This application claims the priority of German Application
No.: 10 2004 015 348.5 filed on Aug. 17, 2004, the disclosure of
which is expressly incorporated by reference herein.
[0002] The invention relates to a process for obtaining a gaseous
pressure product by the cryogenic separation of air. Preferred
embodiments of the invention relate to such a process and system
wherein, in a normal operation: charge air is condensed, cooled and
fed to a distillation column system, a product fraction is
withdrawn in a liquid state from the distillation column system and
is introduced into a liquid tank, product liquid is removed from
the liquid tank via a pump set having one or more
parallel-connected individual pumps, is brought in the liquid
condition to an increased pressure, is evaporated in an indirect
heat exchange with a first heat transfer medium flow, and is
withdrawn as a gaseous pressure product, and wherein, in an
emergency operation: product liquid is removed from the liquid
tank, is brought in the liquid condition to an increased pressure,
is evaporated in an indirect heat exchange with a second heat
transfer medium flow and is withdrawn as a gaseous pressure
product,
[0003] Processes and systems for the cryogenic separation of air
are known, for example, from Hausen/Linde, "Tieftemperaturtechnik"
("Cryogenics"), 2nd Edition 1985, Chapter 4 (Pages 281 to 337). The
distillation column system of the invention may be constructed as a
single-column system for the nitrogen-oxygen separation, as a
two-column system (for example, as a classical Linde double-column
system) or as a three-column or multicolumn system. In addition to
the columns for the nitrogen-oxygen separation, it may have further
devices for obtaining other air constituents, particularly noble
gases, such as argon.
[0004] The process of the invention can be classified as one of the
internal-condensation processes. This means that, in the normal
operation, at least one of the products of the distillation column
system (for example, nitrogen from the single column of a
single-column system, from the high-pressure column of a two- or
three-column system and/or from the MDS or intermediate pressure
column of a three-column system--or as an alternative on in
addition. oxygen from the single column of a single-column system
or from the MDS or intermediate pressure column of a three-column
system and/or from the low-pressure column of a two-column or
three-column system) is taken in liquid form from one of the
columns of the three-column system or from a condenser connected
with one of these columns; is brought to an increased pressure in
the liquid condition; is evaporated or pseudo-evaporated (at a
supercritical pressure) in an indirect heat exchange with a first
heat transfer medium flow; and finally obtained as a gaseous
pressure product. The first heat transfer medium is frequently
formed by charge air and/or nitrogen. The indirect heat exchange
can take place in a separate heat exchanger or in the main heat
exchanger in which the cooling of the charge air also takes
place.
[0005] Internal condensation processes of this type are known, for
example, from German Patent Documents DE 830805, DE 901542 (=U.S.
Pat. No. 2,712,738/U.S. Pat. No. 2,784,572), DE 952908, DE 1103363
(=U.S. Pat. No. 3,083,544), DE 1112997 (=U.S. Patent Document US
32114925), DE 1124529, DE 1117616 (=U.S. Pat. No. 3,280,574), DE
1226616 (=U.S. Pat. No. 3,216,206), DE 1229561 (=U.S. Pat. No.
3,222,878), DE 1199293, DE 1187248 (=U.S. Pat. No. 3,371,496), DE
1235347, DE 1258882 (=U.S. Pat. No. 3,426,543), DE 1263037 (=U.S.
Pat. No. 3,401,531), DE 1501722 (=U.S. Pat. No. 3,416,323), DE
1501723 (=U.S. Pat. No. 3,500,651), DE 2535132 (=U.S. Pat. No.
4,279,631), DE 2646690, European Patent Document EP 93448 B1 (=U.S.
Pat. No. 4,555,256), European Patent Document EP 384483 B1 (=U.S.
Pat. No. 5,036,672), European Patent Document 505812 B1 (--U.S.
Pat. No. 5,263,328), European Patent Document 716280 B1 (=U.S. Pat.
No. 5,644,934), European Patent Document EP 842385 B1 (=U.S. Pat.
No. 5,953,937), European Patent Document EP 758733 B1 (=U.S. Pat.
No. 5,845,517) European Patent Document EP 895045 B1 (=U.S. Pat.
No. 6,038,885), German Patent Document DE 19803437 A1, European
Patent Document 949471 B1 (=U.S. Pat. No. 6,185,960 B1), European
Patent Document 955509 A1 (=U.S. Pat. No. 6,196,022 B1), European
Patent Document 1031804 A1 (=U.S. Pat. No. 6,314,755), German
Patent Document DE 19909744 A1, European Patent Document 1067345
A1=U.S. Pat. No. 6,336,345) European Patent Document 1074805 A1
(U.S. Pat. No. 6,332,337), German Patent Document 19954593 A1,
European Patent Document EP 1134525 A1 (=U.S. Pat. No. 6,477,860),
German Patent Document DE 10013073 A1, European Patent Documents EP
1139046 A1, EP 1146301 A1, EP 1150082 A1, EP 1213552 A1, German
Patent Document DE 10115258 A1, European Patent Document 1284404 A1
(=U.S. Patent Document US 2003051504 A1), European Patent Document
EP 1308680 A1 (=U.S. Pat. No. 6,612,129 B2), German Patent Document
DE 10213212 A1, German Patent Document 10213211 A1, European Patent
Document 1357342 A1 or German Patent Document DE 10238282 A1.
[0006] The pressure increase in the liquid can be achieved by any
known measure, for example, by means of a pump, the utilization of
a hydrostatic potential, and/or the pressure build-up evaporation
in a tank.
[0007] Here, the term "evaporating" includes a pseudo-evaporation
under a supercritical pressure. The pressure to which the product
liquid is pressurized can therefore also be above the critical
pressure; as may the pressure of the heat transfer medium which is
(pseudo)condensed against the nitrogen.
[0008] From European Patent Document EP 895045 B1 (=U.S. Pat. No.
6,038,885), it is known to utilize a liquid tank and connected
devices for increasing the pressure in the liquid tank for the
internal condensation as well as for an emergency operation which,
in the event of a failure of the distillation column system,
permits a continuation of the delivery of gaseous pressure product.
In the emergency operation, the pressurized product liquid is
evaporated against another second heat transfer medium flow,
normally in an atmospheric or in a water bath evaporator. This
integration has many advantages. However, if maintenance or
revision work becomes necessary at the liquid tank, the entire
system has to be switched off, and neither the normal nor the
emergency operation can be implemented.
[0009] It is therefore an object of the invention to further
increase the utility of the above-described system.
[0010] This object is achieved in that, in the case of the process
of the invention, a third operating condition, the bypass
operation, is provided. Here, the product fraction withdrawn in a
liquid state from the distillation column system is guided past the
liquid tank, is pressurized in the pump set in the liquid condition
to an increased pressure, is evaporated in the indirect heat
exchange with a first heat transfer medium flow and is withdrawn as
a gaseous pressure product. For the pressure increase and the
evaporation basically separate devices can be provided. However, as
a rule, it is more advantageous in the bypass operation to utilize
the same devices for this purpose (for example, pumps and heat
exchangers) and the same heat transfer medium flow as in the normal
operation.
[0011] Thus, within the scope of the invention, the internal
condensation can also be continued during times in which the tank
is not available. The system can continue to supply gaseous
pressure product. However, the bypass operation can also be
utilized at temporary fluctuations of the purity of the liquid
product fraction from the distillation column system in order to
prevent a contamination of the product stored in the liquid tank;
in this case also, it may be favorable to bypass the tank in the
manner according to the invention.
[0012] The devices for the pressure increase in the liquid
condition mostly consist of pumps. In principle, it is conceivable
to use a single pump. However, for reasons of redundancy, a pump
set is frequently used, that is, a plurality of pumps connected in
parallel. In this case, a pump set may have approximately two or
three pumps with a 50% capacity respectively; in the case of three
(or more) pumps, one is only held in a standby position in order to
take over the task of one of the other pumps in the event of a
disturbance of their operation.
[0013] Irrespective of their number, the pump quantity delivery is
generally regulated by one pump bypass respectively per individual
pump, by means of which the excess quantity of pumped liquid is
expanded and is returned into the liquid tank.
[0014] In the event that the pressure increase in the liquid
condition in the normal operation is carried out in a pump set
which has one or more parallel-connected individual pumps, at least
one individual pump having a first pump bypass by way of which at
least at times a portion of the product liquid exiting from the
pump is expanded and returned into the liquid tank, and that the
same pump set is utilized also in the bypass operation for the
pressure increase in the liquid condition, it is therefore
advantageous, for at least one individual pump, to have, in
addition to the first pump bypass, a second pump bypass by way of
which in the bypass operation, at least at times, a portion of the
product liquid exiting from the pump is expanded, is guided past
the liquid tank and is returned to the inlet of the pump set.
Preferably several or all pumps of the pump set each have a first
and a second pump bypass in the above-mentioned sense.
[0015] The invention can also be applied to multibranch
distillation column systems which have a common liquid tank, as
described in German Patent Application 102004006283, which is no
prior publication, and the applications corresponding thereto. In
this case, the product fraction is introduced from two or more
branches of the distillation column system into the liquid tank.
The liquid tank as well as the devices for the pressure increase
are jointly utilized by the two or two or more branches of the
distillation column system.
[0016] The invention as well as additional details of the invention
will be explained in the following by means of an embodiment
schematically illustrated in the drawing.
[0017] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The single drawing figure schematically depicts a system
constructed according to preferred embodiments of the present
invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0019] From an air separation system 1, which has a "distillation
column system", a "product fraction" 2 is withdrawn in a liquid
state. In the example shown, the distillation column system is
constructed as a 2-column system with a high-pressure column and a
low-pressure column, and the product fraction 2 is formed by liquid
oxygen from the sump of the low-pressure column.
[0020] A schematically depicted control unit CU is operable to
control the valves of the system to carry out the processes
described herein.
[0021] In the normal operation, the liquid oxygen 2 is fed through
an opened valve 51 by way of a pipe 3 into a liquid tank 4.
Simultaneously, liquid oxygen 5 is withdrawn from the liquid tank
(valve 52 is also opened) and is fed to a pump set 6 which consists
of a single pump or of several parallel-connected individual pumps.
There, the liquid is brought to approximately the desired product
pressure and is guided by way the pipe 7 (valve 53 open) to a first
evaporator 8, and is evaporated there against a "first heat
transfer medium flow". The latter is preferably formed by a
correspondingly highly condensed flow of charge air for the air
separation system 1, or by a high-pressure nitrogen from the air
separation system 1. In the embodiment shown, the evaporator 8 is
formed by the main heat exchanger of the air separation system 1,
in which is charge air is cooled to the fractionating temperature.
As an alternative, it can also be constructed as a heat exchanger,
such as a secondary condenser, separated from the main heat
exchanger. By way of the pipe 9, oxygen exits as a gaseous pressure
product and can be fed to a consuming device or a distributing
system.
[0022] A pump bypass 10 is used for regulating the pumped quantity.
By way of this pipe and a throttle valve 54, as a rule, a portion
of the pumped quantity is returned into the liquid tank 4. Only one
pump bypass 10 is illustrated in the drawing. If the pump set 6
consists of more than a single pump, each individual pump has a
separate pipe with a separate throttle valve and shut-off
valve.
[0023] If the air separation system 1 fails as a result of a
planned or unplanned operational interruption, the system is
switched to an emergency operation. For this purpose, valves 51 and
53 are closed and valve 61 is opened. As a result, liquid oxygen
stored in the liquid tank 4 flows by way of a pipe 60 to a second
evaporator 62 which evaporates by means of a "second heat transfer
medium flow" which differs from the first heat transfer medium
flow. The second evaporator 62 is constructed, for example, as an
atmospheric evaporator or as a water bath evaporator. In the
emergency operation, oxygen leaves the system as a gaseous pressure
product by way of the pipe 63 and is guided to a consuming device
or a distributing system.
[0024] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *