U.S. patent application number 17/142217 was filed with the patent office on 2021-07-08 for air separation system.
This patent application is currently assigned to L'Air Liquide, Societe Anonyme pour l'Etude et l'Exploitation des Procedes Georges Claude. 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 Takuya KANEDA, Hiromu MORI.
Application Number | 20210207885 17/142217 |
Document ID | / |
Family ID | 1000005342224 |
Filed Date | 2021-07-08 |
United States Patent
Application |
20210207885 |
Kind Code |
A1 |
KANEDA; Takuya ; et
al. |
July 8, 2021 |
AIR SEPARATION SYSTEM
Abstract
The air separation system can include: a process control unit
201 for controlling components constituting the air separation
system; an oxygen concentration estimating unit 202 for estimating,
by calculation, the oxygen concentration of oxygen-enriched liquid
that accumulates in a column bottom portion of the higher-pressure
column; a flow rate estimating unit for estimating, by calculation,
the flow rate of oxygen-enriched liquid that has been discharged
from the column bottom portion of the higher-pressure column and
that is to be introduced into a distillation portion of the
lower-pressure column; and a target temperature calculating unit
for calculating a target temperature of an argon extraction portion
on the basis of the flow rate of feed air that has passed through
at least a portion of the main heat exchanger 1 and that is to be
sent to an expansion turbine, the oxygen concentration of the
oxygen-enriched liquid, and the flow rate of the oxygen-enriched
liquid.
Inventors: |
KANEDA; Takuya; (KOBE,
JP) ; MORI; Hiromu; (TAHARA, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
L'Air Liquide, Societe Anonyme pour I'Etude et I'Exploitation des
Procedes Georges Claude |
Paris |
|
FR |
|
|
Assignee: |
L'Air Liquide, Societe Anonyme pour
l'Etude et l'Exploitation des Procedes Georges Claude
Paris
FR
|
Family ID: |
1000005342224 |
Appl. No.: |
17/142217 |
Filed: |
January 5, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25J 3/0409 20130101;
F25J 3/04412 20130101; F25J 2280/50 20130101; F25J 3/04678
20130101 |
International
Class: |
F25J 3/04 20060101
F25J003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 6, 2020 |
JP |
2020-000482 |
Claims
1. An air separation system comprising: a main heat exchanger; a
higher-pressure column into which feed air that has passed through
the main heat exchanger is introduced, a first condensing unit for
condensing gas discharged from a column top portion of the
higher-pressure column, a lower-pressure column into which
oxygen-enriched liquid discharged from a column bottom portion of
the higher-pressure column is introduced, and a crude argon column
into which an argon-containing oxygen-enriched gas-liquid substance
discharged from an argon extraction portion, which is an
intermediate stage of a distillation portion of the lower-pressure
column, is introduced, and also provided with: a process control
unit for controlling components constituting the air separation
system; an oxygen concentration estimating unit for estimating, by
calculation, the oxygen concentration of the oxygen-enriched liquid
that accumulates in the column bottom portion of the
higher-pressure column; a flow rate estimating unit for estimating,
by calculation, the flow rate of the oxygen-enriched liquid that
has been discharged from the column bottom portion of the
higher-pressure column and that is to be introduced into the
distillation portion of the lower-pressure column; and a target
temperature calculating unit for calculating a target temperature
of the argon extraction portion on the basis of the flow rate of
the feed air that has passed through at least a portion of the main
heat exchanger and that is to be sent to the expansion turbine, the
oxygen concentration of the oxygen-enriched liquid, and the flow
rate of the oxygen-enriched liquid.
2. The air separation system according to claim 1, wherein the
process control unit is configured to control a replenishment
amount flow rate of liquid nitrogen, and/or the flow rate of reflux
liquid, such that the measured temperature of the argon extraction
portion reaches the target temperature.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn. 119 (a) and (b) to Japanese patent application No.
JP2020-000482, filed Jan. 6, 2020, the entire contents of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to an air separation system
for improving the extraction rate of product argon.
BACKGROUND OF THE INVENTION
[0003] Conventionally, an oxygen-enriched gas-liquid substance
containing argon, extracted from an air separating device, is sent
to an argon distillation column from which high-purity product
argon is withdrawn.
[0004] For example, French Patent Publication No. 2964451 discloses
an air separating device for the production of products such as
oxygen, nitrogen and argon. The air separation device comprises a
plurality of distillation columns for efficiently producing these
products, such as a high pressure distillation column, a low
pressure distillation column, and a crude argon distillation
column.
SUMMARY OF THE INVENTION
[0005] Conventionally, the extraction rate of product argon is
controlled by controlling the concentration of oxygen in
oxygen-enriched liquid that accumulates in an intermediate stage of
the lower-pressure column of the air separating device, to a
predetermined concentration.
[0006] However, since the state of the lower-pressure column of the
air separating device varies in accordance with changes in
production quantities, such as the quantity of withdrawn product
oxygen or the quantity of withdrawn product nitrogen from the air
separating device, the extraction rate of high-purity product argon
that can be withdrawn from the final stage argon distillation
column varies greatly.
[0007] In view of the circumstances described hereinabove, the
objective of the present invention is to provide an air separation
system with which the extraction rate of high-purity product argon
that can be withdrawn from the argon distillation column can be
improved, even if production quantities such as the quantity of
withdrawn product oxygen or the quantity of withdrawn product
nitrogen change.
[0008] The inventors of the present invention found that nitrogen
(gaseous, liquid, or a mixture thereof) contaminates an argon
extraction portion (intermediate stage of distillation portion of
lower-pressure column of air separating device) for extracting an
oxygen-enriched gas-liquid mixture containing argon, as a result of
changes in the state of the lower-pressure column of the air
separating device concomitant with changes in production quantities
such as the quantity of withdrawn product oxygen or the quantity of
withdrawn product nitrogen from the air separating device. Nitrogen
contamination causes the extraction rate of high-purity product
argon that can be withdrawn from the final stage argon distillation
column to fluctuate greatly and to decrease. Accordingly, the
inventors of the present invention created a novel configuration in
order to resolve the abovementioned problem.
[0009] The air separation system of certain embodiments of the
present invention is provided with: a main heat exchanger (1); a
higher-pressure column (2) into which feed air that has passed
through the main heat exchanger (1) is introduced; a first
condensing unit (3) for condensing gas discharged from a column top
portion (23) of the higher-pressure column (2); a lower-pressure
column (4) into which oxygen-enriched liquid discharged from a
column bottom portion (21) of the higher-pressure column (2) is
introduced; crude argon columns (5, 6) into which an
argon-containing oxygen-enriched gas-liquid substance discharged
from an argon extraction portion, which is an intermediate stage of
a distillation portion of the lower-pressure column (4), is
introduced; and a pure argon distillation column (8) into which an
argon-enriched gas-liquid substance discharged from a distillation
portion (intermediate stage or upper portion) or a column top
portion of the pure argon distillation columns (5, 6) is
introduced.
[0010] The crude argon columns may be separate or may be configured
from a single column.
[0011] In another embodiment, the air separation system can
include: a process control unit (201) for controlling components
(such as the temperatures of heat exchangers, opening and closing
of valves, flow regulating valves, pressure regulating valves,
compressors, expansion turbine) constituting the air separation
system; an oxygen concentration estimating unit (202) for
estimating, by calculation, the oxygen concentration (EC_0.sub.2)
of the oxygen-enriched liquid that accumulates in the column bottom
portion (21) of the higher-pressure column (2); a flow rate
estimating unit (203) for estimating, by calculation, the flow rate
(EF_0.sub.2) of the oxygen-enriched liquid that has been discharged
from the column bottom portion (21) of the higher-pressure column
(2) and that is to be introduced into the distillation portion of
the lower-pressure column (3); a target temperature calculating
unit (204) for calculating a target temperature (T) of the argon
extraction portion on the basis of the flow rate (F_FA) of the feed
air that has passed through at least a portion of the main heat
exchanger (1) and that is to be sent to an expansion turbine (10),
the oxygen concentration (EC-0.sub.2) of the oxygen-enriched
liquid, and the flow rate (EF_0.sub.2) of the oxygen-enriched
liquid; and a memory (208) for storing various types of data.
[0012] The target temperature calculating unit (204) may calculate
the target temperature (T) using a statistical method such as
multivariate analysis or regression analysis.
[0013] The process control unit may control the replenishment
amount flow rate (flowmeter F101 and valve 13) of liquid nitrogen,
and/or the flow rate (flowmeter F102 and valve V12) of reflux
liquid discharged from the column top portion (23) of the
higher-pressure column (2), such that the measured temperature
(T-Ar) of the argon extraction portion reaches a target temperature
(Tt).
[0014] The oxygen concentration estimating unit (202) can estimate
the oxygen concentration (EC_0.sub.2) of the oxygen-enriched liquid
by calculating the material balance in the higher-pressure column
(2).
[0015] The flow rate estimating unit (203) can estimate the flow
rate (EF_0.sub.2) of the oxygen-enriched liquid by calculating the
degree of opening of a valve which supplies the oxygen-enriched
liquid to the lower-pressure column (3), and the pressure
difference before and after the valve.
[0016] Nitrogen contamination of the argon extraction portion can
be prevented, and the argon extraction rate improved, by detecting
a decrease in the temperature of the argon extraction portion
resulting from a fluctuation in the operating pressure in the
lower-pressure column, or a decrease in the temperature of the
argon extraction portion due to other causes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Further developments, advantages and possible applications
of the invention can also be taken from the following description
of the drawing and the exemplary embodiments. All features
described and/or illustrated form the subject-matter of the
invention per se or in any combination, independent of their
inclusion in the claims or their back-references.
[0018] [FIG. 1] is a drawing illustrating a first embodiment of an
air separation system.
[0019] [FIG. 2] is a drawing illustrating an example of the control
elements of the air separation system in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Several modes of embodiment of the present invention will be
described below. The modes of embodiment described below are
exemplary descriptions of the present invention. The present
invention is in no way limited by the following modes of
embodiment, and also includes a number of variant modes which are
implemented within a scope that does not alter the essential point
of the present invention. It should be noted that the constituent
elements described below are not all limited to being essential
constituent elements of the present invention.
[0021] The air separation system in embodiment 1 will be described
with reference to FIG. 1.
[0022] The air separation system is provided with: the main heat
exchanger 1; the higher-pressure column 2 into which feed air that
has passed through the main heat exchanger 1 is introduced via a
pipeline L1; the first condensing unit (nitrogen condenser) 3 for
condensing higher-pressure column distillate discharged through a
pipeline L231 from the column top portion 23 of the higher-pressure
column 2; and the lower-pressure column 4 into which
oxygen-enriched liquid discharged from the column bottom portion 21
of the higher-pressure column 2 is introduced.
[0023] Feed air introduced into the main heat exchanger 1 branches
off midway through the main heat exchanger 1 and is sent to the
expansion turbine 10 via a branched pipeline L11, and is discharged
from the expansion turbine 10 and sent to an intermediate stage 423
of a distillation portion 42 of the lower-pressure column 4.
[0024] The flow rate (F_FA) of the feed air sent to the expansion
turbine 10 is measured using a flowmeter (F103). Measured data are
sent to a control device 200 and are stored as time-series data in
the memory 208.
[0025] A liquid surface level gauge (L101) for measuring the liquid
surface height of oxygen-enriched liquid is provided in the column
bottom portion 21 of the higher-pressure column 2. Measured data
are sent to a control device 200 and are stored as time-series data
in the memory 208.
[0026] The oxygen-enriched liquid discharged from the column bottom
portion 21 is subjected to heat exchange in a heat exchanger E5,
and is then introduced via a pipeline L2 into a distillation stage
that is the same as, or vertically close to, the intermediate stage
423 of the distillation portion 42 of the lower-pressure column 4
into which the feed air discharged from the expansion turbine 10 is
introduced. A control valve V11 is provided in the pipeline L2, and
the control valve V11 is controlled by the control device 1 in
accordance with the measured data from the liquid surface level
gauge (L101), thereby regulating the amount of oxygen-enriched
liquid that is introduced.
[0027] A flowmeter (F104) for measuring the flow rate (F_0.sub.2)
of the oxygen-enriched liquid that has been discharged from the
column bottom portion 21 of the higher-pressure column 2 and that
is to be introduced into the distillation portion 42 of the
lower-pressure column 4 is provided in the pipeline L2. Measured
data are sent to a control device 200 and are stored as time-series
data in the memory 208.
[0028] A pressure gauge (P101) is provided in the column top
portion 23 of the higher-pressure column 2 to measure the pressure
in the column top portion 23. Measured data are sent to a control
device 200 and are stored as time-series data in the memory
208.
[0029] Higher-pressure column distillate (reflux liquid) discharged
through a pipeline L25 from the column top portion 23 of the
higher-pressure column 2 is sent to the main heat exchanger 1.
[0030] A thermometer (T101) for measuring the distillation
atmosphere temperature is provided in the position of the
intermediate stage 422 of the distillation portion 42 of the
lower-pressure column 4 (below the intermediate stage 423 and above
the argon extraction portion 421). An argon-containing
oxygen-enriched gas-liquid substance is introduced via a pipeline
L42 from the argon extraction portion 421, which is the
distillation stage below the intermediate stage 422, into a column
bottom portion 51 of a first crude argon column 5, or below an
intermediate stage of a distillation portion 52 thereof.
[0031] A lower-pressure column distilled gas-liquid substance
discharged through a pipeline L3 from an upper portion of the
distillation portion 42 of the lower-pressure column 4 or from a
column top portion 44 thereof is subjected to heat exchange in the
heat exchanger E5, and is then sent to the main heat exchanger 1. A
pressure gauge (P102) is provided in the pipeline L3 to measure the
pressure of the lower-pressure column distilled gas-liquid
substance. Measured data are sent to a control device 200 and are
stored as time-series data in the memory 208.
[0032] The pipeline L3 merges with the pipeline L33 ahead of the
heat exchanger E5, and vaporised gas-liquid substance discharged
from an upper portion of the first condenser 3 merges and is sent
together to the heat exchanger E5.
[0033] A lower-pressure column top portion distillate discharged
through a pipeline L5 from the column top portion 44 of the
lower-pressure column 4 is subjected to heat exchange in the heat
exchanger E5, and is then sent to the main heat exchanger 1.
[0034] A higher-pressure column distillate (reflux liquid)
discharged through a pipeline L23 from the column top portion 23 of
the higher-pressure column 2 is subjected to heat exchange in the
heat exchanger E5, and is then sent to the column top portion 44 of
the lower-pressure column 4. A flowmeter (F102) for measuring the
flow rate of the higher-pressure column distillate, and a control
valve V12, are provided in the pipeline L23. Measured data are sent
to a control device 200 and are stored as time-series data in the
memory 208. The control valve V12 is controlled by the control
device 200 in accordance with the measured data from the flowmeter
(F102), thereby regulating the amount of higher-pressure column
distillate (reflux liquid) that is introduced.
[0035] Supplementary liquid nitrogen (LIN) is sent to the column
top portion 44 of the lower-pressure column 4 via a pipeline L43. A
flowmeter (F101) for measuring the flow rate of the liquid
nitrogen, and a control valve V13, are provided in the pipeline
L43. Measured data are sent to a control device 200 and are stored
as time-series data in the memory 208. The control valve V13 is
controlled by the control device 200 in accordance with the
measured data from the flowmeter (F103), thereby regulating the
amount of liquid nitrogen that is introduced.
[0036] A gas-liquid substance discharged through a pipeline L4 from
a column bottom portion 41 of the lower-pressure column 4 and a
gas-liquid substance discharged through a pipeline L31 from a top
portion of the first condenser 3 merge and are sent to the main
heat exchanger 1.
[0037] Further, the air separation system is provided with: the
first crude argon column 5 in which the argon-containing
oxygen-enriched gas-liquid substance discharged from the argon
extraction portion 421 of the lower-pressure column 4 is introduced
via the pipeline L42 into the column bottom portion 51, or below
the intermediate stage of the distillation portion 52; and a second
crude argon column 6 in which an argon-enriched gas-liquid
substance discharged via a pipeline L53 from a column bottom
portion 53 of the first crude argon column 5 is introduced into a
column bottom portion 61, or below an intermediate stage of a
distillation portion 62.
[0038] Further, the air separation system is provided with: a third
condenser 7 for condensing second crude argon distillate discharged
from a column top portion 63 of the second crude argon column 6;
and a pure argon distillation column 8 in which a
high-argon-enriched gas-liquid substance discharged through a
pipeline L63 from the column top portion 63 of the second crude
argon column 6 is introduced into an intermediate stage of a
distillation portion 82.
[0039] The argon content concentrations have the following
relationship.
[0040] Argon-containing oxygen-enriched gas-liquid
substance<argon-enriched gas-liquid substance <second crude
argon distillate<high-argon-enriched gas-liquid substance
[0041] A fourth condenser 83 is provided above the distillation
portion 82 of the pure argon column 8 to condense high-purity argon
liquid discharged from a column bottom portion 81. The high-purity
argon liquid discharged from the column bottom portion 81 of the
pure argon column 8 is subjected to heat exchange in a heat
exchanger E6 (or reboiler) and is returned to the column bottom
portion 81. The high-purity argon liquid discharged from the column
bottom portion 81 of the pure argon column 8 is withdrawn as
product argon and is sent to a product tank.
[0042] Valves (such as gate valves, flow-regulating valves, and
pressure regulating valves) may be provided in the pipelines and in
the lines shown in FIG. 1.
[0043] Further, compressors, pressure regulating devices, flow rate
control devices or the like may be provided as necessary in each
pipeline to perform pressure regulation or flow rate
regulation.
[0044] The control device 200 in FIG. 2 will next be described.
[0045] The control device 200 includes a process control unit 201,
an oxygen concentration estimating unit 202, a flow rate estimating
unit 203, a target temperature calculating unit 204, and a memory
208 for storing various types of data (such as setting data,
process data, and the measured data discussed hereinabove).
[0046] The process control unit 201 controls components
constituting the air separation system (such as the temperatures of
the heat exchangers, opening and closing of the valves, the flow
regulating valves, the pressure regulating valves, the compressors,
and the expansion turbine).
[0047] The oxygen concentration estimating unit 202 estimates the
oxygen concentration (EC_0.sub.2) of the oxygen-enriched liquid
that accumulates in the column bottom portion 21 of the
higher-pressure column 2.
[0048] The flow rate estimating unit 203 estimates, by calculation,
the flow rate (EF_0.sub.2) of the oxygen-enriched liquid that has
been discharged from the column bottom portion 21 of the
higher-pressure column 2 and that is to be introduced into the
distillation portion 42 of the lower-pressure column 4.
[0049] The target temperature calculating unit 204 calculates the
target temperature (Tt) of the argon extraction portion 421 on the
basis of flow rate (F_FA) of the feed air that has passed through
at least a portion of the main heat exchanger 1 and that is to be
sent to the expansion turbine 10, the oxygen concentration
(EC-0.sub.2) of the oxygen-enriched liquid, and the flow rate
(EF_0.sub.2) of the oxygen-enriched liquid. The target temperature
calculating unit 204 calculates the target temperature (Tt) using a
statistical method such as multivariate analysis or regression
analysis.
[0050] The process control unit 201 controls the replenishment
amount flow rate (flowmeter F101 and valve V13) of liquid nitrogen,
and/or the flow rate (flowmeter F102 and valve V12) of the
higher-pressure column distillate (reflux liquid) discharged from
the column 23 of the higher-pressure column 2, such that the
measured temperature (T101) of the argon extraction portion 421
reaches the target temperature (Tt).
[0051] The effect on the argon extraction rate was verified using
the configuration in FIG. 1.
[0052] Comparative example: Process control to keep the
concentration of the oxygen-enriched liquid constant was performed
as in a conventional case.
[0053] Exemplary embodiment: Control was performed such that the
temperature of the argon extraction portion reached the target
temperature.
[0054] An improvement in the argon extraction rate of 9% on average
was seen using the exemplary embodiment exhibited compared with the
comparative example.
[0055] While the invention has been described in conjunction with
specific embodiments thereof, it is evident that many alternatives,
modifications, and variations will be apparent to those skilled in
the art in light of the foregoing description. Accordingly, it is
intended to embrace all such alternatives, modifications, and
variations as fall within the spirit and broad scope of the
appended claims. The present invention may suitably comprise,
consist or consist essentially of the elements disclosed and may be
practiced in the absence of an element not disclosed. Furthermore,
if there is language referring to order, such as first and second,
it should be understood in an exemplary sense and not in a limiting
sense. For example, it can be recognized by those skilled in the
art that certain steps can be combined into a single step.
[0056] The singular forms "a", "an" and "the" include plural
referents, unless the context clearly dictates otherwise.
[0057] "Comprising" in a claim is an open transitional term which
means the subsequently identified claim elements are a nonexclusive
listing (i.e., anything else may be additionally included and
remain within the scope of "comprising"). "Comprising" as used
herein may be replaced by the more limited transitional terms
"consisting essentially of" and "consisting of" unless otherwise
indicated herein.
[0058] "Providing" in a claim is defined to mean furnishing,
supplying, making available, or preparing something. The step may
be performed by any actor in the absence of express language in the
claim to the contrary.
[0059] Optional or optionally means that the subsequently described
event or circumstances may or may not occur. The description
includes instances where the event or circumstance occurs and
instances where it does not occur.
[0060] Ranges may be expressed herein as from about one particular
value, and/or to about another particular value. When such a range
is expressed, it is to be understood that another embodiment is
from the one particular value and/or to the other particular value,
along with all combinations within said range.
[0061] All references identified herein are each hereby
incorporated by reference into this application in their
entireties, as well as for the specific information for which each
is cited.
LIST OF REFERENCE NUMERALS
[0062] 1 Main heat exchanger [0063] 2 Higher-pressure column [0064]
21 Column bottom portion [0065] 22 Distillation portion [0066] 23
Column top portion [0067] 3 First condenser [0068] 4 Lower-pressure
column [0069] 41 Column bottom portion [0070] 42 Distillation
portion [0071] 44 Column top portion [0072] 5 First crude argon
column [0073] 6 Second crude argon column [0074] 7 Third condenser
[0075] 8 Pure argon column [0076] 83 Fourth condenser [0077] 10
Expansion turbine [0078] E5 Heat exchanger [0079] E6 Heat
exchanger
* * * * *