U.S. patent application number 17/424555 was filed with the patent office on 2022-03-03 for process and apparatus for supplying a backup gas under pressure.
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 Alain BRIGLIA.
Application Number | 20220065528 17/424555 |
Document ID | / |
Family ID | |
Filed Date | 2022-03-03 |
United States Patent
Application |
20220065528 |
Kind Code |
A1 |
BRIGLIA; Alain |
March 3, 2022 |
PROCESS AND APPARATUS FOR SUPPLYING A BACKUP GAS UNDER PRESSURE
Abstract
The present invention relates to a process and a system for
supplying a backup gas at a higher pressure from a source gas at a
lower pressure. The backup gas at the lower pressure is at least
partially condensed against a backup liquid at a higher pressure in
a reprocessing heat exchanger and as a result, the backup liquid is
at least partially vaporized. The backup liquid at the higher
pressure is formed from boosting liquefied backup gas at the lower
pressure. A backup vaporizer is disposed downstream of the
reprocessing heat exchanger to completely vaporize the backup
liquid at a higher pressure before it was delivered to the
customer. The present invention eliminates the use of costly gas
compressor and mitigates associated safety risks, in particular
when the backup gas is oxygen.
Inventors: |
BRIGLIA; Alain; (Hangzhou,
CN) |
|
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
|
Appl. No.: |
17/424555 |
Filed: |
January 25, 2019 |
PCT Filed: |
January 25, 2019 |
PCT NO: |
PCT/CN2019/073114 |
371 Date: |
July 21, 2021 |
International
Class: |
F25J 1/02 20060101
F25J001/02; F25J 1/00 20060101 F25J001/00 |
Claims
1-14. (canceled)
15. A process for supplying a backup gas at an elevated pressure,
comprising: a) providing a source of backup gas at a first
pressure; b) providing at least a reprocessing heat exchanger, a
backup vaporizer and a liquid pump; c) heat-exchange between the
backup gas at the first pressure and a backup liquid at a second
pressure in the reprocessing heat exchanger to produce the at least
partially liquefied backup gas at the first pressure and the at
least partially vaporized backup liquid at the second pressure; d)
warming up the at least partially vaporized backup liquid at the
second pressure in the backup vaporizer to produce the backup gas
at an elevated pressure; and wherein the second pressure is higher
than the first pressure, and the backup liquid at the second
pressure is obtained from elevating the pressure of the liquefied
backup gas to the second pressure with the liquid pump.
16. The process as claimed in claim 15, further comprising an
expansion valve and a liquid storage tank, wherein the at least
partially liquefied back-up gas at the first pressure is expanded
through the expansion valve before entering the liquid storage
tank.
17. The process as claimed in claim 15, further
comprising:by-passing part of the back-up liquid at the second
pressure from the reprocessing heat exchanger through a by-pass
circuit.
18. The process as claimed in claim 15, wherein the pressure ratio
of the second pressure to the first pressure is in the range of 1
to 3 bar(a).
19. The process as claimed in claim 18, wherein the pressure ratio
of the second pressure to the first pressure is in the range of 1.2
to 2.5 bar(a).
20. The process as claimed in claim 15, wherein the back-up gas and
the back-up liquid comprise oxygen.
21. A system for supplying a back-up gas at an elevated pressure,
comprising: a) a reprocessing heat exchanger, a back-up vaporizer
and a liquid pump; b) a first conduit for delivering a back-up gas
at a first pressure into a warm end of the reprocessing heat
exchanger and a second conduit for transporting an at least
partially liquefied back-up gas at a first pressure from the cold
end of the reprocessing heat exchanger into the liquid pump; c) a
third conduit for delivering a back-up liquid at a second pressure
from the outlet of the liquid pump into a cold end of the
reprocessing heat exchanger; d) a fourth conduit for transporting
an at least partially vaporized back-up liquid at a second pressure
from a warm end of the reprocessing heat exchanger to the back-up
vaporizer; e) a fifth conduit for supplying the back-up gas at an
elevated pressure from the back-up vaporizer, and wherein the
second pressure is higher than the first pressure.
22. The system as claimed in claim 21, wherein an expansion valve
and a liquid storage tank are in fluid communication with the
second conduit.
23. The system as claimed in claim 21, the reprocessing heat
exchanger having separate flow channels for the back-up gas at the
first pressure and the back-up liquid at the second pressure,
further comprising a by-pass circuit, with one end connecting to
the flow channel for the back-up liquid at the second pressure
inside the reprocessing heat exchanger and one end connecting to
the fourth conduit.
24. The system as claimed in claim 23, further comprising a
flow-control valve disposed on the by-pass circuit.
25. The system as claimed in claim 23, the reprocessing heat
exchanger comprises aluminum plate fin exchanger or printed plate
exchanger.
26. The system as claimed in claim 21, wherein a pressure ratio of
the second pressure to the first pressure is in the range of 1 to 3
bar(a).
27. The system as claimed in claim 26, wherein a pressure ratio of
the second pressure to the first pressure is in the range of 1.2 to
2.5 bar(a).
28. The system as claimed in claim 21, wherein the back-up gas and
the back-up liquid comprise oxygen.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a .sctn. 371 of International PCT
Application PCT/CN2019/073114, filed Jan. 25, 2019, which is herein
incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a process and a system for
supplying a backup gas, in particular a backup gas at an elevated
pressure.
BACKGROUND OF THE INVENTION
[0003] In industries such as petrochemical industry, steel
industry, glass industry or coal gasification, large quantities of
gases, including oxygen, nitrogen, hydrogen, argon and so forth are
often requested. These gases maybe supplied through on-site gas
production facilities, such as an air separation unit. Inevitably,
normal production of gaseous production is disrupted upon occasion
by events such as purity upset, scheduled or non-scheduled
shutdowns, or other reasons. Thus, the delivery of gaseous products
to the customer needs to be maintained by a backup system that may
include one or more liquid storage tanks, pumps, or a backup
vaporizer of various types. In some cases, backup gases maybe
supplemented from a network of gas-transporting pipelines.
[0004] Various industrial applications require gases at different
pressure. For instance, the pressure of gaseous products from an
ASU facility or in a pipeline network is commonly below 20.about.30
bara, while partial oxidation reactors could require gases at above
70 bara.
[0005] To comply with such constraints, a backup system needs to
provide gases at elevated pressure, thus a costly gas turbine has
to be employed to raise the pressure of the gaseous product to a
desire level.
[0006] U.S. Pat. No. 7,409,835B2 discloses a method and a system
for reducing pressure fluctuation in the supply of pressurized
gaseous products to consumers during a switch from a normal
operation mode to a standby mode of an air separation unit. In
addition to a normally operating heat exchanger, a backup heat
exchanger is maintained at a cold standby by diverting a small
portion of liquefied gas stream through it. As a result, switching
between the two modes can be effected with low energy consumption
and a fast response time.
[0007] US2008/0184736A1 describes a method for the emergency backup
supply of a gas under pressure by vaporization of a pressurized
liquid, this gas normally being supplied by vaporization of liquid
in a first exchanger of a pumped air separation unit, during the
step of operating a second exchanger in order to produce the
make-up gas, pressurized liquid and high-pressure air continue to
be sent to the first exchanger.
SUMMARY OF THE INVENTION
[0008] During disruption of normal operation in industrial gas
production facilities, a backup system and process to ensure
delivery of pressurized gases within a small pressure fluctuation
is necessary. In addition to liquid storage tanks, pumps or backup
vaporizers, backup gases may also be provided from nearby air
separation unit or pipeline networks.
[0009] When the pressure of gases from the above sources is lower
than that required at the customer's site, they cannot be supplied
directly to the customer; instead, their pressure needs to be
raised by a gas compressor or a booster. Additional gas compressors
increase capital and operational cost of the backup system, and may
also carry certain safety concerns, especially when compressing
oxygen.
[0010] The objective of certain embodiments of the present
invention is to eliminate the use of a gas compressor or a booster
in a backup system, even when the output pressure of the gases
needs to be higher, or even significantly higher than the pressure
of the source gases.
[0011] In one aspect, the present invention discloses a process for
supplying a backup gas at an elevated pressure, comprising the
following steps: providing a source of backup gas at a first
pressure; providing at least a reprocessing heat exchanger, a
backup vaporizer and a liquid pump; then heat-exchange between the
backup gas at the first pressure and a backup liquid at a second
pressure in the reprocessing heat exchanger to produce the at least
partially liquefied backup gas at the first pressure and the at
least partially vaporized backup liquid at the second pressure;
followed up by warming up the at least partially vaporized backup
liquid at the second pressure in the backup vaporizer to produce
the backup gas at an elevated pressure. In this process, the second
pressure is higher than the first pressure, and the backup liquid
at the second pressure is obtained by elevating the liquefied
backup gas to the second pressure with the liquid pump.
[0012] The above process may also comprise a step of expanding the
at least partially liquefied backup gas at the first pressure
through an expansion valve. With the provision of a liquid storage
tank, the process can also include a step of storing the expanded
liquefied backup gas in the liquid storage tank before transferring
it to the liquid pump.
[0013] In another aspect, the process comprises by-passing part of
the backup liquid at the second pressure from the reprocessing heat
exchanger through a by-pass circuit.
[0014] Additionally, certain embodiments of the present invention
describe a system for supplying a backup gas at an elevated
pressure, comprising a reprocessing heat exchanger, a backup
vaporizer and a liquid pump, a first conduit for delivering a
backup gas at a first pressure into a warm end of the reprocessing
heat exchanger and a second conduit for transporting an at least
partially liquefied backup gas at a first pressure from the cold
end of the reprocessing heat exchanger into the liquid pump. It
further comprises a third conduit for delivering a backup liquid at
a second pressure from the outlet of the liquid pump into a cold
end of the reprocessing heat exchanger, a fourth conduit for
transporting an at least partially vaporized backup liquid at the
second pressure from a warm end of the reprocessing heat exchanger
to the backup vaporizer, and a fifth conduit for supplying the
backup gas at an elevated pressure from the backup vaporizer;
wherein the second pressure is higher than the first pressure.
[0015] In one aspect, the system further comprises an expansion
valve and a liquid storage tank.
[0016] In another aspect, the reprocessing heat exchanger of the
system has separate flow channels for the backup gas at the first
pressure and the backup liquid at the second pressure; and there
exists a by-pass circuit, with one end connecting to the flow
channel for the backup liquid at the second pressure inside the
reprocessing heat exchanger and one end connecting to the fourth
conduit. The by-pass circuit may also have a flow-control valve
disposed on it.
[0017] In both the process and the system for supplying backup gas
at an elevated pressure, the reprocessing heat exchanger may
comprise aluminum plate fin exchanger or printed plate exchanger.
The pressure ratio of the second pressure to the first pressure is
in the range of 3.about.1, preferably in the range of
2.5.about.1.2. The backup gas or the backup liquid comprises
oxygen.
[0018] Certain embodiments of the present invention eliminate the
use of a gas compressor (or a booster) when a backup gas stream is
at a pressure lower than required by the customer; thus mitigates
associated cost and safety concerns. They may also provide an
energy-efficient solution for simultaneously vaporizing a backup
liquid and condensing a backup gas through heat exchange in a heat
exchanger. Since the backup liquid is already partially vaporized
before entering the backup vaporizer, the energy consumed therein
is also reduced. In addition, if the backup gas were only supplied
from a liquid storage, the capacity of the liquid storage needs to
be substantial in order to sustain a long backup period. With
certain embodiments of the present invention, the liquid storage
can be supplemented with gases from other sources regardless of
their pressure; as a result, a large capacity of liquid storage is
not necessary.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] For further understanding the nature and objects of the
present invention, references should be made to the following
detailed description, taken in conjunction with the accompanying
drawings.
[0020] FIG. 1 provides an illustration of a backup system for
producing gaseous product in accord with the present invention.
[0021] FIG. 2 is a theoretical representation of the relationship
between the pressure of the backup gas and its condensable flow as
a function of the total liquid flow to be vaporized, using liquid
oxygen (LOX) at 80 bara as an example.
[0022] 1--low pressure pipeline network; 2--a first conduit (a
backup gas at a first pressure); 3--a second conduit (partially
liquefied backup gas at a first pressure); 4--a third conduit (a
backup liquid at a second pressure); 5--by-pass circuit; 6--a
fourth conduit (partially vaporized backup liquid at a second
pressure); 7--a fifth conduit (backup gas at an elevated pressure);
8--customer's facility; 10--a liquid storage tank; 11--a liquid
pump; 12--a reprocessing heat exchanger; 13--a backup vaporizer;
14--an expansion valve; 15--a flow control valve.
DETAILED DESCRIPTION
[0023] Referring to FIG. 1, gases from a low pressure pipeline
network 1 can be utilized as a supplemental source of backup gas.
Here, "a low pressure pipeline network" means the gas transported
in these pipelines is at a lower pressure compared to the pressure
of the final backup gas delivered to the customer, and the actual
value may range from atmospheric pressure to 70 bara. The transfer
line of gaseous product from a nearby air separation unit (ASU) can
also be considered as "a low pressure pipeline network".
[0024] Gases from the low pressure pipeline network 1 are then
transferred via a first conduit 2 into the warm end of a
reprocessing heat exchanger 12. The backup gas inside the first
conduit 2 is at a first pressure. The reprocessing heat exchanger
12 comprises any type that allows indirect heat exchange between
two fluid steams and can sustain pressure over 50 bara, preferably
over 80 bara.
[0025] Inside the reprocessing heat exchanger 12, the backup gas at
a first pressure is cooled and at least partially condensed through
heat exchange with a backup liquid at a second pressure. The backup
gas and backup liquid have the same composition, but the second
pressure is higher than the first pressure. In addition, the backup
gas at a first pressure is usually at room temperature, while the
backup liquid at a second pressure is usually at a cryogenic
temperature, for instance, below -165.degree. C.
[0026] Depending on certain parameters, such as temperature,
pressure and flow differences between the two exchanging streams,
the backup gas at a first pressure may be entirely or partially
condensed or liquefied leaving the cold end of the reprocessing
heat exchanger 12. The partially liquefied backup gas at a first
pressure is then transferred via a second conduit 3 to a liquid
pump 11. Along the second conduit 3, the partially liquefied backup
gas first passes through an expansion valve 14 to be further cooled
and its pressure is reduced. The expansion valve 14 also controls
the flow of the backup gas through the reprocessing heat exchanger
12 to ensure it is cooled to a temperature low enough to avoid
flash during the expansion. Optionally on the second conduit 3, a
liquid storage tank 10 could also be disposed. The liquid storage
tank 10 may hold initial stock of backup liquid to be pumped and
vaporized at the start of the backup process. With the continuous
supplement of liquefied backup gas at the first pressure, the
liquid storage tank does not need to have a capacity to hold the
entire quantity of backup liquid needed for sustaining a long
period of backup operation. In view of the previous description,
the backup liquid at the second pressure may be obtained from
elevating the liquefied backup gas to the second pressure with the
liquid pump, including directly elevating the liquefied backup gas
at the first pressure by a liquid pump to the second pressure; or
expanding and storing the backup gas at around atmospheric pressure
in the liquid storage tank, then withdrawing from the liquid
storage tank a stream to the liquid pump to be boosted to the
second pressure.
[0027] The liquid pump 11 is used to raise the pressure of backup
liquid from the liquid storage tank 10 to a second pressure that is
required at the customer's facility 8. The output backup liquid at
a second pressure is then transferred through a third conduit 4
into the cold end of the reprocessing heat exchanger 12. After heat
exchange with the backup gas at the first pressure, the exit stream
from the warm end of the heat exchanger contains at least partially
vaporized backup liquid at a second pressure. Via a fourth conduit
6, this stream is delivered into a backup vaporizer 13 and fully
vaporized therein. The backup vaporizer has the function to
vaporize the liquid under pressure and on leaving this equipment,
the gas maintains its pressure and is in general close to the
ambient temperature. This backup gas at an elevated pressure is
then transferred through a fifth conduit 7 to the customer's
facility 8. The word "elevated" means higher than atmospheric
pressure, and preferably higher than the first pressure of the
backup gas, but not necessarily higher or equal to the second
pressure. Depending on the energy sources available on the site and
their costs, this vaporizer may use as heat source to vaporize the
liquid under pressure, for example air, stream, hot water or
combustion flue gas. When the backup gas at the first pressure is
not available at some time during the backup operation, the entire
flow of backup liquid may be vaporized in the backup vaporizer.
[0028] For the reprocessing heat exchanger 12, persons skilled in
the art understand that common choices include brazed aluminum
plate-fin heat exchanger or printed plate heat exchanger. The
brazed aluminum plate-fin heat exchanger provides excellent heat
conductivity but cannot withstand great temperature differences
between the cold end and the warm end. Thus, for thermal balancing
purposes, a by-pass line 5 is placed at an intermediate location of
the aluminum plate-fin heat exchanger for the extraction of part of
the cold backup liquid at a second pressure. The extracted cold
backup liquid passes through a flow control valve 15 before being
recombined into the fourth conduit 6. The exit temperature of the
at least partially vaporized backup liquid from the warm end can be
adjusted by controlling the flow via valve 15.
[0029] For other types of heat exchangers, such as printed plate
heat exchanger, since the equipment is robust toward temperature
differences, the above by-pass line is not necessary.
[0030] The present invention may include additional valves, tanks,
pumps, flowlines, variations in connections, locations,
arrangement, and/or other equipment and interrelated
components.
[0031] For a given type of gas, the flow that can be condensed
within the reprocessing heat exchanger of the present invention
depends on a couple factors, such as the initial pressure ratio
between the backup gas at a first pressure and the backup liquid at
a second pressure and the flow of the backup liquid to be
vaporized. FIG. 2 illustrates such a relationship for liquid oxygen
(LOX) to be vaporized at 80 bara in a reprocessing heat exchanger.
In this figure, the y axis P/p represents a ratio between the
higher pressure P of the backup liquid to be vaporized and the
lower pressure p of the backup gas to be condensed; and the x axis
q/Q represents the flow ratio between the backup gas to be
condensed and the backup liquid to be vaporized. For instance,
according to this graph, a P/p value of 2 corresponds to a q/Q
value of 0.42. Since the P of this graph is set at 80 bara, that
means if the backup gas to be condensed is at a pressure of 40 bara
(thus P/p=80/40=2), then the current invention has the capability
to condense as much as 1000 Nm.sup.3/h backup gas at 40 bara by
vaporing every 2400 Nm.sup.3/h of backup liquid at 80 bara.
(q/Q=1000/2400=0.42). Throughout the invention, the flow of both
gas and liquid is converted to normal cubic meter per hour at 1 atm
and 0.degree. C.
[0032] Table 1 and table 2 present simulations of two embodiments
according to the current invention. The initial pressure of the
backup gas is at 40 bara and 60 bara, respectively.
[0033] The required pressure of the product gas is 80 bara. The
flow, temperature and pressure of each stream throughout the
process are listed in the following:
TABLE-US-00001 TABLE 1 Embodiment 1 Temperature Flow Pressure Flow
Phase (.degree. C.) (Nm.sup.3/h) (Bara) 2-backup gas gas 20 480 40
3-liquified liquid -177.8 480 39.9 backup gas Expanded backup
Gas/liquid -182.6 480 1.05 gas 4-backup liquid liquid -179.8 1000
80 after pumping 5-backup liquid in liquid -122 710 79.95 the
bypass line 6-vaporized gas 13 290 79.9 backup liquid 7-backup gas
gas 20 1000 79.8 after backup vaporizer
TABLE-US-00002 TABLE 2 Embodiment 2 Temperature Flow Pressure Flow
Phase (.degree. C.) (Nm.sup.3/h) (Bara) 2-backup gas gas 20 710 60
3-liquified liquid -177.8 710 59.9 backup gas Expanded backup
Gas/liquid -182.6 710 1.05 gas 4-backup liquid liquid -179.8 1000
80 after pumping 5-backup liquid in liquid -110 450 79.95 the
bypass line 6-vaporized gas 11 550 79.9 backup liquid 7-backup gas
gas 20 1000 79.8 after backup vaporizer
[0034] In the column named "Flow", the numerical number represents
the conduit containing the flow, followed by a description of the
nature of the flow. The above two examples illustrate the operation
of the present invention, but they should not be construed as in
any way limiting the scope of the invention.
[0035] Although this invention has been described in detail with
reference to certain embodiments, those skilled in the art will
recognize that variations and modifications of the described
embodiments may be used. Accordingly, these variations and
modifications are also within the spirit and scope of the invention
as defined by the appended claims and their equivalents.
[0036] 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.
[0037] The singular forms "a", "an" and "the" include plural
referents, unless the context clearly dictates otherwise.
[0038] "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.
[0039] "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.
[0040] 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.
[0041] 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.
[0042] 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.
* * * * *