U.S. patent application number 16/680176 was filed with the patent office on 2020-03-12 for short contact, elevated temperature meg reclamation.
This patent application is currently assigned to Cameron International Corporation. The applicant listed for this patent is Cameron International Corporation. Invention is credited to Christopher Stephen King, Brian Edward Messenger, Harihara V. Nemmara, Z. Frank Zheng, Shihui Zhou.
Application Number | 20200079713 16/680176 |
Document ID | / |
Family ID | 57757359 |
Filed Date | 2020-03-12 |
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United States Patent
Application |
20200079713 |
Kind Code |
A1 |
King; Christopher Stephen ;
et al. |
March 12, 2020 |
SHORT CONTACT, ELEVATED TEMPERATURE MEG RECLAMATION
Abstract
Monoethylene glycol (MEG) may be reclaimed by a process that
includes contacting a MEG-water-salt stream with a heat transfer
fluid and then flash separating the MEG and water in the flash
separator vessel where the pressure is higher than 0.3 barA (0.03
MPa), the temperature is in the range of above 120.degree. C. to
about 250.degree. C., and the residence time of the MEG and water
ranges from about 1 second to about 10 minutes, and then removing
the MEG and water in an overhead of the flash separator vessel and
removing the salt from the flash separator vessel. In some
embodiments it is expected that the temperature of the process may
range from above 165.degree. C. to about 250.degree. C. and/or that
the pressure may be atmospheric.
Inventors: |
King; Christopher Stephen;
(Houston, TX) ; Messenger; Brian Edward; (Hook,
GB) ; Nemmara; Harihara V.; (Katy, TX) ;
Zheng; Z. Frank; (Cypress, TX) ; Zhou; Shihui;
(Middlesex, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cameron International Corporation |
Houston |
TX |
US |
|
|
Assignee: |
Cameron International
Corporation
Houston
TX
|
Family ID: |
57757359 |
Appl. No.: |
16/680176 |
Filed: |
November 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14800876 |
Jul 16, 2015 |
|
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16680176 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 29/80 20130101;
B01D 3/06 20130101; C07C 29/80 20130101; C07C 31/202 20130101 |
International
Class: |
C07C 29/80 20060101
C07C029/80; B01D 3/06 20060101 B01D003/06 |
Claims
1. A process to reclaim monoethylene glycol (MEG), the process
comprising: contacting a stream comprising MEG, water, and at least
one salt with a heat transfer fluid; flash separating the MEG and
water from the stream in a flash separator vessel where: the
pressure is higher than 0.3 barA (0.03 MPa); the temperature is in
the range of about 110.degree. C. to about 250.degree. C.; and the
residence time of the MEG and water ranges from about 1 second to
about 10 minutes; and removing the MEG and water in an overhead of
the flash separator vessel; and removing the at least one salt from
the flash separator vessel.
2. The process of claim 1 where the temperature is above
165.degree. C. to about 220.degree. C.
3. The process of claim 1 where the heat transfer fluid is selected
from the group consisting of aromatic hydrocarbons, paraffinic
hydrocarbons, alcohols, glycols, amines, silicone-based liquids and
mixtures thereof.
4. The process of claim 1 where the pressure is atmospheric and
above.
5. The process claim 1 where the process has a parameter different
from a conventional process to reclaim MEG that comprises operating
the flash separator vessel under a vacuum, at a temperature of
165.degree. C. or less and at a residence time longer than 10
minutes, where the parameter is selected from the group consisting
of: reducing the degradation of MEG; reducing the potential for air
ingress; removing the need for a vacuum system; reducing the
diameter of vessels and/or pipework; and combinations thereof; as
compared to the conventional process.
6. A process to reclaim monoethylene glycol (MEG), the process
comprising: contacting a stream comprising MEG, water, and at least
one salt with a heat transfer fluid, where the heat transfer fluid
is selected from the group consisting of aromatic hydrocarbons,
paraffinic hydrocarbons, alcohols, glycols, amines, silicone-based
liquids and mixtures thereof; flash separating the MEG and water
from the stream in a flash separator vessel where: the pressure is
higher than 0.3 barA (0.03 MPa); the temperature is in the range of
above 165.degree. C. to about 250.degree. C.; and the residence
time of the MEG and water ranges from about 1 second to about 10
minutes; and removing the MEG and water in an overhead of the flash
separator vessel; and removing the at least one salt from the flash
separator vessel.
7. The process of claim 6 where the pressure is atmospheric and
above.
8. The process claim 6 where the process has a parameter different
from a conventional process to reclaim MEG that comprises operating
the flash separator vessel under a vacuum, at a temperature of
165.degree. C. or less and at a residence time longer than 10
minutes, where the parameter is selected from the group consisting
of: reducing the degradation of MEG; reducing the potential for air
ingress; removing the need for a vacuum system; reducing the
diameter of vessels and/or pipework; and combinations thereof; as
compared to the conventional process.
9. A process to reclaim monoethylene glycol (MEG), the process
comprising: contacting a stream comprising MEG, water, and at least
one salt with a heat transfer fluid; flash separating the MEG and
water from the stream in a flash separator vessel where: the
pressure is atmospheric and above; the temperature is in the range
of above 165.degree. C. to about 250.degree. C.; and the residence
time of the MEG and water ranges from about 1 second to about 10
minutes; and removing the MEG and water in an overhead of the flash
separator vessel; and removing the at least one salt from the flash
separator vessel.
10. The process of claim 9 where the heat transfer fluid is
selected from the group consisting of aromatic hydrocarbons,
paraffinic hydrocarbons, alcohols, glycols, amines, silicone-based
liquids and mixtures thereof.
11. The process claim 9 where the process has a parameter different
from a conventional process to reclaim MEG that comprises operating
the flash separator vessel under a vacuum, at a temperature of
165.degree. C. or less and at a residence time longer than 10
minutes, where the parameter is selected from the group consisting
of: reducing the degradation of MEG; reducing the potential for air
ingress; removing the need for a vacuum system; reducing the
diameter of vessels and/or pipework; and combinations thereof; as
compared to the conventional process.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 14/800,876, filed Jul. 16, 2015. The
cross-referenced application listed herein is incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to a process for reclaiming
monoethylene glycol (MEG) from a water miscible liquid, and more
particularly relates to methods for reclaiming MEG with a heat
transfer fluid at elevated temperatures and at higher pressures
than are conventionally employed.
[0003] In conventional MEG reclamation processes, which involve the
removal of a salt from a MEG-water solution, a MEG-water-salt
stream is contacted with a recycle stream of salt-saturated MEG
operating at a temperature above the dew point of the incoming feed
such that the volatile components of the feed are fully vaporized
and the dissolved salt components of the feed are precipitated and
removed from the heat transfer fluid. The recycle MEG stream thus
acts as a heat transfer fluid. A hydrocarbon stream (or other
non-volatile fluid) may also be employed as the recycle stream.
[0004] Conventional MEG reclamation processes include, but are not
necessarily limited to, those described in U.S. Pat. No. 6,685,802
("the '802 patent") the process of U.S. Pat. No. 5,993,608, ("the
'608 patent"), the process of U.S. Pat. No. 6,340,373 ("the '373
patent"), the disclosures of which are incorporated in their
entirety.
[0005] As noted, these processes involve the removal of salt from
glycol that is used for dehydrating natural gas and for preventing
hydrate formation in oil and gas production facilities. And as
mentioned, the demineralization is typically done by a flash
vaporization process in which a heated recycle liquid provides heat
to vaporise an aqueous stream of glycol while collecting
precipitated salt and other solid material in a liquid residue that
can then be removed from the process. The processes described in
the '802, '608, and '373 patents each include a flash vaporisation
process similar to the above and such flash vaporisation processes
have been or are being applied in the oil and gas industry to
remove unwanted salt from glycol.
[0006] The temperature above which MEG degrades significantly is
widely accepted to be approximately 165.degree. C. As a result, the
flash vaporization process is carried out at sub-atmospheric
pressures (0.1-0.3 barA; 0.01-0.03 MPa) in order to achieve
complete vaporization of the MEG and water components at
temperatures well below the accepted degradation temperature of
165.degree. C. The recycle heater outlet temperature in
conventional flash separators is typically limited to an upper
value of 150.degree. C. as a consequence of the concern regarding
MEG degradation.
[0007] Conventional MEG reclamation processes employ a large
recirculating inventory of concentrated MEG which is employed to
provide the heating duty, as exemplified in U.S. Pat. No.
8,728,321, incorporated herein by reference in its entirety. This
recirculating MEG has a very long residence time in the MEG
Reclamation system (in the order of several months to several years
at the elevated temperatures required for complete
vaporization.
[0008] The long residence time for the recirculating,
salt-saturated, MEG stream (conventionally referred to as recycle
MEG) makes the degradation process an issue. As a consequence of
this long residence time, operation at reduced pressure has been
conventionally deemed essential in order to prevent significant MEG
degradation with consequential reduction in pH in the system
through degradation of the MEG to formic acid, acetic acid,
glycolic acid, and other carboxylic acids. The reduction in pH
leads, potentially, to increased corrosion rates. Under such
circumstances, in order to maintain an operable system, it is
necessary to periodically blowdown and dispose of the degraded MEG
from the system resulting in significant MEG losses and potential
environmental impact from handling this waste product. Cost of
disposal and replacement of MEG can be significant.
[0009] It would thus be desirable if an improved process for
reclaiming MEG were discovered which minimized or avoided one or
more of these problems.
BRIEF SUMMARY OF THE INVENTION
[0010] In one non-limiting embodiment there is provided a process
to reclaim monoethylene glycol (MEG), where the process includes
contacting a stream comprising MEG, water, and at least one salt
with a heat transfer fluid, optionally in a flash separator vessel,
flash separating the MEG and water from the stream in the flash
separator vessel where the pressure is higher than 0.3 barA (0.03
MPa), the temperature is in the range of 110.degree. C. to about
250.degree. C.; alternatively above 150.degree. C. to about
220.degree. C., and the residence time of the MEG and water ranges
from about 1 second to about 10 minutes. The process further
includes removing the MEG and water in an overhead of the flash
separator vessel and removing at least one salt from the flash
separator vessel.
BRIEF SUMMARY OF THE INVENTION
[0011] FIG. 1 schematically shows a flash separator vessel used in
a process for removing solid matter from the lower portion of a
vessel that contains process liquid and unwanted solid matter and
for removing MEG and water in an overhead.
[0012] It will be appreciated that the FIGURE is a schematic
illustration that is not to scale or proportion, and, as such, some
of the important parts of the invention may be exaggerated for
illustration.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The method relates to a process where a hydrocarbon stream
(or other non-volatile fluid) is employed to provide the heating
duty to vaporize the MEG and water components of the feed. It has
been discovered that MEG degradation is not instantaneous, and it
has been further discovered that a flash separator vessel can be
operated at higher pressures without any significant observed
increase in MEG degradation products provided that the residence
time of the MEG in the flash separator vessel is kept to a minimum.
Tests have been carried out at atmospheric pressure, and higher
pressure operation in principle should also be achievable.
[0014] This finding allows the flash separator vessel to operate at
pressures above the currently recognized range of 0.1 to 0.3 barA
(0.01 to 0.03 MPa); alternatively where the pressure is atmospheric
and above; and in a different non-limiting embodiment where the
pressure is from about atmospheric plus 5 psi (1.34 barA), and
therefore at temperatures significantly higher than the previously
recognized limit of 165.degree. C. The benefits of operating in the
range of 0.1 to 0.3 barA (0.01 to 0.03 MPa) include, but are not
necessarily limited to: [0015] 1) Reduced equipment size due to
reduced vapor phase velocity at higher pressure. The flash
separator vapors can be discharged to the site flare system without
the requirements for a vacuum system. [0016] 2) The potential to
eliminate the vacuum system which not only saves cost and
complexity of the equipment. [0017] 3) Reduced potential for oxygen
ingress, another cause of MEG degradation.
[0018] In more detail, the process involves a MEG/water incoming
stream entering a flash separator vessel where the MEG and water
vaporizes rapidly and completely at temperatures higher than
150.degree. C. and pressures higher than 0.3 barA (0.03 MPa);
alternatively higher than 0.5 barA (0.05 MPa) without any MEG/water
inventory remaining in the device which could be exposed to the
high temperature for a prolonged period. In one non-limiting
embodiment, the temperature of the flash separator is in the range
of about or above 110.degree. C., alternatively about or above
120.degree. C. independently to about 250.degree. C.; in another
non-limiting embodiment above 150.degree. C. independently to about
220.degree. C.; alternatively from above 165.degree. C.
independently to about 220.degree. C. When term "independently" is
used herein with respect to a range, it means that any lower
threshold may be combined with any upper threshold to give a
suitable alternative range. The optimum temperature range is
dependent on the composition of the feed input and on the operating
pressure. Higher MEG content necessitates higher temperatures. In
one non-limiting embodiment, if the liquid pool equilibrium
temperature is maintained at about 220.degree. C., but there is a
differential temperature across the recycle heat exchanger, and if
an elevated temperature is required because the MEG residence time
is kept to a minimum, then the recycle heater outlet temperature,
and thus the recycle heater differential temperature, may be
increased. This may give a further advantage of reducing the
recycle flow rate thereby permitting smaller pumps and smaller
diameter pipework.
[0019] The residence time of the MEG and water ranges from about 1
second independently to about 10 minutes, alternatively from about
10 seconds independently to about 5 minutes, and in a different
non-limiting embodiment, from about 20 seconds independently to
about 1 minute. In general, the shorter the residence time, the
better, but there is a finite amount of time required to warm the
feed to its bubble point, and then to vaporize it.
[0020] Suitable heat transfer fluids include, but are not
necessarily limited to, aromatic hydrocarbons, alcohols, glycols,
amines, silicone-based liquids, and mixtures thereof where these
heat transfer fluids are not miscible with MEG. In one non-limiting
example, a suitable mixture of synthetic aromatic hydrocarbons is
THERM INOL.RTM. ADX-10 heat transfer fluid available from Solutia
Inc. Paraffinic hydrocarbon mixtures such as PARATHERM HE.RTM. and
XCELTHERM.RTM. 600 can also be employed as the heat transfer fluid.
Suitable silicone-based liquids include, but are not necessarily
limited to, DURATHERM S, and the like.
[0021] Salts that may contaminate the feed stream include, but are
not necessarily limited to sodium chloride (NaCl), calcium chloride
(CaCl2)), other chlorides, oxides, sulfates, acetates, nitrates,
phosphates, bicarbonates and carbonates of sodium, potassium,
calcium, magnesium, iron, copper, lead, barium, strontium, and the
like, and combinations thereof. In addition, the feed stream may
also contain a number of optional flow assurance chemicals such as
scale inhibitors, corrosion inhibitors, wax inhibitors and oxygen
scavengers.
[0022] As shown in FIG. 1, the lower portion of a flash separator
vessel 10 contains a mixture including process liquid 12 (i.e. the
heat transfer fluid) that is substantially immiscible with water
and undissolved solid matter or salt in particulate form. The
undissolved solids may be removed from the process by a variety of
technologies including, but not necessarily limited to, a conveying
means such as a downcomer pipe 14 which is connected proximate the
base of the vessel 10 to a solids collection tank 16. Removal of
the solids from the process may be achieved employing one of a
variety of commercially available solids-liquids separation
processes such as settling tanks (as shown in FIG. 1) or
centrifuges. The feed stream 18 is a free flowing mixture including
two or more miscible liquids (e.g. MEG and water) and dissolved
solids (e.g. sodium chloride, magnesium chloride, calcium chloride
from the gas production well and flow assurance chemicals added to
the MEG-water solution to minimize pipescaling and pipeline
corrosion). Examples of such mixtures include glycol/water and
amine/water that are contaminated with dissolved salts, corrosion
products and/or other unwanted solids.
[0023] The present process may be termed a "Flash-on-Oil" process
(FoA). It is true that for FoO as well as for conventional MEG
processes that one or more of the liquid component(s) boils at a
significantly higher temperature than the other liquid components,
but the present FoO process is operated such that, regardless of
the differing boiling points, both (or all) of the components of
the feed are fully vaporized. This is not the case in the
conventional system where there is equilibrium between the incoming
MEG-water and the Recycle MEG such that a substantial inventory of
MEG remains within the vessel. If the FoO process is properly
optimized, then the quantity of MEG (water) present in the liquid
phase in the vessel will be small.
[0024] The feed stream 18 enters the flash separator vessel 10 and
mixes with a larger and hotter stream of recycle liquor 20 that has
also entered the separation vessel 10. The recycle liquor 20 in one
non-limiting embodiment immediately heats the feed stream 18 and
thereby causes the volatile components in the feed stream 18 to
boil rapidly or flash.
[0025] Alternatively, the feed stream 18 and recycle liquor 20 may
be mixed upstream (not shown) of the separator vessel 10 and the
commingled streams injected into the separation vessel 10.
[0026] The vapor 22 generated by the flashing feed stream flows out
of the separation vessel through the outlet channel 24. This vapor
contains essentially no solids unless there is significant
carryover of small particles or liquid droplets into the vapour. In
one non-limiting embodiment the vapor is MEG and water.
[0027] Solids and unvaporised liquid collect in liquid pool 12 in
the lower half of the separation vessel 10. The flash vaporisation
that has occurred ensures that the liquid pool is composed mainly
of the higher boiling point liquid (i.e. the heat transfer fluid)
and solids. A recycle liquor 20, is drawn from the liquid pool and
enters the recycle circuit 26 where it is pumped by the recycle
pump 28, heated by the recycle heater 30 and mixed with the feed
stream 18 as described above. An objective of the process herein is
to minimize or prevent any MEG accumulation in the loop. This may
be achieved by operating at a suitable
temperature-pressure-residence time.
[0028] The method employs short residence time for the MEG
molecules in the Flash Vaporization zone in order to minimize
thermal and oxidative-thermal degradation of the MEG molecules to
organic acids and other species. Employing short residence times
allows operating pressures at or close to ambient (atmospheric) to
be employed. The temperature-pressure regime employed in the method
is such that complete vaporization of the MEG and water components
of the incoming feed stream is achieved.
[0029] There are significant and substantial benefits in operating
at pressures close to atmospheric pressure rather than the 0.1-0.3
barA (0.01-0.03 MPa) conventionally employed for the flash
vaporization process. These are exemplified below: [0030] 1)
Degradation of MEG and Corrosion: In conventional MEG reclamation
methods operated under partial vacuum, there is increased potential
for ingress of air into the flash separator vessel through leakage
at the flanges and fittings. The oxygen present in the incoming air
can result in increased degradation of the MEG to organic acids
which in turn can result in increased corrosion of pipework.
Operating at atmospheric pressure or above will significantly
reduce potential for air ingress. In one non-limiting embodiment
the flash separator vessel will be operated at a pressure slightly
above atmospheric pressure. In another non-restrictive version the
actual operating pressure will be determined by equipment and
pipework downstream of the vessel, but the operating pressure may
likely be around 5 psiG (20 psiA, 1.35 bar A). [0031] 2) Complex
Vacuum System: Operation at the reduced pressure of conventional
MEG reclamation methods requires a vacuum system. The vacuum system
can be complex and adds additional weight, space requirements and
utility (electrical and cooling medium) demand on the MEG package.
Space and weight restrictions are important particularly for
off-shore applications where space and weight are at a premium.
Operation of the Flash Separator at atmospheric pressure as in the
present method would remove the requirement for a vacuum package.
[0032] 3) Large Diameter Vessels and Pipework: Operation at low
pressure (0.1-0.3 barA (0.01-0.03 MPa)) results in the production
of large volumes of low density vapor (MEG-water) from the flash
vaporization process. This large volumetric flow requires a large
flash separator vessel, large diameter pipework and larger
equipment (typically condenser, knockout drum and distillation
column) downstream of the Flash Separator vessel. In the present
method, operating at atmospheric pressure will reduce the size of
the Flash Separator vessel, pipework and downstream equipment
treating the overhead vapors. Size (surface area) of condenser
equipment in the Reclaimer section will also be reduced by
operating at atmospheric pressure. [0033] 4) In the foregoing
specification, the disclosure has been described with reference to
specific embodiments thereof, and is expected to be effective in
providing methods and apparatus that improve the reclamation of MEG
by allowing the flash separator to operate at pressures above the
currently recognized range, even at atmospheric pressure, and
therefore, at temperatures significantly higher than the
conventionally recognized limit of 165.degree. C. However, it will
be evident that various modifications and changes may be made
thereto without departing from the broader scope of the disclosure
as set forth in the appended claims. Accordingly, the specification
is to be regarded in an illustrative rather than a restrictive
sense. For example, the MEG-water-salt composition, heat transfer
fluids, pressures, temperatures, residence times, and/or flow rates
may be changed or optimized from that illustrated and described,
and even though certain additional features are not specifically
identified or tried in a particular system, method or apparatus
described herein, they would be anticipated to be within the scope
of this disclosure. For instance, the parameters, compositions and
treatments any of the described components and equipment would be
expected to find utility and be encompassed by the appended
claims.
[0034] The words "comprising" and "comprises" as used throughout
the claims are to be interpreted as "including but not limited
to".
[0035] The present disclosure may suitably comprise, consist or
consist essentially of the elements disclosed and may be practiced
in the absence of an element not disclosed. For instance, in one
non-limiting embodiment, there may be provided a process to reclaim
monoethylene glycol (MEG), the process consisting essentially of,
or consisting of, contacting a stream comprising MEG, water, and at
least one salt with a heat transfer fluid, optionally in a flash
separator vessel; flash separating the MEG and water from the
stream in the flash separator vessel where: the pressure is higher
than 0.3 barA (0.03 MPa); the temperature is in the range of about
110.degree. C. to about 250.degree. C.; and the residence time of
the MEG and water ranges from about 1 second to about 10 minutes.
The process may further consist essentially of, or consist of,
removing the MEG and water in an overhead of the flash separator
vessel and removing the at least one salt from the flash separator
vessel.
* * * * *