U.S. patent application number 14/059859 was filed with the patent office on 2015-04-23 for processes and systems for discharging amine byproducts formed in an amine-based solvent.
This patent application is currently assigned to UOP LLC. The applicant listed for this patent is UOP LLC. Invention is credited to Graham Ellis, David W. Greer, Edward P. Zbacnik, Lubo Zhou.
Application Number | 20150111292 14/059859 |
Document ID | / |
Family ID | 46063032 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150111292 |
Kind Code |
A1 |
Greer; David W. ; et
al. |
April 23, 2015 |
PROCESSES AND SYSTEMS FOR DISCHARGING AMINE BYPRODUCTS FORMED IN AN
AMINE-BASED SOLVENT
Abstract
Embodiments of a process for discharging amine byproducts formed
in an amine-based solvent are provided. The process comprises the
steps of contacting the amine-based solvent with flue gas
comprising carbon dioxide, oxygen, nitrogen, NO.sub.x, SO.sub.x, or
mixtures thereof to form a carbon dioxide-laden amine-based solvent
that contains the amine byproducts. Carbon dioxide is separated
from the carbon dioxide-laden amine-based solvent to form a carbon
dioxide-depleted amine-based solvent. The amine byproducts from the
carbon dioxide-depleted amine-based solvent are fed to an algae
source.
Inventors: |
Greer; David W.; (Cary,
IL) ; Ellis; Graham; (Guildford, GB) ;
Zbacnik; Edward P.; (Fox River Grove, IL) ; Zhou;
Lubo; (Inverness, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
46063032 |
Appl. No.: |
14/059859 |
Filed: |
October 22, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12953865 |
Nov 24, 2010 |
8563296 |
|
|
14059859 |
|
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Current U.S.
Class: |
435/289.1 |
Current CPC
Class: |
C12M 43/08 20130101;
B01D 53/1475 20130101; B01D 53/1425 20130101; C02F 2209/06
20130101; C02F 3/322 20130101; C02F 1/20 20130101; C02F 2303/16
20130101; C02F 2101/38 20130101; C02F 2103/18 20130101; C12M 29/26
20130101; C12M 43/04 20130101 |
Class at
Publication: |
435/289.1 |
International
Class: |
C12M 1/00 20060101
C12M001/00 |
Claims
1. A system for discharging amine byproducts formed in an
amine-based solvent, the system comprising: a carbon dioxide
absorber unit configured to contact the amine-based solvent with
flue gas comprising carbon dioxide, oxygen, nitrogen, NO.sub.x,
SO.sub.x, or mixtures thereof to form a carbon dioxide-laden
amine-based solvent that contains the amine byproducts; a stripper
unit in fluid communication with the carbon dioxide absorber unit
and configured to separate carbon dioxide from the carbon
dioxide-laden amine-based solvent to form a carbon dioxide-depleted
amine-based solvent; and an algae source that receives the amine
byproducts from the carbon dioxide-depleted amine-based
solvent.
2. The system according to claim 1, wherein the amine-based solvent
comprises an amine selected from the group consisting of
monoethanolamine, diethanolamine, piperazine, diisopropanolamine,
triethanolamine, 2-amino,2-methyl,1-propanol, diamines,
methyldiethanolamine, tertiary amines, and mixtures thereof.
3. The system according to claim 1, wherein the amine byproducts
comprise compounds selected from the group consisting of
nitrogen-based compounds, bicine, amino acids, amine salts,
sulfur-based compounds, thiosulfates, dithiocarbanates, thioureas,
polysulfides, and mixtures thereof
4. The system according to claim 1, further comprising a reclaimer
unit that receives the carbon dioxide-depleted amine-based solvent
and is configured to separate the amine byproducts from the carbon
dioxide-depleted amine-based solvent to form a regenerated
amine-based solvent and an amine byproducts effluent.
5. The system according to claim 4, wherein the algae source is in
fluid communication with the reclaimer unit to receive the amine
byproducts effluent.
6. The system according to claim 4, wherein the reclaimer unit is
in fluid communication with the stripper unit to receive the carbon
dioxide-depleted amine-based solvent.
7. The system according to claim 4, wherein the carbon dioxide
absorber unit is in fluid communication with the reclaimer unit to
receive the regenerated amine-based solvent.
8. The system according to claim 4, further comprising a carbon
dioxide feed and an amine byproducts feed that is separate from the
carbon dioxide feed, the carbon dioxide feed configured to fluidly
communicate carbon dioxide from the carbon dioxide absorber unit to
the algae source, and the amine byproducts feed configured to
fluidly communicate the amine byproducts effluent to the algae
source.
9. The system according to claim 1, further comprising a power
plant configured to burn carbonaceous fuel to generate power and
the flue gas, and wherein the carbon dioxide absorber unit is in
fluid communication with the power plant to receive the flue
gas.
10. The system according to claim 1, wherein the algae source
comprises algae, water, and bacteria, and wherein the bacteria is
effective to convert at least a portion of the amine byproducts to
nutrients for the algae.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Division of copending application Ser.
No. 12/953,865 which was filed on Nov. 24, 2010, the contents of
which are hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to processes and
systems for discharging contaminants formed in a solvent, and more
particularly relates to processes and systems for discharging amine
byproducts formed in an amine-based solvent.
BACKGROUND OF THE INVENTION
[0003] Carbon dioxide is a well known greenhouse gas that is
believed to affect global warming. Attempts to reduce emissions of
carbon dioxide have focused attention on sequestering significant
quantities of carbon dioxide in flue gas released from coal fired
power plants, for example, as a primary means of offsetting global
warming. Current methods for capturing and mitigating the entrance
of carbon dioxide into the atmosphere typically use an amine-based
solvent to absorb the carbon dioxide in the flue gas and then
regenerate the amine-based solvent to release the carbon dioxide
for sequestering and/or subsequent processing and/or
conversion.
[0004] Flue gas is a mixture of various gases including for example
carbon dioxide, oxygen, nitrogen, nitrous oxides (NO.sub.x), sulfur
oxides (SO.sub.x), and water. Unfortunately, several of the gases
in flue gas can react with or degrade the amine-based solvent to
form contaminants, such as, for example, various amine byproducts
which are problematic for many carbon dioxide absorption processes
and systems. As a result, when an amine-based solvent becomes
contaminated with amine byproducts, the solvent is typically purged
from the system and purified for further use or treated further and
disposed of as hazardous waste. Disposing the contaminated
amine-based solvent as hazardous waste is both costly and
environmentally objectionable. Purifying the contaminated
amine-based solvent regenerates the amine-based solvent for further
use. However, the contaminants removed from the solvent may need to
be treated further or disposed of as hazardous waste which can be
costly.
[0005] Accordingly, it is desirable to provide processes and
systems for discharging the contaminants from a contaminated
amine-based solvent without the high cost and environmental
ramifications of current processes and systems. Furthermore, other
desirable features and characteristics of the present invention
will become apparent from the subsequent detailed description of
the invention and the appended claims, when taken in conjunction
with the accompanying drawings and this background of the
invention.
SUMMARY OF THE INVENTION
[0006] Processes and systems for discharging amine byproducts
formed in an amine-based solvent are provided herein. In accordance
with an exemplary embodiment, a process for discharging amine
byproducts formed in an amine-based solvent comprises the steps of
contacting the amine-based solvent with flue gas comprising carbon
dioxide, oxygen, nitrogen, NO.sub.x, SO.sub.x, or mixtures thereof
to form a carbon dioxide-laden amine-based solvent that contains
the amine byproducts. Carbon dioxide is separated from the carbon
dioxide-laden amine-based solvent to form a carbon dioxide-depleted
amine-based solvent. The amine byproducts from the carbon
dioxide-depleted amine-based solvent are fed to an algae
source.
[0007] In accordance with another exemplary embodiment, a system
for discharging amine byproducts formed in an amine-based solvent
is provided. The system comprises a carbon dioxide absorber unit
configured to contact the amine-based solvent with flue gas
comprising carbon dioxide, oxygen, nitrogen, NO.sub.x, SO.sub.x, or
mixtures thereof to form a carbon dioxide-laden amine-based solvent
that contains the amine byproducts. A stripper unit is in fluid
communication with the carbon dioxide absorber unit and is
configured to separate the carbon dioxide from the carbon
dioxide-laden amine-based solvent to form a carbon dioxide-depleted
amine-based solvent. An algae source is for receiving the amine
byproducts from the carbon dioxide-depleted amine-based
solvent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Embodiments of the present invention will hereinafter be
described in conjunction with the following drawing figures,
wherein like numerals denote like elements, and wherein:
[0009] FIG. 1 schematically illustrates a system for discharging
amine byproducts formed in an amine-based solvent in accordance
with an exemplary embodiment.
DETAILED DESCRIPTION
[0010] The following Detailed Description is merely exemplary in
nature and is not intended to limit the invention or the
application and uses of the invention. Furthermore, there is no
intention to be bound by any theory presented in the preceding
Description of Related Art or the following Detailed
Description.
[0011] Various embodiments contemplated herein relate to processes
and systems for discharging amine byproducts formed in an
amine-based solvent that is used for absorbing carbon dioxide from
flue gas. In a carbon dioxide absorber unit, the amine-based
solvent is contacted with flue gas that typically comprises carbon
dioxide, oxygen, nitrogen, nitrous oxides (NO.sub.x), sulfur oxides
(SO.sub.x), and other gaseous components and particulates. The
amine-based solvent readily absorbs the carbon dioxide as well as
some of the other gaseous components of the flue gas. However, over
time and continuous recycling through the carbon dioxide absorber
unit and a carbon dioxide stripper unit that separates the carbon
dioxide from the solvent, some of the other gaseous components
absorbed from the flue gas will tend to break down or degrade the
amine-based solvent forming various amine byproducts, such as, for
example, nitrogen-based compounds, amine salts including heat
stable amine salts (HSAS), and sulfur-based compounds. When this
occurs, the amine-based solvent from the absorber unit will be
laden not only with carbon dioxide but also with the amine
byproducts. As such, when carbon dioxide is subsequently separated
from the carbon dioxide-laden amine-based solvent in the carbon
dioxide stripper unit, the carbon dioxide-depleted amine-based
solvent will contain the amine byproducts.
[0012] The inventors have discovered that many of these amine
byproducts as well as the amine-based solvent are readily
consumable nutrients for algae. In an exemplary embodiment, the
amine byproducts from the carbon dioxide-depleted amine-based
solvent are fed to an algae source for digestion by the algae.
Thus, the amine byproducts are discharged without being disposed of
as hazardous waste. Furthermore, the cost of maintaining an algae
source is nominal especially if the algae source is already on site
and being used to consume carbon dioxide from the flue gas for
photosynthesis.
[0013] In another exemplary embodiment, the amine byproducts are
introduced to a reclaimer unit prior to being fed to the algae
source. The reclaimer unit separates the amine byproducts from the
carbon dioxide-depleted amine-based solvent to form a regenerated
amine-based solvent and an amine byproducts effluent. In this
embodiment, the amine byproducts effluent is fed to the algae
source and the regenerated amine-based solvent is preferably
introduced back to the carbon dioxide absorber unit, and thus,
disposal of the amine-based solvent as hazardous waste is
avoided.
[0014] Referring to FIG. 1, a schematic depiction of an exemplary
system for discharging amine byproducts formed in an amine-based
solvent is provided. The system 10 comprises a flue gas source 12,
such as, for example, a carbonaceous burning power plant, a carbon
dioxide absorber unit 14, a stripper unit 16 and an algae source
18. Preferably, the system 10 also comprises a reclaimer unit 20.
Flue gas from the flue gas source 12 is introduced to the carbon
dioxide absorption unit 14 preferably near a bottom via line 22.
The flue gas typically comprises a mixture of gases including
carbon dioxide, oxygen, nitrogen, NO.sub.x, SO.sub.x, water vapor,
trace amounts of hydrocarbons, hydrogen and carbon monoxide, and
particulates.
[0015] The carbon dioxide absorber unit 14 is operating preferably
at a temperature of from about 40 to 50.degree. C. at the top and
at a temperature of from about 50 to about 60.degree. C. at the
bottom. An amine-based solvent is introduced to the carbon dioxide
absorption unit 14, for example, near a top via line 24. In an
exemplary embodiment, the amine-based solvent comprises an amine
selected from the group consisting of monoethanolamine,
diethanolamine, piperazine, diisopropanolamine, triethanolamine,
2-amino,2-methyl,1-propanol, diamines, methyldiethanolamine,
tertiary amines, and mixtures thereof. In one example, the
amine-based solvent comprises from about 5 to about 30 weight
percent of one or more faster reaction rate amines, which require
relatively less contact time with the flue gas to absorb carbon
dioxide, and from about 5 to about 50 weight percent of one or more
slower reaction rate amines, which require relatively more contact
time with the flue gas to absorb carbon dioxide. Examples of faster
reaction rate amines include monoethanolamine, diethanolamine,
piperazine, and diisopropanolamine. Examples of slower reaction
rate amines include methyldiethanolamine, triethanolamine, and
sterically hindered amines such as 2-amino,2-methyl,1-propanol. In
another example, the total amine concentration in the amine-based
solvent, whether or not a slower or faster reaction rate amine is
present, is of from about 20 to about 80 weight percent, preferably
of from about 30 to about 50 weight percent. In addition to water,
the amine-based solvent may also contain others species such as
diamines and tertiary amines.
[0016] Contacting of the amine-based solvent with flue gas occurs
within the carbon dioxide absorption unit 14 as the flue gas rises
in countercurrent flow against the downward flowing amine-based
solvent. The carbon dioxide absorption unit 14 may contain column
internals or mass transfer elements such as trays or random or
structured packing. As the flue gas rises, carbon dioxide within
the flue gas is absorbed into the downward flowing amine-based
solvent resulting in a carbon dioxide depleted top vapor at the top
of the carbon dioxide absorption unit 14, and a carbon
dioxide-laden amine-based solvent at the bottom of the carbon
dioxide absorption unit 14.
[0017] As discussed previously, over time, continuous use and/or
recycling, some of the gaseous components in the flue gas will tend
to break down the amine-based solvent into various amine
byproducts. In particular, oxygen, NO.sub.x, and SO.sub.x from the
flue gas substantially contribute to the degradation of the
amine-based solvent. Accordingly, a "well used" or "worn-out"
amine-based solvent will contain the amine byproducts when it
absorbs the carbon dioxide from the flue gas in the carbon dioxide
absorption unit 14 and forms a carbon dioxide-laden amine-based
solvent. In an exemplary embodiment, the amine byproducts comprise
compounds selected from the group consisting of nitrogen-based
compounds, bicine, amino acids, amine salts, sulfur-based
compounds, thiosulfates, dithiocarbanates, thioureas, polysulfides,
and mixtures thereof.
[0018] The top vapor is withdrawn from the upper portion of the
carbon dioxide absorption unit 14 in a gas stream through line 26.
The carbon dioxide-laden amine-based solvent is withdrawn from the
lower portion of the carbon dioxide absorption unit 14 in a stream
through line 28, and is passed through a heat exchanger 30 where it
is heated to a temperature preferably of from about 90 to about
120.degree. C., and more preferably of from about 100 to
110.degree. C.
[0019] The heated carbon dioxide-laden amine-based solvent is
passed from the heat exchanger 30 through line 32 into the upper
portion of a stripping unit 16 which is operating preferably at a
temperature of from about 100 to about 110.degree. C. at the top
and at a temperature of from about 115 to about 125.degree. C. at
the bottom. In an exemplary embodiment, as the carbon dioxide-laden
amine-based solvent flows down through the stripping unit 16 over
mass transfer elements, which can be trays or random structured
packing, carbon dioxide is stripped from the amine solvent by an
upward flowing vapor, which is generally steam, to produce a carbon
dioxide rich top vapor and an amine recovery solvent containing a
carbon dioxide-depleted amine-based solvent including the amine
byproducts, and water. The carbon dioxide rich top vapor is
withdrawn from the upper portion of the stripping unit 16 through
line 34 and passed to a reflux condenser 36 where it is separated
into carbon dioxide gas and condensates. The condensates, which
comprise primarily water and amines, may be returned to the upper
portion of the stripping unit 16 via line 38. In an exemplary
embodiment, the carbon dioxide gas is introduced to the algae
source 18 via line 40 for consumption by the algae for
photosynthesis. A portion of the carbon dioxide gas may also be
passed along line 49 for other uses.
[0020] The amine recovery solvent is withdrawn from the lower
portion of the stripping unit 16 through line 42 and passed to a
reboiler 44 where it is heated to a temperature preferably of from
about 115 to about 125.degree. C. In one example, the reboiler 44
is driven by saturated steam 43 at a pressure of about 1.9 bar
(about 28 psig) or higher, which is withdrawn from the reboiler 44
in stream 45. The heating of the amine recovery solvent in the
reboiler 44 drives off the water which is passed as steam in line
46 into the lower portion of the stripping unit 16 where it serves
as the aforementioned upward flowing vapor. The resulting amine
recovery solvent is the carbon dioxide-depleted amine-based solvent
containing the amine byproducts and is withdrawn from the reboiler
44 through line 48.
[0021] In one exemplary embodiment, the carbon dioxide-depleted
amine-based solvent is purged from line 48 at a suitable outlet
point and is collected as a batch where the batch is fed to the
algae source 18 through line 50. The algae source 18 may be a
suitably sized body of water containing algae, such as a pond, or
other suitable environment for supporting algae known to those
skilled in the art. In another exemplary embodiment, the carbon
dioxide-depleted amine-based solvent is fluidly communicated from
line 48 to the algae source 18 via lines 52, 54 and 50. In either
of these exemplary embodiments, the amine byproducts are fed to the
algae source together with the remaining portion of the carbon
dioxide-depleted amine-based solvent but separately from the carbon
dioxide gas, which is fed to the algae source via line 40. Since
the amine-based solvent is typically basic and the algae in the
algae source 18 prefers neutral to moderate basic conditions,
preferably the carbon dioxide-depleted amine-based solvent is
introduced to the algae source 18 at a suitable mass rate so as to
not cause the algae source 18 to have a pH exceeding about 11.
[0022] In an exemplary embodiment, the amine byproducts or at least
a portion of the amine byproducts are nutrients for the algae and
are readily digested by the algae source 18. Moreover, the carbon
dioxide-depleted amine-based solvent may also be nutrients for the
algae, and accordingly, may be readily digested by the algae source
18. In another exemplary embodiment, the algae source 18 contains
bacteria that are effective to convert at least portions of amine
byproducts and/or the carbon dioxide-depleted amine-based solvent
into nutrients for consumption by the algae source 18.
[0023] In another exemplary embodiment, the carbon dioxide-depleted
amine-based solvent is introduced to the reclaimer unit 20 for
separation of the amine byproducts from the solvent prior to
introduction to the algae source 18. In one example, the carbon
dioxide-depleted amine-based solvent is purged from line 48 and
collected as a batch which is introduced to the reclaimer unit 20.
In another example, the carbon dioxide-depleted amine-based solvent
is fluidly communicated from line 48 to the reclaimer unit 20
through lines 52 and 56.
[0024] In an exemplary embodiment, the reclaimer 20 operates in a
semi-continuous batch mode. At the start of a reclaiming cycle, the
carbon dioxide-depleted amine-based solvent is charged to the
reclaimer 20, preferably diluted with water from line 59, to
establish a liquid level. As the solvent is distilled, additional
carbon dioxide-depleted amine-based solvent is fed to the reclaimer
20 to maintain the liquid level. Initially, the overhead vapor in
the reclaimer 20 is mostly water. As the distillation continues,
the liquid and vapor phases become more and more concentrated with
the amine-based solvent. The amine byproducts accumulate as an
effluent in the bottom of the reclaimer 20 and the boiling
temperature of the liquid phase continues to rise until the
condensing temperature remains that of the pure amine-based solvent
and water. In one example, to ensure effective reclaimer operation,
a temperature is specified as the cut off temperature for the
reclaimer 20 defining the endpoint for distillation. To recover
more amine-based solvent, the solution may then be diluted again
with water to lower the boiling point temperature and the batch
distillation is continued until the end point temperature is again
achieved. Multiple reclaiming cycles may be used to achieve the
desired level of purity, thereby producing a regenerated
amine-based solvent.
[0025] In an exemplary embodiment, the amine byproducts effluent,
which contains the amine byproducts, is fed to the algae source 18
for digestion by the algae. In one example, the amine byproducts
effluent is purged from the reclaimer unit 20 as a batch which is
fed to the algae source 18 via line 50. In another example, the
amine byproducts effluent is fluidly communicated from the
reclaimer unit 20 to the algae source 18 via lines 58 and 50.
[0026] In an exemplary embodiment, the regenerated amine-based
solvent is introduced back to the absorber unit 14 by any number of
suitable pathways in the system 10. In one example, the regenerated
amine-based solvent is withdrawn from the reclaimer unit 20 and
passed to pump 62 via line 60. The pump 62 advances the regenerated
amine-based solvent through lines 64, 66 and 48 to the heat
exchanger 30, where it provides at least a portion of heat for
heating the aforementioned carbon dioxide-laden amine-based solvent
stream, and from it emerges partially cooled. The partially cooled
regenerated amine-based solvent is then passed through the cooler
70, which cools the solvent, forming a cooled regenerated
amine-based solvent. As illustrated, a pumped 72 advances the
cooled regenerated amine-based solvent to the absorber unit 14.
[0027] Accordingly, processes and systems for discharging amine
byproducts formed in an amine-based solvent have been described.
The various embodiments comprise contacting the amine-based solvent
with flue gas in a carbon dioxide absorber unit to form a carbon
dioxide-laden amine-based solvent that contains the amine
byproducts. The carbon dioxide is separated from the carbon
dioxide-laden amine-based solvent to form a carbon dioxide-depleted
amine-based solvent. The amine byproducts from a carbon dioxide
depleted amine-based solvent are fed to an algae source for
digestion by the algae. Accordingly, the amine byproducts do not
need to be disposed of as hazardous waste, which would otherwise be
environmentally objectionable. Furthermore, the cost of maintaining
an algae source is nominal especially if the algae source is
already on site and being used to consume carbon dioxide for
photosynthesis. Moreover, a reclaimer unit may be used to separate
the amine byproducts from the carbon dioxide-depleted amine-based
solvent prior to being fed to the algae source to form a
regenerated amine-based solvent and an amine byproducts effluent.
In this embodiment, the amine byproducts effluent is fed to the
algae source and the regenerated amine-based solvent is preferably
introduced back to the carbon dioxide absorber unit, and thus, the
amine-based solvent does not need to be disposed of as hazardous
waste.
[0028] While at least one exemplary embodiment has been presented
in the foregoing Detailed Description, it should be appreciated
that a vast number of variations exist. It should also be
appreciated that the exemplary embodiment or exemplary embodiments
are only examples, and are not intended to limit the scope,
applicability, or configuration of the invention in any way.
Rather, the foregoing Detailed Description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention, it being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set forth in the appended Claims
and their legal equivalents.
* * * * *