U.S. patent application number 16/599864 was filed with the patent office on 2020-04-16 for ammonia-based flue gas desulfurization system and method.
The applicant listed for this patent is Marsulex Environmental Technologies Corporation. Invention is credited to Michael T. Hammer, Paul M. Leicht, Michael L. Mengel.
Application Number | 20200116355 16/599864 |
Document ID | / |
Family ID | 70161210 |
Filed Date | 2020-04-16 |
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United States Patent
Application |
20200116355 |
Kind Code |
A1 |
Leicht; Paul M. ; et
al. |
April 16, 2020 |
AMMONIA-BASED FLUE GAS DESULFURIZATION SYSTEM AND METHOD
Abstract
Wet flue gas desulfurization systems and methods for contacting
a flue gas with a scrubbing liquid to produce ammonium thiosulfate.
The scrubbing liquid absorbs sulfur dioxide and optionally
additional acidic gases from the flue gas to produce a scrubbed
flue gas, the scrubbing liquid with the absorbed sulfur dioxide
therein is collected, and ammonia and elemental sulfur are
introduced into the collected scrubbing liquid to react the
ammonia, the absorbed sulfur dioxide, and the elemental sulfur in
the collected scrubbing liquid to produce ammonium thiosulfate.
Inventors: |
Leicht; Paul M.; (Myerstown,
PA) ; Mengel; Michael L.; (Fredericksburg, PA)
; Hammer; Michael T.; (Birdsboro, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Marsulex Environmental Technologies Corporation |
Lebanon |
PA |
US |
|
|
Family ID: |
70161210 |
Appl. No.: |
16/599864 |
Filed: |
October 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62744338 |
Oct 11, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23J 15/04 20130101;
F23J 2215/20 20130101; F23J 2219/40 20130101; F23J 2217/50
20130101 |
International
Class: |
F23J 15/04 20060101
F23J015/04 |
Claims
1. A wet flue gas desulfurization system comprising: an absorber
through which a flue gas flows; a contact region in the absorber
having means for contacting the flue gas with a scrubbing liquid so
that the scrubbing liquid absorbs sulfur dioxide and optionally
additional acidic gases from the flue gas to produce a scrubbed
flue gas; a reaction tank located so that the scrubbing liquid is
received in the reaction tank after the scrubbing liquid has
absorbed the sulfur dioxide from the flue gas; a source of
elemental sulfur; and a device for introducing the elemental sulfur
from the source into the scrubbing liquid within the reaction tank;
wherein the scrubbing liquid contains ammonia and ammonium
thiosulfate is produced as a byproduct of a reaction of the
ammonia, the sulfur dioxide, and the elemental sulfur in the
scrubbing liquid.
2. The wet flue gas desulfurization system of claim 1, further
comprising an injector that injects the ammonia into the scrubbing
liquid.
3. The wet flue gas desulfurization system of claim 1, wherein the
device for introducing the elemental sulfur is an injector.
4. The wet flue gas desulfurization system of claim, wherein the
absorber is a converted absorber of a pre-existing calcium-based
flue gas desulfurization system.
5. The wet flue gas desulfurization system of claim 1, wherein the
absorber is a converted absorber of a pre-existing ammonia-based
flue gas desulfurization system.
6. A wet flue gas desulfurization method comprising: contacting a
flue gas with a scrubbing liquid so that the scrubbing liquid
absorbs sulfur dioxide and optionally additional acidic gases from
the flue gas to produce a scrubbed flue gas; collecting the
scrubbing liquid with the absorbed sulfur dioxide and introducing
ammonia and elemental sulfur into the collected scrubbing liquid to
react the ammonia, the absorbed sulfur dioxide, and the elemental
sulfur in the collected scrubbing liquid to produce ammonium
thiosulfate.
7. The wet flue gas desulfurization method of claim 6, the method
further comprising controlling operating parameters including
temperature, pH, and sulfur concentration in the collected
scrubbing liquid to form the ammonium thiosulfate without forming a
secondary byproduct.
8. The wet flue gas desulfurization method of claim 7, wherein the
method is performed with a wet flue gas desulfurization system.
9. The wet flue gas desulfurization method of claim 8, the method
further comprising constructing the wet flue gas desulfurization
system by converting a pre-existing calcium-based flue gas
desulfurization system.
10. The wet flue gas desulfurization method of claim 8, the method
further comprises constructing the wet flue gas desulfurization
system by converting a pre-existing ammonia-based flue gas
desulfurization system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/744,338, filed Oct. 11, 2018, the contents of
which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention generally relates to flue gas
desulfurization (FGD) systems and processes for removing acidic
gases from gas streams, including but not limited to utility and
industrial flue gases. The invention particularly relates to an
ammonia-based flue gas desulfurization (FGD) system and method for
producing ammonium thiosulfate as a valuable byproduct.
[0003] Gas-liquid contactors and absorbers (hereinafter
collectively referred to as absorbers) are widely used to remove
substances such as gases and particulate matter from flue gases
produced by utility and industrial plants. Often of particular
concern are sulfur dioxide (SO.sub.2) and other acidic gases
produced by the combustion of fossil fuels and various industrial
operations. These gases are known to be hazardous to the
environment and their emission into the atmosphere is closely
regulated by clean air statutes. The method by which these gases
are removed with an absorber is commonly referred to as wet flue
gas desulfurization (wet FGD, or WFGD).
[0004] Wet FGD systems are typically located downstream of a
baghouse and/or an electrostatic precipitator intended to remove
particulate matter from a flue gas. The cleansing action produced
by absorbers is generally derived from the passage of the flue gas
cocurrently or countercurrently to a descending scrubbing liquid
(typically a slurry or solution) that absorbs the targeted gas(es)
and particulate matter. The scrubbing liquid is typically pumped
through banks of spray nozzles, which atomize the scrubbing liquid
into fine droplets to promote contact with the flue gas. The
droplets absorb SO.sub.2 and other gases from the flue gas to yield
what may be termed a scrubbed or desulfurized flue gas. Introducing
the scrubbing liquid as fine droplets also facilitates the reaction
of the SO.sub.2 with reagents in the scrubbing liquid. The
resulting desulfurized flue gas passes through mist eliminators to
remove entrained droplets before being sent to a stack for release.
The scrubbing liquid with the absorbed SO.sub.2 is collected in a
reaction tank where reactions occur to produce byproducts of the
scrubbing process.
[0005] Wet flue gas desulfurization processes have typically
involved the use of an alkaline scrubbing liquid, such as a
calcium-based slurry, or a sodium-based solution, or an
ammonia-based solution. While effective, absorbers utilizing
calcium-based slurries produce large quantities of wastes or
gypsum, the latter having only nominal commercial value. In
contrast, ammonia-based scrubbing processes have been gaining use
to produce a more valuable ammonium sulfate byproduct that is
usable as a fertilizer. In these processes, sulfur dioxide is
absorbed from flue gases with an ammonium sulfate solution as the
scrubbing liquid, after which the absorbed sulfur dioxide is
reacted with oxygen and anhydrous or aqueous ammonia injected into
the solution to form additional ammonium sulfate solution or
ammonium sulfate crystals ((NH.sub.4).sub.2SO.sub.4). Particular
examples of ammonia-based scrubbing processes are disclosed in U.S.
Pat. Nos. 4,690,807, 5,362,458, 6,187,278, 6,277,343, 7,771,685,
and 9,327,234, whose contents are incorporated herein by reference.
In addition to being required to react with sulfur dioxide to
produce ammonium sulfate, ammonia also serves to increase the
efficiency of sulfur dioxide removal by reducing the acidity of the
ammonium sulfate solution, which becomes more acidic with the
absorption of sulfur dioxide. Compared to calcium-based and
sodium-based scrubbing processes, ammonia-based scrubbing processes
often require a relatively large reaction tank in which the
absorbed sulfur dioxide can be reacted to form the desired ammonium
sulfate byproduct.
BRIEF DESCRIPTION OF THE INVENTION
[0006] The present invention provides ammonia-based flue gas
desulfurization (FGD) systems and methods suitable for removing
sulfur dioxide from flue gases and generating ammonium thiosulfate
as a byproduct.
[0007] According to one aspect of the invention, a flue gas
desulfurization (FGD) system is provided that includes an absorber
through which a flue gas flows. A contact region in the absorber
has means for contacting the flue gas with a scrubbing liquid so
that the scrubbing liquid absorbs sulfur dioxide and optionally
additional acidic gases from the flue gas to produce a scrubbed
flue gas. A reaction tank is located so that the scrubbing liquid
is received in the reaction tank after the scrubbing liquid has
absorbed the sulfur dioxide from the flue gas. The system further
includes a source of elemental sulfur, and a device for introducing
the elemental sulfur from the source into the scrubbing liquid
within the reaction tank. The scrubbing liquid contains ammonia and
ammonium thiosulfate is produced as a byproduct of a reaction of
the ammonia, the sulfur dioxide, and the elemental sulfur in the
scrubbing liquid.
[0008] According to another aspect of the invention, a wet flue gas
desulfurization method includes contacting a flue gas with a
scrubbing liquid so that the scrubbing liquid absorbs sulfur
dioxide and optionally additional acidic gases from the flue gas to
produce a scrubbed flue gas, and collecting the scrubbing liquid
with the absorbed sulfur dioxide and introducing ammonia and
elemental sulfur into the collected scrubbing liquid to react the
ammonia, the absorbed sulfur dioxide, and the elemental sulfur in
the collected scrubbing liquid to produce ammonium thiosulfate.
[0009] Technical effect of systems and methods having features as
described above preferably include the capability of removing
sulfur dioxide from a flue gas and producing ammonium thiosulfate
as a byproduct, which is currently a significantly higher value
byproduct than conventional WFGD byproducts such as gypsum.
[0010] Other aspects and advantages of this invention will be
appreciated from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 schematically represents a cross-sectional view of an
absorber of a wet flue gas desulfurization system configured in
accordance with a nonlimiting embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0012] Disclosed herein are wet flue gas desulfurization (FGD)
systems equipped with an absorber for contacting a flue gas with a
scrubbing liquid to remove sulfur dioxide and potentially other
acidic gases from the flue gas, and further include the injection
of elemental sulfur into the scrubbing solution to produce a
thiosulfate (S.sub.2O.sub.3.sup.-2) byproduct, for example,
ammonium thiosulfate ((NH.sub.4).sub.2S.sub.2O.sub.3; or
H.sub.8N.sub.2O.sub.3S.sub.2).
[0013] Ammonium thiosulfate, which has various uses in industry,
has been typically produced by one of two methods. One method is to
mix solutions of ammonium sulfate and sodium thiosulfate, followed
by cooling and filtration of the resultant products, which are a
solid sodium sulfate precipitant and the highly soluble ammonium
thiosulfate. The second process utilizes hydrogen sulfide, sulfur
dioxide, ammonia, and oxygen to generate ammonium thiosulfate. The
present invention provides for the production of ammonium
thiosulfate as a valuable byproduct of a desulfurization process.
As such, the process disclosed herein does not require feed streams
conventionally required to produce ammonium thiosulfate, and
instead can be incorporated into existing processes intended to
provide the environmental advantage of removing acidic gases from
waste streams, including but not limited to utility and industrial
flue gases.
[0014] FIG. 1 schematically represents a nonlimiting embodiment of
a flue gas absorber 10 of a type that can be employed by the
invention. The absorber 10 is generally of the type that scrubs
flue gases produced by utility and industrial facilities that burn
fossil fuels, as well as other processes that result in a flue gas
that contains sulfur dioxide and often other acidic gas,
nonlimiting examples of which include hydrogen chloride and
hydrogen fluoride. The absorber 10 includes a contact region 14 in
which a contact medium is brought into contact with a flue gas that
enters the absorber 10 through an inlet duct 12. The contact medium
is an alkaline liquor, typically a slurry or solution, referred to
herein as a scrubbing liquid 16 as a matter of convenience. The
scrubbing liquid 16 is shown as being collected in a reaction tank
18 at a lower end of the absorber 10, and circulated with a pump 20
to the contact region 14, where devices 22 (as nonlimiting
examples, spray nozzles) atomize and disperse the scrubbing liquid
16 as fine droplets 24 within the contact region 14 to promote
contact with the flue gas and absorb acidic gases therefrom.
[0015] After being scrubbed by the scrubbing liquid 16, the
scrubbed (desulfurized) flue gas continues upward from the contact
region 14 to enter a section of the absorber 10 intended to remove
liquid carryover of the scrubbing liquid 16, for example, droplets
and/or fine aerosol particulates that are typically entrained in
the scrubbed flue gas. In FIG. 1, the scrubbed flue gas enters a
bulk liquid entrainment separator 34, which is intended to remove
large droplets from the flue gas by causing the droplets to impinge
one or more surfaces that collect the droplets and enable the
collected liquid to be drained from the absorber 10. FIG. 1
schematically represents a mist eliminator 40 located above the
entrainment separator 34 to further remove droplets of the
scrubbing liquid from the scrubbed flue gas, and particularly fine
droplets and/or aerosol particulates that the entrainment separator
34 did not or cannot remove from the scrubbed flue gas. Various
designs for entrainment separators and mist eliminators that are
suitable for use in the absorber 10 are conventional or otherwise
known in the art, and therefore will not be discussed in any detail
here. After passing through the mist eliminator 40, the
desulfurized flue gas is eventually released to atmosphere through
a chimney 26 or other suitable structure.
[0016] In the present invention, in which ammonium thiosulfate
((NH.sub.4).sub.2S.sub.2O.sub.3) is the or an intended byproduct,
the scrubbing liquid 16 represented in FIG. 1 is an aqueous
solution that contains ammonium sulfate and the embodiment of the
absorber 10 is further equipped with means for injecting elemental
sulfur and ammonia (anhydrous or aqueous (ammonium hydroxide)) into
the scrubbing liquid 16 that has collected in the reaction tank 18
below the contact region 14. As part of the chemical reaction to
meet the required sulfur levels for producing ammonium thiosulfate,
FIG. 1 represents elemental sulfur as being introduced directly
into the scrubbing liquid 16 within the tank 18 with an injector 28
connected to a source 30 of elemental sulfur. In FIG. 1, ammonia is
represented as being introduced into the tank 18 with a separate
injector 32. In addition to being required for the reaction that
produces ammonium thiosulfate, ammonia also serves to increase the
efficiency of sulfur dioxide removal from the scrubbing liquid 16
by reducing the acidity of the scrubbing liquid 16, which becomes
more acidic with the absorption of sulfur dioxide. A reaction
occurring in the scrubbing liquid 16 collected in the tank 18 is
summarized as follows.
2NH.sub.3+SO.sub.2+H.sub.2O+S.fwdarw.(NH.sub.4).sub.2S.sub.2O.sub.3
As noted above, the ammonia is present as a result of the anhydrous
and/or aqueous ammonia introduced into the scrubbing liquid 16 by
the injector 32, the sulfur dioxide is present in the scrubbing
liquid 16 as a result of being absorbed from the flue gases, the
water is present as a constituent of the aqueous ammonium sulfate
solution of the scrubbing liquid 16, and the elemental sulfur is
introduced into the scrubbing liquid 16 by the injector 28. A
portion of the scrubbing liquid 16 can be removed from the tank 18
and dewatered to precipitate ammonium thiosulfate, which can then
be sold as a valuable byproduct of the FGD process.
[0017] In preferred embodiments, the absorber 10 is specifically
designed and operated, by controlling such operating parameters as
temperature, pH and sulfur concentration, to generate ammonium
thiosulfate without producing or yielding a secondary byproduct.
The reaction that produces ammonium thiosulfate does not require a
reaction tank of a size (volume) typically required of prior
ammonia-based WFGD systems, allowing pre-existing calcium-,
sodium-, and ammonia-based WFGD systems to be converted to produce
ammonium thiosulfate. As such, the absorber 10 may be part of a new
or pre-existing ammonia-based WFGD system, or be installed as an
upgrade and retrofit of a pre-existing calcium-based
(lime/limestone) or sodium-based WFGD system.
[0018] While the invention has been described in terms of a
specific or particular embodiment, it should be apparent that
alternatives could be adopted by one skilled in the art. For
example, the absorber 10 and its components could differ in
appearance and construction from the embodiment described herein
and shown in the drawing, functions of certain components of the
absorber 10 could be performed by components of different
construction but capable of a similar (though not necessarily
equivalent) function, various materials could be used in the
fabrication of the absorber 10 and/or its components, and the
absorber 10 could be installed in various types of FGD systems. In
addition, the invention encompasses additional or alternative
embodiments in which one or more features or aspects of a
particular embodiment could be eliminated. Accordingly, it should
be understood that the invention is not necessarily limited to any
embodiment described herein or illustrated in the drawing. It
should also be understood that the phraseology and terminology
employed above are for the purpose of describing the disclosed
embodiment, and do not necessarily serve as limitations to the
scope of the invention. Therefore, the scope of the invention is to
be limited only by the following claims.
* * * * *