U.S. patent application number 10/441116 was filed with the patent office on 2003-10-16 for processes and systems for using biomineral by-products as a fuel and for nox removal at coal burning power plants.
Invention is credited to Faulmann, Ervin L., Logan, Terry J..
Application Number | 20030192234 10/441116 |
Document ID | / |
Family ID | 21874415 |
Filed Date | 2003-10-16 |
United States Patent
Application |
20030192234 |
Kind Code |
A1 |
Logan, Terry J. ; et
al. |
October 16, 2003 |
Processes and systems for using biomineral by-products as a fuel
and for NOx removal at coal burning power plants
Abstract
Processes and systems are provided that include introducing
ammonia liberated from organic waste to a coal burner in a coal
burning power plant, preferably for NO.sub.x removal at the power
plant. The ammonia is preferably either ammonia liberated upon
drying a mixture of organic waste and coal combustion byproducts or
ammonia liberated when organic waste is mixed with coal combustion
by-products and one or more alkaline additives. Also provided are
processes and systems of fueling a coal burner of a power plant
with coal and either a dried mixture of organic waste and coal
combustion by-products, or a mixture of organic waste, coal
combustion by-products and one or more alkaline additives. The
present invention is further directed to mixtures of either organic
waste and coal combustion by-products, or mixtures of organic
waste, coal combustion by-products and alkaline additives made by
the processes of the present invention.
Inventors: |
Logan, Terry J.; (Columbus,
OH) ; Faulmann, Ervin L.; (Toledo, OH) |
Correspondence
Address: |
KENYON & KENYON
1500 K STREET, N.W., SUITE 700
WASHINGTON
DC
20005
US
|
Family ID: |
21874415 |
Appl. No.: |
10/441116 |
Filed: |
May 20, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10441116 |
May 20, 2003 |
|
|
|
10034118 |
Jan 3, 2002 |
|
|
|
10034118 |
Jan 3, 2002 |
|
|
|
09839112 |
Apr 23, 2001 |
|
|
|
6405664 |
|
|
|
|
Current U.S.
Class: |
44/504 |
Current CPC
Class: |
C10L 5/46 20130101; F23G
2201/702 20130101; F23G 2204/101 20130101; Y02E 20/12 20130101;
Y02P 20/145 20151101; Y02P 20/129 20151101; Y02E 50/30 20130101;
F23G 2209/26 20130101; F23G 5/02 20130101; C10L 5/44 20130101; F23G
2201/10 20130101; Y02E 50/10 20130101; C05F 11/00 20130101; C10L
5/42 20130101; F23G 2209/22 20130101; F23G 2900/7003 20130101; F23G
7/001 20130101; F23G 2201/701 20130101; C10L 5/48 20130101 |
Class at
Publication: |
44/504 |
International
Class: |
C10L 005/00 |
Claims
We claim:
1. A coal burner feedstock comprising coal and a mixture of organic
waste/coal combustion by-product/alkaline additive formed by a
process comprising mixing organic waste, one or more coal
combustion by-products, and one or more alkaline additives to form
an organic waste/coal combustion byproduct/alkaline additive
mixture having a solids content of at least 50%; and combining the
organic waste/coal combustion by-product/alkaline additive mixture
with coal.
2. The feedstock of claim 1, wherein said organic waste/coal
combustion byproduct/alkaline additive mixture has a solids content
of at least 75%.
3. The feedstock of claim 1, wherein said organic waste/coal
combustion byproduct/alkaline additive mixture has a solids content
of at least 90%.
4. The feedstock of claim 1, wherein said coal comprises pulverized
coal.
5. The feedstock of claim 1, comprising one or more coal combustion
byproducts selected from the group consisting of fly ash, fluidized
bed ash, flue gas desulfurization by-products and mixtures
thereof.
6. The feedstock of claim 5, wherein said coal combustion
by-product comprises fly ash.
7. The feedstock of claim 1, wherein said alkaline additive is
selected from the group consisting of lime, calcium hydroxide,
calcium carbonate, cement kiln dust, lime kiln dust and mixtures
thereof.
8. The feedstock of claim 7, wherein said alkaline additive
comprises lime.
9. The feedstock of claim 7, wherein said alkaline additive
comprises cement kiln dust.
10. The feedstock of claim 7, wherein said alkaline additive
comprises lime kiln dust.
11. The feedstock of claim 1, wherein said organic waste comprises
waste selected from the group consisting of sewage sludges, animal
manures, pulp and paper waste, fermentation waste, food waste,
paper and cardboard, and other industrial organic waste.
12. A coal burner feedstock comprising coal and a mixture of
organic waste/coal combustion by-product formed by a process
comprising mixing organic waste and one or more coal combustion
by-products to form an organic waste/coal combustion by-product
mixture having a solids content of at least 50%; and combining the
organic waste/coal combustion by-product mixture with coal.
13. The process of claim 12, wherein said organic waste/coal
combustion byproduct mixture has a solids content of at least
75%.
14. The process of claim 12, wherein said organic waste/coal
combustion byproduct mixture has a solids content of at least
90%.
15. The process of claim 12, wherein said coal comprises pulverized
coal.
16. The process of claim 12, comprising one or more coal combustion
byproducts selected from the group consisting of fly ash, fluidized
bed ash, flue gas desulfurization by-products and mixtures
thereof.
17. The process of claim 16, wherein said coal combustion
by-product comprises fly ash.
18. The process of claim 12, wherein said organic waste comprises
waste selected from the group consisting of sewage sludges, animal
manures, pulp and paper waste, fermentation waste, food waste,
paper and cardboard, and other industrial organic waste.
19. A coal burner feed stock comprising coal and an organic
waste/coal combustion by-product mixture, wherein said organic
waste/coal combustion by-product mixture has a solids content of at
least 50%.
20. The feedstock of claim 19, wherein said organic waste/coal
combustion by-product mixture has a solids content of at least
75%.
21. The feedstock of claim 19, wherein said organic waste/coal
combustion by-product mixture has a solids content of at least
90%.
22. The feedstock of claim 19, wherein said coal comprises
pulverized coal
23. The feedstock of claim 19, comprising one or more coal
combustion by-products selected from the group consisting of fly
ash, fluidized bed ash, flue gas desulfurization by-products and
mixtures thereof.
24. The feedstock of claim 23, wherein said coal combustion
by-product comprises fly ash.
25. The feedstock of claim 19, wherein said organic waste comprises
waste selected from the group consisting of sewage sludges, animal
manures, pulp and paper waste, fermentation waste, food waste,
paper and cardboard, and other industrial organic waste.
26. The feedstock of claim 19, further comprising an alkaline
additive selected from the group consisting of lime, calcium
hydroxide, calcium carbonate, cement kiln dust, lime kiln dust and
mixtures thereof.
27. The feedstock of claim 26, wherein said alkaline additive
comprises lime.
28. The feedstock of claim 26, wherein said alkaline additive
comprises cement kiln dust.
29. The feedstock of claim 26, wherein said alkaline additive
comprises lime kiln dust.
Description
[0001] This application is a continuation-in-part of co-pending
application U.S. Ser. No. 09/839,112, the subject matter of which
is incorporated by reference hereto.
FIELD OF THE INVENTION
[0002] The present invention is directed to processes and systems
at coal burning power plants, which include introducing ammonia
liberated from organic waste to a coal burner in the power
plant.
[0003] The present invention is also directed to processes and
systems of fueling a coal burner of a power plant with coal and
either a dried mixture of organic waste and one or more coal
combustion by-products, or a mixture of organic waste, one or more
coal combustion by-products, and optionally one or more alkaline
additives.
[0004] The present invention is further directed to dried mixtures
of organic waste and coal combustion by-products or mixtures of
organic waste, coal combustion byproducts and optional alkaline
additives made by the processes of the present invention.
BACKGROUND OF THE INVENTION
[0005] Mineral by-products have been used in stabilizing
semi-solid, odorous organic waste through bulk drying, odor
absorption, and granulation (see e.g., U.S. Pat. Nos. 3,877,920 and
4,554,002). In addition, mineral materials including sand,
diatomaceous earth, perlite, and various mineral reagent powders
have been used in conjunction with fluidized heating, drying and
burning of sludges and oily waste (see e.g., U.S. Pat. Nos.
4,159,682, 4,787,323, 4,970,803, 5,490,907). However, existing
thermal dryers have ongoing problems with drying waste high in
organics, particularly sewage sludges, in the waste sticking to
dryer surfaces, charring and producing burnt organic matter odors,
and catching on fire.
[0006] Organic waste has traditionally been disposed of by
incineration, primarily in stand-alone plants designed for a
particular waste. Wet waste, such as dewatered sewage sludge filter
cake, requires supplemental fuel to initiate and sustain burning,
and sludges are not self-burning until solids contents are greater
than about 30%. Dry organic waste such as paper and cardboard are
net energy producers and municipal refuse incinerators that use
these feedstocks are capable of significant power generation.
Likewise, dried animal manures like broiler chicken litter, which
contains sawdust that is used as bedding, can have a solids content
in excess of 75% and can be incinerated with out supplemental fuel.
Processes of more efficiently disposing of organic waste are
desirable.
[0007] NO.sub.x created during the burning of coal can react with
volatile organic compounds in the presence of heat and sunlight to
form ozone. Gaseous ammonia, in the form of commercial anhydrous
ammonia and its main derivative, urea, are currently used in
treating fossil fuel combustion exhausts for NO.sub.x removal. This
is a very expensive process, however. Therefore, inexpensive
sources of ammonia or methods of recycling ammonia are
desirable.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to processes and systems
at coal burning power plants, which include introducing ammonia
liberated from organic waste to a coal burner in the power plant.
The ammonia may be ammonia that is liberated upon drying a mixture
of organic waste and one or more coal combustion byproducts,
preferably having a pH of at least 9.5, or the ammonia may be
ammonia that is liberated when organic waste is mixed with one or
more coal combustion byproducts, such as fly ash, and one or more
alkaline additives. Preferably, the present processes and systems
remove NO.sub.x at the power plant. The liberated ammonia that is
introduced to the coal burner by the present processes and systems,
may supplement commercial anhydrous ammonia or urea added to the
coal burner, for example, for NO.sub.x removal.
[0009] The present invention is also directed to processes and
systems of fueling a coal burner of a power plant with coal and
either a dried mixture of organic waste and coal combustion
by-products, or a mixture of organic waste, coal combustion
by-products and optionally alkaline additives. The coal is
preferably pulverized coal. In this embodiment, the dried mixture
of organic waste and coal combustion by-products or the mixture of
organic waste, coal combustion by-products and alkaline additives,
is optionally a source of supplemental fuel to the coal burner.
[0010] The present invention is further directed to dried mixtures
of organic waste and coal combustion by-products made by the
processes of the present invention, and to mixtures of organic
waste, coal combustion by-products and optional alkaline additives
made by the processes of the present invention. The mixtures of the
present invention optionally additionally contain lime.
[0011] Non-limiting examples of organic waste used in the process
of the present invention include, but are not limited to, dewatered
sewage sludge filter cake, various animal manures, pulp and paper
waste, fermentation waste, shredded paper and cardboard, food waste
(such as food processing waste), and other organic industrial waste
and mixtures thereof.
[0012] Certain embodiments of the present invention do not require
drying, such as in the case of organic wastes that are already dry.
However, in embodiments that include drying, a mixture of organic
waste and one or more coal combustion byproducts (optionally
including one or more alkaline additives) is dried to preferably at
least 50% solids, more preferably at least 75% solids, even more
preferably at least 90% solids. The drying preferably takes place
in a direct or indirect dryer and preferably uses waste heat from
the power plant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a flow diagram of an organic waste drying and fuel
feed system according to an embodiment of the present processes and
systems.
[0014] FIG. 2 is a flow diagram of the organic waste mixing and
fuel feed system of another embodiment of the present processes and
systems.
DETAILED DESCRIPTION
[0015] The present invention will now be described in detail with
regard to specific preferred embodiments of the invention, it being
understood that these embodiments are intended only as illustrative
examples and the invention is not to be limited thereto.
[0016] Coal-fired power plants must deal with the problems of
NO.sub.x removal from exhaust gases, renewable fossil fuel power
generation, odor, and dissipation of waste energy. The present
inventors have arrived at processes and systems that advantageously
synergistically incorporate processes of releasing ammonia from
organic waste and reducing NO.sub.x emissions at a power plant,
which utilizes waste (including for example, heat and/or
by-products) from each process in the other process.
[0017] Organic waste produces ammonia under certain conditions,
which excess ammonia may be used for example, to reduce NO.sub.x
emissions at a power plant. The present invention provides
processes at coal burning power plants, which include supplying
liberated ammonia from waste treatment to a coal burning power
plant, to preferably remove NO.sub.x from the plant.
[0018] Combining organic waste with one or more coal-combustion
by-products and drying the organic waste is a method by which
ammonia may be released from the waste. Drying waste, which
typically contains from about 12 to about 75% solids, depending on
waste type, is energy intensive. In the present invention, in which
drying is conducted at a power plant, waste heat from the plant can
be used as a heat source in drying the organic waste. Power plants
produce several types of waste heat: hot exhaust gases, hot ash,
steam and hot water. These sources are readily available for
organic waste drying. Whereas, if the power plant did not have a
recipient for the excess heat, the heat would have to be further
treated, e.g., excess steam or hot water must be cooled before they
can be discharged back into the environment. The present invention
reduces or eliminates the excess cooling step in present power
plants because the heat is used directly in the treatment of
organic waste.
[0019] According to an embodiment of the invention, processes are
provided that include mixing organic waste with one or more coal
combustion by-products (for example from a coal burner or furnace
of the power plant or from any other source known to those skilled
in the art) to form an organic waste-coal combustion byproduct
mixture, preferably having a pH of at least 9.5, even more
preferably having a pH of at least 10. As set forth in a U.S.
Provisional Application filed on Apr. 20 2001 entitled "Methods for
Controlling Ignitability of Organic Waste with Mineral
By-Products", which is hereby incorporated by reference herein in
its entirety, the addition of coal combustion by-product to organic
waste prior to drying is preferred in that it may serve to prevent
fires and explosions that are common in conventional organic
materials drying.
[0020] The next step in this embodiment includes drying with heat
the organic waste-coal combustion by-product mixture to preferably
at least 50% solids, more preferably at least 75% solids, even more
preferably at least 90% solids. According to an embodiment of the
invention, the mixture is dried to at least 95% solids, preferably
as near 100% solids as possible, thus forming a "dried organic
waste-coal combustion by-product mixture." The drying causes
ammonia to be liberated from the organic waste.
[0021] According to certain embodiments the organic waste is
sufficiently dry without a drying step that no drying step is
required for ammonia to be liberated from the organic waste. For
example, some poultry manures include 70% or more solids.
Accordingly, the present invention includes mixing organic waste
with one or more coal combustion by-products to form an organic
waste-coal combustion byproduct mixture, which releases ammonia
from the organic waste upon mixing.
[0022] The liberated ammonia is then introduced into a coal burner
of a coal burning power plant, preferably for NO.sub.x removal.
Alternatively, the ammonia may be introduced to the coal burner for
a purpose other than NO.sub.x removal that would be apparent to
those skilled in the art.
[0023] Under certain conditions, such as at pH conditions greater
than about 9.5 or greater than about 10.0, and under dry and hot
conditions, the ammonia in these wastes is converted to free
gaseous ammonia. Organic wastes that are particularly suitable for
use in this embodiment of the present invention contain ammonia
that is liberated under certain conditions (such as when the
organic waste is in a mixture having pH's above about 9.5 or above
about 10.0).
[0024] Examples of organic waste that may be used in accordance
with the present invention include, but are not limited to, sewage
sludges, such as dewatered sewage sludge filter cake; various
animal manures; pulp and paper waste; shredded paper and cardboard;
fermentation waste; food waste; and other industrial organic waste
as would be apparent to those skilled in the art. In particular,
organic waste such as sewage sludges, animal manures, fermentation
biomass, and some food waste are high in protein and ammonia, and
thus, are preferred in embodiments of the present invention that
involves liberating ammonia from the waste. What is meant by the
named types of waste would be readily apparent to those skilled in
the art.
[0025] Coal combustion by-products may include one or more
by-products from a coal burner (preferably from the coal burner
from which NO.sub.x may be removed by the processes of the present
invention) or coal combustion by-products from other sources.
Examples of coal combustion by-products according to the present
invention include, but are not limited to the following
by-products: fly ash, bottom ash, fluidized bed ash, flue gas
desulfurization by-products, lime, calcium hydroxide, and calcium
carbonate, and combinations or mixtures thereof. In particular,
preferred coal combustion by-products include alkaline mineral
by-products. As set forth herein, certain embodiments of the
present invention include one or more alkaline mineral by-products
in addition to the one or more coal combustion by-products that may
include alkaline mineral by-products.
[0026] Fly ashes are the mineral residues of burning coal for
electricity generation. Fly ash can be collected from the smoke
stack of a burner (or furnace) by bag houses, electrostatic
precipitators, or in down washes. Fly ashes have variable fineness,
solids content, and chemical composition. Preferable fly ashes for
use in the present invention are dry ashes. The chemical
composition of ash depends on the type of coal that is burned. For
example, coals from the western U.S. are typically high in calcium
and thus, may contain a higher lime content than coals from the
eastern U.S. Eastern coals are often higher in pyrite (FeS.sub.2),
which oxidizes on burning to SO.sub.2, producing an acidic fly ash.
Fly ashes are high in silicon, and are often in the form of a
spherical glass. Some fly ashes are high in residual carbon in the
form of charcoal and these are effective in absorbing biosolids
odors. Preferably, odors of the present processes and systems are
kept sufficiently low that the present processes and systems are
not unacceptable to plant operators, or others working at or near
the plant. Thus, the amount of coal combustion by-products (or
other ingredients to the mixture) that control odor level, such as
fly ash, for example, is preferably adjusted to as to maintain an
acceptable odor level.
[0027] Fluidized bed ash (FBA) refers to ash that is produced in a
fluidized bed burner, in which a mixture of pulverized coal and
limestone is burnt as a suspended, i.e., fluid, mass, the purpose
of the limestone being to react with SO.sub.2 produced from the
oxidation of pyrite in the coal.
[0028] Flue gas desulfurization by-product (FGD) is a general term
referring to a range of products formed when lime or limestone are
used to remove SO.sub.2 produced from the oxidation of pyrite in
the coal. FGDs may be pure gypsum (CaSO.sub.4.2H.sub.2O), anhydrite
(CaSO.sub.4), or CaSO.sub.3. FGDs may also contain fly ash, unburnt
carbon and unreacted lime.
[0029] Lime (CaO), calcium hydroxide (Ca(OH).sub.2), and limestone,
as calcite (CaCO.sub.3) or dolomite (CaMg(CO.sub.3), limestone,
cement kiln dust, lime kiln dust and FGD are alkaline by-products
familiar to those skilled in the art, many of which are
commercially available.
[0030] An embodiment of the processes of the present invention is
depicted in FIG. 1. As shown in FIG. 1, organic waste from source I
and one or more coal combustion by-products from source 2 are added
to a mixer 3 in which the organic waste and coal combustion
by-products are mixed with one another to form an organic
waste-coal combustion by-product mixture, preferably having a pH of
at least about 9.5, even more preferably at least 10. According to
one embodiment of the present invention, the mixing additionally
includes mixing lime with the organic waste and coal combustion
by-products. The organic waste-coal combustion by-product mixture
is then transferred to a dryer 4. Alternatively, the organic waste
and coal combustion by-products are mixed directly in the dryer 4
eliminating the need for a separate mixer 3.
[0031] Next, according to the embodiment depicted in FIG. 1, the
dryer 4 dries the organic waste-coal combustion by-product mixture
to preferably at least 50% solids, more preferably at least 75%
solids, even more preferably at least 90% solids, forming a dried
organic waste-coal combustion by-product mixture. However, certain
embodiments of the present invention do not require drying, such as
in the case of organic wastes that are already sufficiently dry
that mixing alone causes release of ammonia from the organic
waste.
[0032] Commercial dryers that may be used to accomplish drying, are
available in two forms, direct and indirect. A dryer according to
the present invention may include at least one direct dryer or
indirect dryer. Direct dryers use heated air in direct contact with
the organic waste. According to one embodiment, exhaust stack gases
from the power plant are used directly, or waste steam, hot ash, or
hot water from the power plant is used with a heat exchanger to
heat air for drying.
[0033] Alternatively, indirect dryers may be used for drying, which
heat metal surfaces that come in contact with the organic waste. In
an example of this embodiment, waste steam or hot water from the
power plant is used to heat the drying surfaces via a heat
exchanger in which the waste steam or water is used to heat oil,
the fluid normally used in indirect dryers. Non-limiting examples
of suitable dryers according to the present invention include
direct concurrent flow dryers, horizontal single, double and triple
pass indirect dryers, and vertical counter flow rotating disk
indirect dryers.
[0034] The heat for the drying may include using waste heat 5 from
the coal burning power plant in addition to or instead of heat from
another source, such as a steam turbine 11 in the embodiment
depicted in FIG. 1. As indicated above, the power plant waste heat
5 used in the drying may be in the form of hot exhaust gases, hot
ash, steam or hot water, for example, and may be used with direct
or indirect dryers.
[0035] When hot ash is a source of heat for the drying, hot ash may
be provided from a power plant, for example from the boiler of a
power plant. Either the heat of the hot ash may be used via some
sort of dryer and/or heat exchanger to heat the mixture, and/or hot
ash may be added directly to the mixture to dry it. That is, no
heat exchanger is necessary. For example, hot ash from a silo or
other source may be mixed in a mixer with the organic waste mixture
and through tumbling, heat from the hot ash dries the mixture. The
hot ash may be in any form known to those skilled in the art.
[0036] Drying the mixture of organic waste and coal combustion
by-products, preferably at a pH above 9.5 or 10, preferably causes
ammonia to be liberated from the organic waste. The liberated
ammonia of this embodiment is introduced as shown in stream 7, into
a coal burner 6.
[0037] The liberated ammonia that is introduced to the coal burner
by the present processes and systems, may supplement commercial
anhydrous ammonia or urea added to the coal burner for any purpose,
such as NO.sub.x removal. The amount of ammonia or urea may vary
depending, for example, on the amount of ammonia or urea needed in
order to reduce the NO.sub.x emissions of a particular power plant
to a desired (or required) level. The amount of ammonia or urea to
be introduced to the coal burner may be determined by those skilled
in the art.
[0038] In some embodiments, the mixture of organic waste and coal
combustion byproducts resulting from the present processes may not
produce ammonia. In these embodiments, the mixture may be useful
for other purposes, for example as a fuel source or soil
additive.
[0039] Drying may produce exhaust gases, in addition to the ammonia
and dried organic waste-coal combustion by-product mixture.
According to an embodiment of the present invention, the process
includes reacting scavenged exhaust gases from the drying step with
at least one reactive material to decrease the amount of polutant
gases, such as CO.sub.2, SO.sub.2 and/or SO.sub.3 in the exhaust
gases, preferably decreasing emissions from the drying step.
Examples of suitable reactive materials would be apparent to those
skilled in the art upon reading the present disclosure. Such
reactive materials may include, for example, Ca(OH).sub.2.
[0040] An embodiment of the present invention includes a process
where the coal combustion by-product preferably includes an
alkaline mineral by-product and the drying step produces a further
by-product. Thus, an embodiment includes mixing organic waste with
at least one coal combustion by-product, which preferably includes
at least one alkaline by-product, to form an organic waste-coal
combustion by-product mixture and at least one further by-product.
Another embodiment includes mixing organic waste with at least one
coal combustion by-product, which preferably includes at least one
alkaline by-product, to form an organic waste-coal combustion
by-product mixture, which is then dried with heat to at least 50%
solids, to form a dried organic waste-coal combustion by-product
mixture and at least one further by-product.
[0041] A further embodiment of the present invention includes
further by-products produced these processes. The further
by-products may be useful, for example, as soil additives that may
replace or be added in addition to agricultural limestone, for
example, to neutralize soil acidity.
[0042] Another embodiment of the present invention includes the
preferably dried, organic waste-coal combustion by-product mixture
formed by the above-described processes. This mixture may be added
to a coal burner of a power plant as depicted for example as feed
stream 8 in FIG. 1. A preferred embodiment includes forming a dried
organic waste-coal combustion by-product mixture by a process that
includes mixing organic waste with coal combustion by-products to
form an organic waste-coal combustion by-product mixture, and
drying the organic waste-coal combustion by-product mixture to at
least 50% solids, preferably at least 75% solids, even more
preferably at least 90% solids. The mixture may be used for
example, as a soil additive or as a feed-stock to another
process.
[0043] The processes of producing organic waste-coal combustion
by-product mixture of the present invention do not necessarily
release ammonia from the organic waste. For example, according to
an embodiment of the invention, the coal combustion by-product is
non-alkaline fly ash, which is mixed with organic waste to form an
organic waste-non-alkaline fly ash mixture that is then optionally
dried. The dried organic waste-non-alkaline fly ash mixture may be
used for various purposes, for example, to control burning at the
power plant and/or to control odors.
[0044] A further embodiment of the present invention includes
feeding the (preferably dried) organic waste-coal combustion
by-product mixture to a coal burner, preferably as supplemental
fuel, along with coal. The organic waste-coal combustion by-product
mixture may be suitable as a supplemental fuel because its caloric
content is similar to that of coal. For example, undigested sewage
sludge has a caloric content similar to that of coal, approximately
10,000 BTU per pound. The dried organic waste-coal combustion
by-product mixture is preferably mixed with the coal prior to being
fed to the coal burner. Preferably, the coal is pulverized
coal.
[0045] A further embodiment of the present invention includes
methods of changing the physical characteristics of organic wastes
to be more compatible with pulverized coal. Organic wastes that
have solids contents of 50% or greater have much lower densities
than coal. They may also have to undergo additional costly
processing, such as pelletization, before they can be mixed with
coal and burned. The methods of the present invention include
mixing organic waste with one or more mineral additives such as one
or more coal combustion by-products, or one or more alkaline
additives or combinations thereof to form organic waste mixtures
having densities that are more similar to coal than the organic
wastes alone. In addition, mixtures of organic wastes and mineral
additives have granular characteristics that make the mixtures more
physically compatible with coal. Also included in this embodiment
are organic waste mixtures that exhibit an improved compatibility
with pulverized coal, preferably formed by mixing organic waste
with one or more mineral additives, such as one or more coal
combustion by-products, or one or more alkaline additives or
combinations thereof.
[0046] An example of this embodiment is also depicted in FIG. 1.
According to FIG. 1, the preferably dried, organic waste-coal
combustion by-product mixture leaves the dryer 4 and is carried in
stream 8 to the coal feed 9 where the coal feed is mixed with the
dried organic waste-coal combustion by-product mixture prior to
being introduced to the coal burner 6.
[0047] The present invention is further directed to systems
including a coal burner of a power plant, a coal feed supplying
coal to the coal burner, and an ammonia feed to the coal burner.
The ammonia feed preferably includes ammonia liberated upon drying
an organic waste-coal combustion by product mixture to at least 50%
solids The steps involved in these systems, such as mixing and
drying the organic waste, and the ingredients of the system, such
as the organic waste and coal combustion byproducts, are as
described above with regard to the processes of the present
invention. According to a preferred embodiment, the coal feed
includes coal and a dried mixture of organic waste and one or more
coal combustion by-products. Preferably, the coal is pulverized
coal. According to a further embodiment, the coal and the dried
mixture of organic waste and coal combustion by-product are mixed
and then pulverized.
[0048] A further embodiment of the invention is directed to systems
including a coal burner of a power plant, and a feed of an organic
waste-coal combustion by-product mixture to the coal burner, where
the feed includes organic waste and one or more coal combustion
by-products mixed together and optionally dried. According to a
preferred embodiment, the feed of organic waste-coal combustion
by-product mixture further includes coal. Preferably, the coal is
pulverized coal. According to a further embodiment, the coal and
the dried mixture of organic waste and coal combustion by-product
are mixed and then pulverized.
[0049] Other systems of the present invention include a coal burner
of a coal burning power plant; an ammonia feed to the coal burner,
which preferably includes ammonia liberated upon mixing an organic
waste and one or more coal combustion by-products and/or drying
such a mixture to at least 50% solids; and a coal feed supplying
coal to the coal burner, which coal feed includes coal and the
mixture of organic waste and coal combustion by-product.
[0050] Under certain conditions, when organic waste is mixed with
one or more coal combustion by-products (such as fly ash), and
optionally one or more alkaline additives, ammonia in the organic
waste may be converted to free gaseous ammonia, without the need
for drying the mixture.
[0051] Therefore, according to another embodiment of the invention,
processes are provided that include mixing organic waste with one
or more coal combustion by-products (for example from a coal burner
or furnace of the power plant or from any other source known to
those skilled in the art) and optionally one or more alkaline
additives, preferably causing ammonia to be liberated from the
organic waste. The liberated ammonia of this embodiment is
introduced into a coal burner of a coal burning power plant. As set
forth above with regard to other embodiments of the invention, the
liberated ammonia is then preferably introduced to the coal burner.
Organic waste and the one or more coal combustion by-products
according to these embodiments are as set forth above with regard
to other embodiments of the present invention. Preferably, the one
or more coal combustion by-products of this embodiment include at
least one of fly ash, bottom ash and fluidized bed ash, more
preferably fly ash.
[0052] Alkaline additives according to the present invention,
include but are not limited to lime (CaO), calcium hydroxide
(Ca(OH).sub.2), and limestone, such as calcite (CaCO.sub.3) or
dolomite (CaMg(CO.sub.3), cement kiln dust and lime kiln dust.
Preferably, the alkaline additives are selected in kind and amount
so as to be sufficient to cause ammonia to be released from organic
waste upon mixing with the organic waste and one or more mineral
by-products, or upon heating the organic waste and one or more
mineral by-products.
[0053] An embodiment of the processes of the present invention is
depicted in FIG. 2. As shown in FIG. 2, organic waste from source
12, coal combustion by-products from source 13, and one or more
alkaline additives from source 14 are added to a mixer 15 in which
the organic waste, coal combustion by-products and alkaline
additives are mixed with one another to form an organic waste/coal
combustion by-products/alkaline additive mixture.
[0054] The organic waste/coal combustion by-products/alkaline
additive mixture may optionally be transferred from the mixer to a
dryer (not shown) to dry the mixture such that it preferably
contains at least 50% solids, more preferably at least 75% solids,
even more preferably at least 90% solids, forming a dried organic
waste-coal combustion by-product mixture. Dryers and heat sources
that may be used to accomplish such drying, are as described
above.
[0055] Mixing the organic waste, coal combustion by-products and
alkaline additives preferably causes ammonia to be liberated from
the organic waste. In embodiments, where ammonia is liberated from
the organic waste, the liberated ammonia is preferably fed into the
coal burner, for example in FIG. 2 ammonia is introduced as shown
in stream 16, into a coal burner 18.
[0056] The liberated ammonia that is introduced to the coal burner
18 by the present processes, may supplement commercial anhydrous
ammonia or urea added to the coal burner for any purpose, such as
for NO.sub.x removal. Alternatively, the ammonia may be introduced
to the coal burner for a purpose other than NO.sub.x removal that
would be apparent to those skilled in the art. The amount of
ammonia or urea may vary depending, for example, on the amount of
ammonia or urea needed in order to reduce the NO.sub.x emissions of
a particular power plant to a desired (or required) level. The
amount of ammonia or urea to be introduced to the coal burner for
NO.sub.x removal may be determined by those skilled in the art.
[0057] Exhaust gases (other than ammonia, such as CO.sub.2,
SO.sub.2, and SO.sub.3) may be produced by mixing the organic
waste, coal combustion by-products and alkaline additives or by
drying the resulting mixture. According to an embodiment of the
present invention, a process is provided that includes reacting
scavenged exhaust gases from a mixing or drying step with at least
one reactive material to decrease the amount of polutant gases,
such as CO.sub.2, and other exhaust gases, such as SO.sub.2 and
SO.sub.3, in the exhaust gases and thereby decrease any emissions
from the mixing or drying steps. Examples of suitable reactive
materials would be apparent to those skilled in the art upon
reading the present disclosure. Such reactive materials may
include, for example, Ca(OH).sub.2.
[0058] According to an embodiment of the invention, the coal
combustion byproducts mixed with organic waste and alkaline
additives may be provided in whole or in part from a burner or
furnace (such as coal burner 18 of FIG. 2).
[0059] Another embodiment of the present invention includes an
organic waste/coal combustion by-products/alkaline additive
by-product mixture formed by the above-described processes. This
mixture may be used for example, as a soil additive or as a
feed-stock to another process or may be added to a coal burner of a
power plant as depicted for example as feed stream 17 in FIG. 2.
The mixture may also be used to control odor and/or burning in the
plant. A preferred embodiment includes forming a organic waste/coal
combustion by-products/alkaline additive by-product mixture by a
process that includes mixing organic waste with coal combustion
by-products and at least one alkaline additive to form an organic
waste/coal combustion byproducts/alkaline additive by-product
mixture. The mixture is then optionally dried to at least 50%
solids, preferably at least 75% solids, even more preferably at
least 90% solids.
[0060] Another embodiment of the present invention includes feeding
the organic waste/coal combustion by-products/alkaline mixture to a
coal burner, preferably as supplemental fuel, along with coal. The
organic waste/coal combustion byproducts/alkaline additive
by-product mixture may be suitable as a supplemental fuel because
its caloric content is similar to that of coal. The organic
waste/coal combustion by-products/alkaline additive by-product
mixture is preferably mixed with the coal prior to being fed to the
coal burner. Preferably, the coal is pulverized coal.
[0061] An example of this embodiment is also depicted in FIG. 2.
According to FIG. 2, the organic waste/coal combustion
by-products/alkaline additive by-product mixture leaves the mixer
15 (or the dryer--not shown) and is carried in stream 17 to the
coal feed 19 where the coal feed is mixed with the organic
waste/coal combustion by-products/alkaline additives by-product
mixture before being introduced to the coal burner 18.
[0062] Further embodiments of the present invention include feeding
an organic waste/coal combustion by-products mixture that does not
necessarily include alkaline additives to a coal burner, preferably
as supplemental fuel, along with coal. In these embodiments, the
mixture may include one or more alkaline or non-alkaline additives
or no additives at all. By way of example, the present invention
includes a process that includes mixing organic waste (such as pulp
and paper waste) with one or more coal combustion by-products (such
as non-alkaline fly ash), and optionally one or more non-alkaline
additives that would be apparent to those skilled in the art, and
feeding the organic waste/coal combustion by-product/non-alkaline
additive mixture to a coal burner of a coal burning power plant.
The organic waste/coal combustion by-products mixture is preferably
mixed with the coal prior to being fed to the coal burner.
Preferably, the coal is pulverized coal.
[0063] A preferred embodiment of the present invention includes a
process that includes mixing organic waste with coal combustion
by-products and alkaline additives, thus producing ammonia, and
introducing liberated ammonia from the organic waste into the
burner, preferably for NO.sub.x removal. Preferably the organic
waste/coal combustion by-products/alkaline additive by-product
mixture is mixed with pulverized coal as supplemental fuel for the
coal burner.
[0064] In an embodiment of the invention, lime is added to organic
waste to achieve a pH preferably greater than 9.5, more preferably
greater than 10, and to aid in drying to high solids, in
embodiments where the organic waste is dried. Hot exhaust gases,
hot ash, steam, hot water, or a combination of these heat sources
scavenged from the power plant may be used to dry, in a direct or
indirect dryer, the coal combustion by-products-organic waste
mixture to a solids content of at least 95%, preferably near 100%.
Exhaust gases from the dryer, containing free ammonia from the
organic waste, are piped into the coal burner to supplement ammonia
addition to the coal burner for NO.sub.x removal. Preferably, the
dried mixture is conveyed to the coal feed area of the power plant
and mixed with coal prior to or after coal pulverization to serve
as a supplemental fuel source. Alternatively, the dried mixture can
be used as a soil additive.
[0065] The present invention is further directed to systems
including a coal burner of a power plant, a coal feed supplying
coal to the coal burner, and an ammonia feed to the coal burner.
The ammonia feed preferably includes ammonia liberated from organic
waste upon mixing organic waste, coal combustion by-products and
one or more alkaline additives. The step(s) involved in these
systems, such as mixing and optionally drying the organic waste,
and the ingredients of the system, such as the organic waste, coal
combustion by-products and alkaline additive(s), are as described
above with regard to the processes of the present invention.
According to a preferred embodiment, the coal feed includes coal
and a mixture of organic waste, coal combustion by-products and
alkaline additive(s). Preferably, the coal is pulverized coal.
According to a further embodiment, the coal and the mixture of
organic waste, coal combustion by-products and alkaline additive(s)
are mixed and then pulverized.
[0066] A further embodiment of the invention is directed to systems
including a coal burner of a power plant, and a feed of an organic
waste/coal combustion by-product/alkaline additive mixture to the
coal burner, where the feed includes organic waste, coal combustion
by-products and one or more alkaline additives mixed together.
According to a preferred embodiment, the feed of organic waste/coal
combustion by-products/ alkaline additive by-product mixture
further includes coal. Preferably, the coal is pulverized coal.
According to a further embodiment, the coal and the organic
waste/coal combustion by-products/alkaline additive by-product
mixture are mixed and then pulverized.
[0067] Other systems of the present invention include a coal burner
of a coal burning power plant, an ammonia feed to the coal burner,
which preferably includes ammonia liberated upon mixing organic
waste, coal combustion by-products, and one or more alkaline
additives; and a coal feed supplying coal to the coal burner, which
coal feed includes coal and the organic waste/coal combustion
by-products/ alkaline additive by-product mixture.
[0068] The present invention will now be described in detail with
respect to showing how certain specific representative embodiments
thereof can be made, the materials, apparatus and process steps
being understood as examples that are intended to be illustrative
only. In particular, the invention is not intended to be limited to
the processes, materials, conditions, process parameters, apparatus
and the like specifically recited herein.
EXAMPLES
Example 1
[0069] An anaerobically digested sewage sludge is mixed with spent
fluidized bed coal ash containing 10% by weight CaO at a coal-fired
power plant burning high-S coal. Fly ash and sludge are mixed to
form a mixture having a pH of 12 or above. The mixture is
introduced into a vertical counter-current indirect dryer with
rotating plates in which the rotating plates are heated with excess
steam from the power plant. The sludge contains 2% by dry weight of
ammonia. Due to the high pH, ammonia is released from the sludge in
the dryer and is exhausted and piped to the coal burner to
supplement anhydrous ammonia or urea used for NO.sub.x control from
the coal burner. The mixture is dried to >95% solids.
[0070] The dried mixture is conveyed by covered belt to the coal
feed hopper where it is further mixed with coal. This mixture is
fed into the coal pulverizer and thence into the burner. The mixing
of high CaO fly ash with sludge results in the formation of
Ca(OH).sub.2. The concurrent introduction of exhaust air from the
plant results in carbonation of the Ca(OH).sub.2 to form
CaCO.sub.3. The presence of CaCO.sub.3 in the dried mixture reduces
the amount of commercial limestone required by the power plant for
sulfur removal.
Example 2
[0071] An anaerobically digested sewage sludge is mixed with fly
ash (containing CaO) and lime kiln dust at a coal-fired power plant
burning high-S coal. The resulting mixture has a pH of 10 or above.
Ammonia is released from the sludge in the mixer and is exhausted
and piped to the coal burner to supplement anhydrous ammonia or
urea used for NO.sub.x control from the coal burner.
[0072] The mixture is conveyed by covered belt to the coal feed
hopper where it is further mixed with coal. This mixture is fed
into the coal pulverizer and thence into the burner. The mixing of
high CaO fly ash with sludge results in the formation of
Ca(OH).sub.2. CaO in the lime kiln dust also results in formation
of Ca(OH).sub.2. The concurrent introduction of exhaust air from
the plant results in carbonation of the Ca(OH).sub.2 to form
CaCO.sub.3. The presence of CaCO.sub.3 in the dried mixture reduces
the amount of commercial limestone required by the power plant for
sulfur removal. In addition, CO.sub.2 in exhaust gases is
sequestered by a reaction of Ca(OH).sub.2to form CaCO.sub.3. In a
further embodiment SO.sub.2 and SO.sub.3 in the exhaust air from
the plant are sequestered by reaction with Ca(OH).sub.2 to form
CaSO.sub.3 and CaSO.sub.4.
[0073] Processes and systems of the present invention are
advantageous over previously known processes because enabling the
release of ammonia from organic waste at a power plant allows the
ammonia in the organic waste to be utilized for example, for
NO.sub.x removal, while taking advantage of the fuel value of the
organic waste. The present processes and systems also provide
flexibility in resource utilization in that the organic waste
mixtures formed by the present processes can be used either as fuel
or as a separate product that can be applied to land as a soil
additive.
[0074] While the present invention is described with respect to
particular examples and preferred embodiments, it is understood
that the present invention is not limited to these examples and
embodiments. In particular, the present invention is not limited to
the particular types of waste or by-products. Additionally, the
components of the processes of the present invention are not
limited to those described above or depicted in FIGS. 1 and 2. For
example, the processes of the present invention are not limited to
a single dryer or a single coal burner and additional components
may be added such as a sorbant 10 in FIG. 1, heat exchangers,
belts, and the like.
[0075] The present invention as claimed therefore, includes
variations from the particular examples and preferred embodiments
described herein, as will be apparent to one of skill in the
art.
* * * * *