U.S. patent application number 13/442134 was filed with the patent office on 2013-03-28 for nano-dispersions of carbonaceous material in water as the basis of fuel related technologies and methods of making same.
The applicant listed for this patent is Takeshi Asa, Maria Briceno, Cebers Gomez, Gustavo A. N nez. Invention is credited to Takeshi Asa, Maria Briceno, Cebers Gomez, Gustavo A. N nez.
Application Number | 20130074396 13/442134 |
Document ID | / |
Family ID | 47909671 |
Filed Date | 2013-03-28 |
United States Patent
Application |
20130074396 |
Kind Code |
A1 |
N nez; Gustavo A. ; et
al. |
March 28, 2013 |
NANO-DISPERSIONS OF CARBONACEOUS MATERIAL IN WATER AS THE BASIS OF
FUEL RELATED TECHNOLOGIES AND METHODS OF MAKING SAME
Abstract
Colloidal carbonaceous material-in-water slurries having
nano-particles of carbonaceous material creating a pseudo-fluid.
The colloidal carbonaceous material-in-water slurry generally
includes from about fifty to about seventy two weight percent of
carbonaceous material, with about 20 to about 80 percent of the
carbonaceous material having a particle size of about one micron or
less with a mode particle size of about 250 nanometers. The
carbonaceous material-in-water slurry can also include a surfactant
system containing one surfactant or mixtures of two or more
surfactants, or mixtures of one or more surfactants and an
inorganic or organic salt. The carbonaceous material-in-water
slurry can be used in low NOx burner applications as the main fuel
and/or the reburn fuel, in gasification processes as the input fuel
either alone, or in combination with organic materials, in gas
turbine applications, and in diesel engine applications.
Inventors: |
N nez; Gustavo A.; (Panama
City, PA) ; Briceno; Maria; (Panama City, PA)
; Asa; Takeshi; (Osaka, JP) ; Gomez; Cebers;
(Miranda, VE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
N nez; Gustavo A.
Briceno; Maria
Asa; Takeshi
Gomez; Cebers |
Panama City
Panama City
Osaka
Miranda |
|
PA
PA
JP
VE |
|
|
Family ID: |
47909671 |
Appl. No.: |
13/442134 |
Filed: |
April 9, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12495151 |
Jun 30, 2009 |
8177867 |
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13442134 |
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61473017 |
Apr 7, 2011 |
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61077009 |
Jun 30, 2008 |
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61157089 |
Mar 3, 2009 |
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Current U.S.
Class: |
44/282 ;
44/280 |
Current CPC
Class: |
C10L 2250/082 20130101;
C10L 1/324 20130101; C10L 10/02 20130101; C10L 2290/28 20130101;
C10L 2270/026 20130101; C10J 2300/0943 20130101; C10L 1/00
20130101; C10L 2270/04 20130101; C10L 1/328 20130101; C10L
2200/0295 20130101; C10L 2250/06 20130101; C10L 2270/06 20130101;
C10L 1/326 20130101; C10L 1/1824 20130101; C10J 3/72 20130101; C10L
2250/086 20130101 |
Class at
Publication: |
44/282 ;
44/280 |
International
Class: |
C10L 1/32 20060101
C10L001/32 |
Claims
1. A colloidal slurry of asphaltite in water, the slurry
comprising: a colloidal fraction of asphaltite particles dispersed
in water, the asphaltite particles comprising about 50 to about 80
weight percent of the slurry, the water comprising about 20 to
about 50 weight percent of the slurry, wherein at least ten percent
of the asphaltite particles have a particle size of about one
micron or less.
2. The slurry of claim 1, wherein the colloidal fraction of
asphaltite particles comprises a first plurality of asphaltite
particles having a particle size of about 100 nm to about 1 micron
with an average particle size of about 200 nm to about 300 nm, and
a second plurality of particles having a particle size greater than
one micron to about 10 microns.
3. The slurry of claim 2, wherein the first plurality of asphaltite
particles of the colloidal fraction comprises about 20 percent to
about 80 percent of the asphaltite particles in the slurry.
4. The slurry according to claim 1, wherein the asphaltite
particles comprise about 60 weight percent to about 70 weight
percent of the slurry, and the water comprises about 30 weight
percent to about 40 weight percent of the slurry.
5. The slurry according to claim 1, the slurry further comprising
at least one surfactant system selected from the group consisting
of a nonionic surfactant, an ionic surfactant, an inorganic salt,
an organic salt, and combinations thereof.
6. The slurry according to claim 5, wherein the at least one
surfactant system is present in the slurry in the amount of about
500 to about 3000 parts per million.
7. The slurry according to claim 1, the slurry further comprising a
large fraction of carbonaceous material particles having a size of
about 150 .mu.m to about 400 .mu.m.
8. The slurry according to claim 7, wherein a size ratio of the
large fraction of carbonaceous material particles to the colloidal
fraction of asphaltite particles is greater than 100.
9. The slurry according to claim 8, wherein the colloidal fraction
of asphaltite particles comprise about 58 weight percent to about
62 weight percent of the slurry, and the colloidal fraction of
asphaltite particles and the large fraction of carbonaceous
material particles comprise about 68 weight percent to about 72
weight percent of the slurry.
10. The slurry according to claim 7, wherein the large fraction of
carbonaceous material particles comprise asphaltite.
11. The according to claim 1, wherein at least a portion of the
water is replaced with a volatile component, the volatile component
selected from the group consisting of methanol, ethanol, propanol,
butanol, glycerol or combinations thereof.
12. The slurry according to claim 7, wherein a mass fraction of the
large fraction of carbonaceous material particles is about 25
percent to about 35 percent of the total coal in the slurry.
13. The slurry according to claim 7, wherein the large fraction of
carbonaceous material particles is suspended in the colloidal
fraction of asphaltite particles.
14. The slurry according to claim 1, wherein the slurry has a
viscosity at 120 degrees Fahrenheit in the range of about 350
centipoise to about 1000 centipoise.
15. The slurry according to claim 1, further comprising a second
fraction of asphaltite particles having a size less than 100
microns and greater than 10 microns.
16. The slurry according to claim 2, wherein the second plurality
of asphaltite particles has an average particle size of greater
than 1 micron to about 2 microns.
17. The slurry according to claim 2, wherein the second plurality
of asphaltite partices in the colloidal fraction has a bimodal
size.
18. The slurry according to claim 1, further comprising a
nano-emulsion of an organic liquid or oil.
19. The slurry according to claim 1, wherein the asphaltite
particles are selected from the group consisting of gilsonite,
grahamite, glance pitch, and combinations thereof.
20. A slurry of asphaltite-in-water comprising: a large fraction of
asphaltite particles having a size of about 150 microns to about
400 microns suspended in a colloidal fraction of a nano-dispersion
of asphaltite in water, the nano-dispersion of asphaltite in water
having a plurality of nano-sized asphaltite particles having a size
of about less than 1 micron, and a plurality of micronized
asphaltite particles, wherein between about 30 percent to about 50
percent of the plurality of micronized asphaltite particles have a
size of about 1 micron to about 4 microns, and wherein the slurry
is substantially free of sulfur.
Description
RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional Application No. 61/473,017 filed Apr. 7, 2011, which is
incorporated herein in its entirety by reference, and the present
application is a continuation-in-part of application Ser. No.
12/495,151 filed Jun. 30, 2009, which claims the benefit of U.S.
Provisional Application No. 61/077,009 filed Jun. 30, 2008, and
U.S. Provisional Application No. 61/157,089 filed Mar. 3, 2009,
each of which is hereby fully incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to a nano-dispersion
of carbonaceous material, such as coal, asphaltite, or the like, in
water that is essentially a pseudo-fluid, and optionally other
additives. The present invention also relates to the methods of
making the nano-dispersion of carbonaceous material in water, which
can be used in several applications such as a fuel in boilers,
secondary fuel for re-burning applications, as a feed for
gasification and Oxycoal units, coal cleaning processes, diesel
engines, gas turbines and fuel cells. The nano-dispersion of
carbonaceous material in water can also contain another
water-soluble fuel such as methanol, ethanol, propanol, butanol and
glycerol. An organic immiscible phase, such as spent oil engine or
lube oil, hydrocarbons as heavy crude oils and bitumen, diesel,
biodiesel, petroleum coke and/or biomass, can also be incorporated
into the water in the form of nanodroplets or nanoparticles that
enhance carbonaceous material heat of combustion.
BACKGROUND OF THE INVENTION
[0003] Coal comprises a mixture of hydrocarbons and carbohydrates,
with small amounts of nitrogen, sulfur, water, and minerals. Coal
burns in air with a yellow, smoky flame, leaving ash behind. The
energy content of coal depends upon its type. The heat of
combustion of brown coal or lignite, for example, is about
twenty-five kJ/g, and the heat of combustion of bituminous coal and
anthracite is about thirty-two kJ/g. When coal burns, it mainly
produces water and carbon dioxide, however it also produces harmful
sulfur dioxide, carbon monoxide, hydrocarbons, particulate matter
and soot, and oxides of nitrogen (hereinafter "NOx").
[0004] Coal is also the cheapest and most abundant fuel on the
world. As a consequence, any technology that allows the use of coal
in a cleaner way is necessarily very attractive. Clean coal
technologies require, among other things, more reactive coal in
order to reduce or eliminate particulate matter and soot, carbon
monoxide, hydrocarbons and NOx's emissions. More reactive coal
implies complete combustion of coal particles and improved access
to reactants or adsorbants to coal surface.
[0005] One study that was conducted by Davis et al., uses advanced
calculations demonstrating that only coal particle sized below
eighteen microns, will burn completely inside a 900 MW tangentially
fired boiler retrofitted with low NOx burners (Davis et al.,
"Evaluating the Effects of Low-NOx Retrofits on Caron in Ash
Level", Reaction Engineering International; Presented at the Mega
Symposium: EPRI-DOE-EPA Combined Utility Air Pollutant Control
Symposium in Atlanta, Ga., August, 1999). It is important to note,
however, that currently commercial pulverized coal is typically
ground to sixty micrometer average diameter. Further, commercial
micronized coal has about fifteen microns average particle size,
which means that a significant portion of the particles sizes are
above the eighteen micron size, therefore contributing to the
carbon in ash content. The Davis et al. study in view of the
present invention is incorporated herein by reference.
[0006] Decreasing coal particle size implies increasing specific
surface area, thereby increasing reactivity. Reducing particle size
and obtaining a more reactive coal, opens many other applications,
namely, as a feedstock for conventional but less polluting boilers;
as a reburn fuel to reduce NOx emissions; as a feedstock of
gasification and Oxycoal units; and as a feed in diesel and gas
turbines. Further, coal cleaning processes are greatly enhanced by
increasing specific surface area, facilitating the extraction of
polluting minerals and solid compounds. Hereafter follows a
description of these applications and the way they would benefit by
using a micronized coal.
[0007] Boilers are closed vessels in which water or other fluids
are heated. The heated or vaporized fluids exit the boiler for use
in various processes or heating applications. In particular,
utility boilers, which are typical drum-type boilers, are widely
used in power plants, oil refineries, and petrochemical plants for
steam generation to drive large turbines, producing electricity. In
many instances, these boilers are coal-fired using coal at the
burner to produce heated gases used to heat water, thereby
generating steam.
[0008] Several decades ago, large utility boilers were fitted with
pulverized-coal burners designed to fire pulverized coal using
about fifteen percent to about twenty percent excess air. Under
such conditions, the amount of unburned fuel normally was below two
percent, although NOx levels generated by such burners reached
levels that are now unacceptable according to current emission
standards. In order to meet the current emission standards, low NOx
burners have been developed and most commercial coal-fired boilers
have been retrofitted with these low NOx burners. Low NOx burners
operate to minimize NOx formation by introducing coal and its
associated combustion air into a boiler such that initial
combustion occurs in a manner that promotes rapid coal
devolatilization in a fuel-rich (i.e., oxygen deficient)
environment and introduces additional air to achieve a final
fuel-lean (i.e., oxygen rich) environment to complete the
combustion process. Using these low NOx burners reduces the NOx
emissions up to about fifty to about sixty percent.
[0009] An example of a low NOx combustion system, such as a boiler
with a low NOx burner, available from GE Power Systems is
illustrated in FIG. 1. Such a system can include a reburn zone
including reburn fuel injectors. The reburn zone is a technology
that utilizes fuel and air staging to reduce the NOx emissions by
integrating low NOx burners and over-fire air systems. Reburning is
defined as reducing the coal and combustion air to the main burners
and injecting a reburn fuel, such as coal, gas or oil, to create a
fuel-rich secondary combustion zone above the main burner zone and
final combustion air to create a fuel-lean burnout zone. The
formation of NOx is inhibited in the main burner zone due to
reduced combustion intensity, and NOx is destroyed in the fuel-rich
secondary combustion zone by conversion to molecular nitrogen. A
summary of GE Power System's technology is included in its
publication entitled "Reburn Systems" having reference number
GEA-13207, which is incorporated herein by reference.
[0010] However, the use of low NOx burners increases the carbon
content, or unburned coal, in the boiler ash. FIG. 2 depicts
measurements taken from a utility boiler firing a ten percent ash
coal. The results show the increase of carbon in ash content after
retrofitting the boiler with low NOx burners. Although the increase
of the amount of unburned carbon can also be boiler and coal
dependent, Table 1 shows a common trend toward the increase of
carbon in ash data from several boilers fitted with low NOx
burners.
TABLE-US-00001 TABLE 1 Select Boilers for Which Detailed Carbon in
Ash Analyses Have Been Performed Typical Typical Low Measured
Measured Firing NOx NOx Carbon in Configuration MWe System
Emissions Ash Level Opposed wall 500 FW CFSF 313 ppm 5% fired
burners with AGFA Opposed wall 500 FW CFSF 310 ppm 8% fired burners
without OFA Single wall 160 DBRiley CCVII 245 ppm 22-27% fired
burners and OFA Tangentially 900 ABB LNCFS 275 ppm 8-12% .sup.
fired Level III
[0011] The disposal of boiler ash with increased carbon content is
becoming a pressing issue within the power utilities markets and
will continue to be more so in the future, as the cost of coal and
other fuels continue to rise.
[0012] One method of utilizing coal as a fuel for utility burners
is to create a slurry or dispersion of the coal. For example, the
coal is pulverized and mixed with an amount of water in order to
form a dispersion or slurry of coal in water at a low enough
viscosity so as to enable transportation of the fuel via pipeline
or the like. However, because the pulverized or micronized coal is
only available at the particle sizes described above, the
pulverized coal does not completely burn, and therefore the coal in
water slurry does not solve the issues of high carbon content in
boiler ash as described above.
[0013] Gas turbines can also utilize coal as fuel. A gas turbine is
a rotary machine, similar in principle to a steam turbine. It
consists of three main components--a compressor, a combustion
chamber and a turbine. Air, after being compressed into the
compressor, is heated either by directly burning fuel in it or by
burning fuel externally in a heat exchanger. The heated air, with
or without combustion products, is expanded in a turbine resulting
in work output, a substantial part of which is used to drive the
compressor. The excess is available as useful work output. In one
example, a gas turbine has an upstream air compressor mechanically
coupled to a downstream turbine, with a combustion chamber
positioned in between. Energy is released when compressed air is
mixed with fuel, such as coal, which is then ignited in the
combustion chamber. The resulting gases are directed over the
turbine's blades, spinning the turbine, and mechanically powering
the compressor. Finally, the gases can be passed through a nozzle,
generating additional thrust by accelerating the hot exhaust gases
by expansion back to atmospheric pressure. Energy is extracted in
the form of shaft power, compressed air and thrust, in any
combination, and used to power aircraft, trains, ships, electrical
generators, and even tanks.
[0014] However, commercially available coal-in-water slurries are
not conducive to gas turbine applications. When the pulverized or
micronized coal is combined with the compressed air and burned, the
presence of unburned coal particles can damage the turbine blades,
resulting in a less efficient process, and significant expense in
replacing the turbine blades.
[0015] In diesel engines, a diesel engine relies upon compression
ignition to burn its fuel. If air is compressed to a high degree,
its temperature will increase to a point where fuel will burn upon
contact. Following intake, the cylinder is sealed and the air
charge is highly compressed to heat it to the temperature required
for ignition. As the piston approaches top dead centre (TDC), fuel
oil is injected into the cylinder at high pressure, causing the
fuel charge to be nebulized. Owing to the high air temperature in
the cylinder, ignition instantly occurs, causing a rapid and
considerable increase in cylinder temperature and pressure. The
piston is driven downward with great force, pushing on the
connecting rod and turning the crankshaft. If commercially
available coal-in-water slurries are used as the fuel, the presence
of unburned coal particles after combustion of these fuels can
cause damage to the cylinders, such as damaging the tolerances
between the piston and the cylinder. This in turn may cause damage
or failure to the seal of the cylinder, resulting in a lack of
pressure to increase the temperature to ignite the fuel, for
example.
[0016] Coal can also be used as a combustion fuel for a
gasification process. Gasification is a process that converts
carbonaceous materials, such as coal, petroleum, or biomass, into
carbon monoxide and hydrogen by reacting the raw material at high
temperatures with a controlled amount of oxygen. The resulting gas
mixture is known as synthesis gas or syngas, which can in turn be
used as a fuel. The syngas product can be burned directly as a fuel
in internal combustion engine, processed into high-purity hydrogen,
ammonia, methanol, and other chemicals, or converted via the
Fischer-Tropsch process into synthetic fuel. However, commercially
available coal-in-water slurries produce a lower quality or
contaminated syngas because of the presence of unburned coal
particles, as well as clogging of the particulates in the input
stream. One example of a gasification process is the Texaco
Gasification Process entitled "EPA: Site Technology Capsule--Texaco
Gasification Process" having reference EPA 540/R-94/514a of April
1995, which is incorporated herein by reference.
[0017] There remains a need for a "green" carbonaceous material to
be used as in a carbonaceous material-in-water slurry as a fuel for
multiple applications including low NOx burners, gasification
processes, gas turbine applications, diesel engine applications,
and the like. Such "green" carbonaceous material should completely
burn, leaving no particulates in the downstream ash, products,
and/or byproducts.
SUMMARY OF THE INVENTION
[0018] The present invention overcomes the above-described
deficiencies. In one embodiment of the invention, a nano-dispersion
of carbonaceous material in water creates a relevant colloidal
fraction slurry that can include from about fifty to about eighty
weight percent, and more particularly about sixty to about seventy
weight percent of carbonaceous material. In one embodiment of the
invention, the carbonaceous material slurry has a relatively narrow
particle size distribution with virtually no particles above 100
microns, about forty percent of the carbonaceous material having a
particle size of at least less than ten microns, and at least ten
percent of the carbonaceous material having a particle size of one
micron or less. The total carbonaceous material content of this
kind of relatively narrow particle size distribution has an upper
limit of sixty to sixty two weight percent and the viscosity of the
carbonaceous material slurry is about 1000 centipoise (cP) or less
at 120 degrees Fahrenheit.
[0019] Carbonaceous materials can include, for example one or more
combinations including spent oil engine, hydrocarbons as heavy
crude oils and bitumens such as asphaltite, diesel, petroleum coke,
biodiesel, biomass, and coal such as, but not limited to, lignite,
bituminous coal, anthracite, as describe in U.S. Patent Application
Publication No. 2010/0024282 to Joseph et al., incorporated herein
by reference in its entirety. In one particular embodiment, the
carbonaceous material comprises asphaltite including gilsonite
(uintaite), glance pitch, and grahamite.
[0020] In another embodiment of the invention, the heat derating
can be decreased significantly by increasing the carbonaceous
material content up to seventy to seventy two weight percent. This
can be achieved, for example, in the case of coal, by combining the
relevant colloidal fraction coal slurry with dry large coal
particles or slurry of large coal particles that can be at least
one hundred times larger than the colloidal coal particles. By this
means, coal content may be increased up to seventy to seventy two
weight percent with virtually no increase in slurry viscosity
creating a pseudo-fluid. The mass fraction of the large particle
size coal is about 25 to 35% of the total coal in the slurry.
[0021] In another embodiment of the invention, the heat of
combustion can also be increased by adding to the carbonaceous
material in water slurry a volatile or water-soluble fuel such as
methanol, ethanol, propanol, butanol and glycerol. The component
can also be an organic immiscible phase such as spent oil engine,
hydrocarbons as heavy crude oils and bitumens such as asphaltite
including gilsonite (uintaite), glance pitch, and grahamite,
diesel, petroleum coke, biodiesel and biomass. The organic
immiscible phase is preferably dispersed into nanodroplets or
nanoparticles that enhance the heat of combustion of the
carbonaceous material(s).
[0022] In another embodiment of the invention, the carbonaceous
material slurry also includes from about 500 to about 3000 ppm of
one or more surfactants and/or an inorganic or organic salt, and/or
light and/or heavy alcohols. The surfactants can be ionic or
nonionic. The nonionic surfactants can include, for example,
primary or secondary ethoxylated alcohols with two to thirty
ethoxylate oxide molecules, or ethoxylated nonylphenols with two to
thirty ethoxylate oxide molecules. The ionic surfactants can
include sodium alkyl sulfates, sodium alkyl sulfonates, alpha
olefin sulfonates, alpha olefin sulfates, alkyl benzene sulfonates,
sodium sulphosuccinates, sodium lauryl ether sulphate, quaternary
ammonium chloride, bromide, or imidazolines or betaines. The
inorganic and organic salt cations can include sodium, calcium, or
magnesium.
[0023] In yet another embodiment of the invention, a method for
preparing a carbonaceous material in water slurry includes
optionally mixing the components in the presence of one or more of
the aforementioned chemical additives. The water phase may contain
miscible and volatile components such as methanol, ethanol,
propanol, butanol and glycerol or inmiscible oil nanodroplets or
nanoparticles from biomass. The slurry is mixed in a chamber with a
slit channel that spins a film of the slurry components and creates
a centrifugal field in excess of thirteen thousand gs. Stagnation
regions in the mixing flow field concentrate the carbonaceous
material, and then mill it in a wet-communication process. Cooling
agents, in order to maintain water temperature below evaporation,
control the mixing temperature.
[0024] In another embodiment, the carbonaceous material in water
slurries having nano-dispersions of carbonaceous material can be
used in low NOx burners as a main fuel, reburn fuel or both, as
fuel in gasification and oxycoal processes, as a fuel in diesel
engine applications, and/or as fuel in gas turbine applications and
fuel cells.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 depicts a schematic of a utility boiler having a low
NOx burner;
[0026] FIG. 2 is a graph of the NOx emissions and the carbon-in-ash
percentage in a conventional utility boiler and a utility boiler
retrofitted with a low NOx burner using a coal in water fuel of the
prior art;
[0027] FIG. 3 is a graph of the particle size distribution of
coal-in-water slurries according to embodiments of the
invention.
[0028] FIG. 4A is a micrograph depicting a coal in water slurry
using micronized coal, according to the prior art;
[0029] FIG. 4B is a micrograph depicting a nano-dispersion of coal
in water, according to an embodiment of the present invention;
[0030] FIG. 5 is a graph comparing the flame time of a
coal-in-water slurry of the prior art to the coal-in-water slurry
of the present invention;
[0031] FIG. 6 depicts a block flow diagram of a commercial
gasification process;
[0032] FIGS. 7A-7C are graphs comparing reburn heat input and NOx
reduction;
[0033] FIG. 8 is a graph comparing initial NOx concentration and
NOx reduction;
[0034] FIG. 9 is a graph comparing reburn zone residence time and
NOx reduction;
[0035] FIG. 10 is a graph comparing reburn heat input and NOx
reduction;
[0036] FIG. 11 is a bar graph comparing loss of ignition of the
different slurries;
[0037] FIG. 12 is a histogram of % weight retained between two
sieves, for a 40 mesh ground sample (less than 400 .mu.m) and the
same sample after the wet-comminution process; and
[0038] FIG. 13 a graph of colloidal distributions, before and after
the wet-comminution process.
[0039] The above summary of the invention is not intended to
describe each illustrated embodiment or every implementation of the
present invention. The figures and the detailed description that
follow more particularly exemplify these embodiments.
DETAILED DESCRIPTION OF THE INVENTION
[0040] Nano-dispersions of carbonaceous material-in-water slurries
that contain a relevant colloidal fraction according to embodiments
of the current invention solve the above-mentioned deficiencies.
The carbonaceous material-in-water slurry generally comprises a
micron-sized fraction and a colloidal suspension or nano-dispersion
of milled particles in water, the particles having a large particle
population of sub-micron size. The carbonaceous material-in-water
slurry can further comprise a surfactant system that is
particularly formulated depending on the type and source of
carbonaceous material. The carbonaceous material-in-water slurry
can be used as a fuel for not only the reburn and/or main fuel in a
low NOx burner, but also has potential applications in gasification
processes, gas turbines, and diesel engines. Because of the
carbonaceous material's small particle size, and therefore larger
surface area compared to commercially available carbonaceous
material-in-water slurries, a burning efficiency of the
carbonaceous material is near one hundred percent, leaving
virtually no carbonaceous material particles in the ash or the
resulting gases.
[0041] As discussed above, any of a variety of carbonaceous
materials can be utilized as an alternative to or in addition to
coal. Such carbonaceous materials can include, but are not limited
to, spent engine oil, hydrocarbons including allochthonous
materials, such as heavy crude oils and natural bitumens and
asphalt or asphaltite, diesel, petroleum coke, biodiesel, biomass,
and coal such as, but not limited to, lignite, bituminous coal, and
anthracite, or combinations thereof. In one particular embodiment,
the carbonaceous material comprises one or more soluble natural
bitumens (e.g. CS.sub.2 soluble) including mineral wax, natural
asphalt, and/or asphaltite. More particularly, the soluble natural
bitumen comprises one or more asphaltites including gilsonite
(uintaite), glance pitch, and grahamite. Asphaltite offers lower
sulfur content than conventional coal sources such as lignite,
anthracite, or bituminous coal because asphaltite generally
contains little or no inorganic materials including sulfur. In one
embodiment, an asphaltite in water slurry is substantially free of
sulfur, i.e. it contains negligible amounts, such that when used as
a fuel, little to no sulfur-containing byproducts, such as sulfur
dioxide, are produced.
[0042] In one embodiment of the invention, a carbonaceous
material-in-water slurry, such as a coal-in-water slurry, comprises
from about fifty to about seventy two weight percent of
carbonaceous material dispersed in water, and more particularly
from about sixty to about seventy weight percent of carbonaceous
material. The carbonaceous material can comprise suitable coals to
be used as fuel, such as, for example, lignite, sub-bituminous,
bituminous, and anthracite. In an alternative embodiment, the
carbonaceous material can comprise a natural bitumen, and more
particularly asphaltite.
[0043] The particle size distribution of the carbonaceous
material-in-water slurry can include, for example, a micron-sized
fraction having a particle size of about ten microns to about 1
micron and a sub-micron colloidal fraction having a particle size
less than about one micron to about 100 nm with an average particle
size of the sub-micron colloidal fraction being about 200
nanometers to about 300 nanometers. A person of ordinary skill in
the art will recognize that ranges and subranges within these
explicit ranges are contemplated and are within the present
disclosure. In a preferred embodiment, the sub-micron colloidal
fraction has an average particle size of about 250 nanometers. In
one embodiment of the present invention, the particle size
distribution is bimodal, having one mode with an average particle
size of about one micron or less. In an alternative embodiment of
the present invention, the particle size distribution is unimodal
with a Sauter mean diameter particle size of about five microns or
less. A multi-modal particle size distribution of carbonaceous
material-in-water slurries according to an embodiment of the
invention is shown at FIG. 3, wherein coal is the carbonaceous
material.
[0044] In certain embodiments, the micron and sub-micron colloidal
fractions of carbonaceous material, which have a particle size
(Sauter mean diameter) of about 10 microns or less, can comprise
between about 30 and about 50 weight percent of the carbonaceous
material-in-water slurry, with the sub-micron colloidal fraction
that has a particle size less than about one micron comprising at
least about 20 weight percent to about 85 weight percent of such
carbonaceous material having a particle size of about 10 microns or
less (Sauter mean diameter). In other aspects, the micron and
sub-micron colloidal fractions together comprise about 58 weight
percent to about 62 weight percent of the carbonaceous
material-in-water slurry.
[0045] In one embodiment of the invention, the carbonaceous
material-in-water slurry has a viscosity of about 350 to about 1000
centipoise (cP) at 120 degrees Fahrenheit. A person of ordinary
skill in the art will recognize that ranges and subranges within
these explicit ranges are contemplated and are within the present
disclosure. A viscosity at the lower end of this range allows for
standard fuel transportation means, such as, for example,
pipelining, tanker trucks, and ships and barges. Further, by virtue
of the coal's small particle size, the suspension is relatively
stable, with very little sedimentation.
[0046] In certain embodiments, nano-dispersions of carbonaceous
material in water according to the present invention have a maximum
amount of dispersed carbonaceous material, which when surpasses
causes the nano-dispersion to lose its pseudo-fluid characteristic.
This has to do with carbonaceous material particles running out of
space in the bulk of the water as more carbonaceous material is
added. The upper bound of carbonaceous material content depends on
the way particles arrange among themselves which, in turn, depends
on the geometry of the entire particle assembly. This non-unique
upper bound is known as the maximum packing fraction. When the
carbonaceous material content approaches this mass fraction,
particle interactions are greatly increased because particles
virtually touch each other; once the slurry surpasses the maximum
packing fraction, the slurry no longer behaves like a fluid but
rather as a wet solid or paste. As a consequence, slurry fluidity
diminishes significantly. Besides, colloidal interactions also
contribute to paste like behavior. However, modifying particle size
distribution, in such a way as to reduce local interactions, can
increase the maximum packing fraction. This can be achieved by
combining large particles with much smaller particles, at least 100
times smaller. The smaller particles, along with the continuous
phase, become a pseudo-continuous fluid to the large particles. The
resulting macroscopic effect is a significant reduction of
viscosity, as long as the size ratio of large particles to small
particles is greater than 100.
[0047] In one embodiment of the present invention, about fifty
eight to about sixty two weight percent nano-dispersed carbonaceous
material in water slurry, as described above, is manufactured
followed by the addition of dry large carbonaceous material
particles or a concentrated slurry of large carbonaceous material
particles, having particles sizes in the range of 150 to 400 .mu.m.
A person of ordinary skill in the art will recognize that ranges
and subranges within these explicit ranges are contemplated and are
within the present disclosure. This procedure gives way to more
concentrated carbonaceous material slurry, with about sixty eight
to about seventy two weight percent of carbonaceous material, with
sub-ranges and values within this range contemplated and present
within this disclosure, and a broad particle size distributions,
still having a significant colloidal fraction that behaves as a
pseudo-fluid to the large particles. Since this pseudo-fluid is
more viscous than the continuous phase alone, sedimentation of both
the sub-micron and the large particles is virtually eliminated
because the relevant colloid fraction creates a viscous
pseudo-fluid that suspends the large particles. In other words, the
density difference between the carbonaceous material particles and
the pseudo-fluid to prevent sedimentation is about less than 10%,
preferably less than 5%, and optimally 2% or less. This behavior
has an important economic implication. Since the viscous
pseudo-fluid prevents sedimentation, there is no need of additional
chemical compounds to prevent settling (polymers, for example, that
are necessary in conventional slurries) thereby reducing additives
cost in a significant way.
[0048] Carbonaceous material slurries of the present invention in
which the carbonaceous material content is greater than sixty two
percent are of interest in gasification and oxy combustion
processes. In these applications, boiler temperatures are very high
thus allowing complete carbonaceous material burning while gaining
thermal efficiency associated with less boiler de-rating owing to
the reduced water content in the slurry fuel.
[0049] In yet another embodiment of the invention, a volatile water
miscible component, that also has combustion properties, can be
added to increase heat of combustion. The volatile component can be
methanol, ethanol, butanol and glycerol, or a combination thereof.
While the optimal amount of volatile component is dependent upon
the volatile being added, in certain embodiments the preferred
weight percent of the volatile component is less than 10%, and
optimally 3-6%. A person of ordinary skill in the art will
recognize that ranges and subranges within these explicit ranges
are contemplated and are within the present disclosure. Methanol,
ethanol and butanol are water soluble and volatile, and they can be
obtained as sub-products of biomass fermentation. Biodiesel
production from vegetable oils transesterification implies, in some
cases, the generation of high volumes of glycerol solutions that
can be combined with carbonaceous material to produce a higher heat
value for the fuel slurry.
[0050] In another embodiment of the invention, the heat of
combustion can also be increased by adding to the carbonaceous
material water slurry, an organic liquid or oil that is immiscible
in water. The organic liquid or oil would also be a
nano-dispersion, this is, an oil-in-water nanoemulsion. The organic
or oil phase can comprises spent engine oil or lube oil, crude oil
and bitumen, diesel and biodiesel or any other hydrocarbon product
that is emulsified in the water phase, previous to the preparation
of the carbonaceous material slurry. Alternatively, the organic or
oil phase can also be combined with the previously prepared
carbonaceous material in water suspension. In certain embodiments,
the preferred weight percent of the organic liquid or oil component
is less than 10%, and optimally 3-6% with other ranges and
subranges within these explicit ranges being contemplated and
within the present disclosure.
[0051] In another embodiment of the invention, adding to a coal in
water slurry, finely dispersed solid particles that are
combustible, can also increase the heat of combustion. The origin
of the combustible solid particles may be hydrocarbons as heavy
crude oils and bitumens like asphaltite, diesel, petroleum coke,
biodiesel, and/or biomass. The solid dispersion can be the base for
the preparation of coal slurry, or the solid particle slurry can be
the base for the incorporation of the coal into the slurry. In
certain embodiments that contain the finely dispersed solid
combustible particles, the nano-dispersion of coal-in-water
contains about fifty eight to about sixty two weight percent
nano-dispersed coal in water slurry, as described above, with the
remaining weight percent of the particles dispersed in water
comprising the solid combustible particles of hydrocarbons as heavy
crude oils and bitumens like asphaltite, diesel, petroleum coke,
biodiesel, biomass, or a combination thereof. A person of ordinary
skill in the art will recognize that ranges and subranges within
this explicit range are contemplated and are within the present
disclosure.
[0052] In yet another embodiment of the invention, the carbonaceous
material-in-water slurry comprises a surfactant system. For
example, not all sources of coal have the same properties, but
rather the surface properties of coal can depend on the type and/or
source of the coal being used. Therefore, surfactant systems can be
carefully tailored to each type and/or source of coal, or other
carbonaceous material. Further, if a volatile or combustible
component is added to the slurry, the surfactant system has to
ensure the dispersability and stability of the carbonaceous
material particles in an aqueous phase that may have soluble
components (methanol, ethanol, propanol, butanol, glycerol), or oil
droplets (spent engine and lube oil, diesel and biodiesel, crude
oil or bitumen) or a second type of combustible solid particles
(biomass).
[0053] A surfactant system according to embodiments of the
invention can comprise a single surfactant, a mixture of two or
more surfactants, or mixtures of one or more surfactants and an
inorganic and/or organic salt, or a mixture of one or more
surfactants with amines or light and heavy alcohols. Suitable
surfactants can comprise one or more nonionic surfactants and/or
one or more ionic surfactants. Nonionic surfactants can include,
for example, primary or secondary ethoxylated alcohols having two
to thirty ethoxylate oxyde molecules, and/or ethoxylated
nonylphenols having two to thirty ethoxylate oxyde molecules. Ionic
surfactants can include, for example, sodium alkyl sulfates, sodium
alkyl sulfonates, alpha olefin sulfonates, alpha olefin sulfates,
alkyl benzene sulfonates, sodium sulphosuccinates, sodium lauryl
ether sulphate, quaternary ammonium chloride, quaternary ammonium
bromide, imidazolines, betaines, and combinations thereof. Cations
of suitable inorganic and organic salts can include, for example,
sodium, calcium, and/or magnesium.
[0054] In one embodiment of the invention, a surfactant system is
present in the carbonaceous material-in water-slurry at about 500
to about 3000 parts per million (ppm). A person of ordinary skill
in the art will recognize that ranges and subranges within this
explicit range are contemplated and are within the present
disclosure. In another embodiment of the present invention, a
surfactant system of about up to 1 weight percent is included in
the nano-dispersion of carbonaceous material-in-water when the
slurry contains at least one volatile component and/or at least one
organic liquid or oil component.
[0055] A method of making carbonaceous material-in-water slurries
is dependent upon the milling technology in order to produce
carbonaceous material particles, such as coal particles, in the
sub-micron range. In one embodiment of the invention in which the
carbonaceous material comprises coal, pulverized or non-pulverized
coal, water, and optional surfactant system are combined in a
chamber of a suitable mixer, such as, for example, the Filmics
Mixer, available from the Primix Corporation of Osaka, Japan. The
Filmics Mixer and accompanying technology is set forth in U.S. Pat.
No. 5,582,484 entitled "Method Of, and Apparatus For, Agitating
Treatment Liquid", which is incorporated herein by reference. The
slurry is mixed in the chamber with a slit channel that spins a
film of the slurry components and creates a centrifugal field of
about thirteen gs or more. Stagnation regions in the mixing flow
field then concentrate the coal and mill the coal in a
wet-comminution process, milling the coal into the micron and
submicron particles as previously disclosed. In a preferred
embodiment, the wet-comminution process is a continuous process
with the source of coal having about 3 to about 20 seconds of
residence time, optimally about 9 seconds, with other ranges and
subranges of these explicit ranges contemplated and within the
present disclosure. The formation temperature of the slurry is
controlled by cooling agents to maintain the water temperature
below evaporation. Coal particles micronized by milling according
to commercially standard processes are shown in FIG. 4A. In
contrast, coal particles milled to submicron particles as described
above are shown in FIG. 4B.
[0056] This wet-comminution process also offers safety advantages
over dry milling. Dry milling coal, such as that done in a Fuller
mill, to a micron or submicron size can cause the coal particles to
be released into the air. Often times, costly sophisticated
systems, such as magnetic fields, are used to control the release
of the coal particles. However, the wet-comminution process allows
the coal particles to remain suspended in the water, reducing or
eliminating the introduction of coal particles into the air.
[0057] In yet another embodiment of the invention, if a volatile or
combustible component is required to decrease heat derating, which
may be an ignition problem with the additional dividend of reduced
derating, the slurry preparation may require two mixing steps. In
the first step, water is combined with soluble alcohols (i.e.,
methanol, ethanol and/or butanol) and/or glycerol and then coal and
aqueous phase are mixed and processed in the wet-comminution
apparatus. Alternatively, the soluble alcohols and/or glycerol are
added to the coal slurry after the wet-comminution process.
Regarding the combination with an organic or oil phase, or a finely
dispersed solid biomass, the wet-comminution process is used to
produce a nanoemulsion (organic or oil phase) or nanosuspension
(dispersed solid biomass) that is later combined with coal water
slurry that has also been produced by the wet-comminution process.
In a variant of the present invention, the nanoemulsion is produced
by a conventional mixer using a special surfactant package, or by
means of the wet-comminution method and the special surfactant
package. In yet another alternative embodiment, the wet-comminution
process is used to produce first the nanoemulsion or
nanosuspension, and then used again to mill the coal into micron
and/or submicron size in the nanoemulsion or nanodispersion.
[0058] According to one embodiment of the invention, the
carbonaceous material-in-water slurry with nano-dispersed particles
can be used as the main fuel, the reburn fuel, or both, in a
boiler, such as a low NOx boiler. The small particle size of the
carbonaceous material particles in the slurry increases the surface
area available for firing or burning, as compared to commercially
available micronized carbonaceous material-in-water slurry. The
increased surface area results in increased flame times twice as
long or more compared to commercially available slurries, and
virtually complete or clean burning of the slurry and carbonaceous
material particles, even in low oxygen atmospheres. A graph
comparing the flame times of commercial slurries and the slurries
of the present invention is illustrated at FIG. 5.
[0059] Because of the clean burning characteristics of the
nano-dispersion of carbonaceous material-in-water slurry of the
present invention, there is virtually no carbonaceous material
present in the ash in boiler applications. This clean burning
application can therefore reduce the amount of carbonaceous
material needed for power generation than the current low NOx
burners, producing a savings of upwards of millions of dollars a
year on carbonaceous material supplies, such as coal supplies.
[0060] In another embodiment of the invention, the carbonaceous
material-in-water slurry with nano-dispersed carbonaceous material
particles, such as coal, can be used in gasification processes,
such as the Texaco Gasification Process previously referenced. FIG.
6 depicts a standard gasification process flow diagram. The input
oxygen to slurry ratio of the gasification process must be closely
controlled in order to produce quality syngas. For example,
commercially available slurries often cause spikes in the syngas
due to fluctuations of the oxygen and slurry ratio. The larger
particle size of the coal particulates can cause clogging of
particulates at the input to the reaction chamber. However, because
of the smaller particle size of the coal particulates of the
current invention, the slurry acts more closely to a fluid,
following a fluid path creating a consistent input of coal
particles to the reaction chamber, thereby reducing syngas spikes.
The result is a higher quality syngas, free of coal particulates.
The higher quality syngas can then be used to produce higher
quality chemical or synthetic fuel end products, and higher quality
marketable byproducts.
[0061] In yet another embodiment of the invention, the carbonaceous
material-in-water slurry with nano-dispersed particles can be used
in gas turbine applications. For example, methanol, ethanol,
glycerol or any other similar fluid hydrocarbon can be added to the
slurry to create a water/alcohol or polyalcohol mixture with
carbonaceous material particles for a fuel. Because the
carbonaceous material burns essentially completely, there are few
or no carbonaceous material particles in the resulting gases from
the combustion chamber. Therefore, there is a little danger of
damaging the turbine blades.
[0062] The virtual elimination or mass reduction of carbonaceous
material particles in the combustion of the carbonaceous
material-in-water slurries of the present invention also allows one
to use them as fuels in diesel engines, such as marine diesel
engines, independent power producers (IPP) diesel engines, and
standard diesel engines. The occurrence of damage to the cylinder
and/or piston is greatly reduced due to the clean burning of the
particles.
[0063] In yet another embodiment of the invention, the carbonaceous
material-in-water slurry of the present invention can be used in
any application employing a Rankine cycle. The Rankine cycle is a
thermodynamic cycle which converts heat into work. The heat is
supplied externally to a closed loop, which usually uses water as a
working fluid. There are four processes in the Rankine cycle, each
changing the state of the working fluid: 1) the working fluid is
pumped from low to high pressure, as the fluid is a liquid at this
stage the pump requires little input energy; 2) the high pressure
liquid enters a boiler where it is heated at constant pressure by
an external heat source to become a dry saturated vapor; 3) the dry
saturated vapor expands through a turbine, generating power--this
decreases the temperature and pressure of the vapor, and some
condensation may occur; and 4) the wet vapor then enters a
condenser where it is cooled at a constant pressure and temperature
to become a saturated liquid--the pressure and temperature of the
condenser is fixed by the temperature of the cooling coils as the
fluid is undergoing a phase-change. The Rankine cycle describes a
model of the operation of steam heat engines most commonly found in
power generation plants. However, because of the diesel
applications that can be achieved using the carbonaceous
material-in-water slurry, the boiler of the Rankine cycle can be
replaced with a diesel engine. Alternatively, the carbonaceous
material-in-water slurry can be used as the main fuel and/or reburn
fuel of the boiler of the Rankine cycle, as discussed above.
[0064] In the examples following infra, coal is used as the primary
source of carbonaceous material for exemplary purposes only.
Example
[0065] Combustion characterization studies were performed comparing
colloidal coal-in-water slurries according to embodiments of the
current invention to a slurry made with a conventional coal grind.
The slurries were used in pilot-scale reburning tests to highlight
any performance advantages to using a micronized coal water slurry
product in terms of NO.sub.x reduction and carbon burnout as a
reburn fuel compared with conventional coal water slurry. Nine
reburn tests were conducted. Test variables included reburn zone
residence time, reburn heat input, and initial NO.sub.x
concentrations. The complete study is set forth in "NDT Combustion
Characterization Studies," Oct. 27, 2008, which is incorporated
herein by reference in its entirety. In the study, the
nano-dispersion of coal in water was referred to as
"micronized."
[0066] 1. Equipment, Slurry Preparation, and Test Parameters
[0067] The reburning tests were conducted in a boiler simulation
furnace (BSF) test unit that is designed to simulate a coal-fired
boiler. The BSF used has a firing rate range of 200,000 to
1,000,000 Btu/hr. The atomization air flow rate was held constant
and the air-to-liquid mass ration ranged from approximately 1.0 to
0.5 as reburn heat input varied from about 10-20%.
[0068] The conventional coal water slurry used as the reburn fuel
for the test included a conventional grind with a size distribution
such that approximately 70% of the material passed through a US 200
mesh sieve, typically used in US pulverized coal-fired boilers. The
coal used as the base for the conventional coal water slurry is
shown in the table below:
TABLE-US-00002 TABLE 3-1 ANALYSIS OF EASTERN BITUMINOUS COAL
Parameter Unit Value Ultimate Analysis: As Received Carbon % wt.
70.30 Hydrogen % wt. 4.86 Nitrogen % wt. 1.37 Sulfur % wt. 0.81
Oxygen % wt. 7.63 Ash % wt. 9.70 Moisture % wt. 5.33 Total 100.00
As Received Heating Value Btu/lb 12,584 Ultimate Analysis: Dry
Basis Carbon % wt. 74.26 Hydrogen % wt. 5.13 Nitrogen % wt. 1.45
Sulfur % wt. 0.86 Oxygen % wt. 8.06 Ash % wt. 10.25 Total 100.00
Dry Heating Value Btu/lb 13,292
[0069] The nano-dispersion of coal was prepared according to the
wet-comminution method descirbed herein. Particularly, after
milling coal in an IKA.RTM. mill, particle sizes were, in general
evenly distributed from very large to very small sizes, i.e. mostly
unimodal or slightly bimodal distributions. According to sieving
tests, particle populations below 20 .mu.m increased initially from
a concentration of 10-30% to 50-60% w/2 after the wet-communition
process. Particles could be as small as 100 nm, depending on the
type and content of coal, intial grind and process conditions such
as viscosity prior to the wet-comminution, residence time and total
energy input. In general, it was found that both low viscosity and
high coal content would improve comminution and the best results
were obtained for dispersions having coal contents between 55 to
60%. In this range, coal content was sufficiently high and
viscosity was still manageable.
[0070] Microscopic observations confirmed the sieve results, while
measurements with a Nanotrac showed a significant overall reduction
in size of the colloidal population (<6.5 .mu.m). Typical
sieving results are shown in FIG. 12, which is a histogram of %
weight retained between two sieves, for a 40 mesh ground sample
(less than 400 .mu.m) and the same sample after the wet-comminution
process. Before wet-comminution data is shown in the left-hand
bars, and after wet-comminution data is shown in the right-hand
bars. The population below 20 .mu.m increased significantly as
verified in the microscope. Few particles between 8 and 20 .mu.m
were observed.
[0071] Additionally, the graph in FIG. 13 shows the results of the
Nanotrac apparatus; the figure depicts the colloidal distributions,
before and after the wet-comminution process. The conventional
grind produces a colloidal population that is below 30% weight and
down to 0.7-1 .mu.m, while the wet-comminution process increases
the colloidal population up to 80% and decreases size close to or
in the nanorange (100 nm or 0.1 .mu.m).
[0072] The water content of both the nano-dispersion and the
initial conventional coal slurry was 40% by weight. However, it was
readily apparent that the conventional slurry had different
handling, pumping, and atomization characteristics than the
nano-dispersion slurry. Specifically, the conventional slurry with
40% water had poor atomization quality and tended to plug the
injection system. Therefore, to qualitatively simulate the handling
and atomization characteristics of the nano-dispersion slurry, most
conventional slurry reburning tests were performed with slurry
containing 45% water. It was observed that even after shipment and
storage for several weeks of the nano-dispersion slurry, the slurry
did not settle in the containers and maintained good condition. On
the other hand, the initial conventional coal slurry with 40% water
by weight settled in the bottom of the storage container within a
few hours.
[0073] Two series of reburning tests were performed, including one
with nano-dispersion of coal in water slurry and one with
conventional coal water slurry. The slurry was the reburn fuel,
with natural gas as the main fuel. After stable emissions were
verified during natural gas firing, slurry was pumped and atomized
into the BSF furnace zone. NO.sub.x emissions were measured
throughout the tests to determine the achievable NO.sub.x
reduction, and for selected test conditions, ash samples were
collected from the convective pass of the BSF and loss of ignition
(LOI) was measured.
[0074] Test variables included reburning heat input ranging from
about 10% to about 20% and varied by adjusting the reburn fuel flow
rate, reburn zone residence time (240 to 590 ms) varied by moving
the overfire air injector position, initial NO.sub.x concentration
(250 to 400 ppm) varied by adjusting burner conditions, and slurry
water content (40% and 45%). The following table set forth the test
matrix:
TABLE-US-00003 Rb. Rb. Zone Heat OFA Res. NOx @ Test Input Temp.
Time 0% O2 Atomization Fly Ash Run Reburn Fuel (%) (F.) (ms) (ppm)
Medium Sample 1.1 Micronized CWS 10 2380 590 400 Air 1.2 Micronized
CWS 15 2380 590 400 Air 1.3 Micronized CWS 20 2380 590 400 Air X
1.4 Micronized CWS 10 2550 240 400 Air 1.5 Micronized CWS 15 2550
240 400 Air 1.6 Micronized CWS 20 2550 240 400 Air X 1.7 Micronized
CWS 10 2550 240 250 Air 1.8 Micronized CWS 15 2550 240 250 Air 1.9
Micronized CWS 20 2550 240 250 Air X 2.1 Conventional CWS 10 2380
590 400 Air 2.2 Conventional CWS 15 2380 590 400 Air 2.3
Conventional CWS 20 2380 590 400 Air X 2.4 Conventional CWS 10 2550
240 400 Air 2.5 Conventional CWS 15 2550 240 400 Air 2.6
Conventional CWS 20 2550 240 400 Air X 2.7 Conventional CWS 10 2550
240 250 Air 2.8 Conventional CWS 15 2550 240 250 Air 2.9
Conventional CWS 20 2550 240 250 Air X BSF Conditions: Primary
Firing Rate: 712, 500 Btu/hr SR1: 1.1; SR3: 1.2 Primary Fuel:
Natural gas Reburn Fuel Location: Port 2.5, Injection Temperature:
2760 F.
[0075] 2. Test Results
[0076] At high initial NO.sub.x concentration (400 ppm) and short
reburn zone residence time (240 ms), the reburn performance for
micronized slurry is slightly better compared to that of
conventional slurry, as illustrated in the graph of FIG. 7B.
[0077] At low initial NO.sub.x concentration (250 ppm) and short
reburn zone residence time (240 ms), the reburn performance of
micronized 40% water slurry is comparable to that of 45%
conventional slurry, as illustrated in the graph of FIG. 7C.
[0078] The effect of initial NO.sub.x concentration on reburn
performance while keeping the same reburn zone residence time (240
ms) was also measured. The reburn performance of 40% water
micronized slurry appears to be better compared to that of
conventional 45% slurry at 15% and 20% reburn heat input. Reburn
performance for micronized and conventional slurry is comparable
and within the same range at 10% reburn heat input, as illustrated
in the graph of FIG. 8.
[0079] The effect of reburn zone residence time on reburn
performance while keeping same initial NO.sub.x concentration (400
ppm) was also measured. The reburn performance of micronized slurry
appears to be better compared to that of conventional slurry at 15%
and 20% reburn heat input. Reburn performance for both micronized
and conventional slurry is comparable and within the same range at
10% reburn heat input, as demonstrated in the graph of FIG. 9.
[0080] The current coal-water slurry reburning results were also
compared in the context of other reburning fuels that have been
tested at the BSF. Natural gas is the most reactive of these fuels
due to its ability to readily disperse and react. However, natural
gas is also typically the most expensive reburning fuel, and thus
there is commercial interest in utilizing other fuels such as coal
for reburning. The micronized slurry was generated using a
bituminous coal that on its own would not be expected to be highly
reactive. The results are illustrated in the graph of FIG. 10.
[0081] Three fly ash samples were collected and measured for loss
on ignition (LOI) at 20% reburn heat input for both micronized and
conventional slurry to determine if the micronized slurry is
different from the conventional slurry in terms of carbon content
in ash. The LOI is lightly lower for micronized slurry reburn tests
for all test conditions, as illustrated in the graph of FIG.
11.
[0082] The following table is a summary of all test results, in
which it was observed that for all the reburn test conditions, the
micronized coal water slurry with 40% water performed better than
the conventional coal water slurry with 45% water, and that for all
reburn test conditions the micronized coal water with 40% water
performed at least as well as, and in some cases better than, the
conventional coal water slurry with 45% water. NO.sub.x reduction
performance of micronized slurry appears to have more advantages at
higher reburn heat inputs and longer reburn zone residence times.
The values of Loss on Ignition results were slightly lower for
reburn tests with micronized slurry than with conventional
slurry.
TABLE-US-00004 Rb. Rb. Zone NOx @ Water Heat Res. 0% Test Content
Input Time O2 NOx Run Reburn Fuel (%) (%) (ms) (ppm) Reduction 1.1
Micronized CWS 40 10 590 400 27.9 1.2 Micronized CWS 40 15 590 400
56.0 1.3 Micronized CWS 40 20 590 400 66.7 1.4 Micronized CWS 40 10
240 400 22.9 1.5 Micronized CWS 40 15 240 400 37.4 1.6 Micronized
CWS 40 20 240 400 42.1 1.7 Micronized CWS 40 10 240 250 4.4 1.8
Micronized CWS 40 15 240 250 13.5 1.9 Micronized CWS 40 20 240 250
17.6 1.1 Micronized CWS 45 10 590 400 33.0 1.2 Micronized CWS 45 15
590 400 56.7 1.3 Micronized CWS 45 20 590 400 62.2 2.1 Conventional
CWS 45 10 590 400 29.2 2.2 Conventional CWS 45 15 590 400 45.5 2.3
Conventional CWS 45 20 590 400 54.5 2.4 Conventional CWS 45 10 240
400 25.4 2.5 Conventional CWS 45 15 240 400 33.8 2.6 Conventional
CWS 45 20 240 400 39.5 2.7 Conventional CWS 45 10 240 250 5.6 2.8
Conventional CWS 45 15 240 250 15.5 2.9 Conventional CWS 45 20 240
250 18.1 2.1 Conventional CWS 40 10 590 400 18.5 2.2 Conventional
CWS 45 15 590 400 37.6
[0083] The development of a super green coal to be used as a
carbonaceous material-in-water slurry according to embodiments of
the invention has the potential of massive savings in the
applications as described above, and particularly in the low NOx
burner applications because less carbonaceous material is needed to
produce the same amount of energy produced in today's applications.
Further, the virtually complete burning of the coal reduces the
amount of carbonaceous material present in the waste streams, such
as the ash of a boiler.
[0084] The invention therefore addresses and resolves many of the
deficiencies and drawbacks previously identified. The invention may
be embodied in other specific forms without departing from the
essential attributes thereof; therefore, the illustrated
embodiments should be considered in all respects as illustrative
and not restrictive. The claims provided herein are to ensure
adequacy of the present application for establishing foreign
priority and for no other purpose.
* * * * *