U.S. patent application number 11/414920 was filed with the patent office on 2007-11-01 for continuous real time heating value (btu)/coal flow balancing meter.
This patent application is currently assigned to Energy Technologies, Inc.. Invention is credited to Jack R. Lee, Peter M. Osucha, David K. Swindell.
Application Number | 20070251432 11/414920 |
Document ID | / |
Family ID | 38647120 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251432 |
Kind Code |
A1 |
Osucha; Peter M. ; et
al. |
November 1, 2007 |
Continuous real time heating value (BTU)/Coal flow balancing
meter
Abstract
A method and an apparatus for continuous real time heating
value/coal flow balancing of coal from a coal feeder to a burner.
The apparatus includes a dual-energy Gamma Attenuation
(DGA)/multi-energy Gamma Attenuation (MGA) device for measuring
coal quality at a specific location between the coal silo and the
mill in a coal fired plant in order to control the individual
burner stoichiometries according to the measured coal quality. By
strategically placing the DGA/MGA device, continuous accurate
real-time coal quality information is accomplished for making
individual adjustments in order to improve stoichiometry to
optimize performance of the system.
Inventors: |
Osucha; Peter M.;
(Knoxville, TN) ; Swindell; David K.; (Knoxville,
TN) ; Lee; Jack R.; (Lenoir City, TN) |
Correspondence
Address: |
PITTS AND BRITTIAN P C
P O BOX 51295
KNOXVILLE
TN
37950-1295
US
|
Assignee: |
Energy Technologies, Inc.
Knoxville
TN
|
Family ID: |
38647120 |
Appl. No.: |
11/414920 |
Filed: |
May 1, 2006 |
Current U.S.
Class: |
110/185 ;
110/186; 110/347 |
Current CPC
Class: |
F23N 2239/02 20200101;
F23N 5/184 20130101; F23N 2221/10 20200101 |
Class at
Publication: |
110/185 ;
110/347; 110/186 |
International
Class: |
F23N 5/00 20060101
F23N005/00; F23N 5/18 20060101 F23N005/18; F23D 1/00 20060101
F23D001/00 |
Claims
1. A device for continuous real time heating value/coal flow
balancing of coal from a coal feeder to a burner, said device being
used in association with a coal burning system including at least a
coal feeder, a mill for pulverizing the coal, at least one damper
for controlling oxygen (O.sub.2) introduced in the coal, and at
least one burner for burning coal processed through the at least
one damper, said device comprising: a dual-energy Gamma Attenuation
(DGA)/multi-energy Gamma Attenuation (MGA) device for measuring the
quality of coal, said DGA/MGA device being disposed between the
coal feeder and the mill, said DGA/MGA device measuring coal as the
coal passes between the coal feeder and the mill, said DGA/MGA
device including: at least one DGA/MGA source positioned proximate
to the coal at a location between the coal feeder and the mill; at
least one DGA/MGA detector positioned to detect high energy gamma
rays emitted from the coal; and a DGA/MGA data acquisition unit for
reading output from said at least one DGA/MGA detector; and a
processor in communication with said DGA/MGA data acquisition unit
for processing, said processor further in communication with the at
least one damper, said processor being adapted to control at least
one damper in response to the coal quality information.
2. The device of claim 1 wherein said at least one DGA/MGA source
and said at least one DGA/MGA detector are each placed in proximity
to the coal feeder for analyzing coal before the coal is delivered
to the mill.
3. The device of claim 1 wherein a delay is determined for a
distance between said DGA/MGA device and the at least one damper,
and wherein said processor signals the at least one damper in
response to the coal quality information, said processor signaling
the at least one damper after said delay whereby the at least one
damper is adjusted according to the coal quality information for a
selected volume of coal as the selected volume of coal is processed
through the at least one damper.
4. A coal fire burning system providing continuous real time
heating value/coal flow balancing of coal, said system comprising:
a coal feeder for receiving coal and supplying coal to said system;
a mill for pulverizing coal received from said coal feeder; at
least one damper for controlling oxygen (O.sub.2) introduced in the
pulverized coal; at least one burner for burning coal processed
through the at least one damper, each of said at least one burner
being adapted to receive a mixture of at least coal and O.sub.2
from one of said at least one damper; a dual-energy Gamma
Attenuation (DGA)/multi-energy Gamma Attenuation (MGA) device for
measuring the quality of coal, said DGA/MGA device being disposed
between said coal feeder and said mill, said DGA/MGA device
measuring coal as the coal passes between said coal feeder and said
mill, said DGA/MGA device including: at least one DGA/MGA source
positioned proximate to the coal at a location between said coal
feeder and said mill; at least one DGA/MGA detector positioned to
detect high energy gamma rays emitted from the coal; and a DGA/MGA
data acquisition unit for reading output from said at least one
DGA/MGA detector; and a processor in communication with said
DGA/MGA data acquisition unit for processing, said processor
further in communication with said at least one damper, said
processor being adapted to control said at least one damper in
response to the coal quality information, whereby a stoichiometry
of each of said at least one burner is individually controlled and
optimized.
5. The device of claim 4 wherein said at least one DGA/MGA source
and said at least one DGA/MGA detector are each placed in proximity
to said coal feeder for analyzing coal before the coal is delivered
to said mill.
6. The device of claim 4 wherein a delay is determined for a
distance between said DGA/MGA device and said at least one damper,
and wherein said processor signals said at least one damper in
response to the coal quality information, said processor signaling
said at least one damper after said delay whereby said at least one
damper is adjusted according to the coal quality information for a
selected volume of coal as the selected volume of coal is processed
through said at least one damper.
7. A method for operating a coal fire burning system providing
continuous real time heating value/coal flow balancing of coal,
said system comprising a coal feeder; a mill for pulverizing coal;
at least one damper for controlling oxygen (O.sub.2) introduced in
the pulverized coal; at least one burner for burning coal processed
through the at least one damper; a dual-energy Gamma Attenuation
(DGA)/multi-energy Gamma Attenuation (MGA) device for measuring the
quality of coal including at least one DGA/MGA source positioned
proximate to the coal at a location between said coal feeder and
said mill, at least one DGA/MGA detector positioned to detect high
energy gamma rays emitted from the coal, and a DGA/MGA data
acquisition unit for reading output from said at least one DGA/MGA
detector; and a processor in communication with the DGA/MGA data
acquisition unit for processing, said processor further in
communication with said at least one damper, said processor being
adapted to control said at least one damper in response to the coal
quality information, said method comprising the steps of: (a)
acquiring coal information; and (b) determining whether the quality
of coal presented to the individual burner requires a decrease in
O.sub.2 level; (c) signaling said at least one damper to close
according to the desired decrease in said O.sub.2 level; (d)
determining whether the quality of coal presented to the individual
burner requires an increase in O.sub.2 level; (e) signaling said at
least one damper to open according to the desired increase in said
O.sub.2 level; (f) repeating said steps of (b) acquiring coal
information through (h) signaling said at least one damper.
8. The method of claim 7, before said step of (a) acquiring coal
information, further comprising the step of: (a) determining a
delay approximately equal to a time required for the coal to travel
from said coal feeder to said at least one damper; before said step
of (c) signaling said at least one damper to close according to the
desired decrease in said O.sub.2 level, further comprising the step
of: (b) delaying for a time equal to said delay; and before said
step of (e) signaling said at least one damper to open according to
the desired increase in said O.sub.2 level, further comprising the
step of: (c) delaying for a time equal to said delay.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of Invention
[0004] The present invention relates to the use of nuclear response
measurements of fuel flow and fuel quality combined with a process
control system for optimization of air and coal stoichiometry at
each burner in a coal fired boiler.
[0005] 2. Description of the Related Art
[0006] In the field of coal fired boilers used especially by
utility companies and industrial boiler operators, it is well known
that increasingly stringent emissions limits continue to apply
pressure to reduce NO.sub.x emissions from coal fired boilers.
Years of investigation by utilities, boiler suppliers, and controls
suppliers have determined that stoichiometries local to the burners
must be maintained to achieve very low NO.sub.x emissions without
negatively effecting combustion efficiency or boiler performance.
Common barriers to lower NO.sub.x emissions include poor coal and
air distribution which may also lead to high unburned carbon, high
CO.sub.x, boiler slagging, and oxygen and/or steam temperature
imbalances.
[0007] To date, all low NO.sub.x firing systems are based on a
pre-defined balance of air and coal at the burners. Deviations from
the design air/fuel balance at individual burners results in
burners operating at a fuel lean or fuel rich condition. A fuel
lean burner produces high NO.sub.x levels at elevated O.sub.2
resulting in a flue gas with high CO.sub.x, high NO.sub.x, and
increased LOI due to burners operating with poor stoichiometries. A
fuel rich burner produces large amounts of CO.sub.X, high LOI, and
longer flames while lowering the oxygen level in the flue gas. Many
coal fired boilers with poor air/fuel distribution experience
problems such as: emission problems; increased unburned carbon in
fly ash; distorted oxygen profile at the boiler outlet; uneven
steam temperature profiles; flame impingement; increased slagging;
and water wall heat waste.
[0008] The inventor of the present invention is a co-inventor of
the subject matter disclosed in U.S. Pat. No. 7,006,919, titled
"Real time continuous elemental measurement of bulk material,"
issued on Feb. 28, 2006. In that patent, various methods and an
apparatus for continuous real-time measurement of bulk material
using gamma irradiation and neutron irradiation is disclosed. The
'919 device includes a dual-energy gamma attenuation (DGA) device
for monitoring bulk material flow and for producing a spectrum that
is compared to a baseline spectrum to produce a relative
weight/impurity ratio. A prompt gamma neutron activation analysis
(PGNAA) device monitors the same bulk material flow and produces a
spectrum that is compared to a library of spectrums to produce a
relative component ratio. The relative component ratio is processed
with the relative weight/impurity ratio to produce an absolute
weight and impurity value, which is then processed with the
relative component ratio to produce absolute component, or analyte,
values.
[0009] The DGA analysis technique involves bombarding a bulk
material with gamma rays from two gamma ray emitters of
sufficiently different energies. The gamma rays interact with the
bulk material resulting in the attenuation of the number of gamma
rays transmitted through the bulk material. The gamma rays are
typically detected by a scintillation crystal (typically NaI). The
sum of these released gamma rays at these specific energies is
referred to as an energy spectrum. The technology relies on the
fact that elements with different atomic numbers attenuate gamma
rays at specific energies in different ways. Thus, for low-energy
gamma rays (i.e., those generated by a low energy gamma emitter
such as Am-241), the attenuation of gamma rays is largely dependent
on the atomic number of the atoms/elements present in the bulk
material. For high-energy gamma rays (i.e., those generated by a
high-energy gamma emitter such as Cs-137), attenuation is
independent of the atoms/elements in the bulk material. Analysis of
the energy spectrum leads to a determination of the bulk elemental
composition of the bulk material.
[0010] DGA based sensors are known in the art. DGA devices are
based on the premise that analyzed material will attenuate
different energy gamma rays in fixed repeatable ways. A DGA device
consists of a gamma energy source arrangement consisting of dual
energy gamma emitters. The gamma emitters are chosen in such a way
that the material to be analyzed will attenuate the different
energy gamma rays in ways that are conducive to measuring one or
more specific properties of the material being measured. One such
application of DGA technology uses gamma ray sources to interrogate
coal, with the assumption that the material of which the coal is
composed will attenuate the differing energy gamma rays to produce
a measurement that is conducive to determining coal ash content and
density.
[0011] The PGNAA technique involves bombarding a bulk material
sample with neutrons from a neutron emitter (typically Cf-252). The
neutrons collide with atoms/elements in the sample, emitter
housing, and/or an external moderator and are captured by the
nuclei of atoms/elements present in the sample. The capture process
often involves the release of gamma rays at energies specific to
the captured atom/element. These gamma rays are detected typically
by a scintillation crystal (typically NaI). The sum of the detected
gamma energy at these specific energies is an energy spectrum.
Analysis of the energy spectrum provides analytical information on
the proportion of the various elements present in the bulk
material.
[0012] As discussed in the '919 patent, various PGNAA based sensor
systems are known. One such analyzer is that described in U.S. Pat.
No. 4,582,992, titled "Self-Contained, On-Line, Real-time Bulk
Material Analyzer," issued to Atwell, et al., on Apr. 15, 1986,
which uses PGNAA technology in an attempt to determine the
elemental content of the bulk material. The described analyzer uses
an arrangement of neutron sources and gamma ray detectors in an
enclosed assembly to perform its analysis. A similar device,
described in U.S. Pat. No. 6,362,477, titled "Bulk Material
Analyser for OnConveyor Belt Analysis," issued to Sowerby, et al.,
on Mar. 26, 2002, uses PGNAA technology in a bulk material
on-conveyor belt arrangement to analyze bulk material. Again, this
analyzer uses a neutron source and gamma ray detectors in an
enclosed assembly to perform its analysis.
BRIEF SUMMARY OF THE INVENTION
[0013] The present invention is a method and an apparatus for
continuous real time heating value/coal flow balancing of coal from
a coal feeder to a burner. The apparatus includes a dual-energy
Gamma Attenuation (DGA)/multi-energy Gamma Attenuation (MGA) device
for measuring coal quality at a specific location (i.e., on the
coal feeder tube between the coal silo and the mill) in a coal
fired plant in order to control the parameters of the plant
according to the measured coal quality. By strategically placing
the DGA/MGA device, continuous accurate real-time coal quality
information is accomplished for making individual adjustments in
order to improve stoichiometry to optimize performance of the
system.
[0014] A system incorporating the apparatus of the present
invention is includes a coal silo for receiving and burning coal. A
DGA/MGA device includes at least one DGA/MGA source and at least
one DGA/MGA detector in a fixed position relative to the coal silo.
The analyzed coal flows onto a coal feeder conveyor or is otherwise
moved to a mill. The coal is pulverized before being combined with
air by way of at least one actuated damper. The dampers are
electrically or electromechanically operated to open and close to
adjust the volume of air introduced into the pulverized coal. The
resulting product is then delivered to at least one burner.
[0015] Quality information pertaining to the coal is determined by
the DGA/MGA device and then sent to a processor. The processor is
provided for varying the control of various system components based
upon the coal quality information received from the DGA/MGA
device.
[0016] A time delay is established between the time the coal is
passed through the coal silo feeder tube, at which point the coal
is analyzed by the DGA/MGA device, and the time that the coal is
processed through the dampers. The processor uses the coal quality
information pertaining to the coal and the known time delay to
adjust the actuated dampers, thereby controlling the amount of air
mixed with the coal for optimal burner stoichiometry. Thus when a
selected volume of coal is analyzed and particular settings at the
dampers are required for that volume, the processor waits a
predetermined time equal to the time delay before adjusting the
dampers.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0017] The above-mentioned features of the invention will become
more clearly understood from the following detailed description of
the invention read together with the drawings in which:
[0018] FIG. 1 is a block diagram of the proposed system;
[0019] FIG. 2 is a representative diagram of the online measurement
process; and
[0020] FIG. 3 is a flow diagram of the method steps of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention provides a method and an apparatus for
continuous real time heating value/coal flow balancing of coal from
a coal feeder to a burner. The apparatus includes a dual-energy
Gamma Attenuation (DGA)/multi-energy Gamma Attenuation (MGA) device
for measuring coal quality at a specific location in a coal fired
plant in order to control the parameters of the plant according to
the measured coal quality. By strategically placing the DGA/MGA
device, continuous accurate real-time coal quality information is
accomplished for making individual adjustments in order to improve
stoichiometry to optimize performance of the system.
[0022] The DGA/MGA device of the present invention is illustrated
generally at 10 in the figures. As described below, the DGA/MGA
device 10 is mounted relative to a coal silo feeder tube 28 to
determine the quality of the material flowing to the coal feeder
30. This coal quality information is fed to a processing component
18 where control logic is used to adjust air/coal dampers 34
feeding the burners 36 into the boiler (not shown), resulting in
improved burner stoichiometry.
[0023] Coal feeders of the prior art meter the flow of coal to the
mills based on volume or weight, as opposed to quality or heating
value. Variability in fuel quality across the feeders and
subsequent burners coupled with air (O.sub.2) introduction based
upon design conditions rather than actual on-line parameters
produces the imbalances discussed above, such as poor air/fuel
distribution. In the present invention, density (flow rate) and
coal quality (heating value) are measured continuously and real
time adjustment is provided for air introduced in the system just
prior to combustion. The discrete control of this fuel/air balance
allows for improved stoichiometries local to all burners 36.
[0024] Accordingly, a method and apparatus for continuous real time
heating value/coal flow balancing are illustrated generally in the
figures. A system incorporating the apparatus of the present
invention is illustrated in FIG. 1. A coal silo 26 is provided for
storing coal before transfer to the mill and burners. A DGA/MGA
mounting structure 12 is provided for securing at least one DGA/MGA
source 14 and at least one DGA/MGA detector 16 in a fixed position
relative to the coal silo 26. The DGA/MGA sources 14 and the
DGA/MGA detectors 16 are positioned in the illustrated embodiment
across a coal silo feeder tube 28.
[0025] The analyzed coal flows onto a coal feeder conveyor 30 or is
otherwise moved to a mill 32. The coal 24 is pulverized before
being combined with air by way of at least one actuated damper 34.
The dampers 34 are electrically or electromechanically operated to
open and close to adjust the volume of air introduced into the
pulverized coal 24. The resulting product is then delivered to at
least one burner, shown schematically at 36.
[0026] Quality information pertaining to the coal 24 is determined
by the DGA/MGA device 10 and then sent to a processor 18. The
processor 18 is provided for varying the control of various system
components based upon the coal quality information received from
the DGA/MGA device 10. To this extent, the processor 18 includes at
least one input/output (I/O) control 20 in communication with
existing boiler controls 22 and/or other peripheral devices to
control at least the dampers 34 in response to the coal quality
information obtained via the DGA/MGA device 10. The I/O control 10
is a conventional input and/or output device including but not
limited to a plant network card or an Ethernet card.
[0027] A time delay is established between the time the coal 24 is
passed through the coal silo feeder tube 28, at which point the
coal 24 is analyzed by the DGA/MGA device 10, and the time that the
coal 24 is processed through the dampers 34. The processor 18 uses
the coal quality information pertaining to the coal 24 and the
known time delay to adjust the actuated dampers 34, thereby
controlling the amount of air mixed with the coal for optimal
burner stoichiometry. Thus when a selected volume of coal 24 is
analyzed and particular settings at the dampers 34 are required for
that volume, the processor 18 waits a predetermined time equal to
the time delay before adjusting the dampers 34. Therefore, as any
given volume of coal 24 is processed through the dampers 34, the
dampers 34 are adjusted for that volume of coal 24, as determined
by the DGA/MGA device 10 and the processor 18. Additional boiler
distribution controls and information is obtained as necessary from
a boiler distribution control system. Manual override functionality
is accomplished by way of existing boiler controls 22.
[0028] The present invention may further include a Full Stream
Elemental Analyzer (FSEA) 38 such as that described in the
aforementioned '919 patent. When incorporated in such a system, the
FSEA system 38 is in communication with the processor 18 and allows
for improvements in the coal quality information as well as
provides more specific elemental and slagging indices concerning
the coal stored in the silo and that has been previously measured.
These indices are stored in a database 40 associated with the FSEA
system 38 and communicated to the processor 18.
[0029] FIG. 2 is a schematic illustration in greater detail of the
DGA/MGA device 10 of the present invention. The coal silo 26 is
illustrated in a top plan view, looking into the coal silo feeder
tube 28. The DGA/MGA mounting structure 12 is illustrated as
securing at least one DGA/MGA source 14 on one side of the coal
silo feeder tube 28 and at least one DGA/MGA detector 16 on an
opposing side. The DGA/MGA detectors 16 are in communication with a
DGA/MGA data acquisition unit 18, which reads the output from the
DGA/MGA detectors 16. Data acquired from the DGA/MGA data
acquisition unit 17 is communicated to the processor 18. At least
one input/output (I/O) control 20 is in communication with the
existing boiler controls 22, as described above.
[0030] FIG. 3 illustrates generally the logic by which the
processor 18 operates. A delay 60 is determined for the particular
system to accommodate for the time required to move coal 24 from
the coal silo feeder tube 28 to the dampers 34. As coal 24 is moved
through the coal silo feeder tube 28, the DGA/MGA device 10
analyzes the quality of the coal 24, as shown at 62. The processor
18 then determines whether the coal quality is such that the
O.sub.2 level should be increased at 64. If the O.sub.2 level
requires increasing, the processor 18 delays for a time period
equal to the set delay, illustrated at 66, and then signals the
dampers 34 to reduce the volume of air introduced into the
pulverized coal 24, as illustrated at 68. The processor 18 then
determines whether the coal quality is such that the O.sub.2 level
should be decreased at 70. If the O.sub.2 level requires
decreasing, the processor 18 delays for a time period equal to the
set delay, illustrated at 72, and then signals the dampers 34 to
decrease the volume of air introduced into the pulverized coal 24,
as illustrated at 74. If the coal quality is such that the O.sub.2
level does not need decreasing, then the processor 18 does nothing
with respect to the operation of the dampers 34. In each case where
the dampers 34 are modified, by waiting for the expiration of the
delay, the O.sub.2 level is appropriately increased or decreased
according to the corresponding volume of coal 24. These steps are
repeated continuously throughout the operation of the system. The
present method has the distinct advantage over all current NO.sub.x
lowering methodologies in that it continuously monitors, in real
time, the coal quality information for coal 24 flowing to the
burners 36 instead of relying on an assumed value that may or may
not be accurate. It should be noted that the actual damper
modification might be performed by existing control equipment in
response to a signal provided by the present invention as opposed
to direct modification of the dampers themselves by the present
invention with no loss of generality.
[0031] From the foregoing description, it will be recognized by
those skilled in the art that a method and an apparatus for
continuous real time heating value/coal flow balancing of coal from
a coal feeder to a burner has been provided. The apparatus provides
for a DGA/MGA device disposed for measuring coal quality at a
specific location--between a coal silo and a mill--in a coal fired
plant in order to control the parameters of the plant according to
the measured coal quality. By strategically placing the DGA/MGA
device, continuous accurate real-time coal quality information is
accomplished for making individual adjustments in order to improve
individual burner stoichiometries to optimize performance of the
system.
[0032] While the present invention has been illustrated by
description of several embodiments and while the illustrative
embodiments have been described in considerable detail, it is not
the intention of the applicant to restrict or in any way limit the
scope of the appended claims to such detail. Additional advantages
and modifications will readily appear to those skilled in the art.
The invention in its broader aspects is therefore not limited to
the specific details, representative apparatus and methods, and
illustrative examples shown and described. Accordingly, departures
may be made from such details without departing from the spirit or
scope of applicant's general inventive concept.
* * * * *