Optics: measuring and testing – By alignment in lateral direction
Reexamination Certificate
2000-09-12
2003-10-28
Adams, Russell (Department: 2851)
Optics: measuring and testing
By alignment in lateral direction
C356S400000, C702S024000, C073S023330
Reexamination Certificate
active
06639675
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to sensors that measure the Carbon content of the fly ash produced by the combustion process in a pulverized coal-fired steam generator and more particularly to the alignment of the mirrors used in such a sensor.
DESCRIPTION OF THE PRIOR ART
Fly ash results from the incomplete combustion of pulverized coal in a pulverized coal-fired steam generator. The fly ash is the combination of inert and inorganic residue resulting from the incomplete combustion of the pulverized coal. The pulverized coal contains varying amounts of carbon or coke particles. In general, the inorganic ash particles consist primarily of silicates, oxides and sulfates, together with small quantities of phosphates and other trace compounds.
The presence of unburned Carbon in boiler fly ash has important economic and environmental consequences to the operator of a coal-fired boiler installation. Its presence is a measure of inefficient fuel utilization which means that more fuel must be burned in order to obtain a given output and which in turn directly increases the cost of electrical power generation. Furthermore, inefficient fuel utilization by virtue of requiring more fuel to be burned in order to produce a given output increases the presence of NO
x
emissions which is the basis for environmental concerns. Thus, knowledge of the Carbon content of boiler fly ash is an important element in establishing a low NO
x
boiler emission strategy.
In addition, low Carbon fly ash can be a potential source of income to the operator of a pulverized coal-fired boiler in that fly ash can be employed as a building material if the Carbon content in the fly ash is sufficiently low. Fly ash with a high Carbon content is unsuitable as a building material and normally requires the use of expensive waste disposal methods.
One system for continuous in-situ measurement of Carbon in fly ash is described in U.S. Pat. No. 5,729,470 (“the '470 patent”) which is assigned to the same assignee as the present invention. The system described in the '470 patent includes a resonant cavity for measuring in-situ and in real time the Carbon content of the fly ash.
Referring now to
FIG. 1
(which is FIG. 5 of the '470 Patent), there is shown the resonant cavity
300
in the system of the '470 patent. Also shown in
FIG. 1
, are intelligence
100
, transmitting section
200
and receiving section
400
of the system of the '470 patent. As is shown in
FIG. 2
herein (which is FIG. 3 of the '470 Patent), intelligence
100
includes a CPU
112
.
Returning once again to
FIG. 1
, the transmitting section
200
includes a pressure boundary
202
, an oscillator
204
, a signal coupler
208
, a reference detector
210
, a signal isolator
214
and a waveguide
216
.
The transmitting section
200
further includes a first air purge
218
and a second air purge
220
.
The cavity section
300
is comprised of a first concave spherical mirror
302
, a second concave spherical mirror
304
, a common optical axis
306
, a plurality of alignment screws
308
, an inspection volume
300
′, a first annular ring
302
′ and a second annular ring
304
′. As is shown in
FIG. 3
(which is FIG. 6 of the '470 patent) the first and second concave spherical mirrors
302
,
304
each contain a pattern of circular holes that are drilled therethrough that consist of a central hole
310
, so located as to be on the optical axis
306
, which is common both to the first concave spherical mirror
302
and the second concave spherical mirror
304
and an array of planetary holes
312
symmetrically located about the central hole
310
.
As is shown in
FIG. 4
(which is FIG. 7 of the '470 patent) the first and second concave spherical mirrors
302
,
304
have attached to their nonreflecting sides three screws
308
symmetrically located about the center of the mirrors
302
,
304
for the purpose of aligning said mirrors
302
,
304
along the common optical axis
306
. Two of three alignment screws
308
for each of mirrors
302
,
304
are turned by an associated stepper motor.
FIG. 1A
, which is an enlargement of a portion of
FIG. 1
, shows the stepper motor
320
connected to one of the alignment screws
308
. The motor
320
has a hollow shaft with internal threads and is threaded onto the associated alignment screw
308
. The motor
320
is controlled by CPU
112
of intelligence
100
.
The receiving section
400
includes a pressure boundary
402
, a waveguide
404
and a signal detector
408
.
The receiving section
400
further includes a first air purge
412
and a second air purge
414
.
The oscillator
204
receives as input the electrical drive signal
104
originating from the intelligence section
100
. The oscillator
204
typically may take the form of a free running biased tuned microwave oscillator, the nature of the construction and the mode of operation of which is known and understood by those skilled in the art. As a consequence of the input received thereby, the oscillator
204
generates as output a constant amplitude, sinusoidal signal
206
of electromagnetic radiation which repeatedly sweeps through a certain frequency span, &Dgr;f.
The oscillator output signal
206
is supplied in known fashion to the signal coupler
208
. Again in known fashion, a small fraction
206
′ of the oscillator output signal
206
is diverted by the signal coupler
208
to the reference detector
210
, to be described hereinafter, and the remainder
206
″ of the oscillator output signal
206
is supplied to the waveguide
216
via the signal isolator
214
. Typically the signal isolator
214
may take the form of a waveguide section filled with a ferrite material so aligned that in combination with the magnetic field of a permanent magnet, electromagnetic radiation can propagate in one direction only. The purpose of the signal isolator
214
is to prevent signal return from the cavity section
300
. Since reflected energy is sharply attenuated by the signal isolator
214
it helps ensure the frequency and amplitude stability of the oscillator
204
.
The detector
210
is designed to receive as input the signal
206
′ which is delivered from the signal coupler
208
in the form of electromagnetic radiation and whose power is a small fraction of the oscillator signal
206
power. The reference detector
210
typically may take the form of a full wave rectifier which may or may not be followed by a peak detector. The reference detector
210
is operative upon the input signal
206
′ in a known manner in order to thereby generate as output a reference signal
212
in the nature of a DC voltage proportional to the power of the input signal
206
′ that is supplied to the reference detector
210
.
The signal
206
″ in the form of electromagnetic radiation is supplied as an input to the waveguide
216
which, in accordance with the best mode embodiment of the invention, is rigidly fixed to the non-reflecting side of the first concave spherical mirror
302
so as to be aligned along the common optical axis
306
. The waveguide
216
in turn is designed so as to be operative to deliver the signal
206
″ to the cavity section
300
via the central hole
310
which is illustrated in FIG.
3
. The waveguide
216
, in accordance with the best mode embodiment of the invention, is preferably equipped with a first air purge
218
. The air purge
218
is designed to be operative so as to direct an external source of pressurized air
218
′ into and along the waveguide
216
through to the cavity section
300
via the central hole
310
depicted in FIG.
3
. Such purging activity helps prevent fouling of the mirror
302
and the waveguide
216
which might otherwise occur due to fly ash buildup.
The transmitting section
200
includes a pressure boundary
202
. The pressure boundary
202
may or may not enclose the oscillator
204
, the signal coupler
208
, the reference detector
210
and the signal isolator
214
. The pressure boundar
Boguszewski Stanley J.
Quinn Joseph W.
ABB Automation Inc.
Adams Russell
Rickin Michael M.
Sever Andrew
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