Capacitance-level/density monitor for fluidized-bed combustor
- Morgantown, WV
A multiple segment three-terminal type capacitance probe with segment selection, capacitance detection and compensation circuitry and read-out control for level/density measurements in a fluidized-bed vessel is provided. The probe is driven at a high excitation frequency of up to 50 kHz to sense quadrature (capacitive) current related to probe/vessel capacitance while being relatively insensitive to the resistance current component. Compensation circuitry is provided for generating a negative current of equal magnitude to cancel out only the resistive component current. Clock-operated control circuitry separately selects the probe segments in a predetermined order for detecting and storing this capacitance measurement. The selected segment acts as a guarded electrode and is connected to the read-out circuitry while all unselected segments are connected to the probe body, which together form the probe guard electrode. The selected probe segment capacitance component signal is directed to a corresponding segment channel sample and hold circuit dedicated to that segment to store the signal derived from that segment. This provides parallel outputs for display, computer input, etc., for the detected capacitance values. The rate of segment sampling may be varied to either monitor the dynamic density profile of the bed (high sampling rate) or monitor average bed characteristics (slower sampling rate).
- Research Organization:
- National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV (United States)
- Assignee:
- United States of America as represented by United States (Washington, DC)
- Patent Number(s):
- US 4350040
- OSTI ID:
- 864340
- Country of Publication:
- United States
- Language:
- English
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Capacitance-level/density monitor for fluidized-bed combustor
Design and performance of a capacitance probe for monitoring averaged parameters and individual events in a high-temperature, fluidized-bed reactor
Related Subjects
density
monitor
fluidized-bed
combustor
multiple
segment
three-terminal
type
capacitance
probe
selection
detection
compensation
circuitry
read-out
control
level
measurements
vessel
provided
driven
excitation
frequency
50
khz
sense
quadrature
capacitive
current
related
relatively
insensitive
resistance
component
generating
negative
equal
magnitude
cancel
resistive
clock-operated
separately
selects
segments
predetermined
detecting
storing
measurement
selected
guarded
electrode
connected
unselected
form
guard
signal
directed
corresponding
channel
sample
hold
circuit
dedicated
store
derived
provides
parallel
outputs
display
computer
input
etc
detected
values
rate
sampling
varied
dynamic
profile
bed
average
characteristics
slower
density profile
control circuitry
negative current
excitation frequency
guard electrode
density measurement
control circuit
bed combustor
hold circuit
signal derived
resistive component
capacitance probe
parallel output
relatively insensitive
sampling rate
fluidized-bed combustor
density monitor
selected probe
equal magnitude
compensation circuit
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