Capacitance-level/density monitor for fluidized-bed combustor
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).
- Assignee:
- Department Of Energy
- Patent Number(s):
- US 4350040
- OSTI ID:
- 6728289
- Resource Relation:
- Patent File Date: Filed date 26 Jun 1980; Other Information: PAT-APPL-163368
- 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
DENSIMETERS
DESIGN
FLUIDIZED BED
DENSITY
LEVELS
FLUIDIZED-BED COMBUSTORS
MONITORS
LEVEL INDICATORS
AIR FLOW
CAPACITY
CERAMICS
COAL
CONTROL SYSTEMS
ELECTRIC CONDUCTIVITY
ELECTRICAL INSULATION
ELECTRONIC CIRCUITS
FLOW RATE
MONITORING
CARBONACEOUS MATERIALS
COMBUSTORS
ELECTRICAL PROPERTIES
ENERGY SOURCES
FLUID FLOW
FOSSIL FUELS
FUELS
GAS FLOW
MATERIALS
MEASURING INSTRUMENTS
PHYSICAL PROPERTIES
421000* - Engineering- Combustion Systems