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
- Country of Publication:
- United States
- Language:
- English
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Capacitance-level/density monitor for fluidized-bed combustor
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Related Subjects
421000* -- Engineering-- Combustion Systems
AIR FLOW
CAPACITY
CARBONACEOUS MATERIALS
CERAMICS
COAL
COMBUSTORS
CONTROL SYSTEMS
DENSIMETERS
DENSITY
DESIGN
ELECTRIC CONDUCTIVITY
ELECTRICAL INSULATION
ELECTRICAL PROPERTIES
ELECTRONIC CIRCUITS
ENERGY SOURCES
FLOW RATE
FLUID FLOW
FLUIDIZED BED
FLUIDIZED-BED COMBUSTORS
FOSSIL FUELS
FUELS
GAS FLOW
LEVEL INDICATORS
LEVELS
MATERIALS
MEASURING INSTRUMENTS
MONITORING
MONITORS
PHYSICAL PROPERTIES