Photoacoustic measurement of unburned carbon in fly-ash

Details Photoacoustic measurement of unburned carbon in fly-ash Photoacoustic measurement of unburned carbon in fly-ash

1994-06-06

1997-01-21

Williams, Hezrone E.

Measuring and testing

Vibration

By mechanical waves

356432, G01N 2900

Patent

active

055961460

ABSTRACT:
The present invention provides a method and an apparatus for measuring the amount of unburned carbon in a sample of fly ash using infrared photoacoustic absorption. One preferred method according to the present invention involves directing modulated infrared radiation at a sample of fly ash and measuring the acoustic signal produced when the unburned carbon in the sample absorbs the radiation producing a thermal wave which propagates through the sample to generate a minute acoustic wave at interfaces between the carbon particles and gas surrounding the particles. One preferred apparatus includes a source of modulated infrared radiation, a chamber for containing the sample, a microphone to detect the acoustic signals, lock-in amplifier to separate the desired photoacoustic signal from noise at other frequencies, and a PC computer to provide output from the amplifier. This apparatus identifies the acoustic signal for determination of the amount of unburned carbon in the sample.

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