Document Type

Patent

Publication Date

1-21-1997

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.

Patent Number

US 5,596,146

ISURF Reference Number

1764

Assignee

Iowa State University Research Foundation, Inc.,

Application Number

US 08/254,153

Date Filed

6-4-1994

Language

en

File Format

application/pdf

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