Open AccessMONITORING POWER PLANT EFFICIENCY USING THE MICROWAVE-EXCITED PHOTOACOUSTIC EFFECT TO MEASURE UNBURNED CARBON
Author(s) -
R. C. Brown,
Robert J. Weber,
Andrew A. Suby
Publication year - 2002
Language(s) - English
Resource type - Reports
DOI - 10.2172/809220
Subject(s) - microwave , signal (programming language) , acoustics , test fixture , amplifier , repeatability , ultrasonic sensor , noise (video) , power (physics) , materials science , engineering , electrical engineering , computer science , telecommunications , mechanical engineering , physics , chemistry , cmos , chromatography , artificial intelligence , image (mathematics) , programming language , quantum mechanics
Three test instruments are being evaluated to determine the feasibility of using photo-acoustic technology for measuring unburned carbon in fly ash. The first test instrument is a single microwave frequency system previously constructed to measure photo-acoustic signals in an off-line configuration. This system was assembled and used to test parameters thought important to photo-acoustic signal output. A standard modulation frequency was chosen based upon signal to noise data gained from experimentation. Sample heterogeneity was tested and found not to be influential. Further testing showed that sample compression and photo-acoustic volume do affect photo-acoustic signal. Testing in the fourth quarter focused on signal repeatability, linearity, the effects of ultrasonic shaking, and sample cup variations. Simultaneously, a second instrument is being constructed based in part on lessons learned with the first instrument, but also expands the capabilities of the first instrument. The power amplifiers for this second instrument were recently completed and tested. Improvements were made to the current leveling loop, which will stabilize the microwave power. Other efforts were spent generating a magnetic field or electric field source for the photo-acoustic effect. The intent of this effort is to be able to discriminate between magnetic contaminants such as iron and non-magnetic contaminants such as carbon. A short coaxial test fixture was fabricated and tested showing the promise of another microwave based test method for determining carbon content in fly ash. The third instrument will be designed based on the experiences of the first two instruments and will operate in an on-line carbon-in-ash monitoring system for coal-fired power plants