MONITORING POWER PLANT EFFICIENCY USING THE MICROWAVE-EXCITED PHOTOACOUSTIC EFFECT TO MEASURE UNBURNED CARBON

摘要

Three test instruments are being evaluated to determine the feasibility of using photoacoustic technology for measuring unburned carbon in fly ash. The first test instrument is a single microwave frequency system previously constructed to measure photoacoustic signals in an off-line configuration. A second off-line instrument was constructed based in part on lessons learned with the first instrument, but which also expands the capabilities of the first instrument. Improvements include a control loop to allow more constant microwave power output and an ability to operate over a range of microwave frequencies. The third instrument, the on-line version of the fly ash monitor, has been designed, constructed, and initial efficiency tests have been conducted on the monitor's electrical components. Photoacoustic measurements were collected using the off-line MEPA spectrometer with different microwave frequencies in order to develop photoacoustic microwave spectra of several fly ash samples. Microwaves from 500 MHz to 1800 MHz were used. Modifications to the on-line thermal elastic fly ash monitor include the improving the operation of the agitator for the bottom hopper, and installing a second diaphragm assembly in the freeboard section of the fly ash monitor. This second diaphragm assembly can be used with a second MEMS-based accelerometer and in conjunction with the primary accelerometer as a method of active noise control. Repeatability and linearity experiments have begun using the on-line fly ash monitor, with some results presented in this quarterly technical report.