Recent field testing of mercury control sorbent injection options with a TOXECON configuration has been completed at TXU Power's (TXU) Big Brown Station. Mercury control results at Big Brown were promising and have been reported previously; however, elevated differential pressure across the high air-to-cloth baghouse makes sorbent injection in the TOXECON configuration an unacceptable option for Big Brown. Shortly following the conclusion of field testing, TXU initiated a bag change for the test baghouse module (which is one of four modules serving Unit 2) and discovered that two of the eight hoppers on the test module were plugged and filled with ash. In these two hoppers, unusual deposits were found mixed with the loose ash, and the ash itself was reported to be very hot and smoldering. Some of the deposits appeared to have been molten and, when studied, provided indications that they may have formed at unusually high temperatures (>1800°F). While the cause of the plugged hoppers appears to be unrelated to the sorbent options that were tested, the plugged hoppers did create favorable conditions for potential self-heating of the high carbon-ash mixtures that are typical of TOXECON. This paper presents a review of the findings from Big Brown and the investigation into the self-heating potential of the ash-carbon mixture.
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