Behavior of sulfur and chlorine in coal during combustion and boiler corrosion. [Quarterly] technical report, March 1, 1992--May 31, 1992

The evolution of HCl during coal pyrolysis and its relation to chlorine forms in raw coal were studied using a temperature-programmed pyrolysis and gas combustion in conjunction with a quadrupole gas analyzer (QGA). Using a new filament source in the QGA significantly improved the sensitivity of HCl detection. The major peak at 445{degrees}C showed an increased intensity and a new HCl evolution peak at 600{degrees}C was observed during pyrolysis of Illinois coal IBC-109. Pyrolysis of coal IBC-109 spiked with NaCl solution showed a strong peak of HCl evolution above 700{degrees}C. In the study of boiler deposits, several sample preparation procedures for X-ray diffraction analysis were developed and six minerals were unambiguously determined in superheater and heater deposits from a power plant in Illinois. Effects of composite gases containing 0.2% HCl on six metals were tested at 600{degrees}C and 200{degrees}C, and at 100{degrees}C with moisture for 400 hours. Similar tests were conducted with a composite gas containing no HCl at 600{degrees}C and 200{degrees}C. The results allow us to assess the factors controlling the corrosion rate: Boiler materials, temperature, concentration of HCl in combustion gases, and chloride condensate on metal surfaces.