1. Stoichiometric and Temperature Effects on Boiler Corrosion from High Chlorine and High Alkali Coals Research Group : Shrinivas Lokare, David Dunaway, Douglas Rogers, Marc Anderson, Larry Baxter, Dale Tree, Brigham Young University, Provo, UT- 84602. ACERC 17 th Annual Conference February 20-21, 2003 University of Utah Salt Lake City, Utah Research Background Increased corrosion problems due to increased use of low rank or moderate to high chlorine coals for low NO x emissions. Alkali chlorides have demonstrated significant potential for the corrosion of heat transfer surfaces under the operating temperature range (400-550 o C). Project Objectives To examine the results of reducing and oxidizing combustion on the ash deposition and consequent corrosion. Based on experiments, investigate the mechanisms of chlorine condensation on heat transfer surfaces. Experimental Set-up Reactor design (Multi-fuel Flow Reactor) Premixed fuel burner 1.93 m Auxiliary methane Sample location Cooling water Inside diameter = 12 cm Probe Designs Cross flow type deposit collection probe Gas flow Cooling fluid IN Cooling fluid OUT Thermocouple placement 6.5” 5” 3/8” O.D. Refractory wall Reactor axis Parallel flow type deposit collection probe Coal Illinois #6 (Wet) Illinois #6 (Dry) Black Thunder (Wet) Black Thunder (Dry) % Moisture11.29021.30 % Ash6.267.065.086.46 % C68.9577.755.0169.9 % H4.144.683.975.05 % O6.367.1713.4517.1 % N1.411.590.740.94 % S1.591.790.380.48 % ClN/A0.450.060.08 Fuel analysis Fuel analyses were performed at Commercial Testing & Engineering Co., Denver, CO 80239. Results and Discussion Operating conditions Sampling section temperature - 1000 o C. Sampling period = 30 minutes to 5 hrs. Deposit collection probe surface temperature = 90 - 450 o C. At the probe surface temperatures of 300-450 o C, the absence of alkali chlorides or alkali sulfates under respective stoichiometric conditions is attributed to the fraction of alkali in fuel ash available to form chlorides and the extent of evaporation of these chlorides under given operating conditions. Reducing test - Illinois #6 coal - 30 minutes. aluminum Oxidizing test – Illinois # 6 – 30 minutes Oxidizing test - Illinois #6 - 5 hrsReducing test - Illinois #6 – 30 minutes The co-existence of sulfur and chlorine in longer tests on parallel flow probe supports the hypothesis that sulfate formation is heterogeneous reaction between gas phase sulfur (SO 2, SO 3 or H 2 S) with solid alkali chloride layer on the heat transfer surface. T probe = 91 o CT probe = 240 o CT probe = 350 o C The dew point of the chlorides, and hence the temperature for chloride condensation varies with amount of chlorine and available alkali. The alkali chlorides condense on heat transfer surfaces under both oxidizing and reducing conditions, however, under oxidizing conditions for longer time periods, the heterogeneous reaction starts to form sulfates from alkali chlorides or alkali silicates on the surface. The temperature dependence of chloride condensation is controlled by an additional factor, the chloride content of the fuel. Further investigation is needed for determining the correlation between these. Conclusions Chlorine maps at three different probe surface temperatures Acknowledgements – Arun Mehta, Wate Bakker, Tony Facchiano, Electric Power Research Institute, Palo Alto, California - 94304