Does anyone have experience with a rapid buildup of a light, fluffy, gray, slightly magnetic deposit on the tube side (reaction furnace exhaust gases) of an HRSG? We have sent it to the lab for analysis but don’t have the results back yet. This material was found in both the hot pass and cold pass of the HRSG, with slightly more deposit density in the cold pass. We just retubed this steam generator and replaced the refractory in the reaction furnace in June 2009. Any ideas?