OCR Text |
Show turn caused a total failure of the two shaft bearings of the thrust roller. Since the failure was recognized quickly and kiln rotation was immediately stopped, no other physical damage occurred. The bearing failures were corrected by first ensuring that the Allen set screws on the pillow block bearings were properly fastened and then locked. Additionally, the thrust roller was rebuilt, the groove filled and the roller surface hardened to eliminate the future grooving. o The SCC Exit Venturi and Diffuser The SCC is completely lined with refractory, except for the exit venturi and diffuser, which are made of Inconel 625. After over 3,000 hours of operation, some of which was with highly chlorinated compounds, the exit venturi had completely disintegrated, and its support plate showed severe stress corrosion cracking. Based upon the presence of chlorine in conjunction with the high temperature (2200 0 F) the m~terial for the venturi and diffuser was changed to Haynes alloy 556. Further, a refractory throat was formed upstream of the metal throat. Finally, the water cooling nozzles used to wet the back side of the metal parts were changed to provide a more effective spray pattern. o Spalling of Kiln Refractory Repair Patches During a shutdown of more than one year, the kiln refractory was repaired with patches of refractory material. The startup procedure, as well as the safety interlocks, required that the kiln be rotated prior to lighting the kiln burners. Since the refractory patching material was of the non-hardening nature until it reached 600 0 F, the cold rotation of the kiln caused the patched material to loosen and fallout before the burners were ignited and the refractory had cured. To prevent recurrence the start-up procedure has been changed as follows: The kiln does not need to be rotated until the outside (or shell) temperature begins to rise. Continuous rotation of the kiln is started when the internal temperature reaches approximately 700-900 0 F. During the interim period, the kiln is rotated 1/4 turn every 10-15 minutes to minimize any thermal distortion of the shell. o pH Control Problems The scrubber system for the MIS utilize a caustic solution to neutralize the HCl gas formed and maintain the scrubber water pH in the 7 to 9.5 range. There are three areas in the MIS where the flue gas is scrubbed: -Quench elbow and sump -Lower WEP filler region -Mass transfer (MX) scrubber |