OCR Text |
Show Performance of Third Generation Rotary Kiln Incinerator John Petersen and Mike Keller Callidus Technologies Inc. removal efficiencies were obtained with designed low operating temperatures in the kiln and with careful control of air flows into the system. On a different commercial system, the trial burn test results on a system operating to clean soil contaminated with toluene (TNT) also confirm that high D R E levels can be achieved in a properly operated system that has been designed to control the overall air flow into the kiln. Operating and trial burn results reported3 show that D R E levels exceeding 99.999% were achieved with kiln exit oxygen levels controlled in the 0 % to 4 % range. SYSTEM ANALYSIS In a normal kiln system, the rotary kiln functions to vaporize the waste materials and relies on the secondary combustion chamber (SCC) to achieve the overall system destruction efficiency. The designer must design the S C C to achieve the required overall hydrocarbon D R E . This is necessary to destroy the last portion of the contaminants stripped from the soil and ash at the discharge end of the kiln. However, correct and controlled kiln operation is critical if specified D R E levels are to be achieved in the SCC. For example, abnormally high combustion rates in the kiln will produce excessive volumes of flue gases to be routed to the S C C for final contaminant destruction. This condition may overload the S C C to reduce residence time and local oxygen levels sufficiently to allow excess emissions to occur. To control and avoid this situation, the designer must be able to control the operation in the rotary kiln because all flue gases generated within the kiln should flow to the secondary combustion chamber for final contaminant destruction. If the flue gas volumes and compositions at the kiln discharge are not consistent and change rapidly, the S C C m a y become overloaded and not function properly. It is precisely this condition that requires the designer to control the combustion process in the rotary kiln. The flow of combustion air into the kiln is the primary combustion control element that is readily available to both the system designer and to the system operator. V-33 7 |