OCR Text |
Show • Gas analysis at the incinerator exit (under the incinerator orifice), revealed that the oxygen was maintained at the level of 3.8% during the testing . However, most of the time, the level of combustibles was elevated, occasionally reaching 0.6%. The carbon monoxide concentration followed the pattern of the combustibles, exceeding the 500 ppm level. This suggests that the final "burnout" was taking place in the base of the unit rather than in the cyclonic incinerator. • The temperature curve of the flue gases exiting the Horison tube and entering the convective pass (see Figure 5) suggests that progressive coating of the Horison tube caused reduced heat removal within the 10rison tube. • Pressure drops across the major components of the system are evaluated as follows: Heat Recovery Boiler - remained steady during the first half of the testing. In the second half, the pressure drop started to rise, reaching 1.8 in. wc ,at the end of the test. Air Heater - remained steady during the entire testing in the range of 1.7 to 2.5 in. wc. Baghouse - a steady rise was registered during the testing. It rose from 0.8 in. wc at the beginning of the test to 3.1 in. wc at the end of the test. Discussion and Recommendations As suggested by the flue gas analysis, combustion of the wastewater was not always completed in the incinerator chamber. Based on CO readings, the final burnout of the combustibles took place in the base of the incinerator. This effect is attributed to the following: • Inadequate swirl in the incinerator caused by low secondary air velocity • Inadequate wastewater atomization caused by under-sized atomizers • Uncontrolled air infiltration into the incinerator chamber. Inadequate heat removal within the boiler radiative chamber (Morison tube), caused by particulate deposition on the tube surface, resulted in a high flue gas temperature (up to 1500°F) entering the convective pass. This, in turn, caused the formation of frozen melt on the boiler return plenum walls, on the tube sheet, and on the entrance of the convective tubes. As a result, the pressure drop across the boiler started to rise. The rising pressure drop across the baghouse suggested that modification in baghouse performance was necessary. 12 |