OCR Text |
Show Figure 4 indicates that a volumetric heat release of 50,000 Btu/hr-ft3 indicated by the left hand vertical dashed line should achieve a DRE of 99.99% especially because the hydrocarbon in the waste is of the high chemical reaction rate type. This operating condition would reduce steam production by approximately 35%. Chemical plant engineers reviewed the impact of this reduction in steam production on plant requirements and the capacity of other steam generators and determined that it was acceptable. A volumetric heat release of 50,000 Btu/hr-ft3 resulted in a burner turn down of approximately 60% which means a combustion air and waste pressure drop turn down to approximately 37.5% of design. The combustion air pressure drop remained in the acceptable range but the waste pressure did not. A new fuel oil/waste gun with ports drilled for the design pressure drop at the new firing rate was supplied Data for a firing rate of 30.5 MM Btu/hr for a mixture of #2 fuel oil and the exothermic hazardous waste indicated higher combustion efficiencies, but less than that required to achieve a DRE of 99.99%. Information was not obtained for the endothermic waste. The temperature of the combustion products leaving the radiation section had decreased slightly, lowering the average gas temperature, but not to a level commensurate with the performance achieved. Thus, it was concluded that this lower temperature was a factor, but not the only factor contributing to the lower than expected performance. A regression analysis indicated that the average bulk temperature of the products of combustion could better predict the DRE than residence time, which is a function of temperature. Comparing this relationship with incinerator performance relationships indicated that a temperature correction factor could be applied to the boiler relationship and it would approximately map the incinerator relationship. 5.8.10 |