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Show The Hybrid L o w N Q Process uses a cooling step between the reduction and oxidation catalysts for applications requiring minimum N O , emissions. Studies by Allied- Signal (6) have shown that the formation of N O , resulting from the oxidation of H C N and N H , formed in the reduction steps is temperature dependent. By operating the oxidation step at a lower temperature, N O , formation is prevented. Figure 3 shows a schematic of the Hybrid Low N Q Process as applied to a process vent stream. ^ = > - * k h>-* ® ®- ^ AtUrhmnmt u<* Figure 3. Schematic of the Hybrid Low N O x Process The only operational changes to the existing incinerator were to lower the amount of excess fuel from 5 0 % to 2 0 % in the reduction step and then re-route the combustion air that is used to oxidize excess combustibles in the oxidation step. Instead of injecting the air directly into the oxidation section of the incinerator, it was recommended that secondary air be added to the recycle quench line to premix the two streams prior to injection into the quench section. Additionally, to ensure that lower levels of C O , NO,, and H C N were achieved, the catalyst beds required by the Hybrid Low N O , Process were added prior to venting products of combustion out the stack. A reduction in the percent of excess fuel being fired in the reducing zone will result in lower levels of C O and Hi being produced and have the added benefit of a higher operating temperature. The higher temperature will increase the level of N O, reduction and, combined with lower levels of C O and Hj being formed, result in less H C N leaving the reduction zone. With lower levels of combustibles leaving the 6 111-16 |