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Show PPLICATION OF PREMIX COMBUSTION TO HIGH INPUT BURNER SYSTEf\lS Introduction Pr nllX con1 bustion has been widely appl ied to industrial applica tions <;I nc the turn of the century. The firing of pren1i xed fuel/ air mi xtures pro\ ides both uniforn1, rapid heat re lease and s hort, distinct flan1e envelopes; highly d es irabl e characteristics in n1any con1bustion systenls. Unfortunately, pre n1ix ellso has nlany properties that lin1it both its operation and application . As the input of a pren1ix burner is reduced, flanle holder velocities also drop, resulting in the potential for flashback of the mi xture through the flan1e holder. Not on ly does this Iin1it systen1 turndown, but it can forn1 a detonation vvave that tra vels through the n1i , ture delivery systen1 creating an extren1ely dangerous situation for both personnel and plant equipn1ent. This condition has severely lin1ited the <;ize and types of application that can safely fire gaseous pren1ix. Additionally the use of prenlix involves tight ignition and stability vvindovvs, placing tight constraints on both the ratio control systenl and the ability to fire vvith high levels of excess air that are required in denlanding tenlperature unifornlity applications. With the developnlent of nlany styles of nozzle nlix burners the use of prenlix conlbustion has been alnl0st nonexistent during the last several decades. With the appearance of tight airborne poJIution requirements around the country, prenlix has again attracted the interest of conlbustion researchers and equipnlent nlanufacturers. Flanle temperatures and oxygen concentrations can be tightly controlled in premix firing. If a conlbustor can stabilize a premix fJan1e very close to the lean flanlmability Iinlit, virtually no carbon 1110nO ide or nitrogen oxide enlissions are produced. At these lean conditions, flan1e te nlperature is greatly reduced resulting in the generation of negligible thern1al NOx, while tenlperatures are still sufficiently high to oxidize all r maining CO within the combustion systenl. Equilibriunl NOx enlission I vels for varying (11 ixture ratios are shown in Figure 1. If safety and operational oncerns can be overconle by burner design, the firing of lean premix offers tr nlendous rewards in both enlission and operational performance. 2 |
