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Show 4) Atomize Liquid Fuels With Oxygen, Air or Steam - For application flexibility. 5) Maintain Non-Lofting/Low Momentum Flame - The high flame temperatures generated with oxy-fuel firing can result in a very buoyant, or lofting, flame pattern. The undesirable result can be impingement and overheating of the furnace croWD. Various methods to eliminate this lofting flame were tried in the burner industry. One method called for angling the burners downward. Unfortunately, this method caused hotspots on the glass surface which the batch moved away from. The original OXY -THERM design overcame the lofting problem without the use of high momentum or downward angling of the burner. Several customers requested that this feature be retained in the new design. Experimentation and Proof of Concept With development goals firmly in hand, Maxon conducted trials of various burner concepts, and documented the results. Based on combustion experience outside of oxyfuel, variations on currently available low emissions technology for air-fuel burners were trialed in oxy-fuel modes. While such techniques as fuel staging and aerodynamically induced recirculation were somewhat effective at meeting development goals in the laboratory, the potential for problems in glass furnace applications ruled out many. Further, Maxon felt that the design chosen should require nothing· more from the customer than supplying oxygen and fuel to a burner -- at the required ratios and pressures -- to obtain the desired results. All concepts requiring a change of standard furnace operating methods or additional non-burner penetrations through the furnace walls were rej ected. After several months of testing, a design emerged which utilized a variation of low NOx air-fuel technology first developed over thirty years ago. Staged oxygen combustion, a variation of older staged air combustion technology, met and exceeded all development goals. The problems once associated with staged air combustion in the petrochemical industry (i.e., too much flame volume and incomplete combustion), were now desirable or solved, respectively, by the use of oxygen. Better still, staged oxygen combustion was an effective design for both liquid and gaseous fuels, allowing the use of backup fuels while still meeting all development goals. Staged Oxygen Combustion As noted earlier, despite the use of oxygen for combustion, the production of NOx is still a problem. The majority of NOx emissions form in oxy-fuel combustion via two mechanisms. First, thermal NOx is formed from molecular nitrogen present in the combustion oxygen (5% or less by volume) and air leakage into the melter. As the name implies, thermal NOx is strongly dependent on flame temperatures3. Second, fuel NOx is formed from nitrogen that is chemically bound in the fuel. Its formation has a weak 3 |