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Title	Oscillating Combustion Increases Productivity and Decreases NOx Emissions from Industrial Furnaces
Creator	Wagner, J.; Kurek, Harry S.; Joshi, M.; Charon, O.
Publisher	Digitized by J. Willard Marriott Library, University of Utah
Date	1998
Spatial Coverage	presented at Maui, Hawaii
Abstract	High-temperature, natural gas-fired furnaces, especially those fired with preheated air or industrial oxygen, produce large quantities of NOx per unit of material processed. Regulations on emissions from industrial furnaces are becoming increasingly more stringent. In addition, competition is forcing operators to make their furnaces more productive and/or energy efficient. Oscillating combustion involves the forced, out-of-phase oscillation of the fuel and/or oxidant flow rate(s) to a burner to create successive, fuel-rich and fuel-lean zones within the flame, thus increasing heat transfer (and therefore productivity) by enhancing flame luminosity and turbulence, and retarding NOx formation by avoiding stoichiometric combustion. In its simplest form, oscillating combustion can be accomplished by installing an oscillating valve package on the fuel supply line of each burner. Testing on standard 250,000- and 500,000-Btu/h commercial burners has shown that oscillating combustion can provide 2% - 13% increases in heat transfer and 50% - 75% reductions in NOx emissions using ambient air, preheated air, or even enriched air. Similar results have been obtained with oxy-gas combustion on a 2,000,000 Btu/h burner. Evaluation on several additional burners used in the steel, glass, non-ferrous metals, and ceramics industries is now underway. Two field evaluations have been conducted-one on an oxy-gas-fired iron melter and one on a steel ladle preheater. Both used the CeramPhysics SSP oscillating valve package, which has proven to be superior to other valve options. such as solenoid valves. These evaluations have confirmed that oscillating combustion provides productivity enhancement and NOx reduction, but does not affect the quality of the product. Additional field evaluations are underway on an air-gas-fired steel annealing furnace and an oxy-gas-fired glass melter.
Type	Text
Format	application/pdf
Language	eng
Rights	This material may be protected by copyright. Permission required for use in any form. For further information please contact the American Flame Research Committee.
Conversion Specifications	Original scanned with Canon EOS-1Ds Mark II, 16.7 megapixel digital camera and saved as 400 ppi uncompressed TIFF, 16 bit depth.
Scanning Technician	Cliodhna Davis
ARK	ark:/87278/s6s1853f
Setname	uu_afrc
ID	12177
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6s1853f

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Title	Page 2
Format	application/pdf
OCR Text	Show It has been shown that N O x formation is sensitive to temperature and oxygen concentration3" (see Figure 1). An excess of either fuel or oxygen reduces the flame temperature. The maximum flame temperature is realized with excess air level close to stoichiometric concentrations of fuel and oxygen. At higher oxygen concentrations the dilution effect lowers the flame temperature sufficiently to reduce the N O x emissions. As a result of this sensitivity to temperature and fuel to oxidant proportions, both fuel-rich and fuel-lean flames can generate less N O x than a stoichiometric flame. Oscillating combustion involves the creation of successive, N O x retarding, fuel-rich and fuel-lean zones within the flame (see Figure 2). This patented technique involves forced oscillation of the fuel flow rate to the burner. Heat is removed from the zones before they mix to reduce overall peak flame temperature, thus reducing N O x formation. Heat transfer from the flame to the load (and, therefore, furnace productivity) increases due to the more luminous fuel-rich zones and the breakup of the thermal boundary layer. OSCILLATING PARAMETERS In order to optimize the performance of oscillating combustion, four parameters, as outlined in Table 1, must be adjusted to suit any particular application. Table 1. PARAMETERS USED FOR OSCILLATING COMBUSTION Parameter Frequency Amplitude Duty Cycle Phasing Between Burners Definition Number of oscillation cycles per unit time Relative change in gas flow rate during the oscillation cycle above or below the average flow rate Fraction of time the gas flow rate is above the average flow rate during each oscillating cycle Relative offset in time between the start of oscillating cycles for different burners Unit Hz % % o (deg.) Comments oo H z is used to denote steady (non-oscillating) operation. 0 % is for no oscillations. 100% is for oscillating between zero flow and double the average flow. 5 0 % is for equal time above and below the average flow. 0° is for in-phase oscillations. 180° is for completely out-of-phase oscillations. (afrc98p doc) o Operating at steady stoichiometry produces high NO. levels Oscillating between fuel-rich and fuel-lean conditions substantially reduces NO, levels while maintaining net stoichiometry Fuel-Rich \| • Fuel-Lean Excess Air Level Figure 1. N O x VS. S T O I C H I O M E T RY F u eLlyL-r^ Valve Oxidant Fuel- Rich Average Flow ' ' Fuel- Lean t_J Fuel-Rich Zones ••III V. FIIPI-I pan 7nnpii Flue Gas Distance From Burner Figure 2. OSCILLATING COMBUSTION PROCESS
Setname	uu_afrc
ID	12165
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6s1853f/12165