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Title	Combustion Characteristics of Fuels With Preheated Oxygen Enriched Air
Creator	Guerrero, Pablo S.; Rebello, Wilfred J.; Ally, Moonis R.; Jain, Ramesh
Publisher	University of Utah
Date	1986
Spatial Coverage	presented at Chicago, Illinois
Abstract	Enriching air with oxygen in furnace combustion systems can significantly increase the thermal efficiency of the system and contribute to a savings in fuel and an increase in productivity. If economic feasibility is proven for a given application, the only other potential barrier to the use of oxygen enrichment in industrial combustion processes could be the increase in NOx formation due to the higher flame temperatures. The objectives of this work were to determine the maximum flame temperatures resulting from the combustion of various solid, liquid and gaseous fuels with preheated oxygen enriched air, to determine the maximum (equilibrium) levels of pollutant (NOx) concentrations and to predict actual levels of NOx that could be expected in typical industrial furnaces. The computer program considered thirteen dissociating species, preheat temperatures up to 2000F and oxygen enrichment levels varying from 21% to 50% oxygen. The results indicate that for natural gas above flame temperature of 5165°F, the equilibrium NO values tend to decrease with high levels of 3xygen and high preheat temperatures because other dissociating reactions predominate at these high temperatures. A methodology was developed, using kinetics, to predict the actual NO expected in a typical furnace. The predicted values of NO were compared with measured values for an experimental furnace and found to be in general agreement. Though there are no New Source Performance Standards for industrial furnaces, the analysis indicates that for combustion of nanrral gas with preheated oxygen enriched air, the NOx formed would be conSiderably more than the NSPS for an industrial steam generator of 0.2 lbs N02/million BTU.
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/s6g163cn
Setname	uu_afrc
ID	3897
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6g163cn

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Title	Page 5
Format	application/pdf
OCR Text	Show 4.0 3.5 Fuel: Birmingham Natural Gas ~ x 0 3.0 z '0c 2.5 0 n co u: 2.0 Q) '0 ~ 1.5 E :::J g 1.0 ':; 0- w .5 Preheat Air Temperature, OF -:.:::~ ::.'.~'~' ~ ~ ~ :':'':'~' ;~~ ~ ~ ~ ...... . ...... . · -· -· - · -· -·-:~1164oooo .-.-. .- . . =--: :.:- - -- :.:~ · . "--. -::~ =--:: : =:.:-:-:- . - -- ·1000 -- . -- . -- . -- . ::.-.:- .. -- _ -- _ "::::-"' - '800::7.:.::=.-;:- . __ . -_- __ - 400 -"' -~ -' 100 - - - - - ..::::-... 0.0 0 10 20 30 40 50 60 70 80 90 100 Percentage of Excess Air (%) FIGURE 5. PERCENTAGE OF NO IN COMBUSTION PRODUCTS VS EXCESS AIR FOR VARYING PREHEAT AIR TEMPERATURES (79%N2, 21%02) 4.0,.-----------------------. ~ 3.5 x 0z 3.0 '0 c0 2.5 '0:; (J ~ u. 2.0 Q) '0 ~ E 1.5 :::J ~ ':; 1.0 0- W 0.0 Fuel: Birmingham Natural Gas Excess Air: 0% 35 % Oxygen in Air -.. • • ___ •• --:-:;.::-..;:,.- ::;,M"""'-: ~ . .......... . ............ --.- .. _ ... __ . 30 ......... . . -"----.--- ':--.--' ......... ."...,." ......... ------ 25 ......... --- - -- --~~ 40 ---- --- -"'" 21 - --- -- ---- 0 500 1000 1500 2000 Preheated Air Temperature (F) FIGURE 6. PERCENTAGE OF NO IN COMBUSTION PRODUCTS VS PREHEATED AIR TEMPERATURE FOR VARYING AIR COMPOSITIONS. bustion species including NO have been verified with the results of Marteney6 and found to be in agreement. This indicates that the NOx formation variation with temperature is more complex at high temperatures because it depends on the equilibrium constants of other dissociating react ions. 191 16 14 12 10 8 6 4 2 0 a. ~ Cl -2 0 ~ -4 -6 -8 -10 -12 -14 -16 -18 -20 FIGURE 7. EQUILIBRIUM CONSTANTS AS A FUNCTION OF THE INVERSE OF TEMPERATURE FOR DISSOCIATING GAS PHASE REACTIONS. USE OF THE EQUILIBRIUM NOX TO PREDICT ACTUAL FURNACE NOX FORMATION One of the purposes of this paper is to show a methodology to predict the actual value of the concentration of NO in the post flame zone of a furnace combustion process. The concentrations of NO obtained from the computer program described above are valid only for conditions of equilibrium. In reality, equilibrium is almost never reached and the values of NO obtained above are much higher than the actual values one might expect. Therefore, a kinetic approach of the combustion process is needed. Under a kinetic approach the time the combustion gases spend in a furnace (residence time) is a variable. It is also important to realize that the adiabatic flame temperature is the theoretical flame temperature and because of the losses to the furnace walls and load, actual temperature in the flame(here called peak temperature) is lower than the adiabatic flame temperature. The peak temperature can be determined by direct measurement or predicted by a computer model of the flame structure which goes beyond the scope of this work. For the purpose of illustration of this methodology the values for peak flame temperature are taken from reference9 which were obtained in a personal communication with Mr. Richard Reed from North America Mfg. Co.
Setname	uu_afrc
ID	3891
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6g163cn/3891