| OCR Text |
Show 5. Preliminary Conclusions Based on the flame data gathered to date, the following conclusions regarding the physico-chemistry of low-Btu coal-derived syngas/air flames can be reached: (1) The temperatures of the low-Btu syngas/air flames ranged from 1300 K to 1700 K for burning velocities of 10 to 20 cm/sec. (2) For all the low-Btu syngas/air flames studied: (a) CH, disappeared very rapidly (at 1 mmfromthe burner or at about 1.5 milliseconds) and (b) the concentrations of H2, CO, and 02 decreased rapidly within the first 5 milliseconds, and then continued to decay but at a much slower rate. (3) The formation of NO occurred rapidly in all the low-Btu syngas/air flames, reaching a maximum value by 7-8 milliseconds (5-6 mm from the burner head). (4) The maximum NO concentration occurred at 0 = 1.2 for all flames studied. (5) As the NH„ content to the fuel gas increased, the conversion efficiency of NH„-to-N0 decreased, but the total quantiity of NO increased. For example, at 0 = 1.2, the conversion efficiency was on the order of 65% for NH,. dopings of 300 ppm, but the conversion efficiency was only 27% for an NH„ doping of 3200 ppm. (6) The Lurgi syngas always had an NO yield greater than the Wellman-Galusha syngas; the difference amounted to 5-9%. (7) The OH species increased to maximum at 0 = 1.2 and then decreased for the Wellman-Galusha syngas at both NH dopant levels; The OH maximized at 0 = 1.0 for Lurgi syngas/air flames.Clearly, the free radical flame chemistry is diferent for both of these types of syngas/air flames. (8) The overall global activation energies for both low-Btu syngas/air flames ranged from 24 to 29 kcal/mole; this compares to activation energies of 65, 42, and 37 for stoichiometric methane-, hydrogen-, and carbon monoxide-air flames, respectively. tX-21- |
