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Show The oblique coal injector was s~gnificantly better than the annular injector for optimising the NOx/Tx relationship. Generally NOx -emissions are sensitive to initial mixing levels when the coal is injected at or within the burner throat. This sensitivity is less pronounced when the injector is situated so as to promote the initial devolatilisation within the IRZ. The performance of Burner B, the Air Staged Precombustor Burner, has been shown to be sensitive to stoichiometry and residence time within the precombustor. The effect of precombustor residence time was more pronounced for high SR1 values. At constant Tp, high SR1 results in high NOx emissions. However, as Tp is increased the differential is reduced. When firing Heinrich Robert coal, the trends observed for Scotts Branch were again seen. However, as for the AASB, optimisation was more difficult with Heinrich Robert than Scotts Branch coal. Optimised performance may be summarised as follows: Burner-Injector ASPB-annular ASPB-annular Coal Scotts Branch Heinrich Robert NOx (ppm 0% 02) 261 520 Tx (% ) 98.4 98.1 Both burners would appear, with appropriate scaling criteria, to be applicable for retrofit in pulverised coal systems employing swirled combustion air. Fundamental considerations of the NOx formation mechanism and the dominant turbulent mixing phenomena have been addressed and related to engineering aspects of burner design. The results of the experimental programme have shown that understanding of mixing phenomena in turbulent diffusion flames can be utilised to design practical low NOx combustion equipment. 6 REFERENCES 1 Pershing D Wand Wendt J 0 L. Ind Eng Chern Proc Des Dev, 1979, (18), 60. 2 Pohl J Hand Sarofim A F. 16th Symp (Int) on Comb, The Combustion Institute, 1979, 491. 3 Fenimore C P. 13th Symp (Int) on Comb, The Combustion Institute, 1972, 373. 4 Pershing D Wand Wendt J 0 L. 16th Symp (Int) on Comb, The Combustion Institute, 1977, 389. 5 Bergsma F. Ind Eng Chern Proc Des Dev, 1985, (24), 1. 6 Jungten H. Erdol and Kohle - Erdgas - Petrochemie, 1987 (40),204. 11 |