โ Scribed by Da-Hua Liu; Ali M. Zghoul; Zongwen Li; Bon-Siau Tan; Karl L. Lockwood; Robert H. Essenhigh
No coin nor oath required. For personal study only.
Combustion efficiency and NOx profiles have been measured in a high intensity coal flame with water injection to determine the joint effects on the reaction mechanism of reduced temperature, high moisture, and dilution. The furnace as used in previous experiments is a 2.5 m high vertical refractory tunnel with a square cross section 165 mm on the side. Combustion is staged at two levels using opposed horizontal jets near the top of the furnace. Water is injected at the center of the top. Slurry-equivalent water (mass) precentages for stable flames ranged up to 46%. Overall fuel equivalence ratios were 1.0 and 0.8. The flame extinguished at water percentages equivalent to 60% in a slurry. At the slurry-equivalent of 46% water the flame temperature was reduced by about 20%, and there was a reduction of 2 or 3 percentage points in the final exit combustion efficiency; the effect of water injection was found to be essentially second order except for the reduction in flame temperature. Nevertheless, the fast reaction mechanism was evidently unchanged, and the reaction was still at or close to the diffusion limit as found earlier with dry coal firing in spite of flame temperatures as low as 1200"C. This should have implications for CWS combustion if initial heating of the slurry spray is fast enough. The most important result, however, is this demonstration that the controlling reaction mechanism through the whole temperature range is physical (diffusion), not chemical (kinetic), in direct contrast to coal combustion behavior in normal intensity flames.
๐ SIMILAR VOLUMES
A detailed study of the combustion of coal-water mixtures (70-73% coal, 27-30% water) and formation of nitrogen-containing pollutants has been performed in a vertical, laboratory-scale combustor. Space-resolved, local measurements of solid and gaseous combustion products were made with a stainless s