| OCR Text |
Show It was the objective of this work therefore, to relate on a quantitative basis the stability of pulverized coal combustion to the release of volatile matter from the coal. Inherent to such a model would be means of studying the sensitivity of flame stability to such design variables as burner size, coal feed rate, wall radiation, mixing time scales, particle size distribution, and the proportioning and location of primary and secondary air streams. Extensive prior work in this area of flame stabilization (8) has used a velocity matching approach , and addressed geometry . . (9) and composition effects on gas flame stability. Perfectly stirred reactor theory has been applied to gas turbine (10,11) combustors and the recirculation zone of coal fired (12) . . . .. burners. However, the relationship among fluid mixing time scales of primary coal/air, secondary air, and recirculating combustion products; and the pyrolysate yield and rate from the pulverized coal, has not been extensively treated in terms of combustion stability. 2. VOLATILE RELEASE FROM PULVERIZED COALS For low and medium rank coals, the combustion reactions associated with flame stabilization appears to be dominated by release and gas phase combustion of volatiles. There is some (13) recent evidence that the nascent volatiles are almost exclusively high molecular weight organic compounds, which rapidly decompose in contact with hot gases. There is also very extensive (14,15,16,17) . . data indicating that the quantity of volatile matter released varies with coal rank and thermal history. Numerous research efforts have been directed toward defining this (18) (19) dependence and relating it to coal structure , and a wide range of models proposed to describe the observed (16,17,18,19) behaviors -3- A V C O EVERETT |
