STEADY BURNING OF A SOLID PARTICLE.

The quasi-steady burning of a carbon particle which undergoes gasification at its surface by chemical reactions, followed by a homogeneous reaction in the gas phase is considered. The burning rate M is found as a function of the gas phase Damkohler number D//g for the whole range 0 less than D//g less than infinity . The monotonic M(D//g) curve, obtained for relatively very hot or very cold particles, describes the gradual transition from frozen flow to equilibrium. For moderate particle temperatures the transition is abrupt and the M(D//g) curve is either S-shaped or Z-shaped. In the former the burning is enhanced at ignition while in the latter it is slowed down; this depends on the relative importance of the two competitive surface reactions. At extinction, the reverse is true: burning is slowed down in the case of an S curve and is enhanced in the case of a Z curve.