| OCR Text |
Show M, = molecular mass of species i mco = mass of coal particle (daf) mp = particle mass (g) mpo = initial particle mass (g) mvi> m v2 = mass of volatiles from devolatilisation reactions 1 and 2 Qvap> QVOb Qc = heats of vaporisation, volatilisation, combustion R = universal gas constant (J mol"1 K') Rc = chemical reaction rate coefficient per unit external surface area (g cm"2 s"1 atm"1) Rdiff= diffusional reaction rate coefficient (g cm"2 s"1 atm"1) / = time (s) T0 = initial temperature (K) Tp = particle temperature (assumed to be uniform) (K) T^ Tp Tw, = temperature of particle, gas, wall respectively (K) V= fraction of volatiles already released from the coal V* = total fraction of volatiles in the particle Xt = mol fraction of species i a, p = distribution parameters 5 = mechanism factor (=2) (|> = equivalence ratio T(A) = g a m m a function cp = ratio of reacting surface to external (equivalent sphere) surface area of particle. p = density (g cm"3) a = emissivity oi , = net production rate of species i (mol cm'3 s"1) 13 |
