OCR Text |
Show In the conventional theoretical analysis,the coke combustion reactions have been taken into account so far but the vapor condensation and also the permeability of the sinter bed have not been considered. Because the high temperature gas from the ignitin furnace flows downward through the packed layer of raw materials,the heat exchange occurs between solids and gases. In this packed bed the heat exchange between gas and solid is the most elemental phenomena. From the enthalpy balance on the fluid side S(VCgTg)/SX+S a(Tg-Ts)=5(£ VCgTg)/ <5 0 From the enthalpy balance on the solid side, S a(Tg-Ts)+7 c*- AHc-f 7 e*- A H e = (l- . )6(CsTs)/6 0 + (1- E ) P S-6 H/56 here ( 6 H / 8 0) means solid melting change,as shown in Fig.2. 5 H / 5 0 = - f (Ts)-(fi Is/6 0) Temperature (*C) > , tm1 tm f(t)=-2-H0- (t-tml)/(tm2-tm1)2 Fig. 2 The function of melting and solidification process of Irow materials The gas flow around a simple particle can be expressed empirically by the following equation; a-dp/X=2.0+0.6(n-dp-u- p -,_)1/2-(Cg n/X)m where dp represents particle diameter, i± , p ,and ; X represents gas viscosity,density and thermal conductivety, respectivily .The coke combustion reaction in sinter bed is the most important phenomena. The main reaction of coke is the formation equation of the carbonic acid gas. D is oxygen diffusion coefficient in gas boundary layer. Here assumed there is the analogy between heat transfer and mass transfer, then similar equation derived, Kf-dp/D=2.0+0.6(n-dp-u- p • IL)W-(H/p D) ^ Now,the overall reaction rate is y c* and the overall reaction rate constant, K c* may be expressed |