KINETICS OF THE REACTION OF CH4 GAS WITH LIQUID-IRON

In iron bath smelting and other processes that use coal, the effective use of volatile matter can improve the energy efficiency of the proce ss. The reaction of simulated volatile (CH4) with iron was studied. Th e rate of carburization of liquid iron by CH4 gas was measured between 1400 degrees C and 1700 degrees C under conditions for which the effe ct of mass transfer can be corrected with reasonable accuracy. The rat e was measured for partial pressures of CH4 in Ar in the range of 0.02 to 0.06 atm and sulfur contents in the metal from 0.0006 to 0.5 mass pct. The results indicate that the rate of carburization may be contro lled by the dissociation of CH4 on the surface. Sulfur was found to de crease the rate, and the residual rate phenomenon was observed for hig h sulfur contents. The rate constant may be represented by the followi ng equation: k(C) = k(o)/1 + K(S)a(S) + K(s)a(S)k(r)/1 + K(S)a(S) wher e k(o), k(r), K-S, and a(S) are the bare surface rate constant, residu al rate constant, adsorption coefficient for sulfur, and activity of s ulfur in the metal, respectively. The second term in the rate equation represents the rate of dissociation on the adsorbed sulfur. The rate constants and adsorption coefficient were determined as functions of t emperature to be log k(o) = -12,000/T + 2.95 (mole/cm(2) s atm) log k( r) = -14,000/T + 3.45 (mole/cm(2) s atm) log K-S = 1800/T + 1.04