Dry method preparation and melting point of Cu 2 SO 4
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particular gas composition and temperature trajectories that were depicted previously in Figures 3 to 5. This finding is of considerable interest for two reasons. One of these is that the previous history of the particle is seen to have an important effect on its reaction characteristics.* The other more specific reason is that the prior
g
*This finding appears to be new within the context of coke reactivity, although the effect of prior history on subsequent reaction characteristics has been noted by Turkdogan ~ in connection with iron oxide reduction kinetics.
9 Reaction Temperature Pr }-
o Fractional Weight Loss
=
I100 ~ 1 . 0 ~'
1,5-
,I,
50
~I
f ~. I000
E
".~ 9 0 0
eoc TSO~
f ~ ,
o i 40
t1_ 0 , 6 0 ~) _.l
0.40
o.zo ,,'/ o .~.to I
I 80
I
I 120
I
I 160
J
I 200
I
I
240
Time in minutes
Fig. 5--Reaction of metallurgical coke (IPC-A53) in a nonisothermal environment with variable Pco/Pco2 ratio.
portions of these curves provide a convenient means for characterizing the reaction rate. Figure 6 shows a plot of the rate of reaction, in units of fractional weight loss/time, against the gas composition ratio. Two sets of curves are shown on this plot. The one, where the data points are given by the full circles, represents the nonisothermal experiments, conducted with a fixed gas composition. The curve with the hollow circles represents data with a variable gas composition, deduced from the previously given Figures 3 to 5. Inspection of Figure 6 shows that the reaction rates were much slower for systems that were operated at a fixed gas composition and temperature than those obtained for the
reaction of the coke particle at a low temperature tends to have an activating effect, enhancing the subsequent reactivity of the material. This suggestion seems reasonable on physical grounds because the reaction at low temperatures will be in the chemically controlled regime, so that the internal oxidation of the particle could produce an enhanced and possibly more reactive reaction surface. These preliminary results suggest that the way in which metallurgical coke reacts in the iron blast furnace may depend quite critically on its previous history (in terms of the temperature and gas composition to which the particle was exposed). It follows that the "intrinsic reactivity" of a given coke sample may vary quite markedly with furnace operation and that the currently employed simple coke reactivity tests are unlikely to provide information on this type of behavior. The main purpose of this communication is to draw attention to this potentially important phenomenon, which does deserve further, detailed study. Such a program is currently in progress: REFERENCES 1. R.R. Thompson and L.G. Benedict: lronmaking Proceedings, 1967, vol. 26, p. 91. 2. E.T. Turkdogan: Metall. Trans. B, 1978, vol. 913, p. 163. 3. D. A. Aderibigbe and J. Szekely: lronmaking and Steelmaking, 1981, vol. 8, p. 11. 4. E. T. Turkdogan and J. V. Vinters: Metal1. Trans., 1971, vol. 2, p. 3175; also 1972, vol. 3, p. 1329. 5. I. Gaballah a
