Enhancement of wüstite reducibility in blast furnace: reaction kinetics and morphological changes

Abstract

Two wü stite samples were prepared from reagent grade haematite and Baharia iron ore sinter by gaseous reduction with 50CO-CO 2 gas mixture at 1273 K. Using a thermogravimetric technique, the samples were isothermally reduced at 1173-1373 K by different ratios of H 2 /CO/N 2 to simulate the composition of reducing gas in the case of high natural gas injection with high oxygen enrichment in the blast furnace. The influences of temperature and gas composition on the reduction behaviour and morphology were investigated. As reduction proceeds, the effect of temperature in increasing reduction becomes clearer. The effect of various gas compositions on the reaction rate was not so clear due to the fast reduction process. The apparent activation energy values were calculated and correlated with the gas-solid reaction formulations to elucidate the corresponding mechanism at both early and final reduction stages. The reduction rates of pure samples and wü stite from iron ore sinter at both initial and final stages are most likely controlled by the interfacial chemical reaction mechanism.

Mathematical Analysis of the Reduction of Wüstite at Different Basicity Using Factorial Design

“…The total sum of squares (SS ) has ( − 1) degrees of freedom and the error sum of squares (SS ) has ( − 1) degrees of freedom. They can be calculated by using (9) and (10), respectively. Table 3 summarizes the main effects of variables, sum of squares, and the mean square:…”

“…In order to examine the validity and the efficiency of the current regression model the derived equation is used to estimate the reduction degree of wüstite at different basicity (0.5, 1.0, and 2.0), reduction time (5,10,15,20,25,30, and 35 min), and temperatures (950 ∘ C, 1000 ∘ C, 1050 ∘ C, and 1100 ∘ C). The results are compared to that obtained from the experimental reduction trails as can be seen in Figure 3.…”

“…The Al 2 O 3 was found to decrease the reduction rate in the whole range of applied temperature, 670-930 ∘ C. On the other hand, the simultaneous dissolution of SiO 2 and Al 2 O 3 in wüstite resulted in acceleration of the reduction process. The influence of temperature and gas composition on the reduction of wüstite was studied [10]. It was reported that the effect of temperature on increasing the reduction rate of wüstite was significant as the reduction proceeded while the effect of gas composition was not clear all over the reduction process.…”