An attempt has been made to clarify metallic iron whisker growth and swelling behaviour during iron oxide reduction in the presence of K 2 O alkali. Annealed pure and K 2 O doped wü stite compacts were isothermally reduced in a thermogravimetric apparatus with CO gas at 800-1100uC. The reduction rate increased with temperature but decreased with increasing K 2 O content. Morphologically, by increasing reduction temperature, porosity and whisker growth of the metallic iron produced increased, which in turn leads to the apparent swelling and compact disintegration. The reduction of pure wü stite at both the initial and final stages is most likely controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanisms. For K 2 O doped wü stite samples, the reduction at the initial stages is most likely controlled by gaseous diffusion mechanism, while in the final stages, it is most likely controlled by a chemical reaction mechanism.

The effect of basicity on the metallic iron whisker growth during wü stite reduction was studied in the present investigation. Compacts of pure and CaO/SiO 2 doped wü stite were synthesised. The annealed compacts were isothermally reduced in thermogravimetric apparatus with CO gas at 800-1100uC. The course of reduction was followed by measuring the weight loss as a function of time. X-ray diffraction (XRD), scanning electron microscope (SEM), optical microscope and porosity measurements were used to characterise the annealed and reduced samples. The influence of temperature and basicity (CaO/SiO 2 ) on the reduction behaviour and the morphology of the annealed samples were investigated. The reduction rate increased with temperature but decreased by increasing basicity value. Metallic iron whisker shape structure was detected in the pure wü stite samples after reduction at high temperatures while in basic wü stite samples, whiskers were formed at the surface of the compacts. From the activation energy values, the reduction of pure wü stite is most likely controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanisms. The reduction of basic wü stite compacts with 0?2 and 0?5 basicity ratios are most likely controlled by chemical reaction mechanism while for 0?8 basicity ratio, the reduction rate is most likely controlled by solid state reaction mechanism.

A comparative reduction behavior of wüstite samples prepared from iron ore sinter was investigated to find the optimum way for reducing coke consumption and CO2 emission in blast furnace technology. A series of wüstite reduction experiments was carried out using different gas mixtures. A correlation between the experimental results and real data of blast furnaces at Egyptian Iron and Steel Company (EISCO) was demonstrated in order to optimize the coke consumption inside blast furnaces. Different theoretical models were applied on real data of blast furnaces to calculate the effect of operation parameters on the coke consumption. It was found that the wüstite reducibility can be controlled and enhanced using certain ratio of H2 and CO gases. Such kind of enhancement decreases the remaining quantity of unreduced wüstite which descends to the high temperature region of blast furnace. The theoretical analysis of real data using certain values of H2 and CO shows that increasing the amount of natural gas injection in blast furnace of EISCO will decrease the degree of direct reduction of iron oxide and consequently will decrease the amount of coke consumption.

Two wu ¨stite samples were prepared from reagent grade hematite and Baharia iron ore sinter by a gaseous reduction with 50%CO-CO 2 gas mixture at 1273 K. Both wu ¨stite samples were isothermally reduced at 1173-1373 K by different ratios of CO/CO 2 /N 2 which closely represent the coke gases in the blast furnace. The influences of temperature and gas composition on the reduction behaviour and the morphology were investigated. The reduction rate of both wu ¨stite samples increased gradually with increasing reaction temperature and also by increasing the CO concentration in the reducing gas mixture. 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 rate of pure wu ¨stite samples is most likely controlled by the combined effect of chemical reaction and gaseous diffusion mechanisms while the reduction rate of wu ¨stite from iron ore sinter is most likely controlled by interfacial chemical reaction mechanism.

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.