**1. Introduction**

Current iron and steel-making industries are experiencing challenges, such as lowgrade ore (<35% iron), poor sintering performance, and CO2 gas emissions. FASTMET, ITmk3, and Hi-QIP processes can be adopted to increase the iron concentration of low-grade ores. For such processes, a mixture of powdery iron ore and carbonaceous material is used as raw materials, whereas the conductive heat flow from the surface to the interior of materials is the rate-controlling step, resulting in decreased productivity. The demand for microwave heating is escalating day by day in iron-making industries owing to its faster heating rate, volumetric heat generation for specific materials, energy savings, and less processing time [1–7]. Hematite can be converted to magnetite for iron ore beneficiation purposes. It can be achieved by heating the hematite. There are two ways of heating: one, conventional heating, and

second, microwave heating. In any conventional heating processes, along with hematite, other impurity oxides will be heated, which is not beneficial. This unnecessary heating can be bypassed by adopting microwave heating. In microwave heating, high efficiency in heating can be achieved because not all impurity oxides are heated, such as SiO2 and Al2O3 [8]. Hayashi et al. [7] experimentally generated temperature versus time profile and predicted the effect of graphite content on the temperature characteristic of a mixture of hematite and graphite powders. Standish and Huang [9] investigated the reduction behaviors of hematite fines by mixing carbon and suggested microwave reduction in a non-isothermal process, and the temperature had a significant impact on the reduction of hematite fines. Agrawal and Dhawan [10] evaluated the reduction behavior of low iron hematite ore containing coke and charcoal and reported coke to be a better reductant than charcoal. Mishra and Roy [11] introduced carbon content that had an important effect on the reduction efficiency of the iron ore–coal composite pellet. They [11] obtained a 70% degree of reduction at 1250<sup>o</sup> C for 20 minutes when the C to Fe2O3 molar ratio is three. Zhulin et al. [12] presented the effect of carbon content on the reduction efficiency of iron ore–coal composite pellets at 1200°C for 15 minutes and predicted that higher carboncontaining pellets reduced faster than lower carbon containing pellets. Mourao et al. [13] have demonstrated the reduction rate and maximum temperature of process depending upon the fraction of carbonaceous material. The authors found that if the fraction of carbonaceous material increases in the mixture of hematite ore and carbonaceous material, the maximum temperature increases in the process, which increases the reduction reaction rate of hematite ore. Mishra et al. [14] developed a thermal profile considering powder size, emissivity, and susceptibility using microwave heating, and reported that the model predictions were in good agreement with experimental results. The previous studies [7–14] experimentally demonstrated coke or coal to have a significant effect on temperature and reduction rate of hematite ore. However, their work lacks temperature distribution during the process. Shukla et al. [15] simulated temperature distribution in 2D cylinders of varying radii and physical properties using an explicit infinite method and found that the efficacy of temperature distribution in cylinders depends on the sample size and its thermal conductivity. They considered constant thermal conductivity and heat capacity throughout the process. Peng et al. [16] have demonstrated the heat transfer numerically during microwave heating of magnetite 1D slab. They solved the heat equation using an explicit infinite method based on fewer dimensions. Peng et al. [17] predicted the dielectric and magnetic behavior of the nonstoichiometric ferrous oxide at 823 K and 1373 K, respectively, and evaluated the temperature dependence of the microwave absorption capability of the ferrous oxide by considering the phase transformation during heating. Leo et al. [18] have shown effective permittivity of soils using Lichtenecker's mixing model. Although microwaves have superiority in materials heating, a major drawback known as nonuniform temperature distribution inside materials has also been observed [5, 6]. To address this problem, accurate temperature determination inside the materials under microwave irradiation is necessary. For last 30 years, microwave heating has been utilized extensively in the food processing industry. Most of those works considered heat diffusion and/or convection to predict the temperature distribution in the material.

Although a lot of work has been done on microwave heating, the present study investigates the heat transfer process in microwave heating to predict the temperature distribution inside a 1D hematite slab using an implicit finite-difference approach by considering heat diffusion convection and radiation effects. The objective of the

*Simulation Study of Microwave Heating of Hematite and Coal Mixture DOI: http://dx.doi.org/10.5772/intechopen.106312*

current study is to design and produce a well-defined heating profile in a 1D rectangular slab of hematite ore using microwave heating routes. The resulting temperature profile can be used as a guiding tool to optimize the carbothermal reduction process of hematite in industry, where we studied on large slab (20 cm x 20 cm) as well as laboratory approach small slab (1 cm x 1 cm).
