Abstract
The reduction process inside the ore pre-reduction rotary kiln involves a series of physicochemical reactions, and in-depth understanding of the reduction behavior is helpful to improve the product quality and productivity. This paper reports a three-dimensional steady state mathematical model based on computational fluid dynamics, which considers heat transfer, mass transfer and chemical reactions inside the rotary kiln. A user-defined functions (UDFs) program in C language is developed to define physical parameters and chemical reactions, and calculate the heat and mass transfer between freeboard and bed regions. The model is validated by measurement data and is then used to investigate the detailed information inside the rotary kiln. The results show that there is a temperature gradient in the bed, which is maximal near the kiln tail and decreases gradually as the reduction process progresses. The result also confirms that the reduction of FeO to Fe is the limiting step of the whole reduction process because this reaction requires a higher reduction potential. Furthermore, the influence of C/O mole ratio and fill degree are analyzed by comparing the average bed temperature, reduction potential and metallization ratio.
Highlights
The comparison between the computational and measured results is listed in Table 6, mainly composed of gas composition and temperature of exhaust gas at the kiln tail, metallization rate (MR) of the reduced product outlet and relative error
The metallization rate (MR) and relative error are given by Equations (19) and (20)
The model in this work is reasonably reliable for predicting the inner characteristics of the rotary kiln
Summary
As the most efficient technique, blast furnace ironmaking is currently the most widely used ironmaking process. It has inherent defects, such as long process, high dependence on coke, environmental pollution and so on. With the depletion of coking coal and the strict emission standards of various countries, developing an alternative ironmaking process has always been a hot topic [1,2]. Many research institutions and steel companies have carried out research on smelting reduction technology [3,4,5,6]. A new smelting reduction process for iron ore processing has been presented by China Iron and Steel Research Institute Group (CISRI) [7,8]
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