Mathematical modelling of wustite pellet reduction: grain model in comparison with USCM

Abstract

A mathematical time-dependent and non-isothermal model has been carried out on the basis of the grain model to study the behaviour of a wustite pellet undergoing chemical reactions with reducing gases. The behaviour of wustite pellet reduction analysed by the grain model has been compared with unreacted shrinking core model (USCM). The results show, unlike the grain model, USCM cannot properly predict the impact of gas mixture parameters and pellet characteristics on the local reduction degree. The results also display that when the grain diameter, temperature and tortuosity increase, the diffusivity resistance in the pellet increases which causes more heterogeneous reduction. However, an increment in porosity causes gases to easily diffuse in the pellet and as a result a less heterogeneous reduction will occur.

Reduction of Iron Oxides with Hydrogen—A Review

“…Ghadi et al developed a mathematical model to predict the reduction of wüstite pellets with different gas mixtures; in their study, the grain model and the unreacted‐shrinking‐core model were compared using the finite volume method. The results show that reduction occurs in a confined area and is not homogenous in the pellet.…”

Reduction Mechanism of Fine Hematite Ore Particles in Suspension

“…USCM and its revision are the most popular kinetic models in the pyro-metallurgical field for solid particle-gas reaction. [22][23][24][25][26] According to different rate-determining step in the reduction kinetics, the isothermal reaction can be described by the following equations:…”

Analysis of the Gaseous Reduction of Porous Wustite Pellets by Response Surface Methodology

“…This theory has been widely utilized in the literature. [18][19][20]29,30] In this model, chemical reactions and gaseous diffusion proceed concurrently in the porous pellet made up of fine grains. Therefore, the reduction takes place over the entire pellet from a macroscopic point of view.…”

“…Within each grain, the reduction proceeds topochemically according to the unreacted shrinking core model. [20,[29][30][31] A more comprehensive description of the grain model can be found in the work conducted by Valipour et al [18,19,29,30] and Ghadi et al [20,32] Figure 1a shows a schematic configuration of a typical counter-current moving bed reactor in which iron ores are charged from the top and move downward along the reactor. Meanwhile the reducing gas mixture enters the bottom and ascends along the reactor.…”

“…In recent years, great improvements have been achieved in our understanding of iron ore reduction through significant developments in numerical and experimental investigations. Reports of Warner, [1] Turkdogan and Vinters, [2,3] Szekely and El-Tawil, [4] Towhidi and Szekely, [5] Paul and Mukherjee, [6] Bonalde et al, [7] Piotrowski et al, [8] and Kazemi et al [9] are some of the most important examples of experimental investigations on iron ore reduction, while research by Spitzer et al, [10,11] Negri et al, [12] Tien and Turkdogan, [13] Sohn, [14][15][16] Usui et al, [17] Valipour et al, [18] Valipour and Khoshandam, [19] and Ghadi et al [20] are the most notable relevant examples of numerical modeling. The readers are referred to the authors' recent article [21] for a review of scientific efforts on iron ore reduction over the years.…”