A Comprehensive Study of Pore Characteristics, Formation Mechanism and Reliability Analysis with Advanced Characterizati

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ORIGINAL ARTICLE

A Comprehensive Study of Pore Characteristics, Formation Mechanism and Reliability Analysis with Advanced Characterization Methods Within Pellets Chenyang Xu1 • Jianliang Zhang1,2 • Zhengjian Liu1 • Yaozu Wang1 • Zhanguo Li1 • Liming Ma1

Received: 24 April 2020 / Accepted: 1 August 2020 Ó The Indian Institute of Metals - IIM 2020

Abstract In order to improve the accuracy of the porosity results of pellets, the reliability of three methods for measuring the pore structure was compared. The results show that there is a measurement error in the result of the traditional method, the mercury intrusion porosimetry (MIP) cannot detect closed pores, and the result of scanning electron microscope (SEM) method is more comprehensive. Additionally, three types of pore structures have been proposed to describe the pore formation mechanism of pellets, namely original pores, pores left by shrinkage of liquid phase and pores left by induration of mineral particles. Furthermore, the pore structures of pellets were analyzed by MIP and SEM. The results reveal that MIP can measure the pores with diameters less than 1 lm, and the pore diameters measured by SEM range from 1.2 to 89.2 lm. Finally, the curvature of the pores is measured to evaluate the consolidation degree of the pellet. Keywords Pellet  Pore characterization  Measurement methods  MIP  Curvature

& Zhengjian Liu [email protected] 1

School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30th Xueyuan Road, Haidian District, Beijing 100083, People’s Republic of China

2

School of Chemical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia

1 Introduction The iron ore pellets, as a raw material in the ironmaking process, whose microstructure can be divided into two parts: the mineral and the pores. Many research results indicate that the mineral constituents have a great effect on properties of pellets [1–3]. Porosity and the pore structure are among the most fundamental properties because they affect the compressive strength and metallurgical properties of pellets [4]. The structural characteristics of porous sintered products such as pellets, silicon carbide and ceramics have an important influence on their mechanical strength and performance [5–9]. It is often desirable that pellets have a high compressive strength, high reducibility and low swelling index. Several studies [10–13] found that the compressive strength increases with decreasing porosity; however, the reducibility increases with increasing porosity. Pore provides the diffusion path for reactant gas and inner surface for reaction, which can speed up the reaction rate [14]. However, pore becomes the concentration point of stress, which decreases the compressive strength of pellets [15]. Hence, it becomes necessary to determine the appropriate porosity of pellets for obtaining high compressive strength and reducibility simultaneously. Many researchers have used a variety of advanced methods to characterize the pore s

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