**Xing Peng, Jingsong Wang \*, Haibin Zuo and Qingguo Xue**

State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China; pengxing\_hunan@sina.com (X.P.); zuohaibin@ustb.edu.cn (H.Z.); xueqingguo@ustb.edu.cn (Q.X.)

**\*** Correspondence: wangjingsong@ustb.edu.cn; Tel.: +86-010-82375181

Received: 10 September 2020; Accepted: 17 October 2020; Published: 20 October 2020

**Abstract:** In industrial processes, a semi-cavity area formed by airflow wherein the particles circulate is called a "raceway". In a blast furnace, the role of the raceway is particularly important. To understand and predict the evolution and physical characteristics of the raceway, a three-dimensional transient Eulerian multiphase flow model in a packed particle bed was developed. In the model, it was assumed that the gas and solid (particle) phases constitute an interpenetrating continuum. The gas-phase turbulence was described as a k–ε dispersed model. The gas-phase stress was considered in terms of the effective viscosity of the gas. The solid-phase constitutive relationship was expressed in terms of solid stress. It was found that the evolution process of the raceway can be divided into three stages: (1) rapid expansion, (2) slow contraction, and (3) gradual stabilization. When the blast velocity was increased from 150 m/s to 300 m/s, the surface area of the raceway increased from 0.194 m<sup>2</sup> to 1.644 m2. The depth and height of the raceway increased considerably with velocity, while the width slightly increased.

**Keywords:** raceway evolution; raceway size; flow pattern; Eulerian multiphase flow
