**2. Experimental Work**

The experimental study is based on iron oxide pellets. As the shape of the pellet is close to that of a sphere, spherical particles were used in the simulations to be presented. In fact, particle shape affects the porosity of the pile, but since we focus of pellets, particle shape was not considered. The reader is referred to Reference [25] for more information about this matter.

Pellets used in the experiments come from a steel plant in China. About 10,000 pellets were selected after applying sieves with aperture size in the range 13–15 mm. The experimental apparatus is illustrated in Figure 1a, which is a 1:10 scale charging system of a BF. A stable pellet pile was formed on a table by the discharging method. In order to study the profiles of the arising pile, a camera with the lens level along with the desktop was used to take photographs from four different directions of the pile. The angle of repose was obtained by analyzing the profile of the heap using photograph-processing technology.

The same method was used to form a pile for measuring the porosity distribution. Seven 25 mL (plexiglass) breakers placed beforehand to be buried in the pellet pile were slowly removed afterwards to be able to measure the porosity (P), expressed b y

$$P = \frac{V\_1}{V} \times 100\%,\tag{1}$$

where *V*<sup>1</sup> and *V* denote the void volume (mL) of beakers full of particles and the volume of the empty beaker, respectively. In order to reduce the errors, the experiment was repeated nine times, and the average result was reported.

**Figure 1.** (**a**) Experimental apparatus and schematic of the measurement of pellet pile and (**b**) the geometric models of different packing method in simulation.

#### **3. Simulation Method and Conditions**
