## 2 Experimental Section  
### Experimental Equipment  
As shown in Figure 1, in this study, a pharmaceutical granulation/drying fluidized bed (FBL-10, Xiaolun Pharmaceutical Machinery, Wenzhou, China) was used, which was a negative pressure conical fluidized bed. The conical cylinder was detachable with a bottom diameter of 180 mm and a top diameter of 300 mm, and the cross-sectional area was round; the conical angle \(\alpha\) = 8.88\({}^{\circ}\). There was a distribution plate made of stainless steel with a thickness of 3 mm for supporting materials and ventilation. The holes on the distribution plate were arranged in a square array mode, the diameter of each hole was 1.6 mm, and the total number of holes was 1617, so the overall opening ratio was 12.78%. A double-layer fine screen covered the distribution plate to prevent fine materials from falling through the holes and to force the airflow to be uniformly distributed. A high-pressure fan (2 RB-730N-7 AH26, Ggling Mechanical & Electrical Equipment, Wuxi, China) was placed at the outlet of the gas path, so the pressure in the fluidization chamber was negative with respect to the ambient pressure. The high-pressure fan had a rated power of 3 kW and could generate a maximum negative pressure of \(-\)22 kPa. The power of the fan was controlled by a frequency converter (ATV310 HU30N4, Schneider Electric SA, Paris, France); thus, the gas velocity could be changed. The control range of the fan power was 1-100%, and the minimum control interval was 1%. The ambient pressure was standard atmospheric pressure, the air humidity was controlled by a humidity controller (MDH-40Y, Senjing Motor Manufacturing, Hangzhou, China) to 50-60%, and the ambient temperature was controlled via air conditioning to 25 \({}^{\circ}\)C \(\pm\) 1 \({}^{\circ}\)C.  
A vortex flowmeter (DN100, Meikong Automation Technology, Hangzhou, China) was connected in series at the exhaust pipe to measure the flowrate with an accuracy of 1%. Two air pressure measurement ports were set in the center of the plenum and the front of the filter bag, named P1 and P2, respectively. Two identical high-precision air pressure sensors were connected to the measurement ports, and the measurement range was \(-\)10 kPa-10 kPa with an accuracy of 0.5%. The pressure sensors' signals were sampled by a high-speed data acquisition card (USB-6009, National Instruments, Austin, TX, USA) with a sampling frequency of 40 Hz. The pressure transfer hose (not shown in Figure 1) had a length of 100 mm and an inner diameter of 4 mm, so the transmission time delay of the pressure fluctuations in the hose could be ignored [32]. Micro glass beads were used as fluidized materials in this study, which are nonporous particles. The true density of these particles was 2409 \(\pm\) 8.8 kg/m\({}^{3}\), measured by the drainage method. Using different screen combinations, we screened out a total of 5 kinds of materials with different particle sizes, which were numbered #1, #2, #3, #4, and #5. The average diameter (randomly measuring the diameters of 50 particles and taking the average) and sphericity (replaced by the circularity of the projection photo) of each kind of particle were determined by a digital microscope (GP-660V, Gaopin Precision Instruments, Shanghai, China), and the natural bulk voidage of each kind of particle was measured by a bulk density meter (XF-16913, LICHEN-BX Instrument Technology, Shanghai, China), as shown in Table 2. Since the screen size range of each kind of particles was relatively narrow, the particle distributions of all kinds of particles were considered a typical narrow distribution. The microscopic photograph of the experimental particles is shown in Figure 2, and the bright spots on the particles in the photograph are caused by the microscope's illumination light. Figure 1: Schematic diagram of the experimental equipment.