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At present, centrifugal granulation has become the most promising method for waste heat recovery of molten slag. This paper investigates the effects of rotary disk configurations on particles characteristics with molten aluminum as the working medium. Four types of rotary disks and two kinds of particles characteristics which included particles size distribution and particles mean size were studied. It can be seen that the main particles sizes are populated in the range of 2.0~4.0mm for all disk configurations. Due to the special surface structure, the particles produced by curved-block disk and arc-edge disk configurations are more concentrated compared to other two types of disks. Besides, the results shown that the mean size of particles generated by curved-block disk is smaller. All the conclusions will be helpful for future development of the high-temperature molten slag dry granulation systems.

Numerical studies on molten slag droplets solidification behaviors in humid air were carried out by using the hybrid evaporation and solidification models. The numerical model was firstly validated by the experimental data in the literatures, and then solidification time, temperature distribution, and movement of phase change interface during the solidification process were analyzed. The effects of humidity ratio (content of atomized water), air inlet temperature and velocity, and droplet diameter on solidification behaviors of molten slag were discussed. Finally, a correlation for predicting the solidification time was proposed. The results show that, generally, the solidification time is decreasing by increasing the air inlet velocity and humidity ratio, or decreasing the droplet diameter and air inlet temperature. The solidification rates represent a trend of gradual decline during the solidification process due to the ever-increasing thickness of the solid slag region, and they are normally higher at the upwind side but relatively lower at the leeward side, resulting in an off-center solidification process of a slag droplet. The humidity ratio has significant effect on the cooling air temperature distributions, steeper temperature gradient is observed thanks to the evaporation process of the atomized water. The present work suggests that the operational conditions are: the humidity ratio within the range of 10%∼20%, the air inlet velocity is 1.0 m/s and the air inlet temperature is 303 K, respectively.

Rotary disk centrifugal granulation is one of the most promising methods for molten slag recovery with lower power consumption, compact and coupling with a variety of waste heat devices easily. In this paper, high temperature analogue experiments were performed by four types of disks with molten aluminum as the working fluid. The particles characteristics which include particles size distribution, particles mean size and fiber mass fraction were studied. The results show that the majority of the particles size is populated in the range of 2.0 mm∼4.0 mm for all the ω and Q. Both theoretic and experimental analyses indicate that the ω has more impact on particles size than Q. The particles produced by curved-block disk and arc-edge disk configurations are more concentrated than the other two types of disks. Besides, the mean size of particles generated by curved-block disk is smaller. A simple correlation of dm for four types of disks is proposed, which agrees well with the experimental data (R2 = 0.9172). Meanwhile, when the Q is relative low, a lower ω can contribute to the reduction of produced fiber. The main conclusions drawn from this work will be helpful for future development of the high-temperature molten slag dry granulation systems. Keywords: Rotary disk, Molten slag, Ligament, Disk configuration, Particle size, Fiber fraction

The influence of rotary disk configurations on droplets characteristics in molten slag ligament granulation was investigated by using the high-speed camera visualized system. Rosin/Paraffin mixture was adopted as the analogue of the molten slag according to the similarity theory. Four groups of disks with different configurations were studied. The droplets characteristics, such as droplets size, droplets size distributions, filament mass fraction and particle uniformity were analyzed. Generally, the droplets mean diameters (dm) decreases by increasing the rotary speed (ω) or disk diameter (D), and increases slightly by increasing the liquid flow rate (Q). Based on the experimental data, a simple correlation of dm for four types of disks is presented. The majority of the droplets size is populated in the range of 0.2–1.0 mm for all ω and Q, which accounts for over 70% mass fraction. The ω has significant influence on droplets size distribution and particle uniformity. The flat/arc-edge disk configurations can contribute to produce the narrower size range of droplets and obtain the superior particle uniformity compared to the other two types of disks. In the ligament breakup mode, the filament mass fraction reduces by increasing Q or decreasing ω. Meanwhile, the liquid film breakup mode also has significant impact on the formation of filament.

Rotary disk granulation is an energy saving and more stable method for waste heat recovery from high temperature molten slag, and the quality and values of the generated cement product are primary determined by the granulating characteristic. The present work performed the analogue experiments in four types of rotary disks with Rosin/Paraffin mixture as the working fluid. The influence of rotary disk configurations on characteristics of ligament-type granulation, which include ligament number KL, ligament diameter dL, capillary wavelength λ and droplets mean diameter dm were investigated through visualized method. Also the mechanism of droplets pitch-off process was revealed. The results indicated that the surface tension forces that determine the most of ligament and droplet breakup processes. The KL is predominately affected by We number, while the influence of RP mixture volume flow rate Q, St number and disk configurations is negligible. The dL decreases with the increase in angular speed ω. The dL of arc-edge disk is lower than that of the flat/slotted/bulged-block disks due to the effect of gravity force. The short-wave mode is the dominant mode for droplets pinch-off process. Most of the predicted dm for different disk configurations are within the band of ±15% of the measured values, and the arc-edge disk configuration is recommended because it can produce the smallest droplets compared with the other types of disks. Accordingly, the correlations for KL, dL, λ and dm are proposed in a wide range of operational conditions. Further investigations will focus on the droplets characteristics, as well as the optimal design or selection of different disk configurations.