In leading countries around the world, research is being conducted on the development of dry slag granulation plants (DSGPs) for blast-furnace slag; these plants support production of dry granulated slag and recovery of physical heat from slag. The design and construction of laboratory or pilot dry granulation plants requires engineering techniques that can be used to design the major components of the plant. The most important component of a dry slag granulation plant is a horizontally rotating device (disk) for spraying slag (a disk), with the molten slag being fed onto this disk. As the slag interacts with the disk, the slag is atomized into drops with a diameter of 1–2 mm that move radially at a speed of 5–15 m/sex through the interior of the granulation chamber, where they undergo radiant and convective heat exchange, and solidify before they come into contact with the cylindrical wall of the chamber. Knowing the maximum diameter d of the molten slag droplets and the speed w at which they move through the granulation chamber, it is possible to estimate the geometric and operating parameters of the spraying device (disk): The disk radius r0, the rotation frequency f of the disk, the maximum slag flow rate Gmax at which the slag becomes atomized, as well as the mechanical power N required for rotation of the disk.
In this paper, we obtain fairly simple expressions that enable us to determine the values of r0, f, Gmax, and N as a function of the parameters d and w, and present the results from an analysis of these functions. This analysis also takes into account the thermophysical properties of blast furnace slag: density, coefficient of viscosity, and the coefficient of surface tension. For example, slag droplets with diameter 2 mm and speed 5 m/sec cool in the granulation chamber from 1500 to 1200°C (guaranteed solidification temperature) in about 0.7 sec, in which case the radius of the chamber should be at least 3.5 m. The rotating disk should be approximately 0.047 m in diameter, with a rotation frequency of 16.8 Hz. The maximum volume flow rate of sprayed slag is 0.0035 m3/sec = 12.6 m3/h. The specific consumption of mechanical energy for the disk drive will be ≈ 0.0105 kW·h per metric ton of molten slag. As the droplet velocity w increases, the size of the granulation chamber and the values of r0, Gmax, N will increase significantly, and the rotation frequency of the disk will decrease. As the droplet diameter d decreases, the size of the granulation chamber and the values of r0 and Gmax will significantly decrease, the frequency f will increase, and there will be a slight increase in the power N.
