An experimental and theoretical investigation into the break-up of curved liquid jets in the prilling process

A pilot scale study of the dynamics of the break-up of curved liquid jets is presented. This work is motivated by an industrial process called prilling which is used in the manufacture of pellets. In this process a sieve-like cylindrical can spins rapidly on its central vertical axis. Molten liquid is pumped into the top of the can and flows from the holes in the form of curved liquid jets. Experiments are described which were carried out on a pilot scale rig. Some differences between the break-up modes observed in this study and previous work using a small laboratory scale rig are discussed. Previous theories describing break-up mechanisms of curved liquid jets were extended to include viscosity and gravity. Break-up lengths and drop sizes were obtained theoretically and compared with experimental results. Experiments were carried out using insonification, a process where sound waves are fired at the jet to control satellite drop formation. Three different frequencies of wave were used, 10, 100 and 200 Hz at four different rotation rates. It was observed that insonification was successful at eliminating satellite drops at low rotation rates and when frequencies of 100 or 200 Hz were used. Insonification was included in the theory. The theory predicted that insonification eliminated satellite drops for a large range of frequencies in the experimental regimes for sufficiently large acoustic volume. The theory also predicted that satellite drops were eliminated in parameter regimes outside the experimental regimes. The trajectory of the jet was allowed to become unsteady, in a rotating frame of reference. Simulations were carried out in inviscid and viscous regimes