Multiphase flow mixing in a rotary holding furnace
(Burrows, Liow, Brady)
Rotary holding furnaces (RHF) are used in the metallurgical industry to settle out matte and slag from the Isasmelt furnace. It consists of a cylindrical vessel lying horizontally on its side. The feed mixture is fed at one end of the cylinder and the separated matte and slag is removed at the other end through different spouts. A water model study of the flow in the RHF using kerosene and water with a copper tracer showed that there was mixing in the RHF as the feed moves through the cylinder. Breakthrough curves were obtained for different fill ratios of kerosene and water to investigate the effect of different matte and slag holdups. The breakthrough curves fitted well to a model with a series of three stirred reactors followed by a plug flow reactor and a small amount of stagnant fluid. The model showed that there was a small stagnant region at the outlet end of the RHF as the discharge spouts were located a short distance from the end. As the upper liquid layer of kerosene was increased, the flow behaviour became more complex with an increased tendency for mixing with the bulk of the fluid. This resulted in a long tail for the exit concentration. The use of air bubblers was found not to improve mixing, rather it split the cylinder’s interior into separate compartments and reduced mixing. (Burrows et al. 2010)
