Towards a slag droplet heat exchanger - capillary

Molten slag contains a considerable amount of sensible heat which can be recovered provided that a large specific surface area is created to facilitate heat transfer to an ambient gaseous medium. It is preferable to disperse the molten slag into uniformly sized droplets in order to permit a more reliable process design. The basic concept is to distribute a volume of molten material into coherent ligaments or jets which consecutively break into droplets by action of capillary forces. This can be done either radially using centrifugal forces as currently explored in the dry slag granulation process, or vertically by forming cylindrical liquid jets issuing from capillaries or nozzles as proposed in the direct contact droplet heat exchanger (DHX). The latter option is explored in this paper investigating the controlled breakup of molten calcia/alumina jets at 1660°C in a recently commissioned three-zone high temperature furnace.