Dry Granulation and Solidification of Molten Blast Furnace Slag

Abstract

In order to develop a process of both recovering the heat retained in molten blast furnace slag and producing aggregate for concrete making, characteristics of molten slag in granulation and solidification were investigated.
The newly developed method of dry granulation, consisted in making the molten slag collide with a hard surface that was insulated with a thin coat of oil or water, was found to have several advantages, such as (1) low power consumption for granulation, (2) low heat loss during granulation, and (3) relatively short range of dispersion of the slag granules.
In the solidification study, slag granules of 5mm diameter were subjected to air blast of various velocity. It was found that such a granule was cooled at a rate of about 100°C/sec in the high temperature range, solidifying at about 850°C. As this meant that it took some 5sec to solidify a molten slag granule of 1 350°C, acceleration of cooling was deemed necessary. Thereupon, it was shown that the use of air-fluidised bed of slag powder was effective to cool and solidify the slag granules individually as well as to extract the heat both while molten and after solidified.