Method and device for granulating blast furnace slag

In a method of granulating blast furnace slag comprising

• passing slag through a slag chute into an open explosion room, spraying said slag upon entry into said explosion room with water to granulate the slag and form a water-granules mixture,
• transporting said water-granules mixture to an open granulation pit and onto a dewatering bed to dewater the granules, and removing periodically said dewatered granules from said pit,
• the improvement which comprises flowing the water-granules mixture before debouching into the open granulating pit, through an entrance opening into a vapour separating box which encloses the mixture flow, flowing said mixture through an exit-opening in the bottom of the vapour separating box into the granulating pit, and leading the developed vapour from the upper side of the vapour separating box to a chimney.