PURPOSE: To improve productivity by cooling molten slag at the cooling rates corresponding to prescribed CaO/SiO2 weight ratios, thereby specifying crystalline quality to a specific volumetric ratio.
CONSTITUTION: The molten slag S of raw material ashes is packed into plural molds 4d placed on a chain conveyor 4 in an obliquely disposed casing 2 and is transported. A high-temp. exhaust gas is introduced from an ejector 6 in the central part into the casing 2 to maintain the within thereof at a prescribed temp. The molten slag S is cooled at the rates of ≤0.4°C/min when the CaO/ SiO2 weight ratio of the raw material ashes is below 0.9 in 1000 to 1200°C region including the crystallization point of the molten slag S' at ≤0.7°C/min when 0.9 to 1.0, ≤1.5°C/min when 1.0 to 1.1, ≤2.0°C/min when 1.1 to 1.2, ≤3.0°C/min when 1.2 to 1.3, and ≤5.0°C/min when ≥1.3, thereby 15 to 54vol.% of the ash is crystalized. The mold 4d arriving at the transportation destination is turned over to drop the solidified slag C from a discharge port 2a into a solidified slag container 5, by which the base course material is obtd.
SUZUKI TOMIO
TANAKA HIROYUKI
