| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for grinding shells as industrial waste by an economical method friendly to environment without adapting strong mechanical force. SOLUTION: Shells are heated to 600 deg.C or higher to be baked. As a result, protein or the like being the main constituent part of shells is pyrolyzed and burnt and, subsequently, calcium carbonate is pyrolyzed to change to calcium oxide. Preferable heating temperature is 800-1,200 deg.C and a heating time is different by the kind of shells but usually 5-60 min, preferably, 10-20 min. Shells become considerably fragile by this baking treatment but yet require mechanical force strong to grind. Then, a small amount of water is allowed to act on the baked shells for a short time. As a result, the mechanical strength of shells lowers at a stroke and the shells collapse naturally and can be simply powdered by fingers.
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