| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method which can produce silica powder of a low uranium concentration at a low cost.SOLUTION: The method includes a grinding process in which ground quartz rocks of 1 ppb or below uranium content are made to collide mutually in high velocity gas to be ground into a ground product and a melting spheroidization process in which the ground product is put into a flame to melt and spheroidize it. In other words, the mingling of uranium from a grinder can be prevented by adopting a method for carrying out a grinding operation without contact with the grinder to the utmost. Especially, the grinding process, by being carried out in a grinding container lined with an elastomer, can reduce the possibility of the mingling from the wall of the container which occurs by the collision of silica powder in a high velocity air current with the wall of the grinding container of the grinder. Since the removal of uranium from a polymer material is relatively simple, even if the polymer material is mixed, the mingling of uranium can be suppressed, and if the polymer material is mixed into the ground product, it is oxidized and scattered in a following melting spheroidization process so that there may be no problem. |
