| 摘要 |
PURPOSE:To obtain the title high-purity raw material by calcination and grinding, acid treatment and heating treatment in a conditioning atmosphere, of a natural siliceous powder material in a specific mode, successively in this order to remove esp. radioactive elements or alkali elements. CONSTITUTION:The objective purification of natural siliceous powder material by heating in a conditioning atmosphere along with acid treatment is carried out as follows: firstly, said siliceous material is heated at 500-700 deg.C followed by cooling to obtain a calcined product, which is then ground into 60-200 mesh granules. Second, the granules are heated at 1,000-1,200 deg.C in a halogen or its compound-contg. conditioning atmosphere. Such processes as grinding, dipping and heat treatment are performed successively in this order. In this purification method, high-temperature heating is finally made in a halogen-contg. atmosphere; therefore even impurities present in the calcined product which could not be removed even through the prior dipping treatment will highly efficiently, economically be removed. |
