Published: Jan 1977
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Zircon is the ore from which zirconium and hafnium are produced. It is found as a heavy beach sand in many parts of the world, usually in combination with other minerals. Zircon is a zirconium-hafnium silicate with a ratio of 50 zirconium to 1 hafnium in most ores. The manufacture of reactor grade metal is a long process, the major steps of which are shown on the flow sheet in Fig. 4-1. The first step is the chlorination of the sand to produce “crude” (hafnium containing) tetrachloride and a by-product silicon tetrachloride. The industrial grades can be produced by purifying the crude tetrachloride through a simple sublimation process and then reducing it to metal using magnesium as the reductant, Kroll process. The reduction product is vacuum distilled to remove the excess magnesium and magnesium chloride leaving chunks of porous metal called sponge. A chunk of such a metal is shown in Fig. 4-2. These chunks are crushed to pass a 3/4-in. screen and are blended with other batches to form blends of uniform composition. Crushed sponge is shown in Fig. 4-3.