Handbook of Chemical Engineering, Vol. 2 of 2: Prepared by a Staff of Specialists (Classic Reprint)

Excerpt from Handbook of Chemical Engineering, Vol. 2 of 2: Prepared by a Staff of Specialists

Before proceeding to outline briefly the various heating methods employed in bringing about high temperature melting or reactions, we shall refer in a few words to the subject Of refractories for high-melting-point containers.

High-temperature Refractories - Our choice of materials is very limited especially for temperature work in excess of 2,000°c. Of the various refractories readily obtainable, lime, magnesia and alumina are the most serviceable basic ones at temperatures up to about The purer these oxides the higher their melting points. In laboratory tests thoria crucibles have given very satis factory results at temperatures as high as 2,400°c. Alth'ough pure tungsten melts at crucibles made from this metal, unless constructed with very heavy walls, show marked tendency to collapse at about 2,800°c. In those cases where carbon does not readily combine with the substance to be heated, commercially pure graphite crucibles or supports are serviceable up to tempera tures Of about 3,000°c. The life Of these graphite crucibles at these elevated temperatures is however comparatively short since the amorphous carbon binder. Used in the manufacture Of the crucible rapidly loses its binding qualities as the graphitization temperature is approached.

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