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Abstract

A heating device for heating corrosive vapours includes a casing defining a vapour flow path having an inlet and an outlet. A tubular metallic electric resistance heating element is disposed in the flow path and arranged such that the vapours being heated successively pass in opposite directions along the interior and exterior of the element in flowing from the inlet to the outlet of the casing. To accomodate thermal expansion and contraction, one end of the element is connected to the casing by means of a flexible coupling there being provision to maintain at least a part of the flexible coupling immersed in a body of an electrically non-conductive liquid capable of shielding the coupling from the corrosive vapours during operation of the device. The non-conductive liquid may be maintained in the liquid state by circulation through a heat exchanger. The heating element may be made, for example, of platinum or a platinum alloy and the flexible coupling, for example, of a braid of such a metal or alloy or of tantalum. Preferably the apparatus is used to preheat titanium tetrachloride vapour for use in the manufacture of titanium dioxide by oxidation thereof. Where titanium tetrachloride vapour is to be heated the non-conductive liquid used is preferably titanium tetrachloride liquid.

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First Claim