TECHNOLOGY High Temperature Reaction Kinetics of Tungsten with Sulfur Dioxide

The kinetics of reaction for the tungsten-sulfur dioxide system has been studied within the temperature range 1600~176 and sulfur dioxide con-centrations up to 15 % in helium. The reaction rate for tungsten attack shows a maximum around 1870 ~ the latter temperature being near ly independent of sulfur dioxide concentration. Exper imental data lead to a reaction rate model implying a f irst-order reaction, becoming second order for part icular conditions. Parameters defining the reaction rate equation are calculated and a W-SO2 chemical reaction equation is discussed. As part of a study of the high temperature behavior for refractory metals in adverse surroundings, the re-action for the system tungsten-sul fur dioxide has been investigated at temperatures above 1600 ~ Studies of this kind are useful, for instance, in the case of tung-sten electrodes in plasma industr ial reactors, where corrosive gases are generated by solkl-gas reactions. Litt le information is avai lable in the l i terature on the high temperature r actions of tungsten with sulfur dioxide. Ear ly qual itative observation described the sulfurization of tungsten in the presence of sulfur di-oxide at "red hot " temperatures (1), while oxidation of the metal is observed at higher temperatures (2). Kinetics of synthesis and structure of sulfides includ-ing tungsten sulfide are described in a recent Soviet work (3). However, the latter is related to the sul-furization of the metal by a gaseous mixture of sulfur in helium. In view of the scarcity of information on the sub-ject, the present work was undertaken to study the kinetics of reactions of W with SO2 at high tempera-tures. In this respect, it has been shown that a maxi-mum rate of attack does occur around 1870 ~ The experiments were carried out in a reactor described in the exper imental section. Mixtures of hel ium and up to 15 % sulfur dioxide were used at various tempera-tures within the range 1600~17