The industrial application of plasma technology for the production of fumed Silica

Abstract

The industrial application of plasma chemistry is restricted for the time being to the use of a plasma torch as an efficient heat source for the production of existing chemicals. The techno-economic requirements for products suitable for plasma processing are outlined. There are only very few such processes at or near industrialization, such as the Tafa process for ZrO 2, the Noranda MoS 2 process and the Lonza process for fumed silica. Various types of plasma torches are evaluated according to such criteria as investment cost, efficiency, availability in industrial size, suitability for continuous operation and scale-up etc. The liquid-stabilized torch used in this work is described. The Lonza process for surface-active silica is based on the reduction of sand to silicon monoxide gas in a specially designed reactor, fired by a 200 kW alcohol-stabilized plasma torch. By direct oxidation of the SiO gas in a quench system it is possible to produce a surface-active product. At present the process has reached pilot plant scale and is being optimized. In comparison with the conventional process, based on the gas phase hydrolysis of silicon tetrachloride, the use of cheaper raw materials and the elimination of hydrogen chloride from the process lead to a cheaper process without ecological problems.