GB881741A - Improvements in or relating to apparatus for the preparation of mixtures of powdered solid substances - Google Patents

Abstract

<PICT:0881741/III/1> <PICT:0881741/III/2> A mixing and grinding apparatus suitable for use in chemical reactions in which a solid is reacted with a gas, comprises an inverted substantially frusto-conical vessel a (Fig. 2) adjustably and flexibly supported from a steel framework by rods b and shock absorbers h, and a shaft d extending along the axis of the vessel and carrying arms e, f, supporting two-start tapered spiral members c1, the surfaces of the members c1 (Fig. 3) being inclined by at least 45 degrees radially outwardly and downwardly towards the inside wall of the vessel a and the surfaces of the arms e, f, also being inclined to the horizontal. The gas is injected through the base of the apparatus during mixing. The grinding effect may be increased by narrowing the gap between the vessel side and the members c1. The shaft is driven by a motor and reduction gear supported by the framework and the vessel has a lid j and a filling opening k. Vibrators, either mechanical, electromagnetic or ultra-sonic may be fixed around the outside of the vessel to enhance the mixing. In a modification described with reference to Figs. 4 to 6 (not shown) the spirals are replaced by segments of a spiral or spirals which segments are connected to frames secured to the supporting arms e, f. The materials constituting at least the inside surface of the vessel and the surface of the agitating device are selected, e.g. from metals or alloys or agglomerated, stratified, reinforced plastic or elastic materials. For a mixture containing, e.g. sodium bisulphate, an apparatus made of stainless steel with a high content of molybdenum may be used. If the mixture liberates a volatile mineral acid, e.g. hydrochloric acid, the linings of the vessel and agitating device could be of hard rubber or of acid-proof plastic material. The inside surface of the vessel may be roughened or ribbed.