Powder comminution and blending characteristics of a novel jet multi-operational processor

Conventional wet processing of drug and excipient powders into granules for use in tableting or capsule filling requires up to six different unit operations and eight materials transfers. In order to be competitive with the simplest processing technology, direct compression, which requires just two unit operations, the number of manipulations required in wet processing should be reduced. Our aim is to utilise the principle of controllable fluid dynamics to allow all wet processing operations upstream of tableting or capsule filling to be carried out in a bladeless single vessel. In this part of the initial study, the effect of jet air pressure on comminution and blending characteristics was investigated. A hollow perspex cylindrical vessel, 100 cm high, with a diameter of 30 cm was fitted with 10 radial high pressure jet nozzles, 10 cm above a supporting mesh base through which low pressure air could be fed. The effect of jet pressure on preliminary and secondary particle size reduction was studied. It was found that the median diameter of lactose crystals could be reduced by 50% in approximately 10 mins., with an air pressure of 10 psi (69 kPa). This processing time was found to be reduced to less than 4 mins. using a jet pressure relationship was found for secondary size reduction of dried lactose granuels. The median diameter was reduced from approximately 30 m to approximately 100 m in these periods. In the same vessel, a blending evaluation was carried out using three different mixing systems: manual geometric mixing: turbulent tumbling blending (TurbulaR mixer) and novel jet multi-operation processing (jet m.o.p). 30 samples of 0.5 g were removed at random from each vessel and assayed for model drug content. The results showed that geometric mixing produced a homogeneity characterised by a coefficient of variation (c.v) of 1%. In comparison, the turbulent tumbling blender produced mixes with a c.v. of 15.2%, whereas the novel jet m.o.p. produced blends with a c.v. of 2.4%. It was concluded that a jet multi-operation processor was capable of producing size reduction and blending conditions equivalent or better than those currently possible using individual, separate unit processors