International Journal of Pharmaceutics 181 (1999) 243 – 254 Design of a fluid energy single vessel powder processor for pharmaceutical use Graham R. Kay a, *, John N. Staniforth a , Michael J. Tobyn a , Michael D. Horrill a , Linda B. Newnes b , Stuart A. MacGregor b , Ming Li b , Gerald Atherton b , Richard C. Lamming c , David W. Hajee c a Pharmaceutical Technology Group, Department of Pharmacy and Pharmacology, Uniersity of Bath, Bath BA27AY, UK b Department of Mechanical Engineering, Uniersity of Bath, Bath BA27AY, UK c School of Management, Uniersity of Bath, Bath BA27AY, UK Received 26 May 1998; received in revised form 14 January 1999; accepted 24 January 1999 Abstract This study introduces a motionless novel single vessel powder processor designed to carry out all of the unit operations in the preparation of powders for tableting. The processor used controllable fluid dynamics to provide the energy for each unit operation. The vessel design was evaluated using a computational fluid dynamics model which indicated the flow necessary for the intended processing operations to take place. The processor performance was evaluated experimentally for two unit processes: particle size reduction and dry powder mixing. The processor was found capable of reducing the size of lactose granules from a median particle diameter of 459 m to a median particle diameter of 182 m within 5 min under optimal process conditions. It was found that a formulation containing lactose granules (373 m median particle diameter) and a model drug, sodium chloride (30 m), could be mixed to an improved degree of homogeneity in comparison with equivalent powders blended using a conventional turbulent tumbling technique. It was concluded that a processor having controllable fluid dynamics offered the potential to perform multi-task processing of powders. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Particle size reduction; Powder mixing; Single vessel processing; Granulation; Equipment design 1. Introduction The most commonly used techniques in prepar- ing powders for tableting are wet granulation and direct compression (Armstrong, 1988). Direct compression is the simpler technique, requiring * Corresponding author. Tel.: +44-1225-826826 (ext. 4831); fax: +44-1225-826114. E-mail address: prpgrk@bath.ac.uk (G.R. Kay) 0378-5173/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII:S0378-5173(99)00033-2