Pneumatic conveying performance characteristics of bulk solids

This thesis is concerned with the analysis of the performance of bulk solid pneumatic transport systems. A bulk solid parameter, with the potential to characterise materials on the basis of suitability for this mode of transport, is proposed. Procedures for producing conveying characteristics are developed and linked to conveying models and design requirements. A new model based on the power requirements of the pneumatic conveying process is presented. The deaeration behaviour of bulk solids is analysed in some detail. Theoretical aspects, appropriate test rig arrangements and experimental arrangements are discussed. A characterising parameter, the normalised time constant, is proposed. Extensive experimental data are used to clarify the significance of this performance indicator and to assess its capacity to predict the pneumatic conveying potential of a given bulk solid. The process of generating conveying characteristics for the bulk solid/pipeline configuration from experimental data is discussed. The computerisation of this process and the application of numerical techniques are developed and demonstrated. The advantages and possibilities are explored, and limitations noted. The implementation of a solids friction factor (Barth type) model within the conveying characteristics procedures noted above, is developed and demonstrated. The application of scale up procedures within this model environment is discussed and tested against experimental data. Determination of conveying characteristics for stepped pipelines is demonstrated, as is a method for the optimised design of stepped pipeline configurations. A power based pneumatic conveying model is proposed. This model considers the power available from the isothermal expansion of the gas down the pipeline, and the power consumed by the various components of the system. Features of this model include a solids friction factor correlation, the treatment of bends, a new analysis of the air-only component and a method for the identification of invalid conveying regions. The generation of conveying characteristics curves for single and stepped pipeline systems within this model is demonstrated. The performance of the model is tested against a selection of experimental data. Trends inherent in the model, and its scaling behaviour, are examined. Potential areas for further development of the model are discussed