Predicting the mode of flow in pneumatic conveying systems-- A review

An initial prediction of the particulate mode of flow in pneumatic conveying systems is beneficial as this knowledge can provide clearer direction to the pneumatic conveying design process. There are three general categories of modes of flow, two dense flows: fluidised dense phase and plug flow, and dilute phase only. Detailed in this paper is a review of the commonly used and available techniques for predicting mode of flow. Two types of predictive charts were defined: basic particle parameter based (e.g. particle size and density) and air-particle parameter based (e.g. permeability and de-aeration). The basic particle techniques were found to have strong and weak areas of predictive ability, on the basis of a comparison with data from materials with known mode of flow capability. It was found that there was only slight improvement in predictive ability when the particle density was replaced by loose-poured bulk density in the basic parameter techniques. The air-particle-parameter-based techniques also showed well-defined regions for mode of flow prediction though the data set used was smaller than that for the basic techniques. Also, it was found to be difficult to utilise de-aeration values from different researchers and subsequently, an air-particle-based technique was developed which does not require any de-aeration parameter in its assessment.