Flow of gas—solid mixtures in standpipes. A review

In this paper, the literature on standpipe flow is systematically reviewed. In particular, four possible flow regimes are defined, viz. dense phase fluidized solids flow (DENFLO), lean phase fluidized solids flow (LEANFLO), transition packed bed flow (TRANPACFLO) and packed bed flow (PACFLO). The possibilities of coexistence of more than one of these flow regimes and the prediction of these coexistences are discussed. Available equations pertaining to each flow regime and to flow of gas—solids mixture through a slide valve are summarized. The use of the equations for analysis of industrial standpipe operation is illustrated by means of two case studies. Finally, areas where further work would be fruitful are pinpointed. More experimental work is urged to verify the validity of some of the equations presented and to improve our understanding of the different types of flow instabilities in standpipe operation.