An inequality relating fundamental parameters of horizontal slug flow pneumatic conveying

This paper considers the particle exchange between a slug and its stationary layers to propose a limiting case for slug stability. It is shown that a stable slug must have a length that is greater than the product of its velocity and the time taken to accelerate particles from the stationary layer into the slug. Theoretical analysis and experimental results are utilised to derive an expression for the acceleration time – resulting in an inequality relating slug length and velocity, layer fraction and pipeline diameter. Single slug, horizontal conveying trials of five bulk materials are used for validation, after which the inequality is generalised to a function of only operating conditions using expressions and observations from the literature. The paper concludes with a case study demonstrating the ability of the resulting method to predict the area of the operating conditions space for which slugging can occur.