Initial equilibrium droplet size distribution at the swirl separator with progressive process

Abstract

Tangential separator is widely used in industries as vital demulsification and dewatering separation devices but leads to high breakage rate of droplets. To address this, the swirl separator with progressive process was developed by exploiting operational merits of swirl element to minimize the breakage rate of droplet. The initial droplet size distribution has an influence on the droplet size distribution within the flow field. Accordingly, the droplet size distribution was analyzed numerically and verified through experimental measurements. The evolution of the droplet size distribution from the numerical simulation was then investigated. Based on these, the mechanism of droplet coalescence and breakup were examined. The results show that the initial equilibrium droplet size distribution is d₅₀ = 85–90 μm at V = 5 m/s. Simultaneously, the turbulent dissipation rate is lower than the other initial droplet size distributions. Moreover, the numerical model can reasonably be utilized to the investigation. When the initial droplet size distribution is above d₅₀ = 90 μm, the effect of droplet breakup is dominated. The rate of droplet breakup increases, and the coalescence rate decreases with the draining time of liquid film for coalescence increasing, which is unconducive to improve the separation efficiency. Conversely, if the initial droplet size distribution is below d₅₀ = 85 μm, the swirl element promotes the droplet coalescence. The separation efficiency has an improvement. Additionally, the swirl element enhances the turbulent dissipation rate within the flow field.