The effects of wall friction and solid acceleration on the mal-distribution of gas–solid flow in double identical parallel cyclones

• The effects of wall friction and solid acceleration are investigated.
• The inflection point is the key parameter to distinguish the mal-distribution.
• Different mal-distributions between dilute and dense solid loading are explained.
• The measures to limit the mal-distribution are suggested.

The uneven gas–solid flow in parallel cyclones, which is called as the mal-distribution in publications, has been widely confirmed. Although there is non-uniform gas–solid flow in the riser, the parallel cyclones would influence the distribution of gas–solid flow due to the pressure drop constraint. Based on the pressure drop constraint and an empirical correlation for cyclone pressure drop, this paper analytically investigates the mal-distribution of gas–solid flow in double identical parallel cyclones, and measures to limit the mal-distribution are suggested. Due to the effects of wall friction and solid acceleration, the change of pressure drop with the increase of solid loading shows a nonlinear characteristic. The inflection point (at where the cyclone has the minimum pressure drop) changes depending on the wall friction and solid acceleration. If the upstream solid loading (Gs/Ug/ρg) is far away from the solid loading at the inflection point, the uneven solid distribution in the pair of cyclones could be limited although there exists uneven gas–solid flow in the riser. If the upstream solid loading is almost equivalent to the solid loading at the inflection point, the wall friction and solid acceleration both significantly influence the mal-distribution, and the solid distribution in the cyclones would be much more non-uniform compared with the dilute phase and the dense phase.

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