Coalescing technology and media are also used to separate immiscible liquids. These are typically emulsions or hazy mixtures, and by separating them it can reduce the volume of contaminated liquid effluent, or improve a process or a final product quality. There are many different separation needs in industry, which use similar concepts to those usually found in oil and gas extraction and refining. Water separation from oil, oil from water, or sometimes removal of solids at the same time.
Out coalescing media can greatly improve the efficiency and speed of separation, thereby adding more capacity, and minimise the size of vessels. As shown above a gravity separation vessel can be made smaller and cheaper.
The type of media required is carefully selected and the design tailored to the specific needs of each plant’s operation. We can use knitted metal wire packs, co-knitted metal wire and fibre packs or plate packs (which can also provide a flow stabilising benefit to the liquid flow in the vessel, thereby ensuring the correct performance of the system even under many upset process conditions.) See Fig 1 and Fig 2 below.
We also have a range of unique cylindrical coalescers for Liquid-Liquid separation, instead of meshpads, and these are often used in series with a BCE-DPV Vane pack downstream. The are used to remove the most stable emulsions, while offering the best efficiency in a compact separator.
It is also a coalescing requirement when 2 or 3 phase separation involving vapour is designed. The gas entering a separator vessel should cause most of the entrained liquid to fall out to the bottom, while the gas passes to the exit, via a demister or vane pack. Meantime the 2 liquid phases flow through a coalescer pack (or if there are solids present, first through a plate pack to remove them), and cause the 2 liquid phases to separate and discharge from different outlets. See Fig 3 example below. For example, a distillation column’s overhead reflux drum is a 3-phase separator and the coalesced oil returns to the column – but if the oil still contains too much water then this water will flash when it re-enters the column and could damage the column trays or packing. So a properly functioning coalescer in the reflux drum is critical.