Demisters are mechanical devices used for the purpose of extracting and removing droplets or steam from a gas stream. They are often fitted with a gas-liquid separator vessel to improve the removal of liquid droplets entrained within a gas stream. Demisters can help improve quality of gas produced, reduce separator equipment costs and save on space and weight. One of the most prominent benefits associated with demisters are the fact that using a demister within our modern processes helps with reducing product loss from one process to the next.
Demisters are used in a variety of settings of which the following are only a few: chemical plants, scrubbers, top of distillation columns, mine ventilation shafts, fish canning plants, gold refineries, oil refineries and petrochemical plants.
Different types of demisters can be identified namely the most common ones are mesh demisters and vane demisters. Mesh Demisters are structured in an interlocked knitted mesh. They are assembled in such a way that the strand orientation is random with a 98-99 percent volume retention. The idea behind this is based on the inertia of entrained droplets. The droplets will move in a straight-line due to inertia which will result in impingement on the mesh strands which results in coalesce into larger droplets. Once the droplets weigh enough they will overcome entraining gas flow and flow back down the gas stream. Vane Demisters are a number of bent plates structure parallel to each other. The gas stream is subsequently forced to move along the path set by the plates. Once again, the inertia of the entrained droplets results in impingement on the plates which lead to coalesce.
Demisters can be made from a variety of different materials. The materials most commonly used are stainless steel, monel, polypropylene, alloy, Teflon etc. While most demisters is made from a single material you can also get demisters made of a combination of material knit together.
Advantages or features associated with a demister are: simple structure, high porosity – less pressure drops, easy to install, operate and maintain, lightweight, durable, easy to transport, corrosion and rust resistant.