Introduction to Mist Eliminators

 

The purpose of the mist eliminators is to remove the mist from the components of a gas stream which will in turn recover products with high value, improve the emitting capability of the machine, to make sure downstream machines are protected as well as increase the level of purity of the products.

The most common and widely used kind of mist eliminators are the wire mesh. The pads used by the wire mesh are knitted which is able to remove all the liquid droplets separated from the gas streams and trapped in the pads. The wire mesh type of mist eliminators is made out of metal material that is knitted into mesh. It is the most widely used method of removing all the trapped liquid droplets with diameter 3 mm or less. These droplets are separated from the gas stream that has a velocity of more than 1 foot per second. The pads of wire mesh eliminators are more commonly applied in vertical flows but it can also be used in horizontal flow as well. The wire mesh type of mist eliminators has gained popularity because of its high level of efficiency, the pressure drop is average and the cost for investment as well as during operation is not very high.

There are three ways by which a wire mesh eliminator can separate the liquid droplets present in the gas stream – Brownian diffusion, inertial impaction and direct interception. These three methods require that the mist must have surface contact with the wire mesh. This is when the liquid droplets are collected after having removed from the gas stream. The material used in making the mesh is out of woven metal fibers. These are usually many sheets of mesh that are arranged on top of one another in order to give the pads a high level of control during permeation. The most common type of mesh pad has a thickness of around six inches. The diameters of the pads, on the other hand, are usually three to five per cent more than that of the diameter of the equipment used. This is to make sure that there is less mist that is coming through the pads.

Once area wherein a wire mesh eliminator is commonly seen is the gas-liquid contacting towers. These mesh pads are usually employed in the fume hoods to make sure that 99 per cent of the mist that have a diameter of 2 microns or below will be trapped and separated from the gas stream. The advantage of using wire mesh includes high efficiency, purchasing and operating cost is lower, existing equipment can make use of the pads and each of these pads are manufactured to give specific level of efficiences. The disadvantages includes a higher pressure drop compared to the baffle type, not recommended if the droplets are smaller than 3 mm, while the size of the droplets increases, the efficiency decreases and there is a tendency for the pad to clog.

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By valariearthur

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