Mist eliminator pressure vessels

Gas flows horizontally through the vessel and out through a mist eliminator to a pressure control valve which maintains constant vessel pressure. 

Oxidation Unit The oxidation unit is an empty pressure vessel that takes input reaction gases and blends in additional air from the bleaching column. The extra oxygen provided enables further oxidation to occur and raises the gas mixture temperature to 140°C. At the top of the oxidation unit is a mist eliminator to prevent carry over of acid vapour by entrainment. At the bottom of the vessel is the weak-acid drain. The oxidation unit is constructed from SS304L and has a design pressure of 1200 kPa... 

Pressure. The location of pressure sensors in evaporative crystallizers also affect their reliability. If the operating pressure measurement is made in the vacuum line or condenser, it will be affected by the evaporation rate of the solvent and pressure drop changes due to any incrustation in the lines or mist eliminator. Measurement of the pressure in the vessel headspace circumvents this interaction. The sensor should be equipped with a solvent flush line to ensure that incrustation does not distort the measurement. 

There are other comments to be made about this type of application. The liquid spray nozzle should supply liquid to the face of the mixing elements without appreciably wetting the vessel wall. A 30° full cone nozzle is typically used. Ideally, the spray should consist of droplets in the range 1000 to 2000 p-m range. A quick review of spay nozzle literature indicates that the appropriate spray nozzle for 44 gal/min of alkaline water would operate at about 100 psi pressure drop. Multiple nozzles could be used if a lower liquid-side pressure drop is desired. Fine atomization spray nozzles should be avoided since fine spray drops are difficult to separate in downstream mist eliminator equipment. A Alter or strainer should be installed on the liquid feed to prevent plugging the feed nozzle, especially if the nozzle orifice size is small. 

The scrubbing vessel contains only two internals a gas sparger at the bottom and a mist eliminator at the top. The vessel size is determined by the feed gas flow rate and pressure, the hydrogen sulfide content of the gas, and the desired turnaround time. Design guidelines include... 

For vessels with a mist eliminator, it is preferable to locate the PRV upstream of the mist eliminator. This is to avoid any pressure problem with the blockage of the mist eliminator. 

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