Demisting stages

Pump seals and demister wash receive priority on fresh water additions. In the Research-Cottrell process, two demisting stages insure adequate mist removal. Water sprays are mounted below and above the... 

The low-velocity system was a similar system used on land-based installations, and usually comprised a weather louvre, followed by a prefilter and a high-efficiency bag or cartridge filter. Sometimes a demister stage was added and occasionally, bleed extract inertials were supplied as a first stage. 

The four stage exhaust box Includes the oil box separator, the demister pad, the oil mist eliminator, and the synthetic oil baffle. Additional features include ein automotive type spin-on oil filter, a built-in inlet anti-suckback valve that prevents oil from being drawn into the system when the pump is stopped, eind a built-in gas ballast, available on the RA version, which permits pumping with high water vapor loads. 

Titanium is the only one of the more common structural metals which is not attacked by wet chlorine gas and it is thus widely used as a heat exchange material for cooling the gas after the electrolysis stage. Preheating of sodium chloride brine is carried out in titanium plate heat exchangers, while titanium butterfly valves, demisters, and precipitators handle the chlorine gas produced in the cell. The most important use of titanium in chlorine production is as anodes in place of graphite in the electrolytic process. This is covered in more detail later. 

Demister pads. On large columns, these are sometimes placed between stages, as well as at the top of the columns, to promote liquid-vapor disengagement. 

AFSs typically have weather lonvers that are effective in the removal of large objects or contaminants carried in the flow stream. Louvers are followed by screens to captnre large pieces of paper, cardboard, bags, and other objects. The first stage of AFS uses inertial separators such as a demister vane or cyclone separators to remove entrained water droplets. Moisture coalescers are commonly installed downstream of the vane separator in environments with high concentration of liquid moisture in the air. The combination of vane/ coalescer/vane is effective in the removal of particles >10 pm, water droplets, and wet salt [38]. 

The treatment of this collected oleum is described in section 7.3.1. A small amount of oleum mist is formed which has to be removed before the sulphonation stage. Oleum reacts rapidly with organics, leading to poor colour/charring of organic feedstock and by-product formation (e.g. dioxane). Moreover oleum droplets or crystals can cause maldistribution of organic feedstock in the top of the reactor. The installation of a high-efficiency demister is therefore recommended. 

The cooled gas is passed through a two stage HCl scrubber which produces a dilute solution of HCl. This is distilled in a separate unit to make a 31% HCl product. Gas from the HCl scrubber passes through a demister before entering the next step. 

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