Rubber lining chlorine

Dry chlorine has a great affinity for absorbing moisture, and wet chlorine is extremely corrosive, attacking most common materials except HasteUoy C, titanium, and tantalum. These metals are protected from attack by the acids formed by chlorine hydrolysis because of surface oxide films on the metal. Tantalum is the preferred constmction material for service with wet and dry chlorine. Wet chlorine gas is handled under pressure using fiberglass-reinforced plastics. Rubber-lined steel is suitable for wet chlorine gas handling up to 100°C. At low pressures and low temperatures PVC, chlorinated PVC, and reinforced polyester resins are also used. Polytetrafluoroethylene (PTFE), poly(vinyhdene fluoride) (PVDE), and... 

In spite of the unsaturation of rubber it is said to be resistant to chemical attack since a few chemical derivatives like chlorinated rubbers, cyclised rubbers and chlorides are formed as protective layers retarding further attack by the chemicals. Properly compounded vulcanizates satisfactorily resist the action of most inorganic acids other than oxidizing acids such as nitric, hydrochloric and sulphuric acids. Rubber linings which are to resist swelling to a lower degree should be "tightly" vulcanized. 

When removing chlorine from the brine more hygienic working conditions are conduced and operations facilitated, as cast iron or steel pumps, vessels and manifolds not protected by rubber lining may be used. 

Hydrochloric acid is stored in rubber lined steel storage tanks and shipped in rubber lined tank cars, pot cars or glass carboys. The following commercial grades of hydrochloric acid are known synthetic hydrochloric acid which is prepared by the reaction of hydrogen with chlorine sulphate acid obtained as a by-product in the manufacture of sodium sulphate hydrochloric acid used in the foodstuff industry and finally chemically pure hydrochloric acid. 

In the batch process wide iron cylinders are used as chlorination vessels (of some 2.5 cubic meters content) the cylinders are rubber-lined and cooled by a coil made of rubber-lined steel or PVC. The vessels are filled with an 18% hydroxide solution and the chlorine enters the solution through PVC pipes under cooling and stirring the pipes end in distributors which are placed just above the bottom of the chlorination vessel. The vessels are closed by covers, and tail gases arc sucked off and led above the roof of the building. 

Typically, the entire contents of a calcium hypochlorite container are emptied into a mixing tank where they are readily and completely dissolved in water. The resulting corrosive solution is stored in and fed from a stock solution vessel constructed of corrosion-resistant materials such as plastic, ceramic, glass, or rubber-lined steel. Solutions of 1% or 2% available chlorine can be delivered by a diaphragm-type, chemical feed pump or metering pump. 

Chlorine Chlorine gas produced in the various electrochemical processes is saturated with water vapor at high temperatures and may also contain brine mist and traces of chlorinated hydrocarbons (originating from piping and rubber-lined vessels), and is normally at atmospheric pressure. Before the chlorine can be used it must (in this order) be cooled, purified, dried, compressed, and if necessary liquefied. 

When there is a relative motion between the corroding liquid and the metal or rubber surface the rate of attack of the damage to the surface is increased. The process is called sweating off with the corrosion product thus exposing the base surface again to corrosion. Otherwise the corrosion product (as a newly formed protective layer) would have prevented or slowed down further corrosion, just as in the case of hypochlorous acid solution on natural rubber lining, where the protective corrosion products exhibit very low cohesion and as such prone to be wiped off by the liquid unlike wet chlorine or hydrochloric acid which form a strong layer of corrosion product well adhered to the rubber surface. 

To precipitate the desired potassium sulfonate, the filtrate [collected in receivers (3 and 3A), together with strong wash liquor] is transferred to the 20,000-liter rubber-lined precipitation tank (4) and the concentrated KCl solution is added. The temperature is maintained at 85°C to keep the byproduct 1,5-disulfonate in solution. The precipitated potassium sulfonate is isolated by continuous filtration on a rubber-covered rotary filter (5 and 6), where it is washed with 5 per cent potassium chloride solution and discharged at approximately 45 per hent solids content into a horizontal trough mixer (7), from which it is pumped to one of two 13,000-liter brick-lined paste storage tanks (8). The paste content is adjusted to 35 per cent solids and brought to neutrality with a small amount of soda ash solution, after which it is pumped either to an autoclave for conversion to 1-amino-anthraquinone or to the chlorinators for conversion to 1-chloroanthra-quinone. 

In the second scheme, brine is fed to a rubber-lined steel tank packed with graphite along with caustic to ensure conversion of chlorine to H0C1 and/or OC1 . Alternately, aeration in a perforated plate tower may be employed to dechlorinate the depleted brine as shown by Yokota.35 36... 

Certain seamless extruded thermoplastics (e.g., CPVC) can be suitable when properly supported but are limited in size. In all but the smaller plants, they are not available in the diameters required for chlorine headers. In the past, rubber-lined piping was used, but its service life was limited and it required more Hanged connections than butt-connected piping. The standard choice for chlorine headers today is still FRP. 

Any equipment used for gas-liquid contact can in principle be used to cool chlorine gas. In practice, spray colunms and packed beds are most common. Beds are more expensive Init, because they offer improved staging, more efficient. Ceramic ring or saddle packing is the type most often found in large units. Vessels are of rubber-lined steel or FRP construction. 

The seal pot vessel and its components must be chlorine-resistant. Rubber-lined and FRP construction are the most common. The vessel must be able to withstand the small pressure and vacuum which may exist in the process. Since it is connected to the chlorine header, thermal expansion and contraction of the pipe must be considered in placement and support of the seal vessel. 

A. Electrolytic Cells. Mercury cells are constructed with carbon steel, and the surfaces in contact with chlorine are rubber-lined. Diaphragm cells are also fabricated with carbon steel bodies and FRP or vinylester covers. The external carbon steel surfaces are usually treated with a high performance catalyzed polyamide or amine-cured painting system with 0.05-0.075-mm thick primer, 0.13-0.15-mm thick intermediate and a 0.13-0.15-mm thick finish coat, the thicknesses referring to the dry films. 

PTFE is resistant to liquid chlorine and to both wet and dry chlorine gas up to 200°C. Tantalum, Hastelloy C, PTFE, PVDF, Monel, and nickel are recommended for membranes, rupture discs, and bellows. The materials of construction for heat exchangers and tanks are generally titanium or Ti-clad, rubber-lined carbon steel, PTFE-lined carbon steel to handle wet chlorine gas or aqueous solutions containing chlorine. 

Polystyrene resins are made from polymerized styrene and have good insulating power. Synthetic rubber, known as styrene-butadiene rubber or chlorinated rubber latex, can be used in paints for floor coverings or tank linings (Fischer and Adams 1990). 

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