Carbon tower

Decomposition with Moist Activated Carbon. The waste gas stream is passed through packed activated carbon towers where water is fed at the top of the towers. The water is normally recycled. If the hydrochloric acid concentration in the recycled water exceeds 10%, the decomposition efficiency is greatly reduced. Thus, a sufficient supply of fresh water must be assured and a hydrochloric acid stream continuously taken out (33). 

Waste Disposal. Because of its low Boiling poiat and high, toxicity, measures must be taken to prevent the entrance of phosgene iato drains or sewers. If recycle of phosgene is not feasible, phosgene waste can be handled by one of the decomposition methods mentioned above, ie, caustic scmbbiag, moist activated carbon towers, or combustion. 

Maintenance and production records, along with the used lean and rich glycol analyses, can be very helpful to the troubleshooter. A history of filter element, carbon, tower packing, and firetube changeouts can sometimes be very revealing. The frequency of pump repairs and chemical cleaning jobs is also beneficial. With this type of knowledge, the troubleshooter can quickly eliminate and prevent costly problems. 

If I ever have to design an amine plant I will know, for example, that the temperature of the lean amine solution entering the absorber should be about 10°F higher than the inlet gas temperature to prevent hydrocarbon condensation and subsequent foaming, that the reboiler tube bundle should be placed on a slide about six inches above the bottom of the shell to provide good circulation, that about two percent of the total circulating flow should pass through the carbon towers, and many other necessary requirements. 

Sodium bicarbonate is made by the carbonation of salt and ammonia in carbonation tower (Solvay process) ... 

A detailed description of salt mining will be postponed until the next chapter, but it is important to note that soda ash is made from both limestone and salt, the two major raw materials. As outlined in Fig. 5.2, the brine (salt solution) is mixed with ammonia in a large ammonia absorber. A lime kiln, using technology similar to that discussed earlier, serves as the source of carbon dioxide, which is mixed with the salt and ammonia in carbonation towers to form ammonium bicarbonate and finally sodium bicarbonate and ammonium chloride. Filtration separates the less soluble sodium bicarbonate from the ammonium chloride in solution. 

Fig. 26.2. A carbonating tower in the ammonia-soda process, 69 feet high, and 6 feet in diameter. (1) entry for ammoniated brine, used when the tower is being cleaned (2) entry for the ammoniated brine for the regular bicarbonate precipitation (3) and (4) carbon dioxide entries (5) outlet for bicarbonate slurries (6) cooling water inlet (7) cooling water outlet (8) escape for uncondensed gases.

Calcining the Bicarbonate to Soda Ash. Crude filtered bicarbonate is continuously calcined by indirect heating. Various techniques are used to heat, 2430 kj/kg (581 kcal/kg) this material to 175—225°C in the calciners. Carbon dioxide, produced at 95% or higher purity, is compressed and recycled to the carbonating tower in order to enrich the makeup kiln-gas feed. The hot soda ash discharged from the calciner is cooled, screened, and packaged, or shipped in bulk. This product, called light ash has a bulk density of around 590 kg/m3. A certain amount is sold in this form the majority, however is converted to dense ash. 

About two percent of the total circulation flow should pass through the carbon towers, is invaluable to the design. Seek out advice from experts on a particular process. These can be in-house or consultants. 

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