Water process, gases stripped

The bottoms from the stripper (40—60 wt % acid) are sent to an acid reconcentration unit for upgrading to the proper acid strength and recycling to the reactor. Because of the associated high energy requirements, reconcentration of the diluted sulfuric acid is a cosdy operation. However, a propylene gas stripping process, which utilizes only a small amount of added water for hydrolysis, has been described (63). In this modification, the equiUbrium quantity of isopropyl alcohol is stripped so that acid is recycled without reconcentration. Kquilibrium is attained rapidly at 50°C and isopropyl alcohol is removed from the hydrolysis mixture. Similarly, the weak sulfuric acid process minimizes the reconcentration of the acid and its associated corrosion and pollution problems. 

Hereafter we will treat only perfectly mixed stirred-tank reactors, which are considered, and rightly so, as the reference reactors. We consider a rather general case of biotransformation processes involving aerated systems comprising both water and hydrophobic compounds. These last components are often volatile, as in the case of aroma. As a result, losses by gas stripping can be important. 

Volatilization from surface waters is not expected to be a significant source of isophorone in the atmosphere, since this is anticipated to be a slow process (based on the Henry s Law Constant of 4.55x10 atm m mol"). Wastewater treatment plants may, however, emit some isophorone from influent water to the air, particularly if gas stripping methods are used (Hawthorne and Sievers 1984, Hawthorne et al. 1985). Drinking water plants that practice aeration of influent water may also emit small amounts of isophorone to air. 

Natural gas plants Natural gas Water Glycol Gas drying for further processing or to achieve product specification Stripping practiced for solvent recovery... 

In such processes, the creation of a permanent gas phase by means of an (inert) gas allows a low-boiling compound (often water) to be stripped from the liquid phase at temperatures lower than the reactant boiling points. 

An important feature of Claus plants is their ability to decompose COS effectively and incinerate sour water stripper gas in the thermal reactor section. Sour water stripper gas contains NH3, HCN, and H2S produced in the coal gasification process. As previously discussed in the wet scrubber particulate removal portion of this section, these trace compounds are removed from the coal gas in the scrubber water. This "sour water" is then steam stripped to purify the water and to generate the small sour-water stripper gas stream. The Claus process is generally the simplest and most effective way to dispose of this stream. 

In a biological system, Ng is often bubbled through a fermentor to maintain anaerobic conditions. As the Ng bubbles through the fermentor, the gas strips water from the liquid. Consider an isothermal continuous fermentation process operated at 30°C, where 0.5 min of water are evaporated. 

This carbon dioxide-free solution is usually treated in an external, weU-agitated liming tank called a "prelimer." Then the ammonium chloride reacts with milk of lime and the resultant ammonia gas is vented back to the distiller. Hot calcium chloride solution, containing residual ammonia in the form of ammonium hydroxide, flows back to a lower section of the distiller. Low pressure steam sweeps practically all of the ammonia out of the limed solution. The final solution, known as "distiller waste," contains calcium chloride, unreacted sodium chloride, and excess lime. It is diluted by the condensed steam and the water in which the lime was conveyed to the reaction. Distiller waste also contains inert soHds brought in with the lime. In some plants, calcium chloride [10045-52-4], CaCl, is recovered from part of this solution. Close control of the distillation process is requited in order to thoroughly strip carbon dioxide, avoid waste of lime, and achieve nearly complete ammonia recovery. The hot (56°C) mixture of wet ammonia and carbon dioxide leaving the top of the distiller is cooled to remove water vapor before being sent back to the ammonia absorber. 

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