Ammonia contamination problem

S. cerevisiae is produced by fed-batch processes in which molasses supplemented with sources of nitrogen and phosphoms, such as ammonia, ammonium sulfate, ammonium phosphate, and phosphoric acid, are fed incrementally to meet nutritional requirements of the yeast during growth. Large (150 to 300 m ) total volume aerated fermentors provided with internal coils for cooling water are employed in these processes (5). Substrates and nutrients ate sterilized in a heat exchanger and then fed to a cleaned—sanitized fermentor to minimize contamination problems. 

Nickel is usually alloyed with elements including copper, chromium, molybdenum and then for strengthening and to improve corrosion resistance for specific applications. Nickel-copper alloys (and copper-nickel alloys see Section 53.5.4) are widely used for handling water. Pumps and valve bodies for fresh water, seawater and mildly acidic alkaline conditions are made from cast Ni-30% Cu type alloys. The wrought material is used for shafts and stems. In seawater contaminated with sulfide, these alloys are subject to pitting and corrosion fatigue. Ammonia contamination creates corrosion problems as for commercially pure nickel. 

Cracking of admiralty metal (C 44300) heat-exchanger tubes has been a recurring problem in a number of refining units and petrochemical process units. For example, ammonia is often used to neutralize acidic constituents, such as hydrogen chloride or sulfur dioxide, in overhead systems of crude distillation or alkylation units, respectively. Stripped sour water containing residual ammonia is used as desalter water at some crude distillation units. This practice causes ammonia contamination of the overhead system even if no ammonia is added intentionally. 

Other problems that can be associated with the high dust plant can include alkaH deterioration from sodium or potassium in the stack gas deposition on the bed, calcium deposition, when calcium in the flue gas reacts with sulfur trioxide, or formation and deposition of ammonium bisulfate. In addition, plugging of the air preheater as weU as contamination of flyash and EGD wastewater discharges by ammonia are avoided if the SCR system is located after the FGD (23). 

Fluid catalytic cracking units present formidable emission control problems. Contaminants are present in both reactor product gas and regenerator flue gas. The reactor product contains hydrogen sulfide, ammonia, and cyanides, plus combined sulfur and nitrogen in the liquid products. Hydrogen sulfide, ammonia and cyanides are handled as part of the overall refinery waste water cleanup. The combined sulfur and nitrogen may be removed by hydrotreating. 

Application of an excessive amount of ammonia solution in the precipitation of tantalum and niobium hydroxides from strip solutions usually ensures good quality of the products. Nevertheless, the method has two general problems. First, hydroxides containing low levels of fluorine contamination... 

A-Hydroxyphthalimide 178a (NHPI Chart 4), described for the first time in 1880, is a weak acid (plfa = 7), which forms highly colored salts with alkali metals, heavy metals, ammonia or amines. More precisely, the two crystalline forms of NHPI reported in the literature display different colors, colorless (white) and yellow, with the colors depending on the solvent in which the NHPI is prepared. The variations in physical properties, including color, have been attributed to synthetic problems , such as impurities, and contamination from a fluorescent compound that could not be isolated or characterized. 

Before the americium can be precipitated as the oxalate, the acidity of the solution must be lowered. This cannot be done by the addition of NaOH or KOH as these cations are carried down with the americium oxalate. The acidity adjustment can be made with NH40H with no product contamination, but processing problems resulting from ammonia vapors mixing with nitric acid fumes have to be avoided. Even with the use of efficient traps, some ammonia vapors escape to form solid ammonium nitrate which plugs glovebox exhaust filters plus, ammonium nitrate also slowly sublimes through the entire exhaust system. 

The availability of pure water will certainly be one of the major environmental issues of the 21s1 Century. Water contamination can originate from domestic, agricultural, agroindustrial or industrial activities, and accidental damages. The major pollutants are heavy metals, radionuclides, ammonia, nitrates and organic compounds. Health problems are associated with each of them, such as leukaemia, saturnism..., as well as modifications of the eco-system, e.g. entrophication of lakes and rivers. The nature of water treatments obviously depends on the kind of contaminants, and zeolite-based processes are of great concern in this field. 

The Straz deposit in the Hamr District of the Czech Republic provides a good example of this problem (Slezak, 1997). Starting in 1968, more than 4 Mt of sulfuric acid, 3 X 10 t of nitric acid, and 1.2 X 10 t of ammonia were injected into the subsurface to mine uranium ore. Now, —266 Mm in the North Bohemian Cretaceous Cenomanian and Turonian aquifers are contaminated with uranium, radium, and manganese and other solutes. The contaminated area is more than 24 km and threatens the watershed of the Plucnice River. 

In the production process of an ammonia plant, a lot of process condensate is produced everyday. Usually, this kind of process condensate contains many contaminants, such as ammonia, carbon dioxide, methanol etc, which can pollute the environment if emitted directly. However, several techniques have been developed to remove the pollutants, such as stripping with natural gas and medium pressure steam, which can be applied one at a time or together, so that the recovery condensate can be reused as boiler feed water or as water makeup for other process operating units. It is very important for the plant to design a process which can solve the problem with minimum cost. This is the work that can be solved by the synthesis of MEN. 

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