Ammonia contamination

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. 

Gasiorowski, S. A., Hrach, Jr. Frank, J. 2000. Method for Removing Ammonia from Ammonia Contaminated Fly Ash. US Patent No. 6,077,494. 

If nitrogen compounds are present, the combined chlorine is in the form of chloramines, which are also volatile but exhibit minimal biocidal effect. Under circumstances of high nitrogen (ammonia) contamination in cooling systems, it may not be possible to regularly achieve breakpoint halogenation without a severe risk of corrosion to copper and other system components. 

Ammonia, produced due to the coexistence of H2 and N2 at high temperatures in the presence of catalyst, was estimated to be in the concentration range of 30 to 90 ppm [37, 38], Uribe et al. [39] examined the effects of ammonia trace on PEM fuel cell anode performance and reported that a trace in the order of tens of parts per million could lead to considerable performance loss. They also used EIS in their work. By measuring the high-frequency resistance (HFR, mainly contributed by membrane resistance) with an operation mode of H2 + NH3/air (feeding the anode with hydrogen and ammonia), they obtained some information related to membrane conductivity, and found that conductivity reduction due to ammonia contamination is the major cause of fuel cell degradation. 

Figure 6-1. Frequency of NPL Sites with Ammonia Contamination... 

Ammonia contamination can affect both the air and fuel sides, regardless of from which side the contamination enters. Introduction of acid into the fuel cell to displace the ammonium ion from the proton exchange sites was unsuccessful in promoting performance recovery. Introduction of an air bleed was also of no impact. The cell will slowly recover performance after the contamination introduction is stopped, but the extent of this recovery will depend on the amount of contamination present and the cell might not fully recover even after several days. 

The only method that has served to mitigate contamination by ammonia is by passing the fuel stream through a tube containing a H+ exchange resin, which prevented ammonia contamination of the fuel cell [153]. 

Although the susceptibility to SCC is decreased by annealing the brasses, they are still sensitive to seasonal cracking in ammonia contaminated environments, particularly the agricultural land. Literature is abundant on the subject and the readers may refer to some of the references cited at the end of the chapter. 

Take as one of the earlier samples from overside bottles. Temporary storage in glass bottles appears satisfactory if filtered samples are frozen in a deep freeze and analyzed within a few weeks. Observe all the precautions outlined in II.8.G.2. for exclusion of ammonia. Although ammonia contamination prior to analysis should, theoretically, not affect results for urea it is best kept to a minimum. 

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. 

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