Handling of ammonia

A. Josefson, "Transportation, Storage, Handling of Ammonia," Hmmonia Plant Saf. 27, 175—159, 1986. 

Presently the catalytic selective NOx reduction by ammonia is efficient and widespread through the world for stationary sources. The remarkable beneficial effect of 02 for the complete reduction of NO into nitrogen is usually observed between 200 and 400°C. However, such a technology is not applicable for mobile sources due to the toxicity of ammonia and vanadium, which composes the active phase in vanadia-titania-based catalysts. Main drawbacks related to storing and handling of ammonia as well as changes in the load composition with subsequent ammonia slip considerably affect the reliability of such a process. On the other hand, the use of urea for heavy-duty vehicles is of interest with the in situ formation of ammonia. 

Figure 9-1. Molecular interconversions in handling of ammonia. The major enzyme responsible for interconversion of glutamate and a-ketoglutarate is glutamate dehydrogenase. No free ammonia is ever present during direct transfer of amino groups from alanine or aspartate via transamination to produce glutamate. ALT, alanine aminotransferase AST, aspartate aminotransferase.

D. The overall reaction of the urea cycle indicates that handling of ammonia requires... 

The handling of ammonia safely has been discussed by Brandt(Ref 40) and the toxicity of ammonia fumes by inhalation,by Wheatherby (Ref 55) Ohno(Ref 57) noted that the tojcicity of gaseous ammonia was much smaller than that of sulfur dioxide. Both gases produce irritation of mucous membrane and eyes, bronchitis, hyperemia, hemorrage, endema, exudation and pneumonia. Krop(Ref 58) lists the toxiciry and health hazards of ammonia and other substances used as fuels in rocket propellants[Also see Sax(Ref 82) for additional information on the hazards of ammonia]... 

Safety concerns for the storage and handling of ammonia. This can be minimized by using aqueous ammonia, but with an increase in operating cost. 

Further reductions in NO levels can be achieved by removing NO from the turbine exhaust using selective catalytic reduction (SCR) with ammonia. SCR is an effective method for NO control that can reduce NO levels to about 10 ppm, usually in combination with water or steam injection or lean premix combustors. However, SCR is an expensive technology and the storage and handling of ammonia, a toxic chemical, also pose problems. Possible future restrictions on ammonia emissions may also limit the applieation of this technology. 

The condenser may be dispensed with altogether, but at the expense of convenience in handling of ammonia and with a great reduction in the amoimt of amide that can be made in a given quantity of the solvent. 

Special farm vehicles have been developed for the handling of ammonia as a fertilizer in agriculture. Containers mounted on farm equipment and used as mobile storage for supplying ammonia as it is applied to the soil in the field are called applicator tanks. Containers mounted on farm wagons and used to transport ammonia over the highways and to replenish applicator tanks are called nurse... 

Because an excess of ammonia is fed to the reactor, and because the reactions ate reversible, ammonia and carbon dioxide exit the reactor along with the carbamate and urea. Several process variations have been developed to deal with the efficiency of the conversion and with serious corrosion problems. The three main types of ammonia handling ate once through, partial recycle, and total recycle. Urea plants having capacity up to 1800 t/d ate available. Most advances have dealt with reduction of energy requirements in the total recycle process. The economics of urea production ate most strongly influenced by the cost of the taw material ammonia. When the ammonia cost is representative of production cost in a new plant it can amount to more than 50% of urea cost. 

The tabulation of plant nutrient costs, by product, ia Table 16 shows the principal reasoa for the popularity of anhydrous ammonia as a fertilizer ia the United States. The fob price per ton of nitrogen in the form of ammonia is less than half that for any other nitrogen product. Also, ammonia s relatively high nitrogen content of 82.2% favors low transportation costs, in spite of the need for specialized handling equipment and procedures. 

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

Caution The preparation of methylenecyclopropane must be carried out in an efficient hood because ammonia is evolved. The preparation and handling of oxaspiropentane should be carried out behind a safety screen. 

Guidance on Transfer Connections for the Safe Handling of Anhydrous Ammonia in the UK (1990)... 

Prepare and implement an emergency preparedness and response plan. Such a plan is required because of the large quantities of ammonia and other hazardous materials stored and handled on site. 

The problems of handling liquid ammonia are alleviated in this modification of the sodium acetylide generation procedure. Finely divided sodium is prepared in boiling toluene, the toluene is replaced by THF, and a direct reaction between sodium and acetylene is carried out. The resulting sodium acetylide is employed in ethynylation reactions as before. 

FPN No. 4) For classification of areas involving ammonia atmosphere, see Safety Code for Mechanical Refrigeration, ANSI/ASHRAE 15-1992, and Safety Requirements for the Storage and Handling of Anhydrous Ammonia, ANSI/CCA G2.1-1989. 

Ammonia synthesis is the second largest chemical process, after the production of sulfuric acid (see also Chapter 1). It accounts for about 1 % of the total human-related energy consumption. Roughly 80 % of the ammonia produced is used for fertilizers (either as liquid ammonia or as more easily handled salts such as ammonium nitrate, ammonium phosphate, etc.) and, as such, ammonia synthesis is indispensable for our society. Other applications of ammonia are nitrogen-containing... 

Mass effects due to some ions in salts. It is generally observed that there is a greater instability amongst compounds containing heavy atoms compared with elements in the first periods of the periodic tabie.This can be observed by analysing enthalpies of formation of ammonia, phosphine, arsine and stibine (see previous table for the last three). In the same way, it is easier to handle sodium azide than lead azide, which is a primary explosive for detonators. It is exactly the same with the relatively highly stable zinc and cadmium thiocyanates and the much less stable mercury thiocyanate. 

Hydroxylamine is an oxygenated derivative of ammonia, represented by the chemical formula NH2OH. Hydroxylamine is usually handled as an aqueous solution or as salts. The concentrated free base is susceptible to explosive decomposition. 

Caution. Sodium amide is a very reactive substance it combines with oxygen and reacts explosively with water. The submitters recommended keeping the amide in sealed glass containers in an atmosphere of ammonia. The checkers preferred the use of petroleum fractions for greater convenience in handling they have kept specimens under this solvent for three years without appreciable loss in activity. 

The main advantage of this form of unit is the very great reduction in the volume of gas handled by the compressor. Thus, 1 kg of water vapour at, say, 311 K, with a volume of 22 m3 and latent heat about 2560 kJ/kg, passes this heat to ammonia at a temperature of say 305 K. About 2.1 kg of ammonia will be vaporised to give a vapour with a volume of only about 0.22 m3 at the high pressure used in the ammonia cycle. 

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