Nitrogen economic importance

An appreciable amount of NH3 volatilizes from soil. In some fields, up to 50% of the added ammonium-N volatilizes. In addition to the economic importance of this nitrogen loss, there is also environmental importance. In industrialized regions of the world, NH3 in the atmosphere approaches concentrations high enough to cause toxicity effects on forests. 

Nitrogen, N2, is very unreactive. The Haber process is the economically important industrial process by which atmospheric N2 is converted to ammonia, NH3, a soluble, reactive compound. Innumerable dyes, plastics, explosives, fertilizers, and synthetic fibers are made from ammonia. The Haber process provides insight into kinetic and thermodynamic factors that influence reaction rates and the positions of equilibria. In this process the reaction between N2 and H2 to produce NH3 is never allowed to reach equilibrium, but moves toward it. 

The purine bases are not discussed in the chemical portions of these volumes because of their rather special position in heterocyclic nitrogen chemistry. However, because of their economic importance it seemed advisable to give a short account of some of their effects when administered to animals. 

Photosynthetic bacteria that fix nitrogen are also known to exist in nature but their growth characteristics seem to make certain that they are of negligible economic importance. These anaerobes are of considerable scientific interest because of their unique metabolism and growth characteristics. 

The possibility that the changes which occur in plant nitrogen metabolism under stress conditions may increase the susceptibility of plants to attack by pathogens and predators has important implications with regard to plant performance and adaptation. Most of the work in this area has been carried out with species exhibiting little tolerance to environmental stresses and similar studies of the pathogen-predator relationships of species resistant to particular stresses could be of interest and possible economic importance. 

The economic importance of nitrogen-fixation by leguminous plants has led to extensive study of the process of nodulation and in particular the nature of the host specificity of Rhizobium. Antiserum raised to clover tissue reacts with virulent strains of R. trifolii and to a lesser extent with avirulent strains of the same organism. If the antiserum is pretreated with avirulent cells a purified antibody, specific for the virulent strain, can be prepared. The purified antisera will bind to R. trifolii virulent strains and clover cells, but not to incompatible Rhizobium species. Immunofluorescence can be used to demonstrate that antisera raised against the capsular polysaccharide of R. trifolii binds to the surface of clover root cells, in particular to the tips of the root hairs. Chemical analysis of this capsule shows that it... 

So far we have dealt with weU-defined, intuitively obvious phases gas, liquid solid. But chemical engineers deal with other, less intuitive phases of considerable technical interest and economic importance, for example gases and vapors adsorbed onto solids. Figure 11.21 shows, as an example the equilibrium curve (always called an adsorption isotherm or isotherm in the adsorption literature) for nitrogen adsorbed on zeolite at a temperature well below room temperature, but far above the critical temperature of nitrogen (126.2 K). 

Foamed polymeric materials have several inherent features that combine to make them economically important. Any foamed material is a good heat insulator by virtue of the low conductivity of the gas, usually air, contained in the system. In a rigid foam, the gas contained in the cells may not be exchanged with air for a long time. The thermal conductivities of some common gases in W/m °C at 27°C are as follows air, 0.0262 n-pentane, 0.0144 nitrogen, 0.024 and carbon dioxide, 0.0146. Despite the low conductivity of many chlorofluorocarbons at around 0.012 W/m °C,... 

Urea Process. In a further modification of the fundamental Raschig process, urea (qv) can be used in place of ammonia as the nitrogen source (114—116). This process has been operated commercially. Its principal advantage is low investment because the equipment is relatively simple. For low production levels, this process could be the most economical one. With the rapid growth in hydrazine production and increasing plant size, the urea process has lost importance, although it is reportedly being used, for example, in the People s RepubHc of China (PRC). 

Only nitrogen and water are produced. However, many factors must be considered such as the coproduction of nitrogen oxides, the economics related to retrofitting of auto engines, etc. The following describes the important chemicals based on ammonia. 

There are commercial processes for the direct upgrading of residues under high severe hydroconversion conditions. Other alternatives consider the previous hydrotreatment of the residue, so that the hydrocracking stage does not need to be so harsh. Otherwise, residue conversion could also proceed via carbon rejection methods, these processes fall out the scope of the present book and will not be considered here. However, it is important to mention than VR coking is seen as a more economical alternative than HDP, especially for the more heavy crudes, for which concentrations of metals and nitrogen would require the toughest conditions. 

Anoxic conditions in wastewater of sewer networks require availability of nitrate or other oxidized nitrogen compounds and an extremely low DO concentration. Such conditions are generally not of major importance because of the low nitrate concentrations that typically occur in wastewater. However, anoxic conditions in sewers are artificially established when nitrate is used to control sulfide problems (Section 6.2.7). A low nitrate uptake rate (NUR) is preferred, in this case, to keep the nitrate consumption low for economic reasons. 

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