Metal production factors

The plutonium extracted by the Purex process usually has been in the form of a concentrated nitrate solution or symp, which must be converted to anhydrous PuF [13842-83-6] or PuF, which are charge materials for metal production. The nitrate solution is sufficientiy pure for the processing to be conducted in gloveboxes without P- or y-shielding (130). The Pu is first precipitated as plutonium(IV) peroxide [12412-68-9], plutonium(Ill) oxalate [56609-10-0], plutonium(IV) oxalate [13278-81-4], or plutonium(Ill) fluoride. These precipitates are converted to anhydrous PuF or PuF. The precipitation process used depends on numerous factors, eg, derived purity of product, safety considerations, ease of recovering wastes, and required process equipment. The peroxide precipitation yields the purest product and generally is the preferred route (131). The peroxide precipitate is converted to PuF by HF—O2 gas or to PuF by HF—H2 gas (31,132). 

One factor that has done a great deal to harm the reputation of plastics is that in many cases designers and engineers have, after deciding tentatively to try to introduce plastics, then lavishly copied the metal product it was to replace. Too much emphasis cannot be given to the general principle that plastics are to be used based on their behavior... 

The form in which vanadium metal product is obtained is determined by the physicochemical conditions prevalent during reduction. This factor, elaborated below for vanadium production in ingot and powder forms, is typically illustrative of the calciothermy as... 

The final quality of a cast metal product is broadly dependent upon any factors which will have an effect on the metal solidification. The mechanical properties of the casting will largely be determined by the cast structure. Any structural defects occurring in the cast product may be transferred to the final product. Thus any process which would reduce defects and improve the metal structure of a cast product would clearly be of benefit to the foundry industry. 

At present the iron-based alloys diffusion saturation by nitrogen is widely used in industry for the increase of strength, hardness, corrosion resistance of metal production. Inexhaustible and unrealized potentialities of nitriding are opened when applying it in combination with cold working [1-3], It is connected with one of important factors, which affects diffusion processes and phase formation and determines surface layer structure, mechanical and corrosion properties, like crystal defects and stresses [4, 5], The topical question in this direction is clarification of mechanisms of interstitial atoms diffusion and phase formation in cold worked iron and iron-based alloys under nitriding. 

The emission inventory of dioxin-like compounds in South Korea was determined during two preliminary studies (KMOE, 2001, 2002a). For emission factors, the preliminary study (KMOE, 2001) adopted measured values for waste incinerators and the values of UNEP chemicals Toolkit (UNEP Chemicals, 2001) for the other sources. Estimated PCDDs/DFs emission in 1999 ranged from 1163 to 1595 g I-TEQ yr-1 due to uncertainties in emission factors and activities (Table 2.6). Besides the preliminary estimate, since the late 1990s extensive measurements of PCDDs/ DFs have been performed at waste incinerators and the emission data by 2004 had been compiled for 1800 incinerators. Moreover, nationwide industrial sources have been investigated every year since 2001 34 fer-rous/non-ferrous metal production factories in 2001, 114 non-ferrous metal and mineral production factories in 2002, 73 chemical/energy/ landfill factories and crematories in 2003, and 63 municipal wastewater treatment plants and 9 types of vehicles in 2004. By 2005, measurements of total dioxin emissions had been made on 288 industrial sources. Based on these measurements, KMOE made the first official estimate of PCDDs/DFs emission in South Korea. It has been estimated that the total PCDDs/DFs emission was 1021 g I-TEQ yr-1 in 2001 (KMOE website) (Table 2.6). This emission was approximately 62% of that... 

In order to assess the internal consistency of the emissions, as shown in Table 8, a calculation was made whereby the mean atmospheric input was equated to the world metal production emitted to the atmosphere plus natural emissions and other sources to the atmosphere. With the exceptions of Cu and Zn, the quantities of emissions balance rather well. There is no obvious reason why Cu is out of balance by nearly a factor of 2 (atmospheric input > sources). For Zn, with an imbalance of 1.7 for atmospheric input > sources, there is an obvious problem with other sources in that the impact of rubber tire wear. This source term will be addressed in the next section. However, even with this term, the right side of the equation would increase to a maximum emissions figure of 300,000 tyr (Table 8). It is possible that maximum Cu and Zn emissions to the atmosphere have been overestimated but there is no way to check this with the available data. 

The volume occupied by each approximately spherical Ni metal product particle, 20 to 50 nm diameter [7], is considerably less than that of the salt from which it was derived. The growth of nuclei, interface advance, is less strongly influenced by the availability of water vapour. The factors which determine the limiting size of each small particle of the product metal have not been established. 

Table 4. Nucleosynthesis results for 15 massive star models computed up to silicon ignition (Langer Henkel 1995). The symbols have the following meanings Mi is the initial stellar mass, and Z the metallicity. asc is the semiconvective mixing parameter, with asc = 0 corresponding to the Ledoux criterion, asc = oo to the Schwarzschild criterion for convection. Mf is the final stellar mass, Mco the final CO-core mass and Mrem is the assumed remnant mass. Me and Mo are the total mass of carbon and oxygen ejected by stellar wind mass loss and by the supernova explosion (initially present amounts are not subtracted). The values /13. .. /is designate production factors for 13C, 14N, 170, and lsO, and AY/ AZ is the ratio of the net yields of helium to metals.

FIGURE 5. Dependence of the 17O production factor (ratio of the ejected versus the initial amount of 170) on the initial stellar metallicity Z, according to models of Langer Henkel (1995 LH95) and Woosley Weaver (1995 WW95). The steep increase with Z is atypical for secondary isotopes. This is demonstrated by comparison with the 13C production factor of the 25 M LH95 models (dotted line), which shows no dependence on Z. 

As stated above, 170 is produced as a secondary isotope in the CNO cycle, and its final abundance depends primarily on the initial lsO abundance in the star. However, the latter statement holds only for a fixed burning temperature. That the situation of 170 is more complex can be seen in Fig. 5, which displays the 170 production factor for various stellar masses as function of the initial stellar metallicity Z. Note that the initial metal distribution in the models of Langer Henkel (1995) is the solar distribution scaled according to the actual metallicity. 

Since the initial amount Mm of a metal isotope in a star is proportional to Z, and the produced and expelled amount Mout of a secondary isotope is also proportional to Z, its production factor / = Mout/Min should be independent of Z. This is in fact so for many secondary isotopes as can be seen at the example of 13C in Fig. 5. However, this figure shows also that — in contrast to the expectation — the 170 production factor increases strongly with metallicity. 

Let us compare the behaviour of 170 to that expected for a primary isotope. In this case, again Min oc Z, but the production does not depend on the initial metal content, i.e. Mout — const., and thus / oc A I.e., the production factor of a primary isotope decreases with increasing Z. This is just opposite to the behaviour of 170. 170 is thus not behaving like a primary nor like a secondary isotope its production factor / is roughly proportional to Z, and thus Mout oc Z. I.e., 170 may be called a super-secondary isotope. 

Figure 6. 180 production factor (cf. Fig. 5) in solar metallicity 20M0 models of (Langer Henkel 1995 LH95), as function of the semiconvective mixing parameter asemiconv (cf. Fig. 3 note especially that the entry for the largest value of asemiconv corresponds to aSemiconv = oo). 

Casting Sands. The production of metal products requires that the molten metal be cast into near-net shapes. The steel industry uses casting sand because it is inexpensive, is readily available, efficiently absorbs heat at a predictable rate, and is easy to use. The sand is blended with water, carbon, and other admixture compounds to improve the compaction of the sand, the heat capacity, and other properties. The sand is pounded around a mold, the mold is removed and the molten metal is poured into the sand molds. Unfortunately, the sand immediately next to the cast part is typically not reusable. Carbonization, fusion, and other factors make this material unusable and must be disposed of in landfills. Many of the companies that cast parts are implementing new programs to separate the burned material from undamaged sand to recycle the sand for more castings and reduce the amount shipped to landfills. 

Fig. 11. Production factors for the elements between C and Mo following the SN explosion of stars with metallicity Z = 0.02 and with different masses (13 M triangles 15 iff squares 20 M open circles 25 M filled circles 30 M pentagons 35 iff asterisks in open circles). In all cases, the production factors have been normalised to an oxygen production factor of unity. The lines refer to production factors obtained by integrating over a Salpeter IMF (dn/dM oc M 2,35). The solid line refers to an assumed relation between the mass of the SN residue, which is equivalent to the B6Ni yields, and the progenitor mass (0.15, 0.10, 0.08, 0.07, 0.05 and 0.05 iff for the 13, 15, 20, 25, 30 and 35 M stars). The dotted line is obtained by assuming that the B6Ni yield of each SN is 0.05 M (from [28])...

Ceramics are generally considered to be inert materials that do not undergo corrosion. In fact, however, corrosion of ceramics is generally an important cost factor in metals production and in most other technologies that use them. While the corrosion of metals is an oxidative process, the corrosion of ceramics can be oxidative, reductive, or not involve any electron transfer and still be controlled by the electrochemical nature of the material and environment. 

Nonferrous ores occur mainly in the form of pyrites. The large emission factors associated with nonferrous metal production derive from the fact that sulfur contained in the ores escapes mostly as S02 in spite of control measures. The most significant contribution to S02 emissions from industrial processes lies in the manufacture of sulfuric acid. The conversion of pulp to paper leads to emissions of H2S and organic sulfides, but their magnitude is comparatively small. The combustion of natural gas, which is another important source of energy, causes negligible sulfur emissions so that it is not even listed in Table 10-8. This fuel has a low sulfur content to begin with, and almost all of it is removed before use. 

Emission factors for sulfuric acid production are 27.4 kg/ton acid for traditional technology and only 3.3-5.3 kg/ton acid for the advanced technologies. During smelting of sulfide ores, a simple stoichiometric relationship is assumed to give SO2 released per metal production in kg/ton 2000 for copper (CuFeS2) KXX) for zinc (ZnS) and 320 per lead (PbS). The effectiveness of desulfurization in this industry was about 50% in China during 1990-1995. 

Corrosion processes affect many areas of human activity in which metal products are used. In general, as levels of economic development increase, so do costs incurred as a result of corrosion. It is estimated that the costs attributable to the corrosion of metalfic materials amount to 4 percent of the gross domestic product of the developed coxmtries. And this cost, representing a loss of resources, would be even higher if methods of protection against corrosion were not so widely appfied. It is estimated that because of this protection, populations are able to reduce these potential losses by a factor of about 30 percent. 

In the last decade, the business environment for non-ferrous metals production in Japan experienced severe conditions. The Yen became stronger against the dollar very rapidly and the tariff for metals became lower step by step. These factors caused a fall in the domestic zinc price (Figure 1). In addition, domestic demand of zinc stayed below 800,000 t/y as shown in Figure 2. 

Examination of a corrosion system experiencing MIC should include (1) metal composition (2) macroscopic examination, (a) visible fouling, (b) localized corrosion, (1) forms, (2) location, (3) material within pits, and (c) corrosion products. Factors of interest in evaluating the environment of a corroding system include the following (1) presence, absence, cycles of light, (2) aqueous medium, (a) temperature. 

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