Hydrogen captive

Production. Global hydrogen fluoride production capacity in 1992 was estimated to be 875,000 metric tons. An additional 204,000 metric tons was used captively for production of aluminum fluoride. Worldwide capacity is tabulated in Table 5 (38). Pricing for hydrogen fluoride in 1990 was about 1.52/kg (39). 

North America accounts for about 38% of the worldwide hydrogen fluoride production and 52% of the captive aluminum fluoride production. Table 6 (38) summarizes North American capacity for hydrogen fluoride as weU as this captive capacity for aluminum fluoride production. In North America, HF is produced in the United States, Canada, and Mexico, but represents a single market, as weU over 90% of the consumption is in the United States. 

Use of 1,3 cycloaHphatic diamines in polyamides may be similarly limited by internal amide dehydration of the conformationaHy labile cis isomers to form a tetrahydropyrimidine (38) rather than high molecular weight polyamide. 1,3-Cyclohexanediamine is, however, a component of Spandex polyureas Du Pont uses the hydrogenation product of y -phenylenediamine [108-45-2] (24) captively to produce Lycra (see Fibers, elastomeric). 

Economic Aspects. Most hydrogen sulfide is made and used captively or sold by pipeline at prices which are highly variable, depending on locahty. Production ia the United States exceeds 1.1 X 10 t/yr-It has been estimated that 2.4 x 10 t/yr of sulfur are recovered from H2S-containing refinery streams and 1.8 x 10 t/yr of sulfur are recovered from H S-containing natural gas (120). 

In a study with captive male American kestrels (Drouillard et al. 2001), birds were dosed with Aroclor-contaminated diet and the toxicokinetics of 42 PCB congeners contained therein was stndied. Those congeners that were most rapidly cleared contained vicinal meta-para hydrogen substituents on at least one phenyl ring. This provides further evidence for the importance of open (i.e., not substituted by chlorine) meta-para positions for metabolic attack, an issue that will be returned to in the next section (Section 6.2.3). 

This procedure emphasises the overall division of oxidants into one-equivalent and two-equivalent types defined in terms of how many equivalents of reducing species, e.g. electrons or hydrogen atoms, are taken up by the oxidant in the primary act, as deduced from the behaviour of the oxidant towards either hydrazine , sulphite ion or captive ligand according to the schemes (a)-(c) respectively. 

Caprylic/capric triglyceride, cosmetically useful lipid, 7 833t Capsanthin, 24 560 Capsicum group, 23 164-165 Capsorubin, 24 560 Capsular polysaccharides, 20 455 Capsules. See also Microencapsulation extruding, 16 446 pharmaceutical, 18 708 produced by spray drying, 16 447-448 Capsule standard platinum resistance thermometers, 24 445 Captafol, 23 629, 647 Captan, 23 628 Captiva camera, 19 307 Captive hydrogen, 13 841 Captopril, 5 148... 

Available statistics or market surveys about hydrogen capture the real production volumes only partially, as they usually consider only captive production, i.e., the directly produced hydrogen (e.g., in steam reformers), as for instance in refineries or fertiliser plants.1 Besides this, hydrogen is produced in significant amounts as a by-product from the manufacture of various chemical products, such as chlorine or ethylene, as well as from refinery processes (see also Section 10.9). Where this hydrogen cannot be internally utilised further, for instance for hydrogenation in... 

Hydrogen for industrial facilities is mainly produced where it is also immediately used (so-called captive hydrogen ). Only around 5% of total hydrogen production is sold on the free market and transported in liquid or gaseous form in trailers or pipelines (so-called merchant hydrogen ). Hydrogen pipelines have already been operated by the chemical industry in the United States and in Europe (particularly Germany, France and the Netherlands) for decades (see also Chapter 12). 

Current world hydrogen prodnction is approximately 50 milhon tons per year (45 billion kg per year), which represents 2% of world energy demand (Raman, 2003). However, cnrrent total annnal worldwide hydrogen consumption is in the range of 400-500 billion Nm Of this qnantity, approximately 97% is represented by captive or internal production and only about 3% is provided from merchant sonrces (MEDI, 2003). 

The use of iron oxides in the presence of CO, a very old method for obtaining hydrogen, used during the Second World War to inflate captive anti-aircraft balloons. 

Captive hydrogen Sources Supply (10 mVday) Uses %) ... 

---