Balanced metrics

Total hafnium available worldwide from nuclear zirconium production is estimated to be 130 metric tons annually. The annual usage, in all forms, is about 85 t. The balance is held in inventory in stable intermediate form such as oxide by the producers Teledyne Wah. Chang (Albany, Oregon) and Western Zirconium in the United States Ce2us in France Prinieprovsky Chemical Plant in Ukraine and Chepetsky Mechanical Plant in Russia (crystal bar). 

Strong growth in demand during the period 1985—95 from existing and new appHcations led to firm pricing and expansion of world capacity. Total world demand in 1995 was estimated to be approximately 60,000 metric tons. Balance of capacity and demand at that time resulted in a selling price of 16.00/kg. More recently (ca 1997), prices have dropped to less than 10/kg. 

Partial Oxidation of Ethylene to Ethylene Oxide. About 3.3 million metric tons of ethylene oxide were produced worldwide in 1988. Of this, about 70% was converted into ethylene glycol, and the balance went into detergents and other appHcations. An excellent review of ethylene oxide synthesis has been written (66). 

Ethylene oxide is produced in large, multitubular reactors cooled by pressurized boiling Hquids, eg, kerosene and water. Up to 100 metric tons of catalyst may be used in a plant. Typical feed stream contains about 30% ethylene, 7—9% oxygen, 5—7% carbon dioxide the balance is diluent plus 2—5 ppmw of a halogenated moderator. Typical reactor temperatures are in the range 230—300°C. Most producers use newer versions of the Shell cesium-promoted silver on alumina catalyst developed in the mid-1970s. 

The production of chlorobenzenes in Eastern Europe is concentrated in the former Soviet Union, Poland, and Czechoslovakia. The estimated capacity is 200—250 thousand metric tons the former Soviet Union has most (230 thousand tons) of this capacity. There is trade between Eastern and Western Europe on monochlorobenzene and the dichlorobenzenes, but the net trade balance is probably even at about 20 thousand metric tons. Eastern Europe exported 20 thousand metric tons of monochlorobenzene principally to Germany, Erance, and the United States. 

Cumene production follows the demand for phenol and its derivatives. In 1987, the U.S. cumene demand, estimated at 1.9 million metric tons, was supphed by about 1.8 million metric tons of domestic production imports made up the balance. Based on a trend from 1985 on, the demand is projected to increase at about 3% per year through 1995. 

Fig. 9. Schematic steam balance where the numbers represent steam flows in metric tons per hour. See Table 3.

Table 3. Steam Balance, Flows in Metric Tons per Hour ...

The ISO has published standards for acceptable limits for residual imbalance in various classifications of rotor assemblies. Balancing standards are given in oz-ins or lb-ins per pound of rotor weight or the equivalent in metric units (g-mm/kg). The oz-ins are for each correction plane for which the imbalance is measured and corrected. 

Yield and other mass-related metrics such as atom economy, reaction mass efficiency and mass intensity have been examined by Constable et al with regard to their significance concerning greenness and costs. The importance of using a (product) concentration term, which can be mass intensity or mass index, is additionally emphasized by Laird et al This is in compliance with Winterton, who in his twelve more green chemistry principles demands the establishment of full mass balances. 

The earher the information on resource efficiency is used in synthesis design, the more efficient process development wiU be. Therefore, appropriate metrics are initially applied to a choice of literature protocols and prehminary experimental data. As knowledge about the process increases, for example, during scale up, it is successively fed into the mass balance. In addition, environmental impacts associated with the mass balance can be evaluated. 

Mass balancing unifies all metrics such as yield, atom economy, TON, TOF, and so on. Therefore, the application of mass indices and environmental factors presents itself as an integrating solution with moderate data demands. A fair comparison of alternative... 

These charges exactly balance, and the material is an insulator. Hole doping is achieved by adding oxygen interstitials to the charge reservoir to give a nonstoichio-metric CuOn composition ... 

Fig. 16.1 Mean energy consumption of a 125 000 metric tonnes per year NaOH plant according to the anodic balance and with brine acidification. 

In 1978, U. S. recovered sulfur production and shipments were balanced at 4.1 MM metric tons each (11). Year end capacity has been estimated at 6.2 MMLT and 6.4 MMLT for 1980 and 1985, respectively (12, 13). Assignable daily capacity at year end 1978 was 9,132 metric tons for refineries, 5,464 metric tons for natural gas processing plants, and 1,682 metric tons from H2S and acid gas... 

The determination of OXPHOS activity is best made with the aid of spectrophoto-metric assays [55, 65]. Using a judicious set of electron donors and acceptors, it is possible to measure the activity of MRC complexes either isolated or in combination, as described below. Beside the residual activity of each complex, ratios of their respective activities are of fundamental importance. Indeed, the balance between complexes (the ratio between their activities) determines on the one hand the relative access of each dehydrogenase to the MRC, and on the other hand the amount of superoxides possibly escaping the chain [55]. It is therefore quite important to both analyze residual activities corrected for the variable amount of mitochondria using the citrate synthase as reference enzyme, and the various ratios inside the MRC [66,67]. It is also important to note that enzyme determination is (supposedly at least) done under maximal rate (Vmax) conditions only, often leaving aside any discrete anomalies possibly affecting affinity and regulatory properties. 

Although the principle is easy to state and, as we will show, many of the component properties are measurable, one critical implementation issue is the trade-off when the new chemical is better on some but not all metrics. How these different factors will be balanced in the case of mixed results will require careful consideration of the... 

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