Energy metrics

A metric s robustness can be very much affected by how decision rules, boundaries, and heuristics are set. The energy metric, in particular, may become perverse when defined solely in terms of direct energy use, that is, the energy content of... 

Metrics that cover elements not usually included in the basic metrics, for example, transportation energy metric complements basic energy metric and... 

Uranium Enrichment. Enrichment of uranium-235, from 0.711 percent as present in natural uranium, is essential to the economical operation of the light water reactors. The fuel life for these reactors is a function of the enrichment. With 3.4 percent U-235 fuel, the pressurized light water reactors produce 33,000 megawatt-days of energy/ metric ton during the three years the fuel is in the reactors. In the naval submarine and ship reactors using highly enriched U-235, the fuel life exceeds ten years. 

In simple relaxation (the fixed approximate Hessian method), the step does not depend on the iteration history. More sophisticated optimization teclmiques use infonnation gathered during previous steps to improve the estimate of the minunizer, usually by invoking a quadratic model of the energy surface. These methods can be divided into two classes variable metric methods and interpolation methods. 

Coa.1 Reserves. As indicated in Table 2, coal is more abundant than oil and gas worldwide. Moreover, the U.S. has more coal than other nations U.S. reserves amount to about 270 biUion metric tons, equivalent to about 11 x 10 MJ (1 x 10 ° BTU = 6600 quads), a large number compared to the total transportation energy use of about 3.5 x lO " MJ (21 quads) per year (11). Methanol produced from U.S. coal would obviously provide better energy security benefits than methanol produced from imported natural gas. At present however, the costs of producing methanol from coal are far higher than the costs of producing methanol from natural gas. 

Olefin Feedstock Selection. The selection of feedstock and severity of the cracking process are economic choices, given that the specific plant has flexibiUty to accommodate alternative feedstocks. The feedstock prices are driven primarily by energy markets and secondarily by supply and demand conditions ia the olefins feedstock markets. The prices of iadividual feedstocks vary widely from time to time as shown ia Figure 2, which presents quarterly prices of the various feedstocks ia the United States from 1978 through 1991 ia dollars per metric ton (1000 kg) (4). 

The principal producers of aluminum trifluoride in North America are Alcan, Alcoa, and AUiedSignal. It is also produced in other countries, eg, France, Mexico, Norway, Italy, Tunisia, and Japan. Total worldwide production of aluminum trifluoride in 1990 was 400,000 metric tons and the price was 1100/t. In 1993, because of excess recovery of fluorine values, use of energy efficient smelters, and the worldwide economic climate, the price was down to 750/t. 

Ratio of total final consumption of energy to gross domestic product (GDP). Measured in metric tons of oil equivalent per 1000 of GDP at 1985 prices ... 

MSW incinerators (qv) are typically designed to reduce the volume of soHd waste and to generate electricity in condensing power stations. Incineration of unprocessed municipal waste alone recovers energy from about 34,500 t/d or 109 million metric tons of MSW aimuaHy in some 74 incinerators throughout the United States. This represents 1.1 EJ (1.05 x 10 Btu) of energy recovered aimuaHy (18). Additionally there are some 20 RDE facihties processing from 200 to 2000 t/d of MSW into a more refined fuel (19). Representative projects are shown in Table 10. 

Rates of production of lignite have continued to increase since 1960. In 1980 374 x 10 tons of coal equivalent (tee) were produced. One tee is the amount of energy available from combustion of a metric ton of coal having a heat content of 29.3 GJ, ie, 29.3 MJ/kg (12, 600 Btu/lb) (3). In 1989 this figure had risen to 460 x 10 tee. This 23% increase is somewhat less than the 28% increase in hard coal production during this period (see Coal). In 1990 the 1130 X 10 metric tons of lignite produced worldwide represented 24% of the total coal production. 

Whereas new appHcations of lithium compounds were developed, commercial growth was slow. In 1953 worldwide sales of lithium products, expressed as lithium carbonate, were only ca 1000 metric tons (2). In 1954 the U.S. lithium industry underwent a sudden, very large expansion when the U.S. Atomic Energy Commission required large amounts of lithium hydroxide [1310-65-2] for its nuclear weapons program (see Nuclearreactors). Three domestic producers built 4500-t/yr plants to meet contract commitments with the U.S. government. When these government contracts ended in 1960, capacity exceeded demand and several operations were discontinued. 

Because the peroxodisulfate salts are all made electrochemicaHy, the electrical energy cost is a significant part of thek manufacturing cost. The 1994 world capacity for peroxodisulfate salts was about 75,000 metric tons, valued at about 30 x 10 . The principal appHcations are in polymerization catalysis and the market broadly tracks the plastics business. The Caro s acid business is difficult to quantify because the product itself is not commercial but made on-site from purchased hydrogen peroxide. 

Table 8. Energy Consumption Per Metric Ton of Aluminum Produced ...

The 1990 Amendments to the U.S. Clean Air Act require a 50% reduction of sulfur dioxide emissions by the year 2000. Electric power stations are beheved to be the source of 70% of all sulfur dioxide emissions (see Power generation). As of the mid-1990s, no utiUties were recovering commercial quantities of elemental sulfur ia the United States. Two projects had been aimounced Tampa Electric Company s plan to recover 75,000—90,000 metric tons of sulfuric acid (25,000—30,000 metric tons sulfur equivalent) aimuaHy at its power plant ia Polk County, Elorida, and a full-scale sulfur recovery system to be iastaHed at PSl Energy s Wabash River generating station ia Terre Haute, Indiana. Completed ia 1995, the Terre Haute plant should recover about 14,000 t/yr of elemental sulfur. 

Economic Aspects. As of 1995, two manufacturers produced sodium thiosulfate in the United States with an estimated total capacity of 30,000 metric tons. Despite declining volume, prices have increased, reflecting increased taw material, energy, and labor costs. Production outside of the United States is at least 25%i of the U.S. production, mainly in Germany. 

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