Fuels, comparison

The incremental cost of using methanol in gasoline is approximately equal to the incremental cost of converting the methanol to gasoline by the Mobil process. Such end-use costs must of course be included in overall fuel comparisons. 

Since the introduction of low-sulfur diesel fuel, much study has been completed to determine the lubricity properties of this fuel. Comparison of low-sulfur diesel with high-sulfur diesel has clearly revealed that fuel sulfur has a dramatic impact on the ability of fuel to provide a higher level of lubricity performance. A comparison of the lubricity performance of a typical high-sulfur diesel low-sulfur diesel and low-aromatic, low-sulfur diesel is shown in FIGURE 5-3. 

Tetramethyllead has been also put forward as an antishock additive for engine fuel. Comparison tests have shown that tetramethyllead is more efficient that tetraethyllead, especially in petrols with high content of aromatic hydrocarbons. Tetraalkyl lead derivatives can also be used in the production of lead alkylhalogenides and their derivatives. 

Because different fuels produce different amounts of incipient soot particles at about 1600 K, the smoke height test becomes a measure of the fuel s relative propensity to soot under flame-like conditions. However, if the smoke height is to be used for fuel comparisons, the diffusion flame temperature must be adjusted to be the same for all fuels. The results of such experiments [51] are reported in Fig, 17. The data in this figure are plotted as the log of the reciprocal of the fuel... 

From [2] we present further information on the nature (so-called speciation) of the hydrocarbons emissions in the form of the relationship between fuel and exhaust (engine-out) composition (Fig. 5). It is evident that the fingerprints for compounds of C5 and higher (C5+) are comparable on a fuel-to-exhaust basis. Thus unbumed fuel is a major contributor to the C5+ engine-out profile. Lighter hydrocarbons (C4 ) are produced by the breakdown of larger molecules and other partial oxidation products will also form (e.g. aldehydes and ketones, which are not considered here). Figure 6 provides a more quantitative example of exhaust/fuel comparisons for C5+ components. 

The high C/H ratio for heavy fuels and their high levels of contaminants such as sulfur, water, and sediment, tend to reduce their NHV which can reach as low as 40,000 kJ/kg by comparison to the 42,500 kJ/kg for a conventional home-heating oil. This characteristic is not found in the specifications, but it is a main factor in price negotiations for fuels in terms of cost per ton. Therefore it is subject to frequent verification. 

The tendency of the color to become darker with time is often indicative of chemical degradation. The test is conducted with the aid of a colorimeter (NF T 60-104 and ASTM D 1500) and by comparison with colored glass standards. The scale varies from 0.5 to 8. The French specifications stipulate that diesel fuel color should be less than 5, which corresponds to an orange-brown tint. Generally, commercial products are light yellow with indices from 1 to 2. 

Alcohol Production. Studies to assess the costs of alcohol fuels and to compare the costs to those of conventional fuels contain significant uncertainties. In general, the low cost estimates iadicate that methanol produced on a large scale from low cost natural gas could compete with gasoline when oil prices are around 140/L ( 27/bbl). This comparison does not give methanol any credits for environmental or energy diversification benefits. Ethanol does not become competitive until petroleum prices are much higher. 

A comparison of the characteristics associated with propellant burning, explosive detonation, and the performance of conventional fuels (see Coal Gas, NATURAL Petroleum) is shown ia Table 1. The most notable difference is the rate at which energy is evolved. The energy Hberated by explosives and propellants depends on the thermochemical properties of the reactants. As a rough rule of thumb, these materials yield about 1000 cm of gas and 4.2 kj (1000 cal) of heat per gram of material. 

Natural gas is by far the preferred source of hydrogen. It has been cheap, and its use is more energy efficient than that of other hydrocarbons. The reforming process that is used to produce hydrogen from natural gas is highly developed, environmental controls are simple, and the capital investment is lower than that for any other method. Comparisons of the total energy consumption (fuel and synthesis gas), based on advanced technologies, have been discussed elsewhere (102). 

Laboratory experiments using rodents, or the use of gas analysis, tend to be confused by the dominant variable of fuel—air ratio as well as important effects of burning configuration, heat input, equipment design, and toxicity criteria used, ie, death vs incapacitation, time to death, lethal concentration, etc (154,155). Some comparisons of polyurethane foam combustion toxicity with and without phosphoms flame retardants show no consistent positive or negative effect. Moreover, data from small-scale tests have doubtful relevance to real fine ha2ards. 

The percentage of energy demand that could be satisfied by particular nonfossil energy resources can be estimated by examination of the potential amounts of energy and biofuels that can be produced from renewable carbon resources and comparison of these amounts with fossil fuel demands. 

E. Doetsch and H. DoHwa, "Economical and Process Technology Aspects of Cast Iron Melting," Electrowarmeint. 37(B3), B157 (1979), contains an economic comparison fuel-fired and electric iron foundry melting furnaces. 

Figure 3 provides a comparison of the energy costs in the U.S. residential market for natural gas, electricity, or No. 2 fuel oil (1). The prices of all three forms of energy to residential users have increased for the period shown. Electrical energy has had the largest doUar increase. 

The most common method of converting iron ore to metallic iron utilizes a blast furnace wherein the material is melted to form hot metal (pig iron). Approximately 96% of the world s iron is produced this way (see Iron). However, in the blast furnace process energy costs are relatively high, pollution problems of associated equipment are quite severe, and capital investment requirements are often prohibitively expensive. In comparison to the blast furnace method, direct reduction permits a wider choice of fuels, is environmentally clean, and requires a much lower capital investment. 

Eig. 8. Cost of electricity (COE) comparison where represents capital charges, Hoperation and maintenance charges, and D fuel charges for the reference cycles. A, steam, light water reactor (LWR), uranium B, steam, conventional furnace, scmbber coal C, gas turbine combined cycle, semiclean hquid D, gas turbine, semiclean Hquid, and advanced cycles E, steam atmospheric fluidized bed, coal E, gas turbine (water-cooled) combined low heating value (LHV) gas G, open cycle MHD coal H, steam, pressurized fluidized bed, coal I, closed cycle helium gas turbine, atmospheric fluidized bed (AEB), coal J, metal vapor topping cycle, pressurized fluidized bed (PEB), coal K, gas turbine (water-cooled) combined, semiclean Hquid L, gas turbine... 

MW plant and 3.3% for the 200 MW plant. Not surprisingly, the savings become less as the plant becomes smaller. The costs ia Figure 12b are based on the capital cost curve (Fig. 12a) and fuel costs based on the modified EGAS reference steam plant efficiency of 34.3%. The cost comparisons are based on a coal price of 1.00/GJ ( 1.05/MBtu). Higher fuel costs would iacrease the attractiveness of MHD because of its more efficient use of the fuel. 

If possible comparisons are focused on energy systems, nuclear power safety is also estimated to be superior to all electricity generation methods except for natural gas (30). Figure 3 is a plot of that comparison in terms of estimated total deaths to workers and the pubHc and includes deaths associated with secondary processes in the entire fuel cycle. The poorer safety record of the alternatives to nuclear power can be attributed to fataUties in transportation, where comparatively enormous amounts of fossil fuel transport are involved. Continuous or daily refueling of fossil fuel plants is required as compared to refueling a nuclear plant from a few tmckloads only once over a period of one to two years. This disadvantage appHes to solar and wind as well because of the necessary assumption that their backup power in periods of no or Httie wind or sun is from fossil-fuel generation. Now death or serious injury has resulted from radiation exposure from commercial nuclear power plants in the United States (31). 

Vinyl compares favorably to other packaging materials. In 1992, a lifecycle assessment comparison of specific packages made from glass, paperboard, paper, and selected plastics concluded that vinyl was the material that has the lowest production energy and carbon dioxide emissions, as well as the lowest fossil fuel and raw material requirements of the plastics studied (169). Vinyl saves more than 34 million Btu per 1000 pounds manufactured compared to the highest energy-consuming plastic (170). 

SASOLII a.ndIII. Two additional plants weie built and aie in operation in South Africa near Secunda. The combined annual coal consumption for SASOL II, commissioned in 1980, and SASOL III, in 1983, is 25 x 10 t, and these plants together produce approximately 1.3 x lO" m (80,000 barrels) per day of transportation fuels. A block flow diagram for these processes is shown in Figure 15. The product distribution for SASOL II and III is much narrower in comparison to SASOL I. The later plants use only fluid-bed reactor technology, and extensive use of secondary catalytic processing of intermediates (alkylation, polymerisation, etc) is practiced to maximise the production of transportation fuels. 

Table 3. Comparison of Design Parameters for Fossil Fuel Boilers...

Fuel costs vaiy widely from one area to another because of the cost of the fuel itself and the cost of transportation. Any meaningful cost comparison between fuels requires current costs based on such factors as the amounts used at a particular geographical location, utilization efficiencies or energy-ratio data for the equipment involved, and the effects of Torm v ue. Although the costs given in Table 27-9 do not apply to specific locations, they give fuel-cost trends. 

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