Hydrocarbon fuels, chemical

Liquid fuels methanol, ethanol, higher hydrocarbons, oils Chemicals... 

The third characteristic of interest grows directly from the first, ie, the high thermal conductance of the heat pipe can make possible the physical separation of the heat source and the heat consumer (heat sink). Heat pipes >100 m in length have been constmcted and shown to behave predictably (3). Separation of source and sink is especially important in those appHcations in which chemical incompatibilities exist. For example, it may be necessary to inject heat into a reaction vessel. The lowest cost source of heat may be combustion of hydrocarbon fuels. However, contact with an open flame or with the combustion products might jeopardize the desired reaction process. In such a case it might be feasible to carry heat from the flame through the wall of the reaction vessel by use of a heat pipe. 

Imperial Chemical Industries (ICI) operated a coal hydrogenation plant at a pressure of 20 MPa (2900 psi) and a temperature of 400—500°C to produce Hquid hydrocarbon fuel from 1935 to the outbreak of World War II. As many as 12 such plants operated in Germany during World War II to make the country less dependent on petroleum from natural sources but the process was discontinued when hostihties ceased (see Coal conversion PROCESSES,liquefaction). Currentiy the Fisher-Tropsch process is being used at the Sasol plants in South Africa to convert synthesis gas into largely ahphatic hydrocarbons at 10—20 MPa and about 400°C to supply 70% of the fuel needed for transportation. 

An alternative method of produciag hydrocarbon fuels from biomass uses oils that are produced ia certaia plant seeds, such as rape seed, sunflowers, or oil palms, or from aquatic plants (see Soybeans and other oilseeds). Certain aquatic plants produce oils that can be extracted and upgraded to produce diesel fuel. The primary processiag requirement is to isolate the hydrocarbon portion of the carbon chain that closely matches diesel fuel and modify its combustion characteristics by chemical processiag. 

The specific gravities (s.g.) of liquid chemicals vary widely, e.g. for the majority of hydrocarbon fuels s.g. <1.0 but for some natural oils and fats, chlorinated hydrocarbons, s.g. >1.0. Density is generally reduced by any increase in temperature. As a result ... 

Hydrocarbon fuels used solely for workplace consumption as a fuel (e.g., propane used for comfort heating, gasoline for vehicle refueling), if such fuels are not a part of a process containing another highly hazardous chemical covered by this standard... 

The second important parameter affecting efficiency is air/fuel ratio. For evei y hydrocarbon fuel, there is an air/fuel ratio that, in principle, causes all the hydrogen in the fuel to burn to water vapor and all the carbon in the fuel to burn to carbon dioxide. This chemically correct proportion is called the stoichiometric ratio. 

Many chemicals are produced from synthesis gas. This is a consequence of the high reactivity associated with hydrogen and carhon monoxide gases, the two constituents of synthesis gas. The reactivity of this mixture was demonstrated during World War II, when it was used to produce alternative hydrocarbon fuels using Fischer Tropsch technology. The synthesis gas mixture was produced then hy gasifying coal. Fischer Tropsch synthesis of hydrocarbons is discussed in Chapter 4. 

Although it is attractive to directly convert chemical energy to electricity, PEM fuel cells face significant practical obstacles. Expensive heavy metals like platinum are typically used as catalysts to reduce energy barriers associated with the half-cell reactions. PEM fuel cells also cannot use practical hydrocarbon fuels like diesel without complicated preprocessing steps. Those significantly increase the complexity of the overall system. At this time, it appears likely that PEM fuel cells will be confined to niche applications where high cost and special fuel requirements are tolerable. 

Carbon dioxide and water are the major waste products from most natural and industrial processes and hence are found in large quantities in the environment. If an efficient and cheap means could be found, the reduction of C02 could provide a potentially rich source of carbon for utilisation in the production of, for example, synthetic hydrocarbon fuels to replace petroleum, formic and oxalic acids for the chemical industries and foodstuffs such as glucose. 

A full understanding will be needed of the complex chemistry by which the atmosphere and the earth interact, including the dependence of global climate on carbon dioxide concentrations in the atmosphere. Is there a way to deal with the carbon dioxide produced by burning coal and other hydrocarbon fuels so that it causes no problem Chemical scientists will need to investigate effective ways to trap C02 that would otherwise build up in the atmosphere. Alternatively, it will be necessary to find ways to reduce the generation of carbon dioxide. As human... 

The catalytic activation of carbon monoxide is a research area currently receiving major attention from academic, industrial, and government laboratories. There has been a long standing interest in this area however, the new attention obviously is stimulated by concerns with the present and future costs and availability of petroleum as a feedstock for the production of hydrocarbon fuels and of organic chemicals. One logical alternative source to be considered is synthesis gas, mixtures of carbon monoxide and hydrogen that can be produced from coal and other carbonaceous materials. 

The chemical products from complete combustion of a hydrocarbon fuel are mainly C02 and H20 (vapor). Combustion of gaseous fuel in air can occur in two different modes - one where fuel and oxygen is mixed during the combustion process, and the other where fuel and air are premixed (gas condensing boilers) and the fuel concentration must be within the flammability limits. In general the premixed situation allows the fuel to burn faster, i.e. more fuel is consumed per unit time. 

Rider, D. K., Energy Hydrocarbon Fuels and Chemical Resources, John Wiley Sons, New York, 1981. 

Hinchee, R. E., Downey, D. C., and Beard, T., 1989, Enhancing Biodegradation of Petroleum Hydrocarbon Fuels through Soil Venting In Proceedings of the National Water Well Association Conference on Petroleum Hydrocarbons and Organic Chemicals in Ground-water Prevention, Detection and Restoration, November, pp. 235-248. 

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