Continuous Production of Fuels

4 CONTINUOUS PRODUCTION OF FUELS FROM WASTE PLASTICS 

Bockhorn, J. Hentschel, A. Homung and U. Homung Environmental engineering stepwise pyrolysis of plastic waste, Chem. Eng. ScL, 54, 3043-3051 (1999). 

Bockhorn, A. Homung and U. Homung Stepwise pyrolysis for raw material recovery from plastic waste, J. Anal. Appl. Pyrol, 46, 1-13 (1998). 

Kuroki, T. Sawaguchi, N. Ikebayashi, T. Ikemura and N. Sakikawa Pyrolysis of polystyrene-prediction of product yield, Bull. Chem. Soc. Jpn., 11, 1766-1772 (1976). 

Masuda, Y. Niwa, A. Tamagawa, S. R. Mukai, K. Hashimoto and Y. Ikeda Degradation of waste poly(ethylene terephthalate) in a steam atmosphere to recover terephthalic acid and to minimize carbonaceous Residue, Polym. Degrad. Stab., 58, 315-320 (1997). 

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Figure 6.25(a) shows a novel process for the continuous production of fuels from waste plastics. The proposed process consists primarily of three reactors. A mixture of waste plastics is fed into a pyrolytic reactor with heat-medium-particles stirred by a helical impeller (Figure 6.25(b)), where melted plastics are hydrothermally decomposed with steam and the random scission of C-C bonds. The produced mixture of a heavy oil containing wax and sublimate material is carried by steam stream to the next reactor, which is filled with an FeOOH catalyst (i.e. a catalytic hydrolysis reactor). The gaseous... 

Figure 6.25 (a) Flow scheme of the continuous production of fuels from waste plastics (b) schematic diagram of the pyrolytic reactor used in the pilot plant. (Reproduced with permission from Elsevier)... 

C and 5 kg/cm pressure (see Molecularsieves). Selectivity for toluene and xylenes peaks at 550°C but continues with increasing temperature for hensene. The Cyclar process (Fig. 6) developed joindy by BP and UOP uses a spherical, proprietary seoHte catalyst with a nonnoble metallic promoter to convert C or C paraffins to aromatics. The drawback to the process economics is the production of fuel gas, alow value by-product. BP operated a... 

Uranium hexafluoride [7783-81-5], UF, is an extremely corrosive, colorless, crystalline soHd, which sublimes with ease at room temperature and atmospheric pressure. The complex can be obtained by multiple routes, ie, fluorination of UF [10049-14-6] with F2, oxidation of UF with O2, or fluorination of UO [1344-58-7] by F2. The hexafluoride is monomeric in nature having an octahedral geometry. UF is soluble in H2O, CCl and other chlorinated hydrocarbons, is insoluble in CS2, and decomposes in alcohols and ethers. The importance of UF in isotopic enrichment and the subsequent apphcations of uranium metal cannot be overstated. The U.S. government has approximately 500,000 t of UF stockpiled for enrichment or quick conversion into nuclear weapons had the need arisen (57). With the change in pohtical tides and the downsizing of the nation s nuclear arsenal, debates over releasing the stockpiles for use in the production of fuel for civiUan nuclear reactors continue. 

Since 1978, several papers have examined the potential of using immobilised cells in fuel production. Microbial cells are used advantageously for industrial purposes, such as Escherichia coli for the continuous production of L-aspartic acid from ammonium fur-marate.5,6 Enzymes from microorganisms are classified as extracellular and intracellular. If whole microbial cells can be immobilised directly, procedures for extraction and purification can be omitted and the loss of intracellular enzyme activity can be kept to a minimum. Whole cells are used as a solid catalyst when they are immobilised onto a solid support. 

The environmental problem of sulfur dioxide emission, as has been pointed out, is very much associated with sulfidic sources of metals, among which a peer example is copper production. In this context, it would be beneficial to describe the past and present approaches to copper smelting. In the past, copper metallurgy was dominated by reverberatory furnaces for smelting sulfidic copper concentrate to matte, followed by the use of Pierce-Smith converters to convert the matte into blister copper. The sulfur dioxide stream from the reverberatory furnaces is continuous but not rich in sulfur dioxide (about 1%) because it contains carbon dioxide and water vapor (products of fuel combustion), nitrogen from the air (used in the combustion of that fuel), and excess air. The gas is quite dilute and unworthy of economical conversion of its sulfur content into sulfuric acid. In the past, the course chosen was to construct stacks to disperse the gas into the atmosphere in order to minimize its adverse effects on the immediate surroundings. However, this is not an en-... 

In spite of the fact that all elements of the systems of production, conversion, transportation and consumption of energy are improving continuously, the growth of national incomes calls for an appropriate growth in the utilization of energy. This can be attained through an increased production of fuel and construction of new and more efficient power plants, pipelines, power transmission lines and so on. 

Efforts continue to improve fuel cell technology and utilization which should reduce costs. The General Motors fuel cell program aims at having a commercial fuel cell vehicle by 2010. Volume production of fuel cell cars should reduce costs, but one Department of Energy projection with a production of 500,000 vehicles a year still has the cost too high. 

Organization of biocatalytic photosynthetic systems in the form of integrated assemblies could provide practical photosynthetic devices. ET-communication of the cofactor or artificial electron shuttle with the enzyme active site proceeds in solution by a diffusional mechanism. An integrated biocatalytic photosynthetic device that allows the continuous light-induced production of fuel materials or... 

Continuous fermentation processes are primarily used in the research and development stage. However, more chemostat operations are being used at the production level as the understanding of this reactor increases. Examples include ethanol fermentation for the production of fuel grade ethanol and single-cell protein production from methanol substrates. 

Bunyakiat, K., Makmee, S., Sawangekeaw, R., Ngamprasertsith, S., Continuous production of biodiesel via transesterification from vegetable oils in supercritical methanol, Energy Fuels, 20, 812-817, 2006... 

He, H., Wang, T., Zhu, S., Continuous production of biodiesel fuel from vegetable oil using supercritical methanol process, Fuel, 86, 442 447, 2007... 

These preliminary experiments indicate that pyrolysis of agricultural biomass appears to have a good potential for small scale production of fuels for farm operations. The kiln was easily started and operated and would require little supervision for continuous operation. Thermal efficiencies for a self-sustaining process are expected to be about 65%. 

It is feasible to breed more tritium in a lithium cooled reactor than is used in the reaction. The excess tritium can be used to start other reactors or in a reactor using some coolant other than lithium that prevents it from breeding its own tritium. Nature has been kind with the properties of lithium. It is an excellent choice for transferring heat from the reactor and it is the raw material needed for the continual production of more fuel. Both these functions can be provided by the use of liquid lithium as the blanket material. The isotopic composition of the lithium may be adjusted to provide the proper balance of lithium 6 and lithium 7 to optimum heat transfer and production of tritium. The lithium can also be diluted with metallic sodium or potassium to aid in adjusting the tritium production rate. 

As shown above, neutrons are in particular important for studies of hydride materials. Neutrons can be produced either in nuclear reactors or by pulsed (spallation) neutron sources. In the research nuclear reactors neutrons are produced by fission processes based on U-235 (which is 0.7% in natural uranium, but usually emiched as fuel for reactors). Since the released neutrons from these processes are very energetic, the required chain reaction for continuous production of neutrons requires moderation (to reduce the energy)... 

The primary function of all catabolic pathways is to harvest the chemical energy of fuel molecules and to store that energy by the production of ATP. This continuous production of ATP is what provides the stored potential energy that is used to power most cellular functions. 

Watanabe, Y Y. Shimada A. Sugihara H. Noda H. Fukuda Y. Tominaga. Continuous production of biodiesel fuel from vegetable oil using immobilized Candida antarctica lipase./. Am. Oil Chem. Soc. 2000, 77 355-360. 

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