Residuum fraction

Other factors indicated m the data of Tables 1 and 2 include Pour Point—defined as the lowest temperature at which the material will pour and a function of the composition of the oil in terms of waxiness and bitumen content Salt Content—which is not confined to sodium chloride, but usually is interpreted in terms of NaCl Salt is undesirable because of the tendency to obstruct fluid flow, to accumulate as an undesirable constituent of residual oils and asphalts, and a tendency of certain salt compounds to decompose when heated, causing corrosion of refining equipment Metals Content—heavy metals, such as vanadium, nickel, and iron, tend to accumulate in the heavier gas oil and residuum fractions where the metals may interfere with refining operations, particularly by poisoning catalysts. The heavy metals also contribute to the formation of deposits on heated surfaces in furnaces and boiler fireboxes, leading to permanent failure of equrpment, interference with heat-transfer efficiency, and increased maintenance. 

The distributions of Ni, V, N, and S in several atmospheric residuum fractions (Reynolds, 1985) are shown in Table VII. As is evident from the table, the distributions of heteroatoms and metals in the fractions vary greatly with the petroleum source. The Kern River resid is considerably different than that from the other petroleums in having a low asphaltene... 

The residuum fraction of a full range crude is that fraction remaining after all of the distillate is taken overhead. As noted in Figure 1, this residuum fraction or resid may be obtained with either atmospheric or vacuum fractionation, yielding either long or short resid. 

The distillation tests give an indication of the types of products and the quality of the products that can be obtained from petroleum, and the tests are used to compare different petroleum types through the yield and quality of the 300°C (572°F) residuum fraction. For example, the waxiness or viscosity of this fraction gives an indication of the amount, types, and quality of the residual fuel that can be obtained from the petroleum. In this respect, the determination of the aniline point (ASTM D-6II, IP 2) can be used to determine the aromatic or aliphatic character of petroleum. Although not necessarily the same as the wax content, correlative relationships can be derived from the data. 

The objectives of this chapter are twofold. First is to show the fundamentals of the chemistry and process engineering of asphaltenes during thermal treatment for achieving deep asphaltene cracking to increase and/or improve distillable yields of crude oil. The second is to present the current major processes for utilization of heavy oils and residuum fractions. 

To provide raw material for this comparative study of untreated and heat-treated oils, asphaltenes from Cold Lake crude (crude asphaltenes) and from Cold Lake vacuum residuum (residuum asphaltenes) were prepared by n-heptane precipitation as described in the Experimental section. The Cold Lake residuum fraction was prepared by Imperial Oil Enterprises, Ltd. at Sarnia, Ontario, Canada. The distillation history of this bottoms fraction indicates that the pot material was subjected to temperatures as high as 314-318°C during atmospheric and vacuum distillation. The length of time at 300°C or higher was about two hours. This is well in excess of what would be experienced in a pipestill and should have provided ample time for any decomposition. It should be noted, however, that since it was possible to maintain the system vacuum at 0.35 mm, the maximum temperature experienced by the residuum was not quite as high as it might be during refinery distillation (e.g. ca 350°C). 

The products were usually separated into light oils, middle distillates, and residuum. The residuum fraction was filtered (or centrifuged) to ranove any solid material (unreacted coal, mineral matter, and ash) and the remaining material was nsed as a recycle oil for the liquefaction stage. The lighter liquid products were generally hydrotreated to produce stable liquid fuels. 

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