De-asphalting

ASCOT [Asphalt coking technology] A process combining de-asphalting and decoking, offered by Foster-Wheeler, United States. 

LEDA [Low energy de-asphalting] A process for removing the asphalt fraction from petroleum residues by liquid-liquid extraction in a special rotating disc contactor. The extractant is a C3-C6 aliphatic hydrocarbon or a mixture of such hydrocarbons. Developed in 1955 by Foster Wheeler USA Corporation and still widely used 42 units were operating in 1996. 

Activities in the propane deasphalting (PDA) unit submatrix represent the operations on vacuum tower bottoms from the base crude mix and from the incremental crudes. The de-asphalter overhead streams from all activities enter one stream balance row with common properties. Each deasphalter bottoms enter a separate row for No. 6 fuel oil blending. 

SOLVAHL A petroleum de-asphalting process developed by IFP and now licensed by Axens. See ASVAHL. 

Z Yan. Interfacial behaviour of de-asphalted bitumen. MSc dissertation. University of Alberta, Edmonton, 1997. 

The solvent conditions for those near-critical extraction processes for which data are available are marked on Figure 1.1. With the exception of the Coal Board (now British Coal) pilot plant, all of these are commercial processes, though not all are for the extraction of natural products. The solvent used in all cases except the de-asphalting column and the Coal Board process is compressed carbon dioxide, in either the liquid or the supercritical state. The solvent used in the Coal Board process, work on which has now ceased, was a mixture containing aromatic and fully hydrogenated aromatic compounds with a pseudo-critical pressure of 31 bar and a pseudo-critical temperature of 713 K [3]. It is seen that the solvent reduced densities in the above cases fall in the approximate range 1.3 to 2.1 solvent reduced temperatures are in the selected range 0.9 to 1.3. 

A significant industrial development in the mid-1930s was the use of near-critical compressed propane for de-asphalting petroleum [59]. This is probably the oldest example of the commercial use of a near-critical solvent for purification purposes. 

As far as the authors are aware the only other extraction process with a near-critical solvent to come into use in the period 1924-1960 was the Solexol process for the purification of vegetable and fish oils using compressed propane [60-64]. (The underlying principles for this process are identical to those for the propane de-asphalting process.) In 1952 it appears that about five commercial Solexol plants were in service [45]. The present position is not quite so clear [65]. 

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