STUDY OF LIQUID SOLVENT DEASPHALTING OF HEAVY RESIDUES

In the 1970s، regulations in some countries forced users of heavy residue to limit pollutant emissions at industrial sites، also forced producers to upgrade their heavy products for export and domestic use. For this reason Iran as a producer، exporter and consumer has to develop new upgrading processes. The most common processes for upgrading heavy oil are catalytic processes، but existence of heavy metals، asphaltenes، sulfur and nitrogen compounds in heavy oil poses several serious problems in the process. Hence at first، the unwanted materials must be lowered to the acceptable limit in the feed. Of all the techniques conceived and tested to separate asphaltenes from oily feed، only one has been developed industrially، deasphalting by light solvents. In this study، deasphalting of vacuum bottom of Tehran and Arak refineries were evaluated using light alkane solvents such as n-pentane، n-heptane and L. S. R. G. (Light Straight Run Gasoline) and compared with propane deasphalting units in refineries. Results show that pentane and heptane are good solvents for asphaltene separation as well as nickel، vanadium، sulfur and nitrogen compounds but more efficient compared to propane. Finaly، according to the qualitative and quantitative specification of produced DAOs using pentane، heptane and L. S. R. G. it was shown that liquid solvents are suitable feed for catalytic units (e. g. FCC) after unifining process.