Publication Date: 2012-May-10
The IP.com Prior Art Database
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Crude oil contains materials covering a very wide boiling range. It is normally separated into various fractions which are further processed to produce marketable products. The lower boiling fractions are usually separated and recovered in an atmospheric distillation column. Since petroleum fractions are subject to thermal degradation, there is a limit to how much material can be recovered in this column. (At temperatures in the range of 400°C thermal cracking is excessive.) Additional distillates are normally recovered in a vacuum distillation column. More material can be recovered without thermal degradation by increasing the vacuum. The limit, however, is about 600°C cut point beyond which thermal cracking can impact run lengths. Even after vacuum distillation, there is still some material, suitable for upgrading to valuable products, left in the vacuum residuum.
Solvent deasphalting permits recovery ofnon-asphaltenic material either directly from atmospheric residuum or from vacuum residuum. In the former case high cost and complex vacuum distillation unit is not needed. Solvent deasphalting achieves higher recoveries at relatively low operating temperatures. Low molecular weight paraffin's, propane (C3) to pentane (C5) are normally used as the solvent. The deasphalting process separates hydrocarbons according to their solubility in the solvent. Thus paraffinic and lower molecular weight material is preferentially extracted as deasphalted oil (DAO) and the heavier and more aromatic material is rejected into the asphaltic raffinate.
9.2.2 Evolution of Deasphalting
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Solvent deasphalting was originally developed as a joint effort of Standard Oil Company of New Jersey, Standard Oil Company of Indiana, Union Oil Company of California and
.... ~h~ ~Ii~.~<~l~-o~-C-~yy ~l~-i~e~a-, ~.-~he ~bjective of their combined
research efforts was the recovery of heavy lubricating oils (known as "bright stocks" or cylinder stocks) from asphalt-base crude oils. Since these heavy lubes could not be readily distilled without thermal degradation, they were available only from the paraffin- base crude oils containing little or no asphalt. Only from these crudes, the heavy fractions could be economically recovered by steam or clay refining.
The separation of residual fractions from asphalt-base crudes into oil and asphalt fractions was first performed on a production scale by mixing the residue of vacuum distillation with propane and continuously decanting the resulting phases in a suitable vessel. The temperature was maintained within about 40°C of the critical temperature of the solvent to regulate the yield and properties of the deasphalted oil and reject the undesirable components as asphalt.
From this. original process, pilot plant development progressed through multistage
c o un_t _er_ _c_u. rr e_nLd esi go~ s. Later thee _rn~tis.~ag~ s.ettl~rs ~ye_re_ .r_ .el~l_a_ee_d .1~ y..a~...