(87c) Residue Upgrading by Solvent Deasphalting and Pitch Gasification-a Review

Upgrading of vacuum residue, regardless of origin, has complex economics related to the fact that it is a highly contaminated, hydrogen-deficient fraction. To varying degree, solvent deasphalting, coking, ebbulated bed hydrocracking and more recently, slurry hydrocracking can practically achieve 50-95 % vacuum bottoms conversion. In many recent projects, the goal has been to achieve a zero-residue position by gasification of the remaining residue to produce hydrogen and power, leading to a very interesting technoeconomic problem.

Solvent Deasphalting (SDA) typically uses C3-C5 hydrocarbon under pressure at near-critical conditions to break the colloidal structure of heavy oil, causing a phase separation. Recovered deasphalted oil (DAO) is substantially reduced in metals, polar aromatics and asphaltenes. SDA alone or in combinations can be a low capital cost and very energy-efficient upgrading system.

This tutorial will discuss several recent project examples of solvent deasphalting in conversion refineries and discuss potential hydrogen production from pitch gasification as well as control schemes and the balancing of SDA lift against hydrogen demand, cost of gasification and net value for DAO upgrading. Future trends, such as very deep lift SDA, DAO upgrading and pitch utilization in nonconventional ways will also be briefly discussed.