Environmental concerns, feedstock, flexibility, and residue upgrading are among the various issues facing the refining industry worldwide. Available methods to reduce the amount of refinery residues by physical separation, carbon rejection or hydrogen addition, produce a further residue of their own that needs to be utilized or disposed. One alternative that totally converts the residue and at the same time complies with environmental restraints is the gasification or partial oxidation process. This alternative is one of the noncatalytic options for the utilization and conversion of unmarketable high-Sulfur heavy residues to a range of value-added products such as electric power, steam, hydrogen and/or synthesis gas for chemicals production.
For the Kingdom of Saudi Arabia, the rapid increase in the demand for electric power (10 percent per year) and the surplus of heavy residues justify the addition of a cogeneration plant within the refinery which itself has a significant electric power requirement. The residue gasification option will partly contribute to enhancing the existing power capacity in the Kingdom which stands at about 23 O00 MW and will have to reach 28 O00 MW by the year 2000 and 59000 MW in 2050, according to some industrial analysts. This situation provides the motivation for the present paper which provides configuration and economic analysis of a cogeneration plant in a medium-conversion refinery. The plant is designed to generate 800 MW electric power for internal use and for export as well as 500 ton/hr HP steam. Economic evaluation has been made for this cogeneration plant using 24000 b/d (3800 m3/d) visbreaker tar. The results of our economic analysis show that the investment needed is relatively high at $808 million, however, the payback period is reasonable within 4.7 years.
The percentage of high-Sulfur heavy crude oils processed by refineries worldwide has been increasing, creating a surplus of low-priced and low-quality heavy residues. One common aspect of most conversion refineries that is receiving increased attention is the utilization of heavy residues; not only in terms of refinery economics but also from an environmental point of view. Refineries in many countries are seriously studying various options to modify their process configurations and moving gradually toward zero residue. Refineries that have substantial capacity of visbreaking, solvent deasphalting, or coking are faced with large quantities of visbreaker tar, asphalt or coke which have a high sulfur content (4-6 wt%) with primary consequences reflected in the potential for sulfur emissions. During the last decade global fuel oil sa
