Design of 10,000 Barrels per day Crude Distillation Unit for processing Light Sweet Crude Blend

Abstract

Crude distillation is the most renowned unit operation, and for good reason. The crude is fractionated on the basis of associated volatilities and the mass transfer phenomena occurring at each and every stage of a distillation column. The rising vapors are enriched with more volatile compounds that leave towards the top of the distillation column. The heavier, less volatile compounds leave towards the bottom of the column. However, before crude oil is subjected to this separation, it must undergo pre-treatment processes to remove the impurities it contains at the time of extraction from the well. Sulphur is one of the key impurities that must be removed since it poses a grave threat to the environment. If not removed properly, Sulphur oxidizes during the thermally driven processes forming oxides. These oxides have their own associated health risks and they may combine with rain to form ‘acid rain’. Crude oil with a sulphur content of below 1-2% is known as sweet crude. Sweet crude oil is highly sought after due to the less thorough pretreatment required. Light, sweet crude oil is crude oil with a low specific gravity. As a result, the API gravity is high. According to NYMEX, API gravity for light sweet crude for non-US countries is between 32° and 42°. Light sweet crude is highly sought after due to its high naphtha yields. This high amount of naphtha leads to increased gasoline production after processes like catalytic reforming. This gasoline is a high-grade reformate with a good enough octane number to meet the growing energy demands of the. The current distillation techniques, however, are highly energy intensive. So, to increase gasoline production, it is obligatory to increase the energy investment. This project proposes an alternate approach to the conventional distillation mode called the Heat Integrated Distillation Column (HIDC). The HIDC system reduces the amount of energy required by incorporating a thermosiphon flow of contents between the rectifying and stripping sections, reducing the amount of energy wasted. The heat of the rectifying section is used to vaporize a stream from the stripping section, reducing the overall load on the reboiler. The process is designed to be both economically and technically feasible and sustainable for the long-run.