Propylene is a major industrial chemical intermediate that serves as one of the building blocks for an array of chemical and plastic products, and was also the first petrochemical employed on an industrial scale. Globally, the largest volume of propylene is generated as by-product in steam crackers and through the fluid catalytic cracking (FCC) process in petroleum refineries. FCC units are by far the largest source of this material.

Low purity propylene streams containing large amounts of propane – commonly called refinery grade (RG) propylene – are used internally in refineries to manufacture gasoline or as fuel. These streams may also be sold as a chemical feedstock to plants dedicated to the enhancement of their propylene content, so as to generate a more valuable product. The most pure grade available, polymer grade (PG) propylene, is used as feedstock to various chemicals, including polypropylene, its greatest output. There are several large, centralized facilities on the US Gulf Coast that process propylene/propane streams gathered from surrounding refineries and petrochemical plants into high-purity propylene. Some refineries chose to conduct this separation onsite.

In addition to refineries, PG propylene consumers are also constructing propylene/propane separation units to become more competitive and to diversify their raw material supplier base and production cost structure.

This report is a review of the purification of RG propylene into PG propylene. Also, a comparison of constructing this unit inside a refinery and inside a polypropylene plant is included. Both capital investment and operating costs for a propylene purification unit operating in the US Gulf Coast, China, and Germany are presented. The economic analysis presented in this report is based on a purification unit installed in a 400 kta polypropylene plant. The estimated CAPEX for such unit is USD 67 million on the US Gulf Coast. China presented the lowest CAPEX and OPEX, followed by the USA and Germany, respectively.

Although the internal rate of return (IRR) in building a propylene purification unit inside a polypropylene plant is more than 30% on US Gulf Coast, the best results are obtained in constructing this unit inside a refinery. This is based on the fact that refineries have excess low-level heat sources available, as well as a supply of cooling water, which minimizes additional utilities supply units installation. Polypropylene manufacturing plants, however, do not usually have this advantage. The improvement installation in refineries leads to IRR of more than 35%.

ISBN-13: 978-0615702155