New FCC process developed to meet diesel and propylene demands

The Middle Distillates and Lower Olefins Selective process - known as MILOS – sees the introduction of an additional riser in the FCC, either in a revamp or grass roots unit which provides the refiner with options to simultaneously help maximise production of diesel and propylene.

With the MILOS process, the FCC can be run in a number of different modes. In the propylene mode, propylene production can be doubled compared to a base case FCC unit operating under typical conditions and feedstock properties while maintaining traditional diesel yields and quality (‘base case’). With MILOS in  diesel mode, diesel production can be increased by up to 20 per cent compared to the base case whilst achieving a seven point cetane improvement and an increased propylene production.

The design of the MILOS process also allows the refiner to run the FCC unit anywhere between these modes or even to revert to normal FCC operation, just by changing operating parameters.

The feed to the additional riser in the MILOS design may be one of a number of feedstocks such as FCC naphtha, coker naphtha, Visbreaker naphtha, vegetable oil and gas to liquid process products or even paraffinic Vacuum Gas Oil.  Typical yields obtained by cracking FCC naphtha in the MILOS riser are 15.5%wt propylene, 7.5%wt gas and 5% iso-butane.

The MILOS process can be applied in complex or petrochemical refineries where lower valued by-product streams may be opportunity feeds for the MILOS configuration. In such use, the MILOS riser would be operated at the desired severity to deliver optimum propylene yields while maintaining the normal unit flexibility.

In revamp situations, the additional load on the Reactor and Regenerator circuit, Wet Gas Compressor and Gas Plant needs to be carefully considered and Shell Global Solutions’ advanced technologies in debottlenecking reactors and columns can help minimise the investment required.

Mart Nieskens, Global Manager, Catayltic Cracking at Shell Global Solutions (US) Inc., says: “Changing market demands for less gasoline and more diesel and propylene has proved difficult to achieve with the traditional and inflexible layout of the standard FCC. MILOS addresses this by providing the refiner an operational choice. The process is designed to be simple and easy to change between modes  to help provide greater flexibility.”

Pankaj Desai, Licensing Sales Manager, Shell Global Solutions (US) Inc.,  adds:  “ The MILOS process  should be particularly attractive to refineries linked to petrochemical complexes. Moreover, because  it’s designed to provide increased flexibility, the MILOS  process can help refiners to take advantage of the seasonal demand patterns.”