PEP Review 99-2
ENI Slurry Hydroprocessing Technology For Diesel Fuel
Published: June 2003
The ENI Slurry Technology (EST) developed by Snamprogetti S. p. A. and EniTecnologie S. p. A. is a slurry hydroprocessing process combined with solvent deasphalting of the vacuum residuum effluent. This scheme provides high catalyst concentrations of highly active catalyst to maximize upgrading. Catalyst is recycled with the asphaltenes. Almost complete conversion can be obtained with high selectivity to distillates, optimum hydrogen consumption, low catalyst consumption and a flexible product slate. Overall, hydrodesulfurization is >75%, hydrodemetalization is >99% and Conradson carbon residue is reduced >90%. Low sulfur diesel fuel (<10 ppm with >52 Cetane number) can be produced. A range of feedstocks can be converted from atmospheric residues to oil sands bitumen including extra heavy crude oils, deasphalted oils, vacuum residues and thermal or visbreaker tars. Products are light gases, naphtha, gasoil (diesel), vacuum gas oil (VGO), deasphalted oil (DAO) and a very small purge of asphaltenes. The process can be optimized to produce maximum gasoline or maximum diesel by further processing the VGO and DAO products in either a catalytic cracker or a hydrocracker. Like other slurry processes, the EST process is attractive for heavy feeds, but unlike other processes, it combines the advantages of carbon rejection with the product quality upgrading of hydrogen addition processes. Since dispersed catalyst systems are not prone to plugging from coke, high metals and high Conradson carbon residue feedstocks can be processed. Unlike other slurry processes, problems of product stability are prevented by the use of a more active catalyst in higher concentration than is possible with once through slurry processes that use low cost catalysts. Using active catalyst allows reaction conditions to be less severe in EST. Residue conversion is projected to continue to increase due to decreasing fuel oil demand coupled with increasing light and middle distillate demand. Processes and motor fuels are both subject to more severe environmental requirements. At the same time, the production of heavy crude oils is likely to increase. We conclude the process can be attractive, especially for a plant built within an existing refinery where the costs of general service facilities can be provided incrementally. In this Review, the economics of hydrotreating Ural vacuum residue for diesel fuel are determined based upon a 30,000 B/SD grass-roots EST unit operating on the U.S. Gulf Coast.