Hydroconversion and solvent refining are now well established processes to produce high quality lubricant oils. The choice of a particular process depends mainly on the quality of the end product. - Hydrogen availability and cost - Market demand for by-product of solvent refining and solvent dewaxing (aromatic extracts and waxes) - Capital investment and operating costs.
At the Naftec refinery in Arzew, the first lubricant plant that started in the early seventies was based on the most recent process at that time, to make high quality base oils i.e. furfural extraction plus solvent dewaxing.
Ten years later a newer and bigger lubricating oil plant (twice and a half the size of the old one: 120000 MT/A) started producing the same base oils under the same process. The choice of the same process for the new lubricant oil plant was deliberate since first of all the quality of the base oils already produced was good enough to formulate all qualities of finished oils, there was a great demand for waxes on the national market, and last but not least trained operators on fairly identical units were available to start-up this new plant rapidly.
If new lubricating oil facilities were to be built on the same site today, the choice would probably be different.
Hydrorefining would be competitive against furfural extraction since with this newer process higher yields and higher viscosity index oils can be obtained. Distillates in excess and hydrogen being readily available on site.
Furthermore hydrodewaxing looks very attractive nowadays since high yield and low pour point base oils can be obtained at a lower capital investment and reduced operating costs compared to solvent dewaxing.
Other important factors have also to be considered: I NTRODUCTION Solvent extraction is now the classical way to make high quality raffinates from distillates for a large variety of crude stocks.
The process of extraction has always been a well established chemical operation. However the process was further developed and licensed by TEXACO to obtain good yield and high VI raffinates to make lubricating oils.
The process used phenol as th first extracting solvent and moved on to furfural. Now n-methyl pyrolidone is pushing its way to replace furfural.
Although these changes in solvents have not affected the quality of the raffinates, they brought improvements in operations. One of the highest operating costs is the loss of solvents the change of solvent towards NMP has kept the loss of solvent to a minimum since NMP enables a better recovery. Not to mention health risks for Phenols and the cocking tendency of furfural (increase of maintenance cost).
Typical yields for north-african paraffin crude stocks are 65 to 70%. Depending on the viscosity of the treated distillates, the v
