Application: Bechtel’s Dewaxing/Wax Fractionation processes are used to remove waxy components from lubrication base-oil streams to simultaneously meet desired low-temperature properties for dewaxed oils and produce hard wax as a premium byproduct.
Description: Bechtel’s two-stage solvent dewaxing process can be expanded to simultaneously produce hard wax by adding a third deoiling stage using the Wax Fractionation process. Waxy feedstock (raffinate, distillate or deasphalted oil) is mixed with a binary-solvent system and chilled in a very closely controlled manner in scraped-surface doublepipe exchangers (1) and refrigerated chillers (2) to form a wax/oil/solvent slurry.
The slurry is filtered through the primary filter stage (3) and dewaxed oil mixture is routed to the dewaxed oil recovery section (6) to separate solvent from oil. Prior to solvent recovery, the primary filtrate is used to cool the feed/solvent mixture (1).
Wax from the primary stage is slurried with cold solvent and filtered again in the repulp filter (4) to reduce the oil content to approximately 10%. The repulp filtrate is reused as dilution solvent in the feed chilling train. The low-oil content slack wax is warmed by mixing with warm solvent to melt the low-melting-point waxes (soft wax) and is filtered in a third stage filtration (5) to separate the hard wax from the soft wax. The hard and soft wax mixtures are each routed to solvent recovery sections (7,8) to remove solvent from the product streams (hard wax and soft wax). The recovered solvent is collected, dried (9) and recycled back to the chilling and filtration sections.
Licensor: Bechtel Corp.