| 摘要 |
<p>A continuous solvent dewaxing process wherein a waxy oil (10) is prediluted (18) with a non-autorefrigerative solvent, e.g. ketone, and then passed (24), at a temperature above its cloud point to the top of a chilling zone (26), which is an autorefrigerant chilling zone operating on a continuous basis. The chilling zone (26) comprises a vertical, multi-staged tower, operating at substantially constant pressure. In this chilling zone, wax is precipitated from the oil to form a waxy slurry and the soformed slurry is further chilled down to the wax filtration temperature by stage-wise contact with liquid propylene (28) or other autorefrigerant which is injected into the liquid layer (58) in each of a plurality of said stages and evaporated therein so as to cool the waxy slurry at an average rate of between about 0.06 to 11.12 DEG C per minute with an average temperature drop across each stage of 1.11 to 11.12 DEG C. Some of the propylene remains in the oil which serves to further dilute and reduce the viscosity of the slurry, and the vaporized propylene (34) in cach stage exits therefrom (52) without contacting liquid at least in more elevated stages. Teh dewaxed oil containing slurry may then be fed (40) directly to wax filters (42) without having to pass through scraped-surface chillers and filter feed drum. In one type of embodiment, the non-autorefrigerative solvent is employed cold so as to partially solvent dewax the waxy oil to a temperature within of from about 16.65 to 61.2 DEG C of the final wax filtration temperature before being contacted with autorefrigerant in the autorefrigerative chilling zone (26) to be chilled down to the desired wax filtration temperature.</p> |
