In wax refining, deoiling refers specifically to removing entrained/associated oil from slack wax to obtain harder wax grades. Which process is conventionally used for this deoiling step?

Introduction:
Slack wax from lube refining contains a substantial amount of trapped oil. Deoiling aims to reduce oil content to produce harder wax grades suitable for candles, packaging, and specialty uses. Understanding the classical deoiling method clarifies plant flowsheets and quality control.

Given Data / Assumptions:

• Feed: slack wax containing significant oil.
• Goal: reduce oil content in the wax phase.
• Candidate processes: sweating, solvent-based deoiling, and other mechanical/settling approaches.

Concept / Approach:
Traditional deoiling uses the sweating process: controlled heating causes lower-melting oil-rich portions to liquefy and drain away, leaving a harder, more crystalline wax. Modern plants often complement or replace sweating with solvent deoiling for efficiency and tighter specs, but sweating is the classical, named deoiling step.

Step-by-Step Solution:
1) Identify the specific operation called “deoiling” in wax practice.2) Recognize sweating as the established method for oil removal by selective melting and drainage.3) Select “Sweating (controlled warming and drainage)” as the correct option.

Verification / Alternative check:
Industry references distinguish sweating (deoiling) from solvent dewaxing/deoiling used on lube oils; many wax refineries historically used sweating to meet oil content specs.

Why Other Options Are Wrong:
Solvent extraction only: While solvent deoiling exists, the specifically named traditional deoiling operation for wax is sweating.Resettling: Does not selectively remove oil based on melting behavior.All of the above / Acid treating: Over-broad or unrelated to deoiling by selective melting.

Common Pitfalls:
Confusing wax sweating (deoiling) with lube-oil dewaxing or generic solvent extraction; process names are similar but applied differently.

Final Answer:
Sweating (controlled warming and drainage)