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Abstract

A semi-continuous acidulation process for converting tall oil soap to crude tall oil is disclosed. Reactants are continuously mixed, and the product mixture is continuously transferred to a settling tank having a conical lower section and a capacity at least 25 times that of the mixer. Batches settle to give a solid phase comprising calcium sulfate, a clean spent acid phase, a dirty spent acid phase, and a crude tall oil phase. Each phase is removed sequentially through a port at or near the bottom of the settling tank. Compared with traditional batch acidulation, continuous mixing minimizes the corrosive environment and enables the use of less expensive materials for the settling tank. Sequential removal of four phases from one port allows calcium sulfate to be purged from every batch, permits clean separation of clean spent acid from dirty spent acid, and enables clean recovery of tall oil. Compared with processes that isolate product continuously, inherent difficulties in using centrifuges or continuous decanters to separate four phases are avoided. The process facilitates generation of clean alkaline brine and integration of new soap washing methods that enable improved conversion yields of CTO and better removal of calcium from the soap.

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First Claim