CTO Distillation Products

Crude Tall Oil (CTO), also called as liquid oil, is a by-product of kraft pulping process. Commercially, it is mainly used for fractionally distilled to manufacture Tall Oil Fatty Acids (TOFA) and Tall Oil Rosin (TOR). The TSCA Inventory describes tall oil as, “A complex combination of tall oil rosin and fatty acids derived from acidulation of crude tall oil soap and including that which is further refined. Contains at least 70% rosin.”

The main distillation products of CTO include distilled tall oil (DTO), Tall Oil Fatty Acid, Tall Oil Pitch (TOP), Tall Oil Rosin and tall oil heads. In the recovery process of Tall Oil, the principal method of separating the cellulose fibers from non-fibrous constituents of wood is the sulfate or kraft process.

In this process, the raw wood is reduced to chips, which are then digested under heat and pressure with a solution mixture of sodium hydroxide and sodium sulfide, or “white liquor”. This highly alkaline solution forms soluble sodium salts of the lignin, wood pulp as a dark solution known as “black liquor”. This is partially concentrated in multiple-effect evaporator, then cooled and allowed to settle. The fatty acid and rosin soaps separate as a brown curdy mass called “black liquor soap” which is then skimmed off for further processing into tall oil. Terpenes, which are liberated during cooking of the wood chips, are condensed from the steam blown off the digesters and recovered as crude sulfate turpentine.

The black liquor soap skimmings recovered from the kraft process are reacted with sulfuric acid to convert the sodium soaps into free rosin and fatty acids. The reaction mixture is the allowed to settle. The organic acids making up the crude tall oil separate from the sodium sulfate solution formed during the acidification and from the lignin and other impurities. The sodium sulfate is returned to the alkali recovery liquors of the paper mill. The Crude Tall Oil is washed with hot water and allowed to settle. The Crude Tall Oil is drawn off and placed in storage. The yield of Crude Tall Oil varies somewhat, depending on the source of the wood and the details of its processing, but the national average indicates a recovery of its processing, but the average indicates a recovery of about one percent based on the weight of the pulp wood.

There are six life cycle stages have been identified, starting with softwood tree cultivation and harvesting and ending with CTO distillation products ready to be used in the manufacture of products such as adhesives, surfactants, and coatings.

1. Cultivation through transport of pulpwood to pulp and paper mill
2. Kraft pulping
3. BLS Transportation
4. Acidulation
5. CTO Transportation
6. Distillation