Black Liquor Soap

Black Liquor Soap

A stack of tree trunks being hauled away in a semi truck

Black Liquor Soap is a by-product in the production of pulp in the paper processing industry. It is used in production of Tall Oil (Pine Oil), which may be refined into various value-added products.

As wood chips are cooked to produce kraft pulp, their resins and fatty acids react with sodium hydroxide and sodium sulphide, forming soluble soaps in the spent cooking liquor, known as black liquor. These soaps float to the surface in skimming tanks and are skimmed off, pumped to storage, acidification and then to further processing. The soap is rheologically shear-thinning, and viscosities can vary greatly, from 500 to 25,000 cPs, depending on the feedstock, process and temperature. Temperatures range from 160°-195°F (70°-90°C), and the material is corrosive due to high alkalinity, with pH often exceeding 12. It can also be somewhat abrasive and may hold entrained gases from air flotation processes.

Positive displacement pumps are particularly well-suited for transferring black liquor soap due to their ability to handle high-viscosity fluids efficiently and maintain a consistent flow rate regardless of pressure variations. Black liquor soap presents challenges due to its viscous nature and other characteristics. Positive displacement pumps excel in such environments because they effectively trap a fixed volume of fluid and transport it through the pumping system, ensuring a steady and reliable flow. Additionally, these pumps offer excellent suction capabilities, allowing them to handle the challenging properties of black liquor soap without cavitation issues. This makes positive displacement pumps an ideal choice for processes requiring precision and reliability in the transfer of these materials

Viking in the Process

Viking pumps are commonly used to transfer soap from the skimmer tank to storage and then acidification or to railcar loading for off-site processing. When the crude soap is acidified into crude tall oil (CTO), Viking pumps then transfer that to the on-site refinery for separation processes, or to railcar loading for off-site processing.

Applications

  • Soap transfer from skimmer tank to storage
  • Transfer from storage to acidification
  • Railcar loading for off-site processing
  • Crude tall oil transfer to on-site refining

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