Method Development for Separation of Tall Oil Soap

Abstract

Tall oil soap, one of the components in black liquor that is a byproduct from the kraft process in the paper industry, is essential to be separated and recovered to maximize both efficiency and profitability for a paper industry company. This is achieved through natural separation of soap and mechanically separating through ex. Circular soap skimmer. BIM Kemi AB has additives that increase the separation rate of soap, making it rise faster, and making it more densely packed in the top layer. BIM has variations to these additives, but testing these variants proves difficult, since tall oil soap in black liquor separates naturally. Sending black liquor to BIM’s laboratory won't work, since the soap will have fully separated by the time it arrives in BIM’s laboratory. Thus, a solution to this problem needs to be found. Creating artificial black liquor and developing a method around it to try BIM’s additives was the goal. A simple artificial black liquor was created using a few salts and a custom tall oil. These salts are 10% Sodium Hydroxide (NAOH), 10% Sodium Sulphate (NASO4), 5% Potassium Hydroxide (KOH), and 75% Water. The custom ratio tall oil is created using 60% Rosin acids and 40% Fatty acids. Tests comparing separation with and without additives resulted in no differences over longer periods of time. UV-Vis measurements over a large spectrum (340-1000 nanometres) showed no differences. A method called “speed test method”, measuring separation time within the first minutes of mixing tall oil and the alkaline solution of salts was created. After optimizing the speed test method, some variations between each test were still present. These variations are most likely caused by chaotic flow of soap particles, variations in mixing and the artificial black liquor being too rudimentary, making soap particles separate too fast, thus not allowing the additives to impact the separation process. Future studies should add more chemicals, especially organic to the artificial black liquor to both improve the realism of the artificial black liquor, but also slow down the separation process, so that additives can shop visible improvements to the separation of tall oil soap.