Soap and turpentine in softwood kraft mills

Panu Tikka wrote a short commentary on one of his old publications:

PaT 180721 Tikka, et al.
Solving soap and turpentine related process problems in softwood kraft mills.
P&P Can, 103(2002)6:T 149, p 30 – 35

In the modern more and more sustainable biobased economy the old obnoxious word “pulp mill” is being replaced by a better expression “ bioproduct plant “ which describes the change from a paper mill’s polluting pulp department into a complicated highly closed process integrate, which produces a variety of bio(forest)based commodities: cellulosic fibers, polysaccharides, lignin, tall oil, turpentine, electricity, biogas, distance heating etc. for future bioeconomy.

One distinctive group of these biobased chemicals is the so called “tall oil”, that is a mixture of mainly resin and fatty acids originating from the wood extractive, besides, turpentine is separated and produced. This group of chemicals is quite different from the main wood components – it is only partially and difficultly solubilized and exists first as soap and soap foam in the fiber line process. Thus, it must be removed at several key points in the fiberline and recovery process, collected, concentrated and acidified to obtain an easily separating product, the tall oil. However, this is easier said than done! Especially older pulp mills are definitely not designed for optimum soap separation and clean process. High tall oil and turpentine yields, and stable operation need good process design and identification of case and raw material based situations.

This article gives a comprehensive and practical view on the entire issue of “soap and turpentine related problems” and methods and tools to make “the problem” quantitative and visible – thus easy to understand and cope with. Main soap solubility parameters and accumulation loops and critical process points are presented. A tutorial follows teaching new methods and measurements in process studies and soap & tall oil analytics. As a synthesis, soap separation organs and basic soap process concept is discussed.

You can read the full article below: