Unlocking the green gold: maximising tall oil yield with chemical solutions by Hannu Hämäläinen, Pulp Segment Team Leader, BIM Kemi and Johan Berglund, Senior Product Developer, BIM Kemi

PAPERTECHNOLOGYINTERNATIONAL
The challenges of tall oil recovery
Despite the value it represents, tall oil recovery in kraft pulp
mills is often ineficient. Studies and industry data show that, on
average, only 80–90% of the available tall oil content in wood is
recovered using conventional methods. Several factors contribute to
this limitation:
•
Foam formation during brown stock washing, leading to
soap loss
•
Incomplete separation of soap from black liquor during
evaporation
•
Ineficient separation processes at tall oil plants.
•
Variability in raw material composition and process
conditions
These factors result in typical losses of 5–20% of the
potential tall oil, undermining both profitability and sustainability
performance. Addressing these losses requires a multifaceted
approach that combines process optimisation with targeted chemical
solutions.
Traditional and emerging methods of tall oil recovery
There are several methods available for recovering tall
oil in kraft pulp mills, each varying in complexity, efficiency, and
implementation cost. These methods range from long-established
mechanical separation techniques to more recent advancements
involving chemical additives that enhance each step of the process.
Key approaches used in the industry today are:
1. Soap skimming from black liquor
After brown stock washing, soap is present in the black
liquor. During evaporation, soap is separated by skimming
and collected in a tank. The efficiency of this step depends on
parameters such as:
• Dry solids concentration
• Temperature
• Soap quality
This is a widely used and well-established method in most
pulp mills. However, it is limited by physical process conditions
and efficiency varies by mill and process stability. Typically, this
method allows for recovery of up to 90% of the available soap,
though losses of 1–5% are common due to incomplete separation.
It requires continuous process monitoring and adjustment. Without
effective soap skimming, tall oil recovery is compromised.
2. Acidulation of soap to produce crude tall oil
In this step, the skimmed soap undergoes
acidulation, where it is mixed with an acid to convert the
sodium salts into free fatty and resin acids. This phase
separation produces crude tall oil and an aqueous byproduct. Acidulation can be performed using:
•
Batch reactors (common in older facilities)
•
Continuous systems, such as the HDS (Hydro
Dynamic Separator) process
This is an established process with known
parameters and enables production of crude tall oil with
high value. However, these systems can be slow and
labour-intensive and phase separation can be inefficient
without additives. It requires careful pH and temperature
control to ensure separation. The performance of this phase
separation determines the final tall oil yield and quality and
there is a risk of quality variation if not optimally managed.
30
3. Advanced chemical additives and process optimisation
Recent innovations have introduced chemical solutions to
improve each stage of the tall oil recovery process, using targeted
chemicals. These additives enhance separation efficiency without
requiring capital investment or shutdown and are customisable to
each mill’s unique process.
Chemical additives require expert knowledge for dosing and
implementation, which is why good cooperation with the chemical
supplier, combined with process understanding and on-site support,
can unlock significant value from existing operations. When used
strategically, they significantly improve yield, reduce losses, and
ensure consistent product quality.
A chemical-based approach to maximising tall oil yield
Developed by BIM Kemi, the BIM Talloil Maximisation
concept, BIM TOMAX, is a comprehensive, three-part approach
designed to improve tall oil yield through targeted chemical
applications. According to field data, it can increase tall oil yield by
up to 20% without requiring major capital investment. The concept
improves yield at critical stages of the pulp process — during brown
stock washing, recovery, and at the tall oil plant.
1. BIM Antifoam – reducing washing losses
Foam formed during brown stock washing introduces air into
the system, disrupting the transport of soap and causing losses as
some soap moves to the bleaching stage instead of black liquor. The
average washing loss is around 5%.
BIM Antifoam, a silicone-based formulation, is designed to
reduce foam and promote efficient soap dissolution into the black
liquor. With its application, washing losses can be reduced to as low
as 1%, thereby preserving more soap for later recovery. The dosing
method, dosing point, and speci昀椀c product used for BIM Antifoam
are tailored to each mill, and no shutdown of the process is required
for its implementation.
Key benefits:
•
Reduction in foam formation
•
Improved soap transport
•
No shutdown required for implementation
•
Customised dosing per mill conditions
Figure 2: Composition of good quality soap, containing up to
55 % of tall oil.

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