Specialty chemical technologies for high-quality, sustainable and cost-effective chemical pulp production - Paper Technology International 2023 - Paper Technology International 2023 - Flipbook - Page 33

Specialty chemical technologies for high-quality, sustainable and cost-effective chemical pulp production - Paper Technology International 2023

PAPERTECHNOLOGYINTERNATIONAL Specialty chemical technologies for high-quality, sustainable and cost-effective chemical pulp production - Paper Technology International 2023
Figure 3: Agglomerations without anti-pitch agent vs anti-pitch
agent stabilisation.
Closure of the water loops and the neutral papermaking
processes have caused severe pitch issues in recent years. Optimal
pitch control without talc can be achieved by continuous use of antipitch agents suited for both alkaline and acid conditions.
The benefits of a pitch control are:
Primary:
•
Lower extractive content in pulp
•
Cleaner process and pulp
•
Improved runability
Secondary:
•
Talc free pulp production
•
Reduced holes and spots in paper
•
Increased tensile strength
•
Improved smell and taste of paper and board
To achieve optimal results, a thorough working knowledge
of the process is essential. This knowledge is then applied to
mapping the system in great detail, localising the critical points for
pitch deposits. Test samples are then taken and analysed to provide
indications for product choice as well as dosage amounts and
points.
Different analytical measuring tools, such as BIMPICS, POFanalysis, etc. can help analysing the pitch and choosing the correct
dosing position and correct product.
Figure 4: Conveyor screw covered with pitch- and talcum
deposits.
Protecting the fibre for a uniform cooking
In a chemical pulp process all chips are not treated evenly,
leading to an uneven cooking with following consequences:
•
process variations and uneven quality
•
higher alkali concentration needed to reach the target
kappa
•
increased bleaching chemical consumption due to a
wider kappa variation
•
higher reject amount due to undercooked chip centres
•
decreased yield and pulp mechanical properties
The growing shortage and higher cost of raw materials for
pulp production have increased the need to maximise yield during
the pulping process. Several modifications to the pulping process
have been attempted, such as extended modified continuous
cooking and super batch cooking of all which require major capital
investments and increase boiler recovery load. Chemical additives
are less costly alternatives for a uniform cooking and as replacement of anthraquinone (AQ), since there is a growing concern over
the impact of AQ on downstream operations such as evaporator
fouling and tall oil production.
Figure 5: The same conveyor screw treated with pitch
control agent.
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