Paper360 - January/February 2018 - 26
techlink | PITCH CONTROL
A Novel Synthetic
Adsorbent for Pitch Control
The primary organic contaminant
in the pulping process is pitch. Pitch reduces
pulp mill efficiencies and productivity from
the washers through to the pulp dryer. Talc,
an inorganic adsorbent, is the most common
treatment for pitch control. Talc can cause scaling on evaporators, and is generally applied
after brownstock washing.
Yet talc has been raised as a health concern in personal care products, and its
use is monitored by producers of pulp for
fluff, tissue, and toweling. The application
of talc is dusty, requires dispersion equipment, and demands additional attention
from operations personnel. Overuse of
talc can also damage machine clothing by
Archroma has developed a novel treatment for pitch control utilizing an organic
adsorbent. Cartaspers PLH liquid eliminates
pitch without talc, and minimizes the impact
on other process variables (see sidebar). This
article details the use of Cartaspers PLH liquid
in a mill application, comparing the performance of the product to talc.
A mill located in Brazil had pitch issues
due to high system closure. The plant characteristics before introduction of Cartaspers
PLH liquid were as follows:
* Kraft low solids cooking process
* Kappa 17
* 100 percent eucalyptus hardwood
* DD Washers
* 4.5 kg/t talc divided in two addition
points, after O2 delignification, and after
After performing an in-mill laboratory
study, the mill introduced Cartaspers PLH
liquid at filtrate of press post oxygen delignification at dosage rate of 300 g/adt. The
filtrate is used to wash pulp in the previous
washer stage, and adjusts stock consistency
to the DD Washer located prior to the oxygen reactor. Using a counter current washing
system, pitch is sent to the digester and consequently purged out to the evaporation plant.
A summarized flow sheet is shown in Fig. 1.
A second addition point was introduced
at the Ep Stage to guarantee removal of any
residual pitch that may be extracted. Dosage
at this point was 150 g/adt.
Colloidal pitch counts showed a significant
drop. Figure 2 and Fig. 3 present results of colloidal pitch counts on range of 60 days, split
30 days with talc, and 30 days with Cartaspers
The application of Cartaspers PLH liquid
was effective in controlling pitch in the pulp
mill. The customer was able to guarantee pulp
performance with colloidal pitch counts, which
were below the control (prior to the application of Cartaspers PLH liquid). Ultimately, the
reduction in ash of the cellulose was verified
and the cost of application was 25 percent lower
compared to the talc. These results obtained
on an industrial scale allow the following
* Lab work demonstrated that 0.45 g/t of
Cartaspers PLH liquid replaced 5.0 kg/t of
talc, a ratio of 1:11.
* The mill application validated the ratio, with
450 g/adt of Cartaspers PLH liquid versus
4.50 kg/adt of talc, a 1:10 ratio. Quality was
maintained at normal levels.
* With Cartaspers PLH liquid, pitch counts
were significantly lower, enabling future
optimization, and total cost reduction
Fig. 1: Flow sheet of pulp plant with Cartaspers PLH.
The process of organic passivation with
Cartaspers PLH liquid offers many benefits,
* The product is a water-based emulsion, delivered ready to use, requiring a simple metering pump and no makedown equipment or
dry handling system. It provides a safe, dustfree environment for pulp mill employees. It
is organic, contains no aluminum or metal
ions, and contributes no ash in the pulp.
* Use of an alternative eliminates the health
concerns that are associated with talc in the
personal care industry, which is especially
important in pulp applications for tissue,
toweling, and fluff pulp.