Optimization of enzymatic starch preparation and working station to filmpress including a case study, Wolfgang Schmölzer, Head of Technology Management and Plant Design, GAW technologies

PAPERTECHNOLOGYINTERNATIONAL
Optimazation of Enzymatic Starch Preparation and Working Station to Filmpress including a Case Study.
Wolfgang Schmölzer, Head of Technology Management and Plant Design, GAW technologies
INTRODUCTION:
With high prices for common and widely used raw materials like starch in additive processing within the paper and board industry
as well as extremely high costs for gas and energy, the savings of resources and the reduction energy and electricity consumption is more
important than ever. It is also another step in achieving sustainability goals and reducing the carbon footprint of paper mills worldwide.
Proven technologies can support producers in this matter.
The use of starch as an additive in the paper industry
is very versatile. For example, starch is used to treat the paper
surface, the so-called sizing or impregnation. Thanks to improved
surface properties, starch also helps to improve writing property
and printability. Furthermore, the strength and rigidity of the sheet
is improved by applying surface size. In the manufacturing process
of corrugated cardboard, starch is used as an adhesive to bind and
glue the layers of paper. However, when native (unmodified) starch
is used, it must be prepared in advance in order to be able to use
it as an adhesive. For the processing of starch, the colloquial term
“cooking of starch” is also used.
If you mix starch powder with (cold) water, you get a cloudy
liquid that looks like diluted milk. In contrast to milk, which can be
mixed/diluted with water indefinitely, a water/starch mixture (starch
slurry) is a two-component mixture, since the starch powder does
not dissolve in water. Thus, the starch granules are undissolved
and finely distributed as a solid in the water. Such a two-component
mixture is also referred to as a suspension. If a sample is left to
stand for a longer period of time, the sedimentation of the starch
granules can be observed.
Figure 1: (Above) Starch cells under the microscope.
Figure2: (Left) GAW starch preparation make-down station.
If the starch suspension is heated, the starch granules will
swell. The solid particles “grow” continuously in volume until the
cell walls of the starch granules burst open. Only then the starch
is able to dissolve in the water and can be used as a paste for the
paper web. The swelling and subsequent “going into solution” of
the starch granules is also referred to as “gelatinization” in technical
terminology. As an undesirable side effect, however, there is also an
increase in viscosity during swelling.
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