Paper Technology International 2024 - Journal - Page 101
PAPERTECHNOLOGYINTERNATIONAL
Blow-through control not only prevents steam loss on web
breaks but also offers other technical bene昀椀ts. The dryer DP drops
by roughly 70% on a break, which is in accordance with the process
mechanics when blow-through 昀氀ow is restrained at a steady rate.
The compression work is thus reduced at that time and the controller
reduces the signal to the thermocompressor accordingly. The
thermocompressor remains in normal control range in this case
as well as in all other points of normal steaming load. Not only is
the thermocompressor always in its working range at all operating
conditions but a single semi-permanent blow-through control
setting may be used. This is in great contrast to DP control in
which compression work increases exponentially as dryer pressure
is reduced or on load loss during breaks and thermocompressor
chokes with the nozzle wide open.
The drying process on a paper machine involves numerous
complex factors, therefore it is crucial for all components, particularly
thermocompressors, to operate 昀氀awlessly for maintaining high
ef昀椀ciency operations. To effectively utilize thermocompressors,
addressing various process and control challenges is necessary.
Table 1: summarizes common process issues, their underlying
design causes, and proposed solutions. Process simulation is an
important part for sizing both thermocompressors and entire dryer
drainage systems.
Figure 2 (Top left) and Figure 4: (Above)
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