Countermeasure for low temperature dryer or excessive dryers
| The number of dryers may become excessive when the size press is by-passed.
Similarly, in case with lower basis weight like fine paper, where properly high machine speed
is not available by some limitation, portion of the dryers may be closed.
Then their surfaces without steam heat may give harmful effect on paper by getting
sweated and stained, by rewetting the sheet, or by degrading moisture profile.
ACS can reduce partial drying capacity, by maintaining surface temperature at 50〜80
degree ℃ for no heat exchange with the sheet. It is also possible to give slight heat.
Change-over valves are provided to select proper number of dryers and to switch the
system back to suit the original production capacity.
| When air is mixed in steam, the temperature gets lower than that
of saturated steam even in the same pressure.
This is called steam partial pressure.
Below is a simple explanation (Fig.1)
Air 0.1MPa is put in the left side and steam 0.1MPa
(temperature 119.62℃）in the right side.
When the partition between the boxes are taken away,
though the pressure 0.1 MPa does
not change, the temperature changes to 100℃
which is saturated temperature in 0 MPa.
ACS uses this principle.
This system has made it possible to control the temperature ranging from 60℃ to 90℃
inside the dryer, maintaining the minimum pressure (0.01〜0.02MPa) for drain discharging.
MS Air Circulation System(ACS)
Effects of ACS (Air Circulation System)