Infrared profiling with substantial increase in production speed

Model AG operates at its Weinfelden mill two papermachines producing containerboard. The trimmed width of PM 1 is insufficient for paper grades produced today. The sheet is produced at maximum possible width of 255 cm, even if this causes a wet edge with over 12% moisture.
The machine was equipped 15 years ago with infrared edge dryers just before the winder. On 150 mm width the edge is heated with 48 kW infrared radiation on both, tender and drive side. Nevertheless the edge is too humid and thus production speed and capacity are limited. Additionally we’re facing big problems on the corrugators, which lead to runnability problems.

We searched for a solution which allows bringing the edge immediately to the same moisture as the rest of the sheet to avoid customer complaints. At the same time the solution should allow speeding up the machine in near future to 600 m/min.
Compact Engineering suggested a solution reducing the energy consumption significantly and increase in the future the speed as desired.
For this purpose, two plus two emitters each with a power of 48 kW will be installed in the pre-dryer section on tender and the drive side. These can be used to overdry the edge on 150 mm width before the size press, so that size is not excessively absorbed here.
The emitters on each side of the machine are profile-controlled in four zones of 37.5 mm each to guarantee perfect moisture across the entire width of the edge.
It was suggested by Compact Engineering to dry the edge of the base paper where the shrinkage of the paper on the cylinders occurs - and thus reduce runnability problems during rewetting on the corrugator. For this purpose, the infrared lamps with adapted radius of the drying cylinders are placed over the drying cylinders at the exit of the third and fourth pre-drying groups. One felt roll must be moved to find space for the emitters. The advantage of installation at this point is a long post-evaporation zone before the size press.

The existing emitters remain in the machine for the time being. It will be checked later whether the new, energetically optimized solution will also be suitable for the maximum expansion stage.
In a further step, the profile control can be carried out over the entire width. Since the web is currently overdried in the middle, the moisture fluctuations here are very small. This may change if overdrying is no longer necessary due to excessively moist edges.