Fibre collapse point

Some success has been reported with hardwoods, but only for those species that are not particularly difficult to dry using conventional schedules. Overall drying time can be halved but at the expense of additional degrade such as honeycombing and collapse. Some recalcitrant timbers may be dried successfully but only if they have been pre-dried to the fibre saturation point. Other hardwoods cannot be high-temperature dried at all. 

Collapse precedes conventional shrinkage, only occurring within saturated cells, whereas normal shrinkage occurs below the fibre saturation point. Where present, severe eollapse is revealed by a series of corrugated depressions matching earlywood... 

Newsprint This example is from a mill producing standard newsprint from a furnish mix consisting of TMP and recycled fibre. The machine runs at a temperature of 45-55°C, and production is 600 t/day. Foam build-up is evident only in the wire pit and silo, but without adequate conttol the foam can grow to 15 feet in height. This foam overflows the wire pit and creates a housekeeping problem in the basement of the mill. Also, the wire pit has a mist removal system that will fill up with foam. At one point the duct in the mist removal system collapsed because of foam build-up (a serious safety problem). 

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