Producing quality MDF requires chips that are as free from impurities as possible. Debarking and screening are not enough. Chip washing is essential for producing board of low mineral content. The growing use of purchased chips, e.g. from sawmills, results in an ever-increasing need for chip washing. Existing impurities, in the form of metal, stones and sand, must be removed before the chips enter the process.
Efficient chip washing increases the lifetime of refiner segments and reduces maintenance and replacement costs for other machinery in the process such as plug screws, preheater, feeder screws and other machinery. Efficient chip washing reduce the grit content in the finished panels and enables optimal consumption of chemicals, electricity and raw materials
The raw material are mixed with water in the scrap separator which separates and removes foreign material like sand, stones and metal particles.
After the washing, the raw material are drained from water by a screw drainer.
The collected water is re-used at the chip washer. Excess waste water from the washer and plug screw feeder can be treated and re-used to make the needed steam in the fiber production process.
Valmet Chip Washing concept overview
