Hot water treatment

Pre-steamed chips are discharged from the pre-steaming bin into the plug screw feeder via a chute or a metering conveyor. The plug screw feeder dewaters the chips by compression and conveys them into the digester.

The condensate formed during pre-steaming and the water squeezed out by the plug screw feeder drain from the bottom of the feeder housing. The water is usually carried to the water treatment plant or, if there is a chip washing system, is used to increase the wash water temperature (and washing efficiency).

The ANDRITZ hot water treatment process offers the opportunity to recycle the drain water and reuse it to flush the inlet and compression housing of the plug screw feeder if no chip washing system is installed.

Components of the ANDRITZ hot water treatment process

The drain water from the plug screw feeder flows through the Hydrasieve to separate the impurities from the wash water. The clean wash water is then collected in the hot water tank. The bottom of this tank is designed as a settling chamber for fine impurities, such as sand. The tank also prevents dry running by the hot water pump, which recycles the water back to the plug screw feeder to clean debris from the inlet and compression housing.

The advantage of the hot water system is the use of warm water for cleaning the ANDRITZ plug screw feeder housing instead of fresh water, so the low fresh water demand helps to reduce operating costs.