Abstract: The invention concerns a pulp grinder in which feed devices force the wood against the grinder stone and in which there is an elevated level of water in the grinding zone. Sealing devices or plates extend between the walls of the wood-supply chutes or pusher chambers and the grinder stone to keep the water level high only in the grinding zone. The sealing plates are adjustable for controlling the liquid level in the grinding zone.

Abstract: The disclosure concerns a process for grinding wood on a grinding stone and the grinding stone which grinds the wood. The grinding stone has a central core, which may be comprised of concrete or steel. The core has a free inner space. A water supply line extends along the free inner space. Outlets from the water supply line are directed toward the periphery of the core at the grinding zone of the grinding layer. Around the core is a grinding layer for grinding the wood. The grinding layer is permeable so that water can be transmitted through it. The permeability may arise from the porosity of the material of the grinding layer itself or through the provision of bores or gaps in the grinding layer. The grinding layer may be comprised of a group of segments covering the core and the gaps may be defined between segments. The core may have bores for delivering the water to the inside of the grinding layer. The water may be heated and/or pressurized for improving grinding.