Abstract: Apparatus for continuously processing wood comprises a pressurized grinding chamber, a grinding stone which is mounted for rotation in the grinding chamber, a device for feeding wood into the grinding chamber to form a primary groundwood stock therein, and a device for discharging the primary groundwood stock from the chamber without allowing gas to escape from the chamber to atmosphere. The feeding device comprises a stationary feeding chamber provided with shutters for sequentially pressure-tightly closing the feeding chamber from the atmosphere and from the grinding chamber respectively, thereby to prevent escape of gas from the grinding chamber through the feeding device.

Abstract: Apparatus for continuously processing wood comprises a pressurized grinding chamber, a grinding stone which is mounted for rotation in the grinding chamber, a device for feeding wood into the grinding chamber to form a primary groundwood stock therein, and a device for discharging the primary groundwood stock from the chamber without allowing gas to escape from the chamber to atmosphere. The discharging device comprises a stick crusher for crushing sticks present in the primary groundwood stock thereby to produce a secondary groundwood stock and an outlet for continuously discharging the secondary groundwood stock while preserving a hydraulic seal of groundwood stock thereby to maintain the groundwood stock in the apparatus under superatmospheric pressure.

Abstract: A method of grinding wood under pressurized conditions in a grinder according to which wood is fed in batches into a pressurized gas-filled grinding chamber provided with a rotary grinding means. The wood batches are fed through a feeding chamber provided with means for sequentially opening and pressure-tightly closing said feeding chamber from two sides in and respectively out of communication with the atmosphere and said grinding chamber respectively. The groundwood stock is discharged from the grinding chamber through a pressure lock formed by the groundwood stock. In this way feeding of the wood batches into the grinding chamber and the discharging of the groundwood stock out from said grinding chamber are carried out as sluicing steps, whereby a continuous pressure can be maintained in the grinding chamber in spite of feeding of new wood batches and discharging of groundwood stock.

Abstract: A method of discharging groundwood stock when grinding wood under pressurized conditions in a grinding chamber, according to which the groundwood is suspended into stock and collected in a tank provided with an outflow for groundwood stock to atmospheric pressure. The surface of the stock in said tank is maintained at such a level above said outflow, that the stock in said tank forms a pressure lock in the communication between the grinding chamber and said outflow. In this way the discharging of the groundwood stock out from said grinding chamber is carried out as a sluicing step, whereby a continuous pressure can be maintained in the grinding chamber in spite of discharging of groundwood stock.

Abstract: A process is provided for preparing groundwood pulp from debarked pulpwood logs which comprises grinding the logs under a superatmospheric pressure of a gas selected from the group consisting of steam, air and steam and air, while continuously supplying thereto process white water and water separated in thickening groundwood pulp suspension at a temperature within the range from about 75.degree. to about 100.degree. C.