PRODUCTION OF LIGNOCELLULOSE PULP BY GRINDING AT INCREASED TEMPERATURE

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 DEG to about 100 DEG C., and forming a pulp suspension in the resulting aqueous liquor; centrifugally separating steam from the pulp suspension, and using the separated steam to heat the water supplied to the grinding; thickening the pulp suspension to a pulp concentration within the range from about 5 to about 40%, and supplying water separated therefrom to the grinding; diluting the thickened pulp, and screening the diluted pulp suspension; after thickening the screened rejects suspension to a pulp concentration of at least 10% and defibrating the screened rejects suspension in a refiner, recycling the defibrated screened rejects to the from-steam-separated pulp suspension; and mixing the thickened and refined rejects suspension, having a pulp concentration of at least 8%, with the pulp suspension, thereby increasing the pulp concentration of the from-steam-separated pulp suspension, and thus facilitating its thickening.