Patent ID: 8753476

Claim:
A method of producing a mechanical pulp from lignocellulosic material in a pulping system comprising a pretreatment subsystem comprising a pressure separated feeding device, a high compression device, and an impregnator, and a production subsystem comprising a variable speed pressurized conveyor and a primary mechanical refiner, the method comprising the following steps: providing lignocellulosic material to the pressure separated feeding device and then transferring the lignocellulosic material to the high compression device; wherein the step of destructuring the lignocellulosic material in the high compression device results in a destructured lignocellulosic material in which over 50% of the destructured lignocellulosic material by weight passes through a 16 mm screen perforation; transferring the lignocellulosic material from the high compression device to the impregnator and impregnating the lignocellulosic material; transferring the lignocellulosic material to the variable speed pressurized conveyor, wherein a residence time of the lignocellulosic material in the variable speed pressurized conveyor is 20 seconds, and wherein the variable speed pressurized conveyor operates at a pressure between 7.5 and 12 bar (gauge) and preheats the lignocellulosic material with steam; transferring the lignocellulosic material to the primary mechanical refiner; and mechanically refining the lignocellulosic material in the primary mechanical refiner at a pressure between 7.5 and 12 bar (gauge) to obtain a high freeness pulp.