APPARATUS FOR PRESSURIZED REFINING OF LIGNOCELLULOSE MATERIAL

A multi-stage process, and apparatus for carrying out the process, are provided for refining lignocellulose containing material at high consistency. The lignocellulose material is pretreated to form a mixture of the lignocellulose material and pressurized steam conveyed via the pressure of the pressurized steam to a first refiner, wherein the lignocellulose material is conveyed mechanically into a first refining zone within the first refiner while causing the pressurized steam in the mixture to pass in reverse direction to the lignocellulose to a steam venting outlet to vent the steam from the first refiner. The lignocellulose material fed into the first refining zone is subjected to refining action thereby producing a mixture of partially refined lignocellulose material and pressurized steam developed during the refining action. This mixture of partially refined lignocellulose material and pressurized steam is conveyed via the pressure of the pressurized steam to a second refiner, wherein the partially refined lignocellulose material in the mixture is conveyed mechanically into a second refining zone in said second refiner while causing the pressurized steam in said mixture to pass in reverse direction to the lignocellulose material to a steam venting outlet to vent the steam from the second refiner. The lignocellulose material fed into the second refining zone is subjected to refining action thereby producing a mixture of further refined lignocellulose material and steam developed during said refining action. The further refined lignocellulose material is discharged from the second refiner and separated from the steam developed during the refining action.