Three zone multiple intensity refiner

A disc refiner, comprising:

• a rotatable shaft;
• a rotary disc mounted on said shaft for rotation therewith and having front and back grinding surfaces on respective front and back sides of the disc;
• relatively static front and rear plates in respective opposing spaced relation to the front and back grinding surfaces of said disc;
• means for adjusting at least one of said front and rear plates to vary the spacing between said one plate and the opposed grinding surface on said disc;
• means for directing all the material to be refined radially between said disc and one of said front and rear plates for partial refining of the material and then directing at least some of the partially refined material through the disc to the opposite side of the disc and radially between the opposite side of the disc and the other of said front and rear plates;
• a third grinding surface mounted on the disc and an associated spaced apart, third stationary plate, located at the same side of said disc as said one plate;
• wherein said means for directing includes means for directing some of the partially refined material from said one plate to said third plate;
• means for controlling the pressure upstream of said one plate;
• means for controlling the pressure in said passage;
• and
• means for controlling the pressure downstream of said other plate.

In a disc refiner including a rotatable shaft situated in a housing, a rotating disc situated in a casing and mounted on said shaft for rotation therewith, the disc having front and back grinding surfaces on its opposite sides, front and back relatively static plates in opposing relation to the respective front and back grinding surfaces of the disc to define respective front and back refining zones therebetween, feeder means for introducing feed material to be refined into the casing, and outlet means for directing refined material exiting from the front and rear refining zones out of the casing, wherein the improvement comprises:

• said front refining zone includes
• a first refining zone located relatively near the shaft and into which the feed material is introduced, said first refining zone being defined by a first grinding surface on the front side of the disc and an opposed first stationary plate, and
• a second refining zone located relatively farther from the shaft and defined by a second grinding surface on the front side of the disc and an opposed second stationary plate, said first and second refining zones being radially spaced apart and distinct from each other;
• said disc includes means formed between the first and second refining zones for conveying one portion of the partially refined material exiting from the first refining zone into the second refining zone, and conveying another portion of the refined material exiting the first refining zone into the back refining zone;
• said outlet means directs refined material exiting from the second refining zone and the back refining zone out of the casing;
• and
• wherein each refining zone has a radially inner entrance and associated entrance pressure and a radially outer exit and associated exit pressure, and the improvement further comprises means for independently adjusting the entrance pressure of the first refining zone, and the entrance pressure of the back refining zone.

A pressurized disc refiner for refining wood chips and similar feed material into fiber with integral steam separation, comprising:

• a pressure housing;
• a shaft mounted for rotation in the housing about a rotation axis;
• a rotary disc coaxially mounted on the shaft within the housing for rotation therewith, the disc having a front side and a back side;
• a first substantially radially oriented refining zone at the front side of the disc, the first refining zone having an entrance for receiving feed material at a feed pressure and an exit for discharging a mixture of steam and partially refined material;
• a second substantially radially oriented refining zone at the front side of the disc, the second refining zone being distinct from the first refining zone, and having an entrance adjacent the exit of the first refining zone;
• first means at the front side of the disc and rotatable therewith, for imparting a substantially radially outwardly directed centrifugal force to the mixture discharged from the first refining zone;
• and
• second means including a passageway from the front to the back side of the disc, for imparting a substantially axially directed pneumatic force on the mixture discharged from the first refining zone;
• whereby the centrifugal and pneumatic forces direct at least most of the partially refined material from the first refining zone into the entrance of the second refining zone, and most of the steam from the first refining zone into the passageway to the back side of the disc.

A disc for a disc refiner, comprising:

• a substantially annular body having a central axis of rotation, first and second axially spaced sides extending substantially radially from the axis, a circumferential edge spanning the radially outer ends of the sides, and passageway means extending between the first and second sides at a radial position inward of the circumferential edge;
• a substantially annular first grinding face coaxially formed at a radially inner portion of one side of the disc;
• a substantially annular second grinding face formed at a radially outer portion of said one side of the disc;
• said first grinding face having a first plurality of radially oriented bars, each having a radially inner and outer end, the bars defining a first plurality of radially extending grooves therebetween;
• said second face having a second plurality of radially oriented bars, each having a radially inner and outer end, the second plurality of bars defining a second plurality of radially extending grooves therebetween;
• wherein the outer ends of the bars on the first grinding face are axially offset from and in overlapped relation with the inner ends of the bars on the second grinding face.

A method for refining feed material between opposed, relatively rotating grinding plates in the housing of a pressurized disc refiner, comprising:

• passing all the feed material through a first refining zone on one side of the disc to produce a mixture of steam and partially refined fiber in a first separation region downstream of the first refining zone;
• applying a radially outward, centrifugal force and a substantially axially directed pneumatic force on the mixture, thereby preferentially directing the partially refined fiber radially outwardly and preferentially directing the steam substantially axially;
• passing at least some of the partially refined fibers from the first separation region into a second refining zone situated substantially radially outward of said first refining zone;
• passing at least some of the steam from the first separation region into a second region on the other side of the disc;
• and
• adjusting said pneumatic force in the first separation region to control the distribution of partially refined fibers and steam from the first separation region into said second refining zone and into said second region.