Mechanical pulping refiner plate having curved refining bars with jagged leading sidewalls and method for designing plates
A refiner plate for a mechanical refiner of lignocellulosic material including: a refining surface on a substrate, wherein the refining surface is adapted to face a refining surface of an opposing refiner plate; wherein the refining surface includes bars and grooves between the bars and the bars have at least a radially outer section in which the bars include a leading sidewall having an irregular surface in the outer section.
1. A refiner plate for a mechanical refiner of lignocellulosic material comprising:
a refining surface on a substrate, wherein the refining surface is adapted to face a refining surface of an opposing refiner plate, and
the refining surface including bars and grooves between the bars, wherein the bars have at least a radially outer section having a holdback angle of at least 30 degrees at the outer periphery of the bars, and the bars each include a sidewall having an irregular surface in the outer section, wherein the irregular surface include protrusions extending outwardly from the sidewall towards a sidewall on an adjacent bar,
wherein the bars include a radially inward section in which the sidewalls have a smooth surface and lack the irregular surface.
2. The refiner plate of claim 1 wherein the protrusions of the irregular surface form a pattern that is at least one of a zig-zag, sawtooth, series of bumps, sinusoid, and sideways Z-pattern.
3. The refiner plate of claim 1 wherein the protrusions on the irregular surface vary a width of the bar by at least one-fifth the width of the bar along the portion of the bar having the sidewall with the irregular surface.
4. The refiner plate of claim 1 wherein the refining surface includes an inner annular refining surface having a higher density of bars than a density of bars in the outer section of the refining surface.
5. The refiner plate of claim 1 wherein the refining bars have a curved longitudinal shape.
6. The refining plate of claim 1 wherein the protrusions of the irregular surface are most pronounced at an upper edge of the sidewall and is less pronounced proximate a substrate of the plate.
7. A refining plate for a mechanical refiner of lignocellulosic material comprising:
a refining surface on a substrate, wherein the refining surface is adapted to face a refining surface of an opposing refiner plate, and
the refining surface including bars and grooves between the bars, wherein the bars have at least a radially outer section having a holdback angle of at least 30 degrees at the outer periphery of the bars, and the bars each include a sidewall having an irregular surface in the outer section, wherein the irregular surface include protrusions extending outwardly from the sidewall towards a sidewall on an adjacent bar,
wherein the bars have a curved longitudinal shape which reverses in a direction of curvature with respect to a radial of the plate extending through the bar.
8. The refining plate of claim 7 wherein the holdback angle is at least 45 degrees.
9. The refining plate of claim 7 wherein the holdback angle is at least 60 degrees.
10. The refining plate of claim 7 wherein holdback angle is at least 70 degrees.
11. A refining plate for a mechanical refiner of lignocellulosic material comprising:
a refining surface on a substrate, wherein the refining surface is adapted to face a refining surface of an opposing refiner plate, and
the refining surface including bars and grooves between the bars, wherein the bars have at least a radially outer section having a holdback angle of at least 30 degrees at the outer periphery of the bars, and the bars each include a sidewall having an irregular surface in the outer section, wherein the irregular surface include protrusions extending outwardly from the sidewall towards a sidewall on an adjacent bar,
wherein the bars comprise an inner annular zone of straight bars having a holdback angle of no greater than 15 degrees, an outer annular zone of straight bars having a holdback angle of at least 45 degrees, and a middle annular zone having straight bars and a holdback angle of between 15 degrees and 45 degrees, wherein the middle annular zone is between the inner and outer annular zones.
12. A refining plate for a mechanical refiner of lignocellulosic materials, the plate having a refining surface comprising:
a plurality of bars upstanding from a substrate of the surface, wherein the bars extend outwardly towards an outer periphery of the plate, and
an irregular leading or trailing sidewall on at least a portion of the bars, wherein the irregular surface include protrusions extending outwardly from the leading or trailing sidewall towards an opposite sidewall on an adjacent bar,
wherein the bars comprise an inner annular zone of straight bars having a holdback angle of no greater than 15 degrees, an outer annular zone of straight bars having a holdback angle of at least 45 degrees, and a middle annular zone having straight bars and a holdback angle of between 15 degrees and 45 degrees, wherein the middle annular zone is between the inner and outer annular zones.
13. The refiner plate of claim 12 wherein the protrusions of the irregular surface form a pattern that is at least one of a zig-zag, sawtooth, series of bumps, sinusoid, sideways Z-pattern.
14. The refiner plate of claim 12 wherein the bars are curved along their length and the curve forms an exponential or involute arc.
15. The refiner plate of claim 12 wherein a radially outer portion of the bars have a holdback angle of at least 70 degrees.
16. The refiner plate of claim 12 wherein a radially outer portion of the bars have a holdback angle of at least 60 degrees.
17. The refiner plate of claim 12 wherein a radially outer portion of the bars have a holdback angle of at least 45 degrees.
18. The refiner plate of claim 12 wherein the plate is a rotor plate and is arranged in the refiner opposite to a stator plate or another rotor plate.