Patent ID: 8157195

Claim:
A method of mechanically refining lignocellulosic material in a refiner having opposing refiner plates, the method comprising: introducing the material to an inlet in one of the opposing refiner plates; rotating at least one of the plates with respect to the other plate, wherein the material moves radially outward through a gap between the plates due to centrifugal forces created by the rotation; as the material moves through the gap, passing the material over bars in a refining section of at least one the plates and through grooves between the bars, wherein the bars have at least a radially outer section with a holdback angle of at least thirty degrees and the bars each include a leading sidewall having an irregular surface in the outer sections, wherein the irregular surface include protrusions extending outwardly from the sidewall towards a sidewall on an adjacent bar, inhibiting the movement of the fibrous material through the grooves by the interaction of the fibrous material and the irregular surface on the leading sidewall of the bar adjacent the groove, and discharging the material from the gap at a periphery of the refiner plates.