Study of Refining Effect of Mixed Pulps Using Refiner Plates with Different Bar Patterns

A new lightweight vertical bar plate was developed by inserting individual bars into the plate base rather than the typical sand casting method. The lightweight vertical bar plate has a very sharp bar edge because vertical bars are inserted instead of trapezoidal bars. The refining effects of the mixed stock with softwood bleached kraft pulp (Sw-BKP) and hardwood bleached kraft pulp (Hw-BKP) were compared using two types of lightweight vertical bar plates with cutting edge lengths of 55 km/s (PA55) and 97 km/s (PB97). The fine bar plate (PB97) with large CEL (PB97) was very effective in reducing the refining energy required to reach the final freeness regardless of the mixing ratios of Sw-BKP and Hw-BKP compared to the plate with a small CEL (PA55). PB97 also consumed less refining energy than PA55 until proper sheet strength was achieved. In particular, irrespective of the mixing ratios of Sw-BKP and Hw-BKP, the tensile strength of sheets at the final freeness was greater in PB97 than in PA55. For stock throughput during refining, PA55 with the wide groove was almost similar to PB97 with the narrow groove.