REFINER TRIALS. The first unit was installed in a Brazilian linerboard mill. Initially,the new refiner was installed in parallel with two existing 26-in. double disc refiners in series so that comparisons between the two refining systems could be made. Each refiner in the system was connected to a 450-hp, 885-rpm motor. The production data is:

●Production: 130 tpd

● Raw material: 100% OCC and machine broke

● Freeness in: 575 CSF

●Freeness out: 400 CSF

●Consistency: 4.6%

Trials were run on the mill's standard furnish. Specific refining energy was incrementally increased and samples taken on both systems until no further improvements in sheet properties were obtained. The results are shown in Table 1.

TEST            (2) DD  REFINERS        TRICONIC          UN

Tensile 46.15 47.12 nM/gram

Tear Index 12.99 13.38 nM/m2 /gram

Air Permeability 9.33 7.42 Sec/100 mL

Burst Index 2.38 2.40 kPa.m2 /gram

Shopper

Drainage 39.00 34.30 Degrees

Net Energy 0.43 0.24 kW-

hr/CSF/Ton

The new refiner alone was equal in all measures to the two double disc refiners in series and exhibited significantly better energy efficiency. The results indicated that the new refiner was able to perform better in fibrillation without generating the same level of fines. Although the sheet was formed better-as evidenced in the air permeability and burst indexes-drainage was improved, resulting is less water load in the press and dryer sections. Another sign that less fiber cutting occurred in the new refiner is the reduced degradation of tear while achieving higher tensile. Trials were then conducted on the new refiner alone  comparing unrefined and refined furnish per Table 2.

 TEST UNREFINED REFINED CHANGE

Freeness 575 400 CSF 175 CSF

Tear 133 gm/f 118 gm/f -11%

Tensile 3.6 kGf/mm 4.5 kGf/mm +25%

Mullen 29 lb/pol 2 40#/pol 2 +38%

TABLE 2. Trial data: Triple cone refiner vs. unrefined pulp

Influence of Short Fibres and Fines

Short fibres are defined here as the R200 fraction while fines as the P200 fraction. As seen earlier, the R200 is distinct from other longer fractions by having significantly lower freeness but higher sheet density and tensile strength. It would be of interest to know the impact of the short fibres and fines on sheet properties when they are progressively removed from the whole pulp. In this part of work, the mill TMPi (56 ml CSF) was used. 

Freeness

Removing the fines (P200) from the whole pulp increased the freeness by 935%, indicating an extremely close correlation between freeness and fines in mechanical pulp. Eliminating both the R200 and P200 fractions combined further increased the freeness up to 1100%, an additional rise by 165%. This means that the short fibres have less influence on the freeness when compared to the fines. Further exclusion of R100 fraction did not provoke significant additional increases in freeness, implying that R100 had low fibrillation and remained relatively stiff.