At an installation at a U.S. corrugated medium mill, the triple-cone refiner replaced two 34-in. double disc refiners and one Jordan, all of which operated in series on 350 tpd of OCC. Each of the double disc refiners used a 600-hp motor, and the Jordan used a 400-hp motor. Approximately 150 points of CSF drop are taken across the three refiners. The new refiner was connected to one of the existing 600- hp motors. At startup, the new refiner achieved all paper tests alone, while using only 425 gross horsepower. After initial trials, the refiner was able to improve the sheet characteristics, as shown in Table 3. The projected annual energy savings in this installation are approximately $325,000/year. A second triple-cone refiner is now being considered for the mill's second paper machine.
TABLE 3. Trial data: Conical refiner on corrugating medium
GRADE
TEST
PREVIOUS RESULT AVG.NEW RESULT AVG.
UNITS
26# Medium CMT 49.08 57.04 Pounds Force
26# Medium Ring Crush 31.24 31.92 Pounds Force
30# Bag Mullen Burst 16.88 18.96 PSI
30# Bag Gurley Porosity 24.24 27.52 sec/100 mL
OTHER BENEFITS.
These results have been repeated now in trials and installations on most types of furnish and grades of paper grades and energy savings is available in the online version of this article in the Extra Edition section of www.paperloop.com
In general it was found that the triple-cone refiner did not generate the same level of hydrodynamic forces or flow velocities within the refining zones as an equivalent double disc refiner. This improves the residence time of the fiber in the refining zones, which contributes to the overall energy efficiency. Due to the reduced forces and flow velocities, the new conical refiners are somewhat more sensitive to plugging from furnish contaminants. Good screening is essential to longevity of the tackle, especially in the use of recycled fibers.
The characteristics within the conical refiners improve the flow of the furnish across the bar intersections. The improvement in fibrillation and reduction in fines generation may be the result of more fibers being present at the bar intersections due to this flow characteristic. Lower overall refining intensity also comes into play relative to fibrillation and should be beneficial to the refining of hardwoods and recycled fibers. A secondary result of the improved fiber mat between tackle surfaces is a reduction in metal-to-metal contact and a reduction in the potential of tackle clashing. Both result in improved tackle life when compared with double disc refiners.
CONCLUDING REMARKS
Fibre shortening is a predominant effect of refining. A majority (about 60%) of the separated fibrous elements are poorly developed. The PFI refining of long fibre fractions shows a similar influence on fibre characteristics as does the industrial refining. A probable limiting factor might be the nature of wood itself. Removing the outer layers of cell walls without chemical modification does not significantly enhance fibre bonding.
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