Appl. Sci. 2025 , 15 , 9036
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Table2. Cont.
Conventional Cast Plate
Ultra Low Intensity Plate
Bar dimension
Bar angle ( ◦ ) Bar number
28
52
198
480
30.5 (=12 )
Plate diameter (cm)
CEL (km/s)
37
97
Specific Refining Energy (SRE) consumed during refining was measured using Equation (1) as follows:
kWh
P tot − P 0 f × c
t
(1)
Speci f ic Re f ining Energy =
where P tot is the total refiner load power (kW), P 0 is the refiner’s idling power (kW), f is the flow rate (L/h), and C is the stock consistency (t/L, based on oven-dried pulp weight). 2.3. Fiber Characteristics and Physical Properties The mean fiber length and fines content of pulp fibers were measured using the Fiber Quality Analyzer FQA-360 (Optest Equipment Inc., Hawkesbury, ON, Canada). The water retention value (WRV) of pulp fibers before and after refining was determined following ISO 23714 [20]. Handsheets with a basis weight of 70 g/m 2 were prepared, conditioned, and tested according to ISO 5269-1 to assess paper physical properties [21]. Tensile strength, burst strength, and tear strength were measured in accordance with ISO 5270 [22]. All physical property measurements were conducted with a minimum of six replicates, as recommended by the ISO standards, to ensure statistical reliability [23]. Error bars representing standard deviations have been incorporated into all related figures to clearly indicate data variability and reproducibility. 2.4. Observation of Fiber Morphology Microscopic observations were conducted to examine fiber morphology and structural changes resulting from mechanical treatments. An Olympus BX51 optical microscope (OLYMPUS, Tokyo, Japan) was used to observe samples of bleached softwood and hard- wood kraft pulps, both before and after treatment. Diluted pulp suspensions were placed on glass slides and examined at 10 × magnification. 3. Results 3.1. Stock Throughput Figure 1 compares the stock throughput (g/s) as a function of specific refining en- ergy (kWh/t) for KOCCs refined with plates of two different cutting edge lengths (CELs), 37 km/s and 97 km/s. The conventional plate at 37 km/s presents higher initial throughput, reaching up to approximately 25 g/s at about 70 kWh/t, evidencing greater throughput efficiency at lower energy consumption. This increased throughput is largely due to wider grooves that lower resistance to stock flow, facilitating material passage and reduc-
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