Waste and Biomass Valorization
highest severity treatments of both samples is presented. A clear shift in fiber length distribution to the lower lengths following an increased beating duration is visible. For the SR-MDF (B) sample, the severity of the steam treatment did not seem to significantly alter the general reduction in fiber length as a function of beating duration. For the SR-MDF (A) fiber samples on the other hand, an increase in treatment severity led to a reduction in the small fiber population after prolonged beating, which is reflected in the increase of the L(lw) at more severe treatments and high beating durations. Without additional beating, the treatment severity had the opposite influence, and the highest length weighted fiber length could be determined at the lower severities. This is reflected in the higher amount of fibers found at a length of 1.5 mm and longer after low severity treatments.
the SR-MDF (A) sample following an increase in treatment severity. In comparison to the recycled pulp samples, the SR-MDF fibers are shorter and wider, show less fiber curling and a lower amount of kinks. Following the refining, all of the SR-MDF samples were beaten for an additional 20, 40 and 60 min to evaluate the influence of the treatment severity on the length and width of the steam refined waste MDF fibers and the resulting test paper strengths over a wide range of beating degrees. In Table 3 the measured fiber lengths and widths are presented. In all samples the fiber width increased and the fiber length decreased with beating time, irrespective of treatment severity. After 60 min of beating, a fiber width increase of roughly 10% can be measured. The width increase can be explained with a flattening of the fibers due to a collapse of the lumen in beating [48]. While the arithmetic average fiber lengths of the SR-MDF (A) and SR-MDF (B) sample do not differ much, considerable differences in the length weighted fiber lengths are visible. This implicates differences in the amount of short fiber fragments and therefore the fiber length distribution between the two samples. In Fig. 2, the length-weighted fiber length distribution for the lowest and
Influence of Treatment Severity on the Development of the Beating Degree
In Fig. 3 the beating degree of the different samples as a function of the beating time is presented. The beating degree is a measurement of the drainability of a fiber web and an
Table 3 Influence of the beating duration on the arithmetic average fiber length L(n), the length weighted fiber length L(lw) and the fiber width of the SR-MDF samples
Treatment severity Beating duration SR-MDF (A)
SR-MDF (B)
L(n)
L(lw)
Width L(n)
L(lw)
Width
(Log R 0 )
(min)
(mm)
(mm)
(μm)
(mm)
(mm)
(μm)
2.5
0
0.54 0.33 0.21 0.18 0.46 0.26 0.21 0.18 0.47 0.27 0.21 0.19 0.49 0.28 0.23 0.21 0.48 0.34 0.28 0.25 0.46 0.34 0.28 0.25
0.86 0.53 0.31 0.26 0.75 0.42 0.31 0.26 0.76 0.43 0.31 0.28 0.78 0.43 0.34 0.30 0.76 0.53 0.42 0.37 0.72 0.52 0.44 0.39
25.0 25.0 26.9 27.8 24.7 25.6 26.8 27.4 24.2 24.9 26.5 27.7 25.0 25.1 26.3 26.9 24.8 25.2 25.8 27.4 24.1 24.6 26.2 25.9
0.56 0.37 0.23 0.18 0.55 0.41 0.23 0.20 0.56 0.31 0.22 0.18 0.53 0.31 0.23 0.20 0.50 0.34 0.25 0.20 0.50 0.29 0.21 0.18
0.96 0.65 0.37 0.28 1.00 0.71 0.36 0.31 0.96 0.51 0.34 0.28 0.95 0.50 0.34 0.29 0.93 0.55 0.39 0.29 0.87 0.47 0.33 0.28
30.3 31.1 33.4 34.4 30.1 32.2 33.8 33.6 31.6 32.5 34.6 34.3 30.9 31.8 33.7 34.6 30.8 31.8 33.1 33.2 30.1 31.7 32.8 33.3
20 40 60
2.8
0
20 40 60
3.1
0
20 40 60
3.4
0
20 40 60
3.7
0
20 40 60
0
4.0
20 40 60
1 3
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