Waste and Biomass Valorization
Fig. 1 Process flowchart
Table 1 Chemical composition of the waste MDF samples (untreated) and after steaming refining in [%] w/w [18]
Sample
Severity (Log R 0 )
Glucose
Xylose
Mannose
Lignin
Nitrogen
(%)
(%)
(%)
(%)
(%)
SR-MDF (A)
Untreated
38.3 42.3 42.7 43.0 44.2 45.6 48.2 37.6 46.8 46.7 46.5 48.5 50.4 49.6
12.4 14.0 14.0 13.2 12.6 10.7
4.0 4.3 4.3 4.5 4.2 4.7 4.6 7.2 8.6 8.4 8.4 8.7 8.8 8.1
24.4 27.3 26.5 26.6 27.2 30.0 32.9 26.6 31.6 32.1 33.1 32.6 33.7 35.3
4.2 1.2 1.2 0.9 0.9 1.1 1.2 4.4 1.1 1.1 1.1 1.1 1.0 1.1
2.5 2.8 3.1 3.4 3.7 4.0
8.0 5.7 7.0 6.8 6.5 6.2 5.5 4.4
Untreated
SR-MDF (B)
2.5 2.8 3.1 3.4 3.7 4.0
pulp (RP) samples were taken after sorting, shortly ahead of the headbox.
publication [18]. In the first sample (SR-MDF A) a higher amount of xylose (12.4%), a lower amount of mannose (4.0%) and a lower amount of lignin (24.4%), than in the second sample (SR-MDF B) with 5.7%, 7.2% and 26.6%, respectively, was determined. The high proportion of xylose with only small amount of mannose is characteris- tic for hardwood [55]. This indicates that a high amount of hardwood was used in the manufacturing of the first sample. In contrast to that the proportion of mannose and xylose in SR-MDF B shows a slight preference for man- nose which is characteristic for softwood, indicating a dominance of softwood fibers in this sample. The nitrogen content of both samples were found to be similar, indicat- ing a similar amount of UF-resin used in production. Due to a high amount of extractable resin at a low severity treatment of 2.5, which can be seen in the changes to the nitrogen content, the fiber yield of the steam treated waste MDF fibers drops and the amount of glucose, xylose, man- nose and lignin rises in relation to the raw material. An increasing solubilization of the hemicelluloses following an increase in treatment severity leads to a further increase in fiber yield and consequently, the relative content of lignin and glucose rises. For comparison of the fiber mor- phology and test paper strength, recycling pulp from two different industrial corrugated paperboard producers was evaluated alongside the SR-MDF samples. The recycled
Pulp and Fiber Characterization
All samples were subjected to additional beating in a Jokro mill (FRANK-PTI, Birkenau, Germany) following the pro- cedure described in DIN 54360:2004 [59]. Subsequently, the pulp suspensions were disintegrated according to ISO 5263- 2:2004 [60] for 2 min. Unbeaten samples were disintegrated for 20 min. For representative sampling, the disintegrated pulp was kept in constant movement in a laboratory equal- izer until further processing. The beating degree was meas- ured in a Schopper-Riegler freeness tester type SR1 (Karl Schröder KG, Weinheim, Germany) according to ISO 5267- 1:1999 [61]. For fiber morphology characterization, samples of the pulp were analyzed using a kajaaniFiberLab (Metso, Helsinki, Finland). The arithmetic average fiber length L(n) and the length weighted fiber length L(lw) were calculated according to Eqs. 2 and 3, respectively. A high amount of fine material will significantly affect the arithmetic mean, while having a lower influence on the length weighted fiber length. The fiber width was calculated analogous to the arithmetic fiber length L(n), using the width of the fibers. The average fiber Curl(n) was calculated according to Eq. 5. The average kink index Kink(n) was calculated according to Eq. 7.
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