Date of Award
2026
Document Type
Open Access Master's Thesis
Degree Name
Master of Science in Chemical Engineering (MS)
Administrative Home Department
Department of Chemical Engineering
Advisor 1
Rebecca Ong
Committee Member 1
Timothy Eisele
Committee Member 2
Robert Handler
Abstract
Wheat middlings are grain byproducts that are underused for bioenergy production despite having a high lignocellulose content. Its use as a feedstock for catalytic pyrolysis depends on effective and sustainable fractionation to enhance efficiency and product yield. This study tested mechanical pre-fractionation (sieving and air classification) to reduce ash content of certain fractions to < 1% for catalytic pyrolysis and enrich nutrient levels of other fractions for feed applications. Wheat middlings were separated into 11 fractions using screen sizes from 106 µm to 1651 µm, and the composition of each fraction was characterized (ash, protein, structural carbohydrates, lignin, starch, and simple sugars). For cyclone separation, a full factorial design was used to study the effect of air velocity (15,18, 20 m/s) and feed rate (33, 35, 38 kg/h) on the amount of material collected in the underflow and overflow, and the composition of these fractions was characterized. Sieving showed a pronounced segregation of ash content, from 4.5% to 6.5% in wheat middlings fractions, with 5.7% being the lowest for coarse fractions which has higher lignocellulose content, and 4.5% in the fine fraction (150-212 µm). The same defined enrichment was observed in all nutrients except for protein. Starch enrichment zone were defined in the fine fractions (212 µm and below), for structural carbohydrates and lignin in the coarse fractions (600 µm and above), and for ash in coarse fractions (1180-1651 µm). In contrast, protein content was not significantly different between various fractions (p value=0.787). The fiber rich fraction (> 600 µm), suitable for pyrolysis, which have a composite ash value of 6.0% can be sorted and mixed with intermediate fractions to reduce ash to 5.3% and the remaining fractions rich in digestible nutrients used for animal feed formulation. Compared to sieving, cyclone separations did not show much segregation of nutrients between the underflow and overflow. Although ash level less than 1% was not reached, results indicate potential to use mechanical separation to isolate fractions with reduced ash content that could be further processed using chemical methods to generate materials suitable for catalytic pyrolysis.
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Recommended Citation
Obiakor, Okwudili I., "MECHANICAL FRACTIONATION OF WHEAT MIDDLINGS FOR APPLICATION IN PYROLYSIS AND ANIMAL FEED", Open Access Master's Thesis, Michigan Technological University, 2026.