Optimising the production of microfibrillated cellulose in a stirred media mill

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Taylor, Lewis ORCID: https://orcid.org/0000-0002-1316-8465 (2021). Optimising the production of microfibrillated cellulose in a stirred media mill. University of Birmingham. Eng.D.

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Abstract

Stirred media mills are used to produce microfibrillated cellulose (MFC) in the FiberLean process. This work uses a laboratory-scale mill to investigate the influence of various operating conditions and feed characteristics on product properties. Microscopy and optical image analysis identify fibril breakage and fibrillation as distinct processes, which respond differently to various operating conditions, and must be tailored to optimise MFC quality. Media surface roughness is shown to enhance grinding efficiency, likely by increasing local pressure, and the role of mineral particles in expediting this process is identified. The influence of stress intensity on product particle size and fibrillation is also assessed, along with the interaction of this parameter with media roughness, permitting a general prediction of fibre breakage rate. Large variations in MFC quality between different fibre feedstocks are identified, and analysis of feed fibre properties demonstrates that a high hemicellulose content facilitates liberation of fine fibrils, and a high zero-span tensile strength results in long liberated fibrils. Combining these parameters enables a good prediction of MFC quality from feed measurements. Finally, it was found that optimising grinding conditions for specific feed fibre properties permitted up to a 50 % increase in MFC tensile strength versus standard conditions.

Type of Work:

Thesis (Doctorates > Eng.D.)

Award Type:

Doctorates > Eng.D.

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