Abstract
Abstract Flotation of cellulose pulp suspension in paper industry is primarily used for separation of ink particles from cellulose fibres. Entrainment, an unwanted phenomena well described in the field of mineral flotation, also leads to a removal of fibres with the flotation froth. We find that the entrainment phenomena can be used for the separation of long fibres from a fibre pulp suspension, and hence for pulp fractionation. Specifically, we use a 2D bubble column to investigate the influence of (i) bubble size, (ii) wash rate and (iii) stirring on the separation of long fibres from cellulose pulp suspension. Separation of fibres from fibre pulp suspension is tested for mechanical pulp and chemical pulp. We find that size selective recovery yields best result for (i) large bubbles, and (ii) additional washing due to the increase of small particle drainage. However, both strategies lead to a reduction of the total recovery rate. Stirring significantly improved the total recovery and benefited the selective separation. Best results are achieved with small bubbles for chemical pulp. For mechanical pulp, fractionation is more challenging due to lower froth stability, but still fibres with a reduced amount of smaller fraction can be recovered.
Highlights
In paper and pulp production, effluent streams containing cellulose fibres, fibre fines, and inorganic fines accrue
Results highlight the importance of a controlled bubble size in flotation experiments
Experiments were planned following the suggestions from literature, and focused on maximizing the selective separation of large fibres from pulp suspension
Summary
In paper and pulp production, effluent streams containing cellulose fibres, fibre fines, and inorganic fines accrue. Common strategy to reduce waste in paper and pulp production is to recover fibre and fibre-fines and reuse them in paper and/or paper board production [1,2]. Selectively recovered cellulose fibres could be used as raw material for plastic compounds [3,4,5,6,7,8]. Pulp is typically fed at concentration of several percent. For those obviously the process energy demand increases with decrease of concentration as more water has to be pumped. Flotation can serve as alternative process for recovering cellulose fibres, especially from thin suspension
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