| Improving the utilization of secondary fiber is one of the important ways to solve the paper-making resources increasingly tense. In flotation deinking process, improving the removal rate of ink particles while reducing fiber loss is a key in the secondary fiber recycling. In this paper, aiming at the low selectivity of flotation deinking process, we studied the mass transfer of flotation deinking from the behavior of fiber and ink particles adhere to bubble, the efficiency of bubble capture particles, the micro-behavior of fiber drainage in froth and the behavior of fiber loss by using image analysis method and the others.First, the behavior of fiber and ink particles adhere to bubble was discussed by using microscopic visualization method. We studied the effect of pH, surfactant concentration, the size and surface properties of fiber and ink particles on fibers and ink particles adhering to a static bubble. The result showed that, when the concentration of TX-100is Oppm to100ppm or the concentration of sodium oleate is Oppm to50ppm, increasing surfactant concentration or increasing the hydrophobicity of fibers, help to reduce the adhesion of fibers to the bubble. However, when the concentration of TX-100is Oppm to150ppm or the concentration of sodium oleate is Oppm to200ppm, decreasing surfactant concentration or increasing hydrophobicity of ink particles, help to increase the adhesion of ink particles to the bubble. pH has no effect on the adhesion of fiber and ink particles to the bubble. Due to the difference density between glass bead and ink particle, the result would be different when using the glass beads as models of ink particles.Then, we studied the effect of bubble size, pulp consistency, fiber suspension superficial velocity on the slip velocity of single bubble in pulp with imaging method combined with the conductivity technique. Establish an empirical model equation to characterize the relationship between the bubble slip velocity, bubble size and pulp consistency. The result showed that, when the bubble size is1.5mm～4.5mrn, the bubble slip velocity increased with increasing the bubble size while decreased with increasing the pulp consistency when the mass concentration of fiber suspensions low to1.0%. Measuring Bubbles slip velocity in pulp provides a theoretical basis for modified bubbles captured particles.Again, the micro-behavior of fiber drainage in froth was discussed by studying the fiber critical drainage channel. We studied the fiber drainage with respect to fiber length, bubble size, surface properties of the fiber. The result showed that, when the fiber length is0.3mm～1.1mm, the critical curvature radius of drainage channel increased with increasing fiber length or bubble size, fiber is hard to drain. The surface properties of fiber has no effect on fiber drainage. Finally, the behavior of fiber loss was discussed. We studied the effect of surfactant concentration, pulp consistency, froth height and adding rate of liquid at top on fiber loss in free drainage and in forced drainage respectively. The result showed that, in free drainage state, when the surfactant concentration is20ppm to80ppm, froth height is5cm to25cm and the mass concentration of fiber suspensions is0.6%to1.0%, the fiber loss rate decreased and then increased with increasing surfactant concentration. The fiber loss rate decreased with increasing the froth height. And the fiber loss rate increased with increasing pulp consistency. In forced drainage state, when the surfactant concentration is20ppm to80ppm, the mass concentration of fiber suspensions is0.6%to1.0%, and the adding rate of liquid is60ml/min to140ml/min, the fiber loss rate decreased with increasing surfactant concentration. The total fiber loss rate increased with increasing pulp consistency. The fiber loss rate decreased with increasing the adding rate of liquid. fiber loss rate in forced drainage state is smaller than it in free drainage state under the same experimental conditions. |
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