Power and mass exchange characteristics of a bioreactor equipped with disk perforated mixers

In the implementation of aerobic biosynthesis processes, the productivity of a bioreactor depends on the intensity of oxygen mass transfer. Disk mixers with a perforated surface, providing an increase in the contact surface of the gas and liquid phases, were studied. The power characteristics of disk mixers with bent segments and sectors was experimentally established to depend on the slope of the working surfaces. For multi-tier mixers, the exponent regarding the number of tiers in the expression of total power was determined to be proportional to the value of the distance between tiers in the range of specified distance equal to 0–1.4 of the diameter of the mixer. At a distance between tiers exceeding the diameter of the mixer by 1.5 or more times, the total power is equal to the sum of the powers of single mixers. The energy efficiency of the process of oxygen mass transfer decreases sharply with decreasing distance between tiers. The eff iciency indicator of the oxygen mass transfer depends on the ratio of aeration and power of the mixer, demonstrated in the form of a saturation curve. An analysis of the obtained experimental dependences supports a conclusion concerning the intensive and energy-efficient process of oxygen mass transfer obtained by ensuring a small ratio of the diameter of the unit to its height, use of multi-tier mixers with a distance between tiers greater than the diameter of the mixer and specific aeration of at least 3 min ^-1 . Perforated disk mixers can be recommended for use in bioreactor designs with the optimal implementation in the processes of aerobic microorganism production, including the cultivation of high-density seed crops. At oxygen mass transfer rates exceeding 10 kgO₂/m³ ·h, modes ensuring the achievement of a high population density of aerobic microorganisms are characterised by relatively low energy efficiency (1–1.2 kg O₂/kWh).

The authors declare no conflict of interests regarding the publication of this article.

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