Use the air nozzle to eject high-speed air. The air is dispersed in the liquid in a bubble form. On the vented side, the average density of the liquid drops by 1; on the non-vented side, the liquid density is higher, so the liquid on the vent side is generated. A density difference is generated, thereby forming a circulation of liquid in the bio fermenter. There are many forms of air-lift fermentation tanks, the more common ones are internal circulation tube type, external circulation tube type, tension tube type, and vertical baffle type. The outer circulation-type circulation pipe is designed outside the tank, and the inner circulation pipe is two, designed inside the tank. In air-lift fermentation tanks, the height of the circulation tube is generally not higher than. The liquid level in the tank is not higher than the outlet of the circulation pipe and not lower than the circulation outlet. The advantages of the air-lift fermentation tank are low energy consumption, small frying and cutting effect in the liquid, and simple structure. At the same energy consumption, its oxygen transfer capacity is much higher than that of mechanically agitated aerated fermentation tanks.
The main advantage
(1) The structure is simple, the basic principle is not complicated, and the energy consumption is lower than that of the slurry reactor with agitating blades
(2) Rely on gas to generate directional circulation, not centrifugal pump mechanical equipment, the flow pattern is determined, the liquid circulation is strong, there are no moving parts inside, there is less shear stress, the energy dissipation is very uniform, and the material is sensitive to shear force Of particular importance;
(3) Compared with the traditional bubble column, the operable amount of gas and liquid flow rate range is much larger;
(4) The gas supply efficiency is high, the ventilation in the riser can be greater than the air intake of the bubble reactor, which is conducive to aerobic reactions;
(5) The fluidization effect can be solid particles, and even the heavier particles remain completely suspended.
The main disadvantage
(1) Very large air throughput is required;
(2) Poor interphase mixing contact;
(3) When the circulating organisms and operating conditions change, the amounts of substrates, nutrients, and oxygen cannot be kept the same;
(4) Blending and ventilation are coupling problems, that is, it is difficult to improve the blending condition without changing ventilation.
It is widely used for large-scale production of single-cell proteins. However, it is not suitable for culture medium with high viscosity or a large amount of solids.
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