There are many types of air-lift fermenters, the common ones are air-lift circulation type, bubbling type, air jet type, etc. The air-lift fermenters that have been widely used in the biological industry include air-lift inner circulation fermenters, gas-liquid double jet air-lift circulation fermenters, and tower-type air-lift fermenters with multi-layer distribution plates. The bubbling tank is the original aerated fermentation tank. Of course, there is no guide tube in the bubbling reactor, so the directional flow of the main body of the liquid is not controlled.
The air-lift fermenter uses the air nozzle to spray high-speed air, and the air is dispersed in the liquid in the form of bubbles. On the vented side, the average liquid density decreases. On the non-ventilated side, the density of the liquid is higher, so a density difference is generated with the liquid on the vented side, thereby forming a circulating flow of the liquid in the fermenter. There are many types of airlift fermentation tanks, the more common ones are inner circulation tube type, outer circulation tube type, tension drum type and vertical baffle type.
The outer circulation type circulation pipe is designed outside the tank body, and the inner circulation pipe is two, which is designed inside the tank body. In the air-lift fermenter, the height of the circulation pipe is generally not higher than that of the tank, and the liquid level in the tank is not higher than the outlet of the circulation pipe, and not lower than the outlet of the circulation. The advantages of the airlift fermenter are low energy consumption, small shearing effect in the liquid, and simple structure. Under the same energy consumption, its oxygen transfer capacity is much higher than that of mechanically agitated aerated fermentors.
The main advantages of airlift fermenters
(1) The structure is simple, the basic principle is not complicated, and the energy consumption is lower than that of the slurry reactor with stirring paddle;
(2) Compared with the traditional bubble column, its operable gas and liquid flow rate range is much larger;
(3) The air supply efficiency is high, and the ventilation in the gas riser can be greater than the air intake of the bubbling reactor, which is conducive to aerobic reactions;
(4) The fluidization effect is good, it can be solid particles, and even heavier particles are completely suspended.
(5) Relying on gas to generate directional circulation, rather than centrifugal pump type mechanical equipment, the flow form is determined, the liquid circulation is strong, and there are no moving parts inside. It has small shear stress and uniform energy dissipation, which is particularly important for shear-sensitive materials.