Fermentation equipment is the heart of the fermentation industry and a bridge connecting raw materials and products. With the continuous development of life science and technology, the fermentation industry has also been greatly improved. Fermentation tank is one of the most important equipment in microbial engineering. An excellent culture device should be designed with a tight structure, good liquid mixing performance, high mass and heat transfer rate, and reliable detection and control instruments. Obtain maximum production efficiency.

The main types of fermentation tanks:

(1) Ventilated mechanical stirring tank
aeration mechanical stirring tank is the first choice for many fermentation processes. It has high mass and heat transfer capabilities, ideal gas-liquid mixing effect, longer liquid residence time and wider operating gas velocity. However, the shortcomings are also obvious. The shearing force is large, which damages many shear-sensitive microorganisms. The energy consumption is large and the mixing is uneven. Therefore, developing the advantages of ventilated mixing tanks and overcoming their shortcomings is one of the current focuses of fermenter research. The improvement of the ventilated mixing tank is mainly in the mixing system, including the optimization of the agitator and the multi-layer mixing system. The agitator mainly adopts a new type of agitator or an improved standard agitator, the purpose is to reduce the vortex of the blade wake to save energy, or to change the reaction The fluid state of the reactor allows the shear force to be evenly distributed and protects the microorganisms in the reactor. The multi-layer mixing system has been used very early, but due to the lack of in-depth research on its working mechanism, simple empirical design methods have been used for many years, and its due advantages have not been played.

(2) Airlift fermentation tank
The airlift fermentation tank has obvious advantages and has been widely used in the production of SCP, filamentous fungi, and wastewater treatment. Airlift fermentation tank is the most widely used biological reaction equipment. This type of reactor has the advantages of simple structure, not easy to be infected with bacteria, high dissolved oxygen efficiency, and low energy consumption. There are many types, such as air-lift circulation type, bubbling type, air jet type, etc. The air-lift fermentation tanks that have been widely used in the biological industry include air-lift internal circulation fermentation tanks, gas-liquid dual-jet air-lift circulation fermentation tanks , Tower-type air-lift fermentation tank with multi-layer distribution plate. The bubbling tank is the most primitive aerated fermentation tank. Of course, the bubbling reactor is not equipped with a deflector tube, so the directional flow of the main body of the liquid is not controlled.

(3) Self-priming fermentation tank
The structure of the self-priming fermenter body is roughly the same as that of the general-purpose fermenter, but the main difference lies in the shape and structure of the agitator. The self-priming fermenter uses a stirrer with a central suction port. The agitator is driven by the main shaft extending upward from the bottom of the tank. When the impeller rotates, the blades continuously discharge the surrounding liquid to form a vacuum on the back, so the air outside the tank is sucked into the tank through the suction pipe in the center of the agitator, and sucks people. The air and the fermentation liquid are fully mixed and discharged at the end of the impeller, and immediately dispersed to the tank wall through the guide wheel, baffled by the baffle, and rush to the liquid surface, evenly distributed. The air suction pipe is usually connected to the impeller with a shaft seal at one end to ensure no air leakage. Because the vacuum formed by the high-speed flow of the fermentation liquid sucks people, the gas-liquid contact is very good, and the bubbles are dispersed finely, thereby increasing the dissolution rate of oxygen in the fermentation liquid. The following uses a mechanically stirred fermentation tank as an example to introduce its main structural components and their main functions.

The basic conditions of the fermentation tank

Mechanical stirring fermenter is also called standard or universal fermentor. It uses the function of mechanical agitator to fully mix air and fermentation broth and dissolve it in the fermentation broth to ensure the oxygen required for the growth and reproduction of microorganisms. In order to maximize the production efficiency of the fermentation tank, the fermentation tank must meet several requirements:
①The fermentation tank must be able to withstand a certain amount of pressure.
②The fermenter must have a suitable diameter-to-height ratio.
③The stirring and ventilation equipment of the fermentation tank can mix gas and liquid components, realize mass and heat transfer, and ensure the dissolved oxygen required in the process of microbial fermentation.
④The fermentation tank should have sufficient cooling area.
⑤ Dead corners should be minimized in the fermentation tank to avoid dirt accumulation, ensure thorough sterilization, and prevent bacterial contamination.
⑥ The shaft seal of the agitator should be tight to reduce leakage.

The structure of the fermentation tank

The main components of the mechanical stirring and ventilating fermentation tank include the tank body, agitator, baffle, cooling device, and air distribution device. Shaft seal etc.

1. The tank body is designed according to the maximum working pressure.
(1) First, the tank must be sealed to withstand a certain pressure.
(2) The shape is cylindrical, and the two ends are welded with elliptical or dish-shaped heads, so that the fermenter is evenly stressed, has less dead ends, and the materials are easily discharged.
(3) The material is made of stainless steel or composite stainless steel.
(4) The ratio of height to diameter is 1.7∽4:1.
(5) In addition, there are some auxiliary equipment on the top of the tank, such as vents, receiving holes, etc. The general principle of tank design is that the fewer holes on the tank body, the better, and they can be merged.

2, agitator
Function: Break the air into small bubbles. The gas-liquid contact interface is increased, the oxygen mass transfer rate is increased, and the fermentation broth is fully mixed at the same time, and the solid substances in the fermentation broth remain in the floating state.
Structure: Including a stirring shaft and a stirring blade. A disk is installed in the center of the stirring shaft, and a stirring blade is installed on the disk.
The shape of the mixing blade: flat blade, curved blade and arrow blade. Generally there are six blades, as few as three, and as many as eight.

Generally speaking, the ability to smash air bubbles under the same stirring power is compared. The flat-blade agitator is larger than the curved-blade agitator, and the curved-blade agitator is larger than the arrow-blade agitator, but the ability of turning the liquid is opposite to the above. It is good to configure several agitators on the shaft, but the number of configurations is determined by factors such as the height of the liquid level in the tank, the characteristics of the fermentation liquid and the diameter of the agitator.