Master mixing core principles, customize your own stainless steel mixing tank, double the efficiency of your production line!

The mixing system we commonly refer to is typically installed inside a storage tank. It mainly consists of the motor, gear reducer, base, mixing shaft, coupling, impeller, bottom bearing, heat exchange components, and more. While most people tend to focus on the performance of the impeller, in reality, a well-performing mixing system—such as one used in a fermenter—is the result of the coordinated interaction of multiple components. Overlooking any of these can lead to critical failures.

For example:“ Mixing shaft: solid or hollow? Too large or too small? Coupling type? Bottom bearing and intermediate support? Etc.

Many people focus primarily on the mixer—also known as the impeller—because it directly determines the mixing and dispersion performance within the tank. Therefore, we will mainly discuss the impeller here, as the priority is to first meet the process requirements, and then address the other complementary components.

There is a wide variety of impeller types, but in industrial applications, they are generally classified into four core categories based on fluid flow direction (flow pattern) and material viscosity. Different types of impellers offer vastly different capabilities in terms of mixing, pumping, and shear.

In fact, there are quite a number of mixing configurations—the image above shows only a portion of them. In the HG (Chinese chemical industry standard) for agitators, the list of mixer types is quite extensive, and that does not even include combined configurations.

Types of Agitators

• Axial-Flow Impellers: When this type of impeller rotates, the liquid primarily flows in the axial direction (up and down). They are characterized by strong pumping capacity, low power consumption, and fast mixing speed, making them suitable for liquid mixing and solid-liquid suspension. Common examples include pitched-blade turbines, hydrofoil impellers, and axial-flow impellers.

  

• Radial-Flow Impellers: During rotation, these impellers discharge fluid radially toward the vessel walls. Upon striking the wall, the flow is redirected upward or downward, creating a circulation pattern. These impellers deliver exceptionally high shear rates, though their macro-flow circulation is comparatively limited. As a result, they are well-suited for applications requiring intense disintegration or dispersion of materials—for instance, in gas-liquid dispersion processes, where radial-flow impellers are frequently employed.

  

• High-Viscosity Impellers: When the liquid viscosity is extremely high (e.g., molasses, concentrated sugar syrups, high-molecular-weight polymers, etc.), the fluid cannot establish long-range circulation, and both the axial-flow and radial-flow impellers mentioned above become ineffective. It is necessary to use impellers with very large diameters, positioned close to the tank wall, and operating at low rotational speeds. Typical representatives of this type include frame-type, anchor-type, and helical ribbon impellers.

  

• Special-Process Impellers: These are designed to meet certain extreme or specialized process requirements—such as ultra-high shear or powder dispersion. A typical example is the dispersion disc.

  

Effects Achieved by Agitation

The effect achieved by agitation is our ultimate goal. In terms of the mixing state, some classify the level of mixing effectiveness into 10 grades, representing different mixing states.

In terms of agitation intensity:

1 = quite mild; 3 = normal; 6 = intense; 10 = quite violent

Agitation intensity levels 1 to 2: Use minimum flow velocity to create a flat flow state.

Agitation intensity levels 3 to 6: Typical for most chemical process industry applications.

Agitation intensity levels 7 to 10: For applications requiring high-velocity agitation.

Most mixing effects are achieved through radial flow, axial flow, or a combination of both. Therefore, we must first understand these two flow patterns. However, in some precision mixing applications—such as gas dispersion in biological fermentation—it is not enough to simply look at the flow pattern; we also need to consider microscopic gas dispersion and gas-liquid mass transfer performance.

In summary, whether it is shear, diffusion, tumbling, or convection, different mixing types and principles form the core driving force behind material blending. These sophisticated physical movements ultimately rely on the stainless steel mixing tank as a sturdy industrial carrier for their perfect realization. From paddle-type, anchor-type to turbine-type and helical-type, the precise selection of impeller types—aligned with the characteristics of the materials—is precisely what makes modern stainless steel mixing tanks stand out in industries such as chemicals, pharmaceuticals, and food. It can be said that mixing principles provide the theoretical "soul" to the equipment, while the stainless steel mixing tank serves as the "body" that translates theory into efficient productivity. The two complement each other, jointly driving industrial production toward greater uniformity, higher efficiency, and finer precision.