Industrial mixers- Overview
Stirring and mixing are common key unit operations in industries such as chemistry, pharmaceuticals, food, and environmental protection. For example, in a synthetic fiber factory, there are only two polymerization reactors as the core equipment, while up to 30 auxiliary mixing equipment such as batching tanks, dissolution tanks, dilution tanks, and buffer tanks are matched with them. In the production of polymer materials, 85% of the polymerization reactors used as core equipment are agitation devices. In the pharmaceutical fermentation production process, from seed cultivation to critical fermentation processes, almost all are stirred equipment.

Given the widespread application of stirring equipment, the focus is mainly on experimental research on macroscopic quantities such as stirring power consumption and mixing time of conventional stirring blades in low viscosity and high viscosity non-Newtonian homogeneous systems, solid-liquid suspensions, and gas-liquid dispersions. For a long time, although there has been a wealth of design experience and correlation equations available for analyzing and predicting mixed systems, directly scaling up stirred reactors from laboratory scale to industrial scale is still very dangerous, and it is still necessary to achieve the required mass transfer, heat transfer, and mixing of stirred equipment through step-by-step scaling up.

Development of new mixing and blending equipment
Disk turbine agitators for gas dispersion are widely used in gas-liquid two-phase processes such as fermentation. Since the 1980s, research on this type of agitator has gradually deepened with the development of testing methods and computational fluid dynamics. Various companies and research institutions have also launched many agitators with lower power consumption and better gas dispersion effect.

In the polymer industry, the research and development of efficient polymerization reactors have provided a strong driving force for the development of stirring equipment. For a polymerization reactor, it is not only necessary to have good mixing performance, but also to provide sufficient shear for the material. At the same time, in order to remove the reaction heat in a timely manner, the stirring tank needs to have the highest possible heat transfer capacity. Axial flow mixers often cannot meet these multifaceted requirements. Some large corporate groups, including those in the petrochemical sector, such as Sumitomo Heavy Industries and Mitsubishi Heavy Industries in Japan, have invented large blade, pan energy, and blade combination agitators from the perspective of developing new and efficient polymerization reactors. From a comprehensive performance perspective, these mixers consider mixing, shearing, heat transfer, and adaptability to liquid viscosity in a balanced manner.

A large number of mixing equipment are used for mixing and solid-liquid suspension operations in low viscosity systems, requiring impellers to provide high axial circulation flow with low energy consumption. Traditional ship propulsion impellers can meet this requirement, but their blades are complex three-dimensional surfaces, difficult to manufacture, and difficult to scale up.

Wide viscosity range agitator
For traditional mixers, they can generally be divided into two categories. There are two types of agitators: propeller and turbine agitators used for low viscosity fluids, and spiral and frame agitators used for high viscosity fluids. However, in many reaction processes, such as polymerization, the viscosity of the material is initially low and increases as the reaction progresses. In this case, there will be issues with the selection of the mixer. For this working condition, a combined stirring device can be used, which is to set up a stirrer suitable for low viscosity fluids at the center, and then add a large-diameter frame stirrer suitable for high viscosity fluids. When the viscosity is low, start the central stirring device and stop the frame stirrer to use it as a baffle; After the viscosity increases, two sets of devices are activated simultaneously to work together. However, the transmission mechanism of the combined mixing device is generally more complex.

Testing Techniques for Flow Fields and Computational Fluid Dynamics
There are various methods to evaluate the mixing effect of a stirring device, such as measuring stirring power, measuring heat transfer coefficient, measuring mixing time, etc. However, the basic evaluation is to measure the flow field formed by the materials inside the stirring device. As the core of stirring technology, it is necessary to understand what kind of flow field is required for a certain type of mixing (such as solid-liquid suspension, liquid-liquid dispersion, etc.), what kind of stirrer to use, and what operating conditions can achieve the required flow field with minimal energy consumption. Adopting advanced testing methods and establishing reasonable mathematical models to obtain the velocity field, temperature field, and concentration field inside the mixing tank not only has significant economic significance for the optimization design of mixing equipment, but also has practical theoretical significance for the basic research of amplification and mixing.

Industrial mixers- Development Technology
1. Laser Doppler velocimetry (LDV) technology
2. Particle Imaging Velocimetry (PIV)
3. Electronic Process Tomography (EPT) technology
4. Computational Fluid Dynamics (CFD) technology

Due to the diversity of application systems and the complexity of material rheological properties, fluid mixing has long been studied through experimental methods to investigate macroscopic quantities such as stirring power. Accurately describing and simulating homogeneous and heterogeneous mixing processes, as well as complex mixing and reaction coupling processes, provides theoretical guidance for the design optimization and amplification of mixing equipment, and is an important development direction of mixing technology. The application of new measurement and simulation technologies has brought hybrid technology into a new stage of development, which will directly contribute to designing safer and optimized process equipment, improving process efficiency and reducing the risk of failure, and ultimately increasing reaction yields. The development of new mixers and intelligent auxiliary design of mixing equipment will promote the efficiency and convenience of fluid mixing technology in industrial applications.