Solid-liquid mixing scale

Solid-liquid mixing processes can be simulated with good precision when sound CFD methods are used. The application of a combination of the virtual finite element method and the network-of-zone approach was used in this work to analyze the complex flow and suspension mechanisms in a coaxial mixer. Experiments carried on the laboratory scale confirmed fhe validity of the predictions. 

Testing in the lab or pilot plant will help define the appropriate design and scale-up requirements. The reader is referred to Chapter 10 on solid-liquid mixing and Chapter 13 on reacting solids. 

Key Process Questions for Solid-Liquid Mixing. For each mixing operation, several key process-related issues must be addressed before scale-up and design. For solid-liquid mixing operations, key process questions include the following. 

SELECTION, SCALE-UP, AND DESIGN ISSUES FOR SOLID-LIQUID MIXING EQUIPMENT 573... 

In solid-liquid mixing applications, the purpose of scale-up is to determine the operating conditions at different scales at which mixing yields equivalent process results. The tasks involve ... 

At 577°C the eutectic reaction takes place the liquid decomposes into solid (Al) mixed with solid Si, but on a finer scale than before (bottom of Fig. A1.32). This intimate mixture of secondary (Al) with secondary Si is the eutectic structure. 

A turbine type agitator is commonly used for liquid-solid systems. Mixing rates depend on the forces required to suspend all solid particles. Minimum levels can be determined for (1) lifting the particles, and (2) for suspending them in an homogeneous manner [200]. Similar requirements apply to liquid-liquid systems. For cases where two poorly miscible fluids of about equal volume are used in the reaction, the mixer is placed at the interface. For a bench-scale experimental system of about 2 liters capacity, the minimum rotational speed to obtain well-dispersed system is 300 to 400 rpm [201], depending on the type of mixer. This rotational value decreases as the vessel volume increases. 

For homogeneous reactions agitation is usually not crucial, but agitation rates can have a dramatic influence on reaction rate for viscous or heterogeneous reactions (liquid-liquid, solid-liquid, gas-liquid). Some aspects of mixing are discussed in Chapters 9 and 13. Agitation can also be very important as a scale-up consideration, particularly during crystallization and transfer of a product slurry to the filter (Chapter 11). 

Dielectric spectroscopy techniques are promising for numerous applications that require non-invasive, non-destructive, non-contact, and real-time measurements. Non-invasive measurements with gas, liquid, solid, and mixed samples are possible on distance scales from nanometers to meters and a frequency of excitation from microhertz to terahertz. The main advantages of fringing electric field dielectric sensors include one-side access to material under test, convenience of application... 

The Baylis-Hillman (B-H) reaction is a synthetically useful carbon-carbon bond-forming reaction between an aldehyde and an electrophilic alkene, usually in the presence of a tertiary amine 1,2). One of its main attractions is the high degree of functionality present in the products and their resultant potential transformations. The reaction gives good yields when performed neat, but this would be difficult on a production scale because of mixing problems (the reagents are often solid) and because the reaction is exothermic. However the typical B-H reaction is notoriously slow in liquid solution unless particularly... 

Hence, an equivalent form of the previous scaling law, 5c A.mix ", is Sc l/(Re Sc) where m = for boundary layer theory adjacent to a solid-liquid interface in the creeping flow regime, and m = for gas-liquid interfaces. As expected, the boundary layer thickness at any position along the interface decreases at higher flow rates and increases when the diffusivity is larger. Since... 

Hence, the local mass transfer coefficient scales as the two-thirds power of a, mix for boundary layer theory adjacent to a solid-liquid interface, and the one-half power of A, mix for boundary layer theory adjacent to a gas-liquid interface, as well as unsteady state penetration theory without convective transport. By analogy, the local heat transfer coefficient follows the same scaling laws if one replaces a, mix in the previous equation by the thermal conductivity. 

Reactions of nanoscale materials are classified with respect to the surrounding media solid, liquid, and gas phases. In the solid phase, nanoscale crystals are usually connected with each other to form a powder particle (micron scale) or a pellet (milli scale) see Figure 14.1. Two or more materials (powder or pellet) are mixed and fired to form a new material. The nanosized structure is favored, due to the mixing efficiency and high reaction rate. Alloys (metals), ceramics (oxides), cement (oxides), catalysts (metals and oxide), cosmetics (oxides), plastics (polymers), and many functional materials are produced through solid reaction of nanoscale materials. One recent topic of interest is the production of superconductive mixed oxides, where control of the layered stracture during preparation is a key step. 

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