Solid-liquid mixing equipment

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

In this ehapter, the transport proeesses relating to partiele eonservation and flow are eonsidered. It starts with a brief introduetion to fluid-particle hydrodynamics that deseribes the motion of erystals suspended in liquors (Chapter 3) and also enables solid-liquid separation equipment to be sized (Chapter 4). This is followed by the momentum and population balances respeetively, whieh deseribe the eomplex flows and mixing within erystallizers and, together with partieulate erystal formation proeesses (Chapters 5 and 6), enable partiele size distributions from erystallizers to be analysed and predieted (Chapters 7 and 8). 

Multi-phase mixing is often seen in industries. In general, the distribution of not only the dispersed phase but also the continuous phase depends on the local position in the equipment in the case of a multi-phase operation such as gas-liquid mixing system, liquid-liquid mixing system, solid-liquid mixing system, and gas-liquid-solid mixing system. In order to evaluate the mixing state in such systems, both the dispersed phase and continuous phase should be considered. 

Many operations treat particle-liquid mixing in chemical industry. The first aim of solid-liquid mixing is to make a solid particle float. However, mixing performance of operations/equipment is not clear. Additionally, when many kinds of particles are involved, it is not known whether there is any difference in the mixedness between the following two cases the case where all particles are treated as a particle (two-phase mixing—particle and continuous liquid phase) and the case where every particle is treated individually (multiple-phase mixing—each particle and continuous liquid phase). Therefore, a solution to this unsolved problem is not imperative. 

Clear-liquor advance is used for two purposes (1) to reduce the quantity of liquor that must be processed by the solid-liquid separation equipment (e.g., filter or centrifuge) that follows the crystallizer, and (2) to separate the residence time distributions of crystals and liquor. The reduction in liquor flow through the separation equipment can allow the use of smaller equipment for a fixed production rate or increased production through fixed equipment. Separating the residence time distributions of crystals and liquor means that crystals will have an average residence time longer than that of the liquor. This should, in principle, lead to the production of larger crystals, but because the crystallizer is otherwise well mixed, the crystal population density will have the same form as that for the MSMPR crystallizer (Eq. (54)). 

Before the polymer and additive can be mixed together, the compounder must first introduce the components into the mixing equipment. Since additives come in many different forms, either solid or liquid, and different shapes and sizes, the means of their introduction must be matched to the material being added. 

The most significant improvement came in the early 1940s when a method for preparing thiol-terminated liquid polysulfides was developed. Cure of the liquid polysulfides could be accomplished by oxidative coupling. Thus, in effect, a mbber could be compounded without the need of heavy mixing equipment. One of the first large-scale applications of the liquid polysulfides was as a binder for solid rocket fuel. From about 1946 until 1958, these binders were used in various rocket systems and the aliphatic polysulfides achieved commercial success. The switch to predominately liquid-fueled rockets in 1958 ended this phase of the polysulfide business. 

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