Suspension, Mixed-Product-Removal Crystallizers

Mixed-suspension, mixed-product removal crystallizer... 

Mixed-Suspension, Mixed-Product-Removal Crystallizers. 18-44... 

This results In a set of first-order ordinary differential equations for the dynamics of the moments. However, the population balance Is still required In the model to determine the three Integrals and no state space representation can be formed. Only for simple MSMPR (Mixed Suspension Mixed Product Removal) crystallizers with simple crystal growth behaviour, the population balance Is redundant In the model. For MSMPR crystallizers, Q =0 and hp L)=l, thus ... 

Crystallization of magnesium hydroxide by a continuous mixed suspension mixed product removal crystallizer was conducted to make clear the characteristics of reactive crystallization kinetics of magnesium hydroxide, which was produced by the precipitation from magnesium chloride with calcium hydroxide. The following operating factors were investigated affecting the crystallization kinetics the initial concentration of feeds, residence time of reactants, feed ratio of reactants, and concentrations of hydroxide and chloride ions. 

HEAT STABILIZERS] (Vol 12) Mixed-suspension, mixed-product removal crystallizer... 

ANALYSIS OF DATA FROM A MIXED SUSPENSION—MIXED PRODUCT REMOVAL CRYSTALLIZER (MSMPR) 10.13... 

The first three columns of Table 10.5 show sieve data for a 100-cc slurry sample containing 21.0 g of solids taken from a 20,000-gal (75-m3) mixed suspension-mixed product removal crystallizer (MSMPR) producing cubic ammonium sulfate crystals. Solids density is 1.77 g/cm3, and the density of the clear liquor leaving the crystallizer is 1.18 g/cm3. The hot feed flows to the crystallizer at 374,000 lb/h (47 kg/s). Calculate the residence time r, the crystal size distribution function n, the growth rate G, the nucleation density n°, the nucleation birth rate B°, and the area-weighted average crystal size L3 2 for the product crystals. 

The simplest continuous reactor to consider is that of a constantly stirred tank reactor (CSTR) or precipitator, also called a mixed suspension, mixed product removal crystallizer (MSMPR) [98], shown in Figure 6.23. This tsrpe of precipitator has a constant volume, V, with an input flow rate equal to its output flow rate, Q. The population iJofR) in the precipitator is that which leaves as product. In this case, the population balance is used at steady state (i.e., drjfjdt — 0) ... 

Mixed-Suspension, Mixed-Product-Removal Crystallizers This type of equipment, sometimes called the circulating-magma crystallizer, is by far the most important in use today. In most commercial equipment of this type, the uniformity of suspension of product solids within the crystallizer body is sufficient for the theory [Eqs. (18-34) to (18-36c)] to apply. Although a number of different varieties and features are included within this classification, the equipment operating with the highest capacity is the kind in which the vaporization of a solvent, usually water, occurs. 

Modern industrial crystallization theory dates essentially from the work of Randolph and Larson (1962), who developed the concept of population density insofar as it applies to mixed suspension, mixed product removal crystallization equipment. A detailed treatment of the development of these concepts is given in Chapter 4 of this volume. The population density concept is useful because it allows the user to take the data developed from a crystal screen analysis along with knowledge of the operating parameters of the crystallizer, such as the retention (drawdown) time, slurry density. 

This extremely simplified relation for the number density balance is only valid for the so-called MSMPR (mixed suspension mixed product removal) crystallizers. Integration with the integration constant as the nnmber density at grain size Z = 0 leads to... 

The study started with a batch crystallization experiment using seeded method. The purpose of this batch experiment was to deteimine the parameters needed for the subsequent experiment, i.e. the seeded continuous crystallization experiment using an MSMPR (mixed-suspension-mixed-product-removal) crystallizer. These parameters were levels of supersaturation, residence time, stirring rate, and concentration of additives, respectively. 

The CSD of the product from a continuous crystallizer is determined by a direct relationship between nucleation and crystal growth rates and magma residence time distributions. Since a priori prediction of crystallization kinetics is not yet possible, however, experimentally determined and statistically correlated nucleation and growth rates are needed for the design and analysis of industrial crystallizers. Analysis of the CSD from continuous MSMPR (mixed-suspension, mixed-product-removal) crystallizers has proved to be a popular way of inferring such crystallization kinetics. This approach has been widely... 

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