Crystallizers batch type

India, Goa and Bombay two plants built ca 1950 batch-type open-hearth roasters ceUs are operated discontinuously, the KMnO is crystallized separately in agitated tanks 1,200 114... 

Double-Pipe Scrapea-Surface Crystallizer This type of equipment consists of a double-pipe heat exchanger with an internal agitator fitted with spring-loaded scrapers that wipe the wall of the inner pipe. The cooling hquid passes between the pipes, this annulus being dimensioned to permit reasonable shell-side velocities. The scrapers prevent the buildup of solids and maintain a good film coefficient of heat transfer. The equipment can be operated in a continuous or in a recirculating batch manner. 

The flow scheme of the process(17) is represented in Fig. 2. The required throughput rate of 5 kg Pu/day is obtained in a batch-type operation, where a 5 to 10% substoichometric oxalate precipitation is performed by adding solid oxalic acid to a 3 M HNO - 100 g/L Pu(NO3) 4 solution at 80°C in about 2 hours. Up to 95% of the Pu is precipitated as uniform crystals of 20 yum average size and filtered. After washing and calcination, the average analysis of this product shows less than 1000 ppm total metallic impurities. When evaporating the filtrate to about 5% of its original volume, nitric acid is recovered, and most of the oxalic acid is destroyed. This results from sump temperatures of up to 123°C and the presence of Pu(VI). 

CRYSTALIZATION BATCH FROM SOLUTION Experimental step 1 Check single crystals with X-ray diffraction Question 1 Does the crystallization process yield only one type of single crystals ... 

The second group of the batch type of solid layer techniques are those with moving melts. Here again, three processes must be named the MWB-Sulzer, nowadays called Sulzer falling film (CH-PS 1967 U.S. 1985), the ICI-process (GB-PS 1964), and the BASF-process (DE-PS 1976), which is now distributed by the Kvaerner company. In all processes, the crystallization takes place on the inside of tubes, which are cooled from the outside. The melt coming from a feed tank is continuously circulated through the tubes until the crystal coat at the walls is thick enough, i.e., until... 

In order to set the design procedure for batch-type layer crystallization processes on a somewhat more theoretical basis rather than on empiricism, several authors as, e.g., Neumann (1996), Guardani and Belline (1997), and Bierwirth (1998) developed approaches to predict the separation efficiency of a process as a function of the properties of the mixture and the considered plant principle. However, all approaches still require experimental data keff as the basis for the calculation, even if the total necessary number of tests could be considerably reduced. 

A continuous microwave equipment (CME) has been developed to achieve a rapid and mass production for ZSM-5 and NaY zeolite. A precursor mixture for synthesis of ZSM-5 was prepared by mixing aluminosilicate gel with a nanoseed solution obtained under microwave irradiation, and pumped into the CME. Duration time in the CME was 5 min to accomplish the crystallization of ZSM-5 under microwave irradiation. For NaY zeolite, the precursor gel without nanoseeds was introduced into the CME and crystallization time was within 30 min. XRD and SEM results indicate that the structural properties of ZSM-5 and NaY zeolite obtained are similar to those obtained using batch-type microwave instrument and by conventional hydrothermal synthesis. 

In most cases, crystals are recovered from ammonium sulfate slurry by recycling through the continuous or the automatic batch-type centrifuge, wherein the product is screened and spin-dried, washed with water and weak ammonia, and again spin-dried before being conveyed to the drier. In some plants, continuous top-feed filters -... 

Crystallization cannot occur without supersaturation. A main function of any crystallizer is to cause a supersaturated solution to form. A classification of crystallizing equipment can be made based on the methods used to bring about supersaturation as follows (1) supersaturation produced by cooling the solution with negligible evaporation—tank and batch-type crystallizers (2) supersaturation produced by evaporation of the solvent with little or no cooling—evaporator-crystallizers and crystallizing... 

The first group of commercially available equipment is based on the Hoechst Tropfapparat (sweating apparatus) patented more than 100 years ago. It is a solid layer equipment of the batch type with stagnant melts (only natural convection). These crystallizers are commercially available, for example, as the Proabd type (Befs) using tubes and as the static plate crystallizer from Sulzer Chemtech Ltd (see Figure 17.2). Both crystallizers feature cooled surfaces for crystallization of the melt. 

The concept of programmed operation can also be applied to other types of batch crystallization e.g. precipitation via drowning-out with miscible solvents (Jones and Teodossiev, 1988). 

Influence of pH on the crystallization of ZSM-5 Three identical B -type portions from the same batch have been heated at 130°C at three different pH values. Their synthesis characteristics and various physical parameters are compared in Table IV. Figure 7 illustrates their morphological differences. 

Sensitivity Impure HNF shows a value of impact sensitivity of <1 Nm while pure or recrystallized HNF of the same batch exhibits an improvement to the level of >15 Nm. Some researchers have reported friction sensitivity of 25 N. However, the data on impact and friction sensitivity reported by various groups suggest that sensitivity depends not only on purity but also on particle size, shape of crystals and the type of contaminants. There is a lot of variation in the data reported by various investigators and it appears that this variation is attributed to differences in purity, particle size and morphology of HNF synthesized by different groups [84]. 

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