Extraction mechanical process

In contrast to fluid process technologies such as distillation, absorption, and extraction, mechanical processes are only accessible to a limited extent to mathematical modeling, and process design is dependent on experiment. However, only a few experimental techniques that allow reliable scale-up to be performed are available. 

The interfacial mechanism probably competes to some extent with the extraction mechanism, particularly with the less lipophilic catalysts. The dependence of the rate of many nucleophilic substitution reactions on the stirring rate up to 250-300 rpm and the independence of the reaction rate at higher stirring rates has been taken as evidence for a change over from a predominant interfacial mechanism to an extraction process. The interfacial mechanism is also particularly relevant to base-initiated reactions. 

In this section, we describe three simple cases of rates and mechanisms that have been found suitable for the interpretation of extraction kinetic processes in kinetic regimes. These simple cases deal with the exuaction reaction of a monovalent metal cation (solvation water molecules are omitted in the notation) with a weakly acidic solvent extraction reagent, BH. The overall extraction reaction is... 

FIG. 10-180 Typical weld imperfections. (Extracted from Process Piping, ASME B31.3—2004, with permission of the publisher, the American Society of Mechanical Engineers, New York.)... 

In this paper an overview of the developments in liquid membrane extraction of cephalosporin antibiotics has been presented. The principle of reactive extraction via the so-called liquid-liquid ion exchange extraction mechanism can be exploited to develop liquid membrane processes for extraction of cephalosporin antibiotics. The mathematical models that have been used to simulate experimental data have been discussed. Emulsion liquid membrane and supported liquid membrane could provide high extraction flux for cephalosporins, but stability problems need to be fully resolved for process application. Non-dispersive extraction in hollow fib er membrane is likely to offer an attractive alternative in this respect. The applicability of the liquid membrane process has been discussed from process engineering and design considerations. 

This synthesis was carried out by reaction of polyethylene terephthalate and ethylenediamine in the presence of the metallic salts. Mechanical activation was supplied by vibratory milling in a nitrogen atmosphere. Granular polyethylene terephthalate (supplied by U.F.S.-Jassy) was subjected to mechanical processing in powdered form. It was purified by dissolving in a 40/60 phenol/chloroform mixture and reprecipitating with methanol. After filtration, the polymer was extracted... 

Depending on the amount of amine used and on the milling time, the reaction mass either had a pastelike consistency or that of a fluid dispersion. The experiments were intended to establish some parameters (duration of mechanical processing, amount of diamine and complexing agent, etc.) and correlate them to characterize the polymers obtained, and to determine certain chemical and physical properties of the polymer. In all cases, the samples were purified by extraction in a Soxhlet apparatus with water or alcohol to remove unreacted ethylenediamine and metallic salts. The extractions were carried out until constant weight was obtained. Total removal of chloride was determined by silver nitrate. Purified samples were then washed with methanol, dried, and analyzed. 

Several spectroscopic techniques, namely, Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared (IR), Nuclear Magnetic Resonance (NMR), etc., have been used for understanding the mechanism of solvent-extraction processes and identification of extracted species. Berthon et al. reviewed the use of NMR techniques in solvent-extraction studies for monoamides, malonamides, picolinamides, and TBP (116, 117). NMR spectroscopy was used as a tool to identify the structural parameters that control selectivity and efficiency of extraction of metal ions. 13C NMR relaxation-time data were used to determine the distances between the carbon atoms of the monoamide ligands and the actinides centers. The II, 2H, and 13C NMR spectra analysis of the solvent organic phases indicated malonamide dimer formation at low concentrations. However, at higher ligand concentrations, micelle formation was observed. NMR studies were also used to understand nitric acid extraction mechanisms. Before obtaining conformational information from 13C relaxation times, the stoichiometries of the... 

The DIAMEX-SANEX/HDEHP process is probably the only single-step process that enables a complete selective An(III)/Ln(III) partitioning from non-pretreated PUREX raffinates (245). It combines two organic molecules possessing opposite but complementary extracting mechanisms ... 

For ion-pair extraction, a cation is extracted with an anion into oil. In this case, individual ions or the ion pair species transfer across a microdroplet/water interface and the extraction rate is expected to depend on the Galvani potential between the microdroplet and water, the ion transfer potentials across the liquid/liquid interface, the association constant of the ions in the solution and so forth [46-54]. Therefore, the mass transfer processes are complicated even in the absence of adsorption of an ion at the microdroplet/water interface. In this section, the kinetic analysis of a simple ion-pair extraction without adsorption is described and the extraction mechanism is discussed on the basis of the single microdroplet technique. 

The solvent extraction process of metal ions inherendy depends on the mass transfer across the interface and the reaction that occurs at the interfacial region. Therefore, the elucidation of the kinetic role of the interface was very important in order to clarify the extraction mechanism and to control the extraction rates. In 1982, Watarai and Preiser invented the high-speed stirring (HSS) method [4,5]. Figure 10.1 shows the schematic drawing of the HSS method [6]. When a two-phase system is vigorously stirred in a... 

In this chapter, we derive and apply to data a simple two-step model that involves a chemical step followed by a mechanical removal step. The model is abstract in the sense that most of the specifics of the slurry composition or of the chemical reaction involved are not given in any detail. Although this appears to be a disadvantage, it is necessary for the application of the model to the analysis of removal rates from proprietary slurries whose compositions cannot be directly investigated. When applied as a compact formula, the model can provide a highly accurate description of removal rate variations as a function of polishing pressure and sliding speed. This then makes it possible to extract the relative contributions of chemical and mechanical processes to removal and to confidently interpolate or extrapolate rates based on the calibration data. 

There are four primary reasons why the mechanical extraction process is still selectively used. First, the mechanical extraction process can be furnished in very small scale, as low as 10 tons per day. The capital cost for small mechanical extraction facilities is considerably less than small solvent extraction facilities. In remote locations, freight differential can compensate for higher operating costs and lower yields. Second, there is a niche, high-value market for natural oils that have not been in contact with solvents or chemicals, requiring the use of mechanical extraction. Third, mechanical extraction can create a high bypass protein meal for ruminant animals that sells at a price premium over solvent extracted meal. Finally, mechanical extraction is often considered more reliable than solvent extraction when processing difficult materials (copra and palm kernel) in hot, tropical climates. 

Byproducts of conventional oil extraction and refining have been investigated as raw materials for the concentration of bioactive components. Birtigh et al. (115) investigated SFE of carotenes and tocopherols from waste products of pahn oil production (i.e., the residue of mechanical processing and palm leaves). Ibanez et al. (116) studied the separation of tocopherols from olive byproducts using fractional... 

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