Recovery, multicomponent system

Figure 9.15 Pinch location (zones of constant composition) for binary and multicomponent systems. Brackets indicate key components remaining in a product stream due to incomplete recovery.

This review groups the information published on degradation of the main families of extractants studied in the frame of long-lived minor-actinide and fission-product recovery (1-4) (see Chapter 1) alkyl-phosphorus compounds (phosphates, phosphonic acids, bifunctional compounds like CMPO), amide compounds (dialkyl-amides, malonamides, and diglycolamides), N-donor compounds, and macrocycles like crown ethers and calixarenes (Table 8.1). The multicomponent systems based on the chlorinated cobalt dicarbollide process have not been considered. 

The control of key quality parameters is made easier the particle size distribution, the bulk density and the residual moisture content It produces the most homogeneous product for multicomponent systems and the catalyst particles have the same chemical composition as the feed, therefore affording a very high recovery (99+%) and a minimal level of pollution... 

Another consideration in this area is to keep the reaction simple. Avoid the multicomponent systems that will require complex separation after reaction for chemical recovery. The optimum here would be that the reacting chemical swells the lignocellulosic structure and is the solvent as well. 

In analyzing schemes for separation processes the separation of two-component mbctures or the purification of components with sorbability extremes (lowest or highest) from multicomponent systems will be considered. When separating multicomponent mixtures the problem of providing flow circulation is solved in the same way as in separating two-component mixtures. Some peculiarities in the recovery of components with intermediate sorbability will be dealt with in Sec. II. 

Multicomponent Systems According to Sherwood and Pigford, in the recovery of natural gasoline and the treatment of refinery gases the problem of multi-component solutions was of enormous importance in... 

For multicomponent systems, calculations with the Fenske equation are straightforward if fractional recoveries of the two keys, A and B, are specified. If the relative volatility is not constant, the average defined in equation (6-60) can be approximated by... 

For multicomponent systems calculation with the Fenske equation is straightforward if fractional recoveries of the two keys, A and B, are specified. Equation (7-15) can now be used direcdy to find Nn. The relative volatility can be approximated by a geometric average. Once is known, the fractional recoveries of the non-keys (NK) can be found by writing Eq. (7=15) for an NK conponent, C, and either key conponent. Then solve for (FRc) or (FRc). When this is done, Eq. (7=15) becomes... 

Generally, techniques for designing absorbers and strippers for multicomponent systems have been aimed at the recovery of light hydrocarbons from natural or refinery gas streams usir trqr towers. Numerous shortcut calculation methods have been developed to obviate the need for tedious tray-lqr-ttay calculations however, the importance of these techniques has declined sonrewhat because of (1) the advent of small powerful computers and (2) the use of low-temperature separation instead of oil absorption to recover light hydrocaitwns. As a result, the cahwlational techniques for multicomponent hydrocarbon absorbers are treated rather briefly in this section. 

Microemulsions are microheterogeneous, thermodynamically stable, spontaneously formed mixtures of oil and water under certain conditions by means of surfactants, with or without the aid of a cosurfactant. The first paper on microemulsions appeared in 1943 by Hoar et al but it was Schulman and coworkers who first proposed the word microemulsion in 1959. Since then, the term microemulsions has been used to describe multicomponent systems comprising nonpolar, aqueous, surfactant, and cosurfactant components. The application areas of microemulsions have increased dramatically during the past decades. For example, the major industrial areas are fabricating nanoparticles, oil recovery, pollution control, and food and pharmaceutical industries. This book is a comprehensive reference that provides a complete and systematic assessment of all topics affecting microemulsion performance, discussing the fundamental characteristics, theories, and applications of these dispersions that have been developed over the last decade. 

Except for the consideration of solvent vaporization in the above discussion of adiabatic packed towers, it has thus far been assumed that only one component of the gas stream has an appreciable solubility. When the gas contains several soluble components or the liquid several volatile ones for stripping, some modifications are needed. The almost complete lack of solubility data for multicomponent systems, except where ideal solutions are formed in the liquid phase and the solubilities of the various components are therefore mutually independent, unfortunately makes estimates of even the ordinary cases very difficult. However, some of the more important industrial applications fall in the ideal-solution category, e.g., the absorption of hydrocarbons from gas mixtures in nonvolatile hydrocarbon oils as in the recovery of natural gasoline. 

Multiple Products. If each component of a multicomponent distillation is to be essentially pure when recovered, the number of columns required for the distillation system is N — 1, where AJ is the number of components. Thus, ia a five-component system, recovery of all five components as essentially pure products requires four separate columns. However, those four columns can be arranged ia 14 different ways (43). 

Colistin (COL) is a multicomponent antibiotic (polymyxins E) that is produced by strains of inverse Bacillus polymyxa. It consists of a mixture of several closely related decapeptides with a general structure composed of a cyclic heptapeptide moiety and a side chain acetylated at the N-terminus by a fatty acid. Up to 13 different components have been identified. The two main components of colistin are polymyxins El and E2 they include the same amino acids but a different fatty acid (216). A selective and sensitive HPLC method was developed for the determination of COL residues in milk and four bovine tissues (muscle, liver, kidney, and fat). The sample pretreatment consists of protein precipitation with trichloracetic acid (TCA), solid-phase purification on Cl 8 SPE cartridges, and precolumn derivatization of colistin with o-phthalaldehyde and 2-mercaptoethanol in borate buffer (pH 10.5). The last step was performed automatically, and the resulting reaction mixture was injected into a switching HPLC system including a precolumn and the reversed-phase analytical column. Fluorescence detection was used. The structural study of El and E2 derivatives was carried out by HPLC coupled with an electrospray MS. Recoveries from the preseparation procedure were higher than 60%. 

Before and after the works described above, contributions to the design and fabrication of similar multicomponent films or gels of cholesteric character, mainly based on HPC, EC, or their derivatives were also made [202, 219-224], Some of these [219,220,224] dealt with shear-deformed network systems preserving a unique banded structure, so that the disappearance and recovery of the optical anisotropy could be controlled thermo-reversibly. Special mention should be made of the successful preparation of two novel classes of solid materials maintaining cholesteric liquid-crystalline order. One consists of essentially pure cellulose only, and the other is a ceramic silica with an imprint of cellulosic chiral mesomorphy. 

Generally, alcohols showed higher separation factors when present in model multicomponent solutions than in binary systems with water. On the other hand, aldehydes showed an opposite trend. The acmal tea aroma mixmre showed a rather different behavior from the model aroma mixmre, probably because of the presence of very large numbers of unknown compounds. Overall, the PDMS membrane with vinyl end groups used by Kanani et al. [20] showed higher separation factors and fluxes for most of the aroma compounds. Pervaporation was found to be an attractive technology. However, as mentioned above the varying selectivities for the different aroma compounds alter the sensory prohle and therefore application of PV for recovery of such mixmres needs careful consideration on a case-by-case basis. 

A systematic optimization framework for complex PSA systems has been developed. The results clearly indicate the benefits (in terms of product purity, recovery, and power requirements) that can be achieved by using the proposed approach. Future work will focus on applications in large-scale industrial processes involving complex multicomponent gas separations. 

To illustrate the procedure, we consider a fairly complex process sketched in Fig. 6.4, which shows the process flowsheet and the nomenclature used. In the continuous stirred-tank reactor, a multicomponent, reversible, second-order reaction occurs in the liquid phase A + B C + D. The component volatilities are such that reactant A is the most volatile, product C is the next most volatile, reactant B has intermediate volatility, and product D is the heaviest component a/ > ac > olb > OiQ. The process flowsheet consists of a reactor that is coupled with a stripping column to keep reactant. A in the system, and two distillation columns to achieve the removal of products C and D and the recovery and recycle of reactant B. 

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