Cost of solvent

Recovery of the solvent, sometimes by chemical means but more often by distillation, is almost always required, and the recoveiy system ordinarily is considered an integral part of the absorption-system process design. A more efficient solvent-stripping operation normally will result in a less costly absorber because of a smaller concentration of residual dissolved solute in the regenerated solvent however, this may increase the overall cost of solvent recoveiy. A more detailed discussion of these and other economic considerations is presented later in this section. 

Solvent recovery with adsorption is most feasible when the reusable solvent is valuable and is readily separated from the regeneration agent. When steam-regenerated activated-carbon adsorption is employed, the solvent should be immiscible with water. If more than one compound is to be recycled, the compounds should be easily separated or reused as a mixture. Only very large solvent users can afford the cost of solvent purification by distillation. ... 

EtOH extraction was the most efficient way to improve the flavour of the phloem. A solvent/solid ratio of at least 10 1/kg was needed to achieve a significant change in the taste. The loss of catechins was approximately 27% and that of lignans was 35%. All the catechins and lignans were found from the EtOH extract. Losses of lignans and catechins were smaller with other sovents, but either the taste was not modified or the cost of solvent treatment would be too high. Phenolic compounds like lignans and catechins also have a bitter taste and some improvement in flavour may have occurred because of the lower concentration of these. The disappearance of the characteristic... 

Cost of solvent extraction auxiliaries Cost of absorbtion and distillation column packing, supports and distributors Cost of tanks (surge, etc.)... 

Solvent Formulation System. Another technology area which cuts across product lines is solvent formulation. For each pound of coatings applied, cost of solvents represents an appreciable portion of the total cost. Solvent raw material cost can be as much as one-third of the total raw material cost of coating manufacturers. In addition, solvent formulation affects many end use properties, such as aesthetics, coverage, application latitude, functional properties, etc. For our computerized solvent formulation system, we have developed a number of models which predict properties of solvent blends known to be important in solvent formulation. 

Taking the profit P as the value of A recovered less the cost of solvent, all other costs being equal, then ... 

Entrainment and, therefore, the cost of solvent recovery equipment... 

It Is seen from equation (30) that the optimum flow-rate Is also proportional to the extra column dispersion and, as a consequence, the total volume of mobile phase employed in an analysis will also depend on the extra column dispersion. It follows that the economy of the analysis lies in the hands of the designer of the chromatograph, a responsibility for which, many instrument makers are not aware. Steps taken in the design of the chromatographic system that would reduce the extra column dispersion by a factor of two would also halve the volume and cost of solvent used in the... 

The cost of solvent per unit of DDT dissolved is a prime factor to be considered in the manufacture of DDT solutions. The amoimt of DDT that will remain dissolved in a dollar s worth of solvent is shown in pounds in Table III and Figure 2. The solvent prices upon which these data are based are also included in the table except for nitrocyclo-... 

Liquid propane is employed as the solvent in this process. The use of a petroleum fraction as a solvent for dewaxing is desirable from the standpoint of the availability and cost of solvent, and the higher boiling hydrocarbon fraction has been employed many years for dewaxing of residual stocks. 

Consideration of installation costs cannot be restricted to the solvent refining step. A residuum of 460° F. flash point usually will contain all usable lubricating oil. In addition to the cost of solvent extraction facilities, the expense of equipment to fractionate the oil into usable cuts, to deasphalt, to dewax, and to clay filter, all must be... 

The most common solvent is water. Water dissolves a great many gases, liquids, and solids, and is much used for this purpose. Other liquids similarly dissolve many substances without reacting chemically with them. Important considerations in connection wfith the choice of solvent for a given case are (1) vapor pressure and boiling point, (2) solvent power under stated conditions of temperature. (3) ease and completeness of recoverability by evaporation and condensation, and completeness of separation from dissolved material by evaporation. (4) heat of vaporization, (5) miscibility with water or other liquid, if present, (6) inertness to chemical reaction with the materials present, and with the apparatus, (7) inflammability and explosiveness. (8) odor and toxicity (9) cost of solvent, loss in process, cost of recovering. 

From the time of inception of this process, much concern has been indicated concerning the problem of solvent recovery from the product water and raffinate. This concern stems from two important considerations first, the cost of solvent losses and second, the possible toxicity of the remaining solvent. To investigate solvent recovery... 

A review of HPLC methods for antiepileptic drug analysis was published in 1987 by Juergens.18 Standard analytical separations were compared with narrow-bore separations, and a 70% reduction in the cost of solvents was possible, owing to a reduction in flow rate from 1 ml/min for the analytical column to 0.3 ml/min for the narrow-bore column. Gayden et al.19 developed an isocratic method, using narrow-bore columns, to quantify adenosine (Ado) release by dispersed rat renal outer medullary cells under conditions of normoxia and hypoxia. Standard HPLC with UV detection has been the predominant method for studying the metabolic pathways of adenosine and measuring the Ado breakdown products inosine (Ino) and hypoxanthine (Hyp). However, the conventional methods lack reliability... 

Cost and availability. The less expensive is the solvent, the lower is the cost of solvent losses. Water is the least expensive and most plentiful solvent. 

Since the samples run in prep LC are often very crude, it is to be expected that the column packing will become contaminated with chemicals that did not elute. Cleaning can be accomplished with polar solvents like propanol or ethyl acetate (for normal phase systems), or the packing can simply be discarded. The latter alternative may be cheaper, considering the cost of solvents and waste disposal. 

The often higher costs of solvents, salts, and fabrication methods of nonaqueous systems are weaker deterrents in secondary applications than primary ones since their cost is amortized over many uses. Higher costs indicate they are used to best advantage in relatively short-term, power hungry applications where portability or high product cost are considerations. At present, laptops, cellular phones and camcorders are obvious examples. 

Different designed solvent recovery systems are used. As an example there is the solvent system that consists of fixed bed adsorbers containing activated carbon and a distillation system. The carbon adsorbs the solvent vapors. Then the beds are steamed in sequence to remove the solvent. The solvent and steam are condensed into a large tank. The distillation system is then used to distill the solvent from the water to a purity of 99.99% so that it can be reused. Because of the high cost of solvent, complex monitoring equipment is used to insure a high rate of recover. 

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