Utility costs phase

Fractionation. Kett-McGee developed the ROSE process for separating the heavy components of cmde oil, eg, asphaltenes, resins, and oils, in the 1950s. This process was commercialized in the late 1970s, when cmde oil and utility costs were no longer inexpensive. In the ROSE process (Fig. 11), residuum and pentane ate mixed and the soluble resins and oils recovered in the supetctitical phase. By stepwise isobatic temperature increases, which decrease solvent density, the resin and oil fractions ate precipitated sequentially. 

Although there are several different commercial technologies in use the economic information described below relates only to the liquid phase technology. The cost of EB production consists of three main components raw materials, utilities, and the fixed cost associated with the plant. The cost of utilities includes fuel, electricity, steam, cooling water, catalyst, and chemical costs required to operate the plant. Ethylbenzene plants typically have a small net negative utilities cost because the credit value of steam generated usually exceeds the cost of other utilities used throughout the plant. 

In both of the processes just described, a crystallizer produces a solid and, following a solid-liquid phase separation, a dryer removes the moisture. In some cases, all three of these operations can be carried out in a single piece of equipment, a spray dryer or a drum dryer, but at the expense of increased utility cost because all of the solvent is evaporated. Such dryers are used extensively to produce dried milk and detergents. For these products, spray dryers are particularly desirable, because the drying process produces porous particles that are readily dissolved in water. Spray dryers can also handle slurries and pastes. 

Another key factor for successful cost targeting is capital cost estimation. Capital costs for heat recovery systems include costs for heat exchangers, heaters, and coolers. Improper estimates of capital cost can lead to suboptimal trade-offs between capital and utility costs. One important aspect is good estimates of heat transfer coefficients for individual process streams since heat transfer coefficients determine the size and surface area of heat exchangers. A second consideration for accurate capital costs is realistic cost calculation for process furnaces and cooling towers in the targeting phase of work— these are much more expensive than heat exchangers. 

In the dyestuff industry, anthraquinone still ranks high as an intermediate for the production of dyes and pigments having properties unattainable by any other class of dyes or pigments. Its cost is relatively high and will remain so because of the equipment and operations involved in its manufacture. As of May 1991, anthraquinone sold for 4.4/kg in ton quantities. In the United States and abroad, anthraquinone is manufactured by a few large chemical companies (62). At present, only two processes for its production come into consideration manufacture by the Friedel-Crafts reaction utilizing benzene, phthahc anhydride, and anhydrous aluminum chloride, and by the vapor-phase catalytic oxidation of anthracene the latter method is preferred. 

Availability of large digital computers has made possible rigorous solutions of equilibrium-stage models for multicomponent, multistage distillation-type columns to an exactness limited only by the accuracy of the phase equilibrium and enthalpy data utilized. Time and cost requirements for obtaining such solutions are very low compared with the cost of manual solutions. Methods are available that can accurately solve almost any type of distillation-type problem quickly and efficiently. The material presented here covers, in some... 

Silica gel, per se, is not so frequently used in LC as the reversed phases or the bonded phases, because silica separates substances largely by polar interactions with the silanol groups on the silica surface. In contrast, the reversed and bonded phases separate material largely by interactions with the dispersive components of the solute. As the dispersive character of substances, in general, vary more subtly than does their polar character, the reversed and bonded phases are usually preferred. In addition, silica has a significant solubility in many solvents, particularly aqueous solvents and, thus, silica columns can be less stable than those packed with bonded phases. The analytical procedure can be a little more complex and costly with silica gel columns as, in general, a wider variety of more expensive solvents are required. Reversed and bonded phases utilize blended solvents such as hexane/ethanol, methanol/water or acetonitrile/water mixtures as the mobile phase and, consequently, are considerably more economical. Nevertheless, silica gel has certain areas of application for which it is particularly useful and is very effective for separating polarizable substances such as the polynuclear aromatic hydrocarbons and substances... 

Early examples of enantioselective extractions are the resolution of a-aminoalco-hol salts, such as norephedrine, with lipophilic anions (hexafluorophosphate ion) [184-186] by partition between aqueous and lipophilic phases containing esters of tartaric acid [184-188]. Alkyl derivatives of proline and hydroxyproline with cupric ions showed chiral discrimination abilities for the resolution of neutral amino acid enantiomers in n-butanol/water systems [121, 178, 189-192]. On the other hand, chiral crown ethers are classical selectors utilized for enantioseparations, due to their interesting recognition abilities [171, 178]. However, the large number of steps often required for their synthesis [182] and, consequently, their cost as well as their limited loadability makes them not very suitable for preparative purposes. Examples of ligand-exchange [193] or anion-exchange selectors [183] able to discriminate amino acid derivatives have also been described. 

Calculations of economic profitability can only be predictive in the phase of process development, before a plant is on stream for a long time. Therefore, individual components of costs and market evaluations will bear some uncertainty. This uncertainty is relatively high for pharmaceuticals and agrochemicals. The impact of these uncertainties on the profitability of a process may be quantified by a sensitivity analysis. This analysis provides information about the sensitivity of the process economics to changes in parameters relevant for the profitability (investment costs, price and consumption of raw materials, utility unit costs, product value and demand, etc.), and therefore on the reliability of the result of the economic evaluation. In the early stages of process development, a high sensitivity indicates the areas requiring attention for continued R D work. 

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