Costs of distillation

Distillation is by far the most commonly used method for the separation of homogeneous fluid mixtures. The cost of distillation varies with operating pressure, which, in turn, is mainly determined by the molecular weight of the materials being separated. Its widespread use can be attributed to its ability to... 

A. Pikiilik and H. E. Diaz [Chem. Eng., 84, 106-122 (Oct. 10, 1977)] presented a graphical method for estimating the fabricated cost of distillation cohimns and pressnre vessels, storage tanks, fired heaters, pnmps and drivers, compressors and drivers, and vacnnm eqnipment. 

It should be emphasized that the factors in Table 2.2 are average and only approximate and will vary, amongst other things, according to the type of equipment. As an example, consider the effect of materials of construction on the capital cost of distillation columns. Table 2.3 gives materials of construction cost factors for distillation columns. 

Mulet A, Corripio AB and Evans LB (1981) Estimate Costs of Distillation and Absorption Towers Via Correlations, Chem Eng, Dec 77. 

Another factor increasing the cost of distillation in ion exchange regenerant recovery is the need for supplying reflux to the rectifying columns. The boil-up for the reboilers is the distillate product plus the reflux, where in direct distillation the reboiler has to vaporize only the product. 

Reliable capital and operating cost comparisons between pervaporation and distillation are not available. Pervaporation is less capital and energy intensive than distillation or adsorption processes for small plants treating less than 5000 L/h of feed solution. However, because of the modular nature of the process, the costs of pervaporation are not as sensitive to economies of scale as are the costs of distillation and adsorption processes. Distillation costs, on the other hand, scale at a rate proportional to 0.6-0.7 times the power consumption. Thus, distillation remains the most economical process for large plants. The cross-over point at which distillation becomes preferable to pervaporation from an energy and economic point of view currently appears to be 5000 L/h processing capacity. Bergdorf has made an analysis of the comparative costs of pervaporation, distillation and other processes [43],... 

The process described by Burton et al. (1984) uses proven technology and demonstrates the point that the production of ethanol from wood is likely to be viable only when integrated as a multiproduct operation. The obvious areas for improvement are in increasing the ethanol yield and in encouraging fermentation to continue as the concentration of ethanol builds up in the solution, whieh would significantly reduce the cost of distillation. 

The oldest method of desalination, distillation, accounts for more than 90 percent of the approximately 500 million gallons per day capacity of the desalination systems currently in operation worldwide. The process involves vaporizing seawater and then condensing the pure water vapor. Most distillation systems use heat energy to do this. Attempts to reduce the cost of distillation include the use of solar radiation as the energy source. This approach is attractive because sunshine is normally more intense in arid lands, where the need for water is also greatest. However, despite intensive research and development efforts, several en-... 

Distillation. The cost of fuel is usually not large enough to justify a separate cost heading and it would be included in the hourly cost of distillation. Since plants may vary greatly in size, complexity, capital cost, etc. it is difficult to generalize... 

For on-site separation/purification of recovered solvent it is necessary to consider the number and complexity of distillations needed to obtain materials which are suitably pure for reuse. Where mixtures must be separated into individual solvents this can require several distillations, particularly where the solvents form azeotropes - this can significantly add to costs. The major costs associated with solvent purification are normally the capital required for distillation columns, energy and the additional staffing needs to oversee the operation. Where azeotropic distillations are required the cost of distillation columns can be greater than the capital cost of the recovery unit itself and staffing costs can be a significant variable cost (particularly if batch distillation is required). 

The operation costs of distillation processes are mainly influenced by the enthalpy of vaporization and, to a smaller extent, by the specific isobaric heat capacity of liquids. Therefore, its importance can easily be understood. 

Cd Total capital cost of distillation column = C3 Ce Capacity associated with an electrochemical... 

Ihe two principal factors opposing each other are the use of more raw materials when the recycle rate is low (as a result of low selectivity), and the high cost of distillation when the recycle rate is high. 

Colors in visuals can be a useful tool. However, colors should be used wisely and effectively. Typically, this means no more than four, as a general rule. Also, try to be consistent in the use of colors if you use red for the fixed cost of the heat exchangers and blue for the fixed cost of distillation columns, then use the same colors for operating costs for the same equipment. 

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