Distillation costs

Sommerville, R. F, New Method Gives Quick, Accurate Estimate of Distillation Costs, Chem. Eng., May 1, (1972) p. 71. 

Van Winkle, M., Todd, W.G. Minimizing Distillation Costs Via Graphical Techniques, Chemical Engineering, Mar. 6, 1972, p. 105. 

From this display it can be seen that a 0.1 /lb increase in naphtha price from 1.0 to 1.1 / lb would raise the ethylene production cost from 2.5 to 2.8 /lb. If such a movement did occur, heavy gas oil at current 0.75 /lb levels (based on equivalent heavy fuel oil adjusted for viscosity considerations and vacuum distillation costs) would become competitive with naphtha. 

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 previous section assumed that product composition (or product flow) requirements are fixed. In this very common situation, the optimum design minimizes the costs of achieving these requirements. Often, product specs are not fixed, but depend on economics. Even when a product must obey a "less than" purity spec, better purity may fetch a better price. The better price may justify additional investment in equipment and/or a higher operating cost. Here, a design must optimize product purity value versus distillation cost. This optimization is also important in an operating column and is commonly performed by on-line computer control. It is outlined below, and discussed in detail elsewhere (1,2). 

Cost calculations were made for this modified extractive distillation process they are shown by the dashed curves on Figures 5 and 7. The proposed heat exchange system provides considerable reduction in the annual costs of the extractive distillation process. However, the extractive distillation costs are still greater than those for a binary propane-propylene distillation process as indicated on Figures 5 and 7. 

Product recovety is some combination of rote methods of using processing tools and inspired application of new and conventional separation tools. For example, if aldehydes make distillation infeasible because of polymerization products and/or vacuum distillation costs, then one can consider utilizing the Cannizzaro reaction to make organic acid salts and ketones from the aldehydes before proceeding. Many bench-scale processing techniques such as thin-film evaporation have been scaled up to handle larger quantities of temperature sensitive materials. Assistance in utilization of these techniques can usually be obtained from the equipment vendors. 

One example of whey utilization technologies is the production of alcohol from cheese whey at the Carbery Milk Products Ltd. factory, Ballineen, Ireland. The Carberry plant produces 2.59% v/v of ethanol from 4.7 w/v of lactose in whey permeate (Barry, 1982). Because the Kluveromyces species, used in anaerobic fermentations, have low ethanol tolerance, preconcentration of the lactose is not possible, so fermentation and distillation costs are considerable. Under Irish conditions potable alcohol is the most profitable outlet but in other countries, anhydrous alcohol for industrial or power uses may be more attractive (Ozmihci and Kargi, 2008). 

Sulfuric acid-type processes have the following advantages. First, separation (or distillation) costs are substantially cheaper. Second, costs of feedstocks (and especially isobutane) are smaller by several percentages. Third, higher-quality alkylates can be produced from 1-butene. Fourth, it is often feasible to use Cs olefins as feeds. 

The amount of catalyst relative to EB feed is an important parameter for optimum reactor performance. Too little catalyst will prevent a close approach to equilibrium. If EB conversion is low, then distillation costs associated with recovery and recycle of the unconverted EB can become significant. With too much catalyst, the EB conversion reaches equilibrium before the outlet of the catalyst bed, while the side reactions continue leading to loss of selectivity. 

In liquid phase reactions the choice of the type of solvent is often decided by the reaction mechanism. In the case of organic solvents one may have a choice between homologues. In many cases the solvent will be separated from the main product by distillation, or by extraction followed by distillation. A higher volatility of the solvent will generally reduce the distillation cost, but it will raise the reactor pressure (at a given temperature), which also implies expenses. A solvent with optimum volatility may be found for any given set of reaction conditions. 

Report Date Dote Received Date Distilled Cost Center ... 

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