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Optimization
Published in Yeong Koo Yeo, Chemical Engineering Computation with MATLAB®, 2020
We consider determination of the optimal reflux ratio (L/D) for the operation of a binary distillation column. The rule of thumb about the minimum reflux ratio is to operate 1.2 times the minimum value given by Fenske equation. The minimum reflux ratio (L/D)min by the Fenske equation is as follows: (LD)min=1α−1{xDxF−α(1−xD1−xF)}
Synthesis of Downstream Processes
Published in Juan A. Asenjo, Separation Processes in Biotechnology, 2020
George J. Prokopakis, Juan A. Asenjo
The discussion above establishes a framework for the solution of generalized separation problems. It assumes that reliable models for the separations are available that relate the cost to the operational parameters. In the case of distillation, which due to its industrial significance is the unit operation most thoroughly studied and understood, there are both detailed models and shortcut methods that correlate the operational parameters and the cost of separation. For example, in a typical shortcut procedure (King, 1980), the Geddes equation is used to determine the distribution of the components in the product streams, the Fenske equation to determine the minimum number of trays, the Underwood equations to determine the minimum reflux, Gilliland correlations to determine the number of theoretical trays, and the Fair correlation to determine the tray spacing. After sizing the column, the Guthrie procedure is used to determine the capital costs, and the energy requirements directly provide the operational costs.
MATLAB® for Chemical Engineering
Published in Mariano Martín Martín, Introduction to Software for Chemical Engineers, 2019
Mariano Martín, Luis Martín de Juan
Extending this example to a distillation column, the rules of thumb about the minimum reflux ratio is to operate with 1.2 times the minimum given by Fenske [17]. We formulate a problem to optimize the L/D ratio for the operation of a binary distillation column. The objective function consists of the operating cost of the column involving the annualized vessel cost and the energy in the boiler. We would like to prove that the rule of thumb is also the result of an optimization problem. Fenske equation for comparison purposes is given by eq. (4.132): LD|min=1α−1[xdxf−α(1−xd)(1−xf)]
Conceptual design of distillation columns sequence for separation of pentane and hexane from C5+ stream of LPG unit
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Mahmoud Reza Hojjati, Habibollah Namdari Ghareghani
The calculated temperature should be lower than the critical temperature of the bottoms (Holland 1981). In this research based on heuristic rules, we assume that for all distillation column, the inlet feed is in saturated liquid condition and its pressure is equal to the sum of the column top pressure, the condenser drop pressure and the half of the column pressure drop, its temperature can be computed. In this algorithm, the minimum number of trays was calculated using the Fenske equation in which the light and heavy key components compositions of distillate and bottom products are required.