Packed columns, simulation

One feature which must be retained is the same mode of operation (i.e. countercurrent in our case) thus for packed column simulation one has to think in terms of the liquid running down over some kind of surface, and gas flowing upwards. If the model has also the same flow patterns, that is plug flow of both phases it is easy to show that (69) ... 

The status of packed column simulation is similar to that of tray column. 

A study of industrial apphcatious by Taylor, Kooijmau, and Woodman [IChemE. Symp. Ser. Distillation and Absorption 1992, A415-A427 (1992)] concluded that rate-based models are particularly desirable when simulating or designing (1) packed columns, (2) systems with strongly uonide liquid solutions, (3) systems with trace compo-... 

The design of simulated moving bed chromatography and its application to the separation of cycloheptanone and cyclopentanone as test substances to validate the system for subsequent chiral chromatography has been described.27 Briefly, eight silica-packed columns were hooked up in series to form a cyclic flow path. On the first pair, preliminary separation of the components was performed, with the less-retained raffinate being directed to waste. Following the second pair of columns, eluent was added. After the... 

The cell contains a relatively large volume of liquid so that, when operated as a stirred tank reactor with steady inflow and outflow of the liquid reagent, the composition of the liquid phase can be held constant. In fact, one of the original aims in developing this reactor was to simulate and maintain conditions steady at any particular point in a packed column 3 . The stirrer in the gas phase serves to keep the gas composition uniform and, in many cases, to eliminate any gas-phase mass transfer resistance. 

For all of the above configurations and situations, we have presented both the simulation problem, where the number of trays is given in the multitray case, or the height is given for the packed column, and the design problem, where the number of trays in the multitray case is not known, or the height is unknown for the packed column. 

F. Yin, A. Afacan, K. Nandakumar, K.T. Chuang, Liquid holdup distribution in packed columns gamma ray tomography and CFD simulation, Chem. Eng. Process. 41 (5) (2002) 473-483. 

As an application example, the dynamic model was used for the simulation of the steady-state and semibatch production of methyl acetate, performed in a packed column with a catalytic packing. For the model validation, several experiments were carried out in a pilot-plant column. For the investigated operation range, the simulation results are in good agreement with the experimental data. 

Suchak NJ, Jethani KR, Joshi JB. Modeling and simulation of NOx absorption in pilot-scale packed columns. AIChE J 1991 37 323-339. 

Two resins were tested for the removal of succinic acid from simulated medium on a packed column of sorbent to simulate an actual process on a small scale. It is important to test the sorption with medium, because salts and other nutrients can interfere with the sorption. Table 4 presents the results for XUS 40285 MWA-1 was comparable. This indicates that either sorbent can remove succinic acid efficiently from the fermentation broth without direct loss of product. Both columns were then stripped or regenerated with hot water. Stripping with hot water recovered 70-80% of the succinic acid from the XUS 40285 resin whereas less (50-60%) was recovered from the MWA-1. The XUS 40285 column was stripped with 2 column volumes of hot water with eluent concentrations up to 49 g / L. Succinic acid was concentrated on average to 40 g/L in the XUS resin by this operation and to 30 g/L by the MWA-1. The 10-fold concentration factor bodes well for the use of sorbents to purify the fermentation broth. 

Fig. 1. (A) Loading and breakthrough profile for packed column of sorbent (XUS 40285) exposed to 10 g/L of succinic acid and 10 g/L of acetic acid in simulated media. The column volume was 75 mL and the pH of the feed was 6.0. The pH fell to 5.2 during the breakthrough and slowly rose as the bed loaded. (B) Elution profile of same column with water at 90°C.

Succinic acid was removed from medium on a packed column of sorbent. The resin XUS 40285 was tested in a packed column with simulated medium containing salts, succinic acid, acetic acid, and sugar. The packed column completely separated the fermentationbyproduct, acetate, from succinate. A simple hot water regeneration successfully concentrated succinate from 10 g/L (inlet) to 40-110 g/L in the effluent with a pH of about 5.0. The end pH indicates that succinate salt was sorbed from the "medium" and released in a partially acidic form by the hot water regeneration. If successful, this would lower separation costs by reducing the need for chemicals for the initial purification step. 

Schultes presented an absorption model for packed columns including simulations [81], while Eden [18] developed a non-equilibrium stage model describing the absorption of electrolytes in co-current and countercurrent scrubbers. The simultaneous view of phase and reaction equilibrium and the existence of solids in the liquid phase were emphasized in these reports. 

Mori H., Oda A., Kunimoto Y., Aragaki T. Packed Column Distillation Simulation with a Rate-Based Method. J. Chem. Eng. Japan, Vol. 29, 307-314, 1996. 

However, by examining the adsorption behavior of polypeptides and proteins with comparable porous and nonporous particles in finite baths, packed columns and expanded or fluidized beds, an iterative simulation approach based on the heuristic principles described earlier and along the lines of the flow diagram shown in Fig. 32 can be developed, leading ultimately to the implementation of useful scale-up criteria. Along the way, computer simulations, generated from the analysis of the concentration-time... 

C. Example Stirred Cell Simulating a Packed Column. 119... 

Several laboratory models for simulating large-scale absorbers are shown in Fig. 8. The ranges of contact time for different industrial and laboratory absorbers are given in Table XXV. This table should aid in the selection of laboratory equipment to give a contact time (orfei,) that simulates the industrial absorber. For instance, a wetted wall or stirred vessel can simulate a packed column. 

The use of a stirred cell to simulate a packed column is widespread (D5, K7, D7, Cl 1, L5). Let us consider its use in predicting absorption rates at different levels of a column, when absorption occurs with a fast second-order irreversible chemical reaction and with mass-transfer resistance in both phases. 

Similarly, when values of a, kija, and k(/i are known for the packed column, the variations in and k can be determined as functions of the respective flow rates and Mg, as discussed in Section IV,A. Various stirring speeds for each phase in the laboratory model can then be related to the phase flow rates (in the packed column) which have, respectively, identical ki and kc, as outlined in Fig. 34. Thus pairs of values ofi/ and Uq are simulated by each couple Nl and Nq. 

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