(85f) Design of Packed Column Direct Contact Condensers for Vapor and Vapor Mixtures

In numerous industrial processes direct contact condensers (DCC) are used to condense vapor or vapor mixtures. In many cases, packed columns are used for this purpose, where the condensable vapor gets in direct contact with the liquid phase, which serves as a condensing agent. In this work miscible vapor-liquid systems are investigated.

For the modeling of condensation processes in packed columns, which are characterized by simultaneous heat and mass transfer, mostly empirical correlations are used, e.g. [1]. For the condensation of pure water vapor or vapor mixtures without non-condensable components, only few correlations are present in literature, valid for classical random packing types like Raschig rings or Intalox saddles. In case of the direct condensation of vapor and especially of vapor mixtures with non condensable components no experimentally validated correlations can be found for modern random packing types. Experimental data from relevant process in industrial scale in scarce, although such data would be very useful for the validation of models, which have been developed for direct contact condensation processes, e.g. [2].

In the present work results from experimental investigation of vapor condensation in pilot scale packed columns with diameters of 0,15 and 0,32 m and a packed height of up to 1,3 m are presented. In a first step, the direct contact condensation of pure water vapor using water has been investigated. Therefore, several different packing types and sizes made of stainless steel, ceramics and plastic have been used. Beside the classical Pall ring (1” and 2”), high performance stainless steel random packings types of the latest generation type McPac (1” and 2”), the ceramic R-Pac and ENVIPAC and DTNPAC made from plastic have been tested. Based on the experimental results, a dimensionless empirical correlation considering the packing type has been developed for the heat transfer driven process. It has been shown, that the strong relation between fluid dynamics and mass transfer acc. to the extend channel model [3, 4]can be extended to heat transfer processes as well.

In a second step, condensation of vapor out of saturated air and from vapor mixtures containing noncondensable carbon dioxide (CO2) and ammonia (NH3) has been studied. Due to the additional mass transfer resistance in vapor mixtures with non condensable components, the condensation rate decreases compared to the condensation of pure vapor. The aim of this experimental study was the generation of relevant data for the validation of a rate-based model for the condensation of multicomponent vapor mixtures in packed columns [2].

A comparison of experimental and calculated data shows good agreement for this complex heat and mass transfer process.

[1] BILLET, R., Verdampfung und ihre technischen Anwendungen, Verlag Chemie, Weinheim, 1981.

[2] MAÆKOWIAK, J.F., GÓRAK, A., KENIG, E.Y., Modelling of combined direct contact condensation and reactive absorption in packed columns, Chem. Eng. J. 2009, 149, 362-369.

[3] MAÆKOWIAK, J., Extended channel model for prediction of the pressure drop in single-phase flow in packed columns, Chem. Eng. Res. Des. 2008, 87, 123-134.

[4] MAÆKOWIAK, J., Model for the prediction of liquid phase mass transfer of random packed columns for gas–liquid systems, Chem. Eng. Res. Des. 2011, 89, 1308–1320.