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In this work a Sulzer structured packing, Mellapak 250Y, was studied for applications in the field of absorption. A new model was proposed which makes it possible to estimate the packing surface that actually takes part in the process. In the course of these studies, new experimental data were obtained relating to the absorption of 1,t, t -trichloroethane using Genosorb 300, a mixture of polyethylene glycol dimethyl ethers produced by Hoechst S.p.A., as absorption liquid. The results obtained with the proposed model are in agreement both with the experimental measurements made in the course of the work and with experimental absorption measurements reported by other authors on water systems.

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The effective mass-transfer efficiency in a column equipped with structured packings was investigated experimentally. The packings analyzed in the present work were Sulzer Mellapak 250Y, made of corrugated plastic or metal sheets, and Sulzer BX, made of plastic gauze. In the literature many works have been published on this topic, but they have mainly been oriented toward evaluating overall mass-transfer efficiency or the gas-side coefficient, leaving out closer examination of the liquid-side mass-transfer coefficient. The aim of the present work is to examine liquid film and to identify a relation that allows accurately evaluating the liquid film contribution to overall mass-transfer efficiency. Experimental results showed that column packing height affects the liquid-side mass-transfer coefficient at the usual industrial-scale liquid and gas flow rates. This result agrees with theoretical analysis on stable liquid rivulet flow. IntroductionStructured packings represent a very positive innovation compared with irregular packings. Columns working with this type of packings combine low-pressure drop with excellent mass-transfer efficiency, and thus their use allows reducing both operating costs and column dimensions (Brunazzi et al., 1996). Notwithstanding these positive characteristics, few models are available to design the equipment.The first problem to solve in designing the equipment is to evaluate the effective area available to the mass transfer. Some semiempirical models have been published for this purpose. Most of them agree in identifying the effective surface area of the structured packings as a fraction of the geometric surface (Brunazzi et al. (1995a);Nardini et al. (1996);Bravo et al. (1992); Billet and Shultes (1993)). On the contrary, Henriques de Brito et al. (1994) suggested that, depending on the liquid and gas flow rates, the effective mass-transfer area can be considerably larger than the geometric one. Brunazzi et al. (1995a) limited the number of empirical parameters used to evaluate the surface available to the mass transfer and showed that it can be theoretically evaluated if the liquid holdup of the column is known. Their model, developed on the Mellapak 250Y packing type, has also been tested on gauze packings (Nardini et al. (1996)) with good results. It has been shown that this model allows one to predict not only the masstransfer efficiency (Brunazzi et al. (1995a)) but also the pressure drop in gauze and sheet packings (Brunazzi and Paglianti (1997)). For this reason computation of the surface area taking part in the mass-transfer process is based on this model in the present work.Unlike for gas-phase mass-transfer coefficients, little data are available in the open literature for computing the liquid-side mass-transfer coefficient, probably, as suggested by Laso et al. (1995), because suppliers wish to preserve their proprietary know-how. To our knowledge, the little data published so far regard columns equipped with Mellapak (Laso et al., 1995) and Montz A2 (Weiland et al., 1993)...