HETP evaluation of structured packing distillation column

Abstract

-Several tests with a hydrocarbon mixture of known composition (C 8 -C 14 ), obtained from DETEN Chemistry S.A., have been performed in a laboratory distillation column, having 40mm of nominal diameter and 2.2m high, with internals of Sulzer DX gauze stainless steel structured packing. The main purpose of this work was to evaluate HETP of a structured packing laboratory scale distillation column, operating continuously. Six HETP correlations available in the literature were compared in order to find out which is the most appropriate for structured packing columns working with medium distillates. Prior to the experimental tests, simulation studies using commercial software PRO/II ® were performed in order to establish the optimum operational conditions for the distillation, especially concerning operating pressure, top and bottom temperatures, feed location and reflux ratio. The results of PRO/II ® were very similar to the analysis of the products obtained during continuous operation, therefore permitting the use of the properties calculated by that software on the theoretical models investigated. The theoretical models chosen for HETP evaluation were: Bravo, Rocha and Fair (1985); Fair (1993, 1996); Brunazzi and Pagliant (1997); Carlo, Olujić and Pagliant (2006); Olujić et al., (2004). Modifications concerning calculation of specific areas were performed on the correlations in order to fit them for gauze packing HETP evaluation. As the laboratory distillation column was operated continuously, different HETP values were found by the models investigated for each section of the column. The low liquid flow rates in the top section of the column are a source of error for HETP evaluation by the models; therefore, more reliable HETP values were found in the bottom section, in which liquid flow rates were much greater. Among the theoretical models, Olujić et al. (2004) has shown good results relative to the experimental tests. In addition, the former model by Bravo, Rocha and Fair (1985) underestimates HETP values; however, with the modifications proposed in this work, it has achieved more realistic performance prediction, remaining a good choice for gauze packing HETP evaluation. Having the advantage of avoiding the calculation of effective area and mass transfer coefficients, an empirical model proposed by Carrillo and coworkers (2000) was also investigated, showing low deviations compared to the theoretical models tested.

Determination of heat-mass transfer coefficients within the apparatuses with jet-film contact devices

“…approximation accuracy coefficient of which was 0.9989 in the range of Reynolds numbers from 6.6·10 3 up to 6.0·10 5 (Fig. 3a).…”

“…The device consisted of 3 contact stages and in course of studies, geometrical dimensions of device were changed in the scale, proportional to its characteristic dimensions, namely to the width of the drain cup, taken equal to 100 mm and height of the wall equal to 10 mm. Moreover, actual gas rate was changed from 1 up to 20 m/s, which corresponded to the values of Reynolds number from 6.6·10 3 up to 6.0·10 5 . The liquid level in the drain cup was taken as maximum.…”

“…Efficiency of these processes is mainly determined by improvement of the used contact devices. Moreover, material and energy costs significantly depend upon the design of contact device [4][5][6].…”

Dissolved gas separation for engineered anaerobic wastewater systems

“…For low loading rates, drip plates can be used to distribute water at low hydraulic loading rates whereas for high load rates, spray nozzles are preferred to promote uniform distribution onto the packing media at the top of the column (Vinci et al, 2006). Packing typically comprises of structured media that promotes high specific surface areas of around 250-300 m 2 m -3 (Orlando et al, 2009). The random packing media allows development of a thin water film, with substantial specific interfacial surface area and also provides some interstitial mixing which augments gas-liquid contact (Figure 4c).…”

Dynamic Simulation and Start-up Scenario a Pilot Distillation Column for Separating C6-C8 Hydrocarbons

“…Wesselingh proposed non-equilibrium models for a distillation column [1]. A recent study on the separation of C8-C14 hydrocarbons in a laboratory packing distillation column focused on the development of steady-state models for achieving packing efficiency of a pilot distillation column [2]. Another study proposed the concept of high separation efficiency and column capacity obtained in olefin paraffin distillation using hollow fiber structured packings (HFSPs) [3].…”