A.B. de Haan

Optimization of commercial net spacers in spiral wound membrane modules

CFD simulations have been used to determine mass transfer coefficients and power consumption of commercial net spacers. The simulations show transversal and longitudinal vortices, vortex shedding and instationary flow behavior leading to the enhanced mass transfer in spacer filled-channels compared to empty channels. The results of the simulations were validated with experiments and compared with data reported in literature, showing satisfactory agreement. Furthermore, CFD simulations were used to optimize the geometry of commercial net spacers in terms of mass transfer and power consumption. The performance of these optimized spacer geometries will be used as reference for future work on the development of new high-performance spacer shapes.

Extraction of metal ions from waste water. Modelling of the mass transfer in a supportedliquid-membrane process

Abstract The use of liquid ion exchangers in a supported liquid membrane process with two capillary membrane modules seems an attractive technique for the extraction of metal ions from waste water. This paper presents a mass transfer model for the extraction of copper ions with LIX 84 that may easily be extended to describe the extraction of other metal ions. The effect of the hydrogen and copper ion concentrations on the copper flux through the membrane was measured for the diffusion and for a reaction-limited case to determine the rate parameters in the mass transfer model. The regeneration of the liquid ion exchanger (carrier) was found to be slow compared with the formation of the chelate complex. It is shown that the extraction experiments can be simulated by using the proposed mass transfer model.

Water extraction of pyrolysis oil: The first step for the recovery of renewable chemicals

The interest in biomass as a source of renewable energy and chemicals has been increasing in keeping up with the transition to a sustainable bio-based economy. An important initial step of chemicals recovery from biomass-derived pyrolysis oil is water extraction where most of polar compounds are isolated in the aqueous phase. This study was done to investigate the effects of stirring rate and water-to-oil ratio on the extraction capability (distribution coefficient and yield), water content, and atomic composition of both aqueous and organic phases. The results show that the stirring rate above 300 rpm has no influence on the equilibrium. Increasing the water-to-oil ratio dilutes the aqueous phase without changing the atomic distribution. Forest residue-derived pyrolysis oil should be extracted at a water-to-oil ratio of 0.65-0.7, whereas pine-derived pyrolysis oil is preferably extracted at the lowest feasible water-to-oil ratio where complete phase separation occurs, which is 0.5 in this study.

Optimization of non-woven spacers by CFD and validation by experiments

CFD simulations were used to determine mass transfer coefficients and power consumptions in channels filled with non-woven net spacers. The geometric parameters of a non-woven spacer were found to have a great influence on the performance of a spacer in terms of mass transfer enhancement and power consumption. The results from CFD simulations indicate that an optimal spacer geometry exists. Mass transfer coefficients and power consumptions were determined experimentally by the limiting current method and pressure drop measurements. Close agreement between experiments and simulations was observed.

Economical feasibility of zeolite membranes for industrial scale separations of aromatic hydrocarbons

Naphtha cracker feedstocks contain 10–25 wt% aromatic hydrocarbons, which are not converted into the desired products ethylene and propylene. The conventional processes for the separation of aromatic and aliphatic hydrocarbons are extraction, extractive distillation and azeotropic distillation. These processes are highly complex and demand a high energy consumption. Therefore, alternative separation processes are of interest, such as pervaporation (PV) and vapour permeation (VP) with zeolite membranes. For a feasible process, the purity of both the aromatic and aliphatic products must be 98 wt%. In order to obtain these purities with PV or VP, using a reasonably sized membrane area, the selectivity must be high, at least 40, and preferably above 80, and the flux rate (100 wt% benzene) has to be in the order of 8 kg/m2.h (presently around 0.3 kg/m2.h). For a feed stream of 300 t/h, containing 10 wt% aromatics, a membrane area of more than 60,000 m2 is required with these selectivities and flux rates. The conclusion is that with the current high price level of zeolite membrane modules, around unkeyable??? 2,000/m2, the investments become uneconomical. Therefore, the membrane costs must be reduced, to about unkeyable??? 200/m2.

Extraction of flavors from milk fat with supercritical carbon dioxide

Abstract Next to triglycerides, milk fat contains a large number of components (lactones, ketones, aldehydes) that provide milk fat with its characteristic flavor. In this study, supercritical carbon dioxide has been found to be a good solvent for the extraction of these flavor components from milk fat. Concentration factors varying from 20 to 50 have been measured at carbon dioxide densities of 600 to 700 kg/m3 and extraction temperatures between 40 to 50 °C. It has been observed that, if the the flavor extract is produced in two steps, these flavor components could be concentrated 500 to possibly 1000 times. The height equivalent to a theoretical equilibrium stage in the extraction column used, filled with 5-mm steel raschig rings, appeared to be approximately 20 cm.

Method for experimental determination of the gas transport properties of highly porous fibre membranes: a first step before predictive modelling of a membrane distillation process

For the predictive modelling of a membrane distillation process, the gas transport properties, defined by the dusty-gas model, of three highly permeable polyethylene and polypropylene fibre membranes have been determined. Single gas permeation experiments were carried out to determine the Knudsen diffusion and viscous flow membrane characteristics (K0 and B0, respectively). Binary gas diffusion experiments were carried out to determine the molecular diffusion membrane characteristic (K1). Because of the high permeability of the fibre membranes, new methods were developed to deal with effects such as pressure drop in the single gas permeation experiments and boundary layer resistance in the binary gas diffusion experiments. The K1 values of the fibre membranes were determined with an inaccuracy of 4–8%. It turned out that calculations of K1 with the values of K0 and B0 assuming cylindrical pores are, for the membranes studied, inaccurate by a factor of two.

Extraction of Caprolactam with Toluene in a Pulsed Disc and Doughnut Column—Part I: Recommendation of a Model for Hydraulic Characteristics

Abstract Caprolactam, the monomer for Nylon‐6, is industrially recovered from an aqueous feed containing ammonium sulphate by extraction with organic solvents like benzene, toluene, or chlorinated hydrocarbons followed by back‐extraction with water. Extraction columns like the Rotating Disk Contactor and Pulsed Packed Column are industrially applied. In this paper a model is recommended for the description of the hydraulic characteristics of a pulsed disc and doughnut column for caprolactam extraction with toluene. In Part II and III the hydraulic and mass transfer characteristics, respectively, are determined and described with the developed models. The hydraulic characteristics are correlated as a function of the operating conditions for the experimental conditions covering the industrial operating range. The model is derived for equilibrium conditions in order to avoid the influence of mass transfer. The final model describes the operational window via equations describing flooding due to insufficient pulsation, and flooding due to a too small relative velocity between both phases and phase inversion. In the operational window several operational regimes can be distinguished, being mixer‐settler, dispersion, and emulsion type operation. Finally, two equations are presented for the description of the Sauter drop diameter and hold‐up at each operational point. The hydraulic characteristics are correlated using physical properties, operational parameters, and geometrical characteristics of the column.

Selector screening for enantioseparation of DL-α-methyl phenylglycine amide by liquid-liquid extraction.

Enantioseparation through liquid extraction technology is an emerging field, e.g.,u2009enantioseparations of amino acids (and derivatives thereof), amino alcohols, amines, and carboxylic acids have been reported. Often, when a new selector is developed, the versatility of substrate scope is investigated. From an industrial point of view, the problem is typically approached the other way around, and for a target racemate, a selector needs to be found in order to accomplish the desired enantioseparation. This study presents such a screening approach for the separation of the enantiomers of DL-α-methyl phenylglycine amide (DL-α-MPGA), a model amide racemate with high industrial relevance. Chiral selectors that were reported for other classes of racemates were investigated, i.e.,u2009several macrocyclic selectors and Pd-BINAP complexes. It appeared very challenging to obtain both high extraction yields and good enantioselectivity for most selectors, but Pd-BINAP-based selectors performed well, with enantioselectivities up to 7.4 with an extraction yield of the desired enantiomer of 95.8%. These high enantioselectivities were obtained using dichloromethane as solvent. Using less volatile chlorobenzene or 1-chloropentane, reasonable selectivities of up to 1.7 were measured, making these the best alternative solvents for dichloromethane.

Extraction of Caprolactam with an Alternative Benign Solvent in a Pulsed Disc and Doughnut Column

Abstract Caprolactam is obtained by extraction using organic solvents like benzene, toluene, or chlorinated hydrocarbons. As an alternative solvent, the mixed solvent heptane‐heptanol (40 mass %) was selected in previous studies based on a relatively high distribution ratio of caprolactam, a low mutual solvent solubility, beneficial physical properties, and a low distribution ratio of impurities. Now, the hydraulic and mass transfer characteristics of the extraction of caprolactam in a pulsed disc and doughnut column (PDDC) were investigated using the benign solvent. The results were compared to those for toluene. The PDDC showed qualitatively comparable operational characteristics for both solvents. In the hydraulic experiments the mixed solvent showed smaller drop diameters and hold‐ups, required lower pulsation intensities for regime transitions, but the operational windows are slightly smaller. For both solvents, mass transfer resulted in increasing drop diameters and pulsation intensities required for regime transition. In the forward extraction the mixed solvent was superior, where HETS/m=0.26 to 0.37, compared to 0.42 to 0.67 for toluene, while less theoretical stages are required as well. For the back‐extraction HETS/m=0.33 to 0.40 for the mixed solvent compared to 0.30 to 0.37, but toluene requires the lower amount of theoretical stages. The hydraulic characteristics at equilibrium and concentration profiles in both the forward and back‐extraction were described accurately using the developed models.