Countercurrent exchange

About: Countercurrent exchange is a research topic. Over the lifetime, 2255 publications have been published within this topic receiving 28687 citations. The topic is also known as: Countercurrent exchange.

Hydrodynamics of PEG-phosphate aqueous two-phase systems in a J-type multilayer countercurrent chromatograph

Abstract: Recently, we have shown that countercurrent chromatography (CCC) is an effective method for the purification of plasmid DNA vaccines and gene therapy vectors.1 As a basis for further work, this paper studies the hydrodynamics of various PEG‐Salt aqueous‐aqueous two‐phase systems in a Brunel J‐type countercurrent chromatograph. The degree of stationary phase retention, S f , once a hydrodynamic equilibrium is achieved has been studied as a function of mobile phase flow rate (0.5–2.0 mL·min−1), coil rotational speed (500–850 rpm), column volume (92.3 and 167.3 mL), choice of mobile phase (PEG or phosphate), and mobile phase pumping direction (Head→Tail or Tail→Head). Three different aqueous two‐phase systems (ATPS) were studied, which consisted of PEG 300‐K2HPO4, PEG 600‐ K2HPO4, and PEG 1000‐K2HPO4, having density and viscosity ratios between 1.15–1.13 and 0.27–0.12, respectively. High S f values in comparison to previous aqueous‐aqueous studies with CCC were obtained of up to 73.7%. These high S ...

Effect of fluid dynamic conditions on the recovery of ABE fermentation products by membrane-based dense gas extraction

Abstract: This work is focused on the application of membrane-based supercritical fluid extraction for the removal of fermentation products from an ABE (acetone/butanol/ethanol) mixture. The extraction process was implemented in a hollow fiber contactor where the liquid fed was circulated in the lumenside. Meanwhile, the extraction phase was dense carbon dioxide, circulated through the shell. A model solution, containing the three representative products of ABE fermentation broths was fed to the single PTFE fiber contactor with flow rates varying from 0.1 to 1.5 mL min −1 . Dense CO 2 with pressures between 7.0 and 9.0 MPa at 40 °C was circulated in countercurrent configuration. Experimental extraction percentages reached 70%, 50% and 27% for acetone, butanol and ethanol, respectively, in a single extraction step. When pressure was 9.0 MPa and liquid feed flow rate was higher than 0.5 mL min −1 , the extraction percentage of solutes and its transmembrane fluxes showed an unexpected decreasing, which was described by means of a phenomenological transfer model with variable membrane wettability. Thus, it has been demonstrated that the higher flow rates and pressure values can involve instability of the interface formed at the pore entrance and the liquid feed solution can penetrates into the membrane pores.

Detailed Investigations of the Countercurrent Multiphase (Gas–Liquid and Gas–Liquid–Liquid) Flow Behavior by Three-Dimensional Computational Fluid Dynamics Simulations

Abstract: This paper focuses on the detailed investigations of the (multi-) liquid flow behaviors on an inclined stainless steel plate in simulations and experiments. Simulations are carried out with FLUENT 6.3; a three-dimensional computational fluid dynamics model considering the gravity, surface tension, and local drag force is developed and presented. Experimental data is obtained with optical methods. One main aspect of the paper’s presentation is the validation of the developed model for the case of one-liquid phase with a countercurrent gas phase, where the parameters (e.g., the thickness and the velocity profile of the liquid phase) are compared with the simulation results and the experimental data. The other key part of the presentation is the numerical investigations with the developed model for the case of two immiscible liquid phases with a countercurrent gas phase. Results show that with the current gas flow rate, the complex flow behavior strongly depends on the (multi-) liquid flow rates and the feed...

Hot air heating system

Abstract: A hot air heating system utilizing the otherwise wasted heat and water vapor in the gases of combustion to pre-heat air supplied to the combustion unit. The hot combustion gases discharged from the combustion unit are mechanically induced by a blower to pass through an auxiliary heat exchanger in countercurrent flow to the air being supplied to the combustion unit, thereby preheating the return air and cooling the combustion gases. The products of combustion include a considerable quantity of water vapor. Cooling the combustion gases results in condensation of the water vapor, which is then collected and can be utilized to humidify the room air. Condensation of the vapors releases their latent heat of vaporization adding considerably to the heat recovery of the system.