Extraction of a dissolved organic contaminant from water into an aqueous surfactant solution across a microporous membrane

A novel extraction process, aqueous micellar solvent extraction (AMSE), was demonstrated. In ASME an solute is extracted from a wastewater across a microporous membrane into an aqueous surfactant solution containing micelles that solubilize the solute. The membrane retains the surfactant micelles in the aqueous micellar solvent. ASME was carried out in hollow fiber ultrafiltration modules with benzoic acid as the solute and a fatty amine ethoxylate surfactant. Flowing the micellar solvent through the fibers and the wastewater outside gave good extraction and low contamination of the treated water by surfactant. The major resistance to extraction of solute was diffusion across the wall of the hollow fiber.     

Burning-out of a carbonaceous residue from a porous body

A study of the burning-out of a carbonaceous residue from a porous cylindrical body is presented. The amount of residue in the pores is very small. Only one end surface of the body is in direct contact with the surrounding gas atmosphere during the burning-out process. Experiments are performed in a stream of air at 480, 510, 540 and 660°C. The course of the process is determined by analysing the off-gases from the reactor in which the body is placed.Two successive periods are defined in the process. The end of the first period is reached when the outside of the body which is in contact with the gas is just free of carbon. The second period is completed when all residue is burnt out. Equations based on some simplifying assumptions are derived for the length of the first period and of the total process. The experimental results are explained with the model proposed.     

Extraction from a solid with a bidisperse porous structure

A mathematical model is proposed for the process of extraction from a semi-infinite solid containing the pores of two types: large pores that extend to the surface and small pores that are connected to large pores. Effective transport coefficients in two types of pores are assumed to be different. The dependence of the flux of an extractant through the surface of the solid on time is found using the method of fractional differentiation. Theoretical results are compared with experimental data on the kinetics of the extraction of the target components from raw vegetable materials in apparatuses with an intensive hydrodynamic mode.     

Experimental study of a liquid film flowing over a perforation

Perforations are one of the recognized geometrical features that contribute to liquid redistribution in corrugated sheet packings. Our experimental study focuses on a simplified but relevant configuration: a thin liquid film flowing on either side of a vertical plate with a circular perforation. We focus on the curtain mode when the liquid fills the perforation. Confocal chromatic imaging reveals a capillary ridge upstream of the perforation, an inertial ridge downstream, and a varicose capillary wave standing on the liquid curtain. We show that the wavelength is selected such that the velocity of the wave both satisfies Taylor's dispersion relation and matches the curtain local speed. We examine the effect of perforation size, supply conditions, and liquid properties on the curtain transition. Lastly, we propose a simple model based on a momentum balance that describes the effect of these parameters on the Reynolds number at which curtain forms.     

Tailored surface roughnesses for enhanced deposition of fine liquid droplets from a flowing gas

Separating fine liquid droplets from a gas stream is an important operation in many industrial applications. In this paper, the effect of surface roughness on the deposition of droplets was investigated in a series of wind tunnel experiments. The roughness was modelled by 2-D rectangular ridges oriented at 45° to the flow direction. The rate of droplet deposition onto the surface was measured by a conductivity method. It was found that the deposition of droplets onto the roughened surface was enhanced by the roughness and the enhancement increased with ridge size-based Reynolds number. The maximum enhancement of droplet deposition on roughened surfaces over that of the smooth surfaces was observed to be around 150%. Data obtained for droplets with different sizes also indicated that the deposition rate of fine droplets was more dependent on the Reynolds than that of the large droplets. For relatively larger droplets, the enhancement of deposition is mainly caused by momentum-dominated impact. However, for fine droplets this is mainly due to the enhancement of local turbulence.     

Syngas production from liquid fuels in a non-catalytic porous burner

This paper investigates rich combustion of n-heptane, diesel oil, kerosene and rapeseed-oil methyl ester (RME) bio-diesel for the purpose of producing syngas ready for the clean-up stages for fuel-cell applications or for traditional combustor enrichment. Rich flames have been stabilised in a two-layer inert porous medium combustor and a range of equivalence ratios and porous materials have been examined. n-heptane was successfully reformed up to an equivalence ratio of 3, reaching a conversion efficiency (based on the lower heating value of H₂ and CO over the fuel input) up to 75% for a packed bed of alumina beads. Similarly, diesel, kerosene and bio-diesel were reformed to syngas in a Zirconia foam burner with conversion efficiency over 60%. A preliminary attempt to reduce the content of CO and hydrocarbons in the reformate has been also conducted using commercial steam reforming and water-gas shift reaction catalysts, obtaining encouraging results. Finally, soot emission has been assessed, demonstrating particle formation for diesel oil above φ = 2, whereas bio-diesel showed the lowest soot formation tendency among all the fuels tested.     

Electrolytic generation of hydrogen on Pt-loaded porous graphite electrodes from flowing alkaline solutions

The aim of this work was to test the feasibility of using porous graphite electrodes as cathodes for the electrolytic production of hydrogen fro_m flowing alkaline solutions. The platinum loading on the graphite substrate was found to decrease the potential required to sustain a certain rate of hydrogen production, and hence the energy consumed during electrolysis. The experimental i/E relations agreed with those theoretically predicted on the basis of a mathematical model up to a current density of about 200 mA cm^–2. The excessive polarization at higher current is attributed to trapping of hydrogen gas bubbles within the porous electrode.     

Extraction of a solid substance from linear capillaries during periodic boiling under vacuum

Extraction of a solid substance from linear capillaries is investigated during liquid boiling caused by periodic evacuation. It is shown that the turbulization of the diffusion boundary layer by vapor bubbles, which grow during boiling and collapse after termination of evacuation, leads to the fact that the extraction rate during unsteady-state boiling under vacuum is higher than that under external mechanical stirring and than that during steady-state liquid boiling under vacuum. The optimal process conditions providing the most rapid and complete extraction of the substance from a capillary are determined.     

Wetting of a vertical plate by a liquid flowing through a vertical nozzle

A model has been developed describing the wetting of a vertical plate by a liquid, starting from the exact hydrodynamic equations. By incorporating an approximately chosen wetting force term into the Navier-Stokes equations and using laminar boundary layer theory, the velocity field, the width and the actual contact angle characterizing the flow of the liquid were determined.The results predicted by the model were compared with those experimentally obtained for two limiting cases, and good agreement was demonstrated using the aqueous glycerol mixtures. The model was unsatisfactory for the water film since the boundary layer rapidly became turbulent and it was also observed that poor agreement was obtained with the mineral oil.     

Extraction from a porous solid particle with stagnant zones formed in cavities

A mathematical model describing the extraction from a semi-infinite capillary adjoining the stagnant zones formed in its side cavities over the whole capillary length is considered. Analytical formulas for calculating the time dependence of the yield of the component to be extracted are derived. It is shown that the extraction performance at large times resembles the performance of extraction from an isolated capillary but is characterized by the different value of the effective diffusion coefficient.     

Extraction of polyethylene from a porous composite by the capillary gel flow method

Extraction of low-density polyethylene from the porous base material of synthetic leather in the capillary gel flow mode is considered for the case that the material is subjected to uniaxial compression and is washed by the saturated vapor and the condensate of an extractant. Reported at the Conf. “Liquid-Phase Systems and Nonlinear Processes in Chemistry and Chemical Technology,” Ivanovo, 1999.     

Electroviscous effects in a Carreau liquid flowing through a cylindrical microfluidic contraction

Electroviscous effects in steady, pressure-driven flow of a Carreau shear-thinning liquid in a cylindrical microfluidic 4:1:4 contraction–expansion at low Reynolds number are investigated numerically by solving the equations governing the flow, the electric field, and ion transport, using a finite volume method. The channel wall is considered to have a uniform surface charge density and the liquid is assumed to be a symmetric 1:1 electrolyte solution. Predictions are presented for a range of values of the shear-thinning parameters in the Carreau model for various surface charge densities and Debye lengths. The apparent/physical viscosity ratio is shown to increase as the degree of shear-thinning increases. Thus the electroviscous effect is stronger in shear-thinning liquids than it is when the liquid is Newtonian, a result previously obtained for uniform pipe flow of power-law liquids. The trend holds true regardless of the choice of surface charge density or Debye length, although the magnitude of the trend decreases as the surface charge density and/or the Debye length is reduced. Comparison between uniform pipe flow of a Carreau liquid and the corresponding power-law liquid that approximates it at large shear rates shows that the apparent/physical viscosity ratios for the two models are almost identical. A previous prediction that a near-wall region of reduced velocity can occur for pipe flow of a shear-thinning power-law liquid when EDLs are overlapping and surface charge density is elevated is confirmed for a Carreau liquid.     

Snap‐off of a liquid drop immersed in another liquid flowing through a constricted capillary

Emulsions are encountered at different stages of oil production processes, often impacting many aspects of oilfield operations. Emulsions may form as oil and water come in contact inside the reservoir rock, valves, pumps, and other equipments. Snap‐off is a possible mechanism to explain emulsion formation in two‐phase flow in porous media. Quartz capillary tubes with a constriction (pore neck) served to analyze snap‐off of long (“infinite”) oil droplets as a function of capillary number and oil‐water viscosity ratio. The flow of large oil drops through the constriction and the drop break‐up process were visualized using an optical microscope. Snap‐off occurrence was mapped as a function of flow parameters. High oil viscosity suppresses the breakup process, whereas snap‐up was always observed at low dispersed‐phase viscosity. At moderate viscosity oil/water ratio, snap‐off was observed only at low capillary number. Mechanistic explanations based on competing forces in the liquid phases were proposed. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Gas absorption into a wavy film flowing over a spinning disc

We present results for gas absorption into a liquid film flowing over a spinning disc. The flow is accompanied by the formation of nonlinear waves which strongly influence the diffusion boundary-layer that develops beneath the surface of the film. We use recent advances in modelling of the hydrodynamics and solve a two-dimensional convective-diffusion equation for the solute concentration. Numerical solutions for the finite-amplitude wave regimes and associated integral absorption rates are obtained for flow conditions corresponding to real experiments. Our results show clearly the enhancement of absorption due to the waves.     

Action of a laser on a porous explosive substance,without initiation

We have studied the crater formation in specimens of porous explosive materials, the change in the light transmission of thin explosive layers, and the distortion in the shape of light pulses transmitted through such layers, at laser emission energy densities which do not produce initiation of the explosive. It has been demonstrated that these pehnomena are, a consequence of the optical breakdown of a dielectric (the explosive) and the process separating the ranges, in terms of radiant energy density, of linear and nonlinear light interaction with the explosive material.Chernogolovka. Translated from Fizika Goreniya i Vzryva, No. 2, pp. 97–101, March–April, 1991.     

多孔介质中流动泡沫的压力分布计算

将多孔介质简化为一簇变截面毛细管组成的毛细管束,根据多孔介质的颗粒直径、颗粒排列方式、孔喉尺度比以及束缚水饱和度,计算出变截面毛细管的喉道半径和孔隙半径。在考虑多孔介质喉道和孔隙中单个气泡的受力和变形基础上,利用质量守恒定理和动量守恒定理,推导出单个孔隙单元内液相的压力分布和孔隙单元两端的压力差计算公式,最终得到多孔介质的压力分布以及多孔介质中泡沫当量直径计算方法。利用长U型填砂管对多孔介质中稳定泡沫的流动特性进行了实验研究,并对实验结果和计算结果进行了对比。结果表明:稳定泡沫流动时多孔介质中的压力分布呈线性下降,孔喉结构和泡沫干度是影响泡沫封堵能力的主要因素;泡沫的封堵能力随泡沫干度的增加而先增加后降低,在泡沫干度为85%时达到最强封堵能力。     

Effective viscosity of mineralized water flowing in a porous medium: theory and experiment

A percolation model is suggested for the electrokinetic flow of a binary electrolyte solution in a porous medium. The effects of the ion concentration in the solution, the zeta potential of the surface of the pore space, and the shape of the porosimetric curve on the filtration flow velocity are analyzed. Experiments have been designed and carried out to verify the model. The results of theoretical calculations are compared with experimental data.     

Rate of the biochemical reaction in a biofilm in contact with a flowing liquid

The effect of the liquid flow around the biofilm on the rate of substrate delivery to the biofilm surface is analyzed. The nonmonotonic dependence of the rate of substrate conversion by the biofilm on the volumetric flow rate of the substrate solution is described. An approximate analytical expression is suggested for the substrate flux into the biofilm as a function of the volumetric flow rate of the substrate solution.