Dispersions in porous beds

Dispersions and porous media exist either in nature or in industrial applications. They have been the subject of investigations for a long time, but the complexity of the phenomenon is the major obstacle to its better understanding. Many factors influence the interface interactions, transport, accumulation and detachment of particles in a porous matrix limiting new applications. The current state of investigations which include dispersions in the liquid continuous phase, especially emulsions, liquid/solid interface interactions in porous media and some new mathematical functions were reviewed in this paper

Rheology of unstable mineral emulsions

In this paper, the rheology of mineral oils and their unstable water emulsion were investigated. The oil samples were domestic crude oil UA, its fractions UA1, UA4 and blend semi-product UP1, while the concentration of oil in water emulsions was in the range from 1 up to 30%. The results were analyzed based on shear stress. The oil samples UA, UA1 and UP1 are Newtonian fluids, while UA4 is pseudoplastic fluid. The samples UA and UA4 show higher value of shear stress (83.75 Pa, 297 Pa), then other two samples UA1 and UP1 (18.41 Pa, 17.52 Pa). Rheology of investigated oils due to its complex chemical composition should be analyzed as a simultaneous effect of all their components. Therefore, structural composition of the oils was determined, namely content of paraffins, naphthenes, aromatics and asphaltenes. All samples contain paraffins, naphthenes and aromatics but only oils UA and UA4 contain asphaltenes as well. All investigated emulsions except 30% EUA4 are Newtonian fluids. The EUA4 30% emulsion shows pseudoplastic behaviour, and it is the only 30% emulsion among investigated ones that achieves lower shear stress then its oil. The characteristics of oil samples that could have an influence on their properties and their emulsion rheology, were determined. These characteristics are: neutralization number, interfacial tension, dielectric constant, and emulsivity. Oil samples UA and UA4 have significantly higher values of neutralization number, dielectric constants, and emulsivity. The sample UA has the lowest value of interface tension and the greatest emulsivity, indicating that this oil, among all investigated, has the highest preference for building emulsion. This could be the reason why 20% and 30% emulsions of the oil UA achieve the highest shear stress among all investigated emulsions

Influence of fluid properties and solid surface energy on efficiency of bed coalescence

Emulsion separation is important in industry due to economic, safety, and ecological reasons. It can be applied in liquid-liquid extraction, effluent treatment, heat exchange, and fuel and chemical purification. In case of both oil-in-water and water-in-oil emulsions, regardless of their quantity and phase concentration, bed coalescence is a good and economical solution for separation. Due to the complexity of the bed coalescence phenomenon, the coalescer design relies on the base of the experimental test. The design strategy of a coalescer to separate oils of different quality in time is additionally complicated. This paper presents a literature review on the current understanding of the influence of properties of both liquids and surface phenomena of filter media on emulsion separation efficiency using steady-state bed coalescence. The influence of oil viscosity, interfacial tension, density, molecular weight, emulsivity and dielectric constant of mineral oil is presented. The effect of solid surface roughness and wettability on separation efficiency is also elaborated. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172022

The influence of fibrous bed bulk density on the bed properties

The mean properties of seven different fibrous materials and the properties of their different bed bulk densities were investigated. The morphology of the surface, size and geometry were measured by optical microscopy. The bed porosity was measured by the weighing method. The experimental bed permeability, in a high range of bulk density, was calculated from the values of the sanitary water pressure drop at a constant temperature of 15°C, since the data followed Darcy's law. The Reynolds number for a fibrous bed was calculated using a relation from the literature. The Reynolds number was less than 1 for all ranges of fluid velocity. Three empirical relations for fibrous bed permeability were used and compared with the experimental data. It was determined that the empirical data depended on the fiber diameter and fraction of solid in the bed. The relative error linearly increased with increasing fiber diameter

Liquid-liquid separation using steady-state bed coalescer

This paper presents a literature review on the current understanding of liquid-liquid separation that is immensely widespread in practice, highlighting the steady-state bed coalescer being a good solution in various engineering application. Generally, the fibre bed coalescence has proven to be very effective separation method in the industry. Due to the complexity of bed coalescence phenomenon coalescer design and sizing procedure relies on experimental test. This review provides a research overview of the key phenomena essential for the efficient bed coalescence, such as mechanisms of droplet coalescence and emulsion flow through the fibre bed. In addition to this provides an overview of the current knowledge about coalescer´s design properties and variables such as: fluid velocity, fluid flow orientation/flow mode, fibre bed geometry, and bed length. [[Projekat Ministarstva nauke Republike Srbije, br. 172022

Separation of oil drops from water using stainless steel fiber bed

This study is focused on the separation of oil droplets from water by applying a stainless steel fiber bed. The separation efficiency was followed by monitoring the oil concentration of three mineral oils that have a wide range of viscosity from 10 to 170 mP s, as well as neutralization number from 0.10 to 1.70 mg KOH/l. The bed properties were varied by altering the bulk density of the filter material, which resulted in a change of bed permeability from 0.7Ч10-9 to 5.389Ч10-9 m2 and bed porosity from 91 to 98%. All experiments were conducted in a wide range of superficial velocity from 10 to 50 m/h. It can be concluded that high separation efficiency was achieved using stainless steel fibers, reaching values over 90%. Low bed permeability is most favorable for work at the selected conditions for the separation. The operation of stainless steel fiber bed is very sensitive to changes in the properties of oils. For lower viscosity of oily contaminants, the required efficiency of separation is achieved at lower superficial velocity through the fibrous bed. This phenomenon can be considered as a serious drawback since the bed coalescers often have to separate oils of different quality over time. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172022

Effect of ventilation in enclosure machine system on MWF aerosol properties

In this paper the influence of ventilation air velocity on properties of metal working fluids (MWF) aerosol/mist is presented. Aerosol characteristics were monitored in the chamber as well as at the entrance of ventilation pipe by optical particle size analyzer. Aerosol was generated from 6% water emulsion of three commercial MWF. Four different velocities, less than the velocity of secondary atomization, were examined (1, 3, 6, 8 m/s). Droplets size distribution, mass concentration (mg/m3), as well as number concentration (P/cm3) were measured and analyzed. From the results obtained it may be seen that coalescence is more pronounced as the velocity increases, although the number concentration decreases, due to higher air dilution. Therefore, more droplets are in a whirling motion at higher air velocities, hence more random collisions are possible. Further analysis shows that there is one value of air velocity under which the maximum difference between the aerosol in chamber and the aerosol at the entrance of the pipe can be observed. This velocity could be named specific velocity and depends on the given aerosol properties. It could be assumed that specific velocity is conditioned by the properties of oil from which emulsion is prepared. Oil viscosity and molar mass have greatest influence on the specific velocity