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Many different types of coalescers are used for separation of oil-in-water dispersion. The investigated results of a newly developed two stage coalescer are given in this work. The proposed designofthis coalescer includes two independent stages which are set in the same coalescer body. Expanded polystyrene granules are being used in the first stage. By using this coalescent material, gravity separation and the large oil droplets, coalescence processes are at the same time being insured. The second stage of this new type of coalescer uses polyurethane foam. The surface of this layer has been previously oiled. the proposed two stage coalescer has been tested for different type of oily wastewaters. A high loaded oilywastewater has been treatedby the new coalescer separator in the field In a one year working period, a mean oil separation efficiency has been higher than 98 %. The proposed coalescer can be use for suspended solids separation at the same time. Mean separation efficiency has been 85% duringthe field test.

Article Highlights • Separation of mineral oil droplets with stainless steel fibers bed different geometry was investigated • The separation efficiency for all operating conditions were higher than 90% • Low bed permeability is most favourable for the separation of mineral oil droplet from water • Separation of oil using stainless steel fibers is extremely sensitive to changes in oil properties Abstract 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 0.7×10-9 to 5.389×10-9 m 2 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.

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

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