Experts in filtration and separation

We advance and disseminate knowledge in the design and use of filtration and separation techniques in industry, commerce and other walks of life.

Volume 12, Issue 2 Abstracts from the FILTRATION journal

Annemarieke Maltha, Edgar Berkhout, Pieter Zuuring and Martin Koerntjes (pages 95-98)

This paper presents how a specially designed bicomponent spunbond nonwoven contributes to an improvement in filter design and filter medium efficiency. The spunbond nonwoven is used as a support layer or prefilter for filter media. Its unique properties result in filter media with low pressure drop, high mass evenness, and a high stiffness. Application of this spunbond as a support layer in pleated filter media for cabin air filters, leads to stiffer and sharper (smaller radius of curvature) pleats, without a degradation in overall mechanical properties, thus facilitating a more efficient filter design. Additionally, the bicomponent yarn architecture and nonwoven design allow for adding desired surface functionalities in the skin polymer, like easy lamination, tunable hydrophobicity and colour.

Filip Legein (pages 98-102)

Plasma is the fourth state of matter. By adding energy, matter can be transformed from solid to liquid, from liquid to gas and from gas to plasma. In plasma the molecules are decomposed into neutral and charged particles that will interact with the surface of the material. In low pressure plasma technology a stable and effective plasma is created by an electromagnetic discharge of a gas at low pressure and at low temperature. In recent years low pressure plasma technology has been improved to achieve polymerization of monomers on materials, depositing real nanocoatings on the surface, and adding new and permanent functionalities to the material. Innovative plasma processes allow the deposition of coatings with high levels of hydrophobicity and/or oleophobicity for use in gas filtration, or coatings with permanent hydrophilic effect for liquid filter media and battery separators.

The use of low pressure plasma for surface modification of filter media has become more widespread because it is a dry and clean technology. Filter media producers adopt plasma coating to improve the quality of their products. At the same time it helps these companies to save costs because of a lower consumption of energy and chemicals.

Katharina Menzel, Johannes Lindner and Hermann Nirschl (pages 103-108)

Abrasive particles in gear and hydraulic oils are responsible for increased wear in machine elements like bearings or the breakdown of entire machine systems, e.g. the gears in wind power plants. The monitoring of the lubricant condition as well as its continuous treatment is therefore essential to increase the lifetime of the equipment. The separation of micrometre particles ranging from 1 to 20 µm of a high viscosity lubricant is still challenging in state-of-the-art deep bed filtration because of high pressure drop and the unintentional separation of additives. Wear particles of different chemical composition are magnetisable and therefore magnetic separation is a promising approach to separate these particle clusters, while avoiding the separation of oil additives. The magnetic force is effective at great distance from the separating wire. The HGMS filter is therefore configured to be more porous than a conventional filter material. Hence, the pressure drop in High Gradient Magnetic Separation (HGMS) is negligible which is a great advantage and helps to decrease operating expenses.

K.T. Oladepo, J.O. Jeje, O.O. Fadipe and M.O. Ogedengbe (pages 108-113)

People in the study area believe that rainwater, harvested and stored, would, in due course, have earthworms in it. They consider earthworms in water meant for cooking, let alone drinking, objectionable. These are the known reasons why rainwater harvesting has failed to be accepted. This study was intended to encourage dwellers of rural and semi urban communities to embrace the harvesting and storing of rainwater for domestic use and reduce their use of water from sources which potentially transmit pathogens to users. Rainfall data were collected. Dual media filters were built of palm kernel shells (PKS) over silica sand. Rainwater was harvested and passed to storage, filtered and unfiltered. During 30 days of storage the rainwater was not found to contain earthworms, although it was widely believed that it would. Passing rainwater into storage through the dual media filters produced better quality water. Any approaching earthworm would surely be filtered out.

Kuo-Jen Hwang and Syuan-Jyun Lin (pages 114-119)

The effects of membrane type and operating conditions on the crossflow microfiltration performance of blue dextran are studied experimentally. Three 0.1 µm flat sheet membranes made of polycarbonate (PC), polyvinylidene fluoride (PVDF) and mixed cellulose ester (MCE) were used in experiments as the filter media to separate blue dextran with a molecular weight of 2000 kDa. The filtration rate increased with increasing crossflow velocity and trans-membrane pressure. The filtration rate was highest while the dextran rejection was lowest when the PVDF membrane was used. The use of the PC membrane resulted in the lowest filtration rate but the highest dextran rejection. Therefore, the comparison of the mass flux collected into the filtrate follows the sequence PVDF > MCE > PC membrane. The results indicate that using a PC membrane and operating under high crossflow velocity are optimal for dextran concentration in the original suspension, while the use of PVDF membrane results in the highest filtration rate and collects most blue dextran in the filtrate.

Thomas Laminger, Marcus Stecher and Wilhelm Höflinger (pages 120-128)

This work deals with the development of a standardized filter test method for metal working fluid (MWF) mist separators. In order to compare the separation behaviour of different filter media, a filter medium must reach its stationary condition, which can take a long time. In the study an accelerated filter ageing procedure was developed and tested with six real filter elements of different structure using a laboratory scale filter test rig. A relatively high filter loading value generated by a nozzle spray was used to shorten the time needed to reach a steady state liquid equilibrium, and hence a steady state pressure drop. Thereafter the nozzle spray was shut off and an aerosol generator was used alone to produce a real working fluid mist aerosol. This aerosol facilitated determination of the steady state filter separation efficiency by measurements of the raw and clean gas aerosol concentrations, respectively.

Filter tests with 10 %vol MWF emulsions as the test substance showed that with the accelerated filter ageing procedure all tested filter elements reached the steady state within a period of two hours. Thereafter a steady state filter separation efficiency was determined. According to existing classification norms for dust filters, a classification system with a minimum requested separation efficiency in four particle size ranges for MWF mist separators is proposed. The tested filter elements were also classified using the proposed classification system. The filter class of the elements increases as the filter structure becomes finer. With the developed accelerated filter ageing procedure and the classification system it is now possible to evaluate and compare different mist separators in a short time.

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