A TOOL FOR DESIGNING SUPPLY AIR FILTER CLASS FOR HVAC
Thomas Carlsson and Magnus Johnsson (pages 214-219)
Fine filters (F5-F9) rated according to the standard EN779: 2002 are classified on average removal efficiency for a particle size of 0.4 µm during dust loading of ASHRAE test dust. It is not possible to use the measured efficiency from an EN779 report in order to predict the particle removal from outdoor air passing the filter due to the artificial dust. Particulate matter (PM) is measured locally all over the world, and it is possible to find data for more or less every city in the world. A test method to overcome the problem with dust loading and a calculation procedure has been developed. The procedure is based on data from local measurements of PM and particle removal from a filter. The method makes it possible to design the PM removal for PM1 , PM2,5 and PM10 for a specific filter and from the calculated values an indoor air quality (IAQ) can be predicted. The paper describes the newly developed test method for the filter and the calculation procedure. The paper also presents in-situ measurements showing the correlation between predicted PM values and the actual measured IAQ.
LONG TERM FOULING OF CERAMIC FILTER MEDIA IN THE DEWATERING OF HEMATITE CONCENTRATE
Riina Salmimies, Antti Häkkinen, Bjarne Ekberg, Juha Kallas and Jens-Petter Andreassen (pages 219-222)
The long-term blinding of a filter medium can affect the performance and lifetime of the medium, but can rarely be observed or quantified in the laboratory. Pilot scale experiments can offer additional information for the design of the washing of the filter medium, however they still don’t provide enough time in operation to evaluate the effects of hundreds of dewatering cycles. The long term fouling effects of a ceramic filter medium were investigated in this study by characterising samples taken from an industrial hematite dewatering process. Chemical characterisation was done using X-ray diffraction (XRD) after which scanning electron microscopy (SEM) was employed to identify the shape and size of the foulants on the surface of the filter medium.
The study showed that the ceramic filter medium used in the dewatering of hematite concentrate was primarily affected by slurry particle blockage, and to a lesser extent by precipitate formation, after operation at the plant scale. Whether the sample was taken from the centre or from the edges of the filter element did not to play a role in determining the nature or the extent of blinding.
LIMITING AND CRITICAL FLUXES VERSUS CLEANABILITY OF A POLYETHERSULPHONE MEMBRANE USED IN SKIM MILK ULTRAFILTRATION
Ndéye Wemsy Diagne and Murielle Rabiller-Baudry (pages 223-229)
The main bottleneck in the ultrafiltration of skim milk is the mastering of fouling and thus the subsequent cleaning in place operation. Industrial filtration practice often uses a polyethersulphone membrane of low cut-off to achieve the maximum flux (‘limiting flux’), but this favours severe fouling with a highly irreversible part due to proteins. On the other hand, above and below the critical or threshold flux two fouling behaviours exist. Below the threshold flux, fouling is low and corresponds to proteins adsorbed on the membrane without any applied pressure, whereas above this flux, the irreversible part strongly increases. The increase can be modulated by hydrodynamics. What about the cohesion of the fouling layer and its cleanability? This study shows that regardless of the intrinsic chemical efficiency of the cleaning solution the membrane cleanability is increased when the fouling is formed at threshold conditions instead of limiting ones.
INNOVATIVE COALESCENCE MEDIA (SFM) AND ITS WATER REMOVAL APPLICATIONS IN FUELS
Ruijun Chen, Jino Jose, Patricia Majestic, Tim Mills and Bill Martin (pages 229-236)
An innovative, US patent pending coalescence filtration medium, called SFM, has been developed to effectively and efficiently clean heavy water contaminations from fuels, including petrodiesel fuels and biodiesel blends. The paper focuses on studying four technical issues related to SFM and its water removal applications in fuels. The first proposes the concept of SFM, including filter medium structure and the coalescence filtration mechanism. The second addresses the conceptual designs of two coalescer elements, denoted as advanced and standard – these are made of the SFM coalescence medium and more traditional nonwoven filter media, respectively. The third briefly describes water droplet motion on the downstream surface of the advanced coalescer element. The fourth introduces experimental studies of water removal performance with the two coalescer elements for a No. 2 petrodiesel fuel and a B20 biodiesel blend.
The preliminary experimental results shown demonstrate unprecedented water removal capabilities for the advanced coalescer element. For example, total volumetric water content in 4.8 GPM petrodiesel-water blend flow can be reduced from 10% upstream of the element to 200 ppm or less downstream of the element within a single pass.
ANALYSIS OF DUST DEPOSITION ON AN INDUSTRIAL SURFACE FILTER AS A FUNCTION OF ITS PHYSICAL PROPERTIES
Arunangshu Mukhopadhyay and Awadhesh K. Choudhary (pages 237-246)
This investigation embodies the analysis of dust deposition on an industrial surface filter as a function of its physical properties. The study is augmented by examining the role of inlet dust concentration and pulse cleaning pressure on the performance of the pulse-jet filtration process. The changes in physical properties of the filter media are largely governed by dust deposition on the different segments of a filter bag. There is a consequent decrease in air permeability and compressibility of the filter media depending on the extent of dust deposition over different segments of the bag height. Progressive dust deposition also results in an increase in media stiffness.
DETAILED SIMULATION OF EXHAUST FLOW AND DEPOSITION OF SOOT PARTICLES IN POROUS PARTICULATE FILTER WALLS
Andrew Schermerhorn, Konstantin Khodosevich, Ameya Joshi and Thorsten Boger (pages 246-256)
Particulate filters are a key after-treatment component employed in all modern diesel engines. Key performance criteria of particulate filters are pressure drop and filtration performance. Both are determined by geometric design parameters such as size, cell density and wall thickness, as well as intrinsic wall scale material properties. The latter are usually related to the properties of the pore space such as porosity, pore size and pore morphology.
In this paper tools to simulate the motion and deposition of discrete diesel soot particles through and on a finite section of a porous filter wall are discussed. The tools and models developed are solved for the complex flow through the pore space, either using the commercial software (FLUENT) or an internally developed Lattice-Boltzmann solver. The flow is combined with an internally developed discrete particle dynamics tracking routine to advance the particle motions in time. In the model the flow field is continually updated, taking account of the accumulation of soot. The simulated effect of mean pore size and porosity are discussed for examples of synthetic microstructures. A comparison with experimental data shows good agreement for clean permeability.