DEVELOPMENTS AND CASE STUDIES IN HOT GAS FILTRATION FOR
GASEOUS WASTE STREAMS
Ian Chisem and Richard Lydon (pages 208-210)
Over recent years Clear Edge has been developing its range of specialised filter element technology for a set of challenging applications in hot gas filtration markets. The solutions have been driven by the pressing need for industrial processes to control emissions to meet tighter regulatory standards, both inline and with ‘end of pipe’ technology. As global emissions in the developed world have tightened from PM10 to PM2.5 (particulate matter 2.5 μm), Clear Edge has been developing and testing hot gas filters in a range of industrial processes to meet even tighter emission limits whilst maintaining high flow rates and energy efficient systems. The paper outlines some of the new technology in this family and the next generation of filter products offering commercially competitive air pollution control (APC) solutions.
MEASURING FILTER CUT POINTS AND PORE SIZE DISTRIBUTIONS USING GLASS MICROSPHERES
Graham Rideal (pages 211-216)
In this paper challenge testing with narrow particle size distribution glass microspheres is shown to be a powerful method of measuring both the cut points and pore size distributions of woven stainless steel wire meshes. The key to accuracy and reproducibility was the use of microscopy and image analysis where it was possible to electronically remove any non-spherical particles in the filter calibration standard.
INTRODUCING FUNCTIONALITY TO FILTER MEDIA
Bhavani Vijayakumar, Allan Rennie, Neil Burns, Darren Travis and Paul Battersby (pages 217-222)
Pumps are major consumers of electricity in the process industries and filters are an integral part of the pumping process. This paper discusses the reduction in energy consumption in the filtration process by using additive manufactured, geometrically optimised, conical, in-line filter supports. These are then compared with those currently fabricated by more conventional means.
Based on computational fluid dynamic (CFD) simulations, a new filter support was designed and fabricated using Additive Manufacturing (AM) technology. The comparison was achieved by testing both types of filter supports of similar dimensions with filter mesh in a bespoke test rig at Croft Engineering Services. A 20 gauge, 900 µm filter mesh was used to test the two filter supports with flow rates between 0.0018 m3/s and 0.0062 m3/s. Comparison of the experimental results revealed that the AM filter support mesh arrangement was superior to the conventional filter support mesh arrangement. In comparison to the conventional approach, the AM filter support pressure drop was 0.443 kPa lower when operated in the forward flow direction and 1.852 kPa lower in reverse flow. The reduction in pressure drop correspondingly reduced the energy consumption by 10 kW/h in forward flow and 29 kW/h in reverse flow.
INDISPENSABLE POLYPROPYLENE MATERIAL IN COMPOSITEFIBROUS MEDIA COALESCER FOR OIL-IN-WATER EMULSION SEPARATION
Sunil Kirloskar and H. Veeramani (pages 222-225)
This paper outlines the development of baseline data for the treatment of emulsions with alternative composite media from readily available fibrous materials. The aim was to evolve suitable configurations of composite media that would manifest a moderate pressure drop whilst giving complete phase separation and maximum recovery of oil from oil-water emulsions by coalescence.
EFFECT OF XHANTAN GUM AND PARTICLE SIZE DISTRIBUTION ON THE
PERMEABILITY OF MUD-CAKE PRODUCED DURING DRILLING OPERATIONS
José Angel Sorrentino (pages 226-235)
During drilling operations the drilling mud is injected to the well under pressure, with some solids being added to the mud formulation in order to build a mud-cake on the reservoir walls and prevent further invasion of solid and fluid. Unlike in typical filtration applications, mud-cakes are supposed to be as impermeable and thin as possible. Some water-based drilling muds include in their formulation a polysaccharide (Xhantan Gum) to give the mud a pseudo-plastic rheology. This paper presents the results of mud-cake permeability variations with particle size distribution (PSD) of the bridging material (limestone) for a basic drilling mud composed of water, Xhantan Gum and calcium carbonate in fixed ratios. Most of the results do not agree with the estimations made using the Kozeny-Carman equation, the permeabilities being up to three orders of magnitude smaller than those predicted based solely on particle characteristics.
The suggested hypothesis postulates that the polysaccharide (Xhantan Gum), which hydrolyses with a large amount of water, forms a ‘hydrated macromolecule’ mixed with some free water. This mixture behaves sometimes like a thick fluid (passing with some difficulty through the voids caused by the solid particles) and other times like a particulate system (part of which is able to be retained within the interstices of the porous system). In experiments cakes were prepared using limestone of different PSD with median sizes between 15 and 50 μm and geometric standard deviations ranging between 1.5 and 3. A modified permeability, KεS, was used to minimise the influence of errors in estimating porosity. A plot of KεS /(D3,2)2 against D3,2 allowed identification of the conditions where the Kozeny-Carman functionality is fulfilled (i.e. KεS /(D3,2)2 is independent of D3,2). These results support the hypothesis of a ‘hydrated macromolecule’ binding the voids, as when the pores are big enough then the Kozeny-Carman functionality is satisfied.
THE EFFECT OF FILTER DESIGN AND SURFACE AREA ON FILTER
Iyad Al-Attar (pages 235-240)
The increasing public concern regarding indoor air quality in residential and commercial buildings has led to major developments in high efficiency air filters. Clean air is required for Heating, Ventilation and Air Conditioning (HVAC) systems in buildings, clean rooms, pharmaceutical industries, all enclosed environments, engine intakes and exhausts. Equally important, air filters are an essential component in providing a large mass of clean air to operate gas in order to generate energy. Whether it is intake or exhaust, air filtration remains a common denominator in the mathematics of applications requiring particle removal. This paper describes the importance of effective surface in a filter and the reasons which may cause losses in filter surface area that can lead to a loss in performance.