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Energy-efficient ceramic crossflow microfiltration membranes
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AMICCROSSFLOWMEMBRAN
Energy-effkient ceramic crossflow microfiltration membranes The relatively high energy consumption of crossflow microfiltration has generally restricted its application to higher-value materials. However, this short article describes how a new design for a ceramic crossflow microfiltration element should encourage the application of this technique in lower-value streams such as effluent discharges to rivers.
C demonstrated to perform well in industrial applications. Its drawback rossflow microfiltration
has been
has always been the relatively high energy consumption resulting from the high-crossflow pumping volumes. This reouirement has in the past limited the applications of crossflow microfiltration to the processing of medium- to high-value specialist materials, such as beer, fruit juices, milk and pharmaceuticals. The largest potential future market for crossflow microfiltration is considered to be effluent cleanup, where suspended solids are separated out of a liquid. Thus the solids are separated and concentrated into manageable volumes for safe disposal. Fairey Industrial Ceramics has now acquired a novel ceramic crossflow microfiltration membrane with considerable energy savings - up to 50% from Horsham-based Bio-Design Ltd. Low-value materials can now be effectively processed using much less energy. Waste streams of no intrinsic value can now be treated more economically using these filter membranes. The principle of crossflow filtration is shown in Figure 1. The product to be filtered is pumped continuously across the face of the filter membrane. Filtered liquid passes through the membrane, and contaminant starts to build up on the surface of the membrane. At the high volume flow rates generally used shear forces occur close to the membrane surface; this prevents excessive buildup of the contaminant, which would eventually foul the filter. Typically, ceramic crossflow filter elements consist of several parallel, circular-section channels in a tubular element (Figure 2). The key to the new Filtration
& Separatlon
March/April
1993
F!&UVV 1. lRe principle of cnx&w
microJiltra&n.
technology is the star-shaped crosssection of the flowpaths - normally the flowpaths are circular. With similar outer dimensions of the flowpath, the cross-sectional area of the ‘star’ shape is some 50% less than that of the circular configuration. With similar crossflow velocities (the turbulence created by the velocity is one of the prime factors restricting fouling) the
l+&re
2.
Cuss-sectinal
crossflow volume is halved (Figure 3), and hence the pumping requirement is reduced by a similar amount. The star shape also has the added benefit of increasing the membrane filtration area by about 13%. The new design, because of its reduced cross-sectional area, therefore requires much less energy to pump the contaminated liquid around the
view of the new ceramic multichannel
membrane.
113
8” t f
effective solution to many of today’s effluent discharge problems, as well as those likely to occur in the future. Both plastic and stainless-steel housings are used in these constructions, allowing the membrane to be used for the separation of waste materials as well as for the processing of high-value pharmaceutical materials where hygienic equipment is demanded.
4
2
system. For example, a large effluent filtration ins~llation might well use pumps rated at 200 kW for conventional elements with circular-section channels. The new element requires only about 100 kW for the same
Fittratlon & Separation
March/April
1993
performance, representing a potential energy saving of 2.4 MWh per day. As effluent disposal standards become more stringent, the market for crossflow microfiltration will increase. This new membrane should provide an
tt5
AMICCROSSFLOWMEMBRAN
Energy-effkient ceramic crossflow microfiltration membranes The relatively high energy consumption of crossflow microfiltration has generally restricted its application to higher-value materials. However, this short article describes how a new design for a ceramic crossflow microfiltration element should encourage the application of this technique in lower-value streams such as effluent discharges to rivers.
C demonstrated to perform well in industrial applications. Its drawback rossflow microfiltration
has been
has always been the relatively high energy consumption resulting from the high-crossflow pumping volumes. This reouirement has in the past limited the applications of crossflow microfiltration to the processing of medium- to high-value specialist materials, such as beer, fruit juices, milk and pharmaceuticals. The largest potential future market for crossflow microfiltration is considered to be effluent cleanup, where suspended solids are separated out of a liquid. Thus the solids are separated and concentrated into manageable volumes for safe disposal. Fairey Industrial Ceramics has now acquired a novel ceramic crossflow microfiltration membrane with considerable energy savings - up to 50% from Horsham-based Bio-Design Ltd. Low-value materials can now be effectively processed using much less energy. Waste streams of no intrinsic value can now be treated more economically using these filter membranes. The principle of crossflow filtration is shown in Figure 1. The product to be filtered is pumped continuously across the face of the filter membrane. Filtered liquid passes through the membrane, and contaminant starts to build up on the surface of the membrane. At the high volume flow rates generally used shear forces occur close to the membrane surface; this prevents excessive buildup of the contaminant, which would eventually foul the filter. Typically, ceramic crossflow filter elements consist of several parallel, circular-section channels in a tubular element (Figure 2). The key to the new Filtration
& Separatlon
March/April
1993
F!&UVV 1. lRe principle of cnx&w
microJiltra&n.
technology is the star-shaped crosssection of the flowpaths - normally the flowpaths are circular. With similar outer dimensions of the flowpath, the cross-sectional area of the ‘star’ shape is some 50% less than that of the circular configuration. With similar crossflow velocities (the turbulence created by the velocity is one of the prime factors restricting fouling) the
l+&re
2.
Cuss-sectinal
crossflow volume is halved (Figure 3), and hence the pumping requirement is reduced by a similar amount. The star shape also has the added benefit of increasing the membrane filtration area by about 13%. The new design, because of its reduced cross-sectional area, therefore requires much less energy to pump the contaminated liquid around the
view of the new ceramic multichannel
membrane.
113
8” t f
effective solution to many of today’s effluent discharge problems, as well as those likely to occur in the future. Both plastic and stainless-steel housings are used in these constructions, allowing the membrane to be used for the separation of waste materials as well as for the processing of high-value pharmaceutical materials where hygienic equipment is demanded.
4
2
system. For example, a large effluent filtration ins~llation might well use pumps rated at 200 kW for conventional elements with circular-section channels. The new element requires only about 100 kW for the same
Fittratlon & Separation
March/April
1993
performance, representing a potential energy saving of 2.4 MWh per day. As effluent disposal standards become more stringent, the market for crossflow microfiltration will increase. This new membrane should provide an
tt5