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Hood mask and air filter
INVENTIONSINFILTRATIONANDSEPARATION Abstracts of British Patents Sorting particles In GB 2247195 De Beers Industrial D i a m o n d Division (Proprietary) Ltd d e s c r i b e s a m e t h o d of s e p a r a t i n g particles which are sorted on t h e basis of different t h e r m a l characteristics. The m e t h o d involves wetting the particles -- such as d i a m o n d s a n d rocks -- with water, a n d bringing the w e t t e d particles into c o n t a c t w i t h a surface which is at a temperature lower than the freezing p o i n t of t h e liquid. C o n t a c t is maintained for a period of time sufficient for all t h e particles to a d h e r e to t h e surface as a result of t h e liquid freezing. Thereafter, different classes of particles, d i s t i n g u i s h e d from one ano t h e r by t h e i r t h e r m a l characteristics, are i n d e p e n d e n t l y s e p a r a t e d from the surface, by applying h e a t to the particles, for e x a m p l e from a w a r m w a t e r b a t h or spray. The particles m a y be carried on a rotary, internally cooled d r u m and a d h e r e d to a layer of ice.
(1 figure, 2500 words)
Hood mask and air filter In GB 2247416 ILO Dover Inc describes a h o o d m a s k for p r o t e c t i n g t h e w e a r e r from c h e m i c a l and biological environm e n t a l c o n t a m i n a t e s . It c o m p r i s e s a h o o d of impervious, flexible m a t e r i a l w h i c h seals a r o u n d t h e w e a r e r ' s neck. It has a m u l t i s t a g e filter secured to its i n t e r i o r b e h i n d an aperture. The filter c o m p r i s e s an aerosol filter s h e e t prot e c t e d by a screen. A rigid c a s i n g encloses active carbon, and is located in a second a p e r t u r e in t h e flexible sheet. A s e p a r a t o r layer is l o c a t e d between the s h e e t and casing, and the v a r i o u s s h e e t s are c o n n e c t e d t o g e t h e r by heat-sealing. The casing is s m a l l e r in cross-section t h a n t h e o t h e r components, a n d is t h e only rigid p a r t of the mask; it can be folded a r o u n d t h e casing until required. The aerosol filter s h e e t m a y be of glass fibre or synthetic fibres b e a r i n g a p e r m a n e n t electrostatic charge. (4 figures, 5000 words)
Semipermeable composite memDranes In GB 2247419 Aligena AG describes semipermeable composite membranes. These c o m p r i s e a p o r o u s s u b s t r a t e and a t l e a s t two layers of f i l m - f o r m i n g p o l y m e r s c o a t e d on it. The c o a t e d p o l y m e r s consist of a first layer of monomeric or polymeric dizonium salts, w h i c h have been r e a c t e d w i t h themselves and with an at least difunctional c o m p o u n d ; and a second layer, w h i c h is chemically b o n d e d to the Filtration & Separation
May 1993
first one, of a crosslinked, ionically charged hydrophilic polymer. The m e m branes s h o w good mechanical, physical and chemical stability, and are useful in reverse osmosis and ultrafiltration processes, p a r t i c u l a r l y for d e s a l t i n g s o l u t i o n s of low m o l e c u l a r w e i g h t organic c o m p o u n d s . (No figures, 9000
words).
Filter element In GB 2247189 Pall C o r p o r a t i o n describes a t u b u l a r filter e l e m e n t which h a s l o n g i t u d i n a l l y e x t e n d i n g pleats, and a m e m b e r w r a p p e d a r o u n d t h e m and j o i n e d to the o u t e r peaks of the pleats. These define openings which total l e s s t h a n 50% ( p r e f e r a b l y 6 - - 3 0 % ) of t h e a r e a of a n o t i o n a l cylinder defined by the p l e a t peaks. The w r a p t h u s evens out the flow, and i n c r e a s e s t h e d i r t c a p a c i t y of t h e element. Pleats may include a filter layer, u p s t r e a m and d o w n s t r e a m supp o r t and d r a i n a g e layers, a cushioning layer between the u p s t r e a m s u p p o r t a n d the d r a i n a g e layer, and the filter layer, as well as polymeric beads on t h e d o w n s t r e a m side of the d o w n s t r e a m s u p p o r t and d r a i n a g e layer. An ext r u d e d polymeric m e s h may c o m p r i s e one or b o t h of t h e u p s t r e a m a n d d o w n s t r e a m s u p p o r t s and d r a i n a g e layers. The w r a p m a y be an impervious b a n d w o u n d helically with t u r n s spaced apart, a perforate or m e s h band also wound helically with turns either spaced or overlapping, or a series of axially spaced circumferential bands.
(9 figures, 9000 words)
Counter-electrode for electrochemical filter cleaning In GB 2247469 the UK A t o m i c Energy A u t h o r i t y describes a c o u n t e r - e l e c t r o d e for e l e c t r o c h e m i c a l filter cleaning. In the periodic application d u r i n g filtrat i o n ( s u c h as u l t r a f i l t r a t i o n ) of a p o t e n t i a l difference between an electrically c o n d u c t i n g filter m e d i u m and a c o u n t e r - e l e c t r o d e (as a n o d e ) , t h e c o u n t e r - e l e c t r o d e is a l o w - c h r o m i u m stainless steel, for e x a m p l e 9% chromium. A gaseous p r o d u c t is g e n e r a t e d a t t h e filter, and the air is cleaned to m i n i m i s e corrosion. A sintered stainless steel fibre m e m b r a n e (with a p o r e size of 3 ~m on one surface and 10 p m on t h e other) can, with regular electrocleaning, provide as good a rejection of t h e s e as in ultrafiltration. The steel fibre m e m b r a n e is used with t h e coarse surface facing the liquid to be filtered.
(No figures, 2000 words)
Screen In GB 224 7850 S h a t t o c k Ltd describes a screen c o m p r i s i n g a p a i r of side m e m b e r s s u p p o r t i n g a n u m b e r of transversely e x t e n d i n g screening panels. These p a n e l s are a r r a n g e d in cascade formation, to form a m a t e r i a l p a t h which e x t e n d s from t h e u p s t r e a m end to t h e d o w n s t r e a m end, along which m a t e r i a l to be screened flows. The screening panels have a n u m b e r of tines, e x t e n d i n g from transverse carrier members, which are pivotally m o u n t e d in t h e side m e m b e r s , to f a c i l i t a t e variation of t h e slope of t h e screening panels to vary the flow rate of m a t e r i a l along its path. Brackets secure t h e screening panels at t h e desired slope.
(9figures, 13,000 words)
High-efficiency liquid/liquid hy~lrocyclone In GB 2248198 C o n o c o S p e c i a l t y P r o d u c t s Inc d e s c r i b e s a h i g h efficiency, s m a l l - d i a m e t e r h y d r o c y c l o n e for l i q u i d / l i q u i d s e p a r a t i o n such as for oil a n d w a t e r . The s e p a r a t i o n c h a m b e r begins at a s m a l l - d i a m e t e r throat where the acceleration and velocity of the m i x t u r e cease to increase. The effective p o r t i o n ends at t h e underflow outlet from the s e p a r a t i o n chamber, and has an a r e a / v o l u m e ratio t h a t falls w i t h i n c e r t a i n l i m i t s to p r o m o t e efficient s e p a r a t i o n of t h e m i x t u r e , in p a r t i c u l a r s m a U - d i a m e t e r d r o p l e t s d i s p e r s e d in the chamber. (6
figures, 9000 words)
Filter module In GB 2248408 Seitz-Filter-Werke Theo. & Geo. Seitz GmbH describes a filter m o d u l e for c r o s s f l o w f i l t r a t i o n . It c o m p r i s e s an a n n u l a r s e a l i n g r i n g enclosing a stack of double-sided f l a t hollow filter units s e p a r a t e d by open m e s h spacers. E a c h u n i t is s e a l e d a r o u n d its periphery, p a r t of which is e m b e d d e d in the a n n u l a r scaling ring, w h e r e its interior space opens into a t l e a s t one a x i a l l y e x t e n d i n g f i l t r a t e channel. At least one o t h e r p a r t of the p e r i p h e r y is spaced from the interior face of the a n n u l a r scaling ring, to define c h a n n e l s by which fluid is fed to and r e m o v e d from the u p s t r e a m faces of t h e units; fluid flows f r o m one channel to a n o t h e r within the planes of spacers. In use, several m o d u l e s are stacked within a t u b u l a r casing, and suitable end plates may enable several such stacks of m o d u l e s to o p e r a t e in parallel. (19figures, 11,000 words) ~__~
I ) 223
(1 figure, 2500 words)
Hood mask and air filter In GB 2247416 ILO Dover Inc describes a h o o d m a s k for p r o t e c t i n g t h e w e a r e r from c h e m i c a l and biological environm e n t a l c o n t a m i n a t e s . It c o m p r i s e s a h o o d of impervious, flexible m a t e r i a l w h i c h seals a r o u n d t h e w e a r e r ' s neck. It has a m u l t i s t a g e filter secured to its i n t e r i o r b e h i n d an aperture. The filter c o m p r i s e s an aerosol filter s h e e t prot e c t e d by a screen. A rigid c a s i n g encloses active carbon, and is located in a second a p e r t u r e in t h e flexible sheet. A s e p a r a t o r layer is l o c a t e d between the s h e e t and casing, and the v a r i o u s s h e e t s are c o n n e c t e d t o g e t h e r by heat-sealing. The casing is s m a l l e r in cross-section t h a n t h e o t h e r components, a n d is t h e only rigid p a r t of the mask; it can be folded a r o u n d t h e casing until required. The aerosol filter s h e e t m a y be of glass fibre or synthetic fibres b e a r i n g a p e r m a n e n t electrostatic charge. (4 figures, 5000 words)
Semipermeable composite memDranes In GB 2247419 Aligena AG describes semipermeable composite membranes. These c o m p r i s e a p o r o u s s u b s t r a t e and a t l e a s t two layers of f i l m - f o r m i n g p o l y m e r s c o a t e d on it. The c o a t e d p o l y m e r s consist of a first layer of monomeric or polymeric dizonium salts, w h i c h have been r e a c t e d w i t h themselves and with an at least difunctional c o m p o u n d ; and a second layer, w h i c h is chemically b o n d e d to the Filtration & Separation
May 1993
first one, of a crosslinked, ionically charged hydrophilic polymer. The m e m branes s h o w good mechanical, physical and chemical stability, and are useful in reverse osmosis and ultrafiltration processes, p a r t i c u l a r l y for d e s a l t i n g s o l u t i o n s of low m o l e c u l a r w e i g h t organic c o m p o u n d s . (No figures, 9000
words).
Filter element In GB 2247189 Pall C o r p o r a t i o n describes a t u b u l a r filter e l e m e n t which h a s l o n g i t u d i n a l l y e x t e n d i n g pleats, and a m e m b e r w r a p p e d a r o u n d t h e m and j o i n e d to the o u t e r peaks of the pleats. These define openings which total l e s s t h a n 50% ( p r e f e r a b l y 6 - - 3 0 % ) of t h e a r e a of a n o t i o n a l cylinder defined by the p l e a t peaks. The w r a p t h u s evens out the flow, and i n c r e a s e s t h e d i r t c a p a c i t y of t h e element. Pleats may include a filter layer, u p s t r e a m and d o w n s t r e a m supp o r t and d r a i n a g e layers, a cushioning layer between the u p s t r e a m s u p p o r t a n d the d r a i n a g e layer, and the filter layer, as well as polymeric beads on t h e d o w n s t r e a m side of the d o w n s t r e a m s u p p o r t and d r a i n a g e layer. An ext r u d e d polymeric m e s h may c o m p r i s e one or b o t h of t h e u p s t r e a m a n d d o w n s t r e a m s u p p o r t s and d r a i n a g e layers. The w r a p m a y be an impervious b a n d w o u n d helically with t u r n s spaced apart, a perforate or m e s h band also wound helically with turns either spaced or overlapping, or a series of axially spaced circumferential bands.
(9 figures, 9000 words)
Counter-electrode for electrochemical filter cleaning In GB 2247469 the UK A t o m i c Energy A u t h o r i t y describes a c o u n t e r - e l e c t r o d e for e l e c t r o c h e m i c a l filter cleaning. In the periodic application d u r i n g filtrat i o n ( s u c h as u l t r a f i l t r a t i o n ) of a p o t e n t i a l difference between an electrically c o n d u c t i n g filter m e d i u m and a c o u n t e r - e l e c t r o d e (as a n o d e ) , t h e c o u n t e r - e l e c t r o d e is a l o w - c h r o m i u m stainless steel, for e x a m p l e 9% chromium. A gaseous p r o d u c t is g e n e r a t e d a t t h e filter, and the air is cleaned to m i n i m i s e corrosion. A sintered stainless steel fibre m e m b r a n e (with a p o r e size of 3 ~m on one surface and 10 p m on t h e other) can, with regular electrocleaning, provide as good a rejection of t h e s e as in ultrafiltration. The steel fibre m e m b r a n e is used with t h e coarse surface facing the liquid to be filtered.
(No figures, 2000 words)
Screen In GB 224 7850 S h a t t o c k Ltd describes a screen c o m p r i s i n g a p a i r of side m e m b e r s s u p p o r t i n g a n u m b e r of transversely e x t e n d i n g screening panels. These p a n e l s are a r r a n g e d in cascade formation, to form a m a t e r i a l p a t h which e x t e n d s from t h e u p s t r e a m end to t h e d o w n s t r e a m end, along which m a t e r i a l to be screened flows. The screening panels have a n u m b e r of tines, e x t e n d i n g from transverse carrier members, which are pivotally m o u n t e d in t h e side m e m b e r s , to f a c i l i t a t e variation of t h e slope of t h e screening panels to vary the flow rate of m a t e r i a l along its path. Brackets secure t h e screening panels at t h e desired slope.
(9figures, 13,000 words)
High-efficiency liquid/liquid hy~lrocyclone In GB 2248198 C o n o c o S p e c i a l t y P r o d u c t s Inc d e s c r i b e s a h i g h efficiency, s m a l l - d i a m e t e r h y d r o c y c l o n e for l i q u i d / l i q u i d s e p a r a t i o n such as for oil a n d w a t e r . The s e p a r a t i o n c h a m b e r begins at a s m a l l - d i a m e t e r throat where the acceleration and velocity of the m i x t u r e cease to increase. The effective p o r t i o n ends at t h e underflow outlet from the s e p a r a t i o n chamber, and has an a r e a / v o l u m e ratio t h a t falls w i t h i n c e r t a i n l i m i t s to p r o m o t e efficient s e p a r a t i o n of t h e m i x t u r e , in p a r t i c u l a r s m a U - d i a m e t e r d r o p l e t s d i s p e r s e d in the chamber. (6
figures, 9000 words)
Filter module In GB 2248408 Seitz-Filter-Werke Theo. & Geo. Seitz GmbH describes a filter m o d u l e for c r o s s f l o w f i l t r a t i o n . It c o m p r i s e s an a n n u l a r s e a l i n g r i n g enclosing a stack of double-sided f l a t hollow filter units s e p a r a t e d by open m e s h spacers. E a c h u n i t is s e a l e d a r o u n d its periphery, p a r t of which is e m b e d d e d in the a n n u l a r scaling ring, w h e r e its interior space opens into a t l e a s t one a x i a l l y e x t e n d i n g f i l t r a t e channel. At least one o t h e r p a r t of the p e r i p h e r y is spaced from the interior face of the a n n u l a r scaling ring, to define c h a n n e l s by which fluid is fed to and r e m o v e d from the u p s t r e a m faces of t h e units; fluid flows f r o m one channel to a n o t h e r within the planes of spacers. In use, several m o d u l e s are stacked within a t u b u l a r casing, and suitable end plates may enable several such stacks of m o d u l e s to o p e r a t e in parallel. (19figures, 11,000 words) ~__~
I ) 223