WO1996003193A1

WO1996003193A1 - Filtering and shut-off valve

Info

Publication number: WO1996003193A1
Application number: PCT/CA1995/000446
Authority: WO
Inventors: Keith Daly; Ronald Albert Fenney
Original assignee: Big 'o' Inc.
Priority date: 1994-07-26
Filing date: 1995-07-26
Publication date: 1996-02-08
Also published as: AU3338695A; GB9415045D0

Abstract

A method and apparatus for removal of organic liquids including liquid hydrocarbons from an aqueous stream passing through a conduit comprises interposing in the conduit a housing (30) having a cavity of a predetermined volume through which the aqueous stream must flow, interposing in said cavity a discrete, organic liquid swellable polymer absorbent (64) having a maximum volume upon swelling greater than the predetermined volume of the cavity, whereby the polymer absorbent cannot reach 100 % saturation. This volume limitation of the cavity prevents dissolution of the polymer absorbent and permits the use of non-cross-linked polymers. The polymer preferably will swell to at least four times its volume and not be soluble in less than 20 times its volume. In a preferred aspect of the invention, the polymer absorbent is packed in the cavity in a density in the range of about 280 to about 340 grams per litre of cavity volume, the polymer absorbent functioning as a prefilter at about 300 grams per litre density and as a shut-off valve at about 320 grams per litre density.

Description

FILTERING AND SHUT-OFF VALVE This invention relates to a method and apparatus for filtering organic liquids from agueous streams and for stopping agueous streams containing high levels of organic liquids. More particularly, the invention relates to the use of particulate, organic liquid swellable, polymer absorbent as a filtering agent and for use in a shut-off valve for aqueous streams.

The use of oleophilic imbibing synthetic resinous cross-linked polymers which will swell in but not dissolve in an organic liquid for filtering organic liquids from aqueous streams and for functioning as a shut-off medium in a valve structure are known as typified in U.S. Patents Nos. 3,520,806, 3,750,688, 4,172,031 and 4,302,337. The use of polymers which have been cross-linked in order to obviate the hazard or dissolution of the polymer in the absorbed liquid if 100% saturation should be reached is taught in these patents.

U.S. Patent No. 3,750,688 suggests that the use of uncross-1inked polymers is satisfactory for many applications such as those wherein instrumentation is employed to detect pressure drop. However, it is stated that for most application it is desirable to employ a polymer which is cross-linked to a sufficient degree that it exhibits a swelling index between about 1.5 and 50 to eliminate the hazard of dissolution of polymer over extended periods of time.

Although it normally is desirable to use a cross- linked polymer absorbent to avoid the hazard of dissolution of the absorbent in the organic liquid which it absorbs when the absorbent is fully saturated, it has been found that by controlling the expansion of the absorbent so that it cannot reach 100% saturation the need for relatively expensive cross-linked materials is avoided. In its broad aspect, the method of the present invention for removal of organic liquids including liquid hydrocarbons from an aqueous stream passing through a

SUBSTITUTESHEET conduit comprises interposing in the conduit . housing having a cavity of a predetermined volume through which the aqueous stream must flow, and interposing in said cavity a discrete, organic liquid swellable polymer absorbent having a maximum volume upon swelling greater than the predetermined volume of the cavity, whereby the polymer cannot reach 100% saturation. The polymer preferably will swell to at least four times its volume and not be soluble in less than 20 times its volume. In a preferred aspect of the invention, the polymer is packed in the cavity in a density in the range of about 280 to about 340 grams per litre of cavity volume, the polymer functioning as a prefilter preferably at about 300 grams per litre density and as a shut-off valve preferably at about 320 grams per litre density.

The filter and shut-off valve of the invention for removing organic liquids from an aqueous stream and for stopping said aqueous stream upon high contents of organic liquid in said stream comprises, in a broad aspect: a housing defining a cavity therein, said housing having an inlet end and an outlet end for flow of the aqueous stream therethrough, a permeable restraining means disposed within the cavity adjacent the outlet end, a permeable restraining means disposed within the cavity adjacent the inlet end, a layer of discrete, organic, liquid-swellable, polymer absorbent interposed within the cavity between the outlet permeable restraining means and the inlet permeable restraining means co-extensive with and substantially filling the cavity between said restraining means, means for securing the restraining means within the housing to establish and maintain a predetermined volume in the cavity, the polymer absorbent having a maximum swelling volume upon saturation with an organic liquid greater than the predetermined volume of the cavity, whereby the polymer absorbent cannot achieve 100% saturation.

The filter and shut-off valve of the invention comprises, in a first preferred aspect: a housing defining

SUBSTITUTESHEET a cavity therein, said housing having an upper inlet end and a lower outlet end for flow of the aqueous stream therethrough, a liquid permeable retaining layer suitable to support and contain polymer absorbent, such as a lower perforate screen disposed within the cavity adjacent the outlet end and a lower liquid-permeable textile or open- cell foam layer co-extensive with and seated on the perforate screen, a layer of discrete, organic liquid- swellable polymer absorbent interposed within the cavity coextensive with and seated on the retaining layer, an upper liquid-permeable retaining layer such as a textile or open-cell foam layer co-extensive with and seated on the polymer layer, an upper perforate screen co-extensive with and seated on the upper textile or foam layer, and means for securing the lower and upper retaining layers within the housing to establish and maintain a predetermined volume in the cavity between said layers, the polymer absorbent having a maximum swelling volume upon saturation with organic liquid greater than the predetermined volume of the cavity, whereby the polymer cannot achieve 100% saturation.

The filter and shut-off valve of the invention comprises, in a second preferred aspect: a housing defining a cavity therein, said housing having an inlet end on one side and an outlet end on the opposite side for flow of the aqueous stream through the cavity, a retaining layer such as a perforate screen disposed within the cavity adjacent the outlet end and a liquid-permeable textile or open-cell foam layer co-extensive with and seated against the perforate screen, a layer of discrete, organic liquid- swellable polymer absorbent interposed within the cavity coextensive with and seated against the said retainer layer, a second retaining layer such as a liquid-permeable textile or open-cell foam layer co-extensive with and seated against the polymer layer at the inlet end, a perforate screen co-extensive with and seated against the textile or foam layer at the said inlet end, and means for

SUBSTITUTESHEET securing the retaining layers within the housing to establish and maintain a predetermined volume in the cavity between the retaining layers, the polymer absorbent having a maximum swelling volume upon saturation with an organic liquid greater than the predetermined volume of the cavity, whereby the polymer cannot achieve 100% saturation. This volumetric limitation prevents dissolution of the polymer and permits the use of non cross-linked polymers.

The discrete, organic liquid-swellable polymer is a particulate polymer, preferably with an irregular shape, which is water insoluble and which swells on contact by absorbing organic liquids such as hydrocarbons including gasoline, fuel oil and diesel fuel, chlorinated solvents such as carbon tetrachloride, aromatic solvents such as benzene, toluene and xylene, and polar compounds such as ethyl acrylate. Suitable polymers are polymers containing complex multifunctional monomers that will offer a range of solubility, or a copolymer containing a blend of monomers that will offer the range of absorption that will fit the needs of the system, and which can be non cross-linked. These can include but are not limited to polymers and copolymers of styrene, alkylstyrenes, acrylics, olefins and dienes. A number of different polymers and types of polymers will be effective for different oils and solvents. The system can be effectively constructed using a blend of polymers or consecutively layered, discrete zones of different polymers. This arrangement of polymers would service areas of use where a blend of different chemicals are present. It is preferred that the polymer will swell to at least four times its volume and not be soluble in less than 20 times its volume. If the polymer will not swell to at least four times its volume, it cannot consume all of the available space to prevent liquid flow and produce an osmotic pressure to hold the liquid back. If it can

SUBSTITUTESHEET completely dissolve in a small quantity of solvent, it can erode the oil/polymer block and prevent effective operation.

The volume of particulate polymer in the expanded state is critical. We have found loosely packed polymer having a density of about 280 to about 310 grams per litre, preferably about 300 grams per litre, is useful for applications where complete shut-off is not required. This allows improved water flow while providing oil absorbence, such as in prefilters. A normally packed polymer for a shut-off valve preferably has a density of about 310 to about 340 grams per litre, preferably about 320 grams per litre, for a height of about 3 to 10 inches. In all cases, it is important that the volume of the cavity or chamber in which the polymer is placed is less than the volume of the absorbent polymer when 100% saturated so that it cannot invert and dissolve in the organic liquid. A volumetric relationship between the volume of the cavity and that of the absorbent polymer which will allow up to about 60% absorbent capacity of the polymer for a particular solvent or oil is preferred, balanced against depth of bed, rate of expansion (rate of absorption) and rate of water flow.

The absorbent polymer can be used alone or a wick material such as an insoluble polymer fibrous material typified by melt blown polypropylene or a particulate inorganic solid such as sand or expanded silicate can be uniformly mixed with the absorbent polymer in an amount of up to 80% by weight of the mixture, preferably about 65% by weight of the mixture. The method and apparatus of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a vertical section of an embodiment of shut-off insert cartridge; Figure 2 is a vertical section of an embodiment of shut-off valve with prefilter, Figure 2a being a plan view thereof;

SUBSTITUTESHEET Figure 3 is a schematic of a gravity flow drain insert of the invention showing a shut- off chamber with prefilter; Figure 4 is a schematic of a horizontal flow embodiment of the present invention; and Figure 5 is a schematic of a preferred embodiment of filtration and shut-off system of the invention. With reference to Figure l, a self-contained shut-off insert cartridge 80 having a cylindrical wall 82 with annular filter seat 84 for supporting lower circular perforated screen 86 thereon is illustrated. The liquid- permeable layer 88, which can be a permeable textile or open-cell plastic foam, is seated on screen 86 co-extensive therewith and in turn supports the particulate absorbent polymer particles 90 interposed between lower layer 88 and upper layer 92. The particulate polymer absorbent particles such as sold under the trade-mark EXPANDABEAD™ can be blended with a wick material such as particulate insoluble polymer fibrous material, sand or a particulate silicate, e.g. in a ratio of 35% absorbent material and 65% wick material. An upper perforated screen 94 seated on foam layer 92 co-extensive therewith is secured in position by an upper ring 96 welded to wall 82. A gasket ring 97 is frictionally fitted on the exterior of wall 82 and locked in position by upper and lower annular ribs 98, 100.

Turning now to Figure 2, unit 30 comprises a cylindrical housing 40 formed of galvanized steel or a rigid plastic having a lid 42 with a downwardly depending annular flange 44 with a torus gasket 46 adapted to engage the inner surface 48 of housing 40 to make a liquid-tight seal therewith. A central coupling 50 is attached to lid 42 above a flow separator plate 52 suspended below lid 42 by equispaced spacers 54 shown more clearly in Figure 2a.

SUBSTITUTE SHEET A prefilter 56 formed of loosely packed absorbent particles contained in a sock 58 extends across the diameter of upper cavity 60 of housing 40 and rests on upper perforated plate 62 of the shut-off valve 64. Shut- off valve 64 comprises a lower perforated screen 66 suspended on annular filter seat 68, a thin, open cell, liquid-permeable foam layer 70 co-extensive with and seated on perforate screen 66, and a discrete, organic liquid- swellable polymer absorbent 72 which is interposed between lower foam layer 70 and upper foam layer 74 which is co¬ extensive with and abuts upper screen 62.

The discrete polymer absorbent 56 preferably is loosely packed with a density of about 300 grams per litre to function as a prefilter for absorbing small spills of hydrocarbons, emulsions and other organic liquid pollutants to protect shut-off valve 64. These minor amounts of organic liquids would otherwise shorten the useful life of valve 64. The shut-off valve 64 preferably is more densely packed at about 320 grams per litre with a height of at least 3 to 10 inches to ensure absorption and entrapment of organic liquid with swelling of the absorbent polymer to close all pore spaces between the discrete absorbent and thereby shut off water flow therethrough. Both the prefilter 56 and shut-off valve 64 have predetermined volumes in the housing cavity to ensure that the polymer absorbent has a maximum volume upon swelling greater than the predetermined total volume of the cavity, whereby the polymer cannot reach 100% saturation, preferably not more than about 60% saturation. Figure 3 illustrates an embodiment of prefilter and shut-off valve combination 102 adapted for use as an insert in a floor drain. The cartridge 80 (shut-off chamber) and a prefilter 56 are positioned in a drain opening 119 in floor 117. Drain opening 119 has a circular side wall 120 with an annular recess 124 concentric with opening 119. Cartridge 80 has an upper annular flange 122 adapted to seat in recess 124. O-ring gasket 125 provides

SUBSTITUTE SHEET a liquid-tight seal between flange 122 and the wall of recess 124. A removable circular trash basket 127 has an upper peripheral flange 129 adapted to seat on flange 122. The upper prefilter cartridge 56 can be formed of a loosely packed absorbent polymer having a density of about 300 grams per litre and contained in a sock in the upper portion of unit 102. The lower cartridge 80 which functions as a shut-off valve preferably has a more densely packed absorbent polymer at about 320 grams per litre. Figure 4 illustrates a combination baffle chamber 130, prefilter 131 and shut-off valve 132 coupled in series in a horizontal configuration in unit 133 for lateral flow of water to drain 134. Unit 133 is connected to drain 134 by a union connection or quick-release coupling 135 well known in the art. The flow of water is lateral rather than vertical. Since the water level will rise and fall, the nature of the contact between the absorbent and the oil to be absorbed will vary with the total rate of flow. The absorbent materials at the bottom will be consumed before those at the top and the minimum water depth accordingly will rise as the unit ages. To compensate, a baffle 136 introduced forward upstream of the prefilter 131 across the aqueous stream extends from above the minimum water level to about V from the top of the chamber. The baffle will restrict the oil from draining through the unit, thereby extending the life of the unit. If a large accumulation of oil collects upstream of the baffle or a large spill or leak of oil occurs, the water will be displaced down to a level below the bottom edge 138 of the baffle 136 by the column of oil, whereby the baffle will function as an inverted weir, allowing the oil to drain into the unit, thereby activating the absorbent.

Figure 5 is a schematic of an in-line filtration and shut-off system of the invention in which a source of water contaminated with an organic liquid such as a hydrocarbon is subjected to a series of filters to produce

SUBSTITUTESHEET a water effluent that complies with water quality standards for industrial discharge while functioning as a shut-off valve.

An oil spill from oil-bearing equipment 140 is contained in primary containment berm 142 and directed by drain pipe 144 to secondary containment tank 146 having electronic level detector 148. Secondary reservoir containment tank 146 is positioned over tertiary containment berm 150 for surge capacity in the event of actuation of the shut-off valve, to be discussed, a storm surge, or when components are serviced or replaced. Valve 152 is a by-pass valve operatively connected to level detector 148 for opening when a predetermined liquid level is reached in tank 146. Prefilter 154 containing a relatively light density of organic liquid-swellable polymer absorbent of about 300 grams per litre in an amount such that the maximum swelling volume upon saturation with organic liquid is greater than the predetermined volume of the capacity of prefilter 154, whereby the polymer absorbent cannot reach 100 % saturation, functions as an effective hydrocarbon filter for small quantities of absorbable contaminants in water while allowing optimum water flow. Prefilter 154 thus acts to protect shut-off valve 156 in sequence downstream from small oil spills, emulsions, and high concentrations of organic pollutants that could shorten the useful life of valve 156.

Shut-off valve 156 preferably has a somewhat greater density of organic liquid-swellable polymer absorbent than prefilter 154 of about 320 grams per litre in an amount such that maximum swelling volume upon saturation with organic liquid is greater than the predetermined volume of the capacity of prefilter 154, whereby the polymer absorbent cannot reach 100 % saturation. This unit functions as a shut-off valve for large quantities of absorbable contaminants in water.

Particulate filter 160 and carbon filter 162 in series

SUBSTITUTESHEET with and downstream of prefilter 154 and shut-off valve 156 permit production of effluent water for compliance with current water quality standards. Filter 160 preferably contains a 5 micron particulate filter and filter 162 contains activated carbon.

Particulate filter 160 can trap solids as small as 5 microns in diameter to capture PCB's and other organic contaminants which are adsorbed or adhered to the fine particulate solids and which pass through prefilter 154 and shut-off valve 156. The activated carbon filter 162 efficiently removes small concentrations of a wide range of organic pollutants, including PCB's, dissolved oils, fuels and many solvents which are not adsorbed on fine solids.

The present invention permits the important advantage if desired of allowing the use of non cross- linked absorbent polymers in filtration systems and shut- off valves for aqueous streams. The expense of cross- linking polymers thus can be avoided resulting in substantial savings to the user. It will be understood, or course, that modifications can be made in the embodiment of the invention illustrated and described herein without departing from the scope and purview of the invention as defined by the appended claims.

SUBSTITUTE SHEET

Claims

We claim:

1. A method for removal of organic liquids from an aqueous stream passing through a conduit comprising interposing in the conduit a housing having a cavity of predetermined volume though which the aqueous stream must flow, and packing in said cavity a discrete, organic liquid swellable polymer absorbent having a maximum volume upon swelling greater than the predetermined volume of the cavity, whereby the polymer absorbent cannot reach 100% saturation.

2. A method as claimed in claim 1 in which the polymer absorbent is packed in the cavity in a density in the range of about 280 to about 320 grams per litre.

3. A method as claimed in claim l, in which the discrete, organic liquid-swellable polymer absorbent is a particulate cross-linked or non cross-linked polymer, preferably with an irregular shape, which is water insoluble and which swells on contact by absorbing organic liquids such as hydrocarbons including gasoline, fuel oil and diesel fuel, chlorinated solvents such as carbon tetrachloride, aromatic solvents such as benzene, toluene and xylene, and polar compounds such as ethyl acrylate.

4. A method as claimed in claim 3, in which the polymer absorbent will swell to at least four times its volume and not be soluble in less than 20 times its volume.

5. A method as claimed in claim 3, in which the polymer absorbent cannot exceed about 60% saturation.

6. A filter and shut-off valve for removing organic liquids from an aqueous stream and for stopping said aqueous stream upon high contents of organic liquid in said stream comprising: a housing defining a cavity therein, said housing having an inlet end and an outlet end for flow of the aqueous stream therethrough, a permeable restraining means disposed within the cavity adjacent the outlet end, a permeable restraining means disposed within the cavity adjacent the inlet end, a layer of discrete, organic liquid-swellable, poJγ_mer absorbent interposed within the

SUBSTITUTESHEET cavity between the outlet permeable restraining means and the inlet permeable restraining means co-extensive with and substantially filling the cavity between said restraining means, and means for securing the restraining means within the housing to establish and maintain a predetermined volume in the cavity, the polymer absorbent having a maximum swelling volume upon saturation with an organic liquid greater than the predetermined volume of the cavity, whereby the polymer absorbent cannot achieve 100% saturation.

7. A filter and shut-off valve as claimed in claim 6, in which said housing has an upper inlet end and a lower outlet end for flow of the aqueous stream therethrough, said permeable restraining means adjacent the outlet end comprising a lower perforate screen disposed within the cavity adjacent the outlet end, a lower, liquid-permeable textile or open-cell foam layer co-extensive with and seated on the perforate screen, said layer of discrete, organic liquid-swellable polymer absorbent interposed within the cavity co-extensive with and seated on the textile or foam layer, said permeable restraining means adjacent the inlet end comprising an upper, liquid- permeable textile or foam layer co-extensive with and seated on the polymer absorbent layer, an upper perforate screen co-extensive with and seated on the upper textile or foam layer, and means for securing the lower and upper perforate screens within the cavity to establish and maintain a predetermined volume in the cavity.

8. A filter and shut-off valve as claimed in claim 6, in which said housing has an inlet end on one side and an outlet end on the opposite side for substantially horizontal flow of the aqueous stream through the cavity,said permeable restraining means adjacent the outlet and comprising a perforate screen disposed within the cavity adjacent the outlet end, a liquid-permeable textile or open-cell foam layer co-extensive with and seated against the perforate screen, said layer of discrete,

SUBSTITUTE SHEET organic liquid-swellable polymer absorbent interposed within the cavity coextensive with and seated against the textile or foam layer, said permeable restraining means adjacent the inlet end comprising liquid-permeable textile or open-cell foam layer co-extensive with and seated against the polymer absorbent layer at the inlet end, a perforate screen co-extensive with and seated against the textile or foam layer at the said inlet end, and means for securing the perforate screens within the housing to establish and maintain a predetermined volume in the cavity between the perforate screens.

9. A filter and shut-off valve as claimed in claim 6, 7, or 8, in which the discrete, organic liquid-swellable polymer absorbent is a particulate cross-linked or non cross-linked polymer, with an irregular shape, which is water insoluble and which swells on contact by absorbing organic liquids such as hydrocarbons including gasoline, fuel oil and diesel fuel, chlorinated solvents such as carbon tetrachloride, aromatic solvents such as benzene, toluene and xylene, and polar compounds such as ethyl acrylate.

10. A filter and shut-off valve as claimed in claim

9, in which the polymer absorbent will swell to at least four times its volume and not be soluble in less than 20 times its volume.

11. A filter and shut-off valve as claimed in claim

10, in which the polymer absorbent cannot exceed about 60% saturation.

12. A filter and shut-off valve as claimed in claim 9, in which said polymer absorbent is uniformly mixed with an insoluble polymer fibrous material or a particulate inorganic solid wick material, said wick material comprising up to 80% by weight of the polymer absorbent- wick material mixture.

13. A filter and shut-off valve is claimed in claim 9, in which said polymer absorbent is uniformly mixed with fibrous melt blown polypropylene, sand or particulate

SUBSTITUTE SHEET expanded silicate wick material, said wick material comprising about 65% by weight of the polymer absorbent- wick material mixture.

14. A filter and shut-off valve as claimed in claim 8, which additionally comprises a vertical baffle positioned upstream of the filter and extending across the aqueous stream in proximity to the filter, said baffle having a lower inverted weir edge, whereby organic liquids collecting upstream of the baffle or a large spill of oil will form a column of oil which will displace the water downwardly for drainage of oil into the filter and shut-off valve.

15. A filter and shut-off valve removing organic liquids from an aqueous stream and for stopping said aqueous stream upon high contents of organic liquid in said stream comprising a filter chamber and a shut-off chamber in series, said filter chamber defining a cavity therein and having discrete, organic liquid-swellable polymer absorbent disposed in said cavity with a density in the range of about 280 to 310 grams per litre, and said shut- off chamber defining a cavity therein having a discrete, organic liquid-swellable polymer absorbent in said cavity with a density in the range of 310 to 340 grams per litre, the polymer absorbent in the filter chamber and in the shut-off chamber having a maximum swelling volume upon saturation with the organic liquid relative to the volumes of the cavities whereby the polymer absorbent cannot achieve 100% saturation.

SUBSTITUTESHEET