WO2021014261A1 - Gravity filter filtering device for softening and purifying drinking water - Google Patents

Gravity filter filtering device for softening and purifying drinking water Download PDF

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Publication number
WO2021014261A1
WO2021014261A1 PCT/IB2020/056454 IB2020056454W WO2021014261A1 WO 2021014261 A1 WO2021014261 A1 WO 2021014261A1 IB 2020056454 W IB2020056454 W IB 2020056454W WO 2021014261 A1 WO2021014261 A1 WO 2021014261A1
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WO
WIPO (PCT)
Prior art keywords
filtering device
filter element
flow distributor
water flow
ion
Prior art date
Application number
PCT/IB2020/056454
Other languages
French (fr)
Inventor
Alexander MASLYUKOV
Viktor SAPRYKIN
Vladimir MASLYUKOV
Alexander PECHKUROV
Anna BREKHOVA
Roman PODOBEDOV
Jürgen JOHANN
Original Assignee
Bwt Barrier Rus Jsc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bwt Barrier Rus Jsc filed Critical Bwt Barrier Rus Jsc
Priority to EP20747116.0A priority Critical patent/EP4003919A1/en
Publication of WO2021014261A1 publication Critical patent/WO2021014261A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C02F1/003—Processes for the treatment of water whereby the filtration technique is of importance using household-type filters for producing potable water, e.g. pitchers, bottles, faucet mounted devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D27/00—Cartridge filters of the throw-away type
    • B01D27/02—Cartridge filters of the throw-away type with cartridges made from a mass of loose granular or fibrous material
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C02F2001/425—Treatment of water, waste water, or sewage by ion-exchange using cation exchangers
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/36—Organic compounds containing halogen
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2201/00—Apparatus for treatment of water, waste water or sewage
    • C02F2201/002—Construction details of the apparatus
    • C02F2201/006—Cartridges
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/22—Eliminating or preventing deposits, scale removal, scale prevention
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2307/00—Location of water treatment or water treatment device
    • C02F2307/04—Location of water treatment or water treatment device as part of a pitcher or jug

Definitions

  • the invention relates to gravity-type filtering devices for softening and purifying drinking water and can be used to improve the quality of drinking water purification in household pitcher-type filters.
  • Household filters for the treatment of drinking water are currently widely used among the population as an alternative to bottled drinking water.
  • the most popular among them are gravity filters in the form of pitcher-type filters that are distinguished by their simple design, low price, and the fact that they do not require connection to pressurized water systems.
  • Pitcher-type filters consist of a container with a intake funnel in the upper part thereof, into which the water to be treated is poured, and a filtering device (cartridge), tightly connected to the funnel.
  • pitcher-type filters perform the task of purifying drinking water from the most common toxic contaminants - chlorine and compounds thereof, organic contaminants, in particular organochlorine compounds, and heavy metals.
  • Some filters of this type additionally soften the hard source water by removing calcium and magnesium cations therefrom, as well as bicarbonate ions thereof.
  • Hardness Unit or 2 - 10 mEq/l or hard water (> 10 °dH according to GOST 31865-2012 "Water.
  • Hardness Unit or more than 10 mEq/l
  • RU 2437703, 201 1 ; RU 2617775, 2017; series cartridge BARRIER-Hardness of JSC BWT-Barrier RUS) fail to provide for consistent softening of water during their operation: at the beginning of the filtering device's service life, water is subject to excessive softening: the concentration of Ca ++ and Mg ++ cations is reduced by 80 - 100 %, which makes the water excessively soft, thereby adversely affecting human health and causing a poor taste; and in the course of the further service life of the filtering device the water is softened not sufficiently, by 10 to 15 %, which in fact keeps it in the category of "moderately hard water" or "hard water”.
  • This inconsistency of water softening is due to the design of the filtering devices which comprise filter elements in the form of a plastic vessel that includes a mixture of granular and/or fiber sorbents and materials, including softeners - cation-exchange resins.
  • the water to be treated passes vertically downward through a layer of compacted sorbent material thereby contacting the surface of granules of a cation-exchange resin without possibility to escape, which results in an almost complete extraction of calcium cations and magnesium cations and bicarbonate ions thereof from the water, resulting in excessive softening at the beginning of the service life.
  • a sorption capacity for cations of calcium, magnesium, and bicarbonate ions thereof developed by the cation- exchange resin in the course of further operation of the filtering device is the reason for insufficient softening of the water.
  • Filtering devices are known (patent RU 2163829 C1 , 03/10/2001 ; patent RU 2252062 C2, 05/20/2005), in which the design of the plastic vessel allows the water to be purified to pass through a mixture of granular and/or fiber sorbent and filtering materials from the bottom upwards, thereby loosening the layer of sorbent and fiber materials. This design is intended to facilitate the release of air from the filtering device to thereby ensure stable filtration rates.
  • Drawbacks of such filtering devices are their complex design and the fact that they are not intended for softening water.
  • Filtering devices with the function of partially softening water are known (patent RU 2526377 C1 , 08/20/2014; patent RU 2540159 C1 , 02/10/2015; patent RU 2538746 C2, 01/10/2015), in which the water to be treated flows in radial and vertical (top to bottom) directions in the softening zone.
  • This is achieved by integrating an additional softening unit (second functional zone) into the design of the filtering device, which is in the form of a separate body having openings in the vertical wall and in the cover, which serve as a flow distributor for the water to be treated.
  • the additional softening unit is disposed above the main (first) functional zone, which comprises a plastic vessel (main body) including a mixture of granular and/or fiber sorbent and filtering materials intended to purify the water from contaminants, in particular chlorine, organochlorine compounds and heavy metals.
  • the water is partially softened due to the incomplete contact with the surface of the softener substance due to the absence of a dense sorbent layer, which is facilitated by partial loosening thereof by the horizontal and vertical (top to bottom) flow of the water, and in this way a mitigation in the excessive softening of water is achieved, as well as an increase in the softening capacity.
  • the aforementioned filtering devices with the function of partially softening water have a complex design, since they comprise complex polymer parts and assemblies that are difficult to manufacture, and the assembling of such a filtering device is cumbersome.
  • the small volume of the second functional zone intended for softening the water does not allow to hold a sufficient amount of softener therein to provide a water softening capacity that is satisfying for the consumer (150 - 200 liters). Therefore, such filtering devices have not found practical application yet.
  • one device (patent RU 2526377 C1 , 08/20/2014) was selected as a prototype for the present invention, which provides a mitigation of excessive water softening and an increase in the softening capacity due to multidirectional water flows in the softening functional zone.
  • the filtering device prototype consists of a fixing element and a filter element consisting of two separate functional zones, wherein the upper functional zone (softening zone) comprises a separate housing with an inner cavity filled with filtering (softening) material, and flow distributors for the water to be treated in the form of openings of varying shapes and sizes provided in the side walls and in the housing cover, and wherein the lower functional zone is a plastic housing provided below the body of the upper, second functional zone and includes filtering and sorbent substances intended for water purification.
  • the upper functional zone softening zone
  • the lower functional zone is a plastic housing provided below the body of the upper, second functional zone and includes filtering and sorbent substances intended for water purification.
  • the filtering device prototype works as follows: the water to be treated flows from the filter funnel through the openings of the flow distributor of the housing of the second functional zone into the housing of the second functional zone where it is partially softened by ion exchange using a softener, namely a cation-exchange resin in H + or Na + form. Subsequently, the water flows through an opening in the lower part of the housing of the second functional zone and into the housing of the first functional zone, where it is purified of toxic contaminants. The softened and purified water flows through the lower opening of the housing of the first functional zone and into the bottom area of the pitcher filter which is intended to hold purified water.
  • a softener namely a cation-exchange resin in H + or Na + form
  • Drawbacks of the filtering device prototype are similar to those of other filtering devices with the function of partially softening water, such as complexity of design and manufacture, and insufficient water softening capacity for the consumer due to the small volume of the softening functional zone.
  • a technical object of the present invention is to provide a gravity-type filtering device for softening and purifying drinking water which has a simplified design and which provides an increased capacity for stable softening of water while maintaining highly effective filtering capability.
  • the proposed gravity filter filtering device for softening and purifying drinking water which comprises a system for fixing the filtering device to the filter funnel, which has openings for inlet of water to be treated and for outlet of air; a filter element made of porous block material in the form of a hollow vertical vessel having a porous or hermetically sealed bottom, and arranged therein, a layer of ion-exchange material and a treatment water flow distributor comprising a fixing element, wherein the layer of ion-exchange material is disposed between an inner surface of the filter element and the treatment water flow distributor which is in the form of a vertical or horizontal body having openings of a size smaller than the particle size of the ion-exchange material.
  • the porous block material of the filter element is obtained by compression under heating of a mixture of powdered components comprising activated carbon particles and a polymer binder, and the system for fixing the filtering device is connected to the filter element by a hermetically sealing connection.
  • the proposed filtering device comprises means for fixing the filtering device to the filter funnel, a filter element which includes filter material for purifying the water to be treated, a material for softening the water, and a treatment water flow distributor comprising a fixing element.
  • the material for softening the water is disposed between the inner surface of the filter element and the treatment water flow distributor and comprises a layer of ion-exchange material selected from the class of weakly or strongly acidic cation exchange materials in the H + or Na + form with a sorption exchange capacity of 0.5 - 5 mEq/ml with a particle size from 0.1 mm to 2.0 mm and/or inorganic cation exchange materials selected from the classes of natural or synthetic zeolites, aluminum silicates, silica gels and sulfonated carbon, and fills 20 to 90 % by volume of the inner cavity of the filter element, and the filter material of the filter element intended for water purification comprises a filter element body made of a porous block material in the form of a hollow vertical
  • the treatment water flow distributor comprising the fixing element is disposed in the inner cavity of the filter element and is made of polymer material produced by injection molding or is made of porous block material produced by extrusion or hot pressing with a compression ratio of 12 - 25 % during molding from a mixture of finely dispersed materials comprising activated carbon and a polymer binder with a particle size of the activated carbon and the polymeric binder from 0.1 mm to 1.5 mm, preferably 0.5 mm to 1 mm, and with a ratio of activated carbon to polymer binder of (75 - 95) : (5 - 25) wt%, at a temperature that is higher by 10 - 40 °C than the softening temperature of the polymer binder, or from inorganic finely dispersed materials, for example from the class of silicon oxides with a particle size from 0.1 mm to 1.5 mm, by a compression sintering process, in the form of a single vertical or horizontal body, or in the form of a plurality of vertical bodies with
  • the fixing element of the treatment water flow distributor is made either in the form of a sleeve made of an elastic material tightly engaging on an upper portion of the outer surface of the flow distributor and on an upper portion of the inner surface of the filter element body, or in the form of a collar made of a polymer material by injection molding integrally with the treatment water flow distributor and hermetically joined to an upper portion of the inner surface of the filter element body using either melted polymer or any other adhesive material.
  • a horizontal treatment water flow distributor is made of a mesh or fabric having openings that are smaller than the particle size of the ion-exchange material, with a fixing element in the form of a plastic collar joined to the inner surface or to the end face surface of the filter element body.
  • the system for fixing the filtering device which has openings for inlet of the water to be treated and for outlet of air is made in a form that allows the filtering device to be hermetically sealed to the body of the filter funnel and is either in the form of a threaded unit that is connected to a threaded portion of the funnel, or in the form of a rim which comprises elements for tightly fitting to the funnel opening funnel opening, and is connected to the filter element body by an adhesive joint using either melted polymer or any other adhesive material, or by a mechanical connection engaging on the inner or outer or both inner and outer vertical wall surface(s) of the filter element.
  • the distinctive feature of the claimed invention is a fundamentally novel, simpler design of a filtering device compared to the prototype, which is intended to perform two water treatment processes - softening and purification.
  • the simplicity of design allows to combine two functional zones (two processes) in a single filter element body that performs two functions: the function of the filter and sorbent material and the function of the filter element casing.
  • the functional zone intended for the process of water softening has a large volume, which makes it possible to accommodate therein a much larger amount of ion-exchange material compared to the prototype, which provides a satisfactory water softening capacity of 150-200 liters for the consumer and, what is fundamentally important, this comes in combination with the design of the treatment water flow distributor which allows multidirectional water flows in the softening zone, which causes loosening of the softener layer, which virtually eliminates the effect of excessive softening during initial stages and ensures acceptable softening during subsequent stages of water treatment service life while maintaining a highly effective filtering capability.
  • the end plate (hermetically sealing bottom) may be made of a polymer such as polyethylene or polypropylene.
  • FIG. 1 is a schematic sectional view of a filter pitcher comprising a filtering device according to a first embodiment of the invention
  • FIG. 2 is a schematic sectional view of a filter pitcher with a filtering device according to a second embodiment of the invention
  • FIG. 3 is a schematic sectional view of a filter pitcher with a filtering device according to a third
  • FIGS. 4 to 8 show schematic sectional views of different further embodiments of filtering devices
  • FIGS.10 and 1 1 each show a vertical section and a cross-sectional view of further embodiments of filtering devices according to the invention.
  • FIG. 1 is a schematic view of a filter pitcher 1 comprising a funnel 2 and a filtering device 3 arranged therein, which comprises a filter element 4 in the form of a hollow cylinder with ion-exchange material 6 and a hermetically sealing bottom end plate 7, and a treatment water flow distributor 5 in the form of a hollow cylinder, which comprises a fixing element 1 1.
  • FIG. 2 is a schematic view of a filter pitcher 1 comprising a funnel 2 and a filtering device 3 arranged therein, which comprises a filter element 4 in the form of a hollow cylinder having a porous bottom, with ion-exchange material 6 inside the filter element 4, and comprising a treatment water flow distributor 5 in the form of a hollow cylinder comprising a fixing element 1 1 and having a porous bottom.
  • FIG. 3 is a schematic view of a filter pitcher 1 comprising a funnel 2 and a filtering device 3 arranged therein, which comprises a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with an ion-exchange material 6 accommodated therein, and a treatment water flow distributor 5 in the form of a mesh comprising a fixing element 1 1 in the form of a collar.
  • FIG. 3 is a schematic view of a filter pitcher 1 comprising a funnel 2 and a filtering device 3 arranged therein, which comprises a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with an ion-exchange material 6 accommodated therein, and a treatment water flow distributor 5 in the form of a mesh comprising a fixing element 1 1 in the form of a collar.
  • FIG. 3 is a schematic view of a filter pitcher 1 comprising a funnel 2 and a filtering device 3 arranged therein, which comprises a filter element 4 in
  • a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with an ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and a treatment water flow distributor 5 in the form of a hollow cylinder made of porous block material.
  • the porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 11 made of elastic material.
  • FIG. 5 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a porous bottom, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and a treatment water flow distributor 5 in the form of a hollow cylinder made of porous block material with openings in the bottom.
  • the porous block material of the filter element 4 is connected to the fixing system of the filtering device by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 1 1 made of elastic material.
  • FIG. 6 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with walls of differing thickness and with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and comprising a treatment water flow distributor 5 in the form of a hollow cylinder that has openings of 1 - 5 mm in size in every direction, and with a water-permeable mesh arranged around the outer surface thereof and having mesh cells that are smaller than the particle size of the ion-exchange material.
  • the porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 11 made of elastic material.
  • FIG. 7 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and comprising a treatment water flow distributor 5 in the form of a hollow cylinder that has openings of 1 - 5 mm in size in every direction, and with an open-porous foam polymer disposed in a water-permeable material having cells that are smaller than the particle size of the ion-exchange material.
  • the porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 1 1 made of elastic material.
  • FIG. 8 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and including a treatment water flow distributor 5 in the form of a hollow truncated inverse cone made of porous block material.
  • the porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the flow distributor 5 is connected to the filter element by a sleeve 1 1 made of elastic material.
  • FIG. 9 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and including a treatment water flow distributor 5 in the form of a hollow cylinder with walls of differing thickness made of porous block material obtained by compression sintering of silica powder.
  • the porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 11 made of elastic material.
  • FIG. 10 shows a filtering device 3 (FIG. 10a vertical section; FIG. 10b section along A-A) with a filter element in the form of a hollow vertical vessel 4 having an elliptical cross-sectional shape with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a rim 9 comprising elements for a tight fit with the funnel socket, and including two treatment water flow distributors 5 in the form of hollow cylinders with openings in vertical walls.
  • the porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributors 5 are connected to the filter element by a sleeve 1 1 made of elastic material.
  • FIG. 1 1 shows a filtering device 3 (vertical section; section along A-A) with a filter element in the form of a hollow vertical vessel 4 having an elliptical cross-sectional shape with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system for the filtering device in the form of a rim 9 comprising elements for fitting to the funnel socket, and including a treatment water flow distributor 5 in the form of a hollow vertical vessel with openings in the vertical wall.
  • the porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element using a sleeve 1 1 made of elastic material.
  • source water from the inlet funnel 2 of the filter pitcher 1 passes through the hole in the fixing system of the filtering device in the form of a threaded assembly 8 or in the form of a rim comprising elements for fitting to the funnel socket 2 and into the treatment water flow distributor 5 and flows through the lower part thereof, which has openings for water outlet, and enters the water softening zone which contains the ion-exchange material 6 that fills 20 - 90 % of the inner volume of the filter element body.
  • the softened water enters the zone of porous block material of the filter element 4 directly adjacent to the treatment water softening zone which is provided in the form of the filter element body 4 made of porous block material in the form of a hollow vertical vessel having walls of consistent thickness or differing thickness with pores of a size that is smaller than the particle size of the ion-exchange material.
  • the softened and purified water gets into the lower part of the filter pitcher 1 intended for holding clean water.
  • the filter element of the filtering device is made with a wall thickness in a range from 5 mm to 25 mm and a height from 20 mm to 120 mm.
  • the boundary values of the range of wall thicknesses are selected because if the wall thickness is less than 5 mm, the filter element has insufficient mechanical strength.
  • a wall thickness of the filter element of more than 25 mm adversely affects the filtration rate due to significant hydrodynamic resistance.
  • a filter element with a wall height of less than 20 mm does not provide for effective water purification due to the small contact surface and volume of sorbent material; with a wall height of more than 120 mm, it becomes problematic to place such a filtering device in a pitcher-type filter.
  • the selected embodiment of the filter element in the form of a hollow vertical vessel provides a predetermined water filtration rate by the filter element, which is proportional to the filtration surface area and which is minimal for a filter element in the form of a hollow cylinder with a hermetically sealed bottom end plate, and which is maximal for a filter element with a porous bottom and complex cross- sectional shape, or by virtue of its manufacturing technology: filter elements in the form of a hollow cylinder with an end plate, a hollow vertical vessel with an oval cross-sectional shape with an end plate, or a complex contour with an end plate are produced by an extrusion process; filter elements in the form of a hollow cylinder with a porous bottom, a hollow vertical vessel with an oval cross-sectional shape, or a complex contour with a porous bottom are produced by a hot pressing process.
  • the manufacturing process of the filter block is conducted at a temperature that is higher by 10 - 40 °C than the softening temperature of the polymer binder.
  • a temperature that is higher by less than 10 °C than the softening temperature of the polymer binder the formed block material of the filter element will lack strength, and with a temperature of more than 40 °C higher than the softening temperature of the polymer binder, a significant surface area of the sorbent will be blocked due to flowing of the polymer binder.
  • the compression ratio in a range of 12 - 25 % for a mixture of materials when producing the filter block by extrusion or by hot pressing is selected because with a compression ratio of less than 12 % the filter block will not have sufficient mechanical strength and will not be able to fulfill the function of a housing, and with a compression ratio of more than 25 % the pores resulting in the volume of the filter block material will be small and will cause high hydrodynamic resistance and, consequently, a reduction in the filtration rate.
  • the polymer binder is chosen from the classes of polyolefins (e.g. low pressure polyethylene, high pressure polyethylene, polypropylene) and polyesters (polyethylene terephthalate) or copolymers thereof (e.g. polyethylene vinyl acetate copolymer) due to their chemical inertness and insolubility in water on the one hand, and on the other hand due to their sufficiently low softening temperatures, which allows to intensify the manufacturing process of the filter element of the inventive filtering device in the form of a porous block material.
  • polyolefins e.g. low pressure polyethylene, high pressure polyethylene, polypropylene
  • polyesters polyethylene terephthalate
  • copolymers thereof e.g. polyethylene vinyl acetate copolymer
  • the embodiment of the filter element in the form of a hollow cylinder with walls of differing thickness and with a hermetically sealed bottom ensures consistent passage of the water to be purified through the walls of the filter element over the entire height thereof, since the increase in pressure of the water column in the cavity of the filter element from top to bottom is compensated by an increasing resistance to the passage of water through the walls due to the corresponding increase in the wall thickness of the filter element.
  • the porous block material of the filter element is made using activated carbons with a iodine index of more than 1000 mg/I, since such carbons ensure effective sorption and therefore purification of water over a significant service life, and all components (sorbent and polymer binder) are used in powder form with a particle size from 0.05 to 0.5 mm, preferably from 0.07 to 0.15 mm. If the particle size of the activated carbon and the polymer binder is less than
  • the hydrodynamic resistance of the porous block material increases, which leads to a decrease of the filtration rate. If the particle size of the activated carbon and polymer binder is more than 0.5 mm, the effectiveness of water purification decreases due to a decrease in the actual filtration (sorption) surface area of the sorbent particles.
  • 0.5 to 5 mEq/ml is because materials with an exchange capacity of less than 0.5 mEq/ml would have to be used in an amount incompatible with the volume of the filter element to achieve sufficient effectiveness of water softening over a long softening service life, whereas materials with an exchange capacity of more than 5 mEq/ml are expensive and therefore cannot be used in mass-produced filters.
  • the reason for filling 20 - 90 % of the inner cavity of the filter element with ion-exchange material is that if it is filled by less than 20 %, most of the treatment water flow will get into the filter zone without having contacted the ion-exchange material; if it is filled by more than 90 %, the layer of ion-exchange material will not be loose enough.
  • the particle size of the ion-exchange material is selected in a range from 0.1 to 2.0 mm because particles with a size of less than 0.1 mm might clog the pores of the porous block material of the filter element and thereby block operation thereof; and if the particle size of the ion- exchange material is more than 2 mm, the water contact surface area would be reduced and effective softening of the water will not occur.
  • the selection of the height of the treatment water flow distributor in a range from 1 to 100 % of the height of the filter element body is related to the formation of multidirectional water flows in the softening zone: with a height of less than 1 % of the height of the housing, such flows are not formed.
  • the minimum height of the treatment water flow distributor of 1 % corresponds to a minimum width of the mesh with a collar arranged on the upper end of the filter element body, performing the function of a flow distributor for the water to be treated.
  • the reason for choosing a particle size of the activated carbon and polymer binder in the range from 0.1 to 1.5 mm and a ratio of activated carbon to polymer binder of (75-95):(5-25) wt%, and for using material from the class of silicon oxide with a particle size from 0.1 to 1.5 mm is to obtain an optimal pore size when molding the porous body of the treatment water flow distributor: on the one hand, the pores should be smaller than the particle size of the ion-exchange material, on the other hand, the pore size must provide for a water passage rate through the treatment water flow distributor greater than or equal to the water passage rate through the walls of the filter element.
  • the reason for choosing the temperature range for producing the porous block material of the flow distributor by extrusion or by hot pressing 10 - 40 °C higher than the softening temperature of the polymer binder is that at a temperature of less than 10 °C higher than the softening temperature of the polymer binder the formed block material of the treatment water flow distributor will not have sufficient mechanical strength, and at a temperature of more than 40 °C higher than the softening temperature of the polymer binder, the pores in the walls of the treatment water flow distributor will be blocked as a result of flowing of the polymer binder.
  • the shape of the treatment water flow distributor in the form of a vertical hollow body with a cross section in the form of a circle, square, ellipse, or any other shape, or in the form of a hollow inverse pyramid or inverse cone, or in the form of a hollow truncated inverse pyramid is chosen so as to follow the shape of the filter element body, which may also be made in the form of a vertical hollow body with a cross section in the form of a circle, square, ellipse or any other shape, or in the form of a hollow inverse pyramid or inverse cone, or in a hollow truncated inverse pyramid, which ensures the consistency of the flow of water to be treated in the softening zone.
  • the reason for providing the openings in the vertical walls of the treatment water flow distributor at a height of not more than 60 % from the bottom level of the treatment water flow distributor is because if the openings are located at a height of more than 60 % from the bottom level of the treatment water flow distributor, the vertical component of water flow is not ensured over the entire height of the softening zone (vertically upward), which will cause insufficient loosening of the layer of ion-exchange material, and therefore insufficient mitigation of excessive softening.
  • the reason for choosing the size of the openings in the lateral wall of the treatment water flow distributor in the range from 3 to 5 mm if a porous material with a pore size smaller than the particle size of the ion-exchange material is fixed on the outer surface or inside thereof is because this range is optimal from the point of view of simplicity of the manufacturing technology of the treatment water flow distributor.
  • the filtering device comprises a filter element in the form of a hollow cylinder with a hermetically sealing bottom end plate, and a fixing system in the form of a threaded unit that is connected to the filter element by an adhesive joint using melted polyethylene (FIG. 4).
  • Dimensions of the filter element are as follows: height 70 mm, outer diameter 62 mm, wall thickness 14 mm.
  • the starting mixture for producing the filter element comprises the following composition: 85 wt% of activated carbon; 15 wt% of polymer binder as a mixture of low pressure polyethylene and polyethylene terephthalate (10:90) wt% with a softening temperature of 1 15 °C.
  • the particle size of the mixture components is from 0.08 to 0.1 mm.
  • the porous block material of the filter element body is produced by extrusion with a compression ratio of 15 % during molding at a temperature of 145 °C.
  • the filter element is filled to 80 % of its free volume (inner volume of the filter element minus the volume of the flow distributor) with a weakly acid cation- exchange material of the H + type with a particle size from 0.3 to 1.0 mm.
  • the treatment water flow distributor is made in the form of a hollow tube made of high pressure polyethylene by injection molding, with a height of 70 mm, an inner diameter of 8 mm, and an outer diameter of 10 mm, and with openings of 0.2 mm in diameter in the lateral wall thereof at a height from 1 to 50 mm from the bottom of the tube.
  • the treatment water flow distributor is tightly connected to an upper portion of the inner surface of the filter element by a sleeve made of an elastic material such as silicone.
  • the filter element was placed in the funnel of the filter pitcher and tests were conducted regarding the effectiveness of softening and the effectiveness of water purification. The effectiveness of water softening and purification was assessed in compliance with GOST 31952-2012 WATER TREATMENT DEVICES - General requirements for effectiveness and methods for its determination.
  • the filtering device provides for consistent softening and high effectiveness of water purification from the most common contaminants over its service life which is satisfactory for the consumer.
  • a gravity-type filtering device for softening and purifying drinking water which is of simplified design and provides increased operational capacity for softening water (at least 200 liters), at the same achieving a softening effectiveness of at least 40 %, which is sufficient from a consumer's point of view, while maintaining highly effective water purification from toxic contaminants of up to 98 %.

Abstract

The invention is intended for softening and purifying drinking water and can be used to improve the quality of drinking water purification in household pitcher-type filters. A gravity filter filtering device is proposed for the softening and purification of drinking water, which comprises a fixing system for fixing the filtering device in the filter funnel, which has openings for inlet of water to be treated and outlet of air, a filter element made of porous block material in the form of a hollow vertical vessel having a porous or hermetically sealed bottom, and arranged therein, a layer of ion-exchange material and a treatment water flow distributor comprising a fixing element, wherein the layer of ion-exchange material is disposed between an inner surface of the filter element and the treatment water flow distributor which is in the form of a vertical or horizontal body having openings of a size that are smaller than the particle size of the ion-exchange material. The porous block material of the filter element is obtained by compression under heating of a mixture of powdered components comprising activated carbon particles and a polymer binder. The system for fixing the filtering device is connected to the filter element in a hermetically sealing manner. The technical result is a simplified design, while providing increased capacity for stable softening of water and while maintaining highly effective water purification.

Description

GRAVITY FILTER FILTERING DEVICE FOR SOFTENING AND PURIFYING DRINKING WATER
The invention relates to gravity-type filtering devices for softening and purifying drinking water and can be used to improve the quality of drinking water purification in household pitcher-type filters.
Prior art
Household filters for the treatment of drinking water are currently widely used among the population as an alternative to bottled drinking water. The most popular among them are gravity filters in the form of pitcher-type filters that are distinguished by their simple design, low price, and the fact that they do not require connection to pressurized water systems.
Pitcher-type filters consist of a container with a intake funnel in the upper part thereof, into which the water to be treated is poured, and a filtering device (cartridge), tightly connected to the funnel.
Usually pitcher-type filters perform the task of purifying drinking water from the most common toxic contaminants - chlorine and compounds thereof, organic contaminants, in particular organochlorine compounds, and heavy metals. Some filters of this type additionally soften the hard source water by removing calcium and magnesium cations therefrom, as well as bicarbonate ions thereof.
Reduction of the total water hardness is extremely important for consumers who receive water from drinking water sources of medium hardness (2 - 10 °dH according to GOST 31865-2012 "Water.
Hardness Unit" or 2 - 10 mEq/l) or hard water (> 10 °dH according to GOST 31865-2012 "Water.
Hardness Unit" or more than 10 mEq/l), since such water contributes to the development of a number of human diseases (formation of urinary stones, deposition of salts in joints and vessels, etc.), has an unpleasant taste, transfers this unpleasant taste to drinks prepared therefrom (tea, coffee) and causes scale deposits on heating elements of household appliances.
The reduction of water hardness using pitcher-type filters is facilitated by the presence of granular cation-exchange resins in the filtering devices, which perform the function of exchanging the H+ and Na+ cations contained therein for the Ca++ and Mg++ cations and bicarbonate ions thereof, which are contained in the water to be softened and which are responsible for water hardness.
However, most of prior art pitcher-type filters with replaceable filtering devices (patent DE
000002919901 , 1980; WO 1998/017582, 1998; RU 2236279, 2004; WO 2005/118481 , 2005;
WO 2005/1 18104, 2005; WO 2005/1 18482, 2005; RU 2617775, 2017; RU 2252062, 2005;
RU 2437703, 201 1 ; RU 2617775, 2017; series cartridge BARRIER-Hardness of JSC BWT-Barrier RUS) fail to provide for consistent softening of water during their operation: at the beginning of the filtering device's service life, water is subject to excessive softening: the concentration of Ca++ and Mg++ cations is reduced by 80 - 100 %, which makes the water excessively soft, thereby adversely affecting human health and causing a poor taste; and in the course of the further service life of the filtering device the water is softened not sufficiently, by 10 to 15 %, which in fact keeps it in the category of "moderately hard water" or "hard water".
This inconsistency of water softening is due to the design of the filtering devices which comprise filter elements in the form of a plastic vessel that includes a mixture of granular and/or fiber sorbents and materials, including softeners - cation-exchange resins. In such filtering devices, the water to be treated passes vertically downward through a layer of compacted sorbent material thereby contacting the surface of granules of a cation-exchange resin without possibility to escape, which results in an almost complete extraction of calcium cations and magnesium cations and bicarbonate ions thereof from the water, resulting in excessive softening at the beginning of the service life. Furthermore, a sorption capacity for cations of calcium, magnesium, and bicarbonate ions thereof developed by the cation- exchange resin in the course of further operation of the filtering device is the reason for insufficient softening of the water.
Filtering devices are known (patent RU 2163829 C1 , 03/10/2001 ; patent RU 2252062 C2, 05/20/2005), in which the design of the plastic vessel allows the water to be purified to pass through a mixture of granular and/or fiber sorbent and filtering materials from the bottom upwards, thereby loosening the layer of sorbent and fiber materials. This design is intended to facilitate the release of air from the filtering device to thereby ensure stable filtration rates. Drawbacks of such filtering devices are their complex design and the fact that they are not intended for softening water.
Filtering devices with the function of partially softening water are known (patent RU 2526377 C1 , 08/20/2014; patent RU 2540159 C1 , 02/10/2015; patent RU 2538746 C2, 01/10/2015), in which the water to be treated flows in radial and vertical (top to bottom) directions in the softening zone. This is achieved by integrating an additional softening unit (second functional zone) into the design of the filtering device, which is in the form of a separate body having openings in the vertical wall and in the cover, which serve as a flow distributor for the water to be treated. The additional softening unit is disposed above the main (first) functional zone, which comprises a plastic vessel (main body) including a mixture of granular and/or fiber sorbent and filtering materials intended to purify the water from contaminants, in particular chlorine, organochlorine compounds and heavy metals. When passing through the second functional zone, the water is partially softened due to the incomplete contact with the surface of the softener substance due to the absence of a dense sorbent layer, which is facilitated by partial loosening thereof by the horizontal and vertical (top to bottom) flow of the water, and in this way a mitigation in the excessive softening of water is achieved, as well as an increase in the softening capacity.
However, the aforementioned filtering devices with the function of partially softening water have a complex design, since they comprise complex polymer parts and assemblies that are difficult to manufacture, and the assembling of such a filtering device is cumbersome. Moreover, the small volume of the second functional zone intended for softening the water does not allow to hold a sufficient amount of softener therein to provide a water softening capacity that is satisfying for the consumer (150 - 200 liters). Therefore, such filtering devices have not found practical application yet.
From the filtering devices with the function of partially softening water as mentioned above, one device (patent RU 2526377 C1 , 08/20/2014) was selected as a prototype for the present invention, which provides a mitigation of excessive water softening and an increase in the softening capacity due to multidirectional water flows in the softening functional zone. The filtering device prototype consists of a fixing element and a filter element consisting of two separate functional zones, wherein the upper functional zone (softening zone) comprises a separate housing with an inner cavity filled with filtering (softening) material, and flow distributors for the water to be treated in the form of openings of varying shapes and sizes provided in the side walls and in the housing cover, and wherein the lower functional zone is a plastic housing provided below the body of the upper, second functional zone and includes filtering and sorbent substances intended for water purification. The filtering device prototype works as follows: the water to be treated flows from the filter funnel through the openings of the flow distributor of the housing of the second functional zone into the housing of the second functional zone where it is partially softened by ion exchange using a softener, namely a cation-exchange resin in H+ or Na+ form. Subsequently, the water flows through an opening in the lower part of the housing of the second functional zone and into the housing of the first functional zone, where it is purified of toxic contaminants. The softened and purified water flows through the lower opening of the housing of the first functional zone and into the bottom area of the pitcher filter which is intended to hold purified water.
Drawbacks of the filtering device prototype are similar to those of other filtering devices with the function of partially softening water, such as complexity of design and manufacture, and insufficient water softening capacity for the consumer due to the small volume of the softening functional zone.
Object and Summary of the Invention
A technical object of the present invention is to provide a gravity-type filtering device for softening and purifying drinking water which has a simplified design and which provides an increased capacity for stable softening of water while maintaining highly effective filtering capability.
The technical object stated above is achieved by the proposed gravity filter filtering device for softening and purifying drinking water, which comprises a system for fixing the filtering device to the filter funnel, which has openings for inlet of water to be treated and for outlet of air; a filter element made of porous block material in the form of a hollow vertical vessel having a porous or hermetically sealed bottom, and arranged therein, a layer of ion-exchange material and a treatment water flow distributor comprising a fixing element, wherein the layer of ion-exchange material is disposed between an inner surface of the filter element and the treatment water flow distributor which is in the form of a vertical or horizontal body having openings of a size smaller than the particle size of the ion-exchange material. The porous block material of the filter element is obtained by compression under heating of a mixture of powdered components comprising activated carbon particles and a polymer binder, and the system for fixing the filtering device is connected to the filter element by a hermetically sealing connection.
The proposed filtering device comprises means for fixing the filtering device to the filter funnel, a filter element which includes filter material for purifying the water to be treated, a material for softening the water, and a treatment water flow distributor comprising a fixing element. The material for softening the water is disposed between the inner surface of the filter element and the treatment water flow distributor and comprises a layer of ion-exchange material selected from the class of weakly or strongly acidic cation exchange materials in the H+ or Na+ form with a sorption exchange capacity of 0.5 - 5 mEq/ml with a particle size from 0.1 mm to 2.0 mm and/or inorganic cation exchange materials selected from the classes of natural or synthetic zeolites, aluminum silicates, silica gels and sulfonated carbon, and fills 20 to 90 % by volume of the inner cavity of the filter element, and the filter material of the filter element intended for water purification comprises a filter element body made of a porous block material in the form of a hollow vertical vessel that has walls of consistent or differing thickness from 5 mm to 25 mm, with a pore size smaller than the particle size of the ion-exchange material, with a cross-sectional shape in the form of a circle (hollow cylinder), square, rectangle, oval, or complex contour, or in the form of a hollow inverse pyramid, or a hollow inverse cone or a hollow inverse truncated pyramid or truncated inverse cone with a porous or hermetically sealed bottom, and is made either by extrusion or by hot pressing with a compression ratio during molding of 12 - 25 % at a temperature that is higher by 10 - 40 °C than the softening temperature of the polymer binder, from a mixture of activated carbon particles with a iodine index of at least 1000 mg/g and a polymer binder selected from the classes of polyolefins and/or polyesters and/or copolymers thereof with a melt index of 2 to 20 g per 10 min according to ASTM D 1238 at 190 °C and a load of 25 kgf, with a particle size of the activated carbon and the polymer binder from 0.05 mm to 0.5 mm, preferably from 0.07 mm to 0.15 mm, and with a ratio of activated carbon to polymer binder of (75 - 95):(5 - 25) wt%. The treatment water flow distributor comprising the fixing element is disposed in the inner cavity of the filter element and is made of polymer material produced by injection molding or is made of porous block material produced by extrusion or hot pressing with a compression ratio of 12 - 25 % during molding from a mixture of finely dispersed materials comprising activated carbon and a polymer binder with a particle size of the activated carbon and the polymeric binder from 0.1 mm to 1.5 mm, preferably 0.5 mm to 1 mm, and with a ratio of activated carbon to polymer binder of (75 - 95) : (5 - 25) wt%, at a temperature that is higher by 10 - 40 °C than the softening temperature of the polymer binder, or from inorganic finely dispersed materials, for example from the class of silicon oxides with a particle size from 0.1 mm to 1.5 mm, by a compression sintering process, in the form of a single vertical or horizontal body, or in the form of a plurality of vertical bodies with a height corresponding to 1 to 100 % of the height of the filter element, and with a cross-sectional shape in the form of a circle (hollow cylinder), square, rectangle, oval, or complex contour, or in the form of a hollow inverse pyramid or inverse cone, or in the form of a hollow truncated inverse pyramid or truncated inverse cone, with a porous or hermetically sealing bottom with openings provided in the vertical walls and/or in the bottom of the treatment water flow distributor up to a height of the treatment water flow distributor of not more than 60 % from the lower bottom level of the treatment water flow distributor and with a size of the openings smaller than the particle size of the ion- exchange material, which is achieved either by the size of the openings directly provided in the walls of the treatment water flow distributor as produced by injection molding, extrusion, hot pressing, or compression sintering, or by implementing the treatment water flow distributor in the form of a vertical vessel with openings in the lateral wall from 1 mm to 5 mm in every direction by fixing on an outer surface or inner surface thereof a porous material in the form of a mesh, or fabric, or non-woven fabric, or open-pore foamed polymer with a mesh size smaller than the particle size of the ion-exchange material. The fixing element of the treatment water flow distributor is made either in the form of a sleeve made of an elastic material tightly engaging on an upper portion of the outer surface of the flow distributor and on an upper portion of the inner surface of the filter element body, or in the form of a collar made of a polymer material by injection molding integrally with the treatment water flow distributor and hermetically joined to an upper portion of the inner surface of the filter element body using either melted polymer or any other adhesive material. A horizontal treatment water flow distributor is made of a mesh or fabric having openings that are smaller than the particle size of the ion-exchange material, with a fixing element in the form of a plastic collar joined to the inner surface or to the end face surface of the filter element body. The system for fixing the filtering device which has openings for inlet of the water to be treated and for outlet of air is made in a form that allows the filtering device to be hermetically sealed to the body of the filter funnel and is either in the form of a threaded unit that is connected to a threaded portion of the funnel, or in the form of a rim which comprises elements for tightly fitting to the funnel opening funnel opening, and is connected to the filter element body by an adhesive joint using either melted polymer or any other adhesive material, or by a mechanical connection engaging on the inner or outer or both inner and outer vertical wall surface(s) of the filter element.
The distinctive feature of the claimed invention is a fundamentally novel, simpler design of a filtering device compared to the prototype, which is intended to perform two water treatment processes - softening and purification. The simplicity of design allows to combine two functional zones (two processes) in a single filter element body that performs two functions: the function of the filter and sorbent material and the function of the filter element casing. Furthermore, the functional zone intended for the process of water softening has a large volume, which makes it possible to accommodate therein a much larger amount of ion-exchange material compared to the prototype, which provides a satisfactory water softening capacity of 150-200 liters for the consumer and, what is fundamentally important, this comes in combination with the design of the treatment water flow distributor which allows multidirectional water flows in the softening zone, which causes loosening of the softener layer, which virtually eliminates the effect of excessive softening during initial stages and ensures acceptable softening during subsequent stages of water treatment service life while maintaining a highly effective filtering capability. The essence of the invention will become apparent with reference to the drawings, in which arrows indicate the direction of water flow as it passes through the filtering device. The end plate (hermetically sealing bottom) may be made of a polymer such as polyethylene or polypropylene.
Brief Description of the Drawings
FIG. 1 is a schematic sectional view of a filter pitcher comprising a filtering device according to a first embodiment of the invention;
FIG. 2 is a schematic sectional view of a filter pitcher with a filtering device according to a second embodiment of the invention;
FIG. 3 is a schematic sectional view of a filter pitcher with a filtering device according to a third
embodiment of the invention;
FIGS. 4 to 8 show schematic sectional views of different further embodiments of filtering devices
according to the invention; and
FIGS.10 and 1 1 each show a vertical section and a cross-sectional view of further embodiments of filtering devices according to the invention.
Detailed Description of Exemplary Embodiments
FIG. 1 is a schematic view of a filter pitcher 1 comprising a funnel 2 and a filtering device 3 arranged therein, which comprises a filter element 4 in the form of a hollow cylinder with ion-exchange material 6 and a hermetically sealing bottom end plate 7, and a treatment water flow distributor 5 in the form of a hollow cylinder, which comprises a fixing element 1 1.
FIG. 2 is a schematic view of a filter pitcher 1 comprising a funnel 2 and a filtering device 3 arranged therein, which comprises a filter element 4 in the form of a hollow cylinder having a porous bottom, with ion-exchange material 6 inside the filter element 4, and comprising a treatment water flow distributor 5 in the form of a hollow cylinder comprising a fixing element 1 1 and having a porous bottom.
FIG. 3 is a schematic view of a filter pitcher 1 comprising a funnel 2 and a filtering device 3 arranged therein, which comprises a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with an ion-exchange material 6 accommodated therein, and a treatment water flow distributor 5 in the form of a mesh comprising a fixing element 1 1 in the form of a collar. FIG. 4 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with an ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and a treatment water flow distributor 5 in the form of a hollow cylinder made of porous block material. The porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 11 made of elastic material.
FIG. 5 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a porous bottom, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and a treatment water flow distributor 5 in the form of a hollow cylinder made of porous block material with openings in the bottom. The porous block material of the filter element 4 is connected to the fixing system of the filtering device by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 1 1 made of elastic material.
FIG. 6 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with walls of differing thickness and with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and comprising a treatment water flow distributor 5 in the form of a hollow cylinder that has openings of 1 - 5 mm in size in every direction, and with a water-permeable mesh arranged around the outer surface thereof and having mesh cells that are smaller than the particle size of the ion-exchange material. The porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 11 made of elastic material.
FIG. 7 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and comprising a treatment water flow distributor 5 in the form of a hollow cylinder that has openings of 1 - 5 mm in size in every direction, and with an open-porous foam polymer disposed in a water-permeable material having cells that are smaller than the particle size of the ion-exchange material. The porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 1 1 made of elastic material.
FIG. 8 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and including a treatment water flow distributor 5 in the form of a hollow truncated inverse cone made of porous block material. The porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the flow distributor 5 is connected to the filter element by a sleeve 1 1 made of elastic material.
FIG. 9 shows a filtering device 3 comprising a filter element 4 in the form of a hollow cylinder with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a threaded unit 8, and including a treatment water flow distributor 5 in the form of a hollow cylinder with walls of differing thickness made of porous block material obtained by compression sintering of silica powder. The porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element by a sleeve 11 made of elastic material.
FIG. 10 shows a filtering device 3 (FIG. 10a vertical section; FIG. 10b section along A-A) with a filter element in the form of a hollow vertical vessel 4 having an elliptical cross-sectional shape with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system of the filtering device in the form of a rim 9 comprising elements for a tight fit with the funnel socket, and including two treatment water flow distributors 5 in the form of hollow cylinders with openings in vertical walls. The porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributors 5 are connected to the filter element by a sleeve 1 1 made of elastic material.
FIG. 1 1 shows a filtering device 3 (vertical section; section along A-A) with a filter element in the form of a hollow vertical vessel 4 having an elliptical cross-sectional shape with a hermetically sealing bottom end plate 7, with ion-exchange material 6 accommodated therein, a fixing system for the filtering device in the form of a rim 9 comprising elements for fitting to the funnel socket, and including a treatment water flow distributor 5 in the form of a hollow vertical vessel with openings in the vertical wall. The porous block material of the filter element 4 is connected to the fixing system of the filtering device and to the end plate by an adhesive joint 10 at the end faces of the filter element, and the treatment water flow distributor 5 is connected to the filter element using a sleeve 1 1 made of elastic material.
The operation of the filtering device is as follows: source water from the inlet funnel 2 of the filter pitcher 1 passes through the hole in the fixing system of the filtering device in the form of a threaded assembly 8 or in the form of a rim comprising elements for fitting to the funnel socket 2 and into the treatment water flow distributor 5 and flows through the lower part thereof, which has openings for water outlet, and enters the water softening zone which contains the ion-exchange material 6 that fills 20 - 90 % of the inner volume of the filter element body. Subsequently, for purification, the softened water enters the zone of porous block material of the filter element 4 directly adjacent to the treatment water softening zone which is provided in the form of the filter element body 4 made of porous block material in the form of a hollow vertical vessel having walls of consistent thickness or differing thickness with pores of a size that is smaller than the particle size of the ion-exchange material. Once passed through the porous block material of the filter element 4, the softened and purified water gets into the lower part of the filter pitcher 1 intended for holding clean water.
In order to ensure a high filtration rate in combination with high effectiveness of water purification and prolonged service life, the filter element of the filtering device is made with a wall thickness in a range from 5 mm to 25 mm and a height from 20 mm to 120 mm. The boundary values of the range of wall thicknesses are selected because if the wall thickness is less than 5 mm, the filter element has insufficient mechanical strength. A wall thickness of the filter element of more than 25 mm adversely affects the filtration rate due to significant hydrodynamic resistance. A filter element with a wall height of less than 20 mm does not provide for effective water purification due to the small contact surface and volume of sorbent material; with a wall height of more than 120 mm, it becomes problematic to place such a filtering device in a pitcher-type filter.
The selected embodiment of the filter element in the form of a hollow vertical vessel provides a predetermined water filtration rate by the filter element, which is proportional to the filtration surface area and which is minimal for a filter element in the form of a hollow cylinder with a hermetically sealed bottom end plate, and which is maximal for a filter element with a porous bottom and complex cross- sectional shape, or by virtue of its manufacturing technology: filter elements in the form of a hollow cylinder with an end plate, a hollow vertical vessel with an oval cross-sectional shape with an end plate, or a complex contour with an end plate are produced by an extrusion process; filter elements in the form of a hollow cylinder with a porous bottom, a hollow vertical vessel with an oval cross-sectional shape, or a complex contour with a porous bottom are produced by a hot pressing process. Furthermore, in order to provide the sorbent material of the filter element with a surface area that is accessible to the best possible extent for sorption, the manufacturing process of the filter block is conducted at a temperature that is higher by 10 - 40 °C than the softening temperature of the polymer binder. With a temperature that is higher by less than 10 °C than the softening temperature of the polymer binder, the formed block material of the filter element will lack strength, and with a temperature of more than 40 °C higher than the softening temperature of the polymer binder, a significant surface area of the sorbent will be blocked due to flowing of the polymer binder. The compression ratio in a range of 12 - 25 % for a mixture of materials when producing the filter block by extrusion or by hot pressing is selected because with a compression ratio of less than 12 % the filter block will not have sufficient mechanical strength and will not be able to fulfill the function of a housing, and with a compression ratio of more than 25 % the pores resulting in the volume of the filter block material will be small and will cause high hydrodynamic resistance and, consequently, a reduction in the filtration rate.
The polymer binder is chosen from the classes of polyolefins (e.g. low pressure polyethylene, high pressure polyethylene, polypropylene) and polyesters (polyethylene terephthalate) or copolymers thereof (e.g. polyethylene vinyl acetate copolymer) due to their chemical inertness and insolubility in water on the one hand, and on the other hand due to their sufficiently low softening temperatures, which allows to intensify the manufacturing process of the filter element of the inventive filtering device in the form of a porous block material.
The embodiment of the filter element in the form of a hollow cylinder with walls of differing thickness and with a hermetically sealed bottom ensures consistent passage of the water to be purified through the walls of the filter element over the entire height thereof, since the increase in pressure of the water column in the cavity of the filter element from top to bottom is compensated by an increasing resistance to the passage of water through the walls due to the corresponding increase in the wall thickness of the filter element.
In order to ensure effective purification of the water from chlorine, organic compounds and in particular from organochlorine contaminants, the porous block material of the filter element is made using activated carbons with a iodine index of more than 1000 mg/I, since such carbons ensure effective sorption and therefore purification of water over a significant service life, and all components (sorbent and polymer binder) are used in powder form with a particle size from 0.05 to 0.5 mm, preferably from 0.07 to 0.15 mm. If the particle size of the activated carbon and the polymer binder is less than
0.05 mm, the hydrodynamic resistance of the porous block material increases, which leads to a decrease of the filtration rate. If the particle size of the activated carbon and polymer binder is more than 0.5 mm, the effectiveness of water purification decreases due to a decrease in the actual filtration (sorption) surface area of the sorbent particles.
The reason for selecting sorption capacity of the ion-exchange material in the range from
0.5 to 5 mEq/ml is because materials with an exchange capacity of less than 0.5 mEq/ml would have to be used in an amount incompatible with the volume of the filter element to achieve sufficient effectiveness of water softening over a long softening service life, whereas materials with an exchange capacity of more than 5 mEq/ml are expensive and therefore cannot be used in mass-produced filters.
The reason for filling 20 - 90 % of the inner cavity of the filter element with ion-exchange material is that if it is filled by less than 20 %, most of the treatment water flow will get into the filter zone without having contacted the ion-exchange material; if it is filled by more than 90 %, the layer of ion-exchange material will not be loose enough. The particle size of the ion-exchange material is selected in a range from 0.1 to 2.0 mm because particles with a size of less than 0.1 mm might clog the pores of the porous block material of the filter element and thereby block operation thereof; and if the particle size of the ion- exchange material is more than 2 mm, the water contact surface area would be reduced and effective softening of the water will not occur.
The selection of the height of the treatment water flow distributor in a range from 1 to 100 % of the height of the filter element body is related to the formation of multidirectional water flows in the softening zone: with a height of less than 1 % of the height of the housing, such flows are not formed. The minimum height of the treatment water flow distributor of 1 % corresponds to a minimum width of the mesh with a collar arranged on the upper end of the filter element body, performing the function of a flow distributor for the water to be treated.
The reason for choosing a particle size of the activated carbon and polymer binder in the range from 0.1 to 1.5 mm and a ratio of activated carbon to polymer binder of (75-95):(5-25) wt%, and for using material from the class of silicon oxide with a particle size from 0.1 to 1.5 mm is to obtain an optimal pore size when molding the porous body of the treatment water flow distributor: on the one hand, the pores should be smaller than the particle size of the ion-exchange material, on the other hand, the pore size must provide for a water passage rate through the treatment water flow distributor greater than or equal to the water passage rate through the walls of the filter element. The reason for choosing the temperature range for producing the porous block material of the flow distributor by extrusion or by hot pressing 10 - 40 °C higher than the softening temperature of the polymer binder is that at a temperature of less than 10 °C higher than the softening temperature of the polymer binder the formed block material of the treatment water flow distributor will not have sufficient mechanical strength, and at a temperature of more than 40 °C higher than the softening temperature of the polymer binder, the pores in the walls of the treatment water flow distributor will be blocked as a result of flowing of the polymer binder.
The shape of the treatment water flow distributor in the form of a vertical hollow body with a cross section in the form of a circle, square, ellipse, or any other shape, or in the form of a hollow inverse pyramid or inverse cone, or in the form of a hollow truncated inverse pyramid is chosen so as to follow the shape of the filter element body, which may also be made in the form of a vertical hollow body with a cross section in the form of a circle, square, ellipse or any other shape, or in the form of a hollow inverse pyramid or inverse cone, or in a hollow truncated inverse pyramid, which ensures the consistency of the flow of water to be treated in the softening zone. The reason for providing the openings in the vertical walls of the treatment water flow distributor at a height of not more than 60 % from the bottom level of the treatment water flow distributor is because if the openings are located at a height of more than 60 % from the bottom level of the treatment water flow distributor, the vertical component of water flow is not ensured over the entire height of the softening zone (vertically upward), which will cause insufficient loosening of the layer of ion-exchange material, and therefore insufficient mitigation of excessive softening. The reason for choosing the size of the openings in the lateral wall of the treatment water flow distributor in the range from 3 to 5 mm if a porous material with a pore size smaller than the particle size of the ion-exchange material is fixed on the outer surface or inside thereof is because this range is optimal from the point of view of simplicity of the manufacturing technology of the treatment water flow distributor.
A specific exemplary embodiment of a filtering device will now be described, and test results regarding its effectiveness of softening and effectiveness of water purification are specified in the table below.
This example gives an idea of the characteristics of the claimed filtering device, but should not be construed as exhaustive. Example
The filtering device comprises a filter element in the form of a hollow cylinder with a hermetically sealing bottom end plate, and a fixing system in the form of a threaded unit that is connected to the filter element by an adhesive joint using melted polyethylene (FIG. 4). Dimensions of the filter element are as follows: height 70 mm, outer diameter 62 mm, wall thickness 14 mm. The starting mixture for producing the filter element comprises the following composition: 85 wt% of activated carbon; 15 wt% of polymer binder as a mixture of low pressure polyethylene and polyethylene terephthalate (10:90) wt% with a softening temperature of 1 15 °C. The particle size of the mixture components is from 0.08 to 0.1 mm. The porous block material of the filter element body is produced by extrusion with a compression ratio of 15 % during molding at a temperature of 145 °C. The filter element is filled to 80 % of its free volume (inner volume of the filter element minus the volume of the flow distributor) with a weakly acid cation- exchange material of the H+ type with a particle size from 0.3 to 1.0 mm. The treatment water flow distributor is made in the form of a hollow tube made of high pressure polyethylene by injection molding, with a height of 70 mm, an inner diameter of 8 mm, and an outer diameter of 10 mm, and with openings of 0.2 mm in diameter in the lateral wall thereof at a height from 1 to 50 mm from the bottom of the tube. The treatment water flow distributor is tightly connected to an upper portion of the inner surface of the filter element by a sleeve made of an elastic material such as silicone. The filter element was placed in the funnel of the filter pitcher and tests were conducted regarding the effectiveness of softening and the effectiveness of water purification. The effectiveness of water softening and purification was assessed in compliance with GOST 31952-2012 WATER TREATMENT DEVICES - General requirements for effectiveness and methods for its determination.
The test results are given in the table.
Table: Test results of gravity filter filtering device for softening and purifying drinking water
Figure imgf000016_0001
xx Sample made similar to the prototype acc. to patent RU 2526377 C1 , 08/20/2014
xxx Series cartridge Barrier Hardness of JSC BWT-BARRIER.RUS As follows from the results in the above table of service life tests for softening and purifying water, the filtering device according to the invention provides for consistent softening and high effectiveness of water purification from the most common contaminants over its service life which is satisfactory for the consumer.
In summary, as a technical result, a gravity-type filtering device for softening and purifying drinking water is provided, which is of simplified design and provides increased operational capacity for softening water (at least 200 liters), at the same achieving a softening effectiveness of at least 40 %, which is sufficient from a consumer's point of view, while maintaining highly effective water purification from toxic contaminants of up to 98 %.
List of Reference Numerals:
1 Pitcher
2 Intake funnel
3 Filtering device
4 Filter element made of porous block material (purification zone)
5 Treatment water flow distributor with fixing element
6 Ion-exchange material (softening zone)
7 End plate
8 Fixing system of filtering device (threaded unit)
9 Fixing system of filtering device (rim with elements for fitting to funnel socket)
10 Connection between fixing system of filtering device and filter element
1 1 Fixing element of treatment water flow distributor

Claims

Claims:
1. A gravity filter filtering device (3) for softening and purifying drinking water, comprising
a system (8; 9) for fixing the filtering device (3) to a filter funnel (2), which has openings for inlet of water to be treated and for outlet of air;
a filter element (4) made of porous block material in the form of a hollow vertical vessel having a porous or hermetically sealed bottom, and
arranged therein, a layer of ion-exchange material (6) and a treatment water flow distributor (5) comprising a fixing element (1 1 );
wherein said layer of ion-exchange material (6) is disposed between an inner surface of the filter element (4) and the treatment water flow distributor (5) which is in the form of a vertical or horizontal body having openings that are smaller than the particle size of the ion-exchange material (6);
wherein the porous block material of the filter element (4) is obtained by compression under heating of a mixture of powdered components comprising activated carbon particles and a polymer binder; and
wherein the fixing system (8; 9) of the filtering device (3) is connected to the filter element (4) by a hermetically sealing connection (10).
2. The filtering device (3) according to claim 1 , characterized in that the fixing system (8; 9) of the filtering device (3) is configured for mounting the filtering device (3) to the body of the filter funnel (2) in a hermetically sealing manner and is in the form of a threaded unit (8) that is connected to a threaded portion of the funnel, or in the form of a rim (9) comprising elements for a tight fit to the funnel opening, and which is connected to the filter element body (4) by an adhesive joint using melted polymer or any other adhesive material, or by a mechanical connection engaging on the inner or outer or inner and outer vertical wall surface(s) of the filter element (4).
3. The filtering device (3) according to claim 1 , characterized in that the ion-exchange material (6) in the form of particles having a size from 0.1 mm to 2.0 mm fills 20 - 90 % of the inner cavity of the filter element (4).
4. The filtering device (3) according to claim 1 , characterized in that the ion-exchange material (6) comprises synthetic cation-exchange materials selected from the class of weakly or strongly acidic cationites with a sorption exchange capacity of 0.5 - 5 mEq/ml in H+ or Na+ form, and/or inorganic cation-exchange materials selected from the classes of natural or synthetic zeolites, aluminum silicates, silica gels, or sulfonated carbon.
5. The filtering device (3) according to claim 1 , characterized in that the filter element body (4) is made of porous block material in the form of a hollow vertical vessel with a cross-sectional shape in the form of a circle, square, rectangle, oval, or complex contour, or in the form of a hollow inverse pyramid, or a hollow inverse cone or a hollow inverse truncated pyramid or truncated inverse cone with a porous or hermetically sealed bottom, which has walls of consistent or differing thickness from 5 mm to 25 mm, a height from 20 mm to 120 mm, and with pores in the bottom and the walls of a size that is smaller than the particle size of the ion-exchange material (6).
6. The filtering device (3) according to claim 1 , characterized in that the heat-treated mixture of powdered materials that is used for the porous block material of the filter element (4) comprises activated carbon with a iodine index of more than 1000 mg/g and a polymer binder, with a particle size of the activated carbon and the polymer binder from 0.05 mm to 0.5 mm, preferably from 0.07 mm to 0.15 mm, and with a ratio of activated carbon to polymer binder of
(75 - 95):(5 - 25) wt%.
7. The filtering device (3) according to claim 1 , characterized in that the porous block material of the filter element (4) is made either by an extrusion process or by a hot pressing process with a compression ratio during molding of 12 - 25 %, at a temperature that is higher by 10 - 40 °C than the softening temperature of the polymer binder, and wherein polymers used as the polymer binder include polymers selected from the classes of polyolefins and/or polyesters and/or copolymers thereof with a melt index of 2 to 20 g per 10 min according to ASTM D 1238 at
190 °C and a load of 25 kgf.
8. The filtering device (3) according to claim 1 , characterized in that the treatment water flow
distributor (5) is in the form of a vertical or horizontal body, or in the form of a plurality of vertical bodies with a cross-sectional shape in the form of a circle, square, ellipse, or any other shape, or in the form of a hollow inverse pyramid or inverse cone, or in the form of a hollow inverse truncated pyramid or cone, and has a height corresponding to 1 to 100 % of the height of the filter element (4), and comprises a fixing element (1 1 ) connected to the filter element body (4).
9. The filtering device (3) according to claim 1 , characterized in that the treatment water flow distributor (5) is made of a polymer material produced by an injection molding process, or is made of a porous block material produced from a heat-treated mixture of powdered materials comprising activated carbon and a polymer binder selected from the classes of polyolefins and/or polyesters and/or copolymers thereof, or from inorganic finely dispersed materials by a compression sintering process.
10. The filtering device (3) according to claim 9, characterized in that the treatment water flow
distributor (5) made of porous block material is produced from a mixture of powdered materials comprising activated carbon and a polymeric binder with a particle size of the activated carbon and the polymeric binder from 0.1 mm to 1.5 mm, preferably 0.5 mm to 1 mm, and with a ratio of activated carbon to polymer binder of (75 - 95) : (5 - 25) wt%; and that the treatment water flow distributor (5) made of inorganic finely dispersed materials is made from material selected from the class of silicon oxides with a particle size from 0.1 mm to 1.5 mm.
1 1. The filtering device (3) according to claim 9, characterized in that the porous block material of the treatment water flow distributor (5) made from a mixture of powdered materials comprising activated carbon and a polymer binder is produced by an extrusion process or by a hot pressing process with a compression ratio of 12 - 25 % during molding at a temperature that is higher by 10 - 40 °C than the softening temperature of the polymer binder.
12. The filtering device (3) according to claim 1 , characterized in that the openings in the treatment water flow distributor (5) are provided in the bottom thereof and/or in the vertical walls thereof over a height of not more than 60 % of the height of the walls of the flow distributor from the bottom level thereof.
13. The filtering device (3) according to claim 12, characterized in that the openings in the side wall of the treatment water flow distributor (5) have a size from 1 mm to 5 mm in every direction, and that the openings with a size smaller than the particle size of the ion-exchange material (6) are provided by a porous material in the form of a mesh, or fabric, or non-woven fabric, or open-pore foamed polymer with a mesh size smaller than the particle size of the ion-exchange material (6), which is fixed on an outer surface or inner surface of the treatment water flow distributor (5).
14. The filtering device (3) according to claim 1 , characterized in that the fixing element (1 1 ) of the treatment water flow distributor (5) is in the form of a sleeve made of an elastic material tightly engaging on an upper portion of the outer surface of the flow distributor (5) and on an upper portion of the inner surface of the filter element body (4), or in the form of a collar made of polymer material by injection molding together with the flow distributor (5) and hermetically joined to an upper portion of the inner surface of the filter element body (4) by melted polymer or any other adhesive material.
15. The filtering device (3) according to claim 1 , characterized in that the treatment water flow
distributor (5) is in the form of a horizontal body made of a mesh or fabric having openings that are smaller than the particle size of the ion-exchange material (6), wherein a fixing element in the form of a plastic collar is joined to the inner surface or to the end face of the filter element body (4).
PCT/IB2020/056454 2019-07-25 2020-07-09 Gravity filter filtering device for softening and purifying drinking water WO2021014261A1 (en)

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