FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL
Specification
(See section 10 and rule 13)
METHODS AND DEVICES FOR DEIONIZATION OF
LIQUIDS
THERMAX LIMITED
an Indian Company
Chinchwad, Pune 411 019, Maharashtra, India
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION.
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FIELD OF INVENTION:
This invention relates to methods and devices for deionization of liquids.
PRIOR ART:
The purification of a liquid by reducing the concentration of ions or molecules
in the liquid has been an area of substantial technological interest. Many techniques have been used to purify and isolate liquids or to obtain concentrated pools of specific ions or molecules from a liquid mixture. Known processes include electrodialysis, liquid chromatography, membrane filtration, reverse osmosis, ion exchange and electro-demineralization. This invention envisages
an electro-demineralization apparatus for removing ions from liquids. The apparatus is particularly well adapted for the removal of large, heavily hydrated, highly charged or weakly ionized molecules or complexes from feed water /
DM outlet / RO permeate. Such removal is achieved by substituting, at least one section of the apparatus, with ion exchange membranes, resins and dimensionally stable electrodes. As used herein, the term electro-demineralization refers to the process wherein an ion exchange material such as an ion exchange resin is positioned between anionic and cationic diaphragms. In contrast, the term electrodialysis relates to such a process, which does not utilize ion exchange materials positioned between the anionic and cationic diaphragms. Although electro-demineralization is quite effective in removing ions from liquid, it has never been developed to the degree that it adequately removes certain molecules or complexes that are large, heavily hydrated, weakly ionized or highly charged. The electro-deionization processes are unicells containing mixed bed of ion exchange resins.
Under steady state conditions, present electro-demineralization apparatus is also unable to remove highly charged (i.e. trivalent or greater) ions. For cell designs
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to date, voltage increases that effectively double the electric current across the cell have been sufficient only to increase the removal of highly charged ions by a factor of no more than about 25% of the incoming feed level.
Electro-demineralization devices known in the prior art are unable to efficiently remove, under steady state conditions, large ions (i.e., ions having equivalent weights of greater than about 200). For present cell designs, voltage increases that effectively double the electric current across the cell have been sufficient only to increase the removal of such large ions by a factor of no more than about 25% of the incoming feed level.
The inability to completely remove silica, organics and certain metal ions and the increase in fouling sensitivity greatly reduces the applicability of electro-demineralization and other processes in numerous water treatment applications. Therefore, as currently used, electro-demineralization systems often require extensive pretreatment steps such as softening, organic scavenging, UV destruction of organics or reverse osmosis. They also often require post treatments such as ion exchange polishing. Additionally, in feeds containing mixed ions, electro- demineralization cannot operate at maximum efficiency for high purity water production. These disadvantages increase the costs and complexity of a high purity treatment system thereby decreasing the competitiveness of the process over traditional techniques like ion exchange and reverse osmosis. The disadvantages also decrease the applicability of electro-demineralization processes for water purification applications such as water softening, trace component polishing, electroplating, chemical synthesis and purification, food and beverage processing and waste treatment applications.
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OBJECTS OF THE INVENTION:
An object of this invention is to provide a new concept / apparatus / configuration for demineralization of water.
Another object of this invention is to combine the use of specialized ion exchange resins and membranes to improve the performance of electro-demineralization apparatus and processes.
Another object of the invention is to provide a simple device for electro-demineralization.
Another object of the invention is to enhance the removal of large or highly hydrated ions from feed water using electro-demineralization.
Another object of the invention is to enhance the removal of species, which are only weakly ionized at approximately neutral pH from feed water using electro-demineralization.
Another object of the invention is to reduce the level of fouling in electro-demineralization apparatus caused by slow diffusing molecules such as polar or ionized organics or high valence ions such as heavy metal ions or phosphates.
SUMMARY OF THE INVENTION:
The apparatus and processes provide a simple unicell design for ion exchange resins in which cation and anion exchange resins are placed in separate compartments sandwiched between ion exchange membranes and electrodes.
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The present invention provides methods and devices for improved separation efficiency in electro-demineralization procedures, and is particularly useful for producing water having a reduced content of large and highly hydrated species, highly charged species or species, which are only weakly ionized at approximately neutral pH. The invention is particularly well suited for removal of constituents such as silica from feed water streams thereby allowing electro-demineralization apparatus to be used in the production of high purity water for numerous applications, including boiler feed water.
The apparatus and processes of the invention permit enhanced removal of large or highly hydrated species and also of highly charged or weakly ionized species in electro-demineralization procedures. The invention also reduces membrane fouling, permits differential removal of certain species by adjusting pH, and overall permits more efficient separation in electro-demineralization procedures, whether such procedures are used for purification or separation.
BRIEF DESCRIPTION OF THE DRAWINGS:
In the accompanying drawings:
Figure 1 is an exploded view of an electro-demineralization apparatus in
accordance with this invention; and
Figure 2 is a schematic view illustrating the operation of the apparatus in
accordance with this invention.
DESCRIPTION OF THE INVENTION:
The electro-demineralization apparatus according to this invention comprises an ion exchange resin positioned between an anion exchange membrane and a cation exchange membrane.
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The apparatus comprises two compartments, having an ion exchange resin contained therein.
Electro-demineralization apparatus of this invention wherein the composition of an ion exchange membrane in the concentrating compartment is the same as that of an ion exchange resin.
Electro-demineralization apparatus further includes an electrical current source constructed and arranged to allow operation of the apparatus under conditions in which electrical current is maintained at a substantially constant level.
Electro-demineralization apparatus further constructed and arranged to allow the compartment to be pressurized to a level sufficiently high to maintain.
Electro-demineralization apparatus comprising an ion exchange resin positioned between an anion exchange membrane and a cation exchange membrane, the membranes having a conductance, wherein at least one membrane comprising a material that, when subjected to an increase in voltage across the membrane causes an increase in electric current across the membrane of the order of two or less, allows an increase in the transfer of large or highly charged ions across the membrane.
In the method of using electro-demineralization apparatus adapted to remove ions from a liquid, the apparatus comprising an ion exchange resin positioned between an anion exchange membrane and a cation exchange membrane, the membranes having a conductance.
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Electro-demineralization apparatus comprising an ion exchange resin positioned between an anion exchange membrane and a cation exchange membrane, the membranes having a conductance, wherein at least one membrane comprises a material such that, when subjected to an increase in voltage across the membrane causing an increase in electric current across the membrane of the order of two or less, allows an increase in the transfer of weakly ionized.
The improvement of the apparatus is operated under conditions of elevated pressure in the concentrating compartment sufficiently high to maintain substantially all dissolved gasses in solution.
Electro-demineralization apparatus wherein the ion exchange resin contained in the compartment comprises a plurality of ion exchange resin beads having a substantially uniform bead size.
Electro-demineralization apparatus as constructed and arranged to allow operation of the apparatus under conditions in which electrical current across the apparatus is maintained at a substantially constant level.
While considerable emphasis has been placed herein on the specific structures of the preferred embodiment, it will be appreciated that many alterations can be made and that many modifications can be made in the preferred embodiment without departing from the principles of the invention.
These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing
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descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

Dated this 7th day of April 2006

Mothan Dewan
of R. K. Dewan & Co
Applicant’s Patent Attorney