Patents: Electrodeionisation (EDI)

Two sub-desalination chambers d.sub.1 and d.sub.2 are defined by a cation exchange membrane 3 on one side, an anion exchange membrane 4 on the other side, and an intermediate ion exchange membrane 5 in between and are filled with ion exchange materials 8 to construct a desalination chamber D. Concentrating chambers 1 are provided via the cation exchange membrane 3 and the anion exchange membrane 4 on both sides of the desalination chamber D. The desalination chambers D and the concentrating chambers 1 are provided between an anode 7 and a cathode 6. While a voltage is applied between the anode 7 and the cathode 6, water is supplied to one of the two sub-desalination chambers d.sub.2 and then, water discharged from the first sub-desalination chamber d.sub.2 is supplied to a second sub-desalination chamber d.sub.1. Concentrate water is supplied to the concentrate chambers.

2000, patent number: 6274018

Electrodeionization apparatus

An electrodeionization apparatus is provided 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. Such removal is achieved by substituting, in at least one section of the apparatus, ion exchange membranes and/or resins having lower crosslinking and/or lower selectivity, for the ion exchange membranes commonly used in electrodeionization systems. Methods for reducing the electrical resistance across the membrane also are provided.

1992, patent number: 5316637

Electrodeionisation apparatus

An electrodeionisation apparatus comprising, successively: means defining an anode chamber, means defining one or more anion exchange chambers, means defining one or more mixed exchange chambers, means defining one or more cation exchange chambers, and means defining a cathode chamber, the anion, mixed and cation exchange chambers providing a flow path for water to be purified, is described. The present invention incorporates advantages of both separate resin bed and mixed resin bed technology.

2001, patent number: 7279083

Apparatus and method of recirculating electrodeionization

An electrodeionisation apparatus comprising a first deionising flow path and an integral second deionising flow path is described. The outflow from the first path is held in a holding tank prior to passage through the second flow path, and the outflow from the second path is available for use. Optionally, the second path outflow is partly or fully returned to the holding tank. Me recirculation of the already purified water in the holding tank maintains the water in the holding tank at a higher standard than otherwise "standing" purified water. The water in the holding tank could be separately made available for use. The apparatus requires the use of only a single pair of electrodes and hence one power supply. Moreover, the ion exchange materials in the first deionising flow path can be regenerated when water is not flowing through them such that they have a greater capacity for deionisation when required.

2002, patent number: 6482304

Electrodeionization apparatus and method

Electrodeionization apparatus and method. The electrodeionization apparatus includes an ion-depleting compartment in which alternating layers of an electroactive media are positioned. One of the alternating layers is doped to provide a more balanced current distribution through the apparatus. The method involves reducing the difference in conductivity between the alternating layers positioned in the ion-depleting compartment by adding a dopant material to one of the layers.

1999, patent number: 6284124

Helical electrodeionization apparatus

A helical electrodeionization apparatus is adapted to purify aqueous liquids to effect the production of high purity water. An insulated net-separating wall is positioned between a pair of anion and cation exchange membranes to form a special membrane bag type flow unit I, each flow unit I is linked up with a group of slots on the side walls of central pipe, and is rolled up to form cylinder structure which centers on central pipe as the helical axis, a conductive crust is formed by winding metal strip or wire outside the cylinder. Ion exchange resin is filled up between the adjacent membrane bags to form flow unit II. The present invention has less pressure drop and needs less power, and is suited to multiple-device series operation. Preferably, daily maintenance and renewal of the resin is convenient, and production cost is lower.

1999, patent number: 6190528

Method and apparatus for reducing scaling in electrodeionization systems and for improving efficiency thereof

A method and apparatus for inhibiting scaling in an electrodeionization system or in a combined reverse osmosis/electrodeionization system for water treatment and, more particularly, for increasing tolerance to hardness in the feed water to an electrodeionization unit to inhibit precipitation of metal cations contained in the feed water and for increasing efficiency of the electrodeionization system. Water to be purified is passed through a electrodeionization unit in which a concentrate stream recycling through concentrating compartments and anode and cathode compartments contains effective amounts of an antiscalant to inhibit precipitation of scale. One or more preliminary reverse osmosis units in series with the electrodeionization unit preferably receives a portion of the antiscalants in the concentrate stream. The antiscalant in the water fed to the reverse osmosis unit can be supplemented and adjusted. Electrolyte can be provided to the concentrate stream of the electrodeionization unit from products of the reverse osmosis.

United States Patent 6056878

Method and apparatus for preventing scaling in electrodeionization units

United States Patent 6056878

Electrodeionization apparatus with scaling control

First and second stages are used in electrodeionization to purify water including calcium and carbon dioxide and its hydrates. The diluting flow channels of the first stage include only anion exchange material or cation exchange material, and thus remove either carbon dioxide and its hydrates (and other anions) or calcium (and other cations) but not the other. The diluting flow channels of the second stage receive the diluting channel effluent from the first stage and include the other type of exchange resin (or a mixed resin) and remove the oppositely charged ions. The brine effluent from the concentrating flow channels in the first stage is isolated from the second stage, and calcium and total inorganic carbon tend to be removed in different stages so as to deter calcium carbonate precipitation in any of the concentrating flow channels. Also the concentrating channels can include cation exchange material next the anion membrane, with pH being lowered at the surface of the anion so as to limit calcium carbonate precipitation in the concentrating flow channel.

United States Patent 6187162

Electrodeionization apparatus and method

An electrodeionization apparatus and method for purifying a fluid. A fluid, such as water, can be purified by removing weakly ionizable species from the fluid. Weakly ionizable species may be dissociated at different pH levels to facilitate removal from the fluid in an electrodeionization device.

2001, patent number: 6649037

Electrodeionization process

An electrodeionization-based process for purifying water to remove ionic species is disclosed. Ionic removal is accomplished by supplying an electrical current between an anode and a cathode of an electrodeionization module in the range of about 1.5 to 15 times a "theoretical minimum current". The current is supplied by a power source capable of automatically increasing or decreasing voltage in response to a change in the electrical impedance of the electrodeionization module to maintain constant current. Conduct of the process on pretreated water yields deionized water of good quality, while maintaining conditions that promote the longevity of the electrodeionization module.

2001, patent number: 6365023

Electrodeionization apparatus and packing therefor

Electrodeionization packing including one or more macrostructural elements made up of smaller, microstructural elements. The microstructural elements are in fixed, close contacting position with respect to each other in the macrostructural elements so as to provide porosity in the macrostructural elements. A majority of the microstructural elements have a characteristic dimension between 10 and 50 micrometers, and the macrostructural elements have a void fraction between about 25% and 50%.

Continuous electrodeionization apparatus and method

A continuous electrodeionization apparatus and method. The continuous electrodeionization apparatus and method provide improved removal of weakly ionized ions, particularly silica. The apparatus and method involves using macroporous ion exchange resins that are both highly crosslinked and have a high water content. In preferred embodiments, the ion exchange resin beads also have a substantially uniform diameter.

2000, patent number: 6312577

Electrodeionization apparatus and method

2003, patent number: 6824662

Electrodeionization system

An improved electrodeionization system for removing ions from liquids passed therethrough, comprising a flow-through electrodeionization module, and a power supply electrically connected to the electrodeionization module electrodes so as to establish a voltage gradient thereacross. The invention includes a monitoring device such as a resistivity sensor for monitoring the value of a property (e.g. resistivity) of the liquid output flow from the electrodeionization module, and a controller responsive to the monitoring device, for controlling the amount of time that the power supply is turned on, to maintain output quality within a predetermined range, while conserving power and simplifying power supply design.

2000, patent number: 6391178

Process for producing deionized water by electrodeionization technique

In producing deionized water by electrodeionization according to the present invention, feed water and concentrating water are flowed into the ion depletion compartments and the concentration compartments, respectively, in such a way that the current direction of feed water being fed into the ion depletion compartments is opposite to the current direction of concentrating water being fed into the concentration compartments. Further, feed water flowed into each ion depletion compartment is first passed through an anion exchange material layer, and subsequently passed through other ion exchange material layer(s). The migration of anions into the concentration compartments is promoted in the portions of such anion exchange material layers through which feed water is first passed. As a result, the silica removal rate is improved.

1999, patent number: 6248226

Electrodeionization apparatus with expanded conductive mesh electrode and method

An electrodeionization apparatus and method of use includes an expanded conductive mesh electrode. The expanded conductive mesh electrode may be formed from any conductive material that is dimensionally stable and may be coated with conductive coating. The expanded conductive mesh electrodes typically have a diamond-shaped pattern of any size that provides support for an adjacent ion-permeable membrane while allowing an electrode or fluid stream to flow through. The conductive mesh electrode may also be placed against an endblock having fluid channels. These channels may be serpentine or parallel channels, which allow fluid flow to wash away any accumulation. The electrodeionization apparatus may have a protective ion-permeable membrane adjacent the electrode. The electrodeionization apparatus may also have a spacer, such as a fabric, a screen or a mesh, positioned adjacent the electrode.

2003, patent number: 6607647

High purity electrodeionization

Electrodeionization apparatus for purifying water includes a cathode, an anode, and a plurality of alternating anion permeable membranes and cation permeable membranes between the cathode and anode that define concentrating and diluting flow channels between adjacent pairs of membranes. Each concentrating flow channel includes a first guard channel adjacent to the anion permeable membrane, a second guard channel adjacent to the cation permeable membrane, and a brine channel between the first and second guard channels. The first and second guard channels have water with lower concentration of dissolved ions than water in the brine channel so as limit parasitic transfer from a concentrating flow channel to a diluting flow channel.

1999, patent number: 6254753

Electrodeionization apparatus and pure water producing apparatus

The electrodeionization apparatus 3A has a plurality of cation exchange membrane and plurality of anion exchange membrane alternately arranged between electrodes in such a manner as to alternately form diluting compartments and concentrating compartments. The diluting compartments are filled with an ion exchanger. The product water having pH exceeding pH of the feed water by 1.0 or more when the feed water having pH of equal to or less than 8.5 is treated without adding alkaline agents. The apparatus for producing purified water has plural electrodeionization apparatuses 3A, 3B connected each other so that the feed water flows through the electrodeionization apparatuses.

2000, patent number: 6379518

Electrodeionization apparatus with fixed ion exchange materials

Electrodeionization apparatus for purifying water that includes a cathode, an anode, and a plurality of alternating anion permeable membranes and cation permeable membranes between the cathode and anode that define concentrating and diluting flow channels between adjacent pairs of membranes. The diluting channels include cation exchange materials and anion exchange materials that are fixed in close contacting position with respect to each other and provide conductive paths for cations and anions to the adjacent membranes and provide flow passages for water between the materials. The anion exchange materials and cation exchange materials each have a characteristic dimension that is smaller than the characteristic dimensions of the flow passages. The use of exchange materials with small dimensions and the fixed intimate contact of cation and anion exchange materials provides increased, uniform water splitting and resin regeneration, and a high rate of ion removal from the water flowing through the diluting channels compartments. An increased velocity can be provided in the diluting channels of by reintroducing a portion of the water from the diluting channel outlet to the diluting channel inlet or using flow diverters in the diluting channel to provide a tortuous path for the flowing water.

United States Patent 6241866

Electrochemical water desalination process

A process is provided for purifying salt-containing water into desired form, wherein a salt-containing water stream is mixed with hydrogen and then pumped into an electrochemical cell where hydrogen is ionized into protons. These protons migrating to the counter-electrode, under the influence of an applied potential, entrain liquid water. At the counter-electrode, protons recombine to form hydrogen while releasing liquid water. Hydrogen is recycled and participates into the process only as a vehicle for the transport of water. This process is particularly applicable to the purification of water with high salt content such as sea water.

Patent number: 4118299