Patent Application
20090159448
Embodiments of the present invention relate to electrodialysis devices and associated methods for producing ionized water which is suitable for washing. More specifically, embodiments of the present invention relate to washers, such as laundry machines, dish washers and the like, having electrodialysis devices.
Traditional washers, such as but not limited to laundry machines, usually use detergents to wash. However, the detergents may remain in the washed laundry which may possibly cause sensitivities in certain individuals. In order to prevent the detergent from remaining in the laundry, the laundry must be repeatedly rinsed using a large amount of water, thereby resulting in a great waste. Moreover, the water expelled from the washer after the laundry process contains some detergents which may exceed environmental and municipal regulations.
In order to address the above-recognized problems, electrolysis devices are used in detergentless washers to produce alkaline water with cleaning properties. The conventional electrolysis device usually includes a plurality of anode and cathode units alternately arranged. The anode and cathode units are separated from each other by a plurality of ion exchangeable membranes. An acidic chamber and an alkalic chamber are respectively formed between the membranes. However, the conventional electrolysis devices generate hydroxyls based on water hydrolysis reactions, which involves hydrogen and chlorine gas generation. This gas generation is undesired for home appliances.
An aspect of the invention resides in an electrolysis device for producing alkaline water from water. The electrolysis device includes an electrolysis vessel, a pair of high porous electrodes arranged in the electrolysis vessel, and a cell unit arranged between the positive and negative electrodes. The pair of high porous electrodes respectively serve as a positive electrode and a negative electrode. The cell unit includes a bipolar membrane element and at least one cation exchangeable membrane. The bipolar membrane element has a cation exchangeable side and an anion exchangeable side. The cation exchangeable side is closer to the negative electrode than the anion exchangeable side. The cation exchangeable membrane is arranged between the anion exchangeable side of the bipolar membrane element and the positive electrode, so as to define an alkalic chamber between the bipolar membrane element and the cation exchangeable membrane.
Another aspect of the invention resides in a washer. The washer includes an electrolysis device and a washing container for storing water for washing. The electrolysis device includes a bipolar membrane element and at least one cation exchangeable membrane. The bipolar membrane element includes a cation exchangeable side and an anion exchangeable side. The cation exchangeable side is closer to the negative electrode than the anion exchangeable side. The at least one cation exchangeable membrane is between the anion exchangeable side of the bipolar membrane element and the positive electrode, so as to define an alkalic chamber between the bipolar membrane element and the cation exchangeable membrane and an acidic chamber adjacent to a cation exchangeable side of the bipolar membrane element. The electrolysis device further includes an acidic container communicating with the acidic chamber for storing the acidic water generated. The washing container receives alkalic water generated by the electrolysis device for cleaning purpose.
Still another aspect of the invention resides in an electrolyzing method for producing alkalic water from water. The method includes the steps of passing a direct current through a pair of high porous electrodes in a vessel so as to energize the pair of high porous electrodes respectively as a positive and a negative electrode. Supplying a feed water into the vessel, a bipolar membrane in the vessel splits the water into H+ and OH−. The generated OH− is prevented from moving further by a cation exchangeable membrane, so as to define an alkalic chamber between the bipolar membrane element and the cation exchangeable membrane. Remove the alkalic water out of the vessel.
These and other advantages and features will be more readily understood from the following detailed description of preferred embodiments of the invention that is provided in connection with the accompanying drawings.
Referring to
The cell unit 23 of the electrolysis device 2 according to the first embodiment, shown in
The bipolar membrane element 230 has a water splitting feature to split water directly into H+ and OH−. The application of the bipolar membrane element 230 greatly improves the efficiency of the electrolysis device 2 for producing alkalic water and acidic water from the water. The bipolar membrane element 230 may be a bipolar membrane which includes a cation exchangeable layer and an anion exchangeable layer, or a bipolar module formed by a combination of anion and cation exchangeable membranes which functions as a bipolar membrane. The cation exchangeable side 233 and the anion exchangeable 234 side of the bipolar membrane element 23 has a water diffusion percentage of 0.1-10%.
In one embodiment, the high porous positive and negative electrodes 21, 22 are made from carbon materials selected from any of activated carbon, carbon black, carbon nanotubes, graphite, carbon fiber, carbon cloth, carbon aerogel, or combination thereof. Surface area of the carbon material is in a range of from about 500 to 2000 square meters per gramme as measured by nitrogen adsorption BET method. The high porous positive and negative electrodes 21, 22 each has a shape, size or configuration that is a plate, a block, a cylinder, or a sheet.
It is known in the art that a threshold voltage of water hydrolysis is about 1.23 v. After this threshold is reached, there will be reactions respectively adjacent to the positive and negative electrodes 21, 22 as follows:
2H2O+2e→2OH−+H2 (at the negative electrode 22)
2H2O→4H++O2+4e; (at the positive electrode 21)
Moreover, Cl2 will be generated at the negative electrode 22 if the voltage reaches about 1.36 v for the reaction:
2Cl−2e→Cl2
The high porous electrodes 21, 22 have a feature that the voltage there between increases gradually, and thus there is a time duration t before the threshold voltage is reached. During the time duration t, the bipolar membrane element 230 splits water into H+ and OH−, and there will be no gases, including H2, O2 and Cl2 generated at the positive and negative electrodes 21, 22, respectively.
In certain embodiments, a voltage sensor (not shown) is used for real-timely sensing of the voltage between the positive and negative electrodes 21, 22. Once the voltage has reached a set value, which is lower than the water hydrolysis threshold voltage, for example 1.20 v, the electrolyzing process stops and thus no gas or very little gas will be generated.
In other embodiments, the time duration t required for the voltage between the positive and negative electrodes 21, 22 to reach said threshold voltage can be estimated based on the following relationship:
Q=It=CV
where Q is the electrical charge accumulated onto the porous electrode pair (positive and negative electrodes) 21, 22 during the time duration t; I is the charging current; C is the capacitance of the electrode pair 21, 22, which is determined by the loading and specific capacitance of the active material; V is the capacitive voltage buildup of the electrode pair, which is usually controlled within certain range, e.g. 1.2V. For example, for an electrode pair with a capacitance of 200 Faraday under a charging current of 0.2 Ampere, the time duration time is up to 20 minutes (200 Faraday*1.2 Volt/0.2 Ampere=1200 second).
By calculating the time duration t, the time for an electrolyzing process is controlled to be less than the time duration t, thereby decreasing or eliminating any gas generated during the electrolyzing process.
If the amount of alkalic water generated during one electrolyzing process is not enough or a pH of the generated alkalic water is not high enough, another electrolyzing process can be performed after the porous positive and negative electrodes 21, 22 are recovered. In certain embodiments, a pH sensor (not shown) for measuring the pH of the generated alkalic water is used for real-time detection of the pH value of the water in the alkalic chamber 236.
In certain embodiments, before a pH of the alkalic chamber 236 reaches a desired value, for example 11, the water therein returns back to the vessel as a feed into the alkalic chamber for further electrolyzing.
In certain embodiments, a short-circuiting line 26 is used for short-circuiting the positive and negative high porous electrodes 21, 22 for recovering of the electrodes 21, 22 after the electrolyzing process.
The water typically includes some CO2, and the CO2 consumes some OH− generated from the electrolysis device. This can be disadvantageous for improving the electrolyzing efficiency, because of the following reactions:
H2O+CO2→H2CO3
H2CO3+OH−→HCO3−+H2O
HCO3−+OH−→CO32−+H2O
For solving this problem, in certain embodiments, a CO2 absorber can be used at the inlet of the electrolysis device for absorbing the CO2 in the water before it flows into the electrolysis device. A proper CO2 absorber may include, but is not limited to, polyethylenimine (PEI), Triethanolamine (TEA), Amidine derivatives, Phenethyl piperidine, PLPPZ, 4Aminopiperidine (4AP), 4Trimethylenedipiperidine (4TMDP), 4Aminomethylpiperidine (4AMP), and Carbon Fiber Composite Molecular Sieve (CFCMS).
A washing process for laundry may generally include a cleaning process, a rinsing process, and a drying process. At the cleaning process, the water is induced into the electrolysis device 2 for generating enough alkalic water having a pH of about 9-13. The alkalic water then flows into the washing container 1, and the water flow into the washing container 1 to mix with the alkalic water. The mixed water for washing may have a pH of about 9-11.
In certain embodiments, the acidic water generated by the electrolysis device is stored in the acidic water container 3. At the rinsing process following the cleaning process, the acidic water may flow into the washing container 1 for sterilization purpose. In certain embodiments, the acidic water may also flow through the electrolysis device 2 after the electrolyzing process is finished so as to dissolve scaling, such as CaCO3, on the membranes.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. For example, embodiments of the invention are not limited to the exemplary laundry machines, but also apply to, for example, washers for dishes, sterilizing medical instruments, washing vegetables, meat, fish and etc. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007103015649 | Dec 2007 | CN | national |
