|Publication number||USRE41314 E1|
|Application number||US 10/374,604|
|Publication date||May 4, 2010|
|Filing date||Apr 30, 1991|
|Priority date||May 2, 1990|
|Also published as||DE4190940B4, DE4190940T, US5348922, WO1991016971A1|
|Publication number||10374604, 374604, PCT/1991/592, PCT/JP/1991/000592, PCT/JP/1991/00592, PCT/JP/91/000592, PCT/JP/91/00592, PCT/JP1991/000592, PCT/JP1991/00592, PCT/JP1991000592, PCT/JP199100592, PCT/JP91/000592, PCT/JP91/00592, PCT/JP91000592, PCT/JP9100592, US RE41314 E1, US RE41314E1, US-E1-RE41314, USRE41314 E1, USRE41314E1|
|Original Assignee||Kabushiki Kaisha Seibu Giken|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (11), Non-Patent Citations (3), Classifications (30), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation application of application Ser. No. 09/433,272, filed Nov. 3, 1999, now abandoned, which was a reissue application of U.S. Pat. No. 5,348,922.
1. Field of the Invention
The present invention relates to a gas adsorbing element which selectively adsorbs and removes active gases contained in inert gases such as air, especially harmful gases such as organic solvent vapor, bad odor material, etc., to obtain clean inert gases such as air.
2. Description of the Prior Art
Zeolite is a molecular sieve and is used as an adsorbent because it mainly consists of aluminosilicate. Zeolite also selectively adsorbs water and other gas molecules such as organic solvent vapor, in accordance with the diameter of the molecules, making good use of the difference in diameters of micropores which are formed by elimination of crystal water.
A rotative reactivation type dehumidifier element has been proposed in Japanese Patent Publication No. 19548/1979 (laid open to the public without examination) which consists of a corrugated and laminated cylindrical honeycomb-structure made of sheets of asbestos paper, glass fiber paper, and etc., with a molecular sieve, for example, 4A, 13X, etc., attached to it. Also in Japanese Patent Publication No. 240921/1988 (laid open to the public without examination) a honeycomb-structure dehumidifier element is proposed which is made by adding a binding agent to synthetic zeolite powder of, for example, A type, X type, Y type, or natural zeolite powder such as mordenite and formed, for example, by extruding, press forming, or some other similar method. On the other hand, a honeycomb-structure element is proposed in Japanese Patent Publication No. 50068/1978 (laid open to the public without examination) as a rotative adsorbing element that adsorbs and separates organic solvent vapor, bad odor gas and other gases from the air. The honeycomb-structure element set forth in this publication is made of paper containing fibrous active carbon.
The above mentioned zeolite is able to selectively adsorb gas molecules in accordance with its molecular diameter. In adsorbing/separating organic solvent vapor, bad odor gases and other gases from the air, water vapor is always adsorbed together with organic solvent vapor, bad odor gas and other gases because there is always water vapor coexisting with the air. The molecular diameter of water is 2.8 Å. The molecular diameter or organic solvents or bad odor gases are all larger than that of water. For example, the molecular diameter of benzene is 6.7 Å, that of cyclohexane is 6.1 Å, etc. Therefore, zeolite can adsorb and separate water only but not organic solvent vapor or bad odor gas. Rather, water vapor is preferentially adsorbed and adsorption of organic solvent vapor or bad odor gas is obstructed by the adsorbed water molecules. Therefore, when the absolute humidity of process air is high, zeolite cannot efficiently adsorb and separate organic solvent vapor or bad odor material.
Active carbon is a hydrophobic adsorbent and preferentially adsorbs non-polar molecules such as hydrocarbon. However, it is flammable and has a danger of catching fire when hot air about 130° C. is used for reactivation. Also some types of adsorbed solvent generate high adsorption heat and the adsorbing element has a danger of catching fire. Thus, it is extremely difficult to use. Moreover, the adsorbing capability of the element decreases by the adsorption of oil. After being used for a certain period of time, regeneration of the element at a high temperature of approximately 300° C. is necessary. This active carbon element, however, has a defect such that during high temperature regeneration hot air cannot be used; rather, superheated water vapor should be used for regeneration.
In the present invention, a gas adsorbing element is provided in which zeolite is used as an adsorbent having a high silica content to impart a hydrophobic property, and which is formed into a block, i.e., a honeycomb-shaped laminate, having many small channels penetrating from one end surface to the other. The high silica zeolite is exposed on the surface of the small channels. The gas adsorbing element of the present invention does not adsorb vapor in inert gases such as air which contain water vapor and organic solvent vapor and/or bad odor material, and has the ability to efficiently adsorb the organic solvent vapor and the bad odor material.
The composition of zeolite is generally shown as xM2/nO.Al2O3.ySiO2.zH2O (here M is an alkali metal or alkaline-earth metal, n is its valence and y≧1 , y is usually 1˜10). For example, the adsorbent ‘Zeolum A-4’ manufactured by Toyo Soda Co., Ltd., which is a 4A type zeolite, has a composition of 1.0±0.2 Na2O.Al2O3.1.85±0.5SiO2.zH2O. When high silica zeolite having a high silica content so that y is above approximately 8, is used, it obtains a hydrophobic property. That is, it has a decreased ability to adsorb highly polar materials such as water molecules, and an increased ability to adsorb non-polar or low polar materials such as organic solvent vapor and bad odor materials.
There are methods of obtaining high silica zeolite having a hydrophobic property. A prior art method includes de-aluminizing a typical zeolite having a y of 1-6. Another method is a direct synthesis from a Na2O—Al2O3—SiO2—H2O composition. In the prior art de-aluminizing methods, there include:
For high silica zeolite having a hydrophobic property which can be used in the present invention the value of y should be roughly above 8. Of course, in either method mentioned above, it is necessary as an indispensable condition of a molecular sieve that micropores having a diameter larger than approximately 3 Å are maintained.
In the present invention, a gas adsorbing element is formed into a block having many small channels penetrating from one end surface to the other, i.e., a honeycomb structure, so that the above-mentioned high silica zeolite having a hydrophobic property efficiently adsorbs and separates organic solvent vapor and bad odor material. For forming the honey-comb structure into a block there is a method, for example, in which the above-mentioned high silica zeolite is mixed with inorganic binder such as kaolinite and is formed into a honeycomb structure by extruding, press forming, etc. There is another method in which a sheet carrier such as paper or cloth is formed into a honeycomb block and high silica zeolite powder is bound on and in the sheet carrier with an inorganic binder either before or after the formation of the block. In the latter method the contacting area of high silica zeolite with process gas is larger and is utilized more efficiently. A porous sheet formed of fibers such as paper, cloth and non-woven fabrics are preferable as a sheet carrier than one with a smooth surface and without a permeating property such as a metal sheet and a plastic sheet. This is because high silica zeolite is carried not only on the sheet surface but also in the fiber gaps. Especially bulky sheets of fibers having a high aperture rate are desirable. During gas adsorption, desorption/reactivation is necessary. For desorption, a pressure swing method which does not need heating can be used, but desorption/reactivation by heating can be performed more easily and with simpler equipment. For heating reactivation, the element should be heat resistant and nonflammable, and therefore inorganic fiber papers are used which have no danger of catching fire. These inorganic fiber papers include paper formed from ceramic fibers, rock fibers, slag fibers, or glass fibers, or paper mainly consisting of a mixture of these fibers. The use of asbestos fiber, which is also an inorganic fiber and does not pose a danger of catching fire, is not preferable because asbestos is harmful to the health of humans.
Further, in a suitable step of manufacturing a gas adsorbing element using the above-mentioned paper including mainly inorganic fibers, the paper is baked to burn and the small amount of organic ingredients contained therein are removed. There is also a method which uses a nonflammable paper made by mixing high silica zeolite powder.
It is preferable that in the honeycomb-structure the wavelength 1 is 2.5 to 4.5 mm and the wave height h is 1.0 to 3.0 mm. When these sizes are too large, the total surface area of the gas adsorbing element becomes smaller. Consequently, the efficiency of gas adsorption drops. In contrast, when these sizes are too small, pressure drops in the process air and the reactivation air become large, and subsequently an economical operation is not possible.
A small amount of organic synthetic fiber and a small amount of an inorganic or organic binder were added to ceramic fiber of silica alumina series to prepare low density paper having an apparent specific gravity of approximately 0.3˜0.45 (about 60-150 g/m2 weight) and a thickness of approximately 0.10˜0.30 mm. The paper was then corrugated so that it had a width of 400 mm, a wavelength of 3.4 mm and a wave height of 1.8 mm. Using an adhesive including a mixture of synthetic resin such as polyvinyl acetate and inorganic binder, a flat paper 1 and a corrugated paper 2 were bonded together at all ridged portions of the corrugated paper 2 as shown in
Solvent removal rate in this instance means the value obtained by subtracting the quotient, which is obtained by dividing the solvent containing rate of process air at the outlet by that of process air at each inlet, from 1. Even when the solvent concentration in process air at the inlet changes, the solvent removal rate hardly changes.
As a contrasting example,
In order to observe a change of solvent removal rate with the change of element rotation speed, an element obtained in the above example was put into the equipment of FIG. 3 and the toluene removal rate was measured under the conditions that process air temperature in the inlet was 15° C., process air and reactivation air velocity was 2 m/sec., reactivation air temperature at the inlet was 140° C., process air absolute humidities at the inlet were 5.0 g/kg (as identified by
In order to observe a change of solvent removal rate with a change of length of small channels, elements were prepared in which inorganic fiber paper having a thickness of 0.20 mm after impregnation with zeolite as in the above example was corrugated so that a wavelength was 3.4 mm and a wave height was 1.8 mm, and the length of the small channels L was changed from 100 mm to 500 mm. The prepared elements were then put into the equipment of FIG. 3. The equipment was then operated under the following conditions. The process air temperature at the inlet was 15° C., the reactivation air temperature at the inlet was 150° C., the process air velocity and reactivation air velocity were both 2 m/sec., the absolute humidity of process air at the inlet was 15 g/kg, the solvent vapor concentration in process air at the inlet was 1100 ppm of xylene and the rotation speed of the elements was 15 r.p.h.
In the present invention, a gas adsorbing element manufactured as described above using hydrophobic high silica zeolite as an adsorbent, adsorbs a comparatively small amount of organic solvent vapor or bad odor component contained in an inert gas such as air, and adsorbs very little water vapor which is always in the air. Therefore, the gas adsorbing element of the present invention is capable of effectively adsorbing, concentrating, and removing organic solvent vapor or bad odor components contained in the inert gas such as air regardless of the humidity. Moreover, since an organic solvent or bad odor component adsorbed by the element can be mostly desorbed at a temperature of approximately 100°˜160° C., the element is incorporated into a rotary reactivation type gas adsorbing equipment as shown, for example, in
During the manufacturing process according to the present invention, a sheet of non-flammable paper, etc., is formed into a honeycomb shape, baking the honeycomb at 450°-500° C. and high silica zeolite powder is impregnated using an inorganic binder, etc., and adhered to it. This allows the process to proceed simply and economically without special machinery or equipment, and the majority of the high silica zeolite used in the gas adsorbing element works effectively as an adsorbent. When material consisting of fibers having many apertures such as non-flammable paper, particularly a low density inorganic fiber paper, is used as a carrier, high silica zeolite fixes not only on the surface of the inorganic fiber paper but also in the apertures between the fibers to increase the carrying ability of the element.
The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention and the appended claims and their equivalents.
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|2||*||"Inorganic Silicon Compounds as Fine Chemicals", Shigekazu UDAGAWA et al., p. 285, 1982.|
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|U.S. Classification||502/60, 502/64, 502/63, 502/79, 502/71, 502/77, 423/210, 423/239.2|
|International Classification||B01J20/28, F24F3/14, B01J20/18, B01D53/46, B01J29/06, B01D47/00|
|Cooperative Classification||B01J20/28011, F24F2203/1068, B01J20/28028, B01J20/28045, F24F2203/1056, F24F3/1423, F24F2203/1084, B01J20/28033, F24F2203/1036, F24F2203/1048, F24F2203/1004|
|European Classification||F24F3/14C2, B01J20/28D24, B01J20/28B12, B01J20/28D28B, B01J20/28D16|