Gas adsorbing element and method for forming same

Abstract

A gas adsorbing element is formed into a honeycomb-shaped laminate having many small channels penetrating from one end surface to the other and in which hydrophobic high silica zeolite powder is exposed on the walls of the small channels. The hydrophobic high silica zeolite is, for example, a zeolite which is produced by removing most of the aluminum component from an ordinary zeolite. In forming the honeycomb-shaped laminate, it is favorable that non-flammable sheets are laminated and the laminate is impregnated with a dispersion of high silica zeolite powder and with an inorganic binder, and that the high silica zeolite powder is fixed in fiber gaps and on the surface of the non-flammable paper. It is desirable that the non-flammable sheet is a low density inorganic fiber paper and is baked either before or after forming the honeycomb-shaped laminate. This element adsorbs little water vapor even when the process air is highly humid, and is able to adsorb and remove organic solvent vapor and bad odor material in the air with high efficiency.

Description

≈ ≅1, y≈ ≅200, z≈ ≅9 and having a micropore diameter of approximately 10 Å), such as DAY Zeolite manufactured by Degussa Aktiengesellschaft of the Federal Republic of Germany was used as the high silica zeolite. This zeolite is obtained by treating NaY zeolite, i.e., xNa₂O.Al₂O₃.ySiO₂.zH₂O (here x≈ ≅1, y≈ ≅5, z≈ ≅9 and having a micropore diameter of approximately 10 Å) with silicon tetrachloride and partially substituting the Al₂0₃ Al₂O₃ contained therein with SiO₂. The zeolite was finely pulverized and dispersed in hydrosol of either silica or alumina . The above-mentioned cylindrically formed body was soaked in sol to make the high silica zeolite adhere in fiber apertures of and on the surface of the inorganic fiber papers 1 and 2 with fine particles of silica or alumina in the hydrosol as a binding agent. The element was dried and then baked for 3˜4 hours at 450° C. to remove organic materials in the sheet and to dehydrate the zeolite and thus obtain a gas adsorbing element. The rate of high silica zeolite attached to the inorganic fiber paper is approximately 35 wt. %. This baking may occur before the impregnation of zeolite.

FIG. 3 is a gas adsorbing apparatus using a cylindrical gas adsorbing element shown in FIG. 1. In FIG. 3, 4 is a gas adsorbing element, 5 is a casing, 6 is a separator, 7 is a process zone, 8 is a reactivating zone, 9 is a geared motor, 10 is a driving belt, 11 is process air and 12 is reactivation air. The gas adsorbing element 4 is held rotatably in the casing 5 which is separated by the separator 6 into the process (gas adsorbing) zone 7 and the reactivating zone 8. The element 4 is rotated by the geared motor 9 and the driving belt 10. The process air 11 is input to the process zone 7 and hot reactivation air 12 is input to the reactivating zone 8 to adsorb active ingredients in the process air 11 such as organic solvent vapor and bad odor materials to obtain clean air 13. In addition, in FIG. 3, 14 is a pulley, 15 is a tension pulley, 16 is a rubber seal and 17 is a reactivation air heater.

FIG. 4 is a graph of the solvent removal rate (%) when the cylindrical length of the element 4 is 400 mm, the rotating speed is 10 r.p.h., the ratio of reactivation air volume to process air volume is 1:10, the process air temperature at the inlet is 25° C. ±2° C., the velocity of process air and reactivation air is 2 m/sec. and the reactivation air temperature at the inlet is 150° C.±2° C. Process air is passed as follows:

• • air containing 550 ppm of toluene
  • air containing 1100 ppm of xylene
  • air containing 760 ppm of isopropyl alcohol
  • air containing 340 ppm of n-butyl acetate
    each having an absolute humidity of 2˜19 g/kg.

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, FIG. 5 shows the result of a similar test, i.e., the solvent removal rate of a gas adsorbing element manufactured in the same conditions as the above example using, for example, ‘Zeolum F-9’ (having a micropore diameter of 10 Å) manufactured by Toyo Soda Co., Ltd., which is a hydrophilic zeolite on the market. As is clear from FIG. 5, with a hydrophilic zeolite, solvent removal rates for all organic solvents are above 90% when absolute humidity of process air at the element inlet is roughly below 8 g/kg′. When absolute humidity of process air at the inlet becomes higher than 8 g/kg′ the solvent removal rate rapidly decreases. This is because the used zeolite is hydrophilic and preferentially adsorbs water vapor in the air rather than organic solvent vapor. On the other hand, in the present invention, when high silica zeolite is used, solvent removal rates for all organic solvents tested were above 90% regardless of the absolute humidity of process air at the inlet, as is clear from FIG. 4. Test conditions were variously changed. For example, the range of process air temperature at the inlet was between 5°˜50° C., the air velocity was between 1˜3 m/sec., the reactivation air temperature at the inlet was between 100°˜160° C. and the organic solvent vapor concentration was between 20˜2700 ppm, and the type of organic solvent was changed. In all cases, the solvent recovery rate was 90˜100%. When the concentration of organic solvent vapor in the exhaust air 18 shown in FIG. 3 is high, it may be burnt or it may be used as fuel for a boiler.

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 ) and 16.5 g/kg (as identified by ), and solvent vapor concentration in process air at the inlet was 500 ppm of toluene. Element rotation speed was varied in the range of 6˜26 r.p.h. FIG. 6 is a graph of the result. From this, it can be seen that the solvent removal rate changes with a change in element rotation speed and that for the element used in this test the most appropriate rotation speed that gives the highest solvent removal rate is roughly 12 r.p.h.

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.

FIG. 7 is a graph of the xylene removal rate with respect to varying lengths of the small channels. From the graph of FIG. 7 it can be seen that in small channels having a length of 100 to 300 mm, the removal of solvent is not sufficient. In small channels having a length about approximately 400 mm, the solvent removal rate is above 95%. That is, removal of solvent is nearly total and, the use of small channels longer than approximately 400 mm is wasteful.

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 FIG. 3, to continuously adsorb, concentrate and burn to remove active gas contained in the inert gas such as air. When sheets mainly including an inorganic fiber are used for materials of the honeycomb-shaped laminate that carries high silica zeolite, the honeycomb-shaped laminate including the sheets and the high silica zeolite resists high temperature and avoids catching fire. This fireproof property is made more complete by baking non-flammable paper forming the element or the honeycomb-shaped laminate approximately 3˜4 hours at 450° C. to remove, by decomposing or burning, the small amount of organic material contained in it. When the adsorbing performance of the element decreases due to the adhesion of oil mist of a high boiling point in the micropores of high silica zeolite, hot air of approximately 350° C. is passed through the element to remove the oil mist and to regenerate the element.

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.

Claims

1. A gas adsorbing element device comprising:

a honeycomb-shaped laminate having many small channels penetrating from a first end surface to a second end surface, including a hydrophobic high silica zeolite powder placed fixed on walls of said small channels, said high silica zeolite having the composition of xM₂/_nO—Al₂O₃.ySiO₂.zH₂O, where M is an alkaki metal or alkaline-earth metal, n is its valence, and y is a mol ratio of silica and aluminum which to alumina and is greater than approximately 8 200, wherein

the honeycomb-shaped laminate has an adsorbing zone and a desorbing zone, such that the adsorbing and desorbing zones are repeatedly interchanged with one another.

2. A gas adsorbing element according to claim 1, wherein high silica zeolite is zeolite from which most of an aluminum component is removed.

3. A method of manufacturing a gas adsorbing element, comprising the steps of:

(a) laminating sheets having a main component of inorganic fiber to form single-faced corrugated sheets;

(b) laminating the single-faced corrugated sheets to form a honeycomb-shaped laminate having a shape of a gas adsorbing element having many small channels; and

(c) fixing hydrophobic high silica zeolite powder in fiber gaps and on the wall of the small channels in which a mol ratio of silica and alumina is more than approximately 8:1 using an inorganic binder.

4. A method of manufacturing a gas adsorbing element according to claim 3, wherein high silica zeolite in said step (c) is zeolite from which most of an aluminum component is removed.

5. A method of manufacturing a gas adsorbing element according to claim 3, wherein the sheets in said step (a) are low density papers.

6. A method of manufacturing a gas adsorbing element according to claim 3, wherein the inorganic fiber paper in said step (a) is baked either before or after forming the honeycomb-shaped laminate.

7. A method of manufacturing a gas adsorbing element according to claim 3, wherein the thickness of the inorganic fiber sheet is approximately 0.10˜0.30 mm, the wavelength of the corrugate is approximately 2.5 to 4.5 mm, the wave height of the corrugate is approximately 1.0 to 3.0 mm, and the length of the small channels is approximately 100 to 500 mm.

8. A method of manufacturing a gas adsorbing element according to claim 4, wherein the sheets in said step (a) are low density papers.

9. A method of manufacturing a gas adsorbing element according to claim 4, wherein the inorganic fiber sheets in said step (a) are baked either before or after forming the block.

10. A method of manufacturing a gas adsorbing element according to claim 4, wherein the thickness of the inorganic fiber sheets is approximately 0.10˜0.30 mm, the wavelength of the corrugate is approximately 2.5 to 4.5 mm, the wave height of the corrugate is approximately 1.0 to 3.0 mm, and the length of the small channels is approximately 100 to 500 mm.

11. A method of manufacturing a gas adsorbing element according to claim 5, wherein the inorganic fiber sheets in said step (a) are baked either before or after forming the block.

12. A method of manufacturing a gas adsorbing element according to claim 5, wherein the thickness of the inorganic fiber sheets is approximately 0.10˜0.30 mm, the wavelength of the corrugate is approximately 2.5 to 4.5 mm, the wave height of the corrugate is approximately 1.0 to 3.0 mm, and the length of the small channels is approximately 100 to 500 mm.

13. A method of manufacturing a gas adsorbing element according to claim 6, wherein the thickness of the inorganic fiber sheets is approximately 0.10˜0.30 mm, the wavelength of the corrugate is approximately 2.5 to 4.5 mm, the wave height of the corrugate is approximately 1.0 to 3.0 mm, and the length of the small channels is approximately 100 to 500 mm.

14. A method of manufacturing a gas adsorbing element, comprising the steps of:

(a) laminating sheets having a main component of inorganic fiber to obtain laminated sheets;

(b) forming the laminated sheets into a honeycomb structure having many small channels;

(c) impregnating the honeycomb structure with a dispersion of high silica zeolite powder in which a mol ratio of silica and alumina is more than approximately 8:1 and with an inorganic binder;

(d) fixing the high silica zeolite powder in fiber gaps in the honeycomb structure; and

(e) baking the laminated sheets before or after forming the honeycomb shaped structure.

15. A gas adsorbing device according to claim 1, wherein the honeycomb-shaped laminate is a rotor.

16. A gas adsorbing device according to claim 15, wherein

the adsorbing and desorbing zones are provided in different sectors of the rotor, and

the device further comprises a motor to rotate the rotor so as to interchange the adsorbing and desorbing zones.

17. A gas adsorbing device according to claim 1, further comprising a heater to heat a reactivating gas which is passed through the desorbing zone.

18. A gas adsorbing device according to claim 1, wherein the honeycomb-shaped laminate simultaneously adsorbs and desorbs volatile organic compounds.

19. A gas adsorbing device according to claim 1, wherein

the honeycomb-shaped laminate is a rotor, and

the device further comprises:

a casing to rotatably support the rotor,

a separator to separate the adsorbing zone from the desorbing zone, and

a motor to rotate the rotor within the casing.

20. A gas adsorbing device according to claim 19, further comprising a heater to heat reactivation air supplied to the desorbing zone.

21. A method of adsorbing organic solvent vapor, comprising:

passing the organic solvent vapor over a gas adsorbing element comprising:

a honeycomb-shaped laminate having many small channels penetrating from a first end surface to a second end surface, including a hydrophobic high silica zeolite powder fixed on walls of said small channels, said high silica zeolite having the composition of xM₂/_nO—Al₂O₃.ySiO₂.zH₂O, where M is an alkaki metal or alkaline-earth metal, n is its valence, and y is a mol ratio of silica to alumina and is greater than approximately 200; and

desorbing the organic solvent vapor from the gas adsorbing element to thereby reactivate the gas adsorbing element.

22. A method of adsorbing organic solvent vapor according to claim 21, wherein

the honeycomb-shaped laminate has an adsorbing zone and a desorbing zone, and

organic solvent vapor is passed over the adsorbing zone of the gas adsorbing element at the same time as organic solvent vapor is desorbed from the desorbing zone of the gas adsorbing element.

23. A method of adsorbing organic solvent vapor according to claim 22, wherein the adsorbing and desorbing zones are repeatedly interchanged with one or another.

24. A method of adsorbing organic solvent vapor according to claim 22, wherein

the honeycomb-shaped laminate is rotatably supported in a casing having a separator to separate the adsorbing zone from the desorbing zone, and

the honeycomb-shaped laminate is rotated in the casing.

25. A method of adsorbing organic solvent vapor according to claim 21, wherein the organic solvent vapor is desorbed by passing a heated reactivation air through the honeycomb-shaped laminate.