Abstract:
In regenerating an adsorbent by eliminating water and an adsorbed matter which are contained therein, the adsorbent is indirectly heated while descending within a drying furnace and is indirectly heated while ascending within a regenerating furnace in order to prevent the adsorbent from scattering due to water vapor and the adsorbed gas separated by the heating of the adsorbent and to prevent the adsorbent from burning itself due to heat.

Description:
LIST OF PRIOR ART (37 CFR 1.56 (a)) 
     The following references are cited to show the state of the art: (1) Japanese Patent Application Public-disclosure No. 86495/1975 (2) Japanese Patent Application Public-disclosure No. 45693/1976 
     BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus and a method for regenerating an adsorbent such as active carbon and zeolite by heating. 
     In order to eliminate organic matter, for example dodecylbenzensulfonate and phenol, from industrial waste water, an adsorbent which adsorbs them is used. To the end of reclaiming the adsorbent which has adsorbed the matter and water, it is necessary to eliminate the adsorbed matter and water from the adsorbent by heating the adsorbent. The temperature required for eliminating the water content from the adsorbent is 100° C., whereas the temperature required for desorbing the adsorbed matters from the adsorbent is 600° C. to 800° C. 
     Japanese Patent Application Public-disclosure No. 86495/1975 discloses a method and an apparatus for regenerating an adsorbent wherein the drying of the adsorbent and the regeneration thereof are individually executed. In the method and apparatus, however, furnaces for the respective steps are installed in a manner to be long in the horizontal direction, and the adsorbent having entered the drying furnace is heated while flowing horizontally, so that inevitably the adsorbent and water vapor generated therefrom flow in the same direction. This leads to the disadvantage that the dried adsorbent scatters in the horizontal direction together with the water vapor. Likewise, in the regenerating furnace which is long in the horizontal direction, the adsorbent scatters in the horizontal direction along with desorbed gases. 
     Japanese Patent Application Public-disclosure No. 45693/1976 discloses a method and an apparatus for regenerating an adsorbent wherein the adsorbent is dried and regenerated by directly heating it with a high-temperature gas. In the case of performing the drying and the regeneration by the direct heating, there are such disadvantages that part of the surface of the adsorbent is brought to a high temperature by the high-temperature gas, so the adsorbent itself burns, and that the adsorbent from which adsorbed matter has been eliminated adsorbs impurities in the high-temperature gas, so the purity of the adsorbent lowers. Further, according to the cited reference, the drying and the regeneration are executed in the course in which the adsorbent is caused to descend vertically. This leads to the disadvantage that the desorbed gases ascending are adsorbed to the adsorbent again within a furnace, so the adsorption performance of the adsorbent is degraded. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a method and an apparatus for regenerating an adsorbent wherein the adsorbent is not scattered by water vapor or a desorbed gas produced therefrom. 
     Another object of this invention is to provide a method and an apparatus for regenerating an adsorbent wherein the adsorbent itself does not burn in the step of drying and the step of regenerating the adsorbent. 
     Still another object of this invention is to provide a method and an apparatus for regenerating an adsorbent wherein heating at a high thermal efficiency can be executed in the drying and regeneration of the adsorbent. 
     According to the invention, there are provided a method and an apparatus for regenerating an adsorbent as have the following features: 
     (1) A drying furnace and a regenerating furnace are installed in a manner to be long in the vertical direction, and an adsorbent descending within the drying furnace is heated and dried, while the adsorbent ascending within the regenerating furnace is heated and regenerated. Since the adsorbent introduced into the drying furnace is comparatively heavy on account of a high water content, it is not scattered by ascending water vapor in attendance thereupon. Especially, an expedient of heating in which the temperature of the adsorbent in the uppermost part of the drying furnace is about 100° C. and in which the temperature becomes still higher in lower parts is desirable for the reason that water vapor is produced from the adsorbent in only the uppermost part and that since the adsorbent in the vicinity thereof is heavy, the adsorbent is not scattered by the water vapor in attendance thereupon. In addition, the dried adsorbent introduced into the regenerating furnace is heated while ascending, so that the adsorbent is not scattered by an ascending desorbed gas in attendance thereupon owing to the weight of its own. Especially, with an expedient of heating in which the temperature of the adsorbent in the uppermost part of the regenerating furnace is 600° C. to 800° C. and in which the temperature becomes lower in lower parts, the gas is desorbed from only the adsorbent in the uppermost part. Therefore, the adsorbent is more perfectly prevented from being scattered by the desorbed gas in attendance thereupon. Simultaneously therewith, since the desorbed gas is not adsorbed to the adsorbent again, the degradation of the adsorption power of the adsorbent can be prevented. 
     (2) Since the adsorbent in the drying furnace and the regenerating furnace is indirectly heated by a high-temperature gas, the local burning of the adsorbent itself can be prevented. Further, in case of the indirect heating, the adsorbent is not stained by impurities contained in the high-temperature gas, and hence, the lowering of the purity of the adsorbent can be prevented. 
     (3) In subjecting the adsorbent to the indirect heating, the drying furnace and the regenerating furnace are built into a double structure consisting of an inner container and an outer container so as to indirectly heat the adsorbent moving in the inner container by the high-temperature gas which moves in the interspace between the inner container and the outer container and also by the high-temperature gas which flows through heat transmitting tubes penetrating the inner container, so that the thermal efficiency is enhanced. As the result, the temperature of 600° C. required for regenerating the adsorbent can be reached in a short time, and the quantity of regenerating treatment of the adsorbent can be increased. Especially, when the heat transmitting tubes are disposed in a plurality of stages along the axis of the furnace and they are arranged so that the heat transmitting tubes of the adjacent stages may be orthogonal to each other, the thermal efficiency can be further raised. 
     (4) The high-temperature gas for heating the adsorbent is introduced from above into the interspace between the outer container and the inner container of the regenerating furnace and heats the adsorbent in the inner container successively from upper parts to lower parts, whereupon it is introduced from below into the interspace between the outer container and the inner container of the drying furnace and heats the adsorbent in the inner container successively from lower parts to upper parts. Therefore, the temperature of the adsorbent reaches the optimum temperatures for drying and regeneration in a short time and effectively, and the thermal efficiency rises. 
     (5) There is disposed a heat exchanger which preheats air taken from the outside into a combustor in order to produce the high-temperature gas, by the use of the adsorbent taken out of the regenerating furnace and lying at a comparatively high temperature. Accordingly, the thermal efficiency rises. 
     (6) Since vanes for stirring the adsorbent are disposed in the drying furnace and the regenerating furnace, the adsorbent undergoes horizontal forces and the temperature distribution of the adsorbent at an identical level can be made uniform. As the result, it is avoidable that the adsorbent is taken out without being regenerated on account of a low temperature or that the adsorbent itself burns on account of a high temperature. 
     When the vanes are inclined relative to the rotational direction thereof so as to bestow dynamic lift on the adsorbent descending within the drying furnace and the adsorbent ascending within the regenerating furnace, the adsorbent can be moved at a constant speed while balancing the dynamic lift to the weight of the adsorbent itself. 
     (7) When the distance between the heat transmitting tubes of the adjacent stages is made equal to the distance between the vanes of the adjacent stages, and besides, the heat transmitting tubes of the adjacent stages and the vanes of the adjacent stages are respectively arranged in a manner to be orthogonal, a rotary shaft on which the vanes are mounted can be easily assembled and detached within the furnace in which the heat transmitting tubes are installed. Therefore, the maintenance of the apparatus is simple. 
     Further objects and advantages of the invention will be apparent from a reading of the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view showing an embodiment of this invention. 
     FIG. 2 is a perspective view with part of a cylindrical inner container of a drying furnace broken away, and shows the arrangement within the cylindrical inner container, of the heat transmitting tubes and vanes for agitation. 
     FIG. 3 is a perspective view showing the structure of the interspace between the cylindrical inner container and a cylindrical outer container of the drying furnace. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an apparatus for regenerating an adsorbent according to this invention. FIGS. 2 and 3 are detailed views of the apparatus. As illustrated in the figures, a drying furnace 10 consists mainly of a cylindrical outer container 12 and a cylindrical inner container 14. 
     The diameter of the cylindrical inner container 14 is smaller than that of the cylindrical outer container 12, and both the containers are concentrically arranged. The two containers 12 and 14 are installed in a manner to be long in the vertical direction. An upper part of the cylindrical outer container 12 is provided with an outlet 16 for a high-temperature gas having been used for heating the adsorbent. 
     The interspace defined between the cylindrical inner container 14 and the cylindrical outer container 12 is divided into a plurality of spaces 18 in the axial direction by means of partition plates 20. Each space 18 is further divided by another partition plate 21 into two spaces which communicate through heat transmitting tubes 22. The partition plates 20 are provided with holes 24 so that all the spaces formed between the cylindrical inner container 14 and the cylindrical outer container 12 may join in series. An upper part of the cylindrical inner container 14 has an outlet 26 for water vapor produced from the adsorbent, and a port 27 for supplying the adsorbent. 
     The arrangement of the heat transmitting tubes 22 which penetrate the cylindrical inner container 14 and both ends of which are open to the spaces 18 between the cylindrical inner container 14 and the cylindrical outer container 12, as well as adsorbent stirring vanes 28 which are disposed within the cylindrical inner container 14, is illustrated in detail in FIG. 2. The heat transmitting tubes 22 are disposed in a plurality of stages at equal intervals in the axial direction, and the heat transmitting tubes 22a and the heating transmitting tubes 22b of the adjacent stages and the heat transmitting tubes 22b and the heat transmitting tubes 22c of the same are respectively arranged in directions orthogonal to each other. A shaft 30 is rotatably mounted within the cylindrical inner container 14, and the vanes 28 are disposed thereon in a plurality of stages at equal intervals. The vane 28a and the vane 28b of the adjacent stages and the vane 28b and the vane 28c of the same are respectively arranged in directions orthogonal to each other. Moreover, the distance between the heat transmitting tubes 22 of the adjacent stages and the distance between the vanes 28 of the adjacent stages are equal. The respective vanes 28 are slightly inclined with respect to the rotational direction of the shaft 30, and the adsorbent descending in the cylindrical inner container 14 is endowed with dynamic lift. 
     The structure of a regenerating furnace 32 is substantially the same as that of the drying furnace 10. For example, the constructions, arrangements and dimensions of a cylindrical outer container 34, a cylindrical inner container 36, heat transmitting tubes 38, vanes 40, etc. are identical. A difference is that, whereas the upper part of the cylindrical inner container 14 of the drying furnace 10 has the water vapor-taking out port 26 and the adsorbent-feeding port 27, an upper part of the cylindrical inner container 36 of the regenerating furnace 32 is provided with a port 42 for taking out the regenerated adsorbent and a still higher part thereof with a port 44 for taking out the desorbed gas. Another difference is that, whereas the upper part of the cylindrical outer container 12 of the drying furnace 10 has the outlet 16 for the high-temperature gas, an upper part of the cylindrical outer container 34 of the regenerating furnace 32 is provided with an inlet 46 for the high-temperature gas. 
     The cylindrical inner container 14 of the drying furnace 10 and the cylindrical inner container 36 of the regenerating furnace 32 communicate with each other in their bottom parts by means of a pipe 48. Disposed within the pipe 48 is a screw feeder 50 which serves to feed the adsorbent from the drying furnace 10 to the regenerating furnace 32, and which is driven by a motor 52. 
     The cylindrical outer container 12 of the drying furnace 10 and the cylindrical outer container 34 of the regenerating furnace 32 communicate with each other in their bottom parts by means of a pipe 54. The high-temperature gas is fed from the regenerating furnace 32 to the drying furnace 10 through the pipe 54. 
     A combustor 56 serves to produce the high-temperature gas for heating the adsorbent. The fuel of the combustor 56 may be an ordinary combustible. The gas desorbed from the adsorbent may be fed to the combustor 56 by a pipe 58 so as to utilize it as part of the fuel. Air to be fed to the combustor 56 is preheated within a heat exchanger 60 by the adsorbent which has been taken out of the regenerating furnace 32 and which is in the course of being fed to a storage tank 62. 
     During the descent in the cylindrical inner container 14 of the drying furnace 10, the adsorbent is indirectly heated by the high-temperature gas which ascends in the spaces 18 between the cylindrical inner container 14 and the cylindrical outer container 12 and by the high-temperature gas which passes through the heat transmitting tubes 22. The heating is adjusted so that the temperature of the upper part of the cylindrical inner container 14 may become about 100° C. and that the temperature of the lower part thereof may become about 300° C. In consequence, water having been contained in the adsorbent is separated as water vapor in an upper layer part of the adsorbent within the cylindrical inner container 14. The temperature of the adsorbent increases as it descends, and when it has reached about 300° C., it is fed to the bottom part of the cylindrical inner container 36 of the regenerating furnace 32 through the pipe 48. The adsorbent having entered the cylindrical inner container 36 is caused to ascend in the cylindrical inner container 36 by the transport force of the screw feeder 50 and the dynamic lift of the vanes 40. During the ascent, the adsorbent is heated from about 300° C. to 600° C.-800° C. by the high-temperature gas which descends in the interspace between the cylindrical inner container 36 and the cylindrical outer container 34. The gas is separated from the adsorbent heated to 600° C.-800° C. 
     EXAMPLE 
     A cylindrical inner container used had a diameter of 206 mm and a height of 450 mm. The rate of regenerating treatment of an adsorbent was 1.5 kg/hour. Under these conditions, the regeneration was carried out. Then, 99 weight-% of the adsorbent was recovered. That is, the regeneration loss was 1.0% by weight. It was found that 0.5% of the regeneration loss amounting to 1% was attributed to the scattering and that the remaining 0.5% was attributed to the combustion of the adsorbent itself.