Dehumidified air generator employing adsorbent

Abstract: A dehumidified air generator (10) has a plurality of rotatable absorption columns (12, 14, 16) filled with adsorbents for gen­ erating dehumidified air which will be used to dry a plastic material or the like. A directional control valve for switching between adsorbing and regenerating steps in the adsorption columns comprises a slide valve mechanism com­ posed of a stator (34, 38) and a rotor (32, 36) slidably held against the stator. The rotor has a plurality of openings defined therein and communicating with inlet/outlet ports defined in side walls of the adsorption columns through tubes (40, 42, 44). By rotating the rotor in synchronism with the adsorption columns, the adsorbing and regenerating steps are switched to dehumidify, with the adsorbents, humid air introduced into the adsorption columns through the directional control valve and also to desorb the adsorbents for regenerating them.

Description: The present invention relates to an apparatus for generating dehumidified air by employing an adsorbent such as of synthetic zeolite, and more particularly to a dehumidified air generator suitable for use in drying a plastic material which is to be molded to shape. Various known dehumidified air generators are generally grouped into (a) dehumidified air generators for use in chemical plants, (b) dehumidified air generators for use in air conditioning systems, and (c) dehumidified air generators for use in machines for drying plastic materials to be molded to shape. The dehumidified air generators under the category (c) are finding wide use as a source of dehumidified air for drying a plastic material (mostly in the form of pellets) down to a very low water content before it is charged into a plastic molding machine. These dehumidified air generating apparatus are of growing importance particularly because they are required for the manufacture of engineering plastics which have been developed in recent years. Conditions for designing dehumidified air generators of the above classes (a) through (c) will be described below. (a) Dehumidified air generators for use in chemical plants: When a dehumidified air generator is designed for use in a chemical plant, it should produce air that has been dried to have a very low dew point (lower than - 70°C, for example). These dehumidified air generators are designed individually or customized in almost all applications. Since there are few apparatus size limitations, dehumidified air generators in this group can be designed to ideal specifications which meet operating principles of the generators. In many cases, large and complex dehumidified air generating systems are designed for desired performance. (b) Dehumidified air generators for use in air conditioning systems: Dehumidified air generators of this type find a larger market than those of the class (a). Dehumidified air produced by the dehumidified air generators is not required to have a considerably low dew point, but normally should have a dew point ranging from + 10°C to + 12°C (if air is to be dehumidified to a dew point of + 12°C, then air at 35°C may be dehumidified to a relative humidity of 5 %). Therefore, the dehumidified air generators can easily be designed. (c) Dehumidified air generators for drying plastic materials: Depending on the type and use of plastics to be dried, air should be dehumidified by a dehumidified air generator in this category down to a dew point that ranges from - 50°C to - 60°C. Therefore, the dew point requirement is similar to that of the type (a). Inasmuch as even relatively small-sized plastic molding machines require dehumidified air generators, respectively, cost and space limitations on these dehumidified air generators are strict. It is impossible to scale down a dehumidified air generator which was designed for use in a chemical plant and use it for drying a plastic material. Heretofore, dehumidified air generators for use as plastic material driers have been manufactured and sold without regard for basic technical conditions that should be met when using an adsorbent. Naturally, such dehumidified air generators have proven unsatisfactory in use, and have posed problems especially on certain plastics such as PET, for example, which depend on their water contents introduced into the molding machine for determining the properties of products molded of those plastic materials. Where there are stringent requirements as to the dehumidification of plastics such as PET, most of the conventional dehumidified air generators cannot be used. Even if some of them can be used, they are oversized and require a wasteful expenditure of installing and running costs. Technical conditions to be met by a dehumidified air generator which uses an adsorbent are as follows: 1) Assuming that air flows in a normal direction for adsorption in each step, desorbing air at a high temperature ranging from 250°C to 300°C should flow in the direction opposite to the normal direction. 2) Low-temperature air in a step after desorption, i.e., a cooling step, should flow in the normal direction. 3) It is highly preferable that air to be used in the cooling step be dehumidified air. 4) In an adsorbing step, there is an optimum air flow rate in a range determined by the type and particle diameter of an adsorbent. To keep the air flow rate in that range, it is necessary to provide a cross-sectional area of an adsorbent layer which is suitable for the flow rate of air to be dehumidified, and hold the cross-sectional area perpendicular to the direction in which the air to be dehumidified flows. 5) It is necessary that the adsorbent layer have a minimum required thickness in the direction of flow of the air to be dehumidified, for achieving a desired dew point and keeping that dew point for a suitable period of time. If a dehumidified air generator which satisfies the conditions 1) through 5) while successively switching between cycles of adsorbing and regenerating steps (i.e., desorbing and cooling steps) in a plurality of adsorbing columns are to be constructed, gas passages for the respective step cycles are complicated because of the conditions 1), 2), 3), and a number of automatic directional control valves are required to switch between the gas passages. An adsorption drier including a flat-type slip valve which is free from the complex gas passages and the directional control valves is disclosed, for example, in Japanese Laid-Open Patent Publication No. 46-7440 claiming the Convention priority based on German Patent Application P202505.5 filed on May 23, 1970. As shown in FIGS. 1 and 2 of this publication, a plurality of adsorption columns are horizontally arranged around a vertical rotational shaft, and discs are hermetically coupled to the upper and lower ends of the adsorption columns and positioned upwardly and downwardly of the adsorption columns. The disc is rotatable in unison with the rotors of valves mounted on the disc and held closely against a confronting nonrotatable disc. The nonrotatable disc has openings aligned respectively with the areas where adsorbing and regenerating steps are effected. The openings are held in communication through gas passages with the devices which perform the adsorbing and regenerating steps. In an actual system incorporating the principles of the disclosed adsorption drier, an adsorbent is stored in the gap between vertical double tubes to provide an adsorbent layer with a sufficient vertical cross-sectional area (as defined by the above condition 4)) with respect to air that flows in a horizontal direction. Since the adsorbent layer surface across and through which air passes in each of the adsorption columns extends vertically, it is possible to minimize the installation area for the adsorption drier. If the adsorbent layer surface extended horizontally and air passed vertically therethrough in the disclosed arrangement, the diameter of each adsorbing column would be much greater than that which is disclosed in the publication. Consequently, while the disclosed adsorption drier can meet the conditions 1) and 2), it cannot satisfy both the conditions 4) and 5) while minimizing the installation space. More specifically, if the installation area is reduced, then it is unable to meet the condition 5) which requires the adsorbent layer to have a sufficient thickness. Another problem with the known structure in which air is horizontally passed across and through the vertical surface of the thin adsorbent bed is that the packing density of the adsorbent is rendered irregular due to gravity and hence the speed of air passing through the adsorbent layer is also made irregular. Moreover, the adsorption columns (normally four or five adsorption columns) which are disposed around the vertical rotatable shaft give a considerable large diameter to the entire rotatable assembly, and are not appropriate for use in a plastic molding plant as it takes up a large installation area. Japanese Laid-Open Patent Publication No. 49-7166 claiming the Convention priority based on German Patent Application P2214662.9 filed on March 25, 1972, appears to disclose superficially a plurality of vertically stacked adsorption columns. However, it should be noted that actually, such vertically stacked adsorption columns are not disclosed in this publication for the following reasons: The external dimensions of directional control valves are shown as being quite large as compared with the diameters of inlet and outlet holes (1b, 11b). This indicates that FIGS. 2 and 4 of the publication are conceptual. Conversely, the dimensions of chambers (adsorption columns) filled with molecular sieves (adsorbent) in FIGS. 2, 4, and 6 of the publication are shown as much smaller than the external dimensions of the directional control valves. Technically, it is necessary that the external dimensions of the chambers be much larger than those of the directional control valves even if the directional control valves are not reduced in external dimensions. This fact also shows that FIGS. 2 and 4 of the publication are merely of a conceptual nature. The publication fails to refer to the arrangement and advantages of the adsorption chambers, and does not specifically indicate how the adsorption chambers are attached to valve plates. In addition, although FIG. 6 shows that the adsorption chambers are horizontally arranged and air flows horizontally, any comparison with a vertical stack of adsorption chambers is not described at all. FIGS. 2, 4, 5, and 6 of the publication show the upper and lower valve plates in perspective, whereas lower components such as a heater, an air blower, etc., are depicted as a circuit diagram. Accordingly, the dimensions and positions of the adsorption chambers 5, 6 and conduits connecting them to the valve plates have no significance as indicating directions in these figures. FIGS. 2, 4, 5, and 6 serve the purpose of indicating the angular positions of the holes in the valve plates and their function, with the remaining portions being added simply as system diagrams. As a consequence, FIGS. 2 and 4 do not indicate that the adsorption chambers are vertically stacked, and any vertical stack of adsorption chambers is not disclosed inasmuch as no operation and advantages whatsoever are described with respect to a vertical stack of adsorption chambers. In view of the aforesaid problems of the conventional dehumidified air generators, it is an object of the present invention to provide a dehumidified air generating apparatus employing an adsorbent, which can meet the technical conditions 1) through 3), described above, without employing a complex system of air flow passages in successively switching between adsorbing and reproducing steps in a plurality of adsorption columns, and which can satisfy the conditions 4) and 5) without increasing the installation space for the adsorption columns. Another object of the present invention is to provide a dehumidified air generator employing an adsorbent, which can meet all the technical conditions 1) through 5), and which requires a reduced installation space and can be manufactured at a reduced cost. Still another object of the present invention is to provide a dehumidified air generator employing an adsorbent, which can meet all the technical conditions 1) through 5), and which allows an adsorbent to be replaced quite easily, does not increase the overall height of the generator even if the number of adsorption columns used is increased, and minimizes an installation space. DE-A-1544036 discloses a dehumidified air generator in which adsorbent columns are supported laterally displaced from each other by a rotor and a stator which act as a valve. EP-A-205709 and EP-A-0170349 both disclose gas enriching devices in which employ rotors and stators acting as valves. According to the present invention, there is provided a dehumidified gas generator comprising: a plurality of simultaneously rotatable adsorption columns having respective adsorbent beds housed therein; a rotor, rotatable in synchronism with the adsorption columns, the rotor having a plurality of openings defined therein; a stator fixed opposite the rotor and having openings which can be made to correspond with said rotor openings; the rotor and the stator jointly serving as a directional control valve for switching between adsorbing and regenerating steps in each of the adsorption columns; rotating means for coupling the adsorption columns to each other and rotating the adsorption columns in synchronism with the rotor, the rotating means including a rotatable shaft, the arrangement being such that the adsorbing and regenerating steps in the adsorption columns can be switched by angularly displacing the rotor and the stator with respect to each other with the rotating means; and tubes for passing a gas to and from the adsorbent beds, one end of each tube being connected to the rotor; whereby each of the tubes is connected at its other end to a respective port defined in an outer side wall of an adsorption column; the adsorption columns are supported such that their weight is not carried by the rotor and stator; and the adsorption columns being disposed in different vertical positions, respectively, and divided vertically from each other, the adsorption columns at least partially overlying one another in a vertical direction and being mounted on a support device rotatable about a straight axis extending vertically through the adsorbent bed in at least one of the adsorption columns. The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example. In the drawings: Fig. 1 is a perspective view of a dehumidified air generator in accordance with an embodiment of the present invention; FIG. 2 is a block diagram, partly shown in cross section, illustrating air flows in the dehumidified air generator according to the first embodiment; FIG. 3 is a plan view of a stator used in the dehumidified air generator of the first embodiment; FIG. 4 is a block diagram of a dehumidified air generator according to a second embodiment of the present invention; FIG. 5 is a diagram showing cycles of operation of the dehumidified air generator according to the second embodiment; FIG. 6 is a block diagram of a dehumidified air generator according to a third embodiment of the present invention; FIG. 7 is a diagram showing cycles of operation of the dehumidified air of the third embodiment; FIG. 8A is a plan view of a rotor used in a dehumidified air generator according to a fourth embodiment of the present invention; FIG. 8B is a plan view of a stator in the dehumidified air generator of the fourth embodiment; FIGS. 8C, 8D, 8E, and 8F are plan views illustrating the rotor of FIG. 8A and the stator of FIG. 8B which are combined with each other; FIG. 9 is a plan view of the stator and the rotor which are combined with each other in a different pattern from those shown in FIGS. 8C through 8F; FIG. 10A is a plan view of a rotor used in a dehumidified air generator according to a fifth embodiment of the present invention; FIG. 10B is a plan view of a stator used in the dehumidified air generator of the fifth embodiment; FIGS. 10C, 10D, and 10E are plan views showing the rotor of FIG. 10A and the stator of FIG. 10B which are combined with each other; FIG. 11 is a block diagram of the dehumidified air generator according to the fourth embodiment; and FIG. 12 is a perspective view of the dehumidified air generator of the fourth embodiment. As shown in FIG. 1, a dehumidified air generator, generally designated by the reference numeral 10, according to a first embodiment of the present invention has three cylindrical adsorption columns 12, 14, 16 which are vertically stacked. The adsorption columns 12, 14, 16 are mounted respectively on flat plates 18, 20, 22 attached to a support device which comprises a substantially C-shaped member 26 and vertical rotatable shafts 28, 30 mounted respectively on the upper and lower ends of the member 26. A rotor 32 and a stator 34 facing and fixed to the rotor 32 are disposed upwardly of the three adsorption columns 12, 14, 16, and a rotor 36 and a stator 38 facing and fixed to the rotor 36 are similarly positioned downwardly of the three adsorption columns 12, 14, 16. Gas passages 40, 42, 44 in the form of flexible tubes are connected to the lower stator 38, and gas passages 46, 48, 50 in the form of flexible tubes have ends connected to the rotor 36. The other end of the gas passage 46 is joined to an inlet/outlet port 52 defined in an upper side wall of the adsorption column 12. The other end of the gas passage 48 is joined to an inlet/outlet port 54 defined in an upper side wall of the adsorption column 14. The other end of the gas passage 50 is joined to an inlet/outlet port 56 defined in an upper side wall of the adsorption column 16. Gas passages 58, 60, 62 in the form of flexible tubes are coupled at ends thereof to the upper rotor 32. The other end of the gas passage 58 is joined to an inlet/outlet port 64 defined in a lower side wall of the adsorption column 12. The other end of the gas passage 60 is joined to an inlet/outlet port 66 defined in a lower side wall of the adsorption column 14. The other end of the gas passage 62 is joined to an inlet/outlet port 68 defined in a lower side wall of the adsorption column 16. Gas passages 70, 72, 74 in the form of flexible tubes are connected to the stator 34. Although the gas passages 40, 42, 44, 46, 48, 50, 58, 60, 62, 70, 72, 74 are described as comprising flexible tubes, they are not limited to the flexible tubes. The rotor 32 is fixed to the rotatable shaft 28, whereas the rotor 36 is fixed to the rotatable shaft 30, which extends downwardly through the stator 38 and is rotatably supported on a support base 76. The lower end of the rotatable shaft 30 is connected to an actuator 77 which may comprise a motor with a speed reducer. Air flows, the gas passages, and dehumidifying operation in the dehumidified air generator 10 will be described with reference to the block diagram of FIG. 2. It is assumed in FIG. 2 that the adsorption column 12 is in an adsorbing step, the adsorption column 14 a cooling step, and the adsorption column 16 a desorbing step. A humid plastic material is dried by dehumidified air in a hopper 78, and the dried plastic material is supplied from the hopper 78 into a plastic molding machine (not shown). Humid air discharged from an outlet 80 of the hopper 78 flows through a gas passage 82 and then through a filter 84 and a cooler 86 into an air blower 88. The cooler 86 is employed because humid air can well be dehumidified when it is of a low temperature. The filter 84 and the cooler 86 may be positionally switched around. The air blower 88 has an outlet port connected to the gas passage 40 that is coupled to the stator 38. As shown in FIG. 3, the stator 38 comprises a disc having three angularly equally spaced openings 40A, 42C, 44D defined therein and communicating with the gas passages 40, 42, 44, respectively. The rotor 36 disposed on the stator 38 is also in the form of a disc having three angularly equally spaced openings (not shown) communicating respectively with the gas passages 46, 48, 50. The rotor 36 and the stator 38 are slidably held against each other, jointly serving as a slide valve. The opening 40A in the stator 38 to which the gas passage 40 is joined communicates with the opening (not shown) in the rotor 36 in a hermetically sealed relation. In the position shown in FIG. 2, the gas passage 40 is connected in a hermetically sealed relation to the gas passage 46 through the stator 38 and the rotor 36. Likewise, the gas passages 42, 44 are connected in a hermetically sealed condition to the gas passages 48, 50, respectively, through the stator 38 and the rotor 36 in the position of FIG. 2. The gas passage 46 which is coupled to the gas passage 40 through the stator 38 and the rotor 36 is connected to the inlet/outlet port 52 of the adsorption column 12. The adsorption column 12 has an adsorbent bed 90 housed therein and having a cross-sectional area which meets the condition 4) described above and a thickness which meets the condition 5) described above. Similarly, the adsorption columns 14, 16 have respective adsorbent beds 92, 94 housed therein. The humid air supplied from the gas passage 46 is dehumidified when it flows through the adsorbent bed 90. Dehumidified or dried air then flows through the inlet/outlet port 64 into the gas passage 58, and reaches the rotor 32. As with the rotor 36 and the stator 38, the rotor 32 and the stator 34 jointly serve as a hermetically sealed slide valve. In the position of FIG. 2, the gas passages 58, 60, 62 are held in communication with the gas passages 70, 72, 74 through openings (not shown) defined in the rotor 32 and the stator 34. The dried air from the gas passage 58 is thus delivered into the gas passage 70 without leakage. Since the gas passage 70 is connected to a dried air inlet 98 of the hopper 78, the dried air (which is of a temperature ranging from 60°C to 170°C) is supplied from the inlet 98 into the hopper 78 in which a humid plastic material that has been charged into the hopper 78 through a feed port 100 is dried by the dried air. The air then becomes humid, and fed through the outlet 80 into the gas passage 82. The dried plastic material is supplied into the non-illustrated plastic molding machine through a discharge port 102. The gas passage 70 coupled to the stator 34 is branched into a gas passage 104 which is connected to the gas passage 42 through a coupling means (not shown). Therefore, a portion of the dried air that has been dehumidified by the adsorption column 12 is supplied via the gas passage 42, the stator 38, the rotor 36, and the gas passage 48 into the adsorption column 14 to cool the adsorption column 14 after it has been desorbed by heated air. The air (dried air) flowing out of the adsorption column 14 passes through the gas passage 60, the rotor 32, the stator 34, and the gas passage 72, which is joined to the gas passage 82. Instead of joining the gas passage 72 to the gas passage 82, the gas passage 72 may be connected to the gas passage 70 through a gas passage 73 indicated by the dotted line in FIG. 2. The desorbing step in the adsorption column 16 is effected as follows: Ambient air is drawn through a filter 106 and a gas passage 108 into the gas passage 74 by means of an air blower 110. The air thus introduced into and flowing through the gas passage 74 is heated by a heater 114. The heated air (which is of a temperature in the range of from 250°C to 300°C) flows through the stator 34, the rotor 32, and the gas passage 62, and is then fed through the inlet/outlet port 68 into the adsorption column 16 in which the heated air desorbs the adsorption bed 94 after it has adsorbed a prescribed amount of humidity or humidity over a prescribed period of time. After having desorbed the adsorption bed 94, the heated air flows out of the adsorption column 16 through the inlet/outlet port 56, and is discharged into the atmosphere through the gas passage 50, the rotor 35, the stator 38, and the gas passage 44. The time required to complete the desorbing step is much shorter than the time required for the adsorbent to adsorb humidity to the extent that it needs to be desorbed. In view of this, a sensor 116 such as a humidity sensor is disposed in the gas passage 44 for detecting when the adsorbent bed is sufficiently desorbed and regenerated. An output signal from the sensor 116 is applied via lines 118, 120 to the air blower 110 and the heater 114 to stop the operation of the air blower 110 and the heater 114. With this arrangement, the energy consumed by the air blower 110 and the heater 114 can be saved. When the adsorbent bed 90 in the adsorption column 12 is to be desorbed in the position of FIG. 2, the adsorption columns 12, 14, 16, the rotors 32, 36, and the support device 24 (FIG. 1) are rotated by the actuator 77 to change the steps to be performed by the adsorption columns 12, 14, 16. More specifically, as shown in FIG. 1, the adsorption columns 12, 14, 16, the rotors 32, 36, and the support device 24 are rotated together by the actuator 77 about a Z-axis, i.e., a straight line connecting the rotatable shafts 28, 30 of the support device 24, thus rotating the gas passages 46, 48, 50, 52, 54, 56 about the Z-axis without varying their positions relative to the adsorption columns 12, 14, 16 and the rotors 32, 36. The rotors 32, 36 are now angularly displaced with respect to the respective stators 34, 38. For example, as illustrated in FIG. 2, the gas passages 40, 48 are connected to each other through the stator 38 and the rotor 36, and the gas passages 60, 70 are connected to each other through the rotor 32 and the stator 34, so that the adsorption column 14 is switched from the cooling step to the adsorbing step. At the same time, the gas passages 44, 46 are connected to each other and the gas passages 58, 74 are connected to each other to switch the adsorption column 12 from the adsorbing step to the desorbing step. The gas passages 42, 50 are coupled to each other and the gas passages 62, 72 are coupled to each other to switch the adsorption column 16 from the desorbing step to the cooling step. Thereafter, each of the adsorption columns 12, 14, 16 can repeat the cycle of the adsorbing, desorbing, and cooling steps. In FIG. 1, the weights of the adsorption columns and the gas passages are borne by the support device 24, particularly, the rotatable shaft 30 and the support base 76, but not by the rotor 36 and the stator 38. Therefore, the rotor 36 and the stator 38 may be of relatively small dimensions, and the sealing ability of the slide valve composed of the rotor 36 and the stator 38 may be increased. It can be understood from FIG. 1 that the installation area or space for the dehumidified air generator 10 is reduced substantially to an area in which one adsorption column is projected onto a horizontal plane. Accordingly, the installation space for the dehumidified air generator 10 is very small. According to the first embodiment of the present invention, the adsorption columns 12, 14, 16 are vertically stacked and rotatable about the vertical axis extending through the centers of the adsorption columns 12, 14, 16. This arrangement reduces the installation space for the dehumidified air generator 10 while satisfying the conditions 1) through 5) referred to above. The drive shaft (rotatable shaft) 30 coupled to the actuator 77 extends through the center of the slide valve near the actuator 77, with the stator 38 being independent of the drive shaft 30. Since the entire weights of the adsorption columns 12, 14, 16 are borne by the drive shaft 30 but not by the rotor 36, the rotor 36 may be of a mechanical strength which is large enough as a member of the slide valve. The rotor 36 and the drive shaft 30 may be coupled to each other only with a mechanical strength large enough to transmit rotative power from the drive shaft 30 to the rotor 36. Accordingly, the rotor 36 and the stator 38 may be reduced in size, and the sealing ability of the slide valve composed of the rotor 36 and the stator 38 can be increased. Inasmuch as the cooling step can be carried out by dehumidified air, the amount of humidity that can be desorbed may be made twice that which is desorbed by ambient air that is cooled. Irrespective of the relative angular positions of the rotor and the stator, each of the adsorption columns 12, 14, 16 can be removed for easy maintenance. Another advantage of the dehumidified air generator is that the gas passages, i.e., the passages of air, can be designed with freedom. FIGS. 4 and 5 show a dehumidified air generator constructed in accordance with a second embodiment of the present invention. The dehumidified air generator shown in FIG. 4 is a modification of the dehumidified air generator according to the first embodiment. Those parts of FIG. 4 which are identical to those shown in FIG. 2 are denoted by identical reference numerals. The dehumidified air generator illustrated in FIGS. 4 and 5 have two adsorption columns I, II. A stator 38 has four openings 122, 124, 126, 128 defined therein, whereas a rotor 36 slidable held against the stator 38 has two openings 130, 132. The opening 130 in the rotor 36 is connected to a gas passage 134 communicating with the adsorption column I, and the other opening 132 is connected to a gas passage 136 communicating with the adsorption column II. The adsorption columns I, II are coupled respectively to gas passages 138, 140 which are in turn connected to two openings 142, 144, respectively, defined in a rotor 32. The rotor 32 is slidably held against a stator 34 which has four openings 146, 148, 150, 152 defined therein. The openings 122, 124 in the stator 38 are connected to a gas passage 40 for supplying humid air that is to be dehumidified by the dehumidified air generator. The opening 126 in the stator 38 is connected to a gas passage 42 for supplying dried air which is to be used in a cooling step. The opening 128 is connected to a gas passage 44 for discharging heated air used in a desorbing step into the atmosphere. The openings 146, 148 in the stator 34 are connected to a gas passage 70 for supplying dried air into a hopper. The opening 150 is coupled to a gas passage 72 for delivering dried air used in a cooling step into a gas passage 82. The opening 152 is connected to a gas passage 74 for supplying heated air to be used in a desorbing step. While a adsorbing step is being carried out by one of the adsorption columns I, II, a desorbing step and a cooling step are successively effected by the other adsorption column. In order to enable the adsorption column I to effect the adsorbing step, the opening 130 in the rotor 36 is aligned with either one of the openings 122, 124 in the stator 38, and the opening 142 in the rotor 32 is aligned with either one of the openings 146, 148 in the stator 34. In order to enable the adsorption column I to carry out the desorbing step, the rotors and the stators are angularly displaced relatively to each other to bring the openings 130, 128 into registration with each other and the openings 142, 152 into registration with each other. In order to enable the adsorption column I to effect the cooling step, the opening 130 in the rotor 36 is aligned with the opening 126 in the stator 38, and the opening 142 in the rotor 32 is aligned with the opening 150 in the stator 34. Similarly, the adsorbing, desorbing, and cooling steps can successively be repeated by the adsorption column II by angularly displacing the rotors and the stators relatively to each other. It is preferable to perform dehumidifying/regenerating cycles in the adsorption columns I, II in the sequence shown in FIG. 5. In each of the first and second cycles, righthand steps are carried out after lefthand steps. The reference characters A, D, C in FIG.5 means the adsorbing step, the desorbing step, and the cooling step, respectively. A dehumidified air generator according to a third embodiment of the present invention shown in FIGS. 6 and 7 has four adsorption columns I', II', III', IV'. Rotors 32, 36 have four openings 184, 186, 188, 190 and four openings 160, 162, 164, 166, respectively, which are connected to the adsorption columns I', II', III', IV' through gas passages 168, 170, 172, 174, 176, 178, 180, 182. The adsorption columns I', II', III', IV' repeat cycles of adsorbing, desorbing, and cooling steps as shown in FIG. 7 by angularly displacing the rotors and the stators relatively to each other. The reference characters A, D, C in FIG. 7 indicate the adsorbing, desorbing, and cooling steps, respectively. Operation of the dehumidified air generator of the fourth embodiment is basically the same as that of the previous embodiments, and will not be described in detail. FIGS. 8A through 8F, 13, and 14 show a dehumidified air generator according to a fourth embodiment of the present invention, the dehumidified air generator having two adsorption columns as with the second embodiment shown in FIGS. 4 and 5. The dehumidified air generator of the fourth embodiment only has one pair of a rotor 232 and a stator 234 below adsorption columns I, II. The adsorption columns I, II and the rotor 232 and stator 234 are supported by only a lower support device, with any structure above the adsorption columns I, II being simplified. Therefore, components such as the rotatable shaft 28, the stator 32, the rotor 32, etc., above the adsorption column 12 in the first embodiment of FIG. 1 are not required in the fifth embodiment. As a result, the overall height of the dehumidified air generator is lowered. The rotor 232 and the stator 234, which are provided only in one pair, rather than two pairs as with the third embodiment, are shown in FIGS. 8A and 8B. The rotor 232 shown in FIG. 8A has four openings to which there are connected four respective gas passages communicating with inlet/outlet ports of the two adsorption columns I, II. In FIG. 8A, the reference characters "U", "L" indicate that the openings denoted by U are connected to the upper inlet/outlet ports of the adsorption columns and the openings denoted by L are connected to the lower inlet/outlet ports of the adsorption columns, and the reference characters "I", "II" represent that the openings denoted by I, II are connected to the adsorption columns I, II in FIG. 13 which are the same as those shown in FIG. 4. The stator 234 shown in FIG. 8B has eight openings which are indicated by reference characters "A", "D", "C" that are defined in FIG. 5. One adsorption column is used in the adsorbing step over two stages that are indicated by A1, A2. The reference characters i, o indicate inlet and outlet openings. In the position of FIG. 11, the openings A1i, A2i are connected to a gas passage 40, the openings A1o, A2o to a gas passage 70, the opening Di to a gas passage 74, the opening Do to a gas passage 44, the opening Ci to a gas passage 42, and the opening Co to a gas passage 72. The rotor 232 and the stator 234 which are disposed below the adsorption columns I, II are combined in various relative angular positions in different steps, as shown in FIGS. 8C through 8F, the views being seen from above the rotor 232. The steps A, D, C per cycle are performed in the four positions shown in FIGS. 8C through 8F. The arrows in FIGS. 8C through 8F indicate the direction and angle of rotation of the rotor 232 to reach each of the steps. The rotor 232 and the stator 234 may be combined in a relative angular position as shown in FIG. 9, in addition to the relative angular positions illustrated in FIGS. 8A through 8F. The rotor 232 and the stator 234 shown in FIGS. 8A through 8F may be positioned above the adsorption columns I, II. FIG. 11 shows in block form the dehumidified air generator which has the rotor 232 and the stator 234. Those parts in FIG. 11 which are identical to those of FIG. 4 are denoted by identical reference numerals. FIG. 12 shows the dehumidified air generator in perspective. Those components shown in FIG. 12 which are identical to those of FIG. 1 are designated by identical reference numerals. The structure and operation of the dehumidified air generator shown in FIGS. 11 and 12 are basically the same as described above, and will not be described in detail. While the openings connected to the upper adsorbent bed are indicated by U and those connected to the lower adsorbent bed are indicated by L in FIGS. 8A through 8F and 11, the direction in which air passes through the absorbents is not limited to the vertical direction in the second through fourth embodiments. Only one pair of a rotor and a stator may be disposed above or below the three adsorption columns shown in FIGS. 1, 2, and 3, so that the side of the adsorption columns which is free from any rotor and stator may be simplified in structure. With such an arrangement, the overall height of the dehumidified air generator is reduced to meet space saving requirements. One specific structure according to such a modification will be described below. FIGS. 10A through 10E a dehumidified air generator according to a fifth embodiment, which is a modification of the first embodiment, the dehumidified air generator having only one pair of a rotor and a stator. FIGS. 10A shows a rotor 232 and FIG. 10B shows a stator 234. Various reference characters in FIGS. 10A through 10E are defined in the same manner as in FIGS. 8A through 8F, except that a reference character "III" indicating the third adsorption column is added. According to the fifth embodiment, a dehumidifying step is carried out. The rotor 232 and the stator 234 are combined in various relative angular positions in different steps, as shown in FIGS. 10C through 10E, the views being seen from above the rotor 232. The steps A, D, C per cycle are performed in the three positions shown in FIGS. 10C through 10E. The arrows in FIGS. 10C through 10E indicate the direction and angle of rotation of the rotor 232 to reach each of the steps. The dehumidified air generator having three adsorption columns as with the first embodiment has a considerably large height. The dehumidified air generator which has only one pair of a rotor and a stator has a relatively low height and is made up of a reduced number of parts, so that the cost of the dehumidified air generator is lowered. With the dehumidified air generator having two adsorption columns, while an adsorbing step is being carried out in one of the adsorption columns, two steps, i.e., desorbing and cooling steps, are required to be carried out in the other adsorption column. In addition, since the dehumidified air generator with two adsorption columns is intermittently operated, it is necessary to increase the capacity of the desorbing devices (such as a heater and an air blower). According to the dehumidified air generator having three adsorption columns, however, the adsorbing, desorbing, and cooling steps are effected simultaneously, and the capacity of the desorbing devices (such as a heater and an air blower) may be reduced to half of that of the dehumidified air generator with two adsorption columns. Because of these practical merits, a large-sized dehumidified air generator should advantageously have three adsorption columns. The term "adsorption column" used herein signifies a region or member housing an adsorbent, and does not include upper and lower empty spaces or pipe portions. In the first embodiment, two pairs of rotors and stators may be disposed respectively above and below the adsorption columns, or one pair of a rotor and a stator may be disposed only above or below the adsorption columns. With only one pair of a rotor and a stator being located above or below the adsorption columns, the rotor has four openings and the stator has eight openings if there are two adsorption columns used, and each of the rotor and the stator has sixth openings if there are three adsorption columns used. According to the first embodiment, since the adsorption columns are vertically stacked and are projected onto a common horizontal plane in at least partly overlapping shapes, the installation area or space for the dehumidified air generator may be as wide as that for a dehumidified air generator having a single adsorption column. As a result, the installation area is greatly reduced, an improvement which has not been achieved by the conventional dehumidified air generators. With respect to the greatly reduced installation area, each of the adsorption columns used can meet the conditions 4) and 5) referred to above, i.e., has an appropriate adsorbent layer cross-sectional area and a required adsorbent layer thickness. Additionally, if only one pair of a rotor and a stator is provided only above or below the adsorption columns, the vertical dimension of the dehumidified air generator is further reduced to reduce a necessary installation space. With the present invention, the rotor and the stator jointly constitute a directional control valve, and adsorbing and regenerating steps in each of the adsorption columns can be switched over by rotating the rotor to angularly displace the rotor and the stator relatively to each other. Because the openings in the rotor are connected to the corresponding inlet/outlet ports defined in the outer walls of the adsorption columns through gas passages, the adsorption columns can be smoothly operated even if the dehumidified air generator has a system of tubes or gas passages which meets the conditions 1) through 3) referred to above. Moreover, inasmuch as the adsorption columns are attached to and supported on the support device or the rotatable shaft, the weights of the adsorption columns are not borne by the rotor and the stator. As a consequence, the rotor and the stator may be reduced in size, and the sealing ability of the directional control valve is increased. According to another embodiment, where there are three adsorption columns, the adsorption columns can effect adsorbing, desorbing, and cooling steps, respectively, to permit efficient continuous operation for air dehumidification. It is preferable in the first embodiment that the gas passages be positioned or gathered on one lateral side of the adsorption columns to allow the other lateral side to be used as a working space for maintenance such as adsorbent replacement. In relation to the condition 4), the cross-sectional area of air in each of the adsorption columns should be 15 to 50 times (4 to 7 times if the inside diameter is concerned) the transverse cross-sectional area of pipes or gas passages for delivering adsorbing air. This area ratio is not disclosed in FIGS. 2 and 4 of Japanese Laid-Open Patent Publication No. 49-7166. Therefore, the present invention can satisfy the condition 4) which cannot be met by the invention disclosed in FIG. 2 or 4 of Japanese Laid-Open Patent Publication No. 49-7166. In the first embodiment, the rotatable shaft may not necessarily be positioned in the center of the adsorption columns. While the adsorption columns should preferably be projected onto the horizontal plane in the fully overlapping shapes, they may be projected in relatively displaced shapes, but should be projected in at least partly overlapping shapes. The adsorbent beds housed in the adsorption columns are not required to be oriented such that dehumidified air flows vertically therethrough, but may be oriented such that dehumidified air flows horizontally or obliquely to the vertical direction. A gas to be dehumidified by the dehumidified air generator of the invention is not limited to air, but all kinds of gases may be dehumidified by the dehumidified air generator of the invention insofar as such gases do not adversely affect the adsorbents used. The adsorbents that can be used in practice are not limited to molecular sieves (with the temperature of desorbing air at the inlet ports of the adsorption columns being in the range of from 250°C to 300°C under normal condition), but other adsorbents such as of silica gal, alumina, or a fibrous material such as paper in the form of a honeycomb structure may be employed. In the adsorbing step, the direction of air to be dehumidified is not limited to the downward direction. The principles of the present invention may be applied to a dehumidified air generator which does not satisfy the conditions 1) through 5). In cases where the condition 5) is to be met, i.e., the cooling step is to be carried out by using dried air, a portion of dehumidified air may be returned under the pressure of an air blower for the dried air, or another air blower may be used solely for recycling cooling air. The actuator or power source for rotating the rotor or rotors in synchronism with the adsorption columns may comprise a motor for rotating the adsorption columns, or another actuator or power source. The tubes or gas passages may be used as a small portion or an almost entire portion of the support device by which the adsorption columns are supported. Where there are two adsorption columns used, a suitable means may be provided for shutting off the introduction of dried air into an adsorption column after the time required to effect a cooling step in that adsorption column has elapsed, i.e., after the cooling step is over, in order to prevent wasteful consumption of the dried air used in the cooling steps. Such means may include an additional opening defined in the stator.

Claims: A dehumidified gas generator (10) comprising: a plurality of simultaneously rotatable adsorption columns (12,14,16) having respective adsorbent beds (90,92,94) housed therein; a rotor (36), rotatable in synchronism with the adsorption columns, the rotor having a plurality of openings defined therein; a stator (38) fixed opposite the rotor and having openings which can be made to correspond with said rotor openings; the rotor and the stator jointly serving as a directional control valve for switching between adsorbing and regenerating steps in each of the adsorption columns; rotating means (77,28,30) for coupling the adsorption columns to each other and rotating the adsorption columns in synchronism with the rotor, the rotating means including a rotatable shaft (30), the arrangement being such that the adsorbing and regenerating steps in the adsorption columns can be switched by angularly displacing the rotor and the stator with respect to each other with the rotating means; and tubes (46,48,50,58,60,62) for passing a gas to and from the adsorbent beds, one end of each tube being connected to the rotor; whereby each of the tubes (46,48,50,60,62) is connected at its other end to a respective port defined in an outer side wall of an adsorption column; the adsorption columns (12,14,16) are supported such that their weight is not carried by the rotor (36) and stator (38); and characterised by the adsorption columns (12,14,16) being disposed in different vertical positions, respectively, and divided vertically from each other, the adsorption columns (12,14,16) at least partially overlying one another in a vertical direction and being mounted on a support device (26) rotatable about a straight axis extending vertically through the adsorbent bed in at least one of the adsorption columns. A generator according to claim 1, wherein the tubes (46,48,50,58,60,62) are disposed in one lateral side of the adsorption columns (12,14,16). A generator according to claim 1, wherein the rotor (36) and the stator (38) are disposed either above or below the adsorpotion columns (12,14,16). A generator according to claim 3, wherein the rotor (232) has four openings (IU,IL,IIU,IIL) and the stator (234) has eight openings (A1i,A2i,A1o,A2o,Do,,Ci,Di,Co), the dehumidified gas generator comprising two adsorportion columns (I,II). A generator according to claim 3, wherein the rotor (332) has six openings (IL,IU,IIL,IIU,IIIL,IIIU) and the stator (334) has six openings (Ai,Ao,Do,Di,Ci,Co), the dehumidified gas generator comprising three adsorption columns (I,II,III).

Inventors: NOGUCHI HARUO, NOGUCHI, HARUO
Applicants: COLORTRONIC CO LTD, COLORTRONIC CO., LTD.
Application year: 1989
Main classification: B01D53
IPC codes: B01D53, F26B21, F24F3