SE449182B - DEVICE FOR DRYING OR DEHUMATING A GAS - Google Patents

Description

449 182 with the adsorption capacity of the adsorbent or desiccant applied to the heater.

While some of the known devices operate intermittently, by the adsorption and regeneration processes taking place alternately for the entire amount of adsorbent in the device, other known devices (e.g. those described in U.S. Pat. Nos. 3,467,608 and 3,490,201) _ work continuously fl y _ The applicant's earlier Swedish publication SE-B-7800211-0 (publication number 432.058) describes an apparatus for drying or dehumidifying gas, provided with m- a housing, which forms a number of separate chambers or ducts; each containing separately a regenerable moisture adsorbent medium and selectively activatable electric heating means for selectively heating the adsorbent medium when it is to be regenerated. In one embodiment of the apparatus described in the specification, each of the chambers contains a folded or pleated sheet- or plate-like adsorbent medium of a fibrous material, and electric heating elements are arranged between adjacent layers of the fibrous material. the sorting medium.

A gas to be dehumidified can thus flow through the spaces between adjacent layers of adsorbent medium from the inlet of the apparatus to its outlet and vice versa. However, the flowing gas will then hardly come into contact with the inner parts of the layers of adsorbent medium but mainly only at their outer upper surface. In another described embodiment, a particulate adsorbent medium is disposed in layers extending across the gas stream in the chamber in which the layers are disposed, and the heating means comprises one over the other anoragic bead-shaped portions of a thermally conductive material for receiving them. such a construction does not ensure a completely uniformly distributed gas flow over the entire cross-sectional area of each chamber and, since the bead-shaped portions are to extend substantially horizontally, m; 449 182 the gas flow must be directed substantially vertically, which means that the apparatus can not be oriented as one would like -this._ 'f. . This is achieved according to the invention by means of the features stated in the characterizing part of the following independent claims 1 and of the subsequent dependent claims. The construction according to the invention ensures a uniformly distributed gas flow over the entire cross-sectional area of the chamber, so that the chamber comes into intimate contact with all the parts of the adsorbent. The arrangement of the electric heating means between and in intimate contact with adjacent In addition, layers of adsorbent medium or adsorbent provide that each separate layer, which may have a suitably small thickness, during the regeneration process can be heated directly on both sides of the heating means. This efficient direct heating of the adsorbent means that only a comparatively small amount of dehumidified gas is required for the regeneration process, so that when using the apparatus according to the invention a very advantageous heat economy can be achieved; In addition, the application of the electric heating means or the heating elements between adjacent "layers of the adsorbent" considerably facilitates the mounting of the apparatus, as well as it also facilitates later "replacement" of any defective heating elements.

D The adsorption efficiency of the adsorbent medium will normally decrease as its temperature rises. It is therefore important that the adsorbent is cooled after the regeneration process, before the adsorbent is reused in a new adsorption process. This can be achieved, for example, by forcing cold air or gas to flow through the adsorbent for a certain period of time after the heating means have been inactivated; Z _ 7 Z The adsorbent's adsorption of moisture or steam normally involves the development of heat, whereby the temperature of the adsorbent and the gas flowing through it increases. A higher temperature of the gas to be dehumidified causes the relative humidity of the gas to be reduced by 449 182% 4. Since the moisture adsorbing ability of the adsorbent depends to some extent on the relative humidity of the gas, the evolution of adsorption heat may have the effect that the adsorbent medium 'efficiency is relatively small in a zone at the farthest end of the receptacle chamber. In some cases, for example in appliances that may have a large potential adsorption capacity, it may be advantageous to counteract the temperature rise due to the development of adsorption heat. According to the invention, the moisture-adsorbent medium in each of the chambers or ducts may thereby be divided into axially spaced apart parts or sections, and further between such parts or sections may be arranged cooling means of some suitable type for cooling the gas which 449 182 flows through each chamber. With the apparatus according to the invention, the regeneration process takes place quickly and efficiently. Therefore, an apparatus containing a comparatively small amount of adsorbent medium or adsorbent may have a fairly large capacity. A reduction of the required amount of adsorption means a significant reduction of the flow resistance in the apparatus. Consequently, even a device with a large capacity can have such a small flow resistance that it can be used not only for dehumidifying compressed air but also for dehumidifying air at atmospheric pressure which can be passed through the device by means of a fan. d c The adsorbent or adsorbent material may comprise any known adsorbent material such as molecular sieves or sieves, silica gel, activated alumina, synthetic mineral fibers and ceramic fibers. The adsorbent is preferably a particulate material but may instead be a plate or sheet material. Such a plate or sheet material may, for example, be in the form of an asbestos strip, an asbestos sheet, an asbestos web or an asbestos plate impregnated with a hygroscopic material such as lithium chloride. The invention will now be described in more detail with reference to the drawing. Fig. 7; 1 shows a finally cut side view of a preferred embodiment of the apparatus or dehumidifier according to the invention. Fig. 2 is a cross-section on a larger scale through one end of the apparatus or dehumidifier according to Fig. 1.

Pig. 3 and 4 show possible arrangements of the plate or sheet-like heating elements in the chambers of the dehumidifier according to the invention. d i Pig. 5 is a plan view of a plate or sheet material which can be used as the heating element apparatus according to the invention. Fig. 6 ~ is a diagram illustrating an electrical control system for controlling the apparatus shown in Figs. 1-4. 449 182 6 Fig. 77 and B-are perspective views on a larger scale "of a rotary switch device seen from opposite ends.

Fig. 9 * is a schematic partially cut-away side view of a fourth embodiment of an apparatus according to the invention. Pig. Finally, a partially cut-away view from below of the apparatus shown in Fig. 9. The apparatus or dehumidifier shown in Figs. 1-4 has a stationary cylindrical housing 10, which is divided by means of a number of radially extending partitions 11. in several sector-shaped passages or chambers l2, which are open at opposite ends. At one end of the housing 10 there is an inlet pipe 13 for moist gas or air, and the housing is provided at its other end with an outlet pipe 14 for dried or dehumidified gas or air. The sector-shaped chambers or channels 12 are arranged in an annular arrangement inside the housing, so that they surround and delimit a central space 31. each of the chambers 12 is substantially filled with an adsorbent medium or an adsorbent 15, and between adjacent layers of the adsorbent medium are arranged electric heating elements 43, which will be described in more detail below. The ends of the chambers or passages 12 which are in the vicinity of the inlet pipe 13 are connected thereto. tube through connecting channels 34 and via a rotary valve 20 fixedly mounted at one end of a central shaft 45 and extending axially through the apparatus. The housing 10 has an annular outlet manifold 24 which surrounds the rotary valve 20 and communicates with the atmosphere via an outflow pipe 25. In the inner wall of the manifold 24 is delimited an annular gap 38, which along the main part of its peripheral length is closed by a cylindrical, risky outer wall 36 to valve 20; the valve 20 also has a wall 39 extending across the inlet pipe 13, and the cylindrical wall 36 is cut away along the inner peripheral edge to the transverse wall 39, so that the valve can connect a smaller part (for example one or two) of the chambers 449- 1.82 vi 12 to the manifold 24 via an uncovered part of the column 38, while the others. chambers 12 communicate with the inlet pipe 13.

A switch actuating disc 46 with peripheral actuating actuators or cams 30 is mounted at the end of the shaft 45 opposite the valve 20. The disc 46 has a ring gear 47 which engages a drive gear 48 driving a drive motor 27. The motor 27 is mounted on an end cap 49, which has an outlet pipe 14 and is arranged at the adjacent end wall of the housing. The shaft 45 extends through an annular inner housing 50 defining the central space 31. The inner housing SO includes a rotatable electric switch device 51 having a stator portion 52 which abuts the inner upper surface of the tubular housing, and a rotor 53, which is mounted on the shaft 45, so that it rotates together with the shaft. The switch device 51 will be described in more detail below with reference to Figs. 7 and 8.

Fig. 5 shows a preferred embodiment of the electric heating elements 43 and shows a web comprising a heat-resistant plate or sheet material and electrical circuits "printed" thereon by conventional techniques for printing such circuits. The web material shown in Fig. 5 can be divided into a number of heating elements by cutting the web in the transverse direction, for example along the dotted line indicated in Fig. 5. Each heating element 43 has three modules or a multiple of three modules 54, each of which comprises a printed circuit or a number of series-connected resistor elements 55. The printed circuits of the web also comprise longitudinal bushes 56, which connect the resistor elements 55 in parallel to adjacent modules and which in each module have connection points 57.

The flat or sheet-shaped plastic material used in the heating elements 43 shown in Fig. 5 may, for example, be those marketed by 3M Company under the trademark KAPTON. This material is resistant at temperatures as high as 260-É70 ° C. The heating element 43 can be manufactured by etching a foil of stainless steel, which is laminated with the plastic foil to produce the desired printed circuit. _ 'I å I' I _ It's clear; that a plate or sheet material with printed circuits such as that shown in Fig. 5 can be manufactured in the form of webs of any desired length, after which heating elements containing any desired number of modules can be cut off from this web. heating element 43 of the type shown in Fig. 5 is arranged in each of the chambers or passages of the apparatus 12. The heating element is preferably folded or pleated, for example as shown in Fig. 3 or Ä, and adjacent layers of the heating elements may be spaced apart by means of spacers 581 disposed between the layers. These spacers are preferably in the form of a corrugated sheet or sheet material such as a woven heat-resistant material, for example of polyester. The spacers 58 may be impregnated with a hygroscopic material such as lithium chloride having a cellular structure defined by the walls of the chambers 12, the spaced apart layers of the heating elements 43 and the corrugated spacers 58 being filled with a suitable fibrous or particulate moisture. medium 15, for example molecular sieve or sieve, silica gel, activated alumina or any suitable regenerable adsorbent or a hygroscopic substance) The spaces between the spaced layers of the folded or pleated heating elements 43 should be small enough to The distance can, for example, be of the order of 10 mm.7 Fig. 6 is a diagram showing an electric control system for controlling the apparatus shown in Figs. 1 and 2. The dryer or dehumidifier is set up to be supplied with current from one three-phase network and comprises power supply terminals R, S, T and O. These terminals are connected to the corresponding power supply lines 1R, 15, 1T resp. lo. The power supply through these lines can be controlled by a main switch 59. The power supply through the lines 1R, 1s and 1T is used to conduct power to a fan 60 and selected copies of the heating elements 43 arranged in the chambers 12. The power supply to the fan eo and to the heating elements 43 is controlled by contactors 61 resp. 62 or other suitable switch means. The fan 60 is used to blow air or gas to be dried into the apparatus through the inlet pipe 13. The operation of the motor 27 driving the shaft 45 and the switch actuating plate 46 mounted thereon, the switch device 51 and the rotary valve 20 are controlled by a clock-controlled contactor or switch device 63, a hygrostat 64 or other device sensitive to moisture, which in the flow direction is preferably arranged after the dehumidifier and in the vicinity of its outlet pipe 14 and by projections or cams 30 on the switch activating disk 46. The hygrostat 64 controls a switch S0, while the clock-controlled contactor 63 controls the switches S1 and S4, and the switch means 29 comprise switches S2 and S3. The apparatus shown in Figs. 1 and 2 functions essentially as that described in the applicant's the above-mentioned patent application, which means that air or gas to be dried or dehumidified is passed through the main part of the chambers 12 and the ssa existing adsorbent 15, while a small fraction of the dried gas is returned and passed through the remaining smaller part of the chambers 12 in the opposite direction, so that the adsorbent or adsorbent medium in these chambers is heated and regenerated. At certain time intervals, the chamber or chambers in which the adsorbent is regenerated are changed and this regeneration cycle is controlled by the electrical control system shown in Fig. 6. I 1 II 449 132% sf 10 lWhen the main switch 59 is closed, the contactor 61 will automatically connect the fan eo to the power supply lines 1R, ls and lT, so that the fan will start blowing air or gas, which is to be dried, into the blow-in tube 13; Assuming that the switches SO-S4 are in their positions shown in Fig. 6, current is not conducted to the motor 27. Consequently, the valve 20 is stationary f and allows the flow of air or gas from the inlet pipe 13 through the main part of the chambers or passages 12. to the outlet pipe 14, as indicated by arrows in Fig. 1. However, the transverse wall 39 of the valve 20 closes the passage from the inlet pipe 13 to a smaller part, preferably two of the chambers 11, and at the same time the valve connects this smaller part of chambers to the manifold 24 through the gap 33 as mentioned above. Accordingly, dry gas can flow from the outlet pipe 14 into the said smaller portion of chambers through one or more flow restricting openings 65 and from the chambers into the atmosphere through the manifold 24 and the outflow pipe 25; After a predetermined period of time, the clock-controlled contactor or timer 63 closes the switch Si. If the hygrostat 64 does not determine that the moisture content of the gas leaving the outlet pipe 14 is below a predetermined value, the switch S0 is also closed by the hygrostat 64, where -__ at current is supplied to the motor 27 through the closed contacts S0, S1 and S3. The motor 27 now rotates the rotor 53 of the switch device 51 and the valve 20 one step forward corresponding to 3: 0, where n is the number of sectors against an angular rotation of similar chambers or passages 12 in the apparatus.

The new angular position of the valve will be determined by the cams or projections 30 of the actuating disc 46 which open the switch S3 and at the same time close the switch S2. When the valve 20 is moved to its new position, the contactor 63 closes the switch S4, which causes the contactor 62 to conduct current to the heating elements 43. However, as illustrated in Fig. 6, only the heating elements 43 which L In a preferred embodiment, the apparatus shown in Figs. 1 and 2 contains six chambers or passages 12, and the valve 20 is arranged to allow the flow of gas to be dried. through four of these chambers, while a small fraction of the dried gas is returned through the two remaining chambers, in which the adsorbent medium is regenerated.The engine 27 is controlled so that the valve 20 and the rotor 53 of the switch device 51 are rotated stepwise by steps corresponding to an angular rotation of 600. Consequently, the regeneration period - for the adsorbent in each chamber will amount to twice the time during which the clock-controlled contactor 63 activates the switches S1 and S4. re or passage, the heating elements 43 are supplied with current only during the first of these time periods, and during the subsequent period of time cold dry gas will flow through the chamber, whereby the regenerated adsorbent therein is cooled. It will be appreciated that each time a period of time determined by the clocked contactor or timer 63 has elapsed, the switches S1 and S4 will be activated, the contactor 62 interrupting the power supply to the heating elements, and the motor 27 is then rotated one step forward determined by the activating disk 46. changes the position of the switches S2 and S3, after which the contactor 62 reconnects the heating elements 43 for power supply. The tube 53 has, however, been rotated one step forward, so that the heating element in the subsequent chamber 12, in which the adsorbent is to be regenerated, is supplied with current.

However, insofar as the hygrostat 64 indicates that the moisture content of the dried gas flowing from the apparatus through the outlet pipe 14 is below a predetermined value, the switch S0 is opened. If the switch S0 is continuously open, when the activated contactor 63 opens the switch 64 to cut off the power supply to the heating elements and changes the position of the switch S1, the motor will not be supplied with current until the hygrostat 64 closes 449 182 A: The switch S0, which results in an extension of the air drying period in the main part of the chambers l2 and of the cooling period of the adsorbent regenerated in two of the chambers 12. The electric rotary switch device 51 shown in Figs. 7 and 8 will now be described in more detail. The stator part 52 has a coil-shaped part of an insulating material.

The coil-shaped part is provided at one end with three in radial direction separated and mutually insulated metal? terminal rings 66, '67 and 68, representing the electrical phases R, eS and T; These rings have spaced apart screws 69 or connecting means for electrically connecting the heating elements 43 in the respective chambers 12 thereto. Each heating element 43 comprises three modules 54, as shown in Fig. 5, and one terminal end of each module is connected to a terminal ring 66, 67 and 68 each.

The terminal ends of the three modules 54 in each heating element 43 are connected to three spaced apart spaced terminal connections 7 parts 70 which are arranged concentrically with the rings 66-68.

Axielir leading electrical bearing 71 connects each of the connecting means 70 to a contact means 72, which is arranged at the other end surfaces of the switch device S1, and the contactor 72 is, as shown in Fig. 7, arranged in triangular groups, so that the three contacts in each group are connected to the same heating element 43. The rotor S3 has an arm, on the free end of which a spring-actuated short-circuit member or a contact plate 73 is mounted. As the shaft 43 is rotated stepwise by the motor 27, the rotor 53 is rotated between positions in which the plate 73 abuts all three contacts 72 in a group, so that the clamps or connections of the three modules 54 to associated heating elements 43 are short-circuited, conducting current to this heating element. The electric switch device shown in Figs. 7 and 8 has eight groups of contacts 72 and is thus arranged to be used in connection with an apparatus with eight chambers 12. However, if the dehumidifier has only six chambers, as mentioned above, The switch device of course also only has six groups with contacts 72. Figs. 9 and 10 schematically show an embodiment of 7 of the type described above in connection with Figs. 1-4. In Figs. 9 and 10, however, the chambers or passages 12 are divided into axial parts or sections so that the gas or air to be dried alternately passes cooling or heating parts or sections and adsorbent parts or sections. For example, if the gas to be dried contains a large amount of moisture, the first section 74 may be a condenser section in which moist gas flowing from the inlet pipe 13 is cooled by suitable means so that, some of the moisture in the gas condensers These cooling means may, for example, consist of the evaporator in a conventional cooling system or according to so-called heat pump, which has a compressor 75 and a reduction valve 76. The condenser of the cooling system can then be used for reheating the dried gas or air in a heating section 77, before the gas flows through a filter section 78 to the outlet pipe 14. It may be desirable to avoid cooling. and heating the regeneration gas in the condenser section resp. heating section. The lines in the cooling system or heat pump may therefore be provided with solenoid valves 81, by means of which the flow of coolant or heat-transporting fluid in the lines of the system can be controlled in such a way that the fluid flow is interrupted in the chambers or passages 12 in which the adsorbent is regenerated. The apparatus shown in Figs. 9 and 10 has three adsorbent portions or sections 79 which contain adsorbent media and heating elements as well as intermediate cooling portions or sections 80 for removing the heat of adsorption provided in the former adsorption part.

The intermediate cooling sections 80 may include cooling means of any suitable type, such as water cooling means, an evaporator in a cooling system or a heat pump, etc. The cooling means located in intermediate cooling sections 80 shall be arranged to provide cooling only in chambers. 12 which is passed through by gas to be dried and not in the chambers in which regeneration takes place. Each intermediate cooling part or section may therefore comprise a condenser part and an evaporator part in a conventional cooling system and there may be controllable valve means for controlling the fluid flow in the system in such a way that the condenser part in the system is always in the chamber or chambers. in which the regeneration of the adsorbent takes place, while the evaporator part is in the other chambers. The apparatus shown in Fig. 9 is preferably arranged with its longitudinal axis in an upright position and with the inlet pipe 13 facing downwards. Moisture which is condensed and separated in the condenser part 74 can then flow out through the outflow pipe 25 together with the gas used for regeneration of adsorbents. The adsorption parts 74 may contain different types of adsorbents and, any desired combination of condensing, cooling, heating and adsorbent parts or sections may be used. The dehumidifier according to the invention can operate very economically. This is primarily due to the fact that only a very small amount of regeneration gas is necessary (for example - about 4% of the total amount of gas being dried) and the direct direct heating of the adsorbent during the regeneration thereof and the like. the distribution of the gas flow over the cross section of the chambers and the adsorbent contained therein. Kp 7 7 _ Z It's clear; that within the scope of the invention various changes and modifications may be made to the embodiments described above. Furthermore, the features described in connection with different embodiments can be interchanged. I A

Claims (10)

449 182, 11 p Apparatus for drying or dehumidifying gas and having a housing (10) delimiting at least one passage or at least one chamber (12), having a gas inlet (13) and a * gas outlet (14) and containing a layered regenerable, gas-permeable moisture-absorbing medium (15) and selectively activatable electric heating means (43) in the form of plate-shaped or sheet-shaped material for selectively heating the adsorption medium for regenerating it, characterized in that the layer of the adsorption medium (15) is separated from each other by means of the substantially gas-impermeable plate- or sheet-shaped material (43) which constitute the electric heating means and which are arranged in direct contact with adjacent layers of the absorption medium and between them delimit gas flow passages extending along these layers which each at its ends is connected to the gas inlet (13) resp. gas outlet (14) {"7 Apparatus according to claim 1, characterized in that the plate or sheet material (43) has printed resistance circuits (55-57). '* _- 3. Apparatus according to claim 1 or 2, characterized in that spacers for the plate or sheet-shaped material which delimit the current flow passage are arranged in the gas flow passages, which spacers preferably have the shape of a corrugated plate. or sheet material (58). 4. Apparatus according to any one of claims 1-3, characterized in that at the inlet end (74) of the chamber (12) a cooling means is arranged for cooling the gas to be dehumidified, so that moisture is condensed therein. 5. Apparatus according to claim 4, characterized in that it further has reheating means arranged at the outlet end (77) of the chamber for reheating the dehumidified gas. I 'Z 449 182 16 OJ' Apparatus according to claim 5, characterized in that the cooling means and the heating means comprise an evaporator or a condenser in a heat pump system (75, 76). Apparatus according to any one of claims 1-6, characterized in that the moisture-absorbing medium in said chamber is divided into spaced apart parts or sections (79) and that there are cooling means between the separate parts ( 80). 7 I _ ' Apparatus according to any one of claims 1-7, characterized by; that the heating means (43) in the chambers (12) comprise star-connected heating elements (54) and that the heating means further comprise switch means (51) having a contact means (73) for selectively short-circuiting the heating elements at their neutral points (72) for supplying current to the heating elements in at least one of said chambers. Apparatus according to claim 8 and having a rotary valve for passing gas to be dehumidified through a first number of Q w said chambers and for passing a stream of dehumidified gas from the outlet ends of said chambers through a further number (of said chambers for regeneration of the adsorption medium present therein, characterized in that the neutral points (72) of the star-coupled heating elements (54) accommodated in said chamber (12) T- are grouped in a circular arrangement, and that the short-circuit contact member (73) is rotatably mounted about the axis of the circular arrangement and coupled to the rotary valve (20) to ensure conformity of the rotational movement of the contact member and the valve. Apparatus according to claim 9, characterized in that the switch means (53) are arranged to interrupt the power supply to the heating means (43) in each of said further number of chambers or passages (12) before the flow of dehumidified gas through each chamber or A 7 g and the respective passage are interrupted, whereby the adsorbent medium present in this 27 is cooled by the gas stream. Q