NL8002856A - DEVICE FOR DRYING OR DEHUMIDIFYING GAS. - Google Patents

Description

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Device for drying or dehumidifying gas.

The invention relates to a device for dehumidifying gas and comprising a regenerable vapor or moisture adsorbent medium or an adsorbent. Such a device for dehumidifying air or other gaseous media can, for example, be used for dehumidifying air in compressed air systems and in rooms, and for dehumidifying gas or air to be used in manufacturing processes and the like.

Devices of the type in which the adsorbent medium or adsorbent is divided into a number of layers are known to obtain a more uniform gas flow distribution over the cross section of the adsorbent used. Such devices are described, for example, in -. U.S. Patent No. 3,490.

15 201 and 3,594,990). When the adsorbent medium or adsorbent has been used for a certain period of time and has been enriched with a certain amount of moisture, it must be regenerated. This can be done by passing heated air through the adsorbent (US Pat. No. 3,490,201) or by heating the adsorbent directly and at the same time passing air from the surrounding atmosphere through it (US Pat. No. 3,594,990). The former method involves a relatively high loss of heat energy, while the latter method is more favorable from a heat economics point of view. However, in known devices, in which the adsorbent medium is divided into a number of layers, each of which is heated with electric heating means during regeneration (U.S. Pat. No. 3,594,990), the layers of adsorbent medium are limited to fine amounts of a desiccant, such as lithium chloride, which is applied to heating wires by impregnating these wires covering asbestos yarn. It will be appreciated that the cost of the electric heater in this known construction is relatively high compared to the adsorption capacity of the adsorbent or desiccant supported by the heater 5.

While some of the known devices operate intermittently, because the adsorption and regeneration processes alternate for the total amount of adsorbent used in the device, other known devices (for example, described in U.S. Pat. Nos. 3,487,608 and 3,490,201) may continuously to work.

Applicants earlier Dutch patent application no. 78.00301 describes an apparatus for drying or dehumidifying gases and comprising a housing with a number of separate chambers or channels, each containing a regenerable moisture adsorbing medium and selectively switchable electric heating means for selectively heating the adsorbent medium, if it is to be regenerated. In one embodiment of the device described in said patent application, each of the chambers comprises a folded or pleated plate-shaped adsorption medium of a fibrous material, and electric heating elements are arranged between adjacent layers of the adsorbent medium. Thus, a dehumidifiable gas can flow through the interstices between the adjacent layers of the adsorbent medium from the inlet to the outlet of the device 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 with the outer surface thereof. In another described embodiment, a particulate adsorbent medium is provided in layers that extend transversely to the gas flow through the chamber in which the layers are applied, and the heating means comprise superposed shell members of a heat-conducting material, these layers of particulate material record. This construction does not ensure 800 2 8 56 * * -3- a completely uniformly distributed gas flow across the cross section of each chamber and, since the shell-shaped members must extend substantially horizontally, the gas flow must be directed substantially vertically so that the device does not can be placed in any desired position.

The present invention provides a very economical operating device of the type described, which can be placed in any desired position.

The invention provides an apparatus for drying or dehumidifying gases and comprising a house which defines at least one channel or chamber, this chamber having a gas inlet and a gas outlet and containing a regenerable and gas-permeable moisture-absorbing medium and selectively switchable electric heating means for selectively heating the adsorbent medium to regenerate it, wherein the device according to the invention is characterized in that the adsorbent medium is arranged in layers which are resp. communicate with the gas inlet and the gas outlet, the heating brackets comprising a sheet material which separates and contacts the adjacent layers of adsorbent medium to form a gas flow channel by edk of the layers of adsorbent medium. The construction according to the invention ensures a uniformly distributed gas flow over the cross-section of the chamber, so that the gas flow comes into intimate contact with the adjoining layers of adsorbent medium or adsorbent so that each individual layer - which may have an appropriately small thickness - during the regeneration process. can be heated directly on both sides by the heating means. This effective direct heating of the adsorbent means that only a relatively small amount of the dehumidified gas is required for the regeneration process and therefore a very favorable heat economy can be achieved by using the device according to the invention.

In addition, the construction with the electrical heating means or heating elements between adjacent layers of the adsorbent greatly facilitates the mounting of the device and also facilitates subsequent replacement of potentially broken heating elements.

The adsorption efficiency of the adsorption medium 5 normally decreases as its temperature increases,

It is therefore important that the adsorbent is cooled after regeneration before the adsorbent is used again in a subsequent adsorption process. This can for instance be achieved by allowing cold air or cold gas to flow through the adsorbent for a certain period of time after the heating elements have been switched off.

The adsorption of moisture or vapor by the adsorbent usually involves heat generation, thereby increasing the temperature of the adsorbent and the gas flowing therethrough. A higher temperature of the gas to be dehumidified means that the relative humidity of the gas decreases. Since the moisture adsorbing capacity of adsorbents is highly dependent on the relative humidity of the gas, the generation of adsorption heat can have the effect that the efficiency of the adsorbent medium becomes quite small in the area at the downstream end of the gas. concerning room. In certain instances, for example, in heavy duty devices with a high potential adsorption capacity, it may be beneficial to counteract the temperature increase due to the generation of adsorption heat. According to the invention, the moisture adsorbing medium in each of the chambers or channels can then be divided into axially spaced sections, and suitable type coolants can be placed between those sections to cool the gas flowing through the respective chamber.

In the device according to the invention the regeneration process takes place quickly and efficiently. A device with a relatively small amount of adsorbent medium or adsorbent can therefore have a fairly high capacity. A reduction in the necessary amount of adsorbent 800 2 8 56 * i -5 means a significant reduction in the flow resistance in the device. The result is that even a large capacity device can have such a low flow resistance that it can be used not only for dehumidifying compressed air, but also for dehumidifying air under atmospheric pressure which is blown through the device by means of a fan. can be guided.

The adsorbent or adsorbent material 10 may comprise any known adsorbent material, such as molecular sieves, silica gel, activated alumina, synthetic mineral fibers, and ceramic fibers. The adsorbent is preferably a particulate material, but may also be a plate or web material. Such a plate or web-shaped material can for instance take the form of an asbestos tape, asbestos plate, asbestos web, or an asbestos panel impregnated with a hycroscopic material such as silicon chloride.

The invention will now be further described with reference to the drawings.

Figure 1 is a side view and a partial cross-section of a preferred embodiment of the device or dehumidifier according to the invention.

Figure 2 is a larger-scale section of an end of the device dehumidifier of Figure 1.

Figures 3 and 4 are views showing possible arrangements of the plate-shaped heating elements in the chambers of the dehumidifier according to the invention.

Figure 5 is a top view of a sheet material that can be used as heating elements in the device according to the invention.

Figure 6 is a schematic showing an electrical control system for controlling the operation of the device shown in Figures 1-4.

Figures 7 and 8 are enlarged perspective views showing a rotary shifting device, respectively. from both sides.

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Pigure 9 is a schematic side view and a partial cross-section of a fourth embodiment of the device according to the invention.

Figure 10 is a bottom view and a partial cross-section of the device shown in Figure 9.

The device or dehumidifier shown in Figures 1-4 comprises a stationary cylindrical housing 10 which is divided by means of a number of radially extending partition walls 11 into a number of sensor-shaped channels or chambers 12, which are open at ends. At one end, the housing 10 is provided with an inlet housing 13 for moist gas or moist air, and at the other end, the housing is provided with an outlet tube 14 for dried or dehumidified air or dry or dehumidified gas.

The sector-shaped chambers or channels 12 are placed in the housing 10 in an annular arrangement, so that they surround and define a central space 31. Each chamber 12 is largely filled with an adsorbent medium or adsorbent 15, and electric heating elements 43 are interposed between successive layers of the adsorbent medium, as will be described in more detail below. The ends of the chambers or channels 12 near the inlet tube 13 communicate with those tubes through connecting channels 34 and through a fixed rotary valve 20 mounted at one end of a central shaft 45 extending axially through the device. housing 10 includes an annular exhaust manifold 24 that surrounds the rotary valve 20 and communicates with the atmosphere through an exhaust pipe 25. The inner wall of the manifold 24 forms an annular slot 38 which is closed over most of the circumferential length by a cylindrical outer wall 36 of the valve 20.

The valve 20 also includes a wall 39 extending transversely to the inlet tube 13 and the cylindrical wall 36 is cut away along the inner peripheral edge of the transverse wall 39 so that the valve 20 has a small portion (e.g. 1 or 2) of the chambers 12 the manifold 24 may connect, via an uncovered portion of the slot 38, while the other 800 chambers 12 communicate with the inlet tube 13.

A switch actuating disk 46 with switch operating protrusions or cams 30 mounted on its periphery is mounted on the end of the shaft 45 opposite the valve 20. The disc 46 includes a gear wheel 47 which engages with a pinion 48 of a drive motor 27. The motor 27 is mounted on an end cover 49, which cover includes the exhaust tube 14 and is attached to the adjacent end wall of the housing 10. The shaft 45 10 extends through a tubular inner sleeve 50 defining the central space 31. The inner sleeve 50 includes a rotary electrical shifting device 51 'with a stator portion 52 engaging the inner surface of the tubular housing 50, and a rotor 53 rotatable with the shaft 45 mounted thereon. The shifting device 51 will hereinafter become more detailed. described with reference to Figures 7 and 8.

Figure 5 shows a preferred embodiment of the electric heating elements 43 and shows a web 20 comprising a heat-resistant sheet material and electrical wirings "printed" thereon by a conventional electrical wiring printing technique. The web material shown in Figure 5 can be divided into a number of heating elements by cutting the web in the transverse direction 25, for example along the dashed-dotted line in Figure 5. Each heating element 43 comprises three or a plurality of three modules 54, each comprising a printed circuit consisting of a number of series-connected resistance elements 55. The printed track 30 wirings also include longitudinally extending conduits 56 connecting the heating elements 55 of adjacent modules in parallel and having connection points 57 in each module.

The plastic sheet material used in the heating elements 43 shown may be, for example, the material sold by the 3M Company under the trade name "KAPTON". This material can withstand temperatures of 260-270 ° C. The heating elements 43 O ft ft 9 O R fi -8- can be manufactured by etching a plastic film laminated stainless steel foil to obtain the desired wiring. It will be appreciated that a printed circuit board material, as shown in Figure 5, can be produced in the form of webs of any desired length, and heating elements of any desired number of modules 54 can then be cut from that web.

A heating element 43 of the type shown in Figure 5 is mounted on channels 12 of the device in each of the chambers. The heating element is preferably folded or pleated, for example as shown in Figures 3 or 4, and adjacent layers of the heating elements can be spaced from each other by spacers 48 disposed between the bearings. These spacers are preferably in the form of a corrugated sheet material, such as a woven heat-resistant material, for example of polyester. The spacers 58 can be impregnated with a hygroscopic material such as cellular lithium chloride. The spaces defined by the walls of the chambers 12, the spaced layers of the heating elements 43, and the corrugated spacers 58 are filled with a suitable fiber-like or particulate moisture adsorbent medium 15, such as molecular sieves, silica gel, activated alumina, or other suitable regenerable adsorbent or regenerable hygroscopic substance. The spacing between the layers of the folded or pleated heating elements 30 43 should be sufficiently small to ensure rapid and effective heating of the adsorbent layer interposed therebetween. This distance can for instance be in the order of 10 mm.

Figure 6 is a schematic diagram showing an electrical control system for controlling the operation of the device shown in Figures 1 and 2. The drying or dehumidifying device can be connected to a three-phase voltage source and includes voltage connections R, S, 800 2 8 56 * * -9-T, and Ο. These connections are resp. connected to power lines 1R, Ig / 11 and 1Q. The power supply through these lines can be controlled by a main switch 59.

The power supply through the lines 1, 1 and 1 is used to drive a fan 60 and some of the heating elements 43 in the chambers 12. The power supply to the fan 60 and to the heating elements 43 is controlled by resp. the contactors 61 and 62 or by other suitable switching means. The fan 60 is used for blowing in too dry air or gas through the inlet tube 13. The operation of the shaft 45 driving motor 27, the switch actuating disc 46, the switching device 51, and the rotary valve 20 mounted thereon is controlled by a clock-controlled contactor 15 or switching device 63, a hygrostat 64 or other moisture-sensitive device, which is preferably downstream of the dehumidifier is positioned near the exhaust tube 14 thereof, and through the protrusions or cams 30 on the switch actuating disk 46.

The hygrostat 64 controls a switch Sq while the clock driver contactor 63 controls the switches S1 and S4, and the switching means 29 'includes the switches S2 and S3'

The device shown in Figures 1 and 2 operates essentially in the same manner as the device described in the aforementioned patent application of the applicant, which means that air or gas to be dried or dehumidified through most of the chambers 12 and the adsorbent 15 is introduced therein, while a small portion of the dried gas is recycled and passed through the remaining small portion of the chambers 12 in opposite directions to heat and regenerate the adsorbent or adsorbent medium in these chambers. At certain time intervals, the chamber 35 or chambers in which the adsorbent is regenerated are changed, and this regeneration cycle is controlled by the electrical control system shown in Figure 6.

When the main switch 59 is closed, 800 2 8 56 -10- the contactor 61 will automatically connect the fan 60 to the voltage supply lines 1 ^, 1g, and 1 ^ so that the fan will start to draw air or gas into the inlet pipe 13 too dry. blow. When the shift tube Sq 5 - S4 is in the positions shown in Figure 6, the motor 27 is turned off. As a result, the valve 20 is stationary and air or gas from the inlet tube 13 can flow through a large portion of the chambers or channels 12 to the outlet tube 14, as indicated by the arrow in Figure 1.

However, the transverse wall 39 of the valve 20 closes the channel of the inlet tube 13 to a small part, for example to two of the chambers 12, and at the same time the valve connects this small part of the chambers through the slot 38 to the manifold 24, in the manner described above. As a result, dry gas from the exhaust tube 14 can flow into the small portion of the chambers through one or more flow-restricting openings 65, and from the chambers out into the atmosphere through the manifold 24 and the exhaust pipe 25. After for a certain period of time, the clock-driven contactor or timer 63 closes the switch S ^. Unless the hygrostat 64 determines that the moisture content of the gas leaving the exhaust pipe 14 is below a certain value, the switch Sq through the hygrostat 64 is also closed, whereby current is supplied to the motor 27 via the closed switches Sq, S1 and S ^. The motor 27 now rotates the rotor 53 of the switching device 51 and the valve 20 one step forward, corresponding to an angular rotation of 360 ° / n, where n is the number of sector-shaped chambers or channels in the device. The new angular position of the valve 30 will be determined by the cams or protrusions on the operating disc 46, which open the switch and at the same time close the switch S tegelijkertijd. When the valve 20 has moved to the new position, the contactor 63 closes the switch S ^, whereby the contactor 62 supplies current to the heating elements 43. However, as shown in Figure 6, only the heating elements 43 produced by the rotor 53 are short-circuited with energy. In the preferred embodiment, the device shown in Figures 800, 2, 56, 11, 1 and 2 has six chambers or channels 12, and the valve 20 is allowed to flow gas to be dried through four of these chambers, with a small portion of the dried gas is returned through the remaining two chambers in which the adsorbent medium is regenerated. The motor 27 is controlled to rotate the valve 20 and the rotor 53 of the switching device 51 stepwise through angles of 60 °. As a result, the regeneration period for the adsorbent in each chamber is equal to twice the time interval at which the clock-driven contactor 63 activates the switches Si and. In each chamber or channel 112, the heating elements 43 are turned on only in the first of these two intervals, and in the next time interval, cold, dried gas will flow through the 15 chambers, cooling the regenerated adsorbent.

It will be appreciated that whenever a time interval determined by the clock-driven contactor or timer 63 has elapsed, the switches S1 and 20 are activated, causing the heating elements to be turned off by the contactor 62, and then the motor 27 forward by one angular step. is rotated, which angle step is determined by the disk 46 which changes the positions of the switches S £, after which the contactor 62 reconnects the heating elements 43 to the voltage source. However, the rotor 53 has advanced one angular step forward to turn on the heating element in the next chamber 12 in which the adsorbent is to be regenerated. However, when the hygrostat 64 determines that the moisture content of the gas flowing out of the device through the outlet tube 14 is below a certain value, the switch Sq is opened.

If the switch Sq is still open when the clock-controlled contactor 63 opens the switch to turn off the heating elements and the position of the switch changes, the motor 27 will not be turned on until the hygrostat 64 closes the switch SQ, means extension of the air drying period in most of the chambers 12, and the cooling period of the adsorbent regenerated in two of the chambers 12.

The rotary electric switching device 51 shown in Figures 7 and 8 will now be described in more detail. The stator portion 52 includes a coil-shaped member of insulating material. At one end, the coil member is provided with three radially spaced and insulated metal connection rings 66, 67 and 68 for each. the electrical phases R, S, and T. These rings are provided with screws 69 or connecting members distributed circumferentially for electrically connecting thereto the heating elements 43 of the respective chambers 12. Each heating element 43 comprises three modules 54 , as shown in Figure 5, and one terminal end of each module is connected to one of terminal rings 66, 67 and 68. The terminal ends of the three modules 54 in each heating element 43 are connected to three circumferentially spaced, mutually spaced insulated terminal connector 70 arranged concentrically with rings 66-68. Axially extending electrical conductors 71 connect each of the connectors 70 to the contact member 72 placed on the other end surface of the switching device 51, and the contacts 72 are arranged in triangular groups, as shown in Figure 7, so that the three contacts of each group belong to the same heating element 43. The rotor 53 includes an arm with a spring-loaded shorting means or a spring-loaded contact plate 73 mounted at the free end. When the shaft 45 is rotated stepwise by the motor 27, the rotor 53 is rotated between positions in which the plate 73 is in firm contact with all three contacts 72 of a group, so as to connect the connections of the three modules 54 of the short-circuit the associated heating element 43 and thereby supply it with energy. The electrical switching device shown in Figures 7 and 8 comprises eight groups of contacts 72 and 800, so it can be used for a device with eight chambers 12. However, if the dehumidifier has only six chambers, as described above, the switching device must of course be provided with only groups 5 contacts 7 2.

Figures 9 and 10 schematically show an embodiment of the type described in connection with Figures 1-4.

However, in Figures 9 and 10, the chambers or channels 12 are divided into axial sections so that the gas to be dried or the air to be dried alternately passes through cooling or heating sections and adsorption sections. For example, if the gas to be dried contains a large amount of moisture, the first section 74 may be a condensation section in which gas flowing in from the inlet tube 13 is cooled by suitable means 15, so that part of the moisture in the gas is condensed . These means can for instance be the evaporator of a conventional cooling system or a so-called heat pump, which comprises a compressor 75 and a smoker valve 76. The condenser of the cooling system can then be used to reheat the dried gas or air in a heating section 77 before the gas flows through a filter section 78 to the outlet tube 14.

It may be desirable to provide cooling and heating of the regeneration gas in the condenser section, respectively. avoid the heating section. The pipes of the cooling system or the heating pump can therefore be provided with solenoid valves 81, by means of which the flow of cooling medium or the flow of heat transporting fluid in the pipes of the system can be regulated, so that the flow of fluid in the chambers or channels 12 in which the adsorption - resource is regenerated, stopped.

The apparatus shown in Figures 9 and 10 includes three adsorption sections 79 with adsorbent medium and heating elements, and intermediate cooling sections 80 for removing the adsorption heat generated in the previous adsorption section. The intermediate cooling sections 80 may comprise coolants of any suitable type, such as, for example, water coolants, the evaporator of a cooling system -14 or heat pump, etc. The coolants arranged in the intermediate cooling sections 80 must be designed to operate only in the chambers 12 where gas to be dried is passed through, and not into the rooms in which the regeneration takes place. Thus, each intermediate cooling section may comprise a condenser section and an evaporator section of a conventional cooling system, with adjustable valve means arranged to control the flow of fluid into the system, so that the condenser section of the system 10 is at any time in the room or chambers in which the regeneration of the adsorbent takes place, while the evaporator part is always in the other chambers. The device shown in Figure 9 is preferably arranged with the longitudinal axis in the vertical direction and with the inlet tube 13 pointing downwards. The moisture condensed and separated in the condenser section 74 can then flow out through the exhaust pipe 25 together with the gas used for the regeneration of the adsorbent. The adsorption sections 74 can comprise different types of adsorbents, and any desired combination of condensation, cooling, heating, and adsorption sections can be used.

The dehumidification device according to the invention can operate very economically. This is mainly due to the rather small amount of regeneration gas required (for example, about 4% of the total amount of gas to be dried) and the direct and effective heating of the adsorbent during its regeneration, as well as the uniform distribution of the gas flow across the cross section of the chambers and the adsorbent therein.

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Claims (10)

1. Apparatus for drying or dehumidifying gases, comprising a housing having at least one channel or chamber therein, the chamber having a gas inlet and a gas outlet and comprising a regenerable and gas permeable moisture adsorbent medium and selectively switchable electric heating means for selectively heating the adsorbent medium to regenerate it, "1" characterized in that the adsorbent medium (15) is disposed in the gas inlet (13) or. the gas outlet (14) in communicating layers, the heating means (43) separating and mutually separating the adjacent layers of adsorbent medium (15) and contacting plate material, said plate material adsorbing a gas flow channel through each of the layers medium 15 determined. The device according to claim 1, characterized in that the sheet material (43) comprises printed resistance wires (55-57). Device according to claim 1 or 2, 20, characterized in that means are arranged between adjacent layers of sheet material (43), preferably in the form of a corrugated sheet material (58). Device according to any one of claims 1 to 3, characterized in that cooling means are provided at the inlet end (74) of the chamber to cool the dehumidified gas to condense moisture therein. The device of claim 4, further characterized by reheating means disposed near the outlet end (77) of the chamber for reheating the dehumidified gas. Device as claimed in claim 5, characterized in that the cooling means and the heating means, respectively. an evaporator and a condenser of a heating pump system (75, 76). The device according to any one of claims 1 to 6, characterized in that the moisture adsorbent medium in the chamber is divided into axially spaced sections (79), and between the spaced sections of coolants (80) are provided. Device according to any one of claims 1 to 7, 5, characterized in that the heating means (43) in the chambers (12) comprise heating elements (54) arranged in a star circuit, that the heating means further comprise switching means (51) with a contact means (73) for selectively shorting the heating elements 10 in the neutral points (72) to supply the heating elements in the chamber or channel. 9. Device as claimed in claim 8 and comprising a number of channels or chambers and a rotary valve for passing gas to be dehumidified through a first number of the chambers and returning a stream of dehumidified gas from the outlet end of the chambers through a second number of the chambers, in order to regenerate adsorbent medium therein, characterized in that the sides (72) near the neutral point of the heating elements (54) connected in star connection in the number of chambers (12) in a circular shape are grouped, that the short-circuit contact member (73) is rotatable about the axis of the circular array and coupled to the rotary valve (20) to ensure synchronization between the rotational movements of the contact member and the valve. 10. Device according to claim 9, characterized in that the switching means (53) can terminate the energy supply of the heating elements (43) in each of the second number of chambers or channels before the flow of dehumidified gas through the relevant chamber or the respective channel is terminated, whereby the adsorbent medium therein is cooled by the gas flow. 800 2 8 56