WO2016131991A1

WO2016131991A1 - A method and apparatus for regenerating desiccant

Info

Publication number: WO2016131991A1
Application number: PCT/EP2016/053693
Authority: WO
Inventors: Owen Thomas Leonard
Original assignee: Ozone Industries Ireland Limited
Priority date: 2015-02-20
Filing date: 2016-02-22
Publication date: 2016-08-25
Also published as: GB201502875D0

Abstract

The present invention is directed towards a method of regenerating a desiccant housed within a casing, the method comprising the steps of: activating a heater located within the casing; heating the desiccant using heat from the heater; drawing air adjacent to and over the desiccant housed in the casing; warming the air, prior to drawing the air over the desiccant,by passing the air through one or more elements of thermally conductive media which are arranged adjacent one end of the casing and which have been heated by the heater; and, carrying moisture released from the heated desiccant away from the desiccant by the air as the air passes adjacent the desiccant. The advantage of warming the air prior to the air passing adjacent to and over the desiccant in the casing is that warmed air has a better moisture carrying capability. Therefore, as the desiccant is heated in order to remove the moisture from the desiccant, the warmed air which passes the desiccant will be better able to carry away the moisture from the heated desiccant in order to more effectively and quickly regenerate the desiccant. By placing the one or more elements of thermally conductive media which are arranged adjacent one end of the casing, the one or more elements of thermally conductive media can be heated to form a warm body which will heat the air prior to the air passing through the desiccant to be regenerated.

Description

"A method and apparatus for regenerating desiccant"

Introduction

This invention relates to a method and apparatus for drying desiccant in an air dryer so as to regenerate the desiccant for subsequent use.

In particular, the present invention is directed towards air dryers of the type which comprise desiccant for the purposes of removing humidity from the air as the air is drawn over and passes adjacent to the desiccant. The air dryers are configured to periodically dry the desiccant so as to regenerate the desiccant for future use, or, to dry the desiccant when the moisture level of the desiccant reaches a preset level so as to regenerate the desiccant for future use. It will of course be readily understood that the principles of the present invention are not limited to air dryers only, and other devices which utilise desiccant and require the desiccant to be intermittently dried for regenerative purposes will also benefit from the principles of the present invention. The present invention is therefore in no way limited to air dryers, but for the purposes of the discussion following hereunder, reference shall be made to air dryers throughout the specification.

Throughout this specification, the term "desiccant" shall be understood to encompass any type of media which is capable of attracting and retaining moisture in the form of, inter alia, water molecules, where said media can be regenerated by drying the media and removing the water molecules from the media. Examples of regenerative-type desiccant which could be used in conjunction with the present invention comprise silica beads, activated alumina, bentonite, molecular sieve, zeolite and the like. Air dryers are used in a large number of commercial and industrial processes. One such process is the generation of ozone. Ozone may be generated from oxygen contained in the air using different techniques, such as ultra-violet based techniques or corona discharge based techniques. The type of ozone generators which use corona discharge operate preferably with dried air as the moisture level of the air being feed into a corona discharge-based ozone generator is related to the efficacy of the ozone production. Higher levels of moisture in air which is feed into the ozone generator will result in lower amounts of ozone being output from the corona discharge type of ozone generator. Therefore, an important aspect of ozone generators is the use of an effective air dryer.

An air dryer will comprise a channel through which air is drawn through. Desiccant is provided within the channel in order to remove moisture from the air passing through the channel. The air drawn through the channel will be drawn past the desiccant media by flowing adjacent the media. The desiccant will absorb the moisture from the air as it passes through the desiccant in this manner. As the desiccant removes the moisture from the air, the desiccant becomes saturated with water molecules and the ability of the desiccant to remove further moisture from passing air is reduced.

In order to overcome this problem, the desiccant in the air dryer is periodically regenerated by drying the desiccant through removal of the moisture from the desiccant. In some cases, instead of drying the desiccant at predetermined intervals, the desiccant may be dried when the moisture content of the desiccant has reached a certain level. This could be monitored by tracking the accumulated operating time of the air drier since the previous regeneration action took place.

The regeneration is usually achieved by blowing air over the desiccant so as to detach water molecules from the desiccant which have adhered to the surface of the desiccant. Some desiccants will absorb some of the moisture as well as trapping the moisture on its surface.

Some prior art regenerative air dryers utilise a compressed air pressure switching adsorption method which involves a thermally regenerative or a non-thermally regenerative air dryer having two towers of desiccant. The air dryer selects and active tower and dried air from the active tower is supplied to the target process and also a small take-off can be used to dry the regenerative desiccant in the non- active tower. The active and non-active towers can be switched as necessary to regenerate the desiccant in the two towers. This type of air dryer will typically only work under pressure, whereby the air is forced under pressure through the air dryer.

Other types of prior art regenerative air dryers utilise a fan-driven air supply to regeneration air over the desiccant to be regenerated.

One such example is found in European Patent Publication Number EP1344992 (BEL-ART PRODUCTS INCORPORATED) which discloses an apparatus for removing moisture from air. The apparatus includes a moist air inlet area, a dry air outlet area, a regeneration air inlet area, a regeneration air outlet area and a desiccant medium. A drying fan is provided for drawing the moist air through the moist air inlet area, and over the desiccant, as to exit the unit through the dry air outlet area. Under normal operation, the moist air will be dried by the desiccant in this fashion. In order to occasionally regenerate the desiccant, a regeneration fan is provided for drawing regeneration air through the regeneration air inlet area, and over the desiccant medium, so as to exit the unit through the regeneration air outlet area. In this manner, the desiccant become regenerated as the regeneration air passing through the regeneration air inlet area and over the desiccant medium will remove the moisture from the desiccant.

A further example of regenerating desiccant can be seen from European Patent Publication Number EP2533325 (TESLA MOTORS INCORPORATED) which describes a battery pack dehumidifier system for controlling the relative humidity within a battery pack enclosure. The system heats and reactivates desiccant contained within the battery pack at predetermined time intervals or when the humidity within the system reaches a preset level, thereby allowing the desiccant to regain its potential for absorbing/adsorbing water vapor. A dehumidifier system is disclosed which includes multiple heating elements that are located throughout the volume of desiccant to provide more uniform heating of the desiccant. The heating element is held apart from the desiccant using a porous thermally conductive structure that allows transferring the heat from the heater to the desiccant and prevents the desiccant from falling into the heater volume.

The efficiency of known regenerative processes could be improved. The known processes can take a relative long amount of time which renders the air dryer inoperable during this period. Furthermore, the compressed air pressure switching adsorption type air dryers suffer from a relatively high energy usage as a relatively large amount of electricity is required to pump in the air in the compressed air system. Moreover, when the air dryer is connected to an ozone generator, the use of a vacuum as a means to cause airflow through the air dryer and on to the ozone generator, during the normal air drying operation of the air dryer, acts as a safety feature; the lack of a vacuum will result in no airflow through the air dryer and therefore no supply of dried air to the ozone generator. Hence the ozone generator will automatically stop generating ozone. Excess ozone can be dangerous and the use of a vacuum allows a safety cut-off feature to be automatically implemented.

It is a goal of the present invention to provide a method and apparatus that overcomes at least one of the above mentioned problems.

Summary of the Invention The present invention is directed towards a method of regenerating a desiccant housed within a casing, the method comprising the steps of: activating a heater located within the casing; heating the desiccant using heat from the heater; drawing air adjacent to and over the desiccant housed in the casing; warming the air, prior to drawing the air over the desiccant, by passing the air through one or more elements of thermally conductive media which are arranged adjacent one end of the casing and which have been heated by the heater; and, carrying moisture released from the heated desiccant away from the desiccant by the air as the air passes adjacent the desiccant. The advantage of warming the air prior to the air passing adjacent to and over the desiccant in the casing is that warmed air has a better moisture carrying capability. Therefore, as the desiccant is heated in order to remove the moisture from the desiccant, the warmed air which passes the desiccant will be better able to carry away the moisture from the heated desiccant in order to more effectively and quickly regenerate the desiccant. By placing the one or more elements of thermally conductive media which are arranged adjacent one end of the casing, the one or more elements of thermally conductive media can be heated to form a warm body which will heat the air prior to the air passing through the desiccant to be regenerated.

In a further embodiment, the step of heating the desiccant using heat from the heater comprises the step of heating the casing, so that the heated casing will in turn heat the desiccant. In a further embodiment, the step of warming the air comprises passing the air through one or more elements of thermally conductive media which comprise a plurality of metallic beads.

In a further embodiment, the plurality of metallic beads is a plurality of metallic ball bearings.

In a further embodiment, the step of warming the air comprises passing the air through one or more elements of thermally conductive media which comprises a porous block of thermally conductive material.

In a further embodiment, the method comprises the step of switching the connection to a common port, on a three port valve, from an air dryer outlet to an inlet for drawing the air adjacent to and over the desiccant housed in the casing. In a further embodiment, the method further comprises the step of using a single power transition to cause the heater to be activated and the three port valve to switch connection.

In a further embodiment, the step of drawing air adjacent to and over the desiccant housed in the casing comprises activating an air pump or an air fan.

The present invention is further directed towards an air dryer comprising a casing which houses a regenerative-type of desiccant and one or more elements of thermally conductive media, the one or more elements of thermally conductive media being arranged adjacent one end of the casing and the desiccant being arranged to substantially fill the remaining portion of the casing; a heater located within the casing where the heater is capable of heating the casing and/or the desiccant, and, the one or more elements of thermally conductive media in order to regenerate the desiccant; whereby, a means of creating a flow of air through the casing is used such that the flow of air passes through the one or more elements of thermally conductive media prior to passing through the desiccant.

The advantage of warming the air prior to the air passing adjacent to and over the desiccant in the casing is that warmed air has a better moisture carrying capability. Therefore, as the desiccant is heated in order to remove the moisture from the desiccant, the warmed air which passes the desiccant will be better able to carry away the moisture from the heated desiccant in order to more effectively and quickly regenerate the desiccant. By placing the one or more elements of thermally conductive media which are arranged adjacent one end of the casing, the one or more elements of thermally conductive media can be heated to form a warm body which will heat the air prior to the air passing through the desiccant to be regenerated.

In a further embodiment, the casing is a tubular casing and the heater is an elongated heater which is centrally installed within the casing, along a longitudinal axis of the casing; wherein, the casing comprises a plurality of radially extending fins to transfer heat from the centrally installed heater to desiccant housed within the casing. In a further embodiment, the one or more elements of thermally conductive media is a plurality of metallic beads. In yet a further embodiment, the plurality of metallic beads is a plurality of metallic ball bearings. In another embodiment, the one or more elements of thermally conductive media is a porous block of thermally conductive material.

In a further embodiment, the casing is made of aluminium. In another embodiment, the heater may be an elongated substantially cylindrically-shaped heater element.

In a further embodiment, the air dryer comprises a three port valve which switches a common port connection from the casing to connect to either an air dryer output, or, to the means for creating the flow of air through the casing. In another embodiment, the three port valve may be a three port solenoid valve. In a further embodiment, a single power transition causes the heater in the air dryer to be activated, the three port solenoid valve to switch and the means for creating the flow of air to be activated.

In a further embodiment, the means for creating a flow of air is an air pump.

In a further embodiment, the air dryer supplies dried air to an ozone generator.

In a further embodiment, the air dryer comprises an air diffuser box connected to the air dryer output and housing the three port solenoid valve.

In a further embodiment, desiccant is regenerated by the air dryer when the moisture content in the air dryer is adjudged to have reached a preset level. In a further embodiment, the moisture content in the air dryer may be adjudged to have reached a preset level when the accumulated operating time of the air dryer reached a predetermined amount of time.

In a further embodiment, desiccant is regenerated periodically by the air dryer.

The present invention is directed to a method of regenerating a desiccant housed within a casing, the method comprising the steps of: activating a heater located within the casing; heating the desiccant using heat from the heater; creating a flow of air which passes through the desiccant located in the casing; carrying moisture released from the heated desiccant away from the desiccant by the air as the air passes through the desiccant in the casing; and, warming the air prior to the air passing through the desiccant in the casing.

The advantage of warming the air prior to the air passing through the desiccant in the casing is that warmed air has a better moisture carrying capability. Therefore, as the desiccant is heated in order to remove the moisture from the desiccant, the warmed air which passes the desiccant will be better able to carry away the moisture from the heated desiccant in order to more effectively and quickly regenerate the desiccant.

In a further embodiment, the step of warming the air comprises the step of passing the air through one or more elements of thermally conductive media, whereby the one or more elements of thermally conductive media is heated by the heater.

In a further embodiment, the step of heating the desiccant using heat from the heater comprises the step of heating the casing, so that the heated casing will heat the desiccant.

The present invention is further directed towards an air dryer comprising a casing which houses a regenerative-type desiccant and one or more elements of thermally conductive media, the one or more elements of thermally conductive media being arranged adjacent one end of the casing and the desiccant being arranged to substantially fill the remaining area within the casing; a heater located within the casing where the heater is capable of heating the casing and/or the desiccant, and, the one or more elements of thermally conductive media in order to regenerate the desiccant; whereby, a means of creating a flow of air through the casing is used such that the flow of air passes through the one or more elements of thermally conductive media prior to passing through the desiccant.

The advantage of providing the one or more elements of thermally conductive media being arranged adjacent one end of the casing is that the flow of air passes through the one or more elements of thermally conductive media prior to passing through the desiccant. Thus, the air will be warmed prior to the air passing through the desiccant in the casing. As warm air has a better moisture carrying capability, the warmed air will be better able to carry away the moisture from the desiccant in order to more effectively and quickly regenerate the desiccant.

In a further embodiment, the casing is a tubular casing and the heater is an elongated heater which is centrally installed within the casing, along a longitudinal axis of the casing; wherein, the casing comprises a plurality of radially extending fins protruding outwardly from the centrally installed heater so as to transfer heat from the centrally installed heater to desiccant housed within the casing.

The advantage of providing such a profiled casing with a plurality of radially extending fins is that heat from the centrally installed heater is more evenly distributed and dissipated through the desiccant housed within the casing. Thus, the desiccant is heated in a more effective manner to allow the regeneration of the desiccant to be carried out in a more effective and efficient manner.

In a further embodiment, the one or more elements of thermally conductive media is a plurality of metallic beads. In a further embodiment, the plurality of metallic beads is a plurality of metallic ball bearings. The advantage of using ball bearings is that the one or more thermally conductive elements may be achieved in a relatively inexpensive manner. Furthermore, the desiccant used will preferably be desiccant beads and a further advantage of using ball bearings is that they will be of a substantially spherical shape with a similar size to the desiccant beads and this will allow for an easy passage for the drying air flow.

In a further embodiment, the one or more elements of thermally conductive media is a porous block of thermally conductive material.

In a further embodiment, the casing is made of aluminium. In a further embodiment, the casing is a tubular casing. In a further embodiment, the casing is a rectangular cuboid. In a further embodiment, the air dryer comprises a three port solenoid valve which switches a common port connection from the casing to connect to an air dryer output or to the means for creating the flow of air through the casing.

In a further embodiment, a single power transition causes the heater in the air dryer to be activated, the three port solenoid valve to switch and the means for creating the flow of air to be activated.

In a further embodiment, the means for creating a flow of air is an air pump. ln a further embodiment, the air dryer supplies dried air to an ozone generator.

In a further embodiment, desiccant is regenerated periodically by the air dryer. The present invention is further directed towards an air dryer which draws air through the air dryer using a vacuum at an outlet end of the air dryer. This is advantageous as such a vacuum based system will use less electricity than a compressed air system which must pump air-to-be-dried through the air dryer. Detailed Description of Embodiments

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic view of an air dryer which uses the desiccant regeneration technique of the present invention;

Figure 2 is a perspective view of a casing for the air dryer of Figure 1 ; and,

Figure 3 is a schematic of a three-port valve used in connection with the air dryer of Figure 1 .

Referring to Figure 1 , there is provided an air dryer indicated generally by reference numeral 100. The air dryer 100 comprises a tubular casing 102. It will be readily understood that various shapes of casing may be utilised. The casing 102 is preferably made of aluminium although various materials and composite materials may be alternatively utilised. Regenerative-type desiccant 104 is housed within the casing 102 to form an annular shaped column of desiccant 104 which surrounds a centrally installed elongated substantially cylindrically-shaped heater 106, which extends along a longitudinal axis of the tubular casing 102. In a preferred embodiment, a positive temperature coefficient (PTC) type of heater 106 is used for the heaters temperature control characteristics. At one free end of the casing 102, a vented end plate 108 is arranged in abutment to the free end of the casing 102 so as to provide a cap to the tubular casing 102. A layer of foam 1 10 is arranged intermediate the vented end plate 108 and the desiccant 104. The layer of foam 1 10 is deformable and compresses the annular shaped column of desiccant 104 so that the desiccant 104 is substantially densely packed and fills a majority of the area within the casing 102.

At an opposing free end of the casing 102, one or more elements of thermal conductive media 1 12 are arranged intermediate the desiccant 104 and a vent plate 1 14. An air diffusion box 1 16 is situated adjacent to the vent plate 1 14. The centrally installed elongated heater 106 protrudes into the arrangement of one or more elements of thermal conductive media 1 12 such as to be able to heat the one or more elements of thermal conductive media 1 12 in addition to heating the casing 102 and/or the desiccant 104.

An air diffuser box outlet 1 18 leading from the air diffusion box 1 16 is connected to a three port valve 120. A solenoid valve has been used in the present example although various other types of valves may be used. The air diffuser box outlet 1 18 is connected to the common port on the solenoid valve 120, and, the remaining ports are connected to an ozone generator 124 via a solenoid valve outlet 122, and, to an air pump 130 via a solenoid valve inlet 128. There is an ozone outlet 126 leading from the ozone generator 124 through which ozone which has been produced will be output. An air inlet 132 is connected to the air pump 130 to draw air into the air pump. The solenoid valve 120, air diffuser box outlet 1 18, the solenoid valve outlet 122 and the solenoid valve inlet 128 are enclosed within a housing 134.

Under normal use of the air dryer 100, the three port solenoid valve 120 is configured, by default, to pass air from the air diffuser box outlet 1 18 through the solenoid valve 120 and along the solenoid valve outlet 122, towards the ozone generator 124.

Air is drawn through the ozone generator 124 by a vacuum, although it will be appreciated that other techniques for causing an airflow, could be utilised in place of a vacuum. This same vacuum causes a flow of air through the air dryer 100. In use, air passes through the vented end plate 108 and into the casing 102 of the air dryer 100. The air passes through the layer of foam 1 10 and through the desiccant 104 located in the casing 102. As the air passes adjacent to and over the desiccant 104, which is preferably a plurality of desiccant beads, the desiccant 104 removes moisture from the air by attracting and retaining the water molecules. In this manner, as the air is drawn along the tubular casing 102 and approaches the one or more elements of thermal conductive media 1 12 and the vent plate 1 14, the air will be dried and the level of moisture content of the air passing through the vent plate 1 14 and into the air diffuser box 1 16 will be less than the level of moisture content of the air passing through the vented end plate 108 and into the casing 102 at the beginning of the air drying process. As mentioned above, under normal operation, the dried air in the air diffuser box 1 16 is passed through the solenoid valve 120 and on towards the ozone generator 124 for the generation of ozone.

Over time, the desiccant 104 will become less effective at removing moisture from passing air as the desiccant 104 becomes saturated with water molecules. Periodically therefore, the desiccant 104 is dried in order to regenerate the desiccant 104 for further use. Alternatively, the desiccant is tracked for the level of moisture content which it contains and the regeneration action is only effected when the level of moisture content has been adjudged to reach a certain preset level. This tracking may be accomplished, for example, by monitoring the accumulated running time of the air dryer since the previous regeneration action. To switch the air dryer 100 into a drying mode, the three port solenoid valve 120 is activated to disconnect the common port of the air diffuser outlet 1 18 from the solenoid valve outlet 122, and, to connect the air diffuser outlet 1 18 to the solenoid valve inlet 128 so that air is forced into the air dryer 100 by the air pump 130. As mentioned above, an alternative type of three port valve may be used in place of the three port solenoid valve described.

The air is forced into the air diffuser box 1 16 and the air is forced through the vent plate 1 14, through the one or more elements of thermal conductive media 1 12, and, importantly through the desiccant 104 so as to assist in regenerating the desiccant 104. As the air is forced through the desiccant 104, the air will remove water molecules attached to the desiccant 104 and in this way the desiccant 104 will be dried. The present invention is advantageous as the effectiveness of this drying process is addressed by:

using one or more elements of thermal conductive media 1 12 to warm the air being drawn through the air dryer in reverse direction to the normal direction of airflow under normal operation for a regeneration action to take place; and,

using a profiled tubular casing 102 (which is best seen in Figure 2, and is discussed further hereunder).

Focussing first on the one or more elements of thermally conductive media 1 12, the one or more elements of thermally conductive media 1 12 are heated by the centrally installed elongated substantially cylindrically-shaped heater 106. The heated elements of thermally conductive media 1 12 in turn warm the air which is forced, in reverse direction to the normal airflow direction, through the casing 102. This warmed air is used to assist in drying the desiccant 104 so as to regenerate the desiccant 104. Warm air has a better moisture carrying capability and therefore, the desiccant 104 is dried in a more effective and efficient manner by warming the air first using the elements of thermally conductive media 1 12 prior to drawing warm air through the desiccant 104 to be regenerated.

The desiccant 104 is also warmed by the heater 106 as the casing 102 is heated by the heater 102 and the casing 102 in turn heats the desiccant 104.

The same centrally installed elongated heater 106 heats the one or more elements of thermally conductive media 1 12, and, the casing 102 and/or the desiccant 104.

In a preferred embodiment, the air pump 130, the central heater 106 and the solenoid valve 120 all operate using substantially the same voltage so a single power transition will cause the solenoid valve 120 to switch from its default position for normal operation to a drying cycle positon which connects the air diffuser box outlet 1 18 to the solenoid valve outlet 122. The power transition will substantially simultaneously cause the air pump 130 to be activated and the central heater 106 to become activated. The voltage may be one of 230VAC, 12VDC or 24VDC depending on the requirements for the air dryer 100. The power transition will be understood to be a change in voltage level or current level, or a pulsed control signal, or the like. After the drying cycle is allowed to run for a predetermined amount of time, the power is removed in order to return passively or by spring return the solenoid valve 120 back to its default position, to turn off the air pump 130 and to also turn off the central heater 106.

The use of one or more elements of thermally conductive media 1 12 is an important part of the present invention. The arrangement of the one or more elements of thermally conductive media 1 12 adjacent the air diffuser box 1 16, preceding the desiccant 104 from the perspective of the airflow direction during a drying cycle, is important as it will allow the air to be warmed before passing through the desiccant 104 to be dried, and hence will improve the moisture carry capabilities of the air and dry the desiccant 104 in a faster, more efficient manner. The same heater 106 is used to heat the desiccant 104 and the one or more elements of thermally conductive media 1 12. This is advantageous as the construction of the air drier 100, including the components for regenerating the desiccant 104 is simplified and hence is more cost effective.

Referring to Figure 2, the tubular casing 102 comprises an endless side wall 202 which terminates in a substantially circular rim 204 at one of its free ends. The free end not shown in Figure 2 also terminates in a substantially circular rim. A central tube 206 is co-axial with the tubular casing 102 and extends longitudinally through the tubular casing 102. The central tube 206 forms a cylindrical space indicated generally by reference numeral 208 for installation of the elongated substantially cylindrically- shaped heater (not shown). A plurality of radially extending support plates 210 hold the central tube 206 in a central position relative to the endless side wall 202 of the tubular casing 102. The radially extending support plates 210 extend fully between the central tube 206 and the endless side wall 202. A plurality of radially extending fin plates 212 extend outwardly away from the central tube 206 but do not engage the endless side wall 202 as the radially extending fin plates 212 comprise a free end which terminates within the casing 102. The elongated heater (not shown) will heat the endless side wall 202, the central tube 206, the radially extending support plates 210 and the radially extending fin plates 212 so as to promote good heat distribution and heat dissipation throughout the desiccant (not shown) which is held in the desiccant area 214 of the casing 102. In this manner, during a drying cycle, when the heater 106 is turned on, the desiccant will be heated effectively and relatively quickly due to the profiled nature of the casing 102 which uses the radially extending support plates 210 and the radially extending fin plates 212 to dissipate and distribute the heat amongst the desiccant housed in the casing 102. Referring now to Figure 3, there is shown the three port solenoid valve 120 which comprises the common port connected to the air diffuser box outlet 1 18, and, the solenoid valve outlet 122 and the solenoid valve inlet 128. From the schematic of Figure 3 it will be apparent that there is a push-button option to operate the solenoid valve 120 in addition to the normal solenoid activation; and, that the solenoid valve 120 is defaulted to connect the air diffuser box outlet 1 18 with the solenoid valve outlet 122 under a spring bias. It will be readily understood that a push-button option need not necessarily be provided as such a feature is not an essential feature of the present invention. When the solenoid valve 120 activates, the port of the air diffuser box outlet 1 18 is switched to connect with the solenoid valve inlet 128 and to disconnect from the solenoid valve outlet 122. The solenoid valve 120 switches the operation of the air dryer 100 from an air drying operation mode to a desiccant regeneration/desiccant drying mode.

The profiled tubular casing 102 is preferably constructed from aluminium and is approximately 70mm in diameter and approximately 200mm in length. It will be readily appreciated that alternative materials may be used in place of aluminium, and, that differently sized and differently shaped casings may be used depending on the requirements of the system in which the air dryer operates. In one embodiment of the present invention, the diameter of the central tube 206 of the casing 102 is approximately 12mm in diameter to allow the elongated heater to be installed within the central tube 206. The size of the central tube 206 can be altered to allow different sized and differently shaped heaters to be installed in a substantially central location within the casing 102. In a preferred embodiment of the present invention, the one or more elements of thermal conductive media 1 12 comprise a plurality of metallic beads. In a further embodiment, the plurality of metallic beads is a plurality of metal ball bearings. Alternatively, it will be appreciated that a porous block of thermally conductive material can be used as the one or more elements of thermal conductive media 1 12; however, from a construction costs perspective, the use of metal ball bearings is advantageous. The metal ball bearings are preferably steel ball bearings. In order to allow a consistent throughput of airflow through the air dryer 100, the metallic beads are preferably of a similar size to desiccant beads, where the desiccant 104 comprises desiccant beads. Analogously, the porosity of a porous block of thermally conductive material should be such as to allow a consistent throughput of airflow through the desiccant 104 and the one or more elements of thermal conductive media 112.

The terms "comprise" and "include", and any variations thereof required for grammatical reasons, are to be considered as interchangeable and accorded the widest possible interpretation.

It will be understood that the components shown in any of the drawings are not necessarily drawn to scale, and, like parts shown in several drawings are designated the same reference numerals.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail.

Claims

A method of regenerating a desiccant housed within a casing, the method comprising the steps of: activating a heater located within the casing; heating the desiccant using heat from the heater; drawing air adjacent to and over the desiccant housed in the casing; warming the air, prior to drawing the air over the desiccant, by passing the air through one or more elements of thermally conductive media which are arranged adjacent one end of the casing and which have been heated by the heater; and, carrying moisture released from the heated desiccant away from the desiccant by the air as the air passes adjacent the desiccant.

A method of regenerating a desiccant as claimed in claim 1 , wherein, the step of heating the desiccant using heat from the heater comprises the step of heating the casing, so that the heated casing will in turn heat the desiccant.

A method of regenerating a desiccant as claimed in claims 1 or 2, wherein, the step of warming the air comprises passing the air through one or more elements of thermally conductive media which comprise a plurality of metallic beads.

A method of regenerating a desiccant as claimed in claim 3, wherein, the plurality of metallic beads is a plurality of metallic ball bearings.

5. A method of regenerating a desiccant as claimed in claims 1 or 2, wherein, the step of warming the air comprises passing the air through one or more elements of thermally conductive media which comprises a porous block of thermally conductive material.

A method of regenerating a desiccant as claimed in any preceding claims, wherein, the method comprises the step of switching the connection to a common port, on a three port valve, from an air dryer outlet to an inlet for drawing the air adjacent to and over the desiccant housed in the casing.

A method of regenerating a desiccant as claimed in claim 1 , wherein, the method further comprises the step of using a single power transition to cause the heater to be activated and the three port valve to switch connection.

A method of regenerating a desiccant as claimed in claim 1 , wherein, the step of drawing air adjacent to and over the desiccant housed in the casing comprises activating an air pump or an air fan.

An air dryer comprising a casing which houses a regenerative-type of desiccant and one or more elements of thermally conductive media, the one or more elements of thermally conductive media being arranged adjacent one end of the casing and the desiccant being arranged to substantially fill the remaining portion of the casing; a heater located within the casing where the heater is capable of heating the casing and/or the desiccant, and, the one or more elements of thermally conductive media in order to regenerate the desiccant; whereby, a means of creating a flow of air through the casing is used such that the flow of air passes through the one or more elements of thermally conductive media prior to passing through the desiccant.

An air dryer as claimed in claim 9, wherein, the casing is a tubular casing and the heater is an elongated heater which is centrally installed within the casing, along a longitudinal axis of the casing; wherein, the casing comprises a plurality of radially extending fins to transfer heat from the centrally installed heater to desiccant housed within the casing.

1 1 . An air dryer as claimed in claims 9 or 10, wherein, the one or more elements of thermally conductive media is a plurality of metallic beads.

12. An air dryer as claimed in claim 1 1 , wherein, the plurality of metallic beads is a plurality of metallic ball bearings. 13. An air dryer as claimed in claims 9 or 10, wherein, the one or more elements of thermally conductive media is a porous block of thermally conductive material.

14. An air dryer as claimed in any of claims 9 to 13, wherein, the casing is made of aluminium.

15. An air dryer as claimed in any of claims 9 to 14, wherein, the air dryer comprises a three port valve which switches a common port connection from the casing to connect to either an air dryer output, or, to the means for creating the flow of air through the casing.

An air dryer as claimed in claim 15, wherein, a single power transition causes the heater in the air dryer to be activated, the three port valve to switch and the means for creating the flow of air to be activated.

An air dryer as claimed in any of claims 9 to 16, wherein, the means for creating a flow of air is an air pump.

18. An air dryer as claimed in any of claims 9 to 17, wherein, the air dryer supplies dried air to an ozone generator.

19. An air dryer as claimed in claim 18, wherein, air dryer comprises an air diffuser box connected to the air dryer output and housing the three port valve.

20. An air dryer as claimed in any of claims 9 to 19, wherein, desiccant is regenerated by the air dryer when the moisture content in the air dryer is adjudged to have reached a preset level.

21 . An air dryer as claimed in claim 20, wherein, the moisture content in the air dryer may be adjudged to have reached a preset level when the accumulated operating time of the air dryer reached a predetermined amount of time.

22. An air dryer as claimed in any of claims 9 to 19, wherein, desiccant is regenerated periodically by the air dryer.