Regenerative air dryer

A regenerative air drying system including at least one dryer module including a housing having a inlet air passage, an outlet air passage, and a wash air passage. The air dryer system further includes a desiccant canister mounted to the housing and in communication with the inlet, outlet, and exhaust air passages, and a single controllable valve selectively moveable between a first position and a second position, wherein the single controllable valve, when in the first position, forms a supply air flow path from the inlet air passage, through the desiccant canister in a first direction, and to the outlet air passage, and when in the second position, forms a wash air path from the outlet air passage, through the desiccant canister in a direction opposite the first direction, and to the exhaust air passage.

BACKGROUND

Compressed air systems are used in a wide variety of applications to power a wide variety of devices, such as spray or paint guns in a compressed air painting system, for example. In order to prevent damage to air powered devices, such as through corrosion, for example, or to prevent adversely affecting processes, such as contaminating paint in a spray painting process, for example, the compressed air is dried and other contaminants removed prior to being used.

Air drying systems, including regenerative air drying systems, have been developed for such purposes. Regenerative air drying systems pass air through a desiccant material which removes moisture from the compressed air, with the desiccant material being able to be dried, or regenerated, and reused. Such systems typically employ more than one desiccant container so that one container can continue to provide dry air while the desiccant material in the other container is being regenerated. While such systems are effective at drying air, they employ complex systems for switching between the desiccant containers and have complicated piping and valve systems that produce large pressure losses in the system and make system expansion difficult.

SUMMARY OF THE INVENTION

One embodiment provides a regenerative air dryer which is smaller, has fewer moving parts, has single-point control, has simplified air paths, reduces external piping, and provides decreased air pressure losses relative to conventional air dryers.

One embodiment provides a regenerative air dryer system including at least one dryer module including a housing having an inlet air passage, an outlet air passage, and a wash air passage. The air dryer system further includes a desiccant canister mounted to the housing and in communication with the inlet, outlet, and exhaust air passages, and a single controllable valve selectively moveable between a first position and a second position, wherein the single controllable valve, when in the first position, forms a supply air flow path from the inlet air passage, through the desiccant canister in a first direction, and to the outlet air passage, and when in the second position, forms a wash air path from the outlet air passage, through the desiccant canister in a direction opposite the first direction, and to the exhaust air passage.

DETAILED DESCRIPTION

FIG. 1is a perspective view generally illustrating a modular regenerative air dryer system8, according to one embodiment of the present application, for drying air for compressed air systems (e.g. an air compressor). Modular regenerative air dryer system8includes a dryer module10, with dryer module10including a housing12, a desiccant canister14, and a valve cartridge16including a threaded portion17that serves as a mounting stud for coupling desiccant canister14to housing12. Although illustrated inFIG. 1as including only a single dryer module10, as will be described in greater detail below, modular regenerative air dryer system8may include two or more dryer modules10which are coupled together to provide increased air drying capacity (seeFIGS. 6-9, for example).

According to one embodiment, housing12includes a pair of inlet air ports18on opposite ends of an inlet air passage20extending through housing12from one end face22to an opposing end face24(seeFIG. 2), a pair of outlet air ports26on opposite ends of an outlet air passage28extending through housing12from end face22to opposing end face24(seeFIG. 2), an actuating mechanism, such as a piston or spool valve30, and an exhaust vent, such as a muffler32. According to one embodiment, spool valve30is disposed within housing12via a side face34of and muffler32extends from a bottom face36of housing12. According to one embodiment, housing12includes a device outlet air port35disposed on side face34that is in communication with outlet air passage28and which can be used as a connection point for a compressed air device (e.g. a paint gun), wherein device outlet port35can be plugged when not being used (as illustrated).

FIG. 2is a perspective view of dryer module10illustrating end face24, which opposes end face22, with inlet and outlet air ports18and26, and inlet and outlet air passages20and28extending through housing12. As will be described in greater detail below, dryer module10receives a compressed “wet” supply air flow40, such as from a compressor or compressor system (not shown), via inlet air port18, dries the wet air via desiccant canister14, and provides a “dry” outgoing air flow42via outlet air port46.

The inlet air port18to which a compressor system is connected, and the outlet air port26to which a device is connected, such as compressed air storage tank (not shown), is selectable, with the unused port able to be plugged. For example, inlet air port18on end face22and outlet air port26on opposing end face24can be selected, with inlet and outlet air ports18and26on end faces24and22being plugged, and vice versa. Similarly, inlet and outlet air ports18and26on a same end face, such as end face22, can be selected, with inlet and outlet air ports18and26on opposing end face24being plugged. This flexibility in selection and configuration of inlet and outlet air ports18and28enables modular regenerative air dryer system8to be installed in a wider variety of positions and locations as compared to conventional air drying systems having only one set of inlet and outlet ports which are typically positioned on a front side of the system.

FIG. 3is a perspective view illustrating a top face15of housing12with desiccant canister14being removed, and illustrates generally valve cartridge16and a plurality of canister holes21arrayed in an arced pattern within and along a perimeter edge of desiccant canister14. As will be described in greater detail below, desiccant canister14has an air flow path in communication with outlet air passage28via valve cartridge16, with canister holes21being in communication with a chamber internal to housing12which, in-turn, is in communication with inlet air passage20and a fluid passageway that leads to muffler32.

As will be described and illustrated in greater detail below (seeFIGS. 4 and 5), spool valve30extends within a shaft or bore in housing12and is moveable between at least a first position and a second position (e.g. a retracted position and an extended position) to control the path and direction of air flow between inlet and outlet air passages20and28, desiccant canister14, and muffler32, and thereby control the mode of operation of dryer module10. According to one embodiment, the position of spool valve30dictates whether dryer module10in an air drying mode or a regeneration mode.

According to one embodiment, spool valve30is placed in a retracted position to operate dryer module10in the air drying mode. In air drying mode, wet supply air flow40is received (e.g. ambient air being drawn in by an air compressor or compressor system) via inlet port18and directed through inlet air passage20to desiccant canister14via fluid passages leading to canister holes21. The wet supply air flow40then passes through desiccant canister14, which removes moisture from the wet supply air40, via desiccant media therein, to provide the resulting dry outgoing air flow42which exits canister14via a drying orifice in valve cartridge16and enters outlet air passage28where it is directed via outlet air port26to a downstream device, such as storage tank (not shown).

According to one embodiment, spool valve30is placed in the retracted position to operate dryer module10in the regenerative mode, wherein moisture is removed from desiccant media within desiccant canister14(i.e. the desiccant media is dried). In regenerative mode, dry air42is received via outlet port28from a dry air source (for example, a storage tank or another dryer module10(not illustrated) which is in a drying mode) and is directed through outlet air passage28and into desiccant canister14via a regeneration orifice in valve cartridge16. The flow of dry through the regeneration orifice, also referred to as “wash” air, passes through desiccant canister14in a direction opposite to which the flow of wet supply air40passes through desiccant canister14when dryer module10is operating in the drying mode. The flow of dry wash air removes collected moisture from the desiccant material in desiccant canister14to form a flow of wet wash air44which is directed out of desiccant canister14through canister holes21and is ultimately expelled from dryer module10via muffler32.

FIGS. 4 and 5are cross-sectional views through dryer module10, and illustrate in greater detail housing12, desiccant canister14, valve cartridge16, and spool valve30, and which respectively illustrate the air drying and regenerative operating modes of dryer module10.

With reference toFIG. 4, inlet and outlet air passages20and28extend through housing12in directions into and out of the page, between inlet and outlet air ports18and26(seeFIGS. 1 and 2). Housing12includes a supply air shaft50extending between inlet air passage20and an air chamber52. According to one embodiment, air chamber52is semicircular in shape with a plurality of bi-directional air shafts54along its circumference (only one shaft54is illustrated) which extend through housing12and form a corresponding canister hole21in top face15(seeFIG. 3).

Spool valve30is positioned within a valve shaft56extending into housing12from side face34to supply air shaft50. A first wash air shaft58extends between air chamber52and valve shaft56, and a second wash air shaft60extends between valve shaft56and bottom face36of housing12, terminating at muffler32. According to one embodiment, as illustrated, muffler32is threaded into a threaded vent or muffler opening33in housing12.

According to one embodiment, as illustrated generally byFIG. 4, spool valve30includes a plurality of sealing devices spaced apart along a body31. According to one embodiment, as illustrated, body31has a stepped, cylindrical shape. According to one embodiment, the plurality of sealing devices includes a first gasket62, a second gasket64, a third gasket66, and a fourth gasket68. According to one embodiment, each of the gaskets62,64,66, and68is an O-ring positioned about the stepped, cylindrical body of spool valve30. A spring69is disposed about a portion of body31of spool valve30between second and third gaskets64and66and biases spool valve30to the retracted position (i.e. the position illustrated inFIG. 4). Spool valve30is actuated within valve shaft56between an extended position and a retracted position by any number of actuating means, including pneumatic and electric means, for example.

According to one embodiment, spool valve30is retained within valve shaft56by a retaining cover57which attached to housing12via one or more screws57a. According to one embodiment, to remove spool valve30from valve shaft56, retaining cover57is first removed, and a screw can be temporarily threaded into a threaded female shaft29within spool valve30and employed to pull spool valve30from valve shaft56.

According to one embodiment, as illustrated generally byFIG. 4, valve cartridge16has a body70with a threaded portion71a that screws into a corresponding female threaded opening71bthat extends through housing12from top face15to an outlet air shaft80. Body70further includes threaded portion17which extends above top face15and serves as a mounting stud to which desiccant canister15is threadably mounted. According to one embodiment, body70includes a hexagonal flange77which limits how far valve cartridge16can be screwed into threaded opening70, and also serves as a nut to enable a tool, such as a socket, to be used to install or remove valve cartridge16from housing12(or to remove valve cartridge16from desiccant canister14should it remain attached thereto upon removal of desiccant canister14from housing12) without damaging threaded portions15and71a.

Valve cartridge16further includes a plunger or check valve72disposed within body70having a spring loaded flange portion74extending from a base portion76, with flange portion74including a regeneration orifice75extending there through. As will be described in greater detail below, check valve72opens and closes a drying orifice78in body70to control the flow of dry air42between desiccant canister14and dry outlet air passage28via outlet air shaft80, with the spring-loaded flange portion74being biased so as to close orifice78in the absence of a flow of wet supply air40into desiccant canister14

According to one embodiment, valve cartridge16is modular in design and can be replaced with valve cartridges16having different threaded portions15accommodate different types and sizes of desiccant canisters14. Similarly, different valve cartridges16may have differently sized check valves72, regeneration orifices75, and drying orifices78to provide different volumes of air flow. The modular nature of valve cartridge16enables one valve cartridges to be quickly replaced to accommodate changing system requirements.

According to one embodiment, as illustrated byFIG. 4, desiccant canister14includes a housing81forming an outer air passage82about an inner portion84. According to one embodiment, inner portion84includes beads of a desiccant media forming a molecular sieve bed86. According to one embodiment, desiccant canister14is removable and threads on to valve cartridge70.

FIG. 4illustrates dryer module10when operating in the air drying mode, with spool valve30being in a first or retracted position so that gaskets62,64, and66are positioned to prevent the flow of wet supply air40from exiting housing12via second wash air shaft60and muffler32. With spool valve30in the retracted position, the flow of wet supply air40(as indicated by the unbroken directional arrows) travels from inlet air passage20, through supply air shaft50to air chamber52. From air chamber52, the wet supply air40enters the outer portion of desiccant canister14via the plurality of air shafts54and the corresponding plurality canister holes21. The flow of wet supply air40then travels up through outer air passage82and enters the molecular sieve bed86at the top of the desiccant canister14.

As the flow wet supply air40travels downward through molecular sieve bed86, moisture is removed from the flow of wet supply air40to form the flow of dry output air42(as indicated by the broken directional arrows). The pressure from the flow of dry air42forces check valve72to the open position, and dry output air42flows through orifice78and through valve cartridge16to dry outlet air passage80. The flow of dry output air42then flows through outlet air passage28to a storage container, such as a pressurized storage tank (not shown), with a portion of the flow of dry output air42potentially being employed by a different air dryer module10which is in regenerative mode (seeFIG. 5below) or being employed by a device (e.g. a paint spray gun) via device output port35(seeFIG. 1).

According to one embodiment, housing12is machined in two pieces94and96, which are bolted together with a gasket98disposed there between in a gasket channel.

FIG. 5illustrates dryer module10when operating in the regenerative mode with spool valve30being in a second or extended position such that first gasket62is positioned to seal and prevent a flow wet supply air40from entering supply air shaft50from inlet air passage20. Additionally, third gasket66is in a position such that it no longer seals first wash air shaft58from second wash air shaft60, so that first and second wash air shafts58and60are now in communication with one another via valve shaft56.

With spool valve30in the extended position, there is no flow of wet supply air40to desiccant canister14so that back-pressure from dry output air42(e.g. from a storage tank or another dryer modules10) spring-loaded flange portion74keep check valve72in the closed position thereby sealing drying orifice78. However, regenerative orifice75allows a small flow of dry output air42through flange portion74of check valve72, thereby creating a flow of dry wash air90to flow through desiccant canister14in a direction opposite to the flow of wet supply air40through desiccant canister14when dryer module10is being operating in the air drying mode.

In regenerative mode, the flow of dry wash air90flows from output air passage28, through dry outlet air passage80, through regenerative orifice75of check valve72, and into molecular sieve bed86(as indicated by the broken directional arrow). As the flow of dry wash air90passes through molecular sieve bed86, it absorbs moisture (and potentially other contaminants) collected by the molecular sieve bed86and forms a flow of wet wash air44which exits molecular sieve bed86and enters outer air passage82. The flow of wet wash air44then travels down outer air passage82to air chamber52of housing12via canister holes21and bi-directional air shafts54. The wet wash air44then continues through first wash air shaft58, past third gasket66, and through valve shaft56about a portion of spool valve30where it enters second wash air shaft58and is expelled from housing12via muffler32.

By removing the accumulated water and other contaminants from the desiccant material of molecular sieve bed86in this fashion, the beads of desiccant material are dried and cleaned and can once again be used to clean wet supply air40upon returning spool valve30to the retracted position. The above described process is employed each time the beads of descant material of molecular sieve bed86are cleaned.

While described above in terms of a single dryer module10for ease of illustration, modular regenerative air dryer system8may include multiple dryer modules10which are coupled together to provide increased air drying capacity. For example, modular regenerative air dryer system8may include two, three, four, etc. air dryer modules10coupled together to form a system.

FIG. 6, for example, is a perspective view generally illustrating an embodiment of modular regenerative air dryer system8including two dryer modules10. According to one embodiment, as illustrated, side faces22and24of the two dryer modules10are bolted together at each of the four abutting corners of housings12using bolts, such as indicated at100. When coupled together, the inlet and outlet air passages20and28on side face24of one of the modules10align with the inlet and outlet air passages20and28on side face22of the other one of the modules10so as to combine to form continuous inlet and outlet air passages20and28that extend through both of the housings12. In one embodiment, seals are positioned about inlet and outlet ports18and26of the adjacent modules10prior to their being bolted together so as to eliminate leaks at the “joints” of the continuous inlet and outlet air passage20and28. As before, the non-selected input and output ports18and26of continuous inlet and outlet air passages20and28are sealed with a plug.

Similarly,FIG. 7is a perspective view illustrating an embodiment of modular regenerative air dryer system8including three dryer modules10. Again, the dryer modules10are bolted together at each of the four corners of each of the abutting faces of housings12using bolts, such as indicated at100. When coupled together, the inlet and outlet air passages20and28of each of the modules10align with one another and combine to form continuous inlet and outlet air passages20and28extending through the three housing12.

The modular configuration of air dryer modules10, including the positioning of pars of inlet and outlet air ports18and26on opposing faces of housing12, enables any number of air dryer modules10(e.g. two, three, four, and even more) to be simply and easily coupled together, with no external piping, to form regenerative air dryer system8of varying air drying capacity. Such a modular configuration enables air dryer system8to be easily adapted (e.g. expanded or downsized) to meet changing compressed air requirements. In contrast to simply bolting a pair of housings12together with four bolts, in order to add additional air drying capacity, conventional air drying systems typically require that the existing system be at least partially disassembled and require complicated piping, valves, and connectors to be installed to add system components (e.g. “banjo” fittings, elbows, tees, crosses, etc.), wherein such external piping and components are difficult and time consuming to install and restrict air flow, thereby resulting in increased pressure losses in the system.

Regenerative air dryer system8, according to the present application, also enables one air dryer module10to added (or subtracted) at a time and thereby enables system capacity to be changed in smaller increments relative to conventional systems. Typically, conventional air drying systems require that “pairs” of interconnected desiccant containers (along with the associated piping and control valves) to added at a given time (so that one canister can dry air while the other is being regenerated), thereby forcing system capacity to be expanded (or reduced) in larger increments. As a result, system capacity in such conventional air drying systems may be forced to be greater than what is required due to the restriction of having to expand the system using “pairs” of desiccant containers.

According to one embodiment, each dryer module10of air dryer system8is rated for a 5-horsepower air compressor, such that an air dryer system8having two dryer modules10is rated for a 10-horsepower air compressor, an air dryer system8having three dryer modules10is rated for a 15-horsepower air compressor, and so on. As described above, according to one embodiment, dryer module10has a valve cartridge16with a check valve72having an orifice78sized and selected to correspond to different horsepower requirement. As such, in addition to being able to add one or more air drying modules10in a modular fashion to increase the air drying capacity of a regenerative air drying system8as described herein, the air drying capacity of system8can also be adjusted in a modular fashion by changing out the modular valve cartridge16.

According to one embodiment, each dryer module10is rated for 40 cfm (cubic feet per minute) of flow, with each dryer module10having a flow rate based on specific system requirements, wherein the flow rate can be modified based on the size of orifice openings and on sequencing in the mode of operation between multiple dryer modules10of air dryer systems8employing multiple air dryer modules.

According to one embodiment, when modular regenerative air dryer system8is formed using multiple dryer modules10, air dryer system10is operated so that only one dryer module10is in the regenerative mode at a given time.

FIG. 8is a perspective view generally illustrating modular regenerative air dryer system8including two dryer modules10, and further including a controller110(e.g a PLC controller) for controlling the operation of spool valves30of each dryer module10to coordinate regeneration of the desiccant media of desiccant canisters14. According to one embodiment, as mentioned above, only one dryer module10of air dryer system8is placed in the regenerative mode at a given time.

For example, after both dryer modules10are first pressurized and air dryer system8is providing a stable flow of dry output air42, controller110is configured to direct spool valve30of a first one of the dryer modules10to move to the extended position to begin the regenerative drying process, while spool valve30of a second one of dryer modules10is maintained in the retracted position so as to continue operating in the air drying mode. Upon completion of the regenerative drying process of the first dryer module10, controller110is configured to direct the spool valve30of the first dryer module10to return to the retracted position so as to return the first dryer module10to the air drying mode.

Thereafter, controller110repeats the above described process with the second dryer module10. By controlling the regenerative drying processes of the two dryer modules10so as to have only one of the two dryer modules10operating in the regenerative mode while the other is operating in the air drying mode, modular regenerative air dryer system8, according to the present application, eliminates sudden and undesirable air pressure changes caused by simultaneous or overlapping regeneration of desiccant canisters as done in conventional air drying systems.

It is noted that above control process can be adapted and applied to a modular regenerative air dryer system8formed by any number of coupled dryer modules10. Whatever the number of dryer modules10(other than one), controller110is configured to control the spool valves30of each of the dryer modules10so that only one of the dryer modules10is being operated in the regenerative mode at a given time, with no overlap between the regeneration processes of the air dryer modules10.

According to one embodiment, the normal operation of a regenerative air dryer system8having two dryer modules10, for example, includes the first air dryer module10being operated in a regenerative mode and the second air dryer module10being in an air drying mode. When the desiccant material in canister14of the second air module10needs to be regenerated (i.e. cleaned), the respective positions of spool valves30of the first and second air dryer modules10are reversed so that the second air dryer module10is placed in a regenerative mode and the first air dryer module10is placed in an air drying mode. To avoid a pressure surge or spike that could result from a simultaneous changeover of the respective spool valves30, the first air dryer module10is switched from the regenerative mode to the air drying mode while the second air dryer module10remains in the air drying mode. Only after stable air flow has commenced through the first air dryer module10after being placed in the air drying mode is the second air dryer module10placed in the regenerative mode.

As described above, in operation of regenerative air dryer system8, each of the one or more air dryer modules10includes only two moveable parts, check valve72and spool valve30, and only a single control point, that being spool valve30. The use of only two moving parts, single-point control via spool valve30, modular valve cartridge70, and the reduction/elimination of external piping greatly simplifies control, maintenance, and operation of a regenerative air dryer system8, according to the present application. In contrast, conventional air drying systems include numerous moving parts and multiple control valves that must be operated in precise sequences in order to provide air drying and regenerative operating modes, and further include complicated piping and valve systems that must be disassembled/added in order to modify the air drying capacity of the system, and which require time consuming and costly maintenance.

Additionally, each of the air drying modules10of regenerative air drying system8is configured with short and direct air flow paths within housing12that greatly reduce air pressure losses relative to conventional air drying systems having complex air passages. As mentioned above, whereas conventional air drying systems employ complicated external piping and valve systems, the “piping” of air dryer modules10, according to the present application, is completely internal to housings12and is configured so as to reduce/minimize path lengths and turns in order to reduce pressure losses (wherein pressure losses increase the amount of energy required to provide desired output pressures and flows).

For example, with reference toFIG. 4, according to one embodiment, a flow path of supply air through housing12, when dryer module10is operating in drying mode (excluding desiccant canister14), is through inlet air passage20, through supply air shaft50, air chamber52, and bi-directional air shafts54to desiccant canister14, and then through valve cartridge18to outlet air shaft80, and lastly through outlet air passage28.

According to one embodiment, housing12has dimension of approximately 6-inches between opposing side faces (e.g. between side faces22and24) and a height between top face15and bottom face36of 4-inches (6″×6″×4″). According to one embodiment, a flow path of supply air through housing12, as described above, has a total length of approximately only 12.5 inches and a combined 450 degrees of turns within housing12(excluding desiccant canister14). According to one embodiment, a flow path of supply air through housing12does not exceed 14 inches and does not have more than 450 degrees of turns within housing12. According to one embodiment, to further reduce pressure losses, supply air shaft50is rectangular in shape to increase its surface area and thereby decrease drag on air passing there through, and edges of passages, such as the edges of bi-directional air-shafts54and chamber52, have edges with radiuses to reduce pressure losses as the air transitions from one passage to another.

Additionally, according to one embodiment, housing12of dryer module10is machined from solid billet aluminum, as opposed to cast aluminum typically employed by cast aluminum. According to one embodiment, the machined billet aluminum is hard coat anodized and Teflon-impregnated to reduce friction of the air passages to further reduce air pressure losses within housing12and to minimize corrosion and damage to the air passages from moisture and other contaminants within the supply air as it passes through housing12. The use of hard-coat anodized aluminum greatly reduces the occurrence of oxidation on the surfaces of housing12which otherwise increases air flow resistance and causes increased wear on any moving parts. The use of hard-coat anodized, Teflon-impregnated, machine billet for housing12greatly increases the expected operating life of air dryer modules10, with air drying modules10having an expected operating life of up to 18 years, as opposed to 1-2 years for conventional air compressor systems employing cast aluminum.

Together, the elimination of external piping, the short and simple configuration of internal passages forming a flow path of supply air through housing12, and the materials and coatings on the surfaces of housing12, work together to greatly reduce pressure losses within air drying system8as compared to conventional air drying systems. For example, according to one embodiment, an air drying system8employing two air dryer modules10, as described herein, was measured to have only 2 psi of pressure drop at full flow (40 cfm) as compared to a conventional system having a substantially equal capacity, and being operated under substantially equal parameters, which had a measured pressure drop of 12 psi. In other words, according to such configuration, air drying system8according to the present application had only one-sixth the pressure drop of a conventional regenerative air drying system.

FIG. 9is a block and schematic diagram illustrating generally a compressed air system120, including an air compressor122, a storage container124for storing compressed and dried air, a controller126(e.g. a PLC), and a regenerative air dryer system8, according to the present application, including four air dryer modules10, indicated as dryer modules10a-10d. As described above, the housings12of the four air dryer modules10a-10dare coupled together and form common input and output air passages20and28shared by air dryer modules10a-10d.

In operation, regenerative air dryer system8receives a supply of “wet” compressed supply air40from air compressor122via input air passage20. Dryer modules10a-10ddry the wet supply air40by directing the air through desiccant canisters14and provide a flow of dry output air42to a storage container124(e.g. pressurized tank) via output air passage28.

According to one embodiment, as described above, after all of the air dryer modules10a-10dare pressurized and regenerative air dryer system8is providing a stable flow of dry output air42to storage container124, controller126cycles the air dryer modules10a-10dthrough regeneration modes in order to clean or dry the desiccant media within desiccant canisters14such that the desiccant canister14of only one of the air dryer modules10a-10dis being regenerated at a time while the remaining three of the air dryer modules continue to dry the supply air flow40. According to one embodiment, controller30controls the positions of spool valves30of air dryer modules10a-10dvia control wires128to cycle the air dryer modules10a-10dbetween air drying and media regenerating modes.

FIG. 10is flow diagram illustrating one embodiment of a drying process140employing a modular regenerative air dryer system8according to the present application, such as air dryer system8illustrated byFIG. 9. Process140begins at142wherein all of the air dryer modules10of air dryer system8are pressurized and begin providing a stable flow of dry output air42, such as air dryer modules10a-10dofFIG. 8providing a flow of dry output air42to storage container124.

At144, controller126directs spool valve30of a first air dryer module10of the air dryer system8, such as air dryer module10a, to the extended position to begin the regenerative drying process of the desiccant media within the corresponding desiccant canister14, while the spool valves30of the remaining air dryer modules10b-10dare maintained in the retracted position to so that the remaining air dryer modules10b-10dcontinue operating in the air drying mode.

After the regeneration process of air dryer module10ais complete, process140proceeds to146where it is queried whether the air dryer module10which has just been regenerated is a last one of the four air dryer modules10a-10dto be regenerated. If the answer to the query at146is “no”, process140proceeds to148, where a next air dryer module10of the four air dryer modules10a-10d, for example, air dryer module10b, is regenerated. Process140then returns to144.

If the answer to the query at146is “yes”, meaning that each of the for air dryer modules10a-10dhas been regenerated to complete a regeneration cycle of the air dryer modules10, process140returns to144where the first of the air dryer modules10a-10dis again regenerated to start the next regeneration cycle.

Again, as described above, by controlling the regenerative drying process so that only one of the dryer modules10a-10dis operating in the regenerative mode at a given time, while the remaining modules10a-10dcontinue to operate in the air drying mode, modular regenerative air dryer system8, according to the present application, eliminates sudden and undesirable air pressure changes caused by simultaneous or overlapping regeneration of desiccant canisters as done in conventional air drying systems.

Although described as regenerating air dryer modules10sequentially from air dryer module10ato air dryer module10d, it is noted that the air dryer modules10a-10dcould be regenerated in any selected order. It is also noted that process140can include time delays between the drying of one dryer module10and a next dryer module10. Additionally, the process140can also be applied to air dryer systems8have more or fewer than four air dryer modules10.

In summary, by employing only two moveable parts, spool valve30and check valve72, and having only a single control point via spool valve30to control a mode of operation, air dryer module10of modular regenerative drying system8according to embodiments of the present application, greatly simplifies control, maintenance, and operation relative to conventional air drying systems. Additionally, the small size and modular design of air dryer modules10(e.g., selectable inlet and outlet ports18and26on opposing faces of housing12, modular valve cartridge70, bolt-together housings12, etc.) enable modular air drying system8to be easily installed and repaired, and easily adapted to meet changing compressed air requirements in comparison to conventional compressed air systems. Also, the short and simple flow path for supply air through housing12, and the hard-coat anodized, and Teflon-impregnated surfaces of housing12greatly reduce air pressure losses and greatly increase the operating life (e.g. reduces corrosion) of modular air drying system8relative to conventional compressed air systems. Furthermore, staggering the regeneration of desiccant canisters14through simple control of spool valves30eliminates sudden and undesirable pressure drops during operation of modular air drying system8while continuing to provide a stable flow of dry air.