Patent Publication Number: US-2022233998-A1

Title: Hybrid low dew point compressed air dryer

Description:
TECHNICAL HELD 
     The present invention generally relates to a dryer for compressed air and more particularly, but not exclusively to a refrigeration-desiccant hybrid dryer for producing low dew point temperature compressed air. 
     BACKGROUND 
     Dryers are sometimes used to remove moisture from compressed air downstream of the compression process. Certain prior art dryers incorporate refrigerant based systems or desiccant based systems to remove moisture from compressed air. Some existing dryer systems have various shortcomings relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     One embodiment of the present disclosure includes a hybrid air dryer with a refrigerant system and a desiccant system operating in series. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for a hybrid air dryer are disclosed herein. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view of an exemplary compressor system that may be used in one embodiment of the present disclosure; and 
         FIG. 2  is a schematic view of a hybrid dryer system according to one exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
     An exemplary embodiment of a hybrid air dryer system is disclosed herein. The hybrid air dryer system can be used with any type of fluid compression device and should not be limited to the illustrative compressor system shown in  FIG. 1 . The term “fluid” should be understood to include any gas or liquid medium that can be used in the compressor system as disclosed herein. It should also be understood that air is a typical working fluid, but different fluids or mixtures of fluid constituents can be used and remain within the teachings of the present disclosure, therefore terms such as fluid, air, compressible gas, etc., can be used interchangeably in the present patent application. For example, in some embodiments it is contemplated that a hydrocarbon gaseous fuel including natural gas and propane, or inert gases including nitrogen and argon may be used as a primary working fluid in addition to ambient air. 
     Referring now to  FIG. 1 , an exemplary compressor system  10  can be used to compress a working fluid such as ambient air according to one embodiment of the present application. The compressor system  10  includes a primary motive source  20  such as an electric motor, an internal combustion engine or a fluid-driven turbine and the like. The compressor system  10  can include a compressor  30  with multi-stage compression and in the exemplary embodiment includes a first stage compressor  32 , a second stage compressor  34 , and a third stage compressor  36 . In other embodiments a different number of compressor stages may be employed with the compressor  30 . The primary motive source  20  is operable for driving the compressor  30  via a drive shaft  22  to compress fluids such as air or the like. It should be understood that the compressor  30  for use with the drying system described herein can be of any type including centrifugal, axial, rotary screw and/or other positive displacement compression means. 
     A structural base  12  can be configured to support at least portions of the compressor system  10  on a support surface  13  such as a floor or ground and the like. One or more extensions or arms  14  can extend from the base  12  and is configured to hold portions of the compressor system  10 . Portions of the compressed air discharged from the compressor  30  can be transported through one or more conduits  40 ,  50 ,  60 ,  70  and  80  to one or more intercoolers  100  and/or to another compressor stage. An inlet fluid manifold  90  and an outlet fluid manifold  92  can be fiuidly connected to the intercoolers  100  to provide cooling fluid such as water or other liquid coolant to cool the compressed air after discharge from one or more of the compressor stages of the compressor  30 . The compressor system  10  can also include a controller  110  operable for controlling the primary motive power source and various valving and fluid control mechanisms (not shown) between the compressor  30  and intercoolers  100 . The compressor system of  FIG. 1  is only one exemplary form of a compressor system that can be used with the teachings of the present disclosure. Other forms and configurations are also contemplated herein. By way of example and not limitation, portable compressor systems or compressor systems that are mounted onto engines for industrial operation, land vehicle operation, or water vessel operation as well as screw type or piston type can be used with the teachings of the present disclosure. 
     Referring now to  FIG. 2  a hybrid dryer system  200  is shown in schematic form. The hybrid dryer system  200  includes a refrigeration drying system  202  and a desiccant wheel drying system  204 . A sealed housing  206  can form a pressure vessel about at least a portion of the desiccant wheel drying system  204 . The dryer system  200  includes a gas flow path  210  configured to receive and transport humidified or moist compressed gas such as air from a compressor to the refrigeration drying system  202  and subsequently to the desiccant wheel drying system  204 . The dryer system  200  removes at least a portion of the moisture entrained in the gas so that an end user receives compressed gas with a moisture content below a desired threshold. 
     The gas flow path  210  enters into a first heat exchanger  212  through an inlet  214 . The gas flow path then flows to a pre-cooler portion  216  of the first heat exchanger  212 . The pre-cooler  216  operates to provide an initial cooling to the compressed gas discharged from the compressor. After exiting the first heat exchanger  212  the gas will enter into a first conduit  220  which directs the gas flow path  210  into a second heat exchanger  222 . The second heat exchanger  222  includes an air chiller  224  operable for reducing the temperature of the gas so that liquid water particles condense out of the compressor gas stream. The gas flow path  210  includes a second conduit  230  that is connected between the second heat exchanger and a moisture separator  232 . The moisture separator  232  can include internal features such as baffles or the like that promote separation of liquid content such as water or other liquid material after condensing into liquid particles. The liquid content can then be drained externally from the system through a first drain valve  234 . 
     After passage through the moisture separator  232  the gas flow path  210  is directed into a third conduit  236  that is connected to a coalescing filter  240 . The coalescing filter  240  can filter solid particles as well as liquid particles condensed in the gas flow. The solid and liquid particles can then be drained through a second drain valve  242 . In some forms, the dryer system  200  may omit the coalescing filter  240  and in other forms the moisture separator  232  and coalescing filter  240  can drain into a single drain valve. From the coalescing filter  240 , the gas flow path  210  enters to a fourth conduit  250  and is then separated into a primary first flow stream  252  and into a secondary flow stream  254 . The primary flow stream  252  passes through a fifth conduit  256  and into a drying flow path  260  formed through a desiccant wheel  270 . The drying flow path  260  can include one or more separate flow paths and can include tortuous or linear segments as defined by the internal design of the desiccant wheel  270 . The desiccant wheel  270  includes desiccant material configured to adsorb moisture from the gas flow as the desiccant wheel  270  rotates as one skilled in the art would readily understand. After the compressed gas in the primary flow path has been dried within desiccant wheel  270 , the compressed gas is directed through a sixth conduit  280  back to the first heat exchanger  212 . The first heat exchanger  212  includes a re-heater portion  290  that exchanges heat with compressed gas flowing through the pre-cooler portion  216  at the entrance of the gas flow path  210 . After the dried gas flows through the re-heater  290  the dried gas exits through an outlet  292  of the first heat exchanger  212  and is directed to an end use machine or compressed air system or a storage tank  294 . 
     The secondary flow stream  254  is be directed to a regeneration blower  300  after splitting off from the primary flow stream  252 . The regeneration blower  300  provides additional flow pressure causing the secondary flow stream  254  to flow through a seventh conduit  302  at a desired flow rate to a third heat exchanger  310 . Typically, the secondary flow stream can range from about ten to twenty percent of the total compressed gas flow. However, in some embodiments the flow rate of the secondary flow stream may be above or below this range. The third heat exchanger  310  includes a regeneration gas heater portion  312  operable to increase the temperature of the gas after the gas has been compressed in a refrigeration circuit  330 . The refrigeration circuit  330  will be described below. 
     The secondary flow stream  254  is then directed through an eighth conduit  316  and to a regeneration flow path  320  extending through the desiccant wheel  270 . The regeneration flow path  320  provides a relatively dry and hot gas for drying or regenerating the desiccant in the desiccant wheel  270 . In this manner, the desiccant in the desiccant wheel  270  can be continuously regenerated via the regeneration flow path  320  and continuously dry the compressed gas in the primary flow stream  252  as the desiccant wheel  270  rotates. Similar to the drying flow path  260 , the regeneration flow path  320  can include one or more separate flow paths that can include tortuous portions and linear portions to desorb moisture from the desiccant in the desiccant wheel  270 . 
     An electric motor  272  may rotate the desiccant wheel  270  by way of a rotatable shaft  274  at a speed designed to effectively dry a continuous flow of the compressed gas to a desired pressure dew point temperature while simultaneously regenerating the desiccant with the secondary flow stream  254 . In this manner the desiccant wheel  270  is continuously drying the primary gas flow in one location and is continuously regenerated at another location. After the secondary flow stream  254  exits the regeneration flow path  320  of the desiccant wheel  270 , the secondary flow path is directed to a ninth conduit  322  arid subsequently merges back into the gas flow path  210  upstream of the second heat exchange  222 . 
     The refrigeration circuit flow path  330  includes a compressor inlet  332  configured to direct refrigerant into a refrigerant compressor  340 . The refrigerant compressor  340  will compress a relatively cool low pressure gaseous refrigerant and produce a relatively high pressure and hot gaseous refrigerant that is discharged into a compressor outlet flow path  342 . The high pressure refrigerant then flows into the third heat exchanger  310  through a pre-condenser/cooler portion  346  of the third heat exchanger  310 . The third heat exchanger  310  exchanges heat between the secondary flow stream  254  and the refrigerant flowing through the pre-condenser  346 . The refrigerant gas is cooled in the pre-condenser/cooler  346  prior to exiting through a pre-condenser outlet  348 . The cooled high pressure gaseous refrigerant then passes through a condenser  350  where the refrigerant is further cooled as is known to one skilled in the art. 
     A condenser blower  360  can direct a coolant flow such as ambient air through the condenser  350  to remove heat from the pressurized refrigerant and condense into a liquid form. A temperature or pressure control valve  370  can control the desired pressure and temperature of the refrigerant within the refrigerant condenser  350 . After exiting the condenser  350  the refrigerant can be expanded in an expansion device  380  to cool the refrigerant to a desired temperature. After being cooled in the expansion device  380 , the refrigerant is directed through an evaporator portion  390  of the second heat exchanger  222 . The evaporator portion  390  receives heat from the compressed gas flow and conversely cools the compressed gas flowing through the air chiller  224 . The refrigerant exits the evaporator  390  in a low pressure gaseous form. After exiting the evaporator  390  of the second heat exchanger  222 , the refrigerant will flow through the evaporator outlet  392  and back to the refrigerant compressor  340  to complete the refrigerant circuit flow path  330 . In this manner the compressed gas is dried to a first pressure dew point temperature in a refrigerant dryer system  202  and then further dried to a lower pressure dew point temperature in a desiccant wheel system  204 . In one exemplary form the pressure dew point of compressed gas can be reduced below freezing while the actual temperature, remains above freezing after exiting the desiccant drier system  204 , 
     In one aspect, a system comprises a fluid compressor operable to compress a working fluid; a dryer system in fluid communication with the compressor, the dryer system comprising: a refrigeration drying system operable for removing moisture from the working fluid; and a desiccant drying system located downstream of the refrigeration drying system, the desiccant drying system operable for removing additional moisture from the working fluid. 
     In refining aspects, the desiccant drying system includes a desiccant wheel; wherein the working fluid downstream of the refrigeration drying system is split into a first flow stream and a second flow stream; wherein additional moisture is removed from the first flow stream in the desiccant wheel; wherein the second flow stream regenerates the desiccant wheel; wherein a pressure dew point temperature of the first flow stream is subfreezing and an actual temperature of the first flow stream is above freezing downstream of the desiccant wheel; wherein the pressure dew point temperature is approximately negative 10 degrees F and the actual temperature is approximately 40 degrees F; wherein a mass flow rate of the first flow stream is approximately eighty percent of a combined mass flow rate of the first and second flow streams; wherein the second flow stream merges with the compressed working fluid between a precooler and a refrigerant evaporator after exiting the desiccant wheel; wherein the first flow stream flows through a preheater downstream of the desiccant wheel. 
     In another aspect, a gas dryer comprises a primary gas flow path extending through a refrigerant dryer circuit and subsequently through a desiccant dryer circuit; a secondary gas flow path split off from the primary gas flow path downstream of the refrigerant dryer circuit; a moisture separator positioned in the refrigerant dryer circuit configured to remove moisture from the gas in the primary gas flow path; a desiccant wheel positioned in the desiccant dryer circuit configured to remove additional moisture from the gas in the primary gas flow path; and a regeneration flow path extending through the desiccant wheel, the regeneration flow path in fluid communication with the secondary gas flow path. 
     In refining aspects, the gas dryer further comprises a coalescing filer positioned downstream of the moisture separator; at least one drain valve in fluid communication with the moisture separator and the coalescing filter; a regeneration blower operably connected with the secondary gas flow path; a regeneration gas heater positioned in the secondary gas flow path upstream of the desiccant wheel; comprising a motive source operable to rotate the desiccant wheel; secondary gas flow path includes an outlet downstream of the desiccant wheel connected to the primary gas flow path upstream of an evaporator in the refrigerant drying circuit. 
     In yet another aspect, a method comprises transporting a primary flow stream of pressurized working fluid discharged from a compression device through a primary flow path; cooling the pressurized working fluid in a precooler heat exchanger; chilling the pressurized working fluid in a refrigerant evaporator; separating a first quantity of moisture from the pressurized working fluid in a moisture separator located in a refrigerant circuit downstream of the evaporator; separating a second quantity of moisture from the pressurized working fluid in a desiccant wheel downstream of the first moisture separator; and reheating the pressurized working fluid prior to delivery to an end user. 
     In refining aspects, the method further comprises separating the pressurized working fluid from the primary flow stream into first and second flow streams upstream of the desiccant wheel; flowing the first flow stream through the desiccant wheel; drying the pressurized working fluid in the first flow stream; and wherein the pressure dew point temperature of the pressurized working fluid downstream of the desiccant wheel is below 32 degrees F and the actual temperature is above 32 degrees F; flowing the second flow stream through the desiccant wheel; regenerating the desiccant wheel by removing moisture with the pressurized working fluid in the second flow stream; merging the second flow stream with the primary flow stream upstream of the evaporator. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary. 
     Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.