Abstract:
An integrated absorption refrigeration and air compressor system comprising an air compressor system for compressing air and an absorption system for cooling air. The air compressor system comprises at least one air filter for cleaning entering air, a shut-off valve and plurality of bypass valves for blocking air from entering the absorption system, a compressor for increasing the pressure of the air, an after-cooler for cooling the air, a receiver for storing the air, and a pressure regulation valve for delivering the compressed air to end users. The integrated system also comprises an absorption system for cooling air. The absorption system comprises an evaporator for vaporizing air, an absorber for creating a strong absorbent solution, a pump for pumping the solution through the system, an economizer for heating the solution, a generator for creating steam and weakening the solution, a condenser for condensing the steam into a liquid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0003]    Not Applicable 
       TECHNICAL FIELD 
       [0004]    The disclosed embodiments generally relate to air compressor systems and, more particularly, to air compressor systems used in industrial manufacturing plants, instruments, and other applications. 
       DESCRIPTION OF THE RELATED ART 
       [0005]    An air compressor system decreases the volume and increases the pressure of a quantity of air by mechanical means. Compressed air has a lot of potential energy because air expands rapidly upon the removal of external pressure. The force of compressed air can be used to power tools and devices that use air. 
         [0006]      FIG. 2  is an illustration of the components of a conventional air compressor system in the prior art. Typical prior art air compressor system  200  is shown in  FIG. 2  of the drawings. Air filter  202  is typically located at the entrance of prior art air compressor system  200 . Air filter  202  is located upstream of compressor  204  and filters out particles in the air to protect the compressor from physical damage. Compressors use volumetric or centrifugal compression to increase the air pressure so that it reaches the required level needed. The compressor may be lubricant free or lubricant injected. In the Figure, air separator  208  is located downstream of air compressor  204  and functions to separate the air and the lubricant. An air separator is not a necessary component in lubricant free compressors. Lubricant cooler  206  cools lubricants to a lower temperature range (typically in the range of between 30° C. to 50° C.) to ensure the safe and efficient operation of the compressor. If a lubricant injected compressor is used, coalescing separator  210  is included to separate the lubricant from the air and thus prevent it from being trapped in after-cooler  212 . Compressed air is cooled by after cooler  212  to a lower temperature range (typically within the range of 30° C. to 50° C.) in order to minimize the capacity of the dryer and associated operating costs. After passing through the after-cooler, the air becomes saturated. Cooling is typically accomplished using air or water cooled heat exchangers. Moisture separator  214  removes condensed liquid from the air stream. Dryer  216  removes excess moisture in the system to satisfy the process moisture requirement. Particulate air filter  218  is generally installed downstream of dryer  216  to prevent adsorbed matter from entering the distribution system. Since air is often saturated after passing through air filter  218 , any temperature drop along the pipe has the potential to cause condensation (and thus create issues during industry processes). Air receiver  220  stores enough air to minimize pressure fluctuations if the load changes, and heater  222  is equipped to heat the air and prevent condensation in the duct. Air pressure regulation valve  224  regulates the air pressure at a level required for the operation of the process equipment. 
         [0007]    The previously described compressor system is typical of air compressor systems in the prior art. Such systems have drawbacks. A major issue of prior art air compressor systems like the one described is that high temperatures are needed and the amount of moisture present is excessive. The compressor consumes more power and does not operate very efficiently under these conditions. In fact, when employed in summer weather conditions, it must be sized up to 10% higher to meet the required capacity. In addition, the filter, dryers, and separators of prior art compressor systems are also affected by excessive pressure losses. These pressure losses can equal up to 30% of the compressor head and consume up to 30% of the total compressor power. The dryer and after cooler also consume an excessive amount of energy in prior art systems (or as much as 15% of the total compressor power). The inefficiency of the compressor is related to the low compressed air temperature. In order to remove moisture, the compressed air temperature is often cooled as low as 21° C., thus reducing the air volume by as much as 10%. Thus, in prior art systems, up to 10% of the compressed air is wasted. Prior art compressed air systems (excluding the distribution system) thus often use 20% to 45% more power than is actually necessary. 
         [0008]    Ideally, a system would be devised that can resolve the system drawbacks in the prior art. However, at the current time there is no known method or system which accomplishes this objective. 
       SUMMARY OF THE INVENTION 
       [0009]    The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to an embodiment of the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole. 
         [0010]    In one embodiment, an absorption cooling air compressor system is proposed. The proposed system is comprised of an integrated absorption and air compressor system. The integrated system comprises an air compressor system for compressing air and an absorption system for cooling air. The air compressor system comprises, in series, at least one air filter for cleaning air entering the system. A plurality of valves are located downstream of the at least one air filter to keep air from entering the absorption system. One of the plurality of valves, a shut-off valve, allows air that is at a temperature above freezing to enter the absorption system. The shut-off valve ensures that freezing air is not cycled through the absorption system. The air compressor system further comprises an air compressor located downstream of the at least one air filter and configured to compress air that enters it. An after-cooler is located downstream of the compressor for cooling the air, a receiver downstream of the after-cooler for storing the air, and a pressure regulation valve located downstream of the receiver for delivering the compressed air at the desired pressure to end users. In some embodiments, variable frequency drives are connected to the fan and compressor and are configured to modulate their speeds. In other embodiments, the system comprises only one VFD connected to either the fan or compressor. 
         [0011]    The integrated absorption and air compressor system also comprises an absorption system for cooling air. The absorption system is cyclical in function and comprises an evaporator located on the airflow line downstream of the at least one air filter and shut-off valve and configured to vaporize water and entering air, an absorber in communication with said evaporator and configured to mix the vaporized water with an absorbent material to form a strong absorbent solution, a pump in communication with the absorber for pumping the solution through the system, an economizer in communication with said pump and absorber and configured to heat the solution, and a generator in communication with said economizer and configured to create steam and weaken the solution. The weakened solution then cycles back through the economizer and the absorber, while the steam is cycled through a condenser. The condenser is configured in communication with the generator and condenses the steam into a liquid that is then cycled through at least one expansion valve and back through the absorption system. In some embodiments, the liquid is also cycled through a deep dryer located on the airflow line of the absorption system downstream of the after cooler. 
         [0012]    In embodiments in which the compressor is lubricant injected, the integrated air compressor and absorption system comprises an oil cycle system. In such embodiments, an oil separator and coalescing filter are configured in-line downstream of the compressor for the purpose of separating the compressor oil from the air and to filter the air, respectively. Embodiments that include an oil cycle system also include an oil cooler configured in connection with the compressor, generator, and oil separator that cools the oil. 
       ADVANTAGES 
       [0013]    Accordingly, it is one aspect of an embodiment to reduce the moisture content in the air stream and inlet temperature. As a result, annual energy consumption is reduced by 5% to 10%. 
         [0014]    It is another aspect of an embodiment to eliminate the need for an after cooler, moisture separator, and heaters. 
         [0015]    It is a further aspect of an embodiment to install an H-per filter upstream of the compressor to reduce both the equipment costs and the required compressor head. This has the potential to reduce energy consumed by the compressor by 10 to 20% and by up to 40% in applications that require very dry air. 
         [0016]    It is yet a further aspect of an embodiment to reduce the system pressure by installing an evaporator and fan upstream of the compressor. When dry air is needed, the embodiments of the system can save compressor energy by up to 40%. When it is implemented in large compressed air plants, the proposed embodiment effectively cools buildings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the following figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements for clarity. Advantages, features, and characteristics of the present disclosure, as well as methods and functions of related elements of structure, and the combination of parts and economies of manufacture, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of the specification, wherein like reference numerals designate corresponding parts in the various figures, and wherein: 
           [0018]      FIG. 1  is a schematic diagram of the system embodying the principles of the absorption cooling air compressor system used for compressing air. 
           [0019]      FIG. 2  is a schematic diagram of an air compressor system in the prior art. 
       
    
    
     FIG.  1  DRAWINGS REFERENCE NUMERALS 
       [0000]    
       
           100  Absorption Cooling Air Compressor System 
           102  Air Inlet Filter 
           104  H-per Filter 
           106  Shut-off Valve 
           108  Evaporator 
           110  Bypass Valve I 
           112  Expansion Valve I 
           114  Fan 
           116  Compressor 
           118  VFD I 
           120  VFD II 
           122  Oil Separator 
           124  Coalescing Filter 
           126  Generator 
           128  Bypass Valve  2   
           130  Economizer 
           132  Absorber 
           134  Pump 
           136  Oil Cooler 
           138  Condenser 
           140  After Cooler 
           142  Deep Dryer 
           144  Receiver 
           146  Pressure Regulation Valve 
           148  Expansion Valve II 
           150  Pressure Sensor I 
           152  Temperature Sensor I 
           154  Temperature Sensor II 
           156  Liquid Level Sensor I 
           158  Liquid Level Sensor II 
           160  Temperature Sensor III 
           162  Pressure Sensor II 
           164  Temperature Sensor IV 
       
     
       FIG.  2  PRIOR ART DRAWINGS REFERENCE NUMERALS 
       [0000]    
       
           200  Prior Art Air Compressor System 
           202  Air Filter 
           204  Air Compressor 
           206  Air Separator 
           208  Lubricant Cooler 
           210  Coalescing Separator 
           212  After Cooler 
           214  Moisture Separator 
           216  Dryer 
           218  Air Filter 
           220  Air Receiver 
           222  Heater 
           224  Air Pressure Regulator 
       
     
       DETAILED DESCRIPTION 
       [0066]    Before any embodiments of the invention are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosed is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “attached,” “connected,” “supported,” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “attached,”, “connected”, “supported”, “communicated” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, and supports. Further, “connected” and “communicated” is not restricted to physical or mechanical connections. 
         [0067]      FIG. 1  shown below illustrates an embodiment of the disclosed absorption cooling air compressor system. It is shown that absorption cooling air compressor system  100  is comprised of air inlet filter  102 , H-per filter  104 , shut off valve  106 , evaporator  108 , bypass valve I  110 , expansion valve  112 , fan  114 , compressor  116 , variable frequency drive I (VFD I)  118 , variable frequency drive II (VFD II)  120 , oil separator  122 , coalescing filter  124 , generator  126 , bypass valve II  128 , economizer  130 , absorber  132 , pump  134 , oil cooler  136 , condenser  138 , after-cooler  140 , deep dryer  142 , receiver  144 , pressure regulation valve  146 , and expansion valve II  148 , pressure sensor I  150 , temperature sensor I  152 , temperature sensor II  154 , liquid level sensor I  156 , liquid level sensor II  158 , temperature sensor III  160 , pressure sensor II  162 , and temperature sensor IV  164 . 
         [0068]    Absorption cooling air compressor system  100  is comprised of an integrated absorption air compressor system. In the embodiment illustrated in  FIG. 1 , air that enters absorption cooling air compressor system  100  first enters air inlet filter  102 , a medium grade filter configured upstream of H-per filter  104  and configured to remove mechanical dirt from the incoming air stream. (In other embodiments, air inlet filter  102  may be a filter of a differing grade). In the embodiment shown in the Figure, the entering air then continues along the airflow line to H-per filter  104 , a high performance filter that also removes dirt and particles from the airstream and is configured downstream of air inlet filter  102  on the airflow line. The particular type and use of the H-per filter selected is dependent on the types of applications with which absorption cooling air compressor system  100  is used. While illustrated in the embodiment in  FIG. 1 , H-per filter  104  is not included in all embodiments. Generally, H-per filter  104  is included in absorption cooling air compressor system  100  in applications in which very dry air is needed such as for products in the pharmaceutical industry. In the illustrated embodiment, air filtered by H-per filter  104  proceeds to shut-off valve  106 . Shut-off valve  106  is configured on the airflow line of the absorption system upstream of evaporator  108 . Valve  106  does not let air at a temperature at or lower than 0° C. (adjustable) enter into the absorption system. It is configured to remain open to let air that is at a temperature above 0° C. enter evaporator  108  and continue through the absorption system. Filters  102  and  104  and evaporator  108  function to clean and cool the air so that it is moisture-free before it enters the compressor. Air that passes through shut-off valve  106  enters into evaporator  108  and into the absorption system. Air that does not enter the absorption system continues through the air compressor system airflow line by bypassing evaporator  108  through bypass valve I  110  and continues on to compressor  116 . 
         [0069]    In the illustrated embodiment, supply fan  114  is located on the airflow line downstream of evaporator  108 . It functions to pull outside air into the system through air inlet filter  102  and H-per filter  104 . Notably, supply fan  114  is not included such as in (but not limited to) embodiments that do not include an H-per filter. In embodiments in which the supply fan is included as part of the configuration like that shown in  FIG. 1 , the fan may also be equipped with at least one variable frequency drive (such as VFD I  118  shown here). VFD I  118  controls the fan speed so that the inlet pressure set point is zero or has a slightly positive pressure. The pressure set point is measured by pressure sensor I  150 . In yet other embodiments, however, VFD I  118  is not included. An example of a situation in which VFDs are not included as part of the configuration of absorption cooling air compressor system  100  (but is not limited to this example) include when the compressor has a constant and high load or when the compressor is not configured with a VFD. In the embodiment presented in  FIG. 1 , compressor  116  is configured in connection with VFD II  120 . The configuration illustrated in the  FIG. 1 s    the most energy efficient and best controls the air humidity of the compressed air. When included in the embodiment, variable frequency drive  120  is modulated to maintain the pressure set point as measured by pressure sensor I  150 . The continuous modulation of the speed results in a lower air pressure and significant compressor energy savings. 
         [0070]    As shown in the illustration in  FIG. 1 , compressor  116  is a lubricant injected compressor and is thus connected on the air compression system airflow line in communication with an oil cycle system comprising oil separator  122 , oil cooler  136 , and also involves generator  126 . Oil cooler  136  is configured in connection with compressor  116  and generator  126  and functions to cool the oil temperature of oil from the compressor to below its set point. In an embodiment, oil cooler  136  is a forced air cooler, while in other embodiments it may be a water cooler, or other type of heat exchanger. Oil cooler  136  can be controlled via on/off control or speed modulation. In the embodiment illustrated in  FIG. 1 , oil separator  122  is configured on the air compressor airflow line downstream of compressor  116  and upstream of coalescing filter  124 . As part of the oil cycle, it functions to separate oil from the airstream. Oil that is separated out by oil separator  122  is returned to oil cooler  136 . Compressor  116  is configured to increase the air pressure so that it reaches the level required to enable air compressor system  100  to provide the amount of air required. In some embodiments, compressor  116  is a constant speed compressor that is turned on and off based on the pressure set point. This pressure set point is measured by pressure sensor II  162 . In other embodiments, compressor  116  may be a multiple piston compressor controlled to maintain the required air pressure level based on measurements collected by air pressure sensor I  150 . In embodiments in which compressor  116  is not lubricant injected, oil cooler  136  and oil separator  122  are not needed as part of the configuration of system  100 . 
         [0071]    In the illustration, coalescing filter  124  is configured on the compressor airflow line between oil separator  122  and generator  126  and is configured to remove lubricant from the compressed air stream. In other embodiments, especially those in which compressor  116  is not lubricant injected, coalescing filter  124  may not be included in the configuration of system  100 . As shown in the illustration in  FIG. 1 , air exiting the compressor continues along the air compressor system airflow line to after-cooler  140  by bypassing generator  126  via bypass valve II  128 . The valve is controlled by the temperature set point of generator  126 . Temperature sensor II  154  is configured inside of generator  126  and determines this set point. 
         [0072]    In the illustrated embodiment, after-cooler  140  is configured on the air compressor airflow line between generator  126  and deep dryer  142 . The after-cooler functions to cool air that has been compressed to the desired level. Although the embodiment illustrated in  FIG. 1  includes deep dryer  142 , said deep dryer is not necessary in all embodiments of absorption cooling air compressor system  100 . When included in the system, deep dryer  142  is configured on the airflow line between after-cooler  140  and receiver  144 . It functions to remove vapor from the compressed air as needed and is typically used in applications in which system  100  needs to produce very dry air. Deep dryer  142  can cool the compressed air to as low as 5° C. (adjustable). At this low temperature, the compressed air contains almost no moisture. In the illustration in the Fig., temperature sensor III  160  is configured downstream of deep dryer  142  on the airflow line and is configured to measure the temperature of the air stream after air exits dryer  142 . Receiver  144  is configured downstream of after-cooler  140  (and in some embodiments downstream of the deep dryer) and functions as a reservoir for storing the air. Pressure sensor II  162  is configured in communication with receiver  144  and measures the pressure of the airstream. Air exiting system  100  goes through pressure regulation valve  146 . Valve  146  is configured downstream of receiver  144  and regulates the amount of air delivered to the end users. 
         [0073]    Air that enters system  100  that is at a temperature above 5° C. enters evaporator  108  and continues through the absorption system before it goes through the air compressor system. The absorption system cycle of system  100  comprises evaporator  108 , absorber  132 , pump  134 , economizer  130 , generator  126 , and condenser  138 . The absorption system also comprises a plurality of expansion valves and liquid and temperature sensors. Incoming air that is allowed to enter into evaporator  108  (by valve  106 ) is cooled to about 5° C. (adjustable) in order to ensure that it has a high density and low moisture content. In the illustrated embodiment, evaporator  108  is located on the airflow line downstream of shut-off valve  106  and air filters  102  and  104 . Absorber  132  is configured in connection along the absorption cycle with evaporator  108 . Water vaporized in the economizer proceeds to absorber  132  where it mixes with an absorbent solution (for example LiBr). In absorber  132 , the weak solution absorbs steam to form a strong solution. This strong solution is then pumped into economizer  130  and generator  126  by pump  134 . Pump  134  is configured in communication with absorber  132  and economizer  130 . It primarily functions to recirculate the strong solution from absorber  132  to generator  126 . The speed and on/off status of pump  134  is determined by the liquid level in absorber  132 . This liquid level is measured by liquid level sensor  158  which in  FIG. 1  is located inside absorber  132 . 
         [0074]    Economizer  130  is configured on the absorption cycle in communication with absorber  132  and generator  126  and is operable to recover heat from said weak solution. The heat recovery reduces the liquid circulation and improves the operating performance of absorber  132 . Generator  126  is configured on the absorption cycle line in communication with economizer  130 . The generator generates steam as well as a weak absorbent solution from the high temperature air and oil streams (mixture of LiBr and H 2 O). Generator  126  also reduces the temperature of the compressed air and oil. The weakened LiBr solution then cycles back through economizer  130  and absorber  132  while the generated steam is passed through condenser  138 . Condenser  138  cools the steam to the temperature setpoint determined by temperature sensor IV  164 . The condensed steam then cycles through deep dryer  142  (when included in the embodiment of system  100 ) after passing through expansion valve  2   148 , or goes to evaporator  108  after passing through expansion valve  112 . The expansion valves are configured on the absorption cycle line in communication with condenser  138  and lowers the pressure of the liquid produced from the condenser. Expansion valve  112  is configured to maintain the supply air temperature at a set point of 5° C. (adjustable). 
         [0075]    It will be apparent to those skilled in the art that various modifications can be made in the system for compressor air without departing from the scope or spirit of the given embodiment. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure of this application.