Abstract:
A method and apparatus for enhancing the power output and operational efficiency of a combustion turbine system using a combined refrigerant substantially comprising a first refrigerant and a second refrigerant, whereby the combined refrigerant exhibits a total pressure substantially greater than each respective first and second refrigerant at a temperature inside an evaporative chiller. In a preferred embodiment, the combined refrigerant cools turbine inlet air through the exchange of heat from the inlet air, in an air chiller, with a coolant which is cooled by the combined refrigerant in the evaporative chiller. The combined refrigerant, after it is used to cool the coolant in the evaporative chiller, is separated through the use of a liquid absorbent which absorbs the second refrigerant to form a solution pair. The non-absorbed first refrigerant is compressed, condensed and then recirculated to eventually join the second refrigerant which is desorbed from the solution pair in a regenerator. The economic advantage of the present invention is enhanced by thermally linking the heat required to regenerate the second absorptive refrigerant from the solution pair with the hot exhaust of heat available from the gas turbine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of Provisional Application Serial No. 60/251,928, filed on Dec. 7, 2000. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to systems and methods for increasing the power produced by a gas turbine or combustion turbine for driving a mechanical device or for power generation. More particularly, it provides a more efficient refrigeration method and apparatus for cooling turbine inlet air to enhance its power output and overall combustion efficiency. 
     2. Background of the Invention 
     As used herein, the terms turbine, gas turbine and combustion turbine may be used interchangeably in reference to the same or similar process or system. Gas turbines are widely used in all phases of industrial applications. They are utilized as a source of shaft power to drive compressors, aircraft, and other rotating equipment. They are also coupled to electrical power generators for the generation of electricity extensively in either a simple cycle or a combined cycle power plant. Gas turbines typically consist of an intake air filtration, a compressor for compressing inlet air, a combustion chamber for mixing and igniting the compressed air with fuel to form a compressed hot gas for expansion to a turbine section to generate power. The work extracted from the high temperature gas, after partially used for air compression, will be available for output load. The exhaust gas from the turbine section, which contains a high level of heat energy, can be introduced into a waste heat recovery section, e.g. the heat recovery steam generator (HGSG) in a combined cycle power plant, or in some cases, discarded. 
     The performance of a combustion turbine system operated under the cycle described above is generally proportional to the mass flow rate of the inlet air to the gas turbine compressor, and is therefore largely affected by ambient air conditions. At high ambient temperatures, the available work produced from a gas turbine decreases due to a reduction in the mass flow of air through the system. And ironically, power demand often reaches the peak in most gas turbine applications during the hottest days when the operational efficiency of the turbine is at the lowest. Thus, an inlet air cooling system is commonly adopted to reduce the intake air temperature for minimizing the impact on turbine output, and to augment power output even during hot days when it can be installed cost effectively. 
     Various methods and apparatus for cooling gas-turbine inlet air are available in the art. For example, U.S. Pat. No. 5,930,990 to Zachary, et al. discloses an apparatus for achieving power augmentation in a gas turbine through a wet compression where water is sprayed to the inlet air to induce “latent heat inter-cooling.” Further, a liquid coolant fuel, as exemplified by the disclosure in U.S. Pat. No. 5,806,298, is introduced at the inlet of the air compressor, which vaporizes and cools the air to enhance power output of a gas turbine. Others utilize either a direct or an indirect evaporative cooler where the heat of hot air is transferred into the circulating water, leading to partial vaporization of water. However, the temperature reduction achieved with an evaporative cooler is limited to the daily fluctuating wet bulb temperatures in the areas. An evaporative cooling apparatus may not be applicable for warm and humid areas. Moreover, it often requires a high level of maintenance and relies on the quality and availability of a water source. 
     It is also readily common to introduce an external refrigeration system to chill the inlet air temperature far below that achievable by an evaporative cooler. This approach permits the turbine to operate at a fairly constant and optimal output regardless of the ambient air conditions. Although chilling the air to near 32° F. is possible, a minimum temperature considered suitable for inlet air chilling in a gas turbine application is usually set above 42° F. This prevents moisture contained in the inlet air from freezing and depositing on the inlet guide vanes or compressor blades as the static air temperature decreases further while it accelerates into the compression chamber. U.S. Pat. No. 5,457,951 discloses the use of liquefied natural gas as a refrigerant to improve the capacity and efficiency of a combined cycle power plant. Liquid nitrogen, as disclosed in U.S. Pat. No. 5,697,207, was also proposed to gain additional power from a gas turbine generator. However, the availability of this type of cold refrigerant is extremely limited. In most areas where a cold refrigerant is not readily available, a refrigeration system is proposed. 
     In all refrigeration systems, the refrigeration process depends on the absorption of heat at a low temperature which is achieved by the expansion and evaporation of a liquid refrigerant. Refrigeration systems are distinguished by how the refrigerant vapor is liquefied to repeat the cycle. There are two major types of refrigeration systems in commercial practice today, namely absorption refrigeration and mechanical refrigeration. In a typical absorption refrigeration system, a refrigerant vapor from the evaporator is dissolved in a liquid absorbent to form what is commonly referred to as a “solution pair” in an absorber. The solution pair is transferred to a desorber, or regenerator, where heat energy is applied to desorb the refrigerant in the form of a vapor, which is fed to a condenser. The two most commonly used absorption refrigeration systems are ammonia water and aqueous lithium bromide units. U.S. Pat. No. 5,555,738 improves combined-cycle power plant efficiency by operating an ammonia refrigeration cycle driven by the waste heat from the gas turbine to lower the inlet air temperature. Although absorption refrigeration systems are known and utilized commercially, continuous efforts have been devoted to improving their performance. A multiple effect generator is described in U.S. Pat. Nos. 4,183,228; 4,742,693, and 4,441,3332 to improve the efficiency of an absorption refrigeration circuit. U.S. Pat. Nos. 4,283,918 and 4,413,479 introduce a third fluid, which is at least partially immiscible to allow separation of refrigerant at absorption temperature, in the absorption refrigeration cycle. Other improvements include those described in U.S. Pat. Nos. 4,055,964 and 5,816,070. These systems are driven by heat energy and are relatively inefficient and inflexible unless reliable waste heat or inexpensive fuels are readily available. 
     In a mechanical refrigeration system, the refrigerant vapor is mechanically compressed to a high pressure and is then cooled to total condensation. This type of system has prevailed in industrial installations as a result of the improvement in efficiency. Depending upon temperature requirements, availability, and economics, various pure component refrigerants are commercially available, including light hydrocarbons, ammonia, water, and newly discovered chlorinated fluorocarbons (CFC&#39;s). For instance, an inlet air chilling apparatus using water vapor compression is described in U.S. Pat. No. 5,632,148 to achieve power augmentation of a gas turbine. For the modest cooling goal of inlet air chilling, the CFC refrigerants may be most appealing. However, their usage has become increasingly restricted due to environmental regulations. Conventional mechanical refrigeration using a single component refrigerant capable of achieving much colder refrigeration tends to be less efficient. Besides, the need of additional power to drive the compressor reduces the advantages of inlet air chilling. 
     An enhanced refrigeration system has also been attempted by combining both mechanical refrigeration and absorption refrigeration. For instance, U.S. Pat. No. 5,038,572 discloses a combined refrigeration method and apparatus for an improved efficiency, wherein mechanical refrigeration is alternately connected in series with an aqueous lithium bromide refrigeration. A combustion-powered compound refrigeration system is disclosed in U.S. Pat. No. 4,873,839 to reduce the energy consumption of a refrigeration system wherein the hot exhaust gas from a combustion engine, used to power the refrigerant compressor, is utilized to drive an ammonia absorption unit. U.S. Pat. No. 4,586,344 to Lutz, et al., incorporated herein by reference, introduces a pair of refrigerants which form a substantially immiscible fluid having a total pressure substantially greater than the vapor pressure of either individual refrigerant in the evaporative chiller. This process leads to a higher suction pressure and lower compression horsepower for a mechanical refrigeration system. U.S. Pat. No. 5,816,070 to Mechler teaches the use of vapor recompression absorption to increase the efficiency of an absorption process. 
     Still others, such as U.S. Pat. Nos. 5,353,597; 5,537,813; and 6,119,445, propose to increase inlet air density by a combination of inlet air compression and cooling. 
     As can be seen from the foregoing description, prior art has long sought methods for improving operational capacity and efficiency of a gas turbine, particularly in hot weather conditions. While inlet air chilling appears to offer the most advantages, there continues to be a need for improved methods and apparatus to lower costs and energy consumption associated with the provision of such a system. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a more efficient and economical refrigeration system to augment the power output of a gas turbine. A significant reduction in the power required to drive the refrigerant compressor can be achieved by the addition of an absorptive refrigerant to the evaporative chiller, wherein a substantial increase in pressure results from the combined refrigerant. The absorptive refrigerant vapor from the chiller is subsequently separated from the mechanical refrigerant in an absorber by adding a liquid absorbent, which absorbs the absorptive refrigerant over the mechanical refrigerant. 
     It is another object of the present invention to reduce the usage of the combustion fuel by utilizing the hot exhaust gas from the gas turbine for the generation of the absorptive refrigerant. Consequently, the emissions of greenhouse gases resulting from the integrated inlet air chilling system can be reduced. 
     In carrying out these and other objects of the invention, there is provided, in the broadest sense, an inlet air chiller using a combined refrigerant to increase inlet air density for optimizing the performance of a combustion turbine system. The hybrid refrigeration system is based on a combination of mechanical refrigeration supplemented by an absorption refrigeration cycle to reduce the compression requirements over a conventional refrigeration system using a single component refrigerant. At least two refrigerants, a mechanical refrigerant and an absorptive refrigerant, are utilized in the evaporative chiller wherein the combined refrigerant exhibits the characteristic of a much higher total pressure than the vapor pressure of each individual refrigerant at the refrigeration temperature regardless of their miscibility. Preferably, the system includes two substantially immiscible refrigerants which coexist where the total system pressure, in most cases, is approximately equivalent to the sum of the vapor pressures of each refrigerant. This can be exemplified below by a binary propane-ammonia system where experimental vapor pressures representative of such systems were published in  The Journal of Chemical and Engineering Data , by Noda et al., entitled “Isothermal Vapor-Liquid and Liquid-Liquid Equilibria for the Propane-Ammonia and Propylene-Ammonia Systems.” 
     
       
         
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Vapor Pressure b , psia 
                   
               
             
          
           
               
                   
                 Temperature, ° F. 
                 Pressure a , psia 
                 Propane 
                 Ammonia 
               
               
                   
                   
               
             
          
           
               
                   
                 32.0 
                 129.4 
                 68.6 
                 62.4 
               
               
                   
                 68.0 
                 238.3 
                 121.3 
                 124.3 
               
               
                   
                   
               
               
                   
                   a Liquid-liquid equipibrium at given temperatures  
               
               
                   
                   b Vapor pressure of pure component at given temperatures  
               
             
          
         
       
     
     As shown, the vapor pressure of the two co-existing liquid phases (ammonia and propane) is 129.4 psia at 32° F., which is almost double the vapor pressure of each individual pure refrigerant, namely 68.6 psia for propane and 62.4 psia for ammonia. The compression power needed for the refrigerant compressor is greatly reduced due to a higher suction pressure of the resultant refrigerant vapor from the chiller. 
     In the present invention, the resultant combined refrigerant from the evaporator is preferably preheated to a temperature well above water freezing temperature and then directly fed to an absorber wherein the absorptive refrigerant is separated from the mechanical refrigerant by the addition of a liquid absorbent. The mechanical refrigerant vapor, essentially not soluble in the liquid absorbent, from the absorber is compressed and subsequently condensed. The absorptive refrigerant is heat regenerated from a solution pair in the desorber. By removing one of the refrigerants as in the present invention prior to mechanical compression, the mass flow into the refrigerant compressor, and thereby power requirements, are further reduced. It should be noted that, in some cases, the vaporized combined refrigerant could be compressed to a higher pressure prior to its introduction into the absorber. 
     The economic advantages of the present invention are further enhanced by thermally linking the heat required to generate the absorptive refrigerant from the solution pair with the hot exhaust heat available from the gas turbine or the refrigerant compressor driver, if available. This is of significant importance when the cost of combustion fuel is expensive and/or the reduction in greenhouse gases emissions is desired. 
     The operational efficiency can be further improved in another embodiment of the present invention by applying an economizer to the mechanical refrigerant after the expansion of the mechanical refrigerant. The economizer, operated at an intermediate pressure, permits a portion of the flashed refrigerant vapor to be collected and fed to the refrigerant compressor, thus reducing the flow to the chiller and absorber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The application and advantages of the invention will become more apparent by reference to the following detailed description in connection with the accompanying drawings, wherein: 
     FIG. 1 is a schematic representation of a conventional inlet air chilling process where only mechanical refrigeration is used; 
     FIG. 2 is a schematic representation of an inlet air chilling process incorporating the improvements of the present invention for augmenting the power produced from a gas turbine; 
     FIG. 3 is an alternative arrangement of an inlet air chilling system incorporating the improvements of the present invention, wherein an economizer for the mechanical refrigerant is introduced. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a method of enhancing the operational capacity and efficiency of a gas turbine system by the application of a combined refrigerant comprising at least two refrigerants wherein the combined refrigerant exhibits a total pressure substantially higher than the vapor pressure of each respective refrigerant inside an evaporative chiller. For purposes of comparison only, an exemplary conventional process will be described with reference to FIG.  1  and compared with the inventive process. The methods of the present invention will be described with reference to FIGS. 2, and  3 . 
     Referring to FIG. 1, inlet air stream  100  having a mass flow rate of approximately 995 lb/sec and 60% relative humidity is introduced into an air chiller  19  at an ambient temperature of about 90° F. and a pressure close to 14.7 psia. The inlet air stream  100  enters the air chiller  19 , which utilizes a coolant  40 , e.g. a chilled ethylene glycol-water solution, to significantly cool the inlet air stream  100  to a temperature of about 50° F. Cooled air  102  is then introduced into an air compressor  104  which compresses the cooled air  102  before it is supplied to a combustor  106 . Fuel is added to the compressed air and ignited in combustor  106  to form a compressed hot gas for expansion in a turbine  108  to generate power for driving device  110 . Gas exhausted from turbine  108  may be directed to waste heat recovery unit  112  before being sent to the atmosphere through vent  103 . The air. compressor  104 , combustor  106  and turbine  108  form a conventional gas turbine  120 . 
     Warm coolant  42  from air chiller  19  enters an evaporative chiller  8  where a conventional single refrigerant stream  18 , such as propane in this example, is supplied to the evaporative chiller  8  at approximately 35° F. to cool the warm coolant  42 . The cooled coolant  40  returns to air chiller  19  for use in cooling the inlet air stream  100 . A vapor refrigerant stream  2  from evaporative chiller  8  is directed to a separator  13  to ensure removal of any entrained liquid  105 . After the entrained liquid  105  has been separated from the vapor refrigerant stream  2 , a refined vapor refrigerant stream  9  enters a suction port of a refrigerant compressor  39 . Compressed vapor refrigerant stream  15  is cooled and condensed at approximately 110° F. and 215 psia through a condenser  38  to form a liquid refrigerant stream  16 . An accumulator  37  is applied to the liquid refrigerant stream  16  to provide the necessary surge. The liquid refrigerant stream  17  is expanded through expansion valve  36  to reform refrigerant stream  18 , which completes the cycle and is repeated. 
     The methods of the present invention will now be illustrated with reference to FIGS. 2 and 3. FIG. 2 shows a schematic configuration of one embodiment of the present invention, where the same reference numerals are used from FIG. 1 to describe similar streams and equipment. Various values of temperature and pressure are recited in association with the specific example of mixed propane and ammonia refrigeration as described below. These values are merely illustrative, and depend on the desired refrigeration temperature and the combined refrigerant selected. 
     Referring now to FIG. 2, inlet air stream  100  is cooled to about 50° F. in air chiller  19  as described in reference to FIG.  1 . The warm coolant  42  from air chiller  19  enters evaporative chiller  8  where a combined refrigerant stream  1 , instead of a conventional single refrigerant stream  18  as described in FIG. 1, is supplied to the evaporative chiller  8  at approximately 35° F. to cool the warm coolant  42 . The process of cooling the warm coolant  42 , which returns to air chiller  19  as cooled coolant  40 , causes substantial vaporization of the combined refrigerant stream  1 . As described above, the combined refrigerant stream  1  comprises at least two refrigerants having a total pressure substantially greater than the vapor pressure of each respective refrigerant under the conditions described in reference to the evaporative chiller  8 , in FIG. 1, regardless of miscibility. In FIG. 2, the combined refrigerant stream  1  is preferably a combination of a first refrigerant comprising 50 mol % propane (mechanical refrigerant) and a second refrigerant comprising 50 mol % ammonia (absorptive refrigerant) which is supplied to the evaporative chiller  8  at about 134 psia and 35° F. 
     It should be noted that, depending on the design details of air chiller  19  and the selection of combined refrigerant stream  1 , the use of a coolant  40  for transferring refrigeration available from the combined refrigerant stream  1  to the inlet air stream  100  may not be required. Thus, the air chiller  19  and evaporative chiller  8  may be utilized as a single component eliminating the need for a coolant  40 . 
     A substantially vaporized refrigerant stream  2   a , substantially comprising the first refrigerant and second refrigerant, exits from evaporative chiller  8  which is supplied to a pre-heater  20  where it is heated to well above 32° F. prior to entering the bottom of an absorber  28 . Within absorber  28 , the second refrigerant is separated from the first refrigerant by absorption in a cool liquid absorbent  4  which is supplied through the top of absorber  28 . To improve the absorption efficiency, an inter-cooler  3  could be included to effectively remove the heat generated by the absorption taking place in absorber  28 . The cool liquid absorbent  4  should be selected so that it substantially absorbs the second refrigerant instead of the first refrigerant. For instance, water is a preferred liquid absorbent because of the excellent solubility of the second refrigerant ammonia in water as compared to extremely low solubility of the first refrigerant propane in water. 
     The refined (non-absorbed) vapor refrigerant stream  9 , substantially comprising the first refrigerant, is removed from the absorber  28  at approximately 124 psia and 119° F. Refined vapor refrigerant stream  9  is then compressed to approximately 228 psia by refrigerant compressor  39 . The resulting compressed refrigerant vapor stream  15  is then condensed at about 110° F. in condenser  38  to form the liquid refrigerant stream  16 , substantially comprising the first refrigerant. Depending upon the power requirement and availability of the fuel source, the driver for the refrigerant compressor  39  can be an electrical motor, a gas engine, a steam turbine, or a gas turbine. Accumulator  37 , which is equipped with a water boot  101  for the removal of any water, is applied to the liquid refrigerant stream  16  to provide the necessary surge. A water stream  27  is withdrawn from accumulator  37  and is introduced into the absorber  28  through an expansion valve  26 . 
     A first liquid stream (solution pair)  10 , substantially comprising the liquid absorbent  4  and second refrigerant, is drained from the absorber  26  to solution pump  24 . Solution pump  24  feeds the first liquid stream  10  to a heat exchanger  6  where it is heat exchanged with a hot liquid absorbent  12  to form a heated solution  11 , essentially comprising the first liquid stream  10  at a higher temperature. The heated solution  11  enters a regenerator  30  where a second liquid stream  14 , substantially comprising the second refrigerant, is desorbed from the heated solution  11  by an external heat source through a reboiler  7 . The liquid absorbent  12 , which preferably contains less than 2 mol % of the second refrigerant, is then drained from the regenerator  30  and reintroduced into heat exchanger  6 ,where it is cooled through the exchange of heat with the first liquid stream  10  as thus described. Thus, once the liquid absorbent  12  is cooled through the heat exchanger  6 , it enters absorbent cooler  23  where it is further cooled to form liquid absorbent  5 . Liquid absorbent  5  is then expanded through an expansion valve  34  where it is introduced into the absorber  28  as liquid absorbent  4 . The regenerator  30  is typically equipped with an overhead condenser and reflux systems, which are not shown. The heat source to the reboiler  7  can be carried by a heating medium  25  through the waste heat recovery unit  112  from the gas turbine  120 . Alternatively, the waste heat recovery unit  112  may effectively replace the reboiler  7  as a means of supplying heat to the regenerator, thereby eliminating the need for heating medium  25 . Recoverable waste heat is adequate for the heat requirements in most applications, as in this example. There are no additional needs for combustion fuel for the regeneration process. This hybrid refrigeration cycle further reduces the overall requirements of combustion fuel, thereby improving the operational efficiency. 
     The second liquid stream  14  and liquid refrigerant stream  17  substantially comprise the second refrigerant and first refrigerant, respectively. Each is expanded through respective expansion valves  33  and  36 , and are finally combined to reform the combined refrigerant stream  1 , thus completing the cycle which is repeated. 
     For a conventional gas turbine, an increase of approximately 1% in power output can be achieved for every 2.7° F. reduction in inlet air temperature. In this example, the 40° F. reduction in air temperature would result in an approximately 14.8% enhancement in the output of the turbine. More specifically, a power output of approximately 171,000 HP would be available with inlet air chilled to 50° F., which is compared to 146,500 HP without the inlet air chilling. 
     The required duty for inlet air chilling in such a system is approximately 75 MMbtu/hr. The process performances for providing such duty from the above-mentioned embodiments illustrated in FIG.  1  and FIG. 2 are listed and compared in Table 1 below. As shown, it requires a total compression horsepower of about 2,285 BHP when the combined refrigerant  1  of the present invention illustrated in FIG. 2 is used. This is compared to a total compression horsepower of 8,230 BHP when conventional propane refrigeration demonstrated in FIG. 1 is used. A significant reduction of over 70% in compression horsepower is achieved by the present invention. 
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Performance of Conventional and Inventive Processes 
               
             
          
           
               
                 Description 
                 Conventional - FIG. 1 
                 Inventive - FIG. 2 
               
               
                   
               
             
          
           
               
                 Evaporative Chiller 
                   
                   
               
               
                 Temperature, ° F. 
                 35 
                 35 
               
               
                 Refrigerant Flow, Lbmol/hr 
                 15,334 
                 14,203 
               
               
                 Refrigeration Duty, 
                 74.8 
                 74.8 
               
               
                 MMBtu/hr 
               
               
                 Refrigerant Compressor 39 
               
               
                 Suction flow, Lbmol/hr 
                 15,334 
                 7,223 
               
               
                 Suction Pressure, psia 
                 69 
                 124 
               
               
                 Compression horsepower, 
                 8,230 
                 2,285 
               
               
                 BHP 
               
               
                 Liquid Absorbent Flow, 
                 — 
                 775 
               
               
                 Gal/min 
               
               
                   
               
             
          
         
       
     
     The operational efficiency of the present invention can be further improved by use of an economizer for the mechanical (first) refrigerant as described in reference to FIG.  3 . FIG. 3 represents a schematic embodiment illustrating such an improvement. The system illustrated in FIG. 3 is essentially identical to that described in reference to FIG.  2  and operates in a similar manner, except for the differences detailed below. The same reference numerals have been used to represent the same system components in each figure. 
     With reference to FIG. 3, the liquid refrigerant stream  17 , substantially comprising the first refrigerant, is expanded through expansion valve  36  and transferred to an economizer  41  which is operated at an intermediate pressure. A flashed vapor  42 , generated as a result of pressure reduction through expansion valve  36 , exits through the top of economizer  41 . Flashed vapor  42  is then mixed with vapor refrigerant stream  9  prior to entering the suction port of refrigerant compressor  39 . Alternatively, flashed vapor  42  can be supplied to the inter-stage of compressor  39  as shown by  42   a  when its pressure is considerably higher than that of vapor refrigerant stream  9 . After being drained from the bottom of economizer  41 , liquid refrigerant stream  51 , substantially comprising the first (mechanical) refrigerant, is expanded through an expansion valve  50  and is combined with the expanded liquid stream  14  to form combined refrigerant stream  1  as described above in reference to FIG.  2 . 
     The use of economizer  41  reduces the flashed vapor  42  flowing through the evaporative chiller  8  and subsequent components prior to entering the compressor  39 . Consequently, the size and cost of the equipment can be reduced. In addition, a slight improvement in compression horsepower can be realized in some cases. 
     Depending upon the relative humidity of ambient air, a significant amount of refrigeration may be used for condensing excess moisture. The cool water condensate can be collected in air chiller  19  and used as water markup or liquid absorbent to further improve the overall efficiency. 
     In the foregoing specification, the invention has been described with reference to specific embodiments thereof, and has been demonstrated as effective in providing structures and processes for enhancing operational efficiency of a combustion turbine. However, it will be evident to those skilled in the art that various modifications and changes can be made thereto without departing from the broader spirit or scope of the invention. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, there may be other ways of configuring and/or operating the inventive integration differently or in association with other combined refrigerants from those explicitly described herein which nevertheless fall within the spirit of the invention. Therefore, the invention is not restricted to the preferred embodiments described and illustrated but covers all modifications, which may fall within the scope of the appended claims.