Energy conversion system

Abstract

The invention provides a method and apparatus for recovering work from a gas turbine and providing a cooled inlet air, a refrigeration capacity and that may use a common working fluid in both systems . More importantly the system provides a working fluid for more efficient heat transfer by maintaining a supercritical working fluid in an energy recovery system, for example, recovery of waste heat from a gas turbine exhaust.

We claim:  
     
         1 . A method of recovering energy that comprises: 
 a. providing an energy recovery system having a first working fluid and a first pump;    b. feeding the first working fluid through the first pump to a first heat transfer zone to transfer heat to the working fluid stream thereby heating the stream to a higher temperature,    c. feeding the heated working fluid to an expansion means operative coupled to a refrigeration system compression means;    d. expanding the first working fluid to a lower temperature and pressure;    e. feeding the expanded lower temperature and pressure first working fluid to a second heat exchanger where the first working fluid is cooled by heat exchange while rejecting heat to an external medium;    f. returning the first working fluid to the first pump and repeating the cycle as set out above    g. and in a coupled refrigeration system feeding a second working fluid. to a second heat exchanger and heating the second working fluid;    h. feeding the heated second working fluid to a compressor    i. compressing the heated working fluid to a higher pressure    j. condensing the compressed working fluid by rejecting heat to an external medium    k. feeding the condensed working fluid to an expansion means and    l. expanding the working fluid to a lower temperature and pressure    m. returning the expanded working fluid to inlet side of a heat exchange means in contact with an inlet air stream to a gas turbine and cooling the inlet air stream to the turbine and    n. feeding the turbine exhaust to supply heat to a heat transfer zone in contact with the first working fluid.    
     
     
         2 . The method of  claim 1  further comprising: 
 feeding the first and second working fluids through a plurality of coupled expander/compressor pairs to recover additional energy.  
 
     
     
         3 . The method of  claim 1  wherein the first working fluid and the second working fluid have the same composition.  
     
     
         4 . The method of  claim 1  wherein the first working fluid and the second working fluid are not separated by mechanical seals in the coupled expander compressor.  
     
     
         5 . The method of  claim 1  wherein the first working fluid and the second working fluid are selected from the group consisting of hydrocarbons or refrigerants listed in ASHRAE, or mixtures of these working fluids.  
     
     
         6 . The method of  claim 1  wherein the first and the second working fluids are each isobutane.  
     
     
         7 . The method of  claim 1  that further comprises the steps of feeding a third working fluid to a heat exchange zone in the refrigeration loop positioned after the expansion means and cooling the third working fluid.  
     
     
         8 . The method of  claim 1  wherein the third working fluid cools the inlet air coming to a gas turbine.  
     
     
         9 . The method of  claim 7  wherein the third working fluid is selected from the group consisting of water, aqueous ethylene glycol solution, glycol brines, alcohol brines, or brines.  
     
     
         10 . The method of  claim 1  wherein a plurality of work expanders is provided.  
     
     
         11 . The method of  claim 1  where the working fluid has a pressure enthalpy curve as shown in FIG. 1 and the first working fluid is maintained at a supercritical condition in the waste heat recovery heat exchanger.  
     
     
         12 . An energy recovery apparatus that comprises: 
 a. fluid conduit means and a working fluid contained therein, the conduit means connecting all components listed below    b. pumping means connected to a waste heat transfer means configured to recover waste heat from a gas turbine;    c. an expansion means connected to a heat transfer means and configured to receive a heated working fluid and expand said working fluid to a lower pressure zone, thereby lowering the pressure and temperature;    d. a working fluid in a refrigeration system a component of which is vaporized by heat available from energy to be recovered in sufficient quantity to provide the desired product temperature when expanded in the expansion means while the combined working fluid can be fully condensed by the available heat sink means at pressures acceptable in the heat sink means;    e. a compressor mechanically coupled to the work expander means to compress the working fluid in the refrigeration system , a refrigeration expansion means and a heat exchange means in the refrigeration system;    f. a gas turbine having an inlet air stream and an exhaust stream;    g. a heat exchange means to receive a cooled working fluid from the refrigeration system and positioned to cool the inlet air to the gas turbine;    h. a heat transfer means positioned to recover heat from the turbine exhaust and supply heat to a working fluid prior to the working fluid entering the work expansion means;    
     
     
         13 . The apparatus of  claim 12  further comprising a second pump means for circulating a third working fluid between a heat exchange means downstream from the refrigeration expansion means and a second heat exchange means in contact with inlet air to the gas turbine and a separate fluid conduit containing a working fluid and linking the second pump with the two heat exchange means.  
     
     
         14 . The apparatus of  claim 12  further comprising the same working fluid in the energy recovery apparatus and the refrigeration system.  
     
     
         15 . The apparatus of  claim 12  wherein a working fluid is a hydrocarbon, a mixture of hydrocarbons, or refrigerants listed in ASHRAE, or mixtures of these working fluids.  
     
     
         16 . The apparatus of  claim 12  wherein a working fluid is isobutane.  
     
     
         17 . The apparatus of  claim 13  wherein third working fluid is selected from the group consisting of water, aqueous ethylene glycol solution, glycol brines, alcohol brines, or brines.  
     
     
         18 . The apparatus of  claim 12  wherein the apparatus comprises a plurality of turbo-expanders each coupled to a compressor.  
     
     
         19 . The apparatus of  claim 12  further comprising a flash economizer.  
     
     
         20 . The apparatus of  claim 12  further comprising a plurality of refrigeration expansion means.  
     
     
         22 . The apparatus of  claim 12  further comprising multiple heat recovery stages to provide additional heat recovery  
     
     
         23 . The apparatus of  claim 12  wherein the working fluid has a pressure enthalpy curve with a shape as shown in FIG. 1 and the apparatus is configured to maintain a condition in excess of a critical pressure in the waste heat transfer means.  
     
     
         24 . A method for designing an energy recovery system for increasing the efficiency of a gas turbine by providing an integrated refrigeration capacity comprising the steps of defining a desired product temperature in the refrigeration system, defining an available heat sink, defining a quantity of energy to be recovered in an energy recovery system, defining a means for converting the quantity of energy to be recovered into a recovered energy output while also providing sufficient heat energy to provide a sufficient quantity of a volatile component of at least a portion of the working fluid which is work expander in a system having coupled compressors which compress a working fluid to be expanded to provide cooling to the defined product temperature when evaporated and, defining a group of conditions to be meet by a working fluid, the working fluid in the energy recovery system being substantially vaporized by contacting the energy to be recovered thereafter driving the means for energy recovery while also providing the compression required to generate the desired cooling in the refrigeration loop and selecting a working fluid composition that permits meeting all design constraints.  
     
     
         25 . A method for increasing the efficiency of a gas pipeline which comprises: providing a gas compression system having a gas turbine that provides waste heat in an exhaust and a compressor for pipeline gas and a heat recovery system having a first working fluid and a first pump; feeding the first working fluid through the first pump to a first heat transfer zone to transfer heat to the working fluid stream thereby heating the stream to a higher temperature using heat from the gas turbine exhaust, feeding the heated working fluid to an expansion means operative coupled to a refrigeration system compression means; expanding the first working fluid to a lower temperature and pressure; feeding the expanded lower temperature and pressure first working fluid to a second heat exchanger where the first working fluid is cooled by heat exchange while rejecting heat to an external stream ;returning the first working fluid to the first pump and repeating the cycle as set out above and in a coupled refrigeration system feeding a second working fluid. to a second heat exchanger which heats the second working fluid by providing refrigeration; feeding the heated second working fluid work to a compressor compressing the heated working fluid to a higher pressure feeding the compressed heated working fluid to a condenser rejecting heat to an outside medium and to an expansion means and expanding the working fluid to a lower pressure returning the expanded working fluid to inlet side of a heat exchange means in contact with an inlet gas pipeline stream to a pipeline gas compressor and cooling the inlet gas pipeline stream to the compressor and feeding a gas turbine exhaust to supply heat to the heat transfer zone in contact with the first working fluid.  
     
     
         26 . The method of  claim 25  further comprising: 
 feeding the first and second working fluids through a plurality of coupled expander/compressor pairs.