Abstract:
The power turbine system includes two power turbines communicating with an ion transport membrane (ITM) reactor. Heavy liquid fuel is atomized and burned within the reactor to drive the first turbine, with the first turbine producing useful power. Exhaust from the first turbine is recycled back into the reactor. The reactor includes a series of concentric cylindrical ion transport membranes that separate atmospheric and exhaust gases into suitable components for combustion therein, with at least some of the gases being “cracked” to alter their molecular structure for further combustion to power the second turbine. The second turbine drives a compressor to supply air to the reactor. At least one of the ITMs precludes atmospheric nitrogen from the combustion processes, with the resulting exhaust including pure water and carbon dioxide. The carbon dioxide is either recycled into the reactor to facilitate fuel atomization, or compressed for sequestration.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0001]    The present invention relates generally to power generating systems, and particularly to a power turbine system utilizing oxy-combustion for carbon capture. 
       2. Description of the Related Art 
       [0002]    Increasing population pressures and the demand for increased comfort have resulted in increasing demands for power production. These demands have generally been met conventionally by power plants burning fossil fuels, i.e., coal and various weights or viscosities of fuel oils. The problem with the use of such fuels in conventional power plants is that their exhaust emissions contain massive amounts of carbon dioxide (CO 2 ), which is known as a “greenhouse gas” that contributes substantially to global warming. Also, as gaseous nitrogen (N 2 ) forms about 80% of the earth&#39;s atmosphere, a certain amount of the atmospheric oxygen (O 2 ) used in the combustion of fossil fuels instead combines with some of the atmospheric nitrogen due to the heat developed during the combustion process, producing various oxides of nitrogen (NOx) that are harmful to the atmosphere. 
         [0003]    While certain other energy sources have been developed for the production of power, e.g., hydroelectric, solar, etc., these “clean” energy sources have not been able to keep up with the increasing demands for power in most areas of the world. Accordingly, it is necessary to continue to burn fossil fuels to respond to power demands throughout most of the world, with the resulting CO 2  and NOx emissions being accepted as a necessary evil of such power production. While many advances have been made in the reduction of CO 2  and NOx emissions from power plants and other sources, emissions from fossil fuel burning power plants are by no means perfectly clean in this regard. 
         [0004]    Thus, a power turbine system solving the aforementioned problems is desired. 
       SUMMARY OF THE INVENTION 
       [0005]    The power turbine system essentially comprises two power turbines in communication with an ion transport membrane (ITM) reactor that combusts fuel to provide energy to the turbines. The ITM reactor includes a series of concentric cylindrical ion transport membranes that define corresponding working chambers, and a centrally disposed “button cell” or disc-shaped ion transport membrane. Heavy liquid fuel is injected or pumped into the reactor, and is burned in a two-stage process to promote more complete combustion with fewer undesirable exhaust byproducts. Atmospheric air is pumped into the reactor from the second turbine, which is dedicated to driving a compressor to supply air to the reactor. Some of the ITMs within the reactor serve to separate atmospheric oxygen (O 2 ) from the air, with the oxygen passing through the membranes for combustion with the fuel. Atmospheric nitrogen (N 2 ) is restricted from the combustion process, and is ultimately exhausted from the reactor. The exhaust resulting from combustion is essentially pure water (H 2 O) and carbon dioxide (CO 2 ), with some of the CO 2  being recycled into the reactor at the fuel injector to assist in “cracking” the heavy liquid fuel into extremely fine droplets to optimize combustion. The remaining balance of the CO 2  is collected for sequestration. 
         [0006]    The ITM reactor also produces a synthetic gas (“syngas”) of gaseous hydrogen (H 2 ) and carbon monoxide (CO) that is combusted with gaseous oxygen (O 2 ), with the resulting combustion product (CO 2  and H 2 O) driving the second turbine. The result of the various combustive processes and reactions within the ITM reactor is the production of useful power from the output of the first turbine, with the exhaust products comprising essentially pure water, carbon dioxide that is sequestered to prevent release to the atmosphere, and free gaseous nitrogen that is released back to the atmosphere. 
         [0007]    These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The sole drawing FIGURE is a schematic side view in section of a power turbine system according to the present invention, illustrating its general features. 
       
    
    
       [0009]    Similar reference characters denote corresponding features consistently throughout the attached drawing. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0010]    The power turbine system incorporates two separate power turbines that receive their input energy from an ion transport membrane (ITM) reactor, rather than from a conventional combustion source. For example, the turbines of the ITM reactor can be powered by oxy-combustion of a heavy liquid fuel in the ITM reactor. 
         [0011]    The ITM reactor utilizes a series of ion transport membranes (ITMs) within the reactor that separate oxygen from other atmospheric and exhaust gases in the reactor, resulting in a final exhaust product comprising essentially pure carbon dioxide (CO 2 ) that is recycled or sequestered, and water. Thus, oxygen is separated inside the combustion system using the ion transport membranes (ITMs). Suitable membrane materials which can be used include, for example, lanthanum cobaltite perovskite ceramics, modified proviskite ceramics, brownmillerite structured ceramics, ceramic metal dual phase membranes, in addition to, thin duel phase membranes which includes chemically stable yttria-stabilized zirconia (YSZ). 
         [0012]    For oxy-combustion to occur, the hydrocarbon fuel, e.g., heavy liquid fuel, can be burned in a medium of pure oxygen and some recycled exhaust gases instead of air (nitrogen is not introduced into the combustion chamber). Oxygen is separated inside the ITM reactor using the ion transport membranes (ITM), typically at temperatures ranging from 650° C. to 950° C. The ion transport membranes (ITMs) are activated for oxygen separation from the feed side to the permeate side of the membrane. In the permeate side of the membrane, fuel is being burned with the separated oxygen in a medium of recycled carbon dioxide. In this process, the combustion products consist of a mixture of only carbon dioxide and water vapor. Water vapor can be easily condensed and accordingly carbon dioxide can be captured for industrial use or storage. 
         [0013]    The drawing FIGURE provides a schematic elevation view in section of the power turbine system  10 . The multi-stage ITM reactor  12  can have a cylindrical configuration, with a series of concentric cylindrical ion transport membranes (ITMs) defining a corresponding series of concentric cylindrical working chambers therebetween. A description of the various components of the power turbine system  10 , depicted in the FIGURE, is provided below. 
         [0014]    A fuel pump  14  can pump a heavy liquid fuel, e.g., fuel oil, etc., through a water and carbon dioxide heat exchanger or condenser  16  disposed externally to the reactor  12 . The condenser  16  serves to cool exhaust output (particularly the water vapor fraction) from the reactor  12  while simultaneously warming the incoming heavy liquid fuel. The heavy liquid fuel is indicated schematically in the drawing FIGURE by a single arrow barb followed by a solid arrow head. The fuel can be injected into the ITM reactor  12  by an injector  18  disposed at the bottom of the reactor. The fuel is injected into an elongate fuel evaporation core  20  (also designated by the letter A) disposed centrally within the reactor  12 . A cylindrical fuel partial conversion chamber  26  is disposed concentrically about the fuel evaporation core  20 . The injected fuel is heated in the fuel evaporation core  20  by heat flowing from the cylindrical fuel partial conversion chamber  26 , as described in more detail below, which results in fuel evaporation. Atmospheric air, designated schematically in the drawing as arrows with single barbed arrowheads, is pumped into a first or central air delivery passage  22  disposed concentrically above the fuel evaporation core  20 . A centrally disposed “button cell,” i.e., disc-shaped, ion transport membrane  24  is located between the first air delivery passage  22  and the fuel evaporation core  20 . The button cell ion transport membrane  24  permits only oxygen (O 2 ) to permeate therethrough. The remaining oxygen depleted air (nitrogen and other trace gas) leaves the reactor through a gaseous nitrogen output chamber  28 . Partial combustion or conversion of the vaporized fuel, indicated by arrows having three barbed heads, can occur close to the surface of the button cell ITM  24  in the fuel partial conversion chamber  26  (also designated by the letter B in the drawing FIGURE) due to the oxygen passing through the button cell ITM  24 . The resulting heat is used in heating and evaporating the liquid fuel introduced into the fuel evaporation core  20  to activate it for oxygen permeation. 
         [0015]    The button cell ITM  24  extends diametrically above the fuel partial conversion chamber  26  to provide oxygen to the fuel within the fuel partial conversion chamber  26 , and thereby, provide partially converted or burned fuel. The partial fuel conversion chamber  26  also serves as a heavy liquid fuel heater, as some of the heat developed by the combustion process within the fuel partial conversion chamber  26  is transferred to the central fuel evaporation core  20  to assist in the fuel evaporation process. Oxygen-depleted air comprising nearly pure nitrogen (N 2 , represented by arrows with single barb heads) is blocked by the button cell ITM  24 , and flows upward through the gaseous nitrogen output chamber  28  (also designated by the letter H) disposed concentrically about the first air delivery passage  22  and above the fuel partial conversion chamber  26 , and thence out of the reactor  12  to the atmosphere. 
         [0016]    The partially converted or burned fuel flows from a lower portion of the fuel partial conversion chamber  26  into a cylindrical fuel complete conversion chamber  30  (also designated by the letter C) disposed concentrically about the fuel partial conversion chamber  26  and the gaseous nitrogen output chamber  28 . The outer wall of this chamber  30  is defined by a cylindrical first oxygen separation membrane  32  (an ITM) disposed concentrically about the fuel complete conversion chamber  30 . Atmospheric air (represented by arrows with single barb heads) is pumped into a cylindrical second air delivery passage  34  disposed about the first oxygen separation membrane  32 , with oxygen passing through the first oxygen separation membrane  32  and into the fuel complete conversion chamber  30 , where the fuel is completely converted or combusted to form a first exhaust product. Heat resulting from the combustion process in the fuel complete conversion chamber  30  serves to heat the first oxygen separation membrane (ITM)  32  for greater efficiency, with some of this heat being transferred to the incoming atmospheric air flowing through the second air delivery passage  34 . Excess oxygen depleted air  36  (nearly all gaseous nitrogen, N 2 ) flows from the second air delivery passage  34 , out the bottom of the reactor  12 . 
         [0017]    The first exhaust product is formed in the fuel complete conversion chamber  30  by the combustion of the heavy fuel, comprising various hydrocarbon forms, with essentially pure oxygen, as described above. The resulting first exhaust product includes essentially pure carbon dioxide (CO 2 ) and water (H 2 O), as there is no nitrogen involved in the combustion process to form various oxides of nitrogen (NOx). The carbon dioxide and water first exhaust product departs the top of the fuel complete conversion chamber  30  and flows to a first power turbine  38  to drive the turbine, which produces useful work by means of its output shaft  40 . 
         [0018]    Rather than expelling the carbon dioxide and water first exhaust product to the atmosphere, this first exhaust product is recycled back to the reactor  12  where it flows into a first turbine exhaust collection and synthetic gas production chamber  42  (also designated by the letter F) disposed concentrically about an outermost or third oxygen separation membrane  44 . This flow is indicated by arrows with two barbed heads in the drawing FIGURE. As this first exhaust product reaches the lower end of the chamber  42 , it flows radially inward to flow into and upward into a concentric cylindrical synthetic gas (syngas) combustion chamber  46  disposed between concentric cylindrical second and third oxygen separation membranes, respectively  48  and  44 , disposed respectively about the second air delivery passage  34  and the synthetic gas combustion chamber  46 . 
         [0019]    It should be noted that the gases at the lower or outflow end of the first turbine exhaust and syngas production chamber  42  include carbon monoxide (CO) and gaseous hydrogen (H 2 ), i.e., “syngas.” This is because some of the oxygen bound in the carbon dioxide (CO 2 ) and water (H 2 O) molecules is stripped from its molecules during the passage of the first turbine exhaust through the chamber  42 . However, the second and third ITM oxygen separation membranes  48  and  44  defining the syngas combustion chamber  46  concentrically therebetween, provide oxygen to complete the oxidation process (combustion) of the carbon monoxide and gaseous hydrogen within the syngas combustion chamber  46 , resulting in essentially pure carbon dioxide (CO 2 ) and water (H 2 O) for a second exhaust product, indicated by the solid head arrows within the syngas combustion chamber  46 . 
         [0020]    The second exhaust product flows from the synthetic gas combustion chamber  46  to power a second power turbine  50 . This second power turbine  50  functions primarily to drive an air compressor  52 , which draws in atmospheric air  54  and compresses that air to deliver it to the two air delivery passages  22  and  34 . The second power turbine  50  may also provide useful mechanical power by means of an output shaft  56 . 
         [0021]    Exhaust gases from the second power turbine comprise essentially pure carbon dioxide (CO 2 ) and water (H 2 O), with these gases being returned to the outermost second turbine exhaust collection chamber  58  (also indicated by the letter G), disposed concentrically about the first turbine exhaust collection and synthetic gas production chamber  42 . These second power turbine exhaust gases are represented by arrows having four barbed heads. The placement of the second turbine exhaust collection chamber  58  about the other chambers of the reactor  12  serves to heat the other chambers, which is desirable in order to optimize the efficiency of the various ion transport membranes  24 ,  32 ,  44 , and  48  within the reactor  12 . 
         [0022]    The second turbine exhaust gases are collected and routed to the heat exchanger and condenser  16 , where they warm the incoming heavy liquid fuel to assist in its evaporation. The incoming heavy liquid fuel also cools the exhaust gases, particularly the water vapor therein, with liquid water flowing from the heat exchanger and condenser  16  for collection. The carbon dioxide portion of the exhaust is also collected for sequestration, with a portion of that carbon dioxide exhaust being recirculated to the heavy liquid fuel prior to its injection into the fuel evaporation core  20 . The recirculated CO 2  assists in atomizing the heavy liquid fuel and carrying the atomized and/or evaporated fuel through the fuel evaporation core  20  and further through the fuel partial conversion chamber  26  and fuel complete combustion chamber  30 . 
         [0023]    It will be noted that gas flow through the various chambers of the reactor  12  is configured such that the flow in each chamber, as indicated by the direction of the various gas flow arrows, is in the opposite direction to that of the adjacent chambers, with the exception of the outermost second turbine exhaust collection chamber  58 . This counter-current flow between adjacent chambers serves to increase the oxygen permeation rate of the various ITMs of the system. This flow configuration results in the low oxygen partial pressure region on one side of a given ITM corresponding with the partial pressure region, and vice versa. The net result of this opposite flow direction or counter-current is a more uniform and stable flame distribution and correspondingly more uniform membrane surface temperature, thus enhancing ITM life within the reactor  12 . 
         [0024]    It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.