Patent Publication Number: US-2022216489-A1

Title: Combined natural gas power generation and co2 sequestration system

Description:
FIELD 
     Exemplary embodiments relate to a natural gas power generation and CO 2  sequestration system, and in particular, to a natural gas power generation system including one or more natural gas fuel cell power modules and CO 2  sequestration system configured to convert CO 2  output from the power module into dry ice. 
     BACKGROUND 
     Natural gas (NG) is viewed as a lower carbon substitute to traditional power sources such as coal. NG contains predominantly methane (CH 4 ) with ethane (C 2 H 6 ) propane, carbon dioxide, nitrogen and other compounds included therein. Liquefied natural gas (LNG) is natural gas that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. LNG takes up about 1/600th the volume of NG in the gaseous state (at standard conditions for temperature and pressure). LNG is odorless, colorless, non-toxic and non-corrosive. 
     NG is mainly converted to LNG for transport over the seas where laying pipelines is not technically and economically feasible. The LNG liquefaction process involves removal of certain components, such as dust, acidic gases, helium, water, and heavy hydrocarbons, which could cause difficulty downstream. The NG is then condensed into a liquid at close to atmospheric pressure by cooling it to approximately −162° C. 
     The majority of LNG is transported around the globe via specialized LNG carrier ships. Such ships include containment vessels configured to maintain the LNG at or below a temperature of about −163° C., e.g., below the −161° C. condensation temperature of natural gas. LNG is generally not transported overland, since any lapse in refrigeration may result in a physical explosion known as rapid phase transition (RPT), as the volume of the LNG rapidly increases by 600 times during regasification. As such, LNG transport is generally confined to specialized LNG vessels, and LNG processing is generally confined to seaside natural gas liquefaction/regasification terminals. 
     Controlled LNG regasification is performed by gradually warming the natural gas back up to a temperature of over 0° C. This process generally occurs at high pressures of 60 to 100 bar, usually in a series of seawater percolation heat exchangers, which is the most energy efficient technique when water of the right quality is available. Alternatively, some of the natural gas may be burned to provide the heat necessary for regasification. However, in such methods the energy invested to condense the LNG that is released during gasification is lost. 
     SUMMARY 
     Various embodiments provide a combined system for power generation and CO 2  sequestration, comprising: a fuel cell system configured to generate power using natural gas (NG); a container configured to store liquid natural gas (LNG); and a fluid processor configured to convert LNG received from the container into NG and to convert exhaust output from the fuel cell system to dry ice by transferring heat between and the LNG and the exhaust. 
     Various embodiments provide a method of combined power generation and CO 2  sequestration, comprising: providing natural gas (NG) to a fuel cell system to generate power; cooling exhaust output from fuel cell system using a first heat exchanger; compressing cooled exhaust output from the first heat exchanger using a compressor; cooling compressed exhaust output from the compressor using a second heat exchanger provided with liquid natural gas (LNG), to generate liquid CO 2 ; converting the liquid CO 2  into dry ice; vaporizing the LNG to generate NG; and providing the generated NG to the fuel cell system. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of a SOFC fuel cell system, according to various embodiments of the present disclosure. 
         FIG. 2  is an isometric view of a modular fuel cell system that can be used with the exemplary embodiments. 
         FIG. 3A  is schematic view of a combined LNG fuel cell power and fluid processing system  400  in a vessel, according to various embodiments of the present disclosure, and  FIG. 3B  is a schematic view showing components of a fluid processor of the system  400 . 
         FIG. 4  is a block diagram illustrating a method of combined power generation and CO 2  sequestration, according to various embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes, and are not intended to limit the scope of the invention or the claims. 
     Transportation is a primary source of global CO 2  emissions and/or air pollution. In particular, the shipping industry is subject to increasingly stringent emission controls. Accordingly, it is desirable to reduce shipping emissions. 
     Natural gas (NG) is a fuel source that can provide lower emissions, as compared to fuel oil or diesel fuel commonly used as a maritime fuel. However, NG power generation systems, such as natural gas turbines, still contribute to global CO 2  emissions. In addition, NG has a relatively low power density, making it impractical for use as a fuel source for shipping. 
     In contrast, LNG has a much higher power density. In addition, LNG storage systems currently exist for maritime applications, such as the storage systems found aboard LNG container ships. However, LNG should be regasified prior to being utilized as a fuel source in the shipping industry. 
     According to various embodiments, fuel cell systems are configured to be deployed on ships and that utilize the LNG as a feedstock for power generation. In addition, the systems may be configured to sequester CO 2  emitted from fuel cell exhaust. In particular, the systems may be configured to generate dry ice, while utilizing heat from fuel cell exhaust to regasify LNG. 
     Thus, various embodiments provide systems and methods for efficiently utilizing LNG as a primary and/or secondary power source in shipping applications. Further, various embodiments provide maritime power generation systems that are capable of efficiently capturing CO 2  and regasifying LNG. 
       FIG. 1  is a schematic representation of a solid oxide fuel cell (SOFC) power module  10 , according to various embodiments of the present disclosure. Referring to  FIG. 1 , the module  10  includes a hotbox  100  and various components disposed therein or adjacent thereto. 
     The hot box  100  may contain fuel cell stacks  102 , such as a solid oxide fuel cell stacks (where one solid oxide fuel cell of the stack contains a ceramic electrolyte, such as yttria stabilized zirconia (YSZ) or scandia stabilized zirconia (SSZ), an anode electrode, such as a nickel-YSZ or Ni-SSZ cermet, and a cathode electrode, such as lanthanum strontium manganite (LSM)). The stacks  102  may be arranged over each other in a plurality of columns. 
     The hot box  100  may also contain an anode recuperator  110 , a cathode recuperator  190 , an anode tail gas oxidizer (ATO)  130 , an anode exhaust cooler  140 , an ATO mixer/injector (which is referred herein as an ATO injector for brevity)  120  including a splitter  122  and a vortex generator  124 , and a steam generator  160 . The module  10  may also include a catalytic partial oxidation (CPOx) reactor  170 , a mixer  150 , a CPOx blower  180  (e.g., air blower), a system blower  182  (e.g., air blower), and an anode recycle blower  184 , which may be disposed outside of the hotbox  100 . However, the present disclosure is not limited to any particular location for each of the components with respect to the hotbox  100 . 
     The CPOx reactor  170  receives a fuel inlet stream from a fuel inlet  300 , through fuel conduit  300 A. The fuel inlet  300  may be a utility gas line including a valve to control an amount of fuel provided to the CPOx reactor  170 . The CPOx blower  180  may provide air to the CPOx reactor  170  during module  10  start-up, and then turned off during steady-state operating mode when the fuel cell stacks  102  reach a steady-state operating temperature above 700° C., such as 750 to 900° C. The fuel in the steady state and/or a mixture of fuel and air during start-up may be provided to the mixer  150  by fuel conduit  300 B. Fuel flows from the mixer  150  to the anode recuperator  110  through fuel conduit  300 C. Fuel flows from the anode recuperator  110  to the stack  102  through fuel conduit  300 D. The module  10  may also include one or more fuel reforming catalysts  112 ,  114 , and  116  in the anode recuperator  110 . 
     The main air blower  182  may be configured to provide an air stream (e.g., air inlet stream) to the anode exhaust cooler  140  through air conduit  302 A. Air flows from the anode exhaust cooler  140  to the cathode recuperator  190  through air output conduit  302 B. The air flows from the cathode recuperator  190  to the stack  102  through air conduit  302 C. 
     Anode exhaust (i.e., fuel exhaust) generated in the stack  102  is provided to the anode recuperator  110  through anode exhaust outlet conduit(s)  308 A. The anode exhaust may contain unreacted fuel. The anode exhaust may also be referred to herein as fuel exhaust. The anode exhaust may be provided from the anode recuperator  110  to the splitter  122  by the anode exhaust conduit  308 B. A first portion of the anode exhaust may be provided from the splitter  122  to the ATO  130  via an anode exhaust output conduit  308 D. A second portion of the anode exhaust may be provided from the splitter  122  to the anode exhaust cooler  140  by a first anode exhaust recycling conduit  308 C. Anode exhaust may be provided from the anode exhaust cooler  140  to mixer  150  by a second anode exhaust recycling conduit  308 E. The anode recycle blower  184  may be configured to move anode exhaust though the second anode exhaust recycling conduit  308 E, as discussed below. 
     Cathode exhaust (e.g., air exhaust) generated in the stack  102  flows to the ATO  130  through cathode exhaust conduit  304 A. The cathode exhaust may also be referred to herein as air exhaust. The vortex generator  124  may be disposed in the cathode exhaust conduit  304 A and may be configured to swirl the cathode exhaust. Conduit  308 D may be fluidly connected to the cathode exhaust conduit  304 A, downstream of the vortex generator  124 . The swirled cathode exhaust exiting the vortex generator  124  may mix with the anode exhaust provided by the splitter  122  before being provided to the ATO  130 . The mixture may be oxidized in the ATO  130  to generate ATO exhaust. The ATO exhaust flows from the ATO  130  to the cathode recuperator  190  through exhaust conduit  304 B. Exhaust flows from the cathode recuperator  190  to the steam generator  160  through exhaust conduit  304 C. Exhaust flows from the steam generator  160  and out of the hotbox  100  through system exhaust conduit  304 D. 
     Water flows from a water source  162 , such as a water tank or a water pipe, to the steam generator  160  through water conduit  306 A. The steam generator  160  converts the water into steam using heat from the ATO exhaust provided by exhaust conduit  304 C. Steam is provided from the steam generator  160  to the mixer  150  through water conduit  306 B. Alternatively, if desired, the steam may be provided directly into the fuel inlet stream and/or the anode exhaust stream may be provided directly into the fuel inlet stream followed by humidification of the combined fuel streams. The mixer  150  is configured to mix the steam with anode exhaust and fuel. This fuel mixture may then be heated in the anode recuperator  110 , before being provided to the stack  102 . 
     The module  10  may further a system controller  225  configured to control various elements (e.g., blowers  182  and  184  and the fuel control valve) of the module  10 . The controller  225  may include a central processing unit configured to execute stored instructions. For example, the controller  225  may be configured to control fuel and/or air flow through the module  10 , according to fuel composition data. 
       FIG. 2  illustrates an exemplary modular fuel cell system  200  according to various embodiments of the present disclosure. Referring to  FIG. 2 , the modular system  200  may include the system  100  of  FIG. 1  and may include a modular enclosure that provides flexible system installation and operation. Modules allow scaling of installed generating capacity, reliable generation of power, flexibility of fuel processing, and flexibility of power output voltages and frequencies with a single design set. The modular design results in an “always on” unit with very high availability and reliability. This design also provides an easy means of scale up and meets specific requirements of customer&#39;s installations. The modular design also allows the use of available fuels and required voltages and frequencies which may vary by customer and/or by geographic region. 
     The system  200  includes power modules  10 , one or more fuel processing modules  16 , and one or more power conditioning modules  18 . For example, the system  200  may include any desired number of modules, such as 2-30 power modules  10 , for example 6-12 power modules  10 . 
     The fuel processing modules  16  is configured for pre-processing of fuel, such as desulfurizer beds. The fuel processing modules  16  may be designed to process different types of fuel. For example, a diesel fuel processing module, a natural gas fuel processing module, and an ethanol fuel processing module may be provided in the same or in separate cabinets. A different bed composition tailored for a particular fuel may be provided in each module. The fuel processing module  16  may processes at least one of the following fuels selected from natural gas provided from a pipeline, compressed natural gas, methane, propane, liquid petroleum gas, gasoline, diesel, home heating oil, kerosene, JP-5, JP-8, aviation fuel, hydrogen, ammonia, ethanol, methanol, syn-gas, bio-gas, bio-diesel and other suitable hydrocarbon or hydrogen containing fuels. If desired, a reformer  17  may be located in the fuel processing module  16 . Alternatively, if it is desirable to thermally integrate the reformer  17  with the fuel cell stack(s), then a separate reformer  17  may be located in each hot box  13  in a respective power module  10 . Furthermore, if internally reforming fuel cells are used, then an external reformer  17  may be omitted entirely. 
     The system  200  may also include one or more power conditioning modules  18 . The power conditioning module  18  includes a cabinet which contains the components for converting the fuel cell stack generated DC power to AC power (e.g., DC/DC and DC/AC converters described in U.S. Pat. No. 7,705,490, incorporated herein by reference in its entirety), electrical connectors for AC power output to the grid, circuits for managing electrical transients, a system controller (e.g., a computer or dedicated control logic device or circuit). The power conditioning module  18  may be designed to convert DC power from the fuel cell modules to different AC voltages and frequencies. Designs for 208V, 60 Hz; 480V, 60 Hz; 415V, 50 Hz and other common voltages and frequencies may be provided. 
     The fuel processing module  16  and the power conditioning module  18  may be housed in one input/output cabinet  14 . If a single input/output cabinet  14  is provided, then modules  16  and  18  may be located vertically (e.g., power conditioning module  18  components above the fuel processing module  16  desulfurizer canisters/beds) or side by side in the cabinet  14 . 
     The linear array of power modules  10  is readily scaled. For example, more or fewer power modules  10  may be provided depending on the power needs of the building or other facility serviced by the fuel cell system  200 . The power modules  10  and input/output modules  14  may also be provided in other ratios. 
     The modular fuel cell system  200  may be configured in a way to ease servicing of the system. All of the routinely or high serviced components (such as the consumable components) may be placed in a single module to reduce amount of time required for the service person. For example, the purge gas and desulfurizer material for a natural gas fueled system may be placed in a single module (e.g., a fuel processing module  16  or a combined input/output module  14  cabinet). This would be the only module cabinet accessed during routine maintenance. Thus, each module  10 ,  14 ,  16 , and  18  may be serviced, repaired or removed from the system without opening the other module cabinets and without servicing, repairing or removing the other modules. 
     For example, as described above, the system  200  can include multiple power modules  10 . When at least one power module  10  is taken off line (i.e., no power is generated by the stacks in the hot box  13  in the off line module  10 ), the remaining power modules  10 , the fuel processing module  16  and the power conditioning module  18  (or the combined input/output module  14 ) are not taken off line. Furthermore, the fuel cell enclosure  10  may contain more than one of each type of module  10 ,  14 ,  16 , or  18 . When at least one module of a particular type is taken off line, the remaining modules of the same type are not taken off line. 
     Each of the power modules  10  and input/output modules  14  include a door  30  (e.g., hatch, access panel, etc.) to allow the internal components of the module to be accessed (e.g., for maintenance, repair, replacement, etc.). According to one embodiment, the modules  10  and  14  are arranged in a linear array that has doors  30  only on one face of each cabinet, allowing a continuous row of systems to be installed abutted against each other at the ends. 
     The system  200  may include an exhaust conduit  202  configured to receive exhaust output from the power modules  10 . In particular, the exhaust conduit  202  may be fluidly connected to the system exhaust conduit  304 D of each power module  10  (see  FIG. 1 ). 
       FIG. 3A  is schematic view of a combined LNG fuel cell power and fluid processing system  400  in a vessel, according to various embodiments of the present disclosure, and  FIG. 3B  is a schematic view showing components of a fluid processor  410  of the system  400 . Referring to  FIGS. 3A and 3B , the system  400  may be disposed in a vessel V, such as a container ship or the like. The system  400  may include a fuel cell system  200 , such the SOFC system  200  shown in  FIG. 2 , configured to provide electrical power to an electrical load  401  of the vessel and a fluid processor  410  configured to gasify LNG and sequester CO 2  as dry ice. As shown in  FIG. 3A , the fluid processor  410  may be disposed outside of the fuel cell system  200 . However, in other embodiments, one or more components of the fluid processor  410  may be disposed within the cabinet of the fuel cell system  200 . 
     The fluid processor  410  may be fluidly connected to an LNG container  402  by an LNG conduit  404 . The LNG container  402  may be configured to store LNG at a temperature of about at or below a temperature of about −163° C., e.g., below the −161° C. condensation temperature of natural gas. A pump or blower  403  configured to pump LNG from the container  402  to the fluid processor  410 , may be disposed in the LNG container  402  or outside the LNG container  402  on the LNG conduit  404 . 
     The exhaust conduit  202  of the fuel cell system  200  may be fluidly connected to an inlet of the fluid processor  410  by an exhaust inlet conduit  406 . A fuel conduit  408  may fluidly connect an NG outlet of the fluid processor  410  to a fuel inlet of the fuel cell system  200 . The fuel cell system  200  may be electrically connected to a load  401 , such as a primary and/or secondary electrical load of the vessel V. 
     The fluid processor  410  may include an optional first heat exchanger  412 , a water separator  414 , such as a condenser or a dryer, a compressor  416 , a second heat exchanger  418 , and a dry ice machine  420 , which may be sequentially fluidly connected in series by a processing conduit  422 . The heat exchanger  412 , water separator  414 , and compressor  416  may be fluidly connected to a water collection conduit  424 . 
     The first heat exchanger  412  may be configured to reduce the temperature of the fuel cell system exhaust. For example, in some embodiments, the first heat exchanger  412  may use air to cool the system exhaust. In other embodiments, the first heat exchanger  412  may utilize NG to cool the system exhaust. For example, the first heat exchanger  412  may be configured to cool the system exhaust to a temperature ranging from about 50° C. to about 1° C., to facilitate subsequent compression of CO 2  in the system exhaust. The system exhaust may be maintained above 0° C., in order to prevent freezing of water present in the system exhaust. 
     The first heat exchanger  412  may also increase the temperature of the NG provided thereto, in order to improve the efficiency of the fuel cell system  200 . For example, the first heat exchanger  412  may heat the NG to a temperature ranging from about 300° C. to about 100° C. A first water stream may be removed from the first heat exchanger  412  to the water collection conduit  424  if the temperature of the system exhaust is below 100° C. in the first heat exchanger  412 . 
     The water separator  414  may be configured to remove residual water from the cooled fuel exhaust output from the heat exchanger  412  to the water collection conduit  424 . The water separator  414  may include a condenser or a regeneratable water absorbent, for example, which adsorbs water via temperature swing adsorption or another suitable method. However, in some embodiments, the water separator  414  may be omitted. 
     The compressor  416  may be configured to compress the dried system exhaust received from the water separator  414 . Water extracted by the heat exchanger  412 , water separator  414 , and/or compressor  416  may be collected by the collection conduit  424 . 
     The dried system exhaust output from the compressor  416  comprising mostly carbon dioxide may be provided to the second heat exchanger  418 . The second heat exchanger  418  may be configured to cool the dried exhaust to a temperature sufficient to generate liquid CO 2  using LNG output from the container  402 . For example, the second heat exchanger  418  may be configured to cool the dried exhaust to a temperature ranging from about −20° C. to about −30° C. 
     In some embodiments, the second heat exchanger  418  may be configured to gradually heat the LNG to vaporize the LNG and form NG using the heat from the system exhaust. The second heat exchanger  418  may also permit the gradual expansion of the LNG as it is converted to NG. As shown in  FIG. 3B , the NG may be provided to the first heat exchanger  412  by the fuel conduit  408 . However, in other embodiment, the fuel conduit  408  may provide the NG directly to the fuel cell system  200 , and the first heat exchanger  412  may be provided with air to cool the system exhaust. 
     In some embodiments, the fluid processor  410  may optionally include a vaporizer  430 . For example, if the heat provided by the system exhaust is insufficient to completely vaporize the LNG, the vaporizer  430  may operate to vaporize and expand the LNG using heat extracted from a second fluid. For example, the vaporizer  430  may be operated during system startup, or during periods of the fuel system  200  is operated under low load conditions. The second fluid may be water provided via the water conduit  426  from a water tank on the vessel V, or may be fresh or seawater provided via the water conduit  426  from outside of the vessel V. 
     The liquid CO 2  may be output from the second heat exchanger  418  to the dry ice machine  420 . The dry ice machine  420  may be a block press or pelletizer configured to generate dry ice blocks or pellets, by reducing the pressure applied to the liquid CO 2  to atmospheric pressure, which converts the liquid CO 2  into dry ice. CO 2  vapor generated during the dry ice formation may be returned to the second heat exchanger  418 , via a CO 2  vapor conduit  434 . The dry ice may be provided to a freezer  432  for storage. In other embodiments, the dry ice may be utilized as a coolant on board the vessel V and/or may be offloaded from the vessel V for sequestration once the vessel V returns to a port. For example, the dry ice may be utilized as a CO 2  source for cement manufacturing or may be sequestered underground. 
     In one embodiment, the vessel V comprises a ship (i.e., a boat) containing a ship hull  450 . The system  400  and the load  401  are located in the ship hull  450 . 
     Accordingly, the system  400  may be configured to vaporize LNG using exhaust heat generated during power production. In addition, the system may utilize extreme cold of the LNG to generate dry ice, and thereby capture CO 2  from the system exhaust. The NG provided by the fuel conduit  408  may be used by the power modules  10  of the fuel cell system  200  to generate electricity. The electricity may be used to power one or more loads  401  aboard a vessel. As such, the fuel cell system may operate as a low or zero carbon emission primary or secondary power source of a vessel. 
       FIG. 4  is a block diagram illustrating a method of operating the system  400  of  FIGS. 3A and 3B , according to various embodiments of the present disclosure. Referring to  FIGS. 3A, 3B , and  4 , in step  500 , the method may include operating a fuel cell system, such as system  200 , using NG provided from an LNG storage tank  402  to generate electrical power. The power may be provided to electrical loads of a vessel, such as electrical propulsion system and/or lighting, pumps, climate control, etc. The power may also be provided to operate elements of the fluid processing system, such as pumps, compressors, block presses, etc. 
     In step  502 , the method may include cooling system exhaust generated by the fuel cell system  200 . In particular, the NG and system exhaust can be provided to the first heat exchanger  412  to cool the system exhaust using cool NG and heat the NG using hot system exhaust. In other embodiments, air or water can be substituted for the NG as a cooling fluid in the first heat exchanger  412 . Water vapor condensed from the cooled system exhaust may be collected from the first heat exchanger  412  during the cooling process. 
     In step  504 , the cooled exhaust may be dried and compressed. For example, water vapor may be removed from the cooled exhaust by supplying the cooled exhaust to the water separator  414 . The dried exhaust may be compressed in the compressor  416  to an increased pressure ranging from about 518 KPa to about 10 MPa, thereby generating compressed CO 2 . Water condensed in the compressor  416  may be removed from the compressor  416  and collected in the conduit  424 . 
     In step  506 , the compressed CO 2  may be cooled using the cold LNG to liquefy the CO 2 . For example, the CO 2  may be cooled in the second heat exchanger  418  to a temperature ranging from about −56.6° C. to about −10° C., such as from about −20° C. to about −30° C. The liquid CO 2  may be provided to the dry ice machine  420 , where the pressure applied to the liquid CO 2  may be released to form dry ice. The LNG is heated by the warm compressed system exhaust comprising a majority CO 2  by volume. 
     In step  508 , LNG may be vaporized to generate the NG. For example, the LNG may be heated in the second heat exchanger  418  and allowed to expand, during the generation of the liquid CO 2 . In other embodiments, the LNG and/or a mixture of LNG and NG may be provided to the optional vaporizer  430 , to convert any remaining LNG into NG. The vaporizer  430  may be provided with a fluid, such as sea water, air, or the like, to exchange heat with the LNG. 
     In step  510 , the NG may be provided to the fuel cell system  200  to generate power which may be provided to operate electrical loads  401  onboard a vessel V. In some embodiments, the NG may be provided to the first heat exchanger  412 , before being provided to the fuel cell system  200 . 
     The foregoing method descriptions and diagrams are provided merely as illustrative examples and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As will be appreciated by one of skill in the art the order of steps in the foregoing embodiments may be performed in any order. Further, words such as “thereafter,” “then,” “next,” etc. are not intended to limit the order of the steps; these words are simply used to guide the reader through the description of the methods. In addition, the term “about” refers to a variation of +/−10% or less. 
     One or more diagrams have been used to describe exemplary embodiments. The use of diagrams is not meant to be limiting with respect to the order of operations performed. The foregoing description of exemplary embodiments has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents. 
     Control elements may be implemented using computing devices (such as computer) comprising processors, memory and other components that have been programmed with instructions to perform specific functions or may be implemented in processors designed to perform the specified functions. A processor may be any programmable microprocessor, microcomputer or multiple processor chip or chips that can be configured by software instructions (applications) to perform a variety of functions, including the functions of the various embodiments described herein. In some computing devices, multiple processors may be provided. Typically, software applications may be stored in the internal memory before they are accessed and loaded into the processor. In some computing devices, the processor may include internal memory sufficient to store the application software instructions. 
     The various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. 
     The hardware used to implement the various illustrative logics, logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Alternatively, some blocks or methods may be performed by circuitry that is specific to a given function. 
     The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the described embodiment. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the disclosure. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.