Patent Publication Number: US-11041410-B2

Title: Supercritical CO2 cycle coupled to chemical looping arrangement

Description:
CROSS-REFERENCE TO PRIOR APPLICATION 
     This application is a continuation of, and claims priority from, U.S. patent application Ser. No. 16/018,706, titled SUPERCRITICAL CO2 CYCLE COUPLED TO CHEMICAL LOOPING ARRANGEMENT, filed Jun. 26, 2018, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure is related to systems and methods regarding supercritical CO 2  cycles and chemical looping combustion. In particular, the present disclosure is related to systems and methods for coupling a supercritical CO 2  cycle and a chemical looping combustion arrangement. 
     BACKGROUND OF THE INVENTION 
     As the need for energy continues to grow, so does the use of unconventional energy resources to meet the increasing demand. While well-known energy sources (e.g., coal, natural gas) continue to have value, other energy sources such as unconventional oil resources and unconventional natural gas resources are being used to meet the increasing energy demand. One such unconventional resource is sour gas, which is a natural gas that contains significant levels of hydrogen sulfide (H 2 S). H 2 S presents a problem during processing of the sour gas, as the corrosive nature of H 2 S can damage the mechanical parts of a system, and the processing of H 2 S can result in the production of SO 2 , which is an air pollutant. 
     Combustion is a commonly used reaction in the field of power generation and can be modified to use sour gas as fuel. However, combustion reactions, and specifically direct combustion reactions, still present the same corrosion and pollution issues associated with sour gas fuel. To avoid excessive corrosion and pollution associated with sour gas combustion, pretreatment or “sweetening” of the sour gas has been required to substantially remove the sulfur compounds from the gas stream. However, this “sweetening” process is typically very costly. 
     Chemical looping combustion (CLC), a specific type of combustion reaction, eliminates the need for a “sweetening” pre-treatment and can be used in a system for CO 2  capture as well. In a conventional CLC process, an oxygen carrier acts as an intermediate transporter of oxygen between air and fuel, and thus the air and the fuel are prevented from directly contacting one another. Typically, a solid metal oxide oxygen carrier is used to oxidize the fuel stream in a fuel reactor. This results in the production of CO 2  and H 2 O. The reduced form of the oxygen carrier is then transferred to the air reactor, where it is contacted with air, re-oxidized to its initial state, and then returned to the fuel reactor for further combustion reactions. 
     Despite their advantages over direct combustion processes, CLC processes are still inefficient in terms of their ability to produce energy. Additionally, CLC processes traditionally require coupling to steam cycles to produce power. Accordingly, there is a need for a cost-effective and energy-efficient system that combines the combustion of sour gas with power generation. Further, there is a need for a process for the combustion of sour gas with high efficiency in energy conversion, with reduced amount of water especially in water scarce environments. 
     SUMMARY OF THE INVENTION 
     The present application describes system and methods for coupling a chemical looping arrangement and a supercritical CO 2  cycle. According to a first aspect, a system for coupling a chemical looping arrangement and a supercritical CO 2  cycle is provided in which the system includes a fuel reactor having a fuel inlet configured to receive fuel from a fuel source and a carrier inlet configured to receive oxygen carriers. The fuel reactor is configured to react the fuel with the oxygen carriers resulting in reformed or combusted fuel and reduced oxygen carriers. They system also includes an air reactor in fluid communication with the fuel reactor. The air reactor has an air stream inlet configured to receive an air stream from an air source and is configured to receive the reduced oxygen carriers from the fuel reactor. The air reactor is also configured to re-oxidize the reduced oxygen carriers via the air stream resulting in oxygen-depleted air. The air reactor is also configured to transport a first portion of the re-oxidized oxygen carriers back to the fuel reactor. 
     The system further includes a compressor having a CO 2  inlet configured to receive a CO 2  stream from a CO 2  source. The compressor is configured to increase the pressure of the CO 2  stream thereby creating a high pressure supercritical CO 2  stream. The system also includes, a first heat exchanger in fluid communication with the compressor and the fuel reactor. The first heat exchanger is configured to receive and heat the supercritical CO 2  stream, and is configured to receive at least a portion of the reformed or combusted fuel from the fuel reactor. The energy from the reformed or combusted fuel is used to heat the supercritical CO 2  stream. Also included in the system is a second heat exchanger in fluid communication with the first heat exchanger and the air reactor. The second heat exchanger is configured to receive and further heat the supercritical CO 2  stream received from the first heat exchanger. It is also configured to receive the oxygen-depleted air and a second portion of the re-oxidized oxygen carrier from the air reactor. The energy from the oxygen-depleted air and the second portion of the re-oxidized oxygen carrier is used to heat the supercritical CO 2  stream in the second heat exchanger. 
     The system also includes a turbine in fluid communication with the second heat exchanger. The turbine is configured to receive the supercritical CO 2  stream from the second heat exchanger and expand the supercritical CO 2  such that the expansion of the supercritical CO 2  generates power. The turbine also includes an outlet for the expanded supercritical CO 2 . The expanded supercritical CO 2  is used to heat the fuel from the fuel source and the air stream from the air source prior to their respective deliveries to the fuel reactor and the air reactor. 
     According to a further aspect, the system can include a first conduit in fluid communication with the turbine and configured to receive a first portion of the expanded supercritical CO 2  from the turbine. The system can also include a second conduit in fluid communication with the turbine and configured to receive a second portion of the expanded supercritical CO 2  from the turbine. The system can also include an air preheater and a first fuel preheater. The air preheater is in fluid communication with the first conduit, the air source, and the air reactor. The air preheater is configured to heat the air stream using the energy of the first portion of the expanded supercritical CO 2  prior to delivery of the air stream to the air reactor. The first fuel preheater is in fluid communication with the second conduit, the fuel source, and the fuel reactor, and the first fuel preheater is configured to heat the fuel stream using the energy of the second portion of the expanded supercritical CO 2  prior to delivery of the fuel stream to the fuel reactor. The heating of the air stream in the air preheater and the fuel stream in the first fuel preheater by the respective portions of expanded supercritical CO 2  results in respective low-pressure streams of CO 2 . 
     According to a further aspect, the system includes a cooler in fluid communication with the air preheater and the first fuel preheater. The cooler is configured to receive the respective low-pressure streams of CO 2  from the air preheater and the first fuel preheater and cool the received low pressure CO 2 . The system can further include a third conduit in fluid communication with the cooler and the compressor. The third conduit is configured to receive the cooled low-pressure CO 2  and transfer the cooled low-pressure CO 2  to the compressor. 
     According to another aspect, the system can further include a second fuel preheater in fluid communication with the fuel reactor, the first fuel preheater and the first heat exchanger. The second fuel preheater is configured to receive the fuel stream delivered from the first preheater and at least a portion of the reformed or combusted fuel from the fuel reactor. The second fuel preheater is also configured to further heat the fuel stream via energy from the reformed or combusted fuel prior to the delivery of the fuel stream to the fuel reactor. 
     According to another aspect, the system further includes a solids preheater in fluid communication with the fuel reactor. The solids preheater is configured to receive a portion of the reformed or combusted fuel from the fuel reactor and to heat the oxygen carriers using the energy of the reformed or combusted fuel prior to delivery of the oxygen carriers to the fuel reactor. 
     According to another aspect, the fuel reactor comprises a gas-solid separator configured to separate the reduced oxygen carriers from the reformed or combusted fuel. According to another aspect, the system includes a controller configured to operate the fuel reactor in a temperature range of about 800° C. to about 1100° C. 
     According to another aspect, the air reactor comprises a gas-solid separator configured to separate re-oxidized oxygen carriers from the oxygen-depleted air. According to another aspect, the system includes a controller configured to operate the air reactor in a temperature range of about 900° C. to about 1200° C. 
     According to a further aspect, the compressor is a multistage compressor having intercooling stages. The intercooling stages enable efficient compression of CO 2  from a low-pressure side of the supercritical CO 2  cycle and transfer of the compressed CO 2  to a high-pressure side of the supercritical CO 2  cycle. 
     According to another aspect in which the resulting fuel following reaction in the fuel reactor is a reformed fuel, the system further comprises a fuel cooler in fluid communication with the solids preheater and the first heat exchanger. The fuel cooler is configured to receive the reformed fuel from the solids preheater and the first heat exchanger, and to cool the received reformed fuel to about ambient temperature. The system can further comprise a second compressor in fluid communication with the fuel cooler, the second compressor being configured to compress the ambient temperature reformed fuel received from the fuel cooler. The system can further comprise a combustion chamber in fluid communication with the second compressor and the turbine, the combustion chamber being configured to combust the compressed reformed fuel received from the second compressor to generate a stream of CO 2  and water vapor, and to feed the stream of generated CO 2  and water vapor to the turbine. According to a further aspect, the system can further comprise a gas processing unit in fluid communication with the turbine and downstream of the fuel cooler, the gas processing unit being configured to separate the stream of CO 2  and the water vapor received from the turbine from a low pressure CO 2  stream received from the turbine. 
     According to another aspect, a method for power generation using a coupled chemical looping arrangement and a supercritical CO 2  cycle is provided. In the method, a fuel stream from a fuel source and an air stream from an air source are heated. The fuel stream and oxygen carriers are introduced into a fuel reactor, and the fuel reactor operates under first reaction conditions to result in reformed or combusted fuel and reduced oxygen carriers. The air stream is introduced into an air reactor and the reduced oxygen carriers are transferred from the fuel reactor into the air reactor. The air reactor operates under second reaction conditions to re-oxidize the reduced oxygen carriers resulting in oxygen-depleted air. A first portion of the re-oxidized oxygen carriers is transferred back to the fuel reactor. A CO 2  stream is introduced into a compressor, and the compressor is configured to increase the pressure of the CO 2  stream to create a supercritical CO 2  stream. Both the supercritical CO 2  stream from the compressor and the reformed or combusted fuel from the fuel reactor are transferred to a first heat exchanger, which operates to transfer heat from the reformed or combusted fuel to the supercritical CO 2  stream. The supercritical CO 2  stream from the first heat exchanger, the oxygen-depleted air from the air reactor, and a second portion of the re-oxidized oxygen carriers from the air reactor are all transferred to a second heat exchanger, which operates to transfer heat from the oxygen-depleted air and the re-oxidized oxygen carriers to the supercritical CO 2  stream. The supercritical CO 2  stream from the second heat exchanger is received by a turbine, and the turbine operates under conditions to expand the supercritical CO 2  to generate power. The expanded supercritical CO 2  is used to heat the fuel from the fuel source and the air stream from the air source prior to their respective deliveries to the fuel reactor and the air reactor. 
     According to another aspect, a first portion of the expanded supercritical CO 2  is transferred from the turbine to a first conduit, and a second portion of the expanded supercritical CO 2  is transferred from the turbine to a second conduit. The first portion of the expanded supercritical CO 2  from the first conduit is then received by an air preheater and the second portion of the expanded supercritical CO 2  from the second conduit is then received by a first fuel preheater. The air preheater is configured to transfer energy of the first portion of the expanded supercritical CO 2  to the air stream to heat the air stream. The first fuel preheater is configured to transfer energy of the second portion of the expanded supercritical CO 2  to the fuel stream to heat the fuel stream. The transfer of energy from the respective portions of expanded supercritical CO 2  results in respective streams of low pressure CO 2 . 
     According to a further aspect, the respective streams of low pressure CO 2  from the air preheater and the first fuel preheater are received by a cooler, and the cooler is operated at conditions to cool the received low pressure CO 2 . The cooled low-pressure CO 2  is transferred from the cooler to a third conduit, and the cooled low-pressure CO 2  is then transferred from the third conduit to the compressor. 
     According to another aspect, the fuel stream is transferred from the first fuel preheater to a second fuel preheater, and the second fuel preheater receives at least a portion of the reformed or combusted fuel from the fuel reactor. The fuel stream is heated in the second fuel preheater by transferring energy from the reformed or combusted fuel to the fuel stream. 
     According to another aspect, the oxygen carriers are heated via a solids preheater prior to delivery of the oxygen carriers to the fuel reactor. According to a further aspect, the solids preheater receives a portion of the reformed or combusted fuel from the fuel reactor, and the solids preheater heats the oxygen carriers by transferring energy of the reformed or combusted fuel to the oxygen carriers. 
     According to another aspect, the fuel stream includes a sour gas fuel and the oxygen carriers are calcium-based materials. The reaction between the sour gas fuel and the calcium-based materials causes at least a portion of sulfur in the sour gas fuel to be removed from the fuel stream. 
     According to another aspect, the reduced oxygen carriers and the reformed or combusted fuel are transferred from the fuel reactor to a gas-solid separator, and in the gas-solid separator, the reduced oxygen carriers are separated from the reformed or combusted fuel. 
     According to another aspect, the fuel reactor is operated in a temperature range of about 800° C. to about 1100° C., and the air reactor is operated in a temperature range of about 900° C. to about 1200° C. 
     According to another aspect, the re-oxidized oxygen carriers and the oxygen-depleted air from the air reactor are transferred to a gas-solid separator, and in the gas-solid separator, the re-oxidized oxygen carriers are separated from the oxygen-depleted air. 
     According to another aspect, the compressor is a multistage compressor that includes intercooling stages that enable compression of CO 2  from a low-pressure side of the supercritical CO 2  cycle and transfer of the compressed CO 2  to a high-pressure side of the supercritical CO 2  cycle. According to a further aspect, the low-pressure side of the supercritical CO 2  cycle is operated in a pressure range of about 45 bar to about 90 bar, and the high-pressure side of the supercritical CO 2  cycle is operated in a pressure range of about 200 bar to about 500 bar. 
     According to another aspect, the temperature of the supercritical CO 2  received by the turbine is in a range of about 400° C. to about 1000° C. 
     According to another aspect, in which the fuel resulting from the reaction in the fuel reactor is a reformed fuel, the reformed fuel received from the solids preheater and first heat exchanger is cooled in a fuel cooler. The cooled reformed fuel is then compressing in a second compressor. The compressed reformed fuel is then combusted in a combustion chamber to produce a stream of CO 2  and water vapor, and the produced stream of CO 2  and water vapor is then fed to the turbine. According to a further aspect, the stream of CO 2  and water vapor received from the turbine is separated via a gas processing unit from a low pressure CO 2  stream received from the turbine. 
     These and other aspects, features, and advantages can be appreciated from the accompanying description of certain embodiments of the invention and the accompanying drawing figures and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         FIG. 1  displays a schematic of an exemplary system that includes a supercritical CO 2  cycle coupled to a chemical looping arrangement in accordance with one or more embodiments; 
         FIG. 2  displays a pressure and temperature phase diagram for CO 2 , including the operating ranges for the high- and low-pressure sides of the supercritical CO 2  cycle in accordance with one or more embodiments; and 
         FIG. 3  displays a schematic of another exemplary system that includes a supercritical CO 2  cycle coupled to a chemical looping arrangement in accordance with one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION 
     The present application describes systems and methods for coupling a chemical looping combustion arrangement and a supercritical CO 2  cycle. The present application targets challenges regarding energy conversion efficiency and excessive water usage associated with conventional systems and provides solutions to such technical challenges among others. 
     In one or more embodiments, the system comprises a chemical looping combustion arrangement that comprises an air reactor and a fuel reactor. The fuel reactor receives fuel from a fuel source and receives oxygen carriers. The fuel reactor is configured to heat the received fuel and oxygen carriers. As a result, the fuel is oxidized (combusted) or reformed, resulting in combusted fuel or reformed fuel, respectively, as well as reduced oxygen carriers. The air reactor receives an air stream from an air source and the reduced oxygen carriers from the fuel reactor. The air reactor is configured to re-oxidize the reduced oxygen carriers via a reaction between the reduced oxygen carriers and the air stream. This reaction also results in an oxygen-depleted air stream. A first portion of the re-oxidized oxygen carriers is then transported back to the fuel reactor for additional reactions. 
     The system further comprises a compressor that receives a CO 2  stream from a CO 2  source and that is configured to increase the pressure of the CO 2  stream to create a high pressure supercritical CO 2  stream. The supercritical CO 2  stream is transported to a first heat exchanger, where energy from the reformed fuel/combusted fuel stream is used to heat the supercritical CO 2  stream. The supercritical CO 2  stream is then transported to a second heat exchanger, where energy from the oxygen-depleted air stream and a second portion of the re-oxidized oxygen carrier from the air stream is used to further heat the supercritical CO 2  stream. The heated supercritical CO 2  stream is transported from the second heat exchanger to a turbine, where the turbine is configured to expand the supercritical CO 2  stream to generate power. The expanded supercritical CO 2  stream is then used to heat the fuel stream and the air stream prior to their respective deliveries to the fuel reactor and the air reactor. 
     Thus, the present systems and methods provide a supercritical CO 2  cycle that is integrated with a chemical looping cycle such that the supercritical CO 2  cycle provides heat to pre-heat the incoming streams into the chemical looping cycle, and where the supercritical CO 2  cycle is removing heat from the streams exiting the chemical looping cycle. In other words, in the present system, the hot fluid of a first thermodynamic system (supercritical CO 2  cycle) exchanges heat with the cold side of a second thermodynamic system (chemical looping cycle), while the cold fluid of the first thermodynamic system receives heat from the hot side of the second thermodynamic system. 
     As such, relative to conventional systems, the present systems and methods 1) maximize synergy between the supercritical CO 2  cycle and the chemical looping combustion cycle; 2) provides higher energy efficiency, 3) provides increased operation flexibility, 4) provides lower capex, and 5) provides increased power output, including for embodiments in which the fuel is a sour gas fuel. Additionally, the present systems and methods results in less water usage than previous systems as CO 2  is used as medium to produce power in the first thermodynamic system rather than water and steam. Further, the increased efficiency of the present systems allows for their usage with power generation plants with CO 2  emissions constraints, for example. 
     The referenced systems and methods for coupling a chemical looping combustion arrangement and a supercritical CO 2  cycle are now described more fully with reference to the accompanying drawings, in which one or more illustrated embodiments and/or arrangements of the systems and methods are shown. The systems and methods of the present application are not limited in any way to the illustrated embodiment and/or arrangement. It should be understood that the systems and methods as shown in the accompanying figures are merely exemplary of the systems and methods of the present application, which can be embodied in various forms as appreciated by one skilled in the art. Therefore, it is to be understood that any structural and functional details disclosed herein are not to be interpreted as limiting the systems and methods, but rather are provided as a representative embodiment and/or arrangement for teaching one skilled in the art one or more ways to implement the systems and methods. 
       FIG. 1  displays a diagram of an exemplary system  100  that includes a supercritical CO 2  cycle coupled to a chemical looping arrangement in accordance with one or more embodiments. The system  100  includes a fuel source  102  and a fuel reactor  104  that receives fuel from the fuel source  102  via at least one conduit. In at least one embodiment, the fuel source  102  can be one or more sour gas fields and as such the fuel can be a sour gas fuel comprising high levels of H 2 S or acid gas streams exiting acid removal units. 
     In one or more embodiments, the fuel can be any type of common gaseous fuels (e.g., natural gas, sour gas, acid gas), liquid fuels (e.g., heavy fuel oil, oil residues, tar, crude oil, crude oil byproducts or distillates), or solid fuels (e.g., coal and petroleum coke). In at least one embodiment, the fuels can be fossil fuel based or carbon containing, renewable based fuel such as biomass or bio-fuels, or a combination of fossil fuels and renewable fuels. In at least one embodiment, the fuel can be a synthetic gas issued from reforming or gasification of any type of feedstocks. The fuel can be fed directly to the system, be emulsified or put in slurry. The system can be particularly efficient for difficult to burn fuels or fuels with high sulfur content that require extensive cleaning or operating at lower temperature to mitigate corrosion issues. As shown in  FIG. 1 , in at least one embodiment the fuel from the fuel source  102  is transferred to the fuel reactor  104  via conduits  106  and  108 . In one or more embodiments, the fuel is transferred to at least one fuel preheater before being transferred to the fuel reactor  104  via conduit  108 . As shown in the exemplary system  100  of  FIG. 1 , in at least one embodiment, the fuel is first transferred from the fuel source  102  to a first fuel preheater  110  to heat the fuel. The heated fuel is then transferred from the first fuel preheater  110  to a second fuel preheater  112  via conduit  106  for further heating. After the additionally heating in second fuel preheater  112 , the fuel is transferred from the second fuel preheater  112  to the fuel reactor  104  via conduit  108  that is fluidly connected to the fuel reactor  104  via a fuel inlet. 
     The fuel reactor  104  is also configured to receive oxygen carriers from an oxygen carrier source  114 . The oxygen carriers can be transferred from the source  114  to the fuel reactor  104  via conduit  116 , which is in fluid connection with an oxygen carrier inlet of the fuel reactor  104 . The oxygen carriers are generally solid particles. For instance, in at least one embodiment, the oxygen carriers can be a calcium-based material such as CaCO 3  particles. In one or more embodiments, the oxygen carriers can be CaO or magnesium-based materials or a combination of alkaline earth metals or transition metals such as copper oxides. For sulfur-containing fuels, in one or more embodiments it is preferable to use alkaline earth metals to capture the sulfur in the sulfite and sulfate forms such as CaS and CaSO 4 . In one or more embodiments, prior to entry into the fuel reactor, the oxygen carriers are first transferred from the oxygen carrier source  114  to a solids preheater  118  for heating, the solids preheater  118  being in fluid connection with the fuel reactor  104 . The heated oxygen carriers can then be transferred from the solids preheater  118  to the fuel reactor via conduit  116 . 
     The fuel reactor  104  is generally defined by a housing that defines a hollow interior for receiving the fuel and the oxygen carriers. The fuel reactor is configured to operate at conditions to oxidize (combust) or reform the fuel and oxygen carriers, thereby the resulting in a combusted fuel stream or a reformed fuel stream, respectively, as well as reduced oxygen carriers. The fuel can be either oxidized (combusted) or reformed via this reactor depending on the temperature of the fuel reactor and the composition of the fuel. In other words, the fuel reactor can operate in either a “reforming” mode to produce a reformed fuel stream or a “combust” mode to produce a combusted fuel stream. For example, in embodiments in which the oxygen carriers comprise CaSO 4 , the CaSO 4  oxygen carriers react with the fuel to produce a reformed or combusted fuel stream, CaS (reduced oxygen carriers), and CO 2 . In embodiments in which the fuel comprises sulfur compounds such as H 2 S (e.g., sour gas fuel) and the oxygen carrier is CaCO 3 , at least a portion of the CaCO 3  decomposes into CaO and further reacts with the sulfur components of the fuel to produce CaS as the reduced oxygen carriers. 
     The reformed fuel stream (or combusted fuel stream) and reduced oxygen carriers are then separated from one another and separately exit the fuel reactor  104 . In one or more embodiments, a solid-gas separator, such as a cyclone can be used to separate the reformed (or combusted) fuel stream from the reduced oxygen carriers. 
     The fuel reactor  104  can further include a controller (not shown) configured to operate the fuel reactor in a particular temperature range. For instance, in one or more embodiments, the controller is configured to operate the fuel reactor in a temperature range of about 800° C. to about 1100° C., or in at least one embodiment, in a temperature range of about 850° C. to about 950° C. With regards to the temperature range of the fuel reactor, the term “about” indicates that the ends of the range can vary by plus or minus 5%. 
     The system  100  further includes an air source  120  and an air reactor  122  having an inlet that receives an air stream from the air source  120  via conduit  124 . The air reactor  122  is generally defined by a housing that defines a hollow interior for receiving the air stream and reduced oxygen carriers from the fuel reactor  104 . As shown in  FIG. 1 , in one or more embodiments the air stream from the air source  120  is transferred to an air preheater  126  before being transferred to the air reactor  122  via conduit  124 . The air reactor  122  is also configured to receive reduced oxygen carriers (e.g., CaS) from the fuel reactor  104  via conduit  128 . 
     In the air reactor  122 , the air stream oxidizes the reduced oxygen carriers, which results in re-oxidized oxygen carriers and an oxygen-depleted air stream. In embodiments in which the reduced oxygen carriers received from the fuel reactor comprise CaS, the subsequent re-oxidized oxygen carriers comprise CaSO 4 . The re-oxidized oxygen carriers and the oxygen-depleted air stream then exit the air reactor  122 . The air reactor  122  can further include a controller (not shown) configured to operate the air reactor  122  in a particular temperature range. For instance, in one or more embodiments, the controller is configured to operate the air reactor in a temperature range of about 900° C. to about 1200° C., or in at least one embodiment, in a temperature range of about 1050° C. to about 1150° C. With regards to the temperature range of the air reactor, the term “about” indicates that the ends of the range can vary by plus or minus 5%. In certain embodiments, the same controller that controls the temperature of the air reactor  122  controls the temperature of the fuel reactor  104 , while in at least one embodiment the fuel reactor  104  and air reactor  122  can have separate controllers. In a particular implementation in which the fuel reactor  104  and the air reactor  122  have separate controllers, the output for the fuel reactor controller (i.e., change in temperature) can be an input for the air reactor controller and/or the output of the air reactor controller can be an input for the fuel reactor controller. Accordingly, in this implementation, the controllers of the air reactor and fuel reactor can work in tandem such that changes in temperature implemented in one of the reactors can result in a signal being sent to the controller of the other reactor such that a corresponding temperature change (if necessary) can be made in that reactor. 
     In one or more embodiments, the oxygen-depleted air stream and the re-oxidized oxygen carriers can be separated from one another via a solid-gas separator such as a cyclone, and separately exit the air reactor  122 . As shown in  FIG. 1 , in one or more embodiments, a first portion of the re-oxidized oxygen carriers exit the air reactor  122  via conduit  130 , which delivers a first portion of re-oxidized oxygen carriers back to the fuel reactor  104 . The re-oxidized oxygen carriers received by the fuel reactor  104  are again included in the reaction with the received fuel. Further, in one or more embodiments, a second portion of the re-oxidized oxygen carriers can exit the air reactor  122  via conduit  132 . The oxygen-depleted air stream exits the air reactor  122  via conduit  134 . 
     The air reactor  122  and the fuel reactor  104  are in fluid connection with one another via conduits  128  and  130 . Further, the circulation of reduced oxygen carriers and re-oxidized oxygen carriers between the fuel reactor  104  and the air reactor  122  (via conduits  128  and  130 , respectively) contribute to temperature management of the fuel reactor  104  and the air reactor  122  as the fuel reactor  104  is an endothermic reactor, and the air reactor  122  is an exothermic reactor. 
     With continued reference to  FIG. 1 , the system  100  further comprises a supercritical CO 2  cycle that includes a compressor  136  having an inlet for receiving a CO 2  stream from a CO 2  source  138 . The CO 2  source  138  can be used to initially fill the system and provide a CO 2  make-up that would replenish the CO 2  lost through leaks out of the system. The compressor  136  can be configured to increase the pressure of the CO 2  stream to create a high-pressure supercritical CO 2  stream. Supercritical CO 2  is a fluid state of CO 2  in which the CO 2  is at or above its critical temperature (approximately 31° C.) and its critical pressure (approximately 73.8 bar). A pressure and temperature phase diagram for CO 2  is shown at  FIG. 2 . 
     In one or more embodiments, the temperature of the CO 2  delivered to the system from the CO 2  source  138  can be at ambient temperature, and therefore above or below the critical temperature of CO 2 . When starting to fill the system, the CO 2  delivered to the system from the CO 2  source  138  can be below the critical pressure of CO 2 . The pressure of the CO 2  can then be raised above the critical pressure value once the system is fully filled. In one or more embodiments, the in-line make-up of CO 2  can be done at the operating pressure, which can be controlled by an external unit (e.g., a pump, compressor or expansion valve). 
     In one or more embodiments, the compressor  136  is a multistage compressor with or without intercooling stages. The compressor  136  enables compression of the CO 2  transferring from the low-pressure side of the supercritical CO 2  cycle to the high-pressure side of the supercritical CO 2  cycle. In one or more embodiments, the low-pressure side of the supercritical CO 2  cycle is operated in a pressure range of about 45 bar to about 90 bar, and in at least one embodiment, in a pressure range of about 75 bar to about 80 bar. In one or more embodiments, the high-pressure side of the supercritical CO 2  cycle is operated in a pressure range of about 200 bar to about 500 bar, and in at least one embodiment, in a pressure range of about 300 bar to about 400 bar. The low-pressure side of the supercritical cycle is operated around ambient temperatures, between about −40° C. and about +70° C. The high-pressure side of the supercritical cycle is operated in a temperature range of about 400° C. to about 1200° C. The operating ranges of the high-pressure and low-pressure sides of the supercritical CO 2  cycle are shown in the phase diagram of  FIG. 2 . With regards to the pressure ranges of the high- and low-pressure sides, the term “about” indicates that the ends of the ranges can vary by plus or minus 5%. In at least one embodiment, the compressor  136  can include a controller (not shown) configured to control the pressure range of the supercritical CO 2  cycle. It should be understood that in one or more embodiments, the system  100  can include one or more sensors for measuring the temperature and pressure of the fluids and/or components of the present system. 
     In at least one embodiment, the CO 2  compression is done in a first step via a multistage compressor to compress the CO 2  above the CO 2  critical pressure followed by a second step via a dense phase pump to reach the desired supercritical CO 2  pressure. The CO 2  compressor and dense pump can have direct fluid communication or have an intermediate buffer tank to allow for better operability and control. 
     As mentioned above, the compressor  136  is configured to increase the pressure of the CO 2  stream to create a supercritical CO 2  stream. The compressor  136  is also in fluid communication with a first heat exchanger  140 . The supercritical CO 2  stream from the compressor  136  can then be transported to the first heat exchanger  140  via a conduit  142 . In the first heat exchanger  140 , the supercritical CO 2  stream is heated via heat transferred from the reformed (or combusted) fuel stream. Specifically, the first heat exchanger  140  is also in fluid communication with the fuel reactor  104  via a series of conduits. 
     As exemplified in the embodiment of  FIG. 1 , the reformed (or combusted) fuel resulting from the reaction in the fuel reactor exits the fuel reactor via conduit  144  and at least a first portion of the reformed (or combusted) fuel is transferred to conduit  145 , which is in fluid communication with the second fuel preheater  112 . 
     More specifically, the first portion reformed (or combusted) fuel is transferred from conduit  144  to the second fuel preheater  112  via conduit  145 , and the reformed (or combusted) fuel in the preheater  112  is then used to transfer heat to the fuel stream prior to the fuel stream&#39;s entry into the fuel reactor  104 . It should be understood that the reformed (or combusted) fuel and the fuel stream are separated within the second fuel preheater  112  (e.g., via a solid wall) such that there is no direct contact between the reformed (or combusted) fuel and the fuel stream. 
     The reformed (or combusted) fuel is then transferred from the second fuel preheater  112  to the first heat exchanger  140  via conduit  148 . In the first heat exchanger  140 , the energy of the reformed (or combusted) fuel is transferred to the supercritical CO 2  stream, thereby heating the supercritical CO 2  stream. Again, it should be understood that the reformed (or combusted) fuel and the supercritical CO 2  stream are separated within the first heat exchanger  140  such that there is no direct contact between the reformed (or combusted) fuel and the supercritical CO 2  stream. After transferring heat to the supercritical CO 2  stream, the first portion of reformed (or combusted) fuel exits the first heat exchanger  140  via conduit  150  and exits the system. In one or more embodiments, the first portion of reformed (or combusted) fuel exiting the system via conduit  150  can be further processed for CO 2  removal in instances in which the reformed (or combusted) fuel was the result of complete combustion in the fuel reactor  104 . In at least one embodiment, the reformed (or combusted) fuel exiting the system via conduit  150  can be shifted (i.e., shift the CO to CO 2  using steam and producing more hydrogen) and/or purified for hydrogen separation or can be further used in a power generation block to generate steam or power. 
     In at least one embodiment, a second portion of the reformed (or combusted) fuel is transferred from conduit  144  to a conduit  146 , which is in fluid communication with the solids preheater  118 . The solids preheater  118  is configured to transfer heat from the second portion of the reformed (or combusted) fuel to the oxygen carriers prior to entry of the oxygen carriers into the fuel reactor  104 . In at least one embodiment, the oxygen carriers and the second portion of the reformed (or combusted) fuel are separated within the solids preheater  118  such that there is no direct contact between the reformed (or combusted) fuel and the oxygen carriers. In at least one embodiment, the oxygen carriers and the second portion of the reformed (or combusted) fuel are in intimate contact within the solids preheater  118  such that there is a direct contact between the reformed (or combusted) fuel and the oxygen carriers. In such a configuration, a solid/gas separator (e.g., cyclone) is used to separate the oxygen carrier solid stream from the gaseous reformed (or combusted) fuel stream. After transfer of heat to the oxygen carriers, the second portion of the reformed (or combusted) fuel exit the solids preheater  118  and can be purged from the system  100  via conduit  151 . In one or more embodiments, the reformed (or combusted) fuel exiting the system at conduit  151  can be merged with the reformed (or combusted) fuel stream of conduit  150  or can exit the system separately. In either configuration, the exiting reformed (or combusted) fuel from conduit  151  can then be further processed for CO 2  removal in instances in which the reformed (or combusted) fuel was the result of complete combustion in the fuel reactor  104 . In at least one embodiment, the reformed (or combusted) fuel exiting the system via conduit  151  can be shifted (i.e., shift the CO to CO 2  using steam and producing more hydrogen) and/or purified for hydrogen separation or can be further used in a power generation block to generate steam or power. 
     Returning to the supercritical CO 2  cycle, the heated supercritical CO 2  stream exits the first heat exchanger  140  via conduit  152 . Conduit  152  is also in fluid communication with a second heat exchanger  154  such that the supercritical CO 2  stream is transferred from conduit  152  to the second heat exchanger  154 . 
     In the second heat exchanger  154 , the supercritical CO 2  stream is further heated. The supercritical CO 2  stream receives heat transferred from a second portion of re-oxidized oxygen carriers delivered from the air reactor  122  and/or a stream of oxygen-depleted air delivered from the air reactor  122 . As shown in the embodiment of  FIG. 1 , the oxygen-depleted air stream exits the air reactor  122  via conduit  134 , which is in fluid communication with the second heat exchanger  154 . Similarly, the second portion of the re-oxidized oxygen carriers exits the air reactor  122  via conduit  132 , which is also in fluid communication with the second heat exchanger  154 . In the second heat exchanger  154 , the energy from the oxygen-depleted air stream and/or the second portion of re-oxidized oxygen carriers is transferred to the supercritical CO 2  stream to further heat the supercritical CO 2  stream. In the second heat exchanger  154 , the supercritical CO 2  stream, the oxygen-depleted air stream, and the re-oxidized oxygen carriers can be separated such that there is no direct contact between them. After the heat transfer, the oxygen-depleted air stream exits the second heat exchanger  154  via conduit  156 , which directs the oxygen-depleted air stream out of the system  100 . Likewise, the second portion of re-oxidized oxygen carriers exits the second heat exchanger  154  via conduit  158 , which directs the second portion of re-oxidized oxygen carriers out of the system  100 . 
     As shown in the embodiment of  FIG. 1 , the second heat exchanger  154  can be single multi-channel heat exchanger with three streams. In at least one embodiment, the second heat exchanger can be two separate heat exchangers operating in parallel: one between the supercritical CO 2  stream and the second portion of re-oxidized oxygen carrier, and another between the supercritical CO 2  stream and the oxygen-depleted air stream. 
     The heated supercritical CO 2  stream exits the second heat exchanger  154  via conduit  160  which is in fluid communication with a turbine  162 . In one or more embodiments, the heated supercritical CO 2  stream exits the second heat exchanger  154  at a temperature in the range of about 400° C. to about 1200° C., and in at least one embodiment, at a temperature in the range of about 550° C. to about 850° C. With regards to the temperature range of the heated supercritical CO 2  stream exiting the heat exchanger  154 , the term “about” indicates that the ends of the range can vary by plus or minus 5%. The heated supercritical CO 2  stream enters the turbine  162 , and in the turbine  162  the supercritical CO 2  stream is expanded. The expansion of the supercritical CO 2  stream in the turbine  162  generates power that is used to drive the compressor  136 . In at least one embodiment, the generated power in the turbine  162  can also be used to generate electricity through an electric generator (not shown). Alternatively or additionally, the generated power in the turbine  162  can be used to generate mechanical power to drive process equipment. 
     Expansion of the supercritical CO 2  stream and generation of power by the turbine  162  lowers the pressure of the CO 2  stream, and in certain embodiments can lower the pressure of the CO 2  stream below its critical pressure value (approximately 73.8 bar) when ambient temperature allows it (e.g., when ambient temperature is below the CO 2  critical point temperature or when adding external cooling to reduce the low pressure CO 2  stream temperature below the critical point temperature). Otherwise, the low pressure CO 2  stream remains in supercritical conditions. The reduced pressure CO 2  stream exits the turbine  162  via conduit  164 . In one or more embodiments, conduit  164  splits into two conduits  166  and  168 , such that a first portion of the reduced pressure CO 2  stream enters conduit  166  and a second portion of the reduced pressure CO 2  stream enters conduit  168 . Conduit  166  is in fluid communication with the first fuel preheater  110  such that the first portion of the reduced pressure CO 2  stream is used in the first fuel preheater  110  to transfer heat to the fuel prior to entry of the fuel into the fuel reactor  104 . Similarly, conduit  168  is in fluid communication with the air preheater  126  such that the second portion of the reduced pressure CO 2  stream is used in the air preheater  126  to transfer heat to the air stream prior to entry of the air into the air reactor. The first portion of the reduced pressure CO 2  stream exits the first fuel preheater  110  via conduit  170  and the second portion of the reduced pressure CO 2  stream exits the air preheater  126  via conduit  172 . 
     Conduits  170  and  172  both feed into conduit  174 , such that both portions of the reduced pressure CO 2  stream are transferred into conduit  174 . Conduit  174  then transfers the reduced pressure CO 2  stream into a cooler  176 . In the cooler  176 , the reduced pressure CO 2  stream is cooled to near ambient temperature. The cooled CO 2  stream then exits the cooler  176  via a conduit  178 , which is in fluid communication with the compressor  136 . Thus, via conduit  178 , the cooled CO 2  stream is transferred back to the compressor  136  to complete the supercritical CO 2  cycle. In other words, the cooled CO 2  stream is recycled back to the compressor  136  to continue the supercritical CO 2  cycle. 
     While the systems and methods of the present application have been described above in reference to  FIG. 1 , the present systems and methods are not limited to such a configuration. For example, in at least one embodiment the turbine  162  can have a medium pressure CO 2  extraction point. The extracted, medium-pressure CO 2  stream can then be re-heated in one of the air reactor  122  or fuel reactor  104  or one or more of conduits  132 ,  134 , and  144  before its re-introduction into the turbine  162  for higher output. In this configuration, the turbine is considered a turbine with a single-stage re-heat. Other embodiments can include a turbine with double re-heat, in which two CO 2  streams exit the turbine via separate extraction points at two different intermediate pressures. The two CO 2  streams are both re-heated before injection back into the turbine for more power production. 
     In at least one embodiment, the supercritical CO 2  cycle can include two or three stages in which a re-cycle compressor could be added to the existing CO 2  cycle to improve its efficiency. 
     In at least one embodiment, the supercritical CO 2  cycle can include a CO 2  compressor coupled directly or via an intermediate vessel tank to a CO 2  dense phase pump allowing for the compression of the CO 2  to high pressure supercritical state. 
     In one or more embodiments, the supercritical CO 2  cycle can include a regenerator that exchanges heat between the high pressure-low temperature CO 2  stream (conduit  142 ) and low pressure-high temperature CO 2  stream (conduit  164 ). In this embodiment, the regenerator is designed to reduce the temperature pinch in the system and help heat exchangers  140  and  154  on one side, and air preheater  126  and first fuel preheater  110  on the other side. 
     In at least one embodiment, the high temperature CO 2  stream (conduit  164 ) can exchange heat directly with the fuel reactor  104  through an embedded heat exchanger before feeding the air preheater  126 . Similarly, in at least one embodiment, the high-pressure CO 2  stream (conduit  160  and/or conduit  152 ) can be further heated in the air reactor  122  through a heat exchanger embedded in the air reactor  122 . 
       FIG. 3  discloses a schematic of another embodiment of the exemplary system that includes a supercritical CO 2  cycle coupled to a chemical looping arrangement in accordance with one or more embodiments. As shown in  FIG. 3 , the system  300  has a similar configuration as compared with system  100  (with a few additional features) and the common features of system  100  and system  300  operate in substantially the same fashion as described above in reference to system  100  ( FIG. 1 ). As such, aspects of the system that are common to systems  100  and  300  are displayed in  FIG. 3  with the same numbers that are used to denote them in  FIG. 1 . 
     In system  300 , the fuel reactor  104  operates in “reforming mode” (i.e., the fuel stream is reformed, not combusted, in the fuel reactor) such that a reformed fuel stream (e.g., synthetic gas stream) is produced. The reformed fuel stream exits the fuel reactor  104  via conduit  144 . The reformed fuel stream is then split into two portion that passed through the same routes as shown in  FIG. 1  (i.e., via conduits  145  and  146 ). Specifically, the first portion of the reformed fuel is transferred from conduit  144  to the second fuel preheater  112  via conduit  145 , and the reformed fuel in the preheater  112  is then used to transfer heat to the fuel stream prior to the fuel stream&#39;s entry into the fuel reactor  104 . The reformed fuel is then transferred from the second fuel preheater  112  to the first heat exchanger  140  via conduit  148 . In the first heat exchanger  140 , the energy of the reformed fuel is transferred to the supercritical CO 2  stream, thereby heating the supercritical CO 2  stream. After transferring heat to the supercritical CO 2  stream, the first portion of reformed fuel exits the first heat exchanger  140  via conduit  150 . 
     Similarly, the second portion of the reformed fuel is transferred from conduit  144  to a conduit  146 , which is in fluid communication with the solids preheater  118 . The solids preheater  118  is configured to transfer heat from the second portion of the reformed fuel to the oxygen carriers prior to entry of the oxygen carriers into the fuel reactor  104 . After transferring heat to the oxygen carriers, the second portion of reformed fuel exits the solid preheater  118  via conduit  151 , which then flows into conduit  147 . 
     As such, both portions of reformed fuel transfer heat to other streams after leaving the fuel reactor  104  and are thereby cooled. The conduits  150  and  147  then merge into conduit  149  such that the two cooled streams of reformed fuel are combined back into one stream. Conduit  149  then feeds into a fuel cooler  202 , which runs at ambient conditions (similar to cooler  176 ). The fuel cooler  202  is configured to further cool the combined stream of reformed fuel to about ambient temperature. The reformed fuel at ambient temperature exits fuel cooler  202  via conduit  157  and is fed to a compressor  203 , which causes the pressure of the reformed fuel stream to increase. 
     The reformed fuel stream exits the compressor  203  via conduit  159 , which then feeds the reformed fuel stream to a combustion chamber  201 . Additional fuel can be supplied to the combustion chamber  201  through supply line  190 . The additional fuel supplied through line  190  can be a portion of the fuel provided from fuel source  102  or can be a separate fuel stream. The fuel supplied through line  190  can be a liquid or gas fuel of the type(s) discussed above with regards to the fuel of fuel source  102 . Oxygen can be supplied to the combustion chamber  201  via conduit  180 . The oxygen supplied to combustion chamber  201  enables oxy-combustion firing of the reformed fuel stream (synthetic gas stream). As such, the combustion of the reformed fuel stream in the combustion chamber  201  results in the generation of CO 2  and water vapor. In one or more configurations, the oxygen delivered to the combustion chamber  201  via conduit  180  can be preheated by transfer of heat from one or both of conduits  156  and  158 . In at least one configuration, the oxygen of conduit  180  can be further preheated by a transfer of heat from a conduit stemming off from conduit  134 . In one or more embodiments, the combustion chamber  201  is operated in a temperature range of about 1000° C. to about 2000° C. In at least one embodiment, the combustion chamber is operated in a temperature range of about 1300° C. to about 1800° C. In one or more embodiments, the temperature of the combustion chamber  201  is controlled, at least in part, by the flow rate of recycle CO 2  stream  187 . In one or more embodiments, the supercritical CO 2  stream of conduit  160  from the second heat exchanger  154  also passes to the combustion chamber  201  and is combusted. 
     The flue gas (e.g., CO 2  and water vapor) and the supercritical CO 2  stream exit the combustion chamber  201  via conduit  161 , which feeds to turbine  162 . In the turbine the CO 2  is expanded and its pressure is reduced. The flue gas and resulting reduced pressure CO 2  stream then follow substantially the same route(s) as the reduced pressure CO 2  stream in system  100  of  FIG. 1 . In particular, at least one portion of the flue gas and the reduced pressure CO 2  stream exits the turbine  162  and is fed to air preheater  126 , where it is used to transfer heat to the air stream prior to entry of the air into the air reactor. Similarly, another portion of the flue gas and reduced pressure CO 2  stream exits the turbine  162  and is fed to the first fuel preheater  110 , where it is used to transfer heat to the fuel prior to its entry into the fuel reactor. Both portions of the flue gas and reduced pressure CO 2  stream are then re-combined in conduit  174  and transferred to cooler  176  for cooling to near ambient temperature. The cooled flue gas/reduced pressure CO 2  stream then exits the cooler  176  via a conduit  178 . 
     With continued reference to  FIG. 3 , conduit  178  then feeds the cooled flue gas/reduced pressure CO 2  stream to a gas processing unit  204  that is configured to separate the flue gas (water vapor and CO 2 ) from the main stream of reduced pressure CO 2 . In one or more embodiments, the gas processing unit  204  can be further configured to provide a CO 2  stream of a specified purity for one or more downstream applications (e.g., CO 2  conversion technologies, CO 2  purity requirements, CO 2  sequestration). Off gases and water exit the processing unit  204  via conduits  183  and/or  184 . In one or more embodiments, the gas processing unit  204  can be an adsorption-based unit, a cryogenic type unit, or any type of unit that is typically used in oxy-combustion CO 2  capture technologies. The main stream of cooled reduced pressure CO 2  exits the processing unit  204  via conduit  187 , which returns it to the compressor  136 . The flow rate of the stream of reduced pressure CO 2  in conduit  187  can be regulated to keep the temperature in the combustion chamber  201  within the specified range. Thus, via conduit  187 , the reduced pressure CO 2  stream is transferred back to the compressor  136  to complete the supercritical CO 2  cycle. In other words, the reduced pressure CO 2  stream is recycled back to the compressor  136  to continue the supercritical CO 2  cycle. 
     In one or more embodiments, there is a thermal linkage between conduit  160  and conduit  164 , as the temperature of the flue gases exiting the turbine  162  is very high. In at least one embodiment, conduit  164  can have a thermal linkage to transfer heat to a bottoming cycle based on steam generation or supercritical CO 2  to produce power in the combined cycle. In at least one embodiment, conduit  164  can have a thermal language with gas process unit  204 . 
     Thus, in a salient aspect, the present systems and methods provide a supercritical CO 2  cycle that is integrated with a chemical looping cycle such that the supercritical CO 2  cycle provides heat to pre-heat the incoming streams into the chemical looping cycle, and where the supercritical CO 2  cycle is removing heat from the streams exiting the chemical looping cycle. In other words, in the present system, the hot fluid of a first thermodynamic system (supercritical CO 2  cycle) exchanges heat with the cold side of a second thermodynamic system (chemical looping cycle), while the cold fluid of the first thermodynamic system receives heat from the hot side of the second thermodynamic system. While other systems have combined a chemical looping cycle with a supercritical CO 2  cycle, these other systems comprise heat exchangers that are only exchanging heat within the thermodynamic system in which it is located. Accordingly, these other systems do not exchange a significant amount of heat between the two thermodynamic systems (chemical looping cycle and supercritical CO 2  cycle), and moreover, do not exchange a significant amount of heat in both directions between the two thermodynamic systems. 
     Although much of the foregoing description has been directed to systems and methods for chemical looping and supercritical CO 2  cycles, the system and methods disclosed herein can be similarly deployed and/or implemented in scenarios, situations, and settings far beyond the referenced scenarios. It should be further understood that any such implementation and/or deployment is within the scope of the system and methods described herein. 
     It is to be further understood that like numerals in the drawings represent like elements through the several figures, and that not all components and/or steps described and illustrated with reference to the figures are required for all embodiments or arrangements. Further, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms ““including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     It should be noted that use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. 
     The subject matter described above is provided by way of illustration only and should not be construed as limiting. Various modifications and changes can be made to the subject matter described herein without following the example embodiments and applications illustrated and described, and without departing from the true spirit and scope of the present invention, which is set forth in the following claims.