Chemical-Looping Combustion for Combined Cycles With CO2 Capture

2006 ◽  
Vol 128 (3) ◽  
pp. 525-534 ◽  
Author(s):  
Stefano Consonni ◽  
Giovanni Lozza ◽  
Giampaolo Pelliccia ◽  
Stefano Rossini ◽  
Francesco Saviano
Keyword(s):  
Metal Oxide ◽  
Gas Turbines ◽  
Exothermic Reaction ◽  
Combined Cycle ◽  
Oxidation Products ◽  
Chemical Looping Combustion ◽  
Excess Oxygen ◽  
Chemical Looping ◽  
Combined Cycles ◽  
Oxidation Reactor

Chemical-Looping Combustion (CLC) is a process where fuel oxidation is carried out through an intermediate agent—a metal oxide—circulated across two fluidized bed reactors: a reduction reactor, where an endothermic reaction reduces the metal oxide and oxidizes the fuel, and an oxidation reactor, where an exothermic reaction oxidizes the metal oxide in air. Overall, the system carries out the same job of a conventional combustor, with the fundamental advantage of segregating the oxidation products (CO2 and H2O) into an output flow free of nitrogen and excess oxygen. The flow exiting the reduction reactor consists of water and CO2, the latter readily available for liquefaction, transport and long-term storage. The hot, vitiated air from the oxidation reactor is the means to produce power through a thermodynamic cycle. This paper reports of a study supported by the ENI group to assess the potential of the integration between CLC and combined gas-steam power cycles. More specifically, we focus on four issues: (i) optimization of plant configuration; (ii) prediction of overall efficiency; (iii) use of commercial gas turbines; (iv) preliminary economic estimates. The CLC system is based on iron oxides which, to maintain their physical characteristics, must operate below 900–1000°C. Given the crucial importance of the temperature of the vitiated air generated by CLC on the performance of the combined cycle, we consider two options: (i) “unfired” systems, where natural gas is fed only to the CLC system, (ii) “fired” systems, where the vitiated air is supplementary fired to reach gas turbine inlet temperatures ranging 1000–1200°C. Results show that unfired configurations with maximum process temperature 850–1050°C and zero emissions reach net LHV plant efficiencies ranging 43%–48%. Fired cycles where temperature is raised from 850 to 1200°C by supplementary firing can achieve 52% net LHV efficiency with CO2 emission about one half of those of a state-of-the-art combined cycles. Fired configurations allow significant capital cost and fuel cost savings compared to unfired configurations; however, a carbon tax high enough to make them attractive (close to 50 €/ton) would undermine these advantages.

Chemical-Looping Combustion for Combined Cycles With CO2 Capture

2004 ◽  
Author(s):  
Stefano Consonni ◽  
Giovanni Lozza ◽  
Giampaolo Pelliccia ◽  
Stefano Rossini ◽  
Francesco Saviano
Keyword(s):  
Metal Oxide ◽  
Gas Turbines ◽  
Exothermic Reaction ◽  
Combined Cycle ◽  
Oxidation Products ◽  
Chemical Looping Combustion ◽  
Excess Oxygen ◽  
Chemical Looping ◽  
Combined Cycles ◽  
Oxidation Reactor

Chemical-Looping Combustion (CLC) is a process where fuel oxidation is carried out through an intermediate agent — a metal oxide — circulated across two fluidized bed reactors: a reduction reactor, where an endothermic reaction reduces the metal oxide and oxidizes the fuel, and an oxidation reactor, where an exothermic reaction oxidizes the metal oxide in air. Overall, the system carries out the same job of a conventional combustor, with the fundamental advantage of segregating the oxidation products (CO2 and H2O) into an output flow free of nitrogen and excess oxygen. The flow exiting the reduction reactor consists of water and CO2, the latter readily available for liquefaction, transport and long-term storage. The hot, vitiated air from the oxidation reactor is the means to produce power through a thermodynamic cycle. This paper reports of a study supported by the ENI group to assess the potential of the integration between CLC and combined gas-steam power cycles. More specifically, we focus on four issues: (i) optimization of plant configuration; (ii) prediction of overall efficiency; (iii) use of commercial gas turbines; (iv) preliminary economic estimates. The CLC system is based on iron oxides which, to maintain their physical characteristics, must operate below 900–1000°C. Given the crucial importance of the temperature of the vitiated air generated by CLC on the performance of the combined cycle, we consider two options: (i) “unfired” systems, where natural gas is fed only to the CLC system, (ii) “fired” systems, where the vitiated air is supplementary fired to reach gas turbine inlet temperatures ranging 1000–1200°C. Results show that unfired configurations with maximum process temperature 850–1050°C and zero emissions reach net LHV plant efficiencies ranging 43–48%. Fired cycles where temperature is raised from 850 to 1200°C by supplementary firing can achieve 52% net LHV efficiency with CO2 emission about one half of those of a state-of-the-art combined cycles. Fired configurations allow significant capital cost and fuel cost savings compared to unfired configurations; however, a carbon tax high enough to make them attractive (close to 50 €/ton) would undermine these advantages.

Three Reactors Chemical Looping Combustion for High Efficiency Electricity Generation With CO2 Capture From Natural Gas

2006 ◽  
Author(s):  
Giovanni Lozza ◽  
Paolo Chiesa ◽  
Matteo Romano ◽  
Paolo Savoldelli
Keyword(s):  
Natural Gas ◽  
Metal Oxide ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Specific Power ◽  
Working Fluid ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Water Separation ◽  
Oxidation Reactor

Chemical-Looping Combustion (CLC) is a process where fuel oxidation is accomplished by the oxygen carried by a metal oxide, circulating across two reactors: a reduction reactor (reducing the metal oxide by oxidizing the natural gas fuel) and an oxidation reactor (re-oxidizing the metal by reacting with air, a strongly exothermic reaction). The system produces: (i) a stream of oxidation products (CO2 and H2O), ready for carbon sequestration after water separation and CO2 liquefaction; (ii) a stream of hot air (deprived of some oxygen) used as working fluid of a gas turbine cycle. Due to the moderate temperature (∼850°C) of this stream, sensibly lower than those adopted in commercial gas turbines, the combined cycle arranged around this concept suffers from poor conversion efficiency and, therefore, economics. In the present paper, the basic CLC arrangement is modified by inserting a third reactor in the loop. This reactor, by exploiting an intermediate oxidation state of the circulating metal, produces H2 used as decarbonized fuel to raise the temperature of the air coming from the oxidation reactor, up to the highest value allowed by the modern gas turbine technology (∼1350°C), thus achieving elevated efficiency and specific power output. This paper is aimed to assess the potential of power cycles based on the three reactors (CLC3) arrangement. More specifically, we will discuss the plant configuration, the process optimization and the performance prediction. Results show that the CLC3 system is very promising: the net LHV efficiency of the best configuration exceeds 51%, an outstanding figure for a natural gas power cycle producing liquid, disposal-ready CO2 and negligible NOx emissions. Commercial gas turbines can be easily adapted to operate in the specific conditions of the CLC3 arrangement which, apart from the reactors system, does not require the development of novel technologies and/or high-risk components. The paper also reports a final comparison with a rival technology based on natural gas partial oxidation, water-gas shift reaction and CO2 separation by MDEA absorption. This work has been performed within the research on the Italian Electrical System “Ricerca di Sistema”, Ministerial Decrees of January 26 – 2000, and April 17 – 2001.

Optimal Performance of Combined Cycles With Chemical Looping Combustion for CO2 Capture

2007 ◽  
Author(s):  
Rehan Naqvi ◽  
Olav Bolland
Keyword(s):  
Metal Oxide ◽  
Co2 Capture ◽  
Combined Cycle ◽  
Optimal Performance ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Part Load ◽  
Fuel Reactor ◽  
Combined Cycles ◽  
Base Load

Chemical Looping Combustion (CLC) is an ingenious concept of CO2 capture from fossil fuels combustion. CLC is closely related to oxy-fuel combustion as the chemically bound oxygen reacts in a stoichiometric ratio with the fuel. In CLC, the overall combustion takes place in two steps while air and fuel are kept away from each other in two separate reactors. The necessary oxygen is supplied to the fuel by a certain metal oxide (Me/MeO). In a fuel reactor, the fuel reacts with the metal oxide and reduces it to metal (Me). The reduced metal oxide (Me) circulates to a separate air reactor where it reacts with oxygen in the air and gets oxidised back to metal oxide. The metal oxide keeps circulating between the two reactors in a loop while taking part in the successive chemical reactions. CLC can be applied in conventional circulating fluidised bed reactors. The air reactor product is hot oxygen-depleted air and the fuel reactor exhaust ideally consists of hot CO2/steam mixture. The exhaust can be condensed to separate steam and CO2 is compressed. Hence, energy penalty for CO2 capture is lower as compared to pre- and post-combustion capture methods. When the reactors are pressurised, CLC can be applied in combined cycles. This paper addresses optimal performance of two CLC-combined cycle configurations. In order to obtain optimal efficiency at base-load, thermodynamic analysis has been carried out and design point established. Further, the cycles’ performance at different load conditions has been analysed. The cycles are also compared with two conventional combined cycles including post-combustion CO2 capture in amine solution. The results show that the CLC-combined cycles exhibit higher net plant efficiencies at base-load as well as at part-load with close to 100% CO2 capture as compared to conventional combined cycles with post-combustion CO2 capture. Also, the CLC-combined cycles have better relative net plant efficiencies at part-load compared to conventional combined cycles. This work concludes that the CLC-combined cycles have high potential of efficient power generation with high degree of CO2 capture at base-load as well as part-load. The challenges with respect to cycles control have also been identified and control strategies discussed.

Investigation of a Novel Gas Turbine Cycle With Coal Gas Fueled Chemical-Looping Combustion

2000 ◽  
Author(s):  
Hongguang Jin ◽  
Masaru Ishida
Keyword(s):  
Natural Gas ◽  
Fixed Bed ◽  
Combined Cycle ◽  
Fixed Bed Reactor ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Gas Combustion ◽  
Coal Gas ◽  
New Type ◽  
Oxidation Reactor

Abstract A new type of integrated gasification combined cycle (IGCC) with chemical-looping combustion and saturation for air is proposed and investigated. Chemical-looping combustion may be carried out in two successive reactions between two reactors, a reduction reactor (coal gas with metal oxides) and an oxidation reactor (the reduced metal with oxygen in air). The study on the new system has revealed that the thermal efficiency of this new-generation power plant will be increased by approximately 10–15 percentage points compared to the conventional IGCC with CO2 recovery. Furthermore, to develop the chemical-looping combustor, we have experimentally examined the kinetic behavior between solid looping materials and coal gas in a high-pressure fixed bed reactor. We have identified that the coal gas chemical-looping combustor has much better reactivity, compared to the natural gas one. This finding is completely different from the direct combustion in which combustion with natural gas is much easier than that with other fuels. Hence, this new type of coal gas combustion will make breakthrough in clean coal technology by simultaneously resolving energy and environment problems.

Inherent CO2 Capture Using Chemical Looping Combustion in a Natural Gas Fired Power Cycle

2004 ◽  
Vol 126 (2) ◽  
pp. 316-321 ◽  
Author(s):  
O̸. Brandvoll ◽  
O. Bolland
Keyword(s):  
Metal Oxide ◽  
Co2 Capture ◽  
Exergy Analysis ◽  
Oxygen Carrier ◽  
Fuel Combustion ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Conventional Combustion ◽  
Oxidation Reactor ◽  
Cycle Efficiency

In this paper an alternative to the so-called “oxy-fuel” combustion for CO2 capture is evaluated. “Chemical looping combustion” (CLC), is closely related to oxy-fuel combustion as the chemically bound oxygen reacts in a stoichiometric ratio with the fuel. In the CLC process the overall combustion reaction takes place in two reaction steps in two separate reactors. In the reduction reactor, the fuel is oxidized by the oxygen carrier, i.e., the metal oxide MeO. The metal oxide is reduced to a metal oxide with a lower oxidation number, Me, in the reaction with the fuel. In this manner, pure oxygen is supplied to the reaction with the fuel without using a traditional air separation plant, like cryogenic distillation of air. The paper presents a thermodynamic cycle analysis, where CLC is applied in a humid air turbine concept. Main parameters are identified, and these are varied to examine the influence on cycle efficiency. Results on cycle efficiency are presented and compared to other CO2 capture options. Further, an evaluation of the oxygen carrier, metals/oxides, is presented. An exergy analysis is carried out in order to understand where losses occur, and to explain the difference between CLC and conventional combustion. The oxidation reactor air inlet temperature and the oxidation reactor exhaust temperature have a significant impact on the overall efficiency. This can be attributed to the controlling effect of these parameters on the required airflow rate. An optimum efficiency of 55.9% has been found for a given set of input parameters. Crucial issues of oxygen carrier durability, chemical performance, and mechanical properties have been idealized, and further research on the feasibility of CLC is needed. Whether or not the assumption 100% gas conversion holds, is a crucial issue and remains to be determined experimentally. Successful long-term operation of chemical looping systems of this particular type has not yet been demonstrated. The simulation points out a very promising potential of CLC as a power/heat generating method with inherent capture of CO2. Exergy analysis show reduced irreversibilities for CLC compared to conventional combustion. Simulations of this type will prove useful in designing CLC systems in the future when promizing oxygen carriers have been investigated in more detail .

Chemical Looping Combustion-Analysis of Natural Gas Fired Power Cycles With Inherent CO2 Capture

2004 ◽  
Author(s):  
Rehan Naqvi ◽  
Olav Bolland ◽  
O̸yvind Brandvoll ◽  
Kaare Helle
Keyword(s):  
Metal Oxide ◽  
Co2 Capture ◽  
Oxygen Carrier ◽  
Fuel Combustion ◽  
Combined Cycle ◽  
Reactor System ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Turbine Cooling ◽  
Steam Cycle

In this paper an alternative to so-called ‘oxy-fuel’ combustion has been evaluated. Chemical Looping Combustion (CLC) is an innovative concept of CO2 capture from combustion of fossil fuels in power plants. CLC is closely related to oxy-fuel combustion as the chemically bound oxygen reacts in a stoichiometric ratio with the fuel. In CLC, the overall combustion takes place in two steps. In a reduction reactor fuel is oxidised by the oxygen carrier i.e. the metal oxide MeO which is reduced to metal oxide with a lower oxidation number, Me. Me flows to an oxidation reactor where it is oxidised by oxygen in the air. In this way pure oxygen is supplied to fuel without using an energy intensive traditional air separation unit. This paper presents thermodynamic cycle analysis of a CLC-power plant. A steady-state model has been developed for the solid-gas reactions occurring in the reactor system. The model is applied to analyse the system under two configurations; a combined cycle and a conventional steam cycle. A turbine-cooling model has also been implemented to evaluate the turbine cooling penalty in the combined cycle configuration. Effects of exhaust recirculation for coking prevention and incomplete fuel conversion have also been investigated. Performance of the oxygen carrier has been idealised except for the degrees of reduction and oxidation. Energy needs for CO2 capture have properly been taken into account. The results show that an optimum efficiency of 49.7% can be achieved under given conditions with a CLC-combined cycle at zero emissions level. With turbine cooling, efficiency falls by 1.2% points under the same conditions. The CLC-steam cycle is capable of achieving 40.1% efficiency with zero emissions. The results show that CLC has high potential for power generation with inherent CO2 capture. This work will be useful in designing CLC systems after the reactor system has been analysed experimentally for long-term operations.

Inherent CO2 Capture Using Chemical Looping Combustion in a Natural Gas Fired Power Cycle

2002 ◽  
Author(s):  
O̸yvind Brandvoll ◽  
Olav Bolland
Keyword(s):  
Metal Oxide ◽  
Co2 Capture ◽  
Exergy Analysis ◽  
Oxygen Carrier ◽  
Fuel Combustion ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Conventional Combustion ◽  
Oxidation Reactor ◽  
Cycle Efficiency

In this paper an alternative to the so-called “oxy-fuel” combustion for CO2 capture is evaluated. “Chemical looping combustion” (CLC), is closely related to oxy-fuel combustion as the chemically bound oxygen reacts in a stoichiometric ratio with the fuel. In the CLC process the overall combustion reaction takes place in two reaction steps in two separate reactors. In the reduction reactor, the fuel is oxidised by the oxygen carrier, i.e. the metal oxide MeO. The metal oxide is reduced to a metal oxide with a lower oxidation number, Me, in the reaction with the fuel. In this manner, pure oxygen is supplied to the reaction with the fuel without using a traditional air separation plant, like cryogenic distillation of air. The paper presents a thermodynamic cycle analysis, where CLC is applied in a Humid Air Turbine concept. Main parameters are identified, and these are varied to examine the influence on cycle efficiency. Results on cycle efficiency are presented and compared to other CO2 capture options. Further, an evaluation of the oxygen carrier, metals/oxides, is presented. An exergy analysis is carried out in order to understand where losses occur, and to explain the difference between CLC and conventional combustion. The oxidation reactor air inlet temperature and the oxidation reactor exhaust temperature have a significant impact on the overall efficiency. This can be attributed to the controlling effect of these parameters on the required airflow rate. An optimum efficiency of 55.9% has been found for a given set of input parameters. Crucial issues of oxygen carrier durability, chemical performance and mechanical properties have been idealized, and further research on the feasibility of CLC is needed. Whether or not the assumption 100% gas conversion holds, is a crucial issue and remains to be determined experimentally. Successful long-term operation of chemical looping systems of this particular type has not yet been demonstrated. The simulation points out a very promising potential of CLC as a power/heat generating method with inherent capture of CO2. Exergy analysis show reduced irreversibilities for CLC compared to conventional combustion. Simulations of this type will prove useful in designing CLC systems in the future when promising oxygen carriers have been investigated in more detail.

A Low Temperature Solar Thermochemical Power Plant With CO2 Recovery Using Methanol-Fueled Chemical Looping Combustion

2009 ◽  
Author(s):  
Hui Hong ◽  
Tao Han ◽  
Hongguang Jin
Keyword(s):  
Low Temperature ◽  
Thermal Energy ◽  
Combined Cycle ◽  
Energy Utilization ◽  
Solar Thermal ◽  
Chemical Looping Combustion ◽  
Inlet Temperature ◽  
Chemical Looping ◽  
Solar Thermal Energy ◽  
Oxidation Reactor

A novel solar-hybrid gas turbine combined cycle was proposed. The cycle integrates methanol-fueled chemical-looping combustion and solar thermal energy at around 200°C, and it was investigated with the aid of the Energy-Utilization Diagram (EUD). Solar thermal energy, at approximately 150°C–300°C, is utilized to drive the reduction of Fe2O3 with methanol in the reduction reactor, and is converted into chemical energy associated with the solid fuel FeO. Then it is released as high-temperature thermal energy during the oxidation of FeO in the oxidation reactor to generate electricity through the combined cycle. As a result, the exergy efficiency of the proposed solar thermal cycle may reach 58.4% at a turbine inlet temperature (TIT) of 1400°C, and the net solar-to-electric efficiency would be expected to be more than 30%. The promising results obtained here indicate that this solar-hybrid combined cycle not only offers a new approach for highly efficient use of middle-and-low temperature solar thermal energy to generate electricity, but also provides the possibility of simultaneously utilizing renewable energy and alternative fuel for CO2 capture with low energy penalty.

A Low Temperature Solar Thermochemical Power Plant With CO2 Recovery Using Methanol-Fueled Chemical Looping Combustion

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Hui Hong ◽  
Tao Han ◽  
Hongguang Jin
Keyword(s):  
Low Temperature ◽  
Thermal Energy ◽  
Combined Cycle ◽  
Energy Utilization ◽  
Solar Thermal ◽  
Chemical Looping Combustion ◽  
Inlet Temperature ◽  
Chemical Looping ◽  
Solar Thermal Energy ◽  
Oxidation Reactor

A novel solar-hybrid gas turbine combined cycle was proposed. The cycle integrates methanol-fueled chemical-looping combustion and solar thermal energy at around 200°C, and it was investigated with the aid of the energy-utilization diagram (EUD). Solar thermal energy, at approximately 150°C–300°C, is utilized to drive the reduction in Fe2O3 with methanol in the reduction reactor, and is converted into chemical energy associated with the solid fuel FeO. Then it is released as high-temperature thermal energy during the oxidation of FeO in the oxidation reactor to generate electricity through the combined cycle. As a result, the exergy efficiency of the proposed solar thermal cycle may reach 58.4% at a turbine inlet temperature of 1400°C, and the net solar-to-electric efficiency would be expected to be 22.3%. The promising results obtained here indicate that this solar-hybrid combined cycle not only offers a new approach for highly efficient use of middle-and-low temperature solar thermal energy to generate electricity, but also provides the possibility of simultaneously utilizing renewable energy and alternative fuel for CO2 capture with low energy penalty.

A Novel Solar-Hybrid Gas Turbine Combined Cycle With Inherent CO2 Separation Using Chemical-Looping Combustion by Solar Heat Source

2006 ◽  
Vol 128 (3) ◽  
pp. 275-284 ◽  
Author(s):  
Hui Hong ◽  
Hongguang Jin ◽  
Baiqian Liu
Keyword(s):  
Metal Oxide ◽  
Thermal Energy ◽  
Combined Cycle ◽  
Solar Thermal ◽  
Chemical Looping Combustion ◽  
Co2 Separation ◽  
Inlet Temperature ◽  
Low Grade ◽  
Chemical Looping ◽  
Solar Thermal Energy

In this paper we propose a novel CO2-recovering hybrid solar-fossil combined cycle with the integration of methane-fueled chemical-looping combustion, and investigate the system with the aid of the Energy-Utilization Diagram (EUD). Chemical-looping combustion (CLC) consists of two successive reactions: first, methane fuel is oxidized by metal oxide(NiO)as an oxygen carrier (reduction of metal oxide); and second, the reduced metal (Ni) is successively oxidized by combustion air (the oxidation of metal). The oxidation of methane with NiO requires a relative low-grade thermal energy at 300°C-500°C. Then concentrated solar thermal energy at approximately 450°C-550°C can be utilized to provide the process heat for this reaction. By coupling solar thermal energy with methane-fueled chemical-looping combustion, the energy level of solar thermal energy at around 450°C-550°C can be upgraded to the chemical energy of solid fuel Ni for better utilization of solar energy to generate electricity. The synergistic integration of solar thermal energy and chemical-looping combustion could make the exergy efficiency and the net solar-to-electric efficiency of the solar hybrid system more than 60% and 30%, respectively, at a turbine inlet temperature (TIT) of 1200°C. At the same time, this new system has an extremely important advantage of directly suppressing the environmental impact due to lack of energy penalty for CO2 recovery. Approximately 9–15 percentage points higher efficiency can be achieved compared to the conventional natural gas-fired combined cycle with CO2 separation. The results obtained here are promising and indicate that this novel solar hybrid combined cycle offers the new possibility of CO2 mitigation using both green energy and fossil fuels. These results also provide a new approach for highly efficient use of solar thermal energy to generate electricity.

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