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

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 .

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.

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.

scholarly journals Efficient Production of Clean Power and Hydrogen Through Synergistic Integration of Chemical Looping Combustion and Reforming

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3443
Author(s):  
Mohammed N. Khan ◽  
Schalk Cloete ◽  
Shahriar Amini
Keyword(s):  
Oxygen Carrier ◽  
Combined Cycle ◽  
Chemical Looping Combustion ◽  
Inlet Temperature ◽  
Efficient Production ◽  
Chemical Looping ◽  
Reactor Outlet ◽  
Point Energy ◽  
Highly Efficient ◽  
Energy Penalty

Chemical looping combustion (CLC) technology generates power while capturing CO2 inherently with no direct energy penalty. However, previous studies have shown significant energy penalties due to low turbine inlet temperature (TIT) relative to a standard natural gas combined cycle plant. The low TIT is limited by the oxygen carrier material used in the CLC process. Therefore, in the current study, an additional combustor is included downstream of the CLC air reactor to raise the TIT. The efficient production of clean hydrogen for firing the added combustor is key to the success of this strategy. Therefore, the highly efficient membrane-assisted chemical looping reforming (MA-CLR) technology was selected. Five different integrations between CLC and MA-CLR were investigated, capitalizing on the steam in the CLC fuel reactor outlet stream to achieve highly efficient reforming in MA-CLR. This integration reduced the energy penalty as low as 3.6%-points for power production only (case 2) and 1.9%-points for power and hydrogen co-production (case 4)—a large improvement over the 8%-point energy penalty typically imposed by post-combustion CO2 capture or CLC without added firing.

Producing Hydrogen and Power Using Chemical Looping Combustion and Water-Gas Shift

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
Niall R. McGlashan ◽  
Peter R. N. Childs ◽  
Andrew L. Heyes ◽  
Andrew J. Marquis
Keyword(s):  
Gas Turbines ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Water Gas Shift ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Operating Pressure ◽  
Overall Efficiency ◽  
Water Gas ◽  
Steam Cycle

A cycle capable of generating both hydrogen and power with “inherent” carbon capture is proposed and evaluated. The cycle uses chemical looping combustion to perform the primary energy release from a hydrocarbon, producing an exhaust of CO. This CO is mixed with steam and converted to H2 and CO2 using the water-gas shift reaction (WGSR). Chemical looping uses two reactions with a recirculating oxygen carrier to oxidize hydrocarbons. The resulting oxidation and reduction stages are preformed in separate reactors—the oxidizer and reducer, respectively, and this partitioning facilitates CO2 capture. In addition, by careful selection of the oxygen carrier, the equilibrium temperature of both redox reactions can be reduced to values below the current industry standard metallurgical limit for gas turbines. This means that the irreversibility associated with the combustion process can be reduced significantly, leading to a system of enhanced overall efficiency. The choice of oxygen carrier also affects the ratio of CO versus CO2 in the reducer’s flue gas, with some metal oxide reduction reactions generating almost pure CO. This last feature is desirable if the maximum H2 production is to be achieved using the WGSR reaction. Process flow diagrams of one possible embodiment using a zinc based oxygen carrier are presented. To generate power, the chemical looping system is operated as part of a gas turbine cycle, combined with a bottoming steam cycle to maximize efficiency. The WGSR supplies heat to the bottoming steam cycle, and also helps to raise the steam necessary to complete the reaction. A mass and energy balance of the chemical looping system, the WGSR reactor, steam bottoming cycle, and balance of plant is presented and discussed. The results of this analysis show that the overall efficiency of the complete cycle is dependent on the operating pressure in the oxidizer, and under optimum conditions exceeds 75%.

CuO promoted Mn2O3-based materials for solid fuel combustion with inherent CO2 capture

2015 ◽  
Vol 3 (19) ◽  
pp. 10545-10550 ◽  
Author(s):  
D. Hosseini ◽  
Q. Imtiaz ◽  
P. M. Abdala ◽  
S. Yoon ◽  
A. M. Kierzkowska ◽  
...  
Keyword(s):  
Co2 Capture ◽  
Solid Fuel ◽  
Oxygen Carrier ◽  
Fuel Combustion ◽  
Chemical Looping ◽  
Solid Fuel Combustion

A novel bimetallic Cu–Mn oxygen carrier for Chemical-Looping with Oxygen Uncoupling (CLOU) based CO2 capture.

Techno-Economic Analysis of a Carbon Capture Chemical Looping Combustion Power Plant

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Oghare Victor Ogidiama ◽  
Mohammad Abu Zahra ◽  
Tariq Shamim
Keyword(s):  
Power Plant ◽  
Natural Gas ◽  
Co2 Capture ◽  
Payback Period ◽  
Combined Cycle ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Natural Gas Combined Cycle ◽  
Energy Penalty ◽  
The Cost

High energy penalty and cost are major obstacles in the widespread use of CO2 capture techniques for reducing CO2 emissions. Chemical looping combustion (CLC) is an innovative means of achieving CO2 capture with less cost and low energy penalty. This paper conducts a detailed techno-economic analysis of a natural gas-fired CLC-based power plant. The power plant capacity is 1000 MWth gross power on a lower heating value basis. The analysis was done using Aspen Plus. The cost analysis was done by considering the plant location to be in the United Arab Emirates. The plant performance was analyzed by using the cost of equipment, cost of electricity, payback period, and the cost of capture. The performance of the CLC system was also compared with a conventional natural gas combined cycle plant of the same capacity integrated with post combustion CO2 capture technology. The analysis shows that the CLC system had a plant efficiency of 55.6%, electricity cost of 5.5 cents/kWh, payback time of 3.77 years, and the CO2 capture cost of $27.5/ton. In comparison, a similar natural gas combined cycle (NGCC) power plant with CO2 capture had an efficiency of 50.6%, cost of electricity of 6.1 cents/kWh, payback period of 4.57 years, and the capture cost of $42.9/ton. This analysis shows the economic advantage of the CLC integrated power plants.

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