Oxy-combustion Power Cycles Research Articles

Performance evaluation of a flexible CO2-ORC and sorbent regeneration integrated novel dry gasification oxy-combustion power cycle for in-situ sulphur capture, CO2 capture and power generation

In this work, CO2-Organic Rankine Cycle (CO2-ORC) and sorbent regeneration integrated novel Dry Gasification Oxy-Combustion (DGOC) power cycle has been proposed. Integration of CO2-ORC, a low-temperature heat recovery cycle, further enhances the power cycle efficiency. This work presents the performance evaluation of proposed cycle in terms of optimum conditions of gasifier and regenerator, sulphur capture efficiency, quality of CO2 capture, net plant efficiency, exergy efficiency and economic aspect with different sorbents for in-situ sulphur capture at various operating pressures in the Aspen Plus simulation environment. Results show that optimum gasifier temperature increase with increase in operating pressure and trend is almost similar for all sorbents studied. Optimum regenerator conditions vary significantly with different sorbent and operating pressure. Maximum efficiency was obtained with CuO sorbent of about 39.85%. CuO has the maximum sulphur capture efficiency of 99.98% whereas Fe2O3 has the lowest Sulphur capture efficiency. Exergy analysis shows a similar trend, with CuO having the maximum exergetic efficiency. Economically combined cycle with MnO sorbent performs marginally better than other sorbents.

Conceptual design, energy, exergy, economic and water footprint analysis of CO2-ORC integrated dry gasification oxy-combustion power cycle

Among various techniques for CO2 capture and sequestration from coal-fired power plants, Dry Gasification Oxy-Combustion (DGOC) is a promising technology due to its efficiency, in-situ sulphur capture, and low water usage. In this work, a novel DGOC power cycle integrated with CO2-Organic Rankine Cycle (CO2-ORC) has been proposed for power generation and carbon capture. This study presents Energy, Exergy, Economic, and water footprint analysis of DGOC and its integration with CO2-ORC for different operating pressures and with different types of coal using Aspen Plus simulator. Steam cycle and CO2-ORC have been optimized for the process. Integration of CO2-ORC not only reduces the penalty for CO2 capture but also improves the efficiency by providing extra power output. Integration of CO2-ORC shows improvements in energy, exergy, and economics. Energy analysis shows a maximum increase in efficiency of 6.92% points by integrating CO2-ORC with DGOC for Bituminous coal and a maximum increase of about 6.7% points for high ash coal. The highest thermal energy efficiency of about 41.63% was noticed for Bituminous coal DGOC with CO2-ORC. Exergy analysis shows a positive impact of CO2-ORC integration for all operating pressures with a maximum increase of 5.74% points and 5.87% points for bituminous and high ash coals respectively. Economic analysis shows that combining CO2-ORC improves the specific capital cost of the cycle by 13.17% and 13.27% for the Bituminous and high ash coal cases respectively. Levelized cost of electricity (LCOE) analysis shows an improvement of 12.94% for Bituminous coal and 12.69% for high ash coal by the addition of ORC. The water usage for the plant is also reduced significantly with the addition of CO2-ORC.

Study of recirculating water-based and carbon-based working fluids on the combustion flow field and the cycle performances of semi-closed CO2-capturing Brayton-derived cycles

• A performance analysis was performed in CO 2 and H 2 O recycling cycles. • A CFD combustion study was performed in H 2 O and CO 2 representative conditions. • An economic analysis was performed in CO 2 and H 2 O recycling cycles. • CO 2 fluids give better cycle performances and H 2 O better combustion temperature fields. The transition into new power technologies that utilize fossil fuels with near zero emissions to the ambient is an urgent need to mitigate the worldwide environmental problems. In this study, detailed analyses of carbon-based and water-based oxy-combustion power cycles are introduced. The applied methodologies to perform these analyses comprise CFD analysis of reacting flows for dual recuperative cycle (DRC) and reheated cycle (RHC). The employed CFD methodologies used the non-simplified Navier-Stokes formulation of reacting flows to avoid the use of extra models or assumptions. It was found that recycling carbon-based fluids would allow better overall performances of the resulting cycles. Recycling water-based fluids, however, would provide some interesting features regarding the temperature field in the combustion chamber. Hence, it would avoid in a better way the possibility of facing overheating caused by oxy-combustion, as well as provide some valuable aerodynamic features for the turbines. When analyzing the obtained combustion flow field, CO 2 and H 2 O working fluids create a more important temperature abatement in the flame surrounding areas and trail than Air. When comparing CO 2 and H 2 O working fluids between them, the H 2 O working fluid initially showed a slightly bigger high-temperature zone than the CO 2 working fluid. Despite this fact, and after those initial zones, the H 2 O working fluid showed a more important temperature abatement than the CO 2 working fluid, except for the transversal tip of the flame trail, where temperatures are in a safe range for superalloys. When considering the temperature on the fluid domain symmetry axis and at the outlet, for the 30 atm case (30.4 bar), it was found that the CO 2 fluid presented a temperature equal to 86.9% of the Air one in the same location and pressure, whereas the H 2 O fluid presented an 82% of the Air one. In addition, thermoeconomic analyses were conducted for the DRC and RHC that are working at high pressure of less than 42 bar and operating temperatures of 1100 K to 1450 K to ensure feasible design for the cycle components. Furthermore, it is found that a maximum efficiency of 47.50% is obtained by the carbon-based RHC under wet-cooling conditions and a minimum cycle efficiency of 33.54% is obtained by the water-based DRC under dry-cooling conditions. From an economic point of view, the average LCOE of the present carbon-based and water-based cycles is 4.17 ¢/kWh, which is 28% lower than the average LCOE of the supercritical carbon-based and integrated gas-turbine-based cycles. Moreover, the LCOE of the carbon-based RHC is minimum (3.92 ¢/kWh) at minimum cycle temperature (T min ) of 305 K (wet cooling) and identical to the water-based RHC (4.00 ¢/kWh) at T min of 323 K (dry-cooling).

Energy, economic and environmental analysis and comparison of the novel Oxy- combustion power systems

Oxy-combustion technologies are clean energy systems with zero emission; they have great potential when considering global warming and climate change. This study presents a detailed thermodynamic analysis in terms of energy, environment, and economy. Consequently, the results obtained for an oxy-combustion power system are presented in comparison with a conventional gas turbine power system. The results are presented as a function of the pressure ratio with regard to net power, input heat, system efficiency, sp ecific fue l consumption, equivalence ratio, fuel-air ratio, capital investment cost, fuel cost, oxygen cost, total cost, electricity revenue, and net profit. In addition, the study calculates the pollutant emissions from non-oxy-combustion systems and investigates the environmental costs. The pressure ratio for maximum net power has been obtained as 20.8 in the conventional gas turbine power system. Similarly, the pressure ratios for maximum net power in oxy-combustion power cycles with 26%, 28%, and 30% oxygen ratios are 23.3, 27.4 and 29.7, respectively. Results from 24% to 30% have been displayed to observe the effect of reactant oxygen in the oxy-combustion power cycles. The optimum c ycle c onditions have been determined by calculating the costs of system components, total revenues, and net profits at pressure ratios of 10, 20, 30 and 40. Finally, the results reveal the pressure ratio should be reduced to minimize the total costs per cycle. For maximum net profit, the pressure ratio in a conventional gas turbine power cycle has been calculated as 15.9; similarly, the pressure ratios in oxy-combustion power cycles with 26%, 28%, and 30% oxygen ratios have been respectively calculated as 12.8, 15.2 and 16.4.

Optimal liquified natural gas (LNG) cold energy utilization in an Allam cycle power plant with carbon capture and storage

Oxy-combustion power cycles are an alternative technology for electricity generation to facilitate carbon capture and storage (CCS). Among oxy-combustion power cycles, the Allam cycle is one of the most promising technologies for power generation in terms of both efficiency and economics. Besides, the Allam cycle can also achieve a near-zero emission target at a much lower cost compared to conventional fossil fuel power plants. On the other hand, the flue gas carbon capture process and the recycled flue gas compression process in the Allam cycle consume considerable work. If the compression work can be decreased, the energy efficiency of the system can be further improved, which can enhance the competitiveness over other power generation technologies. When the fuel of the power plant is Liquified Natural Gas (LNG) instead of conventional natural gas, the LNG cold energy can be utilized to reduce the compression work of the carbon capture process and recycled flue gas compression work in the Allam cycle. In this study, we investigated different ways to utilize the LNG cold energy for both a stand-alone power plant and a cogeneration system with power generation and LNG regasification. A superstructure incorporating many possible flowsheets is proposed in this study. A simulation-based optimization framework is adopted to optimize the superstructure. The results indicate that direct integration of LNG regasification and flue gas liquefaction performs well for the stand-alone power plant, while the organic Rankine cycle integration scheme is the best choice for the cogeneration system.

Sensitivity and Techno-Economic Analysis of Leading Oxy-Combustion Power Cycles with Full Carbon Capture: NetPower and Supercritical CES

The increasing concern on climate change has led to global efforts to reduce carbon dioxide (CO2) in the environment. It appears that by far the largest contribution to the greenhouse effect stems from emissions of carbon dioxide CO2. A large part of the CO2 emission are produced by the combustion of fossil fuels in conventional power plants and industrial processes. However, the Carbon Capture and Sequestration (CCS) technologies have been developed to minimise the CO2 emission to the atmosphere. Three main capture technologies (pre-combustion, post-combustion and oxy-fuel combustion) have been mainly developed for solid fuels (e.g., coal, biomass) combustion systems. However, there are many gas-fired power plants and industrial process burning natural gas as a cleaner fuel. Natural gas has the lowest CO2 emissions per unit of energy of all fossil fuels at about 14 kg C/GJ, compared to oil with about 20 kg C/GJ and coal with about 25 kg C/GJ. Although gas-fired plants emit less CO2 but still to achieve the environmental goals of the Paris Agreement it is essential to develop CCS technologies for the growing gas-fired systems. Among the available technologies, turbine-based oxy-combustion cycles (Oxyturbine cycles) are one of the most suitable carbon capture technologies for the gas-fired power plants. In this technology, natural gas is burned with pure oxygen, and temperature moderation is done by Flue Gas Recirculation (FGR) so that the exhaust gas includes mainly CO2 and water vapour ready for sequestration and storage. Recent developments in oxy-combustion technology have reduced the cost of capture and made it competitive with post- combustion technology. Several oxyturbine cycles have been introduced by means of thermodynamic analysis. However, only NetPower and Supercritical CES cycles have recently proceeded to the demonstration phase. The NetPower cycle recirculates only carbon dioxide as the working fluid, and the Supercritical CES cycle uses water as its working fluid. The Supercritical CES cycle that has best efficiency among other type of CES cycles includes high, medium and low-pressure turbines (HP, MP, and LP) and the exhaust gas from the high-pressure turbine is reheated and expanded in an MP and LP. Pure oxygen is produced in an Air Separation Unit (ASU) and directly inject into the combustion chamber. The NetPower cycle includes a single turbine with high inlet pressure and a main multi-stream heat exchanger. Pure oxygen is produced in the ASU and mixed with the recycled carbon dioxide, before being introducing to the combustion chamber. Both cycles include recycling loops and carbon dioxide purification sections. These novel cycles reduce the cost for power generation with complete CO2 capture and sequestration with nearly zero emission. In this paper, The NetPower and Supercritical CES Cycles are investigated by means of process simulation and the technologies and utilised facilities compared using sensitivity analysis. Both cycles are simulated with Aspen Plus software with the same initial conditions, and the simulation results are compared with IEA 2015 report for validation. The sensitivity of both cycles are analysed with respect to the Turbine Inlet Temperature (TIT), Combustion Outlet Pressure (COP) and Heat Exchanger Approach Temperature (HET). The efficiencies are extracted for both the NetPower and CES cycles, and partial load behaviour of the cycles are investigated. The initial results show that the NetPower cycle is more sensitive to the Turbine Inlet Temperature (TIT) variations in comparison with S-CES cycle. The results of this paper provide a platform for a comprehensive techno-economical and sensitivity analysis of the NetPower and Supercritical CES Cycles as the leading Oxy-combustion power cycles with full carbon capture.

Thermodynamic analysis of a novel oxy-combustion supercritical carbon dioxide power cycle integrating solar-driven coal gasification

To advance the utilization of both coal resources and solar energy, a novel oxy-combustion supercritical carbon dioxide (sCO2) power cycle with solar-driven coal gasification integration was proposed and analyzed. In the proposed system, the concentrated solar energy is utilized for coal gasification to produce syngas for oxy-combustion to drive sCO2 power cycle with near-zero emission and the heat from air separation and hot syngas is recovered for coal drying, steam generation and sCO2 heating in a cascade way. Through introducing solar heat for coal gasification, the raw coal consumption is reduced and the oxygen production process can be eliminated, leading to a higher net system efficiency. The oxy-combustion power cycle can also be simplified owing to the better matching between the process waste heat and the steam generation for gasification. Detailed thermodynamic analysis showed that, the proposed system can save 28.3% of coal consumption with the net efficiency improvement of 1.6 percentage points, compared with the reference system. The solar-to-electricity efficiency can also reach as high as 23.3%.

Correction: Conceptual design and analysis of ITM oxy-combustion power cycles.

Correction for 'Conceptual design and analysis of ITM oxy-combustion power cycles' by N. D. Mancini et al., Phys. Chem. Chem. Phys., 2011, 13, 21351-21361.

Oxy-fuel Turbo Machinery Development for Energy Intensive Industrial Applications

Abstract Through the support of the US Department of Energy, Clean Energy Systems, Inc. and its development partners have designed, manufactured, and tested and industrial-scale oxy-fuel turbine, suitable for applications in oxy-combustion power cycles that capture greater than 99% of produced carbon dioxide. To save on development cost and schedule, a used industrial gas turbine, an SGT-900 811/12 engine, was purchase, disassembled and inspected, then retro-fitted to act as an intermediate-pressure, hot gas expander. Also, the engine's air-breathing combustors were converted into oxy-fuel reheaters to boost turbine inlet temperatures and therefore, cycle efficiencies. A dedicated test rig was designed, fabricated, instrumented, and installed at an existing test facility to demonstrate reheater performance prior to install and operations within the oxy-fuel turbine. Component test results prove the feasibility of gas turbine conversion to oxy-fuel turbine, however further testing is recommended to further verify performance at higher power levels, and longer durations.

Integration of thermal desalination methods with membrane-based oxy-combustion power cycles

A large number of resources are dedicated to seawater desalination and will only grow as worldwide water scarcity increases. Seawater desalination methods, in particular thermal desalination methods, are highly energy intensive and are associated with CO2-emitting electricity production. The purpose of this article is to investigate the integration of thermal desalination methods with carbon capture and sequestration (CCS) electricity production in order to implement emissions-free thermal desalination facilities. Specifically, the advanced zero emissions plant (AZEP) oxy-combustion concept is utilized for integration in this study. The performance of several bottoming cycle integrations coupled to multi-effect distillation (MED) with and without thermal vapor compression (TVC) is estimated in order to evaluate the thermodynamic and economic feasibility of such power and water emissions-free plants. It is found that AZEP plants could utilize industry-standard dual-purpose technology and produce water near typical power-to-water ratios as compared to dual-purpose plants without CCS.

Ion transport membrane reactors for oxy-combustion–Part II: Analysis and comparison of alternatives

In order to design ITM-based oxy-combustion power cycles, various reactor engineering analyses must be conducted with detailed modeling and simulation. An intermediate-fidelity ITM model is used to explore the dependence of ITM performance on reactor geometric structure, flow configuration, operating conditions, membrane material properties, and uncertainty in key modeling assumptions, such as the dominant fuel conversion mechanism. Many operational constraints are presented that are usually overlooked by black-box modeling strategies, and the implications of these constraints are explored. Further, a comparison is made between reactive and separation-only ITMs to assess the relative merits and disadvantages of each. The results show that although a reactive ITM significantly improves the partial pressure driving force, practical reactor engineering considerations indicate that this concept is not superior to counter-current separation-only ITMs, mainly because of the stringent temperature limitations of the membrane material. A Second Law assessment of certain ITM configurations is performed to evaluate the potential of ITM technology to reduce the air separation penalty, and to provide insight for effective systems-level integration. Overall, the results of our analyses capture the essential characteristics of ITM air separation systems for power cycles, and enable detailed systems-level studies to be performed.

Conceptual design and analysis of ITM oxy-combustion power cycles

Ion transport membrane (ITM)-based oxy-combustion systems could potentially provide zero-emissions power generation with a significantly reduced thermodynamic penalty compared to conventional carbon capture applications. This article investigates ITM-based oxy-combustion power cycles using an intermediate-fidelity model that captures the complex physical coupling between the two systems and accurately accounts for operational constraints. Coupled ITM-cycle simulation reveals hidden design challenges, facilitates the development of novel cycle concepts, and enables accurate assessment of new and existing power cycles. Simulations of various ITM-based zero and partial-emissions power cycles are performed using an intermediate-fidelity ITM model coupled to power cycle models created in ASPEN Plus®. The objectives herein are to analyze the prevalent ITM-based power cycle designs, develop novel design modifications, and evaluate the implementation of reactive ITMs. An assessment of the potential for these ITM power cycles to reduce both the thermodynamic penalty and reactor size associated with ITM air separation technology is conducted. The power cycle simulation and analysis demonstrate the various challenges associated with implementing reactive ITMs; hybridization (the use of both reactive and separation-only ITMs) is necessary in order to effectively utilize the advantages of reactive ITMs. The novel hybrid cycle developed herein displays the potential to reduce the size of the ITM compared to the best separation-only concept while maintaining a comparable First Law efficiency. Next, the merit of implementing partial-emissions cycles is explored based on a proposed linear-combination metric. The results indicate that the tradeoff between the main thermodynamic performance metrics efficiency and CO(2) emissions does not appear to justify the use of partial-emissions cycles.