Supercritical Coal-fired Power Plant Research Articles

Environmental, technological, and economic analysis of supercritical coal-fired power system.

Developing countries primarily rely on fossil-based energy sources to meet their energy demands. The use of fossil fuels has several adverse environmental repercussions that damage the biosphere both directly and indirectly. Among fossil fuels, coal brings about the heaviest environmental externalities, yet its abundance makes its use widespread, particular in countries having significant power generation deficits, such as Pakistan. This study presents an environmental, technological, and economic analysis of a supercritical coal-based power unit located in Pakistan and used for electricity generation. For environmental assessment, the CML-1A baseline method in OpenLCA software was used, and eight midpoint impact indicators were selected. The functional unit chosen was 1 MWh of generated electricity. The results indicated that the category of ozone layer depletion has the least impact, whereas global warming potential has the highest impact score. Except for photochemical oxidation and human toxicity, the plant operational stage dominated most of the selected impact categories. The current paper also reveals that the removal efficiency of CO2 and other pollutants is higher in supercritical compared to subcritical plants. Moreover, the economic feasibility of supercritical plant is compared with chemical looping combustion (CLC)-based supercritical coal-fired power plant, and results shows that CLC-based coal-fired power plant is a more competitive and environmentally friendly option. The utilization of a scientific cleaner energy-management system in real-time, as exemplified in this study, may facilitate the development of a optimalpolicy framework that encouragesfor the adoption of cleaner coal power generation in developing countries, ultimately resulting in improved energy sustainability. Furthermore, this paper also presents some policy implications which could be helpful for policymakers, researchers, and industrialists to improve the sustainability of energy in emerging economies.

Economic Assessment of Coal-Fired Power Unit Decarbonization Retrofit with High-Temperature Gas-Cooled Reactors

To mitigate global warming, phasing out coal in the global energy system orderly and rapidly is an important near-term strategy. However, the majority of coal-fired plants in China have operated for less than 15 years. Accelerated coal power plant retirements would lead to substantial asset stranding. Coal-to-nuclear (C2N) technology offers a potential solution by replacing coal boilers in existing coal-fired plants with nuclear reactors. In this study, the G4-ECONS model was used to assess the economics of repowering a 600 MW supercritical coal-fired power plant with two 272 MWe high-temperature gas-cooled reactors. The timeline for the C2N project and the additional cost of dispatching electricity from the grid during retrofitting were discussed. Results showed that the C2N total capitalized costs are 19.4% (baseline estimate, USD 5297.6/kW) and 11.1% (conservative estimate, USD 5847.2/kW) lower than the greenfield project (USD 6576.5/kW), respectively. And C2N projects need to reduce LUEC by at least 20% to become competitive. This study can inform engineering design decisions leading to more precise and cost-effective C2N projects.

Thermal energy storage integration for increased flexibility of a power plant with post-combustion CO2 capture

Flexible operation of thermal power plants will become increasingly relevant in the coming years. This work evaluates the effect of integrating a steam accumulator into a 598 MW supercritical coal-fired power plant with moving bed temperature-swing adsorption CO2 capture. Charging the accumulator with reheat steam from the turbine train can reduce the net power output by up to 1.4 % (8.2 MW) for around 200 min. Small charging flow rates are recommended to maximize the final pressure of the accumulator. Covering the sorbent regeneration duty and meeting the demand of two feedwater heaters were considered as alternatives for discharging of the accumulator. Thermal storage discharging was found to give relative power plant load increases between 1.7 and 11.2 % (10.2–66.9 MW) for up to 37.5 min, which exceeds the requirement for primary reserve. Increases in the electrical energy output of 10.5–11 MWh were achieved. The flexibility modes studied in this work are compatible with high CO2 recovery rates.

Review of SCWR research in Japan

SCWR (supercritical water cooled reactor) is one of the Generation IV reactors. This review summarizes the results of SCWR design concept development through numerical simulations carried out by the author-led team at the University of Tokyo and Waseda University from 1989 to 2014. They are core design, subchannel analysis, statistical thermal design, fuel rod design, development of fuel integrity criteria, plant system and heat balance, plant dynamics analysis, plant control, startup system, stability analysis, safety principle, safety criteria, safety analysis, transient subchannel analysis and fast reactor SCWR. A brief summary of experimental results on thermal hydraulics, materials and water chemistry follows. Discussion includes SCPR study by Japanese BWR manufacturers, comments on the 2005 INEEL SCWR report, misconceptions about SCWR and commercialization challenges. The SCWR is an innovation in light water reactors based on supercritical coal-fired power plant technology that has been in use worldwide for over half a century. This review covers most of the SCWR design and analysis. For researchers, it is a good subject to understand the design and analysis of light water reactors.

Performance of Na-Ru/Al2O3 dual function material for integrated CO2 capture and methanation with the presence of coal ashes

Integrated Capture and Methanation of CO2 (ICCM) with H2 produced from renewable energy is a novel Power-to-Gas technology. The combination of ICCM with CO2 point source, such as coal-fired power plant, is anticipated, which greatly motivates the investigations into the influences of coal ash on the key performance of dual function material (DFM) used in ICCM process. Via the experimental study on the coal ash impacts, this work explored the adaptability of DFM and ICCM to coal-fired power plant. Na-Ru/Al2O3 DFM and two ashes collected from the electrical precipitators of supercritical coal-fired power plants were used for experiments. It showed that fly ashes contaminated CO2 adsorbents and active sites of DFMs, and caused successive drops in carbonates conversion and CH4 selectivity upon cyclic ICCM reactions. The CO2-TPD and H2-TPSR tests revealed that the declined supplycapability of hydrogen atoms by Ru sites, and the increased rate gap between CO formation and the following CO hydrogenation were responsible for the declined methanation ability of ash-contaminated DFMs. The roles of SiO2 and Fe2O3 phases in ashes were identified, indicating that SiO2 reacted with adsorbent components and masked Ru sites, and then induced DFM deactivation by affecting the transport processes of key reactants; Fe2O3 successively invaded both Ru sites and Na2CO3/γ-Al2O3 interface, leading to successive losses in methanation ability and CO2 desorption capacity with cyclic ICCM reactions.

One-Step Ahead Control Using Online Interpolated Transfer Function for Supplementary Control of Air-Fuel Ratio in Thermal Power Plants

Recently, the environmental problem has become a global issue. The air to fuel ratio (AFR) in the combustion of thermal power plants directly influences pollutants and thermal efficiency. A research result was published showing that the AFR control performance of thermal power plants can be improved through supplementary control using dynamic matrix control (DMC). However, online optimization of DMC needs an extra computer server in implementation. This paper proposes a practical AFR control with one-step ahead control which does not use online optimization and can be implemented directly in existing distributed control system (DCS) of thermal power plants. Closed-loop transfer function models at three operating points are independently developed offline. Then, an online transfer function using interpolation of offline models is applied at each sampling step. A simple one-step ahead control with online transfer function is applied as a supplementary control of AFR. Simulations with two different type power plants, a 600 MW oil-fired drum-type power plant and a 1000 MW ultra supercritical (USC) coal-fired once-through type power plant, are performed to show the effectiveness of the proposed control structure. Simulation results show that the proposed supplementary control can effectively improve the conventional AFR control performance of power plants.

Generation of allowable stress for indigenously developed 304HCu Stainless steel

The 304HCu stainless steel (SS) is the candidate material for reheater and superheater tubes in Advanced Ultra Supercritical (AUSC) coal-fired power plants of India. In the present study, the creep design data have been generated for indigenously developed 304HCu SS using the creep properties (creep strain and the rupture life) and tensile properties available at the temperatures 923 K, 973 K and 1023 K. The time dependent allowable stresses were obtained for the above steel according to the stress criteria specified in ASME Section III Division 5 Subsection HB. The allowable stresses were also derived in the creep as well as non-creep regimes as per the guidelines in ASME Section IID. In both the cases, the maximum allowable stress at each temperature was dictated by the stress to cause rupture. The allowable stress determined as per Section IID was the same as that estimated according to section III.5 HB for creep exposure of 100,000 h. Further, it must be mentioned that, at the temperature range 923–1023 K, the indigenously developed 304HCu SS possess allowable stresses that are in par with the corresponding values specified in ASME code case 2328–2.

Thermo-economic analysis for a novel grid-scale pumped thermal electricity storage system coupled with a coal-fired power plant

Combining pumped thermal electricity storage with existing thermal power plants can be a promising technical route for developing large-scale grid energy storage technologies for stably consuming renewable power. In this paper, a novel pumped thermal electricity storage system coupled with a supercritical coal-fired power plant is designed based on cascade heat storage. The thermodynamic analysis shows that the round-trip efficiency of the integrated system can reach 0.53–0.56 under 60–100% output load, for a practical design with a recuperation temperature of 280 °C and compressor outlet temperature of 500 °C. An economic analysis is performed and indicates this design can achieve a payback period of around 4 years considering a moderate charging electricity price of 3 ¢/kWh and a long storage period of 12 h. Further decreasing the recuperation temperature and increasing the compressor outlet temperature can reduce the system investment cost and LCOE, while it requires technological advancement of molten salts working at a wider temperature range and more robust compressors. In comparison to the integrated system with conventional two-tank storage, as well as other storage systems like vanadium redox flow batteries, the current design has a more attractive cost and can be scaled up in future multi-energy applications.

Retrofitting coal-fired power plants for grid energy storage by coupling with thermal energy storage

• Thermal storage is coupled with coal-fired power plant for grid energy storage. • The coupled plant has higher efficiency than the original one at low load. • Investment is greatly reduced using existing facilities of coal-fired power plant. • Levelized cost of electricity shows advantage with storage period less than 10 h. Grid energy storage is key to the development of renewable energies for addressing the global warming challenge. Although coal-fired power plant has been coupled with thermal energy storage to enhance their operational flexibility, studies on retrofitting coal-fired power plants for grid energy storage is lacking. In this work, molten salt thermal energy storage is integrated with supercritical coal-fired power plant by replacing the boiler. Electric resistive heating is applied for the charging process using curtailed electricity or during periods with low grid demand. During discharging, the heat stored in the molten salt is exchanged to steam for electricity generation. A techno-economical analysis is performed on the coupled system and compared with other grid energy storage technologies. Results show that the integrated plant has higher thermal efficiency than the original coal-fired power plant, especially at low load for peak shaving purpose, which is due to the less exergy loss by avoiding the exhausted flue gas and the large temperature difference of heat transfer in boiler of the original plant. At full load, the round-trip efficiency of the integrated plant is ∼ 41.8 %. Although this efficiency is lower than other energy storage technologies, the levelized cost of electricity of the integrated plant is generally lower due to the reduction in initial investment utilizing existing infrastructures of coal-fired power plants. With longer discharging duration (≥10 h), the integrated system shows a similar levelized cost of electricity as that of compressed air energy storage. Replacing the boiler with thermal energy storage would also greatly reduce the CO 2 emission and various pollutants from coal combustion.

Energy and Exergy Analysis of a Coal-Fired Supercritical Power Plant

Yenilenebilir enerji kaynaklarıyla elektrik üretimi üzerine araştırmalar hızlı bir şekilde ilerlese de fosil yakıtlarla elektrik üretiminin hem dünyada hem Türkiye’de uzun bir süre daha sürmesi beklenmektedir. Hem çevrede oluşturduğu zararlı etkiler hem de tükenme riskinin yüksek olması, fosil yakıtların termik santrallerde verimli bir şekilde tüketilmesini zorunluluk haline getirmiştir. Fosil yakıtın bir türü olan kömür, elektrik üretmek amacıyla termik santrallerde yaygın olarak kullanılmaktadır. Kömür yakıtlı termik santrallerde kullanılan kazan, süper kritik bir kazan seçildiğinde santral verimi artırılabilir. Bu çalışmada Zonguldak ilinde bulunan Eren Enerji’ye ait kömür yakıtlı süper kritik termik santralin termodinamik performansı, enerji ve ekserji analiz metotlarıyla incelenmiştir. Santralde bulunan her bir elemana ait enerji kayıpları ve tersinmezlikler hesaplanmıştır. Enerji analizi, kömürün kimyasal enerjisinin %48.5’inin kondenserde soğutma suyuna aktarıldığını; ekserji analizi ise kömürün kimyasal ekserjisinin %49.2’sinin kazanda yok edildiğini göstermiştir. Santralin enerji verimi %33.65, ekserji verimi ise %31.42 olarak hesaplanmıştır.

Effect of Ta addition on solidification microstructure and element segregation of IN617B nickel-base superalloy

IN617B nickel-base superalloy is considered as a good candidate material in 700 °C advanced ultra- supercritical coal-fired power plants. The effect of Ta addition on solidification microstructure and element segregation of IN617B alloy was investigated by OM, SEM, TEM, EDS, EPMA and thermodynamic calculation. The results showed that the solidification microstructure exhibited a dendritic segregation pattern with many primary carbides distributed in interdendritic regions, such as network M6C, lath M23C6 and granular Ti(C,N). The addition of Ta promoted the precipitation of Ta-rich MC significantly inhibiting the precipitation of M6C and M23C6, and reduced the segregation degree of Al, Mo and Ti alloying elements. The addition of Ta decreased the melting temperature of MC carbide, but did not impact the solidification path, that was, L→ γ matrix → MC or Ti(C,N) → M6C → M23C6, where MC and Ti(C,N) tended to form symbiotic microstructure with M6C. This study will provide theoretical basis and data support for the alloy optimization and casting structure control of IN617B nickel-based superalloy.

Optimal scheduling of supercritical coal-fired power plant integrated with CO2 capture process considering solvent storage

The deployment of lean/rich solvent storage devices within the solvent-based carbon capture process provides an effective way to upgrade the flexibility of the integrated power plant-CO2 capture process, especially in the scenarios with strict carbon emission requirements. This paper provides an optimal scheduling strategy to fully exploit the roles of solvent storage within the supercritical coal-fired power plant integrated with CO2 capture process, so that the net operating profits of the plant can be maximized. System economy, capacity of carbon emission reduction and operating flexibility are then analyzed through comparison with the same system without using the solvent storage equipment under two different operating modes. The results show that the system considering solvent storage has outstanding economic advantages: it can achieve better carbon emission reduction performance under the flexible carbon capture level mode; and can greatly improve the flexibility in power generation under the fixed carbon capture level mode.

Multi-Attribute Rating Method for Selecting a Clean Coal Energy Generation Technology

The process of technology management contains various stages, such as the identification, selection, acquisition, implementation, and maintenance of technologies. In the case of power generation companies, a key aspect of the selection stage is the choice of generation technologies for newly commissioned units. The investment decision depends on many factors, primarily economic, environmental, social, technological, and legal, and represents a complex multi-criteria problem. Currently, the decision is further complicated by the often unpredictable tightening of environmental standards, forcing the closure of conventional sources, on which many countries have so far based their energy security. The paper analyzes the problem of choosing one of the so-called clean coal technologies to be implemented in conditions of transformation of the power sector. In this paper, five selected clean coal technologies are characterized, and the SMART method is adopted to technology selection. The following technologies were considered: supercritical coal-fired power plant (with and without CCS), IGCC power plant (with and without CCS), and IGCC power plant with CCS and integrated hydrogen production. Nine practical criteria (in three main groups: environmental, technological, economic) for comparing technologies are defined, computational experiments performed, and conclusions from the research presented. The work was based on the literature study of multi-criteria decision support and an analysis of power sector needs based on the example of the Polish power sector. The conducted research, apart from the technology recommendation, led to the conclusion that the chosen method may be applied to decision-making in the field of power generation technology management. The study also indicated the potential direction of the development of a power generation structure in a situation where a component of ensuring energy security is the use of available coal fuels.

Safety and thermal efficiency performance assessment of solar aided coal-fired power plant based on turbine steam double reheat

A novel system of solar double reheat hybrid with coal-fired power plant is proposed in this study. Solar energy is employed to reheat the exhaust steam from intermediate-pressure turbine for raising inlet steam temperature of low-pressure turbine. Solar double reheat hybrid with a N600–24.2/566/566 supercritical coal-fired power plant is investigated. An all-condition mechanism model of the hybrid system is proposed and simulated by MATLAB/Simulink in both power-boosting mode and fuel-saving mode. The heat-resistant temperature limit and maximum permissible steam velocity of the low-pressure turbine are discussed in view of turbine safety. According to the simulation results, the maximum solar energy input for safe operation of the turbine is determined as 24,952 kW and 23,486 kW in the power-boosting mode and fuel-saving mode, respectively. Both the solar-to-electricity efficiency and the standard coal saving rate increase with the increase of solar energy input, but decrease with the increase of unit load. Moreover, the solar-to-electricity efficiency of the hybrid system in the fuel-saving mode is generally 2–3% higher than that in the power-boosting mode. In the fuel-saving mode, the highest solar-to-electricity efficiency of 35.17% and standard coal saving of 19.14 g/kWh are obtained with solar energy input of 23,486 kW under 40%THA for the hybrid system. Finally, operation suggestions of the hybrid system are proposed for a higher solar-to-electricity efficiency of solar energy.

Numerical investigation of 660 MW pulverized coal-fired supercritical power plant retrofitted to oxy-coal combustion

A detailed investigation of the oxy-fuel combustion-based CCS consisting of air separation unit (ASU), supercritical boiler parameters and CO2 compression and purification unit (CPU) has been performed. A 660 MW supercritical power plant retrofitted to oxy-coal combustion has been simulated and analysed to investigate the operational characteristics of the oxy-coal combustion process by employing the process simulation tool Aspen plus. Moreover, the effect of important design parameters such as oxygen concentration of the oxidant, recycle ratio and purity of oxygen produced by ASU on the composition of flue gas, auxiliary power consumptions, CO2 recovery rate, CO2 product purity, and specific energy consumptions of O2 and CO2 has also been studied. The comparison of simulation results of the oxy-coal combustion and conventional air-fired combustion atmosphere has been presented. The excellent performance of oxy-coal combustion power plant has been observed in term of its ability to capture carbon dioxide with 95 % purity and 96 % recovery rate. The net efficiency of oxy-coal combustion power plant reduces by 10.4 % compared to the convention air-fired power plant.

Simultaneous parametric optimization for design and operation of solvent-based post-combustion carbon capture using particle swarm optimization

High investment and operating costs are two barriers hindering the commercial deployment of solvent-based post combustion CO2 capture (PCC) technology in power industry. Since upstream power plants are always in flexible operation, conventional approaches which carry out the design based on a fixed condition fail to achieve the best overall performance. To this end, this paper proposes a simultaneous size and operation parameters optimization strategy for the PCC process, in which the flexible operation of the CFPP is taken into account during the design stage. The technique of particle swarm optimization (PSO) is used in a hierarchical manner to find the design and operating conditions of the PCC with minimal total annualized cost. To further explore the optimization potential, the average CO2 capture level in one day is taken as the environmental constraint rather than the conventional instantaneous one. The proposed approach is tested on the PCC design for an existing 660 MW supercritical coal-fired power plant. The optimization results of four different design approaches are compared with the economic, efficiency and environmental (3E) performance being fully assessed. The simulation results show that by using the proposed optimization method, 14.45% reduction in TAC can be attained compared with the conventional approach.

Exergy and exergo-environmental analysis of a 660 MW supercritical coal-fired power plant

This paper presents the exergy and exergo-environmental analysis of the 660 MW supercritical coal-fired unit situated in western India. The study is based upon the SPECO approach, which is followed in the case of exergoeconomic analysis. The proposed research includes evaluating values of exergy of each stream, using F and P principal to find out exergy of fuel, the product of each component, and its exegetic efficiency. It further includes allocation of Eco-indicator 99 assessment grading values to perform life cycle assessment of each component, solving simultaneous equations by suitable solver formed from the environmental impact of components to calculate the exergo-environmental factor of each stream. The exergy efficiency obtained for the supercritical unit is 35.54%. The effect of variation of exergetic efficiency with an inlet pressure of high-pressure turbine for major components is studied. The major components such as steam generator, high-pressure turbine, intermediate-pressure turbine, low-pressure turbine, condensate extraction pump, and boiler feed pump exhibit higher exergetic efficiency at 247 bar. An increase in environmental impact in the exergy flows has been identified for components with having heat, work or fuel at the inlet. The cooling water used in condenser and flues gases exhausted from the supercritical power plant represent the environmental impact rate per unit electricity generated of 2.89 and 3.689 mPts kWh−1. The electricity generated had an environmental impact rate of 39.71 mPts kWh−1. The environmental impact per unit of electricity generated for 660 MW supercritical power plant is evaluated as 46.29 mPts kWh−1. The result obtained from semi-empirical model for environmental impact per unit of electricity is validated by comparing with subcritical and ultra-critical coal-fired power plant. The supercritical coal-fired power plant is proved to be better technology as compared with subcritical coal-fired power plant. The exergo-environmental variable for the steam generator offers high potential to reduce environmental impact by introducing an exhaust gas treatment unit.

Thermodynamic Analysis of a 500MWe Coal-fired Supercritical Power Plant with CO2 Capture Integrated with Kalina Cycle for Combined Cooling and Power

Thermodynamic Analysis of a 500MWe Coal-fired Supercritical Power Plant with CO2 Capture Integrated with Kalina Cycle for Combined Cooling and Power

Thermodynamic analysis of a 500 MWe coal-fired supercritical power plant with CO2 capture integrated with Kalina cycle for combined cooling and power

Thermodynamic analysis of a 500 MWe coal-fired supercritical power plant with CO2 capture integrated with Kalina cycle for combined cooling and power

Techno-economic evaluation of different operating scenarios for indigenous and imported coal blends and biomass co-firing on supercritical coal fired power plant performance

Pakistan has enormous coal and biomass resources, however, it imports coal from other parts of the world. Whereas, utilization of indigenous coal and biomass may be beneficial for the economy and local energy security. Hence, this study focuses on the likely effects of using coal blends and biomass co-firing with indigenous and imported coal on the performance of a supercritical power plant. A coal fired power plant is modeled using Aspen plus. Three different case studies are considered, which are; constant heat input (CHI), constant fuel input (CFI), and constant Reynold number (CRN). Conclusively, coal blending has resulted in reduced emissions than the use of low rank coal. Further, biomass co-firing has shown reduced emissions. For the CHI case, efficiency remains the same for all fuels. The highest efficiency in the CFI case is for South African coal and the lowest is for biomass. In the CRN case, South African coal has maximum efficiency while Thar coal has the minimum efficiency. Moreover, economic analysis of this study proposes that native resources must be used, provided the technical issues have resolved. Therefore, this study resulted in the comparison and applicability of different coal blends and renewable biomass fuel in a coal fired power plant.