An Innovative Elasto-Hydrodynamic Seal Concept for Supercritical CO2 Power Cycles

2021 ◽  
Author(s):  
Sevki Cesmeci ◽  
Rubayet Hassan ◽  
Mohammad Fuad Hassan ◽  
Ikenna Ejiogu ◽  
Matthew DeMond ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
Power Plants ◽  
Operating Conditions ◽  
Potential Candidate ◽  
Proof Of Concept ◽  
Next Generation ◽  
Shaft Seal ◽  
Power Cycles ◽  
Concept Study ◽  
Seal Design

Abstract Supercritical CO2 (sCO2) power cycles are promising next generation power technologies, holding a great potential in fossil fuel power plants, nuclear power production, solar power, geothermal power, and ship propulsion. To unlock the potential of sCO2 power cycles, technology readiness must be demonstrated on the scale of 10–600 MWe and at sCO2 temperatures and pressures of 350–700 °C and 20–30 MPa for nuclear industries. Amongst many challenges at the component level, the lack of suitable shaft seals for sCO2 operating conditions needs to be addressed for the next generation nuclear turbine and compressor development. In this study, we propose a novel Elasto-Hydrodynamic (EHD) high-pressure, high temperature, and scalable shaft seal for sCO2 turbomachinery that offers low leakage, minimal wear, low cost, and no stress concentration. The focus in this paper was to conduct a proof-of-concept study with the help of physics-based computer simulations. The results showed that the proof-of-concept study was successfully demonstrated, warranting further investigation. Particularly, it was interesting to note the quadratic form of the leakage rate, making its peak of m ˙ = 0.075 kg/s at Pin = 15 MPa and then decaying to less than m ˙ = 0.040 kg/s at Pin = 30 MPa, suggesting that the proposed seal design could be tailored further to become a potential candidate for the shaft seal problems in sCO2 turbomachinery.

Evaluation of Property Methods for Modeling Direct-Supercritical CO2 Power Cycles

2017 ◽  
Author(s):  
Charles W. White ◽  
Nathan T. Weiland
Keyword(s):  
Oil Recovery ◽  
Supercritical Co2 ◽  
Power Plants ◽  
Physical Property ◽  
Aspen Plus ◽  
Cost Effective ◽  
Operating Conditions ◽  
Cycle Performance ◽  
Working Fluid ◽  
Power Cycles

Direct supercritical CO2 (sCO2) power cycles have received considerable attention in recent years as an efficient and potentially cost-effective method of capturing CO2 from fossil-fueled power plants. These cycles combust natural gas or syngas with oxygen in a high pressure (200–300 bar), heavily-diluted sCO2 environment, such that the fluid entering the turbine is 90–95% CO2, with the balance composed primarily of H2O, CO, O2, N2 and Ar. After recuperation of the turbine exhaust thermal energy, water is condensed from the cycle, and the remainder is recompressed for either return to the combustor or for enhanced oil recovery (EOR) or storage. The compression power requirements vary significantly, depending on the proximity of the operating conditions to the CO2 critical point (31 °C, 73.7 bar), as well as to the level of working fluid dilution by minor components. As this has a large impact on cycle and plant thermal efficiency, it is crucial to correctly capture the appropriate thermo-physical properties of these sCO2 mixtures when carrying out performance simulations of direct sCO2 power plants. These properties are also important to determining how water is removed from the cycle, and for accurate modeling of the heat exchange within the recuperator. This paper presents a quantitative evaluation of ten different property methods that can be used for modeling direct sCO2 cycles in Aspen Plus®. REFPROP is used as the de facto standard for analyzing indirect sCO2 systems, where the closed nature of the cycle leads to a high purity CO2 working fluid. The addition of impurities due to the open nature of the direct-sCO2 cycle, however, introduces uncertainty to the REFPROP predictions. There is a limited set of mixtures available for which REFPROP can be reliably used and there are a number of species present in a coal-fired direct-fired sCO2 cycle that REFPROP cannot accommodate. Even with a relatively simplified system in which the trace components are eliminated, simulations made using REFPROP require computation times that often preclude its use in parametric studies of these cycles. Consequently, a series of comparative analyses were performed to identify the best physical property method for use in Aspen Plus® for direct-fired sCO2 cycles. These property methods are assessed against several mixture property measurements, and offer a relative comparison to the accuracy obtained with REFPROP. This study also underscores the necessity of accurate property modeling, where cycle performance predictions are shown to vary significantly with the selection of the physical property method.

scholarly journals Evaluation of Property Methods for Modeling Direct-Supercritical CO2 Power Cycles

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Charles W. White ◽  
Nathan T. Weiland
Keyword(s):  
Power Plants ◽  
Physical Property ◽  
Aspen Plus ◽  
Cost Effective ◽  
Operating Conditions ◽  
Working Fluid ◽  
Power Cycles ◽  
As Species ◽  
Cost Effective Method ◽  
Open Nature

Direct supercritical carbon dioxide (sCO2) power cycles are an efficient and potentially cost-effective method of capturing CO2 from fossil-fueled power plants. These cycles combust natural gas or syngas with oxygen in a high pressure (200–300 bar), heavily diluted sCO2 environment. The cycle thermal efficiency is significantly impacted by the proximity of the operating conditions to the CO2 critical point (31 °C, 73.7 bar) as well as to the level of working fluid dilution by minor components, thus it is crucial to correctly model the appropriate thermophysical properties of these sCO2 mixtures. These properties are also important for determining how water is removed from the cycle and for accurate modeling of the heat exchange within the recuperator. This paper presents a quantitative evaluation of ten different property methods that can be used for modeling direct sCO2 cycles in Aspen Plus®. Reference fluid thermodynamic and transport properties (REFPROP) is used as the de facto standard for analyzing high-purity indirect sCO2 systems, however, the addition of impurities due to the open nature of the direct sCO2 cycle introduces uncertainty to the REFPROP predictions as well as species that REFPROP cannot model. Consequently, a series of comparative analyses were performed to identify the best physical property method for use in Aspen Plus® for direct-fired sCO2 cycles. These property methods are assessed against several mixture property measurements and offer a relative comparison to the accuracy obtained with REFPROP. The Lee–Kessler–Plocker equation of state (EOS) is recommended if REFPROP cannot be used.

scholarly journals Smart material concept: reversible microstructural self-regeneration for catalytic applications

2016 ◽  
Vol 4 (30) ◽  
pp. 11939-11948 ◽  
Author(s):  
Dariusz Burnat ◽  
Roman Kontic ◽  
Lorenz Holzer ◽  
Patrick Steiger ◽  
Davide Ferri ◽  
...  
Keyword(s):  
High Temperature ◽  
Smart Material ◽  
Solid Oxide ◽  
Proof Of Concept ◽  
Next Generation ◽  
Concept Study ◽  
Gas Processing ◽  
Electro Catalysis ◽  
Catalytic Applications ◽  
Material Concept

This paper presents a proof-of-concept study and demonstrates the next generation of a “smart” catalyst material, applicable to high temperature catalysis and electro-catalysis such as gas processing and as a catalyst for solid oxide cells.

scholarly journals Corrosion and Erosion Behavior in Supercritical CO2 Power Cycles

2014 ◽  
Author(s):  
Darryn Fleming ◽  
Alan Kruizenga ◽  
James Pasch ◽  
Tom Conboy ◽  
Matt Carlson
Keyword(s):  
Carbon Dioxide ◽  
Stainless Steel ◽  
Intergranular Corrosion ◽  
Supercritical Co2 ◽  
Power Production ◽  
Operating Conditions ◽  
Working Fluid ◽  
Power Cycles ◽  
Power Cycle ◽  
Potential Issue

Supercritical Carbon Dioxide (S-CO2) is emerging as a potential working fluid in power-production Brayton cycles. As a result, concerns have been raised regarding fluid purity within the power cycle loops. Additionally, investigations into the longevity of the S-CO2 power cycle materials are being conducted to quantify the advantages of using S-CO2 versus other fluids, since S-CO2 promises substantially higher efficiencies. One potential issue with S-CO2 systems is intergranular corrosion [1]. At this time, Sandia National Laboratories (SNL) is establishing a materials baseline through the analysis of 1) “as received” stainless steel piping, and 2) piping exposed to S-CO2 under typical operating conditions with SNL’s Brayton systems. Results from ongoing investigations are presented. A second issue that SNL has discovered involves substantial erosion in the turbine blade and inlet nozzle. It is believed that this is caused by small particulates that originate from different materials around the loop that are entrained by the S-CO2 to the nozzle, where they impact the inlet nozzle vanes, causing erosion. We believe that, in some way, this is linked to the purity of the S-CO2, the corrosion contaminants, and the metal particulates that are present in the loop and its components.

Impact of Plant Siting on Performance and Economics of Indirect Supercritical CO2 Coal Fired Power Plants

2021 ◽  
Author(s):  
Sandeep R. Pidaparti ◽  
Charles W. White ◽  
Nathan T. Weiland
Keyword(s):  
Supercritical Co2 ◽  
Optimization Design ◽  
Power Plants ◽  
Waste Heat ◽  
The United States ◽  
Attractive Alternative ◽  
Plant Design ◽  
Power Cycles ◽  
The Impact ◽  
And Storage

Abstract Indirect-fired supercritical CO2 (sCO2) power cycles are being explored as an attractive alternative to steam Rankine cycles for a variety of heat sources including fossil, concentrated solar power (CSP), nuclear, waste heat, etc. Due to the near-ambient CO2 critical temperature of 31°C, the effects of ambient temperature on sCO2 power cycles performance are expected to be more significant than for steam Rankine cycles. This study presents the impact of plant siting on the performance and economics of coal-fired utility scale power plants based on indirect sCO2 power cycles with carbon capture and storage (CCS). Four different plant sites across the United States have been selected for investigation: Chicago, IL; Kemmerer, WY; Houston, TX; Knoxville, TN. For each plant site, local parameters such as design ambient conditions, coal type and prices, captured CO2 transportation and storage (T&S) costs are considered for the techno-economic analyses (TEA). To determine the optimum plant design for each location, two power cycle configurations (recompression cycle, partial cooling cycle with reheat) and two cooling technologies (dry and adiabatic cooling) are examined. The optimization was conducted using automated derivative-free optimization (DFO) algorithms available under NETL’s Framework for Optimization and Quantification of Uncertainty and Sensitivity (FOQUS) platform. The optimization design variables include parameters such as turbine inlet temperatures and pressure, sCO2 cooler outlet temperatures, recuperators approach temperature and pressure drop etc. The study demonstrates the variability in optimal plant design for different ambient and fuel input conditions. The results will be used in future sCO2 technology market analyses.

Development of a Heat Transfer Correlation for Supercritical CO2 Based on Multiple Data Sets

2012 ◽  
Author(s):  
Tiberiu Preda ◽  
Eugene Saltanov ◽  
Igor Pioro ◽  
Kamiel S. Gabriel
Keyword(s):  
Heat Transfer ◽  
Critical Point ◽  
Supercritical Water ◽  
Wall Temperature ◽  
Supercritical Co2 ◽  
Power Plants ◽  
Operating Conditions ◽  
Thermodynamic Efficiency ◽  
New Correlation ◽  
Multiple Data Sets

Currently, increase in thermodynamic efficiency of water-cooled Nuclear Power Plants (NPPs) can only be achieved by raising the coolant’s operating conditions above the supercritical point. The critical point of water is 22.06 MPa and 373.95°C, making supercritical water research very power-intensive and expensive. CO2 behaves in a similar manner once in the supercritical state, but at significantly lower pressure and temperature, since critical point of CO2 is 7.37 MPa and 30.98°C. The applications of supercritical CO2 research range from using it as a modelling fluid, to supercritical turbine applications in Liquid Metal Fast Breeder Reactors (LMFBRs), and use in a supercritical Brayton cycle. Therefore, it is of prime importance to model its behaviour as accurately as possible. For this purpose, experimental data of Koppel (1960), He (2005), Kim (2005) and Bae (2007) for CO2 were analyzed, and a new correlation was developed. The dataset consists of 1409 wall temperature points with pressures ranging from 7.58 to 9.58 MPa, mass fluxes from 419 to 1200 kg/m2s, and heat fluxes from 20 to 130 kW/m2. All runs take place in bare tubes of inner diameters from 0.948 to 9.00 mm in both vertical and horizontal configurations. The proposed correlation takes a wall-temperature approach to predicting the Nusselt number. This paper compares the new correlation with other work which has been done at the University of Ontario Institute of Technology by Mokry et al. (2009), as well as with correlations by Swenson et al. (1965) and Dittus-Boelter (1930). It was found that the new correlation has an overall RMS error of 13% for Heat Transfer Coefficient (HTC) values and 5% for calculated wall temperature values. The correlation can be used as a conservative approach to predict wall temperature values in Supercritical Water Reactor (SCWR) preliminary calculations, to predict heat transfer in secondary-loop turbine/ heat exchanger applications, as with the LMFBR, and to help validate scaling parameters used for water and other coolants.

scholarly journals T43. PREDNISOLONE VERSUS PLACEBO AS AUGMENTATION THERAPY IN PSYCHOTIC DISORDERS

2020 ◽  
Vol 46 (Supplement_1) ◽  
pp. S248-S248
Author(s):  
Nasib Lyliana ◽  
Inge Winter ◽  
Rene Kahn ◽  
Iris Sommer
Keyword(s):  
Treatment Period ◽  
Psychotic Disorder ◽  
Symptom Severity ◽  
Psychotic Disorders ◽  
Symptom Improvement ◽  
Potential Candidate ◽  
Proof Of Concept ◽  
Augmentation Therapy ◽  
Global Functioning ◽  
Concept Study

Abstract Background An increasing body of evidence suggests that immune dysregulation is involved in the pathophysiology of psychotic disorders. Some, but not all, anti-inflammatory drugs have shown positive effects on symptom severity. Given the need for new treatment options in psychosis, anti-inflammatory medication should be explored as a potential treatment to improve outcome. Being a potent glucocorticosteroid that adequately passes through the blood-brain barrier, prednisolone qualifies as a potential candidate. This proof-of-concept study aims to explore the effect of prednisolone, compared to placebo, on symptom severity in patients with a psychotic disorder who are on a stable dose of antipsychotic medication. Methods The study was conducted from July 2015 until April 2019 in four centers in the Netherlands and Belgium. Patients with a psychotic disorder were randomized, double blind, 1:1 to prednisolone or placebo in addition to their antipsychotic treatment. Patients randomized to prednisolone started with 40 mg/day, tapered down to zero in six weeks. Several procedures were implemented to ensure patient safety during prednisolone exposure (e.g. regular safety labs). The primary objective was to compare change in symptom severity, measured through the Positive and Negative Syndrome Scale (PANSS), in patients treated with prednisolone versus placebo, in additional to a stable antipsychotic regimen. To this end, a mixed model repeated measures ANOVA was applied. Results 42 participants were randomized, equally divided across the treatment arms. The six week treatment period was completed by 20 patients randomized to placebo and 19 patients randomized to prednisolone. There were no baseline differences in demographics, symptom severity, depression or global functioning between the treatment groups. There was no difference in symptom improvement between patients treated with prednisolone compared to placebo at the end of the six week treatment period (p=.304). Global functioning and depression were not significantly different between treatment arms end of treatment. No Serious Adverse Events (SAEs) occurred during the treatment phase. Discussion The results of this proof-of-concept study do not support the immune hypothesis of psychosis: there was no difference in symptom improvement after a six week treatment with prednisolone compared to placebo, in addition to a stable regimen of antipsychotics. The small sample size is the main limitation of this trial. Even though prednisolone did not show to be a potential candidate for augmentation therapy in psychosis, it is of interest to note that patients did not deteriorate when using prednisolone nor were there more SAE’s in the active treatment arm. This argues against the general safety concerns for prescribing prednisolone in patients with psychosis for the treatment of immune disorder, although additional research is needed.

Investigation of Magnetic Journal Bearing Instability Issues in Supercritical CO2 Turbomachinery

2019 ◽  
Author(s):  
Dokyu Kim ◽  
SeungJoon Baik ◽  
Jeong Ik Lee
Keyword(s):  
Supercritical Co2 ◽  
High Speed ◽  
Magnetic Bearing ◽  
Operating Conditions ◽  
Physical Contact ◽  
Analysis Model ◽  
Rotating Shaft ◽  
Power Cycles ◽  
Power Cycle ◽  
Lubrication Performance

Abstract With the increasing emphasis on reducing the CO2 emission while improving power generation efficiency, new power cycles are being developed. One of those promising power cycles is a supercritical CO2 (S-CO2) power cycle. To generate over 10MW electricity with S-CO2 power cycle, a magnetic bearing can be a good option for the hermetic type turbomachinery. However, from several studies on the magnetic bearing, the instability issues under high density fluid and high speed operating conditions were repeatedly mentioned. The instability in the magnetic bearing was observed to be related to the fluid conditions, mostly pressure and density. Because of this issue, the magnetic bearing sometimes cannot maintain enough clearance for the rotor leading to physical contact and consequently damaging the system. Thus, these instability issues should be thoroughly studied and be resolved for the successful and steady operation of the power system. The instability due to fluid force around the rotating shaft can be modeled with the Reynolds lubrication equation. The steady lubrication force analysis model is developed based on this equation. The model results imply that the lubrication performance is quite sensitive to the thermal condition of the CO2 especially density gradient around the shaft. Based on the modeling results, an experimental system is designed to investigate the issue. To study the instability issues experimentally, an impeller of the operating S-CO2 compressor is removed and the discharge line is blocked. Therefore, the main instability factor in this experiment will be the interaction between the rotor and the bearing only. The shaft position can be measured with inductive sensors. The forces exerted from the electromagnet is calculated from the electric current data which is applied by the controller. From these experimental data, the lubrication force is calculated. These results are compared with the analytical lubrication model to verify the model. From this study, it is expected that it will be possible to define the unstable operating conditions and suggest the required magnetic bearing performance for S-CO2 conditions.

scholarly journals Supercritical CO2 Mixtures for Advanced Brayton Power Cycles in Line-Focusing Solar Power Plants

2019 ◽  
Vol 10 (1) ◽  
pp. 55 ◽  
Author(s):  
Robert Valencia-Chapi ◽  
Luis Coco-Enríquez ◽  
Javier Muñoz-Antón
Keyword(s):  
Supercritical Co2 ◽  
Power Plants ◽  
Solar Power ◽  
Plant Performance ◽  
Design Parameters ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Power Cycles ◽  
Solar Power Plants ◽  
Dry Cooling

This work quantifies the impact of using sCO2-mixtures (s-CO2/He, s-CO2/Kr, s-CO2/H2S, s-CO2/CH4, s-CO2/C2H6, s-CO2/C3H8, s-CO2/C4H8, s-CO2/C4H10, s-CO2/C5H10, s-CO2/C5H12 and s-CO2/C6H6) as the working fluid in the supercritical CO2 recompression Brayton cycle coupled with line-focusing solar power plants (with parabolic trough collectors (PTC) or linear Fresnel (LF)). Design parameters assessed are the solar plant performance at the design point, heat exchange dimensions, solar field aperture area, and cost variations in relation with admixtures mole fraction. The adopted methodology for the plant performance calculation is setting a constant heat recuperator total conductance (UAtotal). The main conclusion of this work is that the power cycle thermodynamic efficiency improves by about 3–4%, on a scale comparable to increasing the turbine inlet temperature when the cycle utilizes the mentioned sCO2-mixtures as the working fluid. On one hand, the substances He, Kr, CH4, and C2H6 reduce the critical temperature to approximately 273.15 K; in this scenario, the thermal efficiency is improved from 49% to 53% with pure s-CO2. This solution is very suitable for concentrated solar power plants coupled to s-CO2 Brayton power cycles (CSP-sCO2) with night sky cooling. On the other hand, when adopting an air-cooled heat exchanger (dry-cooling) as the ultimate heat sink, the critical temperatures studied at compressor inlet are from 318.15 K to 333.15 K, for this scenario other substances (C3H8, C4H8, C4H10, C5H10, C5H12 and C6H6) were analyzed. Thermodynamic results confirmed that the Brayton cycle efficiency also increased by about 3–4%. Since the ambient temperature variation plays an important role in solar power plants with dry-cooling systems, a CIT sensitivity analysis was also conducted, which constitutes the first approach to defining the optimum working fluid mixture for a given operating condition.

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