Anode Fuel and Steam Recycling for Internal Methane Reforming SOFCs: Analysis of Carbon Deposition

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Valérie Eveloy
Keyword(s):  
Thermal Stresses ◽  
Carbon Deposition ◽  
Mitigation Strategies ◽  
Methane Reforming ◽  
Carbon Deposits ◽  
Cracking Reaction ◽  
Minor Portion ◽  
A Minor ◽  
Operational Range ◽  
Gas Recycling

Anode fuel and steam recycling are explored as possible mitigation strategies against carbon deposition in an internal methane reforming solid oxide fuel cell (IR-SOFC) operated at steam-to-carbon ratios (S:Cs) of 0.5–1. Using a detailed computational fluid dynamics model, the cell behavior and spatial extent of carbon deposits within the anode are analyzed based on a thermodynamic analysis accounting for both the cracking and Boudouard reactions for fuel and steam recycling fractions of up to 90% (mass percent). At temperatures close to 1173 K, 50% fuel recycling is found to be an effective mitigation strategy against carbon deposition, with only a minor portion of the cell inlet affected by coking. Steam recycling reduces the extent of carbon deposits by a magnitude comparable to that obtained using fuel recycling, provided that recycling ratios on the order of 25% higher than that for fuel recycling are applied. Steam recycling could therefore be considered advantageous in terms of reduced overall mass flow. The mitigating effect of fuel recycling on the susceptibility to coking at the cell inlet is found to be through the direction of the cracking reaction, while steam recycling has a positive (but slightly less effective) impact on both the Boudouard and cracking reactions. The results suggest that partial anode gas recycling could help extend the operational range of IR-SOFCs to lower fuel humidification levels than typically considered, with reduced thermal stresses and risks of carbon deposits, while reducing system cost and complexity in terms of steam production.

Anode Gas and Steam Recycling for Internal Methane Reforming SOFCs: Analysis of Carbon Deposition

2009 ◽  
Author(s):  
Vale´rie Eveloy
Keyword(s):  
Thermal Stresses ◽  
Carbon Deposition ◽  
Positive Impact ◽  
Mitigation Strategies ◽  
Carbon Deposits ◽  
Internal Reforming ◽  
Cracking Reaction ◽  
Minor Portion ◽  
A Minor ◽  
Operational Range

The development of solid oxide fuel cell (SOFCs) systems capable of direct internal reforming (DIR) of methane and higher hydrocarbons is being actively pursued. However, a major challenge with current state-of-the-art nickel-based anodes is their propensity to form deteriorous carbon deposits in DIR, unless excess steam is introduced in the fuel. Reduced fuel humidification levels are desirable from the viewpoints of cell performance, reliability and plant economics. This study explores the use of anodic fuel and steam recycling schemes as possible mitigation strategies against carbon deposits at fuel steam-to-carbon (S:C) ratios less than unity. Using a detailed computational fluid dynamics (CFD) model which couples momentum, heat, mass and charge transport with electrochemical and chemical reactions, the operation of a an internal reforming SOFC and spatial extent of carbon deposition within the anode are analyzed based on a thermodynamic analysis accounting for both the cracking and Boudouard reactions, for several fuel humidification and recycling conditions. 50% (mass %) fuel recycling is shown to be an effective mitigation strategy against carbon deposition at inlet xH2O/xCH4 ratios of 0.5 to 1, with only a minor portion of the cell inlet region affected by coking. For lower recycling ratios at the same fuel compositions, fuel recycling reduces the risk of coking, but does not eliminate it. For the SOFC configuration studied, at a S:C of 0.5, steam recycling is found to reduce the extent of carbon deposits by a magnitude comparable to that obtained using fuel recycling, providing that steam recycling ratios on order 25% higher than the fuel recycling ratios are applied. Steam recycling may therefore be considered advantageous, in terms of reduced overall mass flow. For a S:C = 0.5, the mitigating effect of steam recycling on the susceptibility to coking is through the directions of the cracking and Boudouard reactions, while fuel recycling has a positive impact on the cracking reaction only. The anodic gas recycling strategies considered could help extend the operational range of DIR-SOFCs to lower fuel humidification levels than typically considered, with reduced thermal stresses and risks of carbon deposits, while reducing system cost and complexity in terms of steam production.

Numerical Investigation of the Effect of Fuel Recycling on the Susceptibility of a Direct Internal Methane Reforming SOFC to Carbon Deposition

2008 ◽  
Author(s):  
Valerie Eveloy ◽  
Merwan Daoudi
Keyword(s):  
Carbon Deposition ◽  
Operating Conditions ◽  
Mitigation Strategies ◽  
Major Barrier ◽  
Carbon Deposits ◽  
Internal Reforming ◽  
Current State ◽  
Computational Fluid Dynamics Cfd ◽  
Operational Range ◽  
Steam Production

There is considerable interest in developing solid oxide fuel cell (SOFCs) systems capable of operating directly on methane via direct internal reforming (DIR). However, a major barrier to DIR is the susceptibility of current state-of-the-art nickel based anodes to carbon deposition, particularly at low fuel humidification levels. Overcoming these difficulties will require improved anode designs and identification of suitable operating conditions. In this study, the potential effectiveness of partial fuel recycling in mitigating the risks of carbon deposits is investigated in a planar DIR-SOFC operated on humidified methane at inlet steam-to-carbon ratios (S:Cs) of 0.1 to 1. This is achieved using a detailed computational fluid dynamics (CFD) model which couples momentum, heat, mass and charge transport with electrochemical and chemical reactions. The model thermodynamically predicts the spatial extent of carbon deposits by accounting for both the cracking and Boudouard reactions, for several fuel humidification and recycling conditions. At temperatures close to 1173 K and for inlet fuel S:Cs of 0.5 to 1, 50% (mass %) fuel recycling is found to be an effective strategy against carbon deposition. For lower recycling ratios at the same fuel compositions, or lower S:C ratios (regardless of the recycling ratio), fuel recycling reduces the risk of coking, but does not eliminate it. The results suggest that partial fuel recycling could contribute to extend the operational range of DIR-SOFCs to lower S:C ratios (0.5 to 1.0) than typically considered, with reduced risks of carbon deposition, while reducing system cost and complexity in terms of steam production. For dry or weakly humidified fuels, additional mitigation strategies would be required.

Carbon deposition in methane reforming with carbon dioxide

1996 ◽  
Vol 47 (1) ◽  
pp. 227-234 ◽  
Author(s):  
P. Gronchi ◽  
D. Fumagalli ◽  
R. Del Rosso ◽  
P. Centola
Keyword(s):  
Carbon Dioxide ◽  
Carbon Deposition ◽  
Methane Reforming

scholarly journals Studying the present-day dynamics of Lena delta by space images

2019 ◽  
Vol 46 (6) ◽  
pp. 567-574
Author(s):  
V. I. Kravtsova ◽  
A. N. Inyushin
Keyword(s):  
Marine Terrace ◽  
Southwestern Part ◽  
Space Images ◽  
Delta Coastline ◽  
Local Erosion ◽  
Minor Portion ◽  
Landsat Satellite ◽  
A Minor ◽  
Erosion Material ◽  
Lena Delta

The dynamics of Lena delta coastline since the late XX century up to the present time have been studied using Landsat satellite data. The comparison of different-time images of morphologically different segments of the delta coastline has shown the major portion of the delta to be stable. Minimal changes have been recorded near the mouths of the branches carrying a minor portion of the Lena runoffthe Olenekskaya and Tumatskie. In the eastern part of the delta, near the mouths of copious branches Trofimovskaya and Bykovskaya, no changes have taken place, as well as in its western part, which is represented by a part of abrasion marine terrace embraced by the delta. In the southwestern part, in the Olenek delta, the delta coastline has been eroded with the erosion material transported eastward by along-shore current. Near the mouths of the Tumatskaya branch, the forms of marine accumulation are unstable, and the marine terrace in the northeastern part of the delta shows a minor local erosion. The periods of erosion in different delta areas are not synchronous and the eroded zones are not large in size. No increment in the land, nor shore progradation have been seen.

Efficient removal of the carbon deposits formed during the mixed methane reforming over Ni/Al2O3

2020 ◽  
Vol 37 (2) ◽  
pp. 209-215
Author(s):  
Oleksandr Shtyka ◽  
Mateusz Zakrzewski ◽  
Radoslaw Ciesielski ◽  
Adam Kedziora ◽  
Sergey Dubkov ◽  
...  
Keyword(s):  
Methane Reforming ◽  
Efficient Removal ◽  
Carbon Deposits

Quantitative Histochemical Analysis of Starch, Malate and K+, together with the Activity of Phospho-enolpyruvate Carboxylase along an Elongating Primary Leaf of Hordeum vulgare

1987 ◽  
Vol 42 (9-10) ◽  
pp. 1092-1096 ◽  
Author(s):  
R. Hampp ◽  
W. H. Outlaw ◽  
H. Ziegler
Keyword(s):  
Starch Content ◽  
Solute Concentration ◽  
Leaf Base ◽  
Histochemical Analysis ◽  
Specific Nature ◽  
Mesophyll Cells ◽  
Equivalent Basis ◽  
Intercalary Meristem ◽  
Minor Portion ◽  
A Minor

The content of starch, malate, potassium and the activity of phospho-enolpyruvate carboxylase (PEPC) were analyzed by quantitative histochemistry in mesophyll cells of different zones along the axis of lyophylized primary elongating leaves of barley. The concentrations of potassium and malate were low in the region of the intercalary meristem (close to the point of grain attachment), but concentrations of solutes increased abruptly and stoichiometrically (equivalent basis) in the elongation zone (2 to 10 mm from the leaf base), where they contributed approximately -0.17 megapascal to the solute potential. Although this solute concentration represents only a minor portion of the reported solute potential, the specific nature of the change, its correlation with a decrease of starch content, and the distribution of the activity of PEPC indicate cell expansion in barley could be augmented by a potassium malate osmoregulatory system that utilizes starch as a source of carbon skeletons.

Compensatory effect of the heat increment of feeding on thermoregulation costs of white-tailed deer fawns in winter

1999 ◽  
Vol 77 (9) ◽  
pp. 1474-1485 ◽  
Author(s):  
Paul G Jensen ◽  
Peter J Pekins ◽  
James B Holter
Keyword(s):  
Metabolic Rate ◽  
Heat Production ◽  
Resting Metabolic Rate ◽  
Energetic Cost ◽  
Critical Temperatures ◽  
Metabolic Chamber ◽  
Heat Increment Of Feeding ◽  
Heat Increment ◽  
Minor Portion ◽  
A Minor

For northern white-tailed deer (Odocoileus virginianus) fawns, the energetic cost of thermoregulation (HcE) during severe winters can result in substantial catabolism of body-tissue reserves. The heat increment of feeding (HiE) has the potential to offset thermoregulatory energy expenditure that would otherwise require the catabolism of these reserves. During winters 1996 and 1997, we conducted 18 fasting and 18 on-feed heat-production trials using indirect respiration calorimetry in a metabolic chamber. Nonlinear regression analysis was used to estimate the lower critical temperatures (Tlc) and determine the fasting metabolic rate (FMR) and resting metabolic rate (RMR). Resulting models were used to calculate HiE, HcE, and percent substitution of HiE for HcE. For fawns fed a natural browse diet, estimated FMR and RMR were 352 and 490 kJ·kg body mass (BM)-0.75·d-1, respectively; this 40% increase in thermoneutral heat production reduced Tlc from -0.8 to -11.2°C between the fasted and fed states, respectively, and reduced HcE by 59% for fed fawns. For fawns fed a concentrate diet, estimated FMR and RMR were 377 and 573 kJ·kg BM-0.75·d-1, respectively. Level of browse intake had a significant effect on RMR andTlc. RMR was 12% higher for fawns on a high versus a low level of intake, and estimated Tlc was -15.6 and -5.8°C, respectively. Our data indicate that the energetic cost of thermoregulation is probably a minor portion of the energy budget of a healthy fawn consuming natural forage.

Protein kinase-dependent and Ca2+-independent cAMP inhibition of ANP release in beating rabbit atria

2002 ◽  
Vol 282 (5) ◽  
pp. R1477-R1489 ◽  
Author(s):  
Xun Cui ◽  
Jin Fu Wen ◽  
Jing Yu Jin ◽  
Wen Xie Xu ◽  
Sung Zoo Kim ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Kinase Inhibitor ◽  
Mechanical Stretch ◽  
Dependent Manner ◽  
Calmodulin Kinase ◽  
Minor Portion ◽  
Channel Dependent ◽  
A Minor ◽  
The Relationship ◽  
Rabbit Atria

Regulation of atrial release of atrial natriuretic peptide (ANP) is coupled to changes in atrial dynamics. However, the mechanism by which mechanical stretch controls myocytic ANP release must be defined. The purpose of this study was to define the mechanism by which cAMP controls myocytic ANP release in perfused, beating rabbit atria. The cAMP-elevating agents forskolin and 3-isobutyl-1-methylxanthine (IBMX) inhibited myocytic ANP release. The activation of adenylyl cyclase with forskolin inhibited ANP release, which was a function of an increase in cAMP production. Inhibitors for L-type Ca2+ channels and protein kinase A (PKA) attenuated a minor portion of the forskolin-induced inhibition of ANP release. Gö-6976 and KN-62, which are specific inhibitors for protein kinase C-α and Ca2+/calmodulin kinase, respectively, failed to modulate forskolin-induced inhibition of ANP release. The nonspecific protein kinase inhibitor staurosporine blocked forskolin-induced inhibition of ANP release in a dose-dependent manner. Staurosporine but not nifedipine shifted the relationship between cAMP and ANP release. Inhibitors for L-type Ca2+ channels and PKA and staurosporine blocked forskolin-induced accentuation of atrial dynamics. These results suggest that cAMP inhibits atrial myocytic release of ANP via protein kinase-dependent and L-type Ca2+-channel-dependent and -independent signaling pathways.

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