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.

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.

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.

Study of Self-Propelled Pufferfish Driven by Multiple Fins: A Comparison Between Rigid and Deformable Fins

2017 ◽  
Author(s):  
Ruoxin Li ◽  
Qing Xiao ◽  
Lijun Li ◽  
Hao Liu
Keyword(s):  
Underlying Mechanism ◽  
Operating Conditions ◽  
The Self ◽  
Fish Swimming ◽  
Propulsion Efficiency ◽  
Live Fish ◽  
Body Dynamics ◽  
Computational Fluid Dynamics Cfd ◽  
Multi Body ◽  
Better Than

In this work, we numerically studied the steady swimming of a pufferfish driven by the undulating motion of its dorsal, anal and caudal fins. The simulations are based on experimentally measured kinematics. To model the self-propelled fish swimming, a Computational Fluid Dynamics (CFD) tool was coupled with a Multi-Body-Dynamics (MBD) technique. It is widely accepted that deformable/flexible or undulating fins are better than rigid fins in terms of propulsion efficiency. To elucidate the underlying mechanism, we established an undulating fins model based on the kinematics of live fish, and conducted a simulation under the same operating conditions as rigid fins. The results presented here agree with this view by showing that the contribution of undulating fins to propulsion efficiency is significantly larger than that of rigid fins.

Asphaltene Mitigation in Giant Carbonate Abu Dhabi Fields: A Techno-Economic Comparison Between Continuous Injection and Formation Squeeze

2021 ◽  
Author(s):  
Mark Grutters ◽  
Sameer Punnapala ◽  
Dalia Salem Abdallah ◽  
Zaharia Cristea ◽  
Hossam El Din Mohamed El Nagger ◽  
...  
Keyword(s):  
Cost Effective ◽  
Threshold Value ◽  
Field Trials ◽  
Mitigation Strategy ◽  
Operating Conditions ◽  
Mitigation Strategies ◽  
Production Cycle ◽  
Asphaltene Precipitation ◽  
Coiled Tubing ◽  
Continuous Injection

Abstract Asphaltene deposition is a serious and re-occurring flow assurance problem in several of the ADNOC onshore oilfields. Fluids are intrinsically unstable with respect to asphaltene precipitation, and operating conditions are such that severe deposition occurs in the wellbore. Wells in ADNOC are generally not equipped with downhole chemical injection lines for continuous inhibition, and protection of the wells require frequent shut-in and intervention by wireline and coiled tubing to inspect and clean up. Since some of the mature fields are under EOR recovery strategies, like miscible hydrocarbon WAG and CO2 flood, which exacerbates the asphaltene precipitation and deposition problems, a more robust mitigation strategy is required. In this paper the results of two different mitigation strategies will be discussed; continuous injection of asphaltene inhibitor via a capillary line in the tubular and asphaltene inhibitor formation squeeze. Three asphaltene inhibitors from different suppliers were pre-qualified and selected for field trial. Each inhibitor was selected for a formation squeeze in both one horizontal and one vertical well, and one of the inhibitors was applied via thru-tubing capillary string. The field trials showed that continuous injection in remote wells with no real-time surveillance options (e.g. gauges, flow meters) is technically challenging. The continuous injection trial via the capillary string was stopped due to technical challenges. From the six formation squeezes four were confirmed to be effective. Three out of fours squeezes significantly extended the production cycle, from approximately 1.4 to 6 times the normal uninhibited flow period. The most successful squeezes were in the vertical wells. The results of the trial were used to model the economic benefit of formation squeeze, compared to a ‘do-nothing’ approach where the wells are subject to shut-in and cleanup once the production rates drop below a threshold value. The model clearly indicates that the squeezes applied in ADNOC Onshore are only cost-effective if it extends the normal flow period by approximately three times. However, a net gain can be achieved already if the formation squeeze extends the flow cycle by 15 to 20%, due to reduction of shut-in days required for intervention. Therefore, the results in this paper illustrate that an asphaltene inhibitor formation squeeze can be an attractive mitigation strategy, both technically and economically.

A Holistic Approach to Characterize Mud Loss Using Dynamic Mud Filtration Data

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Chinedum Peter Ezeakacha ◽  
Saeed Salehi
Keyword(s):  
Regression Analysis ◽  
Field Application ◽  
Operating Conditions ◽  
Mitigation Strategies ◽  
Drilling Mud ◽  
Experimental Conditions ◽  
Lost Circulation ◽  
Rotary Speed ◽  
Mud Filtration ◽  
Mud Loss

Drilling mud loss in highly porous media and fractured formations has been one of the industry's focuses in the past decades. Wellbore dynamics and lithology complexities continue to push for more research into accurate quantification and mitigation strategies for lost circulation and mud filtration. Conventional methods of characterizing mud loss with filtration data for field application can be time-consuming, particularly because of the interaction between several factors that impact mud loss and filtration. This paper presents a holistic engineering approach for characterizing lost circulation using pore-scale dynamic water-based mud (WBM) filtration data. The approaches used in this study include: factorial design of experiment (DoE), hypothesis testing, analysis of variance (ANOVA), and multiple regression analysis. The results show that an increase in temperature and rotary speed can increase dynamic mud filtration significantly. An increase in lost circulation material (LCM) concentration showed a significant decrease dynamic mud filtration. A combination of LCM concentration and rotary speed showed a significant decrease in dynamic mud filtration, while a combination of LCM concentration and temperature revealed a significant increase in dynamic mud filtration. Rotary speed and temperature combination showed an increase in dynamic mud filtration. The combined effect of these three factors was not significant in increasing or decreasing dynamic mud filtration. For the experimental conditions in this study, the regression analysis for one of the rocks showed that dynamic mud filtration can be predicted from changes in LCM concentration and rotary speed. The results and approach from this study can provide reliable information for drilling fluids design and selecting operating conditions for field application.

scholarly journals Exploring the 'Cultural Tourism-Sustainable Development' Nexus: the Case of Croatia

2014 ◽  
Vol 61 (2) ◽  
pp. 161-179 ◽  
Author(s):  
Damir Demonja ◽  
Tatjana Gredičak
Keyword(s):  
Sustainable Development ◽  
Cultural Heritage ◽  
Cultural Tourism ◽  
Operating Conditions ◽  
Economic Factors ◽  
The Sustainable Development ◽  
Current State ◽  
Analysis And Synthesis ◽  
High Level ◽  
Historical Methods

Abstract Modern environment in which operate tourism-economic factors is characterized by a high level of instability and the dynamics of change. Changes with its influences determine external operating conditions, over which micro organizational units have no control. In order to successfully survive it is necessary to identify and adapt to them. Marketing strategy of cultural heritage tourist valorisation, in this context, appears as an adequate approach. Strategic management enables planning on an analysis of past events, and in a special way takes into account estimates and projections of future conditions of the environment. Also, it should take into account that the coexistence of cultural heritage with the achievements of modern life is defined with sustainable development syntax. This paper in which research, formulation and presentation of the results were used the methods of analysis and synthesis, comparative, descriptive and historical methods outlines the development and analyzes the current state of cultural tourism in Croatia, and discusses approach to effective strategic marketing management of cultural heritage tourist valorisation, focusing on the sustainable development of tourism.

Initial Findings on the Feasibility of Real-Time Feedback Control of a Hazardous Contaminant Released Into Channel Flow by Means of a Laboratory-Scale Physical Prototype

2014 ◽  
Author(s):  
Sara P. Rimer ◽  
Nikolaos D. Katopodes ◽  
April M. Warnock
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Control ◽  
Real Time ◽  
Public Spaces ◽  
Control Model ◽  
Toxic Chemicals ◽  
Current State ◽  
Physical Prototype ◽  
Computational Fluid Dynamics Cfd

The threat of accidental or deliberate toxic chemicals released into public spaces is a significant concern to public safety. The real-time detection and mitigation of such hazardous contaminants has the potential to minimize harm and save lives. We develop a computational fluid dynamics (CFD) flow control model with the capability of detecting and mitigating such contaminants. Furthermore, we develop a physical prototype to then test the computer model. The physical prototype is in its final stages of construction. Its current state, along with preliminary examples of the flow control model are presented throughout this paper.

Fixing a Boiler with CFD

1998 ◽  
Vol 120 (04) ◽  
pp. 59-61
Author(s):  
Kevin Parker
Keyword(s):  
Three Dimensional ◽  
Paper Mill ◽  
Operating Conditions ◽  
Clear Understanding ◽  
Post Processing ◽  
Processing Program ◽  
Hidden Line ◽  
Computational Fluid Dynamics Cfd ◽  
Animated Sequence ◽  
Light Shading

This article focuses on carryover at a paper mill that had been solved using computational fluid dynamics (CFD) to visualize flow within the boiler. Technicians had tried adjusting airflow and firing arrangements without success. They turned the problem over to analysts who simulated the airflow within the boiler using CFD. An animated sequence of streamlines showing airflow provided engineers with a clear understanding of exactly what was happening inside the boiler, making it relatively easy to adjust operating conditions and solve the problem. McDermott analysts use FIELDVIEW, a commercial post-processing program from Intelligent Light in Lyndhurst, NJ. With the software, the analyst can create three-dimensional perspective views with hidden-line removal and light shading. She or He can trace the path of a marker traveling along with the fluid through a series of animated views. The analysts made a second FIELDVIEW movie of the airflow conditions with the new arrangement, showing the elimination of the center core. They played the two movies simultaneously on two monitors set side-by-side to demonstrate for the customer’s engineers how the recommended changes would solve the problem.

CFD Simulations of the Cold Neutron Source at the OPAL Reactor

2020 ◽  
Author(s):  
James L Spedding ◽  
Mark Ho ◽  
Weijian Lu
Keyword(s):  
Neutron Source ◽  
Cold Neutron ◽  
Operating Conditions ◽  
Convergence Time ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Cold Neutron Source ◽  
Order Of Magnitude ◽  
Computational Fluid Dynamics Cfd ◽  
Polyhedral Mesh

Abstract The Open Pool Australian Light-water (OPAL) reactor Cold Neutron Source (CNS) is a 20 L liquid deuterium thermosiphon system which has performed consistently but will require replacement in the future. The CNS deuterium exploits neutronic heating to passively drive the thermosiphon loop and is cryogenically cooled by forced convective helium flow via a heat exchanger. In this study, a detailed computational fluid dynamics (CFD) model of the complete thermosiphon system was developed for simulation. Unlike previous studies, the simulation employed a novel polyhedral mesh technique. Results demonstrated that the polyhedral technique reduced simulation computational requirements and convergence time by an order of magnitude while predicting thermosiphon performance to within 1% accuracy when compared with prototype experiments. The simulation model was extrapolated to OPAL operating conditions and confirmed the versatility of the CFD model as an engineering design and preventative maintenance tool. Finally, simulations were performed on a proposed second-generation CNS design that increases the CNS moderator deuterium volume by 5 L, and results confirmed that the geometry maintains the thermosiphon deuterium in the liquid state and satisfies the CNS design criteria.

Field-Testing of Biodiesel (B100) and Diesel-Fueled Vehicles: Part 3—Wear Assessment of Liner and Piston Rings, Engine Deposits, and Operational Issues

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Avinash Kumar Agarwal ◽  
Deepak Agarwal
Keyword(s):  
Piston Ring ◽  
Direct Injection ◽  
Cylinder Liner ◽  
Field Testing ◽  
Field Trials ◽  
Operating Conditions ◽  
Piston Rings ◽  
Carbon Deposits ◽  
Bottom Dead Center ◽  
Operational Issues

Abstract This study investigated the use of biodiesel (B100) and baseline mineral diesel in two identical unmodified vehicles to realistically assess different aspects of biodiesel’s compatibility and durability issues with modern common rail direct injection (CRDI) engine-powered vehicles. Two identical vehicles were operated for 30,000 km under identical operating conditions during a field-trial using biodiesel (B100) and mineral diesel. Exhaustive experimental results from this series of tests are divided into four sections, and this is the third paper of this series of four papers, which covers comparative feasibility and wear analyses, underlining the effect of long-term use of biodiesel on wear of cylinder liner and piston rings compared to baseline mineral diesel-fueled vehicle. Surface microstructures at three locations of the cylinder liner were evaluated using scanning electron microscopy (SEM). Wear was found to be relatively lower at all locations of liners from biodiesel-fueled vehicle compared to diesel-fueled vehicle. Surface roughness of cylinder liners measured at different locations showed that it reduced by ∼30–40% at top dead center (TDC), ∼10–20% at mid-stroke, and ∼20–30% at bottom dead center (BDC) for both vehicles, showing higher wear close to TDC compared to mid-stroke and BDC locations. Loss of piston-ring weight was significantly lower for biodiesel-fueled vehicle. Engine tear-down observations and carbon deposits on various engine components were recorded after the conclusion of the field trials. During these field-trials, engine durability-related issues such as fuel-filter plugging, injector coking, piston-ring sticking, carbon deposits in the combustion chamber, and contamination of lubricating oils were found to be relatively lower in biodiesel-fueled vehicle. Overall, no noticeable durability issues were recorded because of the use of biodiesel in CRDI engine-powered vehicle.

Sign in / Sign up

Export Citation Format

Share Document