Synthetic Diesel Research Articles

Development of a Highly Flexible SOFC CCHP System Towards Demand-Oriented Power Generation from Renewable Fuels

This paper presents the current development status of AVLs stationary SOFC CCHP (combined cooling, heat and power) platform with special focus on the coupling of an SOFC with an absorption heat pump. Furthermore, the SOFCs fuel capability was extended towards the utilization of multiple renewable fuels such as biogas, biomass product gas and synthetic diesel. In the past AVL developed a natural gas operated SOFC CHP platform in the power range of 5 – 10 kWel with an electrical efficiency of >55 % using the Plansee/IKTS stack technology. For certain applications such as buildings, a heat driven operation mode leads to low operating hours per year for conventional CHP systems due to the low heat demand during summer season. The option to generate cooling power in addition to heat will increase the annual operating hours per year and thus economic efficiency significantly. This work will show the coupling of a stationary 6 kWel SOFC CHP system developed by AVL using an IKTS stack module with a 5 kWcooling absorption heat pump developed by TU Graz, Institute of Thermal Engineering. The exhaust gas heat from the SOFC which is available at >200 °C will be used to operate the thermally driven heat pump. The SOFC exhaust gas heat is transferred in the generator of the absorption heat pump to be converted to cooling power. To maximize the cooling power output of the SOFC CCHP system it is important to utilize as much SOFC exhaust gas heat as possible in the absorption heat pumping process. Furthermore, it is important to optimize the energy efficiency ratio of the absorption heat pump. In this context the influence of the cold and cooling water temperatures of the absorption heat pumping process on the system size and system total efficiency were investigated. It can be shown that for cold and cooling water temperatures as required in office buildings and hospitals a ratio between electrical power and cooling power of 4 - 6 can be achieved by the SOFC CCHP system. This analysis presents the capability of the SOFC CCHP system for a flexible and demand-oriented generation of electricity, heat and cooling power. As the electrical efficiency of the SOFC determines the exhaust gas heat output the system performance was further investigated towards the operation of renewable fuels. Biogas or synthetic diesel for instance may lead to lower electrical efficiencies compared to natural gas. Therefore, the type of fuel also influences the SOFC exhaust mass flow and temperature which is the main driving power for the absorption heat pump. In this work the fuel capability of the platform was extended from natural gas to renewable fuels. From economic point of view it is desired to benefit from volume effects for stacks and balance of plant components which is why AVLs system development approach is oriented towards a multi-fuel platform which requires only minor design adaptions when it comes to the utilization of different fuels including renewables. As a technology provider this approach is certainly a major advantage for customers who are used to a power generation technology that can be easily applied in various regions all over the world while facing varying fuel specifications. Therefore, this work will provide an overview of the most relevant renewable fuels and its composition for stationary SOFC CHP applications. Consequently, design synergies regarding the process design of the hot anode gas recirculation loop in terms of the recirculation ratio and reforming temperature which are influenced by the specific fuel, are shown. A comparison of system performance results based on process simulations will be discussed. The process simulation uses results from specific reforming tests for e.g. biogas and diesel which will be shown. Furthermore, compared to natural gas based systems a considerably higher effort has to be done in terms of the gas cleaning for biogas and biomass product gas. In case of biogas the main impurities are S, Cl, NH3 which need to be eliminated before sending the fuel to the steam reformer and stack respectively. A low cost gas cleaning concept for biogas based on several low temperature adsorption steps was developed by TU Graz. It can be shown that the absorption efficiency is highly depending on the fuel mixture. The influence of CH4, CO2 and H2O was identified to allow a proper design of the gas cleaning unit. Finally, the build-up of the prototype including first test results will be shown in this work.

In-Operando Detection of Carbon Depositions and Carbon Formation Predictions for Industrial-Sized SOFCs Fueled with Synthetic Diesel Reformate

Solid oxide fuel cells (SOFCs) present an attractive and innovative technology for environmentally-friendly electricity and heat generation. Their high operating temperatures and the excellent catalytic performance make SOFCs the most efficient fuel cell type, with a high level of fuel flexibility. Feeding the SOFCs with conventional or alternative carbon-containing fuels carries the risk of carbon formation and its deposition on the anode, which can reduce cell’s activity, cause irreversible cell degradation, and decrease the cell’s lifetime. In order to prolong the cell’s lifetime and to ensure the undisturbed operation of SOFCs, an in-depth understanding of this degradation phenomenon is required. The problematic of carbon deposition phenomenon is detailed explained and supported with numerical and experimental results for planar, industrial-sized, anode-supported solid oxide fuel cells within this study. Possible reactions to carbon build-up are presented and the methods and calculation principles used to predict the carbon formation are demonstrated. The key parameters that enable carbon predictions are: the components involved in a used gas mixture, temperature, the steam/carbon-ratio, equilibrium state, and C-H-O ternary diagram. All of the mentioned carbon prediction methods and analysis of the basic calculation principles are explicitely explained. For the detailed analysis and prediction of coking propensity, various diesel reformate mixtures, containing H2, CO, CO2, CH4, H2O and N2, are used. In order to examine the impact of water vapor on carbon deposition, the amount of H2O in the fuel mixture is varied between 0 vol%, 11.3 vol% and 20 vol%. The operating conditions, under which carbon can be formed and deposited on the anode side can thus be generated. In the course of the experimental analysis of the carbon deposition phenomenon, the polarized single cells were fed with synthetic diesel reformate mixtures, thus representing realistic operating conditions. In order to obtain information about the degradation of cell performance, such as the critical operating time or degradation voltage, the methane volume fraction in the fuel mixture was varied between 2.3 vol% (as expected in APUs), 9 vol%, 14 vol% and 20.3 vol%. The carbon build-up process on the Ni-catalyst, and, in fact, anywhere in the cell’s fuel supply manifold, was detected at an early stage by means of electrochemical impedance spectroscopy, current/voltage measurement, temperature measuremens and gas analysis. In addition to the in-situ characterization techniques used, an ex-situ post-mortem analysis was introduced to support the knowledge gained in the experimental analysis and to confirm the occurrence of the carbon identified via employed in-situ characterization techniques. Methane, including the decreasing steam/carbon ratio, was identified as having a major impact on the degradation rate at the typical operating temperature of 800°C for anode-supported solid oxide fuel cells. The critical operating time for carbon to form and be deposited on the anode was found to be strongly dependent on the amount of methane in the fuel mixture. For lower amounts of methane in the fuel mixture, such as 2.3 vol%, degradation of the cell performance was observed after 44 h. After accelerated carbon deposition process, due to an increase in the methane concentration of the gas mixture in use, the total critical operating time was significantly reduced. The approaches that allow early identification of carbon build-up in order to avoid irreversible deterioration of cell performance and its microstructure were originated and they are provided. A detailed microscopic investigation showed that carbon was uniformly formed over the Ni- and YSZ-sites. Massive carbon deposits not only caused the degradation of the cell performance, but also changed the Ni-YSZ structure. The crushing of YSZ-particles and their deposition on the Ni-catalyst were determined to be degradation phenomenona that occur if the carbon formation process in not interrupted at an early stage.

Synthetic diesel fuel produced from coal

The characteristics of synthetic diesel fuel are analyzed. The fuel consists of hydrocarbons C3–C32; the content of the middle fractions is 83.26 wt %. The IR spectrum of the synthetic diesel fuel contains deformational vibrations corresponding to paraffins and unsaturated hydrocarbons, as well as aromatic and heteroaromatic compounds. Synthetic fuel produced from coal is recommended as a raw material for DTZ commercial diesel fuel, suitable for use in winter.

Development of a Highly Flexible SOFC CCHP System Towards Demand-Oriented Power Generation from Renewable Fuels

The coupling of AVLs 6 kWEL SOFC CHP system using an IKTS stack module with a 5 kWCOLD absorption heat pump developed by TU Graz will be presented. The exhaust gas heat from the SOFC which is available at >200 °C will be used to operate the thermally driven heat pump. The SOFCs fuel capability was extended towards renewable fuels such as biogas, and synthetic diesel using a novel gas cleaning concept. For buildings, a heat driven operation mode leads to low operating hours per year for conventional CHP systems during summer season. Generating cooling power in addition to heat will increase the annual operating hours per year and thus economic efficiency significantly. This analysis presents the capability of the SOFC CCHP system for a flexible and demand-oriented generation of electricity, heat and cooling power and shows how cold and cooling water temperatures influence the overall system size

Spacial and dynamic energy demand of the E39 highway – Implications on electrification options

The aims of this study were to investigate how the energy demand from transportation on a road varies over time and with location, and to identify the impacts from electrification of the road on the stationary electricity system, assuming different electrification options and drivetrains. European highway route 39 (E39) in western Norway is used as a case study. A vehicle model, together with an analysis of detailed traffic data was used to estimate the energy and power demands for transportation work on E39. This study shows that a road with the characteristics of E39 exhibits large variation in the spatial and time distributions of its energy and power demands. The yearly electricity demand for E39, assuming a full electrification of the current traffic flow is comparable to that of a larger industry, such that the peak power demand for the dimensioning hour of the regional electricity system could be increased by 1–2% if static or electric road systems is applied. However, if all the main roads in Norway were installed with electric road systems, the corresponding peak power increase is 7%. In comparison, if instead using an indirect strategy for electrification of transportation via for instance hydrogen or synthetic diesel, the annual electricity demand for E39 would increase even further, albeit with the possibility to distribute such demand both geographically area and in time compared to electric road systems or static charging.

Effect of hydrocarbon vaporization and gases solubility on performance and cycle length of gas-phase – Trickle bed reactors system used for deep diesel hydrotreatment

The use of high-pressure, high-temperature diesel stripper ahead of the reactors boosts low-sulfur diesel production on existing HDT units. The new hydrotreating process scheme use a combination gas phase and liquid phase reactors to treat Diesel. The gas and liquid properties of the stream were determined in dynamic conditions and hydrocarbon vaporization and gases solubility simulated based on Peng-Robinson state equation with modified pseudo-species properties, interaction coefficients and mixing rules. The gas-liquid pseudo-equilibrium simulation allows calculation of concentration of pseudo-species present in gas-liquid separators and in reactors along the cycle length. The new experimental vapor-liquid equilibria data were developed for synthetic feed, diesel, diesel plus hydrotreated product and product of reaction at high-temperature and high-pressure. This data was used to developed new sets of Akl, Bkl, E and F parameters for interaction coefficients and blending values. The results of simulation using Peng Robinson EOS state equation with new interaction coefficients and rules for blending show an improvement in the prediction of pseudo-species vaporization and solubility of hydrogen, methane, ethane, and hydrogen sulfide on liquid phase (diesel). Prediction of gas-liquid pseudo species concentration and phase properties along the cycle length have significant impact on the economy of the new HDT process. Experimental dynamic VLPE data is included.

Catalytic Thermal Cracking of Postconsumer Waste Plastics to Fuels. 2. Pilot-Scale Thermochemical Conversion

Synthetic gasoline and diesel fuels were prepared via catalytic and noncatalytic pyrolysis of waste polyethylene and polypropylene plastics followed by distillation of plastic crude oils. Reaction conditions optimized using a 2 L batch reactor were applied to pilot-scale production of plastic crude oil from polypropylene. The optimum conditions on the pilot-scale system were a reaction temperature of 500 °C and a residence time of 4.7 min. Plastic crude oil yields at pilot scale were comparable to those of the batch scale (70–80%). Plastic crude oils obtained from pyrolysis were distilled into the boiling point range of motor gasoline, diesel no. 1, gas oil, and vacuum gas oil range fractions. The elemental composition of the crude oil and its distillates were similar to the starting plastic material. Fuel properties were studied for both neat and in blends (5% and 20%) with ultralow sulfur diesel fuel (ULSD). Excellent low temperature properties were obtained for some of the samples, as indicated by a po...

Thermodynamic and economy analysis of solid oxide electrolyser system for syngas production

A pressurized solid oxide electrolyser (SOE) system for syngas production is analyzed. The system is modeled and analyzed considering energy and exergy aspects. The main consideration is to quantify the effect of operating pressure on the system performance when syngas is used for synthetic diesel production. At elevated pressures methanation reaction within the electrolyser causes internal production of methane from syngas. The results show that methane fraction increase from almost zero percent to 14% at 25 bar. Since methane is not a favorable outcome of this system, elevated pressure has adverse effect on the total system performance and consequently system efficiency drops by about 20% points by increasing the electrolyser operating pressure from atmospheric to 25 bar. This effect also results in higher levelized cost of syngas at elevated pressures. Effects of other operating parameters like temperature and utilization factor on the syngas production rate and system performance are also explored. In addition, relative irreversibility of each component is estimated. It is concluded that the solid oxide electrolyser has the highest relative irreversibility amongst other system components which can be minimized by changing operating temperature. At last but not least, levelized cost of produced syngas is estimated.

Determination of Catalytic Rate Constants towards Polymeric Conversion to Synthetic Oils: Bridging the Gap between Kinetics and Thermodynamics

Coal fly ash is being utilized as a recycling material for catalysis due to its aluminosilicate content. Catalytic conversion of polymeric wastes into synthetic gasoline and diesel through pyrolysis requires application of kinetic and thermodynamic principles. This study aimed to identify the catalytic rate constant necessary for rate law involved in reaction mechanisms and activation energy reduction needed for heat transfer rate. Stoichiometric application for balanced total series of elementary reactions is solved for the concentration determination of reactants and products. Unsteady-state in three dimensional directions of thermodynamics is derived for the determination of heat transfer rate, temperatures at any position in a sphere using Gurney and Lurie chart and center temperature in a sphere by Heisler chart. Application principles of rate law and Arrhenius equation can result to thermal conductivity as a function of activation energy leading to synthetic fuel production.

Impact of VOC removal by activated carbon on biodegradation rates of diesel, Syntroleum and biodiesel in contaminated sand

The degradation of conventional diesel (D), synthetic diesel (Syntroleum), and pure fish biodiesel (B100) by indigenous microbes was investigated in laboratory microcosms containing contaminated sand. The fate of volatiles and the influence of volatilization on degradation rates were examined by placing activated carbon (AC) in microcosm headspaces to sorb volatiles. Three AC regimes were compared: no activated carbon (NAC), regular weekly AC change (RAC), and frequent AC change (FAC), where the frequency of activated carbon exchange declined from daily to weekly. Generally, the alternative fuels were biodegraded faster than diesel fuel. Hydrocarbon mineralization percentages for the different fuel types over 28days were between 23% (D) and 48% (B100) in the absence of activated carbon, decreased to 12% (D) – 37% (B100) with weekly AC exchange, and were further reduced to 9–22% for more frequent AC change. Sorption of volatiles to AC lowered their availability as a substrate for microbes, reducing respiration. Volatilization was negligible for the biodiesel. A mass balance for the carbon initially present as hydrocarbons in microcosms with activated carbon in the head space was on average 92% closed, with 45–70% remaining in the soil after 4weeks, 9–37% mineralized and up to 12% volatilized. Based on nutrient consumption, up to 29% of the contaminants were likely converted into biomass.

Effect of particle size, density, and concentration on granular mixing in a double screw pyrolyzer

Double screw pyrolyzers can be used to convert cellulosic biomass into bio-oil. Bio-oil can then be converted into synthetic gasoline, diesel, and other transportation fuels, or can be converted into bio-based chemicals for a wide range of purposes. One method of industrial bio-oil production is called fast pyrolysis, the fast thermal decomposition of organic material in the absence of oxygen. One type of pyrolyzer, a double screw pyrolyzer, features two intermeshing screws encased in a reactor which mechanically conveys and mixes the biomass and heat carrier media. The mixing effectiveness of the two materials in the pyrolyzer is directly correlated to the bio-oil yield—the better the mixing, the higher the yields. This study investigates the effects of particle size, density, and concentration on mixing effectiveness in a double screw pyrolyzer. Using glass beads as simulated heat carrier media and various organic particles as biomass, a cold-flow double screw mixer with 360° of optical access and full sampling capabilities was used to collect mixing data. Unique optical visualization and composition analysis paired with statistical methods were used to evaluate the effects of varying the biomass particle size and density, the heat carrier particle size, and the biomass particle concentration. Both qualitative and quantitative analysis indicated that reducing the biomass particle size, for counter-rotating down pumping screw rotation orientations, noticeably increased mixing effectiveness. Increasing the heat carrier media particle size showed both increases and decreases in mixing effectiveness depending on operating condition. For all screw rotation orientations, a change in biomass particle density resulted in little change in mixing effectiveness, while reducing the biomass particle concentration reduced the overall mixing effectiveness.

Preparation of wrapped carbon nanotubes poly(4-vinylpyridine)/MTO based heterogeneous catalysts for the oxidative desulfurization (ODS) of model and synthetic diesel fuel

The preparation of novel wrapped carbon nanotubes poly(4-vinylpyridine)/methyl trioxorhenium based heterogeneous catalysts has been reported by two different procedures: a) the wrapping by grinding of multiwall carbon nanotubes with pre-formed adducts, respectively, [poly(4-vinylpyridine)·methyltrioxorhenium] or [poly(4-vinylpyridine)-N-oxide·methyltrioxorhenium] and, b) the loading of methyltrioxorhenium on previously wrapped multiwall carbon nanotubes with poly(4-vinylpyridine) and poly(4-vinylpyridine)-N-oxide resins. The novel catalysts were characterized by SEM, TEM, ICP-MS and XPS analyses. Both types of catalysts were efficient systems in the oxidation of recalcitrant aromatic sulfur derivatives with H2O2, as representative models of oxidative desulfurization processes, affording the corresponding sulfones with yields ranging from moderate to quantitative. The oxidation of a complex model fuel oil and of synthetic diesel fuel, under optimal experimental conditions, is also reported. The performance of novel catalysts was dependent on the specific procedure applied for the immobilization of the active species, and was more efficient for both model oil and synthetic diesel fuel samples (with quantitative conversions and selectivities to the corresponding sulfones), than for isolated substrates.

Environmental sustainability assessment of fruit cultivation and processing using fruit and cocoa residues for bioenergy and compost. Case study from Ghana

Agro-industrial businesses often have easy access to agricultural and processing residues with which they may reduce costs and pollution by integrating their production with bioenergy production. In regions with unreliable power supply, on-site electricity generation is a means to secure stable production conditions. Furthermore, recycling of nutrients may help to reduce biomass suppliers' dependence on synthetic fertiliser. In this Environmental Sustainability Assessment (ESA) of fruit production in Ghana we compare two technology options for the production of mixed, fresh, tropical fruit, including cultivation, transport and processing. The option ‘Present practice’ presents data from a case study where production is characterised by soil loss and synthetic fertiliser dependence in cultivation and grid supply of electricity in processing. The option ‘Biogas’ is hypothetical and characterised by biogas and electricity production using farming and processing residues and by recycling of nutrients and carbon to soil. Cocoa shells are used as a co-substrate in the biogas production. Estimating the environmental impact of cocoa shell residues exposes the multifunctionality issue, continuously debated in ESA, particularly concerning bioenergy production. We compare the use of allocation of cocoa production impacts and system expansion that includes cocoa production as possible methods to manage multifunctionality of inputs. In assessments of residue-based production, we recommend using the latter method. Applying the system expansion method, we find that, in comparison with ‘Present practice’, the option ‘Biogas’ eliminates net soil carbon loss and reduces synthetic fertiliser, diesel and external electricity requirements at the expense of a relatively small increase in human labour input. The ESA includes the following indicators and shows that the ‘Biogas’ option is superior to ‘Present practice’ with regard to Cumulative Energy Demand (−39%), Cumulative fossil Energy Demand (−34%), Food Energy Return On energy Investment (+65%), Food Energy Return On fossil energy Investment (+53) and Global Warming Potential (−29%) and similar to ‘Present practice’ in terms of the Emergy Assessment indicators Unit Emergy Value, Global Renewability Fraction, and Local Supply Fraction. Discarding the system expansion method, the same conclusion applies even if the emergy indicators are more ambiguous.

New Bimetal Catalysts Supported on Silica Nanospheres for the Production of Synthetic Diesel

Nowadays we are facing the necessity to find new ways to reduce the use of fossil fuels. This need comes from the excessive use of these sources as energy and the well-known adverse environmental effects than these fuels represents. Currently the fossil fuels represents about the 70% of the world energy sources. This dependency has brought some important problems of contamination such as global warming and climate change, acid rain, alterations of the carbon cycle, among many others. The transportation sector is the largest consumer of petroleum-based fuels in the world, liberating to the atmosphere vast amounts of CO2, NOx, SOx, lead (Pb), mercury (Hg), and many others. These pollutants are not only harmful to the environment but also to the human health, causing lung and heart diseases along with cancer. The increase of price and demand of these fuels and the contamination generated by them makes imperative the search of viable clean technologies looking for the production of clean fuels with high commercial value. Contaminants produced by the combustion of fossil fuels represent a challenging future for the development of new clean fuels. In this regard, an interesting alternative consists in the synthesis of clean diesel fuel thorough the Fischer-Tropsch (FT) reaction. This method produces clean diesel starting from a mixture of H2 and CO obtained from renewable or not renewable energy sources. This synthesis produces high weighted hydrocarbons with high purity. The fuel produced by this process is clean since it does not have aromatic compounds or sulphur or nitrogen-based compounds, preventing the production and release of NOx and SOx during combustion. The FT processes require the use of heterogeneous catalysts. These catalysts are based on active metals (i.e. Co, Ru or Fe) highly dispersed on the surface of appropriate supports. In this research SiO2 nanospheres, synthesized by using the Stӧber procedure, have been used as supports for the deposition of different metals on the surface. The synthesized catalysts were characterized by FE-SEM, HRTEM, XRD and BET, and used for the FT reaction. Preliminary catalytic results are very promising and show that mixtures of low loadings of bimetal nanoparticles dispersed on the surface of SiO2 nanospheres could be efficiently used for the synthesis of paraffin products with different distribution.

Hydrotreating of non-food feedstocks over Raney nickel for the production of synthetic diesel fuel

ABSTRACTNon-food feedstocks including castor oil, palm fatty acid distillate and waste tallow were successfully converted into liquid hydrocarbon mixtures. This was achieved by a batch hydrotreating process over commercial Raney nickel as a catalyst within 5 h at a reaction temperature of 360 °C and an initial hydrogen pressure of 90 bar. The obtained liquid products consist of straight chain alkanes in the range from C8 to C20. Low amounts (2.5–4.4%) of higher n-alkanes (up to C28) could be detected. The occurrence of the latter indicates a Fischer-Tropsch like process under the chosen conditions besides the expected decarbonylation/decarboxylation and accompanying cracking reactions. Products obtained from castor oil also comprised an overall amount of 19% of ketones in the range from C8 to C19. All obtained products were tested on important fuel properties according to well-established methods given in EN 590, the European Standard for diesel fuel. Comparison with the obligatory boundary values given within this specification suggests an excellent suitability as blending components for fossil diesel fuel. For a full replacement further upgrading would be necessary.

Biodegradation of gas-to-liquids synthetic diesel, biodiesel and their blends

Sustainable renewable alternatives to petroleum fuels are being investigated because of the growing demand for transportation fuel. Synthetic fuels like diesel are produced from natural gas and coal feed stocks, via the Fischer-Tropsch synthesis process. Biodiesel can be an attractive alternative to petroleum-derived diesel because its physical properties are similar to those of petrodiesel and it can be transported by and stored in existing infrastructure. The biodegradability of synthetic diesel and biodiesel blends were determined, using respirometry to establish whether the biodiesel could enhance the biodegradability of the blends when compared to the synthetic petroleum diesel. In addition, a model was developed to estimate the biodegradability of the diesel and diesel/biodiesel blends using the molecular composition of the fuels and a prediction software program. The addition of biodiesel to synthetic diesel enhanced the biodegradability of the blends. Less than 1% biodiesel addition improved the degradability classification from inherently biodegradable to readily biodegradable. The addition of biodiesel to petroleumderived diesel could promote the use of renewable alternatives because the blends have superior biodegradability compared to petroleum diesel. The benefit of using biodiesel to enhance the remediation of hydrocarbon contamination was also confirmed.

Analysis of possibilities for carbon removal from porous anode of solid oxide fuel cells after different failure modes

This study focuses on the investigation of possibilities for carbon removal from the fuel electrode of anode supported solid oxide fuel cells (ASC-SOFCs) after different degradation modes. To design the conditions which generally lead the cell in the range of carbon depositions the performed thermodynamic calculations show that the SOFC operating temperature range seems to be appropriate for formation of elemental carbon in various types. Concerning this the loaded large planar single SOFCs are fed with synthetic diesel reformate thus simulating realistic operating conditions and enabling the formation and deposition of carbon on the anode side. A mixture of hydrogen/water vapor/nitrogen is used to remove the detected carbon depositions in a cell-protecting manner. For the purpose of this investigation several failure modes are induced after which determination the already defined regeneration strategy is applied. The cathode degradation is first induced and secondly the fuel supply is interrupted to induce re-oxidation of nickel (Ni) on the anode side. The undertaken investigations determine that carbon can be fully removed from the anode surface after nickel oxidation, while cathode degradation disables the complete cell regeneration.

Three-dimensional numerical and experimental investigation of an industrial-sized SOFC fueled by diesel reformat – Part II: Detailed reforming chemistry and carbon deposition analysis

As an important energy source, liquid diesel can be reformed in order to be used in high temperature solid oxide fuel cells (SOFCs) cleanly and efficiently. However, a big challenge of using carbon containing fuels, such as diesel reformat, is carbon deposition on the porous Ni/YSZ-anode structure caused by internal reforming reactions. In this work a planar industrial-sized 100 × 100 mm2 anode supported SOFC fueled with synthetic diesel reformat was numerically and experimentally investigated, in order to predict carbon depositions in the porous anode substrate. Gas phase as well as detailed wall-surface reactions were scrutinized in order to evaluate reforming mechanisms available in literature. Implementation and simulation was done by one single 3D CFD simulation tool, since such a comparison is missing in the scientific community. It was shown that global reforming mechanisms are capable of correctly predicting the occurring gas phase reactions, but only provide indicators for the thermodynamic equilibria of considered carbon formation pathways. Detailed information about surface adsorbed carbon can only be determined by a heterogeneous reaction mechanism. Elementary carbon was shown to be permanently adsorbed onto the catalytic active sites in the anode by the conducted steady state simulations. The investigations showed that the inlet region of the porous anodic structure is especially susceptible to coking. Simulation results were validated with in-house experimentally determined data. High cell current densities were reached during the single cell experiments, which determine good electrical contacting as well as electrochemical performance and therefore represent reliable validation data.

Anode regeneration following carbon depositions in an industrial-sized anode supported solid oxide fuel cell operating on synthetic diesel reformate

Carbon deposition is a primary concern during operation of solid oxide fuel cells (SOFCs) fueled with carbon-containing fuels. It leads to cell degradation and thus reduces SOFC sustained operation and durability. This paper reports on an experimental investigation of carbon formation on the nickel/yttria-stabilized zirconia (Ni/YSZ) anode of an anode-supported SOFC and its regeneration. The cell was fueled with a synthetically produced diesel reformate to investigate and simulate the cell behavior under real operating conditions. For this purpose the cell was operated under load to determine the critical operating time. Rapid carbon generation, such as at open circuit voltage (OCV), can be prevented when the cell is under load. Carbon depositions were detected using scanning electron microscopy (SEM) and further analyzed by Raman spectroscopy. Industrial-size cells suitable for commercial applications were studied. This study proves the reversibility of carbon formation and the reproducibility of the regeneration process. It shows that carbon formations can be recognized and effectively, fully and cell-protecting regenerated. It indicates the excellent possibility of using SOFCs in the automotive industry as an auxiliary power unit (APU) or combined power-heat unit, operated with diesel reformate, without danger from cell degradation caused by carbon-containing fuels.

Co-Synthesis of Hydrogen and Carbon Fuels from Water and Carbon Dioxide

Non-fossil fuel based, low carbon footprint fuels are needed to ameliorate the effects of anthropogenic climate change. We have previously demonstrated molten hydroxide electrolytes for solar water splitting to hydrogen fuel, and molten carbonate electrolytes for solar carbon dioxide splitting to carbon or carbon monoxide fuels. Solid carbon (as coal) is used as the starting point to generate CO and hydrogen for the Fischer-Tropsch generation of a variety of fuels, such as synthetic diesel. However, that process is carbon dioxide emitting intensive. In this study we present the first molten electrolyte sustaining electrolytic co-production of both hydrogen and carbon products in a single cell (1). Here, hydrogen and carbon products are produced without carbon dioxide emissions and instead produced from water and carbon dioxide. The demonstrated functionality of hydroxide and carbonate electrolytes to co-generate hydrogen and carbon fuels at low electrolysis potentials, and from water and CO2starting points, provides a significant step towards the development of renewable fuels. Fang-Fang Li, Shuzhi Liu, Baochen Cui, Jason Lau, Jessica Stuart, Baohui Wang, and Stuart Licht, "A one-pot synthesis of hydrogen and carbon fuels from water and carbon dioxide," recommended for publication Nov. 20, 2014, Advanced Energy Materials Figure 1