Use Of Hydrocarbon Fuels Research Articles

DIRECT CONVERSION OF BIOMASS TO ELECTRICITY WITH SOLID OXIDE FUEL CELL TECHNOLOGY

Fuel cells are electrochemical devices that convert chemical energy of fuels directly into electrical energy without the Carnot limitation. Even in the smallest power range of less than 10 kW, fuel cells exhibit electrical efficiencies of 35-50 %LHV (lower heating value). Therefore, the fuel cell which can be operated with very low environmental emission levels, is regarded as a promising candidate for a distributed power source in the next generation. Although most fuel cells operate with hydrogen as a fuel, solid oxide fuel cells (SOFCs) operated in a high temperature range between 600 and 900oC accept the direct use of hydrocarbon fuels. Recently, the present research have demonstrated the stable operation of a direct internal reforming SOFC (DIRSOFC) operating not only on non-synthetic biogas over one month using an anode-supported button cell but also on practical palm-biodiesel over 800 h. Here, performances of DIRSOFCs operating on biogas are summarized and roadblocks to overcome for the realization of this type of highly-efficient carbonneutral fuel cell are discussed.

Deep greenhouse gas reduction scenarios for California – Strategic implications from the CA-TIMES energy-economic systems model

California has taken a leading role in regulating greenhouse gas (GHG) emissions, requiring that its economy-wide emissions be brought back down to the 1990 level by 2020. The state also has a long-term, aspirational goal of an 80 percent reduction below the 1990 level by 2050. While the steps needed to achieve the near-term target have already been clearly defined by California policy makers, the suite of transformational technologies and policies required to decarbonize the energy system over the long term have not yet been explored. This paper describes an effort to fill this important gap, introducing CA-TIMES, a bottom-up, technologically-rich, integrated energy–engineering–environmental–economic systems model that has been developed to guide the long-term policy planning process. CA-TIMES is useful for exploring low-carbon scenarios, and the analyses described here focus on the potential evolution of the transportation, fuel supply, and electric generation sectors over the next several decades in response to various energy and climate policies. We find that meeting California’s 80% emission reduction goal can be achieved through a combination of mitigation strategies, including managing the growth in energy service demand, increasing investments in efficiency and low-carbon energy supply technologies, and promoting demand technologies that facilitate end-use device electrification and a decrease in the direct use of hydrocarbon fuels through efficiency improvement and fuel switching. In such deep emission reduction scenarios, we estimate that energy system costs (accounting for investments on the energy supply side and in transportation demand technologies, as well as fuel and O&M costs) could be around 8–17% higher than in a reference case. Meanwhile, average abatement costs could range from $107 to $225/tCO2. These estimates are very much dependent on a range of socio-political and technological uncertainties, for instance, the availability and cost of biomass, nuclear power, carbon capture and storage, and electric and hydrogen vehicles.

First-Principles Analysis of the Activity of Transition and Noble Metals in the Direct Utilization of Hydrocarbon Fuels at Solid Oxide Fuel Cell Operating Conditions

The direct on-cell use of hydrocarbon fuels in solid oxide fuel cells (SOFCs) involves many thermochemical and electrochemical reactions that occur on anode electrocatalysts, both at and away from the three-phase boundary. We have used first-principles density functional theory calculations and kinetic modeling to investigate relevant reactions associated with the direct utilization of methane on different electrocatalysts at SOFC operating conditions. The investigated reactions are steam and dry reforming of methane, electrochemical oxidation of and CO, and direct electrochemical oxidation of methane. These studies allowed us to compare the relative activity of different metals and to identify those metals that offer optimal performance. Our analysis shows that under relevant operating conditions, there exists a family of metals (mainly Ni, Co, Rh, Ru, and Ir) that offer maximum activity for all relevant reactions. The findings suggest that a fairly simple anode design including only one material in combination with yttria-stabilized zirconia performing multiple reactions should offer close to optimal performance. While we outline our results for methane in detail, we also comment on the direct utilization of other hydrocarbons.

Roles of Hydrogen Donors and Organic Selenides in Inhibiting Solid Deposits from Thermal Stressing of n-Dodecane and Chinese RP-3 Jet Fuel

Use of hydrocarbon fuels as coolants for future high-Mach aircraft is challenged by the formation of carbonaceous deposits during thermal stressing at high temperatures (>500 °C). Three hydrogen do...

Internal Reforming of Hydrocarbon Fuels in Tubular Solid Oxide Fuel Cells

The application of heterogeneous catalysis has an important role to play in the successful commercial development of solid oxide fuel cell (SOFC) technology. In this paper, we present a solid oxide fuel cell that combines a catalyst layer with a conventional anode, allowing internal reforming via partial oxidation (POX) of fuels such as methane, propane, butane, biomass gas etc. without coking and yielding stable power output. The catalyst layer is fabricated on the anode simply by catalyst support coating and reforming catalyst impregnation. The composition and microstructure of catalyst support layer as well as the catalyst composition was easily tailored to meet the demand of in-situ reforming. The usage of catalyst layer as an integrated part of the traditional SOFC will provide a simple low-cost power generating system at substantially higher fuel efficiency and faster start-ups, and may accelerate the application of SOFCs through the direct use of hydrocarbon fuels.

Internal reforming of hydrocarbon fuels in tubular solid oxide fuel cells

The application of heterogeneous catalysis has an important role to play in the successful commercial development of solid oxide fuel cell (SOFC) technology. In this paper, we present an SOFC that combines a catalyst layer with a conventional anode, allowing internal reforming via partial oxidation (POX) of fuels such as methane, propane, butane, biomass gas, etc., without coking and yielding stable power output. The catalyst layer is fabricated on the anode simply by catalyst support coating and reforming catalyst impregnation. The composition and microstructure of catalyst support layer as well as the catalyst composition was easily tailored to meet the demand of in situ reforming. The usage of catalyst layer as an integrated part of the traditional SOFC will provide a simple low-cost power-generating system at substantially higher fuel efficiency and faster start-ups, and may accelerate the application of SOFCs through the direct use of hydrocarbon fuels.

Nanostructured thin solid oxide fuel cells with high power density

Nanostructured thin film solid oxide fuel cells (SOFC) have been developed for reduced temperature operation, with high power density, and to be self reforming. A thin film electrolyte (1-2 microm thickness), e.g., yttria-stabilized zirconia (YSZ), is deposited on a nickel foil substrate. The electrolyte thin film is polycrystalline when deposited on a polycrystalline nickel foil substrate, and is (100) textured when deposited on an atomically textured nickel foil substrate. The Ni foil substrate is then converted into a porous SOFC anode by photolithographic patterning and etching to develop porosity. A composite La(0.5)Sr(0.5)CoO(3) cathode is then deposited on the thin film electrolyte. The resultant thin film hetero structure fuel cells have operated at a significantly reduced temperature: as low as 470 degrees C, with a maximum power density of 140 mW cm(-2) at 575 degrees C, and an efficiency of >50%. This drastic reduction in operating temperature for an SOFC now also allows for the use of hydrocarbon fuels without the need for a separate reformer as the nickel anode effectively dissociates hydrocarbons within this temperature range. These nanostructured fuel cells show excellent potential for high power density, small volume, high efficiency fuel cells for power generation applications.

Which elastomer seal materials are suitable for use in biofuels?

There is increasing interest in the use of hydrocarbon fuels derived from renewable resources. This is being driven by a variety of environmental, political and economic concerns and attracting considerable industrial investment for the production of renewable supplies to replace both gasoline and diesel fuel. The introduction of these fuel sources, as a blend with traditional mineral fuel supplies is placing additional demands on the compatibility of the elastomer materials used for seals. This feature reviews information on suitable materials from DuPont for use in butanol and Freudenberg Simrit for biodiesel.

An Experimental Evaluation of the Temperature Gradient in Solid Oxide Fuel Cells

The use of solid oxide fuel cells SOFCs 1,2 as efficient energyconverter devices rests on their high working temperature. These ceramic fuel cells generally operate between 800 and 1000°C, although a major research effort is put forward to reduce their operation below 800°C for reducing manufacturing costs and improving cell lifetime. Depending on the selected range of temperature, a SOFC system would allow for either cogeneration or bottoming cycle, which add significantly to the overall power-generation efficiency. The high operating temperature of SOFC affords, in principle, for the direct use of hydrocarbon fuels by means of their catalytic conversion to carbon monoxide and hydrogen. The most economical way to convert these fuels is to proceed through direct internal reforming DIR, as it is observed in tubular or planar designs, or through catalytic partial oxidation CPOX, which is at the basis of the functioning of single-chamber SOFC SC-SOFC. However, both DIR and CPOX may lead to high temperature variations along the fuel cell. In the case of direct reforming of methane, a significant cooling at the inlet of the fuel cell is expected due to the fast kinetics of the endothermic reforming reaction, especially over conventional Ni– yttria-stabilized zirconia YSZ cermet. 3 It then aggravates the tem

The future of India’s economic growth: the natural resources and energy dimension

The continuation of widespread poverty apart, the biggest danger that India faces is the wanton destruction and degradation of all the country’s natural resources and a growing, unsustainable, dependence on the use of hydrocarbon fuels. We are losing ten percent of our GDP as a result of the damage to and degradation of our natural resources. But environmental decision-making has not yet been merged with mainstream economic decision making. In the developed countries, environmental protection followed a path defined by the Environmental Kuznets curve, involving significant increases in income and pollution levels to a point where the trend changed. A developing country like India cannot pursue the same path, and would need to set up a governance structure and policy regime that allow the turning point to take place at substantially lower levels of income. The internalization of social and environmental externalities would ensure that resources are used in a sustainable and responsible manner. In the matter of energy use, for instance, proactive policies—such as stress on renewable sources and the rationalisation of subsidies—are needed to decrease the dependence on unsustainable imports and to create the conditions under which the dispossessed and poor sections of society are able to meet their basic energy needs. Blindly aping the consumerist approach of the developed world, and neglecting the ecological footprint of lifestyles, could prove disastrous for our populous country.

Hydrocarbons and the evolution of human culture.

Most of the progress in human culture has required the exploitation of energy resources. About 100 years ago, the major source of energy shifted from recent solar to fossil hydrocarbons, including liquid and gaseous petroleum. Technology has generally led to a greater use of hydrocarbon fuels for most human activities, making civilization vulnerable to decreases in supply. At this time our knowledge is not sufficient for us to choose between the different estimates of, for example, resources of conventional oil.

Optimization of Flame Synthesis for Carbon Nanotubes Using Supported Catalyst

A series of rich premixed flames are used to realize a post-flame gas mixture for optimum carbon nanotube (CNT) growth using inexpensive hydrocarbon fuels. The mixture of CO, CO2, H2, and H2O is varied through use of hydrocarbon fuels with different H/C ratio in flames with different fuel/air ratios. Both SEM and HRTEM imaging are used to correlate the nanotube morphology and internal structure to the reaction gas composition. The variations observed are understood in light of the gas composition and the interaction of the reactive components with both the deposited Co catalyst particles and supporting metal substrate. Further comparisons between flames producing the same CO or H2 concentrations identify the roles of these gases in CNT synthesis. Optimal flame synthesis conditions, defined upon a H2 and CO concentration map, are gauged on the basis of CNT length, relative surface density, and level of graphitic structure.

Improved Oxidation of Hydrocarbons with New Electrodes in High Temperature Fuel Cells

Although fuel cells work efficiently with hydrogen as a fuel there are still some major problems related to hydrogen availability and acceptability. In particular, it is still extremely difficult to obtain clean/renewable hydrogen. In the short to medium term future, the only realistic fuels for fuel cells are hydrocarbon based, especially natural gas. In this article, we address the optimal use of hydrocarbon fuels in high temperature, solid oxide fuel cells. In conventional solid oxide fuel cells, the hydrocarbon fuel is typically reformed with large quantities of steam over nickel externally to the fuel cell. Internal reforming is a more attractive process that can occur at the Nickel/zirconia cermets that are generally used as fuel electrodes. The various complicated steps that occur during this process are reviewed and discussed, paying particular attention to the hydrocarbon cracking reactions that often occur at low steam levels. There are a number of new materials, such as those based on lanthanum chromate, that offer improved resistance to hydrocarbon cracking at low steam partial pressures. Of particular relevance; is the concept of gradual internal reforming, whereby steam generated during the initial oxidation reaction is used to drive further reforming reactions. A further process, direct oxidation can also occur at low steam partial pressures. This process offers the ultimate in thermodynamic efficiency, almost 100 percent theoretically, which renders it very attractive. Some very good success has been reported with copper ceria electrodes, with direct oxidation claimed at temperatures up to 700 °C. The performance of a number of new oxide electrodes with perovskite, fluorite and related structures is reviewed. A particularly important conclusion is the importance of mixed conductivity for optimising catalytic performance.

Effect of Electrophysical Factors on Formation of Noxious Emissions during Combustion of Gaseous Hydrocarbons

At present, many problems of detoxification of noxious emissions generated on burning of hydrocarbon fuels (HF) cannot be solved successfully without a detailed theoretical analysis of the combustion process and without taking account of the physicochemical processes that lead to uneven distribution of various components in the gas stream as well as to a change in th e composition of the gas and the internal state of its atoms and molecules. Attempts to apply traditional semiempirical methods of control of noxious emissions produced during use of hydrocarbon fuels (HF) in practice, in general, lead to large expenditures on material resources and greatly impede development and introduction of high-efficiency industrial technologies [1‐6]. The HF combustion process may be regarded as a stream of multicomponent gases undergoing exothermic chemical reactions, and so this process can be described with certain approximations taking recourse to the kinetic theory of gases. The basic equations of gas dynamics based on the Boltzmann equation are the fundamentally important outcome of this theory, which made it possible to establish an unbroken link between the macro- and microprocesses in the stream. This allows one investigating streams of chemically reacting multicomponent gas mixtures to theoretically calculate internal flow, to determine the transport factor as a function of temperature, pressure, molecular weights of the gas components, and parameters that describe the laws of molecular interaction, and to determine the effect of external forces on the multicomponent gas mixture through interaction between the individual components of the gas mixture. We shall make an attempt, on the basis of solution of the Boltzmann equation for slightly unsteady and nonequilibrium states of a gas mixture, to determine the internal microstreams of a flame of gaseous hydrocarbons and the effect of these proce sses on the yield of individual components in the combustion process [1‐3]. The factors affecting the internal stream and the un balanced yield of individual components during combustion of gaseous HF arise from the process of combustion in the stream itself. A steep rise in the internal energy of the stream causes accelerated motion of the gas mixture and separation of the gas components. Moreover, in the space where combustion takes place, there appears thermal inhomogeneity, and if the relationship of the rate of formation of nitrogen oxides (NO x ) with the gas temperature is nonlinear, the yield of nitrogen oxides goes up beyond what is possible thermodynamically. Acceleration of the stream and the consequent thermal inhomogeneity alter the electrophysical parameters of the flame. Consequentially, the key factors affecting the increase in the yield of individual com ponents as a result of internal streams in the flame are thermal, gas dynamic, and electrophysical [1‐5]. These factors lead to disruption of the thermodynamic equilibrium in the combustion process. Even though occurrence of chemical reactions in a gas mixture may disrupt the Boltzmann energy distribution, investigations of the effect of chemical reactions on the transport factors however demonstrate that in many cases [4] this effect can be ignored. Analysis of the solution of the Boltzmann equation shows that in a multicomponent gas mixture diffusion of the components relative to the basic mass may occur due to pressure, temperature, and concentration gradients as well as due to the action of mass forces. These factors are interrelated and affect each other. In a first approximation, the dependence of the d iffusive stream of the components on the gradients of these parameters is linear. Note that if there are no external mass forces , the diffusive streams arising due to gradients of pressure, temperature, and concentration of the individual components do not give rise to macromotion of the system. In the end, they may merely counterbalance each other, and the time and extent of this balancing depend on specific interactions between the particles of the components. For example, in the case of accelerated

97/01541 Plasma chemical reactions at atmospheric pressure for high efficiency use of hydrocarbon fuels

Much of the Miocene Monterey Formation of California is rich in biogenic sediment, especially organic matter and silica. Because of the geologic structure, the Monterey in the subsurface near Lost Hills in the San Joaquin Basin forms a natural laboratory for the study of the diagenetic responses of these materials. Rocks of similar age and lithology are buried to depths ranging between 500 and 3500 m, and are thus exposed to a temperature range of 45–130°C.The diagenetic progression of silica from opal-A to opal-CT to microquartz is well-documented in Monterey burial history studies. However, diagenetic indicators need to be established below the depth of complete conversion of opal-CT to quartz, which may be very shallow (1500 m or less at Lost Hills). Conventional maturity indicators are problematic. The scarcity of vitrinite in many Monterey samples hampers reflectance measurements. In addition, values that are measured may be anomalously low. Maximum pyrolysis temperatures are depressed, due in part to high heavy bitumen content.Biomarker geochemistry provides effective alternative maturity indicators. Of particular interest are the stereochemical variations observed in the assemblages of steranes and triterpanes extracted from oil well core samples. For example, the 20S/20R ratio of 5α(H), 14α(H), 17α(H)-24-ethylcholestane increases from 0.09 to 0.56 over the depth range cited.Samples from petroleum accumulation zones are distinguished by anomalously mature biomarker assemblages considering their depth of burial. This indicates that these bitumens are as mature as the deepest non-production zone sample (3430 m), even though they are from much shallower depths (580–1572 m). Other maturity (and/or migration) indicators confirm this, such as the relative increases in amounts of 14β(H), 17β(H)-steranes, rearranged steranes and tricyclic terpanes. Thus, it appears that any immature indigenous bitumen in production zone samples is overwhelmed by a mature component, which presumably migrated updip, from deeper, warmer strata.Since much oil is produced from shallow, organic-rich fractured Monterey shales, early in situ generation has previously been hypothesized. However, while both source and reservoir rock are lithologically similar and lie within the same formation, biomarker geochemistry indicates that substantial generation occurs only in deeply buried Monterey shales.

Plasma chemical reactions at atmospheric pressure for high efficiency use of hydrocarbon fuels

Direct conversion of methane to methanol with minimum energy consumption could become a key technology for highly efficient utilization of fossil fuel, because low-quality or low-temperature (∼100°C) energy sources can be used and regenerated by converting methanol to hydrogen. For this purpose, a new technique for synthesizing methanol directly from a methane-oxygen mixture has been developed using a highly nonequilibrium, square-pulsed, silent discharge plasma at atmospheric pressure and temperature. Various effects of oxygen concentration, reaction time and discharge parameters on the conversion efficiency and reaction selectivity have been clarified. Reaction mechanisms for this type of plasma have been elucidated by using time-dependent optical emission measurements of CH radicals during the streamer current period just after a sharp, pulsed voltage rise. High values of 2.4 % and 32.6 % for methanol yield and selectivity, respectively, have been successfully obtained in a single-path experiment. These values may be enhanced by optimizing the reacting conditions, combining this technique with catalytic reactions, and introducing a recirculating reaction system. The formation processes for high-energy species just after the sharp, pulsed voltage rise were also analyzed theoretically. Good agreement was found between the experimental data and theoretical predictions.

Sustainable development: A co-evolutionary view

The challenges of sustainable development can be organized around three themes. First, modernization has been unsustainable because it has been supported by the use of hydrocarbon fuels and chemicals which are limited in availability and damaging to the atmosphere and terrestrial and aquatic systems. Sustainable development will require that the use of energy and chemicals be subservient to ecosystem maintenance. Second, political consensus and bureaucratic mobilization will be more difficult because we no longer believe that development is almost inevitable through the application of Western science. On the other hand, we may be less prone to make mistakes. The decline in belief in progress has also increased the opportunities for non-Western cultures to define development for themselves. Third, we are shifting from a mechanical to a co-evolutionary understanding of systems which helps explain why development has been unsustainable and what we must do to attain sustainability.

Endothermic fuels for hypersonic vehicles

The use of hydrocarbon fuels for hypersonic vehicles will require increasing utilization of the fuel as vehicle speed increases. In order to achieve maximum heat sinks endothermic reactions must be employed to augment fuel enthalpy. Various reactions, such as thermal cracking, depolymerization, dehydrogenation, and dehydrocyclization, can be used and have been studied. Of these, the catalytic dehydrogenation of naphthenes shows the most promise for practical application. The dehydrogenation of MCH over a Pt/AJfoOa catalyst can approximately double the 1000 Btu/lb available from fuel enthalpy. This should provide cooling sufficient to allow flight into the range of Mach 10 at optimum altitude. However, the application of cooling to the various portions of the aircraft will present formidable problems. Factors that are important in this consideration such as thermal stability, reaction rate, reactor weight and volume, heat transfer, pressure drop, combustion characteristics, and the mating of the cooling system to the aircraft are discussed.