Conversion of jet fuel and butanol to syngas by filtration combustion

Replacing batteries with fuel cells is a promising approach for powering portable devices; however, hydrogen fuel generation and storage are challenges to the acceptance of this technology. A potential solution to this problem is on-site fuel reforming, in which a rich fuel/air mixture is converted to a hydrogen-rich syngas. In this paper, we present experimental results of the conversion of jet fuel (Jet-A) and butanol to syngas by non-catalytic filtration combustion in a porous media reactor operating over a wide range of equivalence ratios and inlet velocities. Since the focus of this study is the production of syngas, our primary results are the hydrogen yield, the carbon monoxide yield, and the energy conversion efficiency. In addition, the production of soot that occurred during testing is discussed for both fuels. Finally, an analysis of the potential for these fuels and others to be converted to syngas based on the present experiments and data available in the literature is presented. This study is intended to increase the understanding of filtration combustion for syngas production and to illuminate the potential of these fuels for conversion to syngas by non-catalytic methods.     

Combustion chemistry aspects of alternative fuels reforming for high-temperature fuel cell applications

Solid-oxide fuel cells (SOFC) constitute a particularly attractive technology for sustainable, combined heat and power generation, both at domestic and district levels. The elevated operating temperature of SOFC systems, allows the utilization of a wide spectrum of conventional and alternative fuels, through suitable reforming processes. The high temperatures and fuel rich conditions prevailing in SOFC reformers, enhance syngas yield and reforming efficiency but may give rise to unwanted effects, such as ignition, soot and coke formation and deposition. The above phenomena cannot be described via thermodynamic considerations and can only be effectively tackled through a detailed chemical kinetic approach. The present study provides a comparative assessment of SOFC reformer operation on conventional and alternative hydrocarbon fuels in terms of syngas yield, thermal efficiency and pollutants formation. In particular, the reforming of methane, a typical biogas (comprising of 60% CH₄ and 40% CO₂), methanol and ethanol is numerically assessed by utilizing a recently developed and validated comprehensive detailed kinetic mechanism for C₁–C₆ hydrocarbons, augmented with a PAH model. Chemical aspects of the fuel reforming process are investigated through rate-of-production path and sensitivity analyses. The study supports design guidelines aiming towards identification of optimum operating conditions, for specific applications and fuels. The analysis reveals that the extent of coupling between syngas formation and molecular growth processes is strongly dependent on fuel and operating conditions choice and identifies windows of efficient operation, for each case.     

Chemical looping reforming of ethanol for syngas generation: A theoretical investigation

Chemical looping reforming (CLR) is a novel technology that can be used for reforming of cheaply available abundant biofuel like ethanol for the production of hydrogen/syngas for fuel cells. A systematic thermodynamic study for the CLR process using selected oxygen carriers was done to analyze the products and energy requirements of the CLR process in the temperature range of 500–1200 °C at 1 bar pressure for ethanol. The results showed favorable conditions for syngas manufacture from this process. Fe₂O₃ was found to be the best performing oxygen carrier followed by calcium and sodium sulfates, while Mn oxides were the least preferred oxygen carriers for CLR of ethanol process. The optimum process temperature was found to be 1000 °C. The actual CLR‐ethanol process shows exothermicity against the theoretical endothermic partial oxidation of ethanol. The results obtained in this theoretical study can pave the way for experimental programs for syngas generation for SOFC‐type fuel cells. Similar studies can be undertaken for other fuels for fuel processor development by CLR process. Copyright © 2012 John Wiley & Sons, Ltd.     

Improving the performance of a spark-ignited gasoline engine with the addition of syngas produced by onboard ethanol steaming reforming

Producing the syngas by onboard ethanol steam reforming is an effective way for recovering the exhaust heat in the engine tailpipe. Besides, as hydrogen is contained in the syngas, the addition of syngas is also capable of improving engine combustion and emissions characteristics. In this paper, an experimental study was carried out on a four-cylinder 1.6 L spark-ignited engine to explore the effect of syngas addition on the engine performance. A fuel reforming reactor with the copper based catalysts was designed and mounted on the engine tailpipe, so that the ethanol solution could be decomposed to be syngas which is mainly composed of hydrogen and carbon monoxide when the catalysts were heated by the exhaust gas. The intake manifolds was also modified to permit syngas to be injected into the fourth cylinder of the engine. The engine was run at 1800 rpm and a manifolds absolute pressure of 61.5 kPa. The spark timing for the maximum brake torque was adopted for each testing point. The syngas volume fraction in the total intake gas was gradually increased from 0% to 2.43%. Meanwhile, the gasoline injection duration governing by a hybrid electronic control unit was adjusted to keep the excess air ratio of the fuel-air mixture in the fourth cylinder at about 1.00. The experimental results demonstrated that the syngas volume flow rate was markedly enhanced from 90 to 240 L/h when the feedstock flow rate was increased from 18 to 54 mL/min. The peak ethanol conversion efficiency reached 81.16% at a feedstock flow rate of 36 mL/min. The hydrogen concentration was increased whereas carbon monoxide concentration was decreased in the syngas with the increase of the feedstock supply. The engine indicated thermal efficiency was raised to be 39.01% at the syngas volume fraction of 2.43%. The flame development and propagation durations were shortened; HC and NOx emissions were reduced whereas CO emission was increased after the syngas addition at the stoichiometric condition.     

Counter-rotating dual-stage swirling combustion characteristics of hydrogen and carbon monoxide at constant fuel flow rate

In this paper, experimental and numerical methods were used to study the combustion characteristics of a counter-rotating double-stage swirling syngas combustor at constant fuel flow rate, and the effect on it of hydrogen content of syngas. In the experiment, the speed and temperature in the combustor were respectively obtained with PIV and temperature rake, while Reynolds stress equation model and the detailed chemical reaction mechanism of syngas were adopted in the numerical method. The calculation results were in good agreement with the experimental data. Research results indicated that in the working conditions of different hydrogen contents, the flow field structures in the combustor are almost the same, and the maximum temperatures at the outlet remain almost the same. However, as hydrogen content in the fuel increases, the axial velocity in the central area of flow field is increasing, and the outlet temperature distribution coefficient decreases first and then increases. In addition, it was also found in the study that the distribution structure of temperature on the central section of the combustor is almost impervious to the changes in hydrogen content, but with numerical differences, i.e. the higher hydrogen content in the fuel, the farther the stabilization position of flames in the central area is away from the head. It was also indicated in the study that the conventional combustor is no longer applicable to the combustion of syngas, especially the hydrogen-rich fuel. And the work provided the improvement scheme of hydrogen-containing fuel for gas turbine combustor.     

Modeling study on the production of hydrogen/syngas via partial oxidation using a homogeneous charge compression ignition engine fueled with natural gas

The production of hydrogen and syngas from natural gas using a homogeneous charge compression ignition reforming engine is investigated numerically. The simulation tool used was CHEMKIN 3.7, using the GRI-3 natural gas combustion mechanism. This simulation was conducted on the changes in hydrogen and syngas concentration according to the variations of equivalence ratio, intake temperature, oxygen enrichment, engine speed, initial pressure, and fuel additives with partial oxidation combustion. The simulation results indicate that the hydrogen/syngas yields are strongly dependent on the equivalence ratio with maxima occurring at an optimal equivalence ratio varying with engine speed. The hydrogen/syngas yields increase with increasing intake temperature and oxygen contents in air. The hydrogen/syngas yields also increase with increasing initial pressure, especially at lower temperatures, yet high temperature can suppress the pressure effect. Furthermore, it was found that the hydrogen/syngas yields increase when using fuel additives, especially hydrogen peroxide. Through the parametric screening studies, optimum operating conditions for natural gas partial oxidation reforming are recommended at 3.0 equivalence ratio, 530 K intake temperature, 0.3 oxygen enrichment, 500 rpm engine speed, 1 atm initial pressure, and 7.5% hydrogen peroxide.     

A comparison of environmental benefits of transport and electricity applications of carbohydrate derived ethanol and hydrogen

It may soon become possible to produce hydrogen from hydrolysed carbohydrates instead of ethanol via fermentation and distillation, employing aqueous phase reforming. The environmental merits of these two different energy products and their uses are compared on a life cycle basis, based on expanded systems in the context of a coal-intensive energy economy. Eight industrial options are defined: ethanol for peak power generation with or without heat integration, hydrogen for peak power generation with and without heat integration, ethanol for use in a flexi-fuel vehicle and a fuel cell vehicle, and hydrogen use in an internal combustion engine vehicle and a fuel cell vehicle. Aqueous phase reforming to produce hydrogen is shown to generally out-perform the corresponding fermentation–distillation ethanol options. Peak power generated from ethanol would be a preferred short-term option, with peak power from hydrogen in the medium term ceding to the environmentally preferred option of hydrogen fuel cell vehicles in the long-term.     

A novel approach for treatment of CO2 from fossil fired power plants. Part B: The energy suitability of integrated tri-reforming power plants (ITRPPs) for methanol production

In Part A of this two-paper work, a novel approach for treatment of CO₂ from fossil fired power plants was studied. This approach consists of flue gases utilization as co-reactants in a catalytic process, the tri-reforming process, to generate a synthesis gas suitable in chemical industries for production of chemicals (methanol, DME, ammonia and urea, etc.). In particular, the further conversion of syngas to a transportation fuel, such as methanol, is an attractive solution to introduce near zero-emission technologies (i.e. fuel cells) in vehicular applications. In fact, the methanol can be used in DMFC (Direct Methanol Fuel Cell) or as fuel for on-board reforming to produce hydrogen for PEMFC (Proton Exchange Membrane Fuel Cell).     

Stoichiometric analysis of autothermal fuel processing

Fuel processing is one of the major processes for generation of hydrogen for fuel cells. Stoichiometric analysis is used to develop a general framework for comparison of fuel reforming data, in the full range of steam reforming (SR) to combustion. This framework is then applied to determine the reforming reaction space for methanol, ethanol, methane, propane, isooctane, dodecane, and hexadecane. A simple approach is proposed for determination of the thermal efficiency for autothermal reforming (ATR) of a generalized fuel based on fuel atomic analysis and oxygen consumption.     

High temperature steam gasification of wastewater sludge

High temperature steam gasification is one of the most promising, viable, effective and efficient technology for clean conversion of wastes to energy with minimal or negligible environmental impact. Gasification can add value by transforming the waste to low or medium heating value fuel which can be used as a source of clean energy or co-fired with other fuels in current power systems. Wastewater sludge is a good source of sustainable fuel after fuel reforming with steam gasification. The use of steam is shown to provide value added characteristics to the sewage sludge with increased hydrogen content as well total energy. Results obtained on the syngas properties from sewage sludge are presented here at various steam to carbon ratios at a reactor temperature of 1173 K. Effect of steam to carbon ratio on syngas properties are evaluated with specific focus on the amounts of syngas yield, syngas composition, hydrogen yield, energy yield, and apparent thermal efficiency. The apparent thermal efficiency is similar to cold gas efficiency used in industry and was determined from the ratio of energy in syngas to energy in the solid sewage sludge feedstock. A laboratory scale semi-batch type gasifier was used to determine the evolutionary behavior of the syngas properties using calibrated experiments and diagnostic facilities. Results showed an optimum steam to carbon ratio of 5.62 for the range of conditions examined here for syngas yield, hydrogen yield, energy yield and energy ratio of syngas to sewage sludge fuel. The results show that steam gasification provided 25% increase in energy yield as compared to pyrolysis at the same temperature.     

An alternative process for gasoline fuel processors

The article explores the thermodynamics of an alternate hydrogen generation process - dry autothermal reforming and its comparison to autothermal reforming process of isooctane for use in gasoline fuel processors for SOFC. A thermodynamic analysis of isooctane as feed hydrocarbon for autothermal reforming and dry autothermal reforming processes for feed OCIR (oxygen to carbon in isooctane ratio) from 0.5 to 0.7 at 1 bar pressure under analogous thermoneutral operating conditions was done using Gibbs free energy minimization algorithm in HSC Chemistry. The trends in thermoneutral points (TNP), important product gas compositions at TNPs and fuel processor energy requirements were compared and analyzed. Dry autothermal reforming was identified as a less energy consuming alternative to autothermal reforming as the syngas can be produced with lower energy requirements at thermoneutral temperatures, making it a promising candidate for use in gasoline fuel processors to power the solid oxide fuel cells. The dry autothermal reforming process for syngas production can also be used for different fuels.     

A detail study of a RCCI engine performance fueled with diesel fuel and natural gas blended with syngas with different compositions

The catalytic reforming is an applicable method to generate hydrogen as an alliterative fuel directly that is of prime interest to replace hydrocarbon fuels. Although, the use of this type of catalyst has the potential to solve the problem of safe storage of hydrogen in ICEs, but, this method suffers from the simultaneous production of carbon monoxide with hydrogen known as syngas. Depending on the engine operating conditions, different syngas composition in terms of H2/CO volumetric ratio can be produced through the mentioned catalyst. An engine performance which uses onboard hydrogen produced is completely affected by syngas composition. Therefore, the aim of the current simulation study is to evaluate the performance of a heavy-duty diesel engine under RCCI combustion fueled with diesel fuel/natural gas blended with syngas with different compositions. For this purpose, at 9.4 bar gross IMEP, natural gas is gradually replaced by five different compositions of syngas that is H2/CO volumetric ratios of 33.33/66.67, 50/50, 66.67/33.33, 80/20, and 100/0. The simulation results show that not only the engine output power can be improved up to 27.7% by simply increasing of the CO/H2 volumetric ratio in syngas composition to 66.67/33.33, but also the GIE is reduced by less than 9%. In contrast, the risk of the diesel knock occurrence may increase only in higher CO/H2 ratios. Although, the NOx level can be achieved closer to the EURO VI level, but, same level for UHC and CO and also the level of EPA 2007 for formaldehyde are not achievable for syngas with the higher CO/H2 volumetric ratio.     

Hydrogen enrichment of methane and syngas for MILD combustion

Moderate or Intense Low-oxygen Dilution (MILD) combustion is a technology with important characteristics such as significant low emission and high-efficiency combustion. The hydrogen enrichment of conventional fuels is also of interest due to its favorable characteristics, such as low carbon-containing pollutants, high reaction intensity, high flammability, and thus fuel usage flexibility. In this study, the effects of adding hydrogen to methane and syngas fuels have been investigated under conditions of MILD combustion through numerical simulation of a well-set-up MILD burner. The Reynolds-Averaged Navier-Stokes (RANS) approach is adopted along the Eddy Dissipation Concept (EDC) combustion model with two different chemical mechanisms. Molecular diffusion is modeled using the differential diffusion approach. The effects of oxidizer dilution and fuel jet Reynolds number on the reactive flow field have been studied. Results show that with an increase in hydrogen portion of the fuel mixtures, the volume of the high-temperature region of combustion field increases whereas a reduction of oxidizer oxygen content leads to more proximity to the MILD condition. Increasing the fuel jet Reynolds number will result in an expansion of the combustion zone and shifting of this region in the axial direction. Predictions revealed that the methane flame is more sensitive to the oxidizer dilution and fuel jet Reynolds number than syngas. Moreover, enrichment of fuel with hydrogen seems to be better for acquiring condition of the MILD combustion for syngas rather than methane. Indeed, syngas shows more sensitivity to hydrogen enrichment than methane, which makes hydrogen a good additive to syngas in terms of MILD condition benefits.     

Hydrogen production from steam reforming of coke oven gas and its utility for indirect reduction of iron oxides in blast furnace

Hydrogen and synthesis gas (syngas) can be produced from steam reforming (SR) of coke oven gas (COG). When the reforming gas is used for indirect reduction (IR) of iron oxides in blast furnaces (BFs), carbon dioxide emissions can be lessened. Motivated from utilizing hydrogen and mitigating greenhouse gas emissions in ironmaking, the reaction phenomena of SR of COG are investigated thermodynamically. Low-temperature and high-temperature IR of iron oxides using reforming gas as a feedstock is also analyzed. With appropriate operating conditions, the maximum H₂ and syngas yields are 3.5 and 4.2 mol (mol fuel)⁻¹, respectively. Two different reforming gases are employed to reduce iron oxides. When the reforming gas/hematite (R/H) molar ratio is no less than 1, Fe₂O₃ conversion is always higher than 98.5%, whether low-temperature or high-temperature IR is carried out. This reveals that COG possesses the potential as a reducing agent in BFs. The reactions of IR from the two reforming gases are almost identical, implying that the operation of SR from COG for producing hydrogen or syngas and reducing iron oxides in BFs is flexible.     

Design and performance of asymmetric supported membranes for oxygen and hydrogen separation

Producing syngas and hydrogen from biofuels is a promising technology in the modern energy. In this work results of authors’ research aimed at design of supported membranes for oxygen and hydrogen separation are reviewed. Nanocomposites were deposited as thin layers on Ni–Al foam substrates. Oxygen separation membranes were tested in CH₄ selective oxidation/oxi-dry reforming. The hydrogen separation membranes were tested in C₂H₅OH steam reforming. High oxygen/hydrogen fluxes were demonstrated. For oxygen separation membranes syngas yield and methane conversion increase with temperature and contact time. For reactor with hydrogen separation membrane a good performance in ethanol steam reforming was obtained. Hydrogen permeation increases with ethanol inlet concentration, then a slight decrease is observed. The results of tests demonstrated the oxygen/hydrogen permeability promising for the practical application, high catalytic performance and a good thermochemical stability.     

Economics of biomass gasification: A review of the current status

Biomass is a nonorganic fuel that has a high potential for transforming into favorable chemicals in pyrolysis and syngas reaction in gasification reaction. However, economic problems in design and operation of gasification systems are the most important problems in this field. The present research aims to review current conditions and economic characteristics of this process. This research also studied economic characteristics of different produced chemicals such as hydrogen, methanol, and ethanol. Based on the literature data, it was found that the use of a 2000 dry-ton/day plant is more economical than that of 1000 dry-ton/day plant for ethanol production.     

Hydrogen production using plasma gasification with steam injection

Plasma gasification is a promising gasification technology intended at providing sustainable disposal for various wastes. In this work, a process model was developed to simulate the biomass plasma gasification using Aspen Plus simulator. Effects of critical parameters, including gasification temperature, Equivalence Ratio (ER) and Steam-to-Biomass Ratio (SBR) on the composition of fuel gas were discussed. The model is validated against experimental data and found to be in good agreement. The results indicate that low temperatures are more favourable for the production of hydrogen, while high ER has a negative effect on the hydrogen production. The simulation results also demonstrate that steam injection is a key factor to produce more hydrogen rich gas in the SBR range studied, but had a major effect on CO₂ formation. The temperature and the SBR show opposite behavior on the syngas LHV, which is attributed to the CO content in the syngas that increases with temperature and decreases with SBR. Results of plasma gasification show similar syngas LHV trends for the three biomasses cases being the higher syngas LHV obtained for vines pruning. These data are crucial to describe scenarios concerning the potential use of biomass as energy source.     

Ethanol reforming for hydrogen production in a hybrid electric vehicle: process optimisation

This work is focused at optimizing an ethanol reforming process over a Ni/Cu catalyst to produce a hydrogen rich stream in order to feed a solid polymer fuel cell (SPFC). The effect of the reaction temperature, H₂O/EtOH and O₂/EtOH molar ratios of the feed to the reformer was studied under diluted conditions in order to maximize the hydrogen content and the CO₂/CO_x molar ratio at the outlet of the ethanol reformer. Based on the experimental results, a detailed kinetic scheme of the ethanol reforming was discussed as a function of the temperature, special attention was paid to the role of oxygen in the reaction selectivity and coke formation. Moreover, the coke nature was evaluated by transmission electron microscopy (TEM) and TPO and TPH experiments. The tests carried out at on-board reformer conditions allowed a hydrogen rich mixture (33%) in the outlet reformer flow that can be even increased by water gas sift reactions downstream. The high hydrogen content of the flow to the fuel cell together with the stability of the Ni/Cu catalyst, fully demonstrated by long time runs, can be considered of high interest for SPFC applications.     

Syngas suitability for solid oxide fuel cells applications produced via biomass steam gasification process: Experimental and modeling analysis

The technologies and the processes for the use of biomass as an energy source are not always environmental friendly. It is worth to develop approaches aimed at a more sustainable exploitation of biomass, avoiding whenever possible direct combustion and rather pursuing fuel upgrade paths, also considering direct conversion to electricity through fuel cells. In this context, it is of particular interest the development of the biomass gasification technology for synthesis gas (i.e., syngas) production, and the utilization of the obtained gas in fuel cells systems, in order to generate energy from renewable resources. Among the different kind of fuel cells, SOFCs (solid oxide fuel cells), which can be fed with different type of fuels, seem to be also suitable for this type of gaseous fuel. In this work, the syngas composition produced by means of a continuous biomass steam gasifier (fixed bed) has been characterized. The hydrogen concentration in the syngas is around 60%. The system is equipped with a catalytic filter for syngas purification and some preliminary tests coupling the system with a SOFCs stack are shown. The data on the syngas composition and temperature profile measured during the experimental activity have been used to calibrate a 2-dimensional thermodynamic equilibrium model.     

Synergistic catalysis of bi-metals in the reforming of biomass-derived hydrocarbons: A review

Biomass such as ethanol and glycerol has emerged as an alternative feedstock for hydrogen (H₂) production in recent years. Ethanol, which is high in H_2, can easily be derived from renewable biomass sources, whereas; glycerol is a by-product of biodiesel expected to be surplus in the coming years. Several catalytic reforming routes involving biomass such as steam, CO₂, auto thermal, partial oxidation and aqueous-phase reforming can produce syngas or H₂. Bimetallic catalysis is one of the potential solutions to reduce carbon formation and catalysts deactivation in reforming processes since it can produce more stable catalysts from the synergistic effect of the combined metals. There are many reviews on catalyst designs and reaction pathways reported in the literature; nevertheless, comparative literature is lacking on the metal configuration of bimetallic catalyst in biomass reforming particularly for ethanol and glycerol reforming reactions. Therefore, studies linked with the synergistic effects of various bi-metal combinations of catalysts used in biomass reforming processes have been reviewed in the paper. Moreover, the study provides data for the application of bimetallic catalyst for industrial biomass processes.