Syngas Mixtures Research Articles

Laminar burning velocities of H2/CO/CH4/CO2/N2 -air mixtures at elevated temperatures

The laminar burning velocity of nine different syngas compositions has been measured at elevated temperatures (350–650 K) for various equivalence ratios using an externally heated diverging channel method. The measured values are compared with the predictions of two detailed kinetic models (GRI 3.0 and FFCM-1). The predictions of FFCM-1 for various syngas (H2/CO/CH4/CO2/N2) mixtures accurately capture the fundamental combustion characteristics, and GRI 3.0 mechanism overpredicts the laminar burning velocity for fuel rich syngas compositions. Temperature exponents mildly decrease with increase in equivalence ratio for mixtures investigated in the present work.Two correlations, one using linear regression, and another, a linear equation model is proposed to predict the laminar burning velocity accurately for various syngas compositional modifications. The developed linear model can be used for direct calculation of laminar burning velocities of different syngas compositions. Similarly, a temperature exponent correlation and its comparison with present measurements and simulations are also presented. The efficacy of the proposed models is evaluated through a detailed comparison with the literature. The model provides an excellent matching for following syngas compositions; 0.05 <XH2<0.50, 0.08 < XCO < 0.50, 0 <XCH4< 0.13, 0 <XCO2< 0.50, 0 <XN2< 0.65, for an equivalence ratio of ϕ = 0.7–1.25, and mixture temperature from 300 to 650 K.

Sugarcane bagasse gasification: Simulation and analysis of different operating parameters, fluidizing media, and gasifier types

Sugarcane bagasse gasification is a promising thermochemical process that converts this residue mainly into syngas, which may be applied to generate heat, electricity, and liquid fuels. However, little attention has been given to the study of bagasse gasification conditions that generate syngas for future production of liquid fuels and chemicals. Therefore, this work aimed at studying several sugarcane bagasse gasification scenarios in Aspen Plus™ to obtain syngas mixtures to be further conditioned for synthesis processes. The scenarios included the study of the influence of operational parameters (temperature, pressure, steam-to-biomass ratio S/B, and moisture content), fluidized bed configurations (bubbling and circulating), and gasifying media (steam and steam-O2) on syngas composition and process performance. Among the operating parameters, temperature was crucial for higher H2 and CO production, CO2 consumption, higher syngas lower heating value (LHV), and higher cold gas efficiency (CGE). Also, S/B was the only key factor to adjust the H2/CO ratio. In the gasifier configuration analysis, circulating fluidized bed reactor was the most suitable gasifier in most assessed scenarios, since it led to higher H2 and CO generation, lower CO2 and CH4 production, as well as higher H2/CO, dry syngas flow rates, and CGEs. The use of oxygen as an oxidizing agent decreased H2 content and increased CO concentration, and reduced syngas H2/CO ratio, LHV, and CGE. The steam-blown circulating fluidized bed was advised for future synthesis processes, and its corresponding response surfaces for H2/CO ratio and CGE were obtained.

Attempt to yield light hydrocarbons including C3 fraction by supplying ethene and syngas on Co/SiO2 catalyst

When a 1:2 gas mixture of CO and H2, namely syngas, was contacted onto Co/SiO2 catalyst at 513 K with low pressure such as 0.2 kg/cm2, G, methanation was preferentially promoted, whereas chain propagation was suppressed. In contrast to this, when 1:3 gas mixture of ethene and syngas was fed onto Co/SiO2 catalyst under the same conditions, hourly productivity of light hydrocarbons involving C3 fraction was increased 3.3-fold as much as that in the case flowing syngas alone at that condition. It was deduced that formation of light hydrocarbon like C3 was caused by capturing methylidene (=CH2) species by ethene on Co/SiO2 catalyst on which reverse metathesis (C2H4 + 2-C4H8 → 2C3H6) following the dimerization of ethene was not concerned with C3 formation. In addition, a small amount of liquefied hydrocarbons was collected despite the low pressure and chain growth probability (α) was presumed 0.73. It might be suggested that co-feeding ethene and syngas onto FT active catalyst like Co/SiO2 was one of effective methods to obtain light hydrocarbons including C3 fraction at low pressure.

Zn-Cu Alloy Nanofoams as Efficient Catalysts for the Reduction of CO2 to Syngas Mixtures with a Potential-Independent H2 /CO Ratio.

Alloying strategies are commonly used to design electrocatalysts that take on properties of their constituent elements. Herein, such a strategy is used to develop Zn-Cu alloyed electrodes with unique hierarchical porosity and tunable selectivity for CO2 versus H+ reduction. By varying the Zn/Cu ratio, tailored syngas mixtures are obtained without the production of other gaseous products, which is attributed to preferential CO- and H2 -forming pathways on the alloys. The syngas ratios are also significantly less sensitive to the applied potential in the alloys relative to pure metal equivalents; an essential quality when coupling electrocatalysis with renewable power sources that have fluctuating intensity. As such, industrially relevant syngas ratios are achieved at large currents (-60 mA) for extensive operating times (>9 h), demonstrating the potential of this strategy for fossil-free fuel production.

Thermolytic Conversion of Waste Polyolefins into Fuels Fraction with the Use of Reactive Distillation and Hydrogenation with the Syngas under Atmospheric Pressure

Authors studied a method of thermolytic conversion of waste polyolefins in an innovative packed bed reactor which operates on the principle of a distillation column. Vapors of cracked polymers, with a boiling point below 360 °C, are transported with the use of a carrier gas to the next reactor where they are catalytically hydrogenated under atmospheric pressure using syngas. Waste polyolefins obtained from the landfill were used as a raw material. To determine the effect of the carrier gas composition on the quality of the liquid fraction, nitrogen, syngas, and its mixtures were used in conducted experiments. The chemical composition and the selected physicochemical properties of the liquid product were investigated in the laboratory. Mixtures of nitrogen and syngas were tested as a carrier gas which also played the role of the hydrogenation agent in the whole process. Conducted research indicated that the best level of hydrogenation was obtained when only syngas was used as the carrier gas in the cracking reactor and as the hydrogen donor during hydrogenation. The obtained liquid product can be distilled into diesel fuel and gasoline fractions which can be used for fuel production.

WITHDRAWN: Adsorbent screening for CO2/CO separation for applications in syngas production

Abstract Single gas carbon dioxide (CO2) and carbon monoxide (CO) adsorption behaviour is investigated in detail with different adsorbents for the potential separation of syngas. In this study, 20 zeolites, 2 activated aluminas, 3 activated carbons, and 2 silica gels were investigated by determining pure gas isotherms of CO2 and CO at 30 °C. The results were compared to literature to determine which adsorbents would be the most promising for CO2 separation from syngas at this temperature. Since CO2 concentrations vary in syngas based on the method of production, different adsorbents were selected for purification and bulk separation of CO2 from a syngas mixture. The individual adsorption capacities of CO2 and CO were analysed separately using a gravimetric system, modelled, and then compared for all of the adsorbents studied. CO2 is shown to be more favourably adsorbed compared to CO, with CO2 having higher adsorption capacities and heats of adsorption for all adsorbent samples studied. High-density silica gel and H-Y type zeolites were found to be promising adsorbents for the bulk separation of CO2 from syngas due to the shape of their isotherms, large CO2 adsorption capacities, their favourable adsorption capacity ratios for CO2 over CO. For the purification of syngas, Na+ exchanged FAU structured zeolites with their high CO2 adsorption capacity at low pressures, and favourable CO2 over CO adsorption capacity ratios was found to be the most promising adsorbent.

A systematic numerical study of the laminar burning velocity of iso-octane/syngas/air mixtures

The laminar burning velocities of iso-octane/syngas/air mixtures were numerically investigated using a detailed reaction mechanism over a wide range of equivalence ratio (0.4–1.4) at atmospheric and elevated pressure at an initial temperature of 423 K. The mole fraction of syngas in the fuel mixture was varied from the entire range of 0 (pure iso-octane) to 1 (pure syngas). To take into account the large variations of syngas compositions, the following three syngas compositions are considered: 75%H2-25%CO, 50%H2-50%CO, and 25%H2-75%CO by volume. The results show that the laminar burning velocity of iso-octane/syngas/air mixtures increases with the content of syngas, especially for higher H2 content in syngas and rich mixtures. The enhanced burning velocity is attributed to the chemical effects of H2 in syngas. The burning velocity correlates linearly with the level of syngas dilution of the fuel mixture, regardless of how the syngas dilution ratio is defined when the dilution level is low. The linear correlation remains over a wide range of syngas dilution when the dilution ration is defined as that introduced by Yu et al. (1986). H2 addition and CO addition affect the radical pool differently and H is found to be a kinetics indicator for the burning velocity of iso-octane/syngas/air mixtures under the current conditions. Detailed sensitivity and pathway analysis was also conducted to identify reactions that significantly affect the burning velocity of iso-octane/syngas/air mixtures and to illustrate the kinetics interactions between H2, CO, and iso-octane in iso-octane/syngas/air mixtures.

Experimental Study on Low Load Operation Range Extension by Autothermal On-Board Syngas Generation

Volatile renewable energy sources induce power supply fluctuations. These need to be compensated by flexible conventional power plants. Gas turbines in combined cycle power plants adjust the power output quickly but their turn-down ratio is limited by the slow reaction kinetics, which leads to CO and unburned hydrocarbon emissions. To extend the turn-down ratio, part of the fuel can be converted to syngas, which exhibits a higher reactivity. By an increasing fraction of syngas in the fuel, the reactivity of the mixture is increased and total fuel mass flow and the power output can be reduced. An autothermal on-board syngas generator in combination with two different burner concepts for natural gas (NG)/syngas mixtures was presented in a previous study (Baumgärtner, M. H., and Sattelmayer, T., 2017, “Low Load Operation Range Extension by Autothermal On-Board Syngas Generation,” ASME J. Eng. Gas Turbines Power, 140(4), p. 041505). The study at hand shows a mass-flow variation of the reforming process with mass flows, which allow for pure syngas combustion and further improvements of the two burner concepts which result in a more application-oriented operation. The first of the two burner concepts comprises a generic swirl stage with a central lance for syngas injection. Syngas is injected with swirl to avoid a negative impact on the total swirl intensity and nonswirled. The second concept includes a central swirl stage with an outer ring of jets. For this burner, syngas is injected in both stages to avoid NOx emissions from the swirl stage. Increased NOx emissions produced by NG combustion of the swirl pilot were reported in last year's paper. For both burners, combustion performance is analyzed by OH*-chemiluminescence and gaseous emissions. The lowest possible adiabatic flame temperature without a significant increase of CO emissions was 170–210 K lower for the syngas compared to low load pure NG combustion. This corresponds to a decrease of 15–20% in terms of thermal power.

Performance analysis of a water–gas shift membrane reactor for integrated coal gasification combined cycle plant

In integrated gasification combined cycle (IGCC) systems, the water–gas shift reaction, which promotes the conversion of CO present in syngas mixtures into hydrogen, is an important step for hydrogen production. Application of the water–gas shift membrane reactor (WGSMR) in IGCC systems is an attractive option for CO2 capture compared with conventional methods because of smaller heat loss in gas purification and high CO conversion by selectively removing hydrogen from the reaction zone through the membrane. In this study, we proposed and evaluated commercial-scale WGSMR models combined with IGCC using reported laboratory-scale experimental data to optimize their operational parameters. Various models were developed using the Aspen Plus® Ver. 8.6 process simulator to investigate the impacts of hydrogen separation, pressure loss, and the flow direction between the sweep gas on the permeate side and syngas on the retentate side on the WGSMR performance with respect to CO conversion, H2 yield, and reactor temperature. The membrane reactor model gave approximately 20% higher CO conversion than a reactor model without H2 separation and approximately 4% lower CO conversion than a membrane reactor model with a pressure drop. A counter-current membrane reactor model gave approximately 2% higher CO conversion than a co-current model; the H2 yield on the permeate side was 9.3% higher in the counter-current model by separation of H2 through the membrane. A sensitivity analysis indicated that a high flow rate and low pressure of sweep gas are advantageous for H2 recovery, and high catalyst loading and high syngas inlet temperature are preferable for higher CO conversion.

Ignition kinetics of a homogeneous hydrogen/air mixture using a transient hot jet

The ignition characteristics of a homogenous hydrogen/air mixture using a hot transient jet generated by the combustion of syngas (H2/CO) with varying CO concentrations from 33% to 95% in a pre-chamber is numerically investigated with particular attention to the chemical kinetics. Detailed reaction mechanism for hydrogen and syngas mixture oxidation with 15 species and 41 reactions is employed. The hot jet ignition delay time is determined by the onset of OH∗ radicals and found to increase with increasing CO molar fractions in the pre-chamber fuel, and this increase is more profound for high CO content. The radicals that formed in the main chamber are examined separately from the radicals within the hot jet. Their temporal evolutions reveal that O and OH radicals in the jet play a crucial role in abstraction of H atoms form H2/air mixture in the main chamber, which initiates ignition. Further analysis of the H2O2 rate of change identifies two ignition regimes. For high temperature (T > 1000 K) hot jets, ignition is caused by the chain branching reaction H+O2↔O+OH directly, resulting in short ignition delay times (0.14, 0.19, 0.26 ms). For low temperature (T < 1000 K) hot jets, ignition is dominated by the accumulation and decomposition of H2O2, resulting in long ignition delay times (0.4, 0.67, 1.26 ms). By separating the thermal and chemical effects of the hot jet, it is found that the thermal effects are dominant but composition of the hot jet has little effect on the ignition characteristics.

Experimental study of premixed syngas/air flame deflagration in a closed duct

The propagation behaviour of a deflagration premixed syngas/air flame over a wide range of equivalence ratios is investigated experimentally in a closed rectangular duct using a high-speed camera and pressure transducer. The syngas hydrogen volume fraction, φ, ranges from 0.1 to 0.9. The flame propagation parameters such as flame structure, propagation time, velocity and overpressure are obtained from the experiment. The effects of the equivalence ratio and hydrogen fraction on flame propagation behaviour are examined. The results indicate that the hydrogen fraction in a syngas mixture greatly influences the flame propagation behaviour. When φ, the hydrogen fraction, is ≥0.5, the prominently distorted tulip flame can be formed in all equivalence ratios, and the minimum propagation time can be obtained at an equivalence ratio of 2.0. When φ < 0.5, the tulip flame distortion only occurs in a hydrogen fraction of φ = 0.3 with an equivalence ratio of 1.5 and above. The minimum flame propagation time can be acquired at an equivalence ratio of 1.5. The distortion occurs when the maximum flame propagation velocity is larger than 31.27 m s−1. The observable oscillation and stepped rise in the overpressure trajectory indicate that the pressure wave plays an important role in the syngas/air deflagration. The initial tulip distortion time and the plane flame formation time share the same tendency in all equivalence ratios, and the time interval between them is nearly constant, 4.03 ms. This parameter is important for exploring the quantitative theory or models of distorted tulip flames.

SI engine assessment using biogas, natural gas and syngas with different content of hydrogen for application in Brazilian rice industries: Efficiency and pollutant emissions

After Asia, Brazil is the world's largest rice producer. During the processing of the grain, large amounts of husk are generated, corresponding to 22% of its weight. On the other hand, in the process of parboiling, in turn, the final result is considerable volumes of effluents rich in organic matter, generating large amounts of methane gas through anaerobic treatment. Therefore, the SI engine can operate with mixtures of biogas and syngas, generating electricity and heat in the Brazilian rice industries. In addition, it reduces the emissions of polluting gases that are generated with a direct burning of the husks instead of their gasification, as well as the use of methane gas. Accordingly, in this work, it was used the spark-ignition engine operating with one of the typical biogas and syngas compositions generated in the rice industries, named Bio65 (containing 65% of CH4 by vol.), syngas1 (containing 18,3% of H2 by vol.), and syngas2 (containing 13,5% of H2 by vol.), respectively. Additionally, the tests with natural gas as a reference fuel have been performed. It was evaluated the emissions of polluting gases such as CO, NOx and HC, as well as the thermal and electrical efficiency of all tested fuels. An important result that could be observed was that for both natural gas and biogas fuel, the increase in excess ratio (λ) value from 1 to 1.5 led to lower NOx and CO emissions, even if with increased HC emissions. On the other hand, the Indicated Specific Energy Consumption increased to all the fuels tested in lean conditions in almost all ignition advances angles. The research tried to show that biogas and syngas can be used in parboiling rice industries, taking the advantage of the generated gases for energy self-sufficiency as well as reducing emissions.

Shock Tube Study of Ignition-Delay Measurements and Kinetic Mechanism Research for Syngas

Ignition-delay times of syngas mixtures () were measured using a shock tube in the following conditions: temperatures of 910–1290 K, pressures of approximately 1.0 atm, an equivalence ratio of 1.0, ratios of 0.25 and 4.0, and especially Ar dilution rates of 94% and 79%. Simulating results and sensitivity analysis show that Davis Mech, NUIG Mech, and Varga Mech have more accurate computational results than GRI 3.0, SD Mech, and Li Mech at around 1000 K because for reaction the former three mechanisms have a lower reaction rate. Oxidation of occurs mainly through reactions and , whereas is the dominant reaction for the oxidation of CO. Comparative analyses of syngas with the same ratio at 94% and 79% Ar dilution rates show that heat absorption of Ar during combustion is the main cause of long ignition-delay time, although Ar also inhibits the reactivity of syngas through at 1000 K. Moreover, the pressure response curve rises slowly with 94% Ar dilution but sharply with 79% Ar dilution under low-temperature conditions, and detonation (or deflagration to detonation) can be observed under such conditions. In addition, emission was observed behind the incident shock wave when its velocity reached with 79% Ar dilution, and it was unable to measure ignition-delay time behind the reflected shock wave.

Emissions and performance of a spark-ignition gas engine generator operating with hydrogen-rich syngas, methane and biogas blends for application in southern Brazilian rice industries

Brazil is one of the world's largest rice producers with more than 50 industries in this field. During the processing of the grain, high amounts of husk are generated, with a capacity to produce synthesis gas with high hydrogen content. On the other hand, in the process of parboiling, the final result is considerable volumes of effluent rich in organic matter, generating high amounts of methane. Therefore, spark ignition engine (SI) can operate with biogas, syngas or biogas-syngas mixtures, taking advantage of the bioenergy potential of the rice industries in Brazil. Accordingly, in this work, it was used the spark-ignition engine test operating with typical biogas and syngas compositions generated in the rice industries, named Bio70, syngas1 and syngas2, respectively. An important result could be observed. For both methane and biogas fuel the increase in excess ratio (λ) value from 1 to 1.25 lead to lower CO and NOx emissions as well as an increase in indicated efficiency. Using fuel mix, even at low concentration, such as 10% by vol., Bio70 provided increases in the calorific value of air-fuel mixture (edv) equal to 5.4 and 13.2% for syngas 1 and 2, respectively.

Enhanced CO2 Electrochemical Conversion at Bi-Modified Pb Foams

CO2 conversion methods to remediate anthropogenic emissions appear promising, as they offer the potential to produce liquid and gaseous fuels for use either in the aeronautics industry, or as a chemical storage method for intermittent energy produced by windmills and photovoltaic panels. Fuel synthesis may be achieved via either the production of a syngas mixture (H2 and CO) through the water gas shift reaction and subsequent conversion into hydrocarbon fuel, or by direct electrochemical reduction of CO2. Direct electrochemical conversion of CO2 into value-added products is a low-temperature process, with the advantage of requiring relatively simple equipment. Formic acid, or formate salts, are used in a variety of chemical processes such as electrowinning, leather tanning, and aircraft de-icing. Alternatively, formic acid and formate salts may be considered as a hydrogen storage medium. On top of that, direct formic acid, and more recently direct formate, fuel cells, have been investigated as they demonstrate significant benefits over methanol fuel cells, including higher open circuit voltage and lower crossover. Pb and Bi are promising catalysts with good selectivity for formate. In the case of lead, it can be prepared in the form of dendrites with nanometre-sized tips. Local high electric fields can exist at the tip of these dendrites that can induce a concentration of electrolytes which in turn leads to improve electroreduction of CO2 [[1]]. Bismuth is non-toxic and has negligible environmental impact. It has few commercial applications, and its price has been low and relatively stable in recent years. In this work, we studied the activity and stability for CO2 electroreduction onto high surface area metallic Pb films. The latter Pb films were further functionalized by Bi overlayers to enhance CO2 reduction properties. For both materials, the material films were prepared through a potentiostatic method. Both types of films were extensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and x-ray diffraction (XRD), while electrochemical activities were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and potentiostatic measurements. [1] M. Fang, S. Garbarino, G.A. Botton, A.C. Tavares and D. Guay, J. Mater. Chem A 5 (2017) 20747-20756

Liftoff and blowout characteristics of laminar syngas nonpremixed flames

Liftoff and blowout behavior of nonpremixed syngas flames is investigated using a time-accurate CFD code with a detailed description of transport and chemistry. Lifted flames are established in coflowing laminar jets using N2 dilution in the fuel jet. Results focus on the effects of syngas composition and temperature on the liftoff, stabilization, and the edge (triple) flame structure. For a given syngas mixture, as the N2 dilution exceeds certain value, the flame lifts off from the burner rim and propagates along the stoichiometric mixture fraction line, and its structure changes from diffusion to double flame. With further dilution, the flame liftoff height increases rapidly, the base structure transitions from double to triple flame, and its stabilization involves a balance between the triple flame speed and local flow velocity. The temporal evolution of propagating jet flame also exhibits a similar behavior. The transition from diffusion to double and then to triple flame is examined using state relationships in mixture fraction coordinate. As H2 fraction in syngas and/or temperature is increased, the N2 dilution required for flame liftoff and blowout increases. The ratio of the triple flame speed to the unstretched premixed flame speed also increases with the increase in H2 fraction. For H2 fraction above 30%, the flame liftoff and blowout become less sensitive to syngas composition and temperature.

Catalytic Influence of Water Vapor on Lean Blow-Off and NOx Reduction for Pressurized Swirling Syngas Flames

It has become increasingly cost-effective for the steel industry to invest in the capture of heavily carbonaceous basic oxygen furnace or converter gas, and use it to support the intensive energy demands of the integrated facility, or for surplus energy conversion in power plants. As industry strives for greater efficiency via ever more complex technologies, increased attention is being paid to investigate the complex behavior of by-product syngases. Recent studies have described and evidenced the enhancement of fundamental combustion parameters such as laminar flame speed due to the catalytic influence of H2O on heavily carbonaceous syngas mixtures. Direct formation of CO2 from CO is slow due to its high activation energy, and the presence of disassociated radical hydrogen facilitates chain branching species (such as OH), changing the dominant path for oxidation. The observed catalytic effect is nonmonotonic, with the reduction in flame temperature eventually prevailing, and overall reaction rate quenched. The potential benefits of changes in water loading are explored in terms of delayed lean blow-off (LBO), and primary emission reduction in a premixed turbulent swirling flame, scaled for practical relevance at conditions of elevated temperature (423 K) and pressure (0.1–0.3 MPa). Chemical kinetic models are used initially to characterize the influence that H2O has on the burning characteristics of the fuel blend employed, modeling laminar flame speed and extinction strain rate across an experimental range with H2O vapor fraction increased to eventually diminish the catalytic effect. These modeled predictions are used as a foundation to investigate the experimental flame. OH* chemiluminescence and OH planar laser-induced fluorescence (PLIF) are employed as optical diagnostic techniques to analyze changes in heat release structure resulting from the experimental variation in water loading. A comparison is made with a CH4/air flame and changes in LBO stability limits are quantified, measuring the incremental increase in air flow and again compared against chemical models. The compound benefit of CO and NOx reduction is quantified also, with production first decreasing due to the thermal effect of H2O addition from a reduction in flame temperature, coupled with the potential for further reduction from the change in lean stability limit. Power law correlations have been derived for change in pressure, and equivalent water loading. Hence, the catalytic effect of H2O on reaction pathways and reaction rate predicted and observed for laminar flames are appraised within the challenging environment of turbulent, swirl-stabilized flames at elevated temperature and pressure, characteristic of practical systems.

Micro gas turbine running on naturally aspirated syngas: An experimental investigation

Abstract Syngas produced from fixed bed gasifier suffers from high inert diluents (N2+ CO2) in the range of 60–65 vol.%. Hence, higher energy is required for syngas external compression making this concept less profitable for small scale micro gas turbine (MGT) applications. A new method was proposed in this study to eliminate the external compression of syngas by inducing air−syngas mixture directly through the MGT's compressor. Turbocharger based MGT with pressurized cyclone combustor (PCC) were developed to evaluate the new concept experimentally. Annular tube heat recovery unit (HRU) was developed to utilize the exhaust thermal power for hot air production. Stable syngas combustion was achieved with air-fuel ratio in the range of 3.3–4.1. NOx and CO emissions were below 250 ppm and 15 ppm respectively, with turbine inlet temperature below 700 °C. The natural aspiration of syngas directly from the gasifier was sufficient to run the MGT at low pressure ratio of 0.4 barg, but it was not enough to generate any electrical output. Hot air thermal output was 34 kW with overall system efficiency including the gasifier of 37.8%.

A Co3O4-CDots-C3N4 three component electrocatalyst design concept for efficient and tunable CO2 reduction to syngas

Syngas, a CO and H2 mixture mostly generated from non-renewable fossil fuels, is an essential feedstock for production of liquid fuels. Electrochemical reduction of CO2 and H+/H2O is an alternative renewable route to produce syngas. Here we introduce the concept of coupling a hydrogen evolution reaction (HER) catalyst with a CDots/C3N4 composite (a CO2 reduction catalyst) to achieve a cheap, stable, selective and efficient route for tunable syngas production. Co3O4, MoS2, Au and Pt serve as the HER component. The Co3O4-CDots-C3N4 electrocatalyst is found to be the most efficient among the combinations studied. The H2/CO ratio of the produced syngas is tunable from 0.07:1 to 4:1 by controlling the potential. This catalyst is highly stable for syngas generation (over 100 h) with no other products besides CO and H2. Insight into the mechanisms balancing between CO2 reduction and H2 evolution when applying the HER-CDots-C3N4 catalyst concept is provided.

Numerical investigation of the distribution of oxygen atoms in syngas combustion products

The distribution of air oxygen atoms in the oxidation products of rich mixtures of syngas with air in flame and the under autoignition conditions at constant volume has been investigated by numerical simulation using the tracer method. It has been found that in rich mixtures, the oxidation of hydrogen and carbon oxide has a stepwise nature, which is clearly visible in the profiles of the rates of production of H2O and CO2. The observed stepwise nature inevitably results in the heat-release rate occurring in steps. The reaction pathways and the role of the oxygen atom of the CO molecule in the heat release in these flames has been investigated.