Steam Content Research Articles

Catalytic Effects of Potassium Concentration on Steam Gasification of Biofuels Blended from Olive Mill Solid Wastes and Pine Sawdust for a Sustainable Energy of Syngas

The effect of potassium impregnation at different concentrations during gasification, under nitrogen/water steam atmosphere, of char produced via pyrolysis of olive mill residues blended or not with pine sawdust was investigated. Three concentrations (0.1 M, 0.5 M, and 1.5 M) of potassium carbonate solution (K2CO3) were selected to impregnate samples. First, four types of pellets were prepared; one using exhausted olive mill solid waste (G) noted (100G) and three using G blended with pine sawdust (S) in different percentages (50%S–50%G (50S50G); 60%S–40%G (60S40G); 80%S–20%G (80S20G)). Investigations showed that when isothermal temperature increases during the gasification conducted with two water steam percentages of 10% and 30%, the reactivity increases with potassium concentration up to 0.5 M, especially for 100G. Still, higher catalyst concentration (1.5 M) showed adverse effects attributable to silicon release and char pore fouling. Moreover, the effect of the steam concentration on the gasification reactivity was significant with the non-impregnated sample 100G. Finally, a kinetic study was carried out to determine the different kinetic parameters corresponding to the Arrhenius law.

Numerical and experimental investigation of the steam penetration in narrow channels during a dynamic steam sterilization cycle

The most challenging aspect of steam sterilization is the removal of all non-condensable gases (NCGs) from the autoclave. These gases prevent the effective killing of microorganisms, impairing the sterility of medical devices. Special cycles are performed to ensure the penetration of steam, even into the deepest passages. To better understand this process, numerical models were developed to determine the spatial distribution of steam within the chamber, including its penetration into narrow channels. These are the first models that can be used to accurately determine the flow within three-dimensional cavities during a dynamic sterilization cycle. To validate the model, an experiment was designed using direct tunable diode laser absorption spectroscopy at a wavelength of 1364 nm to measure the mole fraction of steam present at the end of an aluminum pipe at a temporal resolution of 1 s. This represents a pioneering application of this technique in the field of steam sterilization. This setup was designed for installation on any autoclave. Both simulation and experimental data exhibit good agreement over the entire pressure range (0.18–3.15 bar). The most interesting observation made during the study was the increase in the steam content at the end of the tube while a vacuum was generated. The numerical results show that the mole fraction of H2O increased from 0.53 to 0.63 over the course of a single vacuum phase. This phenomenon was attributed to a stronger diffusion effect combined with small pressure gradients during low pressures. This finding inspired the idea of taking the diffusion effect more into account when designing sterilization cycles in the future to make them more sustainable and effective. The presented methodologies and models represent an excellent basis for conducting more complex investigations in the future, such as those investigating the influence of condensation effects on steam penetration in cavities.

Comparison of non-premixed and premixed flamelets for ultra WET aero engine combustion conditions

The Water-Enhanced Turbofan (WET) is a future concept for aero engine applications being developed by MTU Aero Engines AG. Steam is injected into the combustion chamber to reduce temperature peaks and emission of pollutants. Depending on the steam content, the combustion process is modified. To analyze the effect of steam on the reaction kinetics and the temperature, detailed chemistry has to be employed. By comparing laminar flame speed and mole fraction distribution across the flame front, an appropriate chemical mechanism for the considered operating conditions including high steam loads was selected. Tabulated chemistry based on flamelets was employed, which enables the use of complex mechanisms in CFD analysis at reasonable computational costs. A comparison of premixed freely propagating flames and non-premixed counterflow diffusion flames to represent the manifolds was investigated. Various definitions of the progress variable are studied for ultra WET combustion considered under aero engine conditions. The manifolds from both model flames are compared from dry to ultra WET conditions with kerosene in an adapted Sandia Flame D large eddy simulation. While the premixed flamelets are generated efficiently, the results obtained with non-premixed flamelets are more reliable for the range of operating conditions investigated.

Evaluation of the chemical looping gasification characteristics of kitchen waste using CuFe2O4 and NiFe2O4 as oxygen carriers

Chemical looping gasification (CLG) technology is promising for renewable energy, efficiently transforming biomass into high-quality syngas with minimal tar and pollutants. In this study, we examined the CLG characteristics of soy protein (SP), a model compound present in kitchen waste (KW), using two different oxygen carriers (OCs): Cu-Fe and Ni-Fe. The study revealed that enhancing the carbon conversion ratio (ηc) could be effectively achieved by increasing the oxygen equivalent coefficient (α) and the steam content. Consequently, the optimal gasification performance was attained when the Cu-Fe and Ni-Fe OCs were operated at the α values of 0.3 and 0.4, and steam contents of 30% and 40%, respectively. After ten cycles of chemical looping, both OCs retained their robust oxidation activity, ensuring that the ηc remained consistent throughout the ten cycles. Under optimized experimental conditions, the CLG characteristics of KW were successfully determined. Notably, the ηc of KW was substantially enhanced, doubling in comparison to previous levels. The Cu-Fe OC emerged as a more suitable candidate for the CLG of KW due to its lower cost and non-toxic nature. This study provides important theoretical support and practical insights for the harmless treatment and resource utilization of KW.

Experimental study on heat transfer characteristics of steam condensation in the presence of air and CO2 outside a vertical tube

Under severe accident conditions, in addition to steam and air, there are also other non-condensable gases inside the containment, such as CO2 produced by the molten corium concrete interaction (MCCI). Due to the significantly higher molecular weight and density of CO2 compared to steam and air, CO2 will have a significantly different impact on the steam condensation process compared to air. However, few scholars have paid attention to the impact of CO2 on the condensation process, and there is no empirical correlation applicable to this condition. Therefore, this article investigates the effect of different CO2 concentrations on the steam condensation heat transfer coefficient (CHTC) in the range of system pressure from 0.2 to 1.3 MPa and subcooling from 30 to 130 °C through experimental methods. Meanwhile, based on relevant experimental data, a new correlation suitable for calculating the steam CHTC in the presence of CO2 and air was fitted. The results indicate that under low steam concentration conditions, the addition of CO2 will reduce CHTC, while under high steam concentration conditions, CO2 will increase CHTC. The increase in system pressure will strengthen the condensation promotion effect of CO2 and weaken its inhibitory effect on condensation. In addition, by comparing experimental data under different component conditions, it was found that the new empirical correlation has high computational accuracy, and the calculation results of this correlation can contain more than 90 % of the data within a 15 % error range.

Numerical investigation of heat and mass transfer characteristics of steam condensation containing non-condensable gas in vertical corrugated tube

A numerical simulation of steam condensation containing non-condensable gas is conducted in this paper to analyze the heat and mass transfer characteristics in vertical corrugated tube. The species transport model, Euler liquid film model and diffusion-balance model with Dehbi factor to correct the diffusion effect are applied to simulate the mass and energy transfer processes. The effects of different corrugated tube structural parameters and inlet steam parameters on steam condensation rate, liquid film distribution and heat transfer are simulated. The results show that vortex and accumulated non-condensable gas in the corrugated region significantly influence condensation heat transfer, which are closely related to corrugation height (H=0–5 mm) and corrugation length (L=13, 16, 19, 22, and 25 mm) of the corrugations, as well as inlet velocity (Vin = 5, 7, 9, 11, 13, and 15 m·s−1) and inlet steam content (Ws = 0.6, 0.7, 0.8, 0.9, 0.99, and 1). The total heat transfer coefficient varies linearly with inlet velocity when inlet velocity increase from 5 m·s−1 to 15 m·s−1, which increase 89.6–108.1 %; total heat transfer coefficient increases almost exponentially when inlet steam content increase from 0.6 to 1, which increase 389–460 %; and the best corrugated tubes are those with corrugation height of 0.075 times diameter of tube and corrugation length of 0.325 times diameter of tube.

(Invited) Dynamic Operation of Solid Oxide Electrolyzers

Electrolysis of steam to generate hydrogen is expected to be a highly dynamic operation if renewable resources such as wind and solar are used as the electrical power input. Rapid fluctuation of input power and intermittent operation of the solid oxide electrolysis stack will result in transient operating conditions at the cell level. All operating variables such as temperature, steam content, voltage, flow rate, etc. may change rapidly in these conditions.To address this situation, this work operates Ni/YSZ-supported and metal-supported cells under highly dynamic conditions, with individual variables isolated. The cells are remarkably robust to dynamic operation. A safe range is found for each operating variable, with accelerated degradation observed outside that range in certain cases. For example, cycling Ni/YSZ-supported cells between 1.3 V and 1.6V at 750°C and 50:50 H2O:H2 is tolerated well, but increasing the upper voltage to 1.7 V and higher leads to increased degradation. Additionally, Steam:hydrogen ratio is cycled between 3:97 and 75:25. Temperature is cycled between 150 and 800°C. Operation is cycled between fuel cell and electrolysis modes, with synchronized steam content. Metal-supported cells tolerate steam cycling, voltage cycling, temperature cycling and redox cycling, and results for button cells and 50 cm2 planar cells will be reported. In many cases, hold times are 1 minute, allowing thousands of cycles to be accumulated over hundreds of hours of operation.Figure 1. Dynamic cycling of a Ni/YSZ-supported button cell at 750C. (Top) Cycling between 1.3 and 1.7V with 1 min holds and 50/50 H2/H2O. (Bottom) Cycling between various steam contents at 1.3 V. Figure 1

Characterization of Proton Exchange in Protonic Ceramic Electrochemical Cells Using Operando Drifts

The protonic ceramic electrochemical cells (PCECs) have attracted tremendous attention for their fast hydrogen production at intermediate temperatures. This work applied in situ Diffuse reflectance infrared Fourier transform infrared spectroscopy (DRIFTS) together with electrochemical impedance spectroscopy (EIS), to characterizes transport and hydration properties of the state-of-the-art electrolyte materials. The adsorption of water molecules and formation of surface hydroxyl groups on the electrolyte surface as a function of temperature, steam concentration, and electrical potential were systematically investigated by DRIFTS under operando conditions. The quantitative information on the concentration of hydroxyl species on the electrolyte materials before and after exposure to steam were obtained. The determination of OH intensity leads to the direct determination of the proton exchange coefficient k, at different steam concentrations and biases. The results are unique and should be able to provide valuable insights into the mechanisms of proton formation, migration, and evolution under various operating conditions, which is critical to design better electrolyte compositions and optimize the operation conditions for next-generation PCECs.

Design and Performance Evaluation of a Specialized Bubbler System for Accurate and Repeatable Solid Oxide Electrolysis Cell (SOEC) Testing

Accurate assessment of Solid Oxide Electrolysis Cell (SOEC) performance demands standardized testing conditions, particularly in stable steam delivery. Fluctuations in steam concentration and flow rate can significantly impact measured open-circuit voltage (OCV) and polarization behavior. Although direct steam injection is straightforward, it is often hindered by instability resulting from intermittent liquid water flux, pressure fluctuations, and fractional distillation effects. Bubbler humidification systems have the potential to offer consistent steam, but tailored designs for SOEC testing are currently absent.This study introduces a specialized bubbler system designed to deliver stable steam to SOEC test stands accommodating both oxygen-conducting (O-SOEC) and proton-conducting (H-SOEC) cells. The bubbler components include a refill water reservoir, a level control module, heating elements, pressure relief valves, check valves, tubing, and fittings integrated with the test stand. The system humidifies the sweep gas, transporting steam to the cell test fixture situated within a high-temperature furnace.The design process involved meticulous considerations of materials compatibility, hydrogen safety, and overtemperature protection. All wetted components employ stainless steel, glass, or PTFE materials in their construction construction. Redundant thermocouples ensure safe process temperatures with automated overtemperature shut off. The refill reservoir and bubbler headspace operate near ambient pressure, facilitated by an exhaust line vent sized for minimal backpressure.In various executed O-SOEC tests, the bubbler maintained OCV stability within ±5 mV over several hundred hours for each cell operating at 750°C, eliminating spikes caused by steam fluctuations observed with direct injection methods. This facilitates precise electrochemical analysis and determination of area-specific resistance losses. Polarization curves align with expected behavior based on the Nernst equation. The system has demonstrated safe and stable functionality for over thousands of hours across various operating conditions.The bubbler design presents researchers with notable advantages over existing steam supply options for SOEC test stands, addressing performance, safety, and flexibility concerns. Online instrumentation enables closed-loop control of steam conditions, enhancing stability. Standardization of test equipment is crucial for quality results, and this work contributes progress toward reproducible protocols in the international SOEC community. The modular bubbler approach, integrated with safety features, also signifies safer methodology choices for lab-scale experimental research.

(Invited) Durability of Solid Oxide Electrolysis Cells Via Accelerated Stress Testing

In this work, we will present a systematic study of state-of-the-art SOEC cells for hydrogen production using Ni-YSZ and LSCF electrodes. SOEC cells were tested in a broad range of experimental conditions, while varying temperature, steam concentration, steam utilization, current, voltage, operating pressure, potential Cr and S contaminants as well as under dynamic operation. Accelerated stress testing was performed to map potential degradations in a shorter period of time and compare to testing under standard operating conditions. Following each test termination, extensive post-test characterization of Ni-YSZ and LSCF microstructures using SEM/EDS and TEM was performed to assess the extent of degradations, if new degradations were imposed, and to predict conditions where cell failure might occur.

Simultaneous electrochemical reduction of water and oxidation of carbon in a solid oxide cell for separately producing hydrogen and carbon monoxide

Hydrogen can be produced from reduction of water at the cathode of a solid oxide electrolysis cell (SOEC) and electricity and CO gas can be co-generated from the oxidation of carbon at the anode of a direct carbon solid oxide fuel cell (DC-SOFC). In the present work, a solid oxide cell (SOC) combining the cathode reaction of the SOEC and the anode reaction of the DC-SOFC is proposed, prepared, and investigated. It is demonstrated that hydrogen and CO can be separately produced from the cathode and anode through simultaneous reduction of water and oxidation of carbon in such a H2O-C SOC. Resistances from electrode polarizations are analyzed through measuring current-voltage characteristics, overpotentials, and AC impedances of the cell. The advantage of the H2O-C SOC over two separately operated SOEC and DC-SOFC is verified by the resistance analysis. An electrolyte-supported H2O-C SOC, with a cermet of silver and gadolinium-doped ceria (Ag-GDC) as the symmetrical electrode material and a steam concentration of 50 % at the cathode, gives an operating current density of 0.67 A cm-2 at the thermal neutral voltage (0.7 V). It stably operates at 0.2 A cm-2 under an applied voltage of only 0.16 V, producing pure hydrogen from the cathode and CO with a concentration of 88 % from the anode. The performance is significantly improved by using an anode-supported H2O-C SOC which gives an operating current density of 2.27 A cm-2 at the thermal neutral voltage.

Combined steam and CO2 reforming of methane over Ni-based catalysts with spherical porous structure

Combined steam and dry reforming of methane (CSDRM) is expected to be promising when considered as a new alternative feedstock for F-T synthesis because it can produce high-quality syngas without carbon deposition. In this study, the support particle sizes were varied independently to assess their influence on the performance of the metallic Ni. The catalytic activity is most influenced by nickel particle size and distribution, and it has also been investigated for its significant role in the metal-support interaction. To perform CSDRM, the Ni-based catalyst was prepared by impregnation method on a spherical nano-silica support prepared by sol–gel method. The size of the spherical silica nanoparticles (40–300 nm) was controlled by varying the ethanol molar concentration; the spherical particles showed high performance on a uniform and evenly drawn support. In the 44 nm spherical silica catalyst, it was confirmed that the maximum dispersion increased to 21 % and the reducibility increased to 36 %. For stable synthesis gas production, various feed gas ratios (0.7:1.3:1.7) were established and the respective feed gas components (CH4, CO2 and steam) and reactions were investigated. Also, with the increase in the concentration of steam in the feed gas ratio, there was a significant increase in CO production. This trend was attributed to competing reactions occurring due to the side reactions (WGS↔RWGS; CO+H2O↔CO2 + H2) and was investigated with equilibrium constant values using thermodynamic equilibrium plot data. From the experimental results obtained, the catalyst showed high performance on a stable support and produced a stable H2/CO ratio of 2 for 100 h, without side reactions, at the feed gas ratio (CH4:CO2:H2O = 1:0.6:0.85).

Thermodynamic Analysis of Chloride Corrosion in Steel for Energy System Applications in Fe-O-Cl-Na Environments

The assumptions of contemporary energy policies are increasing the share of renewable energy sources. Biomass combustion is developing as an alternative to fossil fuels. However, it faces challenges such as limited corrosion resistance of steel boiler components due to chloride compounds in flue gases and fly ash. This paper provides a comprehensive thermodynamic analysis of chloride-induced corrosion in steel in the Fe-O-Cl-Na environment, focusing on the influence of steam concentration in the gas phase. The study was performed by using the general thermodynamic rules, the thermodynamic properties of the pure components involved in the reaction, and the properties of the solutions formed in the liquid and gas phases. The study also examined the impact of alkali metal chlorides, particularly NaCl, on the formation of NaFeO2 in the passive oxide scale layer Fe3O4/Fe2O3. Furthermore, it investigated the condensation of NaCl vapour formation of low-melting eutectic mixtures in deposits and the resulting consequences on the corrosion process. The role of HCl in the chlorination and oxidation process of steel in melted ash deposits was also discussed. The presented thermodynamic analysis was compared with assumptions of an “active oxidation” model. This study can be a valuable resource for experimental research planning and a guide for preventing corrosion in industrial settings.

α-Al2O3-loaded promoted the N-desorption reaction and inhibited NH3 decomposition in chemical looping ammonia generation: Experiments and DFT simulations

Chemical looping ammonia generation is a promising, efficient, and environmentally friendly synthesis of ammonia by cycling N-absorption and N-desorption reactions. A portion of the generated NH3 decomposes at the reaction temperature of the N-desorption reaction. In order to promote the N-desorption reaction and inhibit the decomposition of NH3, the effect of α-Al2O3 loading on the N-desorption reaction was investigated in this paper by fixed-bed experiments. The mechanism was revealed using Density functional theory (DFT) calculations. The results showed that when the reaction temperature increased, the conversion of AlN and the yield of NH3 increased, but the actual NH3 conversion decreased. When the steam concentration increased, the conversion of AlN, the yield of NH3, and the actual NH3 conversion increased. The loading of α-Al2O3 could facilitate the N-desorption reaction and inhibit the decomposition of NH3. The 40 wt% α-Al2O3 had the highest conversion of AlN. The 80 wt% α-Al2O3 had the highest yield of NH3. The actual efficiency of ammonia production at 1075 °C with 80 wt% load increased from 45.5% without load to 58.5%. The DFT calculations revealed the mechanism: α-Al2O3 surface promotes the dissociation of H2O molecules to make more hydroxyl groups in the reaction system, which promotes the transfer of H+ and the N-desorption reaction. Meanwhile, the adsorption of NH3 by the α-Al2O3 surface protected NH3 and inhibited its decomposition.

Emerging trends in hydrogen and synfuel generation: a state-of-the-art review.

The current work investigated emerging fields for generating and consuming hydrogen and synthetic Fischer-Tropsch (FT) fuels, especially from detrimental greenhouse gases, CO2 and CH4. Technologies for syngas generation ranging from partial oxidation, auto-thermal, dry, photothermal and wet or steam reforming of methane were adequately reviewed alongside biomass valorisation for hydrogen generation, water electrolysis and climate challenges due to methane flaring, production, storage, transportation, challenges and opportunities in CO2 and CH4 utilisation. Under the same conditions, dry reforming produces more coke than steam reforming. However, combining the two techniques produces syngas with a high H2/CO ratio, which is suitable for producing long-chain hydrocarbons. Although the steam methane reforming (SMR) process has been industrialised, it is well known to consume significant energy. However, coke production via catalytic methane decomposition, the prime hindrance to large-scale implementation of these techniques for hydrogen production, could be addressed by coupling CO with CO2 conversion to alter the H2/CO ratio of syngas, increasing the reaction temperatures in dry reforming, or increasing the steam content fed in steam reforming. Optimised hydrogen production and generation of green fuels from CO2 and CH4 can be achieved by implementing these strategies.

Synthesis of hierarchically porous Cu-BTC through phase-controlled etching

To enhance diffusion channels and boost active sites within microporous metal–organic frameworks, hierarchically porous structures are indispensable. This study pioneered phase-controlled acetic acid etching techniques, encompassing solution etching and steam etching resulting in the successful synthesis of a series of hierarchically porous Cu-BTC (HP-Cu-BTC). In contrast to etching with an acetic acid solution, acetic acid steam etching offers advantages in terms of reduced etchant usage and minimized damage to the original microporous structure. Noteworthy, by employing steam-controlled recovery etching technology, it is possible to regulate both the steam concentration and the etching degree, while also facilitating the recovery of etchant. The prepared HP-Cu-BTC exhibits adjustable pore sizes (15–45 nm), and mesopore volume (0.14–0.23 cm3/g). Compared to the original Cu-BTC, the well-engineered HP-Cu-BTC demonstrates an 81 % increase in ethylene diffusion rates. The phase-controlled synthesis of HP-MOFs serves as a valuable source of inspiration for the future preparation of hierarchical porous structures.

An Active and Stable Cobalt‐Free Ruddlesden–Popper Nd0.8Sr1.2Ni1‐xFexO4±δ Air Electrode for Reversible Proton‐Conducting Solid Oxide Cells

AbstractReversible proton‐conducting solid oxide cells (R‐PSOCs) are considered to be one of the most promising devices for efficient power generation and hydrogen production. However, the requirement of high catalytic activity for fast oxygen reduction/evolution reaction (ORR/OER) and durability under high steam concentration of air electrode materials remains the major challenge for the practical application of R‐PSOCs. Here, a series of cobalt‐free Ruddlesden–Popper perovskite of Nd0.8Sr1.2Ni1‐xFexO4±δ are reported with mixed conductivity for enhanced ORR/OER kinetics. The R‐PSOCs with an optimal Nd0.8Sr1.2Ni0.7Fe0.3O4±δ air electrode show a high peak power density of 1.28 W cm−2 in the fuel cell mode and a promising current density of 3.24 A cm−2 at 1.3 V in the electrolysis cell mode at 700 °C. In addition, the R‐PSOCs show favorable stability under the fuel cell, electrolysis, and reversible modes for hundreds of hours. This work demonstrates that the Ruddlesden–Popper materials can be utilized as suitable air electrodes for R‐PSOCs.

Large-scale PANDA facility – radiation experiments and CFD calculations

Abstract CFD modelling of the thermo-hydraulic phenomena in the containment during the various phases of a severe accident necessarily requires consideration of radiative heat transfer – in the presence of steam. These radiative phenomena include (i) energy transfer within the gas mixture and (ii) between the gas and surrounding structures. Preliminary calculations carried out for these types of experiments within the OECD/NEA HYMERES-2 project with the CFD code containmentFOAM using a Monte Carlo solver for thermal radiation, demonstrated that the radiative heat transfer is significant even for very small amounts of vapour in the range of ≈0.1 % to ≈2 %. For this reason, the test matrix was tailored to the two opposite extremes: either gas compositions with a low vapour/steam content, where radiative heat transfer can be neglected, or gas mixtures with higher vapour contents, so that radiative heat transfer plays a dominant role. For the selected experiments of the H2P2 series and the corresponding CFD calculations, a vessel with a diameter of 4 m and a height of 8 m was preconditioned with different air-vapour mixtures (a) at room temperature and (b) elevated temperatures. A stable helium layer was then built-up in the upper part of the vessel. The gas was then compressed by injecting helium from above which resembles with best efforts a compression with a piston in a cylinder. This results in a height-dependent and transient increase of the gas temperature. These experiments and the associated CFD calculations were developed to isolate the phenomena of thermal radiation as good as possible from convective and diffusive effects – within the always present experimental limitations. For the reference experiment with ‘dry conditions’ corresponding to the lowest experimentally possible humidity of ≈0.1 %, we show that the use of a model without radiation provides the best agreement between the experimental and numerical results. For the much higher steam content of ≈60 %, the statistical narrow band correlated-k model (SNBCK), non-gray gas model, is the best candidate for future calculations – with computationally forgivable additional effort. We also provide with the Filtered Rayleigh Scattering technique (FRS) an outlook for a possible future instrumentation approach to better meet the requirements of the CFD community.

Waste-derived catalysts for tar cracking in hot syngas cleaning

Catalytic tar cracking is a promising technique for hot syngas cleaning unit in gasification plants because it can preserve tars chemical energy, so increasing the syngas heating value. The cost associated with catalyst preparation is a key issue, together with its deactivation induced by coke deposition. Iron is a cheap and frequently used catalyst, which can also be found in some industrial wastes. The study aims to assess the catalytic efficiency for tar cracking of two waste-derived materials (red mud and sewage sludge) having high content of iron. The catalysts were supported on spheres of γ-Al2O3, and their efficiency was compared to that of a pure iron catalyst. The role of support was investigated by testing pure red mud, with and without the support. A series of long-term tests using naphthalene as tar model compound were carried out under different values of process temperatures (750 °C-800 °C) and steam concentrations (0 %-7.5 %). The waste derived catalysts showed lower hydrogen yields compared to pure iron catalyst, due to their lower content of iron. On the other hand, the conversion efficiencies of all the tested catalysts resulted rather similar, since the Alkali and Alkaline-Earth Metallic species present on the surface of waste-derived catalyst help in preventing coke deposition. The iron oxidation state appears to play an important role, with reduced iron more active than its oxidised form in the tar cracking reactions. This indicates the importance of tuning steam concentration to keep constant the reduced state of iron while limiting coke deposition.

An Artificial Neural Network-Based Fault Diagnostics Approach for Hydrogen-Fueled Micro Gas Turbines

The utilization of hydrogen fuel in gas turbines brings significant changes to the thermophysical properties of flue gas, including higher specific heat capacities and an enhanced steam content. Therefore, hydrogen-fueled gas turbines are susceptible to health degradation in the form of steam-induced corrosion and erosion in the hot gas path. In this context, the fault diagnosis of hydrogen-fueled gas turbines becomes indispensable. To the authors’ knowledge, there is a scarcity of fault diagnosis studies for retrofitted gas turbines considering hydrogen as a potential fuel. The present study, however, develops an artificial neural network (ANN)-based fault diagnosis model using the MATLAB environment. Prior to the fault detection, isolation, and identification modules, physics-based performance data of a 100 kW micro gas turbine (MGT) were synthesized using the GasTurb tool. An ANN-based classification algorithm showed a 96.2% classification accuracy for the fault detection and isolation. Moreover, the feedforward neural network-based regression algorithm showed quite good training, testing, and validation accuracies in terms of the root mean square error (RMSE). The study revealed that the presence of hydrogen-induced corrosion faults (both as a single corrosion fault or as simultaneous fouling and corrosion) led to false alarms, thereby prompting other incorrect faults during the fault detection and isolation modules. Additionally, the performance of the fault identification module for the hydrogen fuel scenario was found to be marginally lower than that of the natural gas case due to assumption of small magnitudes of faults arising from hydrogen-induced corrosion.