Reduction Reactor Research Articles

Discharge reactor for fabricating efficient supported metal catalysts at room temperature in the absence of H2

AbstractSupported metal catalysts have been widely applied and commonly fabricated through the H2 reduction process. Herein, we develop a H2‐free room‐temperature discharge‐driven reduction (RT‐DR) reactor for fabricating supported metal catalysts at room temperature without H2. By RT‐DR reactor, a catalyst with pseudo‐boehmite (PB) as support (CdS/Pt/PB) is fabricated. In visible‐light‐driven photocatalytic H2O splitting to H2, CdS/Pt/PB shows a H2 evolution rate of 1132 μmol h−1, which is greatly enhanced than that on catalyst prepared by traditional H2‐reduction (633 μmol h−1). RT‐DR reactor is also used to prepare a catalyst with low sodium PB (LSPB) as support (CdS/Pt/LSPB). In visible‐light‐driven photocatalytic H2O splitting to H2, CdS/Pt/LSPB shows a H2 evolution rate of 2554 μmol h−1, which is 2.5 times higher than that on catalyst prepared by traditional H2‐reduction (1029 μmol h−1). Thus, RT‐DR reactor has high efficiency and universality in preparing catalysts, thus offering a great potential for commercialization.

Characteristics of dissolved organic matter and their role in membrane fouling during simultaneous sludge thickening and reduction using flat-sheet membranes.

Four parallel simultaneous sludge thickening and reduction reactors using flat-sheet membranes were employed for the aerobic digestion of sludge to explore the characteristics of dissolved organic matter and its membrane fouling effect. During the initial 8 days of using flat-sheet membranes for simultaneous sludge thickening and reduction (MSTR), a notable increase was observed in the concentrations of humic acids and compounds that resemble soluble microbial by-products in the effluent. Subsequently, a fluctuating trend in humic acid levels ensued, accompanied by a gradual decline in soluble microbial by-product-like substances. Post the initial 8-day period, the capillary suction time (CST) rose from approximately 400s to over 800s, the viscosity increased from 20mPas to 38mPas, and the membrane resistance increased from roughly 6.0e+11m-1 to approximately 9.0e+11m-1. This phenomenon can be attributed to the clogging of pores by foulants whose size is similar to that of the membrane pores leading to the accumulation and deposition of macromolecules and larger particulates forming gel layers and cake layers. The interplay among diverse microorganisms engenders functional modules, collectively influencing the distribution and characteristics of dissolved organic matter within the MSTR. These microorganisms exert their metabolic effects individually and interact reciprocally, creating synergistic and inhibitory mechanisms. Notably, the synergistic interactions among microorganisms predominated, culminating in an enhanced effluent quality within the system.

Particle-resolved computational modeling of hydrogen-based direct reduction of iron ore pellets in a fixed bed. Part II: Influence of the pellet sizes and shapes

Full-fledged computational modeling of Direct Reduction reactors encompasses single-pellets models and the step-wise scaling up to industrial-scale reactors. This study delves into the particle-resolved computational modeling of hydrogen-based direct reduction of 0.5 kg iron ore fixed-beds, as a scale-bridging step and focusing on the influence of pellet sizes and shapes. To investigate the effect of particle sizes, two beds with particles sized 10.0–12.5 and 12.5–16.0 mm were characterized and numerically reconstructed using the discrete element method. While to assess the effect of particle shapes, a third numerical bed was generated directly upon a high-resolution CT-scan of a real bed. Through reactive CFD simulations, we investigated the reduction process in these three beds using hydrogen as the reducing gas. Our findings reveal that the bed structure significantly impacts the reduction efficiency and overall conversion degree. This study emphasizes the importance of accurate bed reconstruction and provides critical insights for optimizing the hydrogen-based direct reduction process in industrial applications.

Multilayer polyelectrolyte and palladium nanoparticle decorated porous materials as fixed-bed reactors for efficient reduction of 4-NP

In this study, a continuous flow catalytic reactor based on three-dimensional porous sponge bed with the uniform distribution of catalyst to treat 4-NP wastewater efficiently. The porous sponge is used as a support to construct polyelectrolyte multilayers by loading dopamine. And the multilayer polyelectrolyte is closely bound to dopamine to form polyelectrolyte film, and the nanocatalysts are synthesized by electrostatic adsorption of precursors. The reactor realizes the uniform and stable distribution of the catalyst in the three-dimensional porous sponge, and the reactant transfers from bulk solution to catalyst surface by the way of convection and diffusion, which enhances mass transfer and further improves the reaction efficiency. Under the operating conditions of a catalytic bed as small as 3 cm, a 4-NP concentration up to 4.5 mM, and a flow rate of 300 μL min−1, the conversion rate remained above 96 % for up to 200 h, indicating that the reactor has good catalytic efficiency. The results showed that this continuous flow catalytic system structure has excellent performance in wastewater treatment.

Comparative analysis of eight urea-electricity-heat-cooling multi-generation systems: Energy, exergy, economic, and environmental perspectives

The Haber-Bosch process for urea production is known for its significant carbon emissions. While the chemical looping ammonia generation method presents a potential alternative, its technical and economic feasibility still requires further investigation. This paper conducts a comparative analysis of eight renewable energy-driven urea-electricity-heat-cooling multi-generation systems by developing their energy, exergy, economic, and environmental evaluation models. Considering the fluctuation in renewable energy resources, an annual evaluation of the different systems is conducted based on a monthly time scale. The results indicate that systems based on the Haber-Bosch process have higher average energy and exergy efficiencies of 60–80 % and 40–50 %, respectively. For the chemical looping ammonia generation process, the respective efficiencies are 50–70 % and 30–40 %. Additionally, the system integrating the Haber-Bosch reaction, reduction reactor, and solid oxide fuel cell yields the highest energy and exergy efficiencies among the eight systems, at 68.2 % and 45.78 %, respectively. However, it is inferior to the multi-generation system integrating the chemical looping ammonia generation process in terms of economic and environmental performance. In addition, the system integrating the chemical looping ammonia generation process and solid oxide fuel cell has the shortest discounted payback period of 8 years, with annual revenue and net present value of 32.63 and 11.66 MUSD, respectively. While the operating expenditures of the Haber-Bosch (12.6–15.7 MUSD) are lower than those of the chemical looping ammonia generation process (14.0–17.5 MUSD), its capital expenditures (382.0–410.8 MUSD) are significantly higher than those of the chemical looping ammonia generation process (302.4–307.3 MUSD). Furthermore, the conducted environmental evaluation shows that the multi-generation system integrating the chemical looping ammonia generation process and reduction reactor exhibits lower overall carbon emissions (0.013 t CO2/t urea) compared to the state-of-the-art method of oxy-fuel coal-fired power plant for urea synthesis.

A clean hydrogen and electricity co-production system based on an integrated plant with small modular nuclear reactor

The present study aims to develop a novel configuration of hydrogen and electricity co-production based on a small modular nuclear reactor (SMR) by synergistically integrating the Vanadium Chloride thermochemical (V–Cl) and helium-closed Brayton cycles. For the V–Cl thermochemical cycle, a steady-state simulation model is developed for the first time in the Aspen Plus environment. The entire system is assessed thermodynamically by calculating the exergy destruction rate and exergy efficiency of major components employed in different subsections (nuclear power production, clean hydrogen production, supporting Rankine cycle, hydrogen compression, and storage) of the plant. Various parametric studies are conducted to identify the scope of improvement and evaluate suitable operating parameters that exhibit optimized system performance. It is found that a maximum H2 production rate is achieved when the VCl4 flow is 3.6 kmol/h. A specific hydrogen production rate of 9.63 g/kWh is achieved. The reduction reactor and Deacon reactors are responsible for the highest and lowest exergy destruction with a value of 155.46 kW and 37.60 kW accounting for 49 % and 11.86 % of the overall exergy destruction within the V–Cl cycle. The share of power production from the secondary Rankine cycle in the overall hydrogen compression train is 16.48 %. The parametric study results show that with an outlet helium pressure of 15 bar, the overall work output and electrical efficiency peaked with a value of 4.6 MW and 15.64 % respectively. The overall energy and exergy efficiencies of the proposed system are found to be 16.94 % and 21.42 % respectively.

Modeling Development of a Receiver–Reactor of Type R2Mx for Thermochemical Water Splitting

Abstract This work reports on the development of a transient heat transfer model for a prototype reactor of type R2Mx for thermochemical water splitting by temperature and pressure swing of ceria. Key aspects of the R2Mx concept, which are also incorporated in the prototype design, include a movable monolithic redox structure combined with a linear transport system, a reduction reactor, as well as a dedicated oxidation reactor. With the model, the operation of the prototype is simulated for consecutive water splitting cycles, in which ceria is reduced in a continuously heated reactor, oxidized in a separate oxidation reactor, and transported in between the reaction zones. A 2D axisymmetric numerical model of the prototype reactor was developed in ansys mechanical. The model includes heat transfer calculations in combination with an approximated simulation of the transport of the redox material during cyclic operation. It incorporates the chemical reaction by means of a modified heat capacity for ceria and accounts for internal radiation heat transfer inside the porous redox material by applying effective heat transfer properties. A parametric analysis has been undertaken to evaluate different modes of operation of the oxidation reactor. Model results are used to size the power demand of the reduction reactor and vacuum pump, to define durations of the process steps, as well as to assess operational parameters with respect to achieved temperatures. Findings suggest that suitable operation of the prototype reactor involves reduction durations ranging from 8 to 10 min and oxidations of 6 to 10 min.

Evaluation of the Mineral Manganese OXMN009 and OXMN009P in the Chemical Looping Combustion (CLC) Process Using Thermogravimetry

Indirect combustion with the chemical looping combustion (CLC) of solid oxygen carriers is one of the most promising technologies for capturing carbon dioxide (CO2) in energy production from fossil fuels since the separation of the generated CO2 is inherent to the process itself. Therefore, the cost associated with capturing this gas will be significantly reduced. This technology transfers oxygen from air to fuel through a metal oxide that acts as an oxygen carrier, avoiding direct contact between air and fuel. This oxygen carrier circulates in a fluidized bed reactor called a reduction reactor and an oxidation reactor. (1) This research work has focused on evaluating the behavior of oxygen carriers based on the original and improved manganese mineral (copper-impregnated mineral) named for this study, OXMN009 and OXMN009P, respectively. (2) Equilibrium experiments were carried out on a thermogravimetric balance (TGA) to evaluate the kinetic behavior of these oxygen transporters OXMN009 and OXMN009P, using the gases methane (CH4), carbon monoxide (CO), and hydrogen (H2). (3) The enhanced solid oxygen carrier OXMN009P exhibited good performance for the CLC process with gaseous fuels in terms of reactivity and combustion efficiency, having high reactivity and oxygen transfer properties due to copper impregnation. (4) The results show that OXMN009P has comparable reactivity to other manganese-based materials reported in the literature. It may be an effective option for carbon dioxide capture, as it uses metal oxides as the oxygen transporters (TO). (5) These oxygen transporters, OXMN009 and OXMN009P, are used in a cyclic process that prevents the formation of nitrogen oxides by keeping the air and fuel separate. (6) Thermogravimetric balance (TGA) experiments were conducted to evaluate the kinetic behavior of these copper-modified oxygen transporters. (7) It was found that OXMN009P improved the reactivity and oxygen transfer properties due to copper impregnation. The kinetic parameters obtained in the TGA indicate that the reaction is non-thermal and requires less energy to initiate. (8) The results show that OXMN009P has reactivity comparable to other manganese-based materials reported in the literature and can be an effective option for carbon dioxide capture.

A novel exergy analysis method for cerium-based solar thermochemical cycles

Ce-based thermochemical cycles are characterized by high stability and adaptability to operating temperatures. But few studies have been conducted in terms of exergy prospect. In this study, we propose an exergy analysis model and identify its irreversibility distribution. Through introducing an Energy Level-Enthalpy Change (A-∆H) diagram, we capture this distribution and reveal the trend of irreversibility variation. The results show that irreversibility occurs mainly in heat exchangers and reduction reactors and is influenced by temperature and pressure. Previous studies have focused only on the operating parameters, but this has led to negligible improvement in efficiency, hence the need for a comprehensive analysis using sound mathematical methods. We improve the exergy efficiency by 177% through theoretically optimizing the operating conditions and detail the reasons for the reduction in exergy losses. This study provides theoretical guidance and analytical tools for experiments.

Highly efficient dual-phase hydrogen-transporting membranes for NH3 decomposition coupling with CO2 reduction

Hydrogen-transporting membrane reactors play active roles in ammonia (NH3) decomposition and carbon dioxide (CO2) reduction by combining reaction and separation in one unit, simplifying the processes and reactor design and therefore saving the cost. These important reactions normally occur at high temperatures and in reducing and acidic atmosphere, thus posing great challenges on the membrane stability. Previous effort was devoted to thin Pd membranes, which however, suffer the shortcomings of hydrogen embrittlement, CO poisoning and high costs. Herein, we develop a H2-COx-tolerant and non-noble metal-ceramic dual-phase hydrogen permeable membrane reactors with a nominal composition of 60 vol% Ni-40 vol% La5.5WO11.25-δ (Ni-LWO). NH3 decomposition and hydrogen permeation was observed via the developed mixed protonic and electronic conducting membrane. A considerable production of CO in the sweep (CO2) side could also be achieved from CO2 reduction when the membrane was coupled by NH3 decomposition where the permeated hydrogen can consume the produced oxygen from favorable CO2 decomposition. Furthermore, we systematically investigated the performance of NiO–CeO2 catalyst coated Ni-LWO membrane reactor for CO2 reduction. Noteworthy that the CO generation rate obtained from Ni-LWO membrane reactor was increased in the presence of NiO–CeO2 catalysts. Hydrogen separation process coupled with surface reactions is jointly controlled by hydrogen surface exchange and bulk diffusion kinetics. These findings reveal a vital step towards the development of efficient hydrogen-transporting membrane reactor for the integration of chemical reactions and separation processes.

Detuned reactor for harmonic reduction on 20 kv distribution network Pocut Baren feeder in Banda Aceh

Abstract Nonlinear loads in distribution network have adverse impacts in the form of harmonic distortion. When the harmonic frequency is close to resonance, the harmonic will be amplified and overloading capacitor bank. Here detuned reactor is inserted in series to avoid from that risk. In this study, the impact of detuned reactor on suppressing the harmonics and power factor improvement are investigated, evaluated and analyzed. The Pocut Baren feeder is chosen as the case of the study. It is a radial distribution network with 28 distribution transformers where the starting point is connected to substation transformers and capacitor banks. Simulation is used to verify the efficacy of detuned reactor. The results shown that detuned reactor is able to reduce voltage harmonics and improve power factor across the distribution line. Although the efficacy wane at the distribution end, it can be compensated from adjusting the detuned reactor value to meet the 5% total voltage harmonic distortion (THDv) threshold at the end of the line. Simulation results confirmed that detuned reactor is able to reduce harmonics from 12% to meet the threshold. Power factors have also been improved beyond 0,9 from previously arround 0,8.

Advances in electrocatalytic carbon dioxide reduction reactors, electrolytes and catalysts

With the advance of The Times, people's demand for fossil energy has greatly increased, and it is the main energy for people to develop economy and science and technology. However, the large-scale exploitation of fossil energy has led to environmental pollution and energy crisis, and the concentration of CO2 in the air continues to rise, and the greenhouse effect is becoming more and more serious. Therefore, the conversion of CO2 into the high value-added fuels and chemicals we need will be a major measure to solve environmental problems. So, converting CO2 into fuels or high value-added chemicals using CO2 electrocatalytic reduction (CO2RR) technology is an effective way to alleviate the current problems of energy and environment. In this paper, we summarize the research progress in reaction systems, electrolyte effects, and catalyst development in CO2RR experiments, focusing on the electrocatalytic aspects of CO2. Finally, we provide an outlook on the CO2 electrocatalysis industry.

Integrated Heat Recovery System Based on Mixed Ionic-Electronic Conducting Membrane for Improved Solid Oxide Co-Electrolyzer Performance.

The current state of mixed ionic-electronic conducting ceramic membrane technology presents significant advancements with potential applications in various fields including solid oxide electrolyzers, fuel cells, hydrogen production, CO2 reduction, and membrane reactors for chemical production and oxygen separation. Particularly in oxygen separation applications, optimal conditions closely align with the conditions of oxygen-rich air streams emitted from the anode of solid oxide co-electrolyzers. This paper describes and analyzes a novel integrated heat recovery system based on mixed ionic-electronic conducting membranes. The system operates in two stages: firstly, oxygen is separated from the anode output stream using mixed ionic-electronic conducting membranes aided by a vacuum system, followed by the heat recovery process. Upon oxygen separation, the swept gas stream is recirculated at temperatures near thermoneutral conditions, resulting in performance improvements at both cell and system levels. Additionally, an oxygen stream is generated for various applications. An Aspen HYSYS® model has been developed to calculate heat and material balances, demonstrating the efficiency enhancements of the proposed system configuration.

Analysis of configurational factors that influence the reversibility of nonstoichiometric countercurrent thermal reduction reactors

Recently, thermodynamic modeling has demonstrated that reduction of nonstoichiometric oxides in a counterflow gas current with a single inlet and exit must result in an equilibrium temperature gradient that deviates from the typically assumed isothermal operation at every single point but one, under assumed mass balance constraints. This necessity for a temperature gradient results in real processes that are near isothermal to deviate from the ideal reversible process, except for the single point where the Gibbs free energy change is zero. In this paper, new configurations with additional inlets and exits that can better approximate reversible and isothermal countercurrent flow reactors are considered and thermodynamically modeled. We show that it is possible to decrease irreversibilities while operating under the same maximum temperature, gas flowrates and initial nonstoichiometry simply by employing two or more exits and/or inlets. Under the most optimal conditions where the normalized irreversibilities are lowest, utilizing either an extra exit or extra inlet and exit show improved results in terms of minimizing the Gibbs free energy and lowering the needed separation work for the gases. Generally, as more irreversibilities are generated within the reactor, the more significant the usage of extra inlets/exits becomes.

Alkaline pulping catalyzed ordered conversion of bark in supercritical water

The hydrophilicity of lignocellulosic biomass hinders the application of a high concentration slurry for supercritical water gasification, thereby reducing the gasification efficiency and energy self-sufficiency. A pretreatment method of alkaline pulping with KOH and NaOH was proposed to achieve the high feed concentration for continuous reactor and macromolecular simplification for barrier reduction of conversion. In this study, bark as an example of lignocellulosic biomass, whose 30 wt% and 40 wt% slurries with favorable rheology and stability, was prepared by alkaline pulping successfully. The minimum alkali consumption of NaOH and KOH pulping for 30 wt% and 40 wt% were 11%–14%, 16%–20%, and 16%–21%, 23%–28%, respectively. The most economical conditions were 180 °C and 24% KOH addition. All slurries prepared by NaOH and KOH at 180 and 200 °C could satisfy the industrial standard of coal-water slurry, and only 3–5 times higher than water viscosity. The bark macromolecules were restructured due to the hydrolysis of cellulose and lignin by breaking down the hydrogen bond and ether bond with trivial hydrocarbon matrix loss. The scattered crystal growth facilitated the uniform premixing of bark and water. Meanwhile, a surface particle charges potential increase leading to a heightened repulsive force by alkaline pulping furtherly enhanced the premixing effect. Additionally, metal ions could be deposited onto the bark surface during alkaline pulping. The chemical modification leading by alkaline pulping achieved the premixing of feedstock and water to form bark slurry. The conversion barrier was decreased to fulfill the ordered conversion, and 95.66% gasification efficiency for 40 wt% bark slurry was displayed at 600 °C with a preheated water of 6. Phenolic compounds and hydrocarbons were the most dominant components in liquid products. Polycyclic aromatic hydrocarbons in liquid products were detected at 620 °C with a preheated water of 4. The functional groups of organic matter in the slurry were significantly converted into the gas phase, and lattice oxygen was produced in the solid product. The alkali recovery was 65% at the optimal gasification condition, and achieved the maximum of 80% at 580 °C. The successful completion of this research affirms the dominance of the pulping-alkali recovery-gasification method for expanding the application of SCWG of lignocellulosic biomass in large engineering projects.

Copper-based chemical looping air separation process: Thermodynamics, kinetic modeling, and simulation of the fluidized beds

Chemical looping air separation is one of the potential processes for oxygen separation from air constituents using oxygen carriers with chemical looping oxygen uncoupling properties that are circulated between reduction and oxidation reactors. Copper-based oxygen carriers have been recognized as a suitable class of materials for the process due to their promising properties and low cost. In this study, copper-based material has been investigated for chemical looping air separation to identify the process parameters that affect the performance and oxygen generation. Firstly, thermodynamic analysis was performed to predict the suitable conditions for oxygen generation and oxygen carrier oxidation, and to model oxygen equilibrium partial pressure. Then, CuO (40 wt%)/ZrO2 was prepared by impregnation synthesis technique to examine the oxygen carrier kinetics using a thermogravimetric analyzer. Results showed that 1.5-dimensional Avrami-Erofeev model best fitted the reduction data with an activation energy of 230 ± 25.2 kJ/mol, whereas the oxidation data were fitted by 1.5 reaction order model with an activation energy of 211 ± 8.0 kJ/mol. The process was simulated using Aspen Plus software package, and the reactors were represented using Fluidbed units to account for both the kinetics and hydrodynamics, to identify the suitable fluidization regimes for specific operating conditions. Simulation results showed that the highest oxygen generation occurred while operating both reactors at bubbling fluidization regimes. Moreover, the temperature effects on the process performance and output were examined, and findings indicated that operating the reducer at 1000 °C and the oxidizer at 800 °C would give out the highest solids conversion and oxygen generation flowrate (23.26 ton/day) with specific energy consumption of 132.26 kWh/tonne of oxygen. However, operating the process at high temperatures would increase the energy penalty and the operating costs, and a more comprehensive technoeconomic study will be required to decide whether lower temperatures operation would be feasible.

Carbon Corrosion Behavior of Carbon Support Materials for PGM-Based Catalysts in PEM Fuel Cells

The proton exchange membrane fuel cell (PEMFC) is a promising device for the transportation sector of a fossil free society, using green hydrogen from water electrolysis as a clean and sustainable option. However, sluggish kinetics as well as durability issues limit the implementation until this day. Therefore, modifications to the platinum catalysts [1] and the carbon supports [2] are made to improve the overall performance and durability of the cathode catalyst system.Herein, we present the investigation of the carbon corrosion behavior of different carbon support materials in PEMFCs using online nondispersive infrared (NDIR).The different carbon supports used for this study are commercial materials such as Vulcan, Ketjenblack EC-300J and Ketjenblack EC-600JD as well as self-synthesized mesoporous carbon nanodendrites (MCND). [3] The MCND support material is a highly porous high surface area carbon, which makes it a suitable candidate for fuel cell applications. Onto the support materials, Pt nanoparticles were deposited using a customized fluidized bed reduction reactor [4], resulting in similar Pt particle size and distribution onto the support material, thus making a comparison between different supports possible. Beginning of life (BOL) measurements in a single cell setup, as shown in Figure 1, show promising performance of the platinum catalyst supported on MCND (Pt/CMCND) compared to the platinum catalysts on commercial supports. Furthermore, we will present the investigated carbon corrosion behavior of the different support materials conducted by accelerated stress tests (AST) based on the DOE support degradation protocol. The online quantification of the evolved CO and CO2 from the cathode catalyst layer is measured using our online NDIR giving insight in the carbon corrosion resistivity of the different support materials. Together with the performance measurements, we develop a better understanding of the impact of the carbon support material on the performance and durability of the cathode catalyst layer.Literature:[1] Strasser, P; Kühl, S. Nano Energy 2016, 29, 166.[2] Ott, S. et. al., Nat. Mater. 2020, 19 (1), 77-85.[3] Numao, S. et al., Carbon 2009, 47, 306-312.[4] Hornberger, E. et. Al. J. Electrochem. Soc. 2020, 167, 114509. Figure 1: Air polarization curves of the four different catalysts under the following conditions: 80° C, 100% RH, 150 kPaabs backpressure, stoich.: 1.5 (H2) and 2 (air), min. flow: 50 ml/min (H2) and 800 ml/min (air). Figure 1

Anode Reaction Control for a Single-Compartment Electrochemical CO2 Reduction Reactor with a Surface-Activated Diamond Cathode.

The electrochemical reaction of carbon dioxide (CO2 ) in aqueous electrolyte solutions is attracting increasing attention for sustainable chemical production. Boron-doped diamond (BDD) electrodes have been previously shown to be very effective for the stable electrochemical production of formic acid from CO2 . Typically, the electrochemical production of formic acid by CO2 reduction (CO2 R) reaction is performed with a dual-compartment flow reactor equipped with a membrane separator. The problems caused by the membrane separator, such as scaling-up, complicated operational control and materials costs can be solved using a membrane free single-compartment reactor. Here we demonstrate anode reaction control for a single-compartment CO2 R flow reactor using a surface-activated BDD cathode and achieve a Faradaic efficiency for formic acid production of over 70 %.

H2 producing hybrid solar thermochemical ZnSO4/ZnO water splitting cycle: Thermodynamic efficiency analysis

This investigation reports the thermodynamic efficiency analysis of a hybrid ZnSO4/ZnO water-splitting cycle. The data required for efficiency calculations are gathered from HSC Chemistry Software. The prime goal is to examine the effects of the thermal energy needed for heating inert sweep gas and separating the gaseous components in the cycle on the solar-to-fuel energy conversion efficiency. Complete dissociation of ZnSO4 into ZnO, SO2, and O2 is considered. Besides, a comprehensive re-oxidation of ZnO in the presence of SO2 and H2O is assumed. A thermodynamic process model, which includes reduction and oxidation reactors, two separators, multiple gas-to-gas heat exchangers, two heaters, and one ideal H2/O2 fuel cell, is developed and used to analyze the efficiency. The energy required for the separation of inert/O2/SO2 gas mixture is observed to be one of the significant contributors to the energy needed to drive the ZnSO4/ZnO WS cycle. The solar power required (989.9 kW) is recorded to be the lowest for the inert gas molar flow rate equal to 10 mol/s. Because of the low solar energy requirement, the maximum solar-to-fuel energy conversion efficiency (28.4 %) is attained at the thermal reduction temperature of 1445 K.

Alumino-Silico-thermic synthesis of high purity ferroboron alloy and its characterization

High purity ferroboron (Fe–B) alloy is used as an alloying agent for making special grades of steels, Nd-Fe-B magnets etc. In this study, alumino-silico-thermic co-reduction of Fe2O3 and B2O3 was attempted to prepare high purity Fe–B. Extensive differential thermal analysis (DTA) studies were carried out to understand the reduction behaviour of Fe2O3 and B2O3 by Al and Si. DTA exothermic peaks indicated three step reduction of Fe2O3 (Fe2O3→Fe3O4→FeO→Fe) when reacted with Al and Si separately. B2O3–Si system did not show exothermic peaks while heating indicating sluggish or no reduction, however, B2O3–Al DTA peaks indicated two step reduction behaviour. Differential thermal analysis of Fe2O3–B2O3–Al–Si indicated completion of reduction of oxides, and formation of different intermediate phases. Specially designed reduction reactors were used to produce ferroboron alloy in bulk quantities. Thermal analysis results suggested that the formation of aluminium and silicon borides could be avoided using sub-stoichiometric amount of Al and Si, which was further confirmed from the bulk thermit product. Si acted as reducing agent as well as forming low melting slag comprising of Al(Si)–B–O type oxides. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and Particle Induced Gamma-ray Emission (PIGE) analysis confirmed the presence of 12 wt% boron in the alloy product with lower content (<1 %) of impurity elements like Al and Si. The relationship between the chemical homogeneity with the thermit process parameters was established. Microstructure and mechanical properties confirmed the formation of Fe2B and FeB phase in the thermit alloy.