Reactor Conversion Research Articles

Optimization of C5+ production by CO2 recycle at an integrated Tri-reforming and Fischer-Tropsch process

Integration of Tri-reforming and Fischer-Tropsch processes is a novel approach for conversion of CO2 into C5+ liquid hydrocarbon. Tri-reforming converts CO2 into syngas and does not require external heat source due to methane oxidation reaction that occurs at the beginning of reactor. Fischer-Tropsch synthesis converts produced syngas in the reformer to hydrocarbon fuels. In this research, plug reactors have been modeled in a heterogeneous and one-dimensional form, and the mass and energy equations governing them in steady state have been developed. The accuracy of models is validated with literature data. Then an optimization problem aiming at maximal C5+ production is compiled with specific limitations imposed on operating conditions. Based on the modeling results, 95 % of CO2 produced at Fischer-Tropsch and 92 % CO2 produced at Tri-reforming process is captured and injected into Tri-reforming reactor for conversion into hydrocarbon fuels. Modeling results revealed that the mole fractions of C2-C4 and C5+ at outlet of Fischer-Tropsch are 0.117 and 0.023 which could be purified in separators and used as clean energy carriers. The suggested integrated route for CO2 capture and conversion into green fuels offers both environmental and technical advantages.

In-Situ CO2 Release from Captured Solution and Subsequent Electrolysis: Advancements in Integrated CO2 Capture and Conversion Systems

The electrochemical reduction of carbon dioxide (CO2ER) offers a compelling strategy for sustainable energy and carbon management by transforming CO2 into valuable chemicals and fuels. This approach is particularly attractive when powered by surplus renewable energy, aiding in the closure of the carbon cycle. However, the significant energy requirements for CO2 isolation, pressurization, and purification from capture media pose challenges for industrial-scale implementation. To overcome these obstacles, recently innovative electrolyzers have developed that directly convert reactive carbon solutions, such as bicarbonate-rich effluents from carbon capture units, into higher-value products. This electrolyzers produces CO2 in situ by reacting (bi)carbonate with acid generated within the electrolyzer, facilitating efficient CO2ER at the cathode surface and eliminating the need for costly CO2 recovery and compression steps. This study details recent efforts in advancing this type of electrolyzer, focusing on CO2 sources for capturing step, technical aspect consideration of integrated systems, electrolyzer design consideration and membrane designs for integrated systems. Herein, we emphasize the need for a permeable cathode that allows efficient (bi)carbonate ion transport while maintaining a high catalytic surface area. Additionally, we discuss the critical role of electrolytes, including the impact of (bi)carbonate concentration, their effect on CO2 utilizations and CO2ER selectivity. We also demonstrate the state-of-the-art performance metrics for electrolyzers that utilize CO2-captured solutions, such as Faradaic efficiency, experimental validation of CO2 sources, current density, and CO2 utilization efficiency, a guideline for future studies. Collectively, we believe that this analysis will contribute to the development of industrial-scale electrochemical reactors for CO2 conversion, advancing towards a sustainable and closed-loop carbon cycle.

Solar-integrated biogas reactor for efficient kitchen waste conversion to biogas

This study aimed to improve biogas production by co-digesting kitchen waste and animal manure in a solar-integrated biogas reactor. The panel then heated the substrate mixture to the right temperature for the reactor after turning solar energy into electricity. The experiment was conducted at mesophilic (37°C) and thermophilic (40°C) conditions. After 45 days of co-digestion of animal dung, kitchen trash, cow manure, and grasses, the solar-integrated biogas plant generated 1,445 mL of biogas with 60% CH4, 14% CO, and 21% other gases; in comparison, the conventional biogas digester produced 501 mL, 479 mL, and 525 mL, respectively, with 35-50% Methane, 18% CO, and 22% other gases. The data show that a solar-integrated biogas plant may react faster produce more gas, and have a higher methane concentration using kitchen waste and animal manure. An environmental effect analysis and prediction of biogas plant construction has been accomplished. The proposed biogas plant, supported by a solar-integrated reactor strategy, appears economically viable, projecting a five-year payback period. This research evaluates efficient biogas production techniques, emphasizing their importance in advancing engineering sustainability. It promotes the role of renewable energy, energy efficiency, and environmental sustainability in solving global energy problems and reducing climate change.

Efficient ammonia conversion in proton conducting fuel cells: Combined application of dendritic anodes and nanofiber catalysts

Ammonia, with its high hydrogen content, serves as an optimal carbon-free medium for indirect hydrogen storage, making it ideal for fuel cells. Nevertheless, the limited anodic catalytic activity of Proton-conducting solid oxide fuel cells (PCFCs) significantly hampers NH3 utilization efficiency and overall performance. This study introduces efficient nano-catalysts deposited onto dendritic anodic microchannels, leading to the formation of an in-situ ammonia decomposition reactor for internal ammonia gas conversion. Compared to conventional cells, this cell, equipped with a catalyst bed, shows a 25% increase in peak power density and a 20%–30% enhancement in NH3 utilization efficiency. Additionally, ammonia undergoes efficient decomposition on anodic metallic nickel, which prevents nickel nitridation and improves cell stability. The augmented stability of these cells is evidenced by their prolonged operational lifespan under constant current conditions, extending from 63 to 108 h, thus marking a substantial enhancement in the system's durability and reliability.

Fuel transport mechanisms and power generation enhancement in air-breathing microfluidic fuel cells with discrete-hole anode

Current challenges in air-breathing microfluidic fuel cells (AMFCs) technology include insufficient fuel transfer and unsatisfactory power density. To address these issues, this study develops a three-dimensional computational model to optimize the performance of AMFC with a discrete-hole anode. This model reveals that the "petal-shaped" non-uniform fuel distribution is due to the shearing and dilution effects of the electrolyte. Additionally, discrete-hole structures such as size have a slight influence on fuel transport and current production, with performance deviations under 1.6%. Significant improvements are achieved by reducing the electrolyte flow rate and electrode length. Transitioning from a single cell with a long anode to a series/parallel stack of cells with short electrodes significantly boosts net power output and fuel utilization. Under optimal conditions, a maximum power density of 349.9 mW cm−3 and an output of 19.2 mW are obtained. This research provides valuable insights into fuel transport mechanisms and power enhancement strategies in the AMFCs, guiding the future design and optimization of microfluidic reactors for energy conversion.

Scaling-up a Photo-Electrocatalytic Reactor for CO2 Capture and Conversion to Syngas

The most challenging deal we face today is the need to lower greenhouse gas (GHG) emissions and tackle climate change. Though calls to reduce them are growing louder yearly, emissions remain unsustainably high. CO2 is the key contributor to global climate change in the atmosphere. Electrochemical CO2 reduction (EC CO2R) into chemicals or fuels holds great research interest as a promising approach to mitigate CO2 emissions and reach a carbon-neutral future.1 In this regard, an extraordinary effort has been made to discover new efficient and sustainable catalysts at the laboratory level over recent years. High-performance electrocatalysts in aqueous electrolytes often rely on noble metals, which may hinder their industrial applications. Herein, we successfully synthesized core-shell Cu2O/SnO2 nanoparticles2–4 functionalized with a silane group, using a simple and versatile methodology based on a three-step scalable synthesis method involving wet precipitation followed by salinization and, finally, a rhenium-based complex has been assembled by electro-polymerization.5 The carbon paper-supported Cu2O/SnO2-Re electrocatalyst was characterized at 10 cm2 scale achieving a CO:H2 ratio from 3 to 9, and demonstrating an stable syngas production up to 24 hours at -20 mA·cm-2. To translate those developments from the laboratory level to a higher TRL towards the practical application of CO2 capture and utilization6, an additional chamber was added to the system for the continuous CO2 capture and electrochemical conversion, increasing the electrode area from 10 cm2 to 100 cm2. Captured CO2 co-electrolysis to syngas (H2:CO ratio of 5) in one step was demonstrated with a high CO2 conversion at a current up to -2 A, indicating the scale-up potential of this intensified system. The technology is currently under validation in a TRL4 reactor composed of an array of 5 modules (i.e., 4 x 5 cells x 100 cm2) with a total active area of or 0.2m2 for direct CO2 conversion from simulated anthropogenic sources. The design integrates low-cost photovoltaic (PV) cells to provide any required additional bias to drive the reaction, thus, Perovskite PV panels with a cost of up to 5 times lower (10 €/m2) than Si PV cells were used. The TRL5 demonstration of the developed technology will be done with real flue gas emissions the first semester of 2024. Acknowledgements The financial support of the SUNCOCHEM project (Grant Agreement No 862192) of the European Union’s Horizon 2020 Research and Innovation Action programme is acknowledged. References Guzmán, H., Russo, N. & Hernández, S. CO2 valorisation towards alcohols by Cu-based electrocatalysts: challenges and perspectives. Green Chemistry vol. 23 1896–1920 Preprint at https://doi.org/10.1039/d0gc03334k (2021).Cuatto, G. et al. Standardization of Cu2O nanocubes synthesis: Role of precipitation process parameters on physico-chemical and photo-electrocatalytic properties. Chemical Engineering Research and Design 199, 384–398 (2023).Zoli, M., Guzmán, H., Sacco, A., Russo, N. & Hernández, S. Cu2O/SnO2 Heterostructures: Role of the Synthesis Procedure on PEC CO2 Conversion. Materials 16, (2023).Zoli, M. et al. Facile and scalable synthesis of Cu2O-SnO2 catalyst for the photoelectrochemical CO2 conversion. Catal Today 413–415, 113985 (2023).Miró, R. et al. Solar-driven CO2 reduction catalysed by hybrid supramolecular photocathodes and enhanced by ionic liquids. Catal Sci Technol 13, 1708–1717 (2023).Sullivan, I. et al. Coupling electrochemical CO2 conversion with CO2 capture. Nat Catal 4, 952–958 (2021). Figure 1

Pilot Scale Electrolysis of Peroxodicarbonate as an Oxidizer for Lignin Valorization.

A pilot scale plant at Technology Readiness Level (TRL) 6 comprising an electrochemical ex-cell continuous production of sodium peroxodicarbonate and a thermal depolymerization plug flow reactor for kraft lignin conversion is established. Due to the labile nature of the "green" oxidizer peroxodicarbonate, special attention must be paid to the production parameters in order to optimize its use. A simplified design model describing steady-state and transient operations is formulated and finally validated against experimental data from the electrolysis setup. Design trade-offs are visualized, and their impact on specific energy consumption is evaluated. The pilot plant was operated for a 20-month period for more than 1200 h on-stream. Optimized process conditions result in vanillin yields of 8 wt % and thus prove the successful scale-up.

A techno-economic assessment of conventional and modified Solvay processes for CO2 capture and reject brine desalination

The ongoing discharge of desalination reject brine and emission of carbon dioxide (CO2) into the environment pose a major threat to the ecosystem. In this context, the Solvay process presents a potential mitigation scheme for reducing reject brine salinity while simultaneously sequestering CO2. This work reports for the first time a systematic techno-economic assessment of the conventional (ammonia-based) and modified (calcium hydroxide-based and Potassium hydroxide-based) Solvay processes. The model evaluates the effect of reactor conversion, inlet CO2 weight%, inlet CO2 temperature, gas/liquid ratio, and brine flow rate on the CO2 and Sodium ions removal. In addition, the process cost associated with each parameter was analyzed, and the impact of implementing carbon tax on process profitability was investigated. Furthermore, the Solvay processes were evaluated using economic metrics including Net Present Value (NPV), economy of scale, and Levelized cost of water. The results suggest that the calcium hydroxide-based modified Solvay process outperforms other processes in terms of CO2 and Sodium ions removal. Moreover, for the studied parameters, the calcium hydroxide-based modified Solvay process demonstrated economic viability, yielding a decent annual profit. However, the conventional Solvay process requires a remarkable amount of expenses, yet after the implementation of 40 dollars per metric tons of CO2 as a carbon tax, the conventional Solvay reaches the break-even point. These findings underscore the importance of implementing environmentally friendly practices in the industry, as the modified Solvay process proves to be a promising solution for mitigating environmental threats and promoting sustainable operations.

Development of an ammonia decomposition reactor, afterburner and post-decomposition reactor for 1 kW solid oxide fuel cells using ammonia

Solid oxide fuel cells can overcome the poor flammability of ammonia by directly converting the chemical energy of ammonia into electricity. However, thermal stress by internal decomposition, nitriding at the solid oxide fuel cells stack and nitrogen oxides emissions must be considered when using ammonia in solid oxide fuel cells. In this study, an ammonia fuel processor was developed for stable operation and low emissions of solid oxide fuel cells using ammonia. The ammonia fuel processor consisting of an ammonia decomposition reactor, an afterburner and a post-decomposition reactor was tested using simulated off-gases of solid oxide fuel cells using ammonia. The ammonia conversion of the decomposition reactor varied from 32 % to 84 % with off-gas temperatures from 360 °C to 670 °C. When ammonia conversion after the solid oxide fuel cell stack was 99.70 %, nitrogen oxides emissions of the afterburner was 1.05 g/kWh, which is higher than the regulatory limit of 0.26 g/kWh. High fuel utilization and excess air ratio made nitrogen oxides emission even worse. The regulatory limit was successfully satisfied by using the post-decomposition reactor even when ammonia conversion after the solid oxide fuel cell stack was 99.10 %. The developed ammonia fuel processor could supply fuel at the optimal hydrogen-to-ammonia ratio and prevent nitrogen oxides emissions in solid oxide fuel cells using ammonia.

Preferential formation of uniform spherical vaterite by harnessing vortex flows and integrated CO2 capture and mineralization

The use of calcium bearing resources to facilitate solvent regeneration and CO2 reuse via carbon mineralization offers a low energy pathway for the production of calcium carbonate. However, a crucial challenge is the lack of specificity in the formation of various calcium carbonate polymorphs during carbon mineralization. One of the less explored but highly effective approaches to tune the morphology and crystal structure of specific carbonate phases involves tuning vortex flows. This approach is an alternative to utilizing chemical reagents that need to be regenerated for tuning the morphologies and crystalline structures to direct the formation of specific carbonate phases. In this study, the efficacy of using homogeneous vortex flows in limiting the agglomeration of carbonate particles and directing the formation of metastable vaterite phases is discussed and contrasted with the influence of inhomogeneous conventional feed flow patterns on precipitated calcium carbonate (PCC). Herein, a Taylor-Couette Carbonate Conversion (TC3) reactor is used to direct the formation of spherical vaterite particles with uniform particle size distribution preferentially over calcite and other phases. The formed vortex patterns inside TC3 reactor provide homogeneous reaction spaces conducive to PCC formation, ensuring uniform mixing throughout the process. By increasing the rotational speed and the residence time, higher purity carbonates with more uniform sizes are obtained. Furthermore, preferential vaterite formation is also observed in leachates obtained from alkaline industrial residues such as construction and demolition waste and steel slag. Thus, the proposed approach is effective in harnessing multiple waste streams such as CO2 emissions and alkaline industrial residues to produce calcium carbonate phases such as vaterite with structural and morphological specificity.

SELECTING OF MATRIX COMPOSITION FOR IMMOBILIZATION OF IRRADIATED FUEL OF THE IGR REACTOR

Impulse Graphite Reactor (IGR) is a unique nuclear installation namely research reactor with the core consisting of uranium-graphite fuel elements with 90% enrichment by U235. Possible immobilization of the first core taken from the reactor in 1967 is studied here as part of the IGR reactor conversion to low-enriched uranium fuel. Irradiated fuel is related to the category of mediumactive waste according to the content of beta-emitters. Expected value of highly-enriched uranium fuel (HEU) burnup rate was less than 1 % mass. The experts from the Institute of Atomic Energy (IAE) proposed the way how to immobilize irradiated IGR reactor fuel into the cement matrix. First, the fuel is suggested to dilute with depleted uranium in order to lower the enrichment up to the <20 mass. % by U235. The properties of the matrix should meet the engineering criteria ruled by international and national standards. So, according to aforesaid, The IAE team is facing an actual problem of selection the matrix and understanding its characteristics.The work was aimed at selection of composition of cement mortar for making robust matrix to immobilize irradiated IGR reactor fuel.The paper describes techniques and results of the time identification (start) of solidification, gradual volume change, water separation, velocity and uniform cement mortar.

Direct methanol oxygen-ion conducting solid oxide fuel cell with an integrated in-situ cracking reactor

Methanol, as an indirect hydrogen storage medium rich in hydrogen, is considered an ideal fuel for fuel cells. Oxygen-ion conducting solid oxide fuel cells (O-SOFCs) powered by methanol are renowned for their high energy conversion efficiency and minimal environmental impact, offering broad application prospects. However, challenges to their stable power generation arise from the rate of hydrogen production through methanol decomposition at the anode and carbon deposition on nickel-based anodes. To address these issues, this study explores the optimal operating temperature and concentration of methanol as an O-SOFCs fuel, while also developing a novel cell design. In this design, an in-situ cracking reactor for internal conversion of methanol is constructed by loading Ru-GDC high-efficiency nanofiber catalysts on dendritic anode microchannels, significantly enhancing the cell's power generation performance. Experimental results demonstrate that at 800 °C and a 30 % methanol concentration, the system increases the maximum power density (MPD) from 0.622 W cm−2 to 0.893 W cm−2, exhibiting a 43.57 % increase in power density and a 13.03 % improvement in methanol utilization. Additionally, the system effectively mitigates carbon deposition and nickel anode deactivation, thereby enhancing the cell's operational stability.

The method of research nuclear installation conversion at the decommissioning stage

The article examines the problem of forming scientific and technical programs for the conversion of research nuclear installations at the decommissioning stage, which arose in the aspect of justifying the possibility of extending the designated service life of all existing research nuclear reactors in Russia. To solve this problem, a methodology is proposed, which includes an information model and a process description of the necessary step-by-step actions, as well as a set of appendices in the form of documents justifying the most optimal ways to form a project for managing the quality of nuclear reactor conversion processes in relation to special life cycle conditions of specific nuclear reactors. The general view of the methodology is described: principles and methods of construction, structure. An example of the application of this technique in the conversion of the Hydra salt solution pulsed research reactor for the decommissioning stage is given. The purpose of the conversion of the Hydra reactor is to extend the designated service life by replacing non-repairable equipment ­ the vessel. The main criteria for justifying the residual life of the housing are formulated, which are the presence of a safety margin of the housing material, taking into account the accumulated fluence on more vulnerable areas and the justification of the integrity and tightness of the housing. For clarity, the conceptual information model of the methodology for justifying the safety of the process of replacing the Hydra reactor vessel is presented in the form of an Ishikawa diagram. The methodology represents a series of sequential scientific and technical activities, research and a finite number of step-by-step actions to achieve the final goal – extending the service life. The stages of the methodology for justifying the safety of replacing the Hydra reactor vessel are described, such as «clarification of initial data», «performing computational studies and laboratory experiments», «clarification of the requirements of methodological documentation» and «formation of a work plan» and «registration of licensing documents for operation».

Reactive Carbon Capture Enables CO2 Electrolysis with Liquid Feedstocks.

ConspectusThe electrochemical reduction of carbon dioxide (CO2RR) is a promising strategy for mitigating global CO2 emissions while simultaneously yielding valuable chemicals and fuels, such as CO, HCOO-, and C2H4. This approach becomes especially appealing when integrated with surplus renewable electricity, as the ensuing production of fuels could facilitate the closure of the carbon cycle. Despite these advantages, the realization of industrial-scale electrolyzers fed with CO2 will be challenged by the substantial energy inputs required to isolate, pressurize, and purify CO2 prior to electrolysis.To address these challenges, we devised an electrolyzer capable of directly converting reactive carbon solutions (e.g., a bicarbonate-rich eluent that exits a carbon capture unit) into higher value products. This "reactive carbon electrolyzer" operates by reacting (bi)carbonate with acid generated within the electrolyzer to produce CO2 in situ, thereby facilitating CO2RR at the cathode. This approach eliminates the need for expensive CO2 recovery and compression steps, as the electrolyzer can then then coupled directly to the CO2 capture unit.This Account outlines our endeavors in developing this type of electrolyzer, focusing on the design and implementation of materials for electrocatalytic (bi)carbonate conversion. We highlight the necessity for a permeable cathode that allows the efficient transport of (bi)carbonate ions while maintaining a sufficiently high catalytic surface area. We address the importance of the supporting electrolyte, detailing how (bi)carbonate concentration, counter cations, and ionic impurities impact selectivity for products formed in the electrolyzer. We also catalog state-of-the-art performance metrics for reactive carbon electrolyzers (i.e., Faradaic efficiency, full cell voltage, CO2 utilization efficiency) and outline strategies to bridge the gap between these values and those required for commercial operation Collectively, these findings contribute to the ongoing efforts to realize industrial-scale electrochemical reactors for CO2 conversion, bringing us closer to a sustainable and closed-loop carbon cycle.

Computational Fluid Dynamic study of gas mixtures in a Non-Thermal Plasma reactor for CO2 conversion with Argon as diluent gas

CO2 utilization has been an emerging technology of increasing global interest due to its direct impact in limiting greenhouse gas emissions. In this contribution, the fluid dynamic behavior of a CO2 conversion non-thermal plasma (NTP) in a dielectric barrier discharge (DBD) reactor is studied through computational fluid dynamics (CFD) simulations.
 Calculations are provided in conjunction with experimental results and the thermodynamic characterization of the compounds and mixtures involved. This CFD study utilizes a well-established methodology that allows the optimization of fluid flow with limited computational burden.
 Firstly, results are presented for an Example Case, in which several variables are studied both at the final iteration as well as across iterations. Secondly, a range of Study Cases, changing the inlet composition and volume rate, are presented. Average velocity is one of the most significant variables to predict the reactor’s yield, while the temperature, density and pressure in the reactor remain, in most cases, almost constant.
 The resulting CFD computations describe the behavior of the fluids in the reactor in a predictive manner for future experimental results. Limitations in the fluid’s characterization occur due to not explicitly including the plasma reaction, which will be aimed at in future contributions.

Experimental and numerical study on the offshore adaptability of new FLH2 floating hydrogen liquefaction production storage and offloading unit

With the development of hydrogen production technology from offshore wind power and natural gas, the deep-sea energy interconnection system using hydrogen energy as the medium is constantly improving. The floating hydrogen liquefaction production storage and offloading unit (LH2-FPSO, FLH2) is an effective method for large-scale utilization of offshore hydrogen energy. By filling the heat exchanger with ortho-parahydrogen conversion catalyst, a new porous medium heat exchange channel is formed. Integrating the spiral wound heat exchanger with the ortho-parahydrogen catalytic conversion reactor can reduce the deck area of FLH2 process system and lower the investment cost of floating hydrogen liquefaction device. The performance of FLH2 can be influenced by the offshore wave and typhoon. In this paper, the methods of floating cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the coupled flow and heat transfer mechanism of working fluid applied in FLH2 under offshore conditions. The results show that the sea state has little influence on the ortho-parahydrogen conversion and cooling process of hydrogen in the porous heat exchange tube. The complex flow and heat transfer challenges brought by the integrated process of new floating hydrogen liquefaction and ortho-parahydrogen conversion have been overcome. With the effect of co-current shear of gas-phase mixed refrigerant, a large dry area will not appear on the outer wall surface of porous tube under offshore conditions. The FLH2 process system shows good adaptability at sea.

Process simulation of methanol production via carbon dioxide hydrogenation

The performance of a packed bed reactor for CO2 conversion to methanol was investigated. Because of the exothermic reaction, temperature and concentration gradients happen along the reactor. A 2D packed-bed reactor model was applied for numerical investigations, coupled with detailed reaction kinetics and transport phenomena. The effect of feed inlet pressure and temperature on CO2 conversion and temperature profiles along the reactor was evaluated. The results showed that firstly increase in the temperature in the reactor because of the presence of exothermic reactions and then slight decrease in the temperature at top section of the reactor. Pressure was decrease from 55 bar to around 54 bar along the reactor. It was found that the CO2 conversion at outlet of reactor was 18.18 % at T = 475 K and it was increased to 23 % at temperature of 498 K and 555 K. The CO2 conversion was reached its maximum at short distance from the reactor entrance at T = 555 K. Also, the outlet temperature of gas mixture was increased from 522.53 K to 534.56 K with increasing feed inlet pressure from 35 bar to 55 bar. The CO2 conversion was 18.12 %, 20.77 %, and 22.96 % at pressures equal to 35, 45, and 55 bar respectively.

FISSION PRODUCT RELEASE FROM HIGH AND LOW-ENRICHED URANIUM FUELS OF THE IVG.1M RESEARCH REACTOR

The research involved conducting resource tests on two experimental water-cooled technological channels (WCTCs) utilizing low-enriched uranium (LEU) fuel within the IVG1.M research reactor. This testing was a crucial step in the reactor's conversion from highly enriched uranium (HEU) fuel to LEU. The research focused on two key parameters, namely the specific activity and the relative release of fission products (FPs) into the coolant, to evaluate the tightnessof the fuel element cladding.A gamma-spectrometric sampling method was proposed to determine the relative releaseof FPs, which involved assessing the specific activity of the coolant, calculating the release rate (Release), the born rate (Born), and the R/B ratio of FPs. Comparative gamma-spectrometric measurements were conducted to analyze the content of FPs and activation products (AP) in the coolant of WCTCs utilizing both LEU and HEU during the tests.From the comprehensive list of detected radionuclides in the IVG.1M reactor coolant, well-identified reference radionuclides recommended for monitoringfuel element cladding tightness were carefully selected. The results of the study provided insights into the specific activity and relative release of FPs, demonstrating that quantitative values for the relative release of FPs from WCTCs using LEU and HEU fuel were comparable.

Annular swirling jet reactor for converting hydrocarbons to olefins and aromatics

This paper describes a novel reactor for high temperature thermochemical conversion of ethane to olefins. The central feature is an efficient flow pattern with a large recirculation zone that provides stable and compact 2500 °C flame and a thin conical annular swirling jet that provides fast transfer of mass, momentum, and heat. The jet is directed through a unique converging–diverging nozzle that maintains relatively low wall temperature and consequently reduces the need for external cooling. The hydrocarbons stream is introduced tangentially through volutes in such a way that there is initially heat transfer with minimal mass transfer followed by fast mixing of countercurrent streams. CFD simulations with detailed kinetics were employed to design and optimize this reactor including the order of the volutes to feed ethane, H2 fuel, oxidizer (O2 and N2 mix), and a cooling N2 gas; oxygen enrichment of the air, and also the overall operating conditions of this flexible and robust reactor. This highly intensified reactor was fabricated and tested at a semi-pilot scale with up to 15 kg/hr feed. The optimized reactor has high selectivity to ethylene and acetylene comparable to conventional steam cracker.

Investigation of different configurations of alumina packed bed reactor for coke free conversion of benzene

Conversion of producer gas tar without coke generation is a great challenge. This study investigates conversion of tar model benzene using different configurations of highly non-porous ɣ-Al2O3 packed bed reactor at 1000–1100 0C. The configurations comprised of different positions (relative to top (P1), center (P2) and bottom (P3) of reactor furnace), heights (5, 13 and 25 cm) and particles sizes (0.5, 3 and 5 mm) of alumina packed bed. Steam and CO2 were used as reforming media for tested benzene concentrations (0.4–1.8 vol%). The results showed benzene conversions of 48–91% with negligible steady thin coke generation using a packed bed (height: 25 cm, particles size: 3 mm) at P1. Whereas, relative high benzene conversions of 63–93 and 68–95% at P2 and P3 respectively with unsteady thick coke generation at benzene concentrations greater than 0.4 vol% increased differential upstream pressures (DUPs) of beds. Similar unsteady coke generation at benzene concentrations greater than 0.8 vol% and temperature of 1100 0C was observed with packed beds of heights of 5 and 13 cm, and particles size of 0.5 mm at P1. Generation of unsteady coke with condensed structure as evidenced by its characterization was attributable to increased benzene polymerization and reduced bed surface gasification reactions due to improperly installed packed bed. Developed kinetic model predicted well the generated coke. As conclusion, properly installed alumina packed bed pertaining to tar concentration and other experimental conditions may inhibit coke generation during tar conversion.