Large-scale Reactor Research Articles

Adaptive mesh refinement for a particle level simulation of supercritical water fluidized bed reactors

High-precision computational fluid dynamics-discrete element method (CFD-DEM) simulation serves as a foundation for the detailed design of supercritical water fluidized bed reactors (SCWFBRs). However, as the scale of these reactors increases, the computational domain and reacting particles expand exponentially. Traditional adaptive mesh refinement is constrained in dealing with dense phase zones in SCWFBRs, as the nonlinear characteristics of the dense reacting particle flow render local-field error estimation ineffective. To address this limitation, an efficient and accurate CFD-DEM framework is established, integrating adaptive mesh refinement and heterogeneous computing. The mesh adaptation strategy is based on whole-field error estimation and is defined by a set of cell-marking criteria. The effect of the criteria on the accuracy and efficiency of the computational process is evaluated. This method reduces the demand for computational resources, thereby enabling the simulation of large-scale reactors at the particle level. The optimized adaptation strategy maintains an error of 1.67% while saving 51.59% of mesh cells required and 28.4% computation time. The primary factors influencing computational accuracy are identified as fluid velocity gradient and the particle reaction rate. The scalability of the adaptation strategy is also validated. For a fivefold radial scaled-up reactor, the cell count is reduced by 46.86% and the computation time by 22.2%, while the maximum error is limited to 2.79%. This work provides a solution that can consider both the computational scale and accuracy, thereby enabling the detailed design of large-scale SCWFBRs.

Promoting human-centered manufacturing through Lean Ergonomics – a structural equation model for ergonomics and management data

ABSTRACT The Stress-Strain Concept (SSC) describes central mechanisms in Lean Ergonomics (LE) and Human Factors Engineering (HFE). The SSC can create additional value through content and methodological enrichment based on current economic, technological, and demographic constraints. This article uses the SSC to explore mechanisms of interactions of productivity and ergonomics in empirical shop floor data. Ergonomic (Borg, NASA-Task Load Index (N-TLX), Ergonomic Assessment Worksheet (EAWS), Health, Age) and business data (normalized and absolute standard deviations of work process times) were collected for 24 manual work processes operating large-scale chemical reactors. Data is analyzed using several Structural Equation Models (SEM). Stress (EAWS) and – depending on Health – Physical Strain with a model quality of Adjusted Goodness-of-Fit ≥0.9 were identified as statistically significant regressors for time data. In addition, carry-over effects from ergonomics to productivity were identified in an autoregressive model. Fit indices are in the good to acceptable range.

A parametric study on hydrogen storage in AB5 hydride alloys: Heat and mass transfer, thermodynamics, and design

The design of heat exchangers plays an important role in the performance of solid-state hydrogen storage devices. In this study, three different designs of hydrogen storage devices were investigated, incorporating phase change material (PCM), specifically, RT25HC into their walls in various shapes. A mathematical model, validated using previous experimental data, was employed to calculate heat and mass transfer and determine the reaction time period. The calculations were conducted using ANSYS Fluent, with a constant hydrogen supply pressure of 10 bars and a temperature of 295 K. The absorption properties of the storage reactor were investigated through various parameters such as liquid fraction, hydrogen concentration, and natural convection heat transfer coefficients. Results showed that the geometric structure and PCM distribution significantly impacted the performance of the hydrogen storage devices. Design 1, with a centralized PCM distribution, demonstrated moderate heat transfer rates and a longer reaction time. Design 2, featuring a more distributed PCM layout, improved heat transfer rates and reduced hydrogen kinetics time by 40%. Design 3, which optimized the geometric structure with advanced PCM shapes, achieved the highest heat transfer rates and improved hydrogen kinetics time by 50%. This design also enabled the storage of thermal energy at a high density, ranging from 10.2 J/g to approximately 190.5 J/g. The study provides critical information on the design of efficient solid hydrogen storage processes. The findings suggest significant potential for improved performance in industrial applications such as electric vehicles and domestic energy supply. The high efficiency of the large-scale reactor is due to its well-designed system, which effectively converts chemical energy into thermal energy. Optimizing the reactor geometry and PCM distribution is crucial for achieving superior hydrogen storage and retrieval performance.

Environmental and Economic Evaluation of the Sequential Combination of Coagulation–Flocculation with Different Electro-Fenton-Based Configurations for the Treatment of Raw Textile Wastewater

This study reports, for the first time, on the assessment of a multistage sequential system composed of coagulation–flocculation with different electro-Fenton-based configurations, followed by neutralization (N), for the treatment of raw textile wastewater heavily contaminated with acid black 194 dye and other pollutants. Electrochemical peroxidation (ECP-N), electro-Fenton (EF-N) and peroxi-coagulation (PC-N) were tested at laboratory scale and compared in terms of their efficiency for the removal of organic matter and color, current efficiency and energetic parameter, operating cost and environmental sustainability using life cycle analysis conducted in large-scale virtual reactors. The three electro-Fenton-based systems complied with current environmental standards (color removal > 87%, COD < 400 mg/L, among others) requiring different electrolysis times: ECP-N (52 min) < PC-N (120 min) < EF-N (160 min); energy consumptions: ECP-N (2.27 kWh/m3) < PC-N (4.28 kWh/m3) < EF-N (33.2 kWh/m3); operational costs: ECP-N (2.63 USD/m3) < EF-N (6.65 USD/m3) < PC-N (6.98 USD/m3); among others. Electricity (for ECP-N and EF-N) and reagents (for ECP-N and PC-N) were found as main environmental hotspots. ECP-N presented the lowest carbon footprint of 10.3 kg CO2-Eq/FU (<PC-N (26.3 kg CO2-Eq/FU) < EF-N (38.0 kg CO2-Eq/FU), had lower incidence in all the impact categories analyzed (ReCiPe-2016 at midpoint level) and can be considered technically, economically and environmentally sustainable for large-scale applications.

Evaluation of heat transfer conditions during polydisperse gas–solid flow in an industrial fluidised bed reactor

Knowledge of heat transfer conditions in large-scale circulating fluidised bed reactors plays an essential role in their proper design and optimization of theirs. This work presents an evaluation of the heat transfer conditions taking into account the coordinate height of the furnace chamber and the fluidised bed flow regime in the reactor. Experimental tests used method and measurement technique that provides reliable temperature data. The vertical and horizontal temperature profiles were obtained at different 966MWth fluidised bed reactor operating conditions. Four characteristic areas can be distinguished in the furnace chamber: the bottom region with a high-temperature gradient from 10.6 °C/m to 22.7 °C/m; the dense region with a medium temperature gradient from 4.7 °C/m to 7.3 °C/m; the dilute area with the lowest temperature gradient from 0.7 °C/m to 3.1 °C/m and the exit region with a temperature gradient (4.3 °C ≤ grad T ≤ 9.6 °C) similar to dense region. The horizontal temperature profiles confirmed a core-annular flow structure inside the furnace chamber. At the pressure drop below 5 kPa, the low variation of average temperature (from ±0.7 °C to ±4.2 °C) inside the furnace chamber of the CFB reactor was observed. As a result of fly ash recirculation of 3.86 kg/s, the lowest temperature gradient 0.2 °C/m was achieved in the bottom region of the furnace chamber. In the range of bed material circulation rates of 32 to 68 were registered temperature fluctuations 115 °C. The experimental results also showed the variation of the bed temperature was small and kept at a very low level of ±13 °C whereas the fluidised bed reactor was operated with a fluidisation velocity range of 1.8 to 2.4. Obtained findings provide unique data on heat transfer conditions in industrial facilities and thus fill the gap in literature data for CFB reactors. Based on main tests carried out in a large-scale CFB reactor, it can be concluded that detailed experimental data on thermal conditions provide important information to validate guidelines and for verifying empirical relationships, which are used in the design, optimization, and scaling of heat transfer surfaces in commercial fluidised bed reactors.

Hydrogen bubble management in planarly confined aqueous electrolyte: Fundamental factors for scale-up reactor design

Solar photoelectrochemical water-splitting is a potential process for producing renewable hydrogen. Here, the energy transport phenomena associated with hydrogen bubble generation are investigated for the future design of large-scale reactors. Light transfer analysis shows that using a thin aqueous-electrolyte layer is essential for utilizing the full spectrum of solar radiation. The hydrogen bubble flow needs to be redirected to avoid screening the photoelectrode from incident light. Hence, a bubble flow guide for controlling the stream of bubbles in a planarly confined aqueous electrolyte has been proposed. It is found that the surface wettability and inclination angle are important for designing an effective bubble flow guide. The hydrophilic coating on a polymethyl methacrylate surface inhibits bubble adhesion and reduces energy loss. Furthermore, measuring the electrode potential variation during water electrolysis is useful for comparing the performances of bubble flow guides.

Surface wettability control of bubble flow guide for a thin aqueous electrolyte layer of solar photoelectrochemical reactors

Abstract Hydrogen is a promising energy carrier as no carbon dioxide is emitted during its use in fuel cells or combustion. Solar photoelectrochemical water splitting is a potential process for producing renewable hydrogen. Herein, energy transport phenomena are addressed for the future design of large-scale reactors. First, we show that the thickness of the aqueous electrolyte layer is an essential factor for utilizing the full spectrum of solar radiation. The transport of solar irradiation through the aqueous electrolyte is theoretically analysed. Next, based on the measurement of light transmission through hydrogen bubbles generated from a hydrogen evolving electrode, the energy loss caused by the bubbles covering a photoelectrode is discussed. The bubble size distributions at practical current densities are also presented. Then, a bubble flow guide for controlling the stream of bubbles in a thin electrolyte layer is proposed. A design strategy and experimental results verifying the performance of the bubble flow guide are presented. We demonstrate that surface wettability and inclination angle are important for designing an effective bubble flow guide. We examine the surface wettability control using hydrophilic coatings in detail. Changes in the water contact angles as well as bubble adhesion forces on the coated surfaces are demonstrated. In addition, the current experimental method can be used to identify essential issues in photoelectrochemical processes. Because bubble trapping and growth in a flow guide are reflected in the electrode potential variation, the discussion of electrode potential variation would be useful for further developing bubble flow guides. Overall, this study demonstrates the potential for developing and designing solar photoelectrochemical reactors.

Multiphase Numerical CFD Simulation of the Hydrothermal Liquefaction Process (HTL) of Sewage Sludge in a Tubular Reactor

This article presents multiphase numerical computational fluid dynamics (CFD) for simulating hydrothermal liquefaction of sewage sludge in a continuous plug-flow reactor. The discrete particle method (DPM) was used to analyze the solid particles’ interaction in liquid–solid high shear flows to investigate coupling computational fluid dynamics (CFD). Increasing solid particles’ interactions were observed with the increasing liquid velocity. The study examined the influence of parameters such as flow rate, temperature, and residence time on the efficiency of bio-oil production. An increase in temperature from 500 to 800 K caused an increase in the amount of biocrude oil produced from 12.4 to 32.9% within 60 min. In turn, an increase in the flow rate of the suspension from 10 to 60 mL/min caused a decrease in the amount of biocrude oil produced from 38.9 to 12.9%. This study offers insights into optimizing the flow channel of tubular reactors to enhance the HTL conversion efficiency of sewage sludge into biocrude oil. A parametric study was performed to investigate the effect of the slurry flow rate, temperature, and the external heat transfer coefficient on the biocrude oil production performance. The simulation data will be used in the future to design and scale up a large-scale HTL reactor.

Seismic mitigation analysis of three-dimensional base-isolated nuclear structures with soil-dependent isolation system under extreme earthquakes

The Fukushima nuclear accident in March 2011 has raised more stringent requirements for the ability of nuclear power plants (NPPs) to withstand extreme disasters such as extreme earthquakes. To address this challenge, this study proposed a new hybrid multi-dimensional passive control system that combines three-dimensional base isolation and geotechnical seismic isolation. In this system, high-damper rubber bearings were employed to isolate horizontal seismic motions, whereas disc springs, accounting for frictional forces, were used to mitigate vertical seismic motions. Additionally, a geotechnical seismic isolation system arranged under the base mat was leveraged to further reduce the seismic response of the superstructure. Taking a large-scale reactor building in complex layered sites as an example, the effectiveness of the hybrid multi-dimensional isolation system was studied using a wave motion method. The research results indicate that when subjected to extreme earthquakes, hybrid multi-dimensional isolation exhibits superior isolation performance compared with three-dimensional base isolation, which can significantly reduce the three-dimensional dynamic response of nuclear structures without increasing the displacement of the isolation bearings. The proposed hybrid multi-dimensional isolation system offers an effective solution to the challenges faced by three-dimensional isolation systems, thereby enhancing the seismic resistance of nuclear structures against extreme earthquakes.

Radiation source terms analysis and classification of radioactive waste for the decommissioning of the first HWRR reactor in China.

Nuclear reactors will face the problem of decommissioning at the end of their operating life due to the high radioactivity of reactor components and environmental safety considerations. The Heavy Water Research Reactor (HWRR) is the first large-scale research reactor to be decommissioned in China. The second phase of HWRR decommissioning involves the main components in the reactor block, so the radiation source terms and the radioactive waste level need to be evaluated before demolition and disposal. Based on the operating history, three-dimensional geometry, materials, and other information of the HWRR, the activity of radionuclides in the main components of HWRR is calculated and analyzed, and the MCNP/ORIGEN coupling scheme is utilized for theoretical analysis. The theoretical results indicate that 14C, 54Mn, 55Fe, 60Co, 63Ni, and 152Eu are the main radioactive nuclides. The total activity of radioactive nuclides was 2.36E + 15Bq at the end of 2007, 4.27E + 13Bq at the end of 2021, and 1.83E + 13Bq at the end of 2025. Furthermore, local sampling and radiometric analyses based on the HPGe gamma-ray spectrometer are also performed to verify the theoretical results, the ratio of theoretical activity values to the measured activity of the experimental sample is within 2.5 times, so the theoretical results are conservative. According to the classification standards for radioactive waste, the inner shell, outer shell, cooling water tank, sand layer, and heavy concrete shielding layer are all low-level waste. These results and conclusions can serve as a reference for the second phase decommissioning of the HWRR and the subsequent disposal of radioactive waste.

Numerical Simulation Study on the Gas–Solid Flow Characteristics of a Large-Scale Dual Fluidized Bed Reactor: Verification and Extension

Dual fluidized bed (DFB) reactor systems are widely used in gas–solid two-phase flow applications, whose gas–solid flow characteristics have a significant effect on the performance of many kinds of technologies. A numerical simulation model was established on the basis of a large-scale DFB reactor with a maximum height of 21.6 m, and numerical simulations focused on gas–solid flow characteristics were carried out. The effects of the superficial gas velocity of both beds and the static bed height and particle size on the distribution of the pressure and solid suspension density and the solid circulation rate were studied. The simulation results were in good agreement with the experimental data. With the strong support of the experimental data, the gas–solid flow characteristics of large-scale DFB reactors were innovatively evaluated in this numerical simulation study, which effectively makes up for the shortcomings of the current research. The results showed that the superficial gas velocity of both beds and the static bed height have different degrees of influence on the gas–solid flow characteristics. Specifically, for 282 μm particles, when the superficial gas velocity of both beds and the static bed height were 4.5 m/s, 2.5 m/s, and 0.65 m, respectively, under typical working conditions, the bottom pressure of the two furnaces was 3412.42 Pa and 2812.86 Pa, respectively, and the solid suspension density was 409.44 kg/m3 and 427.89 kg/m3, respectively. Based on the simulation results, the empirical formulas of the solid circulation rate were fitted according to different particle sizes. Under similar conditions, the solid circulation rates of particles with a particle size of 100 μm, 282 μm, 641 μm, and 1000 μm were 2.84–13.28, 0.73–4.91, 0.024–0.216, and 0.0026–0.0095 kg/(m2s), respectively. It can be found that the influence of the particle size on the solid circulation rate is the most significant among all parameters.

Three-Dimensional Model for Bioventing: Mathematical Solution, Calibration and Validation

Bioventing is an established technique extensively employed in the remediation of soil contaminated with petroleum hydrocarbons. In this study, the objective was to develop an improved foundational bioventing model that characterizes gas flow in vadose zones where aqueous and non-aqueous phase liquid (NAPL) are present and immobile, accounting for interphase mass transfer and first order biodegradation kinetics. By incorporating a correlation for the biodegradation rate constant, which is a function of soil properties including initial population of petroleum degrader microorganisms in soil, sand content, clay content, water content, and soil organic matter content, this model offers the ability to integrate a specific biodegradation rate constant tailored to the soil properties for each site. The governing equations were solved using the finite volume method in OpenFOAM employing the “porousMultiphaseFoam v2107” (PMF) toolbox. The equation describing gas flow in unsaturated soil was solved using a mixed pressure-saturation method, where calculated values were employed to solve the component transport equations. Calibration was done against a set of experimental data for a meso-scale reactor considering contaminant volatilization rate as the pre-calibration parameter and the mass transfer coefficient between aqueous and NAPL phase as the main calibration parameter. The calibrated model then was validated by simulating a large-scale reactor. The modelling results showed an error of 2.9% for calibrated case and 4.7% error for validation case which present the fitness to the experimental data, proving that the enhanced bioventing model holds the potential to improve predictions of bioventing and facilitate the development of efficient strategies to remediate soil contaminated with petroleum hydrocarbons.

An Automatic Method for Generation of CFD-Based 3D Compartment Models: Towards Real-Time Mixing Simulations.

This article aims to develop a method to automatically generate CFD-based compartment models. This effort to simplify mixing models aims at capturing the interactions between material transport and chemical/biochemical conversions in large-scale reactors. The proposed method converts the CFD results into a system of mass balance equations for each defined component. The compartmentalization method is applied to two bioreactor geometries and was able to replicate tracer mixing profiles observed in CFD simulations. The generated compartment models were successfully coupled with, a simple Monod-type biokinetic model describing microbial growth, substrate consumption and product formation. The coupled model was used to simulate a four-hour fermentation in a 190 L reactor and a 10 m3 reactor. Resolving the substrate gradients had a clear impact on the biokinetics, increasing with the scale of the reactor. Moreover, the coupled model could simulate the fermentation faster than real-time. Having a real-time-solvable model is essential for implementations in digital twins and other real-time applications using the models as predictive tools.

Synergistic transformation: Kinetic and thermodynamic evaluation of co-pyrolysis for low-rank bituminous coal and polyurethane foam waste

Co-pyrolysis is regarded as a sustainable and ecologically friendly method of improving waste management, pollution control, and renewable energy security. This investigation reports a thermo-kinetic study of low-rank coal-polyurethane foam waste (C-PU) blends through co-pyrolysis and was characterized using a number of techniques such as CHNS-O, GCV, and FTIR. The thermal degradation behavior of C-PU blends during co-pyrolysis via TGA is studied, whereas the degradation process happens in three stages i.e. moisture, devolatilization, and slow degradation of the char in the temperature ranges viz. (25 –140 °C), (140 – 580 °C), and (580 – 900 °C) respectively. Synergistic effects observed may improve product qualities compared to those from separate pyrolysis. The presence of synergistic effects during co-pyrolysis was demonstrated by the positive variation in WL% and DTGmax values. The Coats-Redfern integral method was utilized to investigate the thermo-kinetic parameters of C-PU blends through twelve (12) reaction mechanism models. The activation energy (Ea) for 100C and 100PU was 60.08 kJ/mol and 100.8 kJ/mol via F2 and F3 models, although the optimum blend (50 C-50PU) showed 67.01 kJ/mol and 26.74 kJ/mol via F2 and D3 model in the first and second stage. Thermodynamic characteristics i.e. (∆G) and (∆H) displayed positive values, while (∆S) for each C–PU blend was negative, but the best blend further lowered it. It was found that the fuels could be ranked in the following order 100PU> 50 C-50PU> 100 C based on mean reactivity and pyrolysis factor. The co-pyrolysis of polyurethane foam waste with low-rank coal to develop alternative energy sources has been proposed as a potential method and is critical for designing an effective large-scale reactor system thus understanding the solid-state co-pyrolytic kinetics.

Generic approach to assess the measuring performance of total-radiated power quantities by multi-channel resistive bolometer diagnostics on fusion experiments.

On present-day magnetic-confinement fusion experiments, the performance of multi-channel bolometer diagnostics has typically evolved over time through experience with earlier versions of the diagnostic and experimental results obtained. For future large-scale fusion experiments and reactors, it is necessary to be able to predict the performance as a function of design decisions and constraints. A methodology has been developed to predict the accuracy with which the volume-integrated total radiated power can be estimated from the measurements by a resistive bolometer diagnostic, considering, in particular, its line-of-sight geometry, étendues of individual lines of sight, bolometer-sensor characteristics, and the expected noise level that can be obtained with its electronics and signal chain. The methodology depends on a number of assumptions in order to arrive at analytical expressions but does not restrict the final implementation of data-processing of the diagnostic measurements. The methodology allows us to predict the performance in terms of accuracy, total-radiated power level, and frequency or time resolution and to optimize bolometer-sensor characteristics for a set of performance requirements. This is illustrated for the bolometer diagnostic that is being designed for the ITER experiment. The reasonableness, consequences, and limitations of the assumptions are discussed in detail.

The longevity of light water-cooled large-scale nuclear reactors: A holistic perspective

Current technical opinion paper aims to assess a holistic perspective of the potential lifespan of water-cooled large-scale nuclear reactors, which have maintained a consistent and reliable contribution to the global energy mix over several decades. By examining various factors such as Technological Advancements, Safety Measures, Regulatory Frameworks, Environmental Concerns, Economic Viability, Public Perception and Acceptance, and Future Prospects and Challenges, the current study will provide a comprehensive analysis of the sustainability and longevity of these reactors. Ultimately, this study will shed light on the future of water-cooled large-scale nuclear reactors and their role in meeting the world's growing energy demands. This assessment reveals that while challenges exist, there are clear pathways to ensure their continued operation and contribution to global energy needs. By investing in advanced technologies, fostering regulatory collaboration, embracing integration with renewables, focusing on economic competitiveness, and prioritizing public engagement and education, we can pave the way for a future where water-cooled reactors play a central role in a low-carbon energy landscape.

Research on hydrogen risk prediction in probability safety analysis for severe accidents of nuclear power plants

The risk of hydrogen combustion after the Fukushima nuclear accident has always been a topic of concern for the nuclear power industry. In the hydrogen risk assessment of probability safety analysis (PSA) in nuclear power plants, the traditional methods by using lumped parameter program method is fast but may have large uncertainties, while the newly developed CFD analysis method is more accurate but has not yet been widely applied to the hydrogen risk analysis of PSA due to a variety of factors. The lumped parameter analysis program MAAP is used firstly to obtain the hydrogen parameters under the severe accident of small LOCA in this paper, based on China's third-generation large-scale pressurized water reactor (PWR) nuclear power plant HPR1000, and then the probability of deflagaration to detonation (DDT) for hydrogen risk is analyzed with uncertainty. Secondly, the CFD software GASFLOW program is used to analyze the same accident sequence to obtain more accurate hydrogen distribution and other parameters, and at the same time to obtain the DDT probability value of hydrogen risk. The hydrogen distribution obtained by CFD calculation can be used to guide the uncertainty value of the lumped parameter program to produce more accurate DDT value of hydrogen risk. The analysis results show that there is a certain uncertainty in hydrogen risk assessment when using lumped parameter program method, which can be corrected by combining the gas distribution analysis results given by CFD software, to obtain a more accurate and reliable probability value, so as to provide a more accurate reference for PSA analysis and to improve the overall safety of the nuclear power plant.

Enhanced system for hydrogen storage and conversion into green methanol in a geothermal environment

Variable Renewable Energy Sources are crucial for decarbonizing industries and efficient energy storage. Hydrogen storage technologies are limited in their large-scale capabilities. PtL technology can synthesize alternative fuels like methanol, which can be used in existing energy infrastructures to produce liquid fuel. The paper presents an innovative approach for utilizing in-situ thermal energy, using a hot reservoir rock (HRR) system for methanol synthesis at high temperature and pressure in an underground large-scale natural reservoir reactor. This approach aims to integrate renewable energy technologies into a single energy generation and fuel production system, including the direct utilization of renewable sources. Solutions from the oil and gas industry can be adapted to this action, such as continuous injection, alternate injection, separate injection, or chemical flooding. Conventional geothermal reservoirs, HDR systems, and depleted hydrocarbon reservoirs can be used as “underground reactors”. However, it was also noted that there are challenges, such as catalyst distribution and the complexity of reservoir pore space.

Industrial-scaled Cu-Fe composite oxygen carrier for chemical looping combustion through extrusion-spheronization

It is crucial for the preparation of the high-performance and low-cost oxygen carrier (OC) in an industrial-scaled application to lay the foundation for the commercialization of chemical looping combustion (CLC) technology. In this work, a bimetallic OC (RCu-10 M) is prepared in an industrial-scaled extruder coupling with roller, composited by the red mud (aluminum industrial waste), copper ore and montmorillonite as raw materials. First, a thermogravimetric analyzer (TGA) is used to carry out 100 redox cycles using H2 as the reducing agent. RCu-10 M OC demonstrate remarkable redox stability and sintering-resistance across multiple cycles, and the oxygen donating capacity do not diminish as the number of cycles increases. The effects of temperatures and excess oxygen coefficients on the reactivities of RCu-10 M OC with Shenhua bituminous coal are then investigated by using a batch fluidized bed reactor. RCu-10 M OC maintains high combustion efficiency, exceeding 94.7 % at 950 °C, with an excess oxygen coefficient of 2.0. Finally, a lab-scaled interconnected fluidized bed reactor is applied to examine the realistic performance of RCu-10 M OC using CH4 fuel. The results demonstrate that the RCu-10 M OC successfully operates for ca. 100 min of continuous time, and there is no de-fluidization occurrence, and the bed pressure decrease is stable during operation, indicating that the RCu-10 M OC exhibits good fluidization properties and had the potential to be used in large-scale fluidized bed reactors. Further characterization data reveal that the chemical composition of RCu-10 M OC is stable throughout multiple cycles, as indicated by the almost uniform distribution of elements.

Experimental Research on the Gas-Solid Flow Characteristics in Large-Scale Dual Fluidized Bed Reactor

A dual fluidized bed (DFB) reactor is the main operating system of various energy-efficient and clean utilization technologies. The gas-solid flow characteristics of the DFB reactor greatly affect the efficiency of various technologies. A large-scale DFB reactor with a maximum height of 21.6 m was built and relevant cold mode tests were carried out in this study. The effects of the superficial gas velocity of both beds, static bed height and particle size on the distribution of both pressure and solid suspension density, solid circulation rate, solid inventory distribution ratio and other characteristics were studied. For 282 μm-particles, the solid suspension density in the dense phase zone of the two beds was 100–400 and 400–800 kg/m3, respectively, when the static bed height was 0.65 m; the solid circulation rate was about 0.87–1.75, 1.04–3.04 and 1.13–3.69 kg/(m2s) when the static bed height was 0.65, 0.95 and 1.25 m, respectively. The solid circulation rate was positively correlated with the static bed height and the superficial gas velocity of both beds, yet negatively correlated with the particle size. Additionally, the empirical equation of solid circulation rate and the empirical equation of solid inventory distribution ratio were proposed, respectively. The material control method of the DFB reactor is put forward.