Reactor Temperature Research Articles

Design, Scale‐Up, and Dynamic Simulation of a Patented Bayonet Reactor for Commercial Hydrogen Production via Sulfur‐Iodine Water Splitting

ABSTRACTThe sulfuric acid decomposition reactor is a key component of the iodine‐sulfur thermochemical cycle process. The design of the sulfuric acid decomposition reactor requires excellent corrosion resistance and mechanical strength performance. In this work, a patented reactor on a pilot scale was scaled up to an industrial scale. A plant equipment design for an industrial‐scale reactor was performed. Based on an integrated inherent safety design approach, it was determined that the optimal thickness was 110 mm, and the design passed all stress analysis tests. With a minimum targeted hydrogen production rate of 1000 kg/h, the process design yielded a reactor with a diameter of 7 m and a height of 30 m, while silicon carbide was chosen as the construction material. The scaled‐up reactor was dynamically simulated in MATLAB. Simulink demonstrated that both the reactor temperature and product flow rates successfully produced a stable response within 1.8 and 4 h of operation, respectively.

Enhancing of Acetone Purity and Energy Efficiency in the Isopropyl Alcohol (IPA) Dehydrogenation Process Through Design Modifications, Heat Exchanger Integration Simulation, and Reactor Temperature Optimization

Acetone is an essential ingredient in various industries whose demand continues to increase, thus requiring an efficient production method. This study aims to design an acetone production process by dehydrogenating isopropyl alcohol using Aspen HYSYS simulation and Aspen Energy Analyzer energy analysis. The simulation model was developed to enhance the purity of acetone products and improve energy efficiency by optimizing thermodynamic operating conditions. The dehydrogenation process was designed to produce acetone as the main product and hydrogen as a by-product. The basic process was then modified by integrating thermal energy and increasing the reactor operating temperature to improve energy efficiency and product purity. Simulations showed that the process modification resulted in an acetone purity of 99.76%, higher than the base process of 98.46%. In addition, energy savings in the modified process reached 40.89%, higher than the base process of 32.96%, with a reduction in carbon emissions of up to 40.88%. With these results, the modified process proved more efficient than the basic process and aligned with the research objectives. Copyright © 2024 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Combustion of micron-sized iron particles in a drop tube reactor

Combustion of micron-sized particles of iron, a promising renewable alternative to fossil fuels, was investigated in a drop tube reactor (DTR) under overall lean conditions. A bimodal particle size distribution was observed after combustion: black micron-sized particles consisting of a mixture of iron oxides, with oxidation degrees ranging from 60% to 90%, and reddish fine particles of Fe2O3. The oxidation degree of the products showed no obvious variation with the reactor temperature. The coarse product particles were comparable in size with those of the raw iron particles, independent of temperature. The evaporation of iron represented a mass loss of 1%–2%. The primary nm-sized particles agglomerated to form aggregates of the order of 1μm. A simplified model for the combustion was used to analyze the results. It was based on the Particle Equilibrium Composition approach by van Gool et al. (Appl Energy Combust Sci 2023;13:100115) that assumes the oxidation from Fe to FeO to be limited by external diffusion and further oxidation by thermodynamic equilibrium. The model predicted larger oxidation degrees than observed experimentally. The difference was believed to be due mainly to stratification in the drop tube reactor, resulting in local fuel-rich conditions. The small impact of reactor temperature on the final oxidation stage indicated that diffusion limitations, rather than kinetic barriers, were rate controlling.

Process Simulation, Thermodynamic and System Optimization for the Low-Carbon Alcohols Production via Gasification of Second-Generation Biomass

Biomass-to-liquid fuels technology offers a promising method for high-value biomass conversion, addressing environmental toxicity and fossil fuel non-renewability. However, challenges such as low system efficiency and identifying efficiency losses persist. In this study, a comprehensive process model of a low-carbon alcohols production system via biomass gasification was developed, based on the first demonstration project in China. The innovation of this study lies in its detailed experimental validation, as the model simulation was performed using laboratory data and verified with pilot-scale platform data ensuring high accuracy. Additionally, the study conducted a thorough sensitivity analysis of system parameters, energy, and exergy assessments to find the proper operating conditions, including equivalent ratio, biomass type, and reactor temperature and pressure. The simulation results demonstrated an energy efficiency of 34.67% and an exergy efficiency of 31.24%. Through operating parameters and heat recovery measures, these efficiencies increased by 11.66% and 8%, respectively. This research not only obtains improved operating parameters for the pilot-scale platform but also provides actionable insights for enhancing the yields of target products and upgrading low-grade energy utilization. These findings offer valuable guidance for the commercialization of bio-syngas alcohols production systems, highlighting significant advancements in efficiency and system performance.

Enhancement of hydrogen production from thermal and catalytic cracking of HDPE through Implementation of activated biochar

This study investigated hydrogen production characteristics from thermal and catalytic cracking of high-density polyethylene (HDPE) and role of activated biochar derived from biomass (palm kernel shell, PKS). The objective was to enhance hydrogen yield in response to growing demands for hydrogen and the management of waste plastic. Three experimental setups—pyrolysis, thermal cracking, and char cracking—were employed in a two-stage pyrolysis system to examine the impact of reaction temperature and activated biochar on 1) the decomposition of HDPE into tar, which is a complex hydrocarbon mixture, and 2) the production of hydrogen from the vaporized tar. The findings indicated that the reaction temperature in the first reactor influenced tar vapor formation, whereas the temperature in the second reactor was more closely associated with the production of hydrogen and lighter hydrocarbons such as methane. Under identical temperature conditions, the use of activated biochar increased the hydrogen production by more than six times and adsorbed the solid carbon, resulting in no visible carbon particles. Although the reaction temperatures in this study were higher than those in previous studies involving other catalysts, leading to increased energy costs, the abundant biomass sources for carbon activation and the simplicity of the manufacturing process could position activated biochar as a viable catalyst for the thermochemical recycling of plastic into energy source.

Large-Scale Production of Nanotube Silicon for Lithium-Ion Batteries

Silicon’s relatively high energy density in comparison to the more common anode material, graphite (3580 mA h g-1 for silicon compared to 371 mA h g-1 for graphite) has made silicon an intriguing anode material for lithium-ion batteries. However, during lithiation, the volume of silicon increases by approximately 300% causing irreversible capacity loss. During the initial charging of an anode, a solid electrolyte interface (SEI) forms on the surface of the anode. The formation of the SEI consumes lithium, resulting in irreversible capacity loss. The large volume expansion of silicon can break the SEI layer. This results in a new SEI layer needing to be formed and further irreversible capacity loss. In addition, the expansion of the silicon particles can lead to silicon particles being isolated from the anode where they can no longer participate in the charging and discharging process, lowering the capacity of the anode. To accommodate for this large volume expansion, silicon nanoparticles on the scale of 50 microns are often used to accommodate for the large volume expansion and help retain capacity. Silicon nanotubes provide additional benefits such as increased structural stability, faster lithium-ion diffusion, and greater electrical conductivity than silicon nanoparticles.This work details a process to produce silicon nanotubes from halloysite on a large scale. Halloysite is an alumina-silica-based structure composed of natural nanotubes. Silicon can be obtained from halloysite by etching off the alumina components and further reducing the silica to silicon through a magnesiothermic reduction. However, both the etching step and reducing step are very exothermic. If the heat transfer is not controlled correctly, the heat released during these reactions can destroy the natural tube structure. The reaction temperature is dependent on a variety of variables including: reactor temperature, ramp rate, addition of salts, and quantity of reactants. The processes and parameters used to successfully manage the heat released as a part of scale up this process are described. BET and SEM imaging were used to determine the surface area and structure of the produced silicon. In addition, the electrochemical performance of the silicon was tested and investigated in patch cells. Figure 1

2-D CFD modeling of gasification of a large biomass char particle in CO2 environment

There is a dearth in the literature of simple but robust models for gasification of large biomass particles that can address all important aspects of the reaction. A transient two-dimensional single-particle model of biomass gasification in the CO2 environment was developed in this work that incorporates chemical kinetics and heat transfer resistances, mass transfer inside the particle and boundary layer, non-equimolar counter diffusion including Knudsen diffusion, spatiotemporal variation in specific char surface area and thermophysical properties. The model was validated extensively with experimental results. Detailed simulation was carried out at reactor temperatures of 923–1123 K) using COMSOL Multiphysics software for two biomass samples – casuarina and acacia. Simulated conversion, reaction rate, temperature and gas composition profiles revealed that the reactions initially followed a shrinking core model, shifting subsequently to a shrinking reactive core model. Sensitivity analysis identified the sensitivities of process parameters as: reactor temperature > particle diameter (constant length) > initial specific char surface area > porosity > pore parameter > particle diameter (constant volume). Casuarina was found to be a more reactive and better-suited biomass than acacia for gasification applications. The work has furnished important guidelines for selecting suitable biomass type and process parameters to design an appropriate gasifier for industrial use.

Significantly Improved Stability of Carbon/Air Secondary Battery System By Separating Carbon Deposition Area

Introduction The carbon/air secondary battery (CASB) system is a promising large-capacity energy storage technology [1]. The CASB system utilizes a redox reaction of C + O2 ⇄ CO2 by solid oxide fuel cells/electrolysis cells (SOFCs/SOECs), namely a combination of rechargeable direct carbon fuel cells [1, 2] and CO2 electrolysis cells. Carbon and liquid CO2 are stored in and outside SOFCs/SOECs respectively. The advantages of the CASB system are high theoretical efficiency of close to 100%, high volumetric energy density of 1625 Wh L-1 based on carbon and liquid CO2 (25oC, 6.4 MPa), and high safety due to unflammable CO2 storage. On the fuel electrode side, the electrochemical reaction of 2CO2 + 4e- ⇄ 2CO + 2O2- and the thermochemical (Boudouard) reaction of 2CO ⇄ C + CO2 proceed. On the air electrode side, the electrochemical reaction of 2O2- ⇄ O2 + 4e- proceeds. The previous study [3] demonstrated the reaction mechanism and the charging-discharging for 10 cycles without degradation. However, the carbon deposition on the triple phase boundary (TPB) made an overpotential increase, and there remains a risk of degradation of the fuel electrode in the long term. To suppress overpotential or to avoid degradation, the carbon deposition area is required to separate from TPB. There are two ways considered, namely development of materials and systems for the CASB. We recently demonstrated that two kinds of fuel electrodes with different catalytic abilities, e.g. Ce0.9Gd0.1O2-δ (GDC) fuel electrode and Ni/GDC catalyst section, successfully controlled carbon deposition on the catalyst section selectively [4]. Controlling temperature is another way of separating carbon deposition area from TPB because the Boudouard equilibrium gas composition changes significantly in the range of 500oC to 900oC (Fig. 1). The lower the temperature, the lower the equilibrium partial pressure of CO. Therefore, lowering the temperature of the catalyst section enables selective carbon deposition on the catalyst. In this study, the objective is to propose the carbon deposition area-separated type CASB system controlling temperature and to demonstrate its charging-discharging. Experimental The experimental setup was composed of a cell and a catalytic fixed-bed reactor. Ni/ GDC fuel electrodes were fabricated on an 8 mol% Y2O3 – stabilized ZrO2 disc electrolyte (20 mm diameter, 0.25 mm thickness). La0.8Sr0.2MnO3/10mol%Sc2O3-1mol%CeO2–ZrO2 air electrodes were fabricated on the counter sides. A catalyst for the Boudouard reaction was put in a quartz tube. The temperature of the cell and the catalytic reactor was controlled to be 900oC and 670oC. For charging, CO 40 sccm and CO2 10 sccm were supplied on the fuel electrode side, and the exhausted gas was supplied to the catalytic reactor. For discharging, CO2 10 sccm was supplied to the catalytic reactor, and the exhausted gas was supplied on the fuel electrode side. For both charging and discharging, O2 100 sccm was supplied on the air electrode side, and a current density of 100 mA cm-2 was applied for a couple of hours. Results and discussion Repetitive charging and discharging for a couple of hours were successfully demonstrated. The discharge capacity was above 300 mAh, which is more than 10 times larger than the previous demonstration of the carbon deposition area-integrated type CASB system [3]. Because only CO2 was supplied during the discharging, deposited carbon in the catalytic reactor was mainly used for the fuel. In addition, the partial pressure of CO in the space close to the cell during the charging was not enough for thermochemical carbon deposition. Those results show that lowering the temperature of the catalyst section successfully made selective carbon deposition on the catalyst. Conclusion In this study, the carbon deposition area-separated type CASB system was proposed and its repetitive charging and discharging was demonstrated. Lowering the temperature of the catalytic reactor to the SOFCs/SOECs enables selective carbon deposition in the catalytic reactor. Avoiding carbon deposition on the fuel electrodes can radically improve the stability of the CASB system in the long term.

Optimization of steam-methane reforming process using PSA off gas

This study aims to analyze the effect of PSA off gas utilization on fuel processing system combined with PSA (Pressure Swing Adsorption) system to produce more than 99% hydrogen for LT-PEMFC (Low Temperature Proton Exchange Membrane Fuel Cell) supply. An analysis was performed to optimize the operating conditions of a fuel processing system coupled with a PSA system by utilizing PSA off-gas to supply hydrogen to a 10 kW LT-PEMFC system. The performance and efficiency of the entire system were investigated at a steam-methane reactor temperature of 600 °C–800 °C, a water gas conversion reactor temperature of 200 °C–400 °C, a PSA recovery ratio of 60%–95%, a pressure of 1 bar, and 9 bar using Aspen Plus®, Aspen adsorption®, and Aspen Energy Analyzer® simulators. The sensitivities of various parameters affecting the process were analyzed to obtain optimized conditions for the entire system. Simulation results show that the optimal reformer temperature depends on the PSA recovery. The overall maximum efficiency is 78.67% at a process pressure of 9 bar the PSA recovery ratio of 95% and a temperature of 800 °C. In contrast, the highest efficiency under the 1 bar process condition is 70.55%, with an operating temperature of 600 °C and PSA recovery of 95%, which is relatively lower than the 9 bar process. Subsequently, pinch analysis and economic analysis including exergy analysis according to PSA recovery were conducted on these processes, showing that the thermal efficiency of the 9 bar process is relatively higher. The economic analysis indicated that the optimal profit is achieved at a PSA recovery of approximately 70∼75% and more than 40.2% of energy can be saved by utilizing PSA off gas to supply reaction heat for methane-steam reforming.

Unraveling the role of EPOC during the enhancement of RWGS reaction in a Pt/YSZ/Au single chamber reactor

The hydrogenation of CO2 remains one of the most intriguing and effective strategies for addressing the continuous increase of CO2 emissions in the atmosphere. At the same time, it serves as an effective pathway for the formation of value-added products. This work explores the Electrochemical Promotion of Catalysis (EPOC) phenomenon on the CO2 hydrogenation reaction, utilizing a single chamber reactor with a Pt/YSZ/Au electrochemical cell. Experiments were conducted under ambient pressure conditions, within a temperature range of 200–400 °C, for a reactant flow rate of 100 cm3/min under reducing (PCO2: PH2 = 1:7) and oxidizing (PCO2: PH2 = 2:1) conditions. The effect of reactant ratio, reactor temperature, and applied current/potentials on the reaction rate were thoroughly investigated. The only observed product was carbon monoxide through the Reverse Water Gas Shift Reaction (RWGS). Under purely catalytic operation of the cell (open circuit), reducing conditions were found to be more favorable for the RWGS reaction as compared to oxidizing ones. The imposition of negative potential values under reducing environment resulted in a 2.3-fold increase in the RWGS reaction rate (rCO = 21 × 10−9 mol/s) as compared to open circuit values (rCO = 9 × 10−9 mol/s). On the other hand, application of positive potentials had no profound effect on the catalytic rate, which was attributed to competing electrochemical and surface processes taking place on the catalyst electrode. The kinetic results are discussed in conjunction with the physicochemical and the morphological characteristics of the catalytic film.

Feasibility of successive hydrogen and methane production: Effects of temperature and organic loads on energy potential and microbial dynamics

This study aims to assess the co-digestion of Cassava Wastewater (CW) and glycerol in a two-stage process using fluidized bed reactors (AFBR), verifying the effect of organic loading rate (OLR) and temperature (mesophilic [SMR] and thermophilic [STR]) in sequential reactors on CH4 production. The OLR ranged from 1.2 to 15 g COD.L−1.d−1 and the hydraulic retention time (HRT) was set at 20 h. The mesophilic sequential reactor (MSR) (average temperature of 30 °C) showed greater tolerance to high OLR and its best MPR was 101.12 mL of CH4.d−1.L−1 h−1, obtained at a OLR of 15 g COD.L−1.d−1). The maximum yield was 341.10 mL of CH4.g−1CODcons, found at the OLR of 1.2 g COD.L−1.d−1. The sequential thermophilic reactor (STR) showed the maximum yield and MPR of 333.03 mL of CH4.g−1CODcons (1.2 g COD.L−1.d−1) and 58.84 mL of CH4.d− 1.L−1 h−1 (12 g COD.L−1.d−1), respectively. Through the massive sequencing analysis of the 16S rRNA gene, it was possible to observe a greater diversity of microorganisms in the TSR than in the MSR. A predominance of acetoclastic microorganisms was observed, with the genera Methanobacterium, Methanosarcina and Methanobrevibacter being the most abundant in both reactors. The two-stage system composed of mesophilic acidogenic reactor + MSR was more suitable for the co-digestion of CW and glycerol than the acidogenic reactor + TSR. These results support the notion of standard operating conditions at the industrial plant, where the cassava processing process is carried out at room temperature (25–30 °C).

Hydrogen-Rich Syngas Production Based on a Co-Gasification Process Coupled to a Water–Gas Shift Reactor Without Steam Injection

Future decarbonized applications that rely on renewable and carbon-dioxide-neutral hydrogen production could benefit from the gasification of waste to produce hydrogen. In the current study, an Aspen Plus® model was developed by coupling a co-gasification model to a water–gas shift (WGS) model. The feedstock employed in the simulations was a blend of municipal solid waste (MSW) and biomass from Morocco. A parametric assessment was conducted to analyze the effect of the steam-to-feedstock ratio (SFR) on the syngas composition and the WGS reactor temperature. This study also presents a comparison between the results of the gasification process before and after the WGS reactor, using air and steam as the gasifying agent. The results show an increase in hydrogen volumetric percentage for higher steam-to-feedstock ratios in the gasifier. Moreover, the inclusion of a WGS reactor enhances hydrogen and carbon dioxide while reducing the amount of carbon monoxide in the syngas for both air and steam as the gasifying agents. It can be concluded that a co-gasification process can be intensified by coupling it to a WGS reactor without steam injection to produce hydrogen-rich syngas with reduced operational expenditures.

Comprehensive analysis of energy, exergy, and economic aspects in a multi-generation system: Power, methanol, and heat generation through plastic waste gasification

The growing apprehensions regarding climate change and the rising levels of carbon dioxide emissions due to fossil fuel usage, in conjunction with the upsurge in plastic waste attributable to population expansion, have catalyzed a heightened consideration of alternative energy carriers as substitutes for fossil fuels. Methanol (MeOH) is emerging as a promising contender for mitigating the challenges encountered by hydrogen in the realms of storage and transportation. This study investigates the application of waste polyethylene gasification with steam for the production of syngas and methanol, utilizing the thermal integration of biogas-fueled chemical looping combustion (CLC). A noteworthy feature of this proposed system is its capability to generate methanol, power and heating without the emission of carbon dioxide into the environment. The powerful software Aspen Plus is utilized for an extensive process simulation. The simulation results reveal that the optimal molar ratio of the oxygen carrier to the biogas in the CLC is 2.6 (At air reactor temperature of 1000 °C). The operational performance evaluation reveals that the suggested system achieves energy efficiency of 69.5% and exergy efficiency of 64.2% The most significant energy destructors are related to the components of the air reactor, combustion chamber, and fuel reactor, respectively. Additionally, the production rate of methanol is 466.2 kg/h, and the minimum selling price of methanol is calculated to be 0.7 USD/kg.

Improving the performance of lipases in the full hydrolysis of residual coconut oil by immobilization on hydrophobic supports

The effect of the immobilization via interfacial activation on hydrophobic supports of lipase A from Candida antarctica (CALA) and Eversa Transform 2.0 (ETL) in the hydrolysis of residual coconut oil is herein explored. Firstly, some important process parameters (biocatalyst content, substrates ratio, reactor temperature and stirring) were evaluated using the Taguchi method for both free biocatalysts. For free ETL, it was possible to reach full hydrolysis after 6 h under optimized reaction conditions (9 wt% of ETL, 1:2 (oil/water, w/w), 50 °C and 180 rpm). For free CALA, reaching full hydrolysis was not possible under the same optimized reaction conditions, even after 24 h of reaction. Then, ETL and CALA were immobilized by interfacial activation on a methacrylate macroporous resin particles containing octadecyl groups. After reaction conditions optimization by the Taguchi method, immobilized ETL (ETL@C18) reached full hydrolysis under the same optimized reaction conditions of free ETL, but in only 3 h. Immobilized CALA (CALA@C18), reached full hydrolysis (>99 %) after 24 hours under optimized reaction conditions which was not possible employing free CALA (56 %). Finally, under optimized reaction conditions, ETL@C18 retained 85 % of its initial activity after 10 consecutive hydrolysis cycles, whereas CALA@C18 retained less than 50 % of its initial activity after 5 consecutive hydrolysis cycles.

Performance evaluation on the chemical looping combustion of the chromium-containing leather waste and the fate of chromium using thermodynamic analysis

Leather waste (LW) consistently contains a high content of chromium (Cr), which significantly limits its utilization due to the toxicity of hexavalent chromium formed through oxidation. To prevent this oxidation, chemical looping combustion (CLC) is employed to dispose of the chromium-rich LW. First, the gaseous and solid pollutants generated during air combustion and CLC are compared when LW is used as fuel. The results indicate that CLC is an effective way to significantly decrease the oxidation of chromium (Cr(VI)/Crtotal) at typical operating temperatures. Subsequently, various operating parameters, namely the equivalence ratio of oxygen carrier to leather waste (αOC/LW), the equivalence ratio of steam to leather waste (αS/LW), and air reactor (AR) temperature, are changed to investigate their effects on the CLC combustion and pollutant behaviors. The findings reveal that no chromium is oxidized in the fuel reactor. The oxidation in AR is associated with the presence of Na in the AR, which can react with chromium to form Na2CrO4. Increasing αOC/LW from 0.8 to 1.2 reduces the oxidation of chromium in the AR from 11.68% to 1.76%, while increasing αS/LW from 0.2 to 1.6 has the opposite effect, improving the oxidation of chromium in the AR from 3.16% to 5.18%.

2-D modeling of torrefaction of a large biomass particle: effect of L/D ratio, internal convection and shrinkage

ABSTRACT Torrefaction of a large biomass particle was investigated using a transient 2-D model, including primary and secondary reactions kinetics and heat transfer, internal convection, and shrinkage. The model predictions matched with the experimental results within +2%. Spatial and temporal distributions of temperature, residual mass fraction, velocity, and pressure inside the particle and the effect of reactor temperature, residence time, particle size, and shrinkage on the torrefaction behaviour were investigated. Evolution of moisture, volatiles and gases due to drying and torrefaction increase the pressure inside the particle, setting up a velocity field and internal convection. Average velocity and pressure reached a peak during the initial drying period due to moisture evolution, and a subsequent second peak due to the formation of volatiles and gases by torrefaction at a reactor temperature > 493 K. Internal convection influenced torrefaction significantly but the particle shrinkage did not impact it appreciably. The degree of overshoot of the particle center temperature above the reactor temperature increased with the reactor temperature and the particle diameter. Simulations suggest that a reactor temperature of 550 K and residence of about 30 min would be suitable for torrefaction of a particle with L = D = 25.4 mm.

Methanogenesis—General Principles and Application in Wastewater Remediation

The first discovery of methanogens led to the formation of a new domain of life known as Archaea. The Archaea domain exhibits properties vastly different from previously known Bacteria and Eucarya domains. However, for a certain multi-step process, a syntrophic relationship between organisms from all domains is needed. This process is called methanogenesis and is defined as the biological production of methane. Different methanogenic pathways prevail depending on substrate availability and the employed order of methanogenic Archaea. Most methanogens reduce carbon dioxide to methane with hydrogen through a hydrogenotrophic pathway. For hydrogen activation, a group of enzymes called hydrogenases is required. Regardless of the methanogenic pathway, electrons are carried between microorganisms by hydrogen. Naturally occurring processes, such as methanogenesis, can be engineered for industrial use. With the growth and emergence of new industries, the amount of produced industrial waste is an ever-growing environmental problem. For successful wastewater remediation, a syntrophic correlation between various microorganisms is needed. The composition of microorganisms depends on wastewater type, organic loading rates, anaerobic reactor design, pH, and temperature. The last step of anaerobic wastewater treatment is production of biomethane by methanogenesis, which is thought to be a cost-effective means of energy production for this renewable biogas.

Application of microencapsulated phase change materials for controlling exothermic reactions

Abstract Thermal runaway is a frequent source of process safety issues, and the uncontrolled release of chemical energy puts reactors at risk. The design of the exothermic reactor faces challenges due to the selective sensitivity of the product to high temperatures and the need to increase the lifetime of the catalyst, optimize the product distribution, and improve the thermodynamic properties. Phase change material (PCM) encapsulation is recommended to reduce leakage, phase separation, and volume change problems. This work introduces encapsulated PCMs to improve reactor temperature control and minimize thermal runaway in exothermic processes. The warning temperature value setting effectively inhibits fugitive exothermic reactions and enhances heat transfer. When a sufficient quantity of encapsulated PCMs is input, the response speed will automatically accelerate. Spontaneous acceleration of the reaction rate due to thermal runaway of the reaction may be completely avoided by adding a sufficient amount of encapsulated PCM. Microencapsulation is used to control volume changes and inhibit thermal reactions. Preventive strategies include cooling, depressurization, safety release, emergency resources, and reaction containment. Encapsulated PCMs improve mechanical and thermal properties, surface-to-volume ratio, heat transfer surface, thermal capacity, and efficiency.

Development and performance evaluation of a novel solar mid-and-low temperature receiver/reactor with packed metal foam

Solar-driven hydrogen production from methanol decomposition (MD) is an important method of storing solar energy as clean fuels and improving the solar energy utilization efficiency. Catalyst preparation is one of the key steps, but conventional Cu-ZnO-Al2O3 particle catalysts lead to uneven reactor temperature, reducing the efficient conversion of solar energy into fuels. To alleviate this challenge, a monolithic catalyst utilizing packed foamy copper as a carrier is developed with exceptional thermal and mass transfer properties. The experimental results validate its excellent performance in hydrogen production using MD. The absolute conversion increases by an average of 12.11 % at 250 °C and further by 14.43 % at 270 °C compared to the particle catalyst. Based on these findings, a novel solar reactor is proposed, and a multi-field coupling model is built. The comparative results verify the performance advantage of the developed solar thermochemical receiver/reactor with packed metal foam-based catalyst. It maintains high conversion rates and solar-to-fuel energy efficiency, while alleviating overheating problems caused by traditional particle catalysts. Under the design conditions, the new reactor significantly improves the absolute conversion of methanol and the energy efficiency of solar-to-fuel conversion by 4.57 % and 3.00 %, respectively, resulting in 92.64 % and 67.56 %. This study provides a theoretical basis and technical solution for more stable and efficient use of mid-and-low temperature solar energy.

Optimizing neural network models for predicting nuclear reactor channel temperature: A study on hyperparameter tuning and performance analysis

This study emphasizes how important accurate prediction of channel temperatures in nuclear reactors is for safety and operational efficiency. While traditional methods require long and complex processes such as kernel modeling and mathematical simulations, artificial neural networks (ANN) provide more efficient predictions by accelerating this process. The superior ability of ANNs to process large data sets is intended to demonstrate that this study will provide a valuable alternative compared to conventional methods and increase the accuracy of reactor temperature predictions. In this study, the training performances of Artificial Neural Network (ANN) developed to determine the nuclear reactor channel temperature with different hyperparameter combinations were analysed. It was conducted several experimental studies to assess the influence of hyperparameters on our model for nuclear reactor parameter data prediction. The training and validation results indicates that learning rate, hidden layer sizes and number have critical effects for the more precisive prediction. It was observed that models with a learning rate of 0.05 and 0.5 achieved successful learning with less fluctuation in training and validation errors. When looking at hidden layer sizes, networks with 32 and 64 neurons performed better than networks with 16 neurons. For the test phase our model can successfully predict data with slight error margin. As a result, we demonstrated that neural networks are a powerful tool in nuclear reactor channel temperature prediction through our proposed model.