Inlet Stream Research Articles

Technoeconomic Analysis and Comparison of PBI-Based Aqueous and Anhydrous HCl Electrolysis Processes

In this talk, we develop full electrolysis processes, including balance of plant equipment, and compare the economics and production of both a state-of-the-art aqueous HCl electrolyzer and fully anhydrous HCl electrolyzer. We demonstrated recently that a PBI membrane enables the direct electrolysis of anhydrous HCl1,2 , producing separated and high purity hydrogen and chlorine product streams. Development of this process from lab-scale to industrial-scale, however, requires consideration of not just the electrolyzer itself, but also the pre- and post-electrolyzer equipment needed to handle the inlet and outlet material streams. It is also important to compare any newly proposed or demonstrated process to the current state-of-the-art to better understand where the new process either excels or falls short.Our approach involved developing a full electrolyzer model in Aspen Custom Modeler (ACM), facilitating the comparison of parameters such as single-pass conversion of HCl and current densities across various operating conditions. Notably, this model permits the optimization of operating parameters without presuming fixed conversions, distinguishing it from most models employing Aspen Plus. We also aim to validate this model against our experimental results to assess its accuracy. Furthermore, we conduct a detailed techno-economic analysis of the pre- and post-electrolyzer units, followed by the optimization of post-processing unit operations. Our objective is to identify the most cost-effective and sustainable means of production.We will show that while the anhydrous electrolyzer, taken alone, requires more input power than its aqueous counterpart, the full anhydrous electrolysis process is both cheaper to build and operate and uses less energy overall. We consider the impact of hydrogen production on the economics of the anhydrous process, and we show how operating the anhydrous electrolyzer at different conversion efficiencies impacts the overall production rate and operating cost. Finally, we will note potential improvements in the anhydrous electrolysis process by identifying equipment that represent major impacts on energy and financial costs. K. Likit-anurak et al., International Journal of Hydrogen Energy, 47, 26859–26864 (2022).K. Likit-anurak et al., ACS Appl. Energy Mater., 6, 5429–5434 (2023).

Theoretical Model and Control-Parameter Classification for Solid Oxide Fuel Cell System with Cooling Air Bypass into Burner

When using solid oxide fuel cells (SOFCs) as the auxiliary power unit (APU) of automobiles, a stringent thermal control to limit the temperature and thermal stress of all components of the SOFC system is required. Various thermal management methods have been proposed, mostly involving the use of cooling air (CA). To avoid the thermal shock associated with directly adding CA into the SOFC stack air inlet stream, directing CA into the burner is a desirable alternative. Using CA bypass into the burner is a simple and effective way to control the excessive burner temperature, which in turn limits the temperatures of other system components.In this study, a 5 kW SOFC system fueled by diesel and with CA into the burner is examined. The system consists of an SOFC stack and a balance of plant (BOP) that includes a steam generator, an air heat exchanger, a fuel heat exchanger, a pre-reformer and a burner, a water pump and an air blower. The burner burns the unused fuel and provides heat to the pre-reformer and heat exchangers. A thermocouple is installed near the outlet of the burner, which is connected to a CA pipe. When the burner temperature exceeds its set maximum temperature, TBM, the CA valve opens to allow fresh air to enter directly to the burner through the bypass pipe to maintain the burner temperature at the set value. A comprehensive theoretical model, including detailed sub-models for all system components, is developed and verified with multiple experimental data.The theoretical model is used in a comprehensive control-parameter classification analysis, revealing the impacts of the fuel utilization, Uf, air flow rate, Vair, and TBM = (900 ℃, 1000 ℃) on the system performance. In particular, the effects of (Uf, Vair, TBM) on the system electrical efficiency, Esys, and the characteristic temperatures of the stack and BOP components are determined quantitatively. The main findings are: 1) It is confirmed that the CA bypass into the burner can limit the operating temperatures of all system components. 2) Changing TBM from 900℃ to 1000℃ can notably increase Esys only for low Uf, but may increase the maximum stack temperature, TM. It appears that TBM = 900℃ is more favorable than TBM = 1000℃. 3) Increasing Uf increases Esys, but may also increase TM and the maximum stack temperature difference, Tdiff. 4) TM and Tdiff as well as Esys decrease with the increase of Vair. Overall, the constrains of (TM ≤ 900℃, Tdiff ≤ 200℃) can be satisfied together with Esys > 55%, if Vair is chosen properly.It is concluded that the examined system design is suitable as an APU. Moreover, the system model presented here can be used for the design and operation optimization of similar systems, taking factors such as the stack size and performance, the thermal constrains the stack can withstand into considerations.

Hydrogen–steam separation using mechanical vapor recompression cycle

Solar thermochemical hydrogen production is a promising pathway for producing sustainable fuels and chemicals. One of the main challenges in the development of these processes is their low steam conversion extent, dictated by its restrictive thermodynamics requiring extremely high temperatures over 1500°C and low oxygen partial pressure to obtain a steam conversion over 10%. While condensing the unreacted steam is technically simple, the latent heat is thus rendered useless for the process. In many cases, this lost heat can be larger than the higher heating value of the produced hydrogen. We propose a new separation method based on a mechanical vapor recompression cycle, enabling the recovery of the latent heat by compressing the steam–hydrogen mixture prior to the condensation process, thus creating a temperature difference between the hot exhaust and cold inlet streams. We show that this separation method can recover the latent heat and keep its quality in relevant operating conditions while requiring less than 14% of the recovered heat for compression work, resulting in a coefficient of performance over 7. This method increases the viability of solar thermochemical hydrogen production cycles, especially under limited steam conversion conditions.

The production of biogenic carbon and green hydrogen through biomethane pyrolysis: the environmental benefits for the metallurgy sector

Abstract The iron and steel industry is responsible for around 4% of androgenic CO2 emissions in Europe and 9% worldwide. This is due to the massive use of carbon coke in metallurgy, which is not only linked to energy purposes, but also to the chemical process of iron ore refining. The steel sector urgently needs to find alternative solutions to improve environmental sustainability, with the transition to a low-carbon scenario representing a major challenge. The pyrolysis of methane is gaining more and more attention for the production of hydrogen, as this alternative process to hydrogen production does not generate any CO2 emissions, but provides a solid carbon product that can be re-used in an industrial symbiosis. If biomethane is used, the pathway is even carbon-negative, and generates a net GHG reduction compliant with the EU ETS (Emission Trading Scheme). However, given the high demand for inlet streams in the EU steel sector, the biomethane currently available is not able to meet the entire hydrogen demand assuming that the steel is produced using the DRI-EAF (Direct Reduction Iron-Electric Arc Furnace) route. Only when looking at the European projections for biomethane production in 2050, it is expected that the demand for steel hydrogen can be totally met, in particular by using 48% of the available biomethane, allowing up to 6 million tons of green hydrogen to be produced, and a significant reduction in net CO2 emissions. Finally, the aim of this work is to assess the energy consumption and environmental benefits resulting from the production of green hydrogen and biogenic carbon in Europe for DRI-EAF, compared to the benchmark market (DRI-EAF fed with natural gas) and the electrolysis alternative.

Artificial intelligence assisted prediction of optimum operating conditions of shell and tube heat exchangers: A grey‐box approach

AbstractIn this study, a Grey‐box (GB) model was developed to predict the optimum mass flow rates of inlet streams of a Shell and Tube Heat Exchanger (STHE) under varying process conditions. Aspen Exchanger Design and Rating (Aspen‐EDR) was initially used to construct a first principle model (FP) of the STHE using industrial data. The Genetic Algorithm (GA) was incorporated into the FP model to attain the minimum exit temperature for the hot kerosene process stream under varying process conditions. A dataset comprised of optimum process conditions was generated through FP‐GA integration and was utilised to develop an Artificial Neural Networks (ANN) model. Subsequently, the ANN model was merged with the FP model by substituting the GA, to form a GB model. The developed GB model, that is, ANN and FP integration, achieved higher effectiveness and lower outlet temperature than those derived through the standalone FP model. Performance of the GB framework was also comparable to the FP‐GA approach but it significantly reduced the computation time required for estimating the optimum process conditions. The proposed GB‐based method improved the STHE's ability to extract energy from the process stream and strengthened its resilience to cope with diverse process conditions.

Mechanistic insights into how mixing factors govern polyelectrolyte-surfactant complexation in RNA lipid nanoparticle formulation

Hypothesis: Lipid nanoparticle self-assembly is a complex process that relies on ion pairing between nucleic acids and hydrophobic cationic lipid counterions for encapsulation. The chemical factors influencing this process, such as formulation composition, have been the focus of recent research. However, the physical factors, particularly the mixing protocol, which directly modulates these chemical factors, have yet to be mechanistically examined using a reproducible mixing platform comparable to the industry standard. We here utilize Flash NanoPrecipitation (FNP), a scalable rapid mixing platform, to isolate and systematically investigate how mixing factors influence this complexation step, first by using a model polyelectrolyte-surfactant system and then generalizing to a typical RNA lipid nanoparticle formulation.Experiments: Aqueous polystyrene sulfonate (PSS) and cetrimonium bromide (CTAB) solutions are rapidly homogenized using reproducible FNP mixing and controlled flow rates at different stoichiometric ratios and total solids concentrations to form polyelectrolyte-surfactant complexes (PESCs). Then, key mixing factors such as total flow rate, inlet stream relative volumetric flow rate, and magnitude of flow fluctuation are studied using both this PESC system and an RNA lipid nanoparticle formulation.Findings: Fluctuations in flow as low as ± 5 % of the total flow rate are found to severely compromise PESC formation. This result is replicated in the RNA lipid nanoparticle system, which exhibited significant differences in size (132.7 nm vs. 75.6 nm) and RNA encapsulation efficiency (34.0 % vs. 82.8 %) under fluctuating vs. steady flow. We explain these results in light of the chemical variables isolated and studied; slow or nonuniform mixing generates localized concentration gradients that disrupt the balance between the hydrophobic and electrostatic forces that drive complex formation. These experiments contribute to our understanding of the complexation stage of lipid nanoparticle formation and provide practical insights into the importance of developing controlled mixing protocols in industry.

Dynamic modeling of polymer electrolyte membrane fuel cells under real-world automotive driving cycle with experimental validation on segmented single cell

A 1+1D transient non-isothermal and multiphase polymer electrolyte membrane fuel cell model is developed. The model is validated on experimental data gathered on a segmented single cell and representative of a real-world automotive driving cycle, derived from the stack protocol defined in the ID-FAST H2020 project. During Low-Power operation, cell voltage response is mainly controlled by platinum oxide and water dynamics: the low hydration significantly affects cathode inlet performance. Throughout High-Power operation, instead, voltage transients are ascribable to local mass-transport related phenomena: in particular, liquid water accumulation along the channel strongly decreases the efficiency of cathode outlet region. Finally, the effect of relative humidity at cathode channel inlet is investigated: an increase in the humidification of the air inlet stream from 30% to 50% leads to a better proton conductivity and, therefore, to a significant enhancement of the performance of cathode inlet regions, which also means a slight improvement in the average stack efficiency from 62.2% to 62.8%. Lowering RH of the air-inlet stream from 30% to 15%, a worsening of proton conductivity is observed, which exacerbates performance heterogeneities and leads to a reduction of the average stack efficiency from 62.2% to 61.5%, consistently with experimental results.

A Tandem Photovoltaic-Electrochemical Photothermal Process for CO2 Conversion to Butene

Decarbonizing the chemicals industry requires net carbon negative technologies capable of displacing current greenhouse gas emitting processes. In particular, the generation of valuable monomers, such as butene, are currently produced by significant greenhouse gas emitting processes, including ethylene oligomerization and crude oil refining, which require high temperatures and pressures. Integrated, tandem solar fuels devices for the conversion of CO2 to ethylene, using solar-driven CO2 reduction (CO2R), combined with a photothermal reactor for ethylene oligomerization, offers a potential path to producing clean butene from CO2, using solar energy as the only driving force. A key challenge for the successful operation of a tandem photo-driven electrochemical-photothermal system is the co-design of the two processes, which are typically optimized under different operating conditions. Specifically, photo-driven electrochemical CO2R (pCO2R) reactors operate under ambient temperature and pressure conditions while thermally-driven ethylene oligomerization reactors prefer elevated temperatures (80-140 °C) and pressures (30-150 atm) to promote high activity as well as pure ethylene in the inlet stream. Operation of the tandem process under solar-driven conditions imposes additional constraints on the maximum power output of the pCO2R reactor and the maximum temperature which can be obtained in the photothermal reactor. Herein, we present an unassisted solar-driven tandem system coupling pCO2R with photothermal ethylene oligomerization for the conversion of CO2 to butene in a single pass. This work presents a critical advancement in the development of solar fuels technologies for larger hydrocarbon generation and identifies the co-design principles which must be considered for implementation of tandem, solar-driven electrochemical-thermal processes.

Stability and combustion characteristics of dual annular counter-rotating swirl oxy-methane flames: Effects of equivalence and velocity ratios

An experimental study was carried out to investigate flow/flame interactions, stability, combustion, and emissions properties of CH4/O2/CO2 stratified flames stabilized on a dual annular counter-rotating swirl (DACRS) burner for gas turbine combustion applications. The effects of two targeted parameters, namely equivalence ratios (for primary - ϕp, secondary - ϕs, and global - ϕg streams) and velocity ratio (Vr = Vp/Vs: primary to secondary stream inlet velocity ratio), are studied at fixed volumetric oxygen fraction (OF) in the oxidizer mixture (O2 + CO2) of both primary and secondary streams of 34 % at fixed Vp of 5 m/s. The experimental results indicated that no flame flashback was recorded in the domain of any operational ϕp up to stoichiometric operation of the secondary stream (ϕs = 1.0). At near stoichiometric operation of the primary stream, the main secondary flame can persist in extremely lean conditions (ϕs = 0.45 @ Vr = 3), thereby extending the thresholds of flame blowout. Moreover, raising ϕp from 0.4 to 1.0 results in significant reduction of ϕs at blowout from 0.595 to 0.456, corresponding to reducing the combustor ϕg at blowout from 0.577 to 0.499. At lower ϕp, the oxy-methane flame tends to lift and extinguish earlier.

Combined measures in lake restoration – A powerful approach as exemplified from Lake Groote Melanen (the Netherlands)

Controlling lake eutrophication is a challenge. A case-specific diagnostics driven approach is recommended that will guide to a suite of measures most promising in restoration of eutrophic lakes as exemplified by the case of the shallow lake Groote Melanen, The Netherlands. A lake system analysis identified external and internal nutrient load as main reasons for poor water quality and reoccurring cyanobacterial blooms in the lake. Based on this analysis, a package of restoration measures was implemented between January 2015 and May 2016. These measures included fish removal, dredging, capping of peat rich sediment with sand and an active barrier (lanthanum-modified bentonite), diversion of two inlet streams, reconstruction of banks, and planting macrophytes. Dredging and sand capping caused temporarily elevated turbidity and suspended solids concentrations, while addition of the lanthanum-modified clay caused a temporary exceedance of the Dutch La standard for freshwaters. Diversion of inflow streams caused 35 % less water inflow and larger water level fluctuations, but the lake remained water transporting with strongly improved water quality as was revealed by comparing five years pre-intervention water quality data with five years’ post-intervention data. Total phosphorus concentration in the water column was reduced by 93 % from 0.47 mg P l-1 before the intervention to 0.03 mg P l-1 after the intervention, total nitrogen by 66 % from 1.27 to 0.21 mg N l-1, total chlorophyll-a by 75 % from 68 to 16 µg l-1, cyanobacteria chlorophyll-a by 88 % from 32 to 4 µg l-1. Turbidity had declined by 58 % from 23.5 FTU to on average 9.9 FTU. No cyanobacteria blooms were recorded over the entire post-intervention monitoring period (2016–2021). Submerged macrophytes increased from complete absence before intervention to around 10 %–15 % coverage after intervention. Repeated fish removal lowered the fish stock to below 100 kg ha-1 with 12 % of bream and carp remaining. Hence, the package of cohesive measures that was based on a thorough diagnosis resulted in rapidly, strongly and enduringly improved water quality. This case provides evidence for the power of combining measures in restoring eutrophic lakes.

Effect of Chevron Angles on the Thermal Performance of Corrugated Plate Heat Exchanger (CPHEs)

Corrugated plate heat exchangers (CPHEs) possess a greater surface area for heat transfer and a heightened level of turbulence as a result of the corrugations. This study presents an experimental analysis comparing the thermal performance of a flat plate heat exchanger and a corrugated plate heat exchanger (CPHE) with varied corrugation angles. The analysis was conducted using water as the test fluid. The comprehensive testing has been carried out on CPHEs with different chevron angles (β) of 30°/30°, 45°/45°, and 60°/60°. Experimental data is collected under steady- state conditions, with a single phase (water-water) system, covering Reynolds numbers (Re) ranging from 900 to 1250. The test fluid's mass flow rate, ranging from 0.05 to 0.16 kilograms per second, is measured together with the accompanying steady state temperatures. Each plate was equipped with four thermocouple sensors to detect the bulk temperature of the cold and hot fluids at the intake and output. The performance was evaluated using both parallel and counterflow configurations. Experimental observations are utilized to estimate the temperature difference (∆T) between the inlet and output streams, the logarithmic mean temperature difference (LMTD), and the exergy (E). The measured ∆T and E values for corrugation angles (30°, 45°, and 60°) of CPHE were compared to those of flat plate heat exchangers. For corrugation angles of 30°, 45°, and 60°, the values of ∆T and E (efficiency) increase as the mass flow rate of the fluid increases. An increase in the corrugation angle leads to an increase in turbulence in the flow, which in turn enhances heat transmission. In addition, the thermal effectiveness (ε) was calculated using the NTU method and compared for all of the plates. Key Words: Corrugated plate heat exchanger, Thermal performance, Chevron angle, heat transfer coefficient.

Simulation model of carbon capture with MEA and the effect of temperature and duty on efficiency

Humans continue to rely on fossil fuels to generate electricity. In other words, fossil fuels are the world's largest energy producers. Fossil fuels produce significant carbon dioxide, mostly in areas where humans live. Although the share of carbon dioxide produced in big cities is minimal compared to the carbon dioxide production of volcanoes, the production of carbon dioxide in big cities has destructive effects. Process Simulator is utilized to evaluate the effectiveness of their simulation model by subjecting it to various experimental conditions, including liquid loading, temperature, and CO2 absorption (PPS). Comparing empirical and simulated mass transfer coefficients distinguishes this study from others. This procedure consists of two steps: Carbon dioxide (CO2) absorption in a solvent produces highly concentrated CO2 gas following solvent regeneration. A chemical adsorption process's scalability depends on accurate simulation models, typically validated using data from a pilot plant. With the aid of this study, a simulation model of a desorption column is constructed with ASPEN PLUS and 42% MEA validated. In addition, the effect of the weight percentage of 20-42 MEA in the inlet stream on the efficiency is investigated, and the influence of the MEA inlet temperature on system efficiency is examined. Then, the recommended temperature is confirmed based on the MEA's heat tolerance capacity of 303 Kelvin.

High-accuracy experimental study of performance characteristics of optimised Ranque-Hilsch vortex tube

In this paper we present high-accuracy experimental measurements of the performance characteristics of an optimised Ranque-Hilsch vortex tube of cylindrical counter-flow design. Although this is a relatively mature research area, the published high-accuracy experimental data with quantified measurement uncertainty is very limited. The purpose is to provide a reference data-set for CFD method validation and calibration. The vortex tube design is a performance-optimum based on existing literature. We characterize the temperature separation, energy separation, efficiency, and coefficients of performance for three inlet pressures (3.0 bar, 5.0 bar and 7.0 bar) and for atmospheric back pressure. Performance characteristics are presented as a function of cold gas mass fraction. The lowest non-dimensional cold-exit temperature (normalised by inlet temperature) was 0.87, the highest coefficient of performance (decrease in enthalpy flux of the cold stream normalized by work needed to compress air to the inlet pressure) was 0.137, and the highest isentropic efficiency (ratio of the actual energy lost by cold stream to energy that would have been lost in an isentropic expansion of the entire inlet stream from the inlet pressure to the cold-exit pressure) was 0.16.

Chaotic-flow-driven mixing in T- and V-shaped micromixers

T- and V-shaped (or arrow-shaped) micromixers enable the control of rapid chemical reactions by permitting accelerated mixing. Their mixing performance has been extensively investigated at moderate flow rates, which correspond to Reynolds numbers of the order of several hundreds. However, this operating range does not align with the recent applications of microreactors in organic synthesis. Therefore, this study examined mixing times in T- and V-shaped micromixers with 250-µm-wide channels at high flow rates (Reynolds numbers of up to 1500). The progress of mixing between an acidic solution and a basic solution containing a pH-sensitive fluorescent molecule was visualized by fluorescence microscopy imaging. An image analysis of 200 frames for each condition helped evaluate the degree of mixing and its stability over time under chaotic flow. The performance and stability of the V-shaped micromixer were significantly enhanced when the flow-rate ratio was changed from 1:1 to 1:2. The difference in momentum between the two inlet streams suppressed the undesirable alternation of the flow patterns at the junction. The effects of the choice of fluids (in the lower- and higher-flow-rate sides) on the reaction selectivity were explored through a numerical analysis. It was clarified that the substrate-side flow rate has to be set lower than that of the reactant side in the competing consecutive reaction system. Moreover, a short mixing time of 1 ms was achieved using the V-shaped micromixer at a flow-rate ratio of 1:2 and Re of 1500. These findings provide practical guidelines for the design and operation of microreactor systems.

Delayed Detached-Eddy Simulations of Rough-Wall Turbulent Reactive Flows in a Supersonic Combustor

Reactive delayed detached-eddy simulations (DDESs) of hydrogen injection into a confined transverse supersonic flow of vitiated air are conducted. The corresponding conditions were studied in the LAPCAT-II combustor, which—due to thermal coating—exhibits non-negligible wall roughness. Its effects are taken into account with the equivalent sand-grain roughness model, and, to the best of the authors’ knowledge, it is the first time that this modeling framework is considered within the DDES framework to simulate turbulent reactive flows. Two operating conditions are considered, which differ in the value of the momentum ratio between the hydrogen and vitiated air inlet streams, thus leading to two distinct values of the operating equivalence ratio (ER). For its smallest value, smooth combustion is subject to a preliminary thermal runaway period, while for its largest value, combustion is more strongly intertwined with shock wave dynamics and boundary-layer separation. Since it features large subsonic regions, which are characteristic of situations close to thermal choking, the latter is referred to as the sudden or partially choked combustion mode. Computational results are assessed through comparisons with available experimental data for both operating conditions. The main mechanism through which wall roughness alters the combustion development lies in the reduction of the effective cross-sectional area that is induced by boundary-layer thickening. For the largest ER value, DDES conducted with the sand-grain roughness model does recover the partially choked combustion mode, while smooth wall (i.e., standard) DDES does not.

Toward sustainable production of N-containing products via nonthermal plasma-enhanced conversion of natural gas resources

Nonthermal plasmas can directly activate and cleave the strong chemical bonds in molecular nitrogen and methane to facilitate the transformation of these inherently stable molecules through the application of electrical energy. Here, we report a low temperature, atmospheric pressure, nonthermal plasma for the “one-pot” synthesis of olefins, alkynes, higher molecular weight hydrocarbons, ammonia, and nitrogen-containing liquids from a representative shale gas feed enriched with nitrogen. We reproducibly observe a wide range of valuable and synthetically challenging gas-phase and liquid-phase products containing C–N, C–C, and N–H bonding by controlling the N2 concentration in the inlet feed stream. In nitrogen-lean regimes, hydrocarbon products dominate (e.g., ethylene, acetylene, etc.), while nitrogen-rich regimes promote incorporation of nitrogen into the products, leading to the formation of ammonia and liquid products containing a variety of functionalities (e.g., nitriles, amines, heterocycles). High resolution electrospray ionization mass spectrometry was used to measure molecular weights and identify the chemical formulas of the liquid products. Van Krevelen diagrams were created and showed many products with compositions around H/C= 2 and N/C= 0.5, indicating the potential importance of intermediate species with these ratios for liquid formation (e.g., CH3CN + H).

Deeper Flow Behavior Explanation of Temperature Effects on the Fluid Dynamic inside a Tundish

The continuous casting tundish is non-isothermal due to heat losses and temperature variation from the inlet stream, which generate relevant convection forces. This condition is commonly avoided through qualitative fluid dynamic analysis only. This work searches to establish the conditions for which non-isothermal simulations are mandatory or for which isothermal simulations are enough to accurately describe the fluid dynamics inside the tundish by quantifying the buoyant and inertial forces. The mathematical model, simulated by CFD software, considers the Navier-Stokes equations, the realizable k-ε model for solving the turbulence, and the Lagrangian discrete phase to track the inclusion trajectories. The results show that temperature does not significantly impact the volume fraction percentages or the mean residence time results; nevertheless, bigger velocity magnitudes under non-isothermal conditions than in isothermal conditions and noticeable changes in the fluid dynamics between isothermal and non-isothermal cases in all the zones where buoyancy forces dominate over inertial forces were observed. Because of the results, it is concluded that isothermal simulations can accurately describe the flow behavior in tundishes when the flow control devices control the fluid dynamics, but simulations without control devices or with a weak fluid dynamic dependence on the control devices require non-isothermal simulations.

Метод оценки времени нахождения дисперсных частиц в канале противоточной вихревой трубы

In this paper, the process of removing spherical particles from an incompressible fluid through the hot outlet of a vortex tube is investigated. The removal rate was estimated through computational simulations using OpenFOAM software. The numerical solution was carried out using denseParticleFoam solver of OpenFOAM, which implements the multiphase particle-in-cell (MP-PIC) method using the Eulerian approach for the continuous phase and the Lagrangian approach for the dispersed phase. Five series of numerical experiments were carried out, with variations in the initial particle position in the inlet stream and the density of the dispersed phase. Based on the results of the experiments, a relationship has been established between the density of particles and the time they remain in the vortex tube. The relationship between the particle density and the time it takes for the particles to reach the opposite end of the tube with a hot outlet diaphragm is demonstrated. The method of processing the obtained results is described. The possibility of using linear and quadratic approximations to estimate the residence time of particles in a tube channel is considered. For each set of experiments, confidence intervals and the mean absolute percentage error for the prepared approximation have been calculated.

Comparison of Anion-Exchange Membranes for Diffusion Dialysis of Mixtures of Acids and Their Iron Salts.

This study presents the possibility of using diffusion dialysis for the separation of inorganic acids (hydrochloric, nitric, and hydrofluoric) and their ferric salts whose composition corresponds to that of real spent pickling solutions. At a steady state, the transport properties of three different anion-exchange membranes (Fumasep-FAD, Neosepta-AFN, and Neosepta-AHA) are compared using a continuous counter-current dialyzer. At a constant composition of the solutions (acid concentration 3 mol L-1 and iron concentration 30-40 g L-1), the effects of volumetric liquid flow rates on the transport rate of H+ and Fe3+ ions through the membrane are studied. The dialysis process is characterized by the recovery of acids and the rejection of salts. Furthermore, the values of the dialysis coefficients of acids, iron, and the acid/iron separation factors are calculated and compared. The volumetric flow rates of the inlet streams change in limits from 3 × 10-8 to 6 × 10-8 m3 s-1 (from 3 to 6 L h-1 m-2, relative to the membrane area). A comparison of the tested membranes shows slightly better results for acid recovery, iron rejection, and acid/iron separation factors for the Fumasep-FAD membrane than for the Neosepta-AFN membrane. However, the results obtained show that both of these anion-exchange membranes can be considered good separators for tested mixtures that simulate real spent pickling solutions, and there is a good precondition for using diffusion dialysis for processing these solutions in industrial practice. On the contrary, very low values of acid recovery and the overall dialysis coefficient of acid are found for the Neosepta-AHA membrane in the test range of the volumetric flow rate, and, thus, this membrane is insufficient for the adequate separation of these acids and iron salts.

Polyelectrolyte nanocomplex from sodium caseinate and chitosan as potential vehicles for oil encapsulation by flash nanoprecipitation

A polyelectrolyte complex coacervation technique has been used for emulsion stabilization, nutraceutical encapsulation, and controlled delivery. However, traditional batch-mixing methods suffer from significant insufficiencies in scalability because of batch-to-batch variation and complicated multi-step preparation procedures resulting in uncontrollable size, wide size distribution, instability, and aggregation. This study used a flash nanocomplexation (FNC) method to continuously prepare protein (sodium caseinate) and polysaccharide (chitosan) nanocomplexes with narrow size distributions using a multi-inlet vortex mixer. The size distributions of nanocomplex can be controlled by volumetric flow rates of the inlet streams, the concentration, and the order/ratio of sodium caseinate to chitosan. Furthermore, a novel emulsion preparation method, flash-microemulsion (FME), was introduced. Under rapid mixing conditions, FME prepared emulsion in the presence of soybean or MCT oil by infusing aqueous solutions of sodium caseinate and chitosan in a single step. O/W emulsion prepared successfully by the FME method was confirmed with confocal microscopy. The emulsion droplet size ranged from 4.6 to 1.5 μm and showed elastic-like properties (G' > G″). Optical microscope, SEM, and TEM studies suggested that the FME method could form homogeneous and stable emulsions. The emulsions showed excellent stability over 30 days of storage. In addition, there were no noticeable differences in the size and size distribution of nanocomplex and emulsion prepared at different times, indicating excellent reproducibility. As a result of FNC and FME, other lipophilic bioactive compounds can be encapsulated/stabilized in the food, flavor, pharmaceutical, and cosmetic industries.