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Rotating Packed Bed (RPB) technology has emerged as a promising technology for reducing carbon footprint of various petrochemical processes by leveraging the HiGee field-induced mass transfer enhancement and allow for better capture of greenhouse gases. Despite its potential, there are still significant challenges that hinder the effective utilization of RPB technology in process intensification. Specifically, the hydraulics of liquid and gas phases within RPB packings present a significant challenge. In this study, 2D – VOF approach is employed to study the behavior of liquid droplets impacting on single rotating wire and on a whole rotating wire mesh within a Rotating Packed Bed (RPB). A comprehensive computational fluid dynamics (CFD) model is developed to analyze the influence of rotating speed, liquid velocity, and droplet diameter on the dynamics of liquid droplets. The boundaries of splashing – no splashing and dripping – capture breakup modes were validated for a single rotating wire and identified for wire mesh in RPBs by constructing the corresponding regime maps. This is achieved thanks to a new data processing algorithm that applies the principle of neighborhood aggregation. The proposed data processing algorithm helps reconstruct the regime maps for the various breakup phenomena within RPBs. The results show that the splashing mechanism reproduces higher-velocity detached daughter droplets, while the momentum-induced dripping mechanism results in low velocity daughter droplets. The results also reveal that the deposited liquid film with the wires has a key role in enhancing the splashing phenomena in RPBs. The radial distribution of diameter and velocity of liquid droplets in RPB is also analyzed in light of the droplet impact dynamics. The increase in the average liquid velocity with radial direction was attributed to the increase of splashed drops, which led to a bigger number of high-velocity droplets. The conclusions of this study can be used to help improve the dynamics of the two-phase flow within RPBs through a better packing design and flow conditions. [Display omitted] • 2D–VOF approach is used to simulate liquid flow in rotating packed bed. • Influence of important parameters on the dynamics of liquid droplets is analyzed. • New data processing algorithm based on principle of neighborhood aggregation is used. • Boundaries between different breakup modes are identified. • Corresponding regime maps are constructed for the studied wire mesh. [ABSTRACT FROM AUTHOR]

• Enhancing Hydrogen Production in Scale Fluidized Bed Reactors is investigated. • Computational Fluid Dynamics and Machine learning approaches are deployed. • Analysis of the reactor performance towards boosting hydrogen production is conducted. • Minimizing coke-to-syngas ratio based on multi-objective genetic approach is achieved. This research investigates the optimization and simulation of dry methane reforming (DMR) in fluidized and fixed bed reactors at an industrial scale. By utilizing Computational Fluid Dynamics (CFD) based on the Multi-Phase Particle-in-Cell (MP PIC) approach, we analyze the performance of these reactors under various operating conditions and ascertain the superiority of the fluidized regime at increasing hydrogen and syngas production while suppressing coke formation for an important process such as Dry Methane Reforming (DMR). The study shows that fluidized bed reactors are versatile and effective at managing varying amounts of catalyst reductions, offering a promising pathway for sustainable energy systems. Machine learning models built from the generated CFD data accurately predict DMR process results and have facilitated the analysis of the reactor performance and finding effective ways to boost hydrogen production and conversion rates while minimizing the coke-to-syngas ratio and this via the multi-objective genetic algorithm. The study not only examined the optimization of the DMR process but also supported sustainable development objectives by promoting efficient energy resource utilization and diminishing environmental impacts. The results endorse incorporating fluidized bed reactors into the energy industry, emphasizing their potential to transform hydrogen production methods and significantly contribute to achieving eco-friendly energy solutions. [ABSTRACT FROM AUTHOR]

Parameter estimation in models plays an important role in the development of mathematical models capable of accurate simulation and genuine optimization of real-world processes. This paper presents the results of a computer based optimization of the operation of a commercial acid gas removal unit that uses amine as solvent. The kinetics of CO 2 absorption using Methyldiethanolamine (MDEA) populating an existing model is revisited based on real-data-driven parameters re-estimation. The latter is achieved via an evolutionary technique that uses Particle Swarm Optimization (PSO) algorithm. The new CO 2 kinetic model is then embedded in a first-principle process simulation model and used to quantify and analyze the effects of certain process parameters such as amine circulation rate, amine concentration, lean amine temperature and rich amine temperature on the unit performance and efficiency. Also, patterns of various plant performance indicators such as sweet gas composition profile, reboiler steam rate, pumping and cooling requirements are plotted against the abovementioned parameters and respective optimum conditions are proposed, based on the computer simulation results. Further comprehensive analysis is performed to assess the net monetary benefit of implementing these proposed changes for the studied chemical process. [ABSTRACT FROM AUTHOR]

A three-dimensional reactive gas-particle CFD model was built to study the hydrodynamics, heat transfer and cracking reaction behaviors within an industrial Fluid Catalytic Cracking (FCC) riser reactor designed to maximize propylene production. The two-fluid methodology (TFM) was used to simulate the riser hydrodynamics with solid phase properties derived from the kinetic theory of granular flows (KTGF). An 11-lump kinetic model was selected to represent the cracking reaction network in the CFD model. The selection of the kinetic model is dictated by the properties of the feedstock processed and the aim of the process which is maximizing propylene. A novel treatment of the coke component was conducted by incorporating coke into the secondary granular phase which is more realistic since carbon deposition occurs on catalyst phase. Momentum transfer, heat transfer and reaction behavior inside the riser were discussed in detail and inhomogeneity in these aspects were observed especially above the high speed injection nozzles. The numerical results of this investigation show a good agreement with the process real data on the yield distribution despite the use of a coarse grid to mesh such an industrial scale FCC riser. The methodology employed used and the results obtained should serve as guidelines for possible process redesign and optimization. [ABSTRACT FROM AUTHOR]

A new static analytical apparatus for high-pressure phase equilibrium measurements has been designed and built. The new apparatus enables the measurement of vapor–liquid and liquid–liquid equilibria, which can operate at temperatures ranging from 225 K to 475 K and pressures up to 20 MPa. It is constructed in Titanium and alloy C276, being suitable for highly corrosive systems of interest for the gas industry (e.g., for hydrogen sulfide containing mixtures). The apparatus is equipped with two Rapid Online Sampling Injectors (ROLSI™) enabling the withdrawing of micro-samples without disturbing the equilibrium conditions. A gas chromatograph is connected to the apparatus for direct analysis of the phases' compositions. The quality and performance of the new apparatus has been evaluated by measuring a well reported system (carbon dioxide + methylcyclohexane). [ABSTRACT FROM AUTHOR]

Abstract: Vapor–liquid equilibrium (VLE) of natural gas systems containing light hydrocarbons, water, carbon dioxide (CO2), hydrogen sulfide (H2S), nitrogen (N2), monoethylene glycol (MEG), triethylene glycol (TEG), benzene (C6H6), toluene (C7H8), methanol (CH3OH) and ethanol (C2H5OH) are predicted in this work. A performance comparison between Peng–Robinson equation of state (PR EoS) and the perturbed chain form of the statistical associating fluid theory (PC-SAFT EoS) is made based on their predictability power in modeling such systems at different conditions. Data on saturated liquid densities and vapor pressures are used to optimize pure component PC-SAFT parameters for MEG and TEG. Experimental VLE data is used to fit both temperature dependent and independent binary interaction parameters (k ij ) in the PC-SAFT framework. Peng–Robinson EoS shows better results in predicting phase behavior of dry natural gas systems. However, PC-SAFT EoS exhibits superiority for systems containing water and/or methanol. [Copyright &y& Elsevier]

Abstract: Understanding of droplet transport in indoor environments with thermal effects is very important to comprehend the airborne pathogen infection through expiratory droplets. In this work, a well-resolved Large Eddy Simulation (LES) was performed to compute the concentration profiles of monodisperse aerosols in non-isothermal low-Reynolds turbulent flow taking place in an enclosed environment. Good care was taken to ensure that the main dynamical features of the continuous phase were captured by the present LES. The particle phase was studied in both Lagrangian and Eulerian frameworks. Steady temperature and velocity were measured prior to droplet emission. Evolution of aerosol concentration was measured by a particle counter. Results of the present LES were to compare reasonably well with the experimental findings for both phases. [Copyright &y& Elsevier]

Abstract: Dispersion of heavy particles from a point source in high-Reynolds pipe flow was studied using large-eddy simulation, LES. A stochastic Langevin type Lagrangian model developed by Berrouk et al. was used to account for heavy particle transport by the sub-grid scale motion. In both the LES and in an experiment by Arnason, the larger particles dispersed more than the small ones. The change in diffusivity with particle size is interpreted in terms of the effect of inertia and cross-trajectory effects and qualitatively compared with the analysis of heavy particle dispersion in isotropic turbulence by Wang and Stock. Particle inertia has a much larger influence on the dispersion than the crossing-trajectories effects. [Copyright &y& Elsevier]

Abstract: Aerosols deposition in turbulent bend flows is a major concern that is critical to many industrial, environmental and biomedical applications. In this work, a well-resolved LES was performed to compute the deposition efficiency of aerosols in turbulent circular cross-section bend flow of Dean number . The numerical predictions were compared to the experimental work of Pui et al. [Pui, D.Y.H., Romay-Novas, F., Liu, B.Y.H., 1987. Experimental study of particle deposition in bend of circular cross-section. Aerosol Sci. Technol. 7, 301–315] and the fully-resolved LES of Breuer et al. [Breuer, M., Baytekin, H.T., Matida, E.A., 2006. Prediction of aerosol deposition in 90° bends using LES and an efficient Lagrangian tracking method. J. Aerosol Sci. 37, 1407–1428]. In the present LES, a slightly coarser but unstructured-grid numerical description was adopted, entailing that a portion of the small scales’ contribution to particle dispersion to be discarded. Thus, a Langevin-type stochastic model was used to model the effect of the discarded sub-grid motion on aerosol deposition. This stochastic model was shown to perform well in previous studies [Berrouk, A.S., Laurence, D., Riley, J.J., Stock, D.E., 2007. Stochastic modelling of inertial particle dispersion by subgrid motion for LES of high Reynolds number pipe flow. J. Turbulence, 8, 50]. Good care was taken to ensure that the main dynamical features of the continuous phase were captured by the present LES. An estimation of the filtered-out kinetic energy was provided. Results of the present LES with SGS model for particles were found to compare well with the experimental work and the fully-resolved LES (near-wall DNS) of Breuer for all the range of the Stokes number considered, . Influence of the SGS model for particles was visible for the deposition efficiency of aerosols with Stokes number . [Copyright &y& Elsevier]

• Use of supercritical carbon dioxide (sC O 2 ) as a coolant in microchannel heats sinks. • Numerical simulations are employed to compare sC O 2 and water as coolants for MCHS. • Steep variations in the thermophysical properties of s CO 2 are accounted for. • Complex flow and heat transfer characteristics in MCHS are quantified and analyzed. • sC O 2 -cooled MCHS's performance is up to 2.2 times higher than the water-cooled one. [Display omitted] For compact electronic devices, high-pressure drops that characterize microchannel heat sinks (MCHS) is an issue that needs to be resolved to reduce the size of heat-removing systems. In this regard, supercritical carbon dioxide (sC O 2 ) can be of great value due to its favorable thermophysical properties near the critical point. Thus, the potential of the proposed coolant (sC O 2 ) for microchannel heat sinks (MCHS) is numerically investigated and compared with the conventional liquid coolant. Moreover, a header geometry with minimum flow maldistribution is designed for both coolants. Finally, the impact of various operating conditions on the thermal and hydraulic performance of the proposed sC O 2 -cooled MCHS is investigated to evaluate its optimal operating conditions. To accomplish this, a 3D Reynolds Averaged Navier–Stokes (RANS) model is developed to analyze the thermal and hydraulic performance of both coolants. Thermophysical properties of sC O 2 are implemented through a high-resolution real gas property (RGP) file to capture abrupt variations in its properties and ensure the model's precision. Results suggest that replacing water with sC O 2 can enhance the thermal performance of microchannel heat sinks by up to 32% at higher flow rates of the coolant, while pressure losses can be reduced by up to 7 times compared to water-cooled MCHS. Moreover, it is found that sC O 2 -cooled MCHS can maintain a steady base temperature, even during overload conditions. The proposed coolant can be used to design highly efficient and compact cooling systems with the capability of enhancing the MCHS overall performance by up to 2.2 times. [ABSTRACT FROM AUTHOR]

• New correlations for zigzag channels PCHEs are proposed for broader operational ranges. • Proposed segmental averaged data reduction method is proficient to analyze precooler. • Design value of the flow Reynold number found critical to pinch point location in precooler. • Complex flow and heat transfer characteristics in precooler are analyzed and explained. Since the precooler and the recuperator are the largest components of a supercritical carbon dioxide Brayton cycle, their design can substantially affect the performance and size of the whole system. Although the design of a precooler with zigzag channel geometry as an alternative to straight channels can reduce its size significantly, the applicability of available correlations (e.g. 0.7 < P r < 2.2) for the zigzag channel geometries is limited to the operational range of recuperators only. The current study, therefore, aims to develop correlations and understating of the complex flow and heat transfer characteristics in the zigzag channel printed circuit heat exchangers (PCHEs) operating under precooler conditions (2.2 < P r < 13) of supercritical carbon dioxide Brayton cycle (s C O 2 - B C). Thermal and hydraulic characteristics of the PCHEs are computed numerically for a wide range of Reynolds numbers (5000 < R e < 7000) and Prandtl number (2.2 < P r < 13). Also, a new data reduction method based on segmental averaged values has been proposed to handle adverse variations in the thermophysical properties of C O 2 under precooler conditions. To ensure accurate evaluations, steep variations in the thermophysical properties of C O 2 are implemented by supplying high-resolution real gas (RGP) property tables. Results suggest that thermal and hydraulic characteristics associated with zigzag channel vary substantially along the length of heat exchanger thus the conventional data reduction methods based on the channel average values cannot be used for true evaluations. Instead, segmental average values are used to develop pressure drop and heat transfer correlations for a broader range of Reynolds number and Prandtl number. The proposed correlations should be useful in the design of compact heat exchanger systems using zigzag channels for a wider range of cooling loads. [ABSTRACT FROM AUTHOR]

• • Two novel multi-pressure evaporation Brayton combined cycles are proposed. • • Detailed modeling is conducted based on a one-dimensional radial turbine. • • Machine learning is employed to streamline the cycle simulations and improve speed. • • Genetic algorithm is utilized for multi-objective cycle optimization. • • Detailed analysis of the proposed cycles, based on thermal and exergy, is conducted. The Supercritical Carbon Dioxide Brayton combined cycle is one of the most important ways to enhance the performance of the cycle. Since the considerable exergy loss resulting from large temperature differences in the heat exchangers of combined cycles, the multi-pressure evaporation concept was adopted from Organic Rankine cycle research. Two novel multi-pressure evaporation configurations, namely parallel evaporation Brayton combined cycle and series evaporation Brayton combined cycle, are designed with the purpose of enhancing SCO 2 Brayton cycle performance. The performance of the two new cycles was compared with that of the baseline cycle. Moreover, Printed Circuit Heat Exchangers were employed to improve the overall compactness of the cycles. The results from model calculations were utilized to train an Artificial intelligence neural network model using machine learning techniques which allowed to simplify the cycle and improves the computational speed. Subsequently, genetic algorithm was employed to conduct multi-objective optimization on the three cycles. Finally, a detailed exploration was conducted from the perspective of thermal and exergy to elucidate the reasons for the advantages and differences between the two new cycles compared to the baseline cycle. The results indicate that the series Brayton combined cycle exhibits the highest performance, and the combined cycle of multi-pressure evaporation helps to improve the performance of the combined cycle. Compared to the baseline cycle, the combined cycle efficiency of both series and parallel combined cycles has increased from 45.54% to 46.18% and 46.29%, respectively, while the bottom cycle efficiency has improved from 3.81% to 4.93% and 5.03%. The ratio of heat exchange area to net output power increased from 0.6051 to 0.6614 and 0.6740 for the parallel and series cycles, respectively. Thermal analysis shows that, the fundamental purpose of changing the layout is to improve the specific power per unit of working medium in the cycle. Exergy analysis shows that, the two new combined cycles improve cycle efficiency by reducing exergy losses in the intermediate heat exchanger. Compared to the parallel version, the series version's staged compression allows for a lower temperature difference in intermediate heat exchanger 1, resulting in smaller exergy losses and higher cycle efficiency. This work will contribute to an enhanced understanding of Supercritical Carbon Dioxide combined cycles within the academic community and the introduction of multi-pressure evaporation will further improve the performance of these important cycles. [ABSTRACT FROM AUTHOR]

Abstract: In a recent paper, Gui et al. (2008. DEM-LES study of 3-D bubbling fluidized bed with immersed tubes. Chemical Engineering Science 63, 3654–3663) reported the results of numerical simulations of a bubbling fluidized bed containing internal tubes using discrete element model (DEM) coupled to a large eddy simulation (LES). We comment on the correctness of the numerical set-up regarding the use of LES as well as the worthiness of using a turbulence model for the case of dense two-phase flows. [Copyright &y& Elsevier]

Abstract In natural gas processing plants, acid gas enrichment (AGE) units play a vital role in increasing H 2 S purity in the acid gas feed of sulfur recovery units (SRUs). Moreover, AGE units also produce a CO 2 -rich gas stream that is often vented to atmosphere. If CO 2 purity is sufficiently high, this stream can be used as an injection gas for enhanced oil recovery (EOR) or for sequestration. In hot climates, AGE units operate at significantly low efficiencies owing to the exothermic nature of their operation. Any enhancement in the efficiency can reap significant benefits. In this work, we study the economic and environmental impact of a process scheme wherein a Ranque–Hilsch vortex tube (RHVT) is used as a cooling system for a lean solvent in an AGE unit located in a hot region of the United Arab Emirates. A simulation model is built using the process simulator ProMax® and is validated using plant design data. It is found that reducing the lean solvent temperature increased the purity of H 2 S and CO 2 product streams. At temperatures lower than 25 °C, the inverse occurs as CO 2 absorption becomes favorable thermodynamically. Consequently, a lean solvent temperature of 25 °C is identified to be optimal, thus achieving the lowest energy consumption and carbon footprint, while maintaining high purities of the product gases. At the optimal temperature, the proposed scheme results in steam savings of 13 kg/s (equivalent to 40% reduction in total steam rate). This reduced energy consumption leads to an annual CO 2 footprint reduction of 83.7 million kg (equivalent to 40% reduction in total CO 2 footprint). The optimal lean solvent temperature increases the purity of the H 2 S-rich gas stream (acid gas) to 67.3 mol% compared to its base case value of 45.7 mol%. Further, the purity of CO 2 -rich gas stream increases to 97 mol% compared to its base case value of 89 mol%, thus making it suitable for EOR or sequestration. Economically, the evaluated annual energy savings translate to 11.2 million USD, at a crude oil price of 50 USD. The computed payback period is 1.3 years, thus showing the potential of the proposed process. The process scheme proved to be superior to other commercial alternatives from economic and environmental perspectives. Highlights • A scheme is proposed for cooling the solvent stream in acid gas enrichment unit. • A Model for the proposed scheme is developed using ProMax V 4.0 • Benefits are quantified in terms of monetary savings and CO 2 footprint reduction. • Economic analysis is performed to show the high profitability of the scheme. • Performance of the proposed scheme is compared with that of conventional processes. [ABSTRACT FROM AUTHOR]

Three-dimensional turbulent flow over a circular cylinder performing sinusoidal rotational motions around its axis is investigated using Large Eddy Simulation (LES). The simulation is carried out for Reynolds number equal to 3900 with rotation rate ( Ω = θ osc * r ∕ U 0 , where θ osc is oscillation amplitude, r cylinder radius, and U 0 flow velocity) varying from 0.5 to 2; and with non-dimensional forcing frequencies (ratio of the frequency of the cylinder oscillation and that of the vortex-shedding from a stationary cylinder) from 0 to 8. Time-averaged flow parameters as well as mean drag and lift coefficients, mean base pressure coefficient, and separation angle and mean length of the vortex formation region are obtained and thoroughly analyzed. It was found that under forcing control, 50% of drag reduction was achieved and the flow three-dimensionality was reduced in the lock-on range. [ABSTRACT FROM AUTHOR]

Large amounts of H 2 S are produced globally, mostly from the gas sweetening process of sour natural gas. H 2 S is usually considered to be an industrial waste product but has been identified as a resource for hydrogen and sulfur in recent years to render sweet gas production a cleaner process. In this study, thermal decomposition of H 2 S into hydrogen and sulfur was studied using a process simulator: ProMax ® . A commercial SRU (sulfur recovery unit), located in the region of Abu Dhabi, together with the H 2 S splitting scheme of the Alberta Sulfur Research Limited were modeled and validated using plant data and field test results, respectively. With the net amount fraction of the acid gas feed to cracking coils (split amount fraction) considered as the controlling parameter, its effect on hydrogen production, thermal reactor energy requirement, burner flame stability, steam production, Claus reactors' temperature and sulfur recovery of the primary SRU were investigated using the integrated model and plant data. Reduction in sulfur recovery of about 0.31% of the primary SRU was recorded as a result of the retrofit for a split amount fraction of 0.245. However, optimization of the integrated model proved that the sulfur recovery could be restored to its initial value of 98.67%. Cost estimation analysis of the retrofit indicates that the capital investment could be recovered in less than four years. [ABSTRACT FROM AUTHOR]

• Design of the PCHEs with zigzag channels is evaluated under the precooler's conditions of sC O 2 - B C. • The impact of the various parameters on the design of the precooler is evaluated and rationalized. • The proposed segmental averaged data reduction method is found suitable for precoolers. • Complicated flow and heat transfer characteristics in precooler are examined and explained. • The effect of the precooler's pumping power is computed on the cycle's performance. Printed circuit heat exchangers (PCHEs) with zigzag channel geometry have frequently been investigated under recuperator conditions (0.7 < P r < 2.2) of the supercritical carbon dioxide Brayton Cycle (sC O 2 - B C). However, the characteristics of the zigzag channel under precooler conditions (1 < P r < 20) of sC O 2 - B C are still unclear. For this reason, a 3D Reynolds Averaged Navier–Stokes (RANS) model is developed and validated to scrutinize the impact of various parameters on the design of precooler of sC O 2 - B C using zigzag channels. To ensure the accuracy of the numerical model, sharp variations in the thermo-physical properties of carbon dioxide are incorporated by providing high-resolution real gas property (RGP) tables to the solver. Additionally, a new data reduction method is devised and implemented to account for the adverse variations in carbon dioxide's thermophysical properties. Obtained results suggest that choosing smaller design point values for channel mass flow rates of C O 2 reduce the pressure losses significantly; however, the consequent temperature profiles can draw the undesirable pinch point location inside the heat exchanger. Although pinch points can be avoided for precooler using higher channel mass flow rates, such designs are incredibly compact and exhibit poor hydraulic performance. Furthermore, it was found that pressure losses at the cold side were significantly higher in comparison with the hot side. However, it is shown that the hydraulic performance of the cold side can be improved substantially using sandwiched channel configuration without compromising the thermal characteristics of the precooler. [ABSTRACT FROM AUTHOR]

• Experimental and numerical studies on the PDH process in an FBR are conducted. • Numerical predictions with MP-PIC approach agree well with experimental data. • Temperature and WHSV affect the exergy efficiency of the PDH process in the FBR. • Detailed distributions of physical and chemical exergies in the FBR are quantified. Exergy can be used to evaluate energy utilization in chemical industry. Although the analysis of the energy consumption in the propane dehydrogenation (PDH) process is of great importance, there is hardly any study of energy or exergy analysis on this topic so far. Thus, the present study focusses on exergy analysis of the PDH process in a fluidized bed reactor (FBR) with both experimental and numerical methods. It is found that the operating temperature and weight hourly space velocity (WHSV) have a great influence on the exergy efficiency of each gas component and the total exergy efficiency. As the temperature increases from 830 K to 890 K, the conversion of propane increases and the total exergy efficiency of product gases increases from 99.06% to 99.66%. As the WHSV increases from 0.40 h−1 to 1.00 h−1, the conversion of propane decreases and the total exergy efficiency of products gases decreases from 99.38% to 98.88%. Also, numerical predictions based on Multi-Phase Particle-in-Cell (MP-PIC) methodology for the PDH fluidized bed reactor are found to be in a very good agreement with experimental data. Based on the numerical predictions of the flow field, temperature field and gas species concentration distributions, detailed distributions of chemical and physical exergies and total exergy in the fluidized bed reactor are quantified. This has made possible to examine the effects of operating conditions on the exergy efficiency and to better understand physical and chemical phenomena occurring in the FBR. Moreover, the quantitative exergy analysis and exergy distributions in the FBR makes it possible to confidently decide on the right operating conditions and guide efforts to reduce sources of inefficiency in the existing PDH designs and evaluate their economics. [ABSTRACT FROM AUTHOR]

Highlights • DNS was carried out to study the end effects on mass transfer in a packed bed. • DEM-CFD simulation was performed to create packed bed geometries. • Effect of confining wall on end effects in a packed bed was investigated. • Probability and spatial distribution of the computed ‘local’ Sh were developed. Abstract Direct Numerical Simulation (DNS) was performed to investigate the end effects on mass transfer in a packed bed for Reynolds number (Re) ≤ 100. The system considered in this study was naphthalene-air with a Schmidt number (Sc) ∼ 2.52. The location of the spheres’ centers in a randomly packed bed were obtained from Discrete Element Method – Computational Fluid Dynamics (DEM-CFD) simulations. The influence of the confining wall on how packed bed ends affect mass transfer was studied by examining the axial void fraction profile with varying ratio of the column diameter to the particle sphere diameter (D / d). Overall, it was found that the confining wall has a significant impact. The ‘local’ mass transfer coefficient was calculated based on the obtained DNS results and the probability distribution curve and the spatial distribution of the computed ‘local’ Sherwood numbers as function of the ratio X/L (ratio of the height of the active part of the bed to the total height of the bed) were developed to quantify the end effects on mass transfer within packed beds. For a packed bed with no wall effects (D / d = 11), it was found that the end effects can be eliminated by replacing the active particles located at ∼2 sphere diameters from the entrance and ∼1 sphere diameter from the exit by inert particles. [ABSTRACT FROM AUTHOR]

In this paper, mixing in an oscillating column was experimentally and numerically studied as a function of power applied through vibrations. The mixing experiments were performed using phenolphthalein and NaOH solution, and the mixing time was computed using a simple image processing algorithm to track intensity changes implemented in MATLAB. Numerically, the air-solution interface was tracked using the VOF model and the solution was vertically disturbed by oscillating the base of the column. The bottom boundary was treated as a rigid moving boundary and a compiled user-defined function (UDF) was applied to the boundary to impose a sinusoidal displacement of the lower boundary. The interior of the column was assumed to be a deforming body and a dynamic mesh was employed to improve the mesh quality. It was found that the mixing time is highly nonlinear with respect to the applied power. The stability chart mapped in Benjamin and Ursell (1954) by solving a series of Mathieu equations was applied to our system and the behavior of mixing in the vibrating column was interpreted. Pseudo steady states were observed, however they lasted only for few minutes and then switched back to ‘real’ steady states. These findings were supported by the images captured during experiments and numerically-produced iso-surface and contour plots. [ABSTRACT FROM AUTHOR]

In this paper, Direct Numerical Simulation (DNS) was performed to understand the effects of confining walls on mass transfer through a packed bed for laminar regime ( Re ≤ 100). The X , Y and Z coordinates of the center of the spheres in a randomly packed bed with varying ratios D/d ( D is the diameter of the column and d is the diameter of the particle) were generated using a Discrete Element Method - Computational Fluid Dynamics (DEM-CFD) code. Naphthalene-air system (Sc ∼ 2.52) was considered for all the cases. The grid resolution, method and boundary conditions were validated by comparing the computed (overall) Sherwood number with the published experimental data. Local Sherwood number was computed around each particle for all ratios, D/d, and spatial and probability distributions throughout the packed bed column as a function of D/d are reported. It was observed that for D/d’s ≤ 8.6, the effects of wall on particle’s Sherwood number was evident, while for D/d’s ≥ 10.8, the Sherwood number was predominantly uniform all through the column. [ABSTRACT FROM AUTHOR]

High-profit-margin gas plants are often challenged by low crude price and fluctuations in processed natural gas quality and quantities demanded by markets. A more challenging factor is the rapid variation in the demand of the products across gas supply chain. These challenges require high operational flexibility across the supply chain to adapt its product portfolio to the market-changes. To this end, optimization of the entire supply chain is highly essential to address these pressing challenges. This paper details an optimization analysis of a countrywide gas supply chain typical to the Middle East region. A unified optimization model that encompasses all the supply chain components is formulated. The model, in its most general form, comprises of 446 decision variables and 190 constraints, which is solved using an evolutionary algorithm. The key application of the proposed model is that it can be used in assessing the optimum allocation of the gas across the various layers of supply chain to maximize countrywide total profit. The model shows that an increase of 3% in profit can be achieved. The model is also used to predict future gas allocations under different scenarios based on fifteen-year profile of gas profiles, costs, product yields and contractual terms. • Optimization model is setup to enhance the net profit of a country-wide gas complex. • Large-scale optimization model is solved using an evolutionary algorithm. • Case studies are investigated under present and future scenarios. • New pathways for gas-allocation are proposed based on optimization analysis. • Model results show an increase of at least 3% in the net profit. [ABSTRACT FROM AUTHOR]

During the treatment or transport of natural gas, the presence of water, even in very small quantities, can trigger hydrates formation that causes plugging of gas lines and cryogenic exchangers and even irreversible damages to expansion valves, turbo expanders and other key equipment. Hence, the need for a timely control and monitoring of gas hydrate formation conditions is crucial. This work presents a two-legged approach that combines thermodynamics and artificial neural network modeling to enhance the accuracy with which hydrates formation conditions are predicted particularly for gas mixture systems. For the latter, Van der Waals-Platteeuw thermodynamic model proves very inaccurate. To improve the accuracy of its predictions, an additional corrective term has been approximated using a trained network of artificial neurons. The validation of this approach using a database of 4660 data points shows a significant decrease in the overall relative error on the pressure from around 23.75%–3.15%. The approach can be extended for more complicated systems and for the prediction of other thermodynamics properties related to the formation of hydrates. • Control and monitoring of gas hydrate formation conditions is crucial. • Van der Waals-Platteeuw thermodynamic model proves inaccurate for gas mixture systems. • An additional corrective term has been approximated to improve accuracy. • A trained Artificial Neuron network is deployed for that purpose. • A significant decrease in the overall relative error on the pressure is achieved. [ABSTRACT FROM AUTHOR]