Abdallah S. Berrouk

Experimental measurements and large eddy simulation of expiratory droplet dispersion in a mechanically ventilated enclosure with thermal effects

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.

Effects of residence time on selective absorption of hydrogen sulphide using methyldiethanolamine

Selective absorption of hydrogen sulphide (H 2 S) using methyldiethanolamine (MDEA) has become a point of interest as means of minimising capital and operating costs of gas sweetening plants. This paper discusses the prominence of optimum design of column internals to best achieve H 2 S selectivity using MDEA. To this end, a kinetics-based process simulation model has been developed for a commercial gas sweetening unit. Trends of sweet gas H 2 S and CO 2 contents as function of fraction active area (and hence residence time) have been explained through analysis of interdependent heat and mass transfer phenomena. Guidelines for column internals design in order to achieve desired degree of H 2 S selectivity are provided. Also, the effectiveness of various operating conditions in achieving H 2 S selectivity for an industrial absorber with fixed internals is investigated.

Multiobjective Optimization of a Benfield HiPure Gas Sweetening Unit

We show how a multiobjective bare-bones particle swarm optimization can be used for a process parameter tuning and performance enhancement of a natural gas sweetening unit. This has been made through maximization of hydrocarbon recovery and minimization of the total energy of the process as the two objectives of the optimization. A trade-off exists between these two objectives as illustrated by the Pareto front. This algorithm has been applied to a sweetening unit that uses the Benfield HiPure process. Detailed models of the natural gas unit are developed in ProMax process simulator and integrated to the multi-objective optimization developed in visual basic environment (VBA). In this study, the solvent circulation rates, stripper pressure and reboiler duties are considered as the decision variables while hydrogen sulfide and carbon dioxide concentrations in the sweetened gas are considered as process constraints. The upper and lower bounds of the decision variables are obtained through a parametric sensitivity analysis of the models. The Pareto sets show a significant improvement in hydrocarbon recovery and a decent reduction in the heat consumption of the process.

Tackling increased CO2 concentration in feeds for existing acid gas removal units: A simulation study based on a customized CO2 kinetics model

ABSTRACT A Middle East-based amine sweetening unit, with an overall capacity of about 2.2 BSCFD of gas, is among the world’s largest process plants and currently processes sour gas with 10 mol% of hydrogen sulfide (H2S) and carbon dioxide (CO2) put together. Current expectation is that acid gas contents in the feed may increase beyond the design limit of the plant. The present work is an effort to quantify the effects of the feed gas CO2 increase on the plant and to proffer solutions to handle these effects efficiently. We revised the kinetics of amine-based CO2 absorption correlation of an existing model using real-data-driven parameters re-estimation. Evolutionary technique that employs particle swarm optimization algorithm is used for this purpose. The new CO2 kinetic model is inserted in a first-principle process simulator, ProMax® V4.0, in order to analyze various solutions necessary to mitigate the operational challenges due to increased feed CO2. The process plant with present design and operating conditions is determined to handle up to 8.45 mol% CO2 contents in the sour gas feed. Further results revealed that methyldiethanolamine, diethanolamine, and dimethyl ether propylene glycol (DEPG) could not handle this high feed CO2 challenge, even at maximum (design) steam and solvent usage. However, diglycolamine exclusively renders the solution as it treats high CO2 feed gas efficiently with allowable utility consumption, while satisfying the constraints imposed by product gas specifications.

Advanced Model-Based Optimization of a Commercial Natural Gas Liquid Recovery Unit

Abstract In this paper we use the example of a commercial NGL Plant in Abu Dhabi to explain the practical benefits of Advanced Model-based Optimization. We will describe and show how the key first step in such a study is validation: ensuring that model predictions of key results are matching the actual plant behavior. We will describe how the model is then used to understand the best operational strategies for the facility through modelbased optimization. This demonstrates how the approach used overcomes the limitations of the typical workflow and models used, in particular, the ones based on the Sequential Modular approach. The trial-and-error simulations used in this approach are not only time consuming and error prone but often limited in the operating decisions and constraints that can be considered. We will show how using an Equation Oriented environment overcomes these limitations and allows an optimal solution satisfying all operational and safety constraints to be found using mathematical optimization methods. Finally we will show how this leads to the set-up of operating guidelines to allow operators to drive the plant towards optimal operation; giving them the ability to respond to changes in the plant or economic conditions quicker and with more confidence than previously possible.

Process simulation-based optimization of a commercial amine gas sweetening unit

C fluid transport in the subsurface is important for secondary oil recovery, geothermal heat mining and proppant placement in fractured reservoirs. Limiting fluid loss through fractures in the formation is important for preventing bypassing of oil rich zones. For unconventional gas, larger fractures need to be selectively propped. The process of orthokinetic agglomeration, whereby particles are aggregated by means of fluid shear, has the potential to selectively narrow or block large fractures. This is achieved by coupling the fracture wall shear rate to the fracture size, where higher shear rates in larger fractures result in higher rates of orthokinetic agglomeration. We estimate the differences in shear rate between fracture sizes and perform laboratory investigations on shear-induced particle growth using commercial well mud particulates. Particle growth rates peak at a shear rate of 275s-1. This maximum shows that it is possible to selectively grow particles based on shear. We also show that the availability of precipitating ions act as “glue” maintaining newly formed agglomerates, suggesting the importance of solution chemistry in the process.I adsorptive separation processes have been largely employed for separations in the petrochemical industry. Conventional fixed bed adsorption desorptionseparationis a batch process. As opposed to conventional adsorptive separations, continuous adsorptive separation processes, presents advantages in terms of productivity. Simulated Moving Bed (SMB) technology is a highly selective adsorption desorption process of continuous separation which is often employed in the separation of complex mixtures.This technology has been applied over four decades in the petrochemical industry and currently enjoying preparative an production scale separation of sugars, proteins, pharmaceuticals, fine chemicals, flavorings, foods and enantiomers. This work focuses on mathematical modeling and simulation of SMB systems to be used for xylene isomers separation, which is extensively used in petrochemical industries. Production of polyester fibers and polyethylene terephthalate are the main examples. The operation methodology of SMB is highly complex in nature. Therefore, generally, a model-based control scheme is used so as to obtain a stable operation and better understood SMB process. A great deal of theoretical work has been carried out for developing useful simulation procedures for design and process development purposes. There are several models to be used for adsorptive separations whether it is at the analytical scale or at the preparative/ production scale. The ideal model, the equilibrium dispersive model, the transport dispersive model and the general rate (GR) model, which may be also called non-equilibrium model, are the main examples. The GR model is widely acknowledged as being the most comprehensive among such models available in the literature as it accounts for axial dispersion and all the mass transfer resistances, e.g., external mass transfer of solute molecules from bulk phase to the external surface of the adsorbent, diffusion of the solute molecules through the particle, and adsorption-desorption processes on the site of the particles. The solution of the GR model based SMB governing equations involves the employment of advanced numerical techniques. The solution algorithm usually employs linear adsorption isotherm conditions. This is largely due to the highly complex nature of the resulting equations whennon-linear adsorption isotherms integrated into SMB modeling studies. Ozdural et al. proposed a new algorithm for the numerical solution of non-equilibrium packed-bed adsorption with non-linear adsorption isotherms. Contrary to the generally employed practices, this methodology is not governed by the solution of coupled partial differential equations.The number of partial differential equations to be solved reduces to one. In the present study this technique is extended to SMB systems and applied to Langmuir type nonlinear adsorption isotherm model for xylenes. The solution of the present model predicts the concentration profiles of the components along the columns. For separation of xylenes in petrochemical industry, the present non-equilibrium modelling of SMB under non-linear adsorption isotherms allows a strong perspective and facilitates scale-up procedures.Foamability and foam stability are of main concerns in foam displacement for enhanced oil recovery. This work presents the output of systematic laboratory screening of foam ability and foam Stability of several surfactants. The surfactants examined were Brij 700, Triton X-100, Triton X-405, Zonyl FSO, Hitenol H-10, Hitenol H-20, Noigen N-10 and Noigen N-20. Solution salinity and oil presence effects were explored. Foam was generated by sparging Carbon Dioxide gas at a fixed flow rate through surfactants solutions and R5 parameter as suggested by Lunkenheimera and Malysa (2003) were used for foam stability testing. The results indicate the foam ability of all surfactants except for Triton X-405. Zonyl FSO and Hitenol H-10 were superior in term of foam stability with more stability as surfactants concentration increases. Equivalent optimum foam volumes were obtained for both surfactants but at higher concentrations of Hitenol H-10. Increasing solution salinity from 4% to 10% affected the foam stability negatively for low concentration solutions of Zonyl FSO but had no effect on foam stability of Hitenol H-10 solutions. Foam stability and oil displacement efficiency were tested with different concentrations of Zonyl FSO and Hitenol H-10 solutions at 4% salinity. The presence of oil at the volume fraction implemented, affect the stability of the foam columns. The effect depends on the surfactant-type and surfactants concentrations where stability decreases at low Zonyl FSO concentration range and at all concentrations range tested of Hitenol H-10. In case of Zonyl FSO observations indicate that oil stayed in the lamellas skeleton and plateau boarders with no drain out. To the contrary, Hitenol H-10 was able to lift good portion of the oil column but oil was drained out of the foam structure within a short period of time. Volume 1 • Issue 2 • 2019 Copyright

CFD and process simulations of air gasification of plastic wastes in a conical spouted bed gasifier

C fluid transport in the subsurface is important for secondary oil recovery, geothermal heat mining and proppant placement in fractured reservoirs. Limiting fluid loss through fractures in the formation is important for preventing bypassing of oil rich zones. For unconventional gas, larger fractures need to be selectively propped. The process of orthokinetic agglomeration, whereby particles are aggregated by means of fluid shear, has the potential to selectively narrow or block large fractures. This is achieved by coupling the fracture wall shear rate to the fracture size, where higher shear rates in larger fractures result in higher rates of orthokinetic agglomeration. We estimate the differences in shear rate between fracture sizes and perform laboratory investigations on shear-induced particle growth using commercial well mud particulates. Particle growth rates peak at a shear rate of 275s-1. This maximum shows that it is possible to selectively grow particles based on shear. We also show that the availability of precipitating ions act as “glue” maintaining newly formed agglomerates, suggesting the importance of solution chemistry in the process.I adsorptive separation processes have been largely employed for separations in the petrochemical industry. Conventional fixed bed adsorption desorptionseparationis a batch process. As opposed to conventional adsorptive separations, continuous adsorptive separation processes, presents advantages in terms of productivity. Simulated Moving Bed (SMB) technology is a highly selective adsorption desorption process of continuous separation which is often employed in the separation of complex mixtures.This technology has been applied over four decades in the petrochemical industry and currently enjoying preparative an production scale separation of sugars, proteins, pharmaceuticals, fine chemicals, flavorings, foods and enantiomers. This work focuses on mathematical modeling and simulation of SMB systems to be used for xylene isomers separation, which is extensively used in petrochemical industries. Production of polyester fibers and polyethylene terephthalate are the main examples. The operation methodology of SMB is highly complex in nature. Therefore, generally, a model-based control scheme is used so as to obtain a stable operation and better understood SMB process. A great deal of theoretical work has been carried out for developing useful simulation procedures for design and process development purposes. There are several models to be used for adsorptive separations whether it is at the analytical scale or at the preparative/ production scale. The ideal model, the equilibrium dispersive model, the transport dispersive model and the general rate (GR) model, which may be also called non-equilibrium model, are the main examples. The GR model is widely acknowledged as being the most comprehensive among such models available in the literature as it accounts for axial dispersion and all the mass transfer resistances, e.g., external mass transfer of solute molecules from bulk phase to the external surface of the adsorbent, diffusion of the solute molecules through the particle, and adsorption-desorption processes on the site of the particles. The solution of the GR model based SMB governing equations involves the employment of advanced numerical techniques. The solution algorithm usually employs linear adsorption isotherm conditions. This is largely due to the highly complex nature of the resulting equations whennon-linear adsorption isotherms integrated into SMB modeling studies. Ozdural et al. proposed a new algorithm for the numerical solution of non-equilibrium packed-bed adsorption with non-linear adsorption isotherms. Contrary to the generally employed practices, this methodology is not governed by the solution of coupled partial differential equations.The number of partial differential equations to be solved reduces to one. In the present study this technique is extended to SMB systems and applied to Langmuir type nonlinear adsorption isotherm model for xylenes. The solution of the present model predicts the concentration profiles of the components along the columns. For separation of xylenes in petrochemical industry, the present non-equilibrium modelling of SMB under non-linear adsorption isotherms allows a strong perspective and facilitates scale-up procedures.Foamability and foam stability are of main concerns in foam displacement for enhanced oil recovery. This work presents the output of systematic laboratory screening of foam ability and foam Stability of several surfactants. The surfactants examined were Brij 700, Triton X-100, Triton X-405, Zonyl FSO, Hitenol H-10, Hitenol H-20, Noigen N-10 and Noigen N-20. Solution salinity and oil presence effects were explored. Foam was generated by sparging Carbon Dioxide gas at a fixed flow rate through surfactants solutions and R5 parameter as suggested by Lunkenheimera and Malysa (2003) were used for foam stability testing. The results indicate the foam ability of all surfactants except for Triton X-405. Zonyl FSO and Hitenol H-10 were superior in term of foam stability with more stability as surfactants concentration increases. Equivalent optimum foam volumes were obtained for both surfactants but at higher concentrations of Hitenol H-10. Increasing solution salinity from 4% to 10% affected the foam stability negatively for low concentration solutions of Zonyl FSO but had no effect on foam stability of Hitenol H-10 solutions. Foam stability and oil displacement efficiency were tested with different concentrations of Zonyl FSO and Hitenol H-10 solutions at 4% salinity. The presence of oil at the volume fraction implemented, affect the stability of the foam columns. The effect depends on the surfactant-type and surfactants concentrations where stability decreases at low Zonyl FSO concentration range and at all concentrations range tested of Hitenol H-10. In case of Zonyl FSO observations indicate that oil stayed in the lamellas skeleton and plateau boarders with no drain out. To the contrary, Hitenol H-10 was able to lift good portion of the oil column but oil was drained out of the foam structure within a short period of time. Volume 1 • Issue 2 • 2019 Copyright

Stochastic Large Eddy Simulation of Bluff-Body Two-Way-Coupled Gas-Particle Turbulent Flow

With the steady increase in computing power, there have been numerous efforts to numerically quantify turbulence modulation by inertial particles. However, highly resolving the flow around thousands to millions of particles to get an accurate particle/turbulence interaction has been prohibited by the number of grid points required. Thus, physical models have been developed and “plugged” to well-resolved numerical simulations to render prediction of turbulence modulation tractable. In this work, flow turbulence modulation by dispersed solid particles in a bluff body was studied using two-way-coupled stochastic large eddy simulation. Point-force scheme was used to model the inertial particle back effects on the fluid motion. The fluid velocity field seen by inertial particles was stochastically constructed based on the filtered flow field obtained from well resolved large eddy simulations. For that purpose a Langevin-type stochastic diffusion process was used with the necessary modifications to account for particle inertia, cross-trajectory effects and the two-way coupling. The numerical results regarding mean and turbulence statistics for the fluid phase show a very good agreement with the experimental findings for both low and high mass loadings (22% and 110% respectively). This numerical investigation demonstrates also the ability of the stochastic-LES-particle approach to predict turbulence modification by inertial particles.Copyright