SMX Static Mixer Research Articles

Numerical Simulation of the Mixing and Salt Washing Effects of a Static Mixer in an Electric Desalination Process

Electric desalination units in the crude oil refining process are becoming increasingly important with the growing trend towards heavy and poor crude oils. The oil–water mixing effect of the static mixer plays a crucial role in the electric desalination process. The present study investigated the effect of various variables, such as mixer type, number of mixing elements, washing water consumption, and oil viscosity and density on the oil–water mixing efficiency of a static mixer. In addition, this study also analyzed the effect of these variables on the salt washing process that occurs during mixing using a kinetic equation for the dissolution of inorganic salts. The results showed that the number of mixing elements was the most significant variable, followed by the amount of washing water injected. The density of the crude oil had a negligible effect. Based on these results, the use of four mixing elements in the SMX static mixer was recommended. The injection of washing water should be controlled at about 8%, while ensuring that the interfacial tension between oil and water remains below 0.01 N/m. Under these conditions, the salt washing efficiency reached 46.3%. This study provides a theoretical basis for designing static mixers and optimizing their operation in electric desalination processes.

A Novel CFD Model of SMX Static Mixer Used in Advanced Continuous Manufacturing of Active Pharmaceutical Ingredients (API)

A Novel CFD Model of SMX Static Mixer Used in Advanced Continuous Manufacturing of Active Pharmaceutical Ingredients (API)

Laminar mixing of Newtonian and non‐Newtonian fluids in SMX static mixer

AbstractThis report is focused on understanding the mixing performance of Newtonian and non‐Newtonian fluids in an SMX static mixer through computational fluid dynamics (CFD) study in Simcenter STAR‐CCM+. For this, the standard SMX mixer with four mixer elements of radius 26 mm was chosen. The aspect ratio (L/D) was taken as 1. The model constructed was compared using pressure drop ratio values available in literature. First, the design was validated for Newtonian fluid, then for shear‐thinning fluid (non‐Newtonian). Mixing patterns produced through particle tracking approach revealed how blending improved as the fluid moved downstream and interacted with increasing number of mixer elements. A sensitivity study was undertaken to investigate the effect of particle injection mechanism on the mixing process. Two injection methods, vertical and horizontal, were explored to check the influence of injection position on mixing. The results indicate that for the given configuration irrespective of the injection location, at least four mixing elements are needed to achieve good mixing for both Newtonian and shear‐thinning fluids investigated in this study. Statistical reports were used to quantify mixing to understand the mixing behaviour for Newtonian and non‐Newtonian fluids with change in Reynolds number. At high Reynolds number, non‐Newtonian fluids exhibited better mixing abilities. Further, efforts were taken to optimize the various design parameters to produce the most optimum solution with a single mixer element for Newtonian fluid.

On the dispersion dynamics of liquid–liquid surfactant-laden flows in a SMX static mixer

This study aims to elucidate, for the first time, the intricate fundamental physics governing the dispersion dynamics of a surfactant-laden two-phase liquid–liquid system in the well-known SMX static mixer. Following the analysis carried out in the preceding publication to this work (Valdes et al., 2023), a comparative assessment of the most relevant and recurrent deformation and breakup mechanisms is conducted for a 3-drop scenario and then extrapolated to a more industrially-relevant multi-drop set-up. A parametric study on relevant surfactant physico-chemical parameters (i.e., elasticity, sorption kinetics) is undertaken, isolating each property by considering insoluble and soluble surfactants. In addition, the role of Marangoni stresses on the deformation and breakage dynamics is explored. High fidelity, three-dimensional direct numerical simulations coupled with a state-of-the-art hybrid interface capturing algorithm are carried out, providing a wealth of information previously inaccessible via volume-averaged or experimental approaches.

Investigation on mixing characteristics of hydrogen and natural gas fuel based on SMX static mixer

Hydrogen, as a carbon-free fuel, is significantly for replacing fossil fuels and reaching the ultimate goal of carbon neutrality, and is commonly expected to play a major role in future energy supply. Blending hydrogen into natural gas pipeline networks for end-user consumption as a means of delivering pure hydrogen to the market which not only improves the utilization rate of hydrogen energy, but also reduces the cost of hydrogen transportation. A three-dimensional model of the blending the natural gas and hydrogen with SMX mixing elements is developed to obtain homogeneous mixed gas injected into the natural gas pipeline network. The Reynolds-averaged Navier-Stokes (RANS) method is employed to investigate the flow physics in the static mixer, which was verified by experiments. The numerical results are in good agreement with the experimental data. Based on the static mixer model, the coupling relationship between mixing performance and the crucial parameters including the number of mixing elements, operating conditions and hydrogen blending volume fraction is analyzed in detail, and a compromise design scheme is proposed under the studied conditions to improve the mixing performance of natural gas and hydrogen.

Direct numerical simulations of liquid–liquid dispersions in a SMX mixer under different inlet conditions

The internal dynamics of static mixers handling liquid–liquid flows have been comprehensively explored over the past decade. Although the effect of the inlet configuration is often overlooked, a few studies have suggested a relationship between the phases’ initial set-up and the performance of the mixer in terms of the droplet size distribution (DSD). Accordingly, different dispersed phase morphologies at the inlet of a SMX static mixer have been tested and their effect on the overall dispersion performance of the mixer has been evaluated based on the DSD and growth of interfacial area. In particular, three representative scenarios are considered: (1) Isolated cases, where one and three individual droplets are injected, mimicking a controlled syringe injection; (2) Numerous variable-sized droplets, simulating a pre-mixed/dispersed inlet; and (3) Jet inlet, emulating a standard phase injection from a gear pump. In addition, this study provides novel insight into the underlying physics dictating droplet deformation and breakage in SMX mixers for industrially-relevant scenarios. This can be achieved thanks to the massively-parallel high-fidelity three-dimensional direct numerical simulations computed with a robust hybrid front-tracking/level-set algorithm, which provides a wealth of information on intricate interfacial dynamics; this information cannot be obtained via experimental or volume-averaged modelling techniques implemented in past studies.

Optimization of the SMX static mixer types thermal and hydraulic performance by coupling CFD-Genetic Algorithm

The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow field and heat transfer in turbulent flows. Four types of mixers_ namely: twisted tape turbulator, LPD, SMX, and KSM_ were studied at different Reynolds numbers. The validation of numerical results confirmed their agreement with the experimental results in the literature. According to results, twisted tape and SMX had the lowest and highest effects on enhancing heat transfer rate, respectively. However, SMX showed a higher pressure drop than other mixers. Therefore, Genetic Algorithm (GA) was used to optimize its configuration. Design parameters were considered to be number of mixers, Reynolds number and installation angle of plates. Design of Experiments (DoE) method was used to select the design points. In addition, Response Surface Methodology (RSM) and GA were used to conduct optimization process. Maximum heat transfer rate and minimum pressure drop were defined as objective functions. Sensitivity analysis showed that the objective functions represent maximum sensitivity to Reynolds number. GA derived optimum point at the following conditions: Reynolds number = 96,500, number of mixers = 5, central plate's angle = 45o and lateral plates' angle = 49o. The prediction accuracy of optimization algorithm was assessed by simulation and it was proved that it could predict the thermo-fluid performance of the studied mixers with an acceptable accuracy (prediction error < 3%). The thermo-fluid performance of the optimized mixer (SMX-Optimized) showed that it increases heat transfer rate by 1.78 folds compared to bare pipe.

Mixing Efficiency and Residence Time Distributions of a Side-Injection Tubular Reactor Equipped with Static Mixers

Plug flow behavior in tubular reactors is often highly desirable in industry, since it can ensure high productivity, good selectivity, and enhanced heat transfer. To achieve this, good radial mixing combined with poor axial mixing is required: these conditions are quite easy to obtain if the flow regime is turbulent, but they are much more challenging to achieve if the flow is laminar. In this work radial mixing and residence time distributions in a side-injected tubular reactor equipped with a series of Sulzer SMX static mixers were investigated using Computational Fluid Dynamics. It was found that even at low values of Reynolds number the reactor can efficiently satisfy the plug flow conditions, and operative diagrams were determined to foresee the reactor behavior.

Hydrodynamics of gas-liquid dispersion in transparent Sulzer static mixers SMXTM

The gas-liquid hydrodynamics in a Sulzer SMXTM static mixer was investigated in the present work through two different optical techniques: Backlight Shadowgraph Technique (BST) and Particle Image Velocimetry (PIV). 3D printed static mixers were manufactured using transparent plastic in order to provide optical access. The normal-heptane was used as the continuous liquid phase. Three different lengths of mixers and different gaseous nitrogen flow rates were investigated. The flow pattern in an empty tube without the mixing device was used as a reference. Bubble diameter distributions at the inlet and outlet of the SMX mixer were evaluated. The velocity fields inside the mixers were quantified. The gas holdup was also examined. These original results allow to appreciate the SMX static mixer's performance and thus to open new industrial applications involving gas-liquid flows such as striping and purification of liquids by a gas.

Validation of the pressure drop–flow rate relationship predicted by lattice Boltzmann simulations for immiscible liquid–liquid flows through SMX static mixers

Single-phase and two-phase flows through SMX static mixers were modeled using the color-gradient multiphase lattice Boltzmann method and the results were compared with experimental data from the scientific literature. In particular, the relationship between pressure drop and flow rate was investigated for single-phase and immiscible liquid–liquid interfacial systems in laminar and transitional flow regimes. The hydrodynamic simulations of immiscible liquid–liquid flows at various volume fractions accounted for interfacial effects such as coalescence and breakage. Every simulation was performed at a prescribed pressure drop corresponding to the one observed experimentally, and the resulting dimensionless Reynolds number was predicted and compared to the experimental one. Good agreement between simulations and experiments were obtained. From a practical standpoint, it is also shown that the addition of a more viscous dispersed phase in a continuous phase increases the pressure drop at a given Reynolds number in the laminar flow regime. In the transitional flow regime, the results suggest that the addition of a small fraction of the dispersed phase could actually reduce the pressure drop.

Comparative analysis of different static mixers performance by CFD technique: An innovative mixer

Abstract The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD, with Reynolds numbers ranging from 20 to 160. The performance of the new mixer is compared with those of Kenics, SMX, and Komax static mixers. The pressure drop ratio (Z-factor), coefficient of variation (CoV), and extensional efficiency (α) features have been used to evaluate power consumption, distributive mixing, and dispersive mixing performances, respectively, in all mixers. The model is firstly validated based on experimental data measured for the pressure drop ratio and the coefficient of variation. CFD results are consistent with measured data and those obtained by available correlations in the literature. The new mixer shows a superior mixing performance compared to the other mixers.

Process intensification in a chaotic SMX static mixer to achieve an energy-efficient mixing operation of non-newtonian fluids

The purpose of this novel research was to intensify the mixing performance in a chaotic SMX static mixer at the lower primary flow rates of a yield pseudoplastic fluid. Since lower primary flow rates require less power consumption, this study enlightens the energy-efficient mixing in a chaotic SMX static mixer through the intensification of fluid deformation. Electrical resistance tomography (ERT) and computational fluid dynamics (CFD) techniques were utilized to achieve the objectives of this work. The CFD flow model was validated using the ERT tomograms, experimental pressure drop data, the secondary fluid concentration profile, and the mixing index. The species model was used to study the distribution of the secondary fluid concentration in the primary fluid. The effect of the secondary-to-primary velocity ratio on the degree of fluid deformation caused by the secondary fluid was investigated. The Newtonian secondary fluid (water) deformed the yield-pseudoplastic primary fluid more effectively than the non-Newtonian secondary fluid (0.5wt% xanthan gum solution). Our results revealed that a more uniform radial dispersion of the secondary fluid in the primary fluid was attained through the intensification of fluid deformation at a higher secondary-to-primary velocity ratio.

Efficient mixing of yield-pseudoplastic fluids at low Reynolds numbers in the chaotic SMX static mixer

Complex rheology of non-Newtonian fluids often leads to non-homogenous mixing due to the spatial viscosity gradients. The non-intrusive electrical resistance tomography (ERT) technique was employed to study the mixing of non-Newtonian fluids in a chaotic SMX static mixer. For the first time, the effect of the rheology of the yield-pseudoplastic fluids on the quality of distributive mixing was explored in this study. The non-Newtonian fluid used in this study was the xanthan gum solution, which is a yield-pseudoplastic fluid obeying the Herschel-Bulkley model and its rheological parameters change as the solution mass concentration increases. The tomography images were utilized to investigate the efficacy of the distributive mixing of two different types of the secondary streams (Newtonian and non-Newtonian) in the primary stream of xanthan gum solutions (0.5wt%, 1.0wt%, and 1.5wt%). Experiments were conducted for three different primary flow rates ranging from 3.5L/min to 12.5L/min while keeping the center-line injection of secondary stream fixed at 100mL/min for all experiments. Our results revealed that the Newtonian secondary stream favored effective axial mixing over the non-Newtonian secondary stream. However, interestingly, for both types of the secondary streams, a more effective radial mixing was observed as the xanthan gum mass concentration increased at low Reynolds numbers.

Laminar mixing in a SMX static mixer evaluated by positron emission particle tracking (PEPT) and magnetic resonance imaging (MRI)

Static mixers are implemented across many industries and are used for mixing, heating and reacting processes. This paper reports the combined use of positron emission particle tracking (PEPT) and magnetic resonance imaging (MRI) to assess mixing in the industrially important SMX static mixer geometry. The focus of this study was distributive mixing for a Newtonian fluid, glycerol, flowing in the laminar regime in the standard SMX static mixer. By implementing PEPT and MRI techniques, the work elucidated mixing indices that incorporate both local velocities and concentration fields within the structure of the mixer element at 0.5mm intervals over a length of nine 1.0L/D SMX elements. The experimental results are placed in context with previously published computational studies for this geometry.

A study of mixing performance of polyacrylamide solutions in a new-type static mixer combination

In this paper, the performance of a Kenics and SMX static mixer combination is investigated with regard to the specialty of tertiary oil recovery. The experiment has the same scale with industrial process as the diameter of test static mixers are 50mm and the effective length are 1500mm. The experiment mainly focuses on degradation of polyacrylamide solutions of different concentrations and different relative molecular mass, the pressure drop of the static mixer combination and mixing performance of polyacrylamide solutions through the static mixer combination. The experimental results show that the degradation rate of polyacrylamide solutions and non-uniformity degree are positively related to polyacrylamide solution concentrations, relative molecular mass of polyacrylamide and liquid phase flow rate. With more solvent distributed among the macromolecular chain entanglements, the flow resistance of macromolecules is reduced, which leads to the reduction of the viscosity of HPAM solution. This phenomenon mainly accounts for the degradation of polyacrylamide solutions. In this study, the pressure drop of the static mixer combination and non-uniformity degree of product solution have obvious advantages compared with other static mixers used in the same way. The results show that the static mixer combination is very suitable for mixing process of polymer solution and water from oilfield.

Rheological properties of food foams produced by SMX static mixers

The objective of this work is to produce food foams in a continuous process while maintaining the required end-use properties of the foams such as stability and adequate texture.Foams are elaborated from liquid bases formulated with 3 wt% whey protein isolates as surfactant and xanthan gum (0.35–0.6 wt %) as thickener. A previous work with SMX™ 10 static mixer (Sulzer™) managed to produce foams with air fractions in the range [0.85–0.94], but the target range of the air fraction in food products is [0.5–0.8].This work aims at reducing bubbles size in the matrix in order to develop the interface and therefore to consolidate the structure. A static mixer of smaller size, the SMX+™ 6, is then used to increase the shear rate, and is compared to the SMX™ 10. The effect of the viscosity of the matrix is also investigated by using different formulations. The air fractions obtained are between 0.72 and 0.84, which is more relevant for food applications. The rheological analyses of foams are carried out by flow curves and viscoelasticity in the linear domain.It is shown that the foam shear viscosity ranks in the same order as the liquid base one, and that the yield stress and elastic modulus are in fair agreement with models of the literature.

Laminar liquid–liquid dispersion in the SMX static mixer

The liquid–liquid dispersion of two immiscible viscous fluids was studied in an SMX static mixer in the laminar flow regime. The dispersed and continuous liquid phases were silicone oils and aqueous solutions of high fructose corn syrup, respectively. Several different phase viscosities were used and the effect of interfacial tension was examined by adding different concentrations of sodium dodecyl sulphate in the aqueous phase. Flow rates of the two phases were varied, and the effect of the volume fraction (holdup) of dispersed phase was explored for a few cases. The droplets were photographed with backlighting and the images were analysed using the Hough transform method. The drop size distributions for each set of conditions were typically obtained on the basis of about 200 images. Mean drop size was expressed as the mass mean diameter D43.It was found that the “tail” at the higher end of the droplet size distribution decreased with increasing superficial velocity and continuous phase viscosities and the same effect was seen in the values of D43. It was also found that D43 decreased with lowering of the interfacial tension. The effect of the dispersed phase viscosity was significant only at non-zero surfactant concentrations. The holdup was found to have a minimal effect on D43.A two-stage breakup model has been developed relating D43 to the capillary number. The model uses the concept that primary drops are formed near the entry to the mixer, with a size determined by the spacing between the cross bars in the element. They are then further broken up by a hydrodynamic mechanism based on an energy balance between the energy input due to the viscous flow, and the surface energy increase due to the breakup of the primary drops. This model provides an approximate basis for correlating the data on D43.

Experimental Study of Turbulence Properties in a SMX Mixer

The three-dimensional pulsating velocity distribution of fluid in the three different structure of SMX static mixers were measured by using laser Doppler velocimetry. The results show that the three different structure of SMX static mixers all have good turbulent reinforcement. Especially in the third and the fourth elements are more obvious. The pulse RSM after them gets stability in the main. With the increase of inlet flow, not only the pulse of axial speed increase ,but also the pulse RSM of axial speed and turbulent energy are approximate linear increase .

Dispersed two-phase flow analysis by pulsed ultrasonic velocimetry in SMX static mixer

Dispersed two-phase flow was experimentally investigated, by pulsed ultrasonic velocimetry (PUV) technique, in Sulzer SMX static mixers for turbulent flow regimes (2280<ReP<7980). Data are reported for oil/water ratio of ϕ=1%, 5% and 30% upstream, downstream and within the static mixer. Turbulence intensity as well as rate of mixing were tracked as function of Reynolds number. Most related studies considered the aspect of macromixing, by extracting the residence time distribution (RTD) of mixers which cannot properly reveal the complicated flow characteristics. Furthermore the information regarding micromixing efficiency in a static mixer is still lacking in the literature. In this work a global approach, based on the average and maximum velocity values and turbulence intensity, to estimate the time scale and process governing the mixing in the Sulzer SMX static mixer is discussed.

Flow regimes and drop break-up in SMX and packed bed static mixers

We present experimental investigations with SMX and packed bed (PBM) static mixers for power consumption during steady flow of Newtonian fluids and liquid–liquid dispersion in turbulent flow. Newton (Ne) and Reynolds (Re) numbers for obtaining power characteristics were calculated based on interstitial flow in the static mixers. The proposed correlations agreed well with those in literature and showed that at very high Re, meaning in fully turbulent flow, Ne for PBM is almost half of that for SMX. Furthermore, PBM and SMX were compared by measuring drop size distributions and pressure drops during formation of oil-in-water emulsions with different flow rates and residence times, the latter being varied by passing emulsions several times through static mixers of different lengths. The prediction of median drop diameter in terms of Weber (We) and Newton numbers using Kolmogorov–Hinze theory for isotropic turbulent-inertial flow regime involving specific energy dissipation rate is found to be valid only for SMX static mixer. In contrast, the turbulent flow is anisotropic in PBM resulting in higher exponents of We and Ne than theoretically predicted. In addition, the use of short static mixers enabled to present models including an empirical term to account for kinetic effects. However, the median diameters of drops formed in SMX and PBM are about the same at a given specific energy dissipation rate, even though the corresponding volume flow rate is higher in SMX than that in PBM.