Pipe Mixer Research Articles

Optimization of Pretreatment Technology for Produced Water in Gas Field

In view of the problems of low overall operation efficiency, serious corrosion of methanol recovery system and obvious sludge blockage in water injection pipeline, the pretreatment technology of produced water in gas field treatment plant has been optimized and improved. By prolonging the settling time of produced water in the unloading tank and raw water tank, the oil and water in the produced water are fully stratified, and an emulsifier is added when necessary to further separate the oil from the produced water. In winter, heat tracing is added to the pipe mixer or the outer wall of the reactor tank, or a heated pipe mixer is installed to properly heat the liquid, and the produced water is fully and evenly mixed with the medicament, giving full play to the medicament effect, preventing the flocs from precipitating too quickly, thus improving the settlement effect. The relevant process optimization and improvement measures are put forward to provide reference for the pretreatment process of produced water.

A review on modern variants of the partitioned pipe mixer: designs, performances, and applications

A review on modern variants of the partitioned pipe mixer: designs, performances, and applications

Optimization of the Uniformity Index Performance in the Selective Catalytic Reduction System Using a Metamodel

The significance of the selective catalytic reduction system in vehicles increases in line with the high standards of emission control and enhanced selective catalytic reduction efficiency. This study aims to improve the performance of the selective catalytic reduction system through an optimization method using a metamodel. The objective function is defined as the ammonia uniformity index, and the design parameters are defined in relation to the pipe length and mixer related to the chemical reaction of the urea solution. The range of design parameters has been designated by a trial-and-error method in order to maintain the overall design drawings of the selective catalytic reduction system and prevent modeling errors. Three algorithms, namely, ensemble decision tree, Kriging, and radial basis function, are employed to develop the metamodel. The accuracy of the metamodel is verified based on three indicators: the normalized root mean square error, root mean square error, and maximum absolute error. The metamodel is generated using the Kriging model, which has the highest accuracy among the algorithms, and optimization is also performed. The predicted optimization results are confirmed by computational fluid dynamics numerical analysis with a 99.83% match. The ammonia uniformity index is improved by 1.38% compared to the base model, and it can be said that the NOx purification efficiency is improved by 30.95%. Consequently, optimizing the uniformity index performance through structural optimization is of utmost importance. Furthermore, this study reveals that the design variables related to the mixer play a crucial role in the performance. Therefore, using the metamodel to optimize the selectively catalytic reduction system’s structure should be considered significant. Finally, in the future, the analysis model can be validated using test equipment based on the findings of this study.

Optimization of Liquid−Liquid Mixing in a Novel Mixer Based on Hybrid SVR-DE Model

To solve the problem of evenly mixing flocculant and sewage, a new type of two-chamber mechanical pipe mixer was numerically calculated and its working principle was studied by means of the internal flow field. The single factor numerical simulation and analysis of some of the structural parameters in the mixer were carried out to determine the influence of different parameters on the results. Latin hypercube sampling was used to design 100 sets of test tables for the four variables of the branch pipe diameter, sewage flow rate, the installation height of the impeller, and the angle of the deflector. The results were optimized using the SVR-DE algorithm. After optimization, the variation coefficient of export flocculant mixing uniformity was 16.02%, which was increased by 74.94% compared with the initial 63.921%. The power consumption of the impeller was reduced by 8.30%. The concentration curves of the flocculant at different positions of the outlet tube could quickly converge to the target value.

An improved correlation for dry pressure losses across static mixers at high Reynolds numbers

AbstractCorrugated (SMV‐style) static mixers are industrially important for process intensification and can promote gas–liquid mass transfer in processes such as sour gas sweetening. Current correlations for pressure loss are limited to Reynolds numbers (Re) below 40 000, far below the ranges encountered in natural gas systems (105 < Re < 107). An experimental and numerical study of pressure drop across multiple corrugated mixers in the range of 104 < Re <2 × 105 encompassing different configurations (aligned, rotated), pipe diameters (1–4 in.), and sand grain surface roughness values (10–5000 μm) is reported here. Our previous correlation for pressure loss across a single corrugated element is shown to be extendable to multiple corrugated mixing elements. Through the inclusion of mixer tortuosity (τ), porosity (ε), and macro‐scale (geometric) wall roughness (e), the correlation also matches historical pressure drop data (at different τ, ε) reported in literature, thereby demonstrating the utility of these variables as parameters that can help optimize mixer performance. Experiments and computational fluid dynamics (CFD) modelling revealed that the rotated configuration increased the residence time by up to 13% in comparison to the aligned configuration. This may have implications on the selective absorption of sour gas components that are based on fast kinetics. In addition, the role of wall roughness (both pipe housing and mixer) was demonstrated to be significant in this study (accounting for 55% of the pressure losses) and must be accurately accounted for when scaling laboratory measurements.

Flow and mixing analysis of a thixotropic fluid in a barrier-embedded partitioned pipe mixer (BPPM): A numerical study

Flow and mixing characteristics of a thixotropic fluid in a static mixer were numerically investigated in this study. We selected a barrier-embedded partitioned pipe mixer (BPPM) as the model static mixer, whose geometric design parameters are fixed for the simplicity of the analysis. The Moore structure-kinetics model was employed to describe a thixotropic fluid, whose flow and mixing characteristics were systematically analyzed for cases with specific combinations of three dimensionless numbers: the apparent Reynolds number (Rea), thixotropy number (Th), and destruction parameter (kd). The structure parameter (λ) showed a highly reduced value near the barrier tip, where the highest shear deformation occurred. The average λ dramatically decreased with Th as the fluid thixotropy becomes significant. kd is related to the standard deviation of λ because it controls the magnitude of the material derivative of λ. As Rea increased, more complex flow and mixing behaviors were observed, especially at a higher Th. From the qualitative and quantitative analyses of the Poincaré section and flux-weighted intensity of segregation (Id), the mixing performance was seen to improve with Th in the counter-rotational BPPM, while a more complex trend of the degree of mixing was found in the co-rotational BPPM. This study provides a comprehensive understanding of thixotropic fluid mixing with an emphasis on the complex relationship between the flow characteristics and mixing performance.

Flow and mixing characteristics of a groove-embedded partitioned pipe mixer

We propose a groove-embedded partitioned pipe mixer (GPPM) and conduct an in-depth numerical study on the flow and mixing characteristics of the GPPM in the creeping flow regime. The GPPM is a variant of a previously reported mixer, the barrier-embedded partitioned pipe mixer (BPPM), and is designed to achieve better energy-efficient mixing compared to the BPPM. In this paper, we first introduce the working principle of the GPPM and its mixing protocols. Then, the flow system affected by mixing protocols and geometrical parameters of the GPPM is investigated using Poincare sections. As for mixing characteristics, the flux-weighted intensity of segregation is employed for quantitative mixing analysis. It turns out that a GPPM with a proper set of design parameters can indeed lead to a globally chaotic mixing. More importantly, the best GPPM showed better mixing in terms of energy consumption compared to its counterpart, the best BPPM.

Experimental study and numerical simulation of impact factors on spray impingement of urea water solution

The impingement behavior is inevitable during the injection process of urea water solution in selective catalytic reduction aftertreatment system of diesel engine. The impingement contributes to the formation of liquid film on the pipe wall and mixer, and it will block the pipe and reduce the urea water solution decomposition efficiency. In this work, the morphological changes of the spray during the impingement process were captured by the CCD camera. The liquid film development under different injection flow rates, compressed air pressures, injection heights, injection angles and metal wall temperatures were simulated and analyzed by AVL_FIRE. A good agreement with the experiment results is achieved. The results indicate that the liquid film area increases with higher injection flow rate, compressed air pressure, injection height and lower injection angle. According to Kuhnke model, the behaviors of impingement droplets are dominated by the sub-velocity of droplets which is affected by the injection flow rate and injection angle. Higher metal wall temperature can promote the evaporation of the liquid film and droplets, which reduces the liquid film area. It is an effective way to prevent the liquid film formation through rising the metal wall temperature.

Secondary flow mixing of neutralizing reagent induced by U-bent de-ballast pipes

This study proposes a secondary flow mixer for neutralizing reagent in a de-ballast pipe. Because the proposed mixer has a U-bent pipe configuration, it can be fabricated using commercially available pipe parts at low cost. Numerical simulations were conducted with four computational domains: one straight pipe (SP) and three U-bent pipes. The normalized coefficient of variation (CoV/CoV0) values of the U-bent pipe outlet for UP1, UP2 and UP3 were 0.096, 0.036 and 0.015 (90.4%, 96.4% and 98.5% degree of mixing, respectively). Instability was observed in the secondary flow motion because of the continuous curvature change of the U-bent pipe series and the density difference between mixing fluids. This instability enhances the mixing performance. Despite the high mixing quality, the U-bent pipe mixer caused a pressure drop of 0.5–2.1 % compared to the backpressure of a ballast water treatment system.

Numerical study on the mixing in a barrier-embedded partitioned pipe mixer (BPPM) for non-creeping flow conditions

In this paper we investigated numerically the flow and mixing characteristics of the barrier-embedded partitioned pipe mixer (BPPM) in non-creeping flow conditions. Numerical simulations are conducted for three mixing protocols of the BPPM, co-rotational, mirrored co-rotational, and counter-rotational protocols in the range of the Reynolds number (Re), 0.1≤Re≤300, focusing on the effect of the Reynolds number, the barrier height, and the mixing protocols on the mixing in the BPPM. Each mixing protocol creates two crosssectional flow portraits with crossing streamlines. Poincare sections were plotted to investigate the flow system affected by the Reynolds number and the barrier height. Mixing in a specific BPPM is characterized using the intensity of segregation in terms of the compactness and the energy consumption. The dependency of the barrier height and the Reynolds number on the final mixing state of the BPPMs was identified by mixing analyses. The co-rotational protocol results in an efficient mixing in the creeping flow regime. Meanwhile, mirrored co-rotational and counter-rotational protocols, which lead to poor mixing in the creeping flow regime, turned out to be efficient protocols in the higher Reynolds number regime.

Numerical Simulation Study of Self-rotary Blade Pipeline Mixers

According to the requirements of the online mixing, the new type of blade spin-rotary pipe mixer was designed innovatively and the feature of mixer was analyzed by the numerical simulation method. The result shows that the features of mixer with small size, simple structure, small pressure loss, easy maintenance and good mixing effect meet the usage requirements of online mixing.

Chaotic mixing in a barrier‐embedded partitioned pipe mixer

Inspired by the partitioned pipe mixer (PPM), a barrier‐embedded partitioned pipe mixer (BPPM) is designed and analyzed using a numerical simulation scheme. The BPPM is a static mixer, composed of orthogonally connected rectangular plates with a pair of barriers, which divide, stretch, and fold fluid elements, leading to chaotic mixing via the baker's transformation. The aspect ratio of the plate (α) and the dimensionless height of the barrier (β) are chosen as design parameters to conduct a parameter study on the mixing performance. The flow characteristics and mixing performance are analyzed using the cross‐sectional velocity vectors, Poincaré section, interface tracking, and the intensity of segregation. The results indicate that several designs of the BPPM significantly enhance the PPM's mixing performance. The best BPPMs are identified with regard to compactness and energy consumption. © 2017 American Institute of Chemical Engineers AIChE J, 64: 717–729, 2018

Computer simulation of hydraulic flow in a mixing device with a diaphragm of special design installed in it

The results of computer simulation of hydrodynamic flow were presented using the FlowVision software package (Moscow, Russian Federation). This program has enabled creation of hydrodynamic flow models using three types of mixers: a mixer with the proposed diaphragm of special design, a pipe mixer and an orifice mixer. The complete information on behavior of the processes was obtained taking into account design and technological parameters of the abovementioned types of mixers. Computer simulation of flow in mixers of various types made it possible to substantially shorten time for conducting studies and confirm the results of field experiments presented earlier by the authors [11]. As a result of the analysis of the data obtained in the computer simulation of motion of the flow of waste water with the reagent solution, the following can be distinguished: when using different types of mixers, the best results of intensive flow mixing were obtained by using a mixer with a diaphragm of a special design and an orifice mixer. It is evidenced by the diagrams of distribution of pressure and velocities in these mixers. However, when using an orifice mixer, one can notice intensive mixing only at the center of the flow, and zones were noticeable at the walls of the pipeline in which there was practically no vortex formation and mixing respectively. In the pipe mixer, only a small region could be noticed in an immediate vicinity of the point of injection of the coagulant solution. Pressure and velocity vary in this region but these parameters change insignificantly in the main flow. The obtained hydrodynamic models indicate that the proposed diaphragm of a special design provides more efficient mixing of wastewater with the reagent. Models for pipe and orifice mixers have shown worse results. The proposed diaphragm enabled mixing of wastewater with the reagent as fully and quickly as possible.

Electromagnetically induced chaotic mixing in a pipe mixer

A numerical investigation is carried out to study the mixing by chaotic advection in an electromagnetically driven pipe mixer. It consists of a pipe with two inner electrodes which are energized alternatively. An externally applied magnetic field along the flow direction interacts with the local electric currents inducing a spatially varying electromagnetic body force in the model fluid. The system is an extension of Aref's blinking vortex model to three dimensions. The Lagrangian motion of passive tracer particles is numerically simulated to quantify the degree of stirring. The model predictions indicate that the chaotic mixing is strongly dependent on the modified Hartmann number, the electrode switching frequency and the electrode separation distance. A comparison with numerical simulation results obtained using a dimensional model with glass melt shows that the chaotic mixing behavior of the glass melt is very close to the non-dimensional model predictions. The computational results presented here will be useful for developing efficient glass melt homogenisation systems.

Eulerian indicators for predicting and optimizing mixing quality

Many different methods exist for measuring, quantifying and predicting the quality of a mixture resulting from a fluid mixing device. In general, these rely on Lagrangian information from the system, as they involve the evolution of individual trajectories. In this paper, we propose tools that are formulated using only Eulerian information, and yet can predict the Lagrangian mixing properties of a mixing device. The proposed Eulerian indicators are motivated by the recent linked twist map (LTM) formulation of fluid mixing. We describe their features and application in the context of four different fluid flows: the blinking vortex flow and the partitioned pipe mixer (two paradigm flows from the early studies of chaotic mixing), a model of a channel flow containing ‘separatrices’ in the cross-sectional flow (which is a common flow feature in a large number of micromixers), and a flow generated by pulsed source–sink pairs (which has been used as a model for mixing in DNA microarrays).

Selective Condensation Reaction of Phenols and Hydroxybenzyl Alcohol Using Micromixers Based on Collision of Fluid Segments

In the production of bisphenol F, fast mixing and feed operation with a high flow rate ratio of two reactant fluids are crucial for improvement of product selectivity and productivity. To contribute to these issues, we have developed two micromixers, the K-M mixer and the dual pipe mixer. In the K-M mixer, reactant fluids are divided into fluid segments and, then, the segments collide at a single point, where shear is applied to enhance mixing performance. In the dual pipe mixer, one reactant fluid flows in the inner tube and the other fluid flows from the outer tube into the inner tube through the holes pierced on the inner tube wall. By this geometry, the second reactant fluid is divided into several segments, which penetrate into the first reactant fluid. These two mixers realize high mixing performance and can be operated under a high flow rate ratio of two reactant fluids.

Numerical and analytical investigation of barium sulphate crystallization

This paper considers the crystallization of BaSO 4 in turbulent flows using numerical simulations, since many questions are still open for this important process. The corresponding calculations are performed both for steady state and for time-dependent conditions, for homogeneous as well as for mixing-controlled flows. The employed kinetic model has been coupled with a standard method of moments using the first four moments in order to compute the evolution of the crystal population. Assuming a prescribed function shape, for example a Gaussian, this further allows to depict the crystal size distribution (CSD) as a function of time or of the spatial position in the crystallization reactor. Time-dependent simulations in a homogeneous flow are first validated by comparison with the exact solution of the corresponding full reaction kinetic model. After this successful validation, steady-state calculations are performed for a coaxial pipe mixer using two different reference problems available in the literature. The quality of the employed numerical model is first checked by comparing with experimental results from Marchisio et al. (American Institute of Chemical Engineers Journal 48, 2039–2050). Further simulations are then carried out for a second mixing problem (configuration of Wei and Garside (Chemical Engineering Research & Design 75(A2), 219–227)), for which numerical results are available. For this second case, since the numerical methods and physical models used in the present work have been noticeably improved compared to the original publication (finer grid, higher level of convergence, more accurate computation of the activity coefficient … ), considerable differences in the findings are observed. Nevertheless, the coupling of a Computational Fluid Dynamics code (here Fluent 6.1) with the standard method of moments using User-Defined Functions and Scalars, followed by an extensive post-processing of the results leads to a detailed prediction of the obtained CSD for crystallization processes in non-homogeneous turbulent flows.

Numerical investigation of the influence of the activity coefficient on barium sulphate crystallization

We investigate in this paper the influence of the value and computational method for the activity coefficient on the crystallization process of BaSO 4 . We consider for this a mixing-controlled configuration based on a coaxial pipe mixer. The corresponding flow is turbulent and this problem is solved using numerical simulations until reaching steady-state conditions. The precipitation model has been coupled with the method of moments to describe the crystal population, taking the first four moments into account. All supplementary physical models and transport equations have been defined as User-Defined Functions and Scalars and compiled into a commercial Computational Fluid Dynamics code (here Fluent 6.1). The simulations have been performed for various inlet concentrations with different values and models for computing the activity coefficient in order to analyze its influence on the product quantity and on the crystal size distribution at the pipe outlet. The supersaturation ratio, containing the activity coefficient in its definition, is the driving force for the crystallization process. This is the reason why, as concluded from the present results, it is important to model correctly and accurately the activity coefficient in order to obtain reliable data, a point which has been often neglected in the literature. Even relatively small variations of this coefficient can considerably affect the results, in particular for fast reactions.

Chaotic advection in a braided pipe mixer

Chaotic advection is investigated in a “braided pipe mixer” (BPM). This static mixing device consists of an outer pipe containing several intertwining internal pipes, with fluid pumped down the gap. It has recently been proposed, by analogy with the two-dimensional theory of topological chaos, that the BPM should be an effective mixing device, specifically that (i) good mixing might be achieved with only very thin internal pipes, and (ii) the quality of the mixing should be improved if the internal pipes form a mathematical braid. Our results suggest that neither (i) nor (ii) is the case for the BPM studied.

Synchronized EPI phase contrast velocimetry in a mixing reactor

Notwithstanding its widespread use in cardiovascular and functional MRI studies, Echo Planar Imaging (EPI) has only recently been subjected to systematic validation studies. Most velocity measurement studies employing such ultrafast MRI methods involve the use of phantoms characterized by rigid or deformable solid motion. The current implementation involves a rotating phantom (angular velocity up to 10.5 rpm) with a superimposed swirling liquid flow (with axial velocities ranging between 0.145 and 0.27 cm/s) of water doped with copper sulfate. The standard implementation of single-shot EPI with phase contrast velocity encoding allows the complete mapping of the Eulerian velocity field in slices perpendicular to the rotation axis following a subtractive procedure requiring the synchronized acquisition of each velocity component on each selected transverse slice during two revolutions of the rotor. The image acquisition time is 100 ms (per velocity component) at each 64 × 64 slice. In addition to acquiring full-field velocity data for future direct comparisons with other techniques, EPI is employed here for the first time to reconstruct the three-dimensional flow field between the blades of a partitioned pipe mixer.