Fuzzy Comprehensive Analysis of Static Mixers Used for Selective Catalytic Reduction in Diesel Engines

The proper selection of a relevant mixer generally requires an effective assessment of several models against theapplication requirements. This is a complex task, as traditional evaluation methods generally focus only on a single aspect of performance, such as pressure loss, mixing characteristics, or heat transfer. This study assesses aurea-based selective catalytic reduction (SCR) system installed on a ship, where the installation space is limitedand the distance between the urea aqueous solution injection position and the reactor is low;therefore, the staticmixer installed in this pipeline has special performance requirements. In particular, four evaluation indices areused in this study: The B value, C value, pressure loss correction factor (Z′), and the ratio of the required distanceto the equivalent diameter of the pipe (LV/D) when the velocity field after the mixer attains uniformity. Six typesof static mixers were simulated with varying concentrations, flow speeds, and positions. A fuzzy comprehensiveevaluation method was introduced to evaluate and compare the related advantages and disadvantages. The resultsshowed that 1) mixing performance was related to the shape of the mixer and had no direct relationship with flowvelocity. 2) For the same mixer position, the lower the urea concentration, the greater the difficulty of evenly mixing the solution. 3) At a constant urea concentration, the mixing performance improved when the mixer was closer to the injection inlet. 4) The installation of a GK mixer in the SCR system of a 9L20C diesel engine was best.

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

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.

Transfer Characteristics in Mechanically Stirred Airlift Loop Reactors with or without Static Mixers

The mechanically stirred internal loop airlift reactors equipped with or without static mixers are devised for intensification of gas-liquid mass transfer rate. The influences of superficial gas velocity, agitation or static mixers on gas hold-up, mixing time, liquid circulating velocity and volumetric mass transfer coefficient have been investigated with tap water and carboxymethyl cellulose (CMC) aqueous solution. The experimental results indicate that mechanical agitation is more efficacious than static mixer in highly viscous media for improving mass transfer in airlift reactors. The empirical correlation of volumetric mass transfer coefficient with apparent viscosity, and energy consumption for mechanical agitation and aeration is developed.

CFD-PBM coupled modeling of the liquid-liquid dispersion characteristics and structure optimization for Kenics static mixer

Kenics static mixers(KSM)are extensively used in industrial mixing-reaction processes by virtue of high mixing efficiency,low power homogenization and easy continuous production.Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM.In this work,a computational fluid dynamics-population balance model(CFD-PBM)coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution,to further reveal the liquid-liquid dispersion characteristics.Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation,reducing Sauter mean diameter(SMD)of dispersed phase droplets and with a shift in droplet size distribution(DSD)towards smaller size.Smaller aspect ratios,greater blade twist and assembly angles amplify shear rate,leading to smaller droplet size and a narrower DSD in the smaller range.The degree of impact exerted by the aspect ratio is notably greater.Notably,mixing elements with different spin enhance shear and stretching efficiency.Compared to the same spin,SMD becomes 3.7-5.8 times smaller in the smaller size range with a significantly narrower distribution.Taking into account the pressure drop and efficiency in a comprehensive manner,optimized structural parameters for the mixing element encompass an aspect ratio of 1-1.5,a blade twist angle of 180°,an assembly angle of 90°,and interlaced assembly of adjacent elements with different spin.This work provides vital theoretical underpinning and future reference for enhancing KSM performance.

Combined static mixers for high viscous fluids mixing

A new static mixer Cross-over-Disc has been invented to strip off the boundary layer and to make strong radial mixing.The pressure drop of Cross-over-Disc is 12–26 times as large as that of empty pipe with equivalent diameter and length.The mixing performance of Cross-over-Disc with 14 elements has been investigated in the viscosity range of 190–250 Pa·s by decoloration method,and the gray analysis of images shows that mixing inhomogeneity is about 7.5%and 9.4%for the mixing ratio of 5∶1 and 10∶1,respectively.Furthermore,mixing inhomogeneity for a combination of static mixing elements(four from Cross-over-Disc and three pairs from Sulzer-type)can be decreased to 2.1%–3.1%within a reasonable range of pressure drop.

Advanced Oxidation Wastewater Treatment of 3 LPS of an Avocado Sauce Company,at Morelia,Michoacan,Mexico

This paper describes the wastewater treatment of 3 liters per second of capacity of discharges of capacity,from the avocado washed,as well as the production of avocado sauce.Effluents were pretreated with a grease and oil trap and contained small amounts of oil and grease,dissolved and total solids,organic matter and trace of organic and inorganic compounds from the vitamins and minerals of avocado.The treatment train is located in an small surface and the train is integrated with coagulation in line with alumina in a static mixer,rapid filtration in two steps,double advanced oxidation with ozone and heterocyclic photocatalysis with a nanofilm of zinc oxide as,photocatalyzer and final adsorption of refractory compounds with activated charcoal.The treated wastewater meets the environmental regulation to urban sewerage discharges of the city,according to the results of a Mexican Certified Laboratory.

The numerical simulation of a new double swirl static mixer for gas reactants mixing

For the nitrogen oxide removal processes,high performance gas mixer is deeply needed for the injection of NH3 or O3.In this study,a new type of double swirl static mixer in gas mixing was investigated using computational fluid dynamics(CFD).The results obtained using Particle Image Velocimetry(PIV)correlated well with the results obtained from simulation.The comparisons in pressure loss between the experimental results and the simulation results showed that the model was suitable and accurate for the simulation of the static mixer.Optimal process conditions and design were investigated.When L/D equaled 4,coefficient of variation(COV)was<5%.The inlet velocity did not affect the distributions of turbulent kinetic energy.In terms of both COV and pressure loss,the inner connector is important in the design of the static mixer.The nozzle length should be set at 4 cm.Taking both COV and pressure loss into consideration,the optimal oblique degree is 450.The averaged kinetic energy changed according to process conditions and design.The new static mixer resulted in improved mixing performance in a more compact design.The new static mixer is more energy efficient compared with other SV static mixers.Therefore,the double swirl static mixer is promising in gas mixing.

Conversion enhancement of tubular fixed-bed reactor for Fischer-Tropsch synthesis using static mixer

Recently, Fischer-Tropsch synthesis （FTS） has become an interesting technology because of its potential role in producing biofuels via Biomass- to-Liquids （BTL） processes. In Fischer-Tropsch （FT） section, biomass-derived syngas, mainly composed of a mixture of carbon monoxide （CO） and hydrogen （H2）, is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure. Fixed-bed reactors are typically used for these processes as conventional FT reactors. The fixed-bed or packed-bed type reactor has its drawbacks, which are heat transfer limitation, i.e. a hot spot problem involved highly exothermic characteristics of FT reaction, and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface. This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved, and led to higher throughput and conversion. The main goal of the research is the enhancement of a fixed-bed reactor, focusing on the application of KenicsTM static mixer insertion in the tubular packed-bed reactor. Two FTS experiments were carried out using two reactors i.e., with and without static mixer insertion within catalytic beds. The modeled syngas used was a mixed gas composed of H2/CO in 2 ： 1 molar ratio that was fed at the rate of 30 mL（STP）·min^- 1 （GHSV ≈ 136 mL·gcat^-1 ·h^-1） into the fixed Ru supported aluminum catalyst bed of weight 13.3 g. The reaction was carried out at 180 ℃ and atmospheric pressure continuously for 36 h for both experiments. Both transient and steady-state conversions （in terms of time on stream） were reported. The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer. In both cases, the values of chain growth probability of hydrocarbon products （α） for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer, respectively.

A novel method of utilizing static mixer to obtain mixing homogeneity of multi-species powders in laser metal deposition

Real-time mixing of multi-species powder challenges Laser Metal Deposition(LMD)of Functionally Graded Materials(FGMs).The current work proposes a novel method of using a static mixer to realize rapid,uniform multi-species powder mixing.Firstly,copper powder and 316L stainless steel powder are selected to complete the powder mixing observation experiment with Scanning Electron Microscope(SEM)and Energy Dispersive Spectrometer(EDS).Secondly,computational fluid dynamics and particle mixing simulation models are used to analyze the flow field and particle motion characteristics in the static mixer.Finally,LMD experiment and metallo-graphic observation are carried out with 316L stainless steel powder and WC powder to verify the feasibility of the static mixer.This study provides a theoretical and practical basis for powder mixing in laser processing with a static mixer.The conclusions can also be applied to other processing fields requiring real-time and uniform mixing of multi-species powders.

Examination of Whey Degreasing by Modified Membrane Filtration

The largest amount of dairy by-products, especially the whey, comes from the manufacture of cheese. The whey proteins are used in several different industry technologies. The forage production is used for animal feeding in the forms of various flours mixed in feeds, and the food industry uses whey proteins as human nutrition, such as different dry soups, infant formulas and supplements. The fat components of whey may inhibit the efficient processing and might impair the use of whey in these technologies. Thus, the aim of the experiment was to investigate a cheap and economical separation of the lipid fraction of whey. This separation method was made by microfiltration, which is an inexpensive, effective and energy efficient method for this task. During the measurements, 0.2 μm and 0.45 μm microfiltration membranes were used in a laboratory tubular membrane filtration module, and the membrane separation method was combined and modified by using astatic mixer and/or air insufflation. The same pore size membranes were used in a vibrating membrane filtration equipment （VSEP）, too. The two different membrane filtration devices allowed the comparison of the effect of vibration and the effect of the static mixer and/or air insufflation. The flux values above 0.2 MPa transmembrane pressures strongly decreased on using the tubular membrane. Therefore, it can be determined that the use of the lower transmembrane pressures gave better flux combined with air insufflation and the use of static mixer. The flux values increased three times higher with using vibration during the microfiltration process than that without vibration. Comparing these methods, it can be concluded that the separation made on tubular membrane （0.2 μm） combined with statics mixer gave sufficient result according to the degreasing, retentions and flux values of the other components.

Comparison between Two Urban Wastewater Primary Treatment Trains

This paper evaluated two different wastewater primary treatments of wastewater from the“Universidad Autonoma Metropolitana,Azcapotzalco Campus”,a conventional one integrated for coagulation,flocculation,sedimentation and filtration versus one alternative integrated for in-line coagulation to precondition to rapid filtration.The wastewater was from the Azcapotzalco Campus in Mexico City,and in both cases,we characterized the wastewater,measured:pH,conductivity,temperature,total dissolved solids,dissolved oxygen,ORP(Oxide Reduction Potential),turbidity,and COD(Chemical Oxygen Demand).Conventional treatment was slightly better treatment,but the alternative treatment represents saving in equipment,reactive,energy and time,so it was considered a viable technical and economic wastewater primary treatment.

Design and Engineering Application of Direct Mixing Lubrication System for Emulsion Pipeline in Secondary Cold Rolling Mill

With the benefit fierce competition in the steel industry market in recent years,double cold reduction products have been developed towards strength improvement and thickness reduction.The traditional cold-rolling lubrication process with a fixed flow rate and concentration cannot solve the problems,which are uncontrollable plate shape and the excessive consumption of lubricating oil.Moreover,based on the analysis of the traditional direct aplication lubrication system of double cold reduction mill,a set of design scheme suitable for the emulsion pipeline direct mixing lubrication system of double cold reduction mill unit was proposed.The design completed the selection of key components,which included the static mixer and atomization nozzle selection,pump and oil pump design selection,pipeline design selection,flow type selection,pressure gauge selection,electronic control cabinet design selection and other eight aspects.Equipment of the emulsion pipeline direct mixing lubrication system of double cold reduction has been developed.Comparing with characteristics of the traditional direct aplication lubrication system,the emulsion pipeline direct mixing lubrication system was better applied to the production practice of a 1220 double cold reduction mill.The consumption of ton of steel was reduced by 9.6%.The rolling energy consumption and fuel consumption comprehensive costs decreased by 10.7%,and the strip steel section thickness difference was reduced by 19.3%.In addition,the plate shape quality defect rate decreased by 25.6%,otherwise creating a large economic benefit for the unit and promoting the application value.

Optimizing flow field in an SCR system of a 600 MW power plant:effects of static mixer alignment style

The fluid flow in a selective catalytic reduction(SCR)system of a 600 MW power station is optimized using the numerical simulation method in this work.Given that guide plates and straightening gratings are properly installed,the relative standard deviation(C_(v))of velocity related to the inlet of an ammonia injection grid(AIG)and catalysts satisfy the engineering demand of<15%,suggesting that a relatively uniform velocity field is obtained.The in-line arrangement of static mixers strengthens the disturbance of fluid,promoting the mixing of reductant NH_(3)with flue gas.The NH_(3)mole fraction C_(v)value correlated to the inlet of catalysts drops to ca.3.5%,which is lower than that in the cases when the mixers are aligned in a staggered style.These results indicate that a solid foundation is achieved for the effective abatement of NO_(x)in practical applications.

In-situ powder mixing for laser-based directed energy deposition of functionally graded materials

The mixing of powders is a highly relevant field under additive manufacturing,however,it has attracted limited interest to date.The in-situ mixing of various powders remains a significant challenge.This paper proposes a new method utilizing a static mixer for the in-situ mixing of multiple powders through the laser-based directed energy deposition(DED)of functionally graded materials.Firstly,a powder-mixing experimental platform was established;WC and 316L powders were selected for the mixing experiments.Secondly,scanning electron microscopy,energy dispersive spectroscopy,and image processing were used to visually evaluate the homogeneity and proportion of the in-situ mixed powder.Furthermore,powder-mixing simulations were conducted to determine the powder-mixing mechanism.In the simulations,a powder carrier gas flow field and particle mixing were employed.Finally,a WC/316L metal matrix composite sample was produced using laser-based DED to verify the application potential of the static mixer.It was found that the static mixer could adjust the powder ratio online,and a response time of 1–2 s should be considered when adjusting the ratio of the mixed powder.A feasible approach for in-situ powder mixing for laser-based DED was demonstrated and investigated,creating the basis for functionally graded materials.

Solvent extraction of Ce(Ⅲ) and Pr(Ⅲ) with P507 using SiC foam as a static mixer

Extraction reactor is a major research area of interest within the field of rare earths extraction and separation.SiC foam offers excellent material characteristics as well as three-dimensional(3-D) reticulated structure;however,very little research has been carried out on its application in extraction reactor so far.In this work,a static mixer reactor based on SiC foam was designed and demonstrated to extract and separate Ce(Ⅲ) and Pr(Ⅲ) from nitric acid media by using 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester(P507) as extractant.The structure-performance relationship between SiC foam and extraction performance was studied by experiment combined with computational fluid dynamics(CFD)simulation.The experiment data are in good agreement with the simulation results.Contrast experiment by using a Kenics mixer was carried out,and SiC foam shows better extraction and mass transfer performance.Using the optimal structural SiC foam(pore size D=2.3 mm,open porosity ε=85%,foam length L=80 mm),high extraction efficiency η(Pr(Ⅲ):94.6%,Ce(Ⅲ):88.5%) and separation factor β(2.27) between Ce(Ⅲ) and Pr(Ⅲ) is achieved at a high total throughput of 200 mL/min.Besides,overall volumetric mass transfer coefficient K_(L)a of Pr(Ⅲ) and Ce(Ⅲ) are 0.519 and 0.378 s^(−1) at the residence time τ of 3.6 s,respectively,which reach the high level of microchannel reactors and are better than conventional extractors and other static mixers.SiC foam is found to be applicable as a static mixer for efficient and high-throughput extraction and separation of rare earths.

Model Tests of Coolant Thermal Mixing in the HTR-10 Hot Gas Plenum

The coolant thermal mixing performance in the hot gas plenum (HGP) in the core bottom reflector of the 10MW high temperature gas-cooled reactor test module (HTR-10) was experimentally investigated on a 1:1.5 scale test model. The experimental results show that the HGP installed with a radial partition static mixer results in excellent thermal mixing of the coolant with a nondimensional temperature mixing degree (ε) value of 94%. Within the Re range from 1. 4 ×105～5. 8×105, the ε value reaches 94% at the outlet of the HGP and 99% at the outlet of the hot gas duct (HGD). There is little influence of the inlet flow rate ratio. Gh/Ge. on the thermal mixing performance in the Gh/Ge range from 0.5～2.0.