Effect Of Mixing Rate Research Articles

Effect of mixing rate on molecular structure parameters of polybutadiene rubber based on rheology

Effect of mixing rate on molecular structure parameters of polybutadiene rubber based on rheology

Glycerolysis–interesterification in high-shear reactor using sodium silicate catalyst: effect of mixing rate on reaction kinetics

Glycerolysis–interesterification in high-shear reactor using sodium silicate catalyst: effect of mixing rate on reaction kinetics

Mixing process and nucleation of an Al-Si alloy during controlled diffusion solidification with simultaneous mixing and effect of mixing rate

Mixing process and nucleation of an Al-Si alloy during controlled diffusion solidification with simultaneous mixing and effect of mixing rate

The Effect of Mixing Rate on Performance of Anaerobic Reactor in Methane Production

In this study, a mathematical model was used to predict the dynamic behaviour of the system under conditions of imperfect mixing in an Anaerobic Digestion (AD) process. To evaluate the system performance, the effect of mixing parameters by calculating the quantities of methane gas produced, system power, and effluent quality was investigated. Numerical results showed that with an increase in the mixing rate (α) by 20%, methane production rate, power production, and the effluent COD removal efficiency of the system increased by 19%, 19% and 12%, respectively. At an equal mixing rate, the amount of methane produced in influent with a concentration of 12.1% was 4.5 times higher than the influent with a concentration of 2.5%, while no significant change was observed in the effluent quality. Additionally, it was found that the mixing rate effect is more important than the mean cell retention time in the anaerobic reactor. The best fitted correlations for methane production rate and effluent COD removal efficiency using regression analogy at different organic loads of wastewater are presented.

The effect of mixing rate and gas recirculation on biological CO2 methanation in two-stage CSTR systems

In-situ biological CO2 methanation (BM) in a biogas reactor by the addition of H2 is an attractive low-cost biogas upgrading process, as it does not require investment in a new reactor and can be incorporated into existing biogas plants. On the other hand, maintenance of stable reactor performance during in-situ BM is challenging due to factors such as high H2 partial pressure and CO2 depletion which may lead to an increase in pH. Thus, BM that uses two-serial connected continuous stirred tank reactors (CSTRs) could be an option. For such a process set-up, the second reactor acts as an upgrading reactor (UR) and a secondary CH4 producer for slow-degrading substrates such as straw and manure. In this study, improvement of the BM process was attempted by varying the mixing speed and gas recirculation to enhance hydrogen transfer to the liquid phase of the UR. The experiments showed that the mixing speed and gas recirculation had a significant effect on BM in CSTRs. CH4 production from BM was highest at 170 rpm, but the total CH4 production fell above 140 rpm due to reduced production of CH4 from the manure substrate. The CH4 production rate from CO2 and H2 conversion was further enhanced as the output gas was recirculated at 12.20 mL min−1. Further gas recirculation above 12.20 mL min−1 did not improve BM.

The Effect of Mixing Rate on Struvite Recovery from The Fertilizer Industry

Fertilizer wastewater contains a high concentration of ammonium and phosphate. One method of reducing the ammonium and phosphate contents is to recover them in the form of magnesium ammonium phosphate (MAP) or struvite (MgNH4PO4.6H2O). The objective of this experiment was to obtain the optimum mixing rate, pH, and molar ratio for struvite precipitation. A mixture of wastewater containing [Mg2+]:[NH4 +]:[PO4 3-] in molar ratios of 1:1:1, 1.5:1:1, and 2:1:1 was added to a 0.5-L beaker glass. Samples were then stirred under G.t values of 0.5 × 106, 106, and 1.5 × 106 for 60 minutes and left for 30 minutes for the sedimentation process. pH was set to 7.5, 8, and 8.5. Subsequently, the experimental results were compared with thermodynamic modelling using PHREEQC v3.0. The results showed that the optimum mixing rate was 158 rpm, which is equal to a G.t of 106; the optimum pH was 8.5 ± 0.2; and the optimum molar ratio of [Mg2+]:[NH4 +]:[PO4 3-] was 1:1:1. The removal percentage was 86.14% for ammonium and 98.98% for phosphate. Experimental results displayed a pattern similar to that predicted by the model. Additionally, the morphology of struvite shown by SEM-EDX and XRD analysis also demonstrated that struvite was formed in the precipitate.

The effects of mixing rate on morphology and physical properties of bitumen/organo-modified montmorillonite nanocomposites

The paper reports some experimental data on the effects of mixing rate on the morphology, carbonyl index (ICO), rheological and viscoelastic properties of nanocomposite materials based on bitumen/organo-modified montmorillonite (OMMT) incorporated at 3wt.%. The melt compounding process was carried out at 140°C under various mixing rates, i.e. 750, 1500, 2000, 3000 and 4500rpm. The results indicated through Wide angle X-ray scattering (WAXS) that up to 2000rpm, bitumen/OMMT nanocomposites exhibited an intercalated structure whereas at 3000rpm and more, an exfoliated structure was observed. Atomic force microscopy (AFM) showed an homogeneous dispersion of OMMT in the bituminous matrix accompanied with a decrease in the “bee like” structure, being however more pronounced at higher mixing rate. Differential scanning calorimetry (DSC) data indicated a decrease in the crystalline index (Xc) for both neat bitumen and bitumen nanocomposites with increasing the mixing rate. Complex viscosity (η∗) and complex modulus (G∗) were significantly improved compared to those of neat bitumen. Fourier transform infrared spectroscopy (FTIR) analysis showed a slight increase in the ICO value of bitumen/OMMT nanocomposites, especially at 4500rpm compared to that of neat bitumen, which remained almost constant.

Effect of mixing rate on the morphology of primary Al phase in the controlled diffusion solidification (CDS) process

Controlled diffusion solidification is a novel and promising process wherein near-net-shaped cast product of a desired Al wrought alloy is obtained by mixing two precursor alloys at specific individual composition, mass, and temperature each to obtain a non-dendritic morphology of the primary Al phase in the solidified microstructure. This study is devoted to quantify the effect of the rate of mixing of the two precursor alloys on the morphology of the primary Al phase in the cast component. The results show that the lower mixing rate with a higher mixing velocity is more favorable for the CDS process.

Experimental investigation of the chemical reduction of nitrate ion in aqueous solution by Mg/Cu bimetallic particles

Bimetallic particles have recently been used as a new means of contaminant reduction from water. Comparing with Fe0 and Mg0 alone, synthesized magnesium/copper (Mg/Cu) bimetallic particles have been determined to be potential and efficient agents for nitrate reduction from aqueous solutions. This study suggests that the reductive denitrification of nitrate by Mg/Cu bimetallic particles was dependent on a number of parameters including reductant dose, solution temperature, initial nitrate concentration and contact time. The 1% Mg/Cu (Cu loading of 1 wt.%) bimetallic particles removed the majority of the various nitrate concentrations tested (50, 100, 150, 200 and 300 mg/L) within a short period. The time required for the removal of 90.6% of the NO3 − from a 100-mg/L solution was about 20 min using 2 g/L bimetallic Mg/Cu at an initial solution pH of 6. The activation energy (E a) for the nitrate reduction by 1% Mg/Cu over the temperature range of 5–60 °C was 12.77 kJ/mol. The experimental results of the kinetic analysis from batch studies indicated that a higher initial nitrate concentration yielded a greater reaction rate constant and the denitrification rate increased with increasing 1% Mg/Cu dosage. The effects of mixing rate on the denitrification rate suggested that the reaction rate increases linearly at mixing rate <100 rpm and remained almost constant at rates over that.

Cadmium Biosorption on Vegetal Biomass

Effective removal of heavy metals from wastewater is one of the most important environmental challenges facing the world. Various techniques are used to remove the metals. Biosorption has gained credibility in the last decade because of its good performance and low cost. The objective of this study is to explore the use of olive pits for cadmium wastewater removal. The effects of mixing rate, pH, particle size, biomass and initial concentration and equilibrium metal ion concentration are evaluated. Results indicate nearly linear uptake by the biomass with increasing initial cadmium concentration. Adsorption increases rapidly in the pH range of 3-9, then levels off. Cadmium concentration uptake increase with increasing biomass concentration until reaching 5 g/L. Mixing rates up to 250 rpm increase uptake, however, higher mixing rates result in a vortex that incorporated air into the mixture, this resulted in a decrease in uptake. The adsorption isotherm appears to follow the Langmuir model.

Nitrate and Nitrite Reduction by Fe0: Influence of Mass Transport, Temperature, and Denitrifying Microbes

To evaluate how mass transport, temperature, and denitrifying micro-organisms affect the relative kinetics of nitrate and nitrite reduction by iron metal (Fe0), nitrate and nitrite reduction rates were measured over a range of mixing rates and temperatures. The effect of mixing rate was studied at a polished Fe0 rotating disk electrode (RDE) in an electrochemical cell, and the effect of temperature was studied in batch reactors with granular Fe0 in the absence and presence of Paracoccus denitrificans. Electrode rotation rate had little influence on the cathodic current measured in the presence of nitrate, whereas higher rotation rates resulted in significant increases in current in the presence of nitrite. The heterogeneous reaction rate coefficient (krxn) for nitrite reduction at the Fe0 RDE is several orders of magnitude faster than the surface-area normalized rate coefficient (kSA) for nitrite reduction by granular Fe0. Activation energies for nitrate and nitrite reduction by granular Fe0 were similar ...

Derivation of Heat-Flux Dependence on Pressure Gradient

2Broadwell, J. E., “Effect of Mixing Rate on HF Chemical Laser Performance,” Applied Optics, Vol. 13, No. 4, 1974, pp. 962–967. 3Mirels, H., Ho and, R., and King, W. S., “SimpliŽ ed Model of Continuous-WaveDiffusion-Type Chemical Laser,” AIAA Journal, Vol. 11, No. 2, 1973, pp. 156–164. 4Gross, R. F. W., and Bott, J. F. (eds.), Handbook of Chemical Lasers, Wiley, New York, 1976. 5Driscoll, R. J., “Effect ofReactant-Surface StretchingonChemical Laser Performance,” AIAA Journal, Vol. 22, No. 1, 1984, pp. 65–74. 6Acebal, R., “Hydrogen Fluoride vs Deuterium Fluoride Space-Based Laser Performance Comparison,” AIAA Journal, Vol. 36, No. 3, 1998, pp. 416–419. 7Rose, P.H., “AdvancedLaser TechnologyDevelopment in ShockTubes,” Shock Tube and Shock Wave Research, edited by B. Ahlborn, A. Hertzberg, and D. Russell, Univ. ofWashington Press, Seattle, WA, 1978, pp. 508–518. 8Bott, J. F., and Cohen, N., “A Shock Tube Study of the Reaction of Methyl Radicals with Hydroxyl Radicals,” International Journal of Chemical Kinetics,” Vol. 23, No. 11, 1991, pp. 1017–1033.

Synthesis of nanophase silver particles using an aerosol reactor

In this work, nanophase silver (Ag) particles were produced by an evaporation/condensation aerosol process in a jet flow reactor, and collected via electrostatic precipitation. Silver nitrate (AgNO 3) was used as the precursor and the aqueous AgNO 3 solution was delivered into the reactor by liquid atomization. From transmission electron microscopy, the mean particle diameter was determined to range from 16 to 53 nm at different experimental conditions that were studied, and the formation of rounded and unagglomerated particles was evident. Currently, the effects of mixing rate and precursor concentration on the characteristics of the resulting Ag particles were examined. The mean particle size was also estimated from the measurements of the particle number concentration entering the collection device. Collection efficiency above 90% using an electrostatic precipitator was attributed to a sufficiently high particle charging efficiency. Particles collected by filtration rather than electrostatic precipitation formed agglomerates, suggesting that electrical charging greatly reduced the coagulation rate.

Miscibility, morphology and mechanical properties of rubber-modified biodegradable poly(ester-urethanes)

Biodegradable, lactic acid based amorphous poly(ester-urethane)s (PEU) were modified with poly(L-lactic acid-co-ϵ-caprolactone-urethane) elastomer (P[LA/CL]U) by melt blending. The phase separation of P(LA/CL)U elastomer with three different ϵ-caprolactone (CL) compositions (CL content 30, 50, and 70 mol %) and the mechanical properties of the resulting impact-modified linear and branched PEU were investigated. The amounts of P(LA/CL)U elastomer in the PEU blends were 10, 15, 20, and 30 wt %. Dynamic mechanical thermal analysis (DMTA) of the blends with P(LA50/CL50)U and P(LA30/CL70)U elastomers revealed separate glass transition temperatures for rubber and matrix, indicating phase separation. No phase separation was found for P(LA70/CL30)U elastomer. The effect of mixing rate and temperature during processing on composite properties was tested by blending P(LA30/CL70)U rubber with PEU under various processing conditions. Impact modification studies were also made with two P(LA30/CL70)U elastomers having different amounts of functional groups. The influence of end-functionalization and cross-linking on mechanical properties was investigated in blends containing PEU and 15 wt % of these elastomers. Scanning electron microscopy (SEM) showed the morphology to change dramatically with increase in the degree of cross-linking in the rubber. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1074–1084, 2000

The effect of mixing rate on the synthesis of organoceramics

Organoceramics are a new class of polymer/ceramic nanocomposite materials whereby the polymers are molecularly dispersed within the ceramic lattice. These nanocomposites were synthesized by the precipitation of tetracalcium aluminate in the presence of poly(vinyl alcohol). The concentration of organoceramic produced increased as the rate of mixing was reduced. Transmission electron microscopy shows that, instead of having polymer chains wrapping up the ceramic grains, the tetracalcium aluminate precipitates onto the curled polymer chains resulting in spherical particles rather than the typical ceramic plate-shaped particles.

Melt blending of ultra high molecular weight and high density polyethylene: The effect of mixing rate on thermal, mechanical, and morphological properties

AbstractThe blends of two different ultra high molecular weight polyethylenes (UHMWPE) and high density polyethylene (HDPE) were prepared in melt at different compositions and mixing rates in Brabender Torque Rheometer. The temperature build‐up due to the internal friction during melt blending was recorded and evaluated with respect to the change in the torque. The temperature at maximum torque was considered the fusion point temperature of the UHMWPE in the blend. This fusion point temperature was found to depend on the composition, mixing rate, and molecular weight. The effect of mixing rate on the mechanical properties (measured as yield and tensile strengths and elongation at break), thermal oxidative degradation and melting behavior were studied. The morphology of the blends were investigated by optical microscopy.

Some theoretical aspects of mixing in the British coal twin-bed combustor/pyrolyser

British Coal, in collaboration with Senior Green Ltd., has incorporated a novel twin-bed coal-fired combustor into a 2.8 MWt water tube boiler. The firing system comprises two interconnected shallow fluidized beds operated as a pyrolyser and a char combustor, respectively. Gas temperatures well in excess of bed temperatures are achieved when the hot gas streams from the two beds are mixed in a common chamber. Particular attributes of the system are high combustion intensity (without in-bed tubes), inherently low NOx emission levels and wide turndown range (up to 10: 1). As part of the ongoing R&D programme, mathematical modelling techniques are being applied to provide a sound theoretical understanding of the physical and chemical processes occurring within the system. In order to assess the factors affecting scale-up of the twin-bed unit, Gloucestershire College of Arts and Technology (GLOSCAT), in collaboration with the Coal Research Establishment of British Coal, is currently developing a comprehensive mathematical model of the system. The paper describes one aspect of the system model, namely solids mixing. The application of simple analytic methods has been found useful to describe the process. Assuming uniform conditions in the vertical plane, mixing of coal and sand within a bed has been regarded as a diffusion process, and a system of ordinary differential equations have been established to predict carbon concentration and temperature profiles for each bed. Although a number of simplifying assumptions have been made, the models provide useful sensitivity analyses, allowing an assessment of the factors influencing scale-up, e.g. the effect of mixing rate and char particle size on temperature profiles. Analytic solutions are presented, and the sensitivity analyses are illustrated using standard computer graphics.

モデル燃焼器による低汚染燃焼法の実験的研究

An experimental study was made to investigate the mixing and NOx formation in a swirlstabilized, diffusion-type flame in a model combustor operating at lean fuel/air ratios. The city gas was injected from a fuel injector into an air flow passed through a swirler. The temperature, stable species and NOx concentration profiles in the combustor were measured over a range of air flow velocities through the swirler from 5 to 20m/s, fuel injection velocities from 36.4 to 145.4m/s, overall equivalence ratios Φ from 0.2 to 0.8 and nominal fuel injection angles from 60° to 180°. The effects of these parameters on NOx concentration in the flame zone and the emission level of NOx from the combustor were discussed. The effects of mixing rates were also estimated by examination of the local equivalence ratio profiles across the flame zone.In general, the flame clearly showed the characteristics of a fuel jet flame near the fuel injector. The temperature and the concentration profiles across the main flame zone and the recirculation zone change considerably with change in Φ. In the case of comparatively low value of Φ, it was shown that the high mixing rate had the effect of lowering the local equivalence ratio in the flame zone and the combustion gas temperature early in the post-flame zone. Then, the emission levels of NOx can be reduced by achieving high mixing rate due to the increase of air flow velocity and the variation of the fuel injection angle, at the expense of slight increase of the emission levels of CO.The minimum emission level of NOx obtained is 0.23g NO2/kg fuel at Φ of 0.2. Although the emission levels of NOx from the present combustor are still higher than those from lean premixed system, they were found to be much lower than those from conventional diffusion flame combustor.

Effect of Mixing Rate on HF Chemical Laser Performance

A simple model of a steady-flow HF chemical laser has been formulated in which the excited-state formation rate is limited by the H(2)-F mixing rate. Lasing is allowed to take place between several vibrational levels of the HF molecule simultaneously. With reasonable approximations, the power output and efficiency can be determined analytically. The dependence of these variables on the independent parameters is in qualitative accord with experimental observations on mixing lasers but differs markedly from the predictions for lasers in which the reactants are premixed.