Agitation Intensity Research Articles

Gas induced semi-solid process effects on microstructure and mechanical properties of 319 aluminum alloy

Abstract The exclusive effects of gas induced semi-solid parameters such as rheocasting temperature, agitation intensity and flow rate of gas injection into the melt on the average size and shape factor of primary α-Al particles and subsequently tensile properties of 319 aluminum alloy have been studied. Applying vigorous agitation and rapid heat extraction simultaneously in the early stages of solidification in order to achieve a slurry with fine and dispersed primary α-Al particles is essential. Hence, in order to investigate these two factors separately, three different types of graphite diffusion in three proportional gas flow rates have been used. It was found that a reduction in rheocasting temperature leads to a decrease in the average size of the primary α-Al particles and an increase in their sphericity and improvement of tensile properties as well. The average size of primary particles slightly decreases as the agitation intensity increases as expected; while a decrease in agitation intensity in a given gas flow rate leads to the formation of gas porosity. Also the gas was trapped due to an increase in gas flow rate at constant agitation intensity whereas the decrease in gas flow rate has no significant effect on morphology of primary α-Al particles.

A facile disposal of Bayer red mud based on selective flocculation desliming with organic humics

Humics flocculant was applied in the disposal of Bayer red mud based on selective flocculation desliming process. The parameters affecting selective flocculation behavior such as flocculant dosage, slurry pH and agitation intensity were studied. For flocculating mechanism analysis, the iron mineral and the flocs product were characterized by ζ-potential testing, settling experiments, optical microscope and SEM imaging. The results show that humics exhibits a good selective flocculation performance in the high alkaline pH range. With an optimal condition of 2% solid density, flocculant dosage 30mgL−1, Na2SiO3 dosage 200mgL−1, slurry pH 10.0 and agitation speed 1000rpm, the recovery of iron minerals of 86.25±1.31%, the iron grade of concentrate of 61.12±0.10%, the separation index of 0.69±0.02 can be obtained in the selective flocculation. It is found that the adsorption bridging of humics polymer dominates the selectively flocculating the iron minerals. Large flocs or aggregates with a better settling capacity are generated because of humics occurring. The maximum settling velocity of 38.23±1.51mh−1 is reached at pH 10. This work brings the easiness in directly recovering fine particle size of iron-bearing minerals from red mud.

Heat transfer coefficients during thermal processing of model particulate mixtures in non-Newtonian fluids undergoing reciprocation agitation as affected by process variables

Overall (U) and fluid-to-particle heat-transfer coefficients (hfp) in canned particulates (Nylon spheres) suspended in non-Newtonian fluid (CMC dispersions) undergoing reciprocation agitation thermal processing was evaluated in a pilot-scale reciprocating retort. Five influencing process variables affecting U and hfp were selected. A CCRD and a 3 × 3 × 2 full-factorial design of experiments were used to relate the coefficients U and hfp to the various process variables viz. reciprocation frequency; reciprocation amplitude; temperature; liquid viscosity and headspace.U and hfp varied in the range 524–1124 W/m2oC and 549–1610 W/m2oC respectively. Analysis of variance showed frequency, amplitude, liquid viscosity, headspace and temperature to be significant factors for hfp, and frequency, amplitude and liquid viscosity for U (p < 0.001). Increasing the reciprocation frequency from 1 to 4 Hz almost doubled the value of both the heat transfer coefficients. Similarly increasing the reciprocation amplitude from 5 to 25 cm, resulted in 30–35% increase in the values of heat transfer coefficients. Overall with increase in temperature, frequency, amplitude, and headspace, associated hfp and U values also increased, but with increasing liquid viscosity, both hfp and U showed a decrease. Finally, optimization of processing conditions was carried out to minimize quality losses due to particle motion (agitation intensity) and thermal damage (severity of thermal processing).

Disposal of Oily Sludge

Significant quantities of oily sludge are formed in the process of oil production. As a multiphase mixture, it shares the characteristics of high emulsion stability and faces the challenges of disposing, storing, and discharging. The surface engineering operations are directly affected by the oily sludge, and the petroleum industry environments are threatened simultaneously. An investigation of characterizing the composition properties of oily sludge in Daqing oilfield was carried out recently. One kind of disposal equipment was established, large scale disposal simulation experiments were conducted, and the conditioning demulsification method was presented. The results indicated that oily sludge aggregation are consist of aging oil, wax, asphaltine, colloid, bacterium, salts, and water. Decrease the volume through reducing water-cut is a dominant method that would be beneficial to managing the oily sludge disposal with high efficiency and harmlessness, and conditioning demulsification plays an indispensable role in the whole process. The chemicals dosage, agitation intensity, disposal temperature and action time, as the primary parameters that would affect conditioning effect were all simulated and optimized respectively. Furthermore, the disposal process was designed, and the main equipments are recommended.

Effect of Can Orientation on Heat Transfer Coefficients Associated with Liquid Particulate Mixtures During Reciprocation Agitation Thermal Processing

The objective of this work was to study the effect of container orientation on heat transfer during reciprocation agitation thermal processing of cans filled with liquid particulate mixtures. A vertical steam retort, retrofitted with a mechanism to provide horizontal reciprocation of containers, was used in this study. Cans of size 307 × 409, filled with 30 % (v/v) Nylon particles in a Newtonian fluid (100 % glycerin), were placed inside the reciprocating cage with longer axis in one of the three possible orientations viz. horizontal along axis of reciprocation (HA), horizontal perpendicular to axis of reciprocation (HP), or vertical (V). Reciprocation frequency (1–4 Hz) and amplitude (5–25 cm), and container headspace (2–12 mm) were varied according to a full factorial experimental design, and heat transfer coefficients and process times associated with each orientation were calculated. Additional experiments were also carried out in still mode to study the effect of container orientation in static processing mode. Results showed that for the static mode, HA and HP provided more rapid heating than V. For agitation processing, HA provided more rapid heat transfer followed by HP and then V, respectively. Reciprocation frequency and amplitude affected the heat transfer significantly (p < 0.05) in all orientations, while headspace was significant only for HA. An agitation intensity (AI) parameter was defined based on reciprocation frequency and amplitude. An AI value of 3.0 g was found sufficient for HA cans, while HP and V cans required a higher AI of 6.0 g for optimum heat transfer. This study could be used in designing of reciprocation thermal processes with optimal heat transfer delivery.

Swirling Flows in Side Blowing Reactors and Possible Advantages

Side blown refining units are popularly used in the steel industries and include reactors such as, energy optimizing furnace, AOD converters and so on. In almost all such cases, the tuyeres have their axis orthogonal to the furnace wall and are located typically on the side walls, near the base of the reactor. Depending on requirements, either a reactive or inert gas or both in conjunction is supplied through one or more of such injectors, The present study suggests that at any given gas injection rate, orientation of side tuyeres together with their numbers can significantly influence the nature and intensity of bath agitation. Through an exploratory physical model study, it is demonstrated that by marginally re-orienting a pair of otherwise orthogonal horizontal tuyeres (i.e. entering at an angle of 10°–15° as opposed to the conventional, perpendicular to the reactor wall), a strong swirling motion could be imparted to the bath. Such rotational motion aided by the prevalent three dimensional flow was found to increase heat and mass transfer rates in the system by 25–30 %.

The effect of concentration on transient pool boiling heat transfer of graphene-based aqueous nanofluids

Transient pool boiling experiments were performed by quenching of stainless steel spheres in dilute aqueous nanofluids in the presence of graphene oxide nanosheets (GONs) at various concentrations (by weight) up to 0.1 wt.%. All the experiments were performed for saturated boiling at atmospheric pressure. Quenching and boiling curves were obtained for the nanofluids in comparison to the baseline case of pure water. It was shown that quenching is accelerated upon increasing the concentration of GONs. The enhanced boiling heat transfer by the nanofluids was interpreted in relation to the modified surface properties, including morphology, wettability, and roughness, on the quenched surfaces. Unlike the findings in available relevant studies that point to surface wettability change, however, the primary cause of critical heat flux (CHF) enhancement was observed to be related to the increased surface roughness serving as paths to facilitate solid−liquid contacts. The increases of both nucleation site density and liquid agitation intensity as a result of the presence of porous structures at relatively high concentrations were also found to be responsible for the enhanced CHF.

Semi-solid Paste Binder Dispersion in a Moving Powder Bed

A key difference in detergent agglomeration compared to most agglomeration processes conducted in the food and pharmaceutical industries is the ultra-high viscosity of the surfactant binder. In comparison to water, these surfactants are about 1000 times more viscous. This makes handling the surfactant paste a challenge. The present study aims to understand the importance of initial binder dispersion. Experimental work has revealed how the binder deforms, breaks and assimilates in mass by gathering more powder. The rate of powder assimilation was determined as a function of the agitation intensity. At higher impeller speeds this rate is faster.The influence of the method of binder delivery on granule attributes such as size and strength was also investigated. The binder was either injected into the mixer as a stream/jet or preloaded into the mixer in the form of blobs. At moderate agitation intensity the results showed that binder injection results in faster and steadier granule growth (size), thus demonstrating the influence of binder delivery method on the kinetics of the granulation process.

Enzymatic hydrolysis of steam-exploded sugarcane bagasse using high total solids and low enzyme loadings

Hydrolysis of phosphoric acid-impregnated steam-treated sugarcane bagasse was pre-optimized using a face-centered central composite design in which the process variables were the substrate total solids (TS, %), agitation intensity (AI, rpm) and enzyme loading (EL, gg−1). Pretreatment was carried out at 180°C for 10min using cane bagasse with 50wt% moisture content containing 9.5mg of H3PO4 per gram of dry biomass. Hydrolyses were performed for 96h at 50°C using Cellic CTec2® and water-washed steam-treated substrates. The highest amount of fermentable sugars was obtained with 20wt% TS, producing 76.8gL−1 of glucose equivalents, which corresponded to a total glucan conversion of 69.2wt% and to a theoretical net increase of 39% in ethanol production from the same sugarcane tonnage without considering the use of leaves, tops and the additional yields from C5 sugars.

Agitation Duration, Density and Intensity Predict Rehab Length of Stay And Motor FIMs in TBI

To determine whether longitudinal agitation measures predict rehabilitation length of stay (LOS) and functional outcomes in TBI.

Poster 443 Agitation Duration, Density and Intensity During Acute Inpatient Rehabilitation Predict Length of Stay in Acute Inpatient Rehabilitation and Motor FIMs at Discharge for Patients with Traumatic Brain Injury

Poster 443 Agitation Duration, Density and Intensity During Acute Inpatient Rehabilitation Predict Length of Stay in Acute Inpatient Rehabilitation and Motor FIMs at Discharge for Patients with Traumatic Brain Injury

실험반응조를 이용한 하수관에서의 재포기현상 재현 가능성에 관한 연구

하수관 내에서의 하수와 미생물의 반응에 대한 실험은 이미 매설된 하수관에 적용할 경우 실험조건의 변화가 제한적이며 실험시간에도 한계가 있다. 본 연구에서는 이러한 하수관 내에서의 하수와 미생물의 반응에 대하여 DO를 제한 조건으로 설정하였을 경우, 실험실 내에서 실험반응조를 통해 재현하는 방법에 대하여 연구하였다. 하수관 내에서의 DO 농도는 기상 중의 산소가 하수 내로 이동하는 재포기현상에 의해 조절된다. 이러한 현상을 이용하여 임의로 실험반응조에서 하수관 내의 유하조건을 조절하고 재포기현상을 재현하여 유하조건과 재포기계수와의 상관관계를 얻을 수 있으며, 교반강도(속도경사)에 따른 재포기계수와 하수관거에서의 유하조건에 따른 재포기계수의 상관관계를 통해 동일한 재포기계수 값을 갖는 교반강도와 유하조건을 설정할 수 있다. 이러한 결과를 통해 재포기계수를 제한인자로 설정하여 실험을 실시할 경우 하수관거에서의 상황을 실험반응조를 통해 재현할 수가 있었다. The microorganism decomposition experiment of sewage in the underground sewer has the limit of experiment condition and time. The way to reproduce the microorganism decomposition in the underground sewer was studied using batch reactor setting up the DO as a limiting condition. The DO concentration in the sewer is controlled by reaeration. It is possible to obtain correlation between flow condition and reaeration coefficient through the reproduction of reaeration phenomenon by controlling the flow condition in the sewer using this phenomenon. And it is possible to set the flow condition and agitation intensity (velocity gradient) that has the same reaeration coefficient using the correlation between the reaeration coefficient with the flow condition and reaeration coefficient with the agitation intensity. The circumstances in the sewer system was reproduced using batch reactor setting up the DO as a limiting condition from these results.

Transesterification of palm olein using sodium phosphate impregnated on an alumina support

In the present work, a new heterogeneous catalyst for fatty acid methyl ester (FAME) synthesis consisting of an active sodium phosphate (Na3PO4) component impregnated on an Al2O3 support was developed. Al2O3-supported Na3PO4 was prepared by incipient-wetness impregnation. The catalyst was characterized using XRD, FT-IR, SEM-EDX, and BET. The influences of reaction variables, such as the agitation intensity, the molar ratio of methanol/oil, the reaction temperature, and the catalyst amount, on the conversion of palm olein were investigated. The presence of free fatty acids and water are also studied in this research. The results showed that high FAME contents (>96%) can be achieved within 30min at 210°C with a methanol/oil molar ratio of 18:1 and 1.0wt.% catalyst. The prepared Na3PO4/Al2O3 catalyst exhibited high stability and recyclability. In our tests, FAME production was slightly but not significantly reduced after 5 recycles. Elemental analysis by ICP-OES found a small amount of Na in the products following the reaction.

Characterization of hydromechanical stress in aerated stirred tanks up to 40 m(3) scale by measurement of maximum stable drop size.

BackgroundTurbulence intensity, or hydromechanical stress, is a parameter that influences a broad range of processes in the fields of chemical engineering and biotechnology. Fermentation processes are often characterized by high agitation and aeration intensity resulting in high gas void fractions of up to 20% in large scale reactors. Very little experimental data on hydromechanical stress for such operating conditions exists because of the problems associated with measuring hydromechanical stress under aeration and intense agitation.ResultsAn indirect method to quantify hydromechanical stress for aerated operating conditions by the measurement of maximum stable drop size in a break-up controlled dispersion was applied to characterize hydromechanical stress in reactor scales of 50 L, 3 m3 and 40 m3 volume with a broad range of operating conditions and impeller geometries (Rushton turbines). Results for impellers within each scale for the ratio of maximum to specific energy dissipation rate ϕ based on measured values of maximum stable drop size for aerated operating conditions are qualitatively in agreement with results from literature correlations for unaerated operating conditions. Comparison of data in the different scales shows that there is a scale effect that results in higher values for ϕ in larger reactors. This behavior is not covered by the classic theory of turbulent drop dispersion but is in good agreement with the theory of turbulence intermittency. The data for all impeller configurations and all aeration rates for the three scales can be correlated within ±20% when calculated values for ϕ based on the measured values for dmax are used to calculate the maximum local energy dissipation rate. A correlation of the data for all scales and all impeller configurations in the form ϕ = 2.3∙(ϕunaerated)0.34∙(DR)0.543 is suggested that successfully models the influence of scale and impeller geometry on ϕ for aerated operating conditions.ConclusionsThe results show that besides the impeller geometry, also aeration and scale strongly influence hydromechanical stress. Incorporating these effects is beneficial for a successful scale up or scale down of this parameter. This can be done by applying the suggested correlation or by measuring hydromechanical stress with the experimental method used in this study.

Simple Criterion for Stability of Aqueous Suspensions of Ultrafine Particles of a Poorly Water Soluble Drug

In this work, a simple criterion is proposed for prediction of a long-term stability of aqueous suspensions of ultrafine particles of a poorly water soluble drug, curcumin. A new "stability parameter" (γ0ε/γε0) has been defined, which is a ratio of nondimensional mechanical (mainly ultrasonic) energy (ε/ε0) to nondimensional solid-liquid interfacial energy (γ/γ0). The stability of aqueous suspensions of curcumin particles over a period of 1 year and 9 months has been correlated with this parameter. In order to calculate this parameter, solid-liquid interfacial energies were first estimated, from nucleation rates, which in turn were calculated from size distributions of curcumin particles precipitated using water as antisolvent. The mechanical energy was then estimated from the intensity of ultrasound and mechanical agitation used during precipitation. It was found that precipitations carried out with higher values of γ0ε/γε0 (more than 100) result in aqueous suspensions with particle size less than 1 μm. It was further observed that these suspensions remain stable (i.e., no or negligible change in average particle size) for a period of 1 year and 9 months. On the other hand, the suspensions of particles precipitated at lower values of γ0ε/γε0 (less than 10) were found to be highly unstable (i.e., the average particle size changes drastically). These results suggest that γ0ε/γε0 can be used as a parameter to engineer stable aqueous suspensions of curcumin particles. Further, it was found that the use of the Mersmann equation to estimate solid-liquid interfacial surface tensions can help in making this criterion predictive.

Development and validation of dissolution study of sustained release dextromethorphan hydrobromide tablets.

This study describes the development and validation of dissolution tests for sustained release Dextromethorphan hydrobromide tablets using an HPLC method. Chromatographic separation was achieved on a C18 column utilizing 0.5% triethylamine (pH 7.5) and acetonitrile in the ratio of 50:50. The detection wavelength was 280 nm. The method was validated and response was found to be linear in the drug concentration range of 10-80 microg mL(-1). The suitable conditions were clearly decided after testing sink conditions, dissolution medium and agitation intensity. The most excellent dissolution conditions tested, for the Dextromethorphan hydrobromide was applied to appraise the dissolution profiles. The method was validated and response was found to be linear in the drug concentration range of 10-80 microg mL(-1). The method was established to have sufficient intermediate precision as similar separation was achieved on another instrument handled by different operators. Mean Recovery was 101.82%. Intra precisions for three different concentrations were 1.23, 1.10 0.72 and 1.57, 1.69, 0.95 and inter run precisions were % RSD 0.83, 1.36 and 1.57%, respectively. The method was successfully applied for dissolution study of the developed Dextromethorphan hydrobromide tablets.

Volumetric Oxygen Mass Transfer Coefficient and Surface Tension in Simulated Salt Bioremediation Media

AbstractToluene can be removed from contaminated sites via bioremediation through the addition of biosurfactant compounds, which reduce the surface tension. However, aeration and mixing must be optimized to ensure an effective volumetric oxygen mass transfer coefficient (kLa). Experiments were perfomed with different salt containing solutions, which were tested either as such, or with different supplements. kLa values obtained at different agitation intensities and aeration rates were compared with those in water, and correlated with power number and superficial gas velocity. Surface tension decreased when surfactin was added to toluene‐containing media. The seawater‐simulating medium exhibited the highest surface tension reduction.

Development of a high efficient gas to hydrate (GTH) conversion process using SDS kinetic promoter for maximizing the CO2 recovery with minimum energy consumption

In this work the optimum operating conditions for complete CO2 recovery via gas to hydrate conversion process with minimum energy consumption is investigated. A new series of experiments are carried out at different pressures, temperatures, agitation intensities and kinetic promoter concentrations by using a newly developed fully automated GTH (gas to hydrate) energy converter. According to the presented results at the 27bar and 1°C and in the presence of 4000ppm anionic surfactant sodium dodecyl sulfate (SDS) and proper amount of free water, it is possible to reach a CO2 gas to hydrate conversion of 95% without using any agitating device and without using any help additive at a completely unstirred quiescent condition which is a superb result from engineering viewpoint. The presented approach outperforms the other energy consuming CO2 recovery processes and can have significant industrial application for development of low cost hydrate-based carbon dioxide recovery plants.

Optimization of aeration and agitation rate for lipid and gamma linolenic acid production by Cunninghamella bainieri 2A1 in submerged fermentation using response surface methodology.

The locally isolated filamentous fungus Cunninghamella bainieri 2A1 was cultivated in a 5 L bioreactor to produce lipid and gamma-linolenic acid (GLA). The optimization was carried out using response surface methodology based on a central composite design. A statistical model, second-order polynomial model, was adjusted to the experimental data to evaluate the effect of key operating variables, including aeration rate and agitation speed on lipid production. Process analysis showed that linear and quadratic effect of agitation intensity significantly influenced lipid production process (P < 0.01). The quadratic model also indicated that the interaction between aeration rate and agitation speed had a highly significant effect on lipid production (P < 0.01). Experimental results showed that a lipid content of 38.71% was produced in optimum conditions using an airflow rate and agitation speed of 0.32 vvm and 599 rpm, respectively. Similar results revealed that 0.058 (g/g) gamma-linolenic acid was produced in optimum conditions where 1.0 vvm aeration rate and 441.45 rpm agitation rate were used. The regression model confirmed that aeration and agitation were of prime importance for optimum production of lipid in the bioreactor.

Development of Oral Mucoadhesive Tablets of Losartan Potassium using Natural Gum from Manilkara Zapota Seeds

The present investigation reports the isolation of mucilage from Manilkara zapota seeds as per AOAC guideline and evaluating it as mucoadhesive agent. Manilkara zapota (Linn.) P. Royen syn. a small tree belonging to family sapotaceae. Physiochemical characteristics of mucilage, such as swelling index, microbial count, viscosity, hydration capacity, flow property, and pH were studied. The mucilage was evaluated for its mucoadhesive properties in compressed tablet, using losartan potassium as model drug. Granules were prepared by wet granulation process using polyvinylpirrolidone as binding agent. Mucilage was used in four different concentrations i.e. 20, 40 and 60 % w/w. The tablet were prepared and evaluated for its physical property. Further in vitro dissolution and swelling index was determined. The property of bioadhesive strength of isolated mucilage was compared with guar gum and HPMC E5LV, which was used as standard mucoadhesive agent concentration. Bioadhesive strength of the tablet was measured on the modified physical balance. Result revealed that mucilage had good micromeritcs properties and prepared tablets showed good physical properties, further drug release was retarded as concentration of mucilage was increased. The force of adhesion was obtained 0.2337N, 0.4664N, 0.6210N, 0.8679N and 0.3983N respectively for F1, F2, F3, F4 and F5. Formulations were subjected for study of effect of intensity of agitation at different rpm and electrolyte, formulation showed relative effect on release of drug from formulation. All the formulations were subjected to stability studies for three months all formulation showed stability with respect to release pattern. It is concluded that the seed mucilage of Manilkara zapota can be used as a mucoadhesive excipient in oral mucoadhesive drug delivery systems.