Effect Of Supersaturation Research Articles

Optical coherence tomography and digital image processing for scaling and Co-precipitation investigation on reverse osmosis membrane

Scaling known as the precipitation of inorganic salts is a main concern in the reverse osmosis (RO) process due to its effects on the process performance and life-time of membranes. Although single salt precipitation has been continuously studied, the co-precipitation of salts is rarely investigated due to its complexity, especially under process hydrodynamic conditions. Recently, optical coherence tomography (OCT) has been adopted as an in situ and rapid technique for monitoring the fouling in membrane processes. This study aims to develop an approach using OCT and digital image processing for qualitative and quantitative analysis of single salt precipitation and co-precipitation on RO membrane under hydrodynamic conditions. The effects of supersaturation, sodium chloride (NaCl), flow rate, and applied pressure are investigated. The developed approach enables the detection of crystal growth under the OCT. The morphology of precipitated salt, i.e CaSO4, including crystal shape and size obtained from OCT acquisition, agrees with the images from a scanning electron microscope (SEM). The growth of each crystal in co-precipitation of CaSO4 and CaCO3 is well detected in appearance time and growth pattern. This is beneficial to differentiate crystal morphology in the co-precipitation system. The quantitative surface coverage proportion and total volume are in well correlated the changes of RO performance parameters of permeate flux, conductivity (feed, concentrate, and permeate), and Ca2+ concentrate profile by time, which allows the scaling progress to be directly evaluated over time. This study reveals the high potential of combining OCT acquisition and digital image processing for direct observations and studying single salt and co-precipitation under RO hydrodynamic conditions, which can be extended for another type of composite fouling.

Pore-scale spatiotemporal dynamics of microbial-induced calcium carbonate growth and distribution in porous media

The naturally occurring bio-geochemical microbial-induced calcium carbonate precipitation (MICP) process is an eco-friendly technology for rehabilitating construction materials, reinforcement of soils and sand, heavy metals immobilization and sealing subsurface leakage pathways. We report pore-scale spatiotemporal dynamics of the MICP process in porous media, relevant for reduced environmental risk by leakage during CO2 geological storage. Effects of hydrodynamics and supersaturation on the MICP with Sporosarcina pasteurii stains were studied using a high-pressure, rock-on-a-chip microfluidic device. Bacterial cell numbers and variation in cementation concentration controlled the crystal size and pore-scale distribution by influencing the local supersaturation. Local pore structure determined crystal nucleation, where low velocity regions tended to nucleate more crystals. CaCO3 crystallization was observed at subsurface pressure (100 barg) with a reduced sealing performance due to the low microbial activity from elevated pressure. We identify that hydrodynamics and supersaturation determine crystal nucleation and growth in porous systems, providing important experimental evidence for subsurface environmental applications and validation of upscaled MICP models.

Comparative transcriptome analysis provides insights into the TDG supersaturation stress response of Schizothorax davidi

In the dam discharge season, the supersaturation of total dissolved gas (TDG) in the downstream channel can seriously affect the survival of aquatic organisms. However, few studies have revealed the mechanism by which TDG supersaturation affects the physiology of fish thus far. The present study was conducted to study the mechanism of the effect of TDG supersaturation on Schizothorax davidi, a species that is very sensitive to gas bubble disease. S. davidi was exposed to 116 % TDG supersaturation stress for 24 h. Serum biochemical tests showed that the aspartate aminotransferase and alanine aminotransferase levels after TDG supersaturation exposure were significantly decreased compared to those in the control group, while superoxide dismutase activity was significantly increased. RNA-Seq of gill tissues identified 1890 differentially expressed genes (DEGs), which consisted of 862 upregulated genes and 1028 downregulated genes, in the TDG supersaturation group vs. the control group. Pathway enrichment analysis revealed that the cell cycle, apoptosis and immune signaling pathways were affected by TDG stress. The results of this study may contribute to our understanding of the underlying molecular mechanism of environmental stress in fish.

Design and mechanism of agglomeration of aspirin crystals in pure solvents

Agglomeration with improved flowability for platy crystals is desirable in pharmaceutical downstream processing. The formation of agglomerates in pure solvents without the aid of bridging liquids is a convenient and low-cost method compared with complex spherical crystallization. In this work, the adhesion free energies between aspirin crystals in six solvents were calculated using Lifshitz-van der Waals acid-base theory to screen suitable solvents for agglomeration. The maximum stirring rate for agglomeration was determined by adhesion forces and dispersion forces. Then the agglomerates of plate-shaped aspirin were successfully prepared in acetone, methanol, ethanol, 2-propanol, and ethylene glycol without additives by simple cooling crystallization. The interactions between solvent and crystal surfaces were also used to explain the outcomes. A feasible mechanism for the agglomeration process of platy crystals was elucidated, involving the adhesion of dominant crystal facets at the beginning. The effect of stirring rate, cooling rate, and initial supersaturation on agglomeration degree and particle size of aspirin agglomerates were studied. The obtained aspirin agglomerates under the optimal conditions exhibited a uniform particle size distribution, a high agglomeration degree, and superior flowability.

Chemical inhibition of combined gypsum and iron oxides membrane fouling during reverse osmosis desalination process: Prevention and regeneration of membranes

This paper explores the performance of carboxylic acids as environmentally friendly chemical inhibitors and cleaning agents during combined membrane fouling by gypsum and iron oxides. The efficiency of citric acid and two other carboxylic acids was evaluated during combined fouling trials by measuring normalized fluxes drops, using an RO pilot unit. The effect of acid concentration, pH variation and gypsum supersaturation were evaluated. SEM, EDX, X-Ray diffraction and FTIR were used to identify the composition and morphology of fouled membranes. The results indicated that at low pH, citric acid serves to restore the flux drop. This acid serves to orient the crystals towards the hemihydrate form with a flat, thin structure. By increasing the pH, the acid retains its effectiveness and serves to delay the Fe2+ oxidation ions and the precipitation of calcium sulfate for more than 3 h. By comparing them to the citric acid, ascorbic and tartaric acid showed a similar effect at acidic pH. In both cases, normalized fluxes were recovered with the use of 100 ppm of each acid. However, at alkaline pH, citric shows a better performance. The regeneration of RO membranes fouled by iron oxides and gypsum appears to be more effective with citric acid than the other two acids.

Nucleation kinetics-based solvent selection for the liquid antisolvent crystallization of a lipophilic intermediate

The fundamental understanding of solubility and nucleation kinetics are two primary pillars for liquid antisolvent crystallization (LASC) process development. In our present work, the solubility of intermediate A in four different solvents and binary mixtures with water, in the temperature range from 273 K to 323 K, was determined using a liquid chromatographic method to acquire the fundamental thermodynamic information for the LASC process. Intermediate A was monitored both in the solid phase and in the liquid phase by in line Raman spectroscopy. The importance of selection of the optimum scale and mixing conditions (volume and fluid dynamics dependency) for conducting metastable zone width (MSZW) measurements for the nucleation kinetics study, due to stochastic nature of nucleation, has been demonstrated to translate the findings to larger industrial scales. The 3.5 mL volume in reactor with a 3 blade downflow overhead impeller in the Crystalline™ (Technobis) was found to be an optimal platform for the data generation for the extraction of nucleation kinetics. The minimum detection threshold value (fN) reported in the literature was experimentally derived for the intermediate A-solvent systems used, covering the effect of supersaturation, reaction volume and agitation rate. The combined polythermal and antisolvent addition approach was applied to determine MSZWs and, subsequently, the kinetic parameters were estimated based on both linearized integral and 3D nucleation models. It was demonstrated how the derived parameters complemented with accurate solubility data are required to guide solvent selection for bottom-up generation of nanosuspensions. The findings were validated by conducting batch and continuous LASC of intermediate A. Particle size distributions derived from electron scanning microscopy obtained at similar driving forces confirmed the solvents selection order based on their nucleation tendency of dissolved intermediate A. These results serve as an example for applying a nucleation kinetics-based fundamental approach for solvent selection in the development of LASC process for generation of long-acting injectable suspensions.

Anisotropy of growth hillocks on KDP crystal (101) faces observed by in situ interferometry

In situ interference and AFM were used to study the effect of supersaturation and temperature on the growth rates and slopes of KDP crystal (101) faces.

Effect of solution supersaturation on crystal formation of Vitamin K2 based on near infrared spectroscopy analysis technology

Polymorphism is frequently encountered in most small molecule drugs and vitamin supplements, and the physical and chemical parameters of crystalline drugs may directly affect the solubility, bioavailability and clinical effects of the substances in the human body. Supersaturation is the key driving force of crystal nucleation and growth. Crystal forms and sizes are different under different supersaturation conditions. To rapid and efficient detection concentration of Vitamin K2, we established a solution concentration prediction model using near-infrared (NIR) spectroscopy in this study. The influence of supersaturation on Vitamin K2 crystal formation was explored. The results showed that for freezing crystallization, the supersaturation would be larger than evaporative crystallization and the size of the crystals would be smaller. The particle size of freezing crystallization is mainly in the range of 5–20 μm while the particle size of evaporative crystallization is mostly distributed in the range of 20–40 μm. This study also found that the crystal form obtained by solvent evaporation method was more regular, mostly in flake shape and smooth surface. These results have guiding significance for biological preparation of high-purity Vitamin K2 products with regular crystal shape, uniform particle size and good bioavailability.

Biochemical, transcriptomic and metabolomic responses to total dissolved gas supersaturation and their underlying molecular mechanisms in Yangtze sturgeon (Acipenser dabryanus)

With the rapid development of hydropower facility construction, the total dissolved gas (TDG) generated by dam discharge is seriously threatening the survival of fish and has become an ecological environmental issue of global concern. However, how TDG affects fish physiology and the underlying molecular mechanism remain poorly known. In this study, Acipenser dabryanus, an ancient living fossil that is a flagship species of the Yangtze River, was exposed to water supersaturated with TDG at a level of 116% for 48 h. A comprehensive analysis was performed to study the effect of TDG supersaturation stress on A. dabryanus, including histopathological, biochemical, transcriptomic and metabolomic analyses. The histopathological results showed that mucosal-associated lymphoid tissues were seriously damaged after TDG supersaturation stress. Plasma catalase levels increased significantly under TDG supersaturation stress, while superoxide dismutase levels decreased significantly. Transcriptomic analysis revealed 289 upregulated genes and 162 downregulated genes in gill tissue and 535 upregulated and 104 downregulated genes in liver tissue. Metabolomic analysis revealed 63 and 164 differentially abundant metabolites between the control group and TDG group in gill and liver, respectively. The majority of heat shock proteins and genes related to ubiquitin and various immune-related pathways were significantly upregulated by TDG supersaturation stress. Integrated transcriptomic and metabolomic analyses revealed the upregulation of amino acid metabolism and glycometabolism pathways under TDG supersaturation stress. Glycerophospholipid metabolism was increased which might be associated with maintaining cell membrane integrity. This is the first study revealing the underlying molecular mechanisms of effects of TDG supersaturation on fish. Our results suggested that acute TDG supersaturation stress could enhance immune and antioxidative functions and activate energy metabolic pathways as an adaptive mechanism in A. dabryanus.

CFD simulation and experimental study of antisolvent precipitation through impinging jets for synthesis of nanodrug particles

The nucleation and growth kinetics of loratadine, one of the primary antihistamines among drugs, are determined experimentally in confined liquid impinging jet channels, followed by simulating the anti-solvent precipitation process to obtain ultrafine loratadine nanoparticles. The effect of supersaturation is assessed as the essential factor on the nucleation and growth rates. Based on classical nucleation theory, induction time and nucleation rate showed homogeneous and heterogeneous nucleation regions in high and low supersaturations, respectively. The interfacial free energy measured from the induction time is obtained at about 18.99 mJ/m2. The size-dependent particle growth and growth dispersion effects are assessed through the experimental data. The nonlinear curve fitting with the experimental data in log population density plot at residence time of 7.69 s reveals that the four-parameter model has a better fit, with no growth dispersion. The microchannel mixing performance is assessed by analyzing the Damkohler number under different Reynolds numbers. The loratadine particle size distribution (CSD) is obtained by combining the population balance equation with the computational fluid dynamics in following the discretization method with and without turbulence aggregation kernel. The simulated CSD with turbulence aggregation kernel are 7 % more consistent with experimental results. The effects of collision angle, outlet nozzle length, Reynolds number, and solution concentration on the average particle size are assessed. An increase in the collision angle from 60 to 180°decreases the average particle size. The ultrafine loratadine nanoparticles of 49 nm are obtained with a narrow distribution, related to the angle of 180⁰, outlet nozzle length of 0.5 cm, Reynolds number of 4875, and the solution concentration of 35 mg/ml.

Warm-phase spectral-bin microphysics in ICON: reasons of sensitivity to aerosols

The warm-phase version of the Spectral-Bin Microphysics (SBM) scheme has been implemented into the ICON model and has been tested in a supercell storm simulation. The results of two-moment (2M) bulk scheme which exists in ICON and SBM were compared in all aspects related to warm processes, especially with regards to sensitivity to aerosols.In all simulations a strong storm with maximum updrafts exceeding 25 m/s was simulated. The maximum vertical velocity in the 2M bulk scheme does not depend on aerosols. However, the maximum vertical velocity in SBM with high aerosol concentration was found substantially higher than in the case of low aerosol concentration.Despite the insensitivity of maximum vertical velocity to aerosols, the microphysics of the 2M scheme is sensitive to aerosols. Both SBM and 2M schemes showed faster rain formation in case of low aerosol concentration; both schemes indicate that first raindrops form when the mean volume radius exceeds ~15 μm. In both schemes the first raindrops form near cloud top in an undiluted core and fall along the cloud edges at the mature stage. At the decaying stage, raindrops fall through the cloud core. The zone of rainfall at the lower few kilometers coincides with the zones of strong downdrafts. A substantial effect of aerosols on intensity and spatial distribution of precipitation was found. In the case of low aerosol concentration raindrops form earlier and at lower altitudes. As a result, the area covered by rain is lower, but the maximum of the rain intensity is higher than in case of high aerosol concentration. Finally, we discuss the hindering effects of large supersaturation via mass loading on the cloud development in case of low aerosol concentration, and examine the validity of the well-known saturation adjustment procedure.

The polymorph and crystal habit control of dl-methionine assisted by ultrasound

In this work, ultrasound was applied to the batch crystallization of dl-methionine, dedicated to developing the strategy to achieve pure metastable form, regular crystal habit, and high yields of dl-methionine. Experimental analyses for batch crystallization were performed to investigate the effects of ultrasound field, supersaturation, and temperature on dl-methionine crystal form. It was found that ultrasound was more conducive to the formation of dl-methionine metastable crystals by promoting nucleation. Moreover, the artificial neural network was used to predict crystal form according to the input of experimental samples. Based on the goal of crystal habit optimization, experiments were designed to find the key factors to control product quality, and the experimental results correspond to the prediction results. It was found that ultrasound could result in high bulk density of the product due to the optimization of crystal habit and crystal size distribution, and the mechanism of ultrasound on crystal habit and yield was investigated. This study provided a deeper insight into the mechanisms of ultrasound on nucleation and crystal growth, which could also be used as an effective strategy to improve the physicochemical properties of a product by applying ultrasound to achieve simultaneous multi-objective optimization.

The effect of ice supersaturation and thin cirrus on lapse rates in the upper troposphere

Abstract. In this paper, the effects of ice-supersaturated regions and thin, subvisual cirrus clouds on lapse rates are examined. For that, probability distribution and density functions of the lapse rate and the potential temperature gradients from 10 years of measurement data from the MOZAIC/IAGOS project and ERA5 reanalysis data were produced, and an analysis of an example case of an ice-supersaturated region with a large vertical extent is performed. For the study of the probability distribution and density functions, a distinction is made between ice-subsaturated and ice-supersaturated air masses (persistent contrails) and situations of particularly high ice supersaturation that allow the formation of optically thick and strongly warming contrails. The estimation of the lapse rates involves two adjacent standard pressure levels of the reanalysis surrounding MOZAIC's measurement/flight points. If the upper of these levels is in the stratosphere, the distribution function for subsaturated cases shows much lower lapse rates than those of supersaturated cases. If all levels are in the troposphere, the distributions become more similar, but the average lapse rates are still higher in supersaturated than in subsaturated cases, and the distributions peak at higher values and are narrower in ice-supersaturated regions (ISSRs) than elsewhere. This narrowing is particularly pronounced if there is substantial supersaturation. For the examination of an example case, ERA5 data and forecasts from ICON-EU (DWD) are compared. ERA5 data, in particular, show a large ice-supersaturated region below the tropopause, which was pushed up by uplifting air, while the data of ICON-EU indicate areas of saturation. The lapse rate in this ice-supersaturated region (ISSR), which is large, is associated with clouds and high relative humidity. Supersaturation and cloud formation result from uplifting of air layers. The temperature gradient within an uplifting layer steepens, for both dry and moist air. As soon as condensation or ice formation starts in the upper part of a lifting layer, the release of latent heat begins to decrease the lapse rate, but radiation starts to act in the opposite direction, keeping the lapse rate high. The highest lapse rates close to the stability limit can only be reached in potentially unstable situations.

Small-angle neutron scattering applied to low-dose neutron-irradiated Fe-Cr alloys and ferritic martensitic steel Eurofer97.

Ferritic/martensitic (F/M) Fe-Cr-based steels are candidates for applications in nuclear fission and fusion. Previous experimental results for neutron-irradiated binary Fe-Cr alloys and high-dose neutron-irradiated F/M steels contributed greatly to the understanding of the irradiation behaviour of these groups of materials. However, some details still need to be addressed. Such gaps are related to the effect of secondary alloying and impurity elements, such as Ni and Si, as well as the dose dependence at lower neutron doses [e.g. in the range 0.1-1 displacements per atom (dpa)]. This input is essential, for example, for multiscale modelling of irradiation effects or the evaluation of nuclear fission or fusion components at the first stages of operation. Using small-angle neutron scattering, three issues are addressed: (1) the effect of Cr undersaturation (5% Cr) and supersaturation (14% Cr) on the formation of irradiation-induced solute atom clusters/precipitates in low-dose neutron-irradiated Fe-Cr alloys in the presence of intentionally added levels of Ni, Si and P; (2) the effect of irradiation temperature (290°C versus 450°C); and (3) the effect of neutron dose in the range 0.06-0.6 dpa on the irradiation response of the reduced-activation F/M 9%Cr steel Eurofer97. The irradiation-enhanced formation of Cr-rich α'-phase particles was found to be the dominant effect for supersaturated Fe-14Cr-NiSiP at both irradiation temperatures. In contrast, α' formation is impossible in Fe-5Cr-NiSiP, for which the pronounced irradiation effects observed at 0.1 dpa are mainly attributed to added Ni, Si and P. Finally, Eurofer97 exhibits an exceptionally weak irradiation effect at low neutron doses, the reasons for which are also considered.

Effect of Niobium Supersaturation in Austenite on the Static Recrystallization Behavior of Carbon Structural Steels

This work describes the effect of Nb supersaturation in austenite on the suppression of static recrystallization of austenite during an isothermal holding period following hot deformation. The investigation involved three carbon structural steels with varying Nb concentration at constant C (0.20 pct) and N (0.007 pct) levels. The isothermal double-hit deformation technique led to the determination of T5 pct and T95 pct (recrystallization-stop and full recrystallization temperatures, respectively) as a function of a true strain and interpass time. The results indicate that the T5 pct increases with increasing Nb supersaturation in austenite at a rate of 40 °C per 0.006 pct Nb supersaturation for a true stain ε=0.40. At each respective T5 pct, all tested steels exhibited an Nb supersaturation ratio ≥ 7.5 in austenite. A high, localized strain-induced precipitation of Nb(CN) was observed at the austenite subgrain boundaries in the unrecrystallized microstructure. This translated into higher values for local precipitate-pinning forces (FPIN), which were significantly higher than that predicted from equilibrium thermodynamics. The critical FPIN for retardation of static recrystallization was found to be 1.6 MPa at the respective T5 pct for each steel. The present study has contributed to advancing our knowledge of the interplay between Nb solute supersaturation and volume fraction of Nb(CN) precipitation in particular for carbon structural steels. It has also highlighted an opportunity to apply niobium, even an ultra-low addition (i.e., < 100 ppm) to commodity-grade structural steels to reduce overall alloying costs.

Additive-assisted preferential crystallization of racemic component: A case of norvaline

Herein, we report a successful resolution of L-norvaline, a racemic compound system, performed near the eutectic composition by coupling preferential crystallization with tailor-made additives. The structures of enantiomer and racemate were characterized by PXRD, DSC, and the enantiomeric purity were measured by Chiral HPLC. The preferential crystallization process was designed and established from binary melting phase diagram and ternary solution phase diagram. The effects of supersaturation, solution enantiomer composition, and seed quantity on the preferential crystallization process were investigated. However, the significant improvements of enantiomeric purity and product yield were demonstrated by additive-assisted preferential crystallization approach using tailor-made additives. These additives bearing similar structure motifs to norvaline a highly selective binding to the racemate rather than enantiomer and remarkably suppress nucleation of DL-norvaline, the key factor determining the resultant enantiomer purity and separation efficiency. The underly inhibition principle was revealed due to the centrosymmetric packing of the racemate while the polarity of enantiomer leads to only partial or slight crystallization suppression. The interesting inhibition mode by tailor-made additives is also believed to be applicable for other racemic crystallization systems. Our established additive-assisted preferential crystallization has showed great potential in the development of separation technology and resolution of enantiomer from racemic compounds.

Ultrasound‐Assisted Slug‐Flow Tubular Crystallization for Preparation of Fine Ibuprofen Crystals

AbstractIbuprofen fine crystals prepared by commonly used methods have some problems such as low‐crystallinity product and uneven distributed particle size. An ultrasonic‐assisted tubular crystallization system was developed. The effects of tubular crystallization temperature, supersaturation, residence time, surfactant, and flow pattern on the crystal size distribution and average particle size were studied. It was found that ultrasound promotes nucleation and reduces crystal aggregation. Ibuprofen crystals with an average particle size of 6.23 μm were formed owing to the high degree of continuous supersaturation and promoted micromixing. Finally, a possible mechanism of enhancement of micromixing under ultrasonic and slug flow on tubular crystallization was proposed.

A study of hydromagnesite and nesquehonite precipitation in indirect aqueous carbonation of thermally-activated serpentine in a batch mode

To control and decrease the amount of greenhouse gases in the environment, the process of carbonation is attracting particular attention. Via carbonation, it is possible to control carbon dioxide (CO2) emissions by using mining residues. This study focuses on the precipitation step of aqueous indirect carbonation of serpentine mining wastes using the actual carbonated solution. To our knowledge, studies of magnesium carbonate precipitation have been based on synthetic solutions only, unlike the process in the present study. Three solutions prepared from the carbonation step with different concentrations were precipitated at temperatures ranging from 25 to 90 °C. The solution contained dissolved magnesium and inorganic carbon in addition to impurities, such as calcium and silica that are initially present in serpentine rock. Nesquehonite precipitated at reaction temperatures of 25, 40 and 50 °C. Hydromagnesite was precipitated at 60, 70, 80, and 90 °C via transition from nesquehonite. The study showed that increasing temperatures accelerate precipitation kinetics and hastens the transition period from nesquehonite to hydromagnesite. The investigation of the effects of the initial supersaturation showed that higher supersaturation promotes a better reaction yield and consequently a better sequestration potential, but lower supersaturation is better for crystal growth. However, supersaturation had no effect on the transition phenomenon from nesquehonite to hydromagnesite. Also, the grain sizes of the resulting minerals had different ranges from those obtained in synthetic solutions. The average size of the nesquehonite in our experiments was around 120 μm, while nesquehonite’s size was around 25 µm when prepared from a synthetic solution under relatively comparable operating conditions. The average size of the hydromagnesite was around 50 μm, while its size was around 30 µm when prepared from a synthetic solution, under relatively comparable the same operating conditions.

The Morphology and Solute Segregation of Dendrite Growth in Ti-4.5% Al Alloy: A Phase-Field Study

Ti-Al alloys have excellent high-temperature performance and are often used in the manufacture of high-pressure compressors and low-pressure turbine blades for military aircraft engines. However, solute segregation is easy to occur in the solidification process of Ti-Al alloys, which will affect their properties. In this study, we used the quantitative phase-field model developed by Karma to study the equiaxed dendrite growth of Ti-4.5% Al alloy. The effects of supersaturation, undercooling and thermal disturbance on the dendrite morphology and solute segregation were studied. The results showed that the increase of supersaturation and undercooling will promote the growth of secondary dendrite arms and aggravate the solute segregation. When the undercooling is large, the solute in the root of the primary dendrite arms is seriously enriched, and when the supersaturation is large, the time for the dendrite tips to reach a steady-state will be shortened. The thermal disturbance mainly affects the morphology and distribution of the secondary dendrite arms but has almost no effect on the steady-state of the primary dendrite tips. This is helpful to understand the cause of solute segregation in Ti-Al alloy theoretically.

Frequency response analysis for MSMPR crystallizer with modulated feed flow rate: A method for studying secondary nucleation mechanism

In industrial crystallization, understanding the effect of individual secondary nucleation mechanisms is difficult. This paper presents frequency response of a mixed suspension mixed product removal (MSMPR) crystallizer to a periodic modulation in feed rate. This will help in roughly understanding the effect of magma density or thick solute layer adsorbed on crystals, on the formation of secondary nucleation, which are otherwise practically impossible to understand through stirrer speed modulation (V. Bal and B. Peters, Cryst. Groth Des., 21 (2021) 227–234). Feed rate modulation drives the oscillation in magma density, which in turn drives the supersaturation. Combined effect of magma density and supersaturation controls the oscillation in nucleation rate and hence, damped oscillation in number density. In the intermediate frequency limit, strong oscillation in either amplitude or phase shift can be exploited to study the different secondary nucleation mechanisms. There is a narrow range of frequency and amplitude of feed rate modulation over which the crystallizer should be operated for detectable response.