Pilot Plant Investigation on the Kinetics of Dextrose Cooling Crystallization (original) (raw)
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Prediction of Dextrose Nucleation Kinetics by the Growth Rate of Crystallites
Chemical Engineering & Technology, 2006
An investigation on the dextrose nucleation carried out in the presence of seeds is reported. Induction time and nucleation point were measured in seeded solutions by eye and by using a nephelometer. The nucleation point was interpreted as the instant when crystallites, generated by seeds, grow up to crystals of detectable size. By applying the approach proposed by Kashchiev [1], the induction time values obtained were satisfactorily predicted when a birth and spread growth rate model was assumed. Moreover, by extending the same approach to the prediction of the nucleation point, obtained by linear cooling, a nucleation curve in good agreement with the experimental points was determined.
Particulate Science and Technology, 2009
The crystal growth process of 2n(Met)(A~O)~*H20 from the mixed solution of water and acetone has been investigated using a Calvet microcalorimeter. The heat produced and the rate of heat production during the crystal growth process at 298.15, 301.15, 304.15,307.15 and 310.15 K have been measured. On the basis of experimental and calculated results, the thermodynamics parameters (the apparent activation enthalpy, the activation entropy, and the activation free energy), the rate constant and the kinetic parameters (the activation energy, the pre-exponential factor) during the crystal growth process have been obtained. The results show that the crystal growth proceeds in accordance with the Burton-Cabrera-Frank dislocation theory.
Influence of impurities on the crystallization of dextrose monohydrate
Journal of Crystal Growth, 2012
The effects of impurities on dextrose monohydrate crystallization were investigated. Crystal nucleation and growth kinetics in the presence of impurities were studied using an in-line focused beam reflectance monitoring (FBRM) technique and an in-line process refractometer. Experimental data were obtained from runs carried out at different impurity levels between 4 and 11 wt% in the high dextrose equivalent (DE) syrup. It was found that impurities have no significant influence on the solubility of dextrose in water. However, impurities have a clear influence on the nucleation and growth kinetics of dextrose monohydrate crystallization. Nucleation and growth rate were favored by low levels of impurities in the syrup.
Caking Phenomena During Pilot-Scale Crystallization of Dextrose Monohydrate
Indonesian Journal of Chemistry
Dextrose Monohydrate (DMH) is a bulk chemical used in the food, beverage, and pharmaceutical industries. The caking often appeared in the crystallization of DMH. Caking is an agglomeration that can affect the product quality of DMH and is dependent on the type of impeller. This study aimed to determine the type of impeller to avoid the caking during the DMH crystallization and identify the DMH caking. The results showed that caking did not occur on the helical ribbon and anchor impeller, while caking appeared on the Rushton turbine impeller. Computational fluid mechanics (CFD) analysis showed that caking occurs due to uneven homogeneity of stirring. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) studies showed that DMH caking and non-caking had the same peak pattern. Meanwhile, optical microscope and scanning electron microscope (SEM) analysis showed that the DMH caking seen agglomerate. Density analysis showed that DMH with caking was 1.257–1.350 kg/L, while the non-...
Separation and Purification Technology, 2015
A general technique is derived to formulate and solve the dynamic optimisation problems for crystallisation, in order to re-evaluate the growth rate correlations and search for the optimal cooling and heating strategies (evaporative mode only). The dynamic model of a process making ␣-lactose monohydrate is first revised for these operations using seed crystals: batch cooling, semi-batch cooling and heating, and continuous cooling. Experiments are conducted in 2 and 20 L crystallisers under various seeding, cooling and heating strategies to evaluate the constants in the power law function, which correlates the growth rate of the particles with supersaturation. Using a nonlinear least square method, the best curve fitting of experimental data to the model yields G = 0.007T(100(x ␣ /x w ) − sol ␣ ) 2.7 . The value of n = 2.7, which is applicable to all operations investigated in the study. The value of k however, must be estimated for selected seeding and cooling strategies, and most importantly for the type of syrup fed to the crystalliser. Using k = 0.007 in simulations and experiments of jet-milled seeds at 1.5% seeding ratio, the experimental results agreed well with predictions before the growth became slow. A semi-batch is slightly faster than a batch process and evaporative semi-batch is much faster than cooling operation but is more difficult to control. The performance of a cooling and seeding run in continuous mode is simulated. The system reached steady state after seven residence times but the predicted particle size could only be stabilised after 100 h. The developed methodology can be applied to the crystallisation of many other substances but is not limited to the food or dairy industries.
1998
The work described in this thesis was performed to investigate the effect of altering the conditions used during the crystallisation of dextrose on its physio-chemical and mechanical properties and how these in turn altered its behaviour both during and after compaction. Initial experiments were conducted in an effort to grow large single crystals of dextrose capable of being mechanically tested. Although a gel crystallisation technique capable of growing single crystals of dextrose was developed, the crystals proved unsuitable for testing and the gel crystallisation technique was not flexible enough to permit a wide range of crystallisation conditions to be examined. A second set of crystallisation experiments was conducted using a small batch crystallisation unit. Batches of dextrose were crystallised by altering a wide range of process conditions such as crystallisation cooling rate, level of initial supersaturation, growth time, seed crystal size, presence of impurities and crys...
AIChE Journal, 2012
The batch cooling solution crystallization of Ammonium Oxalate (AO) was performed in water at various constant cooling rates. Measurements of the solute concentration were obtained using in situ ATR FTIR spectroscopy, and discrete-time estimates of the Crystal Size Distribution (CSD) were computed thanks to in situ image acquisition and off-line image analysis. The crystallization process was then simulated using Population Balance Equations (PBE). Estimates of the nucleation and growth parameters were computed through model/experiments fitting. According to the cooling rate, the PBE model allowed distinguishing between two distinct crystallization regimes, separated by an "intermediate regime". The results allow assessing the respective contributions and shortcomings of solute concentration measurements and granulometric data to the identification of nucleation and growth kinetic parameters. It is shown in particular that no real separate estimation of nucleation and growth parameters can be obtained in the absence of CSD data.
Organic Process Research & Development, 2019
Continuous crystallization has recently gained attention in industrial crystallization. This paper summarizes the study of continuous antisolvent crystallization of α-lactose monohydrate using ethanol as an antisolvent. The main objective of the work is to develop a process for continuous antisolvent crystallization and the impact of operating parameters such as initial concentration of solute, residence time, impurity, recycle (with and without fines) and anti-solvent addition rate on the crystal size, shape and the polymorphic form. The mathematical model is developed for continuous antisolvent crystallization comprising of population balance equation (PBE), material balance and crystallization kinetics. Results show that with an increase in residence time and initial lactose concentration, size of lactose crystals increased however, no change in the morphology is observed. It is also observed that incorporation of whey proteins as impurities reduces the crystal size as well as residual lactose recovery. In order to increase the yield, recycle, with and without fines is also studied and a considerably enhancement in the lactose recovery was observed. It is found that with an increase in anti-solvent addition rate, formation of β-lactose occurs preferentially. The kinetic parameters i.e. growth and nucleation parameters are estimated by fitting the model with the experimental data. The transient dynamics shown by the profiles obtained during the trial are also discussed. The work shows that there is a potential to achieve desired the shape, size and the polymorphic form of lactose crystals by changing the process parameters.
The bulk crystallization of α‐lactose monohydrate from aqueous solution
Journal of Pharmaceutical Sciences, 2001
The bulk crystallization of a-lactose monohydrate from aqueous solution by primary nucleation has been studied under controlled conditions of supersaturation, temperature, and pH. The induction times to nucleation were extremely long compared with those generally observed for other materials, even at the high supersaturations used in the experiment. As a result, it was necessary to stir the supersaturated solution vigorously to induce nucleation in a reasonable but still lengthy working time. Even then, nucleation only occurred to a limited extent, following which growth ceased for 8-10 h before resuming. After this period, growth recommenced but again slowed to a low rate after another 8 h. At this stage, the yield of product was low and in most cases the particles had achieved sizes close to the maximum noted. The yields increased with further crystallization time (22-72 h total from the recommencement of growth) to give, under high initial supersaturation conditions, amounts of product close to the theoretical value. For the most part, however, the particle size did not increase with this later increase in yield, showing only significant changes after the extremely long total crystallization times. It is proposed that these extreme properties result from the formation in solution by mutarotation of the anomer a-lactose, which inhibits nucleation as well as its previously observed influence on growth.
Journal of Food and Nutrition Research, 2019
Introduction: In this research work, we investigated the influence of the biodegradation of dextran catalyzed by dextranase enzymes during sugar manufacturing on the rate of sucrose crystallization and growth rate of sucrose crystals in pure sucrose solution at different temperatures. Methods: To elucidate the influence of biodegradation of dextran on the growth rate of sucrose crystals, dextran of Mw 2,000,000 g/mol (T 2000) was admixed in concentrations between (1000-10000 ppm) with (60%-75% w/w) sucrose solution.. The hydrolysis of dextran was carried out at 55.0 °C and pH 5.5 at different dextranase concentration, and then the samples were immediately subjected to the crystallization process. Results: The most pronounced effect of dextran on the growth rate of sucrose crystals was found with T2000 at concentrations more than 5000 ppm at 60°C. From the results it could be shown that an increase of crystallization rate of up to 50% after biodegradation of dextran T 2000 using dextranase enzyme at concentration of 100 ppm, compared to crystallization rate with pure sucrose solution in the presence of dextran T 2000. It was obvious that after dextran hydrolyzed by dextranase, more perfect crystal surfaces are built than at 60°C. Conclusion: Dextran biodegradation catalyzed by dextranase enzyme has increased the crystallization rate of sucrose and more perfect crystal surfaces are built. Such a positive influence of biodegradation of dextran using dextranase enzyme decreases crystallization time in the sugar house and thus decreases the production costs of sugar manufacturing.