Due to the paramagnetic property of liquid oxygen,the Kelvin force can be induced in liquid oxygen under non-uniform magnetic field.Based on the volume of fluid(VOF)model,the positioning effect of the force in liquid ...Due to the paramagnetic property of liquid oxygen,the Kelvin force can be induced in liquid oxygen under non-uniform magnetic field.Based on the volume of fluid(VOF)model,the positioning effect of the force in liquid oxygen tanks is analyzed under various Bond numbers(Bo)and magnetic Bond numbers(Bom).The results show that the magnetic field has the effect of repositioning the liquid oxygen in the tank when the gravity field is not enough or absent.Additionally,the gas-liquid interface has a periodic fluctuation during the process due to the inhomogeneous Kelvin force distribution,and more effective suppression of fluctuation can be achieved under the condition of a larger Bom.The new method of controlling gas-liquid interface of liquid oxygen tank under micro gravity condition is hoped to be developed in the future.展开更多
Crystal nucleation is important to control the product properties in industrial crystallization processes. To investigate crystallization phenomena, methods which rely on microscopic volumes have gained relevance over...Crystal nucleation is important to control the product properties in industrial crystallization processes. To investigate crystallization phenomena, methods which rely on microscopic volumes have gained relevance over the last decade. Microfluidic devices are suitable for carrying out crystallization experiments based on a large set of individual droplets in the nanoliter range. In this work, we propose a simple method to manufacture such devices from polycarbonate as an alternative to conventional chips made of poly (dimethylsiloxane). The microfluidic device consists of two main functional parts: A T-junction for droplet generation and a section for storage and observation of up to 400 individual droplets. Using these manufactured devices, it is easy to produce and store highly monodisperse droplets of substances that require either a hydrophilic or hydrophobic surface of the microchannel. Since crystal nucleation is a stochastic process which depends on the sample volume, a reproducible droplet volume is of great importance for crystallization experiments. The versatile applicability of the manufactured devices is demonstrated for substances which are used in different crystallization applications, for example, solution crystallization (aqueous potassium nitrate solution) and melt crystallization (ethylene glycol distearate). Finally, we demonstrate that the manufactured microfluidic devices in our experimental setup can be used to conduct crystal nucleation measurements. Based on these measurements we discuss our results with respect to state-of-the-art nucleation models.展开更多
Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications,especially for the steel and refractory industry.Accurate turbulent flow and temperature fields are of major importan...Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications,especially for the steel and refractory industry.Accurate turbulent flow and temperature fields are of major importance in order to predict details on the concentration fields.The performances of the GRI-Mech 3.0 and the Jones and Lindstedt mechanisms are compared.Detailed chemistry is included with the GRI-Mech 3.0 and J-L kinetic mechanisms in combination with the laminar flamelet combustion model.The combustion system selected for this comparison is a confined non-premixed methane flame surrounded by co-flowing air The simulation results are compared with experimental data of Lewis and Smoot(2001).展开更多
To predict the particle size and layer-thickness distributions(LTDs)in a continuously operated horizontal fluidized-bed granulation process,two alternative models were considered.A one-dimensional two-zone model was p...To predict the particle size and layer-thickness distributions(LTDs)in a continuously operated horizontal fluidized-bed granulation process,two alternative models were considered.A one-dimensional two-zone model was proposed,which describes with population-balance equations the particle growth in a spraying zone that is separated from the drying zone.The residence-time distribution(RTD)was calculated from a literature correlation and was coupled with a population-balance model via a tank-in-series model with reflux.A two-dimensional,one-zone population-balance model,which was based directly on the RTD and the feed particle-size distribution(PSD)was also used.Granulation experiments were conducted and analyzed microscopically and with a camera optical device to determine the sample PSDs.LTDs over the particle population were derived from the PSDs and were analyzed directly by micro-computer-tomography.To compare the simulated data with the experimentally determined distributions,the PSDs were converted to LTDs.The good agreement shows that both methods are suitable to determine the PSD from an RTD of an arbitrary granulation process in a horizontal fluidized bed.Improvement appears necessary with regards to the LTD spread.展开更多
The paper presents new criteria for calculation of heat transfer coefficients and flow resistance during boiling inside vertical tubes with spring inserts, developed on the basis of own experimental research. Calculat...The paper presents new criteria for calculation of heat transfer coefficients and flow resistance during boiling inside vertical tubes with spring inserts, developed on the basis of own experimental research. Calculations of the geometric parameters of the spring insert were carried out using the Nelder-Mead optimization method for various optimization criteria(maximizing the increase ratios for heat transfer coefficient and flow resistance, minimizing entropy, own optimization criterion). The results of optimization calculations were verified by the optimization procedures available in Statistica.展开更多
This review discusses important research developments and arising challenges in the field of industrial crystallization with an emphasis on recent problems. The most relevant areas of research have been identified. Th...This review discusses important research developments and arising challenges in the field of industrial crystallization with an emphasis on recent problems. The most relevant areas of research have been identified. These are the prediction of phase diagrams; the prediction of effects of impurities and additives; the design of fluid dynamics; the process control with process analytical technologies （PAT） tools; the polymorph and solvate screening; the stabilization of non-stable phases; and the product design. The potential of industrial crystallization in various areas is outlined and discussed with particular reference to the product quality, process design, and control. On this basis, possible future directions for research and development have been pointed out to highlight the importance of crystallization as an outstanding technique for separation, purification as well as for product design.展开更多
Previous work （Hussain et al. （2013）. Chemical Engineering Science, 101, 35） has pointed out that the conventional, one-dimensional population balance equation for aggregation can be expanded to accurately reprodu...Previous work （Hussain et al. （2013）. Chemical Engineering Science, 101, 35） has pointed out that the conventional, one-dimensional population balance equation for aggregation can be expanded to accurately reproduce the results of discrete simulations of spray fluidized bed agglomeration. However, some parameters had to be imported from the discrete simulation （Monte-Carlo）. The present paper shows how the expanded population balance can be run without importing parameters from the Monte-Carlo simulation. The expanded population balance still reproduces the results of Monte-Carlo simulations accurately, taking into account key micro-scale phenomena （sessile droplet drying, efficiency of collisions）, but with much lower computational cost. Required input parameters are just the drying time of sessile droplets （calculated in advance）, and the prefactor of an equation that correlates particle collision frequency with fluidized bed expansion. In this way, the expanded population balance is, apart from autonomous, also （nearly） predictive. Its performance is demonstrated by comparisons with both Monte-Carlo results and experimental data for various operating conditions （binder mass flow rate, gas temperature）. Despite formally being a one-dimensional expression, the expanded population balance captures additional properties, such as the number of wet particles and the number of droplets in the system, which are even difficult to measure in exoeriments.展开更多
The experimental characterization of particle dynamics in fluidized beds is of great importance in fostering an understanding of solid phase motion and its effect on particle properties in granulation processes, Commo...The experimental characterization of particle dynamics in fluidized beds is of great importance in fostering an understanding of solid phase motion and its effect on particle properties in granulation processes, Commonly used techniques such as particle image velocimetry rely on the cross-correlation of illumination intensity and averaging procedures. It is not possible to obtain single particle velocities with such techniques. Moreover, the estimated velocities may not accurately represent the local particle velocities in regions with high velocity gradients. Consequently, there is a need for devices and methods that are capable of acquiring individual particle velocities. This paper describes how particle tracking velocimetry can be adapted to dense particulate flows. The approach presented in this paper couples high-speed imaging with an innovative segmentation algorithm for particle detection, and employs the Voronoi method to solve the assignment problem usually encountered in densely seeded fows. Lagrangian particle tracks are obtained as primary information, and these serve as the basis for calculating sophisticated quantities such as the solid-phase flow field, granular temperature, and solid volume fraction. We show that the consistency of individual trajectories is sufficient to recognize collision events.展开更多
Here a case study ofL-asparaginase II out of a recombinant Escherichia coli is presented. The target protein was obtained by simple cell disintegration and acetone precipitation. The L-asparaginase II has been crystal...Here a case study ofL-asparaginase II out of a recombinant Escherichia coli is presented. The target protein was obtained by simple cell disintegration and acetone precipitation. The L-asparaginase II has been crystallized in three different forms in the following microbatch crystallization. The rod-shaped crystals （-400 μm edge length） were obtained at either 8℃ or 22℃ after 17h by addition of PEG6ooo. The rectangular-shaped crystals were obtained after further recrystallization of the rod-shaped crystals. The rhombic-shaped crystals formed at 8℃ after 12 days when cold ethanol was used instead of PEG6000. All crystallizations were performed in tris-acetate buffer （50mmol-L-1, pH 5.1）. By crystallization, the specific activity of L-asparaginase II has increased 5-fold. The protein content and the purity of the crystals were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE）. The more concentrated L- asparaginase II out of an extract mixture and the presence of only less minor proteins after crystallization demonstrates that crystallization is an effective and mild method to purify the target protein. The single crystal X-ray diffraction pattern reveals that the crystals are proteins and the X-ray powder diffraction （XRPD） pattern shows clearly that the crystals forming in PEG600o and ethanol have different crystal structures.展开更多
Particle coatings are used extensively to generate dispersed solids with well-defined properties, e.g., to protect active ingredients, with most coating processes using core particles of a diameter larger than 200 μm...Particle coatings are used extensively to generate dispersed solids with well-defined properties, e.g., to protect active ingredients, with most coating processes using core particles of a diameter larger than 200 μm. This work contributes to the development of a coating process for fine dispersed particles （diam- eter less than 50 μm） by combining two particle-formulation processes, namely, coating and spray drying. The feasibility of the operation is based on and demonstrated by the innovative application of a two-fluid nozzle. Experiments were conducted by using glass particles as core particles and sodium benzoate as the coating agent. The coating of finely dispersed particles is achieved by the spraying of particles and coating solution as a homogeneous suspension. The aim is to create droplets with only one contained particle at the nozzle outlet. After evaporation of the water in the droplet, a thin solid film is built on the particle surface. The suspension viscosity was measured and compared with empirical equations from the literature. The liquid-film thickness on the particle surface was calculated to predict the building of a uniform coating layer or agglomerates. In this study, the feasibility of pneumatic transport through the nozzle and an investigation of the process were illustrated. The agglomeration fraction and degree of coating of the particle surface were analyzed optically by scanning electron microscopy. In this way, the influence of different processes and suspension parameters on the product quality were determined.展开更多
Dielectric properties are validated to be correlated with the changes of food quality during 4℃ storage,thus it could be used as predictive indicators for the quality parameters of salmon(Salmo salar)during cold stor...Dielectric properties are validated to be correlated with the changes of food quality during 4℃ storage,thus it could be used as predictive indicators for the quality parameters of salmon(Salmo salar)during cold storage.An open-ended coaxial detection method was used to determine the dielectric properties(dielectric constantε'and dielectric lossε")of salmon at the frequency range of 20-2500 MHz,and to explore the relationship between dielectric properties and volatile base nitrogen(TVB-N),thiobarbituric acid reactants(TBARS),total viable counts(TVC),pH and K-value in salmon fillets during storage for 7 d.Results showed that the TVB-N,TBARS,TVC and K-value of salmon increased linearly with the increase of storage time,and the pH decreased firstly and increased subsequently.Also,the dielectric properties(ε'andε")decreased with the increase of frequency,and increased with the increase of storage time.During 7 d storage,ε"increased the most at the frequency of 27.12 and 40.68 MHz,while at the frequency of 915 MHz and 2450 MHz,the increase ofε"was smaller.Results analyzed by Pearson correlation analysis showed that significant correlation(p<0.01)was found betweenε"and TVB-N and TBARS at the frequency of 27.12,40.68,100.00,300 and 915 MHz.The results of the partial least square(PLS)model showed that all the determination coefficients(R2pred)were over 0.900.Especially for TBARS,the R2pred of PLS-ε'and PLS-ε"were 0.913 and 0.920,respectively,and the root mean square error of prediction(RMSEP)were 0.041 and 0.039,respectively.However,the highest R2pred for PLS-ε'and PLS-ε"both occurred in TVB-N.Also,the predicted values against measured values of TVB-N,TBARS and TVC of salmon presented a good linear relationship.The linear coefficient R2 of TVB-N,TBARS and TVC for PLS-ε'were 0.937,0.910 and 0.917 respectively,and 0.942,0.917 and 0.933 respectively for PLS-ε".The results demonstrated the dielectric properties combined with PLS analysis can be used as a rapid and non-destructive method to predict quality parameters of salmon during 4℃ storage and could be further applied to other aquatic products.展开更多
Multistage fluidized beds are frequently used for product drying in industry. One advantage of these fluidized beds is that they can achieve a high throughput, when operated continuously. In this study, γ- A1203 part...Multistage fluidized beds are frequently used for product drying in industry. One advantage of these fluidized beds is that they can achieve a high throughput, when operated continuously. In this study, γ- A1203 particles were dried in a pilot-scale horizontal fluidized bed, without considering any comminution effects. For each experiment, the particle moisture content distribution and residence time distribution were determined. To take into account particle back mixing in our experiments, a one-dimensional pop- ulation balance model that considers particle residence time was introduced into a fluidized bed-drying model. Experimental particle residence time distributions were reproduced using a tank-in-series model. Subsequently, the moisture content distribution was implemented, as a second dimension to the popu- lation balance in this model. These two-dimensional simulations were able to describe the experimental data, especially the spread in the residual particle moisture distribution, much more accurately than one-dimensional simulations. Using this novel two-dimensional model, the effects of different operating parameters （process gas temperature, solid feed rate, superficial air velocity） on the particle moisture content distribution were systematically studied.展开更多
Particle distribution in the cross-section of the flighted rotating drum(FRD)is critical to the analysis of heat and mass transfer between gas and solids.In this work,the particle tracking velocimetry(PTV)method is ap...Particle distribution in the cross-section of the flighted rotating drum(FRD)is critical to the analysis of heat and mass transfer between gas and solids.In this work,the particle tracking velocimetry(PTV)method is applied to study the influence of the number of flights on the particle motion in FRDs.The drum,installed with 1,4,8,or 12 rectangular flights,is filled with plastic balls to 15%and operated at various rotating speeds ranging from 10 rpm to 30 rpm.The results show that the number of flights has different effects on the holdup ratio and cascading rate of single flight and active flights.With 8 and 12 flights,the FRD produces a larger and more stable particle ratio of the dilute phase.Moreover,DEM simulations agree with PTV measurements,whereas literature models show significant deviations.展开更多
Residence time distributions （RTDs） in horizontal fluidised beds have a huge effect on solid product properties and are infuenced by the internal design of the apparatus, e.g. the separation into different compartme...Residence time distributions （RTDs） in horizontal fluidised beds have a huge effect on solid product properties and are infuenced by the internal design of the apparatus, e.g. the separation into different compartments by weirs. Weirs can be passed in or against the overall solid transport direction, with the back-flow resulting in axial dispersion, which is a measure of the spread of the RTD. Therefore, the ratio of exchange rates at weirs under different fluidisation conditions provides information on axial dispersion. In this work, a methodology based on particle tracking velocimetry is presented to obtain information on the exchange rates of particles at weirs in horizontal fluidised beds. The internal recirculation is studied for over-flow weirs with respect to different fluidisation conditions, providing a first step towards determining the effects of weirs and fluidisation conditions on axial dispersion and RTDs in horizontal fluidised beds.展开更多
Emulsions and crystallization are two independent research topics which normally do not overlap although a combination of the two could be applicable to many areas. Here, the importance of emulsions in the field of fa...Emulsions and crystallization are two independent research topics which normally do not overlap although a combination of the two could be applicable to many areas. Here, the importance of emulsions in the field of fat crystallization is described. Three applications with industrial relevance were chosen for investigation： fat fractionation, the solidification of phase change materials and solid lipid nanoparticles. For fat fractionation and phase change materials, emulsification can be applied as a tool to improve the fat crystallization process, and thus the product quality of the crystallized fat. Furthermore, the use of emulsification creates new solid lipid nanoparticles in the application fields such as area of fat crystallization.展开更多
The technique state to design counter-current extraction columns is based on the performance of pilot plant experiments. The modelling is then either with the equilibrium or dispersion model, whereas in the latter the...The technique state to design counter-current extraction columns is based on the performance of pilot plant experiments. The modelling is then either with the equilibrium or dispersion model, whereas in the latter the dispersion coefficient accounts for all hydrodynamic non-idealities. A new approach uses single droplet experiments to obtain the basic laws and functions governing droplet breakage, coalescence, relative velocity, and axial dispersion when using droplet populance balance models （DPBM）. The hydrodynamics simulation results show that the mean Sauter diameter, hold-up, and concentration profiles could be well predicted, which promotes the use of DPBM models for further applications in industrial scale.展开更多
The crystal morphology grown from a solution composed of an organic solvent, solute and additive can be predicted reliably by a computational method. Modeling the supersaturated solution as liquid phase is achieved by...The crystal morphology grown from a solution composed of an organic solvent, solute and additive can be predicted reliably by a computational method. Modeling the supersaturated solution as liquid phase is achieved by employing commercial software. The molecular composition of this solution is a required input parameter. The face specific diffusion coefficient of the solid （crystal surface） and liquid （solution） system is determined using the molecular dynamics procedure. The obtained diffusion coefficient is related to the specific face growth rate via the attachment energy of the pure morphology. The significant improvements are achieved in the morphology prediction because the investigation on the face growth rates in a complex growth environment （as multi-component solutions with additives） can be carried out based on the diffusion coefficients.展开更多
Increasing production effeciency and lowering costs are some of the many advantages melt crystallization technology offers over the conventional methodology of tabletting. A normal tablet consists of a pure shell or a...Increasing production effeciency and lowering costs are some of the many advantages melt crystallization technology offers over the conventional methodology of tabletting. A normal tablet consists of a pure shell or a coat and a separate core constituting the pharmaceutical active ingredient. Great emphasis is put on the purity of the shell since its purpose is to solely protect and deliver the active ingredient to its target. Melt crystallization is a purification （separation） process. It is discussed here for its ability to produce coated tablets, by separating the ＂coating＂ material from the ＂to be coated＂ material coming from one molten mixture. Molten drops of lutrol-ibuprofen mixture are produced using the drop forming technique. The subsequent analysis involves proving and quantifying the phase separation （coat purity）. The mechanism of a crystallizing drop is shown as direct evidence of the ongoing process. Moreover, solidified tablet batches are analyzed for the purity of their coating by measuring the ibuprofen concentration. This optimization process is carried out through multiple stages of development and condition enhancements in order to produce the most pure tablet coating. As a result, a trial showing an almost purely coated tablet is presented here.展开更多
Sugar spray coating is a frequently used process in the pharmaceutical industry. However, this process presents the disadvantage to form an amorphous coating around the active ingredient. A crystalline coating formed ...Sugar spray coating is a frequently used process in the pharmaceutical industry. However, this process presents the disadvantage to form an amorphous coating around the active ingredient. A crystalline coating formed on the surface of a tablet is highly desirable. Recently, a new process of coating by cooling crystallization has been developed and applied on bisacodyl pastilles obtained by melt crystallization. In this work, we investigated the feasibility of coating by cooling crystallization on ibuprofen ＂naked tablets＂ manufactured by compression. In the first part of this work, the solubility and the metastable zone width have been determined experimentally for the coating solution because they are essential factors for any crystallization process. In the second part, the coating process is investigated on the operating conditions that affect the surface morphology and the crystal growth rate. These experimental conditions include concentration of the coating solution, degree of sub-cooling, agitation speed, retention time, and surface properties of the naked ibuprofen tablets. The results show that naked tablet coating by cooling crystallization is feasible and can be applied in the pharmaceutical industry.展开更多
In this work,we demonstrate that particles can be coated in a fluidized bed w让h coating solution provided by a novel aerosol generator.Aerosol droplets are smaller than 1 pim in volume-based diameter,hence they are v...In this work,we demonstrate that particles can be coated in a fluidized bed w让h coating solution provided by a novel aerosol generator.Aerosol droplets are smaller than 1 pim in volume-based diameter,hence they are very much smaller than droplets in conventional spray fluidized bed processes(around 40μm).A proof-of-principle experiment with 30%aqueous coating solution of sodium benzoate and γ-Al2O3 core particles in 150 mm fluidized bed fed with droplet aerosol supplied from the chamber side is presented.To simultaneously coat and dry the particles,inlet of fluidization air was at 50℃ .Moreover,Monte Carlo simulations of coating with small aerosol and large spray droplets were conducted.Due to dramatically smaller building blocks,ultrathin particle coating of high-resolution(very small layer thickness)can be attained with the new aerosol process,with the potential of even going nanoscale.Full coverage of particles is reached substantially faster than in the conv entional process,so that material dema nd is much lower and sensitive materials can be processed in short reside nee time.Solids yield of around 30%was much higher than expected,that is considered to be technically viable and may be enhanced by the recycling of entrained solids or better equipment design.展开更多
基金supported by the Natural Science Foundation of China(No.51706190)the State Scholarship Fund of China Scholarship Council。
文摘Due to the paramagnetic property of liquid oxygen,the Kelvin force can be induced in liquid oxygen under non-uniform magnetic field.Based on the volume of fluid(VOF)model,the positioning effect of the force in liquid oxygen tanks is analyzed under various Bond numbers(Bo)and magnetic Bond numbers(Bom).The results show that the magnetic field has the effect of repositioning the liquid oxygen in the tank when the gravity field is not enough or absent.Additionally,the gas-liquid interface has a periodic fluctuation during the process due to the inhomogeneous Kelvin force distribution,and more effective suppression of fluctuation can be achieved under the condition of a larger Bom.The new method of controlling gas-liquid interface of liquid oxygen tank under micro gravity condition is hoped to be developed in the future.
文摘Crystal nucleation is important to control the product properties in industrial crystallization processes. To investigate crystallization phenomena, methods which rely on microscopic volumes have gained relevance over the last decade. Microfluidic devices are suitable for carrying out crystallization experiments based on a large set of individual droplets in the nanoliter range. In this work, we propose a simple method to manufacture such devices from polycarbonate as an alternative to conventional chips made of poly (dimethylsiloxane). The microfluidic device consists of two main functional parts: A T-junction for droplet generation and a section for storage and observation of up to 400 individual droplets. Using these manufactured devices, it is easy to produce and store highly monodisperse droplets of substances that require either a hydrophilic or hydrophobic surface of the microchannel. Since crystal nucleation is a stochastic process which depends on the sample volume, a reproducible droplet volume is of great importance for crystallization experiments. The versatile applicability of the manufactured devices is demonstrated for substances which are used in different crystallization applications, for example, solution crystallization (aqueous potassium nitrate solution) and melt crystallization (ethylene glycol distearate). Finally, we demonstrate that the manufactured microfluidic devices in our experimental setup can be used to conduct crystal nucleation measurements. Based on these measurements we discuss our results with respect to state-of-the-art nucleation models.
文摘Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications,especially for the steel and refractory industry.Accurate turbulent flow and temperature fields are of major importance in order to predict details on the concentration fields.The performances of the GRI-Mech 3.0 and the Jones and Lindstedt mechanisms are compared.Detailed chemistry is included with the GRI-Mech 3.0 and J-L kinetic mechanisms in combination with the laminar flamelet combustion model.The combustion system selected for this comparison is a confined non-premixed methane flame surrounded by co-flowing air The simulation results are compared with experimental data of Lewis and Smoot(2001).
基金the Forschungs-Gellschaft Verfahrens-Technik(GVT-IGF project no.17633 N)the German Federal Ministry of Science and Education(BMBF,WIGRATEC+project No.03WKCI4B).
文摘To predict the particle size and layer-thickness distributions(LTDs)in a continuously operated horizontal fluidized-bed granulation process,two alternative models were considered.A one-dimensional two-zone model was proposed,which describes with population-balance equations the particle growth in a spraying zone that is separated from the drying zone.The residence-time distribution(RTD)was calculated from a literature correlation and was coupled with a population-balance model via a tank-in-series model with reflux.A two-dimensional,one-zone population-balance model,which was based directly on the RTD and the feed particle-size distribution(PSD)was also used.Granulation experiments were conducted and analyzed microscopically and with a camera optical device to determine the sample PSDs.LTDs over the particle population were derived from the PSDs and were analyzed directly by micro-computer-tomography.To compare the simulated data with the experimentally determined distributions,the PSDs were converted to LTDs.The good agreement shows that both methods are suitable to determine the PSD from an RTD of an arbitrary granulation process in a horizontal fluidized bed.Improvement appears necessary with regards to the LTD spread.
基金part of research project N N512 458040,funded by the Polish National Science Centre
文摘The paper presents new criteria for calculation of heat transfer coefficients and flow resistance during boiling inside vertical tubes with spring inserts, developed on the basis of own experimental research. Calculations of the geometric parameters of the spring insert were carried out using the Nelder-Mead optimization method for various optimization criteria(maximizing the increase ratios for heat transfer coefficient and flow resistance, minimizing entropy, own optimization criterion). The results of optimization calculations were verified by the optimization procedures available in Statistica.
文摘This review discusses important research developments and arising challenges in the field of industrial crystallization with an emphasis on recent problems. The most relevant areas of research have been identified. These are the prediction of phase diagrams; the prediction of effects of impurities and additives; the design of fluid dynamics; the process control with process analytical technologies （PAT） tools; the polymorph and solvate screening; the stabilization of non-stable phases; and the product design. The potential of industrial crystallization in various areas is outlined and discussed with particular reference to the product quality, process design, and control. On this basis, possible future directions for research and development have been pointed out to highlight the importance of crystallization as an outstanding technique for separation, purification as well as for product design.
基金financial support provided by the German Science Foundation(DFG) within the framework of graduate school GRK-1554by the Alexander von Humboldt Foundation(research fellowship for Jitendra Kumar)
文摘Previous work （Hussain et al. （2013）. Chemical Engineering Science, 101, 35） has pointed out that the conventional, one-dimensional population balance equation for aggregation can be expanded to accurately reproduce the results of discrete simulations of spray fluidized bed agglomeration. However, some parameters had to be imported from the discrete simulation （Monte-Carlo）. The present paper shows how the expanded population balance can be run without importing parameters from the Monte-Carlo simulation. The expanded population balance still reproduces the results of Monte-Carlo simulations accurately, taking into account key micro-scale phenomena （sessile droplet drying, efficiency of collisions）, but with much lower computational cost. Required input parameters are just the drying time of sessile droplets （calculated in advance）, and the prefactor of an equation that correlates particle collision frequency with fluidized bed expansion. In this way, the expanded population balance is, apart from autonomous, also （nearly） predictive. Its performance is demonstrated by comparisons with both Monte-Carlo results and experimental data for various operating conditions （binder mass flow rate, gas temperature）. Despite formally being a one-dimensional expression, the expanded population balance captures additional properties, such as the number of wet particles and the number of droplets in the system, which are even difficult to measure in exoeriments.
基金funding of this work by the German Federal Ministry of Science and Education(BMBF) as part of the InnoProfile-Transfer project NaWiTec(03IPT701X)
文摘The experimental characterization of particle dynamics in fluidized beds is of great importance in fostering an understanding of solid phase motion and its effect on particle properties in granulation processes, Commonly used techniques such as particle image velocimetry rely on the cross-correlation of illumination intensity and averaging procedures. It is not possible to obtain single particle velocities with such techniques. Moreover, the estimated velocities may not accurately represent the local particle velocities in regions with high velocity gradients. Consequently, there is a need for devices and methods that are capable of acquiring individual particle velocities. This paper describes how particle tracking velocimetry can be adapted to dense particulate flows. The approach presented in this paper couples high-speed imaging with an innovative segmentation algorithm for particle detection, and employs the Voronoi method to solve the assignment problem usually encountered in densely seeded fows. Lagrangian particle tracks are obtained as primary information, and these serve as the basis for calculating sophisticated quantities such as the solid-phase flow field, granular temperature, and solid volume fraction. We show that the consistency of individual trajectories is sufficient to recognize collision events.
文摘Here a case study ofL-asparaginase II out of a recombinant Escherichia coli is presented. The target protein was obtained by simple cell disintegration and acetone precipitation. The L-asparaginase II has been crystallized in three different forms in the following microbatch crystallization. The rod-shaped crystals （-400 μm edge length） were obtained at either 8℃ or 22℃ after 17h by addition of PEG6ooo. The rectangular-shaped crystals were obtained after further recrystallization of the rod-shaped crystals. The rhombic-shaped crystals formed at 8℃ after 12 days when cold ethanol was used instead of PEG6000. All crystallizations were performed in tris-acetate buffer （50mmol-L-1, pH 5.1）. By crystallization, the specific activity of L-asparaginase II has increased 5-fold. The protein content and the purity of the crystals were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE）. The more concentrated L- asparaginase II out of an extract mixture and the presence of only less minor proteins after crystallization demonstrates that crystallization is an effective and mild method to purify the target protein. The single crystal X-ray diffraction pattern reveals that the crystals are proteins and the X-ray powder diffraction （XRPD） pattern shows clearly that the crystals forming in PEG600o and ethanol have different crystal structures.
文摘Particle coatings are used extensively to generate dispersed solids with well-defined properties, e.g., to protect active ingredients, with most coating processes using core particles of a diameter larger than 200 μm. This work contributes to the development of a coating process for fine dispersed particles （diam- eter less than 50 μm） by combining two particle-formulation processes, namely, coating and spray drying. The feasibility of the operation is based on and demonstrated by the innovative application of a two-fluid nozzle. Experiments were conducted by using glass particles as core particles and sodium benzoate as the coating agent. The coating of finely dispersed particles is achieved by the spraying of particles and coating solution as a homogeneous suspension. The aim is to create droplets with only one contained particle at the nozzle outlet. After evaporation of the water in the droplet, a thin solid film is built on the particle surface. The suspension viscosity was measured and compared with empirical equations from the literature. The liquid-film thickness on the particle surface was calculated to predict the building of a uniform coating layer or agglomerates. In this study, the feasibility of pneumatic transport through the nozzle and an investigation of the process were illustrated. The agglomeration fraction and degree of coating of the particle surface were analyzed optically by scanning electron microscopy. In this way, the influence of different processes and suspension parameters on the product quality were determined.
基金The authors acknowledge the National Natural Science Foundation of China(Grant No.31801613)for financial support to this research,and Professor Peng Zhang from Xidian University for his assistance in the data processing.
文摘Dielectric properties are validated to be correlated with the changes of food quality during 4℃ storage,thus it could be used as predictive indicators for the quality parameters of salmon(Salmo salar)during cold storage.An open-ended coaxial detection method was used to determine the dielectric properties(dielectric constantε'and dielectric lossε")of salmon at the frequency range of 20-2500 MHz,and to explore the relationship between dielectric properties and volatile base nitrogen(TVB-N),thiobarbituric acid reactants(TBARS),total viable counts(TVC),pH and K-value in salmon fillets during storage for 7 d.Results showed that the TVB-N,TBARS,TVC and K-value of salmon increased linearly with the increase of storage time,and the pH decreased firstly and increased subsequently.Also,the dielectric properties(ε'andε")decreased with the increase of frequency,and increased with the increase of storage time.During 7 d storage,ε"increased the most at the frequency of 27.12 and 40.68 MHz,while at the frequency of 915 MHz and 2450 MHz,the increase ofε"was smaller.Results analyzed by Pearson correlation analysis showed that significant correlation(p<0.01)was found betweenε"and TVB-N and TBARS at the frequency of 27.12,40.68,100.00,300 and 915 MHz.The results of the partial least square(PLS)model showed that all the determination coefficients(R2pred)were over 0.900.Especially for TBARS,the R2pred of PLS-ε'and PLS-ε"were 0.913 and 0.920,respectively,and the root mean square error of prediction(RMSEP)were 0.041 and 0.039,respectively.However,the highest R2pred for PLS-ε'and PLS-ε"both occurred in TVB-N.Also,the predicted values against measured values of TVB-N,TBARS and TVC of salmon presented a good linear relationship.The linear coefficient R2 of TVB-N,TBARS and TVC for PLS-ε'were 0.937,0.910 and 0.917 respectively,and 0.942,0.917 and 0.933 respectively for PLS-ε".The results demonstrated the dielectric properties combined with PLS analysis can be used as a rapid and non-destructive method to predict quality parameters of salmon during 4℃ storage and could be further applied to other aquatic products.
文摘Multistage fluidized beds are frequently used for product drying in industry. One advantage of these fluidized beds is that they can achieve a high throughput, when operated continuously. In this study, γ- A1203 particles were dried in a pilot-scale horizontal fluidized bed, without considering any comminution effects. For each experiment, the particle moisture content distribution and residence time distribution were determined. To take into account particle back mixing in our experiments, a one-dimensional pop- ulation balance model that considers particle residence time was introduced into a fluidized bed-drying model. Experimental particle residence time distributions were reproduced using a tank-in-series model. Subsequently, the moisture content distribution was implemented, as a second dimension to the popu- lation balance in this model. These two-dimensional simulations were able to describe the experimental data, especially the spread in the residual particle moisture distribution, much more accurately than one-dimensional simulations. Using this novel two-dimensional model, the effects of different operating parameters （process gas temperature, solid feed rate, superficial air velocity） on the particle moisture content distribution were systematically studied.
文摘Particle distribution in the cross-section of the flighted rotating drum(FRD)is critical to the analysis of heat and mass transfer between gas and solids.In this work,the particle tracking velocimetry(PTV)method is applied to study the influence of the number of flights on the particle motion in FRDs.The drum,installed with 1,4,8,or 12 rectangular flights,is filled with plastic balls to 15%and operated at various rotating speeds ranging from 10 rpm to 30 rpm.The results show that the number of flights has different effects on the holdup ratio and cascading rate of single flight and active flights.With 8 and 12 flights,the FRD produces a larger and more stable particle ratio of the dilute phase.Moreover,DEM simulations agree with PTV measurements,whereas literature models show significant deviations.
文摘Residence time distributions （RTDs） in horizontal fluidised beds have a huge effect on solid product properties and are infuenced by the internal design of the apparatus, e.g. the separation into different compartments by weirs. Weirs can be passed in or against the overall solid transport direction, with the back-flow resulting in axial dispersion, which is a measure of the spread of the RTD. Therefore, the ratio of exchange rates at weirs under different fluidisation conditions provides information on axial dispersion. In this work, a methodology based on particle tracking velocimetry is presented to obtain information on the exchange rates of particles at weirs in horizontal fluidised beds. The internal recirculation is studied for over-flow weirs with respect to different fluidisation conditions, providing a first step towards determining the effects of weirs and fluidisation conditions on axial dispersion and RTDs in horizontal fluidised beds.
文摘Emulsions and crystallization are two independent research topics which normally do not overlap although a combination of the two could be applicable to many areas. Here, the importance of emulsions in the field of fat crystallization is described. Three applications with industrial relevance were chosen for investigation： fat fractionation, the solidification of phase change materials and solid lipid nanoparticles. For fat fractionation and phase change materials, emulsification can be applied as a tool to improve the fat crystallization process, and thus the product quality of the crystallized fat. Furthermore, the use of emulsification creates new solid lipid nanoparticles in the application fields such as area of fat crystallization.
基金Supported by the AiF (Arbeitsgemeinschaft Industrieller Forschungsvereinigungen, "Otto von Guericke" e.V.), the BMWA (Bundesministerium für Wirtschaft und Arbeit) and the DFG (Deutsche Forschungsgemeinschaft)
文摘The technique state to design counter-current extraction columns is based on the performance of pilot plant experiments. The modelling is then either with the equilibrium or dispersion model, whereas in the latter the dispersion coefficient accounts for all hydrodynamic non-idealities. A new approach uses single droplet experiments to obtain the basic laws and functions governing droplet breakage, coalescence, relative velocity, and axial dispersion when using droplet populance balance models （DPBM）. The hydrodynamics simulation results show that the mean Sauter diameter, hold-up, and concentration profiles could be well predicted, which promotes the use of DPBM models for further applications in industrial scale.
文摘The crystal morphology grown from a solution composed of an organic solvent, solute and additive can be predicted reliably by a computational method. Modeling the supersaturated solution as liquid phase is achieved by employing commercial software. The molecular composition of this solution is a required input parameter. The face specific diffusion coefficient of the solid （crystal surface） and liquid （solution） system is determined using the molecular dynamics procedure. The obtained diffusion coefficient is related to the specific face growth rate via the attachment energy of the pure morphology. The significant improvements are achieved in the morphology prediction because the investigation on the face growth rates in a complex growth environment （as multi-component solutions with additives） can be carried out based on the diffusion coefficients.
文摘Increasing production effeciency and lowering costs are some of the many advantages melt crystallization technology offers over the conventional methodology of tabletting. A normal tablet consists of a pure shell or a coat and a separate core constituting the pharmaceutical active ingredient. Great emphasis is put on the purity of the shell since its purpose is to solely protect and deliver the active ingredient to its target. Melt crystallization is a purification （separation） process. It is discussed here for its ability to produce coated tablets, by separating the ＂coating＂ material from the ＂to be coated＂ material coming from one molten mixture. Molten drops of lutrol-ibuprofen mixture are produced using the drop forming technique. The subsequent analysis involves proving and quantifying the phase separation （coat purity）. The mechanism of a crystallizing drop is shown as direct evidence of the ongoing process. Moreover, solidified tablet batches are analyzed for the purity of their coating by measuring the ibuprofen concentration. This optimization process is carried out through multiple stages of development and condition enhancements in order to produce the most pure tablet coating. As a result, a trial showing an almost purely coated tablet is presented here.
文摘Sugar spray coating is a frequently used process in the pharmaceutical industry. However, this process presents the disadvantage to form an amorphous coating around the active ingredient. A crystalline coating formed on the surface of a tablet is highly desirable. Recently, a new process of coating by cooling crystallization has been developed and applied on bisacodyl pastilles obtained by melt crystallization. In this work, we investigated the feasibility of coating by cooling crystallization on ibuprofen ＂naked tablets＂ manufactured by compression. In the first part of this work, the solubility and the metastable zone width have been determined experimentally for the coating solution because they are essential factors for any crystallization process. In the second part, the coating process is investigated on the operating conditions that affect the surface morphology and the crystal growth rate. These experimental conditions include concentration of the coating solution, degree of sub-cooling, agitation speed, retention time, and surface properties of the naked ibuprofen tablets. The results show that naked tablet coating by cooling crystallization is feasible and can be applied in the pharmaceutical industry.
文摘In this work,we demonstrate that particles can be coated in a fluidized bed w让h coating solution provided by a novel aerosol generator.Aerosol droplets are smaller than 1 pim in volume-based diameter,hence they are very much smaller than droplets in conventional spray fluidized bed processes(around 40μm).A proof-of-principle experiment with 30%aqueous coating solution of sodium benzoate and γ-Al2O3 core particles in 150 mm fluidized bed fed with droplet aerosol supplied from the chamber side is presented.To simultaneously coat and dry the particles,inlet of fluidization air was at 50℃ .Moreover,Monte Carlo simulations of coating with small aerosol and large spray droplets were conducted.Due to dramatically smaller building blocks,ultrathin particle coating of high-resolution(very small layer thickness)can be attained with the new aerosol process,with the potential of even going nanoscale.Full coverage of particles is reached substantially faster than in the conv entional process,so that material dema nd is much lower and sensitive materials can be processed in short reside nee time.Solids yield of around 30%was much higher than expected,that is considered to be technically viable and may be enhanced by the recycling of entrained solids or better equipment design.
