Effect of Kinetic Parameters on the Dynamicsof Continuous Crystallizers

1998 ◽  
Vol 63 (1) ◽  
pp. 121-131 ◽  
Author(s):  
Jaroslav Nývlt
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Production Rate ◽  
Crystal Size ◽  
Crystallization Process ◽  
Dynamic Behaviour ◽  
Nucleation And Growth ◽  
Suspension Concentration ◽  
Run Time ◽  
Periodic Cycles

Continuous crystallizers can exhibit periodic cycles of supersaturation, production rate, suspension concentration, crystal size and related quantities. These cycles are most pronounced at the beginning of the crystallization process and depend on the value of kinetic parameters whether they are damped during the run time. Apparently, the cycling behaviour of the crystallizing system depends on the value of ratio of the nucleation and growth exponents n/g. The higher the value of this ratio, the more pronounced is the instability of the system. Admixtures that have a significant effect on the kinetic parameters can dramatically affect the dynamic behaviour of crystallizers so that the steady state may not be established at all.

SIMULATION AND NEW SENSOR TECHNOLOGIES FOR INDUSTRIAL CRYSTALLIZATION: A REVIEW

2002 ◽  
Vol 16 (01n02) ◽  
pp. 346-353 ◽  
Author(s):  
RICHARD D. BRAATZ ◽  
MITSUKO FUJIWARA ◽  
DAVID L. MA ◽  
TIMOKLEIA TOGKALIDOU ◽  
DANESH K. TAFTI
Keyword(s):  
High Resolution ◽  
Size Distribution ◽  
Crystal Size ◽  
Crystallization Process ◽  
Significant Proportion ◽  
Nucleation And Growth ◽  
Crystalline Form ◽  
Industrial Crystallization ◽  
Growth From Solution ◽  
Product Effectiveness

A significant proportion of materials are produced in crystalline form. Many of these crystals are produced by nucleation and growth from solution. In these processes, the control of the crystal size distribution can be critically important for efficient downstream operations such as filtration and drying, and product effectiveness (e.g., flowability, bioavailability, tablet stability). Such control has recently become possible due to new sensor technologies that can peer into the crystallization process as it occurs, and high resolution algorithms which can efficiently simulate crystallization processes. This paper provides an overview of recent advances in areas.

scholarly journals Varing chemical equilibrium gives kinetic parameters

2013 ◽  
Author(s):  
Edward Flach ◽  
Santiago Schnell
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Dynamic Behaviour ◽  
Dynamic Equilibrium ◽  
Parameter Estimates ◽  
Input Rate ◽  
Fitting In ◽  
State Concentration ◽  
Static Behaviour ◽  
Concentration Space

We are interested in finding the kinetic parameters of a chemical reaction. Previous methods for finding these parameters rely on the dynamic behaviour of the system. This means that the methods are time-sensitive and often rely on non-linear curve fitting. In the same manner as previous techniques, we consider the concentrations of chemicals in a reaction. However, we investigate the static behaviour of the reaction at dynamic equilibrium, or steady state. Here too, the chemical concentrations depend on the kinetic parameters of the reaction. In an open reaction, the static concentrations also depends on the rate of input of the source of reacting chemical. Controlling this input rate slides the steady state along a curve in concentration space. This curve is determined by the kinetic parameters. The plane of this curve is sufficient to find the kinetic parameters. The new method we propose uses only the steady state concentration values to determine the kinetic parameters of the reaction. These values are constant once dynamic equilibrium is achieved, and so can be read accurately. Readings can be repeated readily to reduce error. Thus this new technique is simple and could produce accurate kinetic parameter estimates.

scholarly journals Characterization of Nicotinamidases: Steady State Kinetic Parameters, Classwide Inhibition by Nicotinaldehydes, and Catalytic Mechanism

Biochemistry ◽  
2010 ◽  
Vol 49 (49) ◽  
pp. 10421-10439 ◽  
Author(s):  
Jarrod B. French ◽  
Yana Cen ◽  
Tracy L. Vrablik ◽  
Ping Xu ◽  
Eleanor Allen ◽  
...  
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Catalytic Mechanism ◽  
Steady State Kinetic ◽  
State Kinetic

Theoretical Study of Iron Heterogeneous Growth on the Surface of C60 Molecule

2014 ◽  
Vol 1081 ◽  
pp. 115-118
Author(s):  
Qi Cheng Liu ◽  
Yun Fang Li
Keyword(s):  
Crystallization Process ◽  
Theoretical Study ◽  
Covalent Bond ◽  
Md Simulations ◽  
Nucleation And Growth ◽  
Bond Forming ◽  
Regular Icosahedron ◽  
Molecule Dynamics ◽  
Molecule Surface ◽  
Regular Closed

Direct molecule dynamics (MD) simulations have also been performed to study heterogeneous nucleation and growth of iron on C60 molecule. The grown mechanism of this crystallization process was explored. The results indicate that 92 iron atoms attach to C60 molecule surface can form new covalent bond, forming a closed regular icosahedron. More atoms grow in layer to form bigger regular closed clathrate base on the structure of former one. As increase of atoms number, there will appear some crystal faces.

scholarly journals cPCN-Regulated SnO2 Composites Enables Perovskite Solar Cell with Efficiency Beyond 23%

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Zicheng Li ◽  
Yifeng Gao ◽  
Zhihao Zhang ◽  
Qiu Xiong ◽  
Longhui Deng ◽  
...  
Keyword(s):  
Steady State ◽  
Power Conversion ◽  
Perovskite Solar Cells ◽  
Crystallization Rate ◽  
Nucleation And Growth ◽  
Perovskite Solar Cell ◽  
Perovskite Layer ◽  
Carrier Separation ◽  
Polymeric Carbon ◽  
Electron Extraction

AbstractEfficient electron transport layers (ETLs) not only play a crucial role in promoting carrier separation and electron extraction in perovskite solar cells (PSCs) but also significantly affect the process of nucleation and growth of the perovskite layer. Herein, crystalline polymeric carbon nitrides (cPCN) are introduced to regulate the electronic properties of SnO2 nanocrystals, resulting in cPCN-composited SnO2 (SnO2-cPCN) ETLs with enhanced charge transport and perovskite layers with decreased grain boundaries. Firstly, SnO2-cPCN ETLs show three times higher electron mobility than pristine SnO2 while offering better energy level alignment with the perovskite layer. The SnO2-cPCN ETLs with decreased wettability endow the perovskite films with higher crystallinity by retarding the crystallization rate. In the end, the power conversion efficiency (PCE) of planar PSCs can be boosted to 23.17% with negligible hysteresis and a steady-state efficiency output of 21.98%, which is one of the highest PCEs for PSCs with modified SnO2 ETLs. SnO2-cPCN based devices also showed higher stability than pristine SnO2, maintaining 88% of the initial PCE after 2000 h of storage in the ambient environment (with controlled RH of 30% ± 5%) without encapsulation.

The Kinetics of Austenization Process of T91 Ferritic Heat-Resistant Steel

2011 ◽  
Vol 317-319 ◽  
pp. 42-47
Author(s):  
Li Fang Zhang ◽  
Yong Chang Liu
Keyword(s):  
Experimental Data ◽  
Phase Transformation ◽  
Kinetic Parameters ◽  
Nucleation And Growth ◽  
Transformation Model ◽  
Resistant Steel ◽  
Kinetic Characteristics ◽  
Heat Resistant Steel ◽  
Austenite Grain ◽  
Kinetics Of

By fitting the calculated transformed fraction according to developed phase-transformation model to the experimental data obtained by differential dilatometry, the kinetic characteristics of the austenitization process in T91 steels have been investigated. According to the kinetic parameters fitted, we recognize that the nucleation and growth of austenite grain are mainly controlled by the diffusion of carbon in ferritic and austenite respectively. In addition, by increasing the diffusion active energy of carbon in austenite, carbides hinder the motion of interface and thus refine austenite grain.

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