• 제어로봇시스템학회:학술대회논문집
• /
• 1994.10a
• /
• pp.725-730
• /
• 1994

A sodium chloride crystallizer shows oscillatory and nonlinear characteristics under its nucleating and growing process. Because these characteristics vary with operational condition, we can't control the product crystal size exactly with a PID controller or a sequence controller. Then, we make a model with threefold neural networks for the laboratory equipment that is a jet mixing crystallizer. We try to control the product crystal size with its neuro-model, and we reach the conclusion that our neuro-model is applicable to the practical crystallizer.

• Applied Chemistry for Engineering
• /
• v.9 no.7
• /
• pp.974-978
• /
• 1998

The kinetics of crystal growth and nucleation in dependence on the supersaturation of an aqueous solution of 3-nitro-1,2,4-triazol-5-one(NTO) were evaluated on the draft tube-baffle(DTB) crystallizer operated batchwise. The crystal growth rate is proportional to the supersaturation to the 2.9 power, and the nucleation rate to the 4.2 power. The uncleation behavior for NTO-water system in DTB crystallizer was grasped according to Mersmann's criteria. The nucleation in this crystallizer was found to act with heterogeneous nucleation and surface uncleation simultaneously. Simplified relation was derived for calculation of mean crystal size of product crystals from the batch cooling crystallizer. The obtained relation was verified by a set of experiments.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1997.10a
• /
• pp.1-5
• /
• 1997

The growth mechanism of AMT(Ammonium Meta-Tungstate) crystal was interpreted as two-step model. The contribution of the diffusion step increased with the increase of temperature, crystal size, and supersaturation. The crystal size distribution from a batch cooling crystallizer was predicted by the numerical solution of a mathematical model which uses the kinetics of nucleation and crystal growth. Temperature control of a batch crystallizer was studied using Learning control algorithm. The purity of AMT crystal producted in this investigation was above 99.99%.

• Applied Chemistry for Engineering
• /
• v.7 no.2
• /
• pp.308-314
• /
• 1996

The crystal growth rate of benzene from benzene-cyclohexane mixtures at a cylindrical layer crystallizer was determined from the slope of the line of correlation between operating time and layer thickness. The thickness of crystal layer was obtained from the amount of crystal deposited on the cooled wall surface of the crystallizer. The crystal growth rate was related with the degree of subcooling, which was defined as the difference between temperature of melt and that of growing crystal surface. The linear crystal growth rate for binary mixtures was proportional to the second power of the degree of subcooling. Equation model which was obtained from data through the rate of heat and mass transfer in the crystallizer and thus can tell crystal thickness and surface temperature of crystal layer according to the elapsed time was presented and successfully correlated to the experimental data. For the benzene-cyclohexane mixtures contains 5wt% and 10wt% of cyclohexane, the comparison of experimental data with calculation using model equation was done for crystal thickness corresponding to the various cooling temperatures.

• Clean Technology
• /
• v.13 no.1 s.36
• /
• pp.72-78
• /
• 2007

As a basic research fur the separation of effective components included in pyrolysis gas oil, the crystallization on each system of naphthalene with 2-methylnaphthalene, indene and 1-methylnaphthalene as impurity has been carried out in column and cold-finger type crystallizer, respectively. In crystallization operation, the purity of naphthalene has been a tendency of increase with decreasing of cooling rate and in the presence of impurity with lower melting point. In comparison of crystallizer types, naphthalene purity in column type crystallizer was a higher value than that in cold-finger type due to effective sweating operation after crystallization.

• Korean Chemical Engineering Research
• /
• v.57 no.5
• /
• pp.666-671
• /
• 2019

Calcium carbonate involves three phases such as calcite, vaterite, and aragonite. Calcite and aragonite were more thermodynamically stable than vaterite. The synthesis of aragonite crystals by the reaction with sodium carbonate and calcium chloride solutions was investigated focusing on the effect of temperature and rpm in continuous crystallizer. In the batch crystallization test, calcite was synthesized by a relatively low temperature (under $40^{\circ}C$), but aragonite was formed at high temperature. In the continuous process with 100 rpm, no aragonite was found regardless of reaction temperature. But as increasing the stirring rate to 300 rpm and 500 rpm, the ratio of aragonite to calcite increased as increasing the temperature.

• Korean Chemical Engineering Research
• /
• v.44 no.3
• /
• pp.289-293
• /
• 2006

In the CMSMPR (continuous mixed suspension mixed product removal)system, the effect of temperature and RPM on the CSD (crystal size distribution) in the calcium carbonate process was investigated. In the steady state operation, the change of solution pH was small. At the low temperature and below 300 RPM, volume mean size change of calcium carbonate was stable and CSD was narrow. In the SEM view, calcite and aragonite was obtained.

• 제어로봇시스템학회:학술대회논문집
• /
• 1986.10a
• /
• pp.200-204
• /
• 1986

Particle size distribution in a Continuous Mixed Suspension Mixed Crystal Removal (CMSMPR) crystallizer has been analyzed using the Population Balance (PB) model. This method presents difficulties when the growth rate of crystal depends on the crystal size. Recent studies indicate that in many cases the growth rate is dependent on size when the crystal sizes are small. In this study, a Residence Time Distribution(RTD) model was proposed to take the size dependence into account together with an appropriate numerical scheme. When compared with the approximate results based on PB model, RTD model results showed improvements also a nucleation effect which is normally unimportant for steady state analysis. Start-up data for NaCl-Water-Ethanol system was compared with computed values.

• Journal of the Korean Applied Science and Technology
• /
• v.28 no.4
• /
• pp.472-481
• /
• 2011

It is known that the content of saturated fatty acids methyl ester (SFAME) affect the pour point of biodiesel at low temperature. In this study, biodiesel (BD) was produced from beef tallow (TAL) by alkali catalyst. To reduce the saturation in BD, acetone fractionation was applied. Besides, TAL was also solvent-fractionated to reduce the saturated fatty acid (SFA) content for further producing BD. With acetone, TAL or TAL methyl ester (5:1 v/w) were fractionated at 10, 0, -10, and $-15^{\circ}C$, respectively. At $-10^{\circ}C$, 17.35% of SFA was observed in fractionated TAL (liquid part, -10TAL) when 5:1 solvent ratio was used for 24 hr. Under the same condition, fractionated BD (liquid part, -10BD) showed SFA (33.14%) with 78wt % yield. Also, fractionation of BD with different concentration of crystallizer 209 (0.1, 0.5, and 1%) along with different time (2, 6, 12, and 24 hr.) was observed. The best condition for reducing the SFA was 0.5% of crystallizer 209 addition for 12 hr of fractionation time at $-10^{\circ}C$, in which 30.14% of SFA content was observed in BD (liquid part). Among different crystallizer, ps 66 showed the least content of SFA content (23.28%) in BD after fractionation ($-10^{\circ}C$ and 24 hr) with 0.5wt% addition.

• Journal of Institute of Convergence Technology
• /
• v.5 no.1
• /
• pp.1-5
• /
• 2015

SI thermochemical hydrogen production process achieves water splitting into hydrogen and oxygen through three chemical reactions. The process is comprised of three sections and one of them is HI decomposition into $H_2$ and $I_2$ called as Section III. The production of $H_2$ included processes involving EED for concentrating a product stream from Section I. Additionally an $I_2$ crystallization would be considered to reduce burden on EED by removing certain amount of $I_2$ out of a process stream prior to EED. In this study, the current thermodynamic model of SI process was briefly described and the calculation results of the applied Electrolytes NRTL model for phase equilibrium calculations was illustrated for ternary systems of Section III. We calculated temperature and heat duty of an $I_2$ crystallizer and heat duty of heaters using UVa model and heat balance equation of simulation tool. The results were expected to be used as operation information in optimizing HI decomposition process and setting up material balance throughout SI process.