• Korean Chemical Engineering Research
• /
• v.52 no.6
• /
• pp.768-774
• /
• 2014

SI process is a thermochemical process producing hydrogen by decomposing water while recycling sulfur and iodine. Various technologies have been developed to improve the efficiency on Section III of SI process, where iodine is separated and recycled. EED(electro-electrodialysis) could increase the efficiency of Section III without additional chemical compounds but a substantial amount of $I_2$ from a process stream is loaded on EED. In order to reduce the load, a crystallization technology prior to EED is considered as an $I_2$ removal process. In this work, $I_2$ particle sinking behavior was modeled to secure basic data for designing an $I_2$ crystallizer applied to $I_2$-saturated $HI_x$ solutions. The composition of $HI_x$ solution was determined by thermodynamic UVa model and correlation equations and pure properties were used to evaluate the solution properties. A multiphysics computational tool was utilized to calculate particle sinking velocity changes with respect to $I_2$ particle radius and temperature. The terminal velocity of an $I_2$ particle was estimated around 0.5 m/s under considered radius (1.0 to 2.5 mm) and temperature (10 to $50^{\circ}C$) ranges and it was analyzed that the velocity is more dependent on the solution density than the solution viscosity.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.7
• /
• pp.714-719
• /
• 2017

The controlled synthesis of inorganic materials with a specific size and morphology is an important factor in the development of new materials in many fields, such as nanoparticles, medicine, electronics, semiconductors, pharmaceutical sand cosmetics. Solution crystallization is one of the most widely used separation processes in the chemical and pharmaceutical industries. Calcium carbonate has attracted a great deal of attention in industry because of its numerous applications. The mean crystal size, crystal size distribution and morphology are important factors in the continuous crystallization process. In this study, the continuous crystallization of calcium carbonate by the calcium chloride process was investigated. The mean crystal size and crystal size distribution data were obtained by a particle size analyzer. The morphological imaging of the crystalswasper formed by SEM. Under steady state operation, the mean crystal size change was small, but increasing the input concentration and mixing rate increased the crystal size. In this operation, some aragonite was found, but the main crystal phase was calcite.

• Journal of Korean Society on Water Environment
• /
• v.37 no.6
• /
• pp.442-448
• /
• 2021

Seawater desalination is a technology through which salt and other constituents are removed from seawater to produce fresh water. While a significant amount of fresh water is produced, the desalination process is limited by the generation of concentrated brine with a higher salinity than seawater; this imposes environmental and economic problems. In this study, characteristics of seawater from three different locations in South Korea were analyzed to evaluate the feasibility of crystallization to seawater desalination. Organic and inorganic substances participating in crystal formation during concentration were identified. Then, prediction and economic feasibility analysis were conducted on the actual water flux and obtainable salt resources (i.e. Na2SO4) using membrane distillation and energy-saving crystallizer based on multi-stage flash (MSF-Cr). The seawater showed a rather low salinity (29.9~34.4 g/L) and different composition ratios depending on the location. At high concentrations, it was possible to observe the participation of dissolved organic matter and various ionic substances in crystalization. When crystallized, materials capable of forming various crystals are expected. However, it seems that different salt concentrations should be considered for each location. When the model developed using the Aspen Plus modular was applied in Korean seawater conditions, relatively high economic feasibility was confirmed in the MSF-Cr. The results of this study will help solve the environmental and economic problems of concentrated brine from seawater desalination.

• Korean Chemical Engineering Research
• /
• v.51 no.5
• /
• pp.587-590
• /
• 2013

Solid-liquid equilibria for mixtures composed of n-vinyl-2-pyrrolidone (NVP) and 2-pyrrolidone were measured as a basic study for the melt crystallization process to remove 2-pyrrolidone as impurity included in NVP. A differential scanning calorimeter (DSC) and a crystallizer were used and the experimental results obtained from two methods were similar. The mixture showed a eutectic system which has a single composition at the minimum melting temperature. Calculation results from simple thermodynamic equations were found in general agreements with present data. To determine the growth rate of NVP crystal which is important for the design of crystallization process, thicknesses of the crystal were measured with the time using a layer melt crystallizer. The growth rates increased as cooling temperatures decreased. Heat transfer coefficient correlated from present data was found to successfully describe the crystal growth behavior.

• Korean Chemical Engineering Research
• /
• v.48 no.6
• /
• pp.712-716
• /
• 2010

Salting-out technique was adopted to crystallize dye crystals from dye solution. Solubility of dye solution and crystallization kinetics of Reactive Red 218 was investigated. Solubility of dye solution is decreased by higher KCl concentration. The empirical expressions of salting-out crystallization kinetics for Reactive Red 218 in continuous MSMPR crystallizer was $G=6.864{\times}10^{-5}{\Delta}C^{1.207}$ and $B^0=4.8{\times}10^{22}{\Delta}C[1.1{\times}10^{-13}+{({\Delta}C)}^{0.7}{M_T}^2]$.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.10
• /
• pp.1640-1645
• /
• 2006

We studied the diversity of the halophilic archaea and bacteria in crystallizer ponds of a Korean solar saltern by analyzing 16S rRNA gene libraries. Although diverse halophilic archaeal lineages were detected, the majority (56%) were affiliated with the uncultured and cultured Halorubrum group. Halophilic archaea that have been frequently observed in solar saltern environments previously, such as Halogeometricum, Halococcus, Haloarcula, and Haloferax, were not detected in our samples. The majority of clones (53%) belonged to the Cytophaga-Flavobacterium-Bacteroides and ${\alpha}-,\;{\gamma}-,\;and\;{\delta}-Proteobacteria$ groups, with 47% of the clones being affiliated with ${\gamma}-Proteobacteria$. We also identified new ${\delta}-Proteobacteria$-related bacteria that have not been observed in hypersaline environments previously. Our data show that the diversity of the halophilic archaea and bacteria in our Korean saltern differs from that of solar salterns found in other geographic locations. We also showed by quantitative real-time PCR analysis that bacteria can form a significant component of the microbial community in solar salterns.

• Korean Chemical Engineering Research
• /
• v.51 no.1
• /
• pp.151-156
• /
• 2013

Crystallization of $CaCO_3$ is practiced on a polymethylsiloxane (PDMS) - based microfluidic system. Liquid- liquid reaction was investigated by mixing calcium chloride ($CaCl_2$) and sodium carbonate ($Na_2CO_3$) solution to crystallize $CaCO_3$. Aspartic acid (Asp) was added to investigate the morphology change such as vaterite and calcite. Suitable ratio of $Na_2CO_3$ and $CaCl_2$ was searched for initial seed formation. Christmas tree model was used as microfluidic device to form concentration gradient of $Na_2CO_3$ and $CaCl_2$. After observing microfluidic channel by using optical microscope, we found that seeds of $CaCO_3$ were formed under the condition that the ratio of $Na_2CO_3$ and $CaCl_2$ was 2:1. Morphology of crystals were also observed as $CaCO_3$ crystals grow. When Asp was added, vaterite crystal was more frequently found in two morphologies (vaterite and calcite) and seed formation and crystal growth were inhibited.

• Applied Chemistry for Engineering
• /
• v.8 no.3
• /
• pp.389-394
• /
• 1997

The distribution of impurity included in benzene layer crystal was explored in layer crystallization of cyclohexane and benzene mixtures. The influence of crystal growth rate on crystal purity was investigated. All experimental results for bezene-cyclohexane system obtained in layer crystallizer have been evaluated with the criterion of Wintermantel. The purity of crystal decreases with increasing degree of subcooling, decreasing feed concentration and increasing crystal growth rate. The crystal growth rate was a key parameter to determine the inclusion of impurity in crystals. The results obtained from runs performed at increasing crystallization time(i.e. crystal thickness) have clearly shown that migration of inclusions within crystal layer to the melt, leading to the removal of impurity occurs. The diffusion of impurity which takes place during the crystallization from the beginning, enhances a further purification of the crystal layer if that underwent a thermal gradient after growth of the layer crystal stops.

• Korean Chemical Engineering Research
• /
• v.50 no.2
• /
• pp.198-203
• /
• 2012

Salting-out technique was adopted to crystallize dye crystals from dye solution. In this research solubility of dye solution and crystallization kinetics of Reactive dye (RB-8, RB-49, RR-218) was investigated. The empirical expressions of salting-out crystallization kinetics for Reactive dye (RB-8, RB-49, RR-218) in continuous MSMPR crystallizer was RB-8 in crystal growth kinetics $G=7.1{\times}10^{-4}{\Delta}C^{0.67}$ and nucleation kinetics $B^0=3.1{\times}10^{15}{\Delta}C[1.2{\times}10^{-8}+{\Delta}C^{0.7}M_T{^2}]$, RB-49 in crystal growth kinetics $G=5.2{\times}10^{-4}{\Delta}C^{0.3441}$ and nucleation kinetics $B^0=7.2{\times}10^{15}{\Delta}C[3.3{\times}10^{-8}+({\Delta}C)^{0.7}M_T{^2}]$, RR-218 in crystal growth kinetics $G=4.4{\times}10^{-4}{\Delta}C^{0.2361}$ and nucleation kinetics $B^0=6.3{\times}10^{15}{\Delta}C[7.9{\times}10^{-8}+({\Delta}C)^{0.7}M_T{^2}]$. Also, comparison of calculated crystal size distribution applying to characteristic curve method with experimental crystal size showed good agreement.

• Clean Technology
• /
• v.20 no.4
• /
• pp.383-389
• /
• 2014

$CO_2$ absorption processes have a good potential for large scale capture of $CO_2$ but a large amount of absorbing solution has to be regenerated, undesirably increasing the consumption of energy such as sensible heat and latent heat of vaporization. In this study, a cooling crystallization process which would separate the $CO_2$-rich potassium bicarbonate crystals from $CO_2$-lean water was developed to reduce the energy penalty. Sterically hindered alkanolamine additives were used to enhance the $CO_2$ removal efficiency and their antisolvent effect on the crystallization was found in a continuous cooling crystallizer. The production yields of crystals were increased in the sequence of 2-amino-2-methyl-1-propanol (AMP) < 2-amino-2-methyl-1,3-propanediol (AMPD) < 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), which are related to the number of hydroxyl groups in the additive molecules. Using $^{13}carbon$ nuclear magnetic resonance, the additives favored the formation of bicarbonate ions by steric hindrance effect and increased the supersaturation of $KHCO_3$. It is shown that the additives increase the mean size of crystals and crystal growth rate by increasing supersaturation. The additives are promising for enhancing the $CO_2$ removal efficiency and reducing the regeneration energy cost of $CO_2$ absorbing solution by promoting $KHCO_3$ crystallization.