• Applied Chemistry for Engineering
• /
• v.8 no.4
• /
• pp.602-609
• /
• 1997

The seed formation and growth of $\alpha$-ferric oxyhydroxide with aerial oxidative precipitation from aqueous solution of ferrous sulfate with KOH, NaOH, $Na_2CO_3$ and $K_2CO_3$ as precipitants have been studied by free pH drift experiment. It has been shown that all precipitants give same particle formation and growth path, and average particle length from KOH and NaOH as precipitants was about 1.5 times shorter than that of $K_2CO_3$ and $Na_2CO_3$. When initial mole ratio, $R_o=[Fe^{2+}]_o/[OH^-]_o$ of KOH was decreased the particle was grown oxyhydroxide seed growth from aqueous solution of ferrous sulfate with KOH has been studied. The influence of the air flow rate, reaction temperature and initial mole ratio, $R_o=[Fe^{2+}]_o/[OH^-]_o$, on the kinetics of seed growth are investigated by static pH experiment. The oxidation rate of seed growth increased with increase in the air low rate, reaction temperature and initial mole patio. The activation energy of seed growth is 16.16 KJ/mol and the rate equation of seed growth can be written as follows: $-\frac{d[Fe^{2+}]}{dt}=1.46{\times}10^4[P_{o2}]^{0.66}[OH^-]^{2.19}exp(-\frac{16.16}{dt})$.

• Journal of Korea Water Resources Association
• /
• v.44 no.6
• /
• pp.449-459
• /
• 2011

By examining the experimental results, the critical mean velocity which initiates the movement of riprap is increased with the riprap size in mean diameter, the mean diameter over water depth (d/h), Froude number (Fr), and turbulent shear velocity over critical mean velocity (u*/${\nu}$) which have great correlations among them so these parameters are adopted governing hydraulic stability for riprap. The hydraulic stability equation for riprap is developed by regression analysis. The developed equation is expanded from 0.36~0.73 m/s of experimental range to 0~5.0 m/s for the application in engineering discipline. So many useful relations among those parameters including critical mean velocity are derived by expanding to high Reynolds regions. Mean diameter calculation results by expanding to high Reynolds regions coincide with the calculations of ASCE and USBR at the range of 0~3.0 m/s and the calculation result of ASCE at the range of 3.0~5.0 m/s. The results by developed formulae coincide well with the formulae of ASCE in general and also the results by recently developed existing formulae of hydraulic stability for riprap. Thus, the developed equation has the high applicability in engineering discipline to evaluate the hydraulic stability for riprap.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.05a
• /
• pp.253-256
• /
• 2009

In the micro turbojet engine less than 350kw power class, it is not easy to find out the good atomization fuel injector with good spray quality. However conceptually, rotating fuel injection system can give high atomization quality by only the centrifugal force of a high speed rotating shaft of the engine without high-pressure fuel pump. With this motivation, we manufactured very small rotating fuel injector of 40 mm diameter and performed under a variety of injection orifices. We measured droplet size, velocity and spray distribution by the PDPA(Phase Doppler Particle Analyzer) system. Also spray was visualized by using high speed camera. From the test results, we could understand that the length of liquid column from the injection orifice is mainly controlled by the rotational speeds. Furthermore, droplet size(SMD) is decreased with the rotational speeds and is influenced by the diameter of the injection orifice and liquid film thickness.

• Korean Chemical Engineering Research
• /
• v.59 no.4
• /
• pp.565-573
• /
• 2021

Isotherms, kinetics and thermodynamic properties for adsorption of Brilliant Green(BG), Quinoline Yellow(QY) dyes by activated carbon were carried out using variables such as dose of adsorbent, pH, initial concentration, contact time, temperature and competitive. BG showed the highest adsorption rate of 92.4% at pH 11, and QY was adsorbed at 90.9% at pH 3. BG was in good agreement with the Freundlich isothermal model, and QY was well matched with Langmuir model. The separation coefficients of isotherm model indicated that these dyes could be effectively treated by activated carbon. Estimated adsorption energy by Temkin isotherm model indicated that the adsorption of BG and QY by activated carbon is a physical adsorption. The kinetic experimental results showed that the pseudo second order model had a better fit than the pseudo first order model with a smaller in the equilibrium adsorption amount. It was confirmed that surface diffusion was a rate controlling step by the intraparticle diffusion model. The activation energy and enthalpy change of the adsorption process indicated that the adsorption process was a relatively easy endothermic reaction. The entropy change indicated that the disorder of the adsorption system increased as the adsorption of BG and QY dyes to activated carbon proceeded. Gibbs free energy was found that the adsorption reaction became more spontaneous with increasing temperature. As a result of competitive adsorption of the mixed solution, it was found that QY was disturbed by BG and the adsorption reduced.

• Journal of Energy Engineering
• /
• v.24 no.4
• /
• pp.124-129
• /
• 2015

An experimental study was performed estimating COP(Coefficient of Performance) of air-conditioning cycle using inverter scroll compressor with and without $Al_2O_3$ nano particle. All experiments were done for various compressor speeds from 1000~4000 rpm and used the inverter controller called CANDY to change the compressor rpm. The air-conditioning cycle components in the apparatus were used as same with components of YF hybrid car. To estimate the COP, this study measured the temperature and pressure at inlets and outlets of compressor, condenser, and evaporator. And also measured the compressor input power using Powermeter. Through the experiments, the maximum error to estimate COP was shown about ${\pm}6.09%$ at 3500rpm. The COP of refrigeration cycle with $Al_2O_3$ nano-particle was similar with that of the base cycle without nano-particle between 1000~3000 rpm of the compressor speed. But, This study showed that the COP of the cycle with $Al_2O_3$ over 3000 rpm of the compressor speed was higher than that of the base cycle due to the higher heat transfer rate increased in the evaporator from the higher oil flow rate inside the cycle as well known. Those results can be used the basic and fundamental data to design the air-conditioning cycle using inverter scroll compressor with $Al_2O_3$ nano particle.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.37 no.1
• /
• pp.43-53
• /
• 2011

The conditions in fluid-bed processor for nanoencapsulation of azelaic acid-milk nano powder for acne nanocosmetics were optimized by response surface methodology (RSM). The maximum value of yield was 70.97 %. The yield was appreciably influenced by inlet air temperature, atomizing pressure, and feeding speed. The particle size increased with an increase in the feeding speed and a decrease in the atomizing pressure. The elution rate in saline solutions was appreciably influenced by inlet air temperature and atomizing pressure. The moisture content increased with higher atomizing pressure, which was demonstrated to be similar to the nanoencapsulation characteristics related to water activity. The Hunter's L and b values increased with an increase in the inlet air temperature. The optimum conditions estimated by RSM for the maximized values of yield, moisture content, particle size and elution rate in skin suitability were $67{\sim}73^{\circ}C$ of inlet air temperature, 0.6 ~ 0.8 mL/min feeding speed and 1.8 ~ 2.0 kg/$cm^2$ of atomizing pressure, respectively. These estimated values were in agreement with those measured by real experiments.

• Korean Chemical Engineering Research
• /
• v.57 no.6
• /
• pp.853-860
• /
• 2019

In order to meet more severe environmental regulations, oxy-fuel circulating fluidized bed(CFB) boilers or ultra supercritical CFB boilers, which are a kind of process in that solid particles moves similar to fluid, have been developed in the world. In CFB power generation processes, the method to reduce or remove sulfur dioxide is in-situ desulfurization reaction via limestone directly injected into CFB boilers. However, the desulfurization efficiencies have continuously changed because limestones injected into CFB boilers are affected by various operation conditions (Bed temperature, pressure, solid circulating rate, solid holdup, residence time, and so on). In this study, a prediction method with physical and chemical properties of limestone and operation conditions of CFB boiler for in-situ desulfurization reaction in CFB boilers has developed by integrating desulfurization kinetic equations and hydrodynamics equations for CFB previously published. In particular, the prediction equation for in-situ desulfurization was modified by using experimental results from desulfurization reactions of various domestic limestones.

• Clean Technology
• /
• v.26 no.2
• /
• pp.122-130
• /
• 2020

The isotherm, kinetic, and thermodynamic parameters of reactive blue 4 adsorbed by activated carbon were investigated for activated carbon dose, pH, initial concentration, contact time, and temperature data. The adsorption of the RB 4 dye by activated carbon showed a concave shape in which the percentage of adsorption increased in both directions starting from pH 7. The isothermal adsorption data were applied to Langmuir, Freundlich, and Temkin isotherms. Both Freundlich and Langmuir isothermal adsorption models fit well. From determined Freundlich separation factor (1/n = 0.125 ~ 0.232) and Langmuir separation factor (R_L = 1.53 ~ 1.59), adsorption of RB 4 by activated carbon could be employed as an effective treatment method. The constant related to the adsorption heat (B_T = 2.147 ~ 2.562 J mol^-1) of Temkin showed that this process was physical adsorption. From kinetic experiments, the adsorption process followed the pseudo second order model with good agreement. The results of the intraparticle diffusion model showed that the inclination of the first straight line representing the surface diffusion was smaller than that of the second straight line representing the intraparticle pore diffusion. Therefore, it was confirmed that intraparticle pore diffusion is the rate-controlling step. The negative Gibbs free energy change (ΔG = -3.262 ~ -7.581 kJ mol^-1) and the positive enthalpy change (ΔH = 61.08 kJ mol^-1) indicated the spontaneous and endothermic nature of the adsorption process, proving this process to be spontaneous and endothermic.

• Explosives and Blasting
• /
• v.23 no.1
• /
• pp.47-54
• /
• 2005

An explosion modeling technique was developed by using the spherical discrete element code, $PFC^{3D}$, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a $PFC^{3D}$ particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). A test blast was conducted for a RC column, whose dimension was $600\times300\times1800$ in millimeters. The initial velocities of the surface movements were measured to be in the range of $14\~18\;m/s$ with the initiation times of $1.5\~2.0m$. Then the blasting procedure was simulated by using the modeling technique. The particle assembly representing the concrete was made of cement mortar and coarse aggregates, whose mirco-properties were obtained from the calibration processes. As a result, the modeling technique developed in this study made it possible for the burden to move with the velocity of $17\~24\;m/s$, which are slightly higher values compared to those of the test blast.

• Korean Chemical Engineering Research
• /
• v.55 no.6
• /
• pp.798-806
• /
• 2017

A activated carbon (WCAC, waste citrus activated carbon) prepared from an agricultural waste citrus peel material generated in Jeju was utilized for the removal of dimetridazole (DMZ) antibiotics in aqueous solution. The adsorption of DMZ on WCAC was investigated with the change of various parameters such as contact time, dosage of WCAC, particle size of WCAC, temperature, pH, and DMZ concentration. The DMZ adsorption capacity increased with increasing temperature and decreasing particle size. Also it was decreased at less than pH 4 but sustained almost constantly at pH 4 or greater. Isotherm parameters were determined from the Langmuir, Freundlich, Redlich-Peterson and Duinin-Radushkevich (D-R) isotherm models. The isotherm data were best described by the Redlich-Peterson isotherm model. And the adsorption kinetics can be successfully fitted to the pseudo-second-order kinetic model. The results of the intra-particle diffusion model suggested that film diffusion and intra-particle diffusion were occurred simultaneously during the adsorption process. Meanwhile, the thermodynamic parameters indicated that the adsorption reaction of DMZ on WCAC was an endothermic and spontaneous process. The experimental results showed that WCAC is a promising and cheap adsorbent for the removal of DMZ antibiotics.