Kee-Kahb Koo

CO2 Recovery from Flue Gas by PSA Process using Activated Carbon

An experimental study was performed for the recovery of CO2 from flue gas of the electric power plant by pressure swing adsorption process. Activated carbon was used as an adsorbent. The equilibrium adsorption isotherms of pure component and breakthrough curves of their mixture (CO2 : N2 : O2=17 : 79 : 4 vol%) were measured. Pressure equalization step and product purge step were added to basic 4-step PSA for the recovery of strong adsorbates. Through investigation of the effects of each step and total feed rate, highly concentrated CO2 could be obtained by increasing the adsorption time, product purge time, and evacuation time simultaneously with full pressure-equalization. Based on the basic results, the 3-bed, 8-step PSA cycle with the pressure equalization and product purge step was organized. Maximum product purity of CO2 was 99.8% and recovery was 34%.

Reduction of COD and Color of Acid and Reactive Dyestuff Wastewater Using Ozone

Wastewaters obtained from bromamine acid dye and reactive dye manufacturing were treated by ozone bubbling in a cylindrical batch reactor for the purpose of reducing COD to below 150 mg/L, which is the environmental discharge standard of the Republic of Korea. Remarkable COD reduction and decolorization were observed at pH over 11. High inlet gas flowrate and high concentration of ozone gave better results. Little precipitation was observed under the conditions of remarkable COD reduction. At pH of 11, 15 LPM of inlet gas flowrate and 89.3 g/Nm3 of ozone flowrate, the COD of bromamine acid dyestuff wastewater was reduced to 95 mg/L after 90 minutes, and the COD of reactive dyestuff wastewater was reduced to 120 mg/L after 120 minutes. Decolorization was completed after 30 minutes of reaction.

Comparison Study of Mixing Effect on Batch Cooling Crystallization of 3-Nitro-1,2,4-triazol-5-one (NTO) Using Mechanical Stirrer and Ultrasound Irradiation

The insensitive explosive 3-nitro-1,2,4-triazol-5-one (NTO) has been recrystallized from water in an effort to prepare crystals with smaller size and narrower distribution in a batch cooling crystallizer. Two mixing devices, i.e., a mechanically stirred system with and without ultrasound in aqueous media were employed to compare the mixing effect on the crystallization. Under ultrasound irradiation, the metastable zone width was significantly reduced by more than 2 fold and the crystal size was shifted from 140∼160 μm to 50∼70 μm with a narrower CSD compared to the mechanically stirred system. However in the mechanical stirrer, the mixing effect on NTO crystallization was negligible if the impeller speed was sufficient to suspend all crystals in the crystallizer. It was found that the crystal growth was not influenced by mixing. We suggest that the NTO crystals were formed by primary heterogeneous nucleation that is common in batch cooling system. Finally, the population balance model (PBM), with the empirical nucleation and growth kinetic expressions, was solved numerically to predict the crystal size and the CSD with batch time, and the results were in good agreement with the experimental data.

Effect of molar ratio of KOH to Ti-isopropoxide on the formation of BaTiO3 powders by hydrothermal method

Abstract Nano-crystalline BaTiO 3 powders were prepared using acylated titanium and barium acetate with hydrothermal method. The solution pH given by the molar ratio of KOH to Ti-isopropoxide was found to have an important effect on the size, morphology, and crystallinity of BaTiO 3 powders. FT-IR and Raman analyses showed that there were still some Ba–OAc bonds in the structure of as-prepared powders formed from the low pH alkaline solution. As hydrothermal aging time increased, the crystal structure of as-prepared powders was continuously transformed from amorphous to crystalline BaTiO 3 powders with breakage of Ba–OAc bonds and elimination of acetyl groups in the powders. When the solution pH was high, most of the acetyl groups bonded to Ba or Ti atoms were eliminated rapidly by hydrolysis in the solution. As a consequence, crystalline BaTiO 3 directly precipitated from homogeneous solution via condensation reaction between –Ba–OH and –Ti–OH bonds without subsequent hydrothermal reaction.

Thermodynamic design data and performance evaluation of the water + lithium bromide + lithium iodide + lithium nitrate + lithium chloride system for absorption chiller

Abstract Duhring (P–T–X) and enthalpy-concentration (H–X–T) diagrams of the H2O + LiBr + LiNO3 + LiI + LiCl (mole ratio of LiBr : LiNO3 : LiI : LiCl = 5 : 1 : 1 : 2) system were constructed by using the experimental data sets. Thermodynamic design data for a double-effect series-flow absorption chiller were calculated at various operating conditions [ 2≤Te≤14°C, 30≤Ta≤50°C, 30≤Tc≤50°C, T gh COP =0 ≤T gh ≤T gh (crystallization limit)] by a computer simulation. The proposed working fluid was found to be applicable to cycle operation of air-cooled absorption chiller with no crystallization problem at higher absorber temperature.

Solubilities, Vapor Pressures, and Heat Capacities of the Water + Lithium Bromide + Lithium Nitrate + Lithium Iodide + Lithium Chloride System

The optimum mole ratio of lithium salts in the H2O + LiBr + LiNO3 + LiI + LiCl system was experimentally determined to be LiBr : LiNO3 : LiI : LiCl = 5 : 1 : 1 : 2. The solubilities were measured at temperatures from 252.02 to 336.75 K. Regression equations on the solubility data were obtained with a least-squares method. Average absolute deviations of the calculated values from the experimental data were 0.15% at temperatures <285.18 K and 0.05% at temperatures ≥285.18 K. The vapor pressures were measured at concentrations ranging from 50.0 to 70.0 mass% and at temperatures from 330.13 to 434.88 K. The experimental data were correlated with an Antoine-type equation, and the average absolute deviation of the calculated values from the experimental data was 2.25%. The heat capacities were measured at concentrations from 50.0 to 65.0 mass% and temperatures from 298.15 to 328.15 K. The average absolute deviation of the values calculated by the regression equation from the experimental data was 0.24%.

Crystal growth of high silica ZSM-5 at low temperature synthesis conditions

At the temperature of 90°C and under atmospheric pressure, growth kinetics of high silica ZSM-5 was investigated through a long induction, nucleation and crystal growth periods. It was found the entire crystallization mechanism of ZSM-5 seems to be the combined process of the nucleation via solid-solid transformation, intergrowth among seed crystals and the normal growth in the reaction mixture. Nuclei were initially formed on the Si-rich surface of the amorphous intermediates, indicating that the reaction of TPA with Si species was prior to that with Al species. As the reaction time proceeded, various types of intergrowth among the seed crystals were observed along with the crystals growing independently. The intergrowth seems to play a role for forming typical ZSM-5 crystal shapes. And then ZSM-5 crystals further grew in the reaction mixture, so that the bulk Si/Al2 ratio of crystals approached that of the initial reaction mixture.

Effect of reaction temperatures and media on crystal structure of colloidal nanocrystals synthesized from an aerosol flow system

The CdSe and CdTe nanocrystals were successfully synthesized from the ultrasonic-assisted aerosol flow system using a surfactant/solvent system of oleic acid (OA)/trioctylphosphine (TOP)/trioctylphosphine oxide (TOPO)/octadecene (ODE). A comprehensive examination on the control of the CdSe and CdTe crystal structures and optical properties was performed as functions of reaction temperatures and amount of reaction media in the aerosol flow system. CdSe nanocrystals with spherical shape and having zinc blende structure were produced. It was found that the crystal structure and shape of CdSe are not affected by reaction temperature. However, it was found that reaction temperature significantly affects the crystal structure and morphology of CdTe. Zero-dimensional CdTe nanocrystals with spherical shape and having zinc blende structure were obtained at the temperature higher than 300 degrees C. Three-dimensional tetrapod-shaped CdTe nanocrystals having wurtzite structure were obtained at the temperature lower than 250 degrees C. Furthermore, the anisotropic growth was observed to be enhanced as increasing the amount of OA used at the temperature of 250 degrees C.

The gel-crystallization of 1-phenylalanine and aspartame from aqueous solutions

It was observed that 1-phenylalanine and aspartame form thermoreversible gels in aqueous solutions (which include crystals) through nonagitated crystallization. FT-IR spectra of aspartame gel-crystals indicated that the possible interactions involved in gel formation are hydrogen bonding between the carbonyl and the amine groups and electrostatic interactions between NH 3 + and COO − . For gel-crystals of 1-phenylalanine, the main interaction involved was electrostatic interaction between NH 3 + and COO − . According to the thermal analysis of aspartame and 1-phenylalanine solutions, the gel-melting temperature increased with increasing heating rate and the gel-crystallization temperature decreased with increasing cooling rate.

Elimination of aggregates of ferredoxin from its self-assembled monolayer on silicon substrate

Abstract The self-assembled ferredoxin monolayer onto the (100) surface of the silicon substrate was prepared and the nonspecifically adsorbed aggregates of ferredoxin on the substrate were successfully eliminated by using a zwitterionic surfactant, 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS). The AFM image of the self-assembled ferredoxin monolayer on the silicon substrate treated with CHAPS clearly shows that the size of ferredoxin clusters is about 20–30 nm, which is on the order of an aggregate of about five ferredoxin molecules, whereas the size of ferredoxin aggregates on the substrate without CHAPS treatment was measured to be about 100–200 nm. Those results offer a useful method for the elimination of the nonspecific adsorption of proteins onto inorganic substrates, which has been a long-term problem in the fabrication of biomolecular electronic devices by the self-assembly technique.