Korean Journal of Chemical Engineering (v.29, #4)

Using hydrogen as a transportation fuel has been attracting considerable interest due to zero carbon emissions from vehicles. Storing hydrogen compactly, safely and affordably remains a major scientific and technological challenge in on-board applications. Over the past decade, significant efforts have been made in developing solid-state hydrogen storage techniques. Among the chemical storage materials, ammonia borane is one most promising candidate because it has a high hydrogen density of 19.6 wt% and it is a non-flammable and non-explosive crystalline compound at ambient conditions. Hydrogen can be extracted from ammonia borane via thermolysis, hydrolysis, hydrothermolysis, and methanolysis. This review covers various approaches and prospects of facilitating thermolysis, along with a brief discussion of the nature of ammonia borane and the regeneration of spent fuel.
Keywords: Hydrogen Storage; Ammonia Borane; Thermolytic Dehydrogenation

The solubility of 5-mercapto-1-methyltetrazole in pure solvents from (283 to 329) K was measured using a laser monitoring observation technique at atmospheric pressure. The solubility data were accurately correlated by a modified Apelblat equation. The calculated results of which are proved to show fine representation of experimental data.
Keywords: 5-Mercapto-1-methyltetrazole; Solubility; Measurement; Modified Apelblat Equation

Simulated economics assessment of hollow fiber CO2 separation modules by Yoon Ah Jang; Young Moo Lee; Yeong-Koo Yeo (435-443).
Various conditions under which the hollow fiber membrane separation system would be the optimal selection are investigated in terms of cost effectiveness. Numerical simulation is carried out to examine the effects of different configurations such as single-stage, two-stage and three-stage CO2 separation processes. In particular, the hollow fiber membrane processes for CO2 separation with vacuum pumps, heat exchangers, coolers and compressors to provide pressurized feed streams are analyzed. Operating costs are evaluated and compared numerically for the processes with and without recycle streams to compare feasibility for commercial implementation while maintaining the purity and recovery ratio as high as possible.
Keywords: Economic Analysis; Modeling of Separation Process; Carbon Dioxide; Hollow Fiber Membrane

Although the operation of an LNG receiving terminal, especially for LNG unloading process, is important in terms of economics and safety, the systematic approach for this process is deficient with regard to operating variables and inherent terminal characteristics. Because the characteristics of each LNG terminal vary according to its individual condition, it is worth to investigate the operational method manipulating operating variables to reduce operating costs regarding terminal characteristics. In this study, we perform a rigorous and extensive dynamic simulation of LNG unloading process to demonstrate the effects of terminal characteristics, including the total length of the pipeline, the number of storage tanks, the ambient temperature, and the operation cycle. Based on simulation results and cost analyses, we can suggest an operational strategy to minimize the operating cost in LNG receiving terminals.
Keywords: LNG; LNG Receiving Terminal; Operating Cost; Dynamic Simulation

Reduction of unburned carbon fraction in exhaust during co-combustion of various coals in a circulating fluidized bed boiler (CFB) is required to save energy loss and to optimize coal utilization as well as to improve the boiler efficiency. In this study, the effects of operation variables such as coal, air and heat flow rates, co-combustion ratio of each coal, primary to secondary air ratio on unburned carbon fraction were analyzed and evaluated in two units of 200 MWe circulating fluidized bed boiler in the Tonghae thermal power plant. From the results, the comprehensive correlation among unburned carbon fraction and operation variables in #1 and #2 units of the CFB boiler could be derived with a good agreement. This would be expected to give a good guideline to reduce the unburned carbon content in exhaust in the CFB boiler.
Keywords: Unburned Carbon; Operation Variables; CFB; Co-combustion; Tonghae Thermal Power Plant

Effects of ultrasonification and mechanical stirring methods for the production of biodiesel from rapeseed oil by Joungdu Shin; Hyunook Kim; Seung-Gil Hong; Soonik Kwon; Young Eun Na; Sung Ho Bae; Woo-Kyun Park; Kee-Kyoung Kang (460-463).
This study was conducted to compare the effects of ultrasonic energy and mechanical stirring methods in bio-diesel production from rapeseed oil under base catalysis conditions. With the transesterification of rapeseed oil, the molar ratio of methanol to vegetable oil was 6: 1, and the amount of catalysts added to the vegetable oil was 0.3, 0.5 and 1.0% (wt/wt). The main components of methyl esters from the transesterification of rapeseed oil were oleic acid (48.5%, C18:1) and linoleic acid (18.1%, C18:2). In addition, the optimum conditions to produce fatty acid methyl esters (96.6%) were 0.5% KOH after 25 min of ultrasonification at 40 °C as compared to mechanical stirring at 60 °C. The maximum conversion ratio was 75.6% with 1.0% NaOH after 40 min of ultrasonification at 40 °C. These results indicate that ultrasonic energy could be a valuable tool for transesterification of fatty acids from rapeseed oil in terms of the reaction time and temperature.
Keywords: Bio-diesel Production; Fatty Acid Methyl Esters; Rapeseed Oil; Transesterification; Ultrasonification

Coal fouling characteristic to deposit probe with different temperatures under the gasification condition by Hueon Namkung; Tae-Jin Kang; Li-Hua Xu; Young-Shin Jeon; Hyung-Taek Kim (464-472).
Coal gasification was carried out to verify the coal fouling characteristic in a drop tube furnace (DTF). Four pulverized coal samples, in the range of bituminous and sub-bituminous, were used. To analyze the fouling characteristic by different temperature of deposit probe, a two-stage deposit probe was used in the experiment. Ash deposition rate was at upper deposit probe higher than at lower one. The X-ray fluorescence (XRF) results indicated that coal fouling included acid minerals such as SiO2 and Al2O3 at upper deposit probe more than that at lower deposit probe. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that the fouling particles at high deposit temperature were agglomerated more than those at low deposit temperature. And the convective heat transfer efficiency was reduced by ash deposition on probe. Especially, the convective heat transfer coefficient substantially declined with small particle size of fouling and Fe2O3, CaO, and MgO.
Keywords: Fouling; Gasification; Convective Heat Transfer Coefficient; Minerals

Removal of phosphate from aqueous solutions by iron nano-particle resin Lewatit (FO36) by Lida Rafati; Ramin Nabizadeh; Amir Hossein Mahvi; Mohamad Hadi Dehghani (473-477).
Lewatit FO36 resin was covered with Fe (III) nano-particles, and it was used as a new way to eliminate phosphate. Column experiments were carried out in 11 stages in fixed bed columns with constant flow rate of 9 ml/min and the empty bed contact time (EBCT) of 2.1 min. The adsorption capacity was calculated for different concentration of phosphate solutions. After resin was regenerated by using NaOH and NaCl solutions, the adsorption capacity of resin was computed for 6mg/L of phosphate, typically. The adsorption capacity of resin was checked again a typical concentration of phosphate. The adsorption capacity measurements of regenerated resin show that the concentration of phosphate reached to 1.6mg/g after an 8.5% decrease when the initial concentration of phosphate is 6 mg/L. Competition of anions with phosphate was analyzed using chloride, sulfate, bicarbonate and a combination of these anions. Finally the effect of resin in phosphate removal was studied for a typical real sample, and the data was analyzed using statistical software (SPSS 13). The statistical results indicated that Cl, SO 4 3− , HCO 3 and combined competing anions did not have a strong influence on the phosphate removal efficiency.
Keywords: Phosphate Removal; Lewatit FO36; Competing Anions; Adsorption

Influence of operating temperature on CO2-NH3 reaction in an aqueous solution by Bong Gill Choi; Gyo Hee Kim; Kwang Bok Yi; Jong-Nam Kim; Won Hi Hong (478-482).
Although aqueous ammonia solution has been focused on the removal of CO2 from flue gas, there have been very few reports regarding the underlying analysis of the reaction between CO2 and NH3. In this work, we explored the reaction of CO2-NH3-H2O system at various operating temperatures: 40 °C, 20 °C, and 5 °C. The CO2 removal efficiency and the loss of ammonia were influenced by the operating temperatures. Also, infrared spectroscopy measurement was used in order to understand the formation mechanism of ion species in absorbent, such as NH2COO, HCO 3 , CO 3 2− , and NH 4 + , during CO2, NH3, and H2O reaction. The reactions of CO2-NH3-H2O system at 20 °C and 40 °C have similar reaction routes. However, a different reaction route was observed at 5 °C compared to the other operating temperatures, showing the solid products of ammonium bicarbonates, relatively. The CO2 removal efficiency and the formation of carbamate and bicarbonate were strongly influenced by the operating temperatures. In particular, the analysis of the formation carbamate and bicarbonate by infrared spectroscopy measurement provides useful information on the reaction mechanism of CO2 in an aqueous ammonia solution.
Keywords: Ammonia Solution; CO2 Capture; Operating Temperature; Ammonia Loss; FT-IR

Experimental results are presented for the electrolytic ChemDen (Chemical-Denitrification) process which was designed to investigate the effect of operational parameters on the nitrate (NO 3 ) removal from metal-finishing wastewater. The parameters included electrode materials, electrode gap, reducing agent, hydraulic retention time (HRT) and recycle ratio in the single electrolytic ChemDen reactor for lab-scale tests. The removal efficiency of nitrate is based upon a non-biological process which consists of chemical and electrolytic treatment. Results showed that removal efficiency of nitrate was highest when the zinc (Zn) electrodes were used for both anode and cathode. In the case of insoluble electrode, combining Pt anode with Ti cathode provided great improvement of nitrate removal. For the Pt-Ti electrode combination, increasing electrode gap tended to increase removal efficiency of nitrate significantly. However, no further increase in the nitrate removal was observed when the electrode gap was longer than 10mm. Using sulfamic acid and Zn metal powder as reducing agents for the electrolytic ChemDen reaction, highest nitrate removal was achieved when the mole ratio of Zn: sulfamic acid: nitrate was 1.2: 1: 1. Remarkable improvement in the nitrate removal was also observed with increasing HRT from 10 to 30 min, while the effectiveness was limited when HRT was increased to 60 min. Recycling in electrolytic ChemDen reactor affected nitrate removal positively because it could improve both dispersion and reuse of Zn metal powder as reducing agent in the reactor. Recycling effects were thought to be associated with increasing surface reactivity of the Zn metal powder in the electrolytic ChemDen reactor.
Keywords: Electrolytic ChemDen Process; Electrodes; Nitrate Removal; Metal-finishing Wastewater

The removal of the acetonitrile using activated carbon-based sorbent impregnated with sodium carbonate by Jung Je Park; Suk Yong Jung; Chang Geun Park; Soo Chool Lee; Jong Nam Kim; Jae Chang Kim (489-493).
To remove acetonitrile, various activated carbon (AC)-based sorbents impregnated with alkali or alkaline earth metal were tested in a fixed-bed quartz reactor at 30 °C. The AC-based sorbents impregnated with sodium (NaAC) showed more enhanced acetonitrile removal capacities than that of the pure AC sorbent despite a notable decrease in their surface areas and pore volumes. The NaAC-10 sorbent (with 10 wt% sodium carbonate) especially showed an excellent acetonitrile removal capacity (15mg CH3CN/g sorbent) and regeneration ability, which indicates that the alkali metal was the adsorption site of the acetonitrile.
Keywords: Acetonitrile; Activated Carbon; Sorbent; Alkali Metal

Adsorption characteristics of methylene blue (MB) from aqueous solution on natural poplar leaf were investigated. Batch experiments were carried out to study the effects of initial pH, contact time, adsorbent dosage, and initial MB concentration, salt concentration (Ca2+ and Na+) as well as temperature on MB adsorption. The optimum condition for adsorption was found at pH 6–9 and adsorbent dosage of 2 g L−1. The equilibration time was 240 min. The salt concentration had a negative effect on MB removal. The equilibrium data were analyzed with Langmuir, Freundlich and Koble-Corrigan isotherm models using nonlinear regression method. The adsorption process was more effectively described by Langmuir isotherm based on the values of the correlation coefficient R2 and chi-square statistic x2. The maximum monolayer adsorption capacity of poplar leaf from the Langmuir model was 135.35 mg g−1 at 293 K. The pseudo second order equation provided a better fit to experimental data in the kinetic studies. Intraparticle diffusion was involved in adsorption process, but it was not the only rate-controlling step. Thermodynamic quantities such as ΔG, ΔH and ΔS were calculated, indicating that the adsorption process was spontaneous and endothermic. Dye-adsorbent interactions were examined by FTIR and SEM analysis. The FTIR results suggested that there were hydroxyl and carboxyl groups on the surface of poplar leaf, which would make MB adsorption possible. The SEM images showed effective adsorption of MB molecules on the adsorbent surface.
Keywords: Adsorption; Methylene Blue; Poplar Leaf; Isotherm; Kinetics; Thermodynamics

Bioadhesive strength between biofilm from yellowfin tuna (Thunnus albacares) gelatin and rat skin treated with glutaraldehyde was compared with bovine and porcine gelatin. Tuna biofilms treated with 0.5 M glutaraldehyde at 60 °C and neutral pH for 2 h had an increase in bioadhesive strength of approximately five times when compared with intact tuna biofilms. When glutaraldehyde-treated tuna biofilms were applied with sodium borohydride, the bioadhesive strength was reduced to the level of intact tuna biofilms. The bioadhesive strength of tuna biofilms was superior to those of bovine and porcine gelatin biofilms.
Keywords: Biofilm; Bioadhesion; Yellowfin Tuna; Gelatin Film; Glutaraldehyde

Multifunctional wool fiber treated with ɛ-polylysine by Jing Chang; Zhaoxiang Zhong; Hong Xu (507-512).
A creative method for fabricating environmentally-benign multifunctional wool fibers was established and reported. Through coating the wool fibers with ɛ-polylysine, the surface morphology and biochemical properties of the fibers were altered, enhancing their antimicrobial, hygroscopic and finished properties. The process of ɛ-polylysine coating was dependent on the solution environment, which influenced the electrostatic interactions between ɛ-polylysine molecules and wool fibers. The results showed that a maximum ɛ-polylysine coating (23.60 mg/g) on the surface of wool fibers was reached when wool fibers were soaked at 50 °C for 2 h in the solution with 10% on weight of fabric (owf) ɛ-polylysine and pH 8.0. The coated wool fiber showed promising antimicrobial rates of 96.98% and 97.93% against Escherichia coli and Micrococcus luteus, respectively. The wool fiber coated with the ɛ-polylysine was more hydrophilic than the uncoated wool fabrics. The functional wool fibers after water scrubbing for two times still have good antibacterial efficiency against Escherichia coli and Micrococcus luteus, and antimicrobial rates were 96.77% and 97.33%, respectively. This study shows that wool fibers modified by the nontoxic ɛ-polylysine have a great potential to be used in constructing multifunctional textiles.
Keywords: ɛ-Polylysine; Wool Fibers; Antibacterial Property; Hydrophilicity

Exergy analysis of two-stage steam-water jet injector by Qin Cai; Mingwei Tong; Xiujuan Bai (513-518).
Exergy analysis is used as a tool to evaluate exergy losses in the steam-water jet injector so as to improve its overall performance. What this article addresses here is mainly about a parametric study on the injector under various operating conditions, such as different inlet water temperature, inlet steam pressure, pressure ratio, entrainment ratio and flowrate ratio. In addition, the irreversible losses in the component parts of the two-stage injector were analyzed in detail. The results show that the operating parameters have great effects on exergy efficiency of the injector. The average exergy efficiency of the two-stage injector is 21% more than that of the single-stage one. Moreover, calculations based on experimental data indicate that the highest exergy losses due to irreversibility occur in the first-stage mixing chamber. In light of this comparison, the exergy losses occurring in the system are proportional to the exergy efficiency obtained by applying the system.
Keywords: Exergy; Steam-water Jet Injector; Two-stage; Efficiency; Entrainment Ratio

Visible up-conversion luminescence of CaWO4: Er3+,Yb3+ and emission enhancement by tri-doping of Li+ ions by Do-Hwan Kim; Jeong Ho Ryu; Jun Ho Chung; Jong Won Eun; Kwang Bo Shim; Sung-Yong Cho (519-524).
Er3+,Yb3+ co-doped CaWO4 polycrystalline powders were prepared by a solid-state reaction and their up-conversion (UC) luminescence properties were investigated in detail. Under 980 nm laser excitation, CaWO4: Er3+,Yb3+ powder exhibited green UC emission peaks at 530 and 550 nm, which were due to the transitions of Er3+ (2H11/2)→Er3+ (4I15/2) and Er3+ (4S3/2)→Er3+ (4I15/2), respectively. Effects of Li+ tri-doping into CaWO4: Er3+,Yb3+ were investigated. The introduction of Li+ ions reduced the optimum calcinations temperature about 100 °C by a liquid-phase sintering process and the UC emission intensity was remarkably enhanced by Li+ ions, which could be attributed to the lowering of the symmetry of the crystal field around Er3+ ions.
Keywords: UC (Up-conversion) Luminescence; CaWO4 : Er3+ ; Yb3+ ; Solid-state Reaction Method; Li+ Tri-doping

Aluminum-doped ZnO (AZO) thin films are grown by ultrasonic-mist deposition method for the transparent conducting oxides (TCO) applications at low temperatures. The AZO films can be grown at a temperature as low as 200 °C with zinc acetylacetonate and aluminum acetylacetonate sources. The lowest resistivity of grown AZO films is 1.0×10−3 Ω·cm and the lowest sheet resistance of 1 μm thick films is 10 Ω/□, which is close to that of commercial indium tin oxide (ITO) or Asahi U-type SnO2: F glass. The highest carrier concentration and mobility are 5.6×1020 cm−3 and 15 cm2/V·sec, respectively. Optical transmittance of the AZO films is found over 75% for all growth conditions. We believe that the properties of grown AZO films in this study are the best among all reported previously elsewhere by solution processes.
Keywords: Zinc Oxide; Aluminum-doped Zinc Oxide (AZO); Transparent Conducting Oxides; Ultrasonic-mist Deposition

Prevention of blister formation in electrolessly deposited copper film on organic substrates by Jung-Wook Seo; Hyo-Seung Nam; Seonhee Lee; Yong Sun Won (529-533).
Electroless copper (Cu) plating is a key process to provide seed layers for the subsequent Cu electroplating in the printed wiring boards (PWBs). Due to the demand for lower power dissipation at higher temperatures and high signal frequencies, various kinds of organic materials have been newly introduced as substrates. However, they have come with defects such as delamination and/or blisters in the Cu layers on organic substrates, i.e., weak adhesion. Here we demonstrate the root cause and a prevention method of the blister formation. Various parameters affecting the blister formation have been investigated combined with the deposit thickness (internal stress), hydrogen gas evolution, and codeposited Ni content in the electroless Cu plating. It was not obvious that the compressive internal stress in deposits was directly related to the blister formation. Instead, the hydrogen gas evolution clearly turned out to be the key factor, and it was observed that Ni added plating solutions reduced the hydrogen gas evolution significantly and thus produced no blisters in the Cu deposits. The control of blisters would be more critical as the line and space become narrower in the production lines such as ball grid array (BGA) and high density interconnection (HDI).
Keywords: Electroless Copper Plating; Blister; Adhesion; Printed Wiring Board (PWB)

Experimental study on the controlled air oxidation of sawdust in a packed-bed reactor by Qingmin Meng; Xiaoping Chen; Changsheng Bu; Jiliang Ma (534-539).
The controlled air oxidation technology is a promising way of disposing medical waste, which has been a huge challenge in China. It converts waste through partial oxidation into a gaseous mixture, small quantities of char and condensable compounds. But operational performance of the primary chamber of the controlled air incinerator is poorly understood, leading to difficulty in control. In this paper, a packed-bed reactor was established to study the effect of O2 concentration on sawdust oxidation. The feed gas flow rate was kept constant at 0.6 m3/h at room temperature (26 °C) with O2 concentrations varied from 6% to 12%. Temperature profiles of the beds, product yields and gas compositions in the out-of-bed fuel gas were measured in detail. The results showed that the sawdust beds achieved low temperatures for the given O2 concentrations and leveled off in the oxidation processes. The bed temperatures increased and the solid yields decreased with the increase of O2 concentrations. When the O2 concentration was 10%, the gas yield reached a minimum and the liquid reached a maximum correspondingly. When the O2 concentration increased from 6% to 10%, the peak concentrations of CO and CH4 in the gas yield increased. However, when the O2 concentration exceeded 10%, CO and CH4 concentrations decreased. As O2 concentration varied from 6% to 12%, CO2 concentration increased continuously. This study provides a fundamental insight that the reaction processes could be well regulated by means of adjusting the feed air in practical units.
Keywords: Sawdust; Controlled Air Oxidation; Packed-bed

This paper reports on the mathematical modeling of the pyrolysis of single coarse lignite particles using a kinetics model coupled with a heat transfer model. The parallel reaction kinetics model of the lignite pyrolysis makes no assumptions about the activation energy distribution and the conversion of sub-reactions. The pyrolysis kinetics parameters were obtained on the basis of experimental data from thermogravimetric analysis (TGA) tests. The heat transfer model includes diffusive, convective and radiative heat transfer modes. The experimental investigations were carried out for single lignite particles in an electrically heated reactor. Measurements of the temperature and mass loss were performed during the pyrolysis in a nitrogen atmosphere. The model predictions for the temperature and mass loss histories agree well with the experimental data, verifying that the mathematical model accurately evaluates the pyrolysis of lignite particles. The effects of temperature and particle size on the pyrolysis time and final residual mass fraction were evaluated using the numerical model.
Keywords: Lignite; Coarse Particle; Pyrolysis; Kinetics Model