Korean Journal of Chemical Engineering (v.28, #12)

A fractional order integrator can be used for the relay feedback identification of a process Nyquist point in the third quadrant, and to implement the fractional order integrator, it is often approximated by integer order systems. Here, instead of the usual rational transfer function approximation of the fractional order integrator in the relay feedback system, a simple analytic method which utilizes the on-off characteristics of relay output is proposed. Simulation results show that the proposed method can find process Nyquist points in the third quadrant without worrying about the approximation errors and ranges of the fraction order integrator.
Keywords: Fractional Order Integrator; Relay Feedback Identification; Nyquist Point in the Third Quadrant

Turbulent convective heat transfer of nanofluids through a square channel by Mohammad Nasiri; Seyed Gholamreza Etemad; Rohollah Bagheri (2230-2235).
This paper reports the results of experimental investigation on the heat transfer performance of Al2O3/H2O and TiO2/H2O nanofluids through square channel with constant wall temperature boundary condition. The flow regime through channel is turbulent. The nanofluids used in this research are Al2O3/H2O and TiO2/H2O with different nanoparticle concentrations. Based on the results of the present investigation, for specific Peclet number, convective heat transfer coefficient and Nusselt number of nanofluids are higher than those of distilled water. The enhancement increases with increasing nanoparticle concentration. The results also reveal that the convective heat transfer coefficient for Al2O3/H2O nanofluid is relatively the same as that of TiO2/H2O nanofluid.
Keywords: Nanofluid; Square Channel; Heat Transfer Coefficient; Nusselt Number; Nanoparticle

Influence of heat treatment on thermally-reduced graphene oxide/TiO2 composites for photocatalytic applications by Thuy-Duong Nguyen-Phan; Viet Hung Pham; Hyunran Yun; Eui Jung Kim; Seung Hyun Hur; Jin Suk Chung; Eun Woo Shin (2236-2241).
Thermally-reduced graphene oxide/TiO2 composites (TRGO/Ti) were prepared by the thermal reduction of graphene oxide/TiO2 composite that was obtained from a simple, environmentally friendly, one-step colloidal blending method. The changes in structural and textural properties as well as their corresponding photocatalytic activities were investigated as a function of calcination temperature. The presence of stacked TRGO sheets significantly retarded both the aggregation and the crystalline phase transformation of TiO2 as increasing the temperature from 200 to 600 °C. TRGO/Ti composites exhibited higher photocatalytic activity for the degradation of methylene blue in comparison with pure TiO2 due to the increase in specific surface area and the formation of π-π conjugations between dye compounds and aromatic regions of TRGO. However, increasing the calcination temperature resulted in the lower photoactivity and slower kinetics, which can be ascribed to the decrease in surface area, the reduction of oxygen vacancies, and the loss of functional groups at the edges or on the basal planes of the TRGO sheets.
Keywords: TiO2 ; Reduced Graphene Oxide; Nanocomposites; Dye; Photocatalytic Degradation; Porous Materials

Modeling and simulations of a reformer used in direct reduction of iron by Abdelhamid Ajbar; Khalid Alhumaizi; Mustafa Soliman (2242-2249).
This paper presents a detailed modeling and simulations of a reformer unit used in the direct reduction of iron (DRI) process. A one-dimensional heterogeneous model for the catalyst tubes which takes into account the intraparticle mass transfer resistance was developed, while the furnace was modeled with bottom firing configuration. Validation against data from a local iron/steel plant showed satisfactory results. The performance variables of the unit were the process gas temperature, wall temperature and conversions of hydrogen, methane and carbon dioxide. The profiles of these output variables along the distance were calculated. The effect of operating parameters such as inlet temperature, natural gas flow rate and gas composition was also determined.
Keywords: Direct Reduction of Iron; Reformer; Modeling; Simulation; Performance

Methylation of methyltrichlorosilane with methyl chloride over active metals and activated carbon by Yanjun Liu; Yiqian Jiang; Hengbo Yin; Weiguang Chen; Yutang Shen; Yonghai Feng; Lingqin Shen; Aili Wang; Tingshun Jiang; Zhanao Wu (2250-2254).
Gas phase methylation of methyltrichlorosilane with methyl chloride to high-valued dimethyldichlorosilane was carried out by using metallic aluminum as a chlorine acceptor in the co-presence of activated carbon, tin, and zinc. The addition of activated carbon in metallic aluminum significantly enhanced the methylation of methyltrichlorosilane, and dimethyldichlorosilane was dominantly produced. Activated carbon played a catalyst role in the methylation reaction. When active metals, such as tin and zinc, were added in the mixture of aluminum and activated carbon, the active metals and activated carbon synergistically catalyzed the methylation of methyltrichlorosilane with methyl chloride toward the formation of dimethyldichlorosilane.
Keywords: Alkylation; Chlorinated Hydrocarbon; Aluminum; Activated Carbon

Equilibrium, kinetic and thermodynamic study of removal of reactive orange 12 on platinum nanoparticle loaded on activated carbon as novel adsorbent by Mehrorang Ghaedi; Javad Tashkhourian; Arezoo Amiri Pebdani; Batol Sadeghian; Fatemeh Nami Ana (2255-2261).
The proposed research describes the synthesis and characterization of platinum nanoparticles loaded on activated carbon (Pt-NP-AC) and its efficient application as novel adsorbent for efficient removal of reactive orange 12 (RO-12). The influences of effective parameters following the optimization of variables on removal percentages, their value was set as 0.015 g Pt-NP-AC, pH 1, contact time of 13 min. At optimum values of all variables at 25 and 50 mgL−1 of RO-12 enthalpy (ΔH0) and entropy (ΔS0) changes was found to be 59.89 and 225.076, respectively, which negative value of ΔG0 shows a spontaneous nature, and the positive values of ΔH0 and ΔS0 indicate the endothermic nature and adsorption organized of dye molecule on the adsorbent surface. Experimental data was fitted to different kinetic models including first-order, pseudo-second-order, Elovich and intra-particle diffusion models, and it was seen that the adsorption process follows pseudo-second-order model in consideration to intra-particle diffusion mechanism. At optimum values of all variables, the adsorption process follows the second-order kinetic and Langmuir isotherm model with adsorption capacity 285.143 mg g−1 at room temperature.
Keywords: Adsorption; Reactive Orange 12; Platinum Nanoparticle Loaded on Activated Carbon; Adsorption Isotherm; Thermodynamics and Kinetic of Adsorption

Characterization of products from slow pyrolysis of palm kernel cake and cassava pulp residue by Piyarat Weerachanchai; Chaiyot Tangsathitkulchai; Malee Tangsathitkulchai (2262-2274).
Slow pyrolysis studies of palm kernel cake (PKC) and cassava pulp residue (CPR) were conducted in a fixed-bed reactor. Maximum liquid yield (54.3 wt%) was obtained from PKC pyrolysis at 700 °C, heating rate of 20 °C/min, N2 gas flow rate of 200 cm3/min and particle size of 2.03 mm. Fuel properties of bi-oils were in following ranges: density, 1.01–1.16 g/cm3; pH, 2.8–5.6; flash point, 74–110 °C and heating value, 15 MJ/kg for CPR oil and 40 MJ/kg for PKC oil. PKC oil gave main contents of n-C8–C18 carboxylic acids, phenols, and esters, whereas CPR oil gave the highest amount of methanol soluble fraction consisting of polar and non-volatile compounds. On gas compositions, CPR pyrolysis gave the highest yield of syngas produced, while PKC pyrolysis offered the highest content of CO2. Pyrolysis chars possessed high calorific values in range from 29–35 MJ/kg with PKC char showing a characteristic of reasonably high porosity material.
Keywords: Biomass; Pyrolysis; Bio-oil; Fuel Properties; Chemical Compositions

Analysis of the heat of reaction and regeneration in alkanolamine-CO2 system by Seung-Tae Kim; Jeong-Won Kang; Jong-seop Lee; Byoung-Moo Min (2275-2281).
The estimation of regeneration heat of absorbent is important because it is a key factor that has an effect on the process efficiency. In this study, thermal stability and regeneration heat of aqueous amine solutions such as monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), N-methyldiethanolamine (MDEA), and 1,8-diamino-pmenthane (KIER-C3) were investigated by using TGA-DSC analysis. The thermal characteristics of the fresh and CO2 rich amine solutions were estimated. The CO2 rich amine solutions were obtained by VLE experiments at T=40 °C. The regeneration heat of aqueous MEA solution was 76.991–66.707 kJ/mol-CO2, which is similar to heat of absorption. The reproducibility of the results was obtained. The regeneration heat of aqueous KIER-C3 20 wt% solution (1.68 M) was lower than that of aqueous MEA 30 wt% solution (4.91 M). Therefore, the KIER-C3 can be used as an effective absorbent for acid gas removal.
Keywords: Absorption; Carbon Dioxide; Heat of Regeneration

Co-methanation of CO and CO2 on the Ni X -Fe1−X /Al2O3 catalysts; effect of Fe contents by Suk-Hwan Kang; Jae-Hong Ryu; Jin-Ho Kim; Seok-Jung Seo; Yong-Done Yoo; Potharaju S. Sai Prasad; Hyo-Jun Lim; Chang-Dae Byun (2282-2286).
The co-methanation of carbon dioxide containing syngas was carried out on Al2O3 supported Ni x Fe1−x (x is 0.1, 0.3, 0.5, 0.7 and 0.9) catalysts for synthetic natural gas (SNG) production. The catalysts were prepared by wet-impregnation method taking 20 weight percent of the metallic component over the support, and its characteristics were analyzed by BET surface area, XRD and H2-TPR. The maximum carbon conversion and CH4 selectivity are achieved on Ni0.7Fe0.3/Al2O3 catalyst. Further, increase of Fe content led to enhancing the water gas shift reaction and hydrocarbon formation.
Keywords: Methanation; Synthetic Natural Gas; Ni-Fe Catalyst; Syngas

Synthesis of biodiesel from an oil fraction separated from food waste leachate by Mi Jin Yu; Yong-Beom Jo; Sang-Guk Kim; Young-Kwan Lim; Jong-Ki Jeon; Sung Hoon Park; Seung-Soo Kim; Young-Kwon Park (2287-2292).
Biodiesel was produced from an oil fraction separated from food waste leachate, using a batch reactor system, to evaluate its potential as a renewable energy source for the first time. In order to reduce the free fatty acid content of the leachate oil fraction, three different acid catalysts, H2SO4, zeolite and Amberlyst-15, were used in the pretreatment process. The residual oil fraction after pretreatment was further treated over KOH as a base catalyst to produce a fatty acid methyl ester (FAME). The FAME content in the product was analyzed using GC/MS. A large number of different FAMEs were detected, which is characteristic of the food-waste-derived raw material used in this study. The FAME content of the product was highest when pretreated over Amberlyst-15, followed by trans-esterification. Additional refining and process optimization would be expected to further increase the FAME content. Therefore, it was concluded that the production of biodiesel from the oil fraction separated from food waste leachate is promising.
Keywords: Oil Fraction Separated from Food Waste Leachate; Biodiesel; Acid Catalyst; Base Catalyst

The coagulation of soil particles from a soil-washing solution containing the nonionic surfactant Triton X-100 (TX100) was investigated using various coagulants, such as chitosan (CS), polyacrylamide (PAA), and polyaluminum chloride (PAC). Soil contaminated with phenanthrene (PHE) was washed with aqueous TX100 solutions at concentrations ranging from 0.1 to 20 g/L. The effectiveness of CS (5 mg/L) as a coagulant in the system was compared with PAA (50mg/L) and PAC (50 mg/L), and the results indicated that the system with CS exhibited a more effective separation of soil than those with PAA and PAC. The removal efficiency of PHE (R j =81.7%) and the selective separation factor (SSF=14.2) at 10 g/L TX100 were the highest for the system with CS (5 mg/L), indicating that the selection of CS as a coagulant in surfactant-mediated soil washing markedly improved both PHE removal and soil separation.
Keywords: Chitosan; Coagulation; Phenanthrene; Soil Washing; Surfactant

Immobilized trypsin in mesoporous silica foams was used to catalyze dipeptide synthesis in hydrophilic organic solvent instead of soluble form. The area surface of nano support was measured. The catalytic activity, coupled yield and kinetic characterization of immobilized trypsin were examined. Bz-Arg-OEt was chosen as the acyl donor with Lys-OH as the nucleophile. The trypsin-catalyzed synthesis condition was optimized, such as catalytic temperature, pH, reaction time, physical properties and content of organic solvents, together with the added enzyme amount. The immobilized trypsin showed 112.8% of residual activity with 91.9% of coupled yield, and the kinetic parameters exhibited accessibility for transmission. The product yield of 5.8% was reached at the optimum conditions for enzymatic synthesis of dipeptide: 800 mg of wet immobilized trypsin (200 mg/g support) was used in Tris-HCl buffer (0.1 mol/L, pH 8.0) containing 80% (v/v) ethanol solvents for 6 h of reaction time at 35 °C. This attempt of immobilized strategy for trypsin in nanopores renders the possibility of wide application of inorganic nano-sized support in catalytic synthesis process, which can avoid usage of large amounts of organic solvents in washing steps by chemical methods and reduce the tedious purification process of its soluble form.
Keywords: Immobilized Trypsin; Enzymatic Synthesis; Mesoporous Silica Foams; Hydrophilic Organic Solvents

The stoichiometry of the entire reaction in a 50 L scaled-up production culture of bacterial cellulose (BC), using saccharified food wastes (SFW), was analyzed in this study. The stoichiometric analysis was carried out using the chemical formula, yield, degrees of reduction of the major components, and the respiratory quotient (RQ). Based on the stoichiometric analysis, the amounts of substrate, oxygen supply and BC production etc., were able to be predicted. In addition, the amount of energy generated in the culture was predicted based on the oxygen consumption via the stoichiometric analysis. The stoichiometry of BC production using SFW in a 50 L large scale reactor will be useful as a standard for mass production of the culture. The stoichiometric analysis can also help the designers of reactors decide on the boiler capacity and oxygen supply for a large scale bioreactor system. The OUR (oxygen uptake rate) of Acetobacter xylinum KJ1 in a 12 hour-age cultivation was 0.21 mg DO/L·min, from which the critical DO concentration was suggested to be maintained above 3.10 ppm to prevent oxygen limitation during the BC production culture. The results indicated that pure oxygen should be supplied during the exponential phase, where DO depletion was observed. An ascertainment experiment, with the addition of pure oxygen into the culture system, showed BC production of 7.37 g/L, which was considerable productivity.
Keywords: Stoichiometry; OUR; Critical DO; Energy Generation; Bacterial Cellulose; Food Wastes

Effects of three main sugars in cane molasses on the production of butyric acid with Clostridium tyrobutyricum by Lei Huang; Yijuan Xiang; Jin Cai; Ling Jiang; Zhengbing Lv; Yaozhou Zhang; Zhinan Xu (2312-2315).
The effects of three main sugars in cane molasses were investigated systematically to prepare a cost-effective medium for butyric acid bioproduction. Additionally, 30 g/L corn steep liquor was screened out as the suitable nitrogen source. In the batch fermentation of free cells, when 60 g/L glucose was the only carbon source, 21.28 g/L butyric acid was achieved after 30 h cultivation. Similar product concentration, productivity and yield were obtained when 60 g/L fructose was applied. The utilization of sucrose would bring about lower productivity (0.29 g/L·h) and product concentration (18.15 g/L), but the yield of butyric acid/sucrose (0.34 g/g) is almost the same as that from glucose or fructose (0.35 g/g). Finally, the sugar mixture (15 g/L glucose, 20 g/L fructose and 35 g/L sucrose) was employed to produce butyric acid in a fibrous-bed bioreactor (FBB), and 40.11 g/L butyric acid was produced with one simple fed-batch strategy.
Keywords: Butyric Acid; Clostridium tyrobutyricum ; Cane Molasses; Fibrous-bed Bioreactor

The effect of the reducing power on the reduction of methyl-2-chlorobenzoylformate was evaluated by using carbon substrates with different reducing powers. Glucose, sorbitol, and gluconate regenerated 2, 3, and 1 NAD(P)H during its conversion to pyruvate, respectively. When sorbitol was used as the carbon substrate, complete conversion was achieved in 8 h while it took 12 h and 19 h when glucose and gluconate were used, respectively. The enantiomeric excess (ee) value was 96.7% when sorbitol was used.
Keywords: Asymmetric Reduction; Reducing Power; Methyl (R)-2-Chloromandelate; Saccharomyces cerevisiae

Solubility of hinokitiol in supercritical fluids; measurement and correlation by Junhyuk Lim; Hwayong Kim; Hye Kyung Cho; Moon Sam Shin (2319-2323).
Supercritical fluid technology has been an alternative for purification and separation of biological compounds in cosmetic, food, and pharmaceutical products. Solubility information of biological compounds in supercritical fluids is essential for choosing a supercritical fluid processes. The equilibrium solubility of hinokitiol was measured in supercritical carbon dioxide and ethane with a static method in the pressure range from 8 to 40MPa and at temperatures equal to 313.2, 323.2 and 333.2 K. The experimental data were correlated well by Peng-Robinson equation of state and quasi-chemical nonrandom lattice fluid model.
Keywords: Supercritical Fluids; Hinokitiol; Carbon Dioxide; Ethane; Solubility

Isothermal vapor-liquid equilibria for the binary system of dimethyl ether (CH3OCH3)+ methanol (CH3OH) by Seol A. Kim; Joon Hyuk Yim; Hun-Soo Byun; Jong Sung Lim (2324-2328).
Isothermal vapor-liquid equilibrium data for the binary mixture of dimethyl ether (CH3OCH3)+methanol (CH3OH) were measured within the temperature range of 308.15–328.15 K. The data in the two-phase region were measured by using a circulation-type equilibrium apparatus in which both vapor and liquid phases are continuously recirculated. The experimental data were correlated with the Peng-Robinson equation of state (PR-EoS) using the Wong-Sandler mixing rules combined with the NRTL excess Gibbs free energy model. The values calculated by the PR-EOS with the W-S mixing rules show good agreement with our experimental data.
Keywords: Dimethyl Ether (CH3OCH3); Methanol (CH3OH); Vapor-liquid Equilibria (VLE); Peng-Robinson Equation of State (PR-EoS)

Biosynthesis of gold nanoparticles and nanoplates (GNPs) was accomplished using aqueous fractions of pear extract as a safe, reducing, particle-stabilizing, and shape-directing agent. The maximum yields of spherical gold nanoparticles having the average sizes of 40, 20, and 10 nm were achieved at 30, 60, and 90 °C, respectively, at a pear extract concentration of 45% (v/v). The maximum yield of gold nanoplates was obtained with sizes ranging from 20 to 400 nm, particularly at reaction temperatures of 30, 60, and 90 °C, at a pear extract concentration of 5% (v/v). The surface chemistry analysis of the GNPs suggests that the sugars and peptides or proteins as key biomolecules of the pear extract play a crucial role in the reduction of Au(III), subsequently resulting in healthy capping. Therefore, this environmentally friendly synthesis method of GNPs for the particular type of morphologies is expected to be a competitive alternative to existing physical and chemical methods.
Keywords: Pear Extract; Gold Nanoparticles; Stabilization; Green Chemistry; Circular Dichroism

Principles of optimization of combustion by radiant energy signal and its application in a 660 MWe down- and coal-fired boiler by Zixue Luo; Fei Wang; Huaichun Zhou; Rutie Liu; Wenchang Li; Gengzhou Chang (2336-2343).
For the optimization of combustion in utility coal-fired boilers, a simple analytic model was set up to relate the radiant energy signal (RES) with the combustion rate (heat release rate) based on the heat transfer equation inside a boiler furnace. It was pointed out that as the air flow rate into the furnace changes, the highest RES corresponds to the highest efficiency, making RES a sensitive quantity for optimization of combustion in boilers. Experiments carried out in a 660 MW down- and coal-fired utility boiler confirmed the characteristics of RES as an indicator of combustion rate inside the furnace and its ability to reflect the boiler thermal efficiency varied with the air flow rate. The utilization of RES in the optimization of combustion can generally improve the boiler thermal efficiency at different unit loads, and the efficiency was raised about 1.0% especially at the rated and lower unit loads. It should be stated that except the lower unit load, the NOx emission from the boiler after optimization of combustion by RES would increase due to the limitation in supply of adequate air flow rate into the boiler, and some new combustion technologies are now available to solve the contradiction.
Keywords: Optimal Combustion Control; Down-fired Furnace; Radiant Energy Signal; Flame Image Processing

Taixi anthracite was used as a precursor to prepare activated carbons (AC) for SO2 adsorption from flue gas. In this work the activated carbons were prepared by physical activation with steam. Specifically, the effects of activation temperature and burn-off degree on the physico-chemical properties of the resulting AC samples were comparatively studied. The different types of pore volumes, pore size distributions and surface chemistries of the activated carbons on the SO2 adsorption were also analyzed. The results show that the increasing burn-off leads to samples with continuous evolution of all types of pores except ultramicropore. The ultramicropore volume increases to a maximum of 0.169 cm3/g at around 50% burn-off and then decreases for 850 °C activation. At higher activation temperature, the micropore volume decreases and the mesopore structure develops to a certain extent. For all the resulting AC samples, the quantities of the basic surface sites always appear much higher than the amount of the acidic sites. The activated carbon prepared with higher micropore volume, smaller median pore diameter and higher quantities of the basic surface sites represents better SO2 sorption property.
Keywords: Activated Carbon; Steam Activation; Textural Properties; Surface Properties; SO2 Adsorption