• Korean Chemical Engineering Research
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• 제57권2호
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• pp.283-288
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• 2019

Catalytic removal of sulfur compounds from heavy naphtha (HN) was investigated using a combination of an oxidation process using hydrogen peroxide and an adsorption process using granulated activated carbon (GAC) and white eggshell (WES). This study investigated the impact of changing several operating parameters on the desulfurization efficiency. Specifically, the volume ratio of $H_2O_2$ to HN (0.01~0.05), agitation speed ($U_{speed}$) of the water bath shaker ($100-500{\pm}1rpm$), pH of sulfur solution (1~5), amount of adsorbent (0.1~2.5 g), desulfurization temperature ($25{\sim}85{\pm}1^{\circ}C$) and contact time (10~180 minutes) were examined. The results indicate that the desulfurization efficiency resulting from catalytic and adsorption processes of GAC is better than that of WES for oxidation and removing sulfur compounds from HN due to its high surface area. The desulfurization efficiency depends strongly on all investigated operating parameters. The maximum removal efficiency of GAC and WES achieved by this study was 86 and 65, respectively.

• 공업화학
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• 제21권5호
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• pp.488-494
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• 2010

W/O 에멀젼법하에 homogenizer를 사용하여 ${\alpha}$-알루미나 분체 제조 시 O : W 부피비, 교반속도, 계면활성제 사용량과 조성 및 종류 등의 변화에 의하여 분체의 입자형상, 응집성, 평균입경과 입도분포 등의 변화를 분석하였다. 계면활성제는 비이온 계면활성제가 사용되었고 단일 및 혼합계면활성제로는 SP80 및 [SP80 & TW80]을 사용하였고 보조계면활성제로는 n-부탄올을 사용하였다. SP80을 사용하였을 경우, 분체의 입자형상은 구형에 근접하였고 평균입경은 주어진 O : W 부피비 변화 및 16000 rpm 이상의 교반속도에서 큰 차이를 보이지 않았다. [SP80 & TW80]을 사용하였을 경우, 구형에 가까운 분체의 입자간 응집 및 합체현상은 $HLB_m$ = 5일 때 낮았고 평균입경은 단일계면활성제를 사용하였을 때 비하여 다소 감소하였다. $HLB_m$ = 5인 [SP80 & TW80]와 함께 0.1 vol% n-부탄올을 사용하였을 경우, 입자간 응집성이 상대적으로 낮고 나노크기의 입도를 갖는 분체 분율을 증가시킬 수 있었다.

• 펄프종이기술
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• 제47권2호
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• pp.53-60
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• 2015

The effects of stirring speed during filler modification by dual polymers on flocculation and reflocculation of PCC (precipitated calcium carbonate) particles and its effect on handsheet properties were elucidated. PCC surface was modified by adsorbing A-PAM (anionic polyacrylamide) and C-starch (cationic starch) in series at various stirring speeds. It was found that increasing stirring speed during filler modification decreased the initial floc size of PCC. Continuous stirring with the same speed for filler modification resulted in the decrease of a floc size, eventually reached a steady state. The variations in a floc size was influenced by the stirring speed during filler modification: the lower the stirring speed during filler modification, the larger the floc size variations. Conclusively, the stability of PCC floc could be improved by increasing the stirring speed. In addition, the stirring speed influenced the handsheet properties. The smaller the PCC floc, the lower the strength of handseet. However, too much larger floc size also deteriorated paper strength. There exists an optimum floc size in term of paper strength which shall be controlled by stirring speed during filler modification.

• 한국환경과학회지
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• 제26권6호
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• pp.711-717
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• 2017

Dielectric Barrier Discharge (DBD) plasma is a new technique for use in environmental pollutant degradation, which is characterized by the production of hydroxyl radicals as the primary degradation species. Due to the short lifetime of the chemically active species generated during the plasma reaction, the dissolution of the plasma gas has a significant effect on the reaction performance. The plasma reaction performance can be enhanced by combining the basic plasma reactor with a homogenizer system in which the bubbles are destroyed and turned into micro-bubbles. For this purpose, the improvement of the dissolution of plasma gas was evaluated by measuring the RNO (N-dimethyl-4-nitrosoaniline, an indicator of the generation of OH radicals). Experiments were conducted to evaluate the effects of the diameter, rotation speed, and height of the homogenizer, pore size, and number of the diffuser and the applied voltage on the plasma reaction. The results showed that the RNO removal efficiency of the plasma reactor combined with a homogenizer is two times higher than that of the conventional one. The optimum rotor size and rotation speed of the homogenizer were 15.1 mm, and 19,700 rpm, respectively. Except for the lowest pore size distribution of $10-16{\mu}m$, the pore size of the diffuser showed little effect on RNO removal.

• Journal of Microbiology and Biotechnology
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• 제10권3호
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• pp.367-374
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• 2000

The composition of dissolved gases and nutrients in a liquid medium were determined for establishment of the optimum conditions for in vitro culture of Helicobacter pylori. A microaerobic condition facored by the organism was prepared by adjusting the partial pressure of the gas, agitation speed, and viscosity of the medium. The gaseous concentrations were controlled by utilizing CampyPak Plus that reduced oxygen while augmenting carbon dioxide. Agitation of the broth facilitated the oxygen transfer to the cells, yet inhibited the growth at high rates. An increase of viscosity in the medium repressed the culture although this variable was relatively insignificant. The chemical constituents of the liquid broth were examined to establish an economic model for H. pylori cultivation. The microbe required a neutral pH for optimum growth, and yet was also able to proliferate in an acidic condition, presumably by releasing the acidity-modulating enzyme, urease. Cyclodextrin and casamino acid were investigated as growth enhancers in place of serum, while yeast extract unexpectedly inhibited the cells. A low concentration of glucose, the unique carbon source for the organism, increased the cell density, yet high concentrations resulted in an adverse effect. Under optimally dissolved gas conditions, the cell concentration in brucella broth supplemented with serum substitutes and glucose reached $1.6{\times}10^8$ viable cells/ml which was approximately 50% higher than that obtained in the liquid medium added with only cyclodextrin or serum.

• 한국버섯학회지
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• 제6권1호
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• pp.27-31
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• 2008

현재까지 연구로는 흰목이 균사체에서 EPS 생산과 균사생장에 대한 적정 정치배양 조건이 연구되었다. 본 연구로부터 탄소원과 질소원의 처음 농도, 균사 형태와 발효조의 타입의 선택은 흰목이 균사체 EPS 생산에 가장 영향을 미친다는 것을 알게 되었다. 이들 결과는 공기주입식 반응기에서 EPS 생산성은 진탕탱크 반응기 보다 더 높았다는 점을 증명하였다. 또한 흰목이 균사의 정치배양의 생리적 생장에 대한 지식은 아직도 제한적이다.

• KSBB Journal
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• 제14권2호
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• pp.160-166
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• 1999

본 연구에서는 ($\beta$-carotene 생산균주인 미세조류 Dunaliella bardawil을 사용하여 batch flask에서 미세조류의 고농도세포에 관한 최적배양조건(미량원소, pH, agitation speed, nitrate, phosphate, carbon source)을 확립하고자 하였다. 미량원소는 5X 배지에서 교반하였을 때 비생장속도는 $0.0l3hr^{-l}$와 세포농도는 $4.9{\times}10^6$ cells/mL로서 IX. 3X, lOX 배지에서 배양한 것보다. 약 46%, 18%, 69% 높은 세포수율을 얻었으며 세포배양시 교반한 경우, pH는 80에서 최대 세포농도를 얻었다. 초기 nitrate ($KNO_3$)와 phosphate($KH_2PO_4$)의 영향을 조사한 결과 미세조류 생장에 중요한 영양분으로서 질소원의 주입은 매우 효과적임을 확인하였다. 또힌 탄소원으로서 250mM의 $NaHCO_3$와 $CO_2$ 가스를 동시에 사용한 배양조건이 500mM $NaHCO_3$만을 탄소원으로 사용한 실험에 비하여 32% 증가된 세포농도를 나타내었다. light는 white light의 경우 blue light보다 세포생장에 적합하였다. 질소원을 이용한 유기배양시 2회의 nitrate주입만으로써 배양 198hr에 $8.955{\times}10^6$cell/mL의 고농도의 세포를 얻었다.

• KSBB Journal
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• 제30권6호
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• pp.307-312
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• 2015

Transgenic rice cells using RAmy3D promoter can provide high productivity, and the production of recombinant protein is induced by sugar starvation. In this system, productivity was reduced during the scale-up processes. To ensure the influences of shear stress and oxygen transfer rate, working volume and mixing performances were investigated under various agitation speeds and working volumes. In addition, inoculation methods including suspended cells and filtered cells were compared. Working volumes and shaking speeds were 300, 450 mL and 80, 120 rpm, respectively. Hydrodynamic environment of each condition was measured numerically like mixing time and $k_La$. Good mixing performance and high shear stress were measured at high agitation speed and low volume. The highest level of hCTLA4Ig was 30.7 mg/L at 120 rpm, 300 mL. When conditioned medium was used for inoculation, increased cell growth was noticed during the day 0~4 and decreased slower than filtered cells. Compared with filtered cells, the maximum hCTLA4Ig level reached 37.8 mg/L at 120 rpm, 300 mL and lower protease activity level was observed. In conclusion mixing performance is critical factor for productivity and conditioned medium can have a positive effect on damaged cells caused by hydrodynamic shear stress.

• KEPCO Journal on Electric Power and Energy
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• 제3권1호
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• pp.29-34
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• 2017

Leaching kinetics for extracting yttrium from the coal fly ash was investigated in the presence of sulfuric acid during extraction. The leaching kinetics of yttrium were conducted at reactant densities of 5~1,000 g coal fly ash per L of $1.0{\sim}10.0N\;H_2SO_4$, agitation speed of 250 rpm and temperature ranging from 30 to $90^{\circ}C$. As a result, the leaching kinetic model was determined in a two-step model based on the shrinking core model with spherical particles. The first step was proceeded by chemical reaction at ash surface, and the second step was proceeded by ash layer diffusion because the leaching conversion of yttrium by the first chemical reaction increases with increased the time irrelevant to the temperature whereas it increases with increased the leaching temperature. The activation energy of the first chemical leaching step was determined to be $1.163kJmol^{-1}$. After the first chemical reaction, the activation energy of ash layer diffusion leaching was derived to be $41.540kJmol^{-1}$. The optimum conditions for leaching the yttrium metal of 60 % were found to be the slurry density of 250 g fly ash per L of $H_2SO_4$, solvent concentration of $2.0N\;H_2SO_4$, second step leaching of temperatures of $30^{\circ}C$ for 3 hours and then $90^{\circ}C$ for 3 hours at agitation rate of 250 rpm.

• Journal of Microbiology and Biotechnology
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• 제23권10호
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• pp.1445-1453
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• 2013

The scale-up criterion of constant oxygen mass transfer coefficient ($k_La$) was applied for the production of itaconic acid (IA) in a 50 L pilot-scale fermentor by the fungal cells of Aspergillus terreus. Various operating conditions were examined to collect as many $k_La$ data as possible by adjusting the stirring speed and aeration rate in both 5 L and 50 L fermentor systems. In the fermentations performed with the 5 L fermentor, the highest IA production was obtained under the operating conditions of 200 rpm and 1.5 vvm. Accordingly, we intended to find out parallel agitation and aeration rates in the 50 L fermentor system, under which the $k_La$ value measured was almost identical to that ($0.02sec^{-1}$) of the 5 L system. The conditions of 180 rpm and 0.5 vvm in the 50 L system turned out to be optimal for providing almost the same volumetric amount of dissolved oxygen (DO) into the fermentor, without causing shear damage to the producing cells due to excessive agitation. Practically identical fermentation physiologies were observed in both fermentations performed under those respective operating conditions, as demonstrated by nearly the same values of volumetric ($Q_p$) and specific ($q_p$) IA production rates, IA production yield ($Y_{p/s}$), and specific growth rate (${\mu}$). Specifically, the negligible difference of the specific growth rate (${\mu}$) between the two cultures (i.e., $0.029h^{-1}$ vs. $0.031h^{-1}$) was notable, considering the fact that ${\mu}$ normally has a significant influence on $q_p$ in the biosynthesis of secondary metabolites such as itaconic acid.