• Title, Summary, Keyword: Bubble Column

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Gas hold-up variation with pore size of tray in trayed bubble column (Trayed bubble column 반응기에서 tray의 기공크기에 따른 gas hold-up 변화 연구)

  • Yang, Jung Hoon;Yang, Jung-Il;Kim, Hak-Joo;Chun, Dong Hyun;Lee, Ho-Tae;Jung, Heon
    • 한국신재생에너지학회:학술대회논문집
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    • pp.133.1-133.1
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    • 2010
  • 슬러리 기포탑 반응기는 열 및 물질 전달의 용이성, 낮은 운전비용 및 장치의 간단성의 장점을 가지고 있어서 Fischer-Tropsch 반응, bio-reaction 등에 많이 응용되고 있다. 그러나 기포탑 반응기 내의 물질 거동은 매우 복잡하기 때문에 많은 연구가 이루어지고 있음에도 불구하고 그 현상에 대한 명확한 이해는 어려운 상황이다. 특히 기포탑반응기 내에 기체의 포집율(gas hold-up)을 증가시키는 것을 목적으로 하는 연구들이 활발히 진행되고 있다. 본 연구에서는 trayed bubble column 반응기에서 tray의 기공크기에 따른 기체 포집율의 변화를 관찰하였다. 실험에 사용된 반응기는 내경이 0.15 m이고 높이 2.0 m의 아크릴 반응기를 이용하였다. 사용된 연속상은 수돗물을 사용하였고 분산상 기체로는 압축공기를 이용하였다. Tray의 기공크기는 1.1 mm부터 14.0 mm까지 변화시키면서 높이별 기체 포집율의 변화를 관찰하였다. 기체 포집율의 변화를 균일흐름 영역과 불균일 흐름 영역에서 그 양상이 다르게 나타났다. 즉 균일계 영역에서는 기공의 크기가 1.1 mm부터 2.9 mm까지 증가시면 기체포집율이 감소하는 반면 2.9 mm 이상에서는 증가하는 것으로 관찰되었다. 반면 불균일 흐름 영역에서는 전반적으로 기공의 크기가 작아질수록 기체포집율이 증가하였다. 또한 각각의 흐흠 영역에서의 기체포집율 증가정도는 확연한 차이를 보이는 것을 알 수 있었다. 이것은 흐름영역의 유체거동에 따라서 기포와 tray 기공사이의 상호작용 메커니즘이 달라지기 때문인 것으로 보인다.

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Oxygen Transfer and Hydraulic Characteristics in Bubble Column Bioreactor Applied Fine Bubble Air Diffusing System (미세기포 산기장치를 적용한 타워형 생물반응기의 산소전달 및 수력학적 특성)

  • Lee, Seung-Jin;Ko, Kyeong-Han;Ko, Myeong-Han;Yang, Jae-Kyeong;Kim, Yong-Guk
    • Journal of Korean Society of Environmental Engineers
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    • v.34 no.11
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    • pp.772-779
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    • 2012
  • For improving performance of conical air diffuser generating fine bubble, both experimental and numerical simulation method were used. After adapting diffusers inner real scale bubble column, suitable for various diffuser submergence, the effect of diffuser submergence on oxygen transfer performance such as Oxygen Transfer Coefficient ($K_{L}a_{20}$) and Standard Oxygen Transfer Efficiency (SOTE) was investigated empirically. As flow patterns for various diffuser number and submergence were revealed throughout hydrodynamic simulation for 2-phase fluid flow of air-water, the cause of the change for oxygen transfer performance was cleared up. As results of experimental performance, $K_{L}a_{20}$ was increased slightly by 7% and SOTE was increased drastically by 39~72%, 5.6% per meter. As results of numerical analysis, air volume fraction, air and water velocity in bioreactor were increased with analogous flow tendency by increasing diffuser number. As diffuser submergence increased, air volume fraction, air and water velocity were decreased slightly. Because circulative co-flow is determinant factor for bubble diffusion and rising velocity, excessive circulation intensity can result to worsen oxygen transfer by shortening bubble retention time and amount.

A preliminary study on the development of detection techniques for CO2 gas bubble plumes (CO2 가스 기포 누출 탐지 기술 개발을 위한 예비 연구)

  • Kum, Byung-Cheol;Cho, Jin Hyung;Shin, Dong-Hyeok
    • Journal of the Korean Society of Marine Engineering
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    • v.38 no.9
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    • pp.1163-1169
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    • 2014
  • As a preliminary study for detection techniques of $CO_2$ gas bubble plumes, we have conducted a comparative experiment on artificially generated $CO_2$ gas bubbles plume by using multibeam echosounder (MBES), single beam echosounder (SBES), and sub-bottom profiler (SBP). The rising speed of artificial gas bubbles is higher than references because of compulsory release of compressed gas in the tank. Compared to single beam acoustic equipments, the MBES detects wide swath coverage. It provides exact determination of the source position and 3D information on the gas bubble plumes in the water column. Therefore, it is shown that MBES can distinctly detect gas bubble plumes compared to single beam acoustic equipments. We can establish more effective complementary detection technique by simultaneous operation of MBES and SBES. Consequently, it contributes to improve qualitative and quantitative detection techniques by understanding the acoustic characteristics of the specific gas bubbles.

$CO_2$ Fixation by Chlorella HA-1 Cultured in Bubble Columns. (기포탑 반응기에서 Chlorella HA-1의 $CO_2$ 고정화 특성)

  • 성기돈;이진석;신철승;김미선;박순철;김승욱
    • Microbiology and Biotechnology Letters
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    • v.26 no.1
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    • pp.1-6
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    • 1998
  • The characteristics of $CO_2$ fixation by Chlorella HA-1 cultured in bubble columns were studied to achieve high photosynthetic rates per basal area. The influence of experimental conditions such as the diameter of a bubble column and gas flow rate, on photosynthesis of Chlorella HA-1 was investigated. The maximum productivity and the overall $CO_2$ fixation rate obtained in a 0.15 L bubble column was 1.09 g dry biomassa-day and 1048 g CO$_2/\m^2$-day, respectively. Light limitation has been observed in the bubble columns having a diameter larger than 3.5 cm.. As the reactor volume increased, the decrease of the $CO_2$ fixation rate was remarkable. High gas flow rate was helpful to mitigate the light limitation problem.

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Evaluation of the Oxygen Transfer Parameters (α and F) of a Coarse Bubble Aeration System by Off-gas Column Test (Off-gas Column Test를 이용한 하수처리장 심층포기시스템의 산소전달 매개변수(α와 F)의 산정)

  • Kim, Chul Woong;Lee, Se Ho;Shin, Dong Rok;Lee, Ji Yong;Park, Jae Han;Ahn, Yoon Hee;Ko, Kwang Baik
    • Journal of Korean Society on Water Environment
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    • v.22 no.6
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    • pp.1119-1122
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    • 2006
  • Aeration by using diffusers usually requires approximately 50~90% of the total electricity needed to operate WWTP (WasteWater Treatment Plant)s. Accurate evaluation of the oxygen transfer efficiency for an aeration system, and recommendation of a better alternative may help saving WWTP operational costs. Appropriate techniques and methods to achieve this purpose have not been introduced in Korea. In this study, in-process analysis was performed for a coarse bubble aeration system by the off-gas method to evaluate its applicability in Korea. To accomplish this analysis, an off-gas test, unsteady-state clean water test and steady-state off-gas column test was conducted and comparisons to other aeration systems were made. The ${\alpha}$ and the F estimated from the results of the unsteady-state clean water test and the steady-state off-gas column test were 0.61 and 0.90 respectively in a coarse bubble aeration system. The comparison of P.E tube diffusers laid out single spiral roll and ceramic dome diffusers laid out full floor coverage showed that the oxygen transfer efficiency of the coarse bubble aeration system was less than or similar to other aeration systems. But, airflow rates per unit area were 4~5 times greater than other aeration systems. In regards to the oxygen transfer efficiency for airflow rates per unit area, a retrofit to higher efficiency diffusers was urgently needed. This study showed proved that off-gas methods can apply to evaluate diffuser performances to estimate operating factors and to compare other aeration systems in Korea.

Heat Transfer in Bubble Columns with High Viscous and Low Surface Tension Media (고점성 낮은표면장력 매체 기포탑에서 열전달)

  • Kim, Wan Tae;Lim, Dae Ho;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.52 no.4
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    • pp.516-521
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    • 2014
  • Axial and overall heat transfer coefficients were investigated in a bubble column with relatively high viscous and low surface tension media. Effects of superficial gas velocity (0.02~0.1 m/s), liquid viscosity ($0.1{\sim}0.3Pa{\cdot}s$) and surface tension ($66.1{\sim}72.9{\times}10^{-3}N/m$) on the local and overall heat transfer coefficients were examined. The heat transfer field was composed of the immersed heater and the bubble column; a vertical heater was installed at the center of the column coaxially. The heat transfer coefficient was determined by measuring the temperature differences continuously between the heater surface and the column which was bubbling in a given operating condition, with the knowledge of heat supply to the heater. The local heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing axial distance from the gas distributor and liquid surface tension. The overall heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing liquid viscosity or surface tension. The overall heat transfer coefficient was well correlated in terms of operating variables such as superficial gas velocity, liquid surface tension and liquid viscosity with a correlation coefficient of 0.91, and in terms of dimensionless groups such as Nusselt, Reynolds, Prandtl and Weber numbers with a correlation of 0.92; $$h=2502U^{0.236}_{G}{\mu}^{-0.250}_{L}{\sigma}^{-0.028}_L$$ $$Nu=325Re^{0.180}Pr^{-0.067}We^{0.028}$$.

Mass Transfer Characteristics in Pressurized Three-phase Slurry Bubble Columns with Variation of Column Diameter (가압 삼상슬러리 기포탑에서 직경변화에 따른 기체-액체 물질전달 특성)

  • Seo, Myung Jae;Lim, Dae Ho;Shin, Ik Sang;Son, Sung Mo;Kang, Yong
    • Korean Chemical Engineering Research
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    • v.47 no.4
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    • pp.459-464
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    • 2009
  • Gas-liquid mass transfer characteristics were investigated in pressurized three-phase slurry bubble columns with variation of column diameter. Effects of gas velocity, operating pressure, liquid viscosity, solid content in the slurry phase and column diameter on the gas-liquid volumetric mass transfer coefficient($k_La$) were determined. The effects of operating variables on the mass transfer coefficient tended to change with variation of column diameter. The mass transfer coefficient increased with increasing gas velocity or operating pressure but decreased with increasing column diameter, liquid viscosity or solid concentration in the slurry phase. The increase trend of $k_La$ value with increasing gas velocity and the decrease trend of $k_La$ value with increasing liquid viscosity, tended to decrease gradually with increasing column diameter. However, the effects of operating pressure and solid concentration in the slurry phase on the $k_La$ value did not change considerably with variation of column diameter. The values of $k_La$ were well correlated with operating variables with in this experimental conditions as $k_La=0.02D^{-0.26}U_G^{0.28}P^{0.43}{\mu}_L^{-0.04}S_c^{-0.35}$.

Effect of fermentor type on biopolymer production with Cordyceps militaris

  • Kim, Kyoung-Ju;Kim, Dong-Hyun;Park, Yang-Ho;Kwun, Kyu-Hyuk;Lee, Jung-Heon
    • 한국생물공학회:학술대회논문집
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    • pp.249-251
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    • 2003
  • The effects of fermentor types on biopolymer production with Cordyceps militaris has been studied in this articles. Since the shear stresses of stirred tank ferementor and bubble column fermentor were different, the mycelium growth and biopolymer production were different. The mycerial growth was high with the bubble column fermentor for the early stage but biopolymer production was lower than that with stirred tank fermentor. The production of biopolymer was closely related to shear stress to the cells and biopolymer production was increased with increased shear stress.

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