삼상 순환유동층의 상승관에서 연속 액상의 축방향 혼합특성

유명선,손성모,강석환,강용,김상돈 한국공업화학회 2004 공업화학 Vol.15 No.1

직경이 0.102 m이고 높이가 3.5 m인 기체-액체-고체 순환 유동층의 상승관에서 액상의 축방향 혼합특성을 고찰하였다. 기체유속(0.01~0.07 ㎧), 액체유속(0.25~0.31 ㎧) 그리고 고체순환속도(2~8 ㎏/㎡s)를 실험변수로 선정하였으며 이들 변수들이 액상의 축방향 분산계수에 미치는 영향을 고찰하였다. 축방향의 추적자 농도분포로부터 분산모델을 사용하여 액상의 축방향 분산계수를 구하였다. 액상의 축방향 분산계수는 기체유속과 고체순환속도가 증가함에 따라서 증가하였으나 액체의 유속의 증가에 따라서는 약간 감소하였다. 또한, 액상의 축방향 분산계수는 등방성 난류 모델을 적용한 무차원군으로 표현되는 상관식으로 나타낼 수 있었다. Characteristics of liquid dispersion in the axial direction were investigated in the riser of a three-phase circulating fluidized bed whose diameter is 0.102 m and 3.5 m in height. Effects of gas (0.01-0.07 m/sl and liquid (0.25-0.31./s) velocities and the circulation rate of solids (2∼8 kg/m^(2)s) on the dispersion coefficient of the continuous liquid phase in the axial direction were determined. A dispersion model was employed to obtain the axial dispersion coefficient of the liquid phase from the radial concentration profiles of tracer with variations of axial position. The axial dispersion coefficient of the liquid phase increased with increasing gas velocity or solid circulation rate, however, decreased slightly with increasing liquid velocity in the riser bed. The axial dispersion coefficient of the liquid phase was well correlated in terms of dimensionless groups based on the isotropic turbulence theory.

액체-고체 순환유동층에서 액상의 반경 방향 혼합 및 액체-고체 Chaotic 흐름 거동

강석환,이찬기,송평섭,강용,김상돈,김승재 한국화학공학회 2004 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.42 No.2

직경이 0.102m이고 높이가 3.5m인 액체-고체 순환유동층의 상승관에서 압력요동 및 액체의 반경 방향 혼합 특성을 고찰하였다. 상승관에서 얻은 압력요동을 해석하기 위하여 chaos 이론을 도입하였다. 액체 유속, 유동입자의 크기 그리고 고체 유동입자의 순환속도가 연속액상의 반경방향 분산계수 및 압력요동의 위상공간투영과 상관차원에 미치는 영향을 결정하였다. 본 연구의 결과 액상의 반경방향 분산계수는 유동입자의 크기와 순환속도가 증가함에 따라 증가하였으며 액상의 유속이 증가함에 따라 감소하였다. 상승관에서 압력요동의 위상공간투영은 유동입자의 크기가 고체 유동입자의 순환속도가 증가함에 따라 점점 분산되고 복잡하게 되었으나, 액체유속이 증가함에 따라서는 위상공간에서 궤적의 분산이 다소 감소하는 경향을 나타내었다. 압력요동의 상관차원은 유동입자의 크기와 고체 순환속도가 증가함에 따라 증가하였으나, 액체의 유속이 증가함에 따라서는 큰 변화가 없었다. 본 연구의 결과는, 상승관에서 액상의 반경 방향 혼합 특성 압력요동 측정함으로써 실시간으로 예측하는 것을 가능하게 하여 실제공정에 응용함으로써 그 실용적 측면이 크다고 하겠다. Characteristics of pressure fluctuations and liquid dispersion in the radial direction were investigated in the riser of a liquid-solid circulating fluidized bed whose diameter was 0.102m and 3.5m in height. The concept of chaos theory was employed to analyze the pressure fluctuations obtained in the riser. Effects of liquid velocity, particle size, and solid circulation rate on the liquid radial dispersion coefficient and phase space portraits and correlation dimension of pressure fluctuations were determined. It was found that the radial dispersion coefficient of liquid phase increased with increasing particle size or solid circulation rate, but decreased with increasing liquid velocity. The attractor in the phase space portraits became more scattered and complicated with increasing particle size or solid circulation rate, but it became somewhat less scattered with increasing liquid velocity. The correlation dimension of pressure fluctuations increased with increasing particle size or solid circulation rate, but it did not change considerably with increasing liquid velocity. The results of this study enable us to predict the characteristics of liquid radial dispersion by means of the pressure fluctuations for the practical applications.

삼상 순환 유동층 생물반응기에서 열전달 계수

강태규,송평섭,최길수,조용준,강용,최호석,김상돈 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.5

직경이 0.102m이고 높이가 1.0m인 기체-액체 순환 및 삼상 순환유동층 생물반응기의 상승관에서 열전달 특성을 고찰하였다. 기체 및 액체의 유속 그리고 생물막 담체의 체류량이 상승관 내부의 수직 열원과 반응기 사이의 열전달 계수에 미치는 영향을 결정하였다. 기체-액체 순환 반응기에서 열전달 계수는 기체의 유속이 증가함에 따라 증가하였으나 액체 유속의 증가에 따라서는 약간 증가하였다. 삼상 순환유동층 생물반응기에서 열전달 계수는 기체의 유속과 유동 생물막 매체의 체류량이 증가함에 따라 증가하였으나 액체의 유속이 증가함에 따라서는 약간 증가하였다. 본 연구의 실험 범위에서 이들 열전달 계수는 실험 조작 변수의 상관식으로 잘 나타낼 수 있었다. Heat transfer characteristics have been investigated in the riser of gas-liquid circulation and three-phase circulating fluidized-bed bioreactors whose diameter and height are 0.102m and 1.0m, respectively. Effects of gas and liquid velocities and holdup of fluidized biofilm media on the heat transfer coefficient between the immersed vertical heater and the bed have been determined. The heat transfer coefficient in the gas-liquid circulation reactor increases with increasing gas velocity, but increases only slightly with increasing liquid velocity. The h(heat transfer coefficient) value in the three-phase circulating fluidized-bed bioreactor also increases with increasing gas velocity or holdup of fluidized biofilm media, but it increases only slightly with liquid velocity. The value of heat transfer coefficient has been well correlated in terms of operating variables.

액체-고체 순환유동층의 상승관에서 액상의 점도가 고체체류량 및 열전달계수에 미치는 영향

이찬기,강석환,신광식,송평섭,강용,김상돈 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.4

직경이 0.102 m이고 높이가 3.5 m인 액체-고체 순환유동층에서 액체의 점도가 고체입자의 체류량과 열전달계수에 미치는 영향을 검토하였다. 밀도가 2,500 kg/㎥인 유리구슬(d_(p)=1.0, 1.7, 2.1 또는 3.0 mm)과 CMC 용액(μ_(L)=0.96-38 mPas)을 각각 고체상과 액체상으로 사용하였다. 액체-고체 순환유동층에서 고체입자의 체류량은 액체의 유속이나 점도가 증가함에 따라 감소하였고 유동입자의 크기나 입자의 순환속도가 증가함에 따라 증가하였다. 액체-고체 순환유동층에서 열전달계수는 액체의 점도가 증가함에 따라 감소하였고 유동입자의 크기나 순환속도가 증가함에 따라 증가하였으나, 액체의 유속이 증가함에 따라서는 큰 변화가 없었다. 액체-고체 순환유동층에서 고체입자의 체류량과 열전달계수는 다음과 같이 실험변수와 무차원군에 의해 상관식으로 얻을 수 있었다. E_(S) = 0.783U^(-0.100)_(L)G^(0.164)_(S)d^(0.302)_(p)μ^(-0.036)_(L) h = 4349.3U^(0.010)_(L)G^(0.099)_(S)d^(0.151)_(p)μ^(-0.015)_(L) ◁그림삽입▷ Effects of liquid viscosity on the solid holdup and heat transfer coefficient have been investigated in the riser of a liquid-solid circulating fluidized beds, whose diameter is 0.102 m and 3.5 m in height. Glass beads (d_(p)=1.0, 1.7, 2.1 or 3.0 ㎜) whose density is 2,500 ㎏/㎥ and aqueous solutions of carboxymethy cellulose (CMC)(μ_(L)=0.96-38 mPas) have been used as the solid and liquid phase, respectively. It has been found that the solid holdup decreases with increasing liquid velocity or viscosity, but it increases with increasing solid particle size or solid circulation rate. The heat transfer coefficient decreases with increasing liquid viscosity but it increases with increasing particle size or solid circulation rate, however, it does not change considerablely with increasing liquid velocity. The solid holdup and heat transfer coefficient have been well correlated in terms of operating variables or dimensionless groups as fellow: ◁수식원문참조▷

Axial Dispersion Characteristics in Three Phase Fluidized Beds

Kim, Sang Done,Kwon, Hyeuk Woong 한국화학공학회 1990 NICE Vol.8 No.4

Axial dispersion coefficients in three-phase fluidized beds have been measured in a 0.152 m-IDX L8 m high column by the two points measuring technique with the axially dispersed plug flaw model. The effects of liquid velocity (0.05-0.13 m/s), gas velocity (0.02-0.16 m/s) and particle size (3-8 mm) on the axial dispersion coefficient at the different axial positions (0.06-0.46 m) in the bea have determined. The axial dispersion coefficient increases with increasing gas velocity but it decreases with an increase in particle size and exhibits a maximum value with an increase in the axial position from the distributor. The axial dispersion coefficients in terms of the Peclet number have been correlated in terms of the ratio of fluid velocities, the ratio of the particle size to column diameter, and the dimensionless axial position in the bed based on the isotropic theory.

Functionalization of HDPE Powder by CF4 Plasma Surface Treatment in a Fluidized Bed Reactor

Kim, Sang Done,Park, Soung Hee 한국화학공학회 1999 Korean Journal of Chemical Engineering Vol.16 No.6

The surface of HDPE polymer powder was fluorinated by CF₄ plasma in a fluidized bed reactor. Plasma is generated by an inductively coupled electrode at 13.56 MHz (rf) frequency, connected to an auto matching network and an rf power generator. In plasma surface fluorination, the CF_4 gas is diluted with He gas. The experimental variables are treatment time and rf power. The chemical property of the modified powder has been determined by using ESCA and FTIR. Plasma surface fluorination with the powder in a fluidized bed reactor results from the formation of CHF-CH₂, CHF-CHF and CF₂ groups. These fluorine functionalities and the fluorine atomic ratio on the surface increase with the treatment time and rf power. It has been found that the composite parameter is a good measure for determining the effect of total energy input on the plasma surface treatment of polymer powder in a fluidized bed reactor.

MASS TRANSFER IN TWO - AND THREE - PHASE FLUIDIZED BEDS

Kim, Sang Done,Kim, Ihl Yong 한국화학공학회 1990 Korean Journal of Chemical Engineering Vol.7 No.1

Fractal Analysis of Pressure Fluctuations in a Three Phase Bubble Column Reactor Operating at Low Pressure

Kim, Sang Done,Kang, Yong,Ko, Myung Han,Shim, Jung Seob,Kim, Sang Do 한국화학공학회 1996 NICE Vol.14 No.4

Pressure fluctuations in a three phase bubble column reactor operating at relatively low pressure (92 KPa) have been analyzed by adopting the spectral and fractal analyses to get the engineering informations for the online control and fault diagnosis of the reactors. The mean value, standard deviation, skewness and kurtosis of the pressure fluctuations have been obtained. The local fractal dimension has been determined from the Pox diagram obtained by means of the resealed xange analysis of the pressure fluctuations based on the fractional Browni an motion. The local fractal dimension of pressure fluctuations has increased and thus the pressure fluctuation signals have become less persistent and irregular, with increases in the gas flow rate, reaction temperature, particle size and solid content in the slurry phase. The local fractal dimension has been well correlated in terms of the operating variables.

Slug Characteristics of Polymer Particles in a Fluidized Bed with Different Distributors

Kim, Sang Done,Lee, Dong Hyun,Lee, See Hoon 한국화학공학회 2001 Korean Journal of Chemical Engineering Vol.18 No.3

Pressure fluctuations in a fluidized bed (0.38 m-LD.×4.4 m-high) of 1.23-mm polymer particles (LLDPE) were measured with different distributors. Slug characteristics (slug frequency and slug rising velocity) were determined by analyzing pressure fluctuations in the bed. The effects of gas velocity (0.6-1.2 m/s) and distributor geometry (opening area ratio, number of orifices and distributor types) on the slug characteristics were determined. The slug frequency decreases slightly with increasing gas velocity. However, slug rising velocity increases linearly with increasing excess fluidization velocity regardless of the distributors used.

BUBBLE PROPERTIES AND PRESSURE FLUCTUATIONS IN BUBBLE COLUMNS

Kim, Sang Done,Han, Joo Hee,Kown, Hyeuk Woong,Kang, Yong 한국화학공학회 1994 Korean Journal of Chemical Engineering Vol.11 No.3

The effects of gas (0.02-0.1 ㎧) and liquid velocities (0.0-0.10 ㎧) on the bubble properties and pressure fluctuations have been determined in a 0.376 m-ID × 2.1 m-high bubble column. The pressure fluctuations have been analyzed by resorting to the Fractal analysis; the time series of pressure fluctuation signals have been analyzed by means of the Resealed range analysis and the Hurst exponent has been obtained. The bubble chord length and its rising velocity increase but the Hurst exponent decreases with increasing gas velocity. Whereas, the bubble chord length decreases, but the Hurst exponent increases with an increase in liquid velocity in the continuous bubble column (U_L$gt;0.02 ㎧). The Hurst exponent has been found to have a definite relationship with the bubble chord length and its standard deviation.