• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2000.11a
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• pp.101-104
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• 2000

1980년대 중반이후 화력발전소용으로 순환유동층 연소로(Circulating fluidized bed combustor : CFBC)가 많이 건설되고 있다. 이는 기존의 고정층 연소로보다 효율면에서 좋고, 차지하는 부피는 훨씬 적기 때문이다. 순환유동층의 층물질로 사용되는 모래, 석탄회, 석회석 등은 순환하는 입도, 비산유출되는 회재(fly ash)와 하부로 배출되는 회재(bottom ash)로 나누어진다. 주입되는 석탄 및 석회석의 입도는 입자-입자, 입자-연소로의 마모(attrition), 입자의 깨짐(fragmentation), 입자의 축소(shrinking) 등에 의해서 변화하게 된다.(중략)

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.75-79
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• 1999

순환유동층은 주탑에서 비말 동반된 입자를 cyclone과 같은 입자 포집장치에서 회수하여 다시 주탑으로 재 주입함으로써 입자의 순환이 일어나는 외부 순환계와 종래의 유동층내에 원형관(Draft tube)이나 평판을 설치하여 두개의 층으로 분리한 후 가스 분산판 위의 간격을 통해 입자들을 두 구역 사이로 강제 순환시키는 내부순환계로 분류할 수 있다. 드래프트 관을 갖는 내부순환유동층 반응기는 기체와 고체의 적절한 접촉을 통해 반응이 이루어지는 반응기 형태이다.(중략)

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.11a
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• pp.57-60
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• 1999

순환유동층 보일러는 연소로 (상승관: riser)내에 공기를 고속으로 주입하여 비말동반되는 고체입자를 사이클론에서 포집 하여 재주입하는 유동층을 이르는 것으로, 난류유동층(turbulent fluidized bed), 고속유동층(fast fluidized bed) 그리고 희박상 유동(dilute phase flow) 영역에서 조업이 이루어진다. 순환유동층은 비교적 높은 기체 유속에서 조업이 이루어지기 때문에 고체입자의 혼합 및 비산 그리고 재순환이 격렬하게 이루어지고, 기-고체간 접촉효율 및 전열계수가 높아 전체적인 처리량 및 효율이 좋은 장점을 가지고 있다.(중략)

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.790-797
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• 2011

Hydrodynamic similarity was analyzed by employing scaling factor in three phase fluidized beds. The scaling factor was defined based on the holdups of gas, liquid and solid particles and effectivity volumetric flux of fluids between the two kinds of fluidized beds with different column diameter. The column diameter of one was 0.102 m and that of the other was 0.152 m. Filtered compressed air, tap water and glass bead of which density was 2,500 kg/$m^3$ were used as gas, liquid and solid phases, respectively. The individual phase holdups in three phase fluidized beds were determined by means of static pressure drop method. Effects of gas and liquid velocities and particle size on the scaling factors based on the holdups of each phase and effective volumetric flux of fluids were examined. The deviation of gas holdup between the two kinds of three phase fluidized beds decreased with increasing gas or liquid velocity but increased with increasing fluidized particle size. The deviation of liquid holdup between the two fluidized beds decreased with increasing gas or liquid velocity or size of fluidized solid particles. The deviation of solid holdup between the two fluidized beds increased with increasing gas velocity or particle size, however, decreased with increasing liquid velocity. The deviation of effective volumetric flux of fluids between the two fluidized beds decreased with increasing gas velocity or particle size, but increased with increasing liquid velocity. The scaling factor, which was defined in this study, could be effectively used to analyze the hydrodynamic similarity in three phase fluidized processes.

• Korean Chemical Engineering Research
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• v.44 no.5
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• pp.505-512
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• 2006

Characteristics of particle holdup and heat transfer were investigated in a liquid-particle swirling fluidized bed whose diameter was 0.102 m and 2.5 m in height. Effects of liquid velocity, particle size and swirling liquid ratio($R_s$) on the particle holdup and immersed heater-to-bed overall heat transfer coefficient were examined. The particle holdup increased with increasing particle size and swirling liquid ratio but decreased with increasing liquid velocity.The local particle holdup was relatively high in the region near the heater when the $R_s$ value was 0.1~0.3, but the radial particle holdup was almost uniform when the $R_s$ value was 0.5, whereas, when the $R_s$ value was 0.7, the local particle holdup was relatively low in the region near the heater. The heat transfer characteristics between the immersed heater and the bed was well analyzed by means of phase space portraits and Kolmogorov entropy(K) of the time series of temperature difference fluctuations. The phase space portraits of temperature difference fluctuations became stable and periodic and the value of Kolmogorov entropy tended to decrease with increasing the value of $R_s$ from 0.1 to 0.5. The Kolmogorov entropy exhibited its maximum value with increasing liquid velocity. The value of overall heat transfer coefficient(h) showed its maximum value with the variation of liquid velocity, bed porosity or swirling liquid ratio, but it increased with increasing particle size. The value of K exhibited its maximum at the liquid velocity at which the h value attained its maximum. The particle holdup and overall heat transfer coefficient were well correlated in terms of dimensionless groups of operating variables.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.707-713
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• 2008

Characteristics of minimum fluidization velocity and pressure fluctuations were investigated in an annular fluidized bed whose diameter was 0.102 m and 2.0 m in height. Effects of gas velocity, particle size and bed temperature on the minimum fluidization velocity and pressure fluctuations were examined. The values of minimum fluidization velocity obtained by means of three different methods were very similar each other. The correlation dimension could be a quantitative parameter for expression the resultant complex behavior of gas and solid mixture in the annular fluidized bed. The value of correlation dimension increased with increasing gas velocity, fluidized particle size and temperature in the bed. The minimum fluidization velocity could be determined by means of correlation dimension of pressure fluctuations as well as pressure drop in the bed and standard deviation of pressure fluctuations. The minimum fluidization velocity increased with increasing particle size but decreased with increasing bed temperature in annular fluidized beds. The minimum fluidization velocity was well correlated in therms of correlation dimension as well as operating variables within experimented conditions of this study.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.710-716
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• 2013

New and renewable energy sources have drawn attention because of climate change. Many studies have been carried out in waste-to-energy field. Fast pyrolysis of waste lignocelluosic biomass is one of the waste-to-energy technologies. Bubbling fluidized bed (BFB) reactor is widely used for fast pyrolysis of the biomass. In BFB pyrolyzer, bubble behavior influences on the chemical reaction. Accordingly, in the present study, hydrodynamic characteristics and fast pyrolysis reaction of waste lignocellulosic biomass occurring in a BFB pyrolyzer are scrutinized. The computational fluid dynamics (CFD) simulation of the fast pyrolysis reactor is carried out by using Eulerian-Granular approach. And two-stage semi-global kinetics is applied for modeling the fast pyrolysis reaction of waste lignocellulosic biomass. To summarize, generation and ascendant motion of bubbles in the bed affect particle behavior. Thus biomass particles are well mixed with hot sand and consequent rapid heat transfer occurs from sand to biomass particles. As a result, primary reaction is observed throughout the bed. And reaction rate of tar formation is the highest. Consequently, tar accounts for 66wt.% of the product gas. However, secondary reaction occurs mostly in the freeboard. Therefore, it is considered that bubble behavior and particle motions hardly influences on the secondary reaction.

• Resources Recycling
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• v.6 no.1
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• pp.17-22
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• 1997

An electromagnetic fluidized bed was proposed for the continuous separation of magnetic particles from the fine a admixtures with nonHmagnetic particles. The effects of operating variables on the magnetic fraction in the separated p particles were examined, including superficial gas velocity, mixing fraction of magnetic particles (= 100-mixing fraction of n non-magnetic particles) in the admixture, and electric current supplied to the electwmagnet. It was found that the s separation was possible when a magnetic force formed by the electromagnets works on the magnetic particles over the hydrodynamic force caused by a gas stream for fluidizing the fine admixture.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.706-711
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• 2016

Characteristics of solid circulation rate in the liquid-solid circulating fluidized beds with viscous liquid medium were investigated. Effects of primary and secondary liquid velocities, particle size, liquid viscosity and height of solid particles piled up in the solid recycle device on the solid circulation rate were considered. The solid circulation rate increased with increasing primary and secondary liquid velocities, liquid viscosity and height of solid particles in the downcommer, but it decreased with increasing particle size. The particle rising velocity in the riser decreased with increasing the ratio of $U_{L1}/U_{L2}$ and particle size. The slip velocity of liquid and particle, $U_L/U_S$, decreased with increasing liquid viscosity but it increased with increasing particle size. The values of solid circulation rate were well correlated in terms of operating variables and dimensionless groups.

• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.81-87
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• 2014

Flow characteristics and the operating range of gas velocity was investigated for a two-stage bubbling fluidized-bed (0.1 m-i.d., 1.2 m-high) that had continuous solids feed and discharge. Solids were fed in to the upper fluidized-bed and overflowed into the bed section of the lower fluidized-bed through a standpipe (0.025 m-i.d.). The standpipe was simply a dense solids bed with no mechanical or non-mechanical valves. The solids overflowed the lower bed for discharge. The fluidizing gas was fed to the lower fluidized-bed and the exit gas was also used to fluidize the upper bed. Air was used as fluidizing gas and mixture of coarse (< $1000{\mu}m$ in diameter and $3090kg/m^3$ in apparent density) and fine (< $100{\mu}m$ in diameter and $4400kg/m^3$ in apparent density) particles were used as bed materials. The proportion of fine particles was employed as the experimental variable. The gas velocity of the lower fluidized-bed was defined as collapse velocity in the condition that the standpipe was emptied by upflow gas bypassing from the lower fluidized-bed. It could be used as the maximum operating velocity of the present process. The collapse velocity decreased after an initial increase as the proportion of fine particles increased. The maximum took place at the proportion of fine particles 30%. The trend of the collapse velocity was similar with that of standpipe pressure drop. The collapse velocity was expressed as a function of bulk density of particles and voidage of static bed. It increased with an increase of bulk density, however, decreased with an increase of voidage of static bed.