• 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.

• 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)

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.485-490
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• 2005

Effects of gas injectino on the copper recovery form industrial waste water in a fluidized-bed electrolytic reactor were investigated. Effects of gas injection on the individual phase holdup and efficiency of copper recovery for given operating variables such as liquid and gas velocity (0.1~0.4 cm/s), current density ($2.0{\sim}3.5A/dm^2$) and amount of fluidized solid particles (1.0~4.0 wt%) were examined. The solid particle, whose diameter and swelling density were 0.5 mm and $1100kg/m^3$, respectively, was made of polystylene and divinyl benzene. It was found that the holdup of gas and solid phases increased, but that of the liquid phase decreased with increasing velocity of gas injected into the reactor. With increasing gas and/or liquid velocity and increasing amount of fluidized particles is not needed, the rate of copper recovery increased to a maximum value of and subsequently decreased. The recovery rate of copper increased almost linearly with increasing current density in accordance with Faraday's law.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.252-261
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• 1991

A particle trajectory model to simulate two-phase particle-laden crossjets into two-dimensional horizontal free stream has been developed to study the variations of the jet trajectories and velocity variations of the gaseous and the particulate phases. The following conclusions may be drawn from the predicted results, which are in agreement with experimental observations. The penetration of the two-phase jet in a crossflow is greater than that of the single-phase jet. The penetration of particles into the free stream increases with increasing particle size, solids-gas loading ratio and carrier gas to free stream velocity ratio at the jet exit. When the particle size is large, the solid particles separate from the carrier gas , while the particles are completely suspended in the carrier gas for the case of small size particles. As the particle to carrier gas velocity ratio at the jet exit is less than unity, the particles in the vicinity of the jet exit are accelerated by the carrier gas. As the injection angle is increased, the difference of the particle trajectory from that of the pure gas becomes larger. Therefore, it can be concluded that the velocities and trajectories of the particle-laden jets in a crossflow change depending on the solids-gas loading ratio, particle size, carrier gas to free stream velocity ratio and particle to gas velocity ratio at the jet exit.

• 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.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.195-202
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• 2009

As a basic research of developing two-interconnected fluidized beds system for selective solid circulation, a solid separator was developed to separate fine and coarse particles by means of particle size difference with particle size separation system equipped with metal screen. The effects of gas velocity, height of solid separator, and separation area on the solid separation rate were investigated as well. The solid separation rate increased as the gas velocity, height of solid separator, and separation area increased. As the gas velocity and height of the solid separator increased, the variation of the solid separation rate was consistent with that of bubble size. Consequently, coarse($212{\sim}300{\mu}m$) and fine($63{\sim}106{\mu}m$) particles were separated using the solid separator and the solid separation rate was ranged from 4.4 to 127 g/min. We also proposed two interconnenced fluidized beds system for sorption enhanced water-gas shift process equipped with the developed solid separator.

• 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.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.9-17
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• 2013

A considerable deal of work has been carried out to get an insight into the gas-solid suspension flows and to specify the particle motion and its influence on the gas flow field. In this paper an attempt is made to develop an analytical model to study the effect of nozzle inlet/exit pressure ratio, particle/gas loading and the particle diameter effect on gas-solid suspension flow. The effect of the particle/gas loading on the mass flow, Mach number, thrust coefficient and static pressure variation through the nozzle is analyzed. The results obtained show that the presence of particles seems to reduce the strength of the shock wave. It is also found that smaller the particle diameter is, bigger will be the velocity as bigger particle will have larger slip velocity. The suspension flow of smaller diameter particles has almost same trend as that of single phase flow with ideal gas as working fluid. Depending on the ambient pressure, the thrust coefficient is found to be higher for larger particle/gas loading or back pressure ratio.

• 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)

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.654-658
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• 2012

In this study, $CO_2$ capture efficiency in relation to the inlet moisture content of the regenerator was investigated using potassium-based sorbents in the continuous process composed of two bubbling fluidized-bed reactors, where solid outlet configuration in the regenerator was converted from underflow to overflow. XRD (X-ray Diffraction), SEM (Scanning Electron Microscope) and TGA were performed to find out the effect of water pre-treatment according to inlet moisture content in the regenerator. The $K_2CO_3{\cdot}1.5H_2O$ structure of solid sorbents has been increased as inlet moisture content of the regenerator increased. As a result, the $CO_2$ capture efficiency increased as the $K_2CO_3{\cdot}1.5H_2O$ structure of solid sorbents increased since the reactivity of the sorbents has been improved by that structure generated by the water pre-treatment. And $CO_2$ capture efficiency increased about 3~8% after sorbent outlet configuration of the regenerator was changed underflow to overflow.