• Transactions of the Korean hydrogen and new energy society
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• v.28 no.1
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• pp.85-91
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• 2017

To develop a pressurized chemical looping combustor, effect of pressure on minimum fluidization velocity and transition velocity to fast fluidization was investigated in a two-interconnected pressurized fluidized bed system using oxygen carrier particle. The minimum fluidization velocity was measured by bed pressure drop measurement with variation of gas velocity. The measured minimum fluidization velocity decreased as the pressure increased. The transition velocity to fast fluidization was measured by emptying time method and decreased as the pressure increased. Gas velocity in the fuel reactor should be greater than the minimum fluidization velocity and gas velocity in the air reactor should be greater than the transition velocity to fast fluidization to ensure proper operation of two interconnected fluidized bed system.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.4
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• pp.384-391
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• 2017

Effects of operating variables on solid circulation rate were measured and discussed using two-interconnected circulating fluidized bed system at ambient temperature and pressure. OCN 706-1100 particles were used as oxygen carrier. The measured solid circulation rates increased as the lower loop seal gas flow rates and the solid height in the fuel reactor increased. Suitable operating conditions to avoid choking of the air reactor were confirmed. Continuous long-term operations of steady-state solid circulation were also demonstrated at two different conditions based on the operating window.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.222-232
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• 2000

The relationship between carrier electron concentration(n) and atmosphere oxygen partial pressure($P_{O_2}$ for pure ZnO calculated by the mass-action law, well-known as n ${\propto}P^{-1/m}_{O_2}$ where m = 4 or 6 for the single or the double ionization of the native donor defects due to its nonstoichiometry, respectively, is found in competition with the calculation result on the basis that the total defect concentration is the sum of those of unionized and ionized defects. Definitively, it is found inconsistent with the calculation result by employing the Fermi-Dirac(FD) statistics for their ionization processes. By application of the FD statistics law to the ionization while assuming the defect formation is still ruled by the mass-action law, the calculation results shows the concentration is proportional to $P^{-1/2}_{O_2}$ whenever they ionize singly and/or doubly. Conclusively we would like to propose the new theoretical relation n ${\propto}P^{-1/m}_{O_2}$ because the ionization processes of donors in ZnO should be treated with the electronoccupation probability at localized quantum states in its forbidden band created by the donor defects, i.e. the FD statistics

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.269-274
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• 2003

The electrical, optical and structural properties of ZnNiO thin _ films deposited on Si substrates using rf-magnetron sputtering method have been investigated before and after the thermal annealing processes. The crystallinity of the ZnNiO thin film become degraded with increasing the Ni contents. This is mainly because the lattice of the thin film was expanded due to the oxygen-deficient conditions. Concerning the electrical properties of the thin film, the carrier concentration increases ($6.81\times10^{14}\textrm{cm}^{-2}$) and Hall mobility decreases (36.3 $\textrm{cm}^2$/Vㆍs) with higher doping concentration of Ni. However, the carrier concentration and Hall mobility became low ($1.10\times10^{14}\textrm{cm}^2$ and high (209.6 $\textrm{cm}^2$/Vㆍs), respectively, after the thermal annealing process at $1000 ^{\circ}C$. We also observed a strong luminescene center peaking at 546 nm in photoluminescence spectra, which was caused by a deep level center in the ZnO band gap with oxygen deficient ZnNiO structure.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.2
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• pp.170-177
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• 2019

Continuous solid circulation test at high temperature and high pressure conditions and batch type reduction-oxidation tests were performed to check feasibility of a 0.5 MWth chemical looping combustion system. Pressure drop profiles were maintained stable during continuous solid circulation up to 16 hours. Therefore, we could conclude that the solid circulation between an air reactor and a fuel reactor could be smooth and stable. The measured fuel conversion and $CO_2$ selectivity were high enough even at high capacity and even after cyclic tests. Therefore, we could expect high reactivity of oxygen carrier at real operation condition.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.1
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• pp.53-62
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• 2021

Batch type reduction-oxidation tests were performed to check effects of temperature, pressure, gas velocity, and capacity on reduction characteristics of mass produced particle in a 0.5 MWth chemical looping combustion system. The fuel conversion and the CO2 selectivity increased as the temperature increased and as the gas velocity decreased. However the CO2 selectivity showed the maximum and decreased as the capacity increased because the CO emission increased. The results show that high temperature, low gas velocity and low inert gas concentration are preferable to ensure high reactivity of oxygen carrier in the fuel reactor.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.95-105
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• 2016

Spray-dried NiO-based oxygen carriers developed for chemical looping combustion required high calcination temperatures above $1300^{\circ}C$ to obtain high mechanical strength applicable to circulating fluidized-bed process. In this study, the effect of CBB ($CaO{\cdot}BaO{\cdot}B_2O_3$) addition, as a binder, on the physical properties and oxygen transfer reactivity of spray-dried NiO-based oxygen carriers was investigated. CBB addition resulted in several positive effects such as reduction of calcination temperature and increase in oxygen transfer capacity and porosity. However, oxygen transfer rate was considerably decreased. This was more apparent when a higher amount of CBB was added and MgO was added together. From the experimental results, it is concluded that CBB added NiO-based oxygen carriers are not suitable for chemical looping combustion and a new method to reduce calcination temperature while maintaining high oxygen transfer rate of NiO-based oxygen carriers should be found out.

• KSBB Journal
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• v.4 no.1
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• pp.1-7
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• 1989

In order to increase the oxygen transfer in a bioreactor for animal cell culture, a penluorocarbon, $Flutec^R$ ppll was used in a modified Celligen $Celligem^{TM}$. Also, the effects of ppll on the hybridoma cell growth and on the production of monoclonal antibody were investigated. There was no harmful effect of ppl1 on the cell growth and on the production of monoclonal antibody.

• Journal of Energy Engineering
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• v.2 no.3
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• pp.285-292
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• 1993

A cylindrical-shape, horizontal furnace was used to investigate the effect of particle size on the pulverized coal combustion behavior. Three differently-sized fractions (5, 30, and 44 microns in average diameter) of high-volatile bituminous coal, were burned in the test furnace. Ignition characteristics of pulverized coal flame were determined through the amount of methane in the carrier gas for the self-sustaining flame. Easiest ignition occurred with the immediately-sized coal particles. Ignition of coal jet flame appeared to occur through a gas-phase homogeneous process for particles larger than 30 microns. Below this limiting size, heterogeneous process probably dominated ignition of coal flame. Oxygen concentration of combustion air was varied up to 50%, to determine the oxygen-enrichment effect on the coal ignition behavior. Oxygen enrichment of primary air assisted ignition behavior of pulverized coal flame. However, enrichment of secondary air didn't produce any effect on the ignition behavior.

• Nuclear Engineering and Technology
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• v.52 no.8
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• pp.1638-1649
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• 2020

In the case of a severe accident in a Light Water Reactor, the issue of late release of fission products, from the primary circuit surfaces is of particular concern due to the direct impact on the source term. CsI is the main iodine compound present in the primary circuit and can be deposited as particles or condensed species. Its chemistry can be affected by the presence of molybdenum, and can lead to the formation of gaseous iodine. The present work studied chemical reactions on the surfaces involving gaseous iodine release. CsI and MoO₃ were used to highlight the effects of carrier gas composition and oxygen partial pressure on the reactions. The results revealed a noticeable effect of the presence of molybdenum on the formation of gaseous iodine, mainly identified as molecular iodine. In addition, the oxygen partial pressure prevailing in the studied conditions was an influential parameter in the reaction.