• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.522-529
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• 2014

Circulating fluidized bed system consists of SEWGS reactor - lower loop seal - regeneration reactor - riser - cyclone - upper loop seal has been used for solid circulation between the SEWGS reactor and the regeneration reactor in a SEWGS system for pre-combustion $CO_2$ capture. A vertical type lower loop seal has been used in current system but this lower loop seal requires high gas flow rate through the lower loop seal for fluidization and smooth solid circulation, and consequently, causes slugging behavior sometimes. To overcome these disadvantages, inclined type lower loop seal was proposed by this study. Solid circulation characteristics with change of lower loop seal geometry were measured and compared in a bubbling - bubbling - riser type circulating fluidized bed using $CO_2$ absorbent (P-78) as bed material at ambient temperature and pressure. We could conclude that the inclined lower loop seal is better than the vertical type lower loop seal from the viewpoints of minimum flow rate requirement for stable solid circulation and solid height change during solid circulation.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.2
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• pp.201-210
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• 2016

To develop a pressurized chemical looping combustor, conceptual design of 0.5 MWth chemical looping combustor was performed by means of mass and energy balance calculations. Based on the conceptual design, reactivity of oxygen carrier and solid circulation rate were selected as key parameters. Sensitivity analysis of those key parameters were conducted with the change of oxygen carrier utilization percent from 5 to 50% and proper solid circulation rate and solid conversion rate to meet 98% of $CO_2$ selectivity were confirmed. Feasibility of 0.5 MWth pressurized chemical looping combustor was confirmed by experimental studies to find real solid circulation rate and $CO_2$ selectivity within the operating conditions based on the conceptual design. We could varied very wide range of solid circulation rate in two interconnected fluidized bed system. We also got enough $CO_2$ selectivity more than 98% in semi-continuous chemical looping combustor using OCN717 oxygen carrier. Consequently, feasibility of 0.5 MWth pressurized chemical looping combustor was confirmed.

• 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.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.527-532
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• 2016

The effects of gas velocity and solid circulation rate on the axial solid holdup distribution have been determined in a 10 mm-I.D. ${\times}$ 800 mm-high circulating fluidized bed plasma reactor under reduced pressure (1torr). Polystyrene polymer powder and nitrogen gas are used as solid and gas materials respectively. The change of solid circulation rate by a large gas flow rate of the riser (40~80 sccm) is also possible by a relatively small gas flow rate of the solid recirculation part (6.6~9.9 sccm). The solid circulation rate in the reactor under reduced pressure increases with increasing aeration velocity in the solid recirculation part. The axial solid holdup in the riser decreases from the dense at the bottom to the dilute phase at the top section of the riser. Solid holdups at the axial positions in the riser increase linearly with increasing solid circulating velocity. From these results, we could determine the position of plasma load for good plasma ignition, maintain and plasma reaction.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.4
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• pp.419-429
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• 2022

Effects of operating variables on temperature profile and performance of 3 MWth chemical looping combustion system were estimated by mass and energy balance analysis based on configuration and dimension of the system determined by design tool. Air reactor gas velocity, fuel reactor gas velocity, solid circulation rate, and solid input percentage to fluidized bed heat exchanger were considered as representative operating variables. Overall heat output and oxygen concentration in the exhaust gas from the air reactor increased but temperature difference decreased as air reactor gas velocity increased. Overall heat output, required solid circulation rate, and temperature difference increased as fuel reactor gas velocity increased. However, overall heat output and temperature difference decreased as solid circulation rate increased. Temperature difference decreased as solid circulation rate through the fluidized bed heat exchanger increased. Effect of each variables on temperature profile and performance can be determined and these results will be helpful to determine operating range of each variable.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.286-293
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• 2005

An interpretation on the solid circulation characteristics in a fluidized-bed process has been carried out as a first step to simulate the dry entrained-bed absorption and bubbling-bed regeneration system for $CO_2$ removal from flue gas. A particle population balance has been developed to determine the solid flow rates and particle size distributions in the process. Effects of principal process parameters have been discussed in a laboratory scale process (absorption column: 25 mm i.d., 6 m in height; regeneration column: 0.1 m i.d., 1.2 m in height). The particle size distributions in absorption and regeneration columns were nearly the same. As gas velocity or static bed height in the absorption column increased, soild circulation rate and feed rate of fresh sorbent increased, however, mean particle diameter decreased in the absorption column. As cut diameter of the cyclone of the absorption column increased, solid circulation rate decreased, whereas feed rate of fresh sorbent and mean particle diameter in the absorption column increased. As attrition coefficient of sorbent particle increased, solid circulation rate and feed rate of fresh sorbent increased but mean particle diameter in the absorption column decreased.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.2
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• pp.122-130
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• 2014

Attrition characteristics of WGS catalysts for pre-combustion $ CO_2$ capture were investigated to check attrition loss of those catalysts, to check change of particle size distribution during attrition tests, and to determine solid circulation direction of WGS catalysts in a SEWGS system. The cumulative attrition losses of two catalysts increased with increasing time. However, attrition loss under humidified condition was lower than that under non-humidified condition case for long-term attrition tests. Between two catalysts, attrition loss of PC-29 catalyst was higher than that of commercial catalyst for long-term attrition tests. However, the commercial catalyst generated much more fines than PC-29 catalyst during attrition. Therefore, we conclude that the PC-29 catalyst is more suitable for fluidized bed operation if we take into account the separation efficiency of cyclone. Based on the results from the tests for the effect of humidity on the attrition loss, we selected solid circulation direction from SEWGS reactor to regeneration reactor because the SEWGS reactor contains more water vapor than regeneration reactor.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.355-361
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• 2009

Effects of operating variables on solid separation rate in two-interconnected fluidized beds system for selective solid circulation have been investigated. Coarse(212~300 or $425{\sim}600{\mu}m$) and fine($63{\sim}106{\mu}m$) particles were separated using the solid separator and the solid separation rate was ranged from 66 to 987 g/min. The solid separation rate increased as the gas velocity through the solid injection nozzle, solid height, diameter of solid injection nozzle, particle size of coarse particles, aperture of the solid separator, and weight fraction of fines in the solid mixture increased. However, the effect of the fluidization velocity was negligible.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.522-526
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• 2012

New experimental method to measure solid descending velocity in a vertical downcomer was presented and effects of downcomer diameter and particle properties on descending velocities for Geldart group A, B, and D particle have been measured and investigated. The effect of initial solid inventory on solid descending velocity was negligible. However, solid flow rate, solid circulation rate and solid descending velocity increased as the downcomer diameter increased. Moreover, solid descending velocity increased linearly as the downcomer diameter increased and showed distinguishable trend for Geldart group D particle from Geldart group A and B particles. Empirical correlations of solid descending velocity for Geldart group D and Geldart group A and B particles have been derived based on the measured values. The correlations could predict well the solid descending velocities.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.309-316
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• 2016

In this study, sewage was fed with up flow direction into a reactor equipped with a screw to circulate media that had lower specific gravity than water. It was observed that the media in the reactor could be circulated by a screw with reverse flow of the sewage feeding from the top to the bottom direction. Under these conditions, concentrations of inflow and outflow pollutants were measured at the filtration unit. Experimental results revealed stable circulation of the media with a screw in the reactor. Circulation of the media in the reactor showed more efficiency in removing the pollutants (particulate matters and organics) than no circulation. The maximum removal efficiencies of suspended solid (SS), chemical oxygen demand (CODmn), and total phosphorus (T-P) were 96%, 72% and 65%, respectively. Improvements for SS, CODmn and T-P removals with circulation of media were 52.38%, 43.14% and 118.12% respectively, compared to those without circulation.