• Journal of the Korean Society of Safety
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• v.14 no.3
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• pp.101-109
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• 1999

This study attempts to analyse the solid mixing in the feeder and the packing effect for pressure fluctuations in the fluidized bed. To study the mixing characteristics of solid in vibrating feeder for the stable operations of fluidized combustion, the system consisted of two groups of particles such that fine particles were located on the top of the coarse particles before vibratory mixing had started. The effects of packing materials on the pressure fluctuations in a fluidized bed were analysed by using a statistical method to interpret the behavior of fluidized bed. The experiments were carried out in a fluidized bed of 6.7cm-ID, and the experimental variables were particle sizes, of 115 to 1,015$\mu\textrm{m}$ in diameter and the multi-sized particles haying Rosin-Rammler and Gaussian distributions. The settled bed heights of particles to diameter ratios (L/D) were ranged from 0.5 to 2.0. And fluidizing of particles was carried out by air. The packing materials used were screen packing, and the properties of the pressure fluctuations in the fluidized bed were measured by a differential pressure transducer. The properties of the pressure fluctuations calculated were the mean, the standard deviation, and the major frequency of the power spectral density functions. From the characteristics of fluidizing, it was found that the standard deviation of pressure fluctuations could be effectively used to explain the fluidized phenomena, and the packing materials affected severely the properties of the pressure fluctuations. As a result, from the interpretation by spectral analysis, the effects of measuring radius of pressure fluctuations on standard deviation were constant in the case of the fluidized bed with and without packing materials. However, the effects of measuring the height of pressure fluctuations on standard deviations were linear increasing for the fluidized bed with packing materials, but were constant for the fluidized bed without packing materials at 4.5cm above the gas distributor. The major frequency of pressure fluctuations was found to be nearly independent of fluidized system. Also, the major frequency of pressure fluctuations decreased with increasing packing size, and it had maximum value at 10% of the packing amount.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.115-116
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• 2023

In this study, it was confirmed whether kaolin can play a role as a bed materials and a role in reducing clinkers by using kaolin with a bed materials for the purpose of removing clinkers such as slagging and fouling generated in circulating fluidized bed combustion furnaces using solid fuel.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.1
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• pp.66-70
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• 2014

Bed-soils can be used to help plants to overcome unfavorable conditions of soils, especially hydraulic properties of soils. This study was conducted to evaluate the effect of organic and inorganic raw materials on saturated hydraulic conductivity ($K_s$) of bed-soils. Perlite and bottom ash, which are inorganic materials, increased more $K_s$ of bed-soils than coco peat, an organic material. However, vermiculite, an inorganic material, increased less than coco peat. Saturated hydraulic conductivity of bed-soil mixed with fine vermiculite ($0.14{\pm}0.02mh^{-1}$) was much lower than one containing coarse vermiculite ($0.85{\pm}0.21mh^{-1}$). Such effect was more apparent when pressure was added on bed-soils containing fine vermiculite ($0.07{\pm}0.01mh^{-1}$), probably reflecting the decrease in pore size with the expansion of vermiculite wetted. Compacting decreased more $K_s$ in the bed-soils containing coco peat or vermiculite than other mixtures. Those results suggest that perlite and bottom ash in bed-soils play an important role in improving saturated hydraulic conductivity but vermiculite in bed-soils may suppress the improvement of saturated hydraulic conductivity with the decrease of its size and with the increase of compacting pressure.

• Plant Journal
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• v.6 no.2
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• pp.70-77
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• 2010

This study investigated the characteristics of co-combustion of mixed anthracite (domestic and Vietnam) and bituminous coal (Sonoma, Australia) at circulating fluidized bed boiler in Donghae thermal power plant when mixing ratio of bituminous coal is variable. Co-combustion of bituminous coal contributes to improvement in general combustion characteristics such as moderately retaining temperature of furnace and recycle loop, reducing unburned carbon powder, and reducing discharge concentration of NOx and limestone supply owing to improvement in anthracite combustibility as the mixing ratio was increased. However, bed materials were needed to be added externally when the mixing ratio exceeded 40% because of reduction in generating bed materials based on reduction in ash production. When co-combustion was conducted in the section of 40 to 60% in the mixing ratio while the supplied particles of bituminous coal was increased from 6 mm to 10 mm, continuous operation was shown to be possible with upper differential pressure of 100 mmH2O (0.98 kPa) and more without addition of bed materials for the co-combustion of mixed anthracite and bituminous coal (to 50% or less of the ratio) and that of domestic coal and bituminous coal (to 60% of the ratio).

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.2
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• pp.95-104
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• 2010

The purpose of this study is to analyze the correlation between physical stream characteristics and bed materials in natural rivers. Accordingly, four natural rivers were selected reference streams, they were Nam river, Sumjin River, Naesung River and Han River. Grain size distributions of bed materials were gravels, cobbles and boulders in Han river and Nam river, were sand, gravels, cobbles and boulders in Sumjin river and were sand in Naesung river. Four reference streams were divided into each two reference reaches (straight and bend) by plan and profile characteristics of naturally meandering stream. Therefore various reference reaches were chosen in the aspect of physical stream characteristics and grain size distributions. The results investigated and analyzed are as follows. The streams that grain sizes distributions of river bed materials were coarse were stable because they had variety of bed slope without sediment deposition, and then the riffles frequency and the physical characteristics were various. Also, velocitydepth regime were various in four kinds, and the response parts for water level change were small, so that channel flow status were stable and excellent condition. On the other hand, sand river that grain sizes distributions of river bed materials were fine had not the variety of parameters as velocity-depth regimes, sediment deposition, channel flow status and riffles frequency, so that the physical stream characteristics were not various.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2365-2372
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• 1995

The objective of this study is to get the basic data for the development of fluidized bed combustor. For this purpose, various rake angles(.theta.=20.deg., 25.deg., 30.deg., 35.deg.) of finned tubes and a smooth tube were installed horizontally in the fluidized bed combustor of 410*250mm. The effect of fluidized bed temperature, superficial velocity in bed, size of bed materials, rake angle of finned tubes on the heat transfer coefficient was experimentally investigated. The following results were obtained. (1) Under the fluidized bed temperature(750.deg. C-900.deg. C), and the gas velocity in bed(1.1-2.8m/sec), The highest heat transfer coefficient was measured with the rake angle of finned tubes was .theta.=25.deg. and .theta.=35.deg. for the average fluidized material particle size of 1.22mm and 1.54mm, respectively. Generally, the heat transfer coefficient of finned tubes is 1.4 to 2.4 times larger than that of smooth tubes. (2) The size of bed materials influences the rake angle of finned tubes which can have the highest heat transfer coefficient. As the temperature in bed gets higher, the effect of the rake angle of finned tubes on the heat transfer coefficient becomes greater.

• Journal of the Korea Furniture Society
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• v.27 no.1
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• pp.35-42
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• 2016

With radical increase in one-person households, the consumption market in Korea has also rapidly changed. In line with this movement, customized furniture for sing lecustomershas been recently introduced. Since sleeping more than eight hours a day is needed to maintain a healthy lifestyle, a suitable bed for a comfortable sleep is an essential product for single consumers. In order to respond to this trend, a study was conducted to examine the surface materials of a bed designed for singles. A complete enumeration survey was implemented for beds manufactured by ACEBED Co., Ltd., Simmons-k, Co, Ltd,. Keumsung Bed, Hanssem Co,. Ltd., Hyundai Livart Co,. Ltd,. Emons Furniture Co,. Ltd,. and Borneo International Furniture Co., Ltd. This study helped in the proper selection of surface materials that may be used in the development of furniture for single consumers.

• Journal of The Geomorphological Association of Korea
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• v.26 no.1
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• pp.15-26
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• 2019

In this study, we investigated the grain size, lithological type, and shape of coarse bed materials in the upper and middle reaches of Gongneungcheon River. For this purpose, 11 sampling points were selected along the river. For 100 samples of the coarse bed materials at each point, three axes (long, intermediate, and short) of samples were measured, and their lithological types were also identified. By measuring grain size, the sphericity and flatness of samples were calculated. Finally, every particle was classified into four shape categories: sphere, disc, blade and rod. We found that the grain size in incised meandering reach is the largest. This is mainly due to the supply of coarse materials from steep valley sides along the meandering channel. According to the lithological analysis, all samples were identified as granite, gneiss and schist, and quartz. The proportion of granite decreased, whereas the proportion of gneiss and schist increased downstream. These patterns indicate that the bedrock distribution within the study area accounts for the downstream lithological variation of coarse bed materials. With regard to the grain shape, sphericity gradually decreased while flatness gradually increased downstream. In the case of the shape classification, unlike the general downstream pattern of grain shape, the proportion of the sphere type decreased and the proportion of the blade type increased downstream. Such a reversal change in the downstream direction turns out to be determined by the lithology (such as foliation, bedding and the pattern of weathering) of coarse bed materials.

• Journal of Korea Water Resources Association
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• v.37 no.5
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• pp.387-395
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• 2004

A computer model was proposed to simulate channel changes and bed material sorting of the meandering channels with different grain size in time and space simultaneously. The bed at the outside of the meandering channel with mixed sediments was scoured deeply and composed of coarser materials, and at the inside was aggradated and composed of finer materials. The sorting process started at the upstream inflection point and was finished at the downstream inflection point. At the natural with complicated boundaries and non-uniform grain sizes, the bed near the outside at the bend and narrow width was scoured deeper with coarse materials than in the channel with uniform grain sizes. The point bars showed lip at the inside near the bend and the bed materials were finer The bed at the outside near the bend and in the narrow width was scoured deeply with the coarser materials.

• Analytical Science and Technology
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• v.13 no.1
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• pp.5-11
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• 2000

During the commissioning period in Tonghae thermal power plant which is the largest circulating fluidized bed boiler in the nation, a considerable amount of clinker was formed at FBAC and seal pot. Various attempts, for example, concentration analysis, surface phenomena, thermal characterization, and crystal structure of ash, bed sand, limestone, clinker, and mixture of each gradients have been studied to identify the causes of clinker formed in circulating fluidized bed boiler. As the results, the characterization of black particles in which separated from the clinker is more similar to that of bed sand, on the other hand, white particles are more similar to ash. In addition, the sintering temperature of sand is over $1,200^{\circ}C$ and this temperature was decreased as limestone is added to bed material. The cause of clinker was proved that ash was sticked to molten or sintered sand or limestone in the area of high temperature in the circulating system.