• Title, Summary, Keyword: 채수율

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Analysis on the Ore Recovery from Operating the Room & Pillar Hybrid Mining Method in the Korean Limestone Mine (국내 석회석 광산에서 주방식하이브리드 채광법의 채수율 분석)

  • Kwon, Dukjoon;Kim, Jaedong
    • Tunnel and Underground Space
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    • v.27 no.3
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    • pp.161-171
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    • 2017
  • Demand for high-grade limestone is increasing, but the production in the domestic mines has been limited due to the lack of systematic development plans and efforts to develop mining technology to improve the recovery ratio, transition to high-cost underground mining due to increasing social awareness of environmental protection, and the smallness of the domestic mining industry, etc. In this study in connection with this issue, an analysis on the recovery change by improvement of mining method was executed. 3D modeling technique was used to construct a 3D model. 3D model includes the geological structure, the limestone ore body and the underground pits and tunnels excavated at the Daepyeong District of Daesung MDI Donghae District. By using the 3D model, measured resources, reserves and ore recovery were evaluated from the results of pilot operation of the room and pillar hybrid mining method, which is a variant of room and pillar mining method. These results were compared with those obtained from the conventional mining method. The ore recovery obtained by hybrid mining method was found to be up to 71.6%, showing about 26%p. increase compared with the case of conventional mining method.

A Study on Stability Analysis of Large Underground Limestone Openings considering Excavation Damaged Zone (굴착손상영역을 고려한 대형 석회석 갱내채광장의 안정성 분석 연구)

  • Kwon, Min-Hyuk;Choi, Sung-Oong;Kim, Chang-Oh
    • Tunnel and Underground Space
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    • v.26 no.2
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    • pp.131-142
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    • 2016
  • Investigation for rock joints, inspection for rock core, and laboratory tests for rock specimens, in this study, have been performed for identification of the extent and properties of Excavation Damaged Zone in a underground limestone mine, which plans to enlarge the size of openings to improve the production rate. Properties of EDZ and surrounding rock masses have been used numerically for discontinuum analysis, and it is concluded that the effect of EDZ can be increased with increasing the opening size and a blasting pattern of high precision can be suggested for the counterplan.

Stereo-photogrammetry Analysis for Over-break Control (여굴 제어를 위한 입체사진측량기법 분석)

  • Kim, Byung-Ryeol;Jeong, Min-Su;Jin, Yeon-Ho;Choi, Sung-Oong
    • Explosives and Blasting
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    • v.36 no.1
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    • pp.12-19
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    • 2018
  • When an underground limestone mine selects room-and-pillar mining method, in which the stability of mine openings is maintained by leaving safety pillars, the stability of safety pillars is always incompatible with their productivity. Therefore, the engineering decision for stability and productivity is essential. In this study, a progress of excavation faces by conventional blasting pattern has been examined in field for investigating over-break and stereo-photogrammetry method has been applied to this field measurement for improvement of accuracy. Also this result has been reflected instantly to composite blasting pattern by feedback, for minimizing overbreak. Field tests showed the relevant results that $3.5m^2$ in over-break out of $70m^2$ in total excavation face has been decreased, that is 5% of reduction rate in maximum.

Characteristics of Hydrolysis Reaction Using Unsupported Catalyst at High Concentration of NaBH4 Solutions (고농도 NaBH4 수용액에서 비담지 촉매의 가수분해 반응 특성)

  • Lee, Hye-Ri;Na, Il-Chai;Park, Kwon-Pil
    • Korean Chemical Engineering Research
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    • v.54 no.5
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    • pp.587-592
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    • 2016
  • Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). Properties of $NaBH_4$ hydrolysis reaction using unsupported Co-P-B Co-B, catalyst at high concentration $NaBH_4$ solution were studied. In order to enhance the hydrogen generation yield at high concentration of $NaBH_4$, the effect of catalyst type, $NaBH_4$ concentration and recovery of condensing water on the hydrogen yield were measured. The yield of hydrogen evolution increased as the boron ratio increased in preparation process of Co-P-B catalyst. The hydrogen yield decreased as the concentration increased from 20 wt% to 25 wt% in $NaBH_4$ solution during hydrolysis reaction using 1:5 Co-P-B catalyst. Maximum hydrogen yield of 96.4% obtained by recovery of condensing water and thinning of catalyst pack thickness in reactor using Co-P-B with Co-B catalyst and 25 wt% $NaBH_4$ solution.

Changes in Antioxidant Contents and Activities of Adzuki Beans according to Germination Time (발아시간에 따른 팥의 항산화성분 및 항산화활성의 변화)

  • Woo, Koan Sik;Song, Seuk Bo;Ko, Jee Yeon;Lee, Jae Saeng;Jung, Tae Wook;Jeong, Heon Sang
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.44 no.5
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    • pp.687-694
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    • 2015
  • The purpose of this study was to evaluate the yield, antioxidant content, and antioxidant activity of adzuki beans according to germination time. Cultivated varieties were Vigna angularis var. Nipponensis cv. Chungju-pat (CJP), and Yeonduchae (YDC), and Vigna radiata (L.) R. Wilczek cv. Dahyeon (DH). The moisture, crude protein, calcium, and magnesium contents of YDC significantly changed with increasing germination time, whereas potassium, natrium, and aluminium contents did not significantly change. Sprout yield, total polyphenol, flavonoid, and tannin contents of ethanolic extracts from adzuki and mung beans significantly increased with increasing germination time. Total polyphenol contents of ungerminated CJP, YDC, and DH were 1.96, 2.68, and 2.02 mg/g, and those of CJP and YDC germinated for 144 h were 3.33 and 3.47 mg/g, respectively. Total flavonoid content of adzuki beans substantially decreased with increasing germination time. Total tannin content substantially increased with increasing germination time, and YDC showed higher contents (0.85 mg/g) sample germinated for 120 h. DPPH radical scavenging activities of CJP and YDC substantially decreased with increasing germination time, whereas that of DH increased. ABTS radical scavenging activities of ungerminated CJP, YDC, and DH were 4.57, 6.51, and 2.82 mg/g, respectively, and increased after germination for 72~120 h.

Hydrolysis Reaction of NaBH4 using Unsupported Co-B, Co-P-B Catalyst (비담지 Co-B, Co-P-B 촉매를 이용한 NaBH4 가수분해 반응)

  • Oh, Sung-June;Jung, Hyeon-Seong;Jeong, Jae-Jin;Na, Il-Chai;Ahn, Ho-Geun;Park, Kwon-Pil
    • Korean Chemical Engineering Research
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    • v.53 no.1
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    • pp.11-15
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    • 2015
  • Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells(PEMFCs). Properties of $NaBH_4$ hydrolysis reaction using unsupported Co-B, Co-P-B catalyst were studied. BET surface area of catalyst, yield of hydrogen, effect of $NaBH_4$ concentration and durability of catalyst were measured. The BET surface area of unsupported Co-B catalyst was $75.7m^2/g$ and this value was 18 times higher than that of FeCrAlloy supported Co-B catalyst. The hydrogen yield of $NaBH_4$ hydrolysis reaction by unsupported catalysts using 20~25 wt% $NaBH_4$ solution was 97.6~98.5% in batch reactor. The hydrogen yield decrease to 95.3~97.0% as the concentration of $NaBH_4$ solution increase to 30 wt%. The loss of unsupported catalyst was less than that of FeCrAlloy supported catalyst during $NaBH_4$ hydrolysis reaction and the loss increased with increasing of $NaBH_4$ concentration. In continuous reactor, hydrogen yield of $NaBH_4$ hydrolysis was 90% using 1.2 g of unsupported Co-P-B catalyst with $3{\ell}/min$ hydrogen generation rate.

Hydrogen Supply to PEMFC for Unmanned Aero Vehicles Using Hydrolysis Reaction of NaBH4 (NaBH4 가수분해 반응에 의한 무인항공기용 PEMFC 수소공급)

  • Jung, Hyeon-Seong;Jo, Byung-Joo;Lee, Jung-Hoon;Lee, Han-Jong;Na, Il-Chai;Chu, Cheun-Ho;Park, Kwon-Pil
    • Korean Chemical Engineering Research
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    • v.54 no.1
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    • pp.11-15
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    • 2016
  • Proton Exchange Membrane Fuel Cells (PEMFC) instead of batteries is appropriate for long time flight of unmanned aero vehicles (UAV). In this work, $NaBH_4$ hydrolysis system supplying hydrogen to PEMFC was studied. In order to decrease weight of $NaBH_4$ hydrolysis system, enhancement of hydrogen yield, recovery of condensing water and maintenance of stable hydrogen yield were studied. The hydrogen yield of 3.4% was increased by controlling of hydrogen pressure in hydrolysis reactor. Condensing water formed during air cooling of hydrogen was recovered into storage tank of $NaBH_4$ solution. In this process the condensing water dissolved $NaBH_4$ powder and then addition of $NaBH_4$ solution decreased system weight of 14%. $NaBH_4$ hydrolysis system was stably operated with hydrogen yield of 96% by 2.0g Co-P-B catalyst for 10 hours at 2.0L/min hydrogen evolution rate.

Subcarrier-Pairing Scheme for OFDMA based Multi-Hop Cognitive Radio Systems (OFDMA 기반 다중 홉 무선 인지 시스템을 위한 부반송파 페어링 방법)

  • Kim, Jae-Hyun;Shin, Jung-Chae;Cho, Ho-Shin;Jang, Youn-Seon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.6A
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    • pp.601-608
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    • 2011
  • In OFDMA(Orthogonal Frequency Division Multiple Access) based multi-hop networks, the subcarrier-pairing scheme using the SNR(Signal-to-Noise Ratio) has been proposed as the best solution. But, this scheme is not optimal in cognitive radio system, because of the power control due to the interference to the primary user. In this paper, we propose two subcarrier-pairing schemes for OFDMA based 2-hop cognitive radio systems. One is the IT(Interference channel gain) scheme considering only the interference channel gain, and the other is the CI(Channel SNR over interference channel gain) scheme considering the ratio of channel SNR to interference channel gain. The results show that the CI scheme has the best performance in which throughput is improved more than 10% in comparison with other schemes.

A Study on the Mining Method for Limestone Mines with Less Environmental Hazards (환경오염 저감을 위한 석회석 광산개발방안에 대한 연구)

  • 임한욱;김재동;백환조
    • Tunnel and Underground Space
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    • v.10 no.1
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    • pp.80-91
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    • 2000
  • Open cut mining of limestone is generally considered to be more advantageous than underground mining in recovery, grade control, economics, and safety, but it causes substantial environmental pollutants such as ground vibration, noise, dust. It also changes ground surface and may destroy vegetation. The Halla limestone mine which lies adjacent to Baikdu mountains range is selected for a model study. To reduce environmental hazards, and to conserve original surface and woods, both open cut and underground mining methods must be adopted. In case of sub-level sloping. a unit block of 87m high, 70m wide, and 100∼l20m long is suggested with an estimated overall recovery of 42%. Some suggestions to reduce the environmental hazards are also included. The followings must be considered in determining the degree of fragmentation; the discontinuity conditions in the rock mass and the charge concentration both at the bottom and column of the hole. In addition to adopting a barrier wall for reducing environmental hazards, the probable production from underground mining is also discussed.

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APPLICATION OF TELEVIEWER AND COLOR-CORESCANNER FOR THE ESTIMATION OF GNEISS STONE RESOURCES OF HADONG, KYEONGSANNAMDO PROVINCE (하동지역 편마암 석재의 품질 평가를 위한 텔레뷰어 및 칼라 코어스캐너의 응용)

  • Hyun, Hye-Ja;Kim, Jung-Yul
    • Journal of the Korean Geophysical Society
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    • v.7 no.4
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    • pp.255-267
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    • 2004
  • Analysis of fracture system in a stone quarry mine is a critical importance in assessing the recoverable amounts of building stones as well as in establishing the systematic and efficient development plan. Rock formation comprising vein structure, degree of weathering, and compositon of minerals, is a critical factor of estimating the stone quality. The aim of this study is to provide desirable informations about both fracture pattern and rock formation by using Televiewer and Color-corescanner. Televiewer measurement were conducted at 7 boreholes in the gneiss quarry mine, Hadong, Kyeongsangnamdo province and the corresponding cores were scanned using Color-corescanner at the same place. In Televiewer images, all kinds of fractures were clearly observed and a better discrimination of stone quality can be identified. Meanwhile, the core images with high resolution (max. 20 pixels/mm) provided detailed informations on rock formation such as features of particles and fissures that can be nearly undetected by Televiewer.

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