• Title/Summary/Keyword: Limestone

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Morphologies of Aragonite Synthesized from Scallop Shells and Lime Stones by Successive Reaction

  • Keiko Sasaki;Hiroyuki Kobayashi;Yoo, Kyoung-Keun;Masami Tsunekawa
    • Proceedings of the IEEK Conference
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    • 2001.10a
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    • pp.331-336
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    • 2001
  • Aragonite type of precipitated calcium carbonate was synthesized by the successive reaction with hybridization of waste scallop shells with limestone. In the first step, carbonation was performed by using calcined limestone with low brightness, followed by the additional carbonation using calcined-hydrous scallop shells with high brightness. The temperature and the amount ratio of calcined limestone to calcined-hydrous scallop shells were examined as parameters in the experimental conditions. The products were characterized by XRD, SEM. in addition to measurements of brightness index. the specific surface area, and bulk density. The amount ratio of limestone to scallop shell affected not only the brightness but also morphologies of products. The increase in relative amounts of limestone leads to decrease in brightness and bumpy surface of particles. High temperature reaction produces aragonite particles with longer sizes and higher bulk densities. This study has made an attempt to establish the synthesis of aragonite with high brightness and high strength by utilization of waste scallop shells.

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A Study on the Morbidity and the Types of Accident among the Workers of Limestone Industry (석회석 가공 산업 근로자들의 상병 상태 및 사고 유형)

  • Lee, Kyoung Hee
    • The Korean Journal of Emergency Medical Services
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    • v.8 no.1
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    • pp.161-168
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    • 2004
  • The workers of limestone industry have relatively higher rate of accident and injury than other industry workers. This survey was conducted to provide the informations for the planning of safety and health educations to prevent the accident and injury. The purpose of this study is to identify the morbidity rate per month and to determine the related health factors, and to find accident experiences of the limestone workers and to analyze the reasons and types of that accidents. The study design was a descriptive survey. Self reporting questionnaires developed by researcher were used for data collection. The subjects of this study were 225 workers in limestone industries in Jecheon city. The statistical methods utilized for data analysis were frequency analysis, $x^2$-test with SPSS-pc(ver.9.0). The results are as follows, 1. The workers morbidity rate per month was 22%, and morbid factors were Flu., G-I trouble, hypertension, orthopedic trauma, external wound, burn, etc., and the related health factors are self-assessment for health, exercise, accessability for medical facilities. 2. 40% of the subjects have experienced the accidents during last 6 months. The types of the accidents were safety violations, traffic accidents and fire accidents. Injury types were external wounds, fracture/amputation and burn. The workers of limestone industry have higher morbidity rate and experiences of accidents. Therefore the more increased safety and health educations than now for both the workers and the managers are needed. And this study could be helpful to increase the quality and the quantity of the educations needed.

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A Study of Desulfation Characteristics of Circulating Fluidized Bed Combustion for Domestic Anthracite (국내 무연탄의 순환류동층 보일러에서 탈황 특성 연구)

  • 정진도;김장우;하준호
    • Journal of Korean Society for Atmospheric Environment
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    • v.20 no.4
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    • pp.429-436
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    • 2004
  • Circulating fluidized bed combustion (hereafter CFBC) technology enables an efficient combustion for the materials with low heating values such as high ash coal and sludges. It also has desulfation function by adding limestone directly to combustor. The CFBC has been considered as one of the best processes for low grade coal containing with large contents of ash and sulfur. In this paper, in order to various tests were performed to find the optimum desulfation condition for CFBC using Korean Anthracite. We surveyed possible parameters and conducted desulfation efficiency test in D Thermal Power Plant. In addition, the result of some fundamental theoretical consideration was discussed with CFBC. Optimum limestone size could be considered to be 0.1-0.3mm irrespective of combustion temperature and Ca/S molar ratio variation. Desulfation efficiency increased as the molar ratio increased. Because desulfation process occurs at the surface at higher temperature, inner side of limestone can't be utilized. When surface area is not appropriate, some SO$_2$ emit without reaction. Optimum molar ratio should be decided after considering chemical and physical properties of limestone and coal thoroughly such as particle size, pore size and HGI. Commercial CFBC is operated at Ca/S 1.6. Combustor temperature 840-87$0^{\circ}C$ shows good desulfation efficiency.

Hydraulic Reaction Analysis of C3A in Ordinary Portland Cement with Mineral Additions by Rietveld Method (리트벨트법에 의한 혼합재 첨가 보통 포틀랜드 시멘트 중 C3A 수화반응 해석)

  • Lim, Young-Jin;Lee, Seung-Heun;Cho, Jae-Woo
    • Journal of the Korean Ceramic Society
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    • v.51 no.2
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    • pp.82-87
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    • 2014
  • Due to the revised Korean standard KS L 5201 for Ordinary Portland Cement (OPC), the use of mixed cement has grown from 5% to 10%. This study investigates the hydration behavior of $C_3A$, asit is a cement mixture that is more commonly used than granulated blast furnace slag or limestone alone. Paste samples were prepared with either granulated blast furnace slag or limestone alone. Each sample was compared with the widely used Rietveld method with a cement mixture containing blast furnace slag or limestone. The hydration behavior of $C_3A$ in each OPC sample was assessed and results were analyzed. Granulated blast furnace slag promotes a high initial level of ettringite, but as the days passed, it promotes an increase in monosulfate, leading to cracks and expansion due to the penetration of sulfates in the solution. However, when limestone is added to the mixture, a transformation of ettringite to monosulfate occurs in the presence of the $CaCO_3$ in the limestone. It is considered that this produces hemi-carbonate and mono-carbonate and thus maintains the ettringite level.

North Korea Cement Industry in Satellite Imagery (위성사진으로 본 북한의 시멘트 산업)

  • Baek, Chul-Seoung;Seo, Jun-Hyung;Cho, Jin-Sang;Ahn, Ji-Whan;Cho, Kye-Hong
    • Ceramist
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    • v.22 no.2
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    • pp.198-214
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    • 2019
  • The possibility of economic exchange with North Korea is increasing, but there is still a shortage of information of cement industry, which occupies the largest proportion of North Korean construction material industry. Therefore, this study researched the status of cement production facility management using satellite photographs of 16 cement factories in North Korea, and examined the operating status of North Korean cement industry by observing smoke discharged from the chimneys of the cement production facilities. When the satellite photographs were analyzed, it was observed that the monthly stack fog ratio of the North Korean cement factories was 55% in 2016, 60% in 2017 and nearly 65% in 2018. This demonstrates that the average operating ratio has been increasing continuously. However, the operation rate of the five major cement factories reaches the limit, actual cement production is estimated to have maintained the previous level or small increased.

A Study of the Deformation Characteristics in Limestone Cavity Area by Finite Element Method (유한요소해석에 의한 석회암 공동지반의 변형특성에 관한 연구)

  • Chun, Byung-Sik;Park, Hyeong-Jun
    • Journal of the Korean GEO-environmental Society
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    • v.6 no.1
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    • pp.63-72
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    • 2005
  • From the geological and engineering point of view, the limestone is so rigid that it is able to act as a bedrock but if there are some unstable elements which are solubility cavity and cracking zone in the ground, the settlement and bearing capacity of a structure will be required to long-term stability investigations and countermeasures about those problems. When comparing the allowable bearing capacity, the results of Bell's method and the Bowles' method are similar but the results of Hoek-Brown's method are very larger than the others. For weathered limestone, stability is changed by size and depth of the cavity of limestone, but soft and hard rock are stable regardless of size and depth of the cavity.

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Mechanical behavior of HPFRCC using limestone calcined clay cement (LC3) and oxygen plasma treated PP fibers

  • Sajjad Mirzamohammadi;Masoud Soltani
    • Structural Engineering and Mechanics
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    • v.89 no.4
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    • pp.349-362
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    • 2024
  • High-performance fiber-reinforced cement composites (HPFRCC) are new materials created and used to repair, strengthen, and improve the performance of different structural parts. When exposed to tensile tension, these materials show acceptable strain-hardening. All of the countries of the globe currently seem to have a need for these building materials. This study aims to create a low-carbon HPFRCC (high ductility) that is made from materials that are readily available locally which has the right mechanical qualities, especially an increase in tensile strain capacity and environmental compatibility. In order to do this, the effects of fiber volume percent (0%, 0.5%, 1%, and 2%), and determining the appropriate level, filler type (limestone powder and silica sand), cement type (ordinary Portland cement, and limestone calcined clay cement or LC3), matrix hardness, and fiber type (ordinary and oxygen plasma treated polypropylene fiber) were explored. Fibers were subjected to oxygen plasma treatment at several powers and periods (50 W and 200 W, 30, 120, and 300 seconds). The influence of the above listed factors on the samples' three-point bending and direct tensile strength test results has been examined. The results showed that replacing ordinary Portland cement (OPC) with limestone calcined clay cement (LC3) in mixtures reduces the compressive strength, and increases the tensile strain capacity of the samples. Furthermore, using oxygen plasma treatment method (power 200 W and time 300 seconds) enhances the bonding of fibers with the matrix surface; thus, the tensile strain capacity of samples increased on average up to 70%.

A Study on Binary System of Calcium Phosphate-Kaolin, -Quartz, -Feldspar and Limestone (Calcium Phosphate와 Kaolin, Quartz, Feldspar, Limestone과의 이성분계 소성에 관한 연구)

  • 이응상;이성희
    • Journal of the Korean Ceramic Society
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    • v.25 no.5
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    • pp.437-442
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    • 1988
  • We have suffered number of problems in supplying bone ash for bone china bodies as raw materals, because of its impurity and quantity. To reduce these problems, we have synthesized tricalcium phosphate that was reacted by H2PO4 and CaCO3 ; 3Ca(OH)2+2H3PO4longrightarrowCa3(PO4)2+6H2O. Therefore, we have studied solid reactions of synthesized tricalcium phosphate withkaoline, limestone, feldspar and silica, respectively.

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A Study on High Graded Limestone Population Area (석회석 원소재의 고품위대 조사를 위한 연구)

  • Kim, Jun-Kyoung
    • 한국지구물리탐사학회:학술대회논문집
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    • 2007.06a
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    • pp.343-348
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    • 2007
  • Geophysical methodology using GPR(Ground Penetrating Radar) were applied both to the limestone producing area(Sambo Mine Company & Haksanri Area) and to Landfill area(Mureung Landfill Site). The investigation results resultant from both the limestone producing area(Sambo Mine Company & Haksanri Area) showed that there are a few events reflected from boundaries between caves and basement rocks. Those from landfill area showed that more complicated and small size events are found. These events could be from different electric characteristics of various kinds of composition materials in the landfill site.

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An experimental study on engineering properties of concrete containing fly-ash, slag powder and limestone powder (석회석미분말을 사용한 4성분계 콘크리트의 공학적 특성에 관한 실험적 연구)

  • Hong, Ji-Hoon;Yum, Jun-Haun;Kim, Jung-Bin;Jeong, Yong;Lee, Seong-Yeun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.561-564
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    • 2006
  • This study is aimed for investigating the engineering properties of concrete containing fly ash, slag powder and limestone powder. The results of this study are as follows; As limestone powder is incresed, slump, air loss and strength is reduced, variation ratio of length is reduced, dynamic modulus of elasticity and neutralization depth is incresed.

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