• Title/Summary/Keyword: Clinker

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Status of Cement Industry and Cement Properties of North Korea (북한의 시멘트 물성 및 시멘트 산업현황에 관한 연구)

  • Baek, Cheong-Hoon;Park, Won-Jun;Min, Tae-Beom
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.1
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    • pp.64-71
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    • 2020
  • The purpose of this study was to evaluate the North Korea cement industry and technology status by comparing and analyzing the cement standards and properties of South and North Korea. In the literature study, data on North Korea's cement industry and standards were collected and analyzed through the Ministry of Unification's North Korea Data Center and other agency. The facilities, classification, and quality standards of South and North Korea cements were compared. In an experimental study, a survey on the quality of cement in North Korea was carried out through physical and chemical analysis experiments by obtaining a small amount of cement from North Korea, and compared with domestic cement. As a result, North Korea cement was of lower quality than South Korean cements. North Korea cement had lower C3S and higher C2S than South Korea cement, especially the residue content was much higher. In addition, North Korea cement had about 50% of the compressive strength of cement in South Korea because the clinker was not fired at a sufficient temperature due to the poor performance of the cement facilities in North Korea.

Theoretical Proposal for the Mix Design of Recycled Cement Utilizing Inorganic Construction Wastes (무기계 건설폐기물을 이용한 재생시멘트 배합설계에 관한 이론적 제안)

  • Kim, Ji-Hoon;Tae, Sung-Ho;Song, Hun;Shin, Hyeon-Uk
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.4 no.3
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    • pp.250-258
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    • 2016
  • Until now, the construction material industry has been recognized as a typical environmental destruction industry. However, recently, in order to reduce $CO_2$ emission, the main cause of environmental problems, lots of studies have been done about recycling industrial by-products and construction wastes. Therefore, the purpose of this study is to confirm whether it is possible to use as an alternative material in cement production process as a part of the development of recycled cement using an inorganic construction waste. For this study, the inorganic construction wastes was collected and analyzed each chemical component by XRF(X-ray Fluorescene). Also, the inorganic construction wastes were combined based on the chemical component of the cement, to perform this analysis. As a result, when the inorganic construction wastes was properly combined, it is possible to consider the development of the recycled cement used the inorganic construction wastes.

Study on the Correlation between Air Emission Gas and Alternative Fuels Used in Cement Sintering Process (시멘트 소성공정에 사용된 대체연료와 대기배출가스간 상관관계 연구)

  • Choi, Jaewon;Baek, Ju-Ik;Kwon, Sang-Jin;Won, Pil-Sung;Kang, Bong-Hee
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.3
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    • pp.286-293
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    • 2020
  • In this study, we tried to verify the correlation of the amount of combustible industrial by-products, household waste used as fuels on cement sintering process and the amount of NOx, and CO, harmful components in the exhaust gas. The analysis uses coal as natural fuel, soft plastics (plastics with properties that tend to be scattered by wind, such as vinyls), hard plastics (plastics with properties that are not scattered by wind, such as PETs, wate rubbers), and reclaimed oils as alternative fuels. Utilizing the response surface analysis (RSM) technique using the process data of 2019, such as the fuel input and combustion temperature of a domestic A cement manufacturer's sintering facilities as independent variables, and the NOx, and CO emissions to the stack as dependent variables. Correlation was analyzed. As a result, it was confirmed that the impact on the emission material differs for each waste. In particular, it was analyzed that the hard plastics increase the CO emission but have an excellent effect of reducing NOx.

Fabrication of high purified zirconium dioxide (ZrO2) and stabilized zirconia (TZP: tetragonal zirconia polycrystal) powders (고순도 산화지르코늄(ZrO2) 및 안정화 지르코니아 (TZP: tetragonal zirconia polycrystal) 분말제조)

  • 최의석
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • 1996.06b
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    • pp.55-85
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    • 1996
  • 지르코니아 분말은 ZrO2 결정상이 온도변화에 따라 부피변화를 수반하는 상전이변태를 나타낸다. 단사정 ZrO2가 110$0^{\circ}C$에서는 정방정으로, 2$700^{\circ}C$ 내외에서는 입방정으로 결정구조가 가역적으로 변한다. 이 ZrO2에 금속산화물을 고용시키면 형석 (CaF2:Florite)형의 입방정 결정구조가 실온에서도 안정하게 존재하게 된다. 안정화제 산화물은 caO, MgO등 2가 산화물외에 3가 또는 4가의 금속산화물로서 Sc2O3, Y2O3, Sm2O3, Nd2O3, Gd2O3, Y2O3, CeO2 등이며 이들은 금속이온의 원자가가 변하기 쉬운 희토류 산화물이다. 안정화 지르코니아는 형석형 결정구조이며 결정화학적으로 보면 금속양이온이 산소이온에 대해서 정육면체형의 8배위를 하고 있다. 이때 이온반경비(양이온/음이온)에 따라 Zr+4자리와 O-2자리의 격자위치와 모양이 형성되므로 비틀어진 정육면체구조이건 이상적인 정육면체 형석구조를 이룬다. 이는 지르코니아의 결정상의 2상-3상인 부분안정화 지르코니아다결정체(PSZ : partially stabilized zirconia)이거나 단일상-2상인 정방정 지르코니아다결정체(TZP : tetragonal zirconia polycrystal)의 결정구조를 가지는데 기인한다. PSZ는 주로 MgO, CaO를 안정화제로 고용시켜 입방정 영역에서 소결하고 이를 다시 입방정과 정방정의 상 영역에서 열처리하여 입방정 입자내부에 정방정을 석출 형성시킨 것이며 TZP는 Y2O3 및 CeO2를 고용시켜 PSZ와 다르게 일반적인 상압소결한 정방정 결정상의 미립자이다. 산화지르코늄 분말은 지르콘사에서 열분해시킨 지르코늄소결.융해괴(caustic fusion clinker)를 산처리하여얻어진 지르코늄산용액(zirconyl acid solution : cloride, sulfide, nitride 등)으로부터 제조된다. 고순도 산화지르코늄은 용액 결정석출법에 의해 ZrOCl2.8H2O, 5ZrO2.3SO3.15H2O, ZrO(NO3)2.xH2O 등의 지르코늄 수화물만을 재결정화시킨 것으로부터 얻을 수 있으며 이 지르코늄염 수용액으로부터 입자미세구조를 효과적으로 제어하여 산화지르코늄 및 안정화 지르코니아 분말제조가 가능하다. 안정화 지르코니아 분말은 ZrO2와 안정화산화물의 고용을위하여 가열처리를 필요로 하며 일정온도에서 최적상태로 숙성하므로서 2가지 상(phase) 이상의 고용체를 가지게 된다. 안정화 지르코니아 분말은 고용처리온도를 낮추고 효과적으로 생성시키기 위해서는 지르코늄 및 안정화제염을 혼합하고 습식 직접합성하여 저온에서 고용체의 합해진상 영역을 생성시키는 것이다. 이는 지르코니아 원료분말의 미세구조를 제어하므로서 가능하며 이때 화학성분조성과 크기형태가 균일하게 분포된 입자분말을 얻을 수 있다.

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Study on the Effect of Fineness and Substitution Rate of Natural Zeolites on Chemical Reaction and Physical Properties of Cement Mortar (천연 제올라이트의 분말도와 치환율이 시멘트모르타르의 화학반응 및 물리적 특성에 미치는 영향에 관한 연구)

  • Yoon, Chang-Bok;Lee, Han-Seung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.3
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    • pp.96-103
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    • 2020
  • As a basic study for the application of natural zeolite as a concrete admixture, the compressive strength, activity factor, Ca(OH)2 quantitative analysis and XRD experiments were investigated. It is thought that SiO2, which is abundant in natural zeolite, affects the strength development by reacting with the hydration product of cement in all specimens in which natural zeolite was added according to powder level and substitution rate. As the substitution rate increases, the compressive strength decreases, which is considered to be due to the decrease in the amount of C3S and C2S minerals in the clinker, which affects the strength expression compared to the cement content of the reference mortar. The XRD crystal structure did not show a significant difference from the reference mortar, and it was confirmed that the Z2-10 (Blaine: 15,600㎠ / g) specimen with 10% substitution of natural zeolite was the best among the experimental levels. Substitution amount for use as concrete admixture is 10% substitution is most ideally seen.

Calcination Properties of Cement Raw Meal and Limestone with Oxidation/Reduction Condition (산화/환원 소성분위기에서 석회석 및 시멘트 원료물질의 소성거동 특성)

  • Moon, Ki-Yeon;Choi, Moon-Kwan;Cho, Jin-Sang;Cho, Kye-Hong
    • Resources Recycling
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    • v.29 no.5
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    • pp.64-72
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    • 2020
  • When the multi-stage combustion process is applied to the cement kiln to reduce nitrogen oxide emissions in the cement industry, oxidation/reduction section that can increase combustion efficiency by reducing NOx to NO and completely burning unburned materials is essential In this study, when applied the oxidation/reduction system of the cement kiln preheater and calciner, the optimal oxidation/reduction calcination crisis that can secure the quality stability of the final product, cement clinker, was to be observed macroscopically, and the mass change of raw materials according to the burning conditions, decarbonation rate, and calcination rate were investigated. The results showed that the thermal decomposition of raw materials tends to be promoted in the oxidation condition rather than in the reduction condition, and that the thermal decomposition of limestone, which has a relatively high CaO content, is carried out later than that of cement raw meal, which is thought to be caused by the CO2 fractionation in the kiln. The thermal decomposition properties of raw materials according to oxidation/reducing burning condition showed a relatively large difference in temperature range lower than normal limestone themal decomposition temperature, which is thought to be expected to improve the thermal efficiency of raw materials according to the formation of oxidation condition in the section 750℃ of burning temperature. However, for this study, lab scale. Because there is a difference from the field process as a scale study, it is deemed necessary to verify the actual test results of the pilot scale.

Service Life Variation Considering Increasing Initial Chloride Content and Characteristics of Mix Proportions and Design Parameters (초기 염화물량의 증가와 배합 및 설계 변수 특성을 고려한 콘크리트 내구수명의 변동성)

  • Park, Sun-Kyung;Kwon, Seung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.3
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    • pp.236-245
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    • 2021
  • It is very important for structure designer to understand the service life variation since a wide range of service life is evaluated with changing exposure conditions and design parameters. Recently, for zero-carbon, waste plastic has been used for fuel for clinker production and this yields increase in chloride content in cement. This study is for evaluation of changing service life in the concrete with increasing initial chloride content due to usage of plastic-SRF(Solid Refuse Fuel) considering various exposure conditions and design parameters. For this, 4 levels of initial chloride content were assumed, and the service life was assessed using LIFE 365 program considering various environmental conditions including 3 levels of surface chloride content. As for analysis parameters, critical/initial chloride content, blast furnace slag powder replacement ratio, W/B(Water to Binder) ratio, cover depth, and unit mass for binder are adopted. Service life decreases with increasing initial chloride content and a significant reduction of service life is not evaluated permitting up to 1,000ppm of initial chloride content. With increasing slag replacement ratio, a longer service life can be secured since blast furnace slag powder has the effect of reducing the diffusion of external chloride ions and fixing the free chloride. It is thought that increasing initial chloride content up to European standard is helpful for enhancing sustainability and reducing carbon emission. Though the reduction in service life due to an increase in the initial chloride content is not significant in slag-concrete with low surface chloride content, careful consideration for mixing design should be paid for the exposure environment with high surface chloride content.

Characteristics of Manufacturing for Special Cement Using High Chlorine by-product (고염소 부산물을 이용한 특수시멘트 제조 특성)

  • Moon, Kiyeon;Cho, Jinsang;Choi, Moonkwan;Cho, Kyehong
    • Resources Recycling
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    • v.30 no.6
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    • pp.68-75
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    • 2021
  • This study aims to investigate the manufacturing process of calcium chloride-based special cement, i.e., CCA (calcium chloro aluminate, C11A7·CaCl2), which uses limestone, by using one type of random industrial by-product, domestic coal ash, cement kiln dust. The manufacturing process of was examined in detail, and the results suggested that the amount of CCA synthesized increased with an increase in the firing temperature. The manufacturing process of CCA was investigated at 1200℃, which was determined as the optimum firing temperature. The results showed that in general, the amount of CCA synthesized tended to increase with an increase in the firing time; however, the clinker melted when the firing time was more than 30 min, thereby suggesting that a firing time of less than 20 min would be suitable for the clinkering process. The optimal firing conditions for manufacturing CCA were obtained as follows: heating rate of 10 ℃/min, firing temperature of 1200 ℃, and holding time of 20 min. The results also suggest that manufacturing CCA will be easier when high chlorine-containing cement kiln dust is used.

Effect of Blast Furnace Slag and Desulfurized Gypsum on Hardening of CFBC Boiler Coal Ash (CFBC 보일러 석탄회의 경화에 대한 고로슬래그, 탈황석고의 영향)

  • Lee, Woong-Geol;Kim, Jin-Ho;Kim, Kyung-Nam;Song, Myong-Shin
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.4
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    • pp.443-450
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    • 2021
  • The effects of blast furnace slag(BFS) and desulfurized gypsum(FDG) on the compressive strength of CFBA, and self-hydration of CFBA were studied. CFBA has self-hydrating and hardening properties, and it can be seen that the compressive strength of CFBA can be improved by using appropriate amounts of BFS and FDG. In addition, the self-hardening properties of CFBA are similar to the hydration reaction of 4CaO·Al2O3·Fe2O3 (C4AF), a cement clinker mineral, and when free-CaO, CaSO4 and CaCO3 coexist, Compressive strength of CFBA is expressed by the formation of calcium carbo compounds and hydrates of ettringite, calcium silicate, and calcium aluminate.

Evaluation Method of Healing Performance of Self-Healing Materials Based on Equivalent Crack Width (등가균열폭에 기반한 자기치유 재료의 치유성능 평가 방법)

  • Lee, Woong-Jong;Kim, Hyung-Suk;Choi, Sung;Park, Byung-Sun;Lee, Kwang-Myong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.3
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    • pp.383-388
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    • 2021
  • In this study, constant head water permeability test was adopted to evaluate self-healing performance of mortars containing inorganic healing materials which consist of blast furnace slag, sodium sulfate and anhydrite. Clinker powder and sand replaced for a part of cement and fine aggregates. On constant head water permeability test for self-healing mortars, unit water flow rate of mortar specimens were measured according to crack width and healing period. As a result of evaluating the healing performance of self-healing mortar, it was confirmed that with the initial crack width of 0.3mm, the healing rate at healing period of 28 days increased by more than 30%p compared to plain mortar, greatly improving the healing performance. Furthermore, the coefficient(α) which was estimated from the relationship between crack width and unit water flow rate was used for calculating equivalent crack width. By analyzing the correlation of healing rate and equivalent crack width, the time and initial crack width attaining healing target crack width were predicted.