• The Journal of Information Technology
• /
• v.7 no.3
• /
• pp.113-118
• /
• 2004

Recently, diagnosis techniques have been investigated to detect a partial discharge associated with a dielectric material defect in a high voltage electrical apparatus. However, the properties of detection technique of PD aren't completely understood because the physical process of PD. Therefore, this paper analyzes the process on Surface Discharge of Polymer Insulator using Wavelet transform. Wavelet transform provides a direct quantitative measure of spectral content in the time frequency domain. As it is important to develop a non-contact method for detecting the Contamination Degree, this research analyzes the electromagnetic waves emitted from PD using Wavelet transform. This result experimentally shows the process of PD as a two-dimensional distribution in the time-frequency domain. The method is shown to be useful for detecting prediction of contamination degree.

• Clean Technology
• /
• v.29 no.3
• /
• pp.193-199
• /
• 2023

Biomass has been used to secure renewable energy certificates (REC) in domestic and overseas coal-fired power plants. In recent years, biofuel has been diversified from traditional wood pellets to non-woody biomass. Non-woody biomass has a higher content of alkaline metals such as K and Na than wood-based biomass, resulting in a lower melting point and an increase in slagging on boiler tubes, which reduces boiler efficiency. This study analyzed the effect of kaolin, an additive commonly used to increase melting points, on biomass co-firing to coal through thermochemical equilibrium calculations. In a previous experiment on biomass co-firing to coal conducted at 80 kW_th, it was interpreted that the use of kaolin actually increased the amount of fouling. In this study, analysis showed that when kaolin was added, aluminosilicate compounds were generated due to Al₂O₃, which is abundant in coal, and mullite was formed. Thus, it was confirmed that the amount of slag increased when more kaolin was used. Further analysis was conducted by increasing the biomass co-firing rate from 0% to 100% at 10% intervals, and the results showed non-linear liquid slag generation. As a result, it was found that the least amount of liquid slag was generated when the biomass co-firing rate was between 50 and 60%. The phase diagram analysis showed that high melting point compounds such as leucite and feldspar were most abundantly generated under these conditions.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.1
• /
• pp.215-225
• /
• 2011

Metakaolin is a dehydroxylated form of the clay mineral kaolinite. Rocks that are rich in kaolinite are known as china clay or kaolin, traditionally used in the manufacture of porcelain. The particle size of metakaolin is smaller than cement particles, but not as fine as silica fume. This paper investigates the effect of the concrete containing metakaolin as a mineral admixture on the compressive strength and resistance properties to chloride ion penetration. In this study, the experiment was carried out to investigate and analyze the influence of replacement ratio of metakaolin and micro silica fume on the compressive strength and chlorine ion penetration resistance of concrete. All levels were water/binder ratio 30%, replacement ratio of metakaolin and silica fume were 0, 5, 10, 15, 20% respectively. The compressive strength of concrete using metakaolin tends to increase, as the replacement ratio increases but the chlorine ion penetration resistance was not so as lager as silica fume concrete. Therefore, the optimum mixing ratio of metakaoline to satisfy a properties of compressive strength and chlorine ion penetration resistance was was approximately10%.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1998.10a
• /
• pp.133-136
• /
• 1998

0.1 내지 $4 \mum$의 입도분포를 가진 kaolin용액을 dead-end형 여과 장치(Amicon Cell, 8050)를 이용하여 공칭세공이 $0.2 \mum$인 PTFE막으로 농도 및 운전압력에 따른 투과실험을 하였다. Kaolin 용액의 투과유속은 케이크 저항이 지배적이었으며 초기에는 분리막 표면에 케이크가 형성되고 그 후에 분리막 세공의 오염이 발생하는 것으로 관찰되었다.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.12
• /
• pp.787-791
• /
• 2012

Characteristics of particle separation in water using labscale acoustic standing wave were studied. Acoustic standing wave is similar to either sound wave or ultrasonic, which makes a constant wave while returning to the origin by reflector. During that time, particulates dispersed in water are collected on the node of wave, where a sound pressure is zero. Acoustic standing wave transducer as of 28.0 kHz and 1.0 MHz were utilized and $6.8{\mu}m$ kaolin and $100.5{\mu}m$ redmud in average diameter were used as experimental materials in water. Once acoustic standing wave are generated in water, water temperature rises by $0.15{\sim}0.20^{\circ}C/min$ due to a sound pressure. Initial concentration of kaolin and redmud were controlled to have same as of 0.1, 0.2, 0.3, 0.4, 0.5 g/L, respectively. Removal efficiency of the turbidity in a reacting chamber after 5 minutes, when acoustic sound wave was formed in most distinct, was measured to have 18.2~56.2% for kaolin and 23.0~53.6% for redmud at 1.0 MHz. Particle separation was not observed at 28.0 kHz.

• Proceedings of the Korean Institute of Resources Recycling Conference
• /
• 2001.05a
• /
• pp.486-489
• /
• 2001

• Applied Chemistry for Engineering
• /
• v.9 no.4
• /
• pp.481-485
• /
• 1998

Hydrated aluminum sulfate, an inorganic polymer, was synthesized from kaolin in $H_2SO_4$ solution using microwave energy. The maximum rates of alumina extracted from calcined kaolin were 72.8% in a conventional process ($80^{\circ}C$, 1M, and 180min) and 99.9% in a microwave process ($90^{\circ}C$, 1M, and 60 min). Compared with the conventional one, the hydrated aluminum sulfate synthesized under the microwave process had layer structure consisting of plate-shaped large grains. After synthesis and then calcination at $1100^{\circ}C$, both products on conventional and microwave processes were ${\gamma}-Al_2O_3$ with agglomerated powders of spherical shape. The specific area of the products in conventional and microwave processes were 113.5 and $106.6m^2/g$, and their average grain sizes were 46.5 an $26.3{\mu}m$, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.38 no.3
• /
• pp.429-438
• /
• 2018

Cone and T-bar penetrometers have been frequently used to estimate the undrained shear strength of clay. For small-size model tests, miniature penetrometers should be used but their correlation factors have not been well published. In this study, a testing setup was developed to derive empirical factors of the miniature cone and T-bar penetrometers. A 350mm-diameter chamber and kaolin clay were utilized to prepare soil specimens consolidated under four different pre-consolidation pressures controlling undrained shear strength. Two miniature cones with two diameters of 10-mm and 16-mm and a T-bar penetrometer with 10-mm diameter were used to investigate boundary effect, penetration rate effect, and diameter and shape effect. Unconsolidated-undrained triaxial tests were carried out with samples taken from the specimens to measure undrained shear strength. Finally, empirical factors for the penetrometers were constructed to correlate tip resistance to undrained shear strength.

• Korean Journal of Materials Research
• /
• v.2 no.1
• /
• pp.3-11
• /
• 1992

Aluminum sulfate hydrate was prepared using sulfuric acid from Ha-dong kaolin. The effects of calcination-temperature and calcination-time of kaolin, reaction-temperature and reaction-time, and sulfuric acid concentration on the formation of aluminum sulfate hydrate were investigated. The precipitation condition of aluminum sulfate hydrate from sulfuric acid solution was determined. Also, the products heat-treated at different temperatures have been investigated by X-ray diffraction, thermogravimetry, differential thermal analysis, Fourier transform infrared spectrophotometer, scanning electron microscopy, particle size distribution analysis and chemical analysis. In the optimum condition, the conversion of aluminum oxide in kaolin to aluminum sulfate hydrate was 60%. From the results of XRD, TG-DTA, and FT-IR, it is suggested that the aluminum sulfate hydrate is thermally decomposed as follows ; $Al_2(SO_4)_3{\cdot}18H_2O{\rightarrow}Al_2(SO_4)_3{\cdot}6H_2O{\rightarrow}Al_2(SO_4){\rightarrow}\;amorphous\;alumina{\rightarrow}{\gamma}-alumina{\rightarrow}{\delta}-alumina{\rightarrow}{\theta}-alumina{\rightarrow}{\alpha}-alumina$. The purity of alumina powder prepared by calcining aluminum sulfate hydrate at $1200^{\circ}C$ was 99.99 percent.

• Journal of the Mineralogical Society of Korea
• /
• v.13 no.1
• /
• pp.22-36
• /
• 2000

중원지역 지열수의 CO2 가스의 용축과 수반된 탄산염 침전물의 광물학적 특성을 밝히기 위하여 탄산염 침전물에 대해 광물학적 및 지구화학적 분석방법을 적용하여 보았다. 이들은 매년 수 mm의 두께로 저수조내에 침전되며 미세한 층상으로 결정화되어 있고, 검은 갈색의 얇은 층들이 반복적으로 존재하고 있다. 침전물은 비교적 순수한 방해석으로 되어 있으며 1M HCl로 처리하여 잔류물을 XRD 분석한 결과는 카올린 광물 및 일라이트질 광물이 확인되었다. 전자현미분석에 의하면 검은 갈색층은 주로 방해석과 Fe나 Mn 산화광물의 집합체이며 소량의 점토광물도 함께 섞여 있는 것으로 추정된다. Fe의 경우에는 주로 방해석내 Ca자리를 치환하여 존재하며 일부 산화광물로 함께 침전된 것으로 보인다. 반면에 Mn의 경우는 일부는 Fe처럼 방해석결정구조 내에서 Ca를 치환하면서 존재하기도 하지만 주로 산화물의 형태로 존재하는 것으로 보인다. 후방산란전자상(BSEI) 관찰에 의하면 Fe와 Mn 모두 매우 미세한 입자의 산화광물들로 밀집해 있는 부분이 관찰되기도 한다. 중원지역 탄산수로부터 방해석이 침전되는 과정은 CO2 가스가 방출되면서 pH가 증가하면서 방해석 및 Fe, Mn 산화물이 과포화상태가 되어 침전되는 것으로서 해석할 수 있다. 또한 지하 심부를 순환하면서 활발한 물-암석반응의 결과로 Si나 Al 및 기타 이온들의 함량이 상대적으로 높았던 탄산수가 pH가 높아지면서 카올린 광물이나 일라이트질 광물, 석영등의 규산염 광물들이 함께 침전하였을 것이다. 그러나 방해석의 침전과정이 이루어지는 과정 동안에, 온천공으로부터 채수되는 탄산수의 양이 수요에 따라 매우 불규칙해서 탄산수의 수요가 많은 경우 탄산수가 지속적으로 과잉 채수되면 주변 천층지하수가 탄산수에 혼합되어 Fe, Mn 등의 농도를 상대적으로 낮추게 되어 산화물형태로 침전되기가 어려워져서 거의 순수한 방해석만이 침전하게 된다. 결과적으로 거의 순수한 방해석 층에 검붉은 층이 불규칙하게 반복되고 있는 중원지역 탄산염침전물은 침전작용이 일어나는 대부분의 기간 동안 지속적으로 주변 전층지하수의 유입이 일어났음을 지시하고 있다. 또한 Fe, Mn 등의 함량이 높은 탄산수로부터의 침전은 매우 짧은 기간동안 단속적으로 일어났음을 지시한다.