• Journal of the Korean Ceramic Society
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• v.17 no.2
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• pp.69-74
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• 1980

This study deals with the wire content, wire diameter, aspect ratio , it's arrangement of steel, wire fiber and the sorts of castable which affected the character of steel wire fiber reinformced refractory castable. Two kinds of alumina based refractory castables, one is for 1650℃ and the other is for 1800℃, and stainless steel which is SUS 304 type 0.25, 0.34 , 0.37 and 0.50m/min diameter were used respectively. Aspect ratio was adjusted to 50, 75, 100 and steel fiber content was also adjusted to 1-4wt% each. The results of the experiment were as follows : 1. At firing temperature around 1,000℃, MOR is increased with increasing wire content and aspect ratio with decreasing firing temperature, which depends on the Romualdi's Fiber Spacing Theory. But for calculation of the fiber spacing, Swamy equation is more a aplicable to the extensive fiber mixing conditions. However, the condition differs from the above at firing temperature around 1,350℃ ,because of the degradation of wire and the progress of sintering of castable. 2. Linear change is getting larger corresponding to the increase of wire content, and the spaling resistivity is increasing corresponding to the increase of wire content and to aspect ratio, and with decreasing wire diameter. 3. Firing shrinkage under load is getting greater as higher wire content, and the shrinkage of the test pieces which fiber is vertically oriented is getting greater than the test pieces which fiber is randomly oriented.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.345-351
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• 1998

Thermal shock resistance of $Al_2O_3$- and Fe-$Al_2TiO_5$-based Castable Refractories was studied using a central heating technique. Ring type specimens, 10mm thick and 20 and 100mm inner and outer diameters, respectively, were rapidly heated on the internal surface of the centre hole using a high power electrical heating element. The temperature field was measured experimentally and modelled using finite element analysis (FEA). The thermal stress field was also modelled using FEA. A radial notch was introduced to the ring specimens to enable calculation of the thermal stress intensity factors (SIF). A special LVDT device was incorporated in the thermal shock tester to monitor crack mouth opening displacement (COD). The thermal shock fracture initiation and crack propagation behaviour of the castable refractories were ascertained using the COD measurements and the fracture mechanics analysis data.

• The Journal of the Korean dental association
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• v.25 no.11 s.222
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• pp.1019-1028
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• 1987

결손된 치질과 변색된 법랑질을 수복하기 위해 많은 재료와 술식이 개발되어왔다. 즉 silicate cement, PMMA resin, BISGMA composite resin, glass ionomer cement, porcelain등이 이용되어 왔으나 이것들은 biocompatible하지 않아 이상적인 재료는 아니다. 따라서 인간의 결손된 enamel을 수복할 수 있는 새로운 생역학적인 재료가 필요하게 되었다. 필자는 최근 관심의 대상이 되고 있는 porcelain laminate veneer system(층상 도재 전장관)에 관하여 문헌을 중심으로 고찰해 보고자 한다(국내에서는 장완식 교수께서 1987년 6월10일 보철학교실 세미나에서 video tape를 통해 소개한바 있음). 여기서는 Hobo, Iwata(1985)등이 소개한 castable apatite ceramic material을 이용한 laminate veneer술식에 관해 기술하고 내화성 모형(refractory cast)을 이용한 laminate술식과 비교 기술하고자 한다.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.791-797
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• 2003

The special binding mechanism developed provides higher density, lower porosity and higher strengths compared with conventional castables. $\rho$-alumina was employed as a binder materials and nano-sized clay colloidal was added to enhance the drying strength preparing for the alumina vibrated castable. Lower water requirement for casting results in a denser product. The mechanical properties with dimensional stability and corrosion resistance behaviors have been improved by controlling the matrix compositions of the castable. The modulus of rupture and compressive strength after heat treatment at 150$0^{\circ}C$ are 92.34 kgf/$\textrm{cm}^2$ and 370 kgf/$\textrm{cm}^2$ respectively. The activation energy of mullite formation is 11.47 kcal/mol.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.2
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• pp.99-104
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• 2017

Refractories used in low-rank coal gasification reactors are usually exposed in a highly corrosive $H_2S$ gas at less than $1000^{\circ}C$, and their mechanical properties such as erosion resistance and fracture strength decline with the exposure time. However, the cause of the degradation of the mechanical properties has little reported yet. In this paper, two kinds of castable refractories with different refractoriness had been exposed in a $H_2O/N_2/H_2S$ mixed gas with high $H_2S$ content for 100 hours at $900^{\circ}C$, and the changes of microstructure, crystalline phases and erosion resistance were compared before and after the corrosion test. The weight of the refractories decreases due to the elution of silica in the specimens after the corrosion test. The capillary porosities of the samples are reduced, but the erosion resistance of the samples is fatally weakened after the corrosion test. There also are changes in constituent phases; dmitryivanovite ($CaAl_2O_4$) and amorphous silica ($SiO_2$) disappear, and gypsum ($CaSO_4{\cdot}2H_2OS$) and kaolinite ($Al_2Si_2O_5(OH)_4$) newly appear after the corrosion test. It is obvious that the phase change from dmitryivanovite that works as a binding agent in the castable refractory to gypsum is the main reason of the degradation of the erosion resistance, because the mechanical properties of gypsum are much poorer than those of dmitryivanovite.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.27-31
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• 2015

The degradation of refractories can be caused by erosion, friction of abrasive particles, as well as by corrosion by molten slag in the gasification reactors. There was little knowledge about the erosion of refractories so far. The castable refractories of which the maximum applying temperature of 1300 and $1500^{\circ}C$ were abraded using SiC particles varying the incidence angles. It was revealed that the maximum abrasion was occurred at the incidence angle of $60{\sim}75^{\circ}$ not at $90^{\circ}$ and thought that the porosity of the refractories was the principle factor.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.867-870
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• 2009

일반적으로 내화재의 내침식성은 크롬 함량이 증가함에 따라 향상되는 특성을 가지는데, 본 연구에서는 이러한 크롬 내화재의 물성을 보다 향상시키기 위하여 인산염 화합물인 $AlPO_4$를 첨가하는 실험을 진행하였으며, 이러한 실험 결과 선정된 $AlPO_4$ 1% 첨가 크롬 내화재를 대상으로 캐스타블 및 브릭 형태로 각각 제작하였을 때 내침식 특성에 대해 회전 침식 시험장치를 이용한 실험을 실시하였는데, 실험 결과 캐스타블에 비해 브릭 내화재가 내침식성이 우수하지만 일부 spalling이 발생하는 것으로 파악되었다. 그리고, 가스화기로의 석탄 공급 방식에 따라 내화재 벽면에서 발생하는 석탄입자에 의한 내화재 침식 정도에 대한 전산해석을 수행한 결과 top feeding에 비해 side feeding 방식이 내화재 전면에 걸쳐 침식 현상이 크게 발생할 것으로 예측되어 보다 크롬 함량이 많은 내화재를 선정해야 할 것으로 평가되었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.5
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• pp.687-694
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• 1999

An experimental study was carried out in two laboratory-scale reactors to investigate the effect of heating rate on the behavior of flame front in a pulverized coal flame. Each. reactors had different heating mechanisms. For reactor A losing large heat through transparent quartz wall. pulverized coal particles were ignited by secondary air of 1050K. Flame front could be visualized through the transparent wall. Reactor B was insulated with castable refractory to minimize the heat loss through the reactor wall and accompanied with secondary air of 573K. Flame front was estimated from the gas temperature and species concentration measured using R-type thermocouple(Pt-Pt/Rh 13%) and gas chromatograph at various coal-air ratios and swirl intensities. The flame front position was closely related with the magnitude of heating rate. The heating rate for lifted flame was of the order of $10^4$ to $10^5K/s$ and for coal Ignition at least over $10^4K/s$. The heating mechanism had little impact on the extinction limits. The weak swirl number of 0.68 forced the flame front to move toward the upstream by the rapid mixing of coal and air. The primary/secondary momentum ratio was an inappropriate variable to distinct the liftoff of flame.

• Journal of the Korean Ceramic Society
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• v.17 no.2
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• pp.96-100
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• 1980

The castable refractory, CaO.$2Al_2O_3$ is a useful alumina cement for iron, steel and cement for iron, steel and cement industries, however it is difficult to produce CaO.$2Al_2O_3$because of its high melting point(180$0^{\circ}C$) and narrow firing range. In this study, the coprecipitation method was used to produce CaO.$2Al_2O_3$ for lower temperature firing . This method involved the titration of mixed solution of calicum and aluminate which extracted from domestic kaolin with $NH4_OH$ solution under blowing $CO_2$ gas into the solution. The coprecipitate and its clacined products were analyzed by X-ray diffraction and DTA. The calcined products fired between 400 and 90$0^{\circ}C$ were amorphous, but at 100$0^{\circ}C$ the coprecipitate was converted into one compound, CaO$2Al_2O_3$. From those experimental results, it was found that we could synthesizze CaO.$2Al_2O_3$ at about 100$0^{\circ}C$ which is lower than conventional firing temperature by around 80$0^{\circ}C$. The refractoriness of this alumina cement was SK 34 and the compressive strength ( 1 day) was about 250kg/$\textrm{cm}^2$.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.960-966
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• 2013

In this study, operation data from an actual plant in M city were analyzed to evaluate effects of water supply into sewage sludge on the co-incineration of municipal solid waste (MSW) and sewage sludge. Design capacity of the stoker incinerator is 50 m3/day. Maximum portion of sewage sludge in the total waste input was 20%. According to this research, moisture content increase up to 85% of sewage sludge could be possible by water supply on MSW input to the incinerator. Therefore, stable operation of incinerator could be achieved. As water was added into sewage sludge up to 85%, input quantity of sewage sludge to frequency (Hz) was similar to theoretical input. Also, it is concluded that stable management of incinerator without leachate combustion and damages of refractory bricks and castable could be achieved by the reduction of low heating value.