Papers by Keyword: Magnesia Refractory

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Authors: Guo Chao Qi, Feng Jun Shan, Qiang Li, Jing Yuan Yu
Abstract: The present study is related to a process development for producing high purity fused magnesia. A newly designed 3000 kVA electric arc furnace is used in the field experiment. The electric resistance characteristic of fused magnesia is analyzed and the effect of electrode diameters and electrode depth buried in molten magnesia on melting electric resistance and electric arc heat conversion are discussed in detail. It shows that, for the new 3000 kVA electric arc furnace, 350~450 mm diameter electrode and ~300mm depth in molten magnesia are suitable.
Authors: Jacek Szczerba
Abstract: The paper describes formation of the phases in magnesia-zirconia refractories due to reaction with the cement furnace charge in a form of pre-calcined meal or Portland clinker containing sulphur and chlorine in a different content at the temperature 1300°C and 1450°C. The studies were carried out by using the coating test. The microstructure changes of the contact zones between coating and the brick were studied by the scanning electron microscopy, SEM, coupled with EDS. The temperature dependence of reactivity the pre-calcined meal and Portland clinker in relation to the magnesia-zirconia bricks has been documented and discussed.
Authors: Bao Guo Zhang, Zhou Fu Wang, Shao Wei Zhang, Xi Tang Wang, Zi Wei Xu
Abstract: The effects of Y2O3, La2O3 and Nd2O3 on the sintering, microstructure and mechanical properties of magnesia refractories were investigated. Addition of rare earth oxide (ReO) to magnesia refractories increases the bulk density, decreases the porosity and improves the mechanical strength of the refractories. The improved sinterability was attributable to the vacancies generation associated with the solid-solution reactions between MgO and ReO. In the samples with ReO, rare earth silicate phases form at magnesia grain boundaries, providing additional bonding between magnesia grains and between magnesia grains and matrix. Consequently, the samples with ReO showed much higher high temperature strengths than those without ReO.
Authors: Qing Dan Yuan, Shi Hua Liu, Qian Nan Li, Wei Han
Abstract: The method of X-ray fluorescence spectrometry (XRF) for the determination of MgO in magnesia refractories was introduced. The uncertainty of the MgO in refractory materials was analyzed by melting method of XRF. The measurement uncertainty was evaluated, and the related mathematical models was established. The uncertainty of synthetic standard was calculated by the evaluation of the uncertainty of each component standard. And eventually converted to the measurement results to expand the uncertainty. The effects of two melting methods on the uncertainty of magnesium oxide content were compared.
Authors: Guo Chao Qi, Feng Jun Shan, Qiang Li, Jing Yuan Yu
Abstract: Alumina spinel is widely used as a refractory material in metallurgy industries. Arc furnace melting method is suitable to produce high quality alumina spinel. However, the high melting temperature (> 2200 °C) and high electric energy consumption limit the application of this method. There exists huge opportunity for energy saving through process optimization. A newly designed 2400 kVA electric arc furnace is used as melting facility to produce alumina spinal in this study. It shows from the experiments and analysis that melting voltage has much effect on electric power input and electric efficiency. At voltages higher than 150V, stable electric power input and adequate efficiency can be maintained. Stable melting voltage is difficult to maintain at 100-150V range and power efficiency are also apparently lower. For voltage less than100V, the process is very difficult to control and energy efficiency are very poor. Too high voltage on the other hand can lead the electric arc expose directly to the surroundings and increase the energy loss. In practical melting process, controlling the melting voltage at 140-160V range is suitable for high quality alumina spinel production.
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