Preparation method for low-silicon, high-calcium and large-crystal fused magnesia

Abstract

The invention discloses a preparation method for low-silicon, high-calcium and large-crystal fused magnesia. The preparation method comprises the following two steps: preparation of high-activity MgOand smelting with an electric arc furnace, i.e., during preparation of high-activity magnesium oxide powder, adding a sodium carbonate solution with a concentration of 3 to 8%, then adding high-puritygraphite powder into the prepared high-activity magnesium oxide powder as a reducing agent, carrying out balling with a device, after balling is completed, carrying out smelting with a fully-automatic electric arc furnace, carrying out cooling and crystallizing, and carrying out crushing and picking so as to obtain a finished product. According to the invention, through addition of the sodium carbonate solution, the point of melting is effectively reduced; the temperature of calcination is reduced; and energy is saved. Meanwhile, through a reaction between sodium carbonate with silicon dioxide impurities, sodium silicate and carbon dioxide can be generated; the silicon dioxide impurities in magnesite can be effectively removed; and the content of magnesium oxide is improved. The low-silicon, high-calcium and large-crystal fused magnesia provided by the invention reaches an MgO content of 99.90% or above, achieves a calcium-to-silicon ratio of 2.30 or above, has good high-temperature fire resistance and high-temperature scouring resistance, and can be used as a high-quality advanced refractory material to be applied in the industries of aerospace, electronics, steel and iron, metallurgy, etc.

Description

technical field [0001] The invention relates to the technical field of production of fused magnesia, in particular to a preparation method of low-silicon, high-calcium and large-crystal fused magnesia. Background technique [0002] The appearance of large crystal fused magnesia is transparent crystal, which is a high-end product in the field of fused magnesia. It is used in metallurgical aerospace industry, nuclear industry, far-infrared receivers, substrate materials for superconducting materials, and high-temperature windows. [0003] Most of the existing high-purity fused magnesia smelting directly uses natural magnesite or light-burned magnesia to smelt directly in a three-phase electric arc furnace, and fused magnesia is obtained after cooling out of the furnace. The chemical composition of this fused magnesia is roughly as follows: w (MgO) 96-97%, w (CaO) 1-1.5%, w (SiO 2 )1-2.5%, w(Fe 2 o 3 )≤0.5%, w(Al 2 o 3 )≤0.5%. The shortcomings of the current fused magnesi...

AI Technical Summary

Problems solved by technology

The shortcomings of the current fused magnesia smelting method mainly include: (1) long smelting time: in order to obtain large crystal fused magnesia with higher purity and larger grain size, the existing process only continuously increases the fused time, Extending the holding time, etc., this method needs to consume more electric energy, and long-term smelting will produce more CO 2 and dust pollute the environment; (2) Add crushed electrodes as a reducing agent: the existing process uses crushed electrodes as a reducing agent, and the crushed electrodes are not easily broken, the particle size is uneven and there is no graphitization, and its ash, volatile matter, and impurity contents are relatively high

In the production process, the amount of addition is not accurate. If the addition is too much, the reducing atmosphere in the furnace will be too thick, which will not fully burn and cause energy waste. If the amount is too small, the reducing atmosphere in the furnace will not be sufficient, and Fe 2 o 3 The reduction makes the fused magnesia dyed pink, which affects the output rate of the fused magnesia

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