Preparation method of low-silicon high-calcium macrocrystalline fused magnesite

Abstract

The invention discloses a preparation method of a low-silicon high-calcium macrocrystalline fused magnesite. The preparation method comprises the following steps: putting magnesite with the MgO content of over 45% into a light roasting furnace for continuous calcinations for 4 h, uniformly adding an Na2CO3 solution during calcinations, and smashing a product after calcinations to obtain a high-activity MgO powder; adding the high-purity graphite powder into the high-activity MgO powder, putting the mixture into a full-automatic electric smelting electric-arc furnace for smelting for 5 to 8 h,and carrying out classification crushing after the smelting is ended so as to obtain the low-silicon high-calcium macrocrystalline fused magnesite. According to the preparation method, a sodium carbonate solution is added, so that the melting point is effectively reduced, the calcination temperature is reduced, and the energy is saved; moreover, sodium silicate and carbon dioxide can be generatedthrough the reaction of sodium carbonate and impurity silicon dioxide, and the silicon dioxide impurity inside the magnesite can be effectively removed, so that the content of magnesium oxide is improved; the content of MgO inside the product reaches 99.90% or more than 99.90%, the calcium-silicate ratio reaches 2.30 or more, the fused magnesite has high high-temperature fire resistance and high-temperature scouring resistance, and the fused magnesite can be applied to the industries such as spaceflight, electrons, steel, metallurgy and the like as a high-quality advanced refractory material.

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 main disadvantages of the current fu...

AI Technical Summary

Problems solved by technology

The main disadvantages of the current fused magnesia smelting method are: (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 smelting 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 reducing agents: the existing technology uses crushed electrodes as reducing agents, crushed electrodes are not easy to break, 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 of addition is too small, the reducing atmosphere in the furnace will not be sufficient. 2 o 3 Complete reduction, causing the fused magnesia to be dyed pink, affecting the output rate of fused magnesia