Hebei Messi Biology Co., Ltd. stated that silicon steel grade magnesium oxide is specially used as a high temperature annealing isolation agent in the preparation process of oriented silicon steel sheets. The main function of silicon steel grade magnesium oxide in the high temperature annealing of oriented silicon steel sheets is to prevent the sintering of silicon steel sheet coils during high temperature annealing and remove impurities such as S and P in silicon steel sheets. At present, the methods used to prepare magnesium oxide at home and abroad include brine soda ash method, dolomite carbonization method, brine carbon ammonium method and other precipitation methods. The above methods have problems such as long process flow, low raw material utilization rate, high production cost, environmental pollution, and low magnesium content of products.
The technical problem to be solved by the present invention is to provide a method for preparing silicon steel grade magnesium oxide by pyrolysis method with simple production process, good product quality, low cost and no pollution to the environment. The method comprises the following steps:
(1) using magnesium oxide obtained by spray pyrolysis of saturated magnesium chloride solution at 480°C to 750°C as raw material;
(2) adding a hydrating agent and the raw material obtained in step ① into water, hydrating the raw material under the conditions of a water bath temperature of 30°C to 70°C, a liquid-solid mass ratio of 4 to 8:1, and a rotation speed of 30 to 90 rpm, hydrating the raw material for 2 to 4 hours, aging the raw material for 4 to 8 hours, and obtaining a precipitate; the mass of the hydrating agent is 1% to 4% of the mass of the raw material;
(3) filtering the precipitate with 4 to 8 times the mass of washing water to obtain a filter cake;
(4) drying the filter cake to constant weight at 100°C to 120°C, and calcining the filter cake at 900°C to 1200°C for 2 to 4 hours to obtain a sintered product; the sintered product is naturally cooled, crushed, graded and packaged.
The preparation of silicon steel grade magnesium oxide by pyrolysis is characterized in that the magnesium oxide content in the raw material of the step is 85% to 97%. The hydrating agent in the step is one or more of sodium acetate, magnesium acetate and acetic acid.
The preparation of silicon steel grade magnesium oxide by pyrolysis has the following advantages compared with the prior art:
The present invention uses magnesium oxide obtained by pyrolysis of saturated magnesium chloride solution as raw material, making full use of the abundant salt lake brine resources in western my country, and the preparation process requires only magnesium chloride as raw material except a small amount of hydrating agent, so the cost is low. Since the hydrating agent is added in the present invention, the hydration degree is effectively improved and the product quality is guaranteed. The production process is simple, environmentally friendly, and the equipment requirements are low, and it is easy to realize industrial production.