Manufacturing method of magnesium-aluminium spinel brick and magnesium-aluminium spinel brick manufactured by the method

A manufacturing method of a magnesium-aluminium spinel brick, wherein the magnesium-aluminium spinel brick comprises a flame retardant coating and a thermal insulating layer, the manufacturing method of the magnesium-aluminium spinel brick comprises specific manufacturing steps as follows:

• step (1) preparing flame retardant coating raw materials using the following components by mass percent, evenly mixing 40%-70% of sintered magnesia having a granularity ≤5 mm, 10%-40% of fused magnesia having a granularity ≤3 mm, 10%-20% of magnesium-aluminium spinel having a granularity ≤4 mm, and 0%-10% (excluding 0%) of corundum having a granularity ≤2 mm to prepare flame retardant coating raw material mixed powder, then additionally adding 1%-5% of naphthalene binder by taking the flame retardant coating raw material mixed powder as a basis, for an even mixing to prepare the flame retardant coating raw materials;
• step (2) preparing thermal insulating layer raw materials using the following components by mass percent, evenly mixing 40%-60% of forsterite, 10%-40% of fayalite, and 10%-50% of magnesia to obtain mixed powder, adding 1%-5% of naphthalene binder by taking the mixed powder as a basis to obtain a mixed material, moulding the mixed material by a frictional press, drying the mixed material at 110° C.-150° C., and then burning the mixed material at a temperature of above 1000° C. to obtain aggregate composite hortonolite raw materials;
• taking aggregate composite hortonolite having a granularity ≤5 mm from the aggregate composite hortonolite raw materials as a single raw material, adding 1%-5% of naphthalene binder to the aggregate composite hortonolite having the granularity ≤5 mm for an even mixing to prepare the thermal insulating layer raw materials;
• and
• step (3) spacing and loading the flame retardant coating raw materials and the thermal insulating layer raw materials in a mold by using corrugated thin iron sheets, pressing the flame retardant coating raw materials and the thermal insulating layer raw materials into green bricks by a press machine, keeping the green bricks at a temperature of 110° C. for 24 hours, drying the green bricks, and burning the green bricks into the magnesium-aluminium spinel brick at a temperature of 1550° C.-1750° C. in a tunnel kiln;
• wherein a sequence of the step (1) and the step (2) are allowed to be inversed.