How to systematically protect refractory materials in high temperature use (2)

For thermal equipment in metallurgical and other industrial sectors, only continuous automatic control of the status of refractory lining and system protection with refractory materials can make the equipment operate reliably. In addition to cooling the lining in the previous part, the following aspects also need to be focused on:

2 The spraying of refractory lining

In many cases, spraying can significantly improve the lining life. The development of spray (mulch) can calculate the used part of the inner liner that has not been damaged by pouring new mud (as per model). Save raw materials.

3.Educe the erosion of the erosion

This is the new direction of refractory protection. Slag is one of the corrosive factors of refractory failure. The longer the contact time between slag and refractory material, the greater the damage to the lining. The results show that there is a linear relationship between the damage of ladle lining and the thickness of slag layer in ladle. Therefore, the lining of the same refractory material is reduced by slagging method, so that the lining life can be increased by 2 to 3 times. The slag layer in the ladle, covered with various fillers (secondary graphite, porous sintered clay, vermiculite and other materials) can also reduce the erosion of the slag.

In this case, the ladle slag does not react first with the refractory lining, but with the filling material – the neutralizer.

In the dynamic stage of the interaction between slag and refractory, the theoretical premise of the erosion reduction is to implement the complex form of silicon, aluminum and iron in the slag, and reduce the free O2- share in the slag composition by cationic method. In this case, the formation of complex anions AlxO2-y, SixO2-y, FexO2-y to constrain the free oxygen, reduce the erosion of the slag. Neutralization in slag melt occurs. For example, when a ferroolivine composition is implemented in the melt, alumina significantly increases the amount of AlO3- in the melt, while reducing the share of free oxygen.

Another effect of the neutralizer is its effect on the viscosity of the erosion. For example, the introduction of CaO greater than 30% or MGO 20% or Cr2O37% in calcium oxy-silicate slag can increase the viscosity of the slag to 1Pa·s, resulting in much less refractory dissolution. Therefore, 20% neutralizer is added to calcium oxide-silicate slag; At 1600℃, the dissolution strength of the clay refractory is 0.2mg/(cm2·s), while the original slag is 2.6mg/(cm2·s).

4.The specified temperature and gas system quota steelmaking production temperature and oxygen supply, these important enhancer values, in the final analysis depends on economic calculations.

The most appropriate value for these data is a compromise.

There are various methods for protecting refractory materials, and the lining of thermal equipment with cyclic operation should keep the temperature fixed.

For example, ladle, converter, etc., the cover should be closed during the interval between filling, and if the interval is longer, the special burner should be heated.

5.Reasonable refractory masonry structure

In general, it is related to the need to improve the thermal shock resistance of the lining, because the traditional method is to improve the thermal shock resistance of a single product, often does not guarantee the thermal shock resistance of the masonry. The protection of refractory materials in masonry is solved by various methods to prevent damage due to mechanical stress.

When one side heat flow is fixed, the elongated thermal stress in the inner lining can be reduced effectively according to the line method of wall thickness temperature gradient.The linear temperature gradient may be achieved by creating a variable porosity structure.

The thermal stress can be reduced by the thickness of the refractory lining in the heat flow direction. However, the change of lining thickness does not always guarantee the reduction of stress. In addition, the heat loss increases. If there is no role of slag, it is reasonable to use a material, select a comparable shape according to the thickness, and constitute a refractory wall structure by several layers. Under a fixed temperature regime, the temperature and stress distribution are calculated on the hot surface of a multilayer sheet at 1400° C. In order to ensure the overall thermal shock resistance of the plate, it must be replaced by three layers with a thickness equal to 8mm, 1.3mm and 4mm.

With the choice of material and thickness of brick joint, the masonry stress can be substantially reduced. The possibility of improving the life of refractory materials is greater, not only in improving the structure of masonry, but also in rationalizing the shape and size of individual products. For example, using effective methods to reduce the trend of magnesium refractory peeling under the conditions of use, when the temperature of one side of the product is unchanged, and the obvious change on the opposite side, in individual fragments, the appropriate sawing depth of the hot side of the product is less than 10mm.

From the point of view of uniform stress distribution, it is more desirable to compare six-sided products with four-sided products, and six-sided prismatic products should be widely used in iron and steel metallurgy equipment. It is reasonable to make five-sided iron sheet impervious to air without burning oil magnesium dolomite products, and many similar examples can be cited.