Furnace furnace. Furnace lining: materials, technology

In the design of furnace furnaces, the focus is on structural design, the operation of individual components of the structure and the provision of a smoke-evacuating function. Initially, materials for the construction of the structure are also calculated, since the specificity of its operation predetermines the stringent requirements for the characteristics of the unit. At the same time, not always the main material is able to cope with the thermal effects on which a particular furnace is calculated. Lining, as a technological operation of additional processing, allows and minimize thermal negative factors, and prevent mechanical damage to the structure.

In which cases is the lining performed?

The initial choice of building material for the technical implementation of the design is done taking into account its ability to cope with operational loads. As noted above, basic characteristics are not enough. Use additional thermal insulation materials in certain cases, associated with an increase in temperature loads on the surface of the structure. In particular, this applies to furnaces designed to operate in long-fire mode. Also high temperatures give high-calorie fuel, although such units are used rarely and mostly at enterprises.

As for domestic stoves, they usually do not require the implementation of additional protective coatings, but only if it is a construction of small and medium size. Otherwise, if the massive Russian furnace is considered. Lining in this case allows to provide protection functional areas, which can also be used for cooking.

Basic materials for lining

A fireclay fireclay brick is considered a classic material for lining . With its help, an external shielded protection is formed. This option is suitable for sauna ovens, which require in some way complete thermal insulation. In the conventional design, the refractory lining with chamotte is a lining of the furnace part in order to protect against elevated temperatures.

As the development of technologies, other means of providing protection for the furnace facilities appeared. So, if before the concrete solutions were prepared, of which later normal plaster was laid, then in the modern form the same method looks somewhat different. The main difference is that the mixture is applied to the incandescent surface using shotcrete technology. That is, heat-resistant concrete is applied to the target surface layer by layer, using pneumatic means on the basis of compressed air.

Roll lining

A fundamental difference from classic coatings and masonry with thermal insulation function is provided by roll coatings. First, they are easy to apply. Secondly, the coating takes up a minimum of space, increasing the thickness of the structure by no more than 1 cm. For comparison, heat-resistant concrete in the form of plaster increases the thickness of the walls of the oven structure by 1-2 cm, and the brick by this indicator can reach 10 cm. Is presented in several forms, usually on a paper fire-resistant basis.

The most widespread in this segment was mullitokremnezemistaya kaolin wool, which is obtained as a result of the melting of silicon and oxide in the electric furnace. In practice, it is noted that this material has a low thermal conductivity and at the same time increased thermal stability. Also kaolin insulating materials are not subject to destruction under the influence of chemicals, for which they are valued in industrial production.

Induction furnace protection features

First of all, it should be noted that the need to perform the lining of induction furnaces does not arise from the weakness of the structure before thermal impacts, but because of the specificity of their application. Such units are used for melting metals under high temperatures, therefore special means in the form of dry mixtures are used for their protection. In essence, this is a classic coating, but the composition for the mass is fundamentally different from concrete solutions. Thus, the lining of induction furnaces, which melts low-alloy and carbon steel, involves the use of spinel-forming masses. The latter, by the way, are resistant to the formation of slag. Units for cast iron smelting are treated with quartzite compositions, and if color grades with steel are added to this metal, then the technologists add lining and mullite-forming components to the recipe.

Technology execution

There are different techniques and approaches to the implementation of lining, which differ in the coverage of the surfaces and in the manner in which the insulating material is applied. The protective lining can be external and internal. The outer lining is usually applied over the entire height - from the bottom to the crowning edges. Interior finish can provide protection of working surfaces that contact both with the flame directly and with smoke in the form of exhausting high-temperature gases. The greatest effect is given by the protection circuits that complexly isolate the furnace. Lining is performed only on cleaned surfaces. Preparation of the material, as a rule, involves diluting the active substances in solvents. Thus, a mixture for coating is formed, which is applied by means of traditional facing tools on the surface of the structure. The brick, in turn, is laid down according to standard schemes in accordance with the requirements for the protection of structures.

Conclusion

Outer coatings of furnaces should not only provide resistance to thermal effects, but also provide protection against other factors. For example, in the conditions of industrial premises, the risk of mechanical impacts to which the furnace may be exposed increases. Lining in this case involves the performance of tasks of physical protection of the structure. Therefore, special plasticizers can be added to the mixture, modifying the strength properties of the composition. But this applies only to the means of creating external thermal insulation, and the inner coatings are completely oriented towards the formation of effective temperature screens.