Development and Application of Hard Si-Ca Composite High Temperature Coatings

Various kinds of heat insulation materials and their products have their own uses, all have advantages and disadvantages. Rigid products are generally used in the main body of thermal energy equipment, and they also have the functions of structural bearing and fire-resistant insulation. Flexible fiber products are usually attached to rigid products or used for outsourcing of pipelines, mainly for insulation; coating materials are attached to rigid materials. Surface protection material and heat insulation. Because the coating material has the advantages of convenient construction, heat insulation protection of any shape parts, low production cost and good heat insulation effect, it has been rapidly developed in recent years. However, due to the low temperature resistance of the main fillers such as sepiolite, expanded pearl salt and asbestos, mineral wool, and fiber, the application range is limited. The vast majority can only be applied to a temperature of 400. In the range between -800°C. In the metallurgy, petrochemical and electric power sectors, there are a large number of equipment and pipelines that need to work at around IO00°C. The demand for thermal insulation coatings that can withstand heat and temperatures of IO00°C and have good thermal insulation properties and can be applied under hot conditions is very urgent. .

Hard silicon-calcium composite high-temperature coating is based on hard silicon calcium high-temperature thermal insulation powder as the main base material, supplemented with fillers, auxiliaries, binders, reinforcing agents, foaming agents, fiber materials, etc., in a certain proportion, after loose mixing, beating , foaming, and then stirred thick paste. It combines the dual characteristics of paint and insulation materials, smears it on the surface of equipment and pipes that require thermal insulation, and is dried to form a microporous insulation coating with a certain strength and elasticity. It has the characteristics of good overall performance, no chalking, no shedding, no insulation degradation, no dust, no corrosion of equipment, no environmental pollution, etc.

The product is widely used in petrochemical, metallurgy, building materials, power and other industries of high-temperature furnaces, pipes and other high-temperature equipment and facilities. Especially suitable for special equipment, such as valves, spheres, cones and so on. The energy-saving effect can reach 25% to 35%, with significant economic and social benefits.

1 raw materials and formula

In order for the coating layer to have excellent thermal insulation properties, a comprehensive consideration must be taken to prevent heat radiation, convection and conduction as much as possible. In order to prevent radiative heat transfer, the authors introduced sheet-like heat-insulating reflective materials, such as mica and talc, into the formulation; in order to prevent convective heat transfer, during the design of the coating, the particle size distribution of the filler, the control of pores, and control coating The coefficient of expansion of the layer to the addition of appropriate amount of fibers are used to prevent cracking of the coating and generation of through-pores; in order to prevent conduction heat transfer, microporous hard silicon calcium, ceramic fibers, etc., which have low thermal conductivity themselves, are used as main materials.

In order to make the coating can be used normally at IO00°C, the temperature-resistant hard silicon silica, ceramic fiber, mica, talcum powder, and clay are used as fillers. In order to ensure that the coating can not only withstand the high temperature of IO00°C, but also can directly construct and guarantee the low temperature strength under cold conditions under higher temperature. In the study of coating binders, a great deal of work was done. Finally, a composite binder formulation with low-temperature bond strength, high-temperature construction, and high-temperature strength was identified. The main principle is to add proper amount of organic hydrophilic cellulose gum, water glass, silicone high-temperature glue and silica sol to the formulation. Use cellulose glue and water glass with high viscosity to develop low temperature adhesive strength; use water glass and organic silicon gel for rapid curing at high temperature to make the coating suitable for high temperature construction; use water glass and silica sol for curing to achieve high temperature strength and resistance High temperature. In order to reduce the dry bulk density of the coating and improve the heat insulation performance, there are a large number of closed micro pores in the coating after the coating is dried. The authors conducted comparative studies on blowing agents such as rosin soaps, surfactants and fast penetrants. Finally, a blowing agent capable of forming a large number of micropores and stabilizing pores was determined.

In order to overcome the brittleness and softness of the ceramic fiber, under the premise of ensuring the temperature resistance of the coating, after the coating is dried, the coating has high strength and elasticity, and a small amount of alkali-resistant glass fiber and other fiber materials are appropriately added. The amount of such fiber materials added is that even when used at high temperatures, the properties of the fibers are reduced without affecting the overall performance of the coating.

2 Main workmanship process and production equipment

After optimizing the process parameters for production of hard silicon-calcium composite coating and production assessment, determine the production process, as shown in Figure 1.

The main production equipment: boilers, reactors, soaking pools, beaters, foaming pools, mixers, crushers, etc.

3 Brief description of the production process

In the production process, the hard silica-calcium composite high-temperature coating is based on the manufacturing process of foamed asbestos, that is, some of the raw materials are put into the soaking tank first, soaked in a penetrant solution of 70-90~C, the penetrant fully penetrates, and the fiber loosens. It is beaten with a mechanical stirrer and becomes a fiber paste. The fillers, binders and other additives are then added and homogenized to give a finished product. At the same time, the samples are sent to the inspection department for inspection of all the indicators, and they can be delivered after passing the inspection.

4 Key technologies addressed in the development process

4. I Coating Composite Filler Formula

It not only solves the problem of using the coating at 1000% high temperature but also considers the heat conduction method. It insulates all three kinds of heat conduction, so that the coating has excellent temperature resistance and heat insulation performance.

4.2 Compound Binding Agent Formula

The properties of various binders have been fully studied, and the determined composite binders have taken into consideration the sequential strength of the structural strength at low, medium and high temperatures, and have complementary properties. Not only meet the high temperature performance of the coating, but also take into account the coating performance.

5 Product Quality and Performance Comparison with Domestic Similar Products

The product has been tested by the National Building Materials Bureau, and the quality and various indicators are better than the existing domestic similar products. The specific data is shown in the inspection report.

At present, China does not have a unified national standard. Table I lists the comparisons with sepiolite-based insulation coatings and rare earth composite insulation coatings.

Table 1 Comparison of Hard Si-Ca Composite High-Temperature Coatings and Other Coatings

6 Conclusion

The product has passed the municipal appraisal, it can replace imported products, savings, energy-saving effect is significant, the market prospects are broad.