Insulation is an important part of power plant construction, especially thermal power plants such as thermal power plants. Therefore, the commonly used refractories in power plants are lightweight insulating firebricks. Followed by fiber insulation materials, hard materials and insulation coatings.
1, fiber insulation materials
The actual use in power engineering shows that the application effect of high-temperature resistant glass wool products is good, and its insulation performance is better than aluminum silicate cotton products. It can be used as the main insulation layer on equipment pipelines at 400°C, but the content of organic substances should not exceed 5%, density should not be too small, construction should have 5% to 10% of the amount of compression.
For fiber insulation materials can reduce fiber diameter, increase fiber length, reduce the content of the slag ball, can increase the use of temperature. The increase in the use of temperature is very beneficial for the expansion of the use of fiber materials, the current main way to improve the use of temperature is to improve the curing agent, the choice of temperature-resistant inorganic binders. In recent years, Owens Corning Company and Beijing Yisuowei Company have improved the use temperature of glass wool and products, improved formulas and binders, and added amounts to produce glass wools with a temperature resistance of 500°C and 450°C products. The properties are: fiber length 15~20 cm, fiber diameter less than 5 m, no slag ball, thermal conductivity: 0.024+0.00022 tm W/(m·K), using temperature 450°C. The product entered the power engineering application in 1997, and used as the main insulation layer in the furnace wall, hot air duct and electrostatic precipitator of 300,000 kW and 600,000 kW boilers, and the composite steam insulation at 540°C. More than 20 crew use.
2, hard materials
In order to ensure that its performance meets the requirements of the national standard, many manufacturers currently strive to reduce the density and thermal conductivity of calcium silicate insulation products and perlite products. Such as calcium silicate insulation products, some products with a density of 130kg/m3, thermal conductivity of 0.0455 W/(m·K) at 70°C; some products with a density of 115 kg/m3, thermal conductivity of 0.035 W at 23°C /(m·K), the thermal conductivity is 0.042 W/(m·K) at 70 °C; a product with a density of l10kg/m3 has been developed internationally, and its thermal conductivity is 0.034 W/ at normal temperature (20 °C). m·K), 0.040 W/(m·K) at 70°C. Another example is a composite silicate shell (board) product is a composite silicate insulation coating mold processing, drying and release from the product, the performance of the pellet density of 150 ~ 160kg/m3, 70 °C when the thermal conductivity of 0.048~0.055W/(m·K), the water recirculation rate is not less than 98%, and the operating temperature is -40~600°C. It is suitable for thermal insulation of thermal network piping and thermal equipment.
3, spray insulation
Spray insulation is the application of jet technology in adiabatic engineering. It is a new technology developed in the early 1970s. It is used in the domestic metallurgy, petrochemical, construction and power industries, such as in large thermal power plants and nuclear power plants. In terms of steam turbine insulation, most of the steam turbine thermal insulation designs imported in recent years have used spray insulation. For example, the Daya Bay Nuclear Power Station turbine high pressure cylinders, low pressure valves, and steam-powered feed pumps use dry spray insulation. US FW Company supplied 2 sets of 350,000 kW generators for Shandong Rizhao Power Plant, 6 sets of 350,000 kW generator sets for Shanxi Yangcheng Power Plant, 2 sets of Wanfeng kW sets for Hanfeng Power Plant, and steam turbine cylinders for power generation equipment supplied by France, Germany and the United Kingdom. Insulation also uses mineral fiber spraying, and provides spraying equipment, supporting spraying materials, and also sent special personnel to the site for guidance.
The advantages of spray insulation are as follows:
(1) Spraying insulation can greatly reduce the cooling rate after the turbine is shut down, eliminating the temperature difference between the components in the cooling process, and improving the turbine start-stop conditions.
(2) Spraying heat preservation can make the heat-insulating material tightly fit with the cylinder, thus eliminating the occurrence of shelling phenomenon between the heat-insulating layer and the cylinder, especially solving the problem that the lower cylinder insulating layer is easy to fall off.
(3) The thermal insulation structure of the spray coating is good in integrity. Since the fibers are arranged in three dimensions, the heat-preservation structure after being subjected to high temperature will not generate directional shrinkage to eliminate cracks, improve the heat insulation effect, and reduce heat loss.
(4) Spray insulation is especially suitable for parts with complex shapes.
(5) Spray insulation can save insulation materials, insulation thickness can be reduced by 15%, labor saving 1 / #, and improve the insulation structure strength and integrity, sealing and shock resistance.
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