The refractory fiber spraying coating has been widely used in metallurgy, petroleum, chemical industry, machinery, construction and other industries because of its high temperature resistance (600 ~ 1450), (vibration resistance), good heat insulation, sound absorption and light weight. The traditional construction technology of refractory fiber mainly refers to the construction technology of refractory fiber products. Using sticking and splicing technology and technology to carry out construction, construction is difficult, slow, difficult quality control, more joints, poor integrity, labor intensity of workers. Refractory fiber spraying technology is a new technology and process for mechanization of fiber construction. The technology uses a fiber spray gun, and the binder is evenly sprayed into the fiber through a diaphragm pump. The two binders are mixed at the outlet of the spray gun and sprayed directly on the working surface. The spray coating has a three-dimensional network structure. It overcomes the shortcomings of traditional construction technology and greatly improves the thermal efficiency of the kiln.

Types and raw materials

1. The main raw materials of refractory fiber spray coating include rock wool, standard aluminum silicate fiber, high-purity aluminum silicate fiber, high-alumina aluminum silicate fiber, aluminum silicate fiber containing zirconium; polycrystalline mullite fiber, alumina fiber, zirconia fiber, etc. The maximum service temperature of refractory fiber lining varies with fiber type and furnace atmosphere, generally in (1100 ~ 1450). ?

2. there are many kinds of binder for high temperature refractories, and their properties are different. According to the chemical properties of the binder, it is divided into inorganic binder and organic binder. Inorganic binders mainly include silicates, aluminates, phosphates, sulfates, chlorides and sols; organic binders include natural organic compounds and organic compounds.

3. rock wool has good performance in thermal insulation and heat insulation, and the working temperature is between (80 to 70) C. It can be used for thermal insulation of kiln and pipe liner with continuous temperature below 600 C.

4. the density of aluminosilicate series fire-resistant fibers is the smallest under the condition of (250~300) kg/m3. Standard aluminium silicate fiber and high aluminium fiber spraying coatings are used for thermal equipment working at temperatures below 1000 and 1200 respectively. They have remarkable effects on fire resistance, heat insulation and heat preservation. Zirconium-containing composite fiber and polycrystalline mullite fiber spraying coatings are applied to high-temperature furnaces above 1300. ?

5. commonly used aluminosilicate series binders are rigid binding agents. In the range of suitable working temperature, the composition and proportion of binder should be helpful to form bond chain and network structure. It needs rapid acceleration of coagulation, no shrinkage after curing, uniformity, dispersion and activity, and takes into account the initial strength and hot sintering properties. The refractory degree of thermosetting bond is not less than 1750 C, viscosity (6.0~8.0) * 10-3Pa / S.

Two. Application of spray coating construction

1. scope of application

Refractory fiber spraying coating has many advantages, but its strength is still a certain gap compared with refractory bricks and high-strength castables, so it is suitable for non-particle airflow flushing and gas flow rate less than 20m/s (if spraying surface coating can enhance the resistance to airflow flushing) of various industrial furnace lining and composite furnace. Line. In addition, spray construction can also be selected through the selection of fiber materials, external insulation of towers, tanks and containers. Spraying technology is an improvement and progress in the construction technology of refractory fiber, and its construction speed is fast and its quality is better. Spraying technology can be used in areas suitable for the use of refractory fiber products.

　　2. characteristics and advantages

At present, most of the domestic furnace walls are still brick structure, its disadvantages are large heat storage, slow heating rate, increased heat consumption, poor insulation effect, heat loss, bad working environment, thermal inertia, not suitable for automatic control of combustion.

For the lining of composite structure, the lining material has developed from refractory brick to castable material to light fiber felt, blanket and block, although progress has been made to a certain extent, but the construction technology of fiber products is backward, the construction quality is difficult to guarantee, and the lining life has been greatly affected. The main shortcomings are large manpower input, slow construction speed, construction quality is difficult to control; fiber products have through-type straight seams, poor sealing, easy to flee; spherical and special-shaped structure is difficult to construct, maintenance and repair difficult.

For heating furnace lining, fiber spraying technology uses high-quality fiber raw cotton, high-performance fiber series binder as raw materials, forming a network structure in the process of one-off whole spraying. Compared with other construction methods, it has the following advantages:

(1) The seamless lining obtained by one-off spraying effectively avoids the directional shrinkage of fiber products at high temperature, eliminates the hazards of gas channeling and dew point corrosion to furnace shell and anchor nail, strengthens the sealing, heat preservation and fire resistance, and improves the thermal efficiency of furnace.

(2) Fiber spray coating technology can reduce the construction difficulty of integral anchorage of complex surface, such as sphere, corner, furnace door and flue gas pipe joint, and improve the sealing performance of special-shaped joint. The liner is strong, uniform and smooth, and has strong corrosion resistance. Spraying construction is convenient, flexible, less amount of anchor nails, and all embedded in fiber lining, effectively prevent nail burning, avoid thermal short circuit.

(3) The thermal conductivity of sprayed fiber lining is lower than that of flat felt and blanket, and the thermal strength is better than that of vertical folding block. The anchor embedded in the sprayed coating does not transfer heat directly, thus saving energy by 15%~30%.

(4) Spraying coating is economical and practical. According to the working condition of industrial furnace, multi-fiber layered composite spraying can be used to realize the temperature gradient distribution of composite heat transfer mechanism and reduce the comprehensive cost of lining material.

(5) The spraying speed of refractory fiber is 4.5 times faster than that of conventional construction method, especially for emergency repairs. The coating structure is a flexible material, which can be put into use after the completion of the spray coating construction, thus reducing the oven drying time by nearly 4/5.