Types of refractory materials used in various parts of heating furnaces

1. Refractory materials for furnace body

(1) Brick-built furnace body. Furnace lining built with insulation bricks and refractory bricks. The insulation layer of the furnace is built with clay or high-alumina insulation bricks, floating bead bricks, diatomaceous earth bricks and refractory fiber felt, with a thickness of 113 to 300 mm. The working layer of the furnace wall is built with clay refractory bricks, with a thickness of 230 to 400 mm. The openings can be built with brick arches, special-shaped bricks or covered with long strips of clay refractory bricks.

(2) Prefabricated blocks are used to hoist the furnace body. Prefabricated blocks are made of refractory castables such as aluminate cement, phosphate low cement and water glass. If prefabricated blocks are made of clay combined with refractory castables, anchor bricks must be provided. The prefabricated blocks on the furnace roof are divided into arched and long strips. If steel bars are used, they must be placed in the non-working layer.

(3) Refractory plastic ramming furnace body. The working layer of the furnace lining made of refractory plastic ramming and equipped with anchors. The gaps between the anchor bricks or hanging bricks need to be filled with refractory plastic blanks and compacted with a pneumatic hammer or a tamping machine. The refractory plastic, including the furnace bottom, is generally constructed in layers and sections, and the surface is shaved, vent holes are punched, and expansion joints are cut. The advantages of refractory plastic furnace lining are strong integrity, good sinterability and high high temperature strength.

(4) Lining castables are poured into the furnace body. The working layer of the furnace lining is poured on site with refractory castables. The structure of the furnace wall and the top is the same as that of the refractory plastic furnace body. After the anchor bricks or hanging bricks are installed in place, the refractory castable mixture is laid from one side, and then vibrated and compacted with a vibrator (paddle). Continuous construction and timely maintenance should be carried out.

02. Refractory materials for combustion chambers

Heating furnaces used for coal burning are divided into various types such as reciprocating grate type and cyclone combustion type, and are generally composed of bottom, wall and top parts. The lining of an ordinary combustion chamber is usually built with clay bricks or high-alumina bricks. Due to the high operating temperature and large temperature fluctuations, slag erosion and mechanical damage during slag removal, its life is about 1 year. The waist furnace is the passage between the combustion chamber and the furnace of the heating furnace. The operating temperature is about 1600℃. When built with sillimanite bricks or corundum bricks, its life is only about 0.5 years.

03. Refractory materials for furnace doors and steel spouts

Used to close the holes on the furnace wall, it is divided into two types: side-opening type and lifting type. The furnace door is generally lined with clay bricks, refractory castables or refractory plastics, high-alumina insulation bricks or refractory fiber felts; the side-opening furnace door can be used for one furnace service, and the lifting furnace door is affected by factors such as temperature fluctuations and mechanical collisions, and its service life is about 1 year.

The steel spout is used in the heating furnace for side-out of steel billets. In addition to water-cooled cast iron steel spouts, it is generally built with high-alumina bricks or magnesium bricks, with a service life of 3 to 6 months. When sintered or fused mullite bricks are used for masonry, the strength is high and the wear resistance is good, but the thermal shock resistance is poor, it is easy to collapse, and its service life is about 1 year. The corundum refractory castable reinforced with heat-resistant steel fiber is poured on site to form an integral steel trough, and the service life is more than 2 years.

04. Refractory materials for ceramic slides

Small push-steel heating furnaces are composed of brown corundum-silicon carbide slide bricks to form ceramic slides, and refractory bricks are used to build 2 or 4 rows of base walls in the length direction of the furnace. High-aluminum silicon carbide seat bricks are built on the base wall, and then the slide bricks are installed to form a ceramic slide. The steel billet moves on the slide to achieve heating on both the upper and lower sides, with the advantages of low energy consumption and no black marks on the steel billet.

05. Refractory materials for insulation of furnace bottom water-cooling pipes

Large and medium-sized push-steel or walking beam heating furnaces, the furnace bottom water-cooling pipes are composed of thick-walled water-cooling pipes distributed longitudinally and transversely and supporting. The purpose of insulation is to reduce the heat carried away by the cooling medium, reduce the black mark of the steel billet and improve the heating quality. The insulation methods include inlaying special-shaped clay bricks or hanging horseshoe-shaped bricks, welding of prefabricated blocks made of refractory plastic or refractory castables, and on-site wrapping of the materials and refractory fiber felt.

06. Refractory materials for flues and chimneys

The lining of flues is generally built with clay bricks, or can be built with prefabricated blocks of refractory castables or poured on-site, and sometimes can be constructed with refractory spray paint. Red brick or concrete chimneys are built with refractory bricks in high-temperature areas. Metal anchor nails are welded on the inner wall of metal chimneys, and sometimes metal mesh is added. Lightweight refractory castables or refractory spray paints are used as linings, which are easy to construct, have strong integrity and long service life.