Selection of refractory materials for heating furnace lining

Masonry with refractory bricks
Ltd. is a very mature refractory material, which is widely used in various heat treatment and heating furnaces. Heating furnaces mostly use high alumina bricks as the refractory layer, which usually requires the content of Al2O3 ≥ 65%. High alumina bricks have good thermal stability and are suitable for use in forging heating furnaces where temperature changes frequently. The construction method is simple and the masonry standards have been developed for the use of refractory bricks in the construction of furnace walls. According to different use temperature, different furnace type, different parts of the brick seam width, masonry error and other indicators put forward clear indicators. When the heating furnace roof using brick vault structure, the maximum width of the furnace chamber generally does not exceed 5m, and should be far from the press and other equipment with strong vibration. Refractory brick lining thickness is generally used the following size: 348mm thick high alumina brick + 230mm thick lightweight clay brick or diatomaceous earth insulation brick, + 20mm silica calcium plate. When using this thickness of masonry lining, the outside wall temperature of the furnace does not exceed 70℃.

Since the refractory bricks have been sintered, the baking process is mainly baking the free water brought in during the masonry process and the sintering of the refractory mud. When using refractory brick masonry, the baking time is much shorter than that of castables, and the baking time of the heating furnace below 50m2 does not exceed 5d.

Masonry with refractory castables
Due to the requirements of the brick vault structure on the width of the furnace chamber, so large heating furnace, especially the width of the larger heating furnace less use refractory brick masonry roof. High temperature large span furnace roof using low cement castables construction using flat roof hanging structure. At present, castables are used more on large heating furnace. More low cement refractory castables are used, and they are used after adding water to the construction.
The construction of refractory castables is much more complicated than refractory bricks, first of all, the anchors are made and installed, and the anchor bricks are used on the heating furnace to play the role of support and fixation. The length of metal anchor hook should not exceed 1/3 of the thickness of furnace lining, and its spacing should not exceed 600mm horizontally and 500mm vertically. waterproof treatment should be done on the contact surface of heat insulation layer and casting material to prevent the moisture in the construction process of casting material from damaging the heat insulation material. Then make the template according to the drawing, the size of the template should be accurate, the support must be firm to prevent the displacement of the template when pouring, the template should be painted with machine oil before the construction, and the convenience of dismantling the template should be considered when installing.
The mixing process of casting material should strictly control the amount of water added. For heating furnace, the thickness of lining in castables is generally 300mm low cement refractory castables + 230mm light insulation brick + 20mm calcium silicate board. Usually the lining baking time of castables construction is long and there are strict requirements on the heating speed, generally 10~15d for heating furnace.
The size of the prefabricated blocks can be changed according to the different furnaces and pre-baked into shape. The use of prefabricated blocks of castables eliminates the complex construction of castables on site, reduces the workload on site and shortens the baking time at the same time. When using castable precast blocks, the furnace wall structure is exactly the same as the refractory brick lining, and the furnace roof can be designed according to the brick vault structure. It can be said that the prefabricated block of castable material and refractory brick have approximately the same conditions of use.