What type of refractory brick is used for the innermost layer of the furnace?

The chosen answer, firebrick, is indeed the most appropriate type of refractory brick for the innermost layer of a furnace. Firebrick is specifically formulated to withstand high temperatures and maintain structural integrity under extreme thermal stresses. This property is essential in the innermost layer, which is in direct contact with the furnace’s heat source, as it needs to resist not only the heat but also any chemical reactions that might occur.

Firebrick typically has a high alumina content, contributing to its ability to endure high temperatures without deforming or cracking. This makes it ideal for areas subjected to direct heat, such as the walls and hearth of a furnace.

In contrast, insulating brick, while useful for thermal efficiency and minimizing heat loss, is not suitable for the high-wear environment of the innermost layer since it is designed more to reduce heat transfer rather than withstand direct heat. Dense brick, although durable, may not possess the same thermal properties that firebrick has for high-temperature environments. Pumice brick, being lighter and less dense, is generally utilized for insulation purposes rather than as the primary lining in high-temperature applications.

Thus, firebrick is the correct answer for the furnace’s innermost layer, ensuring both durability and heat resistance