Insulation Refractory Bricks...

Insulation Refractory Bricks  Insulating refractory brick (IRB) is the term used for heat insulating bricks and  covers those heat insulating materials which are applied up to 1000 deg C. IRBs are often mistakenly referred to as rear insulation materials. These bricks are assigned to the group of lightweight refractory bricks and are manufactured on the basis of naturally occurring lightweight raw materials. IRB is a class of brick, which consists of highly porous fireclay or kaolin. IRBs are lightweight, low in thermal conductivity, and yet sufficiently resistant to temperature to be used successfully on the hot side of the furnace wall, thus permitting thin walls of low thermal conductivity and low heat content. The low heat content is particularly important in saving fuel and time on heating up, allows rapid changes in temperature to be made, and permits rapid cooling. IRB is characterized by the presence of large amount of porosity in it. The pores are mostly closed pores. The presence of porosity decreases the thermal conductivity of the insulating bricks. IRBs  were developed in the 1930s, and they were the predominant form of insulation until the development of insulating castable and fiber refractories. There are two types of bricks namely (i) bricks based on clay and gypsum using the burnout of sawdust to create high porosity (and thereby provide better insulating value), and (ii) bricks based on lightweight aggregate and clays. Like all alumina-silica brick, IRBs have a duty rating (service limit). Over the years, IRBs have been made in a variety of ways, such as mixing of organic matter with clay and later burning it out to form pores; or a bubble structure incorporated in the clay-water mixture which is later preserved in the fired brick. IRBs are characterized by the presence...