Insulation and Refractories
Thermal insulators are poor conductors of heat and have low thermal conductivity. Insulation materials are used in buildings and manufacturing processes to prevent heat gain or loss. Although its main purpose is economy, it also provides more precise process temperature control and personnel protection. Prevent condensation on cold surfaces and the resulting corrosion. These materials are porous and contain a large number of inactive air pockets. Thermal insulation has the following advantages:
• Reduce total energy consumption
• Provide better process control by maintaining process temperature.
• Prevent corrosion by keeping the exposed surface of the cooling system above the dew point
• Provide fire protection for equipment
• Absorb vibration
Types and applications Insulating materials can be divided into three groups according to the temperature range in which they are used.
- Low-temperature insulation (up to 90°C).This range covers insulation materials for refrigerators, hot and cold water systems, storage tanks, etc.The materials used are cork, wood, 85% magnesium oxide, mineral fiber, polyurethane and expanded polystyrene.
- Medium temperature (90–325°C) insulation in this range is used for low temperature, heating and steam equipment, steam pipes, exhaust pipes, etc. Material types used in this temperature range include 85% magnesium oxide, asbestos, calcium silicate, and mineral fibers.
- High Temperature Insulations (325 °C — above ) Typical uses of such materials are super heated steam system, oven dryer and furnaces etc. The most extensively used materials in this range are Asbestos, Calcium Silicate, Mineral Fibre, Mica and Vermiculite based insulation, Fireclay or Silica based insulation and Ceramic Fibre.
Insulated refractory brick (IRB) is a term used for insulating bricks, covering insulation materials that are applied to 1000 degrees Celsius. IRB is often incorrectly referred to as back insulation. These bricks belong to the group of lightweight refractory bricks and are manufactured on the basis of lightweight raw materials from natural sources.
IRB was developed in the 1930s and is an important insulating material in the development of refractory materials and insulating castings. The bricks are based on (i) clay bricks and gypsum bricks, which use carbon shavings to create high porosity (and therefore improve insulation), and (ii) clay and lightweight aggregates, and there are two types of bricks. Like all aluminum oxide silicate stones, IRB has a service class (limited service). The various types of IRB are mainly composed of traditional materials such as diatomaceous earth, perlite, expanded vermiculite, calcium silicate, fire, kaolin, quartz, alumina and refractory aggregate. Various types of porous structures such as saws, expanded polystyrene, fine coke, binders, organic foams or granular materials such as hollow microspheres and cellular alumina are commonly used in IRBs to obtain low-density porous materials.
IRBs are characterized by high porosity (45–90%). Skin pores are usually clogged pores. Due to their porous structure, these rocks have low values of thermal conductivity. Thermal conductivity depends not only on overall porosity, but also on the size and shape of the pores and the composition of chemicals and minerals. The heat capacity of bricks is also low. Due to the high porosity of this rock, its density and bulk strength are low. The use of this type of brick depends on the temperature component. For example, a kite-based insulating block can be used at temperatures above 1250 °C, while refractory materials can be used at lower temperatures.
IRBs are vulnerable to alkaline attacks. Fly gypsum and sawdust products (high in CaO content) can swell under alkaline conditions. In some cases, this reaction is harmful and shortens lifespan. Conversely, IRB optical aggregates can illuminate surfaces in alkaline environments.
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