Castable refractories

Thermal oxidizers must be built to provide the residence time and temperatures to achieve the desired destruction efficiency (DE). As such, thermal oxidizers are comparatively larger than catalytic oxidizers since their residence time is two to four times greater. Historical designs of thermal oxidizers were comprised of carbon steel for the outer shell and castable refractory or brick as the thermal liner (a refractory is like a cement, which is put on the inside of the rector shell to act as a thermal insulation barrier). Modern units are designed and built using ceramic fiber insulation on the inside, which is a lightweight material, and has a relatively long life. Old refractory would tend to fail over a period of years by attrition of expansion and contraction. 

Insulation - The steel shell of the stack is lined for its entire length with monolithic type castable refractory. 

Castable refractories, ASTM classifications and specifications for, 27 510 Castables, 27 482 Cast alloys, 73 524 Cast copper-beryllium alloys, 3 653t,... 

In many cases, cold spots on the reactor shell will result in condensation and high corrosion rates. Sufficient insulation to maintain the shell and appurtenances above the dew point of the reaction gases is necessary. Hot spots can occur where refractory cracks allow heat to permeate to the shell. These can sometimes be repaired by pumping castable refractory into the hot area from the outside. 

Nonmetallic castable refractories, reinforced with hexagonal steel mesh, are particularly good, since they resist both corrosion and erosion. Conventional refractories are susceptible to deterioration by water sprays, but this difficulty can be overcome by shielding from water impingement or by use of special cements. For best results, the refractory is installed flush with the surface of the steel mesh and is commonly applied with a pneumatic gun to ensure completeness of fill and maximum... 

The combustion cell is fabricated out of carbon steel and is lined with high-temperature block insulation covered by a layer of castable refractory. 

Additional specialist applications include castable refractory ceramics and use as... 

Other binary aluminates include magnesium spinels that are used extensively as castable refractory ceramics. Lithium aluminates are used, potentially, in fuel cells and as materials for new types of nuclear reactors. Again, these applications reflect the refractory nature of aluminates and their chemical resistance. 

The waste container is expected to be a steel box approximately 3 m (10 ft) high, 2.4 m (8 ft) wide, and 7.3 m (24 ft) long. Before waste is placed in it, the container will be lined with insulating board, sand, and a layer of castable refractory. The refractory will be in contact with the waste. A layer of melt-initiating graphite and soil will be placed over the refractory in the bottom of the container. The container will have one or more ports for sampling the vitrified waste after it has cooled. 

The earlier oil black reactors were large and unwieldy, containing tons of brick refractory, and several weeks were required to build or repair them. Today, however, by using the heat exchange principle, reactors can be constructed from pieces of standard black iron pipe with castable refractory weighing less than 1 ton (3). Complete repair is accomplished in less than one 8-hour shift. 

This reactor section containing the fluidized bed is 28 inches od and 15 inches id. The insulation lining is 4 inches of Type 1620-K fire brick (Babcock and Wilcox Co.) and 2 inches of Plicast Tuff-Mix castable refractory (Plibrico Co.). The height of this section is 8 ft. Above the fluidized bed section, the reactor diameter expands to 35 inches od and 22 inches id. This particle-disengaging chamber is 4 ft high and is lined in the same manner as the fluidized bed section. 

In another small fired heater, castable refractory was originally installed for a design refractory face temperature of 1,600° F and a furnace shell temperature of 220° F. After several years of operation, the original castable spalled and cracked resulting in a shell temperature of 300° F. A four-inch ceramic refractory blanket was installed that dropped the furnace shell temperature to less than 200° F and reduced heat losses 55 percent. 

Tabi 9-7C. Characteristics of Hiqh-temperature Insulation. Classification op Refractory Castables (Refractory aggregates plus hydraulic cement)... 

Castable refractories consist of course and fine grains with suitable bonding cement. After mixing with water, these are poured in place using molds or pouring forms. 

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