Refractory Lining Materials

The type and thickness of the refractory material used for kiln lining are critical to heat losses through the kiln shell and play a major 

Materials for refractory lining are chosen based on several factors, including their stability and durability. While the main intention is to protect the steel shell, they can serve as an insulation material necessary to retain the heat within the kiln interior. At the sections near the combustion zone, conductive materials are preferred for lining so as to dissipate some heat away and prevent excessive temperature build-up and thereby avoid thermal stresses and associated refractory damage. Lining materials come in all forms including bricks and mortars of all consistency that can be spread or sprayed on surfaces. The material composition and thermo-physical properties of some lining materials are presented in Table 7.1. 

Chemical Analysis (Calcined Basis), % Refractory Type  

Chemical Analysis High Alumina High Alumina Magnesite 

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Raymon, N. S. and Sadler III, L. Y. "Refractory Lining Materials for Coal Gasifiers—A literature Review of Reactions Involving High-Temperature Gas and Alkali Metal Vapors", 1976. Information Circular, 8721. Bureau of Mines. 

Raymon, N.S. and Saddler, L.Y., III, Refractory Linings Materials for Coal Gasifiers A Literature Review of Reactions Involving High-Temperature Gas and Alkali Metal Vapors, USBM Information Circular 8721, 22, 1976. 

Steam methane reforming is performed in a high-temperature, high-pressure reaction chamber typically operating between 1,250 to 1,575°C at pressures of 20 to 100 atmospheres. Materials issues are the same as those of high-temperature, high-pressure vessels where creep of corrosion-resistant materials is important for the containment vessel and durability of alumina, chromia, or SiC refractory lining materials is critical to the performance of the system. 

Impurities present in the HaU-Heroult process originate mainly from the raw materials, carbon and alumina. Some additional impurities come from bath components (AIF3), tools, anode stubs, and sidelining (SiC) and refractory lining materials. The major part of these impurities is initially present in the electrolyte as dissolved fluoride or oxyfluoride complexes. The dissolution process can be expressed as follows ... 

Furthermore, in order not to reduce the width of shell plate between the openings too much, the latter are oval in shape and are protected by inserted sockets made of heat-resisting cast steel. In a sense, they correspond to the outlet sectors (nose sectors) of rotary kilns with other types of clinker cooler and are embedded in refractory lining material. The refractories that have achieved the best results in this... 

Refractory linings Refractory materials Refractory metals... 

Refractory Linings. The refractory linings (2,3) for the hearth and lower wads of furnaces designed for melting ferrous materials may be acidic, basic, or neutral (see Refractories). Sdica has been widely used in the past, and is stid being used in a number of iron and steel foundries. Alumina, a neutral refractory, is normally used for furnace roofs and in the wads for iron foundries, but basic brick can also be used in roofs (4). 

The basic fluid-bed unit consists of a refractory-lined vessel, a perforated plate that supports a bed of granular material and distributes air, a section above the fluid bed referred to as freeboard, an air blower to move air through the unit, a cyclone to remove all but the smallest particulates and return them to the fluid bed, an air preheater for thermal economy, an auxiUary heater for start-up, and a system to move and distribute the feed in the bed. Air is distributed across the cross section of the bed by a distributor to fluidize the granular soflds. Over a proper range of airflow velocities, usually 0.8-3.0 m/s, the sohds become suspended in the air and move freely through the bed. 

Direct-Flame Incinerators. In direct-flame incineration, the waste gases are heated in a fuel-fired refractory-lined chamber to the autoignition temperature where oxidation occurs with or without a visible flame. A fuel flame aids mixing and ignition. Excess oxygen is required, because incomplete oxidation produces aldehydes, organic acids, carbon monoxide, carbon soot, and other undesirable materials. 

The entire QSL process takes place in a single reactor as shown in Figure 6 (15). The reactor consists of an almost horizontal, refractory-lined cylinder, which can be tilted by 90° when operation is intermpted. Concentrates, fluxes, recirculated flue dust, and normally a small amount of coal, depending on the type of concentrate, are pelletized. The pelletizer ensures that the raw materials are mixed to the required degree of uniformity. 

Fig. 8. Magnetherm reactor central electrode, A secondary circuit, B grounding electrode, C refractory lining, D carbon lining, E primary material feed, F slag taphole to FeSi recovery, G vacuum line, H water spray ring, I condenser, cmcible, K trap, L filter, M and transformer, N.

Refractories are materials that resist the action of hot environments by containing heat energy and hot or molten materials (1). There is no weU-estabhshed line of demarcation between those materials that are and those that are not refractory. The abiUty to withstand temperatures above 1100°C without softening has, however, been cited as a practical requirement of industrial refractory materials (see Ceramics). The type of refractories used in any particular apphcation depends on the critical requirements of the process. For example, processes that demand resistance to gaseous orHquid corrosion require low permeabihty, high physical strength, and abrasion resistance. Conditions that demand low thermal conductivity may require entirely different refractories. Combinations of several refractories are generally employed. 

Carbon and Graphite. Carbon (qv) and graphite [7782 2-5] have been used alone to make refractory products for the lower blast furnace linings, and electrodes for steel and aluminum production. They are also commonly used in conjunction with other refractory raw materials. These materials are highly refractory nonwettable materials and are useful refractories in nonoxidizing environments. Carbon blacks are commercially manufactured, whereas graphite for refractory use has to be mined. 

The metallurgy of the cyclone equipment has in recent years focused primarily on type 304 H stainless steel. The 304 H material is durable and easy to fabricate and repair, withstands the high regenerator temperatures, and is oxidation- and corrosion-resistant. Essentially all internal surfaces of the cyclone that are subject to erosion are protected with a 2 cm layer of erosion-resistant lining. When installed and cured, most refractory linings are highly resistant to erosion. 

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