High-Temperature Batch Furnaces

Kobayashi [8] reported about the development of a high temperature batch cullet preheating system being in development especially for flue gases at very high inlet temperatures e.g. in combination with oxygen-fuel fired glass furnaces. 

High process temperatures generally not achievable by other means are possible when induction heating of a graphite susceptor is combined with the use of low conductivity high temperature insulation such as flake carbon interposed between the coil and the susceptor. Temperatures of 3000°C are routine for both batch or continuous production. Processes include purification, graphitization, chemical vapor deposition, or carbon vapor deposition to produce components for the aircraft and defense industry. Figure 7 illustrates a furnace suitable for the production of aerospace brake components in a batch operation. 

Pyrolysis is an ancient method of decomposing solid matter by heating to high temperatures examples are production of metals, coke furnaces, and obtaining of chemicals from coal prior to petroleum. There are many kinds of pyrolysis batch, semi-batch or continuous catalytic or non-catalytic out under vacuum or at atmospheric or high pressure. Its medium may be inert, oxidative or reductive. Heating rate, temperature, and time are important pyrolysis parameters. 

The furnace has an adjustable rotation rate of 0.5-10 rpm. The kiln is heated externally. The sealing of rotary kilns is a difficult task, especially for a pyrolyzer. The internal pressure of the kiln is higher than atmospheric pressure. A special friction-type seal is required for a pyrolyzer operating at high temperature. Solid waste with different shapes, sizes, and heating values can be fed into rotary kilns in batches or continuously. 

For high-quality wares, temperature control is very important to avoid the above mentioned problems in different processing stages. This can be accomplished easiest and most accurately in batch furnaces. Some materials must be, at least during certain stages, fired in reducing or other special atmosphere that is also best provided in batch kilns. However, many bulk ceramic products need to be of such low cost that continuous furnaces must be used, which operate more economically. 

Whereas batch furnace temperature must be held down to prevent overheating, temperature in the heating zone of a continuous furnace may be very high. 

Fig. 5.24. Batch furnace with one pair of regenerative burners. Recovery is so good that not all poc need to be sent through the air heater, leaving some to help control furnace pressure. For faster brlng-up from cold (when waste gas temperature is low and efficiency high), both burners can be fired simultaneously. After about 20 sec of firing as shown, the system automaticaiiy interchanges the left and right burner functions. (See aiso fig. 5.26.)...

Continuous glass fibers were first manufactured in substantial quantities by Owens-Corning in the 1930s for high-temperature electrical apphca-tions. The raw materials are blended, in the proportions shown in Table 1, to form a glass batch which is melted in a furnace and refined during... 

Filters for Molten Metal Inclusions in molten metals, such as oxide skins, mold sand particles, inoculation reaction byproducts or furnace slags, can be efficiently removed by filtering through pressed cellular, extruded cellular, or foam ceramic filters manufactured from high-temperature-resistant, chemically inert alumina, and also mullite, silicon carbide, and stabilized zirconia. Alumina is particularly useful when filtering liquid aluminum alloys in the range of 750-850 °C, and copper-based alloys at 1000-1200°C (Matthews, 1996). These ceramic filters are designed for use in either batch or in-mold filtration ... 

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