Ceramic recuperators

FIG. 27-59 Ceramic recuperator. In this design the seals are maintained at relatively low temperatures, leading to leakage rates of only a few percent. (From Goldstick Waste Heat Recovery, Faiimont Press, Atlanta, 1986.)... 

Table 7.4 Comparison between metallic and ceramic recuperators.

Metallic recuperators are 10 to 20 times lighter compared to an equivalent ceramic recuperator. 

Metallic recuperators are practically leak-proof and so are also capable ofhandling toxic fuel gases. The ceramic recuperators leak to the extent of about 50% of the volume gases and air handled. 

Metallic recuperators are favorably disposed economically when applied for preheating air below 650 °C. Ceramic recuperators are only economic when applied for preheating air above 650 °C. 

Metallic recuperators can operate with higher pressure differentials between flue gas and air side than ceramic recuperators. 

Figure 16 Ceramic recuperator. (Courtesy of Ceramiques et Composites.)... 

Ceramatec Ceramics Recuperators for high-temperature applications... 

The steel industry has been using soaking pits for at least 125 years. Originally, they were simply refractory boxes in the earth with no combustion systems. From these simple units, the industry graduated to regenerative pits which had no instrumentation to the bottom-fired pits with ceramic recuperators to one-way top-fired pits with or without metallic recuperators. With the one-way top-fired pits, more pit area is under the crane per unit of real estate, so they became the universally accepted standard. Typical size 22 ft (6.7 m) long, 8.5 to 10 ft (2.6 to 3.0 m) wide, and 10 to 17 ft (3.0 to 5.2 m) deep. The combustion system has one or two burners located high on one end of the pit with the flue directly beneath them. 

Typical heat-recuperation devices are finned gas exchangers, ceramic heat wheels, and Ljungstrom air preheaters. 

Metallic recuperators occupy less space than ceramic ones. 

Metallic recuperators are easier to maintain and install than ceramic ones, they also involve less initial cost. 

Use of the ceramic honeycomb packing structure in the recuperator keeps fuel and air substantially isolated as they travel through the recuperator. Various ceramic materials such as cordierite, mullite, alumina and silicon carbide can be used to fabricate honeycomb beds. While metallic materials have the potential to be used in honeycomb bed, corrosion resistance is a major issue... 

Radiation conductivity, 87—91 Raleigh number, 121 Ramming, 266 Rankinite, 240 Rayon, 162 Raw glaze, 308, 409 Raw materials, ceramic, 245— 246 for enamels, 400 for glass melting, 141 — 142 Reaction sintering, 297, 343, 344—345 Reaumur porcelain, 229 Reboil, 119 Recuperator, 144, 147... 

One of the peculiarities of the natural diamond is a considerably lower content of admixtures Ni, Mn, oth. as compared to the synthetic diamond. It is this feature that determines its raised resistance to the action of high temperature in the combustion wave. Figure 3 shows the dependencies of the recuperated synthetic and natural diamond strength on the mass proportion of the charge layers mi/m2 with diamond concentration equal to 25 % vol. on the example of the bi-layered composite with the ceramic binder (Ti,Mo)Ca. The strength of diamond grains is also affected by mi/m is the composites with the binder of NiAl, TiB+Ti, TiC-l-TiAl, TiB2+Si. 

Wire-drawing tools Diesel particulate filters Bearings and rotary seals Cross-flow heat exchangers Recuperators for ceramic kilns Wear- and corrosion-resistant machine parts BalUstic armor... 

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