Ceramic Heat Exchange Media Options
The ceramic heat exchange media is a key element to every installed Regenerative Thermal Oxidizer (RTO). With a wide variety of ceramic media types available the selection of the correct type can be critical to the proper operation of an RTO.
In general, there are two main types of heat exchange media: random packing and monolith block. Each offers unique advantages and disadvantages that must be considered.
Random packing was the first type of ceramic media used in RTO applications and is still used today in certain applications. (The most common form of random packing is the saddle (see adjacent photo) although there are several other shapes that are sometimes employed.)
The advantages of this type of media are 1) ease of installation and removal, 2) good resistance to plugging and 3) lower first cost. The main disadvantage is that random packing requires relatively low gas velocity which means an RTO designed with random packing media needs a large area to maximize its heat exchange properties.
Typically, an RTO designed for +95% Thermal Efficiency Recovery (TER) with random packing will require a random media depth of 8’ depth. This 8’ of depth contributes to a high-pressure drop associated with the RTO fan that moves air through the system.
Over the years a great deal of attention has been focused on the advancement of types of ceramic media for use in RTOs with the intent of reducing fuel and electricity requirements. This focus has led to the development of structured, monolithic, media designs as shown on the adjacent photograph. In contrast to random packing structured media operates with laminar gas flow.
True laminar flow allows this type of media to provide much better heat transfer at significantly higher velocities than with random media which operates in the turbulent gas flow range. This means that much less media is needed to provide the required heat transfer.
For example, an RTO designed with monolith block may only need 5 feet of depth while an RTO with random media would need 8 feet for the equivalent heat exchange duty. This represents a significant savings in the brake horsepower (bhp) requirement for the RTO fans and a much smaller footprint of the unit. The main disadvantage of structured media is susceptibility to fouling.
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