Pebble-heater twins with fluid dynamic valve - an efficient possibility for high combustion air preheating

Pebble-Heaters (PH) with radial fluid flow are very effective regenerators for gas preheating at high temperatures. They can reach a regeneration efficiency of up to 98% and the temperature limit nowadays is around 1,400°C. The investment costs are pretty low, due to the usage of a bulk material (usually alumina pebbles) as the heat storage material. With those characteristics they are very attractive for combustion air preheating in the scope of a regenerative burner system. Their biggest disadvantage is that two units, with corresponding hot gas valves, are required for a continuous operation. For smaller capacities, i.e. less than 10,000 mSTP3/h, those hot gas valves are in fact the most expensive part of the equipment.

In order to overcome that disadvantage, the so-called Fluid Dynamic Valve (FDV) has been developed. That is a system of channels cast in high quality fire clay, which enables a very fast switching between two hot gas streams. As there are no movable mechanical parts, there is no need for any cooling, so the heat losses are minimal. The application temperature depends on the fire clay quality, so that 1,400°C are achievable. The production costs are extremely low, as all parts are cast in fire clay and enforced outside with a steel shell. The operation of a FDV is based on the interaction between the velocity field, pressure field and flow direction. With a convenient design of the channels it is possible to increase the velocity and to decrease the pressure (and vice versa) at the appropriate positions, so that two hot gas streams flow in different directions. Just by switching a four way valve on the cold side (i.e. after the PH regenerators) it is possible to influence the pressure distribution and correspondingly to change the flow directions of the hot streams.

Veröffentlicht in: 6th European Conference on Industrial Furnaces And Boilers: Volume II, Lisbon 2002



Copyright: © OTH Amberg-Weiden
Quelle: Veröffentlichungen 2003 und ältere (August 2005)
Seiten: 11
Preis: € 5,00
Autor: Dr. Dragan Stevanovic
Werner Fischer
 
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