Howden Air Preheaters Trisector

Trisector air preheaters The tri-sector design has been supplied on many recent boilers. This unit has one gas duct and two air ducts. The primary air for drying and transporting the pulverised coal from the coal mill to the furnace is at a much higher pressure. It is very important to minimise the leakage of the air to gas for a number of reasons which will be described later. Key benefits Low capital investment Rotary regenerative air preheaters have a much reduced size and cost relative to recuperative tubular or plate heat exchangers. Low leakage level without drift Most new air preheaters can achieve leakage levels that are close to their design values after initial commissioning or when set up correctly after an outage. However, after a period of operation of up to 2 or 3 years, the leakage can increase dramatically, typically from 5% - 12% on secondary preheaters and to between 12% - 25% (and frequently higher) on high pressure mill preheaters. Similar increases in leakage are experienced on tri-sector preheaters, which are the most common type of air preheater adopted on pulverised coal fired boilers. These increased leakages increase FD, ID &PA fan power and in extreme cases de-rate the Unit. The Howden VN sealing concept maintains low design leakage between outages. Extensive choice of heat transfer elements Howden have designed and developed an extensive range of heat transfer elements over the years. Combinations of elements are selected to optimise performance, pressure drop and cleanability for the given fuels. Low maintenance Conceptual and detailed design targets the achievement of simplicity and minimal maintenance. Fixed sealing surfaces and centre drive greatly reduces maintenance by removing actuators and pin racks. High availability The major cause of reduced availability in air preheaters is due to element fouling. Careful element selection to suit the application, cold end temperature control and the application of the correct cleaning system maintains very high availability. Centre column or bottom girder support Custom designed and optimised to suit arrangement and client preference. Standard features All air preheater types can have a vertical shaft and horizontal rotor arrangement and are termed vertical air preheaters as the rotor shaft is vertical. This unit, with one gas duct and two air ducts is called a tri-sector air preheater.