Howden Air Preheaters Bisector

Bisector air preheaters Power boiler applications require highly efficient and reliable air preheaters to ensure optimum boiler performance. An air preheater with a gas sector and one air sector is called a bi-sector design. Gas and oil fired boilers require only bi-sector design air preheaters. Coal fired boilers also require an air-stream to dry the coal and to transfer the pulverised coal from the coal pulveriser to the furnace. This air is called primary air and it has to be at a higher pressure than the secondary air to overcome the pressure drop through the coal mill, the pulverised fuel pipework and the coal burner. In coal fired boilers there are two air supplies : Secondary Air (SA) which is supplied direct to the burners and is the bulk of the combustion air supply. Primary Air (PA) which is used to dry the coal and transport the pulverized coal from the coal mills to the burners. 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. 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.