Heating furnace

Air preheaters come in three types: plate-type, rotary, and tubular air preheaters. 1. Plate-type air preheater: This type of air preheater is typically made from steel plates with a thickness of 1.5–4 mm. Weld the steel plates into a rectangular box, and assemble several such boxes together to form a set. The flue gas flows from top to bottom, passing along the outside of the box, while the air flows horizontally inside the box, turning upward from below; it intersects with the flue gas twice, resulting in a counterflow between the flue gas and the air and thereby achieving better heat transfer efficiency. 2. Rotary air preheaters come in two types: one is the rotor-type, where it is the heating surface that rotates, and the other is the duct-type, where it is the air duct that rotates. The rotor-type air preheater consists of a rotating cylindrical rotor and a fixed casing. The rotor is the heat-exposed surface; it is divided into numerous compartments containing heat storage plates, while fan-shaped top and bottom plates separate the rotor into flue gas channels and air channels. When on the flue gas side and exposed to heat, the regenerative plate absorbs the heat from the flue gas and stores it; once it moves to the air side, it releases the stored heat to the air, causing its own temperature to drop. As the heated surface keeps rotating, heat is continuously transferred from the flue gas to the air; the air is heated while the flue gas is cooled. This is the working principle of a rotary air preheater. 3. Structural features of the tubular air preheater: It is made up of many thin-walled steel tubes. The tubes are arranged vertically in an interlaced pattern, with their ends welded to the tube sheet, thus forming a cubic tube box. The flue gas flows from top to bottom inside the tubes, while air flows horizontally between the tubes; to enable the air to move back and forth multiple times, an intermediate tube sheet is installed within the tube bank. II. The selection of the flue gas flow rate in the air preheater should take into account factors such as heat transfer, wear, ash accumulation, and power consumption. The higher the flow rate, the better the heat transfer, and it also has a certain self-soot-blowing effect.

Why is the air preheater installed at an angle?

For heating furnaces, air preheaters generally use flue gas to heat the air. As for the installation method of the air preheater, it depends on the type of heat exchanger; if it is a heat pipe, it must be installed vertically, or at least at an angle. If it is a plate type or ordinary tube type, then there is no need to install it at an angle.