What is a rotary air heater?

The heater absorbs waste heat from the flue gas as it leaves the economiser at typical temperatures around (370oC) and transfers this energy to the rotating steel heat transfer element plates. The hot elements then rotate into the inlet air used to provide the oxygen to fire the fuel in the boiler furnace.

What is recuperative air heater?

Tubular air heaters are known as Recuperative type of air preheater. Recuperative air heater is generally called static air heater. The flue gas which is the heating medium passes through inside of the tubes whereas the air entering the air preheater passes through outside of the tubes by conduction.

What is preheater used for?

The purpose of the air preheater is to recover the heat from the boiler flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost in the flue gas.

What do you mean by boiler Draught?

DEFINITION  Boiler draught may be defined as the small difference between the pressure of outside air and that of gases within a furnace or chimney at the grate level, which causes flow of air/hot flue gases to take place through boiler.

What is the difference between recuperative and regenerative heat exchanger?

A Recuperative Heat Exchanger has separate flow paths for each fluid and fluids flow simultaneously through the exchanger exchanging heat across the wall separating the flow paths. A Regenerative Heat Exchanger has a single flow path, which the hot and cold fluids alternately pass through.

What is the benefit of preheating the air?

By preheating the air, damage to machinery can be prevented. Additionally, it promotes higher savings in terms of energy by improving heating efficiency. By preheating the air, industrial systems that consume high amounts of energy or exhaust gases can experience significant energy savings.

How does a air preheater work?

Air Preheaters have a shell and tube type construction where exhaust heat from the flue gases is transferred to the air when they come in indirect contact with each other. Air Preheaters consist of a shell where tubes are arranged in a square or triangular pitch and are welded to a tube plate.

Why economiser is used in boiler?

In boilers, economizers are heat exchange devices that heat fluids, usually water, up to but not normally beyond the boiling point of that fluid. They are a device fitted to a boiler which saves energy by using the exhaust gases from the boiler to preheat the cold water used to fill it (the feed water).

What are the different types of air preheaters?

Two types of air preheaters are used: bisector (one air stream per air heater) and trisector ( two air streams per air heater). The trisector incorporates both primary and secondary air within one housing. The bisector and trisector terminologies are typically associated with the Ljungstrom design.

What kind of air heater does Ljungstrom use?

The Ljungstrom tri-sector air heater (50% gas, 35% secondary air and 15% primary air) as shown in Figure above, is a regenerative type air heater. The heat removed from the outgoing flue gas heats incoming primary and secondary air.

How are parabolic sectorplates used in rotary heaters?

Through continued innovation, Howden have developed the latest Rotary Heater leakage reduction method – Parabolic Sectorplates. Hot End Sectorplates are structurally designed with variable stiffness to deform parabolically, when actuated, to match the shape of the deformed operating rotor. Thereby minimising the hot end leakage gap.

What makes up the rotor of an air heater?

The air heater consists of the heat transfer surface, and the primary rotor driving mechanism, which consists of the motor, coupling, speed reducer, and pinion gear. Auxiliary air drive systems are also provided with each air heater.