Waste Extract Gas Air Heat Exchanger Steam Air Heater Auxiliary Accessory 2 Pass Design

Power station CFB boiler auxiliary accessory boiler air preheater Factory supplier Spare parts

Boiler auxiliary air preheater Introduction

1. Heating combustion air can raise boiler efficiency about 1% for every 40F in temperature increase. The most common way to preheat the air is with a heat exchanger on the flue exhaust. The heat exchanger can be either air-to-air or air-to-liquid-to-air.

2. Combustion air pre-heater technology on large coal-fired boilers dates back to the early 1900’s, and is used on most all large boilers todays. With the increasing price of fuel and technology improvements, the size of a boiler that can be economically equipped with a pre-heater should become smaller. Although still a technology most applicable to large boilers, high energy prices will certainly motivate innovative new applications for economical combustion air pre-heaters on ever smaller boilers.

Air Preheater Pros

• 2 pass design to extract maximum waste heat from flue gases leaving the boiler.
• It is used to extract waste heat from the flue gases leaving the boiler exhaust thereby increasing the efficiency of a boiler by 2-3 %.
• It is used to preheat the fuel which further increases the boiler efficiency.
• Payback time is less.

Air Preheater Cons

• Adding and equipment or accessory in the path of flue gases increases flue gas pressure drop down the line, so the size of Induced Draft Fan increases.

Working of Air Preheaters(APH)

1. 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.

2. Air Preheaters consist of a shell where tubes are arranged in a square or triangular pitch and are welded to a tube plate. Depending upon the type of operation and ease of cleaning, flue gases & air can be allowed to travel either shell side or tube side interchangeably.

Tubular type Air Preheater

1. Tubular preheaters consist of straight tube bundles which pass through the outlet ducting of the boiler and open at each end outside of the ducting.

2. Inside the ducting, the hot furnace gases pass around the preheater tubes, transferring heat from the exhaust gas to the air inside the preheater.

3. Ambient air is forced by a fan through ducting at one end of the preheater tubes and at other end the heated air from inside of the tubes emerges into another set of ducting, which carries it to the boiler furnace for combustion.

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