Q1: Flue gases pass through the following boiler accessories in a high pressure natural circulation boiler.
A. Induced draft fan B. Economiser C. Air preheater D. Steam superheater
Which of the following gives the correct sequence of flow of the flue gases through the above mentioned boiler accessories ?

ANS:B - D, B, C, A

The correct sequence of flow of the flue gases through the mentioned boiler accessories is: D, C, B, A

1. Steam Superheater (D): Flue gases first pass through the steam superheater, where they transfer heat to the steam, increasing its temperature to the desired superheated level.
2. Air Preheater (C): After passing through the steam superheater, the flue gases proceed to the air preheater. Here, they transfer heat to the incoming combustion air, raising its temperature before it enters the furnace for combustion. This process improves the overall efficiency of the boiler by utilizing waste heat from the flue gases.
3. Economiser (B): The flue gases then flow through the economiser, where they further transfer heat to the feedwater before it enters the boiler drum. The economiser preheats the feedwater using the heat recovered from the flue gases, reducing the amount of fuel needed to raise the water temperature to the desired level in the boiler.
4. Induced Draft Fan (A): Finally, the flue gases are drawn out of the boiler by the induced draft fan. This fan creates a negative pressure zone in the boiler, causing the flue gases to flow through the boiler and its accessories and then exhaust them into the atmosphere through the chimney.