What is Forced Draft Fan ?

Forced Draft Fan is a type of a fan supplying pressurized air to a system. In the case of a Steam Boiler Assembly, this fan is of a great importance. As we know, for a Steam Boiler to generate steam, combustion must occur, be it any fuel (wood/coal/rice husk/pet coke/LDO/Furnace oil) and for combustion to exist one of its three main requirements, is the air. And this requirement is compensated by a Forced Draft Fan. This fan supplies air to the Air-preheater, where it captures the heat from the flue gases coming from the Boiler Outlet.

Forced Draft Fan

                                              Forced Draft Fan

Nowadays, fluidized bed combustion is one of the promising ways of collecting more energy through combustion for solid fuels. But this wouldn’t have even been so famous if there wasn’t any Forced Draft Fan. Whether it is Bubbling or Circulating fluidized bed combustion incorporated Boiler. This phenomenon of fluidization is achieved through a Forced Draft Fan only.

Let us consider Bubbling Fluidized Combustion, Proper designing of the Fan as per the weight of the sand placed on the bed is very essential. The pressurized air supplied by the Fan helps in providing enough draft equalizing the weight of the bed and the quantity to be supplied, hence creating fluidization of the sand in the furnace. Not only the pressure head but also the quantity of air supplied for combustion needs to be calculated.

Primary Air Fan, Secondary Air fan are the different names of Forced Draft Fan. They all may be installed in the same Steam Boiler Assembly but they all operate at different levels of flow (m3/hr) and Head generated (mmwc). Sometimes excess air required for complete combustion is compensated by the same FD Fan or a separate FD Fan also known as Secondary Air Fan is installed to carry out the function. Forced Draft in a fan occurs when the fluid handled by the fan (generally air), is retained beyond the atmospheric pressure. Every fan designer must never underestimate the importance of the properties and composition of the fuel to be combusted and the bed height in the furnace.

We at Thermodyne Engineering Systems, have successfully designed, manufactured and supplied Force draft fans to almost all of our customers and have successfully installed and commissioned them for highly efficient boiler operation.  Because it is being rightly said (in terms of Boilers) “A HAPPY FAN, MAKES BOILER HAPPIER

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