Fluidized Bed Combustion: FBC Operation, Woking and Types
Table of Contents
Fluidized Bed Combustion
Utilizing the adaptable technology of fluidized bed combustion, a variety of fuels, including waste, coal, and biomass, can be burned. Compared to conventional combustion techniques, it is a more effective and environmentally friendly way to generate heat and power.
Solid fuels are burned using the fluidized bed combustion (FBC) combustion technology. Solid fuels are burned in a fluidized bed of suspended particles (FBC), which results in a highly effective and sustainable combustion process. In comparison to conventional combustion techniques, the fluidized bed enables better fuel mixing, higher combustion rates, and lower emissions.
- When a gas is injected into a bed of solid particles at a fast enough rate, the result is a fluidized bed. The particles are forced into suspension in the gas stream, much like a fluid, by the gas flow.
- This makes it possible for better fuel and air mixing, which results in more effective combustion. The fluidized bed’s high temperature also aids in the degradation of pollutants like sulfur dioxide and nitrogen oxides.
When a liquid or gas under pressure is passed through a bed of solid particles and, in certain circumstances, causes the solid particles to behave like a fluid, the process is referred to as fluidization. A fluidized bed is created when a bed of solid particles is passed through by a pressurized fluid (liquid or gas), causing the solid particles to become suspended and behave fluidically. In a variety of industrial processes, including combustion and chemical reactions, this fluidization phenomenon improves heat transfer and fosters effective reactions. Solid particles become dynamic as a result of fluidization, changing their static state.
Fluidized Bed Combustion Diagram (FBC Boiler)
The ignition of a solid fuel under the aforementioned circumstances is known as fluidized bed combustion.
Types of Fluidized Bed Combustion
- Bubbling FBC (BFBC)
- Circulating FBC (CFBC)
For fuels with lower heating values, like rice husk, bubbling FBC is used. Due to its capability to effectively burn and utilize such biomass materials, such as rice husk, bubbling FBC is a commonly used combustion technique for fuels with lower heating values. Under such a sort, the following are the primary fluidization-causing factors:
Solid Fuel Particle Size
Air Fuel Mixture
Flowing Bed When the forced draught fan supplies air to the Furnace of the Boiler, combustion occurs. The air enters the furnace bed from the nozzles that are installed there and is heated before fluidization (used for the bubbling phenomenon). Additionally, the sand above the nozzles prevents the air from rising. However, at high enough speeds, fluidization of the sand happens when the air pressure equals the weight of the sand. The fuel conveyor is now feeding preheated bubbling sand with fuel, which ignites and burns away. Additionally, this phenomenon guarantees full fuel combustion.
Steam is produced by heating the nearby boiler tubes with the heat from combustion. Bubbling Fluidized Bed Combustion has improved thermal efficiency and simple ash removal as its main benefits. Circulating Fluidized Bed Combustion is another type, and it is used with fuels like petcoke that have higher heating values. With the aid of a forced draft fan and ducts, the unburned fuel is fed back into the furnace in this method, ensuring improved combustion, greater heating, and excellent fuel flexibility. Additionally, compared to BFBC, the fluidizing velocity of air in CFBC is higher. The power consumption is just one of the many shortcomings.
Due to the higher levels of draught needed to create fluidization, the motors installed in forced-draught fans use more energy than those installed in similarly sized boilers that are fired by wood or coal.