Reciprocating Grate Furnace: Optimizing Low-Quality Coal and Biomass Combustion
Overview of Reciprocating Grate Furnace
The reciprocating grate furnace is an efficient furnace design widely used for the combustion of low-quality coal and biomass fuels. Its primary function is to optimize combustion efficiency, especially for fuels with inconsistent quality or high ash content. The furnace consists of several key components, including fixed grates, movable grates, a driving mechanism, and a reciprocating system.
The movable grates are designed to allow fuel to move gradually across the furnace surface, ensuring thorough combustion through each stage of the burning process. The grate system is stepped, with an inclined angle that facilitates the downward flow of fuel, ensuring efficient air circulation and improving combustion conditions.
Working Principle of Reciprocating Grate Furnace
The combustion process in a reciprocating grate furnace is similar to that of a chain grate furnace. Fuel is fed into the furnace from the hopper and enters through a regulating gate that controls the fuel layer thickness. The reciprocating action of the grates moves the fuel from the front to the rear of the furnace, where it undergoes drying, volatile combustion, coke combustion, and ash disposal.
The continuous raking action of the movable grates helps move fresh fuel onto the burning bed, enhancing the ignition conditions. Additionally, during the return stroke, the grates push burning carbon particles back into the lower layers, providing heat to ignite the lower fuel layers, further improving combustion efficiency.
Design Features of Reciprocating Grate Furnace
The design of the reciprocating grate furnace aims to enhance air mixing and turbulence within the furnace, thereby improving combustion efficiency. Features include front and rear arches or a central baffle wall, along with secondary air systems to optimize the ignition conditions at the furnace bed. Proper airflow direction is crucial to ensure that combustible gases generated at the front of the grate mix with excess air and are fully combusted in the high-temperature zone.
The furnace’s staged air distribution system ensures that the appropriate amount of air is supplied at each combustion stage, preventing instability caused by uneven airflow.
Advantages of Reciprocating Grate Furnace
- High Adaptability: Especially effective for burning low-quality coal and biomass fuels with high ash content.
- High Combustion Efficiency: The continuous raking action of the grates increases combustion intensity and reduces heat loss.
- Simple Structure: Compared to chain grate furnaces, the reciprocating grate furnace uses less metal, which lowers initial investment costs.
- Dual-Sided Combustion: Unlike chain grate furnaces, the reciprocating grate furnace provides dual-side ignition, ensuring more stable combustion.
Disadvantages of Reciprocating Grate Furnace
- High-Temperature Wear: The head of the movable grates frequently rakes hot, glowing coke, making them prone to damage. Damage or detachment of the grates is difficult to detect and replace, which may affect boiler safety.
- Air and Fuel Leakage: Due to the furnace structure, there is a risk of air and fuel leakage along the sides of the grate, which can lead to unstable combustion, especially if the bed is uneven.
Conclusion
The reciprocating grate furnace is an excellent solution for burning various types of fuels, especially low-quality coal and biomass. With appropriate design and adjustments, it can significantly improve combustion efficiency, reduce heat loss, and ensure stable operation of industrial boilers. However, regular maintenance and improvements to the sealing structure are necessary to prevent combustion instability caused by structural issues.
