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The secret of fluidized bed combustion technology: Why does it make coal burn more efficiently?
Fluidized bed combustion (FBC) technology is gradually receiving attention from the energy market. Because of its superior combustion efficiency and environmental protection performance, coal utilization has become more efficient. Compared with traditional combustion technology, fluidized bed combustion has demonstrated good consistency and stability in power production at various scales.
In fluidized bed combustion, fuel particles are suspended in a bed of hot bubbles, which is composed of ash and other particulate materials (such as sand, limestone, etc.).
The reason why such efficient combustion can be achieved is mainly due to the rapid mixing inside the fluidized bed and the intimate contact between gas and solid, which ensures rapid heat transfer and chemical reactions. Fluidized bed combustion systems can efficiently incinerate a variety of low-grade solid fuels, including most types of coal, coal waste and woody biomass, which avoids the need for expensive pre-processing of the fuel (such as comminution).
In addition, fluidized bed combustion units are typically smaller in size than conventional boilers, giving them significant advantages in cost and flexibility.
Using limestone as bed material, fluidized bed combustion can effectively reduce sulfur dioxide (SOx) emissions. Limestone combines with sulfates during the combustion process, increasing heat exchange efficiency. When the preheated residue is heated by direct contact with the water pipe, the heat conduction process makes the heat more concentrated, further improving the overall efficiency. At the same time, because fluidized bed combustion operates at lower temperatures (approximately 800 °C), the amount of nitrogen oxides (NOx) produced is also significantly reduced. However, low-temperature combustion may also lead to increased emissions of PAHs.
Advantages of fluidized bed combustion
Fluidized bed combustion technology is growing rapidly in the energy industry for two main reasons. On the one hand, it provides freedom of choice of fuel, not only allowing the use of fuels that are difficult to burn with other technologies, but also improving combustion efficiency. On the other hand, this technology can effectively reduce nitrogen oxide emissions during the combustion process, and can simply remove sulfur by adding limestone.
The development of fluidized bed combustion stems from the need to control pollutant emissions without relying on external emission control equipment.
The introduction of fluidized bed combustion technology not only helps to improve the combustion efficiency of coal, but also plays a certain positive role in environmental protection. This can provide solutions for energy plants. In today's increasingly stringent environmental standards, fluidized bed combustion is bound to become an important choice in the future.
Types of fluidized bed combustion
Fluidized bed combustion systems are divided into two main types: atmospheric system (FBC) and pressurized system (PFBC). There are also sub-types such as bubble fluidized bed (BFB) and circulating fluidized bed (CFB). Each of these systems has its own characteristics and is suitable for different operating environments.
Atmospheric fluidized bed combustion
In atmospheric fluidized beds, limestone or dolomite is used to capture sulfur released by coal combustion. Air nozzles suspend a mixture of fuel and charred coal, creating a fluid-like flow of red-hot particles. These boilers operate at atmospheric pressure.
Pressurized fluidized bed combustion
First-generation PFBC systems also used adsorbents and air nozzles to suspend the mixture, but they operated at elevated pressures to create high-pressure airflow, which is critical to propelling gas turbines. In this way, the steam generated in the fluidized bed can be used to drive a steam turbine, achieving higher overall cycle efficiency.
Advanced PFBC systems, such as APFBC, further increase the inlet temperature of the gas turbine to achieve higher overall cycle efficiency.
For the further development of this technology, many industry experts have provided many insights on how to balance environmental standards and economic benefits. With continued scientific and technological progress, how will future fluidized bed combustion technology affect the global energy market?
