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How does fluidized-bed combustion aim to improve coal use?
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coal utilization
Cross-regenerative coke oven. (A) Cross section, showing the alternating arrangement of flue walls and ovens; (B) longitudinal section, showing (left) a series of combustion flues in a single flue wall and (right) part of a long, slotlike oven.
Fluidized-bed combustion improves coal utilization by enhancing efficiency and mitigating environmental impacts through the following mechanisms:
- Efficient Heat Transfer: By suspending crushed coal in an upward airstream, the bed behaves like a boiling liquid. This allows for highly efficient and uniform heat transfer, which reduces the surface area required for steam generation and lowers total capital costs.1
- Lower Operating Temperatures: Operating at lower temperatures (850–950 °C) reduces fouling and corrosion of heat-transfer surfaces. Furthermore, these lower temperatures inhibit the formation and emission of nitrogen oxides (NO).1
- Pollutant Control: These systems are particularly effective for low-quality, high-sulfur coals. When limestone or dolomite is added to the bed, it reacts with sulfur dioxide released during combustion to form calcium sulfate, which can be removed as a solid by-product.1
- Fuel Flexibility: The process is capable of burning coals with high or variable ash content, making it a versatile method for diverse coal types.1