CFB Boiler U-Shaped Heat Transfer Surfaces
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Solution Overview
Problem
Conventional circulating fluidized bed (CFB) boilers face challenges in efficiently transferring heat due to limited furnace surface area, leading to mechanical issues and reduced performance when increasing capacity, particularly with U-shaped panels that are prone to vibrations and displacement, which can cause mechanical failures.
Innovation Solution
The design incorporates U-shaped heat transfer surfaces extending from the roof and side walls, fixed to vertical chambers, allowing for a higher extension rate of 40-70% of the combustion chamber height, with bended tubes to accommodate thermal expansion and prevent horizontal displacement, and includes drainage features for condensates during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the height of the furnace is increased to provide additional heating surface area, then the heat transfer efficiency is improved, but the cost increases and mechanical problems occur
Solution Approach 1:
The patent transitions from vertical extension (increasing furnace height) to horizontal extension (U-shaped panels extending 40-70% of chamber height from side walls) to provide additional heating surface area. This dimensional change allows increased heat transfer efficiency without the mechanical and cost issues associated with height increases.
2Area of stationary object
If U-shaped panels are used to increase heating surface area, then the heat exchange capacity is improved, but the panels are prone to vibrations and displacement leading to mechanical failures
Solution Approach 1:
The patent applies different structural qualities to different parts of the U-shaped panel system. The upper portion extending from the roof is designed for maximum heat exchange surface area, while the lower portion (40-70% of chamber height) is anchored to side walls with specific fixation methods to provide local structural support and prevent vibrations in the most vulnerable regions.
Solution Approach 2:
The patent incorporates expansion joints at the roof crossing points of U-shaped panels to beforehand accommodate thermal expansion and contraction. This preventive measure cushions the structure against thermal stresses that would otherwise lead to mechanical failures during operation.
3Reliability
If the furnace enclosure is made gastight to prevent ash leakage, then the sealing performance is improved, but the thermal expansion displacement is constrained causing mechanical stress
Solution Approach 1:
The patent employs expansion joints as flexible connection elements that allow the gastight panels to move slightly with thermal expansion while maintaining the seal. These flexible joints accommodate displacement without compromising either the sealing performance or the structural integrity of the enclosure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances heat transfer efficiency and stability, reducing the risk of mechanical failures by allowing for greater heat exchange surface area without the need for costly height increases, while maintaining structural integrity and facilitating condensate management.
Implementation Method 1
The heat released from the combustion of fuel is transferred to water or steam flowing inside the tubes and also allowing the tubes to be cooled
Implementation Method 2
water or steam flowing inside the tubes
Implementation Method 3
Air is introduced into the furnace to fluidize the solid particles
Implementation Method 4
chemical reactions and/or combustion reactions can take place
Implementation Method 5
bended tubes to accommodate thermal expansion and prevent horizontal displacement
Implementation Method 6
solid particles escaping the furnace and collected by the cyclones before returning to the furnace
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
The invention relates to a circulating fluidized bed boiler (1) comprising a combustion chamber (2), characterized in that the combustion chamber (2) comprises: - first heat transfer surfaces (7) forming at least one vertical chamber extending from a lower part (5) of the combustion chamber (2), and - second heat transfer surfaces (8) having an inlet part and an outlet part which extend both from an upper part (6) of the combustion chamber (2), said second heat transfer surfaces (8) being fixed to vertical chambers (7).