U-Valve Cooling Partitions for Thermal Stress Reduction
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Solution Overview
Problem
The existing thermal insulation loop seals in circulating fluidized bed systems face challenges such as unburned carbon combustion, temperature control issues, and differential expansion between membrane walls and partitions, leading to potential cracking during equipment start-up and shut-down.
Innovation Solution
The cooling partitions for the U-valve include intermediate and material returning partitions with cooling tube bundles covered in refractory, having an independent cooling medium flow path that extends outside the casing, using boiler feedwater or saturated steam as cooling media to match expansion coefficients with the casing, and arranged to simplify the structure and reduce thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal insulation loop seal is used, then temperature control is improved, but unburned carbon combustion and coking occur
Solution Approach 1:
The patent changes the thermal state parameter of the loop seal from thermal insulation to water cooling. The intermediate partition and material returning partition are equipped with cooling water tubes that circulate cooling water, fundamentally changing the temperature parameter to maintain it below the coking temperature, thereby eliminating unburned carbon combustion and coking issues.
Solution Approach 2:
The patent introduces cooling water as an intermediary substance to transfer heat away from the loop seal. The cooling water flows through the cooling water tubes in the intermediate partition and material returning partition, acting as a heat transfer mediator to prevent excessive temperature rise and associated harmful effects.
2Temperature
If thermal insulation loop seal is used, then temperature control is improved, but expansion difference between membrane walls and partitions occurs
Solution Approach 1:
The patent changes the thermal state of the partitions from thermal insulation to water cooling, which fundamentally alters the expansion characteristics. By maintaining the partitions at lower temperatures through cooling water circulation, their thermal expansion coefficient becomes closer to that of the membrane walls, reducing expansion differences during start-up and shut-down operations.
3Device complexity
If refractory partitions are used in water-cooling U-valve, then structure is simplified, but gaps occur between partitions and casing during start-up and shut-down
Solution Approach 1:
The patent changes the thermal state of the partitions from hot (refractory) to cool (water-cooled), which fundamentally alters their expansion characteristics. By maintaining lower temperatures through cooling water circulation, the partitions' expansion coefficients better match the membrane walls, preventing gap formation during temperature transitions while preserving structural simplicity.
4Duration of action of stationary object
If cooling partitions with independent flow path are used, then working life is prolonged, but device complexity increases
Solution Approach 1:
The patent segments the cooling system into two independent flow paths: one for the casing and another for the intermediate partition and material returning partition. This segmentation allows each component to be cooled independently with appropriate cooling water flow rates, preventing thermal stress and cracking while extending working life, despite the increased structural complexity.
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 design effectively prolongs the working life of the partitions, ensuring long-term, safe, and stable operation by reliable cooling and matching thermal expansion, reducing the risk of cracking and improving operational safety.
Implementation Method 1
the intermediate partition 4 and material returning partition 5 comprise cooling tube bundles and refractory covered at the outer surface of cooling tubes
Implementation Method 2
at least one end of the cooling tube bundles extends out of the casing of the loop seal and is connected with a header at the outside of the casing of the loop seal; and a cooling medium flow path for the cooling partitions is independent of a cooling medium flow path in the casing of the U-valve
Implementation Method 3
refractory covered at the outer surface of cooling tubes
Implementation Method 4
the intermediate partition 4 and material returning partition 5 comprise cooling tube bundles and refractory covered at the outer surface of cooling tubes; at least one end of the cooling tube bundles extends out of the casing of the loop seal
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Cooling partitions for the U-valve relates to the solid material returning technology. The cooling partitions include an intermediate partition (4) located vertically between a downcomer (1) and a riser (2) of the U-valve, and a material returning partition (5) located vertically between the riser (2) and a return chute (3). The intermediate partition (4) and the material returning partition (5) comprise the cooling tube bundles and refractory covered at the outer surface of the cooling tubes. At least one end of the cooling tube bundles extends out of the casing of the loop seal and is connected with headers at the outside of the casing of the loop seal. There is cooling medium in the cooling tubes.