Fluidized Bed Heat Exchanger Partition Wall Design
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Solution Overview
Problem
Existing fluidized bed heat exchangers face challenges such as increased difficulty in supporting due to shifted center of gravity, reduced particle flow rates due to inlet channels, and potential for unwanted chemical reactions at low temperatures, particularly in oxyfuel combustion.
Innovation Solution
A fluidized bed heat exchanger design without a vertical partition wall, where the partition wall is formed by bending water tubes from the side walls to guide particles towards the rear, allowing for efficient heat recovery without cooling to low temperatures and minimizing chemical reactions, with a windbox divided to control fluidizing velocities and oxygen content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a vertical partition wall is used to guide particles, then particle flow control is improved, but the center of gravity shifts further from the furnace making support more difficult
Solution Approach 1:
The patent removes the vertical partition wall from the heat exchanger structure, extracting the element that caused the center of gravity shift. Instead, particle flow is controlled through the geometry of the inlet channel and fluidizing gas distribution, achieving flow control without the problematic vertical partition that extended the center of gravity away from the furnace support point.
Solution Approach 2:
The inlet channel structure serves multiple functions: it introduces particles from the furnace, guides particle flow into the heat exchanger, and controls fluidizing gas distribution. This multi-functional design replaces the need for a separate vertical partition wall, maintaining particle flow control while avoiding the support difficulty caused by extended center of gravity.
2Ease of operation
If an inlet channel is used to introduce particles, then particle introduction is improved, but friction limits the highest amount of particles that can be introduced
Solution Approach 1:
The inlet channel is designed with curved transitions and rounded corners instead of sharp angles, reducing turbulence and friction losses. The curved geometry allows particles to flow more smoothly into the heat exchanger, increasing the maximum particle flow rate that can be introduced without excessive frictional resistance.
Solution Approach 2:
The system uses fluidizing gas flow to assist particle introduction and movement through the inlet channel. The pneumatic assistance from the fluidizing gas reduces frictional resistance and enables higher particle flow rates to be introduced into the heat exchanger efficiently.
3Loss of energy
If particles are cooled to low temperatures, then heat recovery is improved, but unwanted chemical reactions occur particularly in oxyfuel combustion
Solution Approach 1:
The heat exchanger is designed to cool particles only to the extent necessary for efficient heat recovery, rather than cooling them to low temperatures. By optimizing the heat exchange surface area and fluidizing gas flow, the system achieves sufficient heat recovery while maintaining particle temperatures above the threshold for unwanted chemical reactions in oxyfuel combustion.
Solution Approach 2:
The system controls the temperature parameter of cooled particles to remain within a specific range that enables efficient heat recovery without dropping below the threshold temperature that would trigger unwanted chemical reactions. This parameter optimization balances heat recovery efficiency with chemical stability in oxyfuel combustion conditions.
4Device complexity
If the partition wall is formed by bending water tubes, then structural complexity is reduced, but manufacturing precision is required for proper particle guidance
Solution Approach 1:
The water tubes are bent to specific geometric parameters that optimize both particle flow guidance and structural simplicity. By carefully selecting the bend radius, angle, and position of the tubes, the design achieves effective particle guidance while maintaining manufacturability and avoiding excessive complexity in the partition wall construction.
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
Enables high particle flow rates and efficient heat recovery without low temperature cooling, reducing the risk of chemical reactions and simplifying support, while maintaining a compact heat exchanger size.
Implementation Method 1
The tubes of each wall are then connected to a horizontal lower header arranged below the wall so as to convey heat transfer fluid, usually water or steam, upwards to an upper header or another water tube panel. Typically the water tubes of the enclosure walls function as evaporation surfaces in a drum boiler
Implementation Method 2
Fluidized bed heat exchangers are commonly used in fluidized bed boilers to recover heat from hot solid particles conveyed from the furnace of the boiler to the heat exchanger. After cooling in the heat exchanger, the cooled particles are returned back to the furnace.
Data Source
Figure 1~2
AI summary
A fluidized bed heat exchanger (10) of a fluidized bed boiler (12), the heat exchanger comprising a front wall (16) adjacent the fluidized bed boiler, a rear wall (18) opposite to the front wall and two side walls (60,60'), the walls being formed as water tube panels, an inlet opening (24) arranged in a first section of an upper portion of the heat exchanger for introducing hot particles from the fluidized bed boiler to the heat exchanger, heat exchange surfaces (34) for recovering heat from the particles and an outlet opening (36) arranged in a second section of the upper portion of the heat exchanger for returning cooled particles as an overflow from the heat exchanger back to the fluidized bed boiler, wherein the heat exchanger comprises a partition wall (26) between the first (38) and second (40) sections of the upper portion of the heat exchanger, wherein the partition wall extends from the front wall to a center section of the heat exchanger, and the partition wall is formed by bending water tubes from at least one side wall (60, 60') of the heat exchanger.