Stepped Grate Assembly for Fluidized Bed Boiler Solids Removal
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Solution Overview
Problem
Nozzle devices in fluidized bed boilers can obstruct the removal of solids, and their orientation and height differences are not optimal, affecting the operation of the combustion chamber, and the protective refractory material layer's shape and structure vary between boilers.
Innovation Solution
A grate assembly with a grate bottom wall, protective refractory material layer, and nozzle devices that include concentric landings and nozzle devices embedded in the refractory material layer, allowing controlled air flow and efficient solid removal through a modular and expandable system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If nozzle devices are installed in the protective refractory material layer to provide air for combustion and fluidization, then combustion efficiency and fluidization are improved, but the nozzle devices obstruct the removal of solids and create non-optimal air jet orientation
Solution Approach 1:
The bottom section is divided into multiple sloping floor sections with different inclinations. The first sloping floor section has a steeper inclination optimized for solids removal, while the second section has a gentler inclination. Nozzle devices are selectively positioned in specific sections based on their function, separating the air injection function from the solids removal path and eliminating obstruction issues.
Solution Approach 2:
Different regions of the bottom section are assigned different functional characteristics. The first sloping floor section is optimized for solids removal with steeper inclination and specific nozzle positioning, while the second section is optimized for combustion with different inclination and nozzle configuration. This local differentiation allows each region to perform its specific function optimally without interfering with other functions.
2Power
If nozzle devices extend to varying heights to optimize air jet orientation, then combustion performance is improved, but height differences in the sloping floor vary strongly affecting fluidized bed operation
Solution Approach 1:
The bottom section is segmented into distinct sloping floor sections with controlled height differences. By dividing the space and assigning specific functions to each section, the patent manages height variations systematically rather than having uncontrolled variations across the entire bottom section, thereby maintaining stable fluidized bed operation.
Solution Approach 2:
The patent creates a more uniform height profile in the fluidized bed region by strategically positioning nozzle devices and designing sloping floor sections that compensate for natural height variations. This equipotential approach ensures consistent fluidization conditions across different regions, preventing operational instability caused by excessive height differences.
3Adaptability or versatility
If the protective refractory material layer is shaped to accommodate varying combustion chamber dimensions, then adaptability to different boiler sizes is improved, but the shape and structure differ between boilers reducing standardization
Solution Approach 1:
The bottom section is divided into modular sloping floor sections that can be configured in different combinations. This segmentation allows the same standardized components to be assembled into different overall shapes and sizes, providing adaptability to various combustion chamber dimensions while maintaining structural consistency through repeated use of standard modules.
Solution Approach 2:
The sloping floor sections and nozzle devices are designed as universal components that can serve multiple functions and be applied across different boiler sizes and configurations. This universality reduces structural variability by using the same standardized elements throughout, eliminating the need for custom-designed refractory structures for each boiler size.
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
The solution provides a controlled and efficient removal of solids, minimizing obstruction and optimizing nozzle device height differences, enhancing the operation of the fluidized bed boiler's combustion chamber.
Implementation Method 1
supplying fluidizing primary air above the grate bottom wall and the protective refractory material layer into the combustion chamber for maintaining combustion of fuel and fluidization of bed material
Implementation Method 2
solids on the refractory material layer are guided downwards to a solids removal conduit adapted to guide the solids through the refractory material layer and the grate bottom wall
Data Source
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AI summary
A grate assembly for use in a bottom section (28) of a combustion chamber(12) of a fluidized bed boiler (10), comprising: a grate bottom wall (32); a protective refractory material layer (36); a plurality of nozzle devices (38) for supplying fluidizing primary air; at least one grate module (40) formed on the grate bottom wall (32). Each grate module (40) comprises a solids removal opening (42); a plurality of concentric landings (46) formed in the refractory material layer (36) and separated by frontal surfaces (48) between the landings. Each frontal surface (48) surrounds one of the landings and follows the shape of the perimeter of a rectangle or a rectangle with at least one shaped corner. The landings (46) define a stepped structure. Each landing comprises a group of the nozzle devices embedded in the refractory material layer (36) and adapted to jet the air through one of the frontal surfaces (48)along one of the landings (46) that is adjacent to the frontal surface.