Pneumatic Ash Recirculation System for Boiler Unburnt Matter Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Coal-fired thermoelectric power plants face challenges in reducing the unburnt matter percentage in ash discharge, particularly in light ashes, which hinders their reuse as concrete additives due to high unburnt content and inefficient handling processes, leading to increased costs and energy consumption in traditional ash extraction and grinding systems.
Innovation Solution
A pneumatic transportation system conveys all ashes, including heavy and light fractions, to a cyclone where the heavier fraction is ground and mixed with coal, then injected into the boiler through burners, undergoing high-temperature combustion to reduce unburnt matter content and achieve a fine granulometric distribution, while the lighter fraction is directly conveyed to the boiler, optimizing ash recirculation and reducing machine wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If traditional grinding mills are used to reduce heavy ash size to match light ash granulometry, then the ash size compatibility is improved, but the energy consumption and wear of grinding mechanisms increase considerably
Solution Approach 1:
The patent replaces the traditional mechanical grinding system with a pneumatic classification system. Ash particles are conveyed through a pneumatic transport system where air flow separates particles by size, with fine particles being carried to the light ash silo and coarse particles returning to the boiler. This substitution eliminates the need for mechanical grinding mills, thereby reducing energy consumption and mechanical wear while achieving the desired granulometric compatibility.
Solution Approach 2:
The invention employs pneumatic principles throughout the ash handling system. A pneumatic conveyance system transports ash from the boiler to the classification chamber, and pneumatic flow in the classification chamber separates particles based on their aerodynamic properties. This pneumatic approach replaces mechanical grinding with fluid-based separation, reducing both energy consumption and mechanical wear.
2Shape
If heavy ash is extracted and ground to fine size, then the granulometry compatibility with light ash is improved, but the wear of grinding mechanisms increases considerably
Solution Approach 1:
The patent replaces the traditional mechanical grinding system with a pneumatic classification system. Ash particles are conveyed through a pneumatic transport system where air flow separates particles by size, with fine particles being carried to the light ash silo and coarse particles returning to the boiler. This substitution eliminates the need for mechanical grinding mills, thereby reducing energy consumption and mechanical wear while achieving the desired granulometric compatibility.
Solution Approach 2:
The invention employs pneumatic principles throughout the ash handling system. A pneumatic conveyance system transports ash from the boiler to the classification chamber, and pneumatic flow in the classification chamber separates particles based on their aerodynamic properties. This pneumatic approach replaces mechanical grinding with fluid-based separation, reducing both energy consumption and mechanical wear.
3Reliability
If heavy ash is conveyed to boiler through fuel burners after grinding, then the unburnt matter content is reduced, but the system complexity increases due to additional conveyance and grinding equipment
Solution Approach 1:
The patent merges the heavy ash handling system with the existing light ash pneumatic conveyance system. Both heavy and light ash streams are combined and fed into a single pneumatic transport line that delivers them to the classification chamber and subsequently to the boiler. This integration eliminates the need for separate grinding and conveyance systems for heavy ash, reducing overall system complexity while maintaining the benefit of reduced unburnt matter content through in-boiler combustion.
Solution Approach 2:
The existing pneumatic conveyance system is designed to handle both heavy and light ash streams, giving it multi-functional capability. The system can transport different types of ash particles through the same infrastructure, eliminating the need for dedicated heavy ash conveyance equipment and reducing overall system complexity.
4Productivity
If independent conveyance and stockage assemblies are used for volatile and heavy ashes, then the handling efficiency is improved, but the investment and management costs increase
Solution Approach 1:
The patent merges the heavy ash handling system with the existing light ash pneumatic conveyance system. Both heavy and light ash streams are combined and fed into a single pneumatic transport line that delivers them to the classification chamber and subsequently to the boiler. This integration eliminates the need for separate grinding and conveyance systems for heavy ash, reducing overall system complexity while maintaining the benefit of reduced unburnt matter content through in-boiler combustion.
Solution Approach 2:
The existing pneumatic conveyance system is designed to handle both heavy and light ash streams, giving it multi-functional capability. The system can transport different types of ash particles through the same infrastructure, eliminating the need for dedicated heavy ash conveyance equipment and reducing overall system 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 approach significantly decreases the unburnt matter content in ashes, enabling their reuse as concrete additives, reduces energy consumption, and minimizes the need for adjustments to existing machinery, thereby transforming ash discharge costs into economic benefits by ensuring compliance with quality standards.
Implementation Method 1
a pneumatic transportation system conveys all ashes
Implementation Method 2
conveys all ashes, including heavy and light fractions, to a cyclone where the heavier fraction is ground
Implementation Method 3
injected into the boiler through burners, undergoing high-temperature combustion to reduce unburnt matter content
Data Source
AI summary
The present invention is about a process for treating all the ashes produced by a coal dust boiler (1), able to reduce the total unburnt matter content, to increase the combustion efficiency of the boiler (1), and to have the light ashes as the only waste arising from the coal combustion. In particular, said process provides for the extraction of the heavy ashes (4) from the boiler bottom (23), the ashes coming from the hoppers of the economizers (5) and the fraction of light ash richer of unburnt matter coming from the filters (11) used to collect the dust from the flue gas; said ashes are mixed in a silo (15), proportioned and transferred in one or more feeders (17) of the coal mills (18), and reintroduced in the boiler (1) after being mixed with the coal through the burners (2).