Oxy-fired Boiler Thermal Control via Segmented Oxygen Distribution
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Solution Overview
Problem
Oxy-fired boilers face challenges in optimizing thermal performance, reducing ash deposition and fireside corrosion, and preventing slagging due to non-uniform heat release profiles and excessive oxygen combustion temperatures, which are not effectively addressed by existing methods.
Innovation Solution
A method involving the controlled distribution and proportioning of oxygen and recycled flue gas streams at various points within the boiler to create a customized heat release profile, using fluid flow control devices to split and mix oxidant streams, allowing for localized oxygen enrichment and modulation of flue gas flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxygen is added to increase combustion intensity and thermal performance, then heat release and steam generation improve, but combustion temperature becomes excessively high causing ash deposition, fireside corrosion, and slagging
Solution Approach 1:
The patent applies local quality by distributing oxygen addition at multiple specific locations within the boiler (windbox, lower overfire air region, upper overfire air region) rather than uniformly throughout. Each region receives oxygen at optimized concentrations tailored to local combustion conditions, enabling high thermal performance in fuel-rich zones while maintaining lower temperatures in areas prone to ash deposition and corrosion.
Solution Approach 2:
The oxygen addition process is segmented into multiple distinct stages and locations: windbox oxygen enrichment for primary combustion, lower overfire air oxygen supplementation, and upper overfire air oxygen addition. This segmentation allows independent optimization of oxygen concentration at each stage, achieving high overall thermal efficiency while controlling peak temperatures to prevent harmful effects.
2Temperature
If recycled flue gas is increased to dilute oxygen and moderate temperature, then combustion temperature is controlled, but thermal efficiency decreases due to excessive dilution
Solution Approach 1:
The patent applies local quality by using recycled flue gas dilution selectively in regions where temperature control is critical (upper overfire air region and furnace outlet) while maintaining oxygen-rich conditions in primary combustion zones. This localized approach ensures combustion temperature remains within safe limits without excessive overall dilution, preserving thermal efficiency.
Solution Approach 2:
The flue gas recirculation is segmented and applied at different stages: partial dilution in the lower overfire air region to moderate temperatures, and more significant dilution in the upper overfire air region to control peak combustion temperatures. This staged segmentation allows temperature control while minimizing the total amount of dilution required, maintaining thermal efficiency.
3Productivity
If oxygen distribution is non-uniform to control heat release profile, then thermal performance improves, but combustion stability and completeness may be compromised
Solution Approach 1:
The patent applies local quality by providing oxygen enrichment specifically in the windbox and lower overfire air regions where fuel combustion is most intense, ensuring stable and complete combustion in these critical zones. Simultaneously, controlled oxygen addition in upper regions maintains appropriate heat release profiles without compromising overall combustion stability.
Solution Approach 2:
The oxygen distribution is segmented into mandatory enrichment zones (windbox, lower overfire air) for combustion stability and optional modulation zones (upper overfire air) for heat release profile control. This segmentation ensures that combustion stability requirements are met in fuel-rich regions while allowing heat release optimization in other areas.
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 enhances thermal performance, reduces ash deposition and corrosion, and prevents slagging by optimizing heat release patterns, enabling more efficient steam generation and reducing material requirements, while also improving emission characteristics and ash properties.
Implementation Method 1
combusting a fuel in a boiler with an oxidant stream that comprises a mixture of oxygen and recycled flue gas
Implementation Method 2
create a customized heat release profile... optimizing heat release patterns
Data Source
AI summary
Disclosed herein is a method of controlling the operation of an oxy-fired boiler; the method comprising combusting a fuel in a boiler; producing a heat absorption pattern in the boiler; discharging flue gases from the boiler; recycling a portion of the flue gases to the boiler; combining a first oxidant stream with the recycled flue gases to form a combined stream; splitting the combined stream into several fractions; and introducing each fraction of the combined stream to the boiler at different points of entry to the boiler.