Staged Oxy-Combustion Fluidized Bed Reactor Oxygen Control
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Solution Overview
Problem
Conventional oxy-combustion in fluidized bed reactors at high pressure faces challenges with overheating and slagging due to high oxygen content, requiring large coal particle diameters and complex handling, which increases operating costs and risks fouling.
Innovation Solution
The method involves staging the combustion process within the reactor, injecting oxygen in close proximity to the carbonaceous fuel, and controlling the oxygen content between 7-20 mole % to prevent reducing atmospheres and manage heat transfer effectively, allowing for efficient combustion and reduced particle temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high oxygen content (20-50% molar percentage) is used in conventional oxy-combustion, then combustion efficiency is improved, but fuel particles overheat and cause slagging agglomeration on heat transfer surfaces
Solution Approach 1:
The combustion process is divided into multiple stages with different oxygen concentrations. The first stage uses 20-50% oxygen for rapid combustion, while subsequent stages use progressively lower oxygen concentrations (7-20% molar percentage) to complete combustion without overheating, thereby resolving the contradiction between combustion efficiency and overheating prevention
Solution Approach 2:
Different regions of the fluidized bed are provided with different oxygen concentrations tailored to local combustion needs. The injection location is optimized to ensure complete combustion in high-oxygen zones while maintaining lower oxygen levels in regions prone to overheating, preventing slagging while maintaining efficiency
2Productivity
If pulverized coal is injected into high oxygen content bed, then complete combustion occurs in very short time, but coal particles burn faster than heat removal and diffuse to heat transfer surfaces causing fouling
Solution Approach 1:
The combustion process is segmented into stages: first stage with high oxygen (20-50%) enables rapid combustion of pulverized coal, while subsequent stages with controlled oxygen (7-20%) complete combustion without excessive temperature rise, preventing particles from reaching heat transfer surfaces and causing fouling
Solution Approach 2:
The first stage combustion is designed to achieve rapid initial combustion of pulverized coal particles before they can migrate to heat transfer surfaces. This preliminary combustion action occurs in a controlled zone with optimized oxygen concentration, preventing the harmful effect of slagging agglomeration on heat transfer surfaces
3Object-affected harmful factors
If large particle diameter fuel is injected to prevent overheating, then overheating is reduced, but complete combustion requires solids circulation outside the bed via cyclones
Solution Approach 1:
The injection location is strategically positioned to create a local combustion zone with optimized oxygen concentration (7-20% molar percentage) that enables complete combustion of larger particles without overheating. This localized quality control eliminates the need for external cyclone circulation systems while preventing slagging
4Productivity
If oxygen content is increased above 20% molar percentage, then combustion intensity is improved, but reducing atmosphere is produced at injection location
Solution Approach 1:
The injection location is designed to provide precise local oxygen concentration control (7-20% molar percentage). This localized quality ensures sufficient oxygen for intense combustion while preventing reducing atmosphere formation, maintaining stable atmosphere composition throughout the reactor
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 enables balanced combustion rates with efficient heat removal, reducing the risk of overheating and slagging, while maintaining high oxygen utilization and minimizing capital costs through staged combustion and optimized oxygen distribution.
Implementation Method 1
a fluidized bed reactor wherein a carbonaceous fuel and an oxygen-containing gas are eluted through a fluidized bed
Implementation Method 2
The carbonaceous fuel reacts with at least a portion of the oxygen-containing to produce at least CO2 and steam
Implementation Method 3
A considerable amount of heat can be removed during flue gas water condensation if the process is carried out at high pressure, which allows more electrical power to be produced with high quality steam, and boiler feedwater can be preheated with the flue gas condensate
Data Source
AI summary
Methods and devices for combusting a carbonaceous fuel in an oxy-combustion fluidized bed reactor involving controlling the local oxygen content within the oxy-combustion reactor to specified levels. The carbonaceous fuel and an oxygen-containing gas are introduced into a fluidized bed reactor and eluted through a fluidized bed of an inert material, dolomite or a combination thereof to combust the fuel and oxygen to produce at least CO2 and steam. The oxygen-containing gas is a mixture of oxygen, recycled CO2 and steam and has sufficient oxygen added to the recycled CO2 and steam that the mixture contains 7-20 mole % oxygen. The carbonaceous fuel and the oxygen-containing gas are introduced into the fluidized bed at a location in sufficiently close proximity to each other to avoid producing a reducing atmosphere at the location. At least a portion of the produced CO2 and steam are recycled to the reactor.