Oxyfuel Boiler Oxygen Buffering to Prevent Burner Backfire
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Solution Overview
Problem
In oxyfuel combustion boiler plants, abnormal combustion such as backfire can occur when pulverized coal enters a high oxygen concentration gas mixture, particularly during the start-up or when operation conditions change, leading to potential burner damage.
Innovation Solution
The implementation of an oxyfuel combustion boiler plant design that includes an oxygen buffer tank, an oxygen supply pipe, and a nitrogen or air supply pipe to control the oxygen concentration in the primary system pipe, reducing the risk of abnormal combustion by mixing nitrogen or air with oxygen downstream of the oxygen buffer tank and upstream of the primary system pipe junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxygen is injected toward the mixture flow of pulverized coal and combustion exhaust gas to accelerate ignition, then ignition speed is improved, but abnormal combustion such as backfire may occur
Solution Approach 1:
The patent introduces a preliminary action by injecting oxygen into the primary system pipe before the mixture of pulverized coal and combustion exhaust gas reaches the high oxygen concentration zone. This preliminary oxygen injection prepares the fuel mixture for faster ignition without causing abnormal combustion, as the oxygen is introduced at a controlled location and timing that prevents direct contact with high oxygen concentration gas that would cause backfire.
Solution Approach 2:
The patent uses the primary system pipe as an intermediary medium to transport oxygen to the combustion zone. By routing oxygen through this intermediate conduit and mixing it with the fuel-exhaust gas mixture in a controlled manner, the system achieves accelerated ignition while preventing the harmful direct injection of oxygen into the high oxygen concentration zone that would cause abnormal combustion.
2Productivity
If high purity oxygen is supplied to the burner to enable oxyfuel combustion, then carbon dioxide capture efficiency is improved, but the risk of abnormal combustion increases during start-up and operation changes
Solution Approach 1:
The patent applies local quality by creating different oxygen concentration zones at different locations in the system. The primary system pipe receives controlled oxygen injection to maintain sufficient oxygen concentration for efficient oxyfuel combustion and CO2 capture, while the secondary system pipe and combustion zone are designed to prevent high oxygen concentration that would cause abnormal combustion. This spatial variation in oxygen quality enables both high productivity and safety.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting oxygen flow rates and concentrations based on operational conditions. During start-up and operation changes, the system modifies oxygen parameters to prevent abnormal combustion, while during stable operation, it optimizes oxygen concentration for maximum CO2 capture efficiency. This dynamic parameter adjustment resolves the contradiction between productivity and safety.
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 design effectively prevents abnormal combustion by maintaining a stable oxygen concentration, reducing the likelihood of backfire and ensuring reliable operation during transitions between air-fuel and oxyfuel combustion modes.
Implementation Method 1
an air separation unit for separating oxygen and nitrogen from air
Implementation Method 2
an oxygen buffer tank disposed on a downstream side of the air separation unit
Implementation Method 3
a nitrogen supply pipe for supplying a part of nitrogen generated from the air separation unit or an air supply pipe for supplying air from outside which is connected to the oxygen supply pipe
Data Source
AI summary
An oxyfuel combustion boiler plant comprising:a boiler having an air separation unit for manufacturing oxygen by separating nitrogen from air, a burner for burning the oxygen supplied from the air separation unit and pulverized coal, and a primary system pipe for supplying the pulverized coal to the burner, exhaust gas recirculation system pipe for supplying combustion exhaust gas discharged from the boiler to the primary system pipe, a carbon dioxide capture unit for capturing carbon dioxide in the exhaust gas discharged from the boiler, the oxyfuel combustion boiler plant is further comprising: an oxygen buffer tank disposed on a downstream side of the air separation unit; an oxygen supply pipe for supplying oxygen to the primary system pipe of the burner from the oxygen buffer tank; and a nitrogen supply pipe for supplying a part of nitrogen generated from the air separation unit or an air supply pipe for supplying air from outside which is connected to the oxygen supply pipe on a downstream side of the oxygen buffer tank and on an upstream side of a junction of the primary system pipe.