Oxyfuel Boiler Oxygen Mixing to Prevent Burner Backfire
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Solution Overview
Problem
In oxyfuel combustion boiler plants, the injection of oxygen into a mixture of pulverized coal and combustion exhaust gas can lead to abnormal combustion, such as backfires, particularly during startup or when operation conditions change, due to high oxygen concentrations.
Innovation Solution
The implementation of an oxyfuel combustion boiler plant design that includes a nitrogen supply pipe and an air supply pipe connected downstream of an oxygen buffer tank to control oxygen concentrations, reducing the risk of abnormal combustion by mixing nitrogen or air with oxygen before it reaches the burner, thereby stabilizing the flame propagation velocity.
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 buffer tank as an intermediary component between the oxygen source and the combustion zone. This buffer tank temporarily stores oxygen and controls its release, preventing direct injection of high-concentration oxygen into the pulverized coal mixture. The intermediary buffer system mediates between the need for rapid ignition and the risk of abnormal combustion, allowing controlled oxygen addition that accelerates ignition without causing backfire.
Solution Approach 2:
The patent implements preliminary action by pre-storing oxygen in a buffer tank before it reaches the combustion zone. This preliminary storage and controlled release mechanism ensures that oxygen is added to the combustion process in a controlled manner rather than directly injecting high-concentration oxygen. The preliminary action in the buffer tank prevents the sudden high oxygen concentration that would cause abnormal combustion while still providing sufficient oxygen for accelerated ignition.
2Productivity
If high purity oxygen is supplied to the burner to maintain combustion, then combustion efficiency is improved, but the risk of abnormal combustion increases during startup and operation changes
Solution Approach 1:
The buffer tank serves as an intermediary that decouples the high purity oxygen source from the burner. It allows high purity oxygen to be stored and then released in controlled amounts to the burner, maintaining combustion efficiency while preventing the sudden high oxygen concentration that would cause abnormal combustion during startup and operation changes.
Solution Approach 2:
The patent changes the oxygen concentration parameter dynamically through the buffer tank system. Instead of directly supplying high purity oxygen that creates harmful conditions, the buffer tank adjusts the oxygen concentration to optimal levels for safe combustion. This parameter change maintains combustion efficiency while eliminating the harmful high oxygen concentration effects during critical operation phases.
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 effectively prevents abnormal combustion by maintaining optimal oxygen concentrations, ensuring reliable operation and reducing the risk of burner damage from high-temperature flames.
Implementation Method 1
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
Implementation Method 2
a part of nitrogen generated from the air separation unit
Data Source
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AI summary
An oxyfuel combustion boiler plant comprising: a boiler (200) having an air separation unit (360) for manufacturing oxygen by separating nitrogen from air, a burner (200) for burning the oxygen supplied from the air separation unit and pulverized coal, and a primary system pipe (216) for supplying the pulverized coal to the burner, exhaust gas recirculation system pipe (390) for supplying combustion exhaust gas discharged from the boiler to the primary system pipe, a carbon dioxide capture unit (350) for capturing carbon dioxide in the exhaust gas discharged from the boiler, the oxyfuel combustion boiler plant is further comprising: an oxygen buffer tank (132) disposed on a downstream side of the air separation unit (360); an oxygen supply pipe (219) for supplying oxygen to the primary system pipe (216) of the burner (210) from the oxygen buffer tank (132); and a nitrogen supply pipe (137) for supplying a part of nitrogen generated from the air separation unit (360) or an air supply pipe (138) for supplying air from outside which is connected to the oxygen supply pipe (219) on a downstream side of the oxygen buffer tank (132) and on an upstream side of a junction of the primary system pipe (216).