Oxyfuel Boiler Oxygen Density Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In oxyfuel combustion boilers, maintaining stable combustion is challenging due to variations in coal properties, as the conventional air combustion system's weight ratio and recirculation methods do not apply, making it difficult to control oxygen supply effectively.
Innovation Solution
The method involves recirculating exhaust gases to the mill, wind box, and OAP, and supplementing with oxygen from an air separation unit to regulate oxygen density and supply ratios, ensuring stable combustion by adjusting the total gas recirculation and directly supplied oxygen based on coal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exhaust gas is recirculated to the mill and wind box in oxyfuel combustion boiler, then stable combustion can be maintained, but the conventional A/C ratio control method becomes inapplicable due to system differences
Solution Approach 1:
The invention changes the control parameter from the conventional A/C ratio (air-to-coal weight ratio) to an oxygen supply control system that regulates the amount of oxygen introduced into the combustion system. This parameter change adapts the control method to the oxyfuel combustion system where air is replaced by oxygen, enabling effective combustion control while maintaining combustion stability.
Solution Approach 2:
The invention implements dynamic control of oxygen supply by continuously adjusting the oxygen flow rate based on combustion conditions, coal properties, and exhaust gas recirculation amounts. This dynamic adjustment mechanism allows the system to adapt to varying operating conditions and maintain stable combustion in the oxyfuel system.
2Productivity
If oxygen supply is increased to maintain combustion stability, then combustion efficiency improves, but oxygen consumption and system complexity increase
Solution Approach 1:
The invention employs feedback control by monitoring combustion conditions (such as flame temperature, exhaust gas composition, and oxygen concentration) and using this information to automatically adjust the oxygen supply rate. This feedback mechanism optimizes combustion efficiency while preventing excessive oxygen consumption and reduces the need for complex manual control systems.
Solution Approach 2:
The control system utilizes information from the combustion process itself (exhaust gas composition, flame characteristics) to automatically regulate oxygen supply without requiring external intervention. The system self-adjusts based on its own operating parameters, reducing complexity while maintaining efficient combustion.
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 ensures stable combustion with oxygen even when coal properties change, maintaining low unburned combustibles and NOx levels, and optimizing boiler performance.
Implementation Method 1
oxygen from an air separation unit
Implementation Method 2
a portion of exhaust gas recirculated is introduced into a mill as primary recirculated exhaust gas; pulverized coal pulverized by the mill is supplied to a burner of the boiler by the primary recirculated exhaust gas
Implementation Method 3
when coal is burned with oxygen, generation of the thermal NOx is not seen and most of the exhaust gas is occupied by carbon dioxide
Data Source
AI summary
Provided are a method and an apparatus of controlling an oxygen supply in an oxyfuel combustion boiler capable of attaining stable oxyfuel combustion even when properties of coal are changed. A boiler-brought-in oxygen density is obtained when coal with a fuel ratio measured by fuel measuring means 39 is burned stably with oxygen in a boiler 4 so that a relationship between the fuel ratio and/or carbon content of the coal and the boiler-brought-in oxygen density is obtained and inputted in advance into the controller. When the coal is changed to the new kind of coal, a total amount of gases recirculated is regulated such that a boiler-brought-in oxygen density becomes accordance with a fuel ratio and/or a carbon content which is measured in advance for the new kind of coal.