Oxyfuel Boiler Oxygen Density Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Standard boilers and two-stage combustion boilers face challenges in controlling NOX and unburned combustibles in exhaust gases, with varying air mass flow ratios providing unsatisfactory control.
Innovation Solution
The method and apparatus for an oxyfuel combustion boiler adjust the recirculating exhaust gas flow to the two-stage combustion port to control oxygen density, allowing for reduced NOX and unburned combustibles by increasing or decreasing the recirculating exhaust gas, thereby optimizing oxygen density at each combustion port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If air mass flow ratio is varied to control NOX and unburned combustibles, then emission control is attempted, but control effectiveness remains unsatisfactory
Solution Approach 1:
The invention changes the parameter from air mass flow ratio to oxygen density in the combustion zone. By controlling the amount of recirculating exhaust gas fed to the two-stage combustion port, the oxygen density is adjusted to optimize combustion, thereby effectively controlling NOX and unburned combustibles in the exhaust gas.
Solution Approach 2:
The invention implements feedback control by monitoring the exhaust gas composition and adjusting the recirculating exhaust gas flow accordingly. The control means adjusts the amount of recirculating exhaust gas fed to the two-stage combustion port based on the actual combustion conditions, creating a closed-loop control system that effectively manages emissions.
2Object-generated harmful factors
If recirculating exhaust gas is increased to reduce oxygen density, then NOX density is lowered, but heat absorption may be reduced
Solution Approach 1:
The invention applies dynamic control by adjusting the recirculating exhaust gas flow rate according to actual combustion conditions. The control means dynamically modifies the oxygen density in the combustion zone to balance NOX reduction with heat absorption requirements, rather than using a fixed recirculation rate.
Solution Approach 2:
The invention changes the oxygen density parameter in the combustion zone by varying the recirculating exhaust gas flow. This parameter adjustment allows optimization of both NOX density and heat absorption, as the system adapts the oxygen level to match actual combustion needs rather than using a constant air-to-fuel ratio.
3Use of energy by moving object
If recirculating exhaust gas is decreased to increase oxygen density, then heat absorption is improved, but unburned combustibles may increase
Solution Approach 1:
The invention uses dynamic adjustment of the recirculating exhaust gas flow rate to match actual combustion conditions. By continuously monitoring combustion quality and adjusting oxygen density accordingly, the system maintains optimal burn completion while preserving heat absorption efficiency, preventing unburned combustibles from increasing.
Solution Approach 2:
The feedback control system monitors exhaust gas composition and adjusts the recirculating exhaust gas flow to maintain proper oxygen density. This ensures that heat absorption is maximized while preventing excessive unburned combustibles, as the system responds to actual combustion quality rather than using a fixed oxygen level.
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 controls NOX density and unburned combustibles in the exhaust gas, enhancing heat absorption and reducing emissions, with precise control achievable through the adjustment of oxygen density at multiple combustion ports.
Implementation Method 1
When coal is burned with oxygen, generation of the thermal NO X is not seen and most of the exhaust gas is occupied by carbon dioxide with the remainder occupied by other gases containing the fuel NO X，SO X and unburned combustibles
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In an apparatus of controlling an exhaust gas in an oxyfuel combustion boiler having the boiler 4 provided with burners 6 and a two-stage combustion port 7, a primary recirculation line 12 through which pulverized coal obtained by a mill 3 is fed to the burners 6 of the boiler 4 by the primary recirculating exhaust gas, a secondary recirculation line 14 through which another portion of the exhaust gas in recirculation is fed to a wind box 5 of the boiler 4, an oxygen producer 23, a direct supply line 25 through which a portion of oxygen produced by the oxygen producer 23 is directly fed to the burner 6 and a secondary oxygen mixing line 24 through which another portion of oxygen produced by the oxygen producer 23 is fed to the secondary recirculation line 14, the apparatus comprises an oxygen supply line 26 through which oxygen is fed to the two-stage combustion port of the boiler 4 and a flow rate regulator 20, 27 in the oxygen supply line for adjusting oxygen density.