Oxyfuel Boiler Plant CO2 Capture at Low Load
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Solution Overview
Problem
Oxyfuel combustion boilers at low load states face challenges in reducing carbon dioxide discharge, as starting with air combustion results in low carbon dioxide concentration in exhaust gases, making CO2 capture inefficient and leading to direct atmospheric discharge.
Innovation Solution
The implementation of an oxyfuel combustion boiler system with a first boiler using air combustion initially, transitioning to oxyfuel combustion, featuring an exhaust gas supply pipe and gas flow rate control apparatus to recirculate exhaust gases, allowing the system to operate efficiently and reduce CO2 discharge even at low loads by maintaining high carbon dioxide concentration in exhaust gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If air combustion is used at low load, then the boiler can start and operate, but carbon dioxide concentration in exhaust gas is low making CO2 capture inefficient
Solution Approach 1:
The patent introduces exhaust gas from the first boiler as an intermediary substance to be supplied to the second boiler. This intermediary exhaust gas (rich in CO2) serves as a mediator that enables the second boiler to operate with high CO2 concentration even at low load, thereby solving the contradiction between productivity and CO2 concentration.
Solution Approach 2:
The patent changes the operational parameters by switching from air combustion to oxyfuel combustion in the second boiler. This parameter change (using oxygen instead of air) fundamentally alters the exhaust gas composition, raising CO2 concentration from typical air combustion levels (about 4%) to over 90%, thus resolving the contradiction.
2Object-generated harmful factors
If oxyfuel combustion is used, then carbon dioxide discharge is reduced, but flame temperature rises extremely causing potential damage to burner and boiler furnace wall surface
Solution Approach 1:
The patent converts the harmful high temperature effect into a beneficial one by using the hot exhaust gas from the first boiler as preheating media for the second boiler. The high temperature exhaust gas that would otherwise be wasted heat is now utilized to preheat the incoming air and fuel, thereby reducing the peak flame temperature in the second boiler while maintaining the CO2 reduction benefits of oxyfuel combustion.
Solution Approach 2:
The patent applies preliminary action by preheating the air and fuel before they enter the second boiler using the hot exhaust gas from the first boiler. This preliminary heating action reduces the temperature rise during combustion, preventing excessive flame temperature while still achieving effective CO2 capture.
3Productivity
If exhaust gas is recirculated to maintain high CO2 concentration, then CO2 capture becomes effective at low load, but system complexity increases
Solution Approach 1:
The patent merges the exhaust gas circulation function with the existing boiler structure by using the exhaust gas from the first boiler to preheat the second boiler. This merging approach utilizes existing components and flow paths, avoiding the need for separate complex recirculation systems while still achieving high CO2 concentration for effective capture.
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 efficient CO2 capture and reduction in CO2 discharge from the outset, enhancing the operational efficiency of the boiler plant and minimizing greenhouse gas emissions.
Implementation Method 1
an exhaust gas supply pipe for supplying exhaust gas discharged from the first boiler to a burner of the second boiler
Implementation Method 2
a gas flow rate control apparatus for controlling a flow rate of exhaust gas flowing through the exhaust gas supply pipe
Implementation Method 3
an exhaust gas circulation system for recirculating exhaust gas discharged from the second boiler to the burner of the second boiler
Implementation Method 4
a burner for burning fuel by mixing and burning the oxygen and exhaust gas of the boiler
Implementation Method 5
the flame temperature rises extremely
Implementation Method 6
generating steam by combustion gas in a furnace
Implementation Method 7
generating steam by combustion gas in a furnace
Data Source
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AI summary
An oxyfuel combustion boiler plant having a first boiler and a second boiler for injecting gas including oxygen in higher concentration than that in the air, gas including carbon dioxide in higher concentration than that in the air, and fuel from a burner and generating steam by combustion gas in a furnace, respectively, comprising: an exhaust gas supply pipe for supplying exhaust gas discharged from the first boiler to a burner of the second boiler, and a gas flow rate control apparatus for controlling a flow rate of exhaust gas flowing through the exhaust gas supply pipe.