CO2 Recovery Circulation Control for Stable Regenerator Liquid Level
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Solution Overview
Problem
In CO2 capture units for gas turbine combined cycles, the startup time is prolonged due to insufficient steam generation, leading to unstable operation and liquid level fluctuations in the regenerator, as the absorption liquid circulation is not balanced during the transition from initial to normal operation.
Innovation Solution
A CO2 capture unit with a control method that adjusts the opening degrees of valves and flow rates in the rich, lean, and bypass lines using controllers and sensors to maintain a stable liquid level in the regenerator, ensuring balanced circulation between the absorber and regenerator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the absorption liquid circulation is switched from initial operation (through each unit) to normal operation (between absorber and regenerator) without proper control, then the CO2 capture unit can operate at full capacity, but liquid level fluctuation occurs in the regenerator and stable operation cannot be maintained
Solution Approach 1:
The control device monitors the liquid level in the regenerator and adjusts the opening degrees of the rich valve, lean valve, and bypass valve based on feedback signals. This closed-loop control ensures that the liquid level remains stable during the transition from initial to normal operation, preventing fluctuations while maintaining full capture capacity.
Solution Approach 2:
The system dynamically adjusts the valve opening degrees during the transition phase. The control device modifies the flow rates through the rich line, lean line, and bypass line in real-time based on operational conditions, enabling a smooth transition that maintains liquid level stability while achieving full productivity.
2Temperature
If the absorption liquid is circulated through each of the absorber and regenerator during startup, then the temperature decrease is suppressed, but the liquid level balance cannot be achieved and stable operation is prevented
Solution Approach 1:
The bypass line acts as an intermediary path that allows partial circulation of absorption liquid back to the regenerator. This intermediate circulation path enables temperature maintenance during startup while gradually transitioning to the normal circulation mode, achieving both temperature stability and liquid level balance.
Solution Approach 2:
The control device changes the flow rate parameters dynamically during startup. By adjusting the opening degrees of the valves, the system transitions from a circulation pattern that prioritizes temperature maintenance to one that achieves liquid level balance, optimizing both parameters at different stages.
3Reliability
If multiple valves are controlled simultaneously during transition to normal operation, then the liquid level stability can be maintained, but the control complexity increases
Solution Approach 1:
The control device combines the control of multiple valves (rich valve, lean valve, and bypass valve) into a single integrated control system. By coordinating the opening degrees of all valves simultaneously based on a unified control algorithm, the system maintains liquid level stability while managing control complexity through consolidation rather than independent control of each valve.
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
The method stabilizes the liquid level in the regenerator, minimizing fluctuations and enabling smooth transition to normal operation, thereby reducing startup time and maintaining efficient CO2 capture.
Implementation Method 1
a rich valve that controls a flow rate of the absorption liquid flowing through the rich line; a lean valve that controls a flow rate of the absorption liquid flowing through the lean line; a bypass valve that controls a flow rate of the absorption liquid returning through the bypass line
Implementation Method 2
an absorption liquid is circulated between a regenerator and an absorber to recover CO2 from an exhaust gas
Implementation Method 3
it is necessary to heat the absorption liquid, and in the case where the CO2 capture unit is applied to the GTCC, the steam generated in the heat recovery boiler of the GTCC is used for heating the absorption liquid
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
Provided is a control device that actuates a blower on the basis of operable conditions. This CO2 recovery device comprises: a regeneration tower; an absorption tower; a rich line; a flowmeter and a rich valve provided to the rich line; a lean line; a flowmeter and a lean valve provided to the lean line; a bypass line that returns, to the regeneration tower, absorption liquid flowing through the lean line; a bypass valve provided to the bypass line; and a control device that, when starting the circulation operation during normal times, controls opening degrees of the rich valve, the lean valve, and the bypass valve such that the liquid surface height of the absorption liquid in the regeneration tower reaches a prescribed target value.