Oxy-Fuel Boiler Pressure Control via Recirculation Fan
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Solution Overview
Problem
Oxy-fuel combustion systems face pressure peaks and instability due to compressor failures, leading to potential equipment damage and power plant trips, with existing solutions lacking reliability to prevent these issues.
Innovation Solution
Implementing a pressure control system and flow control system that measure and control pressure and flow to predetermined set values, along with a recirculation system to manage compressor capacity and prevent pressure peaks, and optionally incorporating feed forward control for stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bypass arrangement is used to recirculate compressed carbon dioxide stream back to the compressor inlet to maintain volume flow and avoid surge, then compressor operation stability is improved, but pressure peaks occur when the bypass is fully opened during compressor failure, causing equipment damage and power plant trips
Solution Approach 1:
A recirculation fan is introduced as an intermediary device to handle the recirculation of carbon dioxide stream. The fan can operate independently of the compressor and provide controlled recirculation flow, acting as a mediator between the compressor discharge and inlet. This allows the system to maintain compressor stability without relying on full bypass opening during failures, thus avoiding pressure peaks while preventing surge conditions.
Solution Approach 2:
The system dynamically switches between different operational modes: normal compression mode, recirculation mode using the fan, and emergency bypass mode. The recirculation fan provides dynamic control over the recirculation flow rate, allowing the system to adapt to varying load conditions and maintain compressor operation within stable parameters without causing harmful pressure peaks during transitions.
2Productivity
If components downstream of the boiler are designed based on boiler output capacity, then the system can handle maximum production requirements, but components become oversized and cannot operate at full capacity when the oxy-fuel process does not run at full load
Solution Approach 1:
The recirculation fan enables the system to change operational parameters by introducing a controllable recirculation flow that compensates for reduced process flow during part-load operation. This allows downstream components to receive a more stable and consistent flow rate, maintaining them at optimal operating conditions even when the overall plant production capacity is reduced, thereby improving component utilization stability.
3Reliability
If the recirculation system is designed to handle full compressor flow, then it can provide adequate recirculation capacity, but the recirculation system becomes oversized for partial load operations
Solution Approach 1:
The recirculation fan provides dynamic control over recirculation flow rates, allowing the system to scale the recirculation capacity according to actual process needs. During full load operation, the fan can operate at maximum capacity to provide adequate recirculation. During part-load operation, the fan reduces its output proportionally, matching the recirculation capacity to the actual requirements and avoiding the need for an oversized fixed-capacity recirculation system.
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 reduces or eliminates pressure peaks, prevents compressor damage, and ensures stable operation by managing compressor capacity, thereby enhancing the flexibility and safety of the oxy-fuel process.
Implementation Method 1
CO2 capture often comprises cooling, or compression and cooling, of the flue gas to separate CO2 in liquid form from non-condensable flue gas components, such as N2 and O2
Implementation Method 2
an oxyfuel boiler in which a stream of oxygen and a fuel are combusted to generate a stream of flue gas
Implementation Method 3
oxygen gas oxidizes the fuel
Data Source
AI summary
The present disclosure relates to a boiler system that includes an oxyfuel boiler in which a stream of oxygen and a fuel are combusted to generate a stream of flue gas. A flue gas condenser condenses the cleaned flue gas. A flue gas compression unit produces a stream of pressurized carbon dioxide rich flue gas. A pressure control system measures and controls the pressure after the flue gas conditioning system to a predetermined set value. A flow control system measures and controls the flow after the flue gas compression unit to a predetermined set value. The present disclosure further relates to a method of operating such a boiler system for an oxy-fuel process as well as to a power plant comprising such a system.