PFBC CO2 Capture Interface with VFD and Expander
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Solution Overview
Problem
Current carbon capture technologies, such as the Benfield process, are not readily adaptable for use with pressurized fluidized bed combustion (PFBC) due to limitations in temperature and pollutant levels, necessitating an interface to enable efficient carbon dioxide capture and minimize energy losses in power generation facilities.
Innovation Solution
A readiness interface is introduced, incorporating a heat recovery steam generator (HRSG) and a flue gas expander driven by an electrical variable frequency drive (VFD) motor, allowing for flexible compressor capacity and gas temperature selection, and enabling the bypass of carbon dioxide capture systems during startup or maintenance, while using a Benfield process with a PFBC boiler to achieve high CO2 capture efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Benfield process is used for CO2 capture from PFBC flue gas, then CO2 capture efficiency is improved, but the process cannot be readily adapted due to temperature and pollutant level limitations
Solution Approach 1:
A flue gas conditioning system is introduced as an intermediary between the PFBC process and the Benfield CO2 capture unit. This conditioning system adjusts the flue gas parameters (temperature, pressure, pollutant levels) to make them compatible with the Benfield process requirements, enabling effective CO2 capture while resolving the incompatibility between raw PFBC flue gas and the capture technology
Solution Approach 2:
The flue gas parameters are actively modified through the conditioning system to match the optimal operating range of the Benfield process. This includes adjusting temperature, pressure, and pollutant concentrations to levels that enable high CO2 capture efficiency while protecting the capture technology from damage
2Productivity
If a gas turbine is used to drive the combustion air compressor in standard PFBC, then power generation efficiency is improved, but the system lacks flexibility in compressor capacity and gas temperature selection
Solution Approach 1:
The system replaces the fixed-speed gas turbine driver with a variable frequency drive (VFD) motor that can dynamically adjust its operating speed and torque output. This dynamic control capability allows the compressor to operate efficiently across a wide range of capacities and gas temperatures, providing operational flexibility while maintaining power generation efficiency
Solution Approach 2:
The VFD motor system is designed to universally accommodate different operating conditions and capacity requirements. It can function effectively whether the CO2 capture system is online or offline, and can adapt to various gas temperature and pressure conditions, making the overall system more versatile
3Object-generated harmful factors
If the CO2 capture system is operated continuously, then CO2 emissions are reduced, but the system cannot be serviced or repaired without shutting down the PFBC facility
Solution Approach 1:
The flue gas handling system is divided into separate functional segments: the PFBC boiler, the CO2 capture unit, and the flue gas recombination system. This segmentation allows the capture unit to be isolated, maintained, or repaired independently while the PFBC facility continues to operate, enabling maintenance without facility shutdown while maintaining CO2 emission reductions
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 solution allows for up to 95% reduction in CO2 emissions, flexibility in power generation, and compliance with emission limits, including low emissions of sulfur oxides, nitrogen oxides, volatile organic compounds, carbon monoxide, and particulate matter, making the PFBC technology viable for commercial-scale use with carbonaceous fuels.
Implementation Method 1
a heat recovery steam generator (HRSG) configured to cool the pressurized flue gas from the carbonaceous fuel combustion unit and convert the energy in the flue gas temperature reduction to steam
Implementation Method 2
carbon dioxide, hydrogen sulfide and other acid gas components are removed from a hydrocarbon containing vapor steam by absorption into a pressurized aqueous potassium carbonate solution
Implementation Method 3
a flue gas expander to expand the pressurized flue gas and convert the energy in the pressure reduction to additional torque to assist the variable frequency drive motor in driving the combustion air compressor
Data Source
AI summary
An interface for a pressurized fluidized bed combustion facility is disclosed that enables future addition of carbon dioxide capture technology to capture facility flue gas emissions. The interface includes a gas to water pressurized heat recovery steam generator to cool facility flue gas and provide steam to the facility steam turbine generator. A VFD motor and flue gas expander are coupled to a combustion air compressor to energize the facility. The expander is synchronized over a SSS-clutch to drive the compressor. The interface in combination with carbon capture technology and methods for conditioning flue gas are also disclosed.