Abstract
Flexibility in power plants with amine based carbon dioxide (CO2) capture is widely recognised as a way of improving power plant revenues. Despite the prior art, its value as a way to improve power plant revenues is still unclear. Most studies are based on simplifying assumptions about the capabilities of power plants to operate at part load and to regenerate additional solvent after interim storage of solvent. This work addresses this gap by examining the operational flexibility of supercritical coal power plants with amine based CO2 capture, using a rigorous fully integrated model. The part-load performance with capture and with additional solvent regeneration, of two coal-fired supercritical power plant configurations designed for base load operation with capture, and with the ability to fully bypass capture, is reported. With advanced integration options configuration, including boiler sliding pressure control, uncontrolled steam extraction with a floating crossover pressure, constant stripper pressure operation and compressor inlet guide vanes, a significant reduction of the electricity output penalty at part load is observed. For instance at 50% fuel input and 90% capture, the electricity output penalty reduces from 458kWh/tCO2 (with conventional integration options) to 345kWh/tCO2 (with advanced integration options), compared to a reduction from 361kWh/tCO2 to 342kWh/tCO2 at 100% fuel input and 90% capture. However, advanced integration options allow for additional solvent regeneration to a lower magnitude than conventional integration options. The latter can maintain CO2 flow export within 10% of maximum flow across 30–78% of MCR (maximum continuous rating). For this configuration, one hour of interim solvent storage at 100% MCR is evaluated to be optimally regenerated in 4h at 55% MCR, and 3h at 30% MCR, providing rigorously validated useful guidelines for the increasing number of techno-economic studies on power plant flexibility, and CO2 flow profiles for further studies on integrated CO2 networks.
Highlights
Reducing carbon dioxide emissions to prevent climate change has become one of the key priorities for the energy sector
It is referred to as conventional integration options (CIO) power plant, and is compared to a configuration with advanced integration options (AIO) that improve part-load efficiency: sliding pressure for boiler control without throttling at the HP turbine inlet, an IP turbine and an LP turbine designed to operate with a floating crossover pressure, and a compressor with inlet guide vanes (IGV) for load control
The performance maps for a power plant with conventional capture integration options, mainly based on a throttled LP steam turbine and a CO2 compressor with recycling for flow control, and a power plant with advanced integration based on floating pressure LP turbine and CO2 compressor with inlet guide vanes for flow control, are provided for a range of fuel loads (40–100%) based on rigorous integrated model of the boiler, steam cycle, post-combustion capture and compression system
Summary
Reducing carbon dioxide emissions to prevent climate change has become one of the key priorities for the energy sector. One route to achieve decarbonised electricity systems within the targets highlighted by the latest IPCC report (IPCC, 2013) will entail expanding renewable energy supply and using nuclear energy and fossil fuel plants with carbon capture and storage (CCS). Given the current installed capacity and expansion plans for electricity generation from variable renewable sources, future power systems will favour resources that provide system flexibility (ability to follow changes in variable energy plant output). In this respect, fossil fuel power plants with integrated CO2 capture (for transportation and storage) could play an important role in balancing low carbon electricity grids.
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