Core Research Projects: Combined systems & capture, AC2 – Advanced, high-efficient cycles using gas turbines with S-CO₂ or direct oxy-fired CCGT-CCS

Why is this research needed?

Here, we investigate a novel system for CO₂ capture from a gas turbine.

The use of supercritical CO₂ as a combustion moderator is a challenging area of scientific research, since the operating conditions require pressures far beyond existing engine technologies. The understanding of properties such as heat transfer and molecular diffusion are importing in designing S-CO₂ cycles and there is much scope for fundamental research to build the technical knowledge base.

This is researched across different scales at the institutions involved, detailed investigations of the combustor at Cardiff GTRC, with complementary assessments across the whole turbine cycle by Sheffield (at PACT/TERC), along with simulations and modelling.

Studies of the impact of exhaust gas recycling, including selective CO₂ recycling using separation membranes, to enhance exhaust gas CO₂ levels, reduce volumetric flow rates and therefore to reduce the size and costs of the capture plant have been carried out during the past five years by the applicants (for example, GASFACTS, SELECT, Call-1-UKCCSRC^[1]). Our research has demonstrated significant changes to combustion and hot gas path environments, and potential impacts on operability, materials and component lives while maintaining pollutant emissions within limits.

^[1] EP/J020788/1, EP/M001482/1, UKCCSRC-C1-26

What is this research investigating?

CCGT power plants with EGR/CO₂-rich strategies, can be “recoded” with a closed supercritical CO₂ (s-CO₂) cycle with oxy fuel high pressure combustion for improved efficiency and plant flexibility. Furthermore, the S-CO₂/oxy-combustion strategy can be an effective solution for the full integration of Power-to-Gas, CCS, and S-CO₂ pumping (Enhanced Oil Recovery, water-free shalegas extraction). Availability of detailed reaction schemes is essential to design the high pressure combustor by providing information on the timescale of chemical reactions. However, the use of validated reaction schemes at high pressure is subject to many uncertainties. We will focus on the following tasks:

• assessing the capability of the available reaction scheme for NG combustion at high pressure by collecting available data generated by different investigators using Quantum Mechanic simulation and Boxed Molecular Dynamic simulation (up to 200 bar).
• evaluating kinetic models for both direct fired oxy-combustion and an indirect fired sCO₂ energy system
• developing a reduced reaction scheme and then integrating with CFD for flow field design.

Finally, different cycles will be evaluated and optimised to determine combustor design parameters, cycle layout and efficiency, including optimal start and enhanced operational flexibility.

What does the research hope to achieve?

The aim is to boost the concentration of CO₂ in the exhaust of the system by partially recycling the gas. We will also investigate the potential for a radically new cycle involving oxygen firing (with recycled CO₂ to keep the temperature down). The work started at the University of Sheffield’s PACT will be continued and broadened under this research theme at TERC.