TPS 2024: Q&A with Siemens Energy on Carbon Capture

Turbo & Pump Symposia 2024 kicked off this morning in Houston. Early this morning folks from Siemens Energy, including Lukas Biyikli, R&D Portfolio Manager of Integrally Geared Compressors, presented on the Integration of CO₂ Capture Plants with Open Cycle Gas Turbines.

Carbon capture is viewed by many in the energy industry as an essential step to a fully decarbonized world. Folks are familiar with carbon-capture technologies’ ability to remove CO₂ from flue gas streams, but the challenges of providing the flue gas in the correct conditions and the supply of the energy required for the CO₂ capture process are less well-known.

Biyikli offered further insights into the role of gas turbines in carbon capture, the challenges with removing CO₂ from flue gas streams, methods to boost the CO₂ concentration in the exhaust gas, and more.

TURBO: What role do gas turbines play in carbon capture?

BIYIKLI: Natural gas is considered an important bridge technology for providing reliable and affordable mechanical and electrical energy via gas turbines, even beyond 2050. Even though many gas turbines are hydrogen-ready, the quantities of hydrogen available mid-term will not be sufficient to decarbonize all gas turbine systems worldwide. Therefore, carbon capture is an excellent technological and economical approach to producing carbon-free power via gas turbines.

TURBO: What are the challenges with removing CO₂ from flue-gas streams?

BIYIKLI: The biggest impact comes from the CO₂ concentration in the flue gas. The higher the concentration, the easier it is to remove the CO₂ from the flue gas. This directly relates to the challenge with carbon capture in gas turbines since the exhaust only has a flue-gas concentration of around 4%. In industrial processes, for example, like cement, CO₂ concentration in the exhaust is already at 20 - 25%, which makes carbon capture a lot easier and less energy-intensive.

TURBO: What are some novel approaches to carbon-capture technologies?

BIYIKLI: There are plenty of innovative technologies to reduce the energy demand and costs behind carbon capture, some even advantageous for gas turbines. For example, hot potassium carbonate technology can use and recover heat from the exhaust of a simple-cycle gas turbine to cover the energy demand of the capture process. Exhaust gas recirculation (EGR) enriches flue gas from the exhaust of a gas turbine to a CO₂ concentration above 10%. In addition to that, cryogenic technologies are on the rise as alternatives to conventional amine systems, particularly for carbon capture from industrial processes with CO₂ concentrations between 15 and 25%.

TURBO: What are the benefits and challenges of EGR?

BIYIKLI: EGR is a great technique for reducing the energy demand and costs of capture systems. One challenge is retrofitting existing machines in brownfield applications in terms of applying EGR—it’s possible, but the cost and time required are high. For greenfield applications, it creates additional costs and should be considered in the design, but this is manageable from a total cost-of-ownership perspective.

TURBO: How does waste heat recovery from carbon compressors satisfy some of the process heat required by the CO₂ capture plant?

BIYIKLI: Through heat recovery from compressors, hot water for district heating or process steam up to 10 bar is available via heat exchangers by adapting the compressor design slightly. There is a great synergy between the heat and steam demand that conventional amine-based capture systems have and the steam that is provided by the compressors since amine systems typically require high amounts of saturated steam between 3 and 6 bar, in range of what the compressor can deliver. Siemens Energy’s concept provides up to 80% of the steam demand for an amine system while only increasing the power requirement of the compressor by one-sixth of that heat provided compared to conventional compressor operation, which means a coefficient of performance of up to 6.0 for the system.