Exhaust gas recirculation (EGR) and carbon capture
Reducing cost while unlocking efficiency during your combined cycle gas turbine’s (CCGT) carbon capture operations.
Providing additional value
Recycling exhaust for boosted power and improved carbon capture operations
Gas turbines use exhaust gas recirculation (EGR) to modify the combustion process resulting in higher levels of CO2 in the exhaust stream and lower levels of oxygen while simultaneously reducing total exhaust flow to the carbon capture system. Overall this results in boosted power and improved carbon capture operations.
EGR is a technique which reintroduces part of the exhaust gas into the gas turbine inlet. EGR, while historically explored for NOx control & part-load efficiency benefits, can also add significant value for a carbon capture system integrated with a CCGT power plant.
Why choose EGR?
EGR and its expected benefits to the power plant
Once EGR is used to modify the combustion process and overall exhaust stream, the carbon capture system absorber tower size can be reduced significantly and can result in the following benefits.
A closer look
How the system's components work
The EGR system is comprised of several components. The system is broken out below in a step by step guide that explains how recycled flue gas goes from the exhaust back to the inlet.
1) Inlet and flue gas mixer
This mixes the recycled flue gas with the fresh air that enters through the inlet. It is crucial to 1) have a low pressure drop through the gas turbine inlet and 2) achieve a well-mixed flow before it enters the gas turbine.
2) Gas turbine and controls
The controls system has three primary features: 1) it manages the startup and shutdown of the EGR system, 2) it controls its activity during normal operations and 3) it provides protection if there is an unexpected event.
3) Flue gas fan
The fan drives the recycled flue gas down the duct so it can reach the inlet. Alternatively, the gas turbine can run on high back pressure and eliminate the need for a flue gas fan.
4) Direct contact cooler
The DCC acts as a spray of cold water. This reduces the recycled flue gas temperature to improve performance. Furthermore, an enhanced DCC (eDCC) reduces SOx, NOx, and particulate matter.
5) Flue gas inlet
The flue gas inlet controls the EGR flow back into the gas turbine system during operation and provides isolation when the EGR system is off for maintenance.
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