Membranes have excellent turn down and can track the variable load conditions typical of many natural gas power plants.
Opportunity
Abundant and inexpensive natural gas has driven an expansion of its use to produce electricity. New and efficient natural gas combined cycle (NGCC) power plants generate electricity at low cost and have the operational flexibility required to provide both steady baseload power and can track fast moving intermittent renewables (wind and solar). To maintain the flexibility of the NGCC plant, the capture plant must also be flexible. This requirement, combined with the lower CO2 concentration (4%) and higher O2 content (12%) in the flue gas, makes capture from NGCCs a challenging proposition for amine-base capture processes.
Membrane Solution
MTR’s process for capturing CO2 from a natural gas power plant uses incoming combustion air as a sweep stream in a selective exhaust gas recycle (S-EGR) configuration which pre-concentrates CO2 from 4% to ~20% with little energy input. This is a far better concentrating effect than is possibly from simple exhaust gas recycle. Depending on the process configuration, the selective recycle membrane design reduces the minimum energy of a CO2 capture step by up to 40%. An all-membrane design using a capture step in series with a selective recycle membrane can capture 80% of CO2 from an NGCC power plant using less energy and at a lower cost than typical amine processes.
Benefits
- Fast response time and excellent turn down
- Modular membrane units are scalable, compact, and easily configurable for retrofit applications
- No use of chemicals, so no chemical handing or emissions issues
- Simple and passive operation
- Low maintenance and operator requirements
- No steam use; minimal/low cooling water requirements/use
System Performance
- System size: 5 MWe simple cycle turbines to F, G, and H-class NGCC plants
- CO2capture rate up to 90%
- Produces high purity liquid CO2
Application Options
- Natural gas fired boilers and turbines: NGCC, OTSG, CHP plants
- Coal fired power plants
- Fossil fueled industrial plants: cement, steel, waste-to-energy, refinery
- Biogas sources: digesters, fermenters, and landfills
