ASME FEATURE changes, enabling operation of the cycles with power production only and all the way to pure heat production. The work will extend the investigation presented previously, and present alternative system layouts to combine power production from a CO2 bottoming cycle with heat generation.
Alternative layout and boundary conditions Two options were investigated for heat production integrated with a CO2 bottoming cycle, as shown in Figure 1. The first layout simply uses a secondary WHRU after the bottoming cycle WHRU. The mass flow of CO2 is controlled to make sure that the necessary heat is available for the secondary WHRU. It will be referred to as the dual waste heat recovery unit (DWHRU). The second layout exploits the large amount of super-heat available at the CO2 turbine outlet to produce process heat. It will be referred to as the internal heat recovery unit (IHRU). Two locations are considered: 1. Northern climate: For this location, cold cooling water (10°C is available) and the CO2 bottoming cycle is able to condense at sub-critical temperature (31°C). This is the standard Rankine cycle layout. A pump (at point “g” in) is used to compress the liquid CO2 before waste heat recovery. 2. Southern climate: The cooling water temperature is higher (25°C) and the CO2 remains in the gas phase all along the cycle. The CO2 is compressed (at point “g”
Figure 2. Produced power vs. produced heat
ASME Power Division: Combined-Cycle Committee
A Message from the Chair The ASME Power Division Committee for CombinedCycles is a group of industry professionals who meet to discuss technology improvements, performance enhancements, design, operation and maintenance of power plants operating in a combined-cycle mode. In most cases, this refers to a gas turbine connected to a heat recovery steam generator and steam turbine for additional power generation, but not always – as can be seen in the ASME feature article in this issue. The use of CO2 as a bottoming cycle fluid is just one example of some of the new concepts being discussed within the Combined-Cycle Committee and at the ASME Power Conference every year. In addition to new combined-cycle concepts, the conference sessions supervised by the combined-cycle committee include presentations on new gas turbine technologies, performance considerations and O&M issues. Each year our committee brings together a panel of experts to discuss pertinent issues for combined-cycle power plants. In recent years, there has been significant interest on facility start cycles – both from a reliability standpoint and a schedule optimization standpoint. This year we are still researching the topic and searching for members to be on our panel of experts. If you’d like to be involved, we would welcome your input. Our committee generally meets twice a year, with the main meeting held at the ASME Power Conference (www.asmeconferences.org/powerenergy2015). Attendance at the meeting is not required; we typically have dial-in and internet connections for members who aren’t able to join us. But if you do attend the ASME Power Conference, be sure to join our track – which this year includes a tutorial on Combined-Cycle Plant Performance Monitoring. We look forward to seeing you there! Tina L. Toburen, P.E. Chair – ASME Power Division; Combined Cycle Committee President - T2E3 Inc. Phone: 425-821-6036 Email: email@example.com
Figure 3. CO2 mass flow rate vs. produced heat APRIL 2015 | ASME Power Division Special Section
Heat Exchangers – Retrofit/Rebuild/Equipment Upgrade – Bearings – Turbine Tech: Steam – ASME: Combined-Cycle Plants