Abstract
Carbon capture and storage (CCS) plays a uniquely important role in the future clean and dispatchable power generation portfolio to achieve the ambitious goals set at COP21. The Graz Cycle, a zero emission oxy-combustion power plant, is one of the most promising representatives of CCS power generation plants. The present work introduces different control strategies for the Graz Cycle and the corresponding part-load performances. The process simulation is composed of a design-point (full-load) and off-design (part-load) of the cycle. In order to do this, the process simulation tool IPSEpro was used. Individual cycle components were modelled for both investigations, full load and part load, and control strategies were developed in order to achieve optimum performances and operating efficiencies by means of the assumptions given. This work distinguishes from previous studies by the development of different control strategies and comparison of corresponding part-load performances. In the simulation, the Graz Cycle operating at nominal design conditions achieved a net plant efficiency of 53.1%. The part-load simulation generated results down to 40% load by applying three different control strategies. These control operation modes differ from each other in two basic parameters, boiler pressure and turbine inlet temperature. Optimum part-load performances were achieved by control strategy, where the pressure of the heat recovery steam generator is allowed to vary. However, other parameters, e.g. costs, did not appear to be favourable for this operation mode. The comparison with a readily available technology, such as a natural gas combined cycle, showed that the Graz Cycle is more efficient as loads are reduced below 50%.
Highlights
The average earth surface temperature has risen by 0.8 ∘C since the industrial revolution as a result of the increased atmospheric concen tration of greenhouse gases due to anthropogenic ac tivities (Fischedick et al, 2015)
Since the Graz Cycle is different from common combined cycles and has a recycled mass flow rate, it is not a priori self-evident how the cycle reacts in part-load conditions and how far the cycle load can be reduced
Optimal part-load operation consists in a reduction of the fuel mass flow rate (i.e. m Natural gas (NG)) proportional to the turbine mass flow rate and the net power production just like that the pressures and temperatures of the power cycle remain constant compared to design-point values (Zaryab et al, 2020)
Summary
The average earth surface temperature has risen by 0.8 ∘C since the industrial revolution as a result of the increased atmospheric concen tration of greenhouse gases (primarily CO2) due to anthropogenic ac tivities (Fischedick et al, 2015). In light of the commitments agreed on COP21, the temperature increase must not exceed the 1.5–2 ∘C tem perature level in order to limit the consequences of climate warming in ecosystems (Bui et al, 2018) These challenges will primarily concern the electricity and heat generating sector, which produces the lion’s share of man-made greenhouse gas emissions (Center for Climate and Energy Solutions, 2017; European Commission, 2011; IEA, 2020). The whole power system and every unit of the electricity supply pool has to operate dynamically to overcome the intermittent nature of renewables, which demands high flexibility of power plants in order to do load changes and part-load operation (Johnsson et al, 2013) In this context lays the ut terly importance of this study. Oxy-combustion gas turbine power plants are generally “highly integrated, involving energy and mass recycle, and optimizing efficiency might lead to operational (control) challenges. Appendix A discusses the integration of the Graz Cycle in the future power grid framework, whereas Appendix B shows the performance tables of the control strategies and the natural gas combined cycle
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
