Off-Design Performance Modeling of the Natural Gas-Fired Allam Cycle

This work focuses on modeling the performance of the natural gas-fired Allam cycle under off-design conditions. Key thermodynamic parameters, such as turbine inlet pressure (TIP), turbine inlet temperature (TIT), and turbine outlet temperature (TOT), were evaluated at part-load and varying environmental conditions. In the former case, different control strategies were implemented in the simulation code (Thermoflex®) to reduce the power output. In the latter case, the impact of ambient temperature (Tamb) on the minimum cycle temperature (Tmin) was evaluated. The ultimate goal is to predict the thermal efficiency (ηth) and its decrease due to partial load operation and warm climate, without thermal recovery from the air separation unit (ASU). With the most efficient partial load strategy, ηth decreased from 50.4% at full load to 40.3% at about 30% load, at nominal Tmin. The penalty caused by the increase in Tmin due to hot weather, up to Tamb = 30 °C, was significant at loads above 60%, but limited to 0.5 percentage points (pp).