Abstract
Around 50% of the world’s electrical power supply comes from the Rankine cycle, and the majority of existing Rankine cycle plants are driven by coal. The problem is that coal power plants are environmentally unfriendly; particularly, older plants have low thermal efficiency and poor emissions. In addition, the conventional and common practices for retrofitting those older plants can only provide incremental improvements for plant performance and emissions. This paper introduces the concept of the Integrated Mild/Partial Gasification Combined (IMPGC) Cycle as one promising new technology that has the potential to significantly increase the thermal efficiency of these older plants as well as reduce their emissions. In contrast to the conventional Integrated Gasification Combined Cycle (IGCC), IMPGC makes use of warm gas cleanup as well as mild and partial gasification to conveniently and seamlessly convert a simple Rankine cycle to a combined cycle, greatly improving the efficiency of the plant without altering the base plant’s design. Three different scenarios in total were simulated in addition to a simple subcritical Rankine cycle plant as a baseline for comparison: (1) a case using the same fuel input as the original baseline, (2) a case with the same total maximum power output as the baseline, and (3) a case where the turbine with the highest steam pressure (HPST) has the same mass flow rate through it as the equivalent turbine from the baseline case. The results show that IMPGC can improve the efficiency of Rankine cycles by up to nine (9) points (or ∼23%) and has the potential to augment total net power output by up to 2.5 times. This paper will analyze the specific challenges associated with retrofitting these plants and examine how the retrofit affects the plant performance and emissions.