Simultaneous sequestration and extraction of geothermal energy using CO₂ from an IGCC plant as a heat transfer fluid for power generation from EGS

Utilization of CO₂ from fossil fuel power plants is an important aspect to be considered as an alternative to sequestration in mitigating the global climate change. Utilizing the heat energy from the geothermal sites for the production of electricity presents a great opportunity for the simultaneous extraction of geothermal energy and sequestration of CO₂ emitted from the fossil fuel power plants. CO₂ captured by pre-combustion method is more suitable for heat extraction compared to that captured by post combustion method as it is discharged at high pressure suitable for sequestration. Therefore, after considering air-blown combustion, oxy-combustion and Integrated Gasification Combined Cycle (IGCC), pairing IGCC with Enhanced Geothermal System (EGS) was found to produce a symbiotic combination for the simultaneous extraction of geothermal heat energy and sequestration of CO ₂. This paper models the utilization of CO₂ as a heat transfer uid for the extraction of geothermal energy and utilizing the heat for the production of electricity from the Organic Rankine Cycle (ORC). The simulations were performed in ASPEN Plus version 7.3. The first part focused on well simulation with CO₂ as a heat transfer uid for extraction of geothermal heat energy to predict the temperature profile and pressure profile along the length of the injection well and the production well. The second part focused on the modeling of organic Rankine cycle for the generation of electricity by utilizing the pressure and geothermal heat energy of CO ₂. These simulations showed that an additional total power output of 63 MWe and 29MW_e for a geothermal source temperature of 300 °C and 200 °C, respectively could be obtained for an IGCC plant output of 315 MWe.