An innovative hybrid system for the polygeneration of power, heat, and liquid carbon dioxide using solid oxide fuel cell/electrolyzer technology and oxyfuel power generation cycle

Abstract

An innovative polygeneration structure is proposed based on the oxyfuel power generation (OPG) system integration with carbon dioxide (CO2) capture, CO2 power system, NH3/H2O absorption refrigeration (AR) unit, and organic Rankine power (ORP) cycle. In this regard, a combination of solid oxide electrolysis cell (SOEC) and solid oxide fuel cell (SOFC) is applied to produce the required pure oxygen for the OPG system. The proposed system simultaneously produces 7204 kmol/h hot water, 149.3 kmol/h liquid CO2, and 102.4 MW power in different cycles. Energy and exergy analyses are performed to evaluate the proposed system. The thermodynamic modeling and simulation of power and refrigeration cycles are performed in Aspen HYSYS software, and verified with high accuracy. Also, an integrated SOEC/SOFC simulation has been done using developed computer code in MATLAB programming. The overall electrical efficiency and the AR coefficient of performance are calculated at 31.55% and 0.4803, respectively. In addition, the thermal and exergy efficiencies of the proposed system are 65.10% and 70.60%, respectively. The exergy analysis indicates the combustion chamber's highest exergy destruction with a share of 35.26%. In the next rank, the heat exchangers (26.42%) and turbines (16.98%) have the largest share of degraded exergy among other devices. The sensitivity analysis demonstrates that when the oxygen productivity increases from 9050 to 9275 kg/h, the electrical efficiency in the total integrated structure and the liquid CO2 productivity rise to 34.57% and 6480 kg/h, respectively. Also, by increasing the natural gas entering the proposed structure from 2375 to 2550 kg/h, the exergy efficiency of the structure increases to 71.19% and its thermal efficiency decreases to 58.70%. Highlights A novel polygeneration system to produce power, liquid CO2, and heat is introduced. Integration of oxyfuel/ORC/CO2 power plants and absorption cooling unit is applied. A solid oxide fuel cell/electrolyzer technology is used to produce pure oxygen. The electrical and exergy efficiencies of the overall system are 31.55% and 70.60%. The exergy analysis indicates the combustion chamber has the highest exergy destruction.