摘要

The thermo-economic performance of a coal-fired power plant combined with CO₂ capture system is studied with different configurations of organic Rankine cycle (ORC) systems. The liquefied natural gas (LNG) cold energy is used to assist carbon capture, due to which the CO₂ compressor can be omitted. The effects of turbine inlet temperature, mass flow rate and different working fluids on the energy, exergy efficiency, and CO₂ capture quantity are investigated. The studied results show that the reductions of the turbine inlet temperature and mass flow rate have a beneficial effect on the thermodynamic performance of the system and CO₂ capture quantity of a coal-fired power plant. Although the addition of a regenerator to ORC can reduce the exergy loss of condensers, the power generation and exergy efficiency of simple cycle (S-ORC) are higher than that of recuperated cycle (Rec-ORC). Ethane/ethylene and isopentane/propane are the best working fluid combinations of dual-fluids cycle (DF-ORC) and cascade cycle (Cas-ORC), respectively. The process of DF-ORC and Cas-ORC are more complex, resulting in a greater capital cost of investment. However, the temperature matching performance between the heat and cold source of heat exchangers in the combined system is higher than a single cycle, so the capital cost of the heat exchanger is lower. The cycle with CO₂ capture system increases the capital cost, but the increased power generation is enough to reduce the unit power generation costs of power plants. It is noted that S-ORC system is the most profitable of the four kinds of ORC systems.