A low-carbon polygeneration system based on a waste heat recovery system, a LNG cold energy process, and a CO2 liquefaction and separation unit

Expanding energy conversion plants that simultaneously produce water and energy can address multiple issues in these two major fields. Additionally, utilizing waste heat energy from fossil fuel-driven plants rather than releasing it into the atmosphere can provide both thermodynamic and environmental benefits. A new polygeneration plant that integrates a waste heat recovery process and a CO2 liquefaction and separation process is developed and analyzed through a multi-criteria assessment (thermodynamic, economic, and environmental). The plant is capable of producing several advantageous products, including power, natural gas, desalinated water, and liquefied CO2. The polygeneration plant employs cold energy of liquefied natural gas (LNG) for condensation processes, a novel approach. Results indicate a net power rate of ~41.96 MW, with 166.8, 4912.8, and 972.6 mol/s for liquefied CO2, natural gas, and desalinated water, sequentially. The plant exhibits energy efficiency and exergy efficiency of ~31.6% and ~86.5%, respectively. The cost feasibility shows that electricity production carries a unit cost of 0.0474 US$/kWh, while liquefied CO2 production cost was about 0.0742 US$/kgCO2. The plant is estimated to emit roughly 0.0343 kg/kWh of carbon dioxide. The energy and exergy efficiencies decrease by ~9% and 2%, respectively, as the seawater feed rate increases from 13 to 23 kg/s. A comprehensive comparison indicates that the studied polygeneration plant yields superior economic, thermodynamic, and environmental performance compared to similar facilities. Furthermore, the proposed plant is capable of meeting its own power demands and does not require electricity from the grid.