Carbon Neutral Design of Waste Energy Recovery System for LNG Power Plant Using Organic Rankine Cycle

In liquefied natural gas (LNG) power plants, a significant amount of heat and cold energy is consumed to capture and store carbon dioxide (CO 2 ) emitted during the combustion of fossil fuels. The proposed system addresses this problem by utilizing the temperature difference between waste heat and cold energy as a power source to generate electricity. In this study, a novel waste heat and cold energy recovery system for a postcombustion LNG power plant was developed using an organic Rankine cycle (ORC). To design the proposed system, a process model was developed with the following five parts: (i) LNG vaporization, (ii) natural gas combined cycle (NGCC), (iii) amine scrubbing, (iv) CO 2 liquefaction, and (v) CO 2 injection. In the proposed system, waste LNG cold energy is used for lean amine cooling and CO 2 liquefaction. The liquefied CO 2 was pressurized to meet the injection pressure requirements. The ORC uses high-temperature exhaust gas from the NGCC as the heat source and high-pressure liquefied CO 2 as the heat sink. The economic feasibility of the proposed system was demonstrated by an economic assessment, with the net profit evaluated by a sensitivity analysis considering variations in water, electricity, and equipment costs. Consequently, the proposed system exhibited an 18.6% increase in net power production compared to the conventional system. In addition, the net profit of the proposed system exhibited a 76.7% increase compared to the conventional system, confirming its economic feasibility.