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    LNG冷能与BOG驱动的冷热电多联供耦合碳捕集系统设计优化

    Design and Optimization of a LNG Cold Energy and BOG Driven CCHP System Integrating Carbon Capture

    • 摘要: 为解决当前液化天然气(LNG)再气化过程中冷能浪费以及LNG储罐中产生的蒸发气(BOG)处理问题,减少生产过程中的碳排放,本文构建了LNG冷能与BOG驱动的冷热电多联供耦合碳捕集系统,建立了以㶲效率、净电功率和总成本率为目标的优化模型,采用非支配排序遗传算法(NSGA-Ⅱ)与多目标粒子群优化算法(MOPSO)对系统进行多目标优化,再利用线性规划法(LINMAP)和逼近理想解排序法(TOPSIS)确定最优性能点,最后针对最优性能点对系统进行性能分析以评估优化后的系统性能。研究结果表明:当LNG气化压力为7200 kPa,烟气膨胀机出口压力为140 kPa,ORC膨胀机入口压力为19500 kPa,BOG燃烧压力为990 kPa,膨胀机T-4出口压力为2500 kPa时,系统综合性能最佳,㶲效率、净电功率和总成本率分别达到58.22%、2505.73 kW、0.531 M/year。通过过程集成,优化后系统实现了能量的高效梯级利用,CO2捕获量、产出淡水及氮气量分别为1981 kg/h、1620 kg/h、9689 kg/h,实现了系统经济性利用;碳捕集率达99.58%,实现近零碳排放;系统浪费冷能42.35 kW,仅占总冷能的2.23%。为LNG接收终端节能减排提供了可推广的技术方案。

       

      Abstract: To address the issues of cold energy waste during the liquefied natural gas (LNG) regasification process and the treatment of boil-off gas (BOG) generated in LNG storage tanks, while also reducing the carbon emissions in the production process, this study proposes an LNG cold energy and BOG-driven combined cooling, heating, and power (CCHP) system integrated with carbon capture. An optimization model targeting exergy efficiency, net electrical power, and total cost ratio was developed. The Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi-objective Particle Swarm Optimization (MOPSO) were employed for multi-objective optimization. Linear Programming (LINMAP) and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) were subsequently applied to identify the optimal performance point. Performance analyses were then conducted at this point to evaluate the system’s optimized performance. The results indicate that the optimal system performance is achieved when the LNG vaporization pressure is 7200 kPa, the gas expander outlet pressure is 140 kPa, the ORC expander inlet pressure is 19500 kPa, the BOG combustion pressure is 990 kPa, and the expander T-4 outlet pressure is 2500 kPa. At this point, exergy efficiency, net electrical power, and total cost ratio reach 58.22%, 2505.73 kW, and 0.531 M/year, respectively. Through process integration, the optimized system achieves efficient cascade utilization of energy, with CO2 capture, freshwater production, and nitrogen output reaching 1981 kg/h, 1620 kg/h, and 9689 kg/h, respectively, ensuring the economic operation of the system. The carbon capture efficiency reaches 99.58%, achieving near-zero carbon emissions. The system wastes only 42.35 kW of cold energy, accounting for just 2.23% of the total cold energy.This provides a replicable technical solution for energy conservation and emission reduction in LNG receiving terminals.

       

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