【作者】 李胜；

【导师】 金红光；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2012， 博士

【摘要】 解决能源利用与环境协调相容的难题是二十一世纪能源科学研究的重要课题。为解决传统煤制天然气系统的能量利用难点以及目前能源动力系统CO2捕集能耗高、成本高的普遍难题,本学位论文在工程热物理与化工学科交叉层面,开展了能源系统化学能梯级利用和CO2分离的耦合机理研究,煤制天然气动力多联产系统集成研究以及成本潜力分析。在机理层面,从燃料转化过程中吉布斯自由能利用思路出发,探索了燃料转化过程中吉布斯自由能损失规律与C02的富集机制,建立并阐明了吉布斯自由能利用和CO2分离能耗之间的耦合关系,进而揭示了利用吉布斯自由能实现CO2捕集能耗最小化的机理。研究表明,通过燃料的适度转化,可避免燃料转化过程过高的吉布斯自由能损失,并且能够富集C02,实现燃料化学能梯级利用和降低CO2分离功的双重目的。基于CO2捕集能耗最小化机理,提出了回收CO2的化工未反应气适度循环型煤制天然气化工动力联产系统,分析了联产系统的热力性能、节能机理以及特性规律。结果表明,相对于IGCC+CC和SNG分产系统,回收CO2的天然气动力联产系统具有良好的节能效果,在设计条件下系统能源利用效率59.7%,相对节能率19.5%；系统最佳效率可达62.0%,相对节能率最高达21.5%。通过适度循环,回收CO2的联产系统能够避免SNG化工合成能耗随转化率急剧上升的现象,并能够实现C02的富集,在燃料化学能梯级利用的同时能够低能耗的捕集CO2,且存在最佳化工循环倍率,使得联产系统热力性能最佳。联产系统相对于IGCC和SNG分产系统的吉布斯自由能收益可弥补C02的分离功,甚至负能耗代价捕集CO2。与回收C02的甲醇电力多联产系统相比,回收CO2的天然气动力多联产系统C02分离前浓度约高5个百分点,CO2的单位捕集能耗更小。围绕多联产系统,分析了回收CO2联产系统的成本下降潜力,揭示了国产化、效率提升、装机规模对成本下降潜力的贡献。目前,联产系统的比投资约为1700$/kW,空分系统、煤气化系统和联合循环系统的投资成本占联产系统总投资的60%以上,尤其是煤气化系统的投资,超过系统总投资的30%。联产系统的折合SNG生产成本为0.18～0.36$/Nm3。与IGCC+CC系统和SNG单产系统相比,在产品输出相同的情况下,联产系统的总投资比分产系统略高,年总成本比分产系统约低3.8%；与IGCC和SNG单产系统比,联产系统CO2捕集成本约为7.9$/t,能够实现低成本的CO2捕集。当前,通过国产化措施,联产系统的比投资可下降约29.4%,大型气化技术、SNG合成技术和高性能燃气轮机技术的国产化程度相对偏低,是未来国产化的关键。联产系统总规模、技术进一步国产化和系统效率的提升将对联产系统成本下降起重要作用,通过成本学习,联产系统的比投资可下降到700～1100$/kW,低于IGCC+CC系统,甚至能够低于PC+CC系统。更多还原

【Abstract】 It is an important issue to coordinate the energy utilization and evironment protection. To solve the the energy utilizaion problem in the traditional coal to SNG sytem and to explore the low energy penalty and low cost for CO2capture, this essay studied the coupling mechanism the cascade utilization of chemical energy in fuel and CO2separation, then proposed a polygeneration system with CO2capture which produces SNG and power, and also analyzed the cost reduction potential of the polygeneration system.First, the law of Gibbs free energy loss and the mechanism of CO2enrichment during fuel conversion were explored, the relationship between the utilization of Gibbs free energy and CO2separation work was built and illustrated, and the mechanism of minimal energy penalty for CO2capture by utilizing Gibbs free energy was disclosed.Based on the mechanism for minimal energy penalty for CO2capture, this work proposed a new polygneration system (PG) for SNG and power, simulated the thermal performance of this system, analyzed its energy-saving mechanism and made performance sensitivities. Results show that, at designed condition, the thermal efficiency of the new polygeneration system with CO2capture is as high as59.7%, and the energy saving ratio is19.5%compared with IGCC+CC and traditional coal to SNG systems. The optimal thermal efficiency can be62%, and optimal energy saving ratio is21.5%. Through moderate recycle of the off gas in the new polygeneration system, the sharp increase of the energy consumption for unit SNG production can be avoided and the CO2can be enriched during chemical synthesis. The optimal recycle ratio of the off gas, which yields best system thermal efficiency and ESR, is observed. Compared to IGCC and traditional coal to SNG system, the benefit from Gibbs free energy utilization can make up or even can be greater than the work for CO2separation in the polygeneration system, which makes the zero or even negative energy penalty for CO2capture possible. Compared to the polygeneration system which recover CO2and produces methanol and power, the CO2concentration before separation in the proposed system can be5percentage higher, and the unit energy penalty for CO2capture is less.Also, the cost reduction potential of the polygeneration system is analyzed, and the roles of localization, efficiency improvement and capacity scale in cost reduction are disclosed. Currently, the unit investment of this PG system with CO2capture is around1700$/kW. The investment of air separation unit, coal gasification unit and the combined cycle unit takes over60%portion of the whole investment, and especially the investment of gasification unit takes over30%portion. The SNG production cost varies from0.18-0.36$/Nm3with different coal price. Compared with IGCC+CC and traditional coal to SNG system, when the product outputs are the same, the total investment of the polygeneration system is slightly higher but the total annual cost is around3.8%lower. Compared to IGCC and SNG system, the CO2capture cost of the PG is around7.9$/t. Through localization, the unit investment of the polygeneration system can be decreased by29.4%currently. The current localization levels of coal gasification, SNG synthesis and gas turbine technologies are relatively low, and these technologies are the key of further localization. The installed capacity, technology further localization and efficiency upgrade will take an important role in cost reduction, which will make the unit investment of the PG decrease to700~1100$/kW that is possibly lower than IGCC+CC or even than PC+CC system.更多还原