【作者】 张丹；

【导师】 徐明厚；

【作者基本信息】 华中科技大学 ， 热能工程， 2013， 博士

【摘要】 温室气体的排放给全球气候带来了巨大灾难，而燃煤发电所造成的CO₂排放量巨大，因此，对燃煤发电系统进行CO₂减排刻不容缓。对燃煤电厂进行CO₂捕集，目前面临的最大困难就在于，由于CO₂捕集装置所带来的巨大的能耗和投资成本的增加。对减排CO₂的燃煤发电系统进行详细的系统热力性能分析和经济性分析，是进一步对系统进行技术和经济优化设计的关键，开展这部分研究工作具有实际意义，但是目前相关研究还较少。首先对一国内典型的600MW燃煤机组的传统发电系统、燃烧后捕集改造系统和氧/燃料燃烧改造系统进行了模拟仿真计算，搭建了三种发电系统的仿真模型，对系统的能量平衡和质量平衡进行计算，获得系统的主要能耗模拟结果和详细的热力学参数，为进一步的火用分析提供基础。研究结果表明，在燃烧后MEA捕集发电系统中，再生塔的再沸器能耗是能耗增加的主要部分，可以通过抽取低品位的热能来对其进行供热，有效降低该能耗。氧/燃料燃烧发电系统中，空分系统的能耗占系统发电量的18%左右，是能耗增加的主要原因。CO₂压缩系统消耗的能量仅次于再沸器热耗和空分系统，其压缩过程中每一级压缩气体的温度可达到120℃左右。氧燃料方式的系统发电效率略高于燃烧后捕集方式。其次基于热力学第二定律对减排CO₂的燃煤发电系统进行详细的火用分析计算和比较。分析了减排CO₂的燃煤发电系统与传统燃煤发电系统中能量的利用状况，损失发生的部位和各个子系统的能量利用效率。研究结构表明，燃烧后CO₂捕集整合系统的火用效率为35.59%，氧/燃料燃烧系统的火用效率为37.75%，相较传统燃煤发电系统均有大幅度下降，锅炉设备在燃烧后捕集系统与传统燃煤系统中，均为火用损失最大的设备，这是由于燃烧和传热的不可逆造成的。通过对汽水循环系统的火用分析研究，发现汽水循环系统与MEA捕集系统整合时，除了要考虑合理的抽汽温度和压力，还要考虑尽可能利用低压缸排汽对再沸器供热，这样有利于低品质热源的利用，减少系统的火用损失，在减排CO₂的燃煤发电系统中，CO₂压缩系统的火用损失比较较小，但有较大的热能浪费，可以用于加热给水以减少系统火用损失。然后运用矩阵模式的热经济学方法对传统燃煤发电系统、燃烧后捕集发电系统和氧/燃料燃烧发电系统进行热经济性分析，分析其发电成本的形成过程和系统中各个子系统的热经济性优劣。研究结果表明，传统燃煤发电系统为0.28￥/KWh，燃烧后捕集发电系统为0.53￥/KWh，氧燃料发电系统为0.40￥/KWh，矩阵模式热经济学对减排CO₂的燃煤发电系统有良好的适应性，能够科学合理的对其进行成本核算。在三种燃煤发电系统中，凝汽器的热经济学产品—燃料成本差值最大，其火用经济性较好，虽然能量损失很大，但是其能量品味很低，所以损失的燃料火用并不大。锅炉换热系统的火用经济系数均较小，应考虑对锅炉及换热系统进行合理优化。燃烧后捕集和氧/燃料燃烧系统中CO₂压缩装置的非能量成本较高，应考虑如何降低其非能量费用。氧/燃料燃烧系统中空分系统的产品—燃料热经济学成本相差巨大，火用损失巨大，火用效率很低，具有优化潜力。最后基于夹点分析技术对燃烧后捕集发电系统和氧/燃料燃烧系统与CO₂多级压缩系统进行了热能分析与整合，提出了合理的换热器网络设计，达到了热能回收降低系统能耗的目的。通过对燃烧后捕集发电系统的夹点优化改造，节约了42.55%的加热工程用量和70.15%的冷却工程用量。通过对氧/燃料燃烧发电系统的夹点优化改造，节约了约58.15%的外加热公用工程和88.93%的外加冷却公用工程量。优化设计之后的CO₂多级压缩与CCS发电系统的整合系统，间接增加发电产量约为10.8MW左右，提高系统发电效率约为0.78%。更多还原

【Abstract】 Greenhouse gas leads to global warming. About half of CO₂emission comes from coalfired plants. Therefore, it is great urgency to control CO₂emission from coal-fired powerplant. However, capturing CO₂from coal-fired power plant will leads to huge energyconsumption and investment increase, which is the biggest problem for commercialapplications. Thermoeconomic and thermodynamic analyses that evaluate coal fired powerplant with CO₂capture is the basis of the further technical and economic optimization.There is little research about this topic, although it has important significance in thereality..Two different kinds of CO₂capture process, post capture and oxy-fuel technologybased on a Chinese typical600MW power plant, were simulated and analyzed in this thesis.Mass and energy balance were calculated. Main energy consumption and detailthermodynamic parameters were obtained. The results showed that the reboiler duty of theregenerator is the biggest energy consumption in the post capture coal fired power plant.The low quality steam could be extracted for this duty to reduce the energy consumption.The air seperation unit takes up18%of the oxy-fuel power plant energy consumptionincrement. The energy consumption with CO₂compress unit was huge whether in post oroxy-fuel coal fired power plant, and the temperature of the exit gas from each stage of themulti-compress system could reach to about120℃. The net efficiency of the oxy-fuelsystem was higher than the post capture system, but the net efficiency of both abovesystems were lower than the efficiency of conventional coal fired power plant.Exergy analysis and assessment of the conventional, post and oxy coal fired powerplant were carried out based on the second law of thermodynamic. The exergy destruction,exergy efficiency and the situation of the energy utilization were analyzed. The exergyefficiency of the post capture power plant is35.59%, and which of the oxy-fuel power plant is37.75%. All boiler units had the biggest exergy destructions in the conventional, postcapture and oxy-fuel coal fired power plant. The steam extracted position would affect thenet output, so the low pressure expansion and the heat of the multi-compress intercoolershould be considered. to integrate with the water-steam cycle.The termoeconomics of the conventional, post capture and oxy power plant werecalculated and analyzed using the matrix model thermoeconomic tool. The formingprocess of the power generation cost（COE） and the thermoeconomics of the units with thisthree power plants were obtained. The COE of the conventional coal fired power plant was0.28￥/KWh, which of the post capture power plant was0.53￥/KWh, and the oxy-fuelwas0.40￥/KWh. The cost of the CO₂reduction could be accurately calculated by thematrix model thermoecnomic the for the power plant. The difference of the “fuel” and“product” in the condenser was the biggest in this three systems, but its exergy destructionswere small because of its low fuel exergy. The exergoeconomic parameter of the boier unitin three power plants were all very low, so it should be considered in the optimization.There is huge potential for energy saving because the difference of the “fuel” and “product”in the air seperation unit was also very large.Reducing the energy penalty burdened by integrating the multi-compress unit to thepost capture and oxy-fuel power plant was investigated via pinch analysis. Themodifications of the heat networks were proposed.42.55%heat energy and70.15%coolenergy were saved in the post capture coal fired power plant through pinch analysis.58.15%heat energy and88.93%cool energy were saved for the oxy-fuel coal fired power plantusing the same analysis method. The net output of both post and oxy-fuel power plantincreased about10.8MW. The net efficiency had been increased by0.78%.更多还原