【作者】 米翠丽；

【导师】 阎维平；

【作者基本信息】 华北电力大学（北京） ， 动力工程及工程热物理， 2010， 博士

【摘要】 矿物燃料的大量使用所造成的地球温室效应日益显现。近年来在火力发电领域CO2的捕集、压缩液化与封存技术的研究与工程示范已经成为一项非常重要的任务。富氧燃烧技术又称O2／CO2燃烧技术,或者空气分离／烟气再循环技术,是一种既能直接捕集高浓度CO2,又能综合控制燃煤污染物排放的新一代洁净煤发电技术。以300MW燃煤锅炉为研究对象,燃高水分、低硫褐煤,从能量平衡的角度对炉膛辐射、对流受热面、尾部受热面及制粉系统等方面进行了富氧燃烧锅炉系统的概念设计,将空分制氧过程及CO2压缩过程的系统能量进行了回收整合利用；建立了一种改进的宽带关联k模型对富氧燃烧方式下高浓度三原子混合气体的辐射特性进行分析研究；通过数值模拟研究了初始氧浓度对NOx排放量及燃尽率的影响规律；从传热学的基本理论出发,研究了富氧燃烧方式下烟气的对流传热特性；对富氧燃煤锅炉系统的整体经济性进行了分析,综合考虑受热面投资,提出了一项评价锅炉对流受热面经济性的指标——单位传热量的总费用,分析了在不同烟气流速下受热面单位传热量总费用的变化规律,确定出富氧燃烧方式下锅炉受热面的合理布置方式。在30%O2/70%CO2混合气氛下,炉膛辐射换热量较空气燃烧增加约7%,其中,三原子气体对辐射换热的贡献由24%左右增加至40%左右；对流换热所占份额相对于空气燃烧减少约9%,锅炉烟气侧的运行阻力大幅减小。随着炉内压力的逐渐升高,三原子气体的辐射强度和发射率均增大,但增大的幅度逐渐减小。富氧燃烧方式下,初始高浓度CO2的存在增加了CO形成的机会,还原气氛的形成使得产生的NO被还原降解,30%O2/70%CO2工况下炉膛出口NO排放量为480mg/m3左右,较空气气氛降低约38%。富氧燃烧方式下管壁表面换热系数较空气燃烧方式升高。随着烟气流速的增大,换热器单位传热量的总费用先降低后增大；以单位传热量的总费用为目标函数对富氧燃烧方式下锅炉受热面进行优化设计后,锅炉本体尺寸减小,部分过热受热面需移入炉膛上部；数值模拟结果显示炉膛优化设计后,飞灰可燃物的含量较锅炉原始尺寸在相同配风方式下的运行数据有所增大,但仍低于锅炉原始尺寸在空气燃烧方式下的运行数据。在我国目前的市场经济条件下,基于当前的煤价,富氧燃烧方式下的脱碳费用较MEA化学吸附法降低约80%,若计及空分制氧及CO2压缩过程的能量整合利用,则富氧燃烧电厂CO2脱除费用进一步降低约23%。更多还原

【Abstract】 Slather using of the fossil fuel makes the greenhouse effect increasing greatly. The research and demonstration project of the carbon capture and storage (CCS) have become a very important task in the field of thermal power generation. Oxy-fuel combustion technology is also known as O2/CO2 combustion technology, or air separation/flue gas recycling technology, which can trap high concentration CO2 directly without separation and control pollutant emission comprehensively. It is a new generation of clean coal power generation technology.In terms of energy balance, a 300MW boiler was taken as the research object for the conceptual design under oxy-fuel combustion on the aspects such as furnace radiation, convection heating surfaces, back-end surfaces, coal pulverizing system and so on. The designed coal was lignite with high moisture and low sulfur. This system recycled the system energy in the courses of generating oxygen by air separation and compressing CO2. An improved wide-band correlated-κdistribution model was developed to calculate the radiation characteristics of the triatomic gases with high concentrations under oxy-fuel combustion. The influence rule of the initial oxygen concentration to NOx emission and burn-out rate were revealed by numerical simulation. From the view of the basic theory of heat transfer, the convective heat transfer characteristic of flue gas under oxy-fuel combustion was analyzed. The whole economy of the oxy-coal fired boiler system was analyzed. By comprehensive consideration of heating surface investment, an index was proposed to evaluate the economy of the boiler convective heating surfaces, defined as the total cost per unit quantity of heat transferred. Variation of the total cost per unit quantity of heat transferred at different gas velocity was obtained. The reasonable arrangement of the boiler heating surfaces under oxy-fuel combustion was determined.Compared with air combustion, the radiative heat transfer in the furnace increased by about 7% in 30%O2/70%CO2 atmosphere, among which the contribution of triatomic gases to radiative heat transfer increased from 24% to 40% approximately. The convective heat transfer decreased by 9% compared with air combustion. The operation resistance of flue gas side decreases largely. With the gradual rising of the pressure in the furnace, the radiation intensity and emissivity of triatomic gases increase, but the increasing range deduce.Under oxy-fuel combustion, the existence of CO2 with high concentration increase the formation of CO, which promotes the reductive degradation of NO. The furnace outlet NO concentration is about 480mg/m3 under the 30%O2/70%CO2 operating condition, decreased by about 38% compared with air atmosphere.Compared with air combustion, the wall surface heat transfer coefficient increased under oxy-fuel combustion. As the gas velocity increasing, the total cost per unit quantity of heat transferred decreases first and then increases. The total cost per unit quantity of heat transferred is regarded as the objective function to exercise optimization design. As a result, boiler body size is reduced and part of the superheaters should be moved to the upper part of the furnace. Simulation results show that the carbon in fly ash increases slightly under this smaller cavity operation compared with that of primary size, which is still lower than the operating data of air combustion with primary boiler size.Under our country’s present market economy condition, on the basis of the present coal price, the cost of CO2 removal under oxy-fuel combustion decresed by about 80% compared with MEA chemical absorption. When the system energy utilization in the courses of generating oxygen and compressing CO2 is taken into account, the cost of CO2 removal can be reduced by about 23% further under oxy-fuel combustion.更多还原