【作者】 周昊；

【导师】 岑可法； 樊建人；

【作者基本信息】 浙江大学 ， 工程热物理， 2004， 博士

【摘要】 能源与环境是制约人类发展的重要问题，兼顾能源工业的发展和环境保护的需要，是中国这样一个产煤大国可持续发展的重要课题。煤燃烧的污染排放已成为中国最大的大气污染源。本论文围绕大型电站锅炉低NOx燃烧优化开展研究，采用试验、数值模拟和现场试验相结合的方法，理论结合实践，研究完成了一整套适合中国国情具有自主知识产权的低NOx燃烧和运行优化系统技术。 论文通过热态试验对不同煤种的生成NOx的前驱物特性进行试验研究：研究了不同煤种的NOx排放特性。编制了模拟煤中含氮组分析出、反应和NOx生成的颗粒模型，获得了不同煤种挥发氮和焦炭氮的比例，以提高后续炉内NOx生成过程模拟的准确性。对600 MW同心反切燃烧锅炉的低NOx燃烧特性进行了系统试验，并基于数值模拟方法对600 MW锅炉NOx生成过程采用了联合PDF模拟，评价了低NOx同心燃烧系统和炉内分级燃烧对炉内流动、燃烧和NOx排放的影响。 论文创新性地引入以CaS为中间固硫产物的煤粉炉内同时脱硫脱硝思想进行热态燃烧试验，验证这一思想的可行性，并获得实现炉内同时脱硫脱硝技术所需的各种燃烧参数，定量分析各参数对炉内同时脱硫脱硝技术的影响。试验结果表明在煤粉炉内采用以CaS中间固硫产物的两段脱硫方法具备可行性，但其可行性需要建立在炉内强烈空气分级基础之上，而炉内强烈空气分级带来的锅炉结渣、高温腐蚀问题需要采用作者提出的复合型多功能直流燃烧系统来解决。 作者提出了复合型多功能直流燃烧系统，在炉内有效地模拟低NOx燃烧过程。采用数值模拟方法分析了复合型多功能直流燃烧系统各种参数的影响。研究表明，尽管同心反切系统目前在大型电站锅炉上得到广泛应用，但是其燃烧模式在防结渣和降低NOx排放方面的能力是有限的。作者采用复合型多功能直流燃烧技术，有效地解决了一批燃用极低灰熔点(ST约为1 100℃)煤种的四角切圆锅炉的炉内防止结渣、高温腐蚀、低负荷稳燃问题，并能显著降低NOx排放，降低幅度达35％左右，是一种有前途的、可以替代同心反切系统的新一代燃烧技术。 论文创新性地采用分离涡模拟(Detached eddy simulation，DES)这一湍流高级模拟技术，对水平浓淡燃烧器内和浓淡燃烧器出口的湍流流动和拟序结构进行数值模拟，着重描绘涡的脱落过程，观察燃烧器内部和燃烧器出口涡的形成、卷浙江大学博士学位论文起的拟序特征，分析涡的形成对浓淡分离效果的影响。采用DES与非稳态颗粒轨道模型相结合的方法，对燃烧器内和燃烧器出口的气固两相流动进行了数值模拟，并与常规的RANS模拟进行比较。DES方法将湍流的直接模拟技术扩展到了可实现的工业实际应用中，对今后的湍流流动模拟又湍流燃烧模拟和揣流.Nox生成的准确模拟都具有重要意义。 以往针对气固两相射流的研究通常采用PDA等方法，但由于PDA等方法对颗粒浓度有所限制，难以进行高浓度的气固两相流的测量。论文首次采用基于光学波动法的激光光纤探针，对高浓度的低Nox燃烧器出口的气固两相流动的详细结构进行了试验，研究了配300 MW煤粉燃烧锅炉的燃烧器出口高浓度气固相射斌中颗粒浓度、粒度随射流发展的演变规律，分析了利用水平浓淡燃烧器和齿形燃烧器实现对低Nox燃烧有利的气固结构，并验证了基于DES方法的气固两相数值模拟的计算结果。 论文针对目前大型电站锅炉低Nox优化运行急需的入炉煤粉量在线检测问题，创新性地开发了一种基于电磁波发射、接收原理的直吹式制粉系统煤粉管道内缈浓度在线侧量就，并己在“60 Mw配直吹式制粉系统的大型电站锅炉上得到应用与考脸，使用效果优良，有效解决了低NC坛燃烧技术中急需的管内煤粉浓度测量问题。 二论文独创开发了，整套基于计算智能的锅炉低NC瓜燃烧优化运行系统，利用人对申经网络对哪M取和3”0 Mw燃煤锅炉的低·NOx排放特性、飞灰含碳量特性与锅炉翩煤冬锅炉运行参数之间的函数关系进行学习建模。在锅炉燃烧特性建模完成的基础上，利用遗传算法和模拟退火方法等全局寻优算法对锅炉的最佳燃烧工况进行寻优，获得了不同煤种的各燃烧参数的最佳设定值，可以直接指导运行人员运行或输入集散控制系统(DCs)参与闭环控制。系统可实现低Nox高效徽烧的在线控制于对提高锅炉燃烧优化控制水平，降低NOx排放和提高锅炉效率具有重要意义。关键词:锅炉;氮氧化物;数值模拟;结渣;气固两相流;燃烧优化更多还原

【Abstract】 Energy and Environment are very important topics for human’s development, especially for China - a country with great coal resource. The pollution from coal combustion has been the biggest pollution source in China. This work was involved in the low NOx combustion technology for the large capacity utility boilers, a set of low NOx pulverized coal combustion approaches have been developed in this work by the means of experiments, numerical simulation and field tests.The formation characteristics of the NOx precursor from various types of Chinese coal were investigated using a drop-tube furnace, and experiments on the NOx formation and destruction mechanisms were also studied experimentally. A particle model was developed to simulate the release of volatile fuel-nitrogen and its subsequent conversion to nitrogen oxide during the devolatilization. The different devolatilization models were employed, one is the two competing reactions model and the other is the universal model. The conversion efficiencies of volatile fuel-nitrogen to nitric oxide and the amount of char-nitrogen are presented.In this work, the detailed experiments on the NOx emission characteristics of a 600 MW capacity boiler with concentric firing system were carried out, the numerical approaches employing the joint PDF method were used to simulate the NOx formation process in the furnace. The performance of the concentric firing system on the flow field, coal combustion and NOx emission were evaluated, which shows that concentric firing system has some effects on the reduction of NOx emission, also the prevention of furnace slag, but its effect is limited.The two-stage high temperature desulphurization method using the CaS as the intermedium is developed in this work to obtain the simultaneous reduction of NOx and SOx in the pulverized coal fired furnace. The experimental results show that it is possible to perform such a two-stage high temperature desulfurization in the pulverized coal fired furnace if a deep air stage can be employed in the lower furnace. Such a deep air stage may lead to the dangerous high temperature corrosion and serious furnace slag.To avoid the high temperature corrosion and serious furnace slag caused by deep air stage, a novel low NOx combustion configure named as "the Compound multi-function combustion system" was developed by the author, it has much betterperformance than that of the concentric firing system. A number of boilers firing coals with low ash fusing temperature (ST is about HOOT?) met serious furnace slag problem, the compound multi-function combustion system has solved their problems and achieved a NO* emission reduction of 35%.In this work, the detached-eddy-simulation (DES) approach was employed to study the turbulent flow in the fuel rich-lean separator and the gas-solid multiphase jet from the exit of a fuel rich-lean burner. The vortex shedding process was simulated and its effect on the fuel rich-lean separate performance was evaluated. Combined with the stochastic particle tracking method, the particle motion characteristics in the gas-solid fuel rich-lean jet was tracked, which show the fuel-rich stream and the fuel lean stream will not mix quickly downstream of the exit of the nozzle, the fuel rich-lean combustion can be kept in a rather long distance from the nozzle. Compared with the Reynolds Average Navier Stocks (RANS) method, DES method can give more information about the vortex structure of the gas-solid jet. DES can be used for numerical simulation in large geometry, it will find its more wide employment in the combustion science.Usually, the Particle Doppler anemometry is employed to study the gas-solid two-phase flow, but it cannot do measurements in the gas-solid flow with high solid concentration. In this work, a novel fiber probe was employed to investigate the gas-solid two-phase flow structure downstream of the exit of two low NO* burner nozzle. The gas solid interaction was studied, the solid concentration and particle size distribution contours downstream of the nozzle were obtained. The更多还原