【作者】 温存；

【导师】 邱建荣；

【作者基本信息】 华中科技大学 ， 热能工程， 2007， 硕士

【摘要】 煤是中国目前及今后相当长一段时期内电站燃料的主体,煤粉燃烧为我们提供必需的热源和电力资源的同时,同时还会产生各种各样的问题,这其中控制重金属的排放已成为当务之急,而锅炉内部由于矿物质的沉积而产生的问题一直困扰着能源领域。氧燃烧方式是目前发现的一种污染综合控制新技术。该种方式是将O2与循环烟气(含高浓度CO2)代替空气作为介质参与燃烧。目前对燃烧技术下矿物质变化和重金属排放的研究还未有过多开展。在沉降炉上对西部煤种DHB和SJT在1200℃以及1400℃进行了氧燃烧动态燃烧实验,对各种工况下所的收集底灰进行了XRD和XRF测试,对颗粒物排放做了研究,探讨不同温度下以及不同燃烧气氛下矿物质的变化行为。在1200℃时煤粉燃烧完全煤灰中所产生的非晶体含量在氧燃烧方式下要低于空气燃烧方式,在氧浓度提高的情况下非晶体含量回升,同等氧浓度下的氧燃烧方式利于缓解锅炉内熔融相的形成,对缓解沉积亦有利;颗粒物排放在同等氧浓度氧燃烧方式下减少,亚微米颗粒物的减少反映了矿物质蒸发的减少,超微米颗粒物的减少反映了煤焦颗粒反应剧烈程度降低,氧浓度的升高使得趋势回升。对实验中反应后的煤灰进行了微波消解并采用ICP-AES对灰中痕量元素含量进行了定量的测试,研究了变氧浓度氧燃烧气氛对痕量元素排放的影响,结果表明氧燃烧方式对痕量元素的排放有一定的抑制作用,抑制程度与具体元素且与其挥发性密切相关,CaO的加入导致煤中As、Se的释放率分别降低,对于Cr基本无影响;Fe2O3的加入使得As、Cr的释放率略有降低。通过热分析动力学的计算可得出纯SeO2挥发和CaSeO4的热分析反应机理函数,氧燃烧气氛使得CaSeO4分解的活化能升高,更难以产生分解挥发。最后通过热力学计算对矿物质以及重金属在两种气氛下的挥发做出了初步预测。更多还原

【Abstract】 Most of fuel consumed in power stations in China, now and in the future, is coal. Coal combustion supplies a large amount of thermal energy, at the same time it will bring about tons of problems. It is imperative to remove trace elements from coal combustion. And deposition in boiler caused by the minerals is a great problem. Oxy-coal combustion is a kind of new technology which can joint control the pollution. It uses O2 and recycled flue gas(mainly CO2)as medium to replace air in combustion process. It’s lack of the research on mineral transformation and trace elements emission.Experiments were taken out in a Drop-tube furnace under the temperatures of 1200℃and 1400℃to study the dynamic oxy-coal combustion. The ash was collected under all conditions to analyzed by XRD as well as XRF to study the mineral transformation. The experimental results indicate that the concentration of non-crystal phase is lower under the oxy-coal combustion with equal oxy-concentration of air combustion compared to it. Non-crystal phase concentration increased with the increase of oxy-concentration, the fusion phase in the boiler may decrease under oxy-coal combustion, which can ease the deposition; the PM can be decreased under the equal oxy-concentration combustion, the vaporization of the mineral and the reaction extent is decreased, but higher oxy-concentration make the trend higher.The technology of micro-wave digesting is used to digest the ash produced by the experiments above, and the ICP-AES method is applied to measured the trace elements concentration precisely. The results indicate oxy-coal combustion we used can restrain the emission of trace elements, and the restrainablility is related to the positive elements and its volatity. The injection of CaO makes the vaporization of As、Se decreased, while it has little influence on Cr; the injection of Fe2O3 makes the vaporization of As、Se lightly lower. And the clean of Cr is showed throughed the results, Thermogravimetric methods is used to investigate the resolved of CaSeO4 after SeO2 is blended with CaO, the calculation shows the active energy is higher under the oxy-combustion than air,which means it is more difficult to resolve under the oxy-coal combustion.Finally the thermal-equilibrium method is used to calculate the vaporization of typical minerals and trace elements, and prediction is made by the calculation.更多还原