活性焦氨法联合脱硫脱硝循环吸附-热再生研究

Activated coke has been widely applied in flue gas purification at low temperatures (100-200℃) due to its rich supply, low price, low water-consumption, capability of multi-pollutant removal, no demand for flue gas reheating, and so on. For the combined desulfurization and denitrification by activated coke with ammonia, there are two unsolved problems: activated coke deactivation due to the formation of ammonium sulfate salts, and the carbon consumption due to the thermal regeneration. The sedimentary characteristics of ammonium sulfate salts on the activated coke surface and the effects of thermal regeneration on the activity and carbon consumption are investigated to reduce the sediment and carbon consumption. An experimental platform combining a fix bed and a mass spectrometer is designed to determine on line breakthrough curves for the activated coke in the adsorption-thermal-regeneration process to evaluate the regeneration activity, such as adsorption capability, regeneration time and regeneration efficiency. XRD, N2-BET and TPD (X-ray diffraction analyzer, Nitrogen adsorption analyzer and Temperature programmed desorption) will be used to measure the sediment compositions, plugged pore structure, and occupied surface activity sites, so as to reveal the sedimentary characteristics of ammonium sulfate salts. N2-BET, FTIR and MS (Nitrogen adsorption analyzer, Fourier transform infrared spectrometer and Mass spectrometer) will be applied to test the pore size distributions, surface functional groups and adsorption capability after several adsorption-thermal-regeneration circles, as to evaluate the effects of the regeneration atmosphere on the regeneration activity and carbon consumption, eventually to optimize the thermal regeneration parameters. The mechanism investigation will provide a theoretical guidance for the industrial application of activated cokes.

活性焦以其来源广、价廉、可以脱除和转化多种污染物、烟气无需再热、耗水少等优点适用于低温（100-200℃）烟气联合脱硫脱硝。然而活性焦氨法联合脱硫脱硝存在喷氨产生硫铵盐引起活性焦失活和热再生过程碳消耗问题，研究活性焦吸附过程中硫铵盐沉积特征和热再生过程中气氛对活性焦再生活性及碳消耗的影响，以期减缓硫铵盐沉积，降低碳消耗。本研究拟采用固定床-真空质谱仪联用实验台，在线监测活性焦循环吸附-热再生过程，评价活性焦的吸附容量、再生时间、再生效率。借助X射线衍射仪、氮吸附仪、程序升温脱附等方法检测沉积物成分、活性焦孔隙堵塞、表面活性位占据等参数，阐明硫铵盐沉积特征。借助氮吸附仪、红外光谱仪、质谱仪等方法获得活性焦循环再生后孔径分布、表面官能团、吸附容量等参数变化趋势，评价再生气氛对活性焦再生活性和碳消耗的影响，获得适宜的热再生工艺参数，为该技术的工业应用提供理论参考。

针对活性焦氨法联合脱硫脱硝过程的活性焦失活和热再生过程碳消耗问题，开展了系列研究。.（1）研究了活性焦表面的硫铵盐沉积特征，发现氨存在于气氛中或者预吸附在活性焦表面时，均使得表面硝酸盐物种很少，沉积物的主要成分是NH4HSO4。NO的选择性催化还原反应增加含硫物种的摩尔沉积量约1.68倍。含硫物种包含的SO3物种约占总沉积物的57.5%。随着反应时间延长，沉积物的稳定性增加。在含水气氛下，NH4HSO4使得NO的转化率由80%降低至60%。NH4HSO4对脱硝反应的抑制作用小于气氛中SO2的抑制作用，此时NO的转化率仅有20%左右。活性焦的SCR反应包括两类活性位点：石墨微晶结构的缺陷位点和酸性位点。拉曼光谱检测发现，石墨微晶结构的无序性有利于SCR脱硝，该促进作用与官能团是否存在无关。.（2）在不喷入氨气的条件下，研究了SO2和NO在活性炭表面的吸附反应。在单组份气氛时，硫容是30.9 mg/g，氮容是11.3 mg/g。SO2与活性炭表面的结合力大于NO与活性炭的结合力，但是吸附容量与吸附力的大小无关。与单组份气氛相比，在复杂气氛下的硫容增加了202%，而氮容下降了95.6%。复杂的气氛有利于SO2脱除，然而NO应该在低硫的条件下脱除。NO吸附增加了碳基，其对SO2吸附有促进作用。NO的吸附受SO2抑制，主要是因为二者对相同吸附位的竞争吸附。复杂气氛中的水蒸气对某组分促进或者抑制其它组分的吸附具有强化作用，但是减弱吸附气体与活性炭间的结合力。 .（3）研究了活性焦理化性质及再生气氛对再生活性的影响。红外表征及程序升温脱附揭示了SCR脱硝过程占用酸性位点，再生过程中NO转化率的下降仅与酸性官能团的含量正相关，为减缓NO转化率下降应选用内酯基含量较高的活性焦。活性焦再生后活性降低主要因为微孔增加和内酯基官能团稍有降低。活性焦的碳消耗随着再生温度的升高而增加，将再生温度由400℃降低到325℃左右，SO2的回收率仅稍有降低。使用含氨气氛再生时，能够提高脱硫脱硝效率，降低碳消耗，但是SO2的回收率降低不明显。在快速反应阶段，活性焦的硫容接近于100 mg/g，氮容约为10mg/g。再生温度、硫容/氮容、碳消耗的获得为活性焦工业应用提供了理论依据。