常温（70~120℃）钙基吸收剂同时脱硫脱硝技术可以实现工业烟气中SO2和NOX的较低成本脱除。然而，该技术脱除NOx和SO2的反应机理尚不完全清楚，多种机理解释存在相互矛盾之处，因此制约了该技术进行大规模的工业应用。本文内容重点分为两部分。首先，使用固定床实验装置、原位红外实验装置（DRIFT）、低场核磁共振成像仪（Low Field-NMR）和固体核磁共振波谱仪（Solid State-NMR）等手段氢氧化钙同时脱硫脱硝反应机理中的关键问题进行了深入研究。实验结果证实在常温半干法脱硫脱硝温湿度区间Ca(OH)2表面不存在液膜，存在三种不同化学环境的氢原子，分别为化学位移为1.19ppm的氢氧根（OH-）、4.90ppm的表面羟基（*OH）和6.56ppm的结合水（H2O）。使用Ca(OH)2混合TEMPO进行同时脱硫脱硝实验证明表面羟基是SO2可以被氧化的关键，也是NO可以被脱除的核心。实验证实SO2先与Ca(OH)2表面羟基反应生成HOSO2*然后再被氧化为CaSO4。同时脱硫脱硝过程中NO被氧化为NO2再被脱除。O2对NO2的反应路径有较大影响，无氧条件下NO2会直接与HOSO2*反应释放出NO，有氧条件下则进行催化氧化S(IV)的反应。根据实验结果提出三条反应机理路径，分别为Ca(OH)2同时脱除NO和SO2反应机理，无O2条件下同时脱除NO2和SO2反应机理和有O2条件下同时脱除NO2和SO2反应机理。其次，论文使用热重-红外联用（TG-FTIR）、DRIFT和热重-质谱联用（TG-MS）等手段对脱硫脱硝产物CaSO3，Ca(NO3)2，Ca(NO2)2的热稳定性进行了深入研究，明确了它们的热解反应路径和产物。发现CaSO3热解过程中存在自分解反应、歧化反应、脱硫反应和歧化逆反应，弥补了文献中对热解最终阶段CaSO4生成机理解释的不足。Ca(NO2)2会先热解为Ca(NO3)2、CaO和NO；Ca(NO3)2的分解主要生成NO、CaO、O2和NO2。在反应温度低于580℃时，Ca(NO3)2主要分解生成CaO，NO和O2，在更高温度下，还会生成NO2。Ca(NO3)2分解生成的NO和NO2的比例是随温度发生变化的，温度越高NO2越多。此外，实验证实O2对Ca(NO3)2和Ca(NO2)2的热解反应路径无影响。
The simultaneous desulfurization and denitrification technology with calcium absorbent at normal temperature (70~120℃) can achieve low cost removal of SO2 and NOX in the industrial flue gas. However, the reaction mechanism of NOX and SO2 removal by this technology is not completely clear, and there are conflicting explanations for various mechanisms, restricting the large-scale industrial application of this technology. This paper is divided into two parts. Firstly, the key problems in the simultaneous desulfurization and denitration reaction mechanism of calcium hydroxide were studied by means of fixed-bed experiment, Diffusion Reflective Infrared Fourier Transformation spectroscopy (DRIFT), Low field-NMR and Solid state-NMR. The experimental results show that there is no liquid film on the surface of Ca(OH)2 in the temperature and humidity range of semi-dry desulphurization and denitration at normal temperature, and there are three kinds of hydrogen atoms in different chemical environment, which are 1.19ppm hydroxide (OH-), 4.90ppm surface hydroxyl (*OH) and 6.56ppm bound water (H2O) respectively. Simultaneous desulfurization and denitration experiments using Ca(OH)2 mixed with TEMPO proved that the surface hydroxyl group was the key to the oxidation of SO2 and NO. It was confirmed that SO2 reacted with the surface hydroxyl group of Ca(OH)2 to form HOSO2* and then was oxidized to CaSO4, and NO is oxidized to NO2 at the same time. O2 has a great influence on the reaction path of NO2, which will directly react with HOSO2* to release NO in the absence of oxygen, while catalyze S(IV) in the presence of oxygen. According to the experimental results, three reaction mechanisms of the simultaneous removal of NOX and SO2 by Ca(OH)2 are proposed, which are NO and SO2, NO2 and SO2 without O2, and the simultaneous removal of NO2 and SO2 with O2. Secondly, the thermal stability of desulfurization and denitrification products CaSO3, Ca(NO3)2 and Ca(NO2)2 were studied by TG-FTIR, DRIFT and TG-MS. It was found that there were self-decomposition reaction, disproportionation reaction, desulfurization reaction and disproportionation reverse reaction in the pyrolysis process of CaSO3, which made up for the lack of explanations on the formation mechanism of CaSO4 in the final stage of pyrolysis in literatures. Ca(NO2)2 was first pyrolyzed to Ca(NO3)2, CaO and NO. The decomposition of Ca(NO3)2 mainly produces NO, CaO, O2 and NO2. When the reaction temperature is lower than 580℃, Ca(NO3)2 mainly pyrolysis into CaO, NO and O2, and at higher temperature, it will produce NO2 as well. The ratio of NO2 and NO produced by pyrolysis will increase with temperature. Besides, O2 has no effect on the pyrolysis reaction paths of Ca(NO3)2 and Ca(NO2)2.
