油页岩流化床连续燃烧的氮转化特性研究

Investigation on Nitrogen Conversion Characteristics of Oil Shale in Fluidized Bed Continuous Combustion

在半工业化流化床实验台上,进行了低热值、高灰分油页岩的燃烧实验,通过对床温以及分离器出口烟气成分(包括O2、H2O、CO2、NO和N2O)的测量,详细分析在稳定连续的燃烧状态下,床温分布以及气体产物的生成规律,床温和分离器出口O2浓度对N2O和NO排放量的影响,着重对N2O和NO的氮转化特性进行了研究。实验结果表明,随床温升高,NO和N2O排放量逐渐降低,NO和N2O随着烟气中氧浓度增加而显著增加。对N2O和NO的主要气相生成反应和分解反应进行机理分析,得出NO重要分解反应的产物之一为N2O,NO和NO2是生成N2O的关键反应物;另外,油页岩中所含CaO对N2O还原反应具有一定的催化作用。床温和氧化自由基团对反应速率有重要影响,结果表明,床温达到850℃以上运行时可使氮氧化物总转化率保持在较低水平,过量空气系数不能过高是保持N2O和NO排放量低的运行条件。

At the large-scale thermal state circulating fluidized bed （CFB） test rig, the experimental investigation on continuous combustion of oil shale which has low heat value and high ash content was carried out. Based on the continuous stable combustion state, the change trade of bed temperature distribution and cyclone outlet flue gas components including O2, moisture （H20）, carbon dioxide （CO2）, NO and N20 are analyzed in detail. The impact rules of nitrous oxide （N20） and nitrogen oxide （NO） emission at different factors consisting of bed temperature and cyclone outlet oxygen （02） concentration are analyzed, and the characteristics of N conversion are studied in emphasis. The investigation results indicate that N20 and NO emissions decrease gradually with bed temperature increasing, and increase considerably when raising 02 concentration. The mechanism analysis about key formation and decomposition of N20 and NO was carried out, which indicates that the key products of NO decomposition conclude N20, and NO and ]N!O2 are the key reactants of N20 formation. In addition, CaOin oil shale has catalysis effect on reduction of N20. It is important affection to reaction rate that bed temperature and oxidative free radical, which shows that N gross conversion would stay at the lower level when operating stably as bed temperature reaching to 850 ~C and higher, low N20 and NO emissions demand excessive air not being too high.