双基碳材促进的NOx/SO2协同吸附及解耦还原机制

The synchronous reduction of NOx and SO2 could retrench the space of the environmental equipment, have the cost efficiency, and reduce the pollutant emissions. Besides, this technology would also realize the resource utilization of pollutants. However, the catalytic reduction of NOx/SO2 by CO and other reductants is negatively affected by oxygen in the flue gas. Therefore, a novel NOx/SO2 synergistic adsorption- synchronous reduction process is proposed here, in order to solve the O2 inhibition. In this process, the rotating reactor could separate the adsorption-reduction into two different zones: in the adsorption zone, pre-loaded carbon-based materials could adsorb NOx and SO2; in the reduction zone, the adsorbed N-S compounds could decompose enhanced by CO. This decoupled adsorption-reduction process could take advantage of the promotion effect of oxygen in the adsorption and avoid the negative effect in the reduction. Based on this adsorption-reduction swing process, the proposing will investigate the following. In the NOx/SO2 synergistic adsorption process, the interaction between physical-chemical structure of carbon materials and NOx/SO2, the synergistic promoting mechanism of the temperature and atmosphere on the adsorption, and the synergistic evolution of NOx and SO2 on the surface of carbon-based materials, will be discussed and studied. In the reduction of adsorbed N-S compounds, the decoupled reduction mechanism of N-S compound, the influence mechanism of metals on the reduction process, the promoting mechanism of temperature and CO, and the desorption mechanism of the reduced compounds, are to be established. Besides, in the swing process, the decoupled mechanism of the whole process, the analysis and coupling of the elementary reaction, the study of reaction kinetics, and the influence of heat and mass transferring, as well as the coupling rule between the temperature, atmosphere, swing frequency, and the operation of the reactor, will be systematically discussed. this decoupled model of the adsorption-reduction swing system could provide the theoretical basis of the resource utilization of pollutants. Furthermore, this model could also contribute to the designing and the industrial application of the novel reactor.

NOx和SO2的同步还原，可以节约占地、节省成本，实现污染物的资源化利用。但是采用CO等还原两种污染物时，氧气会严重降低还原效率。本申请提出一种新型的NOx/SO2协同吸附-还原的工艺路线，利用回转式交替循环反应器实现吸附-还原过程的解耦分区：吸附区NOx/SO2吸附于碳基材料表面；还原区CO还原吸附态N-S化合物，利用O2促进吸附同时避开其负面作用。本申请拟研究：NOx和SO2协同吸附过程中，双基碳材料物化结构的作用机制、氧气和温度协同促进机制以及NOx/SO2的协同演化机制；吸附态N-S化合物的还原过程中，N-S的解耦还原机制、金属的影响规律、CO/温度促进机制以及还原态物质的脱附机制；NOx/SO2吸附-还原交替过程中，过程解耦机制，基元反应的解析耦合，反应动力学的研究及热质传递的影响机理，以及温度、氛围、频率等与反应器运行的耦合规律。本申请可为新型硫硝一体化脱除的开发提供重要指导。

本项目基于回转式交替循环反应器的开发，提出一种碳基多孔材料吸附脱除NOx和SO2工艺路线，同时采用精确的温度和氛围调控来实现碳基材料的再生和循环。依据项目申请书的研究预想，在项目执行期，团队对碳基多孔材料的孔结构定向调控及表面官能团定向修饰、碳基多孔碳材料对NO的吸附机制、SO2与NOx共同吸附行为、双基碳材的制备及活性性能、NO催化还原过程研究及相关催化剂制备、NO吸附脱附解耦过程等内容进行了系统研究。研究中发现以准东煤为前驱体，以酸化+水热+高温气蚀为活化方式制备的多孔碳材料，表面含有较为丰富的羰基R2C=O和羧基O-C=O结构，这有利于极性NOx的吸附。K元素的存在促进了表面含氧官能团的产生，而且K在 CO2+C反应以及NOx吸附配位过程中，都促进了电子的转移。SO2会抑制NOx的吸附，机理研究发现在没有SO2时，配位硝酸盐以及羧基容易产生，这是促进NOx吸附容积提升的关键。但是当引入SO2后，亚硫酸盐的产生会阻碍NOx与C-O等结构的结合，从而抑制NOx的吸附。在碳材料添加稀土元素后，稀土元素会成为SO2选择性吸附中心，使得NOx有机会与碳材料接触，达到削弱SO2抑制的作用。解耦过程的研究发现，低温情况下，NO的吸附容积较高，在温度低于某一个阈值时，氧气对吸附容积的影响较大，而该温度下NO的脱附较为困难，即使将CO的浓度提高，对脱附过程的影响也较小。通过挺高脱附过程的温度，可以有效的提高NO的脱附率，但是此时会使得NO的吸附性能降低。本项目以低品质碳基吸附材料开发及碳再生过程的低碳循环为目标，对多个工业应用场景都有很好的经济和社会效益。研究中提出的NOx/SO2协同吸附-解耦还原思路，可以指导燃烧污染物脱除工艺向着集约化、小型化方向发展。而以CO作为脱硝还原剂的工艺路线，对企业节能、降碳具有重要意义。