焦炉烟气钢渣联合脱硫脱硝过程NOx强化脱除机理研究

There is urgent demand for low cost desulfurization and denitrogenation technology from coke oven flue gas in coking industry. Based on desulfurization technology by steelmaking slag, a novel route that simultaneous removal of SO2 and NOx via ozone oxidation and wet absorption by steelmaking slag is proposed, in order to promote the NOx removal efficiency and decrease the amount of ozone. Focusing on the mechanism of enhanced-NOx removal by steelmaking slag, the following research will be conducted such as the process parameters optimization, leaching behavior of metal ions combined phase transformation form of steelmaking slag, and the reaction mechanism of NOx in a gas-liquid-solid multiphase. The transfer and convert mechanism of metal ions and the transform of solid phase in steelmaking slag, and the reaction principle between NO/NO2 and metal ions in steelmaking slag will be determined, for revealing the enhanced mechanism of NOx removal. Based on these research, the NOx removal efficiency will be further improved by developing the process for enhanced-leaching of active composition from steelmaking slag and designing novel agent for NOx removal, and the amount of ozone will be decreased. All of these efforts will be conducted to achieve a low cost technology for simultaneous removal of SO2 and NOx from coke oven flue gas, supporting the pollutant reduction and clean production of coking industry.

焦化行业对焦炉烟气低成本脱硫脱硝技术需求迫切。本项目在钢渣法脱硫技术的基础上，提出了焦炉烟气臭氧氧化钢渣联合脱硫脱硝的技术路线，提高钢渣脱硝效率，解决传统臭氧氧化脱硫脱硝技术臭氧用量大、成本高的问题。以钢渣强化脱硝为核心，开展臭氧氧化钢渣联合脱硫脱硝过程控制与工艺优化、钢渣中金属浸出行为与矿相变化规律、NOx气-液-固三相反应体系中转化机理等研究，明晰钢渣浆液复杂体系中金属离子迁移路径与物相转化规律、NO/NO2共存体系与钢渣浆液中不同金属离子及固相的相互作用机理等关键科学问题，揭示脱硫脱硝过程中钢渣强化脱硝机理。在此基础上，通过研究钢渣活性组分强化浸出方法和设计筛选强化脱硝助剂等手段，进一步提升钢渣强化脱硝效果，实现减小臭氧用量，降低成本的目的，形成焦炉烟气钢渣低成本联合脱硫脱硝新技术，为焦化行业节能减排和绿色化发展提供支撑。

焦化行业对焦炉烟气低成本脱硫脱硝技术需求迫切。本项目在钢渣法脱硫技术的基础上，以钢渣强化脱硝为核心，开展钢渣中金属浸出行为与矿相变化规律、NOx气-液-固三相反应体系中转化机理等研究，揭示脱硫脱硝过程中钢渣强化脱硝机理。在此基础上，围绕钢渣湿法脱硫脱硝过程中NO高效氧化与NO2快速吸收两个关键环节，开展了脱硝过程强化手段研究，开发了钢渣基NO氧化催化剂和NO2吸收强化复合助剂，实现了臭氧的绿色替代，NO2脱除率由30%显著提升至70%以上。主要成果如下：.1、开展了钢渣中金属离子浸出行为与矿相变化规律研究，弱酸性条件下（pH=5.0−6.0），钢渣中各元素的浸出顺序为：Ca>Mg>Mn>Si/Al>Fe，钙、镁元素浸出动力学符合avrami模型，反应活化能分别为37.69 kJ/mol、91.68 kJ/mol。钢渣中各矿相的酸解前后顺序应为Ca(OH)2＞CaCO3/MgO/CaMgSiO4/ CaMg(SiO4)2＞C2S/C3S＞RO相/FeOx。.2、开展了钢渣脱硝机理研究，结果表明Mn2+的存在促进NOx的脱除，液相中Mn2+可以与NO2发生氧化还原反应生成Mn3O4和MnO(OH)，从而促进NOx的脱除。在此基础上，得出了钢渣体系下NO2的脱除路径包括：1）NO2的水解反应；2）液相中还原性的Mn2+、S(IV)与NO2的氧化还原反应。.3、开发了用于H2O2氧化NO为NO2等高价态NOx过程的酸化钢渣催化剂，优化条件下NO转化率稳定在90.0%以上，SO2平均转化率<1.8%；催化反应机理研究发现酸化钢渣表面Fe(III)分散在多孔C-S-H和SiO2凝胶中所形成的FeOSi是高催化活性位点，能够催化H2O2产生∙OH和HO2∙/O2∙−，将NO氧化为NO2、HNO3和N2O5。.4、开发了适用于钙基体系下的低成本NO2强化吸收复合助剂。优化条件下运行24 h表明，脱硫率100%，脱硝率稳定在78.0%左右；当NO2−浓度达到3.0 mol/L时，脱硝率仍能保持在70.0%以上，表明复合助剂能够耐受高浓度NO2−；复合助剂中的S2O32−、NH4+和钢渣中浸出的Mg2+对NOx的脱除具有协同作用，S2O32−作为还原剂和MgSO30的氧化抑制剂促进了NO2的脱除，NH4+有效抑制了脱硝产物（NO2−）分解为NO和NO2，有利于NOx的脱除。