加压O2/H2O条件下气化反应对焦炭富氧燃烧过程的影响机制

O2/H2O oxy-fuel combustion is recognized as the next generation of oxy-fuel combustion technology. Pressurized and oxygen enriched combustion can improve the overall power generation efficiency and be with good application prospects. Exploring the mechanism of char combustion reaction in O2/H2O under pressurized conditions is an important theoretical basis for coal-oxygen-steam combustion, and it is also the foundation and key to the realization of the third-generation oxy-fuel combustion technology. In this project, a pressurized DTF was used to study the competition between CO/H2 combustion in the boundary layer of char particles and the heterogenous combustion on the char surface under pressurized conditions. The FSG model and RSP pressure correction were used to investigate the mass transfer of oxygen under pressurized O2/H2O environment. It reveals the effect of steam on oxygen diffusion-transport and adsorption-occurrence pathways during multiphase combustion at char particle boundary in pressurized O2/H2O atmosphere. The use of temperature programmed desorption (TPD) reactors in conjunction with first-principles study of pressure-effect mechanisms for the conversion of active sites during char combustion-gasification reactions in O2/H2O atmospheres. Based on the research ideas of the SKIPPY model, a kinetic model for char combustion-gasification synergistic reaction under high pressure steam-enriched conditions was established. According to the quantitative relationship between combustion and gasification of char under decoupling pressurization conditions, the interaction mechanism between char combustion and gasification reactions under high pressure and steam-oxygen was revealed.

O2/H2O富氧燃烧方式被公认为下一代富氧燃烧技术，增压富氧燃烧可提高整体发电效率。探索加压高浓度水蒸气-富氧条件下气化反应对焦炭燃烧反应的影响机制，是实现第三代富氧燃烧技术的基础和关键。本项目采用加压沉降炉，研究加压O2/H2O条件下焦炭颗粒边界层空间燃烧与颗粒表面异相燃烧对氧气的竞争机制、焦炭颗粒理化结构的演化规律和氧在加压H2O气氛中的传质特性，获得加压O2/H2O气氛下焦炭颗粒表面多相燃烧过程中氧的反应路径。采用程序升温脱附反应器，结合第一性原理研究加压O2/H2O条件下焦炭表面燃烧反应活性位的结构形态、数量、分布及其稳定性，揭示加压O2/H2O条件下焦炭-H2O气化对焦炭颗粒表面燃烧反应活性位的作用机制。借鉴SKIPPY模型，建立加压O2/H2O气氛下焦炭燃烧-气化协同反应的动力学模型。定量分析压力效应和水蒸气效应对焦炭燃烧过程中气化作用的影响规律。

O2/H2O富氧燃烧方式被认为是下一代富氧燃烧技术，本项目探索了加压高浓度水蒸气-富氧条件下气化反应对焦炭燃烧反应的影响机制。主要研究加压高浓度水蒸气-富氧条件下焦炭-H2O气化反应对焦炭颗粒表面燃烧反应活性位的作用机制、建立焦炭燃烧-气化协同作用的动力学模型，定量分析压力效应和水蒸气效应对焦炭燃烧过程中气化协同作用的影响规律、加压高浓度水蒸气-富氧条件下焦炭颗粒边界层的空间燃烧与颗粒表面异相燃烧对氧气的竞争机制、焦炭颗粒理化结构的演化规律和氧气在高浓度H2O气氛中的传质特性。.在实施过程中搭建了加压实验系统（1000℃下达到1.5MPa），完成了加压O2/H2O条件下焦炭热化学转化特性分析。量化了压力效应和水蒸气效应对焦炭转化的促进作用。得到了燃烧过程中焦炭孔隙结构、表面碳原子成键、碳骨架结构、活性位数量与形态、焦炭反应性的演化、AAEMs元素迁移规律。揭示了压力对焦炭孔隙结构的选择性作用、压力和H2O对活性位数量作用的拐点、生成空余活性位的碳氧复合物赋存形态及其热稳定性。发现加压促进焦炭表面C-O生成，H2O促进C-H消耗。在1000℃下，0.7MPa-40%H2O工况，焦炭表面空余活性位最少。.建立了焦炭-O2/H2O燃烧动力学模型。得到了压力和H2O对燃烧过程中碳元素转化的影响规律、焦炭颗粒温度的变化、颗粒内气体浓度分布、边界层均相燃烧消耗的O2比例、氧化和气化对焦炭消耗的贡献、动力学控制/扩散控制的边界条件、O2和H2O的内外扩散特性等。H2O能减缓焦炭燃烧过程中颗粒温度的波动程度，压力的影响小于H2O。在1400℃-5%O2/20%H2O条件下，边界层均相燃烧对O2的竞争作用随压力的升高而减弱。当压力达到0.4MPa，其消耗O2的比例降低到50%以下。 随温度和压力升高焦炭-O2/H2O燃烧反应向扩散控制区偏移。当压力达到1.0MPa，仅有23.6%的O2从焦炭表面扩散至中心。.基于量子化学方法得到了水对OH氧化CO反应动力学过程的影响。得到了单个水分子的加入对体系能垒和反应速率常数的作用。.相关成果发表SCI论文5篇，申请发明专利2项，培养博士研究生3名，多次在学术会议上进行汇报。