铝硅铁共存体系对生物质燃烧中钾的定向转化及调控机制

Combustion for electricity is an important way for efficient and clean utilization of biomass renewable energy on a large scale. But the problems of particulate matter emission caused by gaseous potassium and agglomeration caused by low melting point potassium salt have become important bottleneck to limit the combustion and utilization of biomass. This project intends to regulate the conversion behavior of potassium by coal gangue during biomass combustion. Aiming at the scientific problem of the interaction between coexisting system of kaolinite, quartz, iron-bearing mineral in coal gangue and potassium in biomass and combining the experimental analysis and FactSage calculation, the capture behaviors of coal gangue for gaseous potassium were studied. The relationship between change of mineral crystal structure, form of gaseous potassium and the conversion efficiency of potassium from gaseous state to solid state was determined. The conversion mechanism of solid potassium by coal gangue was investigated. The effect of the interaction of potassium, kaolinite, quartz and iron-bearing mineral on the conversion efficiency of potassium from low melting point salt to high melting point salt was revealed. The regulation mechanism of potassium by coal gangue during biomass combustion was established through changing the reaction path of kaolinite, quartz, iron-bearing mineral and potassium selectively. The research will break through the limitation of alkali metal potassium for biomass combustion and provide theoretical basis for using coal gangue to alleviate alkali metal problem during biomass combustion.

燃烧发电是大规模高效洁净利用生物质可再生能源的重要方式。但生物质燃烧过程中气态钾引起的颗粒物排放和固态低熔点钾盐导致的粘结聚团问题已成为限制其燃烧利用的重要瓶颈。本项目拟利用固废煤矸石调控生物质燃烧中钾的转化行为，针对煤矸石中高岭石-石英-含铁矿物共存体系与生物质中钾的相互作用这一科学问题，结合实验和FactSage计算，通过研究煤矸石对气态钾的捕集行为，探明矿物晶体结构变化、气态钾的存在形式与钾由气态向固态转化效率的关联；通过研究煤矸石对固态钾的转化机制，揭示钾与高岭石、石英、含铁矿物的交互反应对钾由低熔点钾盐向高熔点钾盐转化效率的作用规律；进而通过选择性改变高岭石-石英-含铁矿物与钾的反应路径，建立煤矸石对生物质燃烧中钾的调控机制，突破碱金属钾问题对生物质燃烧利用的限制，为固废煤矸石用于缓解生物质燃烧中的碱金属问题提供理论依据。

针对生物质燃烧中碱金属钾引起的积灰结渣、粘结聚团问题，本项目聚焦煤矸石对生物质燃烧中钾转化的作用，主要研究了煤矸石存在下玉米秸秆燃烧中碱金属钾的分布规律、煤矸石和玉米秸秆混合对灰熔融特性的影响及多元共存体系中化学组成与矿相反应的关系，结果表明：相比玉米秸秆单独燃烧时钾14~16%的损失率，高铝、高硅及高铁煤矸石的加入均促进了玉米秸秆灰中钾向煤矸石的固相转移，煤矸石表面钾元素含量随燃烧反应时间的增加也证明了其固钾作用。不同性质煤矸石对玉米秸秆软化、半球、流动温度均有不同程度提升，当混合比例低于10%时，高硅和高铁煤矸石可将变形温度提高至近1250oC，当混合比较高于30%时，高铝煤矸石可将变形温度提高至近1300oC，故煤矸石加入有利于高熔点物质的生成进而改善灰熔融特性，且改善程度与煤矸石性质及比例相关。矿相反应进一步验证了高熔点物质生成对灰熔融特性的改善机制，高铝和高铁煤矸石与玉米秸秆混合后的主要矿相随温度变化逐渐由高岭石、石英转变为钙铝黄长石和硅铝酸钾，且不同煤矸石混合比例展现出不同的矿相变化特征，整体呈现无定形相向晶相的转变，混合比例主要影响铝硅比、铁钾比及钙钾比等化学组成，进而通过矿相反应影响灰熔融特性。Al-Si-Fe-Ca-K共存体系的平衡物相组成理论计算及分析表明，当铝硅铁共存体系中有含钙组分存在时，生成白榴石的同时还会有钙长石生成，当含钙组分比例发生变化时，还会有钙钾硫酸盐石和钙铝黄长石等新物相生成。基于多元体系相平衡结果调控煤矸石与玉米秸秆的化学组成，可为固废煤矸石用于缓解生物质燃烧中的碱金属问题提供理论基础。.在项目资助下，已在国内外期刊发表学术论文8篇，SCI收录3篇；申请发明专利1项，授权发明专利1项；出版专著1部；参加国内外学术会议5次，其中口头报告3次，墙报2次；培养硕士毕业生3人。