煤中碱金属钠对煤灰黏温特性的影响及机理研究

A large amount of high sodium coals are reserved in Zhundong District of Xinjiang Province. The utilization of these coals is of great significance to the economic development of this region. Coal gasification has been identified as one of the most important technologies for chemical production from coal. The flow properties of coal ash are key factors for the successful and long term operation of the entrained flow gasifier. However, little researches have been reported about the effect of sodium from coal on ash flow properties in gasifier. The lack of understanding and knowledge has severely limited the utilization of high sodium coals in gasification. This project focuses on the influence of sodium on ash viscosity-temperature characteristics and the mechanisms. The effect of sodium on mineral transformations at high temperatures is to be investigated, which is the fundamental to understand its influence on viscosity properties. Effect of sodium on viscosity of typical ashes and mechanisms are to be carefully studied. The precipitation of sodium mineral at high temperatures and its effect on viscosity are also studied. The influence of ash flow properties on gasifier operation and the guidelines for adjusting the viscosity properties of high sodium coals through adding additives or coal blending are expected to be raised based on this research. It is also the support for the design and operation of entrained flow gasifier with such coals and the results in this study fills the blank of related knowledge in ash chemistry.

新疆准东地区高钠煤炭资源丰富，高钠煤的利用对该地区的经济发展意义重大。煤气化是实现高钠煤清洁高效转化利用的重要途径之一，而煤灰的流动性质是决定气流床气化炉稳定运行的关键因素。然而，由于缺乏气化过程中煤中碱金属钠对煤灰流动性质的认识，无法准确预测高钠煤对气化炉运行的影响，制约了煤气化技术在高钠煤的应用。本项目以煤中碱金属钠为研究对象，对碱金属钠对煤灰黏温特性的影响和机理进行科学基础研究。具体内容包括：高温气化条件下钠对煤灰矿物质演化的影响；钠对典型化学组成煤灰黏温特性的影响规律及本质；高温下含钠矿物质析出的条件及其对黏温特性的影响。在此基础上，阐明气化过程中高钠煤煤灰的流动性质对气化操作的影响，提出有效地通过添加助剂或配煤方法来调控高钠煤灰黏温特性的原则和方法。并为此类煤质气流床气化的设计和操作提供科学依据，同时填补煤的灰化学研究中关于碱金属影响的空白。

本项目针对新疆高钠煤的大规模气化利用，以煤中碱金属钠为研究对象，对碱金属钠对煤灰黏温特性的影响和机理进行科学基础研究。深入研究了煤灰中氧化钠含量与高温下矿物质组成的关系，确定了煤灰中含钠矿物质种类与煤灰化学组成的关系；研究了不同气氛下高钠高硫煤灰熔融性差异的根本原因，阐明了氧化性气氛下硫酸钠生成的机制和与煤灰化学组成的关系，建立了氧化性气氛下硫酸钠析出的预测方法；研究了不同坩埚材质对高钠煤灰黏温特性的影响，揭示了不同材质坩埚与煤灰的相互作用机制，为高钠煤灰黏温特性的准确测定提供了依据；深入研究了煤灰中氧化钠含量对熔渣黏度、临界黏度温度、熔渣类型的影响，阐明了钠在熔渣结构中的电荷补偿效应及其对熔渣结构的影响，建立了粘滞活性能预测熔渣类型的方法；研究了阻熔剂高岭土的添加对新疆高钠煤熔渣黏温特性及其对气流床气化炉液态排渣过程的影响，为新疆高钠煤的大规模气流床气化利用提供了理论基础。另外，针对煤灰熔渣黏温特性的影响因素，深入研究了降温速率、熔渣中残炭含量对熔渣黏温特性的影响以及熔渣类型的本质，阐明了降温速率影响结晶过程中固相含量、熔渣中碳热反应的发生对熔渣黏温特性的影响是根本原因，揭示了固相含量的平均增加速率是影响熔渣类型的本质原因，全面地认识熔渣黏温特性的影响因素及机理。