高压还原性气氛下粉煤气化熔渣流变特性与调控机制的研究

Refractory losses and slagging are often observed on the membrane wall of the reaction chamber in pressurized entrained-flow gasifiers. The refractory matter, the ash sintering temperature, the rheology characteristics of molten slag and chamber temperature are interacted on each other. Considering the effect of temperature on carbon conversion, reaction rate and refractory materials of the membrane wall , the ash flow temperature should be controlled in a reasonable range to ensure a continuous flow of the slag, so the regulatory mechanisms of molten slag fusion temperature is very important. The results based on the atmospheric conditions are unable to meet the requirements of the industrial gasifier operating, for the effect of pressure on the mineral reaction can not be ignored, specially on the sintering and flow temperature . In this project, we used a high pressure (4 MPa) and high temperature (1500°C) tube furnace with a CCD image capture as well as an infrared temperature measurement system, focusing on : The sintering temperatures and flow temperatures of different kinds of ashes under reducing conditions, and the effect of different ratios of fluxing agents on the ash fusibility; Investigating on the effect of pressure on sintering temperature and rheology characteristics of the ash, by comparing the results of atmospheric experiments with high-pressure experiments; Building the equations of sintering temperature, critical temperature and viscosity with ash compositons under high-pressure reducing conditions. To provide reliable experimental data for controlling the rheology characteristics of molten slag in pressurized industrial gasifier. This work lays a theoretical foundation for accurately controlling the rheology characteristics of slag to ensure continuous slag flow in industrial pressurized gasifiers.

高压气流床气化炉反应室膜式壁耐火材料的烧损和排渣不畅时常发生。耐火材料与灰的烧结温度、渣流变特性和反应室温度是相互制约的。由于碳的转化率、转化速率和膜式壁耐火材料对温度的要求，灰渣的流动温度过高或过低都不利于挂渣和排渣，因此熔渣灰熔点的调控十分重要。由于压力对气体组分摩尔浓度的影响，进而影响气体与矿物的反应和灰的烧结温度与流动温度，常压下的试验结果已无法满足指导气化炉运行的要求。拟采用4 MPa高压和1500°C高温管式反应炉，辅以CCD图像采集和红外测温系统，主要研究：还原性气氛下覆盖高中低不同灰熔点的灰渣的烧结温度、流动温度以及不同配比的助溶剂对灰熔融特性的影响规律；与常压下的试验结果对比研究，探索压力对灰烧结温度和流变特性的影响规律；建立加压还原性气氛条件下灰的烧结温度、临界温度和粘度与矿物组分间的经验关系。为工业加压气化炉灰渣流变特性的准确调控，可靠地实现挂渣和排渣奠定理论基础。

深入认知高压下粉煤气化熔渣的烧结熔融特性的变化规律，建立合适的反应动力学模型、粘温预测模型以及熔渣调控机制，是工业气化炉可靠地实现挂渣和排渣的理论基础。.研究项目揭示了晶体结构和压力对粉煤气化熔渣的烧结熔融特性的影响机制：煤灰矿物中晶体尺寸越大，晶胞数越少，其能量态越高，越不易烧结。压力改变了煤灰中矿物的赋存形态，压下小于1.5 Mpa时，增压导致Fe的赋存形态从三价向二价转变，降低了煤灰的烧结熔融温度；而压力的进一步增加会使长石类矿物转变为高熔点的莫来石，从而增加煤灰的烧结熔融温度。.在动力学研究方面，我们发现压力和升温速率不影响煤焦燃烧的反应性；提出了一种表面活化函数算法确定煤焦燃烧的本征反应性：通过等温实验得到的表面活化函数拟合非等温实验数据，可消除非等温实验中存在的与氧浓度相关的动力学补偿效应，从而得到不同氧浓度条件下的唯一的动力学参数。这对加压燃烧反应性的预测具有重要意义。.在粘温预测模型研究方面，我们建立了与煤灰成分（硅铝比）和温度（变形温度和全液相温度）相关的晶体体积分数模型，并结合Roscoe非均相粘度模型准确地预测了煤灰的粘温特性。.在熔渣调控机制研究方面，我们研究了SiC耐火材料和灰的烧结熔融特性：耐火材料降低了煤灰的烧结温度，使其易于挂渣，但同时可增加煤灰的HT和FT，更加利于煤灰在耐火材料表面形成牢固稳定的熔渣保护层。针对全烧高碱煤，提出了上行水激冷液态排渣方式：激冷水可以给煤灰带来OH基团，具有保持颗粒均匀性抑制颗粒烧结熔融的作用，从而降低飞灰在受热面上的积灰可能性，故该排渣方式具有全烧高碱煤的潜力；同时为了保证该炉型能正常运行，需保持合理的氧/煤比。这些工作对液态排渣炉的运行具有重要的指导意义。