高炉多相多场复杂体系内焦炭消耗过程及影响因素研究

The use of high-quality coke is a prerequisite for the stable operation of the blast furnace. The blast furnace is a complex multi-phase and multi-field system, in which the high temperature, gasification reaction, mechanical damage, and slag-iron erosion cause the deterioration of strength and size of coke. Only by mastering detailedly and accurately consumption process of coke and its influencing factors in blast furnace, can we make a proper evaluation of coke quality. This project focuses on studying the mechanism of coke consumption in each region through the simulation of multi-phase and multi-field environment in blast furnace, aiming to explore the evaluation system of coke performance. The main research contents are as follows: 1) This project studies coupled reaction characteristics of gasification of coke and reduction of iron-bearing material under different temperature and atmosphere, which clears the influence rule of iron ore reducibility on coke gasification behavior. The mechanism of coke consumption under high temperature gasification, mechanical pressure and friction force is also analyzed. 2) This project researches the microstructure evolution of coke in the process of coke-molten iron-slag reaction, exploring evolution characteristics of coke particle size under the effect of high temperature, mechanical extrusion and iron/slag erosion. 3) This project investigates synergy combustion behavior of pulverized coal and coke, analyzing the effect of collision between cokes on damage behavior of coke during the combustion process, aiming to find out the consumption mechanism of coke under multi-phase and multi-field environment in raceway. 4) This project studies the evolution characteristics of coke during its total consumption cycle in blast furnace, and explores the coke quality evaluation index in each region of the blast furnace, which can establish the evaluation system of coke quality.

使用高品质焦炭是高炉稳定顺行的前提，高炉是复杂的多相多场体系，炉内高温、气化反应、机械破坏、渣铁冲刷等作用使焦炭发生强度劣化和粒度降级，只有翔实掌握焦炭在炉内的消耗过程和影响因素，才能有根据地对焦炭质量做出恰当的评价。项目通过模拟高炉内的多场多相环境，研究焦炭在各区域的消耗机理，探索焦炭性能评价体系。研究内容有：1）研究焦炭与含铁炉料在不同温度和气氛下气化-还原耦合反应特性，明确铁矿还原性对焦炭气化行为的影响规律；分析焦炭在高温气化和机械压力及摩擦力作用下的消耗机理。2）研究焦炭-铁水-熔渣反应过程中焦炭微观结构的演变规律，探究焦炭在高温、机械挤压和渣铁侵蚀作用下的粒度演变特征。3）研究焦炭-煤粉协同燃烧行为，分析燃烧过程中焦炭间的碰撞对其破损行为的影响，探明焦炭在回旋区多相多场环境下的消耗机理。4）研究焦炭在炉内全消耗周期的演变特征，探索高炉各区域焦炭质量评价指标，构建焦炭质量评价体系。

本项目通过模拟高炉内的多场多相环境，研究焦炭在各区域消耗机理，探索焦炭性能评价体系，现有主要结论如下：.（1）通过气化-还原耦合反应行为实验对铁矿和焦炭在块状区的反应研究，观察焦炭层下层焦炭的溶损率最高，越往上焦炭的溶损率越低，温度越高对焦炭溶损反应的促进作用更明显。高炉内有害元素K、Na会造成焦炭基体结构的破坏及对孔壁的侵蚀，增加焦炭孔隙率降低焦炭强度，Zn对焦炭溶损反应具有催化作用较弱，反应后强度下降较为明显，Pb对焦炭溶损反应具有催化作用较强，反应后强度下降不明显。.（2）在接触面上分别观察熔融铁液、炉渣与焦炭的润湿特性，发现在常压下二者均只在焦炭表面浅接触。铁在焦炭内部气孔中以单质或氧化物游离存在，与硫分结合成FeS，与灰分结合对形貌造成较大破坏。铁滴表面观察到大量C，内部含量相对较低且分布零散均匀，而在炉渣内部可以观察到聚集状的颗粒C。对停炉后风口区取样研究发现，渣相中焦炭一般为大颗粒状镶嵌在内部；铁相中的焦炭主要以线条状或者颗粒状分布，少数作为交接相处于渣相与铁相之间。.（3）对焦炭-煤粉协同燃烧的模拟实验表明，最大燃烧速率受氧浓度的影响最大外，初始燃烧温度、综合燃烧特性指数和可燃性指数均受焦-煤掺混比影响最大，粒度和焦炭气化度对燃烧情况的影响较小。对比炉缸区的焦炭和初始焦炭，发现前者石墨化程度显著增加，部分渣相也黏附于其上。死料柱位置焦炭固定碳含量大幅减少而灰分含量大增，且多填充与焦炭气孔之内。.（4）对焦炭在不同气化环境下的热态强度检测得知，温度与气化均对焦炭的强度下降有着不可忽视的影响。因此，提出了一种针对焦炭在高炉内实际消耗过程下的质量评价指标，命名为焦炭区段热强度指标。该指标系统反映了焦炭颗粒从高炉上部块状带开始，到软熔带下沿结束，在高炉不同位置经历了不同热作用和气化作用后的失重和热态强度降解情况，该指标在评价焦炭在高炉内的实时热态强度方面具有一定的先进性。