摘要
粉煤加压气化技术合成气热量回收装置内的积灰使其换热效率大幅降低,如何避免或减少积灰是该技术研发的关键。为分析不同粉煤气化工艺中热量回收装置内的积灰问题,选取2种典型粉煤气化工艺产生的细灰,即来源于上行气激冷工艺的细灰A和来源于下行水激冷工艺的细灰B,对其微观结构及表面特性进行了试验研究,分析了2种细灰的黏附特性,探究了2种细灰差异的主要原因。采用激光粒度分析仪测量了细灰的粒径分布,采用扫描电镜观测细灰的微观形貌,并根据能谱分析测定细灰表面的元素含量,采用毛细渗透法测得了2种细灰的超纯水接触角,并根据Neumann状态方程计算得到细灰的表面能。结果表明,细灰A的颗粒呈规则球形,体积分数累积分布最大的颗粒直径d d为1.2μm,表面不含碳元素;而细灰B大部分为结构疏松的不规则大颗粒(d d为45μm),表面含碳量高;细灰A和细灰B的超纯水接触角分别为39.69°,79.06°,表面能分别为56.77和26.85 mJ/m^(2),细灰B的表面能显著低于细灰A;基于黏附功及临界黏附力的分析发现,在热回收装置中以范德华力为主要黏附作用力的区域,细灰A将比细灰B更容易黏附,且难以靠重力或机械振打清除。结合气化工艺过程的分析认为,造成2种细灰差异的主要原因是气化工艺中细灰和粗渣分离方式的不同,上行气激冷工艺中决定分离的主要作用是气化室内的旋流作用,而下行水激冷工艺中则是激冷室内的水浴分离作用;热回收装置内的积灰除考虑细灰本身的特性外,还需考虑工艺条件对于细灰量的影响。表面能测量方法降低了堆积状态差异造成的试验结果偏差,可作为粉煤气化细灰表面能的定量分析方法。
The ash accumulation in the heat recovery unit of the pulverized coal pressurized gasification technology seriously affects its heat transfer efficiency.The avoidance or reduction of ash accumulation in heat recovery unit plays a key role in the development of this technology.In order to analyze the ash accumulation problem,two kinds of fine ashes which were generated in two typical coal gasification processes(i.e.,ash A obtained from the upstream gas quench process and ash B obtained from the downstream water quench process)are studied.Based on the microstructure observation and surface property determination,the adhesion characteristics of these two fine ashes are analyzed,and the main reason for the difference between these two fine ashes is explored.The particle size distribution,microscopic morphology,and surface element content of these fine ashes are measured using laser particle size analyzer,scanning electron microscope and energy spectrum analysis,respectively.The ultra-pure water contact angles on the two fine ashes are determined with the capillary penetration method,and the surface energies of fine ashes are calculated by interpreting contact angle via the Neumann equation of state.The results indicate that the fine ash A particles are regular spherical with no carbon element on the surface,and have the largest volume particle diameter(i.e.,d d)of 1.2μm.Whereas,the fine ash B is mostly large particles(d d=45μm)with loose structure and high carbon content on the surface.The ultra-pure water contact angles on fine ash A and fine ash B are 39.69°and 79.06°,respectively,and the surface energies are 56.77 and 26.85 mJ/m^(2),respectively.The surface energy of fine ash B is significantly lower than that of fine ash A.The adhesion work and critical adhesion force analysis suggests that in the area where the Van der Waals force is the main force of adhesion,the fine ash A is easier to adhere on surface compared with the fine ash B,thus,the fine ash A is difficult to remove by gravity or mechanical rapping.The main reason for the difference between these two ashes may be the difference in the separation method.In the upstream gas quench process,the swirling effect in the gasification chamber plays a major role in the separation of fine ash and coarse slag.While,in the downstream water quench process,the effect of water bath in the quench chamber plays a dominant role.In addition,the amount of fine ash also affects the ash accumulation in the heat recovery unit.The surface energy determination method reduces the result deviation caused by the difference in accumulation state of particles,and has wide applications in characterizing the property of coal gasification fine ash.
作者
张燕
乐恺
于卓艺
张欣茹
张欣欣
ZHANG Yan;YUE Kai;YU Zhuoyi;ZHANG Xinru;ZHANG Xinxin(School of Energy and Environmental Engineering,University of Science and Technology Beijing,Beijing 100083,China;Beijing MWAY Technology Co.,Ltd.,Beijing 100176,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2021年第8期2681-2689,共9页
Journal of China Coal Society
基金
国家重点研发计划资助项目(2016YFB0600701)。
关键词
粉煤气化
细灰
微观结构
表面能
毛细渗透法
pulverized coal gasification
fine ash
microstructure
surface energy
capillary penetration
