典型工业粉体的料仓下料特征及优化研究

发布时间：2018-11-25 07:04

【摘要】：以气流床粉煤加压气化技术供料系统中的锁斗下料环节为研究背景,利用有机玻璃料仓常压下料系统,研究了多种工业气化粉体的通气下料流动情况。通过FT4、粒度仪等测量了晋城煤、羊场湾煤及石油焦三种典型工业粉体的物性参数,经粉体间Carr流动性指数、HR(Hausner Ratio)指数等物性参数的对比后发现所用工业粉体均有流动性较差,黏附程度较强的共性,综合比较后发现HR指数,Carr指数及剪切特性是预测粉体在料仓内流动的有效参数。借助于称重模块、压力传感器及ECT(Electrical Capacitance Tomography)等测量手段,归纳并总结了不同粉体所表现出的下料特征现象。分析压力信号变化时发现仓内粉体静置时间能够严重影响粉体的重力下料过程;通气对促进粒径较小、黏附性较强粉体下料流动更为有效。对于流动性稍好的粉体,下料初期的料仓壁面的压力增加幅度更高,而下料过程中在料仓锥口壁面附近又会产生持续负压状态。分析ECT信号变化可知,下料后粉体在竖直管内流型一般呈环核流形式,粒级较大粉体流动连续性好,颗粒运动过程不易受通气影响;黏附性较强粉体则会出现管内流型向满管流的转变。由粉体堆积性质及下料现象提出了粉体下料过程中存在临界堆积强度,粉体整体堆积强度小于临界强度时下料才会发生,通气的作用之一在于下料前降低仓内粉体堆积强度。结合流化床中的气泡运动理论,建立了以气相运动角度描述颗粒下落运动的下料分区模型,解释了通气下料流率拱形变化曲线、气压平衡拱等现象。基于实验数据关联气泡尺寸与通气高度及通气气速间的关系,通过分区模型分别计算了工业粉体最优相对通气高度H/D=12.25和最优通气气速U_g=1.58 m·s~(-1)即2.4Umf。模型计算值与实验值的吻合效果良好,在5.56H/D18、U_gUmf的范围内,下料流率的计算偏差小于±20%。证明了优化方法的有效性。
[Abstract]:Based on the research background of the locking hopper in the feeding system of pressurized pulverized coal gasification with airflow flow of various industrial gasification powders was studied by using the normal pressure discharge system of organic glass bunker. The physical properties of three typical industrial powders, Jincheng coal, Yangchang Bay coal and petroleum coke, were measured by FT4, granularity analyzer. The Carr fluidity index between the powders was also measured. The comparison of physical property parameters such as HR (Hausner Ratio) index found that the industrial powder used has the commonness of poor fluidity and strong adhesion. After comprehensive comparison, the HR index was found. Carr exponent and shear characteristic are effective parameters to predict the flow of powder in silo. By means of weighing module, pressure sensor and ECT (Electrical Capacitance Tomography), the characteristics of different powders are summarized and summarized. When the pressure signal changes, it is found that the static time of the powder in the silo can seriously affect the process of gravity blanking, and the aeration is more effective to promote the flow of the powder with smaller particle size and stronger adhesion. For the powder with better fluidity, the pressure on the wall of the silo at the initial stage of blanking is higher, and the continuous negative pressure will occur near the wall of the tapered opening of the silo during the process of blanking. By analyzing the change of ECT signal, it can be seen that the flow pattern of the powder in the vertical tube is generally in the form of annular nuclear flow, the flow continuity of the larger particle size is good, and the particle movement process is not easily affected by aeration. The strong adhesion of the powder will lead to the change of the flow pattern to the full flow in the tube. According to the properties of powder stacking and the phenomenon of blanking, it is pointed out that there is critical stacking strength in the process of powder blanking, and when the overall stacking strength of powder is less than the critical strength, the effect of aeration is to reduce the stacking strength of powder in silo. Based on the theory of bubble motion in fluidized bed, a cutting zone model is established to describe the falling movement of particles from the angle of gas movement, and the phenomena such as the arch curve of flow rate under ventilation and the equilibrium arch of air pressure are explained. Based on the experimental data, the relationship between bubble size and ventilation height and velocity is correlated. The optimal relative aeration height (H/D=12.25) and the optimal aeration velocity (U_g=1.58 MS-1) of industrial powder were calculated by using the zoning model, i.e. 2.4 Umf. respectively. The calculated value of the model is in good agreement with the experimental value. In the range of 5.56 H / D 18 UgUmf, the deviation of calculation of discharge rate is less than 卤20. The effectiveness of the optimization method is proved.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ546;TB44

【参考文献】