Abstract:

The discrete element method (DEM) was used to simulate the flow and mixing of binary particles in rotary retorts with stirring internals. The cylindrical stirring internals, front semicircular stirring internals, rear semicircular stirring internals and rectangular stirring internals with same radius of circumscribed circle were installed in rotary retorts according to the location and size of core region. The influence of the stirring internals′ shape on averaged velocities and mixing of binary particles was analyzed. Results showed that there were leftward wake flow, approximately symmetrical wake flow and right wake flow existed when the stirring internal traversed the particles. The sizes of wake flows were different at the same moment for different stirring internals. The fluctuation ranges of particles′ averaged velocities were small for the rotary retort without internals or installing rectangular stirring internals. For the rotary retort with cylindrical stirring internals, front semicircular stirring internals or rear semicircular stirring internals, the fluctuation range of particles′ averaged velocities were wide, and the fluctuation was regular. One fluctuating process included one major fluctuation and one small fluctuation. For the cylindrical stirring internals and front semicircular stirring internals, the small fluctuations were in the low value range of the fluctuation range. For the rear semicircular stirring internals, the small fluctuations were in the median value range of the fluctuation range. The mixing enhancement of rectangular stirring internal was worst and that of rear semicircular stirring internal was best, when the radii of circumscribed circles were same, for the binary particle in rotary retorts. The energy consumption of rotary retort with rear semicircular stirring internals was fastest and that of rotary retort with front semicircular stirring internals was slowest. Higher terminal angle of unloading was beneficial for mixing enhancement.

Key words: numerical simulation, granular flow, core region, stirring internals, mixing

摘要：

采用离散单元法（DEM）模拟了二组元颗粒体系在有扰流件回转干馏炉内的流动和混合。根据涡心区（混合死区）的位置和尺寸在回转干馏炉中分别安装了外接圆半径相等的圆柱、前半圆、后半圆和直板扰流件，研究了扰流件类型对扰流件尾流、颗粒平均速度和大小颗粒混合程度的影响。研究表明：当各扰流件穿过颗粒物料时，其尾流分别经历了左偏尾流、近似对称尾流和右偏尾流。扰流件类型不同，在相同的时刻其尾流的大小存在差异。当回转干馏炉内无扰流件或者有直板扰流件时，颗粒平均速度的波动范围较小，且波动较为不规则。当安装圆柱、前半圆和后半圆扰流件时，平均速度的波动范围较大，且波动规律性较强，每一个波动过程均由一个大波动和一个小波动构成。对于圆柱和前半圆扰流件，小波动位于波动范围的低值区，对于后半圆扰流件，小波动位于波动范围的中值区。对于二组元颗粒系统，当外接圆半径相等时，后半圆扰流件的增混效果最好，但干馏炉耗能最快。圆柱和前半圆扰流件的增混效果次之。直板增混效果最差，但相比于其他绕流件耗能最慢。较大的绕流件终末卸料角更有利于颗粒的增混。

关键词: 数值模拟, 颗粒流, 涡心, 扰流件, 混合