摘要
为了提高煤炭利用率,解决环境污染问题,我国充分重视煤炭直接液化技术的应用。作为煤炭直接液化技术中煤浆制备单元的关键装备—媒浆混合槽的作用也显得越来越重要。目前,国内外对卧式混合槽内部流动情况的研究不多,本课题组曾对卧式混合槽进行过研究,但受时间和条件限制,仅研究了一种结构的几组参数。
本文采用Computational Fluid Dynamics(CFD)方法,个别模型配合物理实验,对三种煤浆混合槽进行结构优化研究,得到了一系列结论。
首先就课题组曾研究的涡轮式煤浆混合槽结构展开后续研究,更多地改变模型参数,寻找更合理结构,为工程应用提供技术依据。研究结果表明:在其他参数不变的情况下,选择倾斜角度为60°的直涡轮桨,并且将桨叶圆盘定为188mm,挡板与槽体之间留有2mm间隙的混合槽会获得最佳搅拌混合效果。
随后,提出螺旋式煤浆混合槽结构。该混合槽的桨叶整体上倾斜布置,构成螺旋走向,使得桨叶不仅具有传统的搅拌与混合功能,而且可以引导物料沿螺旋轨迹运动,同时也给物料一定的反混机会,让搅拌更充分。数值模拟结果显示,该装置基本能够满足设计要求。
最后,在总结前两种结构的基础上,提出了犁刀式煤浆混合槽结构。该混合槽用犁刀式桨叶代替涡轮式桨叶,使得桨叶对流体的剪切力更大。尤其在槽体内部混合物出口管前设置挡板之后,搅拌效果得到明显改善,并在相应的实验装置上进行试验运行,试验结果验证了数值模拟结果,两者吻合较好。
In order to increase the energy utilization ratio of coal and solve the problem of environment pollution, our country attaches much importance to coal direct liquefaction technology. As the key equipment of coal slurry preparation unit coal slurry mixing tank plays a significant role in coal direct liquefaction. However, few researches focused on horizontal mixing tank both domestically and abroad at present. Our research team had researched horizontal mixing tank, but only several groups of parameters in a structure were concerned due to the limitation of time and conditions.
Optimization of three coal slurry mixing tanks using computational fluid dynamics (CFD) method and physical experiment was studied in this paper, some conclusions were obtained.
The further researches were initially done in turbine coal mixing tank with various model parameters to find more suitable structures for engineering application. It was found that the best mixing result was achieved using 60°inclination straight turbine oar with 188mm disc diameter and 2mm interval between baffle and tank body, while other parameters were constant.
Spiral coal slurry mixing tank was also evaluated. In this tank oars were sloping arranged forming spiral trend, which not only has the traditional agitating and mixing function, but also leads the material flow along spiral orbit. At the same time, back-mixing enhanced the mixing more plenitude. Numerical simulation results showed that this equipment basically meets design demands.
Based on preceding structures, colter coal slurry mixing tank was finally raised, instead of using turbine oar. This tank used colter oar to achieve higher shearing force. Especially, agitating effect was obviously improved after setting a baffle before mixture outlet. The physical experiment was carried out and validated the numerical simulation results.
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