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基于自保守混凝动力学的煤泥水絮凝沉降研究

发布时间:2018-10-24 07:20
【摘要】:本文探索占地面积小、絮凝效果好的一种新型自保守混凝反应设备,通过数值模拟和絮凝沉降实验考察不同流速和反应器结构对絮凝效果的影响,探索最优的设备结构及最佳的水力学条件。首先,根据自保守混凝动力学理论,推导出螺旋导流装置的结构参数计算方法。在此基础上,计算G0为300-1,煤泥水浓度为40g/L,粒度为0.02mm时的絮凝反应器结构参数,用于模拟和设计;同时放大螺旋外径、改变流道长度以探讨反应器结构对絮凝效果的影响。数值模拟结果表明:煤泥水沿螺旋导流装置Z轴(竖直)方向,流体速度逐渐减小;由中心面上湍动能及有效能耗变化可知,较多的螺旋圈数和较大的入口流速对絮凝更有利;经理论计算得到的速度梯度与模拟得到的速度梯度变化趋势相同,均逐渐较小,但前者数值比后者大;同时也验证了自保守絮凝沉降反应器设计的合理性。煤泥水絮凝沉降试验结果表明:对于同一絮凝反应器而言,随着初始流速的增加,溢流浊度呈现先下降,后上升的趋势;而底流浓度则呈现先上升后下降的趋势。因此存在最佳初始流速,初始流速过低或过高均对絮凝过程不利。由不同的絮凝反应器实验结果对比可知,多螺旋大直径的反应器絮凝沉降效果更好,最佳初始流速为0.151m/s。结合实验结果与模拟分析结果可以得出:当反应器内部体积加权湍动能在0.0068m2s-2~0.0027m2s-2之间,体积加权有效能耗在0.166m2s-3~0.042m2s-3之间时能有利于保证较好的絮凝效果。分段采样的粒度分析结果表明:当初始流速均为0.151m/s时,对于同一反应器而言,絮体平均粒径及分形维数随着颗粒在螺旋流道中的流动而逐步增大,未出现明显剪切破碎现象。在本文考察的反应器中,当结构参数为:外筒高度1500mm,外筒直径100mm,内筒直径80mm时,絮体的分形维数最大,为2.1103,密实最好,沉降效果最佳。因此,依据自保守混凝动力学设计的絮凝沉降反应器能较好的满足煤粒沉降过程的水力条件要求。
[Abstract]:In this paper, a new type of self-conserved coagulation reaction equipment with small area and good flocculation effect was explored. The effects of different flow rate and reactor structure on flocculation effect were investigated by numerical simulation and flocculation settlement experiment. To explore the optimal equipment structure and hydraulic conditions. Firstly, according to the theory of self-conservative coagulation dynamics, the calculation method of structural parameters of helical diversion device is derived. On this basis, the structural parameters of the flocculation reactor are calculated when G _ 0 is 300-1, slurry concentration is 40 g / L, particle size is 0.02mm, and the influence of reactor structure on flocculation efficiency is discussed by enlarging the outer diameter of screw and changing the length of flow channel. The numerical simulation results show that the velocity of coal slurry decreases gradually along the Z axis (vertical) direction of the helical diversion device, and from the change of turbulent kinetic energy and effective energy consumption on the center surface, it is found that more spiral circles and larger inlet velocity are more favorable for flocculation. The variation trend of velocity gradient obtained by theoretical calculation is the same as that obtained by simulation, which is gradually smaller, but the former value is larger than the latter, and the rationality of the design of self-conservative flocculation settling reactor is also verified. The results of flocculation settlement test show that for the same flocculation reactor, with the increase of initial flow rate, the turbidity of overflow decreases first and then increases, while the concentration of bottom flow increases first and then decreases. Therefore, there is an optimal initial flow rate, which is unfavorable to the flocculation process if the initial velocity is too low or too high. Compared with the experimental results of different flocculation reactors, the flocculation settling effect of multi-helix large diameter reactor is better, and the optimum initial velocity is 0.151 m / s. Combined with the experimental results and simulation results, it can be concluded that when the volume-weighted turbulent kinetic energy in the reactor is between 0.0068m2s-2~0.0027m2s-2 and the volume-weighted effective energy consumption in the range of 0.166m2s-3~0.042m2s-3, the better flocculation effect can be guaranteed. The results of particle size analysis show that when the initial flow rate is 0.151m/s, the average particle size and fractal dimension of the flocs increase gradually with the flow of particles in the spiral channel, and no obvious shear breakage occurs for the same reactor. In the reactor investigated in this paper, when the structural parameters are as follows: the height of the outer cylinder is 1500mm, the diameter of the outer cylinder is 100mm, and the diameter of the inner cylinder is 80mm, the fractal dimension of the floc is the largest, which is 2.1103, and the compactness is the best and the settlement effect is the best. Therefore, the flocculation settling reactor designed according to self-conserved coagulation kinetics can meet the hydraulic requirements of coal settling process.
【学位授予单位】:中国矿业大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:TD94

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