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摘要: 在初始泥層高75 cm和耙架轉速為0、0.1、1和10 r·min?1條件，以及耙架轉速為0.1 r·min?1和初始泥層高度為75、45和25 cm條件下，采用FBRM和PVM實時在線監測技術，對動態濃密系統泥層脫水過程絮團結構演化進行原位連續觀測，獲得了泥層脫水過程中，絮團直徑、數量分布特征和實時圖像。研究結果表明，尾礦濃密過程中絮團直徑和數量隨剪切時間延長呈現先增長后降低，再保持穩定的狀態。根據絮團直徑變化程度，將絮團密實化過程分為絮團生長期、絮團重構期和絮團破碎期3個階段。在剪切速率0.1 r·min?1和初始泥層高度75 cm實驗條件下，有利于絮團生長和絮團快速破裂重構，并提高絮團密實化程度，但過高的剪切速率作用對絮團結構影響程度下降。剪切速率的增加造成絮團平均直徑減小，同時絮團平均直徑減小的速率上升。隨著初始泥層高度增大，絮團生長階段時間更長，絮團直徑峰值更大，重構期較長，絮團平均直徑隨初始泥層高度增加而增大。尾礦絮團分形維數可以反映絮團結構變化特征，結合PVM圖像的分形維數和孔隙率計算，分析了剪切破壞力與絮團凝聚力存在的相互平衡關系，基于這種動態平衡對絮團破裂程度的影響，研究了尾礦濃密過程中的絮團密實化規律。Abstract: The real-time inline monitoring technologies of focused beam reflectance measurement (FBRM) and particle video microscopy (PVM) were used to analyze the aggregate structure evolution during the operation of a dynamic thickening system. The tailings dewatering studies were performed under two series of conditions: (i) rake rotation speeds of 0, 0.1, 1, and 10 r·min?1 and an initial mud bed height of 75 cm and (ii) initial mud bed heights of 75, 45, and 25 cm and a rake rotation speed of 0.1 r·min?1. The aggregate diameter, particle size distribution, and real-time images of the tailings thickening process were obtained. The results show that with the increase in the shearing time, the diameter and counts of aggregate first increase, then decrease, and then become stable. According to the aggregate diameter variation, the aggregate evolution can be divided into three stages: growth, reconstruction, and densification periods. The condition of a shear rate of 0.1 r·min?1 and an initial mud bed height of 75 cm has the best effects on the aggregate growth, structure breaking acceleration, aggregate reconstruction, and aggregate densification improvement, as determined in the laboratory; however, high shear rate has a degrading effect on the aggregate structure evolution. The aggregate diameter progressively decreases with the increase in the shear rate. The longer the aggregate growth period, the larger the maximum aggregate diameter, and a longer reconstruction period is observed at higher initial mud bed heights. Moreover, the aggregate diameter increases with the increase in the initial mud bed height. The fractal dimension of tailings aggregate reflects the change characteristics of the aggregate structure. According to the calculation of fractal dimension and porosity of the PVM image, the dynamic equilibrium relastionship between the breaking force and cohesive force of aggregates was analyzed, the influence on the aggregate breaking was analyzed. The aggregate densification rule in the tailings thickening process was revealed analyzed, based on the dynamic equilibrium relationship between the breaking force and cohesive force of aggregates.
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圖 3 不同剪切條件下絮團平均弦長變化曲線
Figure 3. Average chord length of aggregates under different shear conditions
圖 4 不同初始泥層高度條件下絮團平均弦長變化曲線
Figure 4. Average chord length of aggregates under different initial mud bed heights
圖 5 初始泥層高度75 cm耙架轉速0.1 r·min?1條件下不同時刻的絮團結構PVM圖像
Figure 5. PVM image of aggregate structure at different time under initial mud bed height of 75 cm and rake frame rotating speed of 0.1 r·min?1
圖 6 不同剪切速率條件下絮團分形維數和孔隙率的關系曲線
Figure 6. Relationship between aggregate fractal dimension and porosity under different shear rates
圖 7 不同初始泥層高度條件下絮團分形維數和孔隙率的關系曲線
Figure 7. Relationship between aggregate fractal dimension and porosity under different initial mud bed heights
圖 8 耙架剪切速率與絮團直徑的關系
Figure 8. Relationship between shear rate of rake and aggregate diameter
圖 9 初始泥層高度與絮團直徑的關系
Figure 9. Relationship between initial mud layer height and aggregate diameter
圖 10 不同實驗條件下的絮團破裂程度與絮團分析維數和剪切時間的關系
Figure 10. Relationship of aggregate breakage with fractal dimension and shear time under different test conditions
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