Analysis of thickening performance of unclassified tailings in rakeless deep cone thickener
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摘要: 結合沉降和壓濾實驗, 對脫水性能數據進行曲線擬合獲得連續網狀結構形成濃度、壓縮屈服應力和干涉沉降系數, 引入Usher提出的穩態濃密性能預測算法, 建立了無耙深錐濃密模型, 分析了絮凝劑單耗、底流中固相的體積分數、泥層高度等對固體通量和固體處理能力的影響規律.研究結果表明: 絮凝劑添加量對沉降區域影響大于壓密區域, 20 g·t-1時濃密性能較好, 底流中固相的體積分數越大固體通量越小; 在沉降區域, 固體通量僅與濃度有關, 不受泥層高度影響; 在壓密區域, 固體通量為濃度與泥層高度的方程; 模型參數范圍內, 當泥層高度 < 3.5 m時, 固體處理能力為濃度與泥層高度的方程, 當泥層高度>3.5 m時, 固體處理能力與固體通量隨底流中固相的體積分數變化規律一致.Abstract: Typical tailings discharge at low solids concentrations can cause serious environmental pollution and disasters, including tailings dam failures and the collapse of underground voids. High-density cemented backfill, which consists of unclassified mine tailings, binders, additive agents, and water, are increasingly being considered as simple and effective means for reducing the hazards of conventional slurry deposition and recovering water for recycling. Gravity thickening has been widely used in the minerals industry to increase solids concentrations of tailings. The prediction of gravity thickener performance by characterizing relevant material properties is of great importance, and batch settling and pressure filtration have proven to be the most useful methods for characterizing the dewaterability of tailings for gravity thickener performance predictions. In this research, batch settling and pressure filtration experiments were conducted to obtain dewatering data with respect to gel point, compressive yield stress, and hindered settling function by curve fitting. A predictive algorithm of steady-state thickening, proposed by Usher, was introduced and a rakeless deep cone thickener model was constructed to analyze the effect of flocculant dosage, underflow concentration, and mud height on solid flux and solid throughput. The results indicate that flocculant dosage has a greater impact on the settling zone than on the compaction zone, optimum thickening performance is obtained at a dosage of 20 g·t-1, and as underflow concentration increases, solid flux decreases. Solid flux was determined to be related to the concentration, and not influenced by mud height in the settling zone, whereas, in the compaction zone, solid flux is a function of concentration and mud height. In the range of the model's parameters, solid throughput is a function of concentration and mud height at heights less than 3.5 m, and the change law of solid throughput is similar to that of solid flux.
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Key words:
- rakeless deep cone thickener /
- flocculant dosage /
- mud height /
- underflow concentration /
- solid flux /
- solid throughput
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圖 2 壓濾實驗裝置. (a) 示意圖；(b) 測試圖
Figure 2. Filtration rig: (a) diagrammatic sketch; (b) photograph of test program equipment
圖 3 不同絮凝劑單耗壓縮屈服應力與底流中固相的體積分數擬合曲線
Figure 3. Fitting curves between compressive yield stress and underflow concentration for different flocculant dosages
圖 4 不同絮凝劑單耗干涉沉降系數與底流中固相的體積分數擬合曲線
Figure 4. Fitting curves of hindered settling function and underflow concentration for different flocculant dosages
圖 5 無耙深錐濃密模型
z—濃密機高度; hb—泥層高度; hc—錐體高度; dmin—濃密機最小直徑; dmax—濃密機最大直徑; ht—濃密機高度; ϕg—連續網狀結構形成體積分數
Figure 5. Model of rakeless deep cone thickener
圖 6 不同泥層高度固體通量隨濃度變化規律
Figure 6. Relation between solids flux and concentration for different mud heights
圖 7 不同泥層高度固體處理能力隨濃度變化規律
Figure 7. Relation between solids throughput and concentration for different mud heights
圖 8 泥層高度8 m時不同絮凝劑單耗固體通量隨濃度變化規律
Figure 8. Relation between solids flux and concentration for different flocculant dosages at a mud height of 8 m
圖 9 不同絮凝劑單耗下固體通量與處理能力變化
Figure 9. Change in solids flux and throughput for different flocculant dosages
表 1 連續網狀結構形成體積分數與絮凝劑單耗關系
Table 1. Relation between gel point and flocculant dosage
絮凝劑單耗/(g·t-1) 連續網狀結構形成體積分數 5 0.260 10 0.277 20 0.301 40 0.265 80 0.258 
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表 2 不同絮凝劑單耗壓縮屈服應力與底流中固相的體積分數模型擬合參數
Table 2. Fitting parameters of model of compressive yield stress and underflow concentration for different flocculant dosages
絮凝劑單耗/
(g·t-1)經驗參數 pa pb pm pn 5 304.732 51.432 2.941 -4.605 10 498.823 52.281 2.964 -4.724 20 385.464 54.000 2.952 -5.201 40 500.833 49.904 2.945 -4.205 80 344.351 48.469 2.944 -3.909
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表 3 不同絮凝劑單耗干涉沉降系數與底流中固相的體積分數模型擬合參數
Table 3. Fitting parameters of model of hindered settling function and underflow concentration for different flocculant dosages
絮凝劑單耗/(g·t-1) 經驗參數 ra rg rn rb 5 5.31×1014 -0.04 4.21×109 6.71×1011 10 8.12×1014 -0.09 1.82×109 3.51×1011 20 6.69×1014 -0.05 1.39×109 3.34×1011 40 3.45×1014 -0.07 9.45×109 2.64×1011 80 8.45×1014 -0.06 2.23×109 8.19×1011
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表 4 無耙深錐濃密模型參數取值
Table 4. Parameters of model of rakeless deep cone thickener
dmin/m dmax/m hc/m hb/m ht/m 2 14 3.5 0~12 14
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