Effect of flocculation sedimentation on the yield stress of thickened ultrafine tailings slurry
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摘要: 深錐濃密機內底部料漿的屈服應力過高容易導致壓耙，為此通過對不同絮凝沉降條件下獲得的濃縮超細尾砂料漿的屈服應力進行原位測量，并通過對絮凝前后料漿總有機碳的測試來分析超細尾砂顆粒表面的絮凝劑吸附量，進而分析了絮凝沉降對濃縮超細尾砂料漿屈服應力的影響規律。研究發現，絮凝沉降對濃縮超細尾砂料漿的屈服應力有顯著影響，pH和絮凝劑單耗通過影響尾砂顆粒表面的絮凝劑吸附量進而影響濃縮超細尾砂料漿的屈服應力，屈服應力隨著pH和絮凝劑單耗的增大均不斷增大。綜合考慮尾砂料漿的絮凝沉降效果和所得濃縮超細尾砂料漿的屈服應力，最佳絮凝條件是pH值為11和絮凝劑單耗為15 g·t?1，在此最優條件下料漿固液界面的初始沉降速率為0.4565 mm·s?1，沉降后上清液濁度為143 NTU，底部沉積尾砂料漿的固相質量分數為51.56%、屈服應力為243.18 Pa。初步建立了適用于超細人造尾砂的基于絮凝劑吸附量的屈服應力模型，屈服應力隨尾砂顆粒表面單位面積的絮凝劑吸附量的增大而增大，為實際生產中控制全尾砂絮凝沉降參數提供參考。Abstract: With the advantages of efficiency and economy, deep-cone thickener (DCT) has been increasingly applied in tailings management. The rake in the DCT is essential for obtaining high-concentration underflow slurry; thus, more emphasis was placed on the effects of rakes on the underflow concentration. However, high concentration means high yield stress, which may lead to rake blockage. Therefore, this study investigated the effects of flocculation and sedimentation on the yield stress of thickened ultrafine tailings slurry. First, flocculation and sedimentation experiments were conducted under a pH range of 8 to 11 and flocculant dosage of 0 to 45 g·t?1 to obtain different thickened ultrafine tailings slurries. Then, the yield stress was measured through an in situ test. Finally, the amount of flocculant adsorbed on the tailings particle surface was analyzed by total organic carbon analysis. The amount of flocculant adsorbed on the tailings particles surface increased with the pH and flocculant dosage over the entire experiment range. Then, the yield stress increased with the increase in the amount of adsorbed flocculant, indicating that flocculation sedimentation has a significant influence on the yield stress. Based on the flocculation sedimentation behavior and yield stress, the optimal conditions were a pH of 8 and flocculant dosage of 15 g·t?1. Under these conditions, the initial settling rate of the solid–liquid interface was 0.4565 mm·s?1, supernate turbidity was 143 NTU, solid mass fraction of sediment was 51.56%, and yield stress was 243.18 Pa. The relationship between yield stress and the amount of flocculant adsorbed and yield stress was investigated, and an empirical model for yield stress based on flocculant adsorption was established. It was found that the yield stress increased with the amount of flocculant adsorbed, providing a reference for the control of flocculation sedimentation parameters in actual production.
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Key words:
- tailings /
- flocculation sedimentation /
- total organic carbon /
- flocculant adsorption /
- yield stress
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圖 2 絮凝條件對絮凝沉降的影響。（a）pH；（b）絮凝劑單耗
Figure 2. Effects of conditions on flocculation and settling: (a) pH; (b) flocculant dosage
圖 3 絮凝條件對絮凝劑吸附效率的影響。（a）pH；（b）絮凝劑單耗
Figure 3. Effects of conditions on efficiency of flocc adsorption: (a) pH; (b) flocculant dosage
圖 4 絮凝條件對屈服應力的影響。（a）pH；（b）絮凝劑單耗
Figure 4. Effects of conditions on yield stress: (a) pH; (b) flocculant dosage
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