Effect of flocculation sedimentation on the yield stress of thickened ultrafine tailings slurry
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摘要: 深锥浓密机内底部料浆的屈服应力过高容易导致压耙，为此通过对不同絮凝沉降条件下获得的浓缩超细尾砂料浆的屈服应力进行原位测量，并通过对絮凝前后料浆总有机碳的测试来分析超细尾砂颗粒表面的絮凝剂吸附量，进而分析了絮凝沉降对浓缩超细尾砂料浆屈服应力的影响规律。研究发现，絮凝沉降对浓缩超细尾砂料浆的屈服应力有显著影响，pH和絮凝剂单耗通过影响尾砂颗粒表面的絮凝剂吸附量进而影响浓缩超细尾砂料浆的屈服应力，屈服应力随着pH和絮凝剂单耗的增大均不断增大。综合考虑尾砂料浆的絮凝沉降效果和所得浓缩超细尾砂料浆的屈服应力，最佳絮凝条件是pH值为11和絮凝剂单耗为15 g·t−1，在此最优条件下料浆固液界面的初始沉降速率为0.4565 mm·s−1，沉降后上清液浊度为143 NTU，底部沉积尾砂料浆的固相质量分数为51.56%、屈服应力为243.18 Pa。初步建立了适用于超细人造尾砂的基于絮凝剂吸附量的屈服应力模型，屈服应力随尾砂颗粒表面单位面积的絮凝剂吸附量的增大而增大，为实际生产中控制全尾砂絮凝沉降参数提供参考。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 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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图 2 絮凝条件对絮凝沉降的影响。（a）pH；（b）絮凝剂单耗
Figure 2. Effects of conditions on flocculation and settling: (a) pH; (b) flocculant dosage
图 3 絮凝条件对絮凝剂吸附效率的影响。（a）pH；（b）絮凝剂单耗。
Figure 3. Effects of conditions on efficiency of flocc adsorption: (a) pH; (b) flocculant dosage
图 4 絮凝条件对屈服应力的影响。（a）pH；（b）絮凝剂单耗
Figure 4. Effects of conditions on yield stress: (a) pH; (b) flocculant dosage
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