Strengthening Floc Structure During Pressure Filtration of Flocculated Tailings

点击翻译按钮获取中文摘要

Recycling of water and minimizing the volume of fine mineral tailings from oil sands and mineral processing plants are the main objectives of dewatering operations. The dewatering process is usually carried out as a series of smaller interconnected unit operations, such as coagulation-flocculation, thickening, filtration or centrifuging, and even thermal drying in extreme cases, all before final tailings disposal. Each of these stages recovers only a portion of water, and the difficulty of dewatering increases as the target moisture/water content decreases. Since fine particles are inherently difficult to separate from water, the overall strategy is to gradually increase the effective size of solids to be separated from water through a series of aggregation processes (coagulation and flocculation) that lead to fast settling of the aggregates to form a thickened sediment (thickening), which can finally undergo pressure filtration and/or centrifuging. The proposed research focuses on the transition from flocculation and thickening to filtration, and the main objective is to manipulate the physico-chemical properties of a flocculated sediment (i.e., product of flocculation and thickening) in order to improve the performance of the subsequent filtration stage. It is expected that this objective can be achieved through careful addition of selected chemicals whose role would be to enhance the mechanical resistance of the flocculated sediment to the applied pressure thus allowing water to more readily flow out of the sediment. Since tailings disposal and water recycling are arguably the most pressing challenges of the oil sands and mineral processing industries, the results of the proposed research will lead to more efficient and more environmentally friendly methods of tailings treatment.Methodology will involve flocculation tests in dilute and concentrated mineral suspensions under a range of condition (pH, ionic strength), followed by pressure filtration of the flocculated sediment. The strength of the sediment will be assessed through rheological measurements. Other surface-chemical characterization methods will also be used to elucidate the mechanisms of the observed phenomena.