絮凝流场对煤泥水絮凝沉降效率有重要影响。流化床在床层中有丰富的流化颗粒诱导的微涡旋,有望为煤泥水的高效絮凝沉降提供一种新的解决方案。在优化的药剂制度下,利用反式流化床分别进行了单级流化和两级流化絮凝沉降试验,以絮凝体大小、分形维数和溢流水浊度为指标,分析了流化床的速度梯度G和停留时间T等动力学参数对絮凝效果的影响。结果表明,以3mm保利龙小球为充填介质的单级流化,表观流速为2.75cm/s、初始充填高度为16cm时可获得平均粒径约0.35mm的致密絮体,溢流浊度为4.8NTU,效果最好;在流化床中充填8cm高的3mm保利龙小球和16cm高的5mmPP球组成的两级流化床可得到直径大于0.5mm的均匀致密絮体。研究结果表明,流化床的表观速度决定着床层中流体的流动状态,进而对絮凝效果起决定性作用。G和GT值与絮凝效果没有明确的相关性,但GT值与絮体的分形维度近正相关。合理配置的两级流化床能够提供速度梯度递减、涡旋尺度递增的水力学条件,与絮体成长过程需求相吻合,可以获得粒度达到523mm,溢流浊度3.5NTU,分形维数1.91的絮体,优于搅拌流场絮凝。

The flow field has an important effect on the flocculation settling efficiency of coal slurry. There are abundant micro-vortices induced by fluidized particles in the fluidized bed, which may provide a new solution for efficient flocculation and sedimentation of coal slurry. Under the optimized reagent system, single - stage and two - stage fluidized flocculation sedimentation tests were carried out in a reverse - fluidized bed, and the kinetic indexes such as velocity gradient G and residence time T in the fluidized bed were analyzed. The flocculation effect was evaluated by the size and fractal dimension of floc and the turbidity of overflow. The results show that a single-stage fluidization with 3 mm styrofoam ball as filling medium and an apparent flow rate of 2. 75 cm/ s and an initial filling height of 16 cm, can obtain dense flocs with average particle size of about 0. 35 mm and the overflow turbidity of 4. 8 NTU. A two-stage fluidized bed consisting of 8-cm-high 3-mm styrofoam ball and 16-cm-high 5-mm PP pellets could obtain uniform dense floc larger than 0. 5 mm in diameter. It was concluded that the apparent velocity of the fluidized bed determines the flow state of the fluid in the bed, and then plays a decisive role in the flocculation effect. G and GT have no definite correlation with flocculation effect, but GT have positive effect to fractal dimension of floc. The reasonable two-stage fluidized bed can provide hydraulic conditions of decreasing velocity gradient and increasing vortex scale, which is in accordance with the requirement of floc growth process and can obtain better flocculation effect. Under the optimal conditions, floc with mean particle size of 523 m, overflow turbidity of 3. 5 NTU and fractal dimension of 1. 91 were obtained, they are better than that of agitation flow field.