填料气浮柱处理造纸废水的研究

采用填料气浮柱处理造纸行业纸机白水 ,通过对絮凝药剂碱式氯化铝的用量 ,废水进料表观流速、溶气水表观流速的大小 ,柱体回收段、分离段、浓缩段的深度和废水进料位置等因素的考察 ,表明在一定的条件下 ,该设备和工艺对降低废水CODCr和悬浮物含量 ,提高浮渣污泥固含量等指标具有明显的效果。同时 ,连续试验结果也说明该设备对降低废水BOD5 也有较好的作用。

二种柱式气浮法处理纸浆废水的试验研究

采用分散空气法和加压溶气法两种充填式气浮柱处理纸浆废水,通过对工艺参数和结构参数等因素的考察,表明这两种工艺对降低废水化学需氧量CODCr和悬浮物含量SS,提高浮渣污泥固含量都具有明显的效果,且加压溶气法的处理性能优于分散空气法。加压溶气法对SS的去除率达98%,CODCr、BOD5的去除率分别为84.3%和79.4%。

柱状气浮分离器处理含油污水实验研究

乳化后的含油污水中,油滴细小分散、稳定不易团聚上浮。常规采用药剂破乳和加热处理方法,会增大企业生产成本。柱状气浮除油技术因其设备结构简单、节能高效,无二次污染等优点受到相关企业重视。气浮除油效率受到多种参数制约,而压力、分流比、污水的矿化度和单位时间内的气浮强度是几个关键因素。该文以实验研究为主,提出了综合除油率和气浮强度两个评价指标。尝试在实际生产环境内的可控制因素中,找到影响气浮除油效率的关键因素,用以改进柱状气浮分离工艺。

Nanobubble generation and its applications in froth flotation(part IV):mechanical cells and specially designed column flotation of coal

Coal is the world's most abundant fossil fuel.Coal froth flotation is a widely used cleaning process to separate coal from mineral impurities.Flotation of coarse coal particles,ultrafine coal particles and oxidized coal particles is well known to be difficult and complex.In this paper,the nanobubbles' effects on the flotation of the varying particle size,particle density and floatability coal samples were evaluated using a bank of pilot scale flotation cells,a laboratory scale and a pilot scale specially designed flotation column.The parameters evaluated during this study include the flow rate ratio between the nanobubble generator and the conventional size bubble generator,the superficial air velocity,collector dosage,frother concentration,flotation feed rate,feed solids concentration,feed particle size,and the superficial wash water flow rate,etc.The results show that the use of nanobubbles in a bank of mechanical cells flotation and column flotation increased the flotation recovery by 8%～27% at a given product grade.Nanobubbles increased the flotation rate constants of 600～355,355～180,180～75,and 75～0 microns size coal particles by 98.0%,98.4%,50.0% and 41.6%,respectively.The separation selectivity index was increased by up to 34%,depending on the flotation feed characteristics and the flotation conditions.

Numerical simulation of a self-absorbing microbubble generator for a cyclonic-static microbubble flotation column

The Cyclonic-Static Microbubble Flotation Column (FCSMC) is currently a widely used, novel type of flotation device. The self-absorbing microbubble generator is the core component of this device. The structure of the microbubble generator directly influences flotation column performance by affecting bubble size and distribution as well as gas holdup in the column. However, the complicated flow inside the generator results in high R&D costs and difficulty in testing. Thus, the CFD software, FLUENT, was used to simulate the gas-liquid two-phase flow inside a self-absorbing microbubble generator. The effect of area ratio, a key structural parameter, was studied in detail. Critical flow-field parameters including velocity, turbulent kinetic energy, minimum static pressure and gas holdup were obtained. The simulation results demonstrate that the optimum area ratio is 3.

Pico–nano bubble column flotation using static mixer-venturi tube for Pittsburgh No.8 coal seam

The flotation process is a particle-hydrophobic surface-based separation technique. To improve the essential flotation steps of collision and attachment probabilities, and reduce the step of detachment probabilities between air bubbles and hydrophobic particles, a selectively designed cavitation venturi tube combined with a static mixer can be used to generate very high numbers of pico and nano bubbles in a flotation column. Fully embraced by those high numbers of tiny bubbles, hydrophobic particles readily attract the tiny bubbles to their surfaces. The results of column flotation of Pittsburgh No. 8 seam coal are obtained in a 5.08 cm ID and 162 cm height flotation column equipped with a static mixer and cavitation venturi tube, using kerosene as collector and MIBC as frother. Design of the experimental procedure is combined with a statistical two-stepwise analysis to determine the optimal operating conditions for maximum recovery at a specified grade. The effect of independent variables on the responses has been explained. Combustible material recovery of 85–90% at clean coal product of 10–11% ash is obtained from feed of 29.6% ash, with a much-reduced amount of frother and collector than that used in conventional column flotation. The column flotation process utilizing pico and nano bubbles can also be extended to the lower limit and upper limit of particle size ranges, minus 75 lm and 300–600 lm, respectively, for better recovery.

Effect of a cyclonic flotation column on the separation of magnesium from phosphate ore

This study was performed to investigate the effects of the cyclonic separation mechanism on the removal of magnesium from phosphate ore. An analysis of the particle-bubble collision mechanism in a cyclonic force field was used to design two different pulp circulation systems for a cyclonic-static micro-bubble flotation column （FCSMC）. Experiments comparing the two conditions were then conducted. Size analysis of the feed and separated products was conducted with a BXF cyclone size analyzer. The results show that about 34.60% of the total MgO content in the feed exists in the -10 μm fraction. This demonstrates that magnesium removal from phosphate ore has the characteristics of a micro-fine particle flotation problem. Under conditions of cyclonic circulation the MgO level of the concentrate is 1.74g, which is lower than that obtained from the column operated in direct-flow circulation by 0.34%, These results indicate that the cyclonic circulation mechanism of the FCSMC can promote removal of micro-fine particles containing magnesium. This is attributed to the function of surface flotation and to the reduction of the lower separation limit under conditions of cyclonic circulation.

Reliability of gas holdup measurements using the differential pressure method in a cyclone-static micro-bubble flotation column

Gas holdup is one of the key parameters in flotation process. Gas holdup as measured by a differential pressure method was investigated and the relative errors compared to the average gas holdup from the volume expansion method. The errors were used to establish optimum measurement positions. The results show that the measurement position should be in the middle of the column and in the region half way from the center to the wall (the half-radius). The gas holdup along the axial direction is lower at the bottom and higher at the top of the floatation column. The gas holdup along the radial direction is lower near the wall and higher near the center of the flotation column. The average gas holdup measure- ment can be replaced by regional gas holdup values.