黄河流域煤炭开发区地下水污染成因分析及防治建议

[研究目的]黄河流域内由于煤炭资源开发导致地下水污染严重,从整体角度对流域内重点煤炭开发区地下水进行归纳总结,为其可持续健康发展和地下水资源改善提供防治建议。[研究方法]从黄河流域战略地位出发,对地下水污染成因和污染模式进行归纳总结。采用改进后的综合水质指数法对流域内九大煤炭基地的地下水进行水质评价。选用主成分分析法赋权指标,并引入改进的内梅罗污染指数法,按照WPI分级法进行评价。[研究结果]通过对黄河流域各重点断面水质评价,得到目前流域内煤炭基地水质结果中Ⅲ、Ⅳ类占比较多,水质较差。分析成因当前流域内存在高矿化度矿井水、酸性矿井水和含特殊组分矿井水污染,同时阐述污染地下水形成的浅层和深层两种污染模式。[结论]对3种矿井水采用相应防治方法,并提出膏体充填技术和微生物修复技术2种防治技术建议,通过应用实际矿山为例,印证污染防治技术能够改善由煤炭开采引发的流域内地下水污染严重的问题,以期研究结果能够对成功推动中国绿色矿山的快速发展具有参考意义。

Nanobubble generation and its applications in froth flotation(part Ⅱ):fundamental study and theoretical analysis

Froth flotation is a commonly employed technology to improve the quality of raw coal and minerals.Coal and minerals particle size and surface hydrophobicity are two main parameters that affect three key steps in froth flotation process:particle-bubble collision,adhesion,and detachment.This paper fundamentally investigated the effects of nanobubble on coal and phosphate flotation.It has been found that the presence of nanobubble in flotation pulp could widen the coal and phosphate flotation particle size range,increase the particle surface hydrophobicity,and thus improve the coal and phosphate froth flotation recovery.

Nanobubble generation and its application in froth flotation (part I): nanobubble generation and its effects on properties of microbubble and millimeter scale bubble solutions

A special nanobubble generation system has been developed for evaluating the effect of nanobubble on froth flotation. In this study, an eight-factor five-level Central Composite Experimental Design was conducted for investigating eight important parameters governing the median size and the volume of nanobubbles. These process parameters included surfactant concentration, dissolved oxygen (O2) content, dissolved carbon dioxide gas (CO2) content, pressure drop in cavitation tube nozzle, <50 nm hydrophobic particle concentration, <50 nm hydrophilic particle concentration, slurry temperature and the time interval after nanobubble generation. The properties, stability and uniformity of nanobubbles were investigated. The study of the produced nanobubble’s effects on the characteristics of microbubble solutions and millimeter scale bubble solutions was performed in a 50.8 mm column.

Nanobubble generation and its applications in froth flotation(partⅢ):specially designed laboratory scale column flotation of phosphate

Froth flotation is used widely for upgrading raw phosphate.The flotation recovery of coarse phosphate(-1.18+0.425 mm) is much lower than that achieved on the-0.425+0.15 mm size fraction.Enhanced recovery of coarse phosphate particles is of great economic and environmental importance for phosphate industry.In this investigation,four different phosphate samples were aquired,characterized and tested in a specially designed laboratory-scale flotation column.Significant recovery improvement of coarse phosphate flotation was achieved using cavitation-generated nanobubble though its effects differ among the four testing phosphate samples.The laboratory-scale flotation column test results indicate that nanobubble increased P_2O_5 recovery by up to 10%～30%for a given Acid Insoluble(A.I.) rejection,depending on the characteristic of phosphate samples.The improvement effect of nanobubble on the hard-to-float particles was more significant than that on easy-to-float particles,especially at lower collector dosages.Nanobubbles reduced the collector dosage by 1/3 to 1/2.Nanobubbles almost doubled the coarse phosphate flotation rate constant and increased the flotation selectivity index by up to 25%.

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.

Parametric study of electrostatic separation of South African fine coal

The fact that water requirements are a major problem for present and future developments in material beneficiation, and the construction of a new power plant in South Africa, forms the basis for the utilization of a Rotary Triboelectrostatic Separator (RTS) for beneficiation of South African pulverized coal. The cleaning potential of Majuba and Koorfontein coal was first evaluated using kinetic froth flotation tests on the -177 μm coal fraction. The RTS tests were conducted under varied process parameters. Parameters such as applied separating voltage, air injection velocity, particle feed rate and splitter position were investigated. Two stage separation results show that the RTS reduced Majuba coal initially containing about 30% ash to a clean product of 14.30%, or 19.46%, ash at a combustible recovery of 15.10%, or 53.02%, respectively. Similar separation performance was also achieved with the Koorfontein coal. The mineral and organic compositions in the feed, after single stage and after the second stage separations were characterized using X-ray diffraction analysis. The results show a better separation for the second stage coal products.