美国佛州磷矿重选废水絮凝脱水及底泥输送流变特性研究

【作者】 杨丽芳；

【导师】 徐晓军； Daniel Tao；

【作者基本信息】 昆明理工大学 ， 矿物加工工程， 2008， 博士

【摘要】 目前世界范围内,磷矿重选废水由于其悬浮物具有典型的胶体特性,使其固液分离非常困难,绝大部分废水贮存于大型水池、尾矿库或地下废矿井中,这种将废水贮存起来的处置方式,不仅造成土地资源、水资源的巨大浪费,而且还存在决堤、渗漏的潜在威胁。由于现有处理技术难以实现工业化应用,寻找一种技术上可行、经济上合理的处理工艺,一直是全世界关注的问题。美国佛罗里达的磷矿重选废水处理长期未能解决,对环境及水资源利用造成了很大压力。本文针对佛罗里达磷矿重选废水处理及水循环利用工艺进行探讨,在分析了国内外迄今为止的有关矿山废水及磷矿选矿废水处理工艺的基础上,依据相关理论和研究手段,开始了对该废水的小型处理工艺条件的实验研究,在取得最佳综合条件的基础上,进行了半工业化实践,并取得了与小型实验相吻合的结果,在此基础上进行了工业性实验的技术设计。该研究不仅对解决佛罗里达磷酸盐公司的水污染问题及水资源、土地资源的回用有非常重要的意义,而且对我国磷矿选矿废水的处理也有十分得要的借鉴作用。1.本文采用美国Ciba化学工业公司生产的具有特殊分子结构的新型有机高分子絮凝剂,解决了磷酸盐矿重选废水的高效絮凝问题,确定了絮凝效果与絮凝剂浓度、剂量及溶液pH的关系。2.通过多次加药和加尾砂的助凝试验研究,明确了在有机高分子絮凝剂的浓度、剂量和混合方式相同的情况下,絮凝效果随加砂量和加药次数的变化关系,为最佳絮凝工艺的选择提供依据。3.根据胶体颗粒的组成及表面性质分析,认为颗粒的底面和侧面具有不同的表面性质,颗粒的活性部位主要位于侧面上。4.通过K⁺、Ca²⁺和Al³⁺与有机高分子絮凝剂的协同作用研究,认为絮凝剂长链在悬浮颗粒表面的吸附位置在颗粒侧面的活性点上。K⁺对絮凝的促进作用大大优于Ca²⁺和Al³⁺,在一定浓度和pH范围内,Ca²⁺和Al³⁺对絮凝有抑制作用,这种现象与传统的Schulze-Hardy聚沉规则相反。本文从胶体与表面化学和溶液化学的角度出发对这一现象进行了分析。5.通过对多次加药和尾砂助凝的动力学研究,发现投加尾砂后,增加了絮凝反应中的晶核颗粒数,在涡旋惯性离心力和剪切力作用下,使脱稳胶体迅速成长;多次加药能够增加颗粒间的有效碰撞次数,絮凝的半衰期随之大大缩短。6.通过对废水进行脉冲电絮凝研究,发现在各种电极配置和脉冲供电条件下,电絮凝均未能取得理想的效果。将电絮凝与物化絮凝相结合也未取得理想的效果,研究认为电场对有机高分子絮凝剂DPW-1-1355的絮凝起到抑制作用。7.综合所有絮凝试验,“小试”得出的最佳絮凝工艺是:废水加10^-3M KCl和5%的尾砂,然后五次平均加入18×10^-6g Ciba絮凝剂DPW-1-1355,该工艺条件下的絮凝沉降速度大、上清液浊度低、底泥含固率高。该研究结果为半工业化试验提供了依据。8.根据实验研究,得出最佳絮凝工艺条件下底泥的流变性规律:（1）底泥的表观粘度随切变速度的增大而增大,粘土含固率为15%和20%时,二者之间符合幂律关系η_α=kD^n-1,且n＞1,因此底泥符合胀流体的特性,即越搅越稠。（2）底泥的切应力随粘土含固率的增加而增大,二者之间存在一元二次方程的关系:τ=5.436C²-80.489C+215.67,相关系数R²=0.9639。（3）粘土含固率为20%底泥的切应力随温度的升高而缓慢降低,二者间存在较好的线性关系:τ=-0.7264T+829,相关系数R²=0.9528。（4）通过流变性与时间的关系研究,发现当切变速率不变时,粘土含固率为20%底泥的粘度随旋转时间的增加而降低,由此可以判断底泥具有触变性。（5）通过pH对底泥流变性的影响研究,发现pH=8时粘土含固率为20%底泥的切应力最小。（6）通过底泥流变性的改良试验,发现改良剂DP-203具有降低底泥切应力的作用。9.将Ciba絮凝剂和KCl复配使用,采用多次加药、尾砂助凝工艺,以深锥形浓密机为主要设备进行了半工业化试验,试验结果表明处理出水水质达到回用要求,底泥含固率满足地下矿井回填的需要。研究不仅解决了磷矿重选废水的净化与底泥浓缩问题,而且实现了废水和底泥的资源化利用。10.通过工业化模拟设计,说明研究成果在工业化应用中的投资和运行费用经济合理,具有广阔的应用前景。更多还原

【Abstract】 At present phosphatic waste clay produced from phosphate weight -beneficiation has typical colloidal character and it is very difficult to separate solids from suspension in the world.Most of phosphatic waste clay was stored in huge clay ponds,tailing dams or useless mines of underground,which leads large areas of land to be occupied and a lot of water resource to be wasted,this store phosphatic waste clay approach also brings potential danger of dam failure and seepage.So how to find an economical and practical technology for processing phosphatic waste clay is a crucial problem in the world.The phosphate weight -beneficiation waste clay cann’t be solved in Florida of USA,so there was a great pressure on entironment and water resources used.This paper discussed the technology that how to treat phosphate weight-beneficiation waste clay and reuse water in Florida.Through analyzing treatment technology of mine wastewater and phosphate beneficiation wastewater in the world,according to correlative theories and research methods to study experimental treatment technology for processing phosphatic waste clay.Base on the best integration experimental conditions,and pilot scale tests were done which results was accorded with experimental tests.Then design the technology of industrial test use for processing phosphatic waste clay.This research is not only significant for solving the pollution of phosphate waste clay,reusing water and land resource for phosphate company in Florida,but also is a important for consulting on processing phosphatic waste clay in China.1.This paper uses American Ciba UMA organic macromolecule flocculants came from Ciba chemical company to treat phosphate waste clays.High effective flocculation can be performed to phosphatic waste clay produced from phosphate weight-beneficiation.The relationships between flocculation effects and flocculant’s concentration,dosages and pH values is mastered.2.By adding flocculants time after time and adding sand to help flocculate,the relationship between flocculating effects with adding sand dosage and flocculant times had been found when flocculant’s concentration,dosage and mixing style is constant.All these will be used to choose the best flocculation technology.3.According to colloid particles’ composition and surface characters,it is found that particle’ base faces are different from edge faces in surface character,particle’s active position.is on its edge faces.4.When we combined K⁺ ion,Ca²⁺ion and Al³⁺ion with organic macromolecule flocculants together to research,it is found that the place flocculant’s long trains was adsorbed on was located on particles’ edge faces.The promotion effect of K⁺ ion on flocculation is much better than the action of Ca²⁺ion and Al³⁺ion,Ca²⁺ion and Al³⁺ ion even has an averse effect on flocculation in a certain range of concentrations and pH values,this phenomena deviates from traditional Schulze-Hard aggregating settling- rule.This paper analyzed this phenomena according to colloid-surface chemistry and solution chemistry.5.Through dynamics researches on adding flocculants time after time and adding sand,it is found that crystal-core particles’ amounts is increased in flocculation reaction after sand is added,by action of inertia centrifugal power and yield stress, the unstabilized particles grow up quickly.Adding flocculants time after time can increase effective impact times between particles,making flocculation’s half life to be shorten.6.Our research did some tests about pulse- electric flocculation,but it is found there was a bad flocculent action in various different conditions of electrode stations and pulse-electric current.When we combine pulse-electric flocculation with physical-chemistry flocculation together,no good result was get,it was found that the electric field has a restraining effect on flocculating of organic macromolecule flocculant DPW-1-1355.7.According to all the flocculation tests,it was found that the best technics of pilot-scale testing is KCl,5%sands arid 18×10^-6gram flocculant DPW-1-1355 is added into 482ml suspension in turn and KCl’s concentration is 10^-3M,flocculant DPW-1-1355 is averagely added five times.In this condition the flocculent settling rate is fast,supernatant turbidity is low,underflow solid concentration is high,and run cost is low.8.According to various tests,the underflow rheology law under the best technics condition is get:（1）The underflow’s apparent viscosity is increased with shear rate increasing.When clay concentration is 15%and 20%,both relationship is accord with power relation(η_α=kD^n-1and n＞1,so underflow is characterized by an increasing viscosity with an increase in shear rate that is namely dilatant.It means that the underflow is more denser with stirring going on.（2）The underflow’s yield stress is increased with clay solid concentration increasing.It was found that relationship between both them can be expressed by a unitary quadratic equation:τ=5.436C²-80.489C+215.67,correlative coefficient R² is 0.9639.（3）It is found that the yield stress of underflow that its clay solid concentration is 20%is slowly decreased with increasing temperature.The relationship between both them can be expressed by a linear equation:τ=-0.7264T+829,correlative coefficient R² is 0.9528.（4）By the research of relationship between theology and time,when clay solid concentration is 20%and under condition of a constant shear rate,the viscosity of underflow is depressed with increasing rotating time is found.So it can be judged that underflow is thixotropic..（5）By the research of pH’s effect on rheology,it is found that when pH value is 8, and unerflow clay solid concentration is 20%,the yield stress of unerflow will reaches the lowest.（6）By the research of modifying under-paste’ s rheology,it was found that modifier DP-203 had an effect on reducing under-paste ’ s yield stress.9.Ciba flocculant and K⁺ ion was complexed together to be used.Half-industrialized test was performed that "deep cone thickener" was the primary equipment,added flocculants time after time and added tailing sand to help flocculation.It was found that outlet water’s quality was fit for being reused and under-paste’s solid concentration is fit for filling underground mine well.This research not only solved purifying problems of phosphatic waste clay produced from phosphate weight -beneficiation and under-paste’s concentrating problems,but also came true resource uses of wastewater and under-paste.10.Through industrialized simulative design,it is found if research results is performed in industry,the project’s investment and run cost will be cost-effective,it is also proved that there will be a wide application foreground for research results.更多还原