煤化工浓盐水对煤泥水沉降特性的影响

Effect of saline wastewater of coal chemical industry on the sedimentation characteristics of coal slurry

煤化工浓盐水中含有大量无机盐离子,外排污染环境,且处理和回收成本较高。由于煤化工浓盐水含有的无机盐离子与选煤常用凝聚剂有效离子成分类似,本文以煤化工浓盐水作为煤泥水处理的凝聚剂,以内蒙古某地区难沉降不黏煤为研究对象,研究了浓盐水用量对煤泥水沉降特性的影响。采用多重散射光分析仪对煤泥水系统稳定性进行分析,通过激光粒度分析仪分析了煤泥颗粒粒度变化,以聚丙烯酰胺作为絮凝剂,研究了浓盐水用量对煤泥水沉降和澄清液浊度的影响。结果表明,结晶盐用量0~62.5kg/t,未添加浓盐水时,煤泥水系统比较稳定,动力学稳定性指数(TSI)无明显变化;随着结晶盐用量增加,煤泥颗粒开始凝聚,TSI值显著增加,结晶盐用量为50kg/t时,煤泥水顶部TSI达到最大值,此后TSI值随结晶盐用量的增加开始减小。同时,煤泥表面Zeta电位随着结晶盐用量增加先迅速升高后趋于稳定,表明结晶盐中的阳离子具有压缩双电层,降低表面电位的作用。粒度分析结果表明,未添加浓盐水时,煤泥水颗粒D50为9.43μm,D90为45.57μm;结晶盐用量为12.5kg/t时,煤泥水颗粒D50增加至11.92μm,D90增加至63.77μm,说明浓盐水的加入促进了颗粒凝聚。煤泥水沉降试验结果与TSI变化规律基本一致,随着结晶盐用量的增加,煤泥沉降速度逐渐加快,结晶盐用量为50kg/t时,沉降速率达到最大值,上层澄清液浊度达到最小值。试验结果表明,煤化工浓盐水可有效促进煤泥颗粒之间的凝聚,提高难沉降煤泥水的沉降效果。可考虑将煤化工浓盐水作为煤泥水处理凝聚剂引入煤泥水处理系统中,以降低浓盐水处理成本,提高煤泥水处理效果,但浓盐水对于整个选煤工艺系统分选指标、产品性能和设备寿命等方面的影响仍需进一步研究。

The saline wastewater of coal chemical industry contains a large amount of inorganic salt ions.For saline wastewater,the discharge will cause environmental pollution,while the treatment and recovery cost is relatively high.In this paper,saline wastewater of coal chemical industry was used as a coagulant for coal slurry as the inorganic salt ions in the saline wastewater were similar to the effective ionic components of the coagulant.The influence of saline dosage on the sedimentation characteristics of coal slurry was discussed with non-stick coal sample from Inner Mongolia.The stability of coal slurry was analyzed by a turbiscan lab.The changes of the coal particle size were measured by a laser particle size analyzer.The effects of saline dosage on the sedimentation effect and supernatant turbidity were studied with polyacrylamide as a flocculant.The results show that the coal slurry system is relatively stable when no saline wastewater is added and the turbiscan ability index (TSI) has no obvious change.With the increase of saline dosage at 0-62.5 kg/t,the coal particles begin to agglomerate,and the TSI value increases significantly.The TSI at the top area of the coal slurry reaches a maximum value when saline dosage is 50.0 kg/t,then the TSI value begins to decrease when saline dosage is further added.Simultaneously,the zeta potential of the coal slime surface increases rapidly and then tends to be steady with the increase of saline dosage,indicating that the cations in the saline have an effect on compressing electric double layer and reducing the surface potential.The results of particle size analysis show that the D 50 and D 90 of the coal slime particles is 9.43 μm and 45.57 μm separately without adding saline wastewater.And these two values increase to 11.92 μm and 63.77 μm,separately,when 12.5 kg/t saline dosage is added,demonstrating that the addition of saline wastewater promot the coagulation among particles.The results of slurry water sedimentation test are basically consistent with TSI,and the settling rate of the coal slurry gradually accelerates with the increase of saline dosage.When the saline dosage is 50 kg/t,the settling rate reaches the maximum value and the supernatant turbidity reaches the minimum value.The results show that the saline wastewater can effectively promote the coagulation of coal slime particles and improve the sedimentation effect of difficult-to-settle slurry water.Therefore,saline wastewater from coal chemical industry can be considered to use as a coagulant for coal slurry in order to reduce the treatment cost of saline wastewater and improve the sedimentation effect of coal slurry.However,the influences of saline wastewater on the separation index,product performance and equipment life in the whole coal preparation process system need further study.