不同粉磨工艺对粉煤灰颗粒群分布特征的影响

以燃煤电厂粉煤灰为研究对象,利用球磨工艺和蒸汽动能磨粉碎工艺对粉煤灰进行粉碎,并对粉体颗粒的粒径分布、矿物组成、颗粒形貌、Zeta电位和28 d活性指数等性能进行对比研究。结果表明:蒸汽动能磨制备的超细粉煤灰颗粒尺寸分布均匀,且其活性指数明显高于球磨机制备的超细粉煤灰;粉煤灰的活性随着其粒径的减小而明显增大,掺入质量分数为30%、中位粒径D50为5.14μm的超细粉煤灰,其活性指数可达104.5%。     

超细粉煤灰物理特性对浆体性能的影响与机理

利用蒸汽动能磨和球磨2种工艺制备超细粉煤灰,研究超细粉煤灰物理特性差异对水泥浆体力学性能的影响,并利用背散射扫描电子显微镜,分析粉煤灰在水泥浆体中的水化进程。结果表明:蒸汽动能磨制备的超细粉煤灰粒度分布范围窄,颗粒分布均匀,球形颗粒多,分散性好,有利于减少需水量,提高强度活性指数;且在水泥浆体中,水化速率快有利于提高复合胶凝材料净浆抗压强度。     

煤粉超细化技术及设备研究

根据双向旋转球磨机的超细粉碎原理,研究开发制备超细煤粉的技术及设备,并采用该设备进行煤粉的超细粉碎实验,分析各种工艺参数对超细煤粉产品粒度影响。结果表明:采用双向旋转球磨机制备超细煤粉的最佳工艺条件为:筒体及搅拌器转数25r/min,球料质量比为8,研磨时间为4～5h,磨球尺寸为10～20mm,制备出超细煤粉产品的粒度为d50=1.15μm,d90=2.67μm。     

大型蒸汽动能磨制备超细固硫灰的工艺

利用电厂温度为250℃、入口压力为0.25 MPa的过热蒸汽,采用LNSJ-350A型蒸汽动能磨对固硫灰渣进行超细加工。结果表明,制得的超细固硫灰平均粒径为4.42μm,产量为10.8 t/h,加工每吨固硫灰消耗蒸汽0.93 t,电耗为19.97 kW·h;以质量分数为10%的超细固硫灰为掺合料制备强度等级为32.5的复合硅酸盐水泥,其强度和安定性均符合国家的标准要求。     

超细含能固体粉料流动性测试及加料仓设计

为解决实际火炸药生产中因超细含能固体粉料流动性差而造成的加料不畅等问题,采用基于Jenike剪切测试原理的粉体流动测试仪,对超细化后的高氯酸铵(d50=4.284μm)、硝基胍(d50=2.150μm)、硝酸钾(d50=4.794μm)3种含能固体粉料的流动性进行测试,得到相应的流动性参数和流动函数。选用整体流料仓为流动模型,经料仓设计计算公式计算得到高氯酸铵、硝基胍、硝酸钾3种超细含能固体粉料加料仓的最大半顶角θc分别为13.13、8.64、19.20°,最小出料口口径Dc分别为0.42、0.59、0.25 m。试验表明,当加料仓的半顶角θ≤θc,出料口口径D≥Dc,可保证超细含能固体粉料连续均匀稳定加料。     

电厂余热蒸汽粉碎Ⅲ级粉煤灰的研究

介绍了以余热蒸汽为动力的超微粉碎技术。该技术利用超音速蒸汽加速粉煤灰颗粒,使其相互碰撞并粉碎。通过对设备工况的调节,能高效、廉价地制备各种微米尺度的粉煤灰超微粉体。粒度分析和SEM图像显示,粉碎后粉煤灰平均粒度细,粒度分布较窄,能有效地保护粉煤灰颗粒的球状结构。在砂浆中应用结果表明,细化后的Ⅲ级粉煤灰具有较高的火山灰活性,并具有一定的减水作用,d50为10μm左右磨细灰具有最佳的减水效果。     

用硅藻土制备超微细二氧化硅

硅藻土是一种生物颗粒成因的硅质沉积岩,其化学成分主要是无定型SiO2.文中介绍了用低品位硅藻土为原料制备超微细二氧化硅的方法及超微细二氧化硅的主要技术性能.用物理方法制备的超细二氧化硅平均粒径达到0.54μm,90%＜1.0μm,并含有许多纳米微孔,比表面积77.0m2/g用化学方法制备的纳米二氧化硅,SiO2含量(干基)≥99%,BEr比表面积335～750m2/g,孔体积≥1.0cm3/g;紧堆密度≥0.15g/mL.     

黑索今超细化技术研究

文章针对如何实现超细黑索今（RDX）的安全连续批量生产问题,提出了采用卧式搅拌球磨机制备超细RDX粉体的工艺方法,介绍了卧式搅拌球磨机粉碎原理,详细分析了卧式搅拌球磨机搅拌器转速、研磨时间、磨球种类、介质球填充率及RDX浆料浓度等工艺参数对超细RDX粉体产品粒度的影响。试验结果表明：搅拌球磨这种粉碎方式能制备粒度为D90=3．05μm的超细RDX粉体产品,工艺安全可控,产品质量稳定。这种超细RDX粉体产品能满足高性能炸药及高能推进剂的需要。     

电子级高纯超细结晶型硅微粉的制备

用钇稳定氧化锆球为研磨介质,用研磨筒内壁和搅拌器都衬以聚氨酯的搅拌磨制备了电子级高纯超细环氧塑封料用石英微粉,研究了石英微粉特征参数d50随搅拌粉磨时间延长的变化规律,考察了钇稳定氧化锆球对石英微粉的污染大小,分析和探讨了1μm以下超细石英微粉的化学成分和形貌特征。实验证明,用该搅拌磨磨细石英砂可获得1μm以下、SiO2的质量分数达到99.91%的高纯超细石英微粉,但难以获得球形石英微粉。     

白云石的湿法超细粉碎工艺研究

为对白云石进行超细粉碎,利用介质搅拌磨对白云石的湿法超细粉碎工艺进行优化研究。通过对白云石湿法超细粉碎过程中主要工艺参数的优化研究,确定白云石湿法超细粉碎最佳工艺参数。结果表明:当助磨剂为聚丙烯酸钠,用量为白云石质量的0.5%,料浆中物料的质量分数为60%,球料质量比为5∶1,累积研磨时间为3~4h,转速为1200r/min,在此工艺条件下研磨4h后,其d50=0.70μm,d97=1.97μm。     

粉煤灰粒度分布及其活性的灰系统研究

用激光粒度仪测定不同细度粉煤灰的粒度分布,以灰色关联方法分析了粉煤灰粒度分布与其胶砂性能之间的相关性,并建立了粉煤灰粒度分布与其活性指数的灰系统模型。结果表明:粉煤灰粒度分布明显影响胶砂性能;19.953～45.709μm颗粒含量与胶砂需水量的正关联度最大;5.012～19.953μm颗粒含量与粉煤灰活性的正关联度最大;根据抗压强度活性指数的灰色模型可以预测粉煤灰活性大小。     

过热蒸汽制备石油焦粉体的试验研究

利用玻璃厂中工业余热转化的过热蒸汽对石油焦粉体的制备工艺进行现场工业试验,对分级机轴承、除尘器等进行温度测试与分析。结果表明,当过热蒸汽温度为280℃,压力为0.65 MPa,质量流量为2.6 t/h时,测试石油焦粉体产量为5 t/h;粒径为165、38μm的产品通过率分别为100%、61%,出料水分的质量分数为0.2%;分级机轴承和布袋除尘器均处于安全工作状态,蒸汽磨机能连续稳定运转;通过蒸汽磨机制备石油焦,比传统机械磨单位产量能耗节能38.9%,节电80.7%。     

Decoupling the effects of chemical composition and fineness of fly ash in mitigating alkali-silica reaction

A comprehensive investigation was conducted to determine the individual effects of the chemical composition and particle size of fly ash on alkali-silica reaction (ASR). Test results indicated that the combined oxides content of fly ash showed a better correlation with the ASR expansions than its individual oxides. Mixtures containing finer fly ash fractions registered lower expansions than those containing the corresponding virgin fly ashes or its coarser fractions.Within the usual range of average particle size of 10 to 30 microns, of fly ash, the chemical composition had a more dominant influence on ASR mitigation than the particle size. However, when the average particle size of fly ash decreases below 10 microns, the fineness of fly ash becomes significant in mitigating ASR. In addition, the fineness of fly ash had a more significant influence in mitigating ASR in mixtures containing high-lime fly ashes than those containing low-lime fly ashes. Hence, reducing the particle size of fly ash to finer fractions is an effective strategy to mitigate ASR. The decoupling of the chemical composition of fly ash from its particle size indicated that ASR mitigation can be achieved with any fly ash having a D₅₀ below 5 μm. However, low-lime fly ashes were effective in mitigating ASR even without reducing their particle size.     

Removals of fly ash and NO in a fluidized-bed reactor with CuO/activated carbon catalysts

This study investigates the effects of fly ash compositions (SiO(2) and Al(2)O(3)), particle sizes (4-10 μm and 40 μm), and concentrations on the simultaneous removals of fly ash and NO using a fluidized-bed catalyst reactor. Experimental results show that the removal efficiencies of fly ash and NO at particle concentrations of 968-11,181 mg m(-3) are 71-97% and 42-57%, respectively. SiO(2) particles have more influences than Al(2)O(3) particles on the performances of fluidized-bed CuO/AC catalyst. As the concentration of fine particle increases, the pores and active sites on catalyst surface are obstructed and therefore the activities of catalysts are depressed.     

Synthesis of fly ash particle reinforced A356 Al composites and their characterization

A356 Al–fly ash particle composites were fabricated using stir-cast technique and hot extrusion. Composites containing 6 and 12 vol.% fly ash particles were processed. Narrow size range (53–106 μm) and wide size range (0.5–400 μm) fly ash particles were used. Hardness, tensile strength, compressive strength and damping characteristics of the unreinforced alloy and composites have been measured. Bulk hardness, matrix microhardness, 0.2% proof stress of A356 Al–fly ash composites are higher compared to that of the unreinforced alloy. Additions of fly ash lead to increase in hardness, elastic modulus and 0.2% proof stress. Composites reinforced with narrow size range fly ash particle exhibit superior mechanical properties compared to composites with wide size range particles. A356 Al–fly ash MMCs were found to exhibit improved damping capacity when compared to unreinforced alloy at ambient temperature.     

Effect of fly ash fineness on compressive strength and pore size of blended cement paste

This paper presents an experimental investigation on the effect of fly ash fineness on compressive strength, porosity, and pore size distribution of hardened cement pastes. Class F fly ash with two fineness, an original fly ash and a classified fly ash, with median particle size of 19.1 and 6.4 μm respectively were used to partially replace portland cement at 0%, 20%, and 40% by weight. The water to binder ratio (w/b) of 0.35 was used for all the blended cement paste mixes.Test results indicated that the blended cement paste with classified fly ash produced paste with higher compressive strength than that with original fly ash. The porosity and pore size of blended cement paste was significantly affected by the replacement of fly ash and its fineness. The replacement of portland cement by original fly ash increased the porosity but decreased the average pore size of the paste. The measured gel porosity (5.7–10 nm) increased with an increase in the fly ash content. The incorporation of classified fly ash decreased the porosity and average pore size of the paste as compared to that with ordinary fly ash. The total porosity and capillary pores decreased while the gel pore increased as a result of the addition of finer fly ash at all replacement levels.     

Reaction kinetics of fly ash geopolymerization: Role of particle size controlled by using ball mill

Fly ash is milled for 0, 30 and 90?min and used to study the role of particle size on the kinetics of geopolymer formation. The increase in particle fineness is very prominent in the initial milling stage, and then slows down due to agglomeration effect of finer fraction. The fly ash geopolymerization kinetics and its mechanism is determined using heat of reaction data measured by isothermal conduction calorimeter. The improvement in reaction rate with milling is correlated with the median particle size of the fly ash. The apparent activation energy decreases with size reduction because finer fractions are more prone to alkali activation. Although the kinetics changes with particle fineness, but no alternation is detected in the reaction mechanism, governed by nucleation and growth. The apparent activation energy evaluated by rate method is showing three major steps of geopolymerization such as dissolution, gel formation and restructuring.